Polyimide film, laminate, semiconductor device, and flexible device

Abstract

This polyimide film comprises a polyimide as a main component in an amount exceeding 50 wt% with respect to all the resin components, and satisfies, in a tensile test, that a) the elongation at break at 25°C is 100% or higher, b) the stress at 100% elongation at a pulling speed of 10 mm / min is 10.0 MPa or less, and c) when the film is elongated 100% at a tensile speed of 10 mm / min and then released from the tensile load, the degree of restoration at 24 hours thereafter is 85% or higher.

Description

Polyimide films, laminates, semiconductor devices and flexible devices

[0001] The present invention relates to a polyimide film that can be suitably used as a material for, for example, wearable devices, a laminate equipped therewith, a semiconductor device, and a flexible device.

[0002] Polyimide films are widely used as insulating layers in flexible printed circuit boards (FPCs) and other applications due to their excellent properties in terms of heat resistance, cold resistance, chemical resistance, electrical insulation, and mechanical strength.

[0003] Incidentally, in recent years, devices that require application to complex shapes or large deformations or ranges of motion, such as wearable devices, FHE (Flexible Hybrid Electronics) devices, flexible tactile patches, glove-type VR devices, and flexible displays, have been developed one after another. In particular, the proliferation of wearable devices and FHE devices, such as healthcare devices and medical sensors that are attached to the skin, robotic arm control systems, smartwatches, and fitness trackers, is progressing rapidly. Many of these require complex deformations.

[0004] Polyimide films are considered to have considerable potential as materials for devices that require complex or large deformations or ranges of motion, such as wearable devices (which may be collectively referred to as "flexible devices" in this specification). However, applying polyimide films to flexible devices requires even greater elasticity than before. In other words, elasticity requires high elongation, low stress under tensile force, and the ability to return to its original shape after stretching.

[0005] Furthermore, if the polyimide film has high tackiness, adhesion and sticking may occur between films or between films and other components during the manufacturing process of flexible devices. Therefore, it is preferable to suppress tackiness to ensure handling. However, polyimide films with excellent elasticity tend to have high tackiness.

[0006] As a prior art for improving the elasticity of polymers, Patent Document 1 proposes a polyurethane with excellent elasticity properties such as elastic recovery, tensile strength, and tensile elongation, produced by reacting a polyether polyol (a) having a carbonate bond in its structure with an isocyanate compound (b). Although the polyurethane in Patent Document 1 has excellent flexibility, it has the drawbacks of being highly tacky and difficult to handle, and having insufficient heat resistance (easily decomposed by heat).

[0007] Patent Document 2 proposes a stretchable polyimide film for circuits that has flexibility to follow expansion and contraction and excellent heat resistance, with a thickness of 1 to 13 μm and a loop stiffness of 1.0 mN / cm or less. However, the polyimide film in Patent Document 2 is composed only of aromatic diamines and aromatic acid dianhydrides as raw material monomers, resulting in strong intermolecular interactions and difficulty in generating micro-Brownian motion. As a result, it has a yield point in the stress-strain curve and the stress is high, which presents a problem in that it cannot be easily stretched with little force.

[0008] Patent Document 3 proposes a resin composition that can suppress tackiness and provide a cured product with excellent flexibility and excellent insulation reliability. This composition includes a siloxane skeleton-containing epoxy resin, an inorganic filler, and a polyimide resin, and when the non-volatile components in the composition are considered to be 100% by mass, the inorganic filler content is 40% by mass or less. In Patent Document 3, the number of folding cycles in the MIT folding fatigue test can be ensured by using a low amount of inorganic filler to suppress tackiness. However, because it contains inorganic filler even at a low concentration, the filler can get between the polymer chains, which may hinder the movement of the polymer chains and lead to a decrease in elongation, an increase in stress, and a decrease in resilience.

[0009] Furthermore, the following proposals have also been made: Patent Document 4 discloses a urethane acrylate resin film that is excellent in heat resistance in addition to flexibility and resilience by forming chemical crosslinks at a low density within the film. Patent Document 5 discloses a laminate of a urethane resin having urethane bonds and siloxane bonds and a silicone-modified polyimide resin. Patent Document 6 discloses a silicone-modified polyimide resin that can be applied to the resin layer of a bioelectrode.

[0010] Japanese Patent Publication No. 6413298, International Publication No. 2022 / 259841, Japanese Unexamined Patent Publication No. 2023-138760, Japanese Patent Publication No. 7226324, Japanese Unexamined Patent Publication No. 2022-156876, Japanese Unexamined Patent Publication No. 2018-11931

[0011] Flexible devices are expected to become increasingly widespread in the future, and therefore, the development of polyimide films that can satisfy their required characteristics is desired. Accordingly, the first object of the present invention is to provide a polyimide film with excellent stretchability.

[0012] Furthermore, as the elasticity of a polyimide film increases, its tackiness tends to increase as well. Therefore, conventional techniques have made it difficult to achieve both improved elasticity and low tackiness. Accordingly, the second objective of the present invention is to provide a polyimide film that not only exhibits excellent elasticity but also low tackiness and good handling properties.

[0013] As a result of diligent research, the inventors of the present invention have found that the above problems can be solved with a polyimide film that satisfies specific physical properties, and have completed the present invention.

[0014] In other words, the polyimide film of the present invention is a polyimide film containing polyimide as the main component in an amount exceeding 50% by weight of the total resin components. The polyimide film of the present invention satisfies the following conditions a) to c): a) The elongation at break at 25°C in a tensile test is 100% or more; b) In the tensile test, the stress at 100% elongation at a tensile speed of 10 mm / min is 10.0 MPa or less; c) In the tensile test, after 100% elongation at a tensile speed of 10 mm / min, the recovery rate after 24 hours after releasing the tensile load is 85% or more.

[0015] The polyimide film of the present invention may further satisfy the following condition d): d) When a tacking tester with a sensor load of 5 kg is used at a temperature of 25°C, a stainless steel probe with a diameter of 5 mm is pressed against a test piece at a speed of 0.5 mm / second and a load of 300 gf, held for 10 seconds, and then pulled away at a pulling speed of 2 mm / second, the resistance experienced by the probe is measured as the load, and the average of the peak load values ​​at any three locations on the test piece is 100 gf or less.

[0016] The polyimide film of the present invention may further satisfy the following condition e): e) not having a clear yield point in the stress-strain curve;

[0017] The polyimide film of the present invention may have a breaking elongation of 200% or more in the tensile test, and the stress at 100% elongation at a tensile speed of 10 mm / min may be less than 5.0 MPa.

[0018] The polyimide film of the present invention may contain, with respect to the total structural units derived from the diamine, structural units derived from silicon-containing diamine represented by general formula (1) in an amount of 65 mol% or more and less than 85 mol%, and structural units derived from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride in an amount exceeding 50 mol%, relative to the total structural units derived from the acid dianhydride.

[0019]

[0020] In general formula (1), R１ and R ２ is each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbon atoms, and R ３ , R ４ , R ５ , R ６ , R ７ and R ８ is each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms or a monovalent aromatic group having 6 to 18 carbon atoms, m is an integer of 0 or more and is smaller than n, and n is an integer of 1 or more. However, it is assumed that m + n > 1 is satisfied.

[0021] The polyimide film of the present invention is such that the polyimide contains, based on the total structural units derived from diamine, 85 mol% or more of the structural units derived from the silicon-containing diamine represented by the above general formula (1), and contains, based on the total structural units derived from acid dianhydride, the structural units derived from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride within the range of 50 mol% or more and 90 mol% or less, and may contain 10 mol% or more of the structural units derived from an acid dianhydride having no ether bond in the molecule.

[0022] The polyimide film of the present invention may have a 1% thermal decomposition temperature (Td1), which is the temperature at which the weight loss rate becomes 1% based on the weight at 200°C in thermogravimetric analysis, of 300°C or higher.

[0023] The laminate of the present invention is provided with a conductive layer on one or both sides of the above polyimide film.

[0024] The semiconductor device of the present invention further includes a semiconductor component in the above laminate.

[0025] The flexible device of the present invention includes the above laminate.

[0026] The flexible device of the present invention may be selected from a wearable device, an FHE device, or a 3D-shaped device.

[0027] The polyimide film of the present invention possesses excellent elasticity, making it less prone to defects such as tearing. Furthermore, in its preferred embodiment, the polyimide film of the present invention has low tackiness in addition to excellent elasticity, resulting in excellent handling during processing. For these reasons, the polyimide film of the present invention can be preferably used, for example, as a material for flexible devices. Moreover, by using the polyimide film of the present invention, the reliability and yield of flexible devices can be improved.

[0028] This is an explanatory diagram of the stress-strain curve and yield point.

[0029] Embodiments of the present invention will be described below. In this specification, the upper and lower limits of numerical values ​​can be arbitrarily combined to form a numerical range.

[0030] [Polyimide Film] A polyimide film according to one embodiment of the present invention contains polyimide as the main component in an amount exceeding 50% by weight of the total resin components. The polyimide film of the present invention may contain resin components other than polyimide as long as the effects of the invention are not impaired, but it is preferable that the polyimide content be in the range of 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, and most preferably 95% by weight or more and 100% by weight or less, relative to the total resin components. The polyimide film of the present invention may be a single layer or a multilayer structure as long as the effects of the invention are not impaired, but a single layer is preferred. Furthermore, there is no preclude laminating the polyimide film of the present invention with other resin layers to form a part of a resin film.

[0031] The polyimide film of the present invention satisfies the following conditions a) to c).

[0032] Condition a) The elongation at break at 25°C in the tensile test is 100% or more. An elongation at break of 100% or more means that the film does not break when the elongation reaches 100% (twice the length before the start of elongation). An elongation at break of 100% or more makes it easy to apply to complex surface shapes such as the human body, allows for large deformations and movements, and enables application to flexible devices. From this viewpoint, an elongation at break of 200% or more is preferred, and is more preferably 300% or more, 400% or more, 500% or more, and 600% or more, in that order. There is no particular upper limit, and it may be, for example, 1000%. The elongation at break can be measured by the method described in the examples below.

[0033] Condition b) In the tensile test, the stress at 100% elongation at a tensile speed of 10 mm / min is 10.0 MPa or less. The stress at 100% elongation refers to the stress of the film when the elongation reaches 100% when the tensile test is performed under the condition of a tensile speed of 10 mm / min. By having a stress at 100% elongation of 10.0 MPa or less, it becomes easier to attach to complex surface shapes such as the human body, it becomes easier to follow large deformations and movements, and it becomes possible to apply it to flexible devices. From this viewpoint, the stress at 100% elongation is preferably less than 5.0 MPa, and more preferably in the order of 4.5 MPa or less, 4.0 MPa or less, 3.5 MPa or less, 3.0 MPa or less, 2.0 MPa or less, and 1.0 MPa or less. There is no particular lower limit to the stress at 100% elongation, and it may be, for example, 0.1 MPa. The stress at 100% elongation can be measured by the method described in the examples below.

[0034] Condition c) In a tensile test, after elongation to 100% at a tensile speed of 10 mm / min, the tensile load is released, and the recovery rate after 24 hours is 85% or higher. The polyimide film of the present invention has high elasticity, so it is not only easy to stretch, but also has excellent recovery after stretching. Recovery can be determined as the recovery rate when the load is released after being pulled to 100% elongation in a tensile test. A recovery rate of 100% means that the film is elastically deformable, so the closer the recovery rate is to 100%, the more suitable it is for flexible devices that are subjected to repeated stretching and contraction. From this viewpoint, the polyimide film of the present invention has a recovery rate of 85% or higher, preferably 90% or higher, and more preferably 93% or higher, 95% or higher, and 98% or higher in that order. Furthermore, the upper limit of the recovery rate is preferably 115% or lower, and more preferably 110% or lower, 105% or lower, and 102% or lower in that order. The recovery rate can be evaluated by the method described in the examples below.

[0035] The polyimide film of the present invention is preferably further possessing the following physical properties or characteristics.

[0036] <Tackiness> Condition d) Using a tacking tester with a sensor load of 5 kg, at a temperature of 25°C, a 5 mm diameter stainless steel probe is pressed against the test piece at a speed of 0.5 mm / second and a load of 300 gf, held for 10 seconds, and then pulled away at a speed of 2 mm / second. The resistance the probe experiences during this process is measured as the load, and the average of the peak load values ​​at three arbitrary locations on the test piece (hereinafter sometimes referred to as the "tackiness evaluation value") is 100 gf or less. When the tackiness evaluation value is 100 gf or less, the tackiness is kept low, resulting in good handling properties for the polyimide film. In other words, by keeping the tackiness evaluation value at 100 gf or less, adhesion and sticking of the polyimide film itself, or between the polyimide film and other resin films or components, is suppressed. As a result, in the process of processing the polyimide film into various devices, processing becomes easier without surface treatment, and the yield can be improved. From this viewpoint, a tackiness evaluation value of 85 gf or less is preferred, and is more preferably 75 gf or less, 60 gf or less, 50 gf or less, 40 gf or less, 30 gf or less, and 20 gf or less, in that order. There is no particular limit to the lower limit of the tackiness evaluation value, and it may be 0 gf, for example. The tackiness evaluation value can be measured by the method described in the examples below. Although polyimide films with low tackiness have been proposed in the prior art, such as in Patent Document 3, the present invention achieves a low tackiness evaluation value of 100 gf or less in a polyimide film with high elongation and low stress that satisfies conditions a and b.

[0037] <Yield Point> Condition e) The stress-strain curve does not have a clear yield point. The stress-strain curve is a physical property that represents the mechanical properties of an object measured by a tensile testing machine, and is drawn with strain on the horizontal axis and stress on the vertical axis. When the external force acting on an object is increased, in the stress-strain curve, the proportional relationship between stress and strain is broken and the strain increases preferentially. This phenomenon is called yielding, and the stress at that point is called the yield point. When the tensile force exceeds the yield point, the film begins irreversible plastic deformation. In this invention, when the film is stretched in a tensile test and the strain of the film is increased, if the phenomenon of stress decreasing in proportion to the increasing strain is observed, as shown in the upper curve of Figure 1, then a yield point is considered to exist. If the phenomenon of stress decreasing in proportion to the increasing strain is not observed, as shown in the lower curve of Figure 1, then a yield point is considered to be absent. The presence or absence of a yield point can be measured by the method described in the embodiments below.

[0038] <Breaking Strength> The breaking strength at 25°C in a tensile test shall be 25 MPa or less. Breaking strength refers to the stress at which the film breaks when a tensile test is performed under the condition of a tensile speed of 10 mm / min. Films with high breaking strength show a significant increase in stress with increasing elongation, and for example, they lack flexibility when stretched to 200% or more. By having a breaking strength of 25 MPa or less, flexibility can be ensured even when used at high elongation, making it possible to apply to various flexible devices. From this viewpoint, a breaking strength of 20 MPa or less is preferable, and is more preferably 15 MPa or less, and then 10 MPa or less. On the other hand, if the breaking strength is too low, the film lacks rigidity and is easily torn, resulting in poor processability. Therefore, the lower limit of the breaking strength is preferably 1 MPa or more, and is more preferably 3 MPa or more, and then 5 MPa or more. The breaking strength can be measured by the method described in the examples below.

[0039] <Feel and Processability> The polyimide film of the present invention combines high elasticity and low tack, resulting in excellent feel and processability. Specifically, it can be easily stretched with light force, and even when the film is folded during processing, it does not adhere to the surrounding tissue, making adhesion unlikely. While feel and processability are difficult to quantify, they are extremely important characteristics when processing polyimide film into various devices. Therefore, in this invention, feel and processability are evaluated using the methods described in the examples below.

[0040] <Thermal Decomposition Temperature (Td1)> The polyimide film of the present invention is measured for weight loss when heated from 30°C to 550°C at a constant heating rate. The temperature at which the weight loss rate of the polyimide film is 1% relative to the weight at 200°C is defined as the "thermal decomposition temperature (Td1)". Preferably, the thermal decomposition temperature (Td1) is 300°C or higher, and more preferably in the order of 350°C or higher, 360°C or higher, 370°C or higher, 380°C or higher, 390°C or higher, and 400°C or higher. A thermal decomposition temperature (Td1) of 300°C or higher makes it less likely for thermal decomposition or deformation to occur when the polyimide film is heated during the process of processing it into a flexible device, thereby improving the reliability and yield of the product. The thermal decomposition temperature (Td1) can be evaluated by the method described in the examples below.

[0041] A particularly preferred embodiment of the polyimide film of the present invention is one that satisfies all of the following characteristics: - Breaking elongation at 25°C in a tensile test of 500% or more; - Stress at 100% elongation at a tensile speed of 10 mm / min in a tensile test of 3.0 MPa or less; - Tackiness evaluation value of 75 gf or less; - Recovery rate within the range of 98 to 102%; - Thermal decomposition temperature of 360°C or higher. A polyimide film that satisfies all of the above characteristics is particularly suitable as a material for flexible devices. There are no particular limitations as long as the polyimide film satisfies all of the above characteristics, but it is preferable that it is a polyimide film containing siloxane-modified polyimide.

[0042] <Polyimide> The polyimide constituting the polyimide film of the present invention (hereinafter sometimes referred to as "the polyimide of the present invention") contains a structural unit derived from a diamine (hereinafter sometimes referred to as "diamine unit") and a structural unit derived from an acid dianhydride (hereinafter sometimes referred to as "acid dianhydride unit"). In the present invention, the diamine unit means a divalent group derived from a diamine compound, and the acid dianhydride unit means a tetravalent group derived from a tetracarboxylic dianhydride.

[0043] <Diamine unit> The polyimide of the present invention preferably contains, as a diamine unit, a structural unit derived from a silicon-containing diamine represented by the general formula (1) (hereinafter sometimes referred to as "structural unit (1)"). By using the silicon-containing diamine represented by the general formula (1) as a raw material, a siloxane skeleton is introduced into the polyimide chain, so that the flexibility of the polyimide film can be enhanced, the elongation at break can be increased, and the tensile stress can be reduced.

[0044]

[0045] In the general formula (1), R １ and R ２ are each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbon atoms, and R ３ , R ４ , R ５ , R ６ , R ７ and R ８ are each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms or a monovalent aromatic group having 6 to 18 carbon atoms, m is an integer of 0 or more and smaller than n, and n is an integer of 1 or more. However, it is assumed that m + n> 1 is satisfied. It is also possible to use a mixture of a plurality of silicon-containing diamines represented by the general formula (1). In that case, the structural unit (1) is derived from a plurality of compounds.

[0046] In the general formula (1), as the groups R １ and R ２ , for example, an alkylene group having 3 to 12 carbon atoms is preferable, and a propylene group, a butylene group, a pentyl group and the like are more preferable. Further, the groups R ３ , R４ , R ５ , R ６ , R ７ and R ８ For example, methyl, ethyl, propyl, phenyl, naphthyl, toluyl, and benzyl groups are preferred. The reason for setting m+n>1 in general formula (1) is that diamines with m+n of 1 or less have low flexibility and poor elasticity when used alone, making them undesirable for achieving conditions a) and b). However, it is possible to use a diamine with m+n of 1 or less in combination with a diamine represented by general formula (1) that satisfies m+n>1.

[0047] Furthermore, from the viewpoint of increasing the flexibility of the polyimide film, increasing the elongation at break, and decreasing the tensile stress, the number-average molecular weight of the silicon-containing diamine represented by general formula (1) is preferably in the range of 200 to 2000, and more preferably in the range of 400 to 1500. The number-average molecular weight of the silicon-containing diamine was calculated as twice the amine equivalent.

[0048] <Acid Dianhydride Units> The polyimide of the present invention preferably contains structural units derived from 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride (4,4'-oxydiphthalic acid dianhydride; ODPA) as acid dianhydride units (hereinafter sometimes referred to as "ODPA units"). Since ODPA units have an ether bond between two benzene rings, rotation occurs at the ether bond site, making it easier for the molecule to adopt a three-dimensional structure, thereby suppressing intermolecular interactions. As a result, micro-Brownian motion of the polymer chain is easily generated, which increases the flexibility of the polyimide film, increases the elongation at break, and reduces tensile stress.

[0049] The polyimide of the present invention may also use diamines and acid dianhydrides commonly used as raw materials for polyimides, in addition to the silicon-containing diamine represented by general formula (1) and ODPA, as long as the effects of the invention are not impaired. However, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA) is less desirable because it is more rigid than other common acid dianhydride components, which may impair the flexibility of the polyimide film and negatively affect the satisfaction of conditions a) and b).

[0050] In the polyimide of the present invention, the conditions of the polyimide film a) to c), tackiness, thermal decomposition temperature, etc., can be controlled by selecting the types of diamines and acidic dianhydrides used as raw materials, and the molar ratios of each when two or more diamines or acidic dianhydrides are used. Below, two embodiments relating to preferred combinations of diamines and acidic dianhydrides will be described as representative examples.

[0051] (First Embodiment) In a preferred first embodiment, the polyimide of the present invention preferably contains structural unit (1) in an amount of 65 mol% or more and less than 85 mol% relative to the total diamine units, and preferably contains ODPA units in an amount exceeding 50 mol% relative to the total acid dianhydride units. In the first embodiment, a balance is achieved between elasticity and low tack by containing structural unit (1) and ODPA units within the above ranges. That is, flexibility is imparted to the polyimide film by structural unit (1) and ODPA units, satisfying conditions a) and b), while the tackiness is suppressed by setting the upper limit of the structural unit (1) content to less than 85 mol%. From the above viewpoint, the lower limit of the structural unit (1) content in the first embodiment is more preferably 68 mol% or more, and even more preferably in the order of 70 mol% or more, 73 mol% or more, 75 mol% or more, 78 mol% or more, and 80 mol% or more. Furthermore, the upper limit of the content of structural unit (1) is more preferably 84 mol% or less, and even more preferably 83 mol% or less, 82 mol% or less, and 81 mol% or less, in that order. From a similar viewpoint, the lower limit of the content of ODPA units is more preferably 60 mol% or more, and even more preferably 70 mol% or more, 80 mol% or more, and 90 mol% or more, in that order. Furthermore, the upper limit of the content of ODPA units is preferably 100 mol% or less.

[0052] Furthermore, in the first embodiment, since the content of structural unit (1) is limited to within the range of 65 mol% or more and less than 85 mol% of the total diamine units, it is essential that 15 mol% or more of other diamine units are contained together with structural unit (1). In this case, it is preferable that the other diamine units include diamine units derived from aromatic diamines having a highly flexible molecular structure. Preferred aromatic diamines having a highly flexible molecular structure are those having the following structural characteristics (i): (i) having three or more benzene rings in the molecule, and at least two of the benzene rings being linked by ether bonds.

[0053] Examples of diamines that satisfy structural feature (i) include 1,4-bis(4-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzeneamine, 3-[3-(4-aminophenoxy)phenoxy]benzeneamine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy) Examples of diamines include bis[4,4'-(3-aminophenoxy)]benzanilide, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(3-aminophenoxy)phenyl]sulfone (M-BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-bis(3-aminophenoxy)biphenyl (4,3-BAPOBP), etc. By using these diamines, it is possible to impart flexibility to polyimides.

[0054] Furthermore, in the first aspect of the present invention, in order to achieve both significantly superior elasticity and low tack compared to conventional polyimides, among diamines that satisfy structural characteristic (i), those having the following structural characteristics (ii) or (iii): (ii) all benzene rings are linked by ether bonds; or (iii) the terminal amino group and ether bond are positioned at the meta position via the benzene ring; are more preferable. Diamines that satisfy structural characteristics (ii) or (iii) can impart high elasticity to the polyimide chain. In particular, when other diamine units are included in 20 mol% or more, for example, in the range of 20 to 35 mol%, together with structural unit (1), it is most preferable to use a diamine that satisfies all of the above structural characteristics (i) to (iii) as the other diamine in order to ensure the excellent elasticity of the polyimide. Examples of diamines that satisfy all of the above structural characteristics (i) to (iii) include 1,3-bis(3-aminophenoxy)benzene (APB) and bis[4-(3-aminophenoxy)phenyl] ether.

[0055] (Second Embodiment) In a preferred second embodiment, the polyimide of the present invention preferably contains 85 mol% or more of structural unit (1) relative to the total structural units derived from diamine, and contains ODPA units in a range of 50 mol% to 90 mol% relative to the total acid dianhydride units. In the second embodiment, by containing structural unit (1) and ODPA units within the above range, the flexibility of the polyimide film is increased, and the elongation at break and tensile stress can satisfy conditions a) and b). However, since there is a concern that the tackiness will become too high if structural unit (1) is contained in an amount of 85 mol% or more, in the second embodiment, from the viewpoint of maintaining a balance between elasticity and low tackiness, it is preferable to include, together with ODPA units, structural units derived from acid dianhydrides that do not have an ether bond in the molecule (hereinafter, "non-ether structural units") as structural units derived from acid dianhydrides. By including non-ether structural units as essential, it is possible to suppress the excessive expression of tackiness. From the above viewpoint, the lower limit of the content of structural unit (1) in the second embodiment is more preferably 88 mol% or more, and even more preferably 90 mol% or more. Also, there is no particular limit to the upper limit of the content of structural unit (1), but it is preferably 100 mol% or less. From a similar viewpoint, the lower limit of the content of ODPA units is more preferably 55 mol% or more, and even more preferably 60 mol% or more, and 65 mol% or more. Also, the upper limit of the content of ODPA units is more preferably 85 mol% or less, and even more preferably 80 mol% or less, and 75 mol% or less.

[0056] In a second embodiment, as an acid dianhydride that does not have an ether bond in the molecule and is used in combination with ODPA, it is preferable to use, for example, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 1,2,4,5-benzenetetracarboxylic acid dianhydride (pyromellitic acid dianhydride; PMDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (a-BPDA), 2,3,2',3'-biphenyltetracarboxylic acid dianhydride (i-BPDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride (6FDA), etc. Among these, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA) is particularly preferred. In the second embodiment, the lower limit of the content of non-ether structural units is preferably 10 mol% or more, more preferably 15 mol% or more, and still more preferably 20 mol% or more, and 25 mol% or more, from the viewpoint of suppressing the development of excessive tackiness. The upper limit of the content of non-ether structural units is more preferably 45 mol% or less, and still more preferably 40 mol% or less, and 35 mol% or less, in that order.

[0057] <Synthesis of Polyimide> The polyimide of the present invention can be produced by reacting the above-mentioned dianhydride and diamine in a solvent to produce a precursor polyamic acid, which is then cyclized. For example, polyamic acid can be obtained by dissolving the dianhydride component and the diamine component in approximately equimolar amounts in an organic solvent and stirring at room temperature for 30 minutes to 24 hours to carry out a polymerization reaction. The reaction may be accelerated by heating to 40 to 100°C. Alternatively, a polyimide solution can be obtained by heating at a temperature of 150 to 200°C at this stage to carry out a cyclization reaction. In the reaction, the reaction components are dissolved in the organic solvent in a range of 5 to 40% by weight, preferably 10 to 30% by weight, of which the precursor produced is. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, etc. These solvents can be used in combination of two or more types, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. While there are no particular restrictions on the amount of such organic solvents used, it is preferable to adjust the amount used so that the concentration of the polyamic acid solution obtained by the polymerization reaction is approximately 5 to 40% by weight.

[0058] The synthesized polyamic acid is usually advantageous to use as a reaction solvent solution, but it can be concentrated, diluted, or replaced with other organic solvents as needed. The method for imidizing the polyamic acid is not particularly limited and may be chemical imidization or thermal imidization, but thermal imidization treatment, such as heating in the solvent at a temperature in the range of 80 to 400°C for 1 to 24 hours, is preferably employed.

[0059] The weight-average molecular weight of the polyamic acid is preferably in the range of 10,000 to 500,000, and more preferably in the range of 30,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the film tends to decrease and it becomes prone to embrittlement. On the other hand, if the weight-average molecular weight exceeds 500,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during the coating process. The preferred weight-average molecular weight of the polyimide in this invention is equivalent to that of the polyamic acid.

[0060] <Form of the polyimide film> The polyimide film of this embodiment may be laminated on a substrate such as copper foil, glass plate, or resin sheet.

[0061] The thickness of the polyimide film in this embodiment can be adjusted as appropriate depending on the purpose, so there are no particular restrictions, but it is preferably in the range of 10 μm to 60 μm, more preferably in the range of 20 μm to 50 μm, and even more preferably in the range of 25 μm to 45 μm.

[0062] The polyimide film of this embodiment may contain inorganic or organic fillers, to the extent that it does not impair the effects of the invention. Examples of inorganic fillers include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride. Examples of organic fillers include liquid crystal polymers, synthetic fibers, natural fibers, and elastomers. These inorganic and organic fillers can be used individually or in combination of two or more.

[0063] <Method for Manufacturing Polyimide Film> The method for forming the polyimide film in this embodiment is not particularly limited, but examples include: [1] a method of manufacturing a polyimide film by applying and drying a polyamic acid or polyimide solution to a support substrate, then imidizing it as necessary, and then peeling it off (hereinafter referred to as the casting method); [2] a method of manufacturing a polyimide film by applying and drying a polyamic acid solution to a support substrate, then peeling off the polyamic acid gel film from the support substrate and imidizing it. Furthermore, if the polyimide film manufactured in this embodiment consists of multiple polyimide layers, examples of the manufacturing method include: [3] a method of repeatedly applying and drying a polyamic acid or polyimide solution to a support substrate multiple times, and then imidizing it as necessary (hereinafter referred to as the sequential coating method); [4] a method of simultaneously applying and drying a polyamic acid or polyimide laminated structure to a support substrate by multilayer extrusion, and then imidizing it as necessary (hereinafter referred to as the multilayer extrusion method). The method of applying the polyimide solution (or polyamic acid solution) onto the substrate is not particularly limited, and it is possible to apply it using a coater such as a comma, die, knife, or lip. When forming a multilayer polyimide layer, a method is preferred in which a polyamic acid solution or polyimide solution is applied to a substrate and dried repeatedly.

[0064] The method described in [1] above may include, for example, the following steps 1a to 1c: (1a) applying a polyamic acid or polyimide solution to a support substrate and drying it; (1b) forming a polyimide layer by heat-treating the polyamic acid on the support substrate to imide it; and (1c) obtaining a polyimide film by separating the support substrate and the polyimide layer. Note that step 1b can be omitted when using a polyimide solution.

[0065] The method described in [2] above may include, for example, the following steps 2a to 2c: (2a) applying a polyamic acid solution to a support substrate and drying it; (2b) separating the support substrate from the polyamic acid gel film; and (2c) obtaining a polyimide film by heat-treating the polyamic acid gel film to imide it.

[0066] The method described in [3] above can be carried out in the same manner as the method described in [1] or [2] above, except that step 1a or step 2a is repeated multiple times to form a laminated structure of polyamic acid or polyimide on a support substrate.

[0067] The method described in [4] above can be carried out in the same manner as the method described in [1] or [2] above, except that in step 1a of the method described in [1] or step 2a of the method described in [2] above, a laminated structure of polyamic acid or polyimide is simultaneously applied by multilayer extrusion and dried.

[0068] <Laminate> A laminate can be formed by laminating a conductive layer on one or both sides of the polyimide film of the present invention. A preferred example of a laminate is a flexible metal-clad laminate. The flexible metal-clad laminate has an insulating resin layer and a metal layer laminated on at least one side of the insulating resin layer. In this case, it is sufficient that at least one layer of the insulating resin layer is formed from the polyimide film of the present invention.

[0069] In the flexible metal-clad laminate of this embodiment, for example, if the layer made of the polyimide film of the present invention is P1, an arbitrary polyimide layer is P2, and the metal layers are M1 and M2, then the following configurations 1 to 9 are preferably exemplified. Here, the total thickness of P1 is preferably more than 50%, preferably 60% or more, and more preferably 70% or more, of the total thickness of the insulating resin layer.

[0070] Configuration 1; M1 / P1 Configuration 2; M1 / P1 / P2 Configuration 3; M1 / P1 / P2 / M2 Configuration 4; M1 / P2 / P1 Configuration 5; M1 / P2 / P1 / P2 Configuration 6; M1 / P2 / P1 / P2 / M2 Configuration 7; M1 / P1 / P2 / P1 Configuration 8; M1 / P1 / P2 / P1 / P2 / M2 Configuration 9; M1 / P1 / M2

[0071] (Metal layer) There are no particular restrictions on the material of the metal layer in the flexible metal-clad laminate of this embodiment, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof.

[0072] The thickness of the metal layer is not particularly limited, but is preferably 100 μm or less, and more preferably in the range of 10 to 50 μm. From the viewpoint of production stability and handling, it is preferable that the lower limit of the metal layer thickness be 5 μm or more.

[0073] The flexible metal-clad laminate of this embodiment may be prepared, for example, by preparing the polyimide film of this embodiment, forming a seed layer by sputtering metal onto it, and then forming a metal layer by, for example, plating.

[0074] Furthermore, the flexible metal-clad laminate of this embodiment may also be prepared by preparing the polyimide film of this embodiment and laminating a metal foil to it by a method such as heat-pressing.

[0075] Furthermore, the flexible metal-clad laminate of this embodiment may also be prepared by a method (casting method) in which a coating solution containing polyamic acid or polyimide is cast onto a metal layer, dried to form a coating film, and then, if necessary, heat-treated to imidize it and form a polyimide layer.

[0076] A preferred embodiment of the flexible metal-clad laminate of this embodiment is a copper-clad laminate. The copper-clad laminate comprises a single or multiple polyimide layer and copper foil on at least one side of the polyimide layer, wherein at least one layer of the polyimide layer is made of the polyimide film of the present invention. The copper foil can be provided on one or both sides of the insulating layer. In other words, the copper-clad laminate of this embodiment may be a single-sided copper-clad laminate (single-sided CCL) or a double-sided copper-clad laminate (double-sided CCL). The copper-clad laminate of this embodiment can be used, for example, as an FPC by processing the copper foil to form a wiring circuit and creating copper wiring.

[0077] The flexible metal-clad laminate of this embodiment is useful as a circuit board material, for example, in the case of an FPC (Flexible Printed Circuit). That is, by processing the metal layer of the flexible metal-clad laminate of this embodiment into a pattern using a conventional method, a wiring layer can be formed and an FPC can be created.

[0078] [Circuit board] The circuit board of the present invention comprises an insulating resin layer having the polyimide film of the present invention, and a circuit wiring layer laminated on at least one or both sides of the insulating resin layer. One embodiment of the present invention, a circuit board, can be manufactured by processing the metal layer of a flexible metal-clad laminate into a pattern by a conventional method to form a wiring layer.

[0079] Furthermore, in another embodiment of the present invention, the circuit board can be manufactured using printable electronics technology. In printable electronics, conductive inks, conductive pastes, liquid metals, etc., are formed in a circuit shape on a substrate using methods such as screen printing or inkjet printing. In its preferred embodiment, the polyimide film of the present invention has low tackiness, and by using it as a substrate, it is possible to prevent problems such as the printing plate (screen mesh) sticking to the substrate and becoming impossible to peel off when screen printing wiring. Thus, the polyimide film of the present invention is also useful as a material for printable electronics, in which electronic circuits and electronic devices are manufactured by printing technology.

[0080] [Electronic Devices and Electronic Devices] The electronic devices and electronic devices according to embodiments of the present invention include the circuit board described above. Examples of electronic devices of the present invention include flexible devices, semiconductor devices, display devices such as liquid crystal displays, organic EL displays, and electronic paper, organic EL lighting, solar cells, touch panels, camera modules, inverters, converters, and their components. Examples of electronic devices include HDDs, DVDs, mobile phones, smartphones, tablet terminals, electronic control units (ECUs) and power control units (PCUs) for automobiles. Circuit boards are preferably used in these electronic devices and electronic devices as components such as wiring for movable parts, cables, and connectors.

[0081] Flexible devices are preferably applied to wearable devices, FHE devices, pressure and temperature sensors, glove-type VR devices, 3D shape devices, flexible antennas, flexible solar cells, flexible displays, etc., with wearable devices and FHE devices being particularly preferred. Examples of wearable devices include healthcare devices and medical sensors used by being attached to the skin, flexible tactile patches, robotic arm control systems using body-worn sensor devices, smartwatches, and fitness trackers.

[0082] Furthermore, it is also preferable to use the polyimide film of the present invention as a substrate and provide an adhesive layer for fixing silicon wafers on one side thereof to create a silicon wafer fixing film that can be suitably used in the manufacture of semiconductor components. For example, a semiconductor component can be manufactured by sequentially performing the following steps: a fixing step of using the polyimide film of the present invention as a substrate and providing an adhesive layer on one side thereof, attaching and fixing a silicon wafer onto the adhesive layer; a processing step of processing the silicon wafer; a dicing step of cutting the silicon wafer attached to the substrate to obtain a semiconductor chip; and a pick-up step of peeling the substrate off the semiconductor chip.

[0083] In the semiconductor component manufacturing method, the fixing step involves using the polyimide film of the present invention as a substrate, providing an adhesive layer on one side thereof, and detachably attaching and fixing a silicon wafer to the adhesive layer on the substrate. The adhesive layer is formed by applying an adhesive to one side of the polyimide film. A heat-resistant resin is used as the adhesive, for example, epoxy resin or acrylic resin can be used. The processing step is a process of processing a silicon wafer in a high-temperature environment using the substrate to which the silicon wafer is attached via the adhesive layer. The ambient temperature for the processing step is, for example, 350°C. The polyimide film of the present invention, which serves as the substrate, hardly deteriorates even in such a high-temperature environment. The dicing step is a process of cutting the silicon wafer together with the substrate after the processing step to obtain a semiconductor chip. The pickup step is a process of peeling and obtaining the semiconductor chip from the substrate to which the semiconductor chip is attached after the dicing step. By performing these steps in order, a processed semiconductor chip can be manufactured. Other steps may be added between and before / after each step.

[0084] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. The measurement and evaluation of various physical properties were as follows: [Measurement of film thickness] Measured using a micrometer.

[0085] [Measurement of elongation at break, strength at break, stress at 100% elongation, and stress at 200% elongation] A film sample (thickness A (mm) before testing × width 10 mm × length 110 mm) was stretched using a tensile testing machine (Toyo Seiki Co., Ltd., Strograph VG1F) with an initial tensile chuck distance of 40 mm and a tensile speed of 10 mm / min. The film was stretched until it broke at a measurement temperature of 25°C, and a tensile test was performed.

[0086] For the tensile test of the aforementioned sample, the load F (N) applied to the sample when the chuck distance was L mm was read, and the elongation ε (%) and stress δ (MPa) were calculated using the following formulas: Elongation: ε = ((L - 40) / 40) × 100 Stress: δ = F / (A × 10)

[0087] Of the data obtained from the tensile tests described above, the elongation ε at the time of film breakage was defined as the break elongation (%), and the stress δ was defined as the break point strength. Furthermore, the stress δ when elongation ε = 100% was defined as the stress at 100% elongation, and the stress δ when elongation ε = 200% was defined as the stress at 200% elongation.

[0088] [Evaluation of Recovery Rate] For a film sample (width 10 mm x length 110 mm), a gauge mark (L' = 40 mm) was drawn to match the initial tensile distance between the chucks of 40 mm. Using a tensile testing machine (Toyo Seiki Co., Ltd., Strograph VG1F), the initial tensile distance between the chucks was set to 40 mm and the tensile speed to 10 mm / min. At a measurement temperature of 25°C, the film was stretched to 100% elongation (displacement 40 mm), then stopped and the tensile load was released. After the test, the film sample was placed on graph paper and the gauge mark length (L') was measured after approximately 24 hours, and the recovery rate (%) was calculated using the following formula: Recovery rate (%) = (40 + 40 - L') / 40 × 100

[0089] [Confirmation of the presence or absence of the yield point] The presence or absence of the yield point was determined from the stress-strain curve of the film obtained by the above tensile test. When the film was stretched and the strain of the film was increased, if the phenomenon of stress decreasing in proportion to the increasing strain was observed, as shown in the upper curve of Figure 1, it was determined that there was a yield point. If the phenomenon of stress decreasing in proportion to the increasing strain was not observed, as shown in the lower curve of Figure 1, it was determined that there was no yield point.

[0090] [Evaluation of Usability] The following criteria were used to evaluate the performance of a film sample (5 cm x 10 cm) when stretched by an adult male at room temperature. ◎: Can be easily stretched with light force. 〇: Can be stretched with moderate force. ×: Can hardly be stretched even with considerable force. Or, even if it can be stretched, it breaks immediately.

[0091] [Evaluation of processability] At room temperature, a film sample (5 cm x 10 cm) was folded in half, a 500 g weight was placed on top, and it was left for 10 minutes. After removing the weight, the film was returned to its original state and judged according to the following criteria: ◎: The films do not stick together and return to their original state easily. 〇: It returns to its original state, but not easily. Or, it returns to its original state partially and is partially bonded. ×: The entire film is bonded and does not return to its original state at all.

[0092] [Evaluation of Tackiness] A tacking test machine (TAC1000, manufactured by Resca Co., Ltd.) with a sensor load of 5 kg was used on a film sample (approximately 5 cm square). The pressing speed was set to 0.5 mm / sec, the pressing load to 300 gf, the pressing and holding time to 10 seconds, and the lifting speed to 2 mm / sec. A 5 mm diameter stainless steel probe was pressed onto the sample at 25°C, and the resistance the probe experienced when it was pulled away was measured as the load. The average value of the peak load measured at three locations on the sample was calculated.

[0093] [Measurement of Pyrolysis Temperature (Td1)] Under a nitrogen atmosphere, a polyimide film weighing 10-20 mg was heated from 30°C to 550°C at a constant heating rate of 10°C per minute using a thermogravimetric analyzer (Hitachi High-Tech Science Corporation, TG / DTA7220). The weight loss was measured, and the temperature at which the weight loss rate of the polyimide film was 1% (based on the weight at 200°C) was defined as the pyrolysis temperature (Td1).

[0094] [Measurement of Number-Average Molecular Weight (Mn) and Weight-Average Molecular Weight (Mw)] The molecular weight distribution of the synthesized polyimide solution was measured using gel permeation chromatography (Tosoh Corporation, product name: HLC-8220GPC). Polystyrene was used as the standard substance, and N,N-dimethylacetamide was used as the developing solvent.

[0095] Synthesis Example 1: Under a nitrogen atmosphere, equal amounts of N-methyl-2-pyrrolidone (NMP) and xylene were added to a 1000 ml separable flask as solvents. The diamine and tetracarboxylic dianhydride components shown in Table 1 were added and dissolved. The total concentration of the diamine and tetracarboxylic dianhydride components in the solution was 30% by weight. The solution was then heated to 190°C and heated and stirred for a further 5 hours to obtain a polyimide solution containing polyimide A.

[0096] In Table 1, the diamine content is the percentage (mol%) of the diamine in the total diamine components, and corresponds to the diamine component and its proportion (mol%) relative to the structural units derived from the diamine constituting the polyimide. Similarly, the acid dianhydride content is the percentage (mol%) of the acid dianhydride in the total acid dianhydride components, and corresponds to the tetracarboxylic acid dianhydride component and its proportion (mol%) relative to the structural units derived from the aromatic acid dianhydrides constituting the polyimide.

[0097] In Synthesis Examples 2-19, the diamine and acid dianhydride components shown in Table 1 were changed, and polymerization was carried out in the same manner as in Synthesis Example 1 to prepare polyimide solutions containing polyimides B-S.

[0098] Table 1 shows the chemical composition of each polyimide prepared in Synthesis Examples 1 to 19. The abbreviations used for the diamines and acidic dianhydrides in Table 1 refer to the following compounds: APB: 1,3-bis(3-aminophenoxy)benzene M-BAPS: bis[4-(3-aminophenoxy)phenyl]sulfone BAPP: 2,2-bis(4-aminophenoxyphenyl)propane TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl

[0099] ODPA: 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride HQDA: 1,4,-bis(3,4-dicarboxyphenoxy)benzene acid dianhydride BTDA: 3,3',4,4'-benzophenone tetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyl tetracarboxylic dianhydride PMDA: pyromellitic acid dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride

[0100] PSX-A: In general formula (1), R １ and R ２ Both are propylene groups, R ３ , R ４ , R ５ , R ６ , R ７ and R ８ Diaminosiloxane PSX-B: General formula (1) is a mixture in which all are methyl groups, m is 0 or 1, and n is in the range of 1 to 19, and the number average molecular weight is 740. １ and R ２ Both are propylene groups, R ３ , R ４ , R ５ , R ６ , R ７ and R ８ Diaminosiloxane BY16-871: In general formula (1), one or more of the groups are phenyl groups, m is 0 or 1, n is in the range of 1 to 19, and the number average molecular weight is 1340. １ and R ２ Both are propylene groups, R ３ ~R ８ All are methyl groups, m is 0, n is 1, and the amine equivalent is 125 g / mol of diaminopropyltetramethyldisiloxane (manufactured by Toray Dow Corning).

[0101] RT-1000: Polyetheramine represented by the following formula (2) (manufactured by HUNTSMAN)

[0102]

[0103] ED-600: Polyetheramine (manufactured by HUNTSMAN) represented by the following formula (3) (where y ≤ 9, x + z ≤ 3.6)

[0104]

[0105]

[0106] Example 1 A solution of polyimide A was uniformly applied to a release film, and then the solvent was removed by heating and drying. After that, the release film was peeled off to obtain a polyimide film with a thickness of 32 μm.

[0107] Examples 2-9: Polyimide films with a thickness of 27-35 μm were obtained from solutions of polyimides B-I in the same manner as in Example 1.

[0108] Comparative Example 1: A polyimide film with a thickness of 26 μm was obtained using a solution of polyimide J in the same manner as in Example 1.

[0109] Comparative Examples 2-10: Polyimide films with a thickness of 10-47 μm were obtained from polyimide K-S solutions in the same manner as in Comparative Example 1.

[0110] Comparative Examples 11-13: PDMS (silicone rubber sheets, manufactured by Asahi Rubber Co., Ltd.) with thicknesses of 30 μm, 50 μm, and 75 μm were purchased and evaluated.

[0111] Table 2 shows the physical properties and evaluation results measured for the polyimide films and silicone rubber sheets prepared in Examples 1-9 and Comparative Examples 1-13. Note that the polyimide films of Comparative Examples 6 and 7, which used a large amount of polyetheramine, were very sticky, making it difficult to measure their physical properties.

[0112]

[0113] Table 2 shows that the polyimide films of Examples 1 to 9, which satisfy all conditions a) to c), not only possessed excellent stretchability but also received good evaluations for usability and processability, and had the handling properties necessary for practical use. On the other hand, Table 2 shows that the polyimide films of Comparative Examples 1 to 8 and 10, which did not satisfy any of conditions a) to c), received poor evaluations for either usability or processability, and lacked practicality. Furthermore, although the polyimide film of Comparative Example 9 received good evaluations for usability and processability, its recovery rate was low, making it unsuitable for application to flexible devices that undergo repeated stretching and bending. For reference, the silicone rubber listed as Comparative Examples 11 to 13 had excellent stretchability, but had a low 1% thermal decomposition temperature (Td1), resulting in poor heat resistance.

[0114] Although embodiments of the present invention have been described in detail above for illustrative purposes, the present invention is not limited to the above embodiments.

[0115] This application claims priority under Japanese Patent Application No. 2024-220247, filed in Japan on 16 December 2024, and Japanese Patent Application No. 2025-160936, filed in Japan on 29 September 2025, the entire contents of these applications are incorporated herein by reference.

Claims

1. A polyimide film containing polyimide as the main component in an amount exceeding 50% by weight of the total resin components, characterized in that it satisfies the following conditions a) to c): a) The elongation at break at 25°C in a tensile test is 100% or more; b) In the tensile test, the stress at 100% elongation at a tensile speed of 10 mm / min is 10.0 MPa or less; and c) In the tensile test, after 100% elongation at a tensile speed of 10 mm / min, the recovery rate after 24 hours following the release of the tensile load is 85% or more.

2. Furthermore, the polyimide film according to claim 1, satisfying condition d); d) When a tacking tester with a sensor load of 5 kg is used at a temperature of 25°C, a stainless steel probe with a diameter of 5 mm is pressed against the test piece at a speed of 0.5 mm / second and a load of 300 gf, held for 10 seconds, and then pulled away at a pulling speed of 2 mm / second, the resistance experienced by the probe is measured as the load, and the average of the peak load values ​​at any three locations on the test piece is 100 gf or less; 3. Furthermore, the polyimide film according to claim 1 that satisfies condition e); e) having no clear yield point in the stress-strain curve; 4. The polyimide film according to claim 1, wherein, in the tensile test, the elongation at break is 200% or more, and the stress at 100% elongation at a tensile speed of 10 mm / min is less than 5.0 MPa.

5. The polyimide film according to claim 1, wherein the polyimide contains, with respect to the total structural units derived from the diamine, structural units derived from a silicon-containing diamine represented by general formula (1) in an amount of 65 mol% or more and less than 85 mol%, and structural units derived from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride in an amount of more than 50 mol%, with respect to the total structural units derived from the acid dianhydride. [In the formula, R １ and R ２ Each of these is independently a divalent aliphatic hydrocarbon group having 3 to 20 carbon atoms, and R ３ , R ４ , R ５ , R ６ , R ７ and R ８ Each of these is independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms or a monovalent aromatic group having 6 to 18 carbon atoms, where m is a non-negative integer less than n, and n is a non-negative integer of 1 or greater. However, the condition m + n > 1 must be satisfied.

6. The polyimide film according to claim 1, wherein the polyimide contains, based on the total structural units derived from diamine, 85 mol% or more of the structural units derived from the silicon-containing diamine represented by the general formula (1), and contains, based on the total structural units derived from the acid dianhydride, 50 mol% or more and 90 mol% or less of the structural units derived from 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride, and contains 10 mol% or more of the structural units derived from the acid dianhydride having no ether bond in the molecule. [In the formula, R １ and R ２ are each independently a divalent aliphatic hydrocarbon group having 3 to 20 carbon atoms, and R ３ , R ４ , R ５ , R ６ , R ７ and R ８ are each independently a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms or a monovalent aromatic group having 6 to 18 carbon atoms, m is an integer of 0 or more and is smaller than n, and n is an integer of 1 or more. However, it is assumed that m + n > 1 is satisfied. ] 7. The polyimide film according to claim 1, wherein, in thermogravimetric analysis, the 1% thermal decomposition temperature (Td1), which is the temperature at which the weight loss rate is 1% based on the weight at 200°C, is 300°C or higher.

8. A laminate comprising a conductive layer on one or both sides of a polyimide film according to any one of claims 1 to 7.

9. A semiconductor device comprising a semiconductor component further in the laminate described in claim 8.

10. A flexible device comprising the laminate described in claim 8.

11. The flexible device according to claim 10, which is selected from a wearable device, an FHE device, or a 3D shape device.

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