JP2018059075A - Polyimide film, laminate and display surface material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin film in which while adhesiveness on one surface thereof is improved, failures caused by peeling on the other surface thereof from a support body are suppressed and decrease in transparency and decrease in surface hardness are suppressed.SOLUTION: A polyimide film is provided, which comprises polyimide containing silicon atoms, has a total light transmittance of 85% or more measured in accordance with JIS K7361-1; and a test piece in 15 (mm)×40 (mm) size of the film shows a tensile elastic modulus of 1.8 GPa or more measured at 25°C in accordance with JIS K7127 under the conditions of a tension speed of 10 mm/min and a chuck spacing of 20 mm. The polyimide film contains silicon atoms in both surfaces thereof, in which the silicon atom concentration in one surface is different from the silicon atom concentration in the other surface, and the silicon atom concentration in a surface having a relatively higher silicon atom concentration is 10.0 atomic% or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyimide film, a laminate, and a display surface material.

  Thin plate glass is excellent in hardness, heat resistance, etc., but it is difficult to bend, it is easy to break when dropped, there are problems in workability, and it is heavy compared to plastic products. Therefore, in recent years, resin products such as resin base materials and resin films are being replaced with glass products from the viewpoint of processability and weight reduction, and research on resin products that are glass substitute products has been conducted.

  For example, with the rapid progress of electronics such as liquid crystal and organic EL displays and touch panels, devices have been required to be thinner and lighter, and more flexible. Conventionally, these devices have various electronic elements such as thin transistors and transparent electrodes formed on a thin glass plate. By changing this thin glass plate to a resin film, the impact resistance of the panel itself is enhanced. , Flexible, thin and light.

  Generally, a polyimide resin is a highly heat-resistant resin obtained by subjecting a polyamic acid (polyamic acid) obtained by a condensation reaction of an aromatic tetracarboxylic acid anhydride and an aromatic diamine to a dehydration ring-closing reaction. However, since polyimide resins generally show yellow or brown coloration, it has been difficult to use them in fields that require transparency, such as display applications and optical applications. Therefore, it has been studied to apply a polyimide having improved transparency to a display member. For example, Patent Document 1 discloses 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid dicarboxylic acid as polyimide resins having high heat resistance, high transparency, and low water absorption. At least one acyl-containing compound selected from the group consisting of anhydrides and reactive derivatives thereof, and at least one compound selected from compounds having at least one phenylene group and isopropylidene group represented by a specific formula A polyimide resin obtained by reacting with an imino forming compound is disclosed, and is described as being suitable for a substrate material such as a flat panel display or a mobile phone device.

  Patent Document 2 states that as a polyimide film used for a substrate of a flexible device, a polyimide film that is colorless and transparent, has a low residual stress generated between the inorganic film, and has excellent mechanical and thermal properties. For the purpose, a polyimide film obtained by imidizing a polyimide precursor using a specific fluorine-based aromatic diamine and a silicone compound having a siloxane skeleton having 3 to 200 silicon atoms as a monomer component is disclosed. In Patent Document 2, when a polyimide film with an inorganic film (SiN film) is formed using the polyimide precursor, cracks and peeling are not observed after a bending test in which bending is repeated 10 times (◯). Observed (Δ).

  On the other hand, in Patent Document 3, as a water repellent polyimide film, a polyimide siloxane solution coating film is imidized or applied onto a polyamic acid solution coating film. A polyimide film having a surface atom concentration of silicon atoms of 1% or more is disclosed by imidization after forming a film.

JP 2006-199945 A International Publication No. 2014/098235 JP 10-1110032 A

The inventors considered that a laminate of a polyimide film and various functional layers containing a resin is effective as a resin product to replace glass. The improvement of adhesion was one of the problems. According to the inventors' investigation, the polyimide film appropriately containing silicon atoms improves the adhesion to the resin-containing layer, but on the other hand, the peelability deteriorates, so the film is peeled off from the support during the manufacturing process. It has been found that the film is difficult to peel off, and the film has problems such as wrinkles, cracks, streaks, or the film breaks. Therefore, in the polyimide film, coexistence with the peelability from the support body in a manufacture process and the adhesiveness at the time of laminating | stacking another layer is calculated | required.
Moreover, even if it is a polyimide film containing a silicon atom, the water-repellent polyimide film described in Patent Document 3 has low light transmittance and is used in fields such as display applications and optical applications where transparency is required. It is difficult to use.
In addition, the conventional polyimide film containing a silicone component has insufficient elastic modulus, low surface hardness, is easily scratched, or transmits an impact to a light-emitting panel or circuit, resulting in insufficient function as a protective film. There was also.
From the above, while having both peelability from the support in the production process and adhesion when other layers are laminated, it has sufficient transparency as a transparent film and sufficient surface hardness as a protective film There is a need for a resin film that can be used.

The present invention has been made in view of the above problems. While improving the adhesion of one surface, defects due to peeling from the support on the other surface are suppressed, and the transparency is improved. The main object is to provide a polyimide film in which the decrease and the decrease in surface hardness are suppressed.
Another object of the present invention is to provide a laminate having the polyimide film and a display surface material that is the polyimide film or the laminate.

One embodiment of the polyimide film of the present invention contains a polyimide containing silicon atoms,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. The atomic concentration is 10.0 atomic% or less.

1 embodiment of the polyimide film of this invention contains the polyimide containing a silicon atom, contains a silicon atom in the ratio of 0.2 mass% or more and 4.1 mass% or less in all the polyimides,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. The atomic concentration is 10.0 atomic% or less.

1 embodiment of the polyimide film of this invention contains the polyimide which has a structure represented by the following general formula (1-1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. The atomic concentration is 10.0 atomic% or less.

(In General Formula (1-1), R ^{1 ′} represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and R ^{2 ′} is a divalent group that is a diamine residue. Represents a group, wherein 2.5 mol% or more and 50 mol% or less of the total amount of R ^{2 ′} is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less contains silicon atoms. (It is a diamine residue having no aromatic ring or aliphatic ring. N ′ represents the number of repeating units.)

1 embodiment of the polyimide film of this invention contains the polyimide which has a structure represented by following General formula (1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
Although one surface and the other surface contain silicon atoms, the silicon atom concentration on one surface is different from the silicon atom concentration on the other surface, and the silicon atom concentration on at least one surface is 1. It is 0 atomic% or more.

(In the general formula (1), R ¹ represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, R ² represents a divalent group which is a diamine residue, 50 mol% 10 mol% or more of the total amount of R ² or less is a main one silicon atom in a chain or two with diamine residue, at least 50 mol% 90 mol% or less, having no silicon atom, (A diamine residue having an aromatic ring or an aliphatic ring. N represents the number of repeating units.)

  In one embodiment of the polyimide film of the present invention, the polyimide contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) an aromatic ring is a sulfonyl group or fluorine. It is preferable from the point of light transmittance and surface hardness to include at least one selected from the group consisting of a structure linked by an alkylene group which may be substituted with.

In one embodiment of the polyimide film of the present invention, R ^{1 ′} in the general formula (1-1) in the polyimide having the structure represented by the general formula (1-1), and the general formula (1) R ¹ in the general formula (1) in the polyimide having the structure represented by) is respectively cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic dianhydride residue, dicyclohexane-3, 4,3 ′, 4′-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Dianhydride residue, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride residue, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,4 ′-( Hexafluoro Sopropylidene) diphthalic anhydride residue, 3,3 '-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue It is preferably at least one tetravalent group selected from the group consisting of residues from the viewpoints of light transmittance and surface hardness and bending resistance.

In one embodiment of the polyimide film of the present invention, the aromatic ring or aliphatic in R ^{2 ′} in the general formula (1-1) in the polyimide having the structure represented by the general formula (1-1). A diamine residue having a ring, and a diamine residue having the aromatic ring or the aliphatic ring in R ² in the general formula (1) in the polyimide having the structure represented by the general formula (1), Trans-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue, 2,2-bis ( 4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue, and divalent compounds represented by the following general formula (2) It is preferable from the viewpoint of the points and bending resistance of the light transmittance and surface hardness is at least one divalent group selected from the group consisting of groups.

(In the general formula (2), R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

  In the polyimide film of the present invention, a surface having a relatively large silicon atom concentration can be used as an adhesion surface with a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound.

  The laminate of the present invention is a laminate in which the polyimide film of the present invention and a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound are located adjacent to each other.

  In the laminate of the present invention, the radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is one molecule of at least one of an epoxy group and an oxetanyl group. A compound having two or more compounds is preferable from the viewpoint of adhesion between the polyimide film and the resin-containing layer, light transmittance, and surface hardness.

  The display surface material of the present invention is the polyimide film of the present invention or the laminate of the present invention.

  The display surface material of the present invention can be used for a flexible display.

According to the present invention, while improving the adhesion of one surface, defects due to peeling from the support on the other surface are suppressed, and a decrease in transparency and a decrease in surface hardness are suppressed. A polyimide film can be provided.
Moreover, this invention can provide the surface material for a display which is the laminated body which has the said polyimide film, and the said polyimide film or the said laminated body.

It is a figure for demonstrating the method of a static bending test.

I. Polyimide film The first embodiment of the polyimide film of the present invention contains a polyimide containing silicon atoms,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. It is a polyimide film whose atomic concentration is 10.0 atomic% or less.

2nd Embodiment of the polyimide film of this invention contains the polyimide containing a silicon atom, contains a silicon atom in the ratio of 0.2 mass% or more and 4.1 mass% or less in all the polyimides,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. It is a polyimide film whose atomic concentration is 10.0 atomic% or less.

  The second embodiment includes silicon atoms in the proportion of 0.2% by mass or more and 4.1% by mass or less in the total polyimide in the first embodiment. This is a form that can easily improve the adhesion and the peelability of the other surface.

3rd Embodiment of the polyimide film of this invention contains the polyimide which has a structure represented by the following general formula (1-1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. It is a polyimide film whose atomic concentration is 10.0 atomic% or less.

(In General Formula (1-1), R ^{1 ′} represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and R ^{2 ′} is a divalent group that is a diamine residue. Represents a group, wherein 2.5 mol% or more and 50 mol% or less of the total amount of R ^{2 ′} is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less contains silicon atoms. (It is a diamine residue having no aromatic ring or aliphatic ring. N ′ represents the number of repeating units.)

  The third embodiment uses a polyimide having a structure represented by the general formula (1-1) as a polyimide containing a silicon atom in the first embodiment. It is the form which is easy to improve the adhesiveness of one surface and the peelability of the other surface.

4th Embodiment of the polyimide film of this invention contains the polyimide which has a structure represented by following General formula (1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
Although one surface and the other surface contain silicon atoms, the silicon atom concentration on one surface is different from the silicon atom concentration on the other surface, and the silicon atom concentration on at least one surface is 1. It is a polyimide film which is 0 atomic% or more.

(In the general formula (1), R ¹ represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, R ² represents a divalent group which is a diamine residue, 50 mol% 10 mol% or more of the total amount of R ² or less is a main one silicon atom in a chain or two with diamine residue, at least 50 mol% 90 mol% or less, having no silicon atom, (A diamine residue having an aromatic ring or an aliphatic ring. N represents the number of repeating units.)

  In the fourth embodiment, in the first embodiment, a polyimide having a structure represented by the general formula (1) is used as the polyimide containing silicon atoms, and the silicon atom concentration on at least one surface is 1. It is a polyimide film that is 0.0 atomic% or more, and has a form that can easily improve the adhesion of one surface of the polyimide film and the peelability of the other surface. In the fourth embodiment, by using the polyimide having the structure represented by the general formula (1), the silicon atom concentration on the surface having a relatively large silicon atom concentration is set to 10.0 atom% or less. be able to.

The polyimide film of the present invention has a total light transmittance of 85% or more as measured in accordance with JIS K7361-1. Thus, since the transmittance | permeability is high, transparency becomes favorable and it can become a glass substitute material. The total light transmittance of the polyimide film of the present invention measured according to JIS K7361-1 is preferably 88% or more, more preferably 89% or more, particularly 90% or more. It is preferable.
The polyimide film of the present invention preferably has a total light transmittance of 85% or more, more preferably 88% or more, measured in accordance with JIS K7361-1 at a thickness of 5 μm to 100 μm. Further, it is preferably 89% or more, and particularly preferably 90% or more.
Moreover, the polyimide film of the present invention preferably has a total light transmittance of 85% or more, more preferably 88% or more, measured in accordance with JIS K7361-1 at a thickness of 50 μm ± 5 μm. Further, it is preferably 89% or more, and particularly preferably 90% or more.
The total light transmittance measured according to JIS K7361-1 can be measured, for example, with a haze meter (for example, HM150 manufactured by Murakami Color Research Laboratory). In addition, from the measured value of the total light transmittance of a certain thickness, the converted value of the total light transmittance of different thickness can be obtained by Lambert Beer's law and can be used.

In addition, the polyimide film of the present invention preferably has a yellowness (YI value) calculated in accordance with JIS K7373-2006 of 30 or less. Thus, since yellowness is low, coloring of yellowishness is suppressed, light transmittance improves, and it can become a glass substitute material. Above all, the yellowness (YI value) calculated in accordance with JIS K7373-2006 is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.
The polyimide film of the present invention has a thickness of 5 μm or more and 100 μm or less, the yellowness (YI value) calculated in accordance with JIS K7373-2006 is preferably 30 or less, more preferably 20 or less, More preferably, it is 15 or less, and it is especially preferable that it is 10 or less.
The polyimide film of the present invention preferably has a yellowness (YI value) of 10 or less, preferably 7 or less, calculated in accordance with JIS K7373-2006 at a thickness of 50 μm ± 5 μm. Preferably, it is 5 or less and still more preferable.
The yellowness (YI value) is measured according to JIS Z8722 using an ultraviolet-visible near-infrared spectrophotometer (for example, JASCO Corporation V-7100) in accordance with JIS K7373-2006. It can be calculated based on the transmittance measured by the color method.
It should be noted that, from the measurement value of yellowness of a certain thickness, the yellowness of different thicknesses is calculated for each transmittance at each wavelength measured at 5 nm intervals between 380 nm and 780 nm of a sample with a specific thickness. Similar to the light transmittance, a conversion value of each transmittance at each wavelength of different thickness can be obtained by Lambert Beer's law, and can be calculated and used based on it.

In addition, the polyimide film of the present invention has a tensile elastic modulus at 25 ° C. of 1.8 GPa or more when a 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile speed is 10 mm / min, and the distance between chucks is 20 mm. is there. Thus, since the tensile elastic modulus at 25 ° C. (room temperature) is high, surface hardness sufficient as a protective film can be maintained even at room temperature, and it can be used as a surface material. Above all, the tensile elastic modulus is preferably 2.0 GPa or more, and more preferably 2.4 GPa or more. On the other hand, the tensile elastic modulus is preferably 5.2 GPa or less from the viewpoint of improving bending resistance. From the viewpoint of improving bending resistance, the tensile elastic modulus may be 4.0 GPa or less, or 3.5 GPa or less.
The tensile elastic modulus was obtained by cutting a test piece having a width of 15 mm and a length of 40 mm from a polyimide film using a tensile tester (for example, manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) at 25 ° C. The tensile speed can be 10 mm / min, and the distance between chucks can be 20 mm. The polyimide film for obtaining the tensile modulus of elasticity preferably has a thickness of 50 μm ± 5 μm.

The polyimide films of the first, second and third embodiments of the present invention contain silicon atoms on one side and the other side, but the silicon atom concentration on one side and the other side The silicon atom concentration on the surface having a relatively high silicon atom concentration is 10.0 atom% or less.
The polyimide film according to the fourth embodiment of the present invention contains silicon atoms on one side and the other side, but the silicon atom concentration on one side and the silicon atoms on the other side. Unlike the concentration, the silicon atom concentration on at least one surface is 1.0 atomic% or more.
In the present invention, the atomic% value of each atom is a value obtained by rounding the measured value to the first decimal place according to the rule B of JIS Z8401: 1999. For example, the silicon atom concentration of 1.0 atom% or more is included if the silicon atom concentration is 0.950 atom% or more.
In the polyimide film of the present invention, the silicon atom concentration on at least one surface is 1.0 atom% or more, and the silicon atom concentration on the surface having a relatively large silicon atom concentration is 10.0 atom% or less. Is preferable in terms of adhesion, peelability, and surface hardness.
The absolute value of the difference between the silicon atom concentration on one surface and the silicon atom concentration on the other surface is 0.1 from the point of improving the adhesion of one surface and the peelability of the other surface. It is preferably at least atomic percent, more preferably at least 0.4 atomic percent, and even more preferably at least 0.8 atomic percent.
In addition, the silicon atom concentration on the surface having a relatively large silicon atom concentration is preferably 1.2 atom% or more, more preferably 1.6 atom% or more, and even more preferably 2. From the viewpoint of adhesion and surface hardness, it is preferably 8.0 atomic% or less, more preferably 5.0 atomic% or less.
The silicon atom concentration on the surface having a relatively small silicon atom concentration is preferably 4.0 atom% or less, more preferably 2.0 atom% or less, still more preferably 1.5 atom% or less, from the viewpoint of peelability. From the viewpoint of bending resistance, it is preferably 0.1 atomic% or more, more preferably 0.2 atomic% or more, and still more preferably 0.5 atomic% or more.
In addition, the silicon atom concentration on the surface having a relatively large silicon atom concentration is 1.6 atom% or more and 10.0 atom% or less, and the silicon atom concentration on one surface and the silicon atom concentration on the other surface When the absolute value of the difference between the two is 0.8 atomic% or more, it is preferable from the viewpoint that both the adhesiveness and the peelability are compatible and the adhesiveness of the surface having a relatively large silicon atom concentration is particularly excellent.
The silicon atom concentration on the surface having a relatively low silicon atom concentration is 1.5 atomic% or less, and the absolute value of the difference between the silicon atom concentration on one surface and the silicon atom concentration on the other surface is 0. When it is at least 8 atomic%, it is preferable from the viewpoint of excellent releasability on a surface having a relatively low silicon atom concentration while achieving both adhesion and releasability.
In addition, the silicon atom concentration on the surface having a relatively high silicon atom concentration is 1.6 atom% or more and 10.0 atom% or less, and the silicon atom concentration on the surface having a relatively low silicon atom concentration is 1.5 atom%. When it is at most atomic%, it is preferable from the viewpoint of improving both adhesion and peelability.
In the present invention, the concentration of each atom on the polyimide film surface is measured by the X-ray photoelectron spectroscopy (XPS) using the X-ray photoelectron spectrometer (for example, Thermo Scientific Thea Probe) under the following conditions. It can be determined from the atomic% value.
Incident X-ray: Monochromated Al Kα ray (monochromated X-ray, hν = 1486.6 eV)
・ X-ray irradiation area (measurement area): 400 μmφ
・ X-ray output: 100 W (15 kV, 6.7 mA)
Photoelectron uptake angle: 53 ° (sample normal is 0 °)
・ Charge neutralization conditions: electron neutralization gun (+6 V, 0.05 mA), low acceleration Ar ⁺ ion irradiation
Measurement peak: Si2p, C1s, N1s, O1s, F1s
Quantification: The background is obtained by the Shirley method, and the atomic ratio is calculated from the obtained peak area using the relative sensitivity coefficient method.

According to the present invention, the polyimide contained in the polyimide film contains silicon atoms, has the specific total light transmittance, and the specific tensile elastic modulus, and is on either one surface or the other surface. A polyimide containing silicon atoms, but having a silicon atom concentration on one surface different from a silicon atom concentration on the other surface, and a silicon atom concentration on a surface having a relatively large silicon atom concentration is 10.0 atom% or less By using the film, while improving the adhesion of one surface, defects due to peeling from the support on the other surface were suppressed, and a decrease in transparency and a decrease in surface hardness were suppressed. A polyimide film can be provided.
About this reason, it estimates as follows.

The present inventors paid attention to polyimide as a resin used as a glass substitute product. Polyimide is known to have excellent heat resistance due to its chemical structure. Further, the present inventors have found that the adhesion between the polyimide film and a resin-containing layer such as a hard coat layer is improved by introducing silicon atoms into the polyimide. This is presumed to be reasonably excellent in mixing the polyimide film and the resin-containing layer when the resin-containing layer is laminated by introducing silicon atoms into the polyimide.
On the other hand, the polyimide film with silicon atoms introduced into the polyimide is difficult to peel off when peeling from the support during the manufacturing process, and it is confirmed that defects such as wrinkles, cracks, streaks may occur, or the film may break It was done. However, as described above, it is considered that the adhesiveness and peelability of the resin film are contradictory properties, and it is difficult to achieve both adhesiveness and peelability with a single polyimide film having no multilayer structure.
In contrast, when the present inventors use polyimide containing silicon atoms, silicon atoms in the polyimide film are likely to be unevenly distributed, and the silicon atom concentration on the surface of the produced polyimide film may be different between the front and back surfaces. I found out. In such polyimide films having different silicon atom concentrations on the front and back surfaces, the silicon atom concentration on the surface having a relatively large silicon atom concentration is 10.0 atom% or less, and the tensile elasticity at room temperature. A polyimide film having a rate of 1.8 GPa or more and a total light transmittance of 85% or more can achieve both adhesion and releasability from the support in the production process, and has sufficient surface hardness as a protective film. It was found that the film has sufficient transparency as a transparent resin film while maintaining the above. The polyimide film of the present invention has improved adhesion to a resin-containing layer such as a hard coat layer on the surface having a relatively high silicon atom concentration, and a support in the production process on a surface having a relatively low silicon atom concentration. The peelability when peeled from is improved. In the polyimide film of the present invention, the silicon atom concentrations on the front and back surfaces are different from each other because the molecular chains are arranged so that the amount of silicon atoms exposed on the front and back surfaces is different. The reason why the molecular chain of the polyimide resin is so arranged is not clear, but the polyimide resin contains silicon atoms, so that the drying process before peeling the support is appropriately adjusted in the production process of the polyimide film. Thus, it is considered that the molecular chain is arranged so that silicon atoms are exposed on the surface in contact with air compared to the surface in contact with the support. In addition, it is presumed that silicon atoms are more easily exposed on the surface in contact with the air by increasing the temperature stepwise in the drying step before peeling the support. Specifically, it is first dried at a low temperature of less than 70 ° C. At this stage, since the solvent is sufficiently present in the film, it is presumed that the silicon atoms in the coating film are present almost uniformly in the film. Next, when heating is performed at a temperature of 70 ° C. or more and further drying is performed, it is presumed that a part containing silicon atoms tends to aggregate on the film surface. Moreover, when the silicon atom density | concentration on the surface of a polyimide film was too large like the comparative example 2 mentioned later, the tendency for adhesiveness with a resin content layer to become inadequate was seen. This is because the surface of the polyimide film is excessively dissolved by the solvent in the resin-containing layer forming composition used when forming the resin-containing layer, and when the resin-containing layer forming composition is cured, the polyimide film In the process where the dissolved part of the surface is cured again, wrinkles or cracks are generated, and a brittle part is generated at the interface between the polyimide film and the resin-containing layer, so that the adhesion is estimated to be lowered. The On the other hand, the polyimide films of the first, second, and third embodiments of the present invention have such adhesion because the silicon atom concentration on the surface having a relatively large silicon atom concentration is 10.0 atom% or less. It is considered that the decrease in sex is suppressed.
Moreover, since the polyimide film of this invention is excellent in the peelability from the support body in a manufacture process, when performing thermal imidation, it can peel from a support body in the state of the coating film before imidation. Therefore, when manufacturing the polyimide film of the present invention, the stretching treatment can be performed in the state of the coating film before imidization, thereby suppressing the shrinkage of the produced polyimide film and improving the elastic modulus. Can do. When the support is peeled off after thermal imidization on the support, the polyimide film shrinks on the support during the thermal imidization, so that the end is lifted from the support and curled. Or problems such as cracking may occur. On the other hand, in this invention, since it can peel from a support body in the state of the coating film before imidation, it can be set as the highly elastic polyimide film by which generation | occurrence | production of the curl and the crack was suppressed.
Also, if the strength of the coating film before imidization is insufficient, the coating film will be stretched due to peeling stress when it is peeled off from the support, causing streaks, or the stretched coating film shrinking after imidization. Therefore, it tends to cause defects such as wrinkles. The polyimide film of the present invention has a relatively low silicon atom concentration on the cast surface, and the coating film before imidization for forming a polyimide film having a tensile modulus of 1.8 GPa or more has sufficient strength. , Generation of streaks and wrinkles can be suppressed.
On the other hand, when performing imidization by chemical imidization without performing thermal imidization, it is not necessary to perform a high-temperature heat treatment that is performed during thermal imidization, so that the film shrinkage due to heat is suppressed. be able to. However, even in the case of chemical imidization, if the strength of the polyimide resin coating film itself peeled off from the support is insufficient, the coating film stretches due to peeling stress when it peels off from the support, and streaks are generated. Such a peeling failure is likely to occur. Since the polyimide film of the present invention has a relatively low silicon atom concentration on the cast surface, and the polyimide resin coating film for forming a polyimide film having a tensile modulus of 1.8 GPa or more has sufficient strength, Debonding failure can be suppressed.
Moreover, it was confirmed that the surface hardness becomes insufficient when the tensile modulus of the film is small as in Comparative Examples 1 and 2 described later. In contrast, the polyimide film of the present invention has a tensile elastic modulus at room temperature of 1.8 GPa or more, so that a decrease in surface hardness at room temperature is suppressed, and a sufficient surface hardness as a protective film is maintained even at room temperature. be able to. Therefore, the polyimide film of the present invention has excellent scratch resistance that prevents the surface from being scratched, and also has excellent impact resistance that prevents damage to the member located therebelow.
Moreover, since the polyimide film of this invention can be made into a single layer structure, it is easy to improve transparency. Since the polyimide film of this invention can achieve the said subject with a single layer structure, its productivity is also high.

Hereinafter, the polyimide film according to the present invention will be described in detail.
The polyimide film which concerns on this invention contains the polyimide containing a silicon atom, and has the said specific characteristic. As long as the effects of the present invention are not impaired, other components may be contained or other configurations may be included.

1. Polyimide Polyimide is obtained by reacting a tetracarboxylic acid component and a diamine component. It is preferable to obtain imidization by obtaining a polyamic acid by polymerization of a tetracarboxylic acid component and a diamine component. The imidization may be performed by thermal imidization or chemical imidization. Moreover, it can also manufacture by the method which used thermal imidation and chemical imidization together.

The polyimide used in the polyimide film according to the present invention contains a polyimide containing silicon atoms.
Although the content rate (mass%) of the silicon atom in all the polyimides which the polyimide film concerning this invention contains is not specifically limited, the silicon atom density | concentration of the surface with a relatively large silicon atom density | concentration shall be 10.0 atomic% or less. However, it is easy to make the silicon atom concentrations different from each other on the front and back surfaces of the polyimide film, from the viewpoint of coexistence of adhesion and peelability of the polyimide film, and from the viewpoint of coexistence of bending resistance and surface hardness. It is preferably 2% by mass or more and 4.1% by mass or less, and more preferably 0.5% by mass or more and 4.1% by mass or less.
Here, the content ratio (% by mass) of silicon atoms in all the polyimides included in the polyimide film can be determined from the molecular weight of the charge at the time of polyimide production. Moreover, the content rate (mass%) of the silicon atom in all the polyimides which a polyimide film contains is a high performance liquid chromatography, a gas chromatograph mass spectrometer, NMR, elemental analysis, XPS / ESCA, and TOF-SIMS about the decomposition product of a polyimide. Can be obtained using
In addition, the polyimide used for this invention can contain 1 type (s) or 2 or more types.

As a polyimide containing a silicon atom, the polyimide containing either the tetracarboxylic-acid residue which has a silicon atom, and the diamine residue which has a silicon atom is mentioned, for example. Above all, silicon is easy to make the silicon atom concentrations different from each other on the front and back surfaces of the polyimide film, from the standpoint of compatibility and adhesion of the polyimide film, and from the standpoint of both bending resistance and surface hardness. A polyimide containing a diamine residue having an atom is preferred, and a polyimide containing a diamine residue having a silicon atom in the main chain is more preferred.
Here, the tetracarboxylic acid residue means a residue obtained by removing four carboxyl groups from tetracarboxylic acid, and represents the same structure as a residue obtained by removing acid dianhydride structure from tetracarboxylic dianhydride. . Moreover, a diamine residue means the residue remove | excluding two amino groups from diamine.

  In the polyimide containing a diamine residue having a silicon atom, the ratio of the diamine residue having a silicon atom in the total amount of 100 mol% of the diamine residue is 10.0% of the silicon atom concentration on the surface having a relatively large silicon atom concentration. It is easy to make the silicon atom concentrations different from each other on the front and back surfaces of the polyimide film while keeping the atomic% or less, the compatibility of the adhesion and peelability of the polyimide film, and the compatibility of bending resistance and surface hardness. From the viewpoint, it is preferably 2.5 mol% or more and 50 mol% or less.

  As the polyimide containing a silicon atom, a polyimide having a structure represented by the following general formula (1-1) is particularly preferable.

(In General Formula (1-1), R ^{1 ′} represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and R ^{2 ′} is a divalent group that is a diamine residue. Represents a group, wherein 2.5 mol% or more and 50 mol% or less of the total amount of R ^{2 ′} is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less contains silicon atoms. (It is a diamine residue having no aromatic ring or aliphatic ring. N ′ represents the number of repeating units.)

  In the polyimide having the structure represented by the general formula (1-1), a specific amount of a flexible molecular skeleton having a silicon atom in the main chain is introduced between molecular skeletons containing an aromatic ring or an aliphatic ring. By having a specific structure, it is considered that molecular chains are likely to be arranged so that silicon atoms are exposed on the surface, and silicon atoms in the polyimide film are more unevenly distributed. Compatibility can be further improved. Furthermore, the polyimide having the structure represented by the general formula (1-1) has a molecular skeleton containing an aromatic ring or an aliphatic ring, and thus has a high tensile elastic modulus and excellent surface hardness.

The tetracarboxylic acid residue in R ^{1 ′} of the general formula (1-1) has a residue obtained by removing an acid dianhydride structure from a tetracarboxylic dianhydride having an aromatic ring, or an aliphatic ring. It can be a residue obtained by removing the acid dianhydride structure from tetracarboxylic dianhydride.
Examples of the tetracarboxylic dianhydride having an aromatic ring include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3 ′. -Benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis ( 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3 , 4-Zika Boxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (2,3 -Dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 1,4- Bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4 -[3- (1,2-dicarboxy) Phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4′-bis [3- (1,2-dicarboxy) Phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} Ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfone Anhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride, 4′-oxydiphthalic anhydride, 3,4′-oxydiphthalic anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2 3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like.
Examples of the tetracarboxylic dianhydride having an aliphatic ring include, for example, cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, dicyclohexane-3,4,3 ′, 4′-tetracarboxylic dianhydride. An anhydride, cyclobutane tetracarboxylic dianhydride, etc. are mentioned.
These may be used alone or in combination of two or more.

In R ^{2 ′} of the general formula (1-1), the diamine residue having a silicon atom in the main chain can be a residue obtained by removing two amino groups from a diamine having a silicon atom in the main chain.
As a diamine residue which has a silicon atom in a principal chain, the diamine represented by the following general formula (A) is mentioned, for example.

(In General Formula (A), each L is independently a direct bond or —O— bond, and each R ¹⁰ may independently have a substituent, and includes an oxygen atom or a nitrogen atom. R ¹¹ represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ¹¹ independently has a substituent and may contain an oxygen atom or a nitrogen atom. Represents a divalent hydrocarbon group having a number of 1 or more and 20 or less, k is a number of 0 or more and 200 or less, and a plurality of L, R ¹⁰ and R ¹¹ may be the same or different.

Examples of the monovalent hydrocarbon group represented by R ¹⁰ include an alkyl group having 1 to 20 carbon atoms, an aryl group, and combinations thereof. The alkyl group may be linear, branched or cyclic, and may be linear or a combination of branched and cyclic.
The alkyl group having 1 to 20 carbon atoms is preferably an alkyl group having 1 to 10 carbon atoms. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, Examples thereof include a t-butyl group, a pentyl group, and a hexyl group. The cyclic alkyl group is preferably a cycloalkyl group having 3 to 10 carbon atoms, and specific examples include a cyclopentyl group and a cyclohexyl group. The aryl group is preferably an aryl group having 6 to 12 carbon atoms, and specific examples include a phenyl group, a tolyl group, and a naphthyl group. Further, the monovalent hydrocarbon group represented by R ¹⁰ may be an aralkyl group, and examples thereof include a benzyl group, a phenylethyl group, and a phenylpropyl group.
Examples of the hydrocarbon group that may contain an oxygen atom or a nitrogen atom include an ether bond, a carbonyl bond, an ester bond, an amide bond, and an imino bond between a divalent hydrocarbon group described later and the monovalent hydrocarbon group. And a group bonded by at least one bond (—NH—).
The substituent which the monovalent hydrocarbon group represented by R ¹⁰ may have is not particularly limited as long as the effects of the present invention are not impaired. For example, a halogen atom such as a fluorine atom or a chlorine atom And a hydroxyl group.

The monovalent hydrocarbon group represented by R ¹⁰ is an alkyl group having 1 to 3 carbon atoms or an aryl group having 6 to 10 carbon atoms from the viewpoint of compatibility between improvement in bending resistance and surface hardness. Preferably there is. The alkyl group having 1 to 3 carbon atoms is more preferably a methyl group, and the aryl group having 6 to 10 carbon atoms is more preferably a phenyl group.

Examples of the divalent hydrocarbon group represented by R ¹¹ include an alkylene group having 1 to 20 carbon atoms, an arylene group, and a combination thereof. The alkylene group may be linear, branched or cyclic, and may be linear or a combination of branched and cyclic.
The alkylene group having 1 to 20 carbon atoms is preferably an alkylene group having 1 to 10 carbon atoms. And a combination of a linear or branched alkylene group and a cyclic alkylene group.
The arylene group is preferably an arylene group having 6 to 12 carbon atoms. Examples of the arylene group include a phenylene group, a biphenylene group, a naphthylene group, and the like, and further has a substituent for an aromatic ring described later. May be.
As the divalent hydrocarbon group which may contain an oxygen atom or a nitrogen atom, the divalent hydrocarbon groups are ether bonds, carbonyl bonds, ester bonds, amide bonds, and imino bonds (—NH—). A group bonded with at least one is exemplified.
The substituent that the divalent hydrocarbon group represented by R ¹¹ may have is the same as the substituent that the monovalent hydrocarbon group represented by R ¹⁰ may have. Good.

The divalent hydrocarbon group represented by R ¹¹ is an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms from the viewpoint of compatibility between improvement in bending resistance and surface hardness. Preferably, it is more preferably an alkylene group having 2 to 4 carbon atoms.

K in the general formula (A) is a number of 0 or more and 200 or less, preferably 0 or more and 20 or less, and more preferably 0 or 1. That is, the diamine residue having a silicon atom in the main chain in R ^{2 ′} of the general formula (1-1) is preferably a diamine residue having one or two silicon atoms in the main chain. Examples of the diamine residue having one or two silicon atoms in the main chain include those similar to the diamine residue having one or two silicon atoms in the main chain in R ² of the general formula (1) described later. Can be mentioned.

The molecular weight of the diamine residue having a silicon atom in the main chain is preferably 3000 or less, preferably 2000 or less, from the viewpoint of imparting bending resistance while suppressing the mobility of the molecule and the compatibility of surface hardness. Is preferably 1000 or less, more preferably 800 or less, even more preferably 500 or less, and particularly preferably 300 or less.
The diamine residues having a silicon atom in the main chain can be used alone or in admixture of two or more.

In R ^{2 ′} of the general formula (1-1), the diamine residue having no silicon atom and having an aromatic ring is obtained by removing two amino groups from the diamine having no silicon atom and having an aromatic ring. It can be a residue.
Examples of the diamine having no silicon atom and having an aromatic ring include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4, 4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone 4,4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzanilide, 3,3′-diaminodiphenylmethane 4,4'-diaminodiphenylmethane 3,4'-diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) ) Propane, 2,2-di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3 , 3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3 -Aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminopheno B) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3 -Aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) Benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis ( 4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α- Ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, N, N′-bis (4-aminophenyl) terephthalamide, 9 , 9-bis (4-aminophenyl) fluorene, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro -4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-bis ( -Aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [ 4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) Phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-amino Phenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3- Hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3 -Aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4′-bis [4- (4-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] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenyl sulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3 ′ -Diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis (3-aminophenoxy) -3,3,3 ', 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, and the like A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group can also be used.
These may be used alone or in combination of two or more.

In R ^{2 ′} of the general formula (1-1), the diamine residue having an aliphatic ring and not having a silicon atom is obtained by removing two amino groups from the diamine having an aliphatic ring without a silicon atom. It can be a residue.
Examples of the diamine having no aliphatic atom and having an aliphatic ring include trans-cyclohexanediamine, trans-1,4-bismethylenecyclohexanediamine, and 2,6-bis (aminomethyl) bicyclo [2,2,1]. Examples include heptane and 2,5-bis (aminomethyl) bicyclo [2,2,1] heptane.
These may be used alone or in combination of two or more.

In the polyimide having the structure represented by the general formula (1-1), the ratio of the diamine residue having a silicon atom in the main chain produces a laminate with a resin-containing layer such as a hard coat layer described later. From the point of improving the adhesion with the resin-containing layer at the time, it is preferably 10 mol% or more of the total amount of R ^{2 ′} , more preferably 15 mol% or more, and more than 15 mol%. Even more preferably, it is particularly preferably 20 mol% or more. On the other hand, R ^{2 ′} in the general formula (1-1) improves the peelability from the support in the process of producing the polyimide film, and improves the surface hardness and light transmittance. The diamine residue is preferably less than 50 mol% of the total amount of R2 ^' , more preferably 45 mol% or less, and even more preferably 40 mol% or less.
Incidentally, R ^{2 '50} mol% 2.5 mol% or more of the total amount of the following, a diamine residue having a silicon atom in the main chain, R ^2' below 97.5 mol% 50 mol% or more of the total amount of If it is satisfied that the diamine residue does not have a silicon atom and has an aromatic ring or an aliphatic ring, the diamine residue having a silicon atom in the main chain in R ^{2 ′} of the general formula (1-1). It does not preclude the inclusion of other diamine residues different from diamine residues having no group and no silicon atom and having an aromatic ring or an aliphatic ring. The other diamine residue is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 3 mol% or less, particularly 1 mol of the total amount of R ^{2 ′.} % Or less is preferable. Examples of the other diamine residue include a diamine residue that does not have a silicon atom and does not have an aromatic ring or an aliphatic ring. Moreover, it is preferable not to contain a diamine residue having 3 or more silicon atoms in the main chain from the viewpoint of increasing the tensile modulus and improving the surface hardness.
Among them, 2.5 mol% or more and 50 mol% or less of the total amount of R ^{2 ′} is a diamine residue having a silicon atom in the main chain, and among the total amount (100 mol%) of R ^{2 ′} , 50 mol% or more and 97.5 mol% or less, which is the remainder (100% -x%) of the mol% (xmol%) of the diamine residue having a silicon atom, does not have a silicon atom, and is an aromatic ring or a fat A diamine residue having an aromatic ring is preferred.

  As the polyimide containing a silicon atom, a polyimide having a structure represented by the following general formula (1) is also preferable.

(In the general formula (1), R ¹ represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, R ² represents a divalent group which is a diamine residue, 50 mol% 10 mol% or more of the total amount of R ² or less is a main one silicon atom in a chain or two with diamine residue, at least 50 mol% 90 mol% or less, having no silicon atom, (A diamine residue having an aromatic ring or an aliphatic ring. N represents the number of repeating units.)

Examples of the tetracarboxylic acid residue in R ¹ of the general formula (1) include those similar to the tetracarboxylic acid residue in R ^{1 ′} of the general formula (1-1) described above.

In R ² of the general formula (1), the diamine residue having one or two silicon atoms in the main chain is the residue obtained by removing two amino groups from the diamine having one or two silicon atoms in the main chain. It can be based. Orientation is suppressed by introducing a specific amount of a flexible molecular skeleton having one or two silicon atoms in the main chain between molecular skeletons containing aromatic or aliphatic rings as the main component of the polyimide film. The silicon atom concentration on the front and back surfaces of the polyimide film can be easily made different from each other, and the birefringence is easily reduced. In addition, when the polyimide has a molecular skeleton as described above, a specific amount of the flexible molecular skeleton having a short specific main chain is introduced into the rigid molecular skeleton, thereby lowering the modulus of elasticity at room temperature of the polyimide film. Therefore, sufficient surface hardness as a protective film can be maintained even at room temperature. Furthermore, when the polyimide has a molecular skeleton as described above, the bending resistance can be improved and the film can be bent for a long time as well as the restorability after repeated folding of the film, that is, the dynamic bending resistance. Since it can improve the restorability after being brought into the state, that is, static bending resistance, it can be used more suitably for a flexible display.

  Examples of the diamine having one silicon atom in the main chain include diamines represented by the following general formula (A-1) where k = 0 among the diamines represented by the general formula (A). . Moreover, as a diamine which has two silicon atoms in a principal chain, the diamine represented by the following general formula (A-2) which is k = 1 among the diamine represented by the said general formula (A), for example. Can be mentioned.

(In General Formula (A-1) and General Formula (A-2), each L is independently a direct bond or —O— bond, and each R ¹⁰ independently has a substituent. And represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, which may contain an oxygen atom or a nitrogen atom, and each R ¹¹ may independently have a substituent, Or a divalent hydrocarbon group having 1 to 20 carbon atoms which may contain a nitrogen atom, and a plurality of L, R ¹⁰ and R ¹¹ may be the same or different.

The molecular weight of the diamine residue having one or two silicon atoms in the main chain is preferably 1000 or less from the viewpoints of bending resistance and surface hardness and the tendency of silicon atoms in the polyimide film to be unevenly distributed. Or less, more preferably 500 or less, even more preferably 300 or less.
The diamine residues having one or two silicon atoms in the main chain can be used alone or in combination of two or more.

In R ² of the general formula (1), the diamine residue having no aromatic ring and no silicon atom, and the diamine residue having no aliphatic atom and an aliphatic ring are represented by the general formula (1). The same thing as what was demonstrated by R2 ^' of -1) is mentioned.

In ^{R 2} of the general formula (1), 50 mol% 10 mol% or more of the total amount of ^{R 2} or less, a diamine residue having one or two silicon atoms in the main chain, 50 of the total amount of ^{R 2} The mol% or more and 90 mol% or less is a diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring, so that silicon atoms in the polyimide film are easily unevenly distributed, It becomes easy to make a density | concentration different from each other, and it has sufficient bending tolerance as a flexible display use, and can have sufficient surface hardness as a protective film. R ^{2 in the} general formula (1) is a silicon atom in the main chain from the viewpoint of improving the adhesion to the resin-containing layer when producing a laminate with a resin-containing layer such as a hard coat layer described later. one or two with the diamine residues is preferably 10 mol% excess of the total amount of R ^2, more preferably 15 mol% or more, more preferably more from 15 mol% excess, more It is preferable that it is 20 mol% or more. On the other hand, R ^{2 in the} general formula (1) improves the peelability from the support in the process of producing the polyimide film and improves the surface hardness and light transmittance, so that one silicon atom in the main chain or diamine residue having two of preferably less than 50 mole% of the total amount of R ^2, more preferably 45 mol% or less, preferably not more than an additional 40 mole%.
Incidentally, 50 mol% 10 mol% or more of the total amount of R ² or less, a diamine residue having one or two silicon atoms in the main chain, 90 mol% 50 mol% or more of the total amount of R ² or less, A diamine having one or two silicon atoms in the main chain in R ² of the general formula (1) as long as it is a diamine residue having no silicon atom and having an aromatic ring or an aliphatic ring It does not preclude inclusion of other diamine residues that are different from diamine residues having no residue and no silicon atom and having an aromatic ring or an aliphatic ring. The other diamine residue is preferably 10 mol% or less of the total amount of R ² , more preferably 5 mol% or less, still more preferably 3 mol% or less, particularly 1 mol%. The following is preferable. Examples of the other diamine residue include a diamine residue that does not have a silicon atom and does not have an aromatic ring or an aliphatic ring. Moreover, it is preferable not to contain a diamine residue having 3 or more silicon atoms in the main chain from the viewpoint of increasing the tensile modulus and improving the surface hardness.
Among them, 50 mole% 10 mole% or more of the total amount of R ² or less is a main one silicon atom in a chain or two with diamine residue, of the total amount of R ² (100 mol%), the main chain 50 mol% or more and 90 mol% or less of the remainder (100% −x%) of the mol% (x mol%) of the diamine residue having 1 or 2 silicon atoms in the A diamine residue having an aromatic ring or an aliphatic ring is preferred.

The polyimide used in the present invention includes an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and, from the viewpoint of improving light transmittance and improving surface hardness. (Iii) A polyimide containing at least one selected from the group consisting of a structure in which aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine. The polyimide used in the present invention contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, whereby the molecular skeleton becomes rigid and the orientation is increased, and the surface hardness is increased. Although improved, the rigid aromatic ring skeleton tends to increase the absorption wavelength to a long wavelength, and tends to decrease the transmittance in the visible light region.
When (i) a fluorine atom is contained in the polyimide, the light transmittance is improved from the point that it is possible to make the electronic state in the polyimide skeleton difficult to charge transfer.
When (ii) an aliphatic ring is included in the polyimide, light transmittance is improved because the transfer of charges in the skeleton can be inhibited by breaking the π-electron conjugation in the polyimide skeleton.
When (iii) a structure in which aromatic rings are connected to each other by a sulfonyl group or an alkylene group that may be substituted with fluorine is included in the polyimide, the charge transfer in the skeleton is prevented by breaking the π-electron conjugation in the polyimide skeleton. The light transmittance improves from the point which can be inhibited.

  As the polyimide used in the present invention, among them, a polyimide containing a fluorine atom improves the light transmittance and improves the surface hardness, and improves the peelability of the coating film from the support. It is preferably used from the viewpoint. Moreover, when the polyimide which has a structure represented by the said General formula (1) contains a fluorine atom, there exists a tendency for the adhesiveness of a polyimide film and a resin content layer to improve more.

The fluorine atom content ratio is preferably such that the ratio (F / C) of the number of fluorine atoms (F) and the number of carbon atoms (C) measured on the polyimide surface by X-ray photoelectron spectroscopy is 0.01 or more, Furthermore, it is preferably 0.05 or more, more preferably 0.1 or more. On the other hand, if the content ratio of fluorine atoms is too high, the inherent heat resistance of the polyimide may be lowered. Therefore, the ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) is 1. It is preferably 0 or less, more preferably 0.8 or less.
Here, the said ratio by the measurement of X-ray photoelectron spectroscopy (XPS) can be calculated | required from the value of atomic% of each atom measured using an X-ray photoelectron spectrometer (for example, Thermo Scientific Thea Probe). .

  In addition, the polyimide used in the present invention has a tetracarboxylic acid residue and an aromatic ring having an aromatic ring when the total of the tetracarboxylic acid residue and the diamine residue is 100 mol% from the viewpoint of improving the surface hardness. The total of diamine residues having an aromatic ring is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more.

In addition, the polyimide used in the present invention includes an aromatic ring and a fluorine atom at least one of a tetracarboxylic acid residue and a diamine residue having no silicon atom, from the viewpoint of improving surface hardness and light transmittance. In addition, it is preferable that both the tetracarboxylic acid residue and the diamine residue having no silicon atom contain an aromatic ring and a fluorine atom.
The polyimide used in the present invention has a tetracarboxylic acid having an aromatic ring and a fluorine atom when the total of the tetracarboxylic acid residue and the diamine residue is 100 mol%, because the surface hardness and light transmittance are improved. The total of the acid residue, aromatic ring and diamine residue having a fluorine atom is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 75 mol% or more. .

Further, the polyimide used in the present invention is a polyimide in which 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are hydrogen atoms directly bonded to the aromatic ring, thereby improving the light transmittance. And it is preferably used from the viewpoint of improving the surface hardness. The proportion of hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to carbon atoms contained in the polyimide is preferably 60% or more, and more preferably 70% or more. It is preferable that
When 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide is a polyimide that is a hydrogen atom directly bonded to the aromatic ring, the film is stretched at, for example, 200 ° C. or higher even after a heating step in the atmosphere. Is preferable from the viewpoint of little change in optical characteristics, particularly total light transmittance and yellowness YI value. When polyimide is a polyimide in which 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are hydrogen atoms directly bonded to the aromatic ring, the chemical structure of the polyimide changes due to low reactivity with oxygen. It is estimated that it is difficult. Polyimide film uses its high heat resistance and is often used in devices that require processing steps involving heating, but more than 50% of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are in the aromatic ring. In the case of polyimide, which is a hydrogen atom that is directly bonded, there is no need to carry out these subsequent processes in an inert atmosphere in order to maintain transparency, so that the cost of equipment costs and atmospheric control can be suppressed. There is.
Here, the ratio of the hydrogen atom (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to carbon atoms contained in the polyimide is determined by high-performance liquid chromatography or gas chromatograph mass of the polyimide decomposition product. It can be determined using an analyzer and NMR. For example, the sample is decomposed with an alkaline aqueous solution or supercritical methanol, and the resulting decomposition product is separated by high performance liquid chromatography, and a qualitative analysis of each separated peak is performed by a gas chromatograph mass spectrometer, NMR, etc. The ratio of hydrogen atoms (numbers) directly bonded to the aromatic ring in the total hydrogen atoms (numbers) contained in the polyimide can be determined by performing determination using high performance liquid chromatography.

Formula R ¹ of the polyimide having the structure represented by (1-1) ^', and, R ¹ of the polyimide having the structure represented by the general formula (1) are, inter alia, light transmitting point, From the point of bending resistance and surface hardness, and the point that silicon atoms in the film are likely to be unevenly distributed, cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic dianhydride residue, dicyclohexane-3,4,3 ', 4'-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3,3', 4,4'-biphenyltetracarboxylic dianhydride Residue, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride residue, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,4 ′-(hexafluoroisopropylidene Lide ) Diphthalic anhydride residue, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4′-oxydiphthalic anhydride residue, and 3,4′-oxydiphthalic anhydride residue It is preferably at least one tetravalent group selected from the group consisting of groups.
In R ¹ ′ and R ¹ , these suitable residues are preferably contained in a total amount of 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.
Particularly from the point balance of light transmittance and surface hardness are good, the general formula (1-1) R ¹ in ^{'R 1} and of the general formula (1), 4,4' - (hexafluoro isopropylidene ) Diphthalic anhydride residue, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4′-oxydiphthalate More preferably, it is at least one tetravalent group selected from the group consisting of an acid anhydride residue and a 3,4′-oxydiphthalic anhydride residue.

The ^{'The R 1} and of the general formula (1), pyromellitic acid dianhydride residue, 3,3' general formula (1-1) R ¹ in, 4,4'-biphenyltetracarboxylic acid Tetracarboxylic suitable for improving rigidity such as at least one selected from the group consisting of dianhydride residues and 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride residues Acid residue group (Group A), cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic dianhydride residue, dicyclohexane-3,4,3 ′, 4′-tetracarboxylic dianhydride Residue, cyclobutanetetracarboxylic dianhydride residue, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3 , 3'- (heki Fluoroisopropylidene) diphthalic anhydride residue, 4,4′-oxydiphthalic anhydride residue, and at least one selected from the group consisting of 3,4′-oxydiphthalic anhydride residue It is also preferable to use a mixture of a tetracarboxylic acid residue group (group B) suitable for improving the properties. In this case, the content ratio of the tetracarboxylic acid residue group (group A) suitable for improving the rigidity and the tetracarboxylic acid residue group (group B) suitable for improving light transmittance is , 1 mol of tetracarboxylic acid residue group (group B) suitable for improving light transmittance is 0.4% of tetracarboxylic acid residue group (group A) suitable for improving rigidity. It is preferably from 05 mol to 9 mol, more preferably from 0.1 mol to 5 mol, and still more preferably from 0.3 mol to 4 mol.
Among them, the group B includes 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residues and 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residues containing fluorine atoms. It is preferable to use at least one kind from the viewpoint of improving surface hardness and light transmittance.

A diamine residue having an aromatic ring or an aliphatic ring in R ^{2 ′} in the general formula (1-1), and a diamine having an aromatic ring or an aliphatic ring in R ² in the general formula (1) The residues are trans-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue, 2,2- At least one selected from the group consisting of a bis (4-aminophenyl) propane, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (2) The divalent group is preferably from the viewpoint of light transmission, bending resistance and surface hardness, and from the point that silicon atoms in the film are likely to be unevenly distributed. In addition, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4 -Aminophenyl) It is preferably at least one divalent group selected from the group consisting of a hexafluoropropane residue and a divalent group represented by the following general formula (2). As the divalent group represented by the following general formula (2), R ³ and R ⁴ are more preferably perfluoroalkyl groups.

(In the general formula (2), R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

Moreover, the diamine residue which has a silicon atom in the principal chain in R < ^{2 '} > in the said General formula (1-1), and one or two silicon atoms in the principal chain in R < ² > in the said General formula (1) The diamine residue having two silicon atoms is preferably a diamine residue having two silicon atoms from the viewpoint of light transmittance, bending resistance and surface hardness, and the point that silicon atoms in the film are likely to be unevenly distributed. 1,3-bis (3-aminopropyl) tetramethyldisiloxane residue, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, 1,3-bis (5-aminopentyl) tetramethyldisiloxane Etc. are preferable from the viewpoints of availability and compatibility between light transmittance and surface hardness.

N ′ in the structure represented by the general formula (1-1) and n in the structure represented by the general formula (1) each represent the number of repeating units and are 1 or more.
The number of repeating units in the polyimide is preferably selected as appropriate according to the structure so as to exhibit a preferable glass transition temperature described later, and is not particularly limited.
The average number of repeating units is usually from 10 to 2000, and more preferably from 15 to 1000.

In addition, the polyimide used in the present invention has a structure represented by the general formula (1-1) and a structure represented by the general formula (1) as long as the effects of the present invention are not impaired. May have different structures. In the polyimide used in the present invention, the structure represented by the general formula (1-1) or the structure represented by the general formula (1) is 95% or more of the total number of repeating units of the polyimide used in the present invention. It is preferable that it is 98% or more, and it is still more preferable that it is 100%.
Examples of the structure different from the structure represented by the general formula (1-1) and the structure represented by the general formula (1) include, for example, a tetracarboxylic acid residue having no aromatic ring or aliphatic ring Or a polyamide structure.
Examples of the polyamide structure that may be included include a polyamideimide structure containing a tricarboxylic acid residue such as trimellitic anhydride and a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

The polyimide used in the present invention preferably has a glass transition temperature in a temperature range of 150 ° C. or higher and 400 ° C. or lower. When the glass transition temperature is 150 ° C. or higher, it is excellent in heat resistance and is preferably 200 ° C. or higher. Moreover, when the glass transition temperature is 400 ° C. or lower, the baking temperature can be reduced, and is preferably 380 ° C. or lower.
Moreover, it is preferable that the polyimide used in the present invention does not have a peak of a tan δ curve in a temperature range of −150 ° C. or more and 0 ° C. or less, thereby improving the tensile modulus of the polyimide film at room temperature. , Surface hardness can be improved. In addition, the polyimide used in the present invention may further have a tan δ curve peak in a temperature range of more than 0 ° C. and less than 150 ° C., but has a peak of the tan δ curve only in a temperature region of 150 ° C. or higher. It is preferable from the viewpoint of easily improving the tensile modulus and bending resistance. In the tan δ curve, if the peak apex is lower than 150 ° C., the molecular chain of polyimide tends to move, plastic deformation tends to occur, and the bending resistance may deteriorate, whereas the peak apex of the tan δ curve Is not present below 150 ° C., the mobility of the molecular chain is suppressed, plastic deformation is difficult, and bending resistance is easily improved.
The glass transition temperature of the polyimide used in the present invention can be measured in the same manner as the glass transition temperature of the polyimide film described later.

2. Additives The polyimide film of the present invention may further contain additives as necessary in addition to the polyimide. Examples of the additive include inorganic particles, a silica filler for facilitating winding, and a surfactant that improves film-forming properties and defoaming properties.

3. Characteristics of Polyimide Film The polyimide film of the present invention has the specific total light transmittance and the specific tensile elastic modulus, and preferably has the specific yellowness. Moreover, it is preferable that the polyimide film of this invention has the characteristic further mentioned later.

In the polyimide film of the present invention, the pencil hardness is preferably 2B or more, more preferably B or more, and even more preferably HB or more.
The pencil hardness of the polyimide film is JIS K5600-5-4 using a test pencil specified by JIS-S-6006 after the measurement sample is conditioned for 2 hours at a temperature of 25 ° C. and a relative humidity of 60%. (1999), a pencil hardness test (0.98 N load) is performed on the film surface, and the highest pencil hardness that does not cause scratches can be evaluated. For example, a pencil scratch coating film hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.

The haze value of the polyimide film of the present invention is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less, from the viewpoint of light transmittance. It is preferable that the haze value can be achieved when the thickness of the polyimide film is 5 μm or more and 100 μm or less.
The haze value can be measured by a method based on JIS K-7105, and can be measured by, for example, a haze meter HM150 manufactured by Murakami Color Research Laboratory.

In the polyimide film of the present invention, the polyimide film and the resin are not peeled off when the adhesion test is performed according to the following adhesion test method on the surface having a relatively large silicon atom concentration. From the point of adhesiveness with a content layer, and the point of the surface hardness of the laminated body which laminated | stacked the resin content layer adjacent to the polyimide film, it is preferable.
[Adhesion test method]
Resin composition for adhesion evaluation prepared by adding 10 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone to 100 parts by weight of pentaerythritol triacrylate in a 40% by weight methyl isobutyl ketone solution of pentaerythritol triacrylate Is applied on a test piece of polyimide film cut out to 10 cm × 10 cm, and cured by irradiating ultraviolet rays with an exposure amount of 200 mJ / cm ² under a nitrogen stream, thereby forming a cured film having a thickness of 10 μm. About the said cured film, the crosscut test based on JISK5600-5-6 is performed, and the peeling operation by a tape is repeatedly implemented 5 times, Then, the presence or absence of peeling of a coating film is observed.

In the polyimide film of the present invention, from the viewpoint of excellent bending resistance, when a static bending test is performed according to the following static bending test method, the internal angle measured in the test is preferably 120 ° or more, More preferably, it is 125 ° or more.
[Static bending test method]
A test piece of polyimide film cut out to 15 mm × 40 mm is bent at a half of the long side, and both ends of the long side of the test piece sandwich a metal piece (100 mm × 30 mm × 6 mm) having a thickness of 6 mm from the upper and lower surfaces. Placed between glass plates (100 mm x 100 mm x 0.7 mm) from above and below with the tape fixed so that the overlap between the top and bottom surfaces of the test piece and the metal piece is 10 mm each. The test piece is fixed in a bent state with an inner diameter of 6 mm. At that time, a dummy test piece is sandwiched between the metal piece and the glass plate where there is no test piece, and is fixed with tape so that the glass plate is parallel. The test piece fixed in a bent state in this way was allowed to stand for 24 hours in an environment of 60 ± 2 ° C. and 93 ± 2% relative humidity (RH), and then the glass plate and the fixing tape were removed, Release the force on the specimen. Thereafter, one end of the test piece is fixed, and the internal angle of the test piece 30 minutes after the force applied to the test piece is released is measured.

Moreover, in the polyimide film of this invention, from the point which is excellent in bending tolerance, according to the following dynamic bending test method, the dynamic bending test was done in the environment of 60 +/- 2 degreeC and 93 +/- 2% relative humidity (RH). In this case, the inner angle of the test piece is preferably 155 ° or more, and more preferably 160 ° or more. Furthermore, the polyimide film of the present invention was subjected to a dynamic bending test in an environment of 25 ± 2 ° C. and 50 ± 2% relative humidity (RH) in accordance with the following dynamic bending test method because of its excellent bending resistance. In this case, the inner angle of the test piece is preferably 170 ° or more, and more preferably 175 ° or more.
[Dynamic bending test method]
Fix a polyimide film specimen cut to a size of 20 mm x 100 mm to a constant temperature and humidity chamber endurance test system (manufactured by Yuasa System Equipment Co., Ltd., planar loadless U-shaped expansion and contraction test jig DMX-FS) with tape. . The test piece was set in the same bent state as in the static bending test, that is, the distance between both ends of the long side of the bent test piece was set to 6 mm (fixed in a bent state with an inner diameter of 6 mm). After that, in an environment of 60 ± 2 ° C. and 93 ± 2% relative humidity (RH), or in an environment of 25 ± 2 ° C. and 50 ± 2% relative humidity (RH), the number of bendings is 90 times per minute. Repeat flexing 10,000 times.
Thereafter, the test piece is removed, one end of the obtained test piece is fixed, and the inner angle of the test piece 30 minutes after measuring 200,000 times of bending is measured.

From the viewpoint of heat resistance, the polyimide film of the present invention preferably has a glass transition temperature in a temperature range of 150 ° C. or more and 400 ° C. or less, more preferably 200 ° C. or more, and can reduce the baking temperature. From the viewpoint, it is preferably 380 ° C. or lower.
The glass transition temperature is obtained from the peak temperature of a temperature-tan δ (tan δ = loss elastic modulus (E ″) / storage elastic modulus (E ′)) curve obtained by dynamic viscoelasticity measurement. The glass transition temperature of the polyimide film refers to the temperature of the peak where the maximum value of the peak is maximum when there are a plurality of peaks of the tan δ curve.
As the dynamic viscoelasticity measurement, for example, with a dynamic viscoelasticity measuring device RSA III (TA Instruments Japan Co., Ltd.), the measurement range is -150 ° C to 400 ° C, the frequency is 1 Hz, and the temperature rises. This can be done at a rate of 5 ° C./min. Further, the measurement can be performed with a sample width of 5 mm and a distance between chucks of 20 mm.
In the present invention, the peak of the tan δ curve refers to a peak having an inflection point that is a maximum value, and a peak width between peak valleys of 3 ° C. or more, which is derived from measurement such as noise. The fine vertical fluctuation is not interpreted as the peak.
Moreover, it is preferable that the polyimide film of this invention does not have a peak of a tan-delta curve in the temperature range of -150 degreeC or more and 0 degrees C or less. In the case of having a diamine residue having a long siloxane bond in the main chain, such a polyimide film having a tan δ curve peak in the low temperature region has such a diamine residue having a long siloxane bond in the main chain. In comparison with the above, a decrease in the tensile modulus at room temperature is suppressed, and a sufficient surface hardness as a protective film can be maintained.
Moreover, it is preferable that the polyimide film of the present invention has a peak of the tan δ curve only in a temperature region of 150 ° C. or more from the viewpoint of easily improving the tensile elastic modulus and bending resistance.

Moreover, it is preferable that the birefringence of the thickness direction in the said wavelength 590nm is 0.020 or less from the point which the polyimide film of this invention reduces an optical distortion. Thereby, when the polyimide film of this invention is used as a surface material for a display, the fall of the display quality of a display can be suppressed. The birefringence in the thickness direction at the wavelength of 590 nm is preferably smaller, preferably 0.015 or less, more preferably 0.010 or less, and even more preferably less than 0.008. .
In addition, the birefringence of the thickness direction in the said wavelength 590nm of the polyimide film of this invention can be calculated | required as follows.
First, the thickness direction retardation value (Rth) of a polyimide film is measured with light of 25 ° C. and a wavelength of 590 nm using a phase difference measuring device (for example, product name “KOBRA-WR” manufactured by Oji Scientific Instruments Co., Ltd.). To do. For the thickness direction retardation value (Rth), a phase difference value at 0 degree incidence and a phase difference value at an incidence angle of 40 degrees are measured, and the thickness direction retardation value Rth is calculated from these phase difference values. The retardation value at an oblique incidence of 40 degrees is measured by making light having a wavelength of 590 nm incident on the retardation film from a direction inclined by 40 degrees from the normal line of the retardation film.
The birefringence in the thickness direction of the polyimide film can be obtained by substituting it into the formula: Rth / d. Said d represents the film thickness (nm) of a polyimide film.
The thickness direction retardation value is nx the refractive index in the slow axis direction in the in-plane direction of the film (the direction in which the refractive index in the film in-plane direction is maximum), and the fast axis direction in the film plane (film surface). Rth [nm] = {(nx + ny) / 2−nz} × d, where ny is the refractive index in the direction in which the refractive index in the inner direction is the minimum) and nz is the refractive index in the thickness direction of the film. be able to.

As a preferred embodiment, the ratio (F / C) of the number of fluorine atoms (F) and the number of carbon atoms (C) on the film surface measured by X-ray photoelectron spectroscopy of the polyimide film is 0.01 or more and 1. It is preferably 0 or less, more preferably 0.05 or more and 0.8 or less, and still more preferably 0.1 or more and 0.8 or less. These are preferably filled on both sides of the polyimide film.
The ratio (F / N) of the number of fluorine atoms (F) and the number of nitrogen atoms (N) on the film surface, measured by X-ray photoelectron spectroscopy of the polyimide film, is preferably 0.1 or more and 20 or less. Further, it is preferably 0.5 or more and 15 or less.
Further, the ratio (F / Si) of the number of fluorine atoms (F) and the number of silicon atoms (Si) on the film surface, measured by X-ray photoelectron spectroscopy of the polyimide film, is preferably 1 or more and 50 or less. It is preferably 3 or more and 30 or less.

4). Composition of Polyimide Film The thickness of the polyimide film of the present invention may be appropriately selected depending on the use, but is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. . On the other hand, it is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.
If the thickness is thin, the strength is reduced and breakage is liable to occur. If the thickness is thick, the difference between the inner diameter and the outer diameter at the time of bending is increased, and the load on the film is increased.

  In addition, the polyimide film of the present invention may be subjected to surface treatment such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet treatment, or flame treatment.

5. Production method of polyimide film The production method of the polyimide film of the present invention is not particularly limited as long as it can produce the above-described polyimide film of the present invention. For example, as the first production method,
A step of preparing a polyimide precursor resin composition containing a silicon atom-containing polyimide precursor and an organic solvent (hereinafter referred to as a polyimide precursor resin composition preparation step);
Applying the polyimide precursor resin composition to a support and drying to form a polyimide precursor resin coating film (hereinafter referred to as a polyimide precursor resin coating film forming process);
A step of peeling the polyimide precursor resin coating film from the support (hereinafter referred to as a peeling step);
A method for producing a polyimide film including a step of imidizing the polyimide precursor by heating the polyimide precursor resin coating film (hereinafter referred to as an imidization step) is exemplified.

  In the first production method, the step of stretching at least one of the polyimide precursor resin coating film after the peeling step and the imidized coating film imidized from the polyimide precursor resin coating film (hereinafter, stretching) Process). Especially, it is preferable to have the process of extending | stretching the said polyimide precursor resin coating film after the said peeling process from the point which suppresses shrinkage | contraction of a polyimide film and improves a tensile elasticity modulus.

In the first production method, the surface of the polyimide precursor resin coating film that is in contact with the support has good peelability, and therefore the polyimide precursor resin coating film is easily peeled from the support. It is difficult to cause defects. The polyimide precursor resin coating film formed by the polyimide precursor resin coating film forming step has a smaller silicon atom concentration on the surface in contact with the support than on the surface in contact with air. Easy to peel off the support.
Hereinafter, each step will be described in detail.

(1) Polyimide precursor resin composition preparation step The polyimide precursor resin composition prepared in the first production method contains a polyimide precursor containing a silicon atom and an organic solvent, and an additive as necessary. Etc. may be contained.
The polyimide precursor is a polyamic acid obtained by polymerization of a tetracarboxylic acid component and a diamine component. In the first production method, as the polyimide precursor containing a silicon atom, a polyamic acid that becomes the above-described polyimide containing a silicon atom by an imidization reaction is used.

  The polyamic acid that becomes a polyimide having the structure represented by the general formula (1-1) by the imidation reaction is a polyimide precursor having a structure represented by the following general formula (1-1 ').

(In general formula (1-1 ′), R ^{1 ′} , R ^{2 ′} and n ′ are the same as those in general formula (1-1).)

The polyimide precursor represented by the general formula (1-1 ′) includes a tetracarboxylic acid component that becomes a tetracarboxylic acid residue in R ^{1 ′} of the general formula (1-1 ′), and the general formula (1). -1 ′) is a polyamic acid obtained by polymerization with a diamine component which becomes a diamine residue in R ^{2 ′} .
Here, the general formula (1-1 ') R ^{1 in',} R ^{2 'and} n', the formula described in the polyimide (1-1) R ¹ in ^', R ^2' and and n ' Similar ones can be used.

  The polyamic acid that becomes a polyimide having the structure represented by the general formula (1) by the imidation reaction is a polyimide precursor having a structure represented by the following general formula (1 ').

(In the general formula (1 ′), R ¹ , R ² and n are the same as those in the general formula (1).)

The polyimide precursor represented by the general formula (1 ′) includes a tetracarboxylic acid component that becomes a tetracarboxylic acid residue in R ¹ of the general formula (1 ′), and R ^{2 of the} general formula (1 ′). It is a polyamic acid obtained by polymerization with a diamine component to be a diamine residue in
Here, as R ¹ , R ² and n in the general formula (1 ′), those similar to R ¹ , R ² and n in the general formula (1) described in the polyimide can be used.

The polyimide precursor represented by the general formula (1-1 ′) and the polyimide precursor represented by the general formula (1 ′) are films having at least one of a number average molecular weight and a weight average molecular weight. From the viewpoint of strength when it is, it is preferably 10,000 or more, and more preferably 20,000 or more. On the other hand, if the average molecular weight is too large, the viscosity becomes high and the workability such as filtration may be reduced, and therefore it is preferably 10000000 or less, and more preferably 500000 or less.
The number average molecular weight of the polyimide precursor can be determined by NMR (for example, AVANCE III manufactured by BRUKER). For example, after applying a polyimide precursor solution to a glass plate and drying at 100 ° C. for 5 minutes, 10 mg of solid content is dissolved in 7.5 ml of dimethyl sulfoxide-d6 solvent, NMR measurement is performed, and the aromatic ring is bonded. The number average molecular weight can be calculated from the peak intensity ratio of hydrogen atoms.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC). For example, a polyimide precursor is used as an N-methylpyrrolidone (NMP) solution having a concentration of 0.5% by weight, and a developing solvent is a 10 mmol% LiBr-NMP solution having a water content of 500 ppm or less, and a GPC apparatus (HLC-8120 manufactured by Tosoh Corporation). , Column used: GPC LF-804 manufactured by SHODEX), and measurement is performed under the conditions of a sample injection amount of 50 μL, a solvent flow rate of 0.5 mL / min, and 40 ° C. The weight average molecular weight is determined based on a polystyrene standard sample having the same concentration as the sample.

  The polyimide precursor solution is obtained by reacting the above-described tetracarboxylic dianhydride and the above-described diamine in a solvent. The solvent used for the synthesis of the polyimide precursor (polyamic acid) is not particularly limited as long as it can dissolve the above-described tetracarboxylic dianhydride and diamine. For example, an aprotic polar solvent or a water-soluble alcohol solvent is used. Can be used. In the present invention, among others, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, etc. It is preferable to use an organic solvent containing a nitrogen atom of γ-butyrolactone or the like. In particular, when the polyimide precursor solution (polyamic acid solution) is used as it is for the preparation of the polyimide precursor resin composition, it is preferable to use an organic solvent containing a nitrogen atom, among which N, N-dimethylacetamide, N- It is preferable to use methyl-2-pyrrolidone or a combination thereof. The organic solvent is a solvent containing carbon atoms.

The polyimide precursor solution is prepared by combining at least two kinds of diamines. An acid dianhydride may be added to a mixed solution of at least two kinds of diamines to synthesize polyamic acid, or at least Two kinds of diamine components may be added to the reaction solution step by step at an appropriate molar ratio, and the sequence in which each raw material is incorporated into the polymer chain may be controlled to some extent.
For example, an acid dianhydride having a molar ratio of 0.5 equivalent of a diamine having a silicon atom in the main chain is charged into a reaction solution in which a diamine having a silicon atom in the main chain is dissolved, and reacted. Amidic acid in which a diamine having a silicon atom in the main chain was reacted at both ends of the anhydride was synthesized, and all or part of the remaining diamine was added thereto, and acid dianhydride was added to polymerize the polyamic acid. Also good. When polymerized by this method, a diamine having a silicon atom in the main chain is introduced into the polyamic acid in a linked form via one acid dianhydride.
Polymerization of the polyamic acid by such a method is preferable because the positional relationship of the amic acid having a silicon atom in the main chain is specified to some extent, and it is easy to obtain a film having excellent bending resistance while maintaining the surface hardness.

When the number of moles of diamine in the polyimide precursor solution (polyamic acid solution) is X and the number of moles of tetracarboxylic dianhydride is Y, Y / X may be 0.9 or more and 1.1 or less. Preferably, it is 0.95 or more and 1.05 or less, more preferably 0.97 or more and 1.03 or less, and particularly preferably 0.99 or more and 1.01 or less. By setting it as such a range, the molecular weight (polymerization degree) of the polyamic acid obtained can be adjusted moderately.
The procedure of the polymerization reaction can be appropriately selected from known methods and is not particularly limited.
Moreover, the polyimide precursor solution obtained by the synthesis reaction may be used as it is, and other components may be mixed there if necessary. The solvent of the polyimide precursor solution is dried and dissolved in another solvent. It may be used.

The viscosity of the polyimide precursor solution at 25 ° C. is preferably 500 cps or more and 200,000 cps or less from the viewpoint of forming a uniform coating film and a polyimide film.
The viscosity of the polyimide precursor solution can be measured at 25 ° C. using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.).

  The polyimide precursor resin composition may contain an additive as necessary. Examples of the additive include inorganic particles, silica filler for facilitating winding, and surfactants for improving film-forming properties and defoaming properties, and those described in the polyimide film described above. Similar ones can be used.

  The organic solvent used for the polyimide precursor resin composition is not particularly limited as long as the polyimide precursor can be dissolved. For example, nitrogen atoms such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone are included. Organic solvent: γ-butyrolactone or the like can be used, and among them, an organic solvent containing a nitrogen atom is preferably used.

The content of the polyimide precursor in the polyimide precursor resin composition is 50% by weight or more in the solid content of the resin composition from the point of forming a polyimide film having a uniform coating film and a handleable strength. Preferably, it is preferably 60% by weight or more, and the upper limit may be appropriately adjusted depending on the components contained.
The organic solvent in the polyimide precursor resin composition is preferably 40% by weight or more, more preferably 50% by weight or more in the resin composition from the viewpoint of forming a uniform coating film and a polyimide film. Preferably, it is preferably 99% by weight or less.

The polyimide precursor resin composition preferably has a water content of 1000 ppm or less from the viewpoint of improving the storage stability of the polyimide precursor resin composition and improving the productivity. If the polyimide precursor resin composition contains a large amount of moisture, the polyimide precursor may be easily decomposed.
In addition, the moisture content of a polyimide precursor resin composition can be calculated | required using a Karl Fischer moisture meter (For example, Mitsubishi Chemical Corporation make, trace moisture measuring device CA-200 type).

  Although the method for preparing the polyimide precursor resin composition is not particularly limited, as described above, in order to reduce the water content to 1000 ppm or less, the organic solvent to be used is dehydrated or the water content is controlled. In addition, it is preferable to handle in an environment with a humidity of 5% or less.

The viscosity of the polyimide precursor resin composition at 25 ° C. is preferably 500 cps or more and 100,000 cps or less from the viewpoint of forming a uniform coating film and a polyimide film.
The viscosity of the polyimide precursor resin composition can be measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. and a sample amount of 0.8 ml.

(2) Polyimide precursor resin coating film forming step In the step of applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating film, the support used has a smooth surface and heat resistance. The material is not particularly limited as long as the material is resistant and solvent resistant. For example, an inorganic material such as a glass plate, a metal plate having a mirror-finished surface, and the like can be given. The shape of the support is selected depending on the coating method, and may be, for example, a plate shape, a drum shape, a belt shape, a sheet shape that can be wound around a roll, or the like.

The application means is not particularly limited as long as it can be applied at a desired film thickness, and for example, a known one such as a die coater, a comma coater, a roll coater, a gravure coater, a curtain coater, a spray coater, or a lip coater can be used. .
Application may be performed by a single-wafer coating apparatus or a roll-to-roll coating apparatus.

  After apply | coating a polyimide precursor resin composition to a support body, the solvent in the said coating film is dried. By setting the drying temperature of the solvent to 150 ° C. or lower, imidization of the polyamic acid can be suppressed.

The drying temperature and time may be appropriately adjusted according to the film thickness of the polyimide precursor resin coating film, the type of solvent, and the like. The drying temperature is preferably 150 ° C. or lower, more preferably 30 ° C. or higher and 120 ° C. or lower.
The drying is preferably performed while increasing the temperature stepwise, and is preferably performed while increasing the temperature stepwise in at least two steps. The drying is preferably performed for 10 minutes or more in total, and more preferably for 20 minutes or more. Thereby, it is estimated that the silicon atoms in the coating film are likely to be unevenly distributed, and the difference in silicon atom concentration between the front and back surfaces is likely to increase. Specifically, the drying method is, for example, 40 ° C. or higher and lower than 70 ° C., more preferably 40 ° C. or higher and 65 ° C. or lower for 5 minutes to 60 minutes, and then 70 ° C. or higher and 140 ° C. or lower, more preferably 80 ° C. A method of drying for 5 to 60 minutes at a temperature of from ℃ to 140 ℃ and higher by 30 ℃ than the previous drying can be preferably used.
Drying at a high temperature from the beginning even in two stages or drying at a high temperature in one stage for a short time may make it difficult for silicon atoms to be unevenly distributed, and may cause film thickness unevenness or bubbles. is there.

The method for drying the solvent is not particularly limited as long as the solvent can be dried at the above temperature. For example, an oven, a drying furnace, a hot plate, infrared heating, or the like can be used.
When high management of optical properties is required, the atmosphere during drying of the solvent is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, the oxygen concentration is preferably 100 ppm or less, and more preferably 50 ppm or less. When heat treatment is performed in the atmosphere, the film may be oxidized and colored, or the performance may deteriorate.

(3) Peeling step The polyimide precursor resin coating film is dried and then peeled from the support.
The method for peeling the polyimide precursor resin coating film from the support is not particularly limited, and a general peeling method can be used. In this invention, since the surface which contact | connects the said support body of the said polyimide precursor resin coating film is excellent in peelability, it can peel easily from the said support body by pulling the said polyimide precursor resin coating film.
The peeling conditions in the peeling step are not particularly limited. For example, the peeling strength between the support and the polyimide precursor resin coating film is 0.05 N / 25 mm or more and 2.0 N / 25 mm or less, and the peeling speed is 100 mm / min or more. The peeling angle can be set to 135 ° or more and 180 ° or less. The peeling is performed by peeling at a substantially constant speed so that separation proceeds along the longitudinal direction of the polyimide precursor resin coating film, starting from the open end of the support and the polyimide precursor resin coating film. Can do.

In the first production method, in the peeling step, the amount of residual solvent in the polyimide precursor resin coating film is preferably 40% by weight or less from the viewpoint of facilitating peeling of the support, More preferably, it is 30% by weight or less. Further, the amount of residual solvent in the polyimide precursor resin coating film in the peeling step may be 10% by weight or more from the viewpoint of suppressing unevenness in the film thickness of the polyimide film and making the surface quality uniform.
In addition, the amount of residual solvent in the polyimide precursor resin coating film at the time of the peeling process is about the polyimide precursor resin coating film immediately after the peeling process, using ¹ H-NMR, It can be measured by obtaining an integral intensity ratio with a solvent-derived hydrogen atom.

Moreover, in the said 1st manufacturing method, it is preferable in the said peeling process that the imidation ratio of the said polyimide precursor resin coating film is 1% or more and 50% or less from the point which makes peeling of a support body easy. More preferably, it is 5% or more and 30% or less.
The imidation rate can be measured by analyzing the spectrum by infrared measurement (IR).

(4) Imidization process In the said 1st manufacturing method, the said polyimide precursor resin coating film is heated, and the said polyimide precursor is imidized.
Moreover, in the said 1st manufacturing method, it is preferable to have an extending process, and when it has the said extending process, an imidation process is with respect to the polyimide precursor in the said polyimide precursor resin coating film before an extending process. Or may be performed on the polyimide precursor in the polyimide precursor resin coating film after the stretching process, or the polyimide precursor and the stretching process in the polyimide precursor resin coating film before the stretching process. You may carry out with respect to both the polyimide precursors which exist in a subsequent film | membrane.

The imidization temperature may be appropriately selected according to the structure of the polyimide precursor.
Usually, the temperature rise start temperature is preferably 30 ° C. or higher, more preferably 100 ° C. or higher. On the other hand, the temperature rise end temperature is preferably 250 ° C. or higher.

The rate of temperature increase is preferably selected as appropriate depending on the film thickness of the polyimide film to be obtained. When the film thickness of the polyimide film is thick, it is preferable to decrease the temperature increase rate.
From the viewpoint of the production efficiency of the polyimide film, it is preferably 5 ° C./min or more, more preferably 10 ° C./min or more. On the other hand, the upper limit of the heating rate is usually 50 ° C./min, preferably 40 ° C./min or less, more preferably 30 ° C./min or less. It is preferable to set the temperature increase rate from the viewpoint that the appearance defect and strength reduction of the film can be suppressed, and the whitening associated with the imidization reaction can be controlled, and the light transmittance is improved.

  The temperature rise may be continuous or stepwise, but it is preferable to make it continuous from the viewpoint of controlling the appearance of the film, suppressing the decrease in strength, and controlling the whitening associated with the imidization reaction. Moreover, in the above-mentioned whole temperature range, the temperature rising rate may be constant or may be changed in the middle.

The atmosphere at the time of temperature increase in imidation is preferably an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, the oxygen concentration is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. When heat treatment is performed in the atmosphere, the film may be oxidized and colored, or the performance may deteriorate.
However, when 50% or more of the hydrogen atoms bonded to the carbon atoms contained in the polyimide are hydrogen atoms directly bonded to the aromatic ring, there is little influence of oxygen on the optical properties, and an inert gas atmosphere is not used. In addition, a polyimide having a high light transmittance can be obtained.

  The heating method for imidation is not particularly limited as long as the temperature can be raised at the above temperature. For example, an oven, a heating furnace, infrared heating, electromagnetic induction heating, or the like can be used.

In order to obtain a final polyimide film, it is preferable to proceed the reaction to 90% or more, further 95% or more, and further 100%.
In order to proceed the imidization to 90% or more, further 100%, it is preferable to hold at a temperature rising end temperature for a certain time, and the holding time is usually 1 minute to 180 minutes, and further 5 minutes to 150 minutes. Minutes are preferred.

(5) Stretching step The first production method includes a stretching step of stretching at least one of the polyimide precursor resin coating film and a post-imidation coating film obtained by imidizing the polyimide precursor resin coating film. It may be. Among these, after the peeling step, and before the imidization step, including a stretching step of stretching the polyimide precursor resin coating film suppresses shrinkage of the polyimide film and improves the tensile elastic modulus. preferable. Moreover, it is also preferable to further include the process of extending | stretching the coating film after imidation from the point of the surface hardness of a polyimide film.

In the first manufacturing method, it is preferable to perform the step of stretching 101% or more and 10000% or less while heating at 80 ° C. or higher when the initial dimension before stretching is 100%.
The heating temperature during stretching is preferably in the range of glass transition temperature ± 50 ° C. of the polyimide or polyimide precursor, and more preferably in the range of glass transition temperature ± 40 ° C. If the stretching temperature is too low, the film may not be deformed and the orientation may not be sufficiently induced. On the other hand, if the stretching temperature is too high, the orientation obtained by stretching is relaxed by the temperature, and there is a possibility that sufficient orientation cannot be obtained.
The stretching step may be performed simultaneously with the imidization step. From the point of improving the surface hardness of the polyimide film by stretching the imidized film after imidization rate of 80% or more, further 90% or more, further 95% or more, particularly substantially 100% imidization. preferable.

  The final draw ratio of the polyimide film is preferably from 101% to 10,000%, and more preferably from 101% to 500%. By stretching in the above range, shrinkage of the resulting polyimide film can be suppressed, and the tensile modulus and surface hardness can be further improved.

  There is no restriction | limiting in particular in the fixing method of the polyimide film at the time of extending | stretching, It selects according to the kind etc. of extending | stretching apparatus. Moreover, there is no restriction | limiting in particular in the extending | stretching method, For example, it can extend | stretch through a heating furnace using the extending | stretching apparatus which has conveyance apparatuses, such as a tenter. The polyimide film may be stretched only in one direction (longitudinal stretching or lateral stretching), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, oblique stretching, or the like. Among these, after the peeling step and before the imidization step, the polyimide precursor resin coating film is stretched in two directions to suppress the shrinkage of the polyimide film and improve the tensile elastic modulus. This is preferable.

Moreover, as a manufacturing method of the polyimide film of this invention, as a 2nd manufacturing method,
A step of preparing a polyimide resin composition containing a silicon atom-containing polyimide and an organic solvent (hereinafter referred to as a polyimide resin composition preparation step);
Applying the polyimide resin composition to a support, drying the solvent to form a polyimide resin coating film (hereinafter referred to as a polyimide resin coating film forming process),
A step of peeling the support from the polyimide resin coating (hereinafter referred to as a peeling step);
The manufacturing method of the polyimide film containing is mentioned.
In the second production method, the surface of the polyimide resin coating film that has been in contact with the support has good peelability, and thus the polyimide resin coating film can be easily peeled off from the support. It is difficult to cause defects. The polyimide resin coating film formed by the polyimide resin coating film forming process peels off the support because the silicon atom concentration is lower on the surface in contact with the support than on the surface in contact with air. It's easy to do.

When the polyimide used in the present invention dissolves well in an organic solvent, it is not a polyimide precursor resin composition, but a polyimide resin composition in which the polyimide is dissolved in an organic solvent and an additive is added as necessary. Can also be suitably used.
In the case where the polyimide used in the present invention has a solvent solubility such that 5% by weight or more is dissolved in an organic solvent at 25 ° C., the second production method can be suitably used.

  In the polyimide resin composition preparation step, as the polyimide containing silicon atoms, the above-mentioned solvent-soluble polyimide can be selected and used from the same polyimides as described in the polyimide film. As a method for imidization, it is preferable to use chemical imidation using a chemical imidizing agent instead of heat dehydration for the dehydration ring-closing reaction of the polyimide precursor. In the case of performing chemical imidization, known compounds such as amines such as pyridine and β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride may be used as a dehydration catalyst. Examples of the acid anhydride include, but are not limited to, acetic anhydride, propionic acid anhydride, n-butyric acid anhydride, benzoic acid anhydride, trifluoroacetic acid anhydride, and the like. At that time, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, when these amines remain in the film, the optical properties, particularly the yellowness (YI value), are reduced. Therefore, the reaction liquid reacted from the precursor to the polyimide is not cast as it is, It is preferable to form the film after purification by reprecipitation or the like, and removing components other than polyimide to 100 ppm or less of the total weight of the polyimide.

  As an organic solvent used in a polyimide resin composition preparation process, the thing similar to what was demonstrated in the said polyimide precursor resin composition preparation process in a said 1st manufacturing method can be used.

The polyimide resin composition may contain an additive as necessary. As said additive, the thing similar to what was demonstrated in the said polyimide precursor resin composition preparation process in a said 1st manufacturing method can be used.
Moreover, in the said 2nd method, as a method of setting the moisture content of the said polyimide resin composition to 1000 ppm or less, the method similar to the method demonstrated in the said polyimide precursor resin composition preparation process in a said 1st manufacturing method Can be used.

  Further, in the polyimide resin coating film forming step in the second manufacturing method, the support and the coating method are the same as those described in the polyimide precursor resin coating film forming step of the first manufacturing method. be able to.

In the polyimide resin coating film forming step in the second production method, the drying temperature is preferably 80 ° C. or higher and 150 ° C. or lower under normal pressure. It is preferable that the pressure be in the range of 10 ° C. to 100 ° C. under reduced pressure.
Moreover, it is preferable to perform the drying of the polyimide resin coating film forming step in the second production method while increasing the temperature stepwise in at least two stages. The drying is preferably performed for 10 minutes or more in total, and more preferably for 20 minutes or more. Thereby, it is estimated that the silicon atoms in the coating film are likely to be unevenly distributed, and the difference in silicon atom concentration between the front and back surfaces is likely to increase. As the drying method, the drying method preferably used in the first production method can be preferably used also in the second production method. Examples of the solvent drying method in the second manufacturing method include the same methods as those used in the first manufacturing method.

Moreover, the peeling process in the second manufacturing method can be the same as the peeling method and the peeling conditions in the peeling process of the first manufacturing method.
In the second production method, in the peeling step, the residual solvent amount in the polyimide resin coating film is preferably 40% by weight or less, and preferably 30% by weight or less from the viewpoint of facilitating peeling of the support. It is more preferable that Further, the residual solvent amount in the polyimide resin coating film in the peeling step may be 10% by weight or more from the viewpoint of suppressing unevenness in the film thickness of the polyimide film and uniforming the surface quality.
The residual solvent amount of the polyimide resin in the coating film during the peeling step, for the polyimide resin coating film immediately after peeling step, using a ^{1 H-NMR,} and the hydrogen atoms from polyimide, and a hydrogen atom from the solvent It can measure by calculating | requiring the integral intensity ratio.

  Moreover, the said 2nd manufacturing method may have the extending process which extends a polyimide resin coating film after the said peeling process. The said extending process can be made to be the same as that of the extending process in the said 1st manufacturing method.

  The second manufacturing method may further include a drying step for removing the residual solvent in the polyimide resin coating film. The drying temperature and time in the drying step may be appropriately adjusted according to the thickness of the polyimide resin coating film, the type of solvent, and the like, and are not particularly limited, but are 100 ° C. or higher and 400 ° C. or lower, 1 minute or longer and 180 °. It is preferable to make it less than minutes. Moreover, it is preferable that the said drying process is in inert gas atmosphere from the point which suppresses the fall of the optical characteristic of a polyimide film. The inert gas atmosphere is preferably a nitrogen atmosphere, the oxygen concentration is preferably 100 ppm or less, and more preferably 50 ppm or less.

6). Use of polyimide film The use of the polyimide film of the present invention is not particularly limited, and can be used as a member such as a base material or a surface material for which a glass product such as a thin plate glass has been conventionally used. The polyimide film of the present invention is suitable as a surface material for a display that can cope with a curved surface, because it has improved bending resistance, has sufficient surface hardness as a protective film, and can reduce optical distortion. Can be used.
Specifically, the polyimide film of the present invention is, for example, a thin and bent flexible type organic EL display, a portable terminal such as a smartphone or a wristwatch type terminal, a display device inside an automobile, a flexible panel used for a wristwatch, or the like. It can be used suitably. Further, the polyimide film of the present invention is a member for an image display device such as a liquid crystal display device or an organic EL display device, a member for a touch panel, a flexible printed circuit board, a surface protection film or a substrate material for a solar cell panel, an optical waveguide, etc. The present invention can also be applied to other members, other semiconductor-related members and the like.

In addition, the polyimide film of the present invention has a surface with a relatively large silicon atom concentration and excellent adhesion, in particular, with a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound. Excellent adhesion. Therefore, in the polyimide film of the present invention, a surface having a relatively large silicon atom concentration can be suitably used as an adhesion surface with the resin-containing layer.
Since the resin-containing layer can be the same as the resin-containing layer used in the laminate described later, description thereof is omitted here.

II. Laminate The laminate of the present invention is a laminate in which the polyimide film of the present invention described above and a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound are located adjacent to each other. is there.

The laminate of the present invention can improve the adhesion between the polyimide film and the resin-containing layer by bringing the resin-containing layer into close contact with the surface of the polyimide film of the present invention having a relatively high silicon atom concentration. And thereby the surface hardness can be further improved. Moreover, since the laminated body of this invention uses the polyimide film of this invention mentioned above, the defect of a polyimide film is suppressed and the fall of the quality of a laminated body is also suppressed.
Moreover, since the laminated body of this invention uses the polyimide film of this invention, the fall of transparency is suppressed, Furthermore, optical distortion can be reduced. Therefore, when the laminated body of this invention is used as a surface material for a display, the fall of the display quality of a display can be suppressed. Furthermore, since the laminated body of this invention uses the polyimide film of this invention, it can improve bending tolerance and can be used suitably for flexible displays.

1. Polyimide film Since the polyimide film of the present invention described above can be used as the polyimide film used in the laminate of the present invention, description thereof is omitted here.

2. Resin-containing layer The resin-containing layer used in the laminate of the present invention contains at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and further contains a polymerization initiator and other additives as necessary. You may contain.
As said resin content layer, the functional layer etc. which are used for a display are mentioned, for example, Specifically, a hard-coat layer etc. are mentioned, for example.

(1) Radical polymerizable compound The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group possessed by the radical polymerizable compound is not particularly limited as long as it is a functional group capable of causing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond. Specific examples include a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different from each other.

The number of radically polymerizable groups contained in one molecule of the radically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the resin-containing layer.
As the radical polymerizable compound, a compound having a (meth) acryloyl group is preferable from the viewpoint of high reactivity, and a polyfunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in one molecule and Preferred are oligomers having several (meth) acryloyl groups in the molecule called several (meth) acryloyl groups in the molecule called urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate. Can be used.
In this specification, (meth) acryloyl represents each of acryloyl and methacryloyl, and (meth) acrylate represents each of acrylate and methacrylate.

  Specific examples of the radical polymerizable compound include vinyl compounds such as divinylbenzene; ethylene glycol di (meth) acrylate, bisphenol A epoxy di (meth) acrylate, 9,9-bis [4- (2- ( Meth) acryloyloxyethoxy) phenyl] fluorene, alkylene oxide modified bisphenol A di (meth) acrylate (eg ethoxylated (ethylene oxide modified) bisphenol A di (meth) acrylate), trimethylolpropane tri (meth) acrylate, tri Methylolethane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaeryth Polyol polyacrylates such as tall tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether, etc. Examples thereof include epoxy acrylates, urethane acrylates obtained by the reaction of polyisocyanate and hydroxyl group-containing acrylates such as hydroxyethyl acrylate.

(2) Cationic polymerizable compound The cationic polymerizable compound is a compound having a cationic polymerizable group. The cationic polymerizable group of the cationic polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationic polymerizable compound has two or more cationic polymerizable groups, these cationic polymerizable groups may be the same or different from each other.

The number of cation polymerizable groups in the molecule of the cation polymerizable compound is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the resin-containing layer.
In addition, the cationic polymerizable compound is preferably a compound having at least one of an epoxy group and an oxetanyl group as a cationic polymerizable group. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred from the viewpoint of small shrinkage accompanying the polymerization reaction. In addition, compounds having an epoxy group among the cyclic ether groups are easily available as compounds having various structures, do not adversely affect the durability of the obtained resin-containing layer, and can easily control the compatibility with the radical polymerizable compound. There is an advantage. Of the cyclic ether groups, the oxetanyl group has a high degree of polymerization and low toxicity compared to the epoxy group. When the obtained resin-containing layer is combined with a compound having an epoxy group, a cation in the coating film is obtained. There are advantages such as speeding up the network formation obtained from the polymerizable compound and forming an independent network without leaving unreacted monomer in the film even in a region mixed with the radical polymerizable compound.

  As the cationically polymerizable compound having an epoxy group, for example, a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, a cyclohexene ring or a cyclopentene ring-containing compound may be used with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or alkylene oxide adduct thereof, polyglycidyl ester of aliphatic long-chain polybasic acid, homopolymer of glycidyl (meth) acrylate, Aliphatic epoxy resins such as copolymers; glycidyl esters produced by the reaction of bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts, and epichlorohydrin. Ether, and novolac epoxy resins such as a and glycidyl ether type epoxy resins derived from bisphenols are exemplified.

  Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (UVR-6105, UVR-6107, UVR-6110), bis-3,4-epoxycyclohexylmethyl adipate. (UVR-6128) (In the above, the names in parentheses are trade names, manufactured by Dow Chemical).

  Examples of the glycidyl ether type epoxy resin include sorbitol polyglycidyl ether (Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, Denacol EX-622), Polyglycerol polyglycidyl ether (Denacol EX). -512, Denacol EX-521), pentaerythritol polyglycidyl ether (Denacol EX-411), diglycerol polyglycidyl ether (Denacol EX-421), glycerol polyglycidyl ether (Denacol EX-313, Denacol EX-314), Trimethylolpropane polyglycidyl ether (Denacol EX-321), resortinol diglycidyl ether (Denacol EX-201), neopentyl glycol diglyci Luether (Denacol EX-211), 1,6 hexanediol diglycidyl ether (Denacol EX-212), Hydrodibisphenol A diglycidyl ether (Denacol EX-252), Ethylene glycol diglycidyl ether (Denacol EX-810, Denacol EX) -811), polyethylene glycol diglycidyl ether (Denacol EX-850, Denacol EX-851, Denacol EX-821), propylene glycol glycidyl ether (Denacol EX-911), polypropylene glycol glycidyl ether (Denacol EX-941, Denacol EX- 920), allyl glycidyl ether (Denacol EX-111), 2-ethylhexyl glycidyl ether (Denacol EX-121), phenyl glycidyl ether (Denacol EX-141), phenol glycidyl ether (Denacol EX-145), butylphenyl glycidyl ether (Denacol EX-146), diglycidyl phthalate (Denacol EX-721), hydroquinone diglycidyl ether (Denacol EX-203), di Glycidyl terephthalate (Denacol EX-711), Glycidyl phthalimide (Denacol EX-731), Dibromophenyl glycidyl ether (Denacol EX-147), Dibromoneopentylglycol diglycidyl ether (Denacol EX-221) And manufactured by Nagase ChemteX).

  Other commercially available epoxy resins include trade names such as Epicoat 825, Epicoat 827, Epicoat 828, Epicoat 828EL, Epicoat 828XA, Epicoat 834, Epicoat 801, Epicoat 801P, Epicoat 802, Epicoat 815, Epicoat 815XA, Epicoat 816A, Epicoat 819, Epicoat 834X90, Epicoat 1001B80, Epicoat 1001X70, Epicoat 1001X75, Epicoat 1001T75, Epicoat 806, Epicoat 806P, Epicoat 807, Epicoat 152, Epicoat 154, Epicoat 871, Epicoat 191P, Epicoat YX310, Epicoat DX255, Epicoat YX8000, Etc. (above product name, di Bread epoxy resin) and the like.

  Examples of the cationically polymerizable compound having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101) and 1,4-bis-3-ethyloxetane-3-ylmethoxymethylbenzene (OXT-121). Bis-1-ethyl-3-oxetanyl methyl ether (OXT-221), 3-ethyl-3--2-ethylhexyloxymethyl oxetane (OXT-212), 3-ethyl-3-phenoxymethyl oxetane (OXT- 211) (the name in parentheses is a product name manufactured by Toa Gosei Co., Ltd.), and the product names Etanacol EHO, Etanacol OXBP, Etanacol OXTP, Etanacol OXMA (above, trade name, manufactured by Ube Industries).

(3) Polymerization initiator At least one polymer of the radical polymerizable compound and the cationic polymerizable compound contained in the resin-containing layer used in the present invention is, for example, the radical polymerizable compound or the cationic polymerizable compound. It can be obtained by adding a polymerization initiator to at least one kind, if necessary, and carrying out a polymerization reaction by a known method.

  As the polymerization initiator, radical polymerization initiators, cationic polymerization initiators, radicals and cationic polymerization initiators can be appropriately selected and used. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization.

  Any radical polymerization initiator may be used as long as it can release a substance that initiates radical polymerization by light irradiation and / or heating. For example, examples of the photo radical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-aryl glycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, thioxanthone derivatives, and the like. More specifically, 1,3-di (tert-butyldioxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetrakis (tert-butyldioxycarbonyl) benzophenone, 3-phenyl-5- Isoxazolone, 2-mercaptobenzimidazole, bis (2,4,5-triphenyl) imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name Irgacure 651, Ciba Japan Co., Ltd.) 1-hydroxy-cyclohexyl-phenyl) Ketone (trade name Irgacure 184, manufactured by Ciba Japan), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one (trade names Irgacure 369, Ciba Japan ( Co., Ltd.), bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium) (trade name Irgacure 784 However, it is not limited to these.

  In addition to the above, commercially available products can be used. Specifically, Irgacure 907, Irgacure 379, Irgacure 819, Irgacure 127, Irgacure 500, Irgacure 754, Irgacure 250, Irgacure 1800, Irgacure 1870 manufactured by Ciba Japan Co., Ltd. , Irgacure OXE01, DAROCUR TPO, DAROCUR1173, Japan Siber Hegner Co., Ltd. of SpeedcureMBB, SpeedcurePBZ, SpeedcureITX, SpeedcureCTX, SpeedcureEDB, Esacure ONE, Esacure KIP150, Esacure KTO46, manufactured by Nippon Kayaku Co., of (stock) KAYACURE DETX-S, KAYACURE CTX , KAYACURE BMS, K YACURE DMBI, and the like.

Moreover, the cationic polymerization initiator should just be able to discharge | release the substance which starts cationic polymerization by at least any one of light irradiation and a heating. Examples of the cationic polymerization initiator include sulfonic acid ester, imide sulfonate, dialkyl-4-hydroxysulfonium salt, arylsulfonic acid-p-nitrobenzyl ester, silanol-aluminum complex, (η ⁶ -benzene) (η ⁵ -cyclopentadidiene). Enyl) iron (II) and the like are exemplified, and more specifically, benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosiphthalimide and the like are exemplified, but not limited thereto.

  Examples of radical polymerization initiators that can be used as cationic polymerization initiators include aromatic iodonium salts, aromatic sulfonium salts, aromatic diazonium salts, aromatic phosphonium salts, triazine compounds, iron arene complexes, and the like. More specifically, iodonium chloride such as diphenyliodonium, ditolyliodonium, bis (p-tert-butylphenyl) iodonium, bis (p-chlorophenyl) iodonium, bromide, borofluoride, hexafluorophosphate salt, hexafluoro Iodonium salts such as antimonate salts, chlorides of sulfonium such as triphenylsulfonium, 4-tert-butyltriphenylsulfonium, tris (4-methylphenyl) sulfonium, bromides, borofluorides, hexaf Sulfonium salts such as orophosphate salts and hexafluoroantimonate salts, 2,4,6-tris (trichloromethyl) -1,3,5-triazine, 2-phenyl-4,6-bis (trichloromethyl) -1, 2,4,6-substituted-1,3,5 triazine compounds such as 3,5-triazine, 2-methyl-4,6-bis (trichloromethyl) -1,3,5-triazine, etc. It is not limited to these.

(4) Additive In addition to the polymer, the resin-containing layer used in the present invention, if necessary, an antistatic agent, an antiglare agent, an antifouling agent, inorganic or organic fine particles for improving hardness, You may contain additives, such as a leveling agent and various sensitizers.
As the particles for improving the hardness, inorganic fine particles such as silica particles are preferably used. However, when silica particles are used, it is preferable from the viewpoint of improving the adhesion between the polyimide film and the resin-containing layer.

3. Configuration of Laminate The laminate of the present invention is one in which the polyimide film and the resin-containing layer are located adjacent to each other. It is preferable from the point of the adhesiveness of a polyimide film and this resin containing layer that a content layer is closely_contact | adhered.
In addition, the laminate of the present invention is a laminate in which other layers such as gel containing urethane or acrylic resin are further laminated in addition to the polyimide film and the resin-containing layer as long as the effects of the present invention are not impaired. The resin-containing layer may have a multilayer structure of two or more layers. In the laminate of the present invention, the resin-containing layer and the other layers may be laminated on the surface side of the polyimide film having a relatively low silicon atom concentration.

The total thickness of the laminate of the present invention may be appropriately selected depending on the application, but is preferably 10 μm or more, and more preferably 40 μm or more from the viewpoint of strength. On the other hand, from the viewpoint of bending resistance, it is preferably 300 μm or less, and more preferably 250 μm or less.
In the laminate of the present invention, the thickness of each resin-containing layer may be appropriately selected depending on the use, but is preferably 2 μm or more and 80 μm or less, and more preferably 3 μm or more and 50 μm or less. Moreover, you may form a resin content layer on both surfaces of a polyimide film from a viewpoint of curl prevention.

4). Characteristics of Laminate In the laminate of the present invention, the pencil hardness of the resin-containing layer side surface is preferably H or more, more preferably 2H or more, and even more preferably 3H or more. In addition, in the case of the laminated body which has a resin containing layer on both surfaces, it is preferable that it is the said pencil hardness in at least one surface.
The pencil hardness of the laminate of the present invention can be measured in the same manner as the pencil hardness of the polyimide film.

In the laminate of the present invention, the total light transmittance measured in accordance with JIS K7361-1 is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. Is preferred. Thus, since the transmittance | permeability is high, transparency becomes favorable and it can become a glass substitute material.
The said total light transmittance of the laminated body of this invention can be measured similarly to the total light transmittance measured based on JISK7361-1 of the said polyimide film.

In the laminate of the present invention, the yellowness degree (YI value) calculated in accordance with JIS K7373-2006 is preferably 30 or less, more preferably 20 or less, and more preferably 15 or less. More preferred is 10 or less.
The yellowness (YI value) of the laminate of the present invention can be measured in the same manner as the yellowness (YI value) calculated based on JIS K7373-2006 of the polyimide film.

The haze value of the laminate of the present invention is preferably 10 or less, more preferably 8 or less, and even more preferably 5 or less, from the viewpoint of light transmittance.
The haze value of the laminate of the present invention can be measured in the same manner as the haze value of the polyimide film.

The birefringence in the thickness direction of the laminate of the present invention at a wavelength of 590 nm is preferably 0.020 or less, preferably 0.015 or less, more preferably 0.010 or less, and still more. Preferably it is less than 0.008.
The birefringence of the laminate of the present invention can be measured in the same manner as the birefringence in the thickness direction at a wavelength of 590 nm of the polyimide film.

5. Use of laminated body The use of the laminated body of this invention is not specifically limited, For example, it can be used for the use similar to the use of the polyimide film of this invention mentioned above.

6). Manufacturing method of laminate As a manufacturing method of the laminate of the present invention, for example,
Forming a coating film of a resin-containing layer forming composition containing at least one of a radically polymerizable compound and a cationically polymerizable compound on the surface of the polyimide film of the present invention having a relatively large silicon atom concentration;
And a step of curing the coating film.

The composition for forming a resin-containing layer contains at least one of a radically polymerizable compound and a cationically polymerizable compound, and may further contain a polymerization initiator, a solvent, an additive, and the like as necessary.
Here, the radical polymerizable compound, the cationic polymerizable compound, the polymerization initiator and the additive contained in the resin-containing layer forming composition can be the same as those described in the resin-containing layer. The solvent can be appropriately selected from known solvents.

Examples of a method for forming a coating film of the resin-containing layer forming composition on a surface of the polyimide film having a relatively high silicon atom concentration include, for example, the resin on the surface of the polyimide film having a relatively high silicon atom concentration. The method of apply | coating the composition for content layer formation by a well-known application means is mentioned.
The application means is not particularly limited as long as it is a method that can be applied with a target film thickness, and examples thereof include the same means as the means for applying the polyimide precursor resin composition to a support.

  The coating film of the resin-containing layer forming composition is dried as necessary to remove the solvent. Examples of the drying method include reduced-pressure drying or heat drying, and a method combining these drying methods. Moreover, when drying at a normal pressure, it is preferable to dry at 30 degreeC or more and 110 degrees C or less.

  Applying the composition for forming a resin-containing layer and drying the coating as necessary, light irradiation and heating according to the polymerizable group of the radical polymerizable compound and the cationic polymerizable compound contained in the composition A resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound is formed on the surface of the polyimide film having a relatively large silicon atom concentration by curing the coating film with at least one of Can be formed.

For light irradiation, ultraviolet rays, visible light, electron beams, ionizing radiation, etc. are mainly used. In the case of ultraviolet curing, ultraviolet rays emitted from light such as an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, and a metal halide lamp are used. The irradiation amount of the energy ray source is about 50 to 5000 mJ / cm ² as an integrated exposure amount at an ultraviolet wavelength of 365 nm.
When heating, the treatment is usually performed at a temperature of 40 ° C. or higher and 120 ° C. or lower. Moreover, you may react by leaving it to stand for 24 hours or more at room temperature (25 degreeC).

III. Display Surface Material The display surface material of the present invention is the above-described polyimide film of the present invention or the laminate of the present invention.

  The display surface material of the present invention is used by being disposed so as to be positioned on the surface of various displays. Since the surface material for display of the present invention can improve bending resistance and has a sufficient surface hardness as a protective film, like the polyimide film of the present invention and the laminate of the present invention described above, it is suitable for use in flexible displays. It can be particularly preferably used. Moreover, since the surface material for display of the present invention has sufficient transparency as a transparent film and can reduce optical distortion, as with the polyimide film of the present invention and the laminate of the present invention described above, A decrease in display quality of the display can be suppressed.

  The display surface material of the present invention can be used for various known displays, and is not particularly limited. For example, it can be used for the display described in the application of the polyimide film of the present invention.

  When the display surface material of the present invention is the laminate of the present invention, the surface that is the outermost surface after being arranged on the surface of the display may be a polyimide film-side surface, or a resin-containing layer However, when a hard coat layer is used as the resin-containing layer, it is preferable to arrange the display surface material of the present invention so that the surface on the hard coat layer side is the surface. The display surface material of the present invention may have a fingerprint adhesion preventing layer on the outermost surface.

  The method for disposing the display surface material of the present invention on the surface of the display is not particularly limited, and examples thereof include a method through an adhesive layer. As the adhesive layer, a conventionally known adhesive layer that can be used for adhesion of a display surface material can be used.

[Evaluation method]
Hereinafter, among the surfaces of the polyimide film, the surface in contact with the support in the drying step may be referred to as a cast surface, and the surface opposite to the cast surface may be referred to as an atmosphere surface.

<Weight average molecular weight of polyimide precursor>
The weight-average molecular weight of the polyimide precursor was determined using GPC using a polyimide precursor as an N-methylpyrrolidone (NMP) solution having a concentration of 0.5% by weight, and using a 10 mmol% LiBr-NMP solution having a water content of 500 ppm or less as a developing solvent. Using an apparatus (manufactured by Tosoh Corporation, HLC-8120, column used: GPC LF-804, manufactured by SHODEX), measurement was performed under conditions of a sample injection amount of 50 μL, a solvent flow rate of 0.5 mL / min, and 40 ° C. The weight average molecular weight of the polyimide precursor was determined based on a polystyrene standard sample having the same concentration as the sample.
<Viscosity of polyimide precursor solution>
The viscosity of the polyimide precursor solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. with a sample amount of 0.8 ml.

<Weight average molecular weight of polyimide>
The weight average molecular weight of the polyimide is a GPC apparatus (manufactured by Tosoh Corporation) using polyimide as an N-methylpyrrolidone (NMP) solution having a concentration of 0.2% by weight, and using a 30 mmol% LiBr-NMP solution having a water content of 500 ppm or less as a developing solvent. , HLC-8120, column used: GPC LF-804 manufactured by SHODEX), and measurement was performed under the conditions of a sample injection amount of 50 μL, a solvent flow rate of 0.4 mL / min, and 40 ° C. The weight average molecular weight of the polyimide was determined based on a polystyrene standard sample having the same concentration as the sample.
<Viscosity of polyimide solution>
The viscosity of the polyimide solution was measured using a viscometer (for example, TVE-22HT, Toki Sangyo Co., Ltd.) at 25 ° C. and a sample amount of 0.8 ml.

<Silicon atom content of polyimide (mass%)>
The silicon atom content (% by mass) of the polyimide was calculated from the charged molecular weight.
For example, as in the polyimide of Example 8, 2,2′-bis as the diamine component with respect to 1 mol of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as the acid dianhydride component. When 0.9 mol of (trifluoromethyl) benzidine (TFMB) and 0.1 mol of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) are used, it can be calculated as follows. .
The molecular weight of one mole of polyimide repeating unit is
6FDA origin: (C) 12.01 × 19 + (F) 19.00 × 6 + (O) 16.00 × 4 + (H) 1.01 × 6 = 412.25
TFMB origin: {(C) 12.01 × 14 + (F) 19.00 × 6 + (N) 14.01 × 2 + (H) 1.01 × 6} × 0.9 = 284.60
From AprTMOS: {(C) 12.01 × 10 + (O) 16.00 × 1 + (N) 14.01 × 2 + (Si) 28.09 × 2 + (H) 1.01 × 24} × 0.1 = 24.45
From this, it is calculated as 412.25 + 284.60 + 24.45 = 721.30.
Silicon atom content ratio (% by mass) in 1 mol of polyimide repeating unit is:
It is calculated as (28.09 × 2 × 0.1) /721.30×100=0.8 (mass%).
Incidentally, both terminal amine-modified diphenyl silicone oil of Comparative Example 2 (Shin-Etsu Chemical Co., Ltd.: X22-1660B-3, the side chain phenyl type, number average molecular weight 4400) for, - _{(CH 2) 3} - amino group via an As a result, it is calculated that the number of repeating units of diphenylsiloxane is 19.7 on average from the number average molecular weight 4400, and an average of 21.7 silicon atoms are contained in one molecule. Calculated as being.

<Total light transmittance>
Based on JIS K7361-1, it measured with the haze meter (HM150 by Murakami Color Research Laboratory).
For example, the total light transmittance at a thickness of 100 μm can be converted according to Lambert Beer's law.
Specifically, according to Lambert Beer's law, the transmittance T is
Log ₁₀ (1 / T) = kcb
(K = constant specific to substance, c = concentration, b = optical path length).
For the transmittance of the film, so even if the film thickness is changed density is also constant c assuming a constant, the above formula, Log ₁₀ using constants f (1 / T) = fb
(F = kc). Here, if the transmittance at a certain film thickness is known, a specific constant f of each substance can be obtained. Therefore, the transmittance at a desired film thickness can be obtained by substituting a constant specific to f and a target film thickness into b using the formula T = 1/10 ^{f · b} .

<YI value (yellowness)>
The YI value is a transmittance measured by a spectrocolorimetric method specified in JIS Z8720 using an ultraviolet-visible near-infrared spectrophotometer (JASCO Corporation V-7100) in accordance with JIS K7373-2006. And calculated.
Further, for example, the YI value at a thickness of 100 μm is the same as the Lambert for each transmittance at each wavelength measured at 5 nm intervals between 380 nm and 780 nm of a sample having a specific thickness. A converted value of each transmittance at each wavelength of different thickness can be obtained according to Beer's law, and calculated and used based on that.

<Haze value>
Based on JIS K-7105, it measured with the haze meter (HM150 made by Murakami Color Research Laboratory).

<Birefractive index>
Using a phase difference measuring device (manufactured by Oji Scientific Instruments, product name “KOBRA-WR”), the thickness direction retardation value (Rth) of the polyimide film was measured with light at 25 ° C. and a wavelength of 590 nm. For the thickness direction retardation value (Rth), a phase difference value at 0 ° incidence and a phase difference value at an incidence angle of 40 ° were measured, and a thickness direction retardation value Rth was calculated from these retardation values. The retardation value at an oblique incidence of 40 degrees was measured by making light having a wavelength of 590 nm incident on the retardation film from a direction inclined by 40 degrees from the normal line of the retardation film.
The birefringence of the polyimide film was determined by substituting it into the formula: Rth / d (polyimide film thickness (nm)).

<Glass transition temperature>
Using a dynamic viscoelasticity measuring device RSA III (TA Instruments Japan Co., Ltd.), the measurement range is -150 ° C to 400 ° C, the frequency is 1 Hz, the heating rate is 5 ° C / min, and the sample width is Dynamic viscoelasticity measurement is performed at 5 mm and the distance between chucks is 20 mm, and the glass transition temperature (Tg) is obtained from the peak temperature of tan δ (tan δ = loss elastic modulus (E ″) / storage elastic modulus (E ′)). It was.

<Tensile modulus>
A polyimide film test piece cut out to 15 mm × 40 mm was conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, and in accordance with JIS K7127, the tensile speed was 10 mm / min and the distance between chucks was 20 mm. The tensile elastic modulus at 25 ° C. was measured. A tensile tester (manufactured by Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) was used.

<Static bending test>
Hereinafter, the method of the static bending test will be described with reference to FIG.
The polyimide film test piece 1 cut out to 15 mm × 40 mm is bent at the half of the long side, and the metal piece 2 (100 mm × 30 mm × 6 mm) having a thickness of 6 mm at both ends of the long side of the test piece 1 is sandwiched from above and below. The test piece 1 was fixed with tape so that the overlap between the upper and lower surfaces of the test piece 1 and the metal piece 2 was 10 mm each. The metal piece 2 on which the test piece 1 was fixed was sandwiched between glass plates (100 mm × 100 mm × 0.7 mm) 3a and 3b from above and below, and the test piece 1 was fixed in a state of being bent with an inner diameter of 6 mm. At that time, dummy test pieces 4a and 4b were sandwiched between portions of the metal piece 2 where the test piece 1 was not provided, and fixed with tape so that the glass plates 3a and 3b were parallel.
After the test piece fixed in the bent state in this manner is left to stand for 24 hours in an environment of 60 ± 2 ° C. and 93 ± 2% relative humidity (RH), the glass plate and the test piece fixing tape are removed. The force applied to the test piece was released. Thereafter, one end of the test piece was fixed, and the internal angle of the test piece was measured 30 minutes after releasing the force applied to the test piece.
In addition, when the film returns completely without being affected by the static bending test, the inner angle is 180 °.

<Dynamic bending test>
The test piece cut out to a size of 20 mm × 100 mm was fixed with a tape to a constant temperature and humidity chamber durability test system (manufactured by Yuasa System Equipment Co., Ltd., planar body no-load U-shaped expansion / contraction test jig DMX-FS). After setting the test piece to be in the same folded state as in the static bending test, that is, the distance between both ends of the long side of the test piece in the folded state is 6 mm, it is 93 at 60 ± 2 ° C. Bending was repeated 200,000 times with 90 bendings per minute in an environment of ± 2% relative humidity (RH) or 50 ± 10% relative humidity (RH) at 25 ° C. ± 2 ° C.
Thereafter, 30 minutes after removing the test piece, one end of the obtained test piece was fixed, and the inner angle of the test piece was measured.
In addition, when the film returns completely without being affected by the dynamic bending test, the inner angle becomes 180 °.

<Pencil hardness>
After the measurement sample was conditioned for 2 hours under the conditions of a temperature of 25 ° C. and a relative humidity of 60%, a pencil scratch coating film hardness tester manufactured by Toyo Seiki Co., Ltd. The pencil hardness test (0.98N load) defined in JIS K5600-5-4 (1999) was performed on the atmosphere surface of the film, and the highest pencil hardness without scratches was evaluated.

<Peelability evaluation>
The polyimide film was visually observed, and the peelability from the support during production was evaluated according to the following evaluation criteria.
A: Due to good peelability from the support, wrinkles, cracks, streaks and breakage did not occur in the film.
B: Although slight streaks and wrinkles were generated on the film due to peeling from the support, it was at a practical level.
C: Peeling failure. Remarkable stripes and wrinkles were generated on the film, and the film was partially broken.
In addition, a streak refers to the pattern which generate | occur | produces in a short side direction (TD direction), when a film extends nonuniformly by peeling stress. A wrinkle refers to a wrinkle generated in the longitudinal direction when the film is stretched when peeled from the support and then contracted.

<Atomic concentration measurement>
Each atomic concentration of the atmosphere surface and cast surface of the polyimide film was measured by X-ray photoelectron spectroscopy (XPS) under the following measurement conditions. Table 2 shows the average value of n = 2. In addition, together with the value rounded to the first decimal place according to JIS Z8401: 1999, the value to the second decimal place measured in parentheses is shown.
・ Device used: Theta-Probe (Thermo Scientific XPS device)
Incident X-ray: Monochromated Al Kα ray (monochromated X-ray, hν = 1486.6 eV)
・ X-ray irradiation area (measurement area): 400 μmφ
・ X-ray output: 100 W (15 kV, 6.7 mA)
Photoelectron uptake angle: 53 ° (sample normal is 0 °)
・ Charge neutralization conditions: electron neutralization gun (+6 V, 0.05 mA), low acceleration Ar ⁺ ion irradiation
Measurement peak: Si2p, C1s, N1s, O1s, F1s
-Quantification: The background was determined by the Shirley method, and the atomic ratio was calculated from the obtained peak area using the relative sensitivity coefficient method.

(Synthesis Example 1)
A solution in which 302.0 g of dehydrated dimethylacetamide and 3.735 g (15 mmol) of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) were dissolved in a 500 ml separable flask was liquidized. To the place where the temperature is controlled to 30 ° C., 2.22 g (5 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) is gradually added so that the temperature rise is 2 ° C. or less. The mixture was stirred with a mechanical stirrer for 4 hours. 2,2′-bis (trifluoromethyl) benzidine (TFMB) 27.2 g (85 mmol) was added thereto, and after confirming complete dissolution, 4,4 ′-(hexafluoroisopropylidene) diphthalic acid Anhydrous anhydride (6FDA) 42.0 g (94.5 mmol) was gradually added in several portions so that the temperature rise was 2 ° C. or less, and polyimide precursor solution 1 (solid content 20) in which polyimide precursor 1 was dissolved was added. % By weight) was synthesized. The molar ratio of TFMB used for the polyimide precursor 1 to AprTMOS was 85:15. The viscosity at 25 ° C. of the polyimide precursor solution 1 (solid content 20% by weight) was 17770 cps, and the weight average molecular weight of the polyimide precursor 1 measured by GPC was 117,000.

(Synthesis Examples 2 to 8)
In the procedure of Synthesis Example 1, the reaction was carried out so that the raw material and solid content concentrations shown in Table 1 were obtained, to obtain polyimide precursor solutions 2 to 8.

(Comparative Synthesis Example 1)
A solution obtained by dissolving 345.3 g of dehydrated dimethylacetamide and 49.7 g (200 mmol) of 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) in a 500 ml separable flask was liquidized. To the place where the temperature was controlled to 30 ° C., 88.4 g (199 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was gradually added so that the temperature rise was 2 ° C. or less. Comparative polyimide precursor solution 1 (solid content 40 wt%) in which comparative polyimide precursor 1 was dissolved was synthesized. The viscosity at 25 ° C. of the comparative polyimide precursor solution 1 (solid content 40% by weight) was 3900 cps, and the weight average molecular weight of the comparative polyimide precursor 1 measured by GPC was 42,000.

(Comparative Synthesis Example 2)
While introducing nitrogen gas into a 3 L separable flask equipped with a stir bar equipped with an oil bath, 12.25 g of both-end amine-modified dimethylphenyl silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: X22-1660B-3 (number average molecular weight 4400)) 3432 g of N-methyl-2-pyrrolidone (NMP) was added, followed by 222.12 g (0.5 mol) of 6FDA, and the mixture was stirred at room temperature for 30 minutes. Thereafter, it was confirmed that 152.99 g (0.478 mol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) was added and dissolved, and the mixture was stirred at room temperature for 3 hours and then raised to 80 ° C. After warming and stirring for 4 hours, the oil bath was removed and the temperature was returned to room temperature to obtain a comparative polyimide precursor solution 2 (solid content 10% by weight). The viscosity at 25 ° C. of the comparative polyimide precursor solution 2 (solid content 10% by weight) was 89 cps, and the weight average molecular weight of the comparative polyimide precursor 2 measured by GPC was 66900.

(Synthesis Example 9 (chemical imidization))
Dehydrated dimethylacetamide (367.1 g) and 1,3-bis (3-aminopropyl) tetramethyldisiloxane (AprTMOS) (2.33 g, 9.4 mmol) were dissolved in a 500 mL separable flask. To the place where the solution temperature was controlled at 30 ° C., 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (2.08 g, 4.7 mmol) was brought to a temperature rise of 2 ° C. or less. The mixture was gradually added and stirred with a mechanical stirrer for 1 hour. 2,2′-bis (trifluoromethyl) benzidine (TFMB) (57.07 g, 178.2 mmol) was added thereto, and after confirming complete dissolution, 4,4 ′-(hexafluoroisopropylidene) was confirmed. ) Diphthalic anhydride (6FDA) (80.83 g, 182.0 mmol) was gradually added several times so that the temperature rise was 2 ° C. or less, and the polyimide precursor solution in which the polyimide precursor 1 ′ was dissolved 1 ′ (solid content 28% by weight) was synthesized.
The solution was cooled to room temperature and dehydrated dimethylacetamide (202.2 g) was added and stirred until homogeneous. Next, pyridine (59.05 g, 0.747 mmol) as a catalyst and acetic anhydride (76.22 g, 0.747 mol) were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. A part (692.2 g) of the obtained polyimide solution was transferred to a 5 L separable flask, and butyl acetate (471.1 g) was added and stirred until uniform. Next, methanol (1046 g) was gradually added to obtain a solution with slight turbidity. Methanol (2443 kg) was added all at once to the cloudy solution to obtain a white slurry. The slurry was filtered and washed 5 times with methanol to obtain polyimide 1 (104.7 g). The weight average molecular weight of the polyimide 1 measured by GPC was 180000.
Polyimide 1 was dissolved in a mixed solvent of butyl acetate and PGMEA (8: 2, volume ratio) to prepare a polyimide solution 1 having a solid content of 25% by mass. The viscosity of the polyimide solution 1 (solid content: 25% by weight) at 25 ° C. was 58500 cps.

In the following, the abbreviations in the table are as follows.
TFMB: 2,2′-bis (trifluoromethyl) benzidine AprTMOS: 1,3-bis (3-aminopropyl) tetramethyldisiloxane 6FDA: 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride

[Preparation of polyimide film]
(Examples 1-8, Comparative Examples 1-2)
By using the polyimide precursor solutions 1 to 8 and the comparative polyimide precursor solutions 1 and 2, the following steps (1) to (4) were performed to prepare polyimide films having thicknesses shown in Table 2, respectively.
(1) Each polyimide precursor solution was coated on a steel support, dried in a circulation oven at 40 ° C. for 60 minutes, and further dried at 100 ° C. for 30 minutes to form a coating film.
(2) The coating film was peeled from the support (peel strength 0.1 N / 25 mm, peel rate 200 mm / min, peel angle 180 °).
(3) After peeling, the outer periphery of the coating film was fixed to a frame-shaped metal jig.
(4) In a nitrogen stream (oxygen concentration of 100 ppm or less), the temperature was raised to 350 ° C. at a rate of temperature increase of 10 ° C./min. Each polyimide film was obtained.

Example 9
Using the polyimide solution 1 obtained in Synthesis Example 9, the following steps (1) to (4) were performed to prepare polyimide films having thicknesses shown in Table 2.
(1) The polyimide solution 1 was applied on a steel support, dried in a circulating oven at 40 ° C. for 60 minutes, and further dried at 100 ° C. for 30 minutes to form a coating film.
(2) The coating film was peeled from the support (peel strength 0.1 N / 25 mm, peel rate 200 mm / min, peel angle 180 °).
(3) After peeling, the outer periphery of the coating film was fixed to a frame-shaped metal jig.
(4) Under a nitrogen stream (oxygen concentration of 100 ppm or less), the temperature is raised to 250 ° C. at a rate of temperature increase of 10 ° C./min. A polyimide film was obtained.

  About each obtained polyimide film, it evaluated using the said evaluation method. The evaluation results are shown in Table 2.

[Production of laminate]
Resin by adding 10 parts by weight of 1-hydroxy-cyclohexyl-phenyl-ketone (BASF, Irgacure 184) to 100 parts by weight of pentaerythritol triacrylate to a 40% by weight methyl isobutyl ketone solution of pentaerythritol triacrylate A resin composition for forming a containing layer was prepared.
The polyimide film obtained above is cut out to 10 cm × 10 cm, the resin composition for forming a resin-containing layer is applied to the atmosphere surface, and ultraviolet rays are irradiated and cured at an exposure amount of 200 mJ / cm ² under a nitrogen stream to form a 10 μm film. A resin-containing layer that is a thick cured film was formed to produce a laminate.

<Adhesion evaluation>
About the adhesiveness of the resin-containing layer of each obtained laminate, a cross-cut test based on JIS K 5600-5-6 was performed, and after repeating the peeling operation with the tape 5 times, the presence or absence of peeling of the resin-containing layer Were observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.
A: No peeling of the resin-containing layer occurred even after repeating the peeling operation with the tape 5 times.
B: After the peeling operation with the tape was performed once, the resin-containing layer was not peeled off, but until the peeling operation with the tape was repeated 5 times, the resin-containing layer was peeled off.
C: After performing the peeling operation with the tape once, the resin-containing layer was peeled entirely along the edge of the cut.

<Pencil hardness>
About the resin content layer side surface of each obtained laminated body, pencil hardness was evaluated by the method similar to a polyimide film. The evaluation results are shown in Table 2.

From Table 2, the polyimide films of Examples 1 to 9 corresponding to the polyimide film of the present invention contain silicon atoms in both the atmosphere surface and the cast surface, but the atmosphere surface has a higher silicon atom concentration and the atmosphere. When the silicon atom concentration on the surface is 10.0 atomic% or less and the tensile modulus is 1.8 GPa or more, the adhesion to the resin-containing layer on the atmosphere surface is improved, and the peelability from the support of the cast surface is improved. The defect resulting from peeling from the support was suppressed. Moreover, it was shown that the polyimide film of Examples 1-9 is what the transparency fall and the fall of surface hardness were suppressed, and the bending tolerance improved. Moreover, in Examples 1-9, the laminated body which the adhesiveness of a polyimide film and a resin content layer improved was able to be obtained.
Moreover, the laminated body of Examples 1-5 had high pencil hardness compared with the laminated body of Examples 6-9. This is because the laminates of Examples 1 to 5 have a reasonably high silicon atom concentration on the polyimide film surface compared to the laminates of Examples 6 to 9, and excellent adhesion between the polyimide film and the hard coat layer. It is presumed that it was caused by what was.
The polyimide film of Comparative Example 1 had a defect due to peeling from the support. This is because the content of silicon atoms in the polyimide is large, the Si concentration on the front and back surfaces of the film is substantially the same, the Si concentration on the cast surface is too large, and the strength of the coating film when peeling the support Is presumed to have been insufficient. In addition, the polyimide film of Comparative Example 1 has a tensile modulus of less than 1.8 GPa, and the result of the static bending test is 0 degree. The pencil hardness was greatly inferior.
The polyimide film of Comparative Example 2 was defective due to peeling from the support. This is presumably because the strength of the coating film was insufficient when the support was peeled off. The polyimide film of Comparative Example 2 had a tensile modulus of less than 1.8 GPa, was inferior in static bending resistance, and was inferior in pencil hardness. Moreover, the laminated body of the comparative example 2 was inferior to the adhesiveness of a polyimide film and a resin content layer. In Comparative Example 2, since the silicon atom concentration on the atmosphere surface exceeded 10 atomic%, the surface of the polyimide film was excessively dissolved by the solvent in the resin-containing layer forming composition. This is probably because a fragile part was generated at the interface.

Claims (14)

Containing polyimide containing silicon atoms,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. A polyimide film having an atomic concentration of 10.0 atomic% or less. Containing polyimides containing silicon atoms, including silicon atoms in a proportion of 0.2% by mass or more and 4.1% by mass or less in all polyimides,
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. A polyimide film having an atomic concentration of 10.0 atomic% or less. Containing polyimide having a structure represented by the following general formula (1-1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
One side and the other side contain silicon atoms, but the silicon atom concentration on one side is different from the silicon atom concentration on the other side and the silicon atom concentration is relatively high. A polyimide film having an atomic concentration of 10.0 atomic% or less.
(In General Formula (1-1), R ^{1 ′} represents a tetravalent group that is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and R ^{2 ′} is a divalent group that is a diamine residue. Represents a group, wherein 2.5 mol% or more and 50 mol% or less of the total amount of R ^{2 ′} is a diamine residue having a silicon atom in the main chain, and 50 mol% or more and 97.5 mol% or less contains silicon atoms. (It is a diamine residue having no aromatic ring or aliphatic ring. N ′ represents the number of repeating units.) Containing polyimide having a structure represented by the following general formula (1),
The total light transmittance measured according to JIS K7361-1 is 85% or more,
Yellowness calculated in accordance with JIS K7373-2006 is 30 or less,
A 15 mm × 40 mm test piece is measured according to JIS K7127, the tensile velocity is 10 mm / min, and the distance between chucks is 20 mm. The tensile elastic modulus at 25 ° C. is 1.8 GPa or more,
Although one surface and the other surface contain silicon atoms, the silicon atom concentration on one surface is different from the silicon atom concentration on the other surface, and the silicon atom concentration on at least one surface is 1. A polyimide film which is 0 atomic% or more.
(In the general formula (1), R ¹ represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, R ² represents a divalent group which is a diamine residue, 50 mol% 10 mol% or more of the total amount of R ² or less is a main one silicon atom in a chain or two with diamine residue, at least 50 mol% 90 mol% or less, having no silicon atom, (A diamine residue having an aromatic ring or an aliphatic ring. N represents the number of repeating units.)   The polyimide contains an aromatic ring, and (i) a fluorine atom, (ii) an aliphatic ring, and (iii) the aromatic rings are connected to each other with a sulfonyl group or an alkylene group which may be substituted with fluorine. The polyimide film according to claim 1, comprising at least one selected from the group consisting of structures. In the polyimide having the structure represented by the general formula (1-1), R ^{1 ′} in the general formula (1-1) is a cyclohexanetetracarboxylic dianhydride residue or cyclopentanetetracarboxylic dianhydride. Product residue, dicyclohexane-3,4,3 ′, 4′-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride residue, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride residue, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride Residues, 3,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4′-oxydiphthalic anhydride residue , And Is at least one tetravalent group selected from the group consisting of 3,4'-oxydiphthalic anhydride residue, a polyimide film according to claim 3. In the polyimide having the structure represented by the general formula (1-1), the diamine residue having the aromatic ring or the aliphatic ring in R ^{2 ′} in the general formula (1-1) is trans- Cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue, 2,2-bis (4-aminophenyl) ) At least one divalent group selected from the group consisting of a propane residue, a 2,2-bis (4-aminophenyl) hexafluoropropane residue, and a divalent group represented by the following general formula (2) The polyimide film according to claim 3 or 6, which is a group.
(In the general formula (2), R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) In the polyimide having the structure represented by the general formula (1), R ¹ in the general formula (1) is a cyclohexanetetracarboxylic dianhydride residue, a cyclopentanetetracarboxylic dianhydride residue, a di Cyclohexane-3,4,3 ′, 4′-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, pyromellitic dianhydride residue, 3,3 ′, 4,4′- Biphenyltetracarboxylic dianhydride residue, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride residue, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3, 4 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 ′-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4′-oxydiphthalic anhydride residue, and 3, '- is at least one tetravalent group selected from the group consisting of oxydiphthalic anhydride residue, a polyimide film according to claim 4. In the polyimide having the structure represented by the general formula (1), the diamine residue having the aromatic ring or the aliphatic ring in R ² in the general formula (1) is a trans-cyclohexanediamine residue, trans-1,4-bismethylenecyclohexanediamine residue, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue, 2,2-bis (4-aminophenyl) propane residue, 2,2-bis (4-aminophenyl) hexafluoropropane residue and at least one divalent group selected from the group consisting of divalent groups represented by the following general formula (2): Item 9. The polyimide film according to Item 4 or 8.
(In the general formula (2), R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)   The surface having a relatively large silicon atom concentration is used for an adhesive surface with a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound. The polyimide film described in 1.   A laminate in which the polyimide film according to any one of claims 1 to 10 and a resin-containing layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound are adjacent to each other.   The radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is a compound having two or more epoxy groups or oxetanyl groups in one molecule. The laminate according to claim 11, wherein   A surface material for display, which is the polyimide film according to any one of claims 1 to 10, or the laminate according to claim 11 or 12.   The display surface material according to claim 13, which is used for a flexible display.