TW201841994A - Polyimide film, laminate, and surface material for display - Google Patents

Abstract

A polyimide film comprising a polyimide that has a structure represented by the following general formula (1), wherein the polyimide contains an aromatic ring and at least one selected from the group consisting of (i) a fluorine atom and (ii) a structure that aromatic rings are bound by a sulfonyl group or an alkylene group that may be substituted with fluorine; a tan [delta] curve that is a value obtained by dividing a loss elastic modulus by a storage elastic modulus, has a peak top only in a temperature range of 150 DEG C or more; a total light transmittance measured in accordance with JIS K7361-1 is 85% or more; a yellowness index calculated in accordance with JIS K7373-2006 is 12 or less; and a humidity expansion coefficient is 10.0 ppm/%RH or less: (the symbols in the general formula (1) are as described in the specification.).

Description

   Polyimide film, laminate, and surface material for display   

The embodiment of the present invention relates to a polyimide film, a laminate, and a surface material for a display.

The thinner plate glass is excellent in hardness and heat resistance, but it is not easy to bend, and it is easy to break when dropped, and there is a problem with workability, and it has the disadvantage of being heavier than plastic products. Therefore, in recent years, from the viewpoint of processability and weight reduction, resin products such as resin base materials and resin films have been replaced with glass products, and research into resin products that have become glass substitute products has been conducted.

For example, with the rapid advancement of electronic devices such as displays such as liquid crystals or organic ELs, and touch panels, the devices are required to be thinner or lighter, and thus to be flexible. In the past, these devices have formed various electronic components, such as thin transistors or transparent electrodes, on a thin plate glass, but by turning the thin plate glass into a resin film, the impact resistance of the panel itself can be achieved Strengthened, flexible, thin or lightweight.

Generally, the polyimide resin is a resin with high heat resistance obtained by subjecting polyamic acid to dehydration ring-closure reaction. The polyamic acid is obtained by the condensation reaction of an aromatic tetracarboxylic anhydride and an aromatic diamine obtain. However, the polyimide resin is usually colored yellow or brown, and therefore it is difficult to use in fields requiring transparency such as display applications or optical applications. Therefore, research is being conducted on applying transparency-improving polyimide to display members. For example, Patent Document 1 describes that as a polyimide resin having high heat resistance, high transparency, and low water absorption, it is disclosed that a compound containing the following amide group and a subgroup represented by the following specific formula Polyimide resin formed by the reaction of amine group-forming compounds and suitable for substrate materials such as flat panel displays or mobile phone devices. The compound containing an amide group is selected from the group consisting of 1,2,4,5-cyclohexanetetracarboxylic acid, 1 , 2,4,5-Cyclohexanetetracarboxylic dianhydride and at least one of the reactive derivatives of the group, the imine-forming compound represented by the specific formula is selected from having at least one At least one compound of phenylene and isopropylidene.

Furthermore, Patent Document 2 discloses a transparent polyimide film, which includes a unit structure derived from an aromatic dianhydride and an aromatic diamine, and further includes an additive derived from tensile strength improvement, or A unit structure of a monomer having a functional group selected from the group consisting of hexafluoro group, sulfone group and oxy group. In Patent Document 3, as a polyimide film excellent in transparency and heat resistance, there is disclosed a polyimide film whose loss elastic modulus is divided by the peak value in the tan δ curve of the value obtained by storing the elastic modulus The vertex is within a certain range.

In addition, in Patent Document 4, a polyimide film used as a substrate of a flexible device discloses that in order to obtain colorless and transparent, the residual stress generated between the inorganic films is low, and the mechanical properties and thermal properties are excellent Polyimide film, using a specific fluorine-based aromatic diamine and a polysiloxane compound having a silicon atom number of 3 to 200 with a siloxane skeleton as the monomer component of the polyimide precursor, acetylene Polyimide film formed by imidization. In Patent Document 4, after forming a polyimide film with an inorganic film (SiN film) using the polyimide precursor described above, no cracks or cracks were observed after repeating the bending test 10 times. The case of peeling is described as (○), and the case where cracking is observed is described as (△).

On the other hand, in Patent Document 5, among the polyimide films used for base films of flexible printed wiring boards and the like, the following polyimide films are disclosed in order to avoid warpage or curling. Polyimide film obtained by using polyamic acid synthesized mainly from aromatic diamine and aromatic tetracarboxylic dianhydride, and the average linear expansion coefficient at 100 ~ 200 ℃ is 18 ~ 28ppm, and the elastic modulus is 4.5GPa or more, hygroscopic expansion coefficient is 13ppm or less, and uses 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride as an essential component as aromatic tetracarboxylic dianhydride.

[Prior Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2006-199945

Patent Document 2: Japanese Special Publication No. 2014-501301

Patent Document 3: Japanese Special Publication No. 2012-503701

Patent Document 4: International Publication No. 2014/098235

Patent Literature 5: Japanese Patent Laid-Open No. 2004-124091

As a conventional flexible display, a display whose display screen is gently curved may be mentioned. Therefore, as the base material or surface material used in the conventional flexible display, it is required to be thin, light, and flexible, that is, different from the glass substrate, even if it is bent, it does not break to a degree of flexibility. However, as a recent flexible display, it is required that the display screen can be folded or bent with a greater curvature and restored without creases.

Mobile devices with folded screens are often transported in a folded state, so the flexible display mounted on the mobile device is required to be in the original state when it returns to a flat state even if it is bent for a long time. The substrate or surface material for flexible displays requires recovery after being bent for a long time (hereinafter, sometimes referred to as static bending resistance).

In the conventional resin film using transparent polyimide, even in the test of flat state and bending state repeated at a fixed cycle, it showed good results. If the bending state is continued for a long time, there will be a fold. Marks, it is difficult to restore to flat, especially the problem of poor static bending resistance in high humidity environments.

In addition, the polyimide film described in Patent Document 5 has poor transparency, and thus it is difficult to use it in fields such as display applications or optical applications.

In view of the above, a resin film having excellent transparency and improved bending resistance in a high humidity environment is required.

The present invention has been completed in view of the above problems, and its main object is to provide a resin film having excellent transparency and improved bending resistance in a high humidity environment.

Furthermore, an object of the present invention is to provide a laminate having the resin film and a surface material for a display as the resin film or the laminate.

An embodiment of the present invention provides a polyimide film containing a polyimide having a structure represented by the following general formula (1). The polyimide includes an aromatic ring and includes a compound selected from (i ) At least one of the group consisting of a fluorine atom and (ii) an aromatic ring connected to each other by a sulfonyl group or a structure which can be substituted by fluorine-substituted alkylene, divided by the loss elastic modulus divided by the storage elasticity In the tanδ curve of the value obtained by the modulus, the peak of the peak is only in the temperature region above 150 ° C, the total light transmittance measured according to JIS K7361-1 is 85% or more, and the yellow calculated according to JIS K7373-2006 The degree is 12 or less, and the humidity expansion coefficient is 10.0 ppm /% RH or less.

(In the general formula (1), R ¹ represents a tetravalent residue of a tetracarboxylic acid residue, R ² represents a divalent residue of a diamine residue, and in the total amount of R ² , the diamine residue having a silicon atom in the main chain The content ratio of the base is 50 mol% or less; n represents the number of repeating units).

In one embodiment of the present invention, there is provided a polyimide film, wherein, in the above general formula (1), R ² represents a diamine residue selected from a group having no silicon atom, and the main chain has one or two Among the diamine residues of at least one silicon atom, there is at least one kind of divalent group. In the total amount of R ^2, the content of diamine residues having 1 or 2 silicon atoms in the main chain is 50 mol% or less.

In one embodiment of the present invention, there is provided a polyimide film, wherein, when a static bending test is performed according to the following static bending test method, the internal angle measured in the test is 120 ° or more.

[Static bending test method]

Bend the test piece of polyimide film cut into 15mm × 40mm at the position of one and a half of the long side, and use the two ends of the long side of the test piece to cut the metal piece with a thickness of 6mm (100mm × 30mm × 6mm ) It is arranged by sandwiching it from the top to the bottom, and fixed with tape in such a way that the overlap between the two ends of the test piece and the metal sheet on the top and bottom is 10mm, and in this state, a glass plate (100mm × 100mm × 0.7mm) clamped from above and below, and the test piece was fixed in a state of being bent with an inner diameter of 6mm. At this time, a dummy test piece is sandwiched between the metal piece and the glass plate where the test piece does not exist, and is fixed with adhesive tape so that the glass plate becomes parallel. After the test piece fixed in the state bent in the above manner is allowed to stand for 24 hours in an environment of 60 ° C and 90% relative humidity (RH), the glass plate and the fixing tape are removed, and the applied to the test piece is released. The power of the test piece. Thereafter, one end of the test piece was fixed, and the inner angle of the test piece 30 minutes after the release of the force applied to the test piece was measured.

In one embodiment of the present invention, there is provided a polyimide film, wherein, in the polyimide having the structure represented by the general formula (1), R ¹ in the general formula (1) includes 4,4 '-(Hexafluoroisopropylidene) diphthalic anhydride residue, 3,4'-(Hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 '-( (Hexafluoroisopropylidene) diphthalic anhydride residues, 4,4'-oxydiphthalic anhydride residues, and 3,4'-oxydiphthalic anhydride residues At least one of the four valence groups.

In one embodiment of the present invention, there is provided a polyimide film, wherein, in the polyimide having the structure represented by the above general formula (1), R ² in the above general formula (1) does not The diamine residue having a silicon atom is at least one kind of divalent group selected from the group consisting of the following divalent groups, the divalent group consisting of: (i) a fluorine atom, and (ii) aromatic At least one kind of divalent group in a group consisting of a structure in which the rings are connected by a sulfonyl group or an alkylene group which may be substituted with fluorine, and a divalent group represented by the following general formula (2).

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

In one embodiment of the present invention, a polyimide film is provided, wherein the value calculated by dividing the yellowness calculated according to the above-mentioned JIS K7373-2006 by the film thickness (μm) is 0.10 or less.

In one embodiment of the present invention, there is provided a polyimide film, wherein, in the above general formula (1), R ² represents at least one divalent group selected from diamine residues having no silicon atom And contains a diamine residue with a hexafluoroisopropylidene skeleton in the main chain, or R ² represents a diamine residue selected from a diamine residue without a silicon atom and a main chain with 1 or 2 silicon atoms At least one kind of divalent group among the residues, and the content of diamine residues having 1 or 2 silicon atoms in the main chain in the total amount of R ² is 2.5 mol% or more and 50 mol% or less.

In one embodiment of the present invention, there is provided a laminate including the polyimide film and the hard coat layer according to one embodiment of the present invention, the hard coat layer containing at least a radically polymerizable compound and a cationic polymerizable compound 1 polymer.

In one embodiment of the present invention, there is provided a laminate in which the radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is in one molecule At least one compound of two or more epoxy groups and oxetanyl groups.

In one embodiment of the present invention, there is provided a surface material for a display, which is a polyimide film according to an embodiment of the present invention described above or a laminate according to an embodiment of the present invention described above.

In one embodiment of the present invention, there is provided a surface material for a flexible display, which is a polyimide film according to an embodiment of the present invention described above or a laminate according to an embodiment of the present invention described above.

According to the present invention, it is possible to provide a resin film having excellent transparency and improved bending resistance in a high humidity environment.

Furthermore, according to the present invention, it is possible to provide a laminate having the resin film and a surface material for a display as the resin film or the laminate.

1‧‧‧Sample

2‧‧‧Metal sheet

3a‧‧‧glass plate

3b‧‧‧glass plate

4a‧‧‧Dummy test piece

4b‧‧‧Dummy test piece

Figure 1 is a diagram for explaining the method of static bending test.

2 is a graph showing the tan δ curve of Example 2. FIG.

I. Polyimide film

A polyimide film according to an embodiment of the present invention is a polyimide film containing polyimide having a structure represented by the following general formula (1), and the polyimide contains an aromatic ring , And contains at least one selected from the group consisting of (i) fluorine atoms, and (ii) aromatic rings connected to each other by a sulfonyl group or a fluorine-substituted alkylene structure, which is a loss The tan δ curve of the value obtained by dividing the elastic modulus by the storage elastic modulus has the peak of the peak only in the temperature region above 150 ° C, and the total light transmittance measured according to JIS K7361-1 is 85% or more, based on JIS For K7373-2006, the calculated yellowness is 12 or less, and the humidity expansion coefficient is 10.0 ppm /% RH or less.

(In the general formula (1), R ¹ represents a tetravalent residue of a tetracarboxylic acid residue, R ² represents a divalent residue of a diamine residue, and in the total amount of R ² , the diamine residue having a silicon atom in the main chain The content ratio of the base is 50 mol% or less; n represents the number of repeating units)

The polyimide film of the present invention has the peak of the peak only in the temperature region above 150 ° C in the tan δ curve which is the value obtained by dividing the loss elastic modulus by the storage elastic modulus. In the above tan δ curve, if the peak of the peak is less than 150 ° C, the molecular chain of the polyimide is likely to move and be easily plastically deformed, which may deteriorate the bending resistance. In contrast, in the present invention The peak of the peak does not exist below 150 ℃, so the mobility of the molecular chain is suppressed and it is not easy to plastically deform, which can improve the bending resistance.

In addition, in the above tan δ curve, if the peak of the peak is only in the temperature range above 150 ° C, even in a high-temperature environment, such as in a car in summer, the bending resistance will be damaged due to thermal deformation. It is suppressed, so the bending resistance is improved even in a high-temperature environment.

In addition, in the above tan δ curve, if the peak of the peak is only in the temperature range of 150 ° C. or higher, the tensile elastic modulus tends to increase, and the surface hardness tends to increase.

In terms of improving bending resistance or surface hardness, the polyimide film of the present invention is more preferably in the above tan δ curve, only having a peak of the peak in the temperature region above 200 ° C, and even more preferably only 220 The temperature region above ℃ has the peak of the peak. On the other hand, in terms of lowering the baking temperature, it is preferable that the tan δ curve has a peak of a peak in a temperature range of 380 ° C or lower.

In addition, the polyimide film of the present invention preferably has a temperature range of -150 ° C or more and less than 150 ° C, and more preferably a temperature range of -70 ° C or more and less than 150 ° C. The apex of the peak in the tanδ curve is more preferably not in the temperature region below 100 ° C without the apex of the peak in the tanδ curve, more preferably in the temperature region below 0 ° C without the peak in the tanδ curve vertex. In the case of having a diamine residue with a long siloxane bond in the main chain or a large amount of diamine residues with a silicon atom in the main chain, it exists in such a low temperature region in the above tanδ curve. The peak of the peak, but the silicon atom-containing diamine residue used in the present invention has a relatively short amount of relatively short siloxane bond like the peak of the peak in the above tan δ curve in such a low temperature region Choice. Therefore, as compared with a polyimide film having a diamine residue with a main chain having a long siloxane bond like a glass transition temperature in a temperature range of -150 ° C to 0 ° C, the room temperature The decrease in tensile modulus of elasticity is also suppressed, and sufficient surface hardness as a protective film can be maintained.

The above tanδ curve is determined by dynamic viscoelasticity measurement and based on the relationship between temperature and tanδ (tanδ = loss elastic modulus (E ") / storage elastic modulus (E ')), the maximum value of the peak can be maximized The temperature of the apex of the peak is set as an index of the glass transition temperature. For dynamic viscoelasticity measurement, for example, the dynamic viscoelasticity measurement device RSA-G2 (TA Instruments Japan) can be used to set the measurement range to -150 ° C or more and 490 ° C The following is based on a frequency of 1 Hz and a heating rate of 5 ° C./min. In addition, the sample width can be measured at 5 mm and the distance between the fixtures at 20 mm. In the analysis of peaks and bending points, visual evaluation is not performed but After digitizing the data, it is analyzed according to the numerical values.

In addition, in the curve of temperature (horizontal axis) and tanδ (tanδ = loss elastic modulus (E ") / storage elastic modulus (E ')) (vertical axis), the so-called peak means the value of tanδ is 0.2 Above, preferably 0.3 or more and having a bending point as a maximum value, and the peak width between the peak and valley of the peak is 3 ° C or more, the noise from the measured curve is thinner The change was not observed as the peak of the peak of the above-mentioned peak.

The polyimide film of the present invention has a total light transmittance of 85% or more measured in accordance with the aforementioned JIS K7361-1. In this way, due to the high penetration rate, the transparency becomes good and can be used as a substitute for glass. The total light transmittance of the polyimide film of the present invention measured in accordance with the above-mentioned JIS K7361-1 is more preferably 88% or more, still more preferably 89% or more, and particularly preferably 90% or more.

In the case of the polyimide film of the present invention having a thickness of 5 μm or more and 100 μm or less, the total light transmittance measured according to the above-mentioned JIS K7361-1 is preferably 85% or more, more preferably 88% or more, and still more Good is more than 89%, especially good is more than 90%.

In addition, in the case of the polyimide film of the present invention having a thickness of 50 μm ± 5 μm, the total light transmittance measured according to the above JIS K7361-1 is preferably 85% or more, more preferably 88% or more, and still more Good is more than 89%, especially good is more than 90%.

The total light transmittance measured according to JIS K7361-1 can be measured, for example, by a haze meter (for example, HM150 manufactured by Murakami Color Technology Research Institute). In addition, the total light transmittance of different thicknesses can be calculated according to the measured value of the total light transmittance of a certain thickness and according to the law of Lambert-Beer's Law, and the conversion can be used value.

Specifically, according to Lambert-Beer law, the penetration rate T is expressed as follows: Log ₁₀ (1 / T) = kcb

(k = constant constant of substance, c = concentration, b = optical path length)

Assuming that in the case of the penetration rate of the film, even if the film thickness changes and the density is fixed, c becomes a constant, so the above formula can be expressed as follows using the constant f: Log ₁₀ (1 / T) = fb

(f = kc). Here, if the penetration rate at a certain film thickness is known, the inherent constant f of each substance can be obtained. Therefore, if T = 1/10 ^{f is used. In} the formula of ^b , substituting the inherent constant into f and substituting the target film thickness into b, the penetration rate at the required film thickness can be obtained.

In addition, the polyimide film of the present invention has a yellowness (YI value) calculated in accordance with the above-mentioned JIS K7373-2006 of 12 or less. In this way, due to the low yellowness, the coloration of the yellow tone is suppressed, the light transmittance is improved, and it can be used as a glass substitute material. The yellowness (YI value) calculated based on the aforementioned JIS K7373-2006 is preferably 10 or less, more preferably 7 or less, and still more preferably 5 or less.

In the case of the polyimide film of the present invention having a thickness of 5 μm or more and 100 μm or less, the yellowness (YI value) calculated according to the above JIS K7373-2006 is preferably 12 or less, more preferably 10 or less, and even more preferably 7 or less, especially 5 or less.

In addition, in the case of the polyimide film of the present invention having a thickness of 50 μm ± 5 μm, the yellowness (YI value) calculated according to the above JIS K7373-2006 is preferably 12 or less, more preferably 10 or less, and even more preferably 7 or less, especially 5 or less.

Furthermore, the yellowness (YI value) can be based on JIS K7373-2006, using an ultraviolet-visible near-infrared spectrophotometer (for example, Japanese Spectroscopy Co., Ltd. V-7100), using a spectrophotometric method and using auxiliary illuminant C, 2 degree field of view, measuring the penetration rate in the range from 250nm to 800nm at 1nm intervals to obtain the three stimulus values X, Y, Z in the XYZ color system, according to the values of X, Y, Z and according to Calculated by the following formula.

YI = 100 (1.2769X-1.0592Z) / Y

In addition, according to the measured value of the yellowness of a certain thickness, the yellowness of different thicknesses is for each penetration at each wavelength measured at 5nm intervals between 380nm and 780nm for a sample with a specific film thickness The rate is calculated in accordance with the Lambert-Beer law in the same way as the above-mentioned total light transmittance, and the converted value of each transmittance at each wavelength with different thickness is calculated and used based on the converted value.

In addition, in terms of suppressing the coloration of the yellow tone, improving the light transmittance, and suitable for use as a glass substitute material, the polyimide film of the present invention is divided by the yellowness (YI value) calculated according to the above JIS K7373-2006 The value obtained by the film thickness (μm) (YI value / film thickness (μm)) is preferably 0.10 or less, more preferably 0.04 or less, and still more preferably 0.03 or less.

In addition, in the present invention, the value obtained by dividing the above-mentioned yellowness (YI value) by the film thickness (μm) (YI value / film thickness (μm)) is rounded to a decimal point in accordance with Rule B of JIS Z8401: 1999 The value obtained from the second digit.

In addition, the moisture expansion coefficient of the polyimide film of the present invention is 10.0 ppm /% RH or less. In this way, because it is a polyimide film with a small humidity expansion coefficient, it is not easily affected by humidity. Even in a high humidity environment, it can suppress the damage to bending resistance caused by the deformation caused by moisture absorption. Therefore, the bending resistance in a high humidity environment is improved. Regarding the above-mentioned humidity expansion coefficient, among them, it is preferably 9.0 ppm /% RH or less, more preferably 8.0 ppm /% RH or less, still more preferably 7.5 ppm /% RH or less, still more preferably 6.5 ppm /% RH or less, Furthermore, it is more preferably 3.0 ppm /% RH or less.

Furthermore, in the present invention, the humidity expansion coefficient of the polyimide film can be measured by the following method.

The test piece cut into a polyimide film of 5 mm × 20 mm was sufficiently dried, and the test piece was set so that the distance between the jigs was 15 mm and the tensile load in the longitudinal direction was 5 g. Fix the temperature at 25 ° C and change the humidity to 15% RH, 20% RH, 50% RH. Calculate the average elongation per unit humidity of 1% based on the tensile strength of the test pieces at 20% RH and 50% RH, and Set as the humidity expansion coefficient. In addition, the calculation formula is shown below.

Humidity expansion coefficient (ppm /% RH) = (X × 10 ⁶ ) / (Y × Z)

X: the value of the test piece length at 50% RH minus the test piece length at 20% RH

Y: Humidity change from 20% RH to 50% RH (50-20 (% RH))

Z: Length of test piece at 20% RH

As a measuring device, steam TMA / S 8227A1 manufactured by Rigaku can be used.

In addition, the elongation of the test piece is always monitored, recorded every 1 second, and measured in the following order.

In the following measurement, the so-called fixed length of the test piece means that the change in the sample length in 30 minutes is 0.1 μm or less.

1. The environment of the test piece is stable at a humidity of 15% RH. After the length of the test piece becomes fixed without change, it is maintained for more than 30 minutes

2. Then, the environment of the test piece is stabilized at a humidity of 20% RH, and the length of the test piece becomes fixed without change, and it is kept for more than 30 minutes (measure the length of the test piece)

3. Then, the environment of the test piece is stable at a humidity of 50% RH, and the length of the test piece becomes fixed without change, and it is kept for more than 30 minutes (measure the length of the test piece)

4. Calculate the difference between the length of the test piece at 20% RH and 50% RH, divide by 30 to calculate the elongation per unit humidity of 1%

The thickness of the test piece of the polyimide film is not particularly limited, but it is preferably in the range of 5 μm or more and 200 μm or less, more preferably in the range of 10 μm or more and 150 μm or less, and still more preferably in the range of 15 μm or more and 100 μm or less. Within.

According to the present invention, the polyimide system contained in the polyimide film includes an aromatic ring and is selected from the group consisting of (i) fluorine atoms and (ii) aromatic rings substituted with sulfonyl groups or fluorine-substituted At least one of the group consisting of the structures connected by alkylene extension, and further, when the diamine residue is based on the main chain having silicon atoms, the main chain has two of the silicon atoms in the total amount of diamine residues A polyimide with a specific structure with an amine residue content of 50 mol% or less, and by making a specific temperature range with the peak of the above tan δ curve, the above specific total light transmittance, the above specific The polyimide film with yellowness and the above-mentioned specific humidity expansion coefficient can provide a resin film with excellent transparency and improved bending resistance in a high humidity environment.

The inventors focused on polyimide in resin. Polyimide is known to be excellent in heat resistance due to its chemical structure. In addition, regarding the polyimide film, it is known that the arrangement of molecular chains inside thereof will form a certain order structure. Therefore, it is considered that the polyimide film can be restored from a bent state to a flat state at room temperature.

On the other hand, it was confirmed that if the polyimide is in a high-humidity environment, the recovery from the bent state tends to be deteriorated, especially if the state of bending the film for a long time continues, there will be creases that will not recover To a flat situation. Polyimide absorbs moisture in a high-humidity environment, by which the absorbed moisture acts like a plasticizer and the film is easily plastically deformed, so it is speculated that even if the bending force is removed, it is not easy to recover.

In contrast, the present inventors have found that a polyimide film containing the above-mentioned specific polyimide and having the above-mentioned specific characteristics has excellent transparency and has excellent bending resistance even in a high-humidity environment . It is considered that the polyimide film of the present invention contains an aromatic ring by the above-mentioned specific polyimide, and contains an aromatic ring selected from (i) a fluorine atom, and (ii) the aromatic ring is mutually substituted with a sulfonyl group or may be substituted with fluorine At least one of the groups formed by the structure of the alkylene linkages is improved in transparency, and when the diamine residue does not have a silicon atom or has a silicon atom, the main chain has silicon atoms The diamine residue is 50 mol% or less based on the total amount of diamine residues, and the peak of the above tan δ curve is within a specific temperature range, and the deterioration of the bending resistance is suppressed, and then the humidity of the polyimide film The expansion coefficient is 10.0ppm /% RH or less, and is not easily affected by humidity, so it has excellent transparency and has excellent bending resistance even in a high humidity environment.

It is considered that when the content of diamine residues with silicon atoms is excessive or the peak of the peak of the above tan δ curve exists in a lower temperature range, such as 150 ° C, the polyimide in the polyimide film The mobility of amine molecules is improved, plastic deformation is easy and bending resistance is easily deteriorated. If the humidity expansion coefficient of the polyimide film exceeds 10.0ppm /% RH, even if the bending resistance is good under a dry environment such as humidity below 20% RH, the impact of moisture absorption is also large, so high humidity The bending resistance under the environment becomes poor. It is presumed that the reason is that the polyimide film having a large humidity expansion coefficient expands in volume under high-temperature and high-humidity environment, and the interaction between molecular chains becomes insufficient. Therefore, when a curved shape is obtained, the curved portion is easily plastically deformed.

Hereinafter, the polyimide film of the present invention will be described in detail.

The polyimide film of the present invention contains a polyimide having the structure represented by the above general formula (1), and has the above-mentioned specific characteristics. As long as the effect of the present invention is not impaired, it may further contain other components and may have other configurations.

Polyimide is obtained by reacting a tetracarboxylic acid component and a diamine component. It is preferable to obtain a polyamic acid by polymerization of a tetracarboxylic acid component and a diamine component, and then perform imidate. Acetylimidization can be carried out either thermally or chemically. In addition, it can also be produced by a method using a combination of thermal imidization and chemical imidization.

The polyimide film of the present invention contains a polyimide having the structure represented by the general formula (1).

Here, the term "tetracarboxylic acid residue" refers to a residue obtained by removing four carboxyl groups from tetracarboxylic acid, and represents the same structure as the residue obtained by removing the acid dianhydride structure from tetracarboxylic dianhydride .

The diamine residue refers to a residue obtained by removing two amine groups from the diamine.

In the present invention, the polyimide having the structure represented by the above general formula (1) contains an aromatic ring, and includes a group selected from (i) a fluorine atom, and (ii) the aromatic ring each with a sulfonyl group or a At least one member of the group consisting of structures connected by fluorine-substituted alkylene groups. The polyimide having the structure represented by the above general formula (1) 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 The rigidity and alignment are improved, and the surface hardness is improved, but the rigid aromatic ring skeleton tends to extend the absorption wavelength to a longer wavelength, and the tendency of the transmittance of the visible light region to decrease.

If the polyimide contains (i) a fluorine atom, the electronic state in the polyimide skeleton is less likely to cause charge migration, and in this respect, the light transmittance is improved.

If the polyimide contains (ii) a structure in which the aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine, by conjugation of the π electrons in the polyimide skeleton Break, can suppress the charge migration within the skeleton, in this respect, the light transmittance is improved.

As the polyimide having the structure represented by the general formula (1), among them, in terms of improving the light transmittance and increasing the surface hardness, a polyimide containing a fluorine atom can be preferably used.

In the structure in which (ii) the aromatic rings are connected to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine, in terms of improving the bending resistance in a high humidity environment, the The alkyl group is preferably 40% or more of hydrogen atoms, more preferably 70% or more, and still more preferably 90% or more substituted by fluorine.

In addition, in terms of improving bending resistance in a high humidity environment, the alkylene group preferably has a carbon number of 1 or more and 5 or less, and more preferably a carbon number of 1 or more and 3 or less.

In addition, regarding the polyimide having the structure represented by the general formula (1), in terms of bending resistance in a high humidity environment, the total amount of R ¹ in the general formula (1) and When the total amount of R ² is set to 100 mol%, the main chain or side chain has at least one selected from the group consisting of aliphatic hydrocarbon groups having 4 or more carbon atoms, amide groups, alkoxy groups, and carboxyl groups 1 kind, and the total of tetracarboxylic acid residues and diamine residues excluding any of silicon atom and fluorine atom is preferably less than 20 mol%, more preferably 5 mol% or less, and even more preferably 0 mol%. If it contains a tetracarboxylic acid residue having at least one member selected from the group consisting of an aliphatic hydrocarbon group having 4 or more carbon atoms, an amide group, an alkoxy group, and a carboxyl group, and excluding any one of silicon atoms and fluorine atoms And diamine residues, the humidity expansion coefficient tends to increase.

In addition, the polyimide having the structure represented by the general formula (1) above does not contain a silicon atom in terms of bending resistance in a high-humidity environment, and R ¹ and R ² in the general formula (1) above In the case of any one of fluorine atoms and fluorine atoms, the total carbon number of the aliphatic hydrocarbon groups possessed by R ¹ and R ² in the general formula (1) is preferably 7 or less, more preferably 6 or less, and still more preferably 5 or less.

In terms of bending resistance in a high humidity environment, the total number of repeating units having the structure represented by the above general formula (1) in which R ¹ and R ² do not include any of silicon atoms and fluorine atoms is 100 moles In%, the ratio of repeating units in which R ¹ and R ² do not include any of silicon atoms and fluorine atoms and the total carbon number of the aliphatic hydrocarbon groups possessed by R ¹ and R ² exceeds the above upper limit value is preferably not It is 10 mol%, preferably 5 mol% or less, and more preferably 0 mol%.

The tetracarboxylic acid residue in R ¹ of the above general formula (1) is not particularly limited, and in terms of surface hardness, it is preferably removed from the tetracarboxylic dianhydride having an aromatic ring without a silicon atom Residue after acid dianhydride structure.

Examples of the tetracarboxylic dianhydride having no silicon atom and having an aromatic ring include pyromellitic dianhydride, 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, and 2, 2 ', 3,3'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyl Tetracarboxylic 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) lanthanide dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3- Dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) 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] phthalic anhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] phthalic anhydride, 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 Anhydride, 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} benzene dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] benzene } Benzene dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} thioether dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy Group] phenyl) sulfide dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride, 3,4'-(hexafluoroisopropylidene) diphthalic anhydride, 3,3 '-(Hexafluoroisopropylidene) diphthalic anhydride, 4,4'-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-benzene Tetracarboxylic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrene tetracarboxylic dianhydride Wait.

These can be used alone or in combination of two or more.

Regarding the tetracarboxylic acid residue in R ¹ of the above general formula (1), it is preferable to include a member selected from the group consisting of 4,4 ′-(in terms of light transmittance and bending resistance and surface hardness) Hexafluoroisopropylidene) diphthalic anhydride residue, 3,4 '-(hexafluoroisopropylidene) diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene) ) At least one of the group consisting of diphthalic anhydride residues, 4,4'-oxydiphthalic anhydride residues, and 3,4'-oxydiphthalic anhydride residues 4 Valence group, R ¹ in the above general formula (1) more preferably contains a residue selected from 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride, 3,4 ^′ -(hexafluorosulfide (Isopropyl) diphthalic anhydride residue, 3,3 '-(hexafluoroisopropylidene) diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, And 3,4'-oxydiphthalic anhydride residues, at least one kind of tetravalent group, and further preferably selected from 4,4 '-(hexafluoroisopropylidene) di-ortho Phthalic anhydride residues, 3,4 '-(hexafluoroisopropylidene) diphthalic anhydride residues, and 3,3'-(hexafluoroisopropylidene) diphthalic anhydride residues At least one kind of four-valent group in the group consisting of groups.

In the above R ¹ , it is preferred that the total contains more than 50 mol% of the appropriate residues, further preferably 70 mol% or more of the appropriate residues, and more preferably 90 mols. % Of these appropriate residues.

In the above general formula (1), R ² represents a diamine residue, which is a divalent group. In the total amount of R ² , the content ratio of the diamine residue having a silicon atom in the main chain is 50 mol% or less. Wherein, the diamine residue in R ² is at least one kind of divalent residue selected from diamine residues having no silicon atom and diamine residues having 1 or 2 silicon atoms in the main chain, In terms of excellent bending resistance in a high-humidity environment and excellent compatibility with surface hardness, the content of diamine residues having 1 or 2 silicon atoms in the main chain of the total amount of R ² is better It is below 50 mol%.

As the diamine residue not having a silicon atom, in terms of surface hardness, a diamine residue not having a silicon atom and having an aromatic ring is preferred. Here, the diamine residue having no silicon atom and having an aromatic ring may be a residue obtained by removing two amine groups from the diamine having no silicon atom and having an aromatic ring.

As the diamine having no silicon atom and having an aromatic ring, for example, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 2,2-bis ( 4-aminophenyl) propane, 2,2-bis (4-aminophenyl) hexafluoropropane, p-phenylenediamine, o-phenylenediamine, 3,4'-diaminodiphenyl ether, 4 , 4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl Methone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzylanilide, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenyl Phenylmethane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1, 1,1,3,3,3-hexafluoropropane, 1,1-bis (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4- Aminophenyl) -1-phenylethane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis ( 4-aminobenzyl) benzene, 1,4-bis (4-aminobenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene , 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-bis (trifluoromethyl) benzyl) benzene , 1,4-bis (4-amino-α, α-bis (trifluoromethyl) benzyl) benzene, N, N'-bis (4-aminophenyl) p-xylylenediamine, 9 , 9-bis (4-aminophenyl) stilbene, 3,3'-dichloro-4,4'-diaminobiphenyl, diaminobiphenyl, 3,3'-dimethoxy-4,4'- Diamine biphenyl, 3,3'-dimethyl-4,4'-diamine biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (4-amine Phenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] phenanthrene, bis [4- (4-aminophenoxy) phenyl] ether, 2,2- Bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3 -Hexafluoropropane, 1,3-bis [4- (4-aminophenoxy) benzyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzyl group ] Benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzyl] diphenyl ether, 4,4'-bis [4- (4-Amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4'-bis (4- (4-amino-α, α-dimethylbenzyl) Phenoxy] diphenyl sulfone, 4,4'-bis [4- (4-aminophenoxy) phenoxy] diphenyl sulfone, 3,3'-diamino-4,4'- Diphenoxybenzophenone, 3,3'-diamino-4, 4'-diphenyloxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone Ketone, 6,6'-bis (4-aminophenoxy) -3,3,3 ', 3'-tetramethyl-1,1'-spirobiindan (spirobiindan), etc., and the above-mentioned diamines The diamine in which a part or all of the hydrogen atoms on the aromatic ring is substituted with a substituent selected from fluoro, methyl, methoxy, trifluoromethyl, or trifluoromethoxy.

These can be used alone or in combination of two or more.

Regarding the diamine residue not having a silicon atom in R ² of the above general formula (1), in terms of light transmittance and bending resistance and surface hardness, it is preferably selected from the following 2 At least one kind of divalent group in the group consisting of valence groups, the divalent group: comprising an alkylene group selected from (i) fluorine atom, and (ii) aromatic ring with sulfonyl group or fluorine substitution At least one kind of divalent group in the group consisting of a structure in which the groups are connected, and a divalent group represented by the following general formula (2), the above-mentioned fluorine-substituted alkylene group preferably has a carbon number of 3 or less. Further, regarding the diamine residue having no silicon atom in R ² of the above general formula (1), among them, at least one divalent group selected from the group consisting of the following divalent groups is preferred, Bivalent group: comprising at least one selected from the group consisting of (i) fluorine atom, and (ii) a structure formed by linking aromatic rings with sulfonyl group or fluorine-substituted alkylene group The divalent group and the divalent group represented by the following general formula (2).

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

Regarding the alkyl group in R ³ and R ⁴ in the general formula (2), in terms of improving the bending resistance under high humidity, the carbon number is preferably 1 or more and 3 or less, more preferably the carbon number 1 or more and 2 or less.

From the viewpoint of light transmittance and bending resistance, surface hardness, and low hygroscopicity, the diamine residue having no silicon atom in R ² of the above general formula (1) is more preferably selected Free 4,4'-diaminodiphenylsulfone residue, 3,4'-diaminodiphenylsulfone residue, 2,2-bis (4-aminophenyl) propane residue, 3, 3'-bis (trifluoromethyl) -4,4 '-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl) bis (4,1-phenoxy Radical)] diphenylamine residue, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane residue, 2,2 -Bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane residue, represented by the above general formula (2) and R ³ and R ⁴ is at least one divalent group in the group consisting of divalent groups of perfluoroalkyl groups, and is more preferably selected from 3,3'-bis (trifluoromethyl) -4,4 '-[(1 , 1,1,3,3,3-hexafluoropropane-2,2-diyl) bis (4,1-phenoxy)] diphenylamine residue, and represented by the general formula (2) above and R ³ and R ⁴ are at least one divalent group in the group consisting of perfluoroalkyl divalent groups.

In the above R ² , in a total of 100 mol% of diamine residues having no silicon atom, it is preferable that the total contains more than 50 mol% of these suitable residues, and further preferably contains 65 mol More than% of these suitable residues, and more preferably more than 80 mole% of these suitable residues.

In terms of the improvement of bending resistance in a high-humidity environment and the aspect of light transmittance, as a preferred embodiment, it can be listed in the above general formula (1), R ² represents At least one kind of divalent residue in the diamine residue of the silicon atom, and including the case where the main chain has a diamine residue having a hexafluoroisopropylidene skeleton. The diamine residue having a hexafluoroisopropylidene skeleton in the main chain preferably includes a structure in which aromatic rings are connected to each other by a hexafluoroisopropylidene group.

When in the above general formula (1) R ² is not contained in the main chain of silicon atoms of a diamine having the case of residues, R in the general formula (1) represents the ^2-diamine having no silicon atom is selected from the residues of At least one kind of divalent group, with respect to the diamine residue having no silicon atom, in terms of light transmittance and bending resistance, surface hardness, and low hygroscopicity, it is more preferable 1 A diamine residue containing a hexafluoroisopropylidene skeleton in the main chain and a ratio (number%) of fluorine atoms to carbon atoms of 30% or more in the molecule, more preferably including the use of hexafluoroisopropylidene A structure in which an aromatic ring is connected to each other by a group, and a structure in which an aromatic ring is connected to each other by an oxy group, and the ratio (number%) of fluorine atoms to carbon atoms is 30% or more of diamine residues.

When R ² in the general formula (1) does not contain a diamine residue having a silicon atom in the main chain, the diamine residue having no silicon atom is specifically selected from the group consisting of 3, 3 '-Bis (trifluoromethyl) -4,4'-((1,1,1,3,3,3-hexafluoropropane-2,2-diyl) bis (4,1-phenoxy )] Diphenylamine residue, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane residue, 2,2- Bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane residue, 2- (3-aminophenyl) -2- (4 -Aminophenyl) -1,1,1,3,3,3-hexafluoropropane and 2,2-bis (4-aminophenyl) hexafluoropropane Diamine residues, preferably selected from 3,3'-bis (trifluoromethyl) -4,4 '-[(1,1,1,3,3,3-hexafluoropropane-2,2- Diyl) bis (4,1-phenoxy)] diphenylamine residue, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3 , 3-Hexafluoropropane residue, and 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane residue One or more diamine residues in the group, preferably 3,3'-bis (trifluoromethyl) -4,4 '-[(1,1,1,3,3,3-hexa Fluoropropane-2,2-diyl) bis (4,1-phenoxy)] diphenylamine residue.

In the case where R ² in the above general formula (1) does not contain a diamine residue having a silicon atom in the main chain, in the above R ² , in the total 100 mole% of the diamine residues having no silicon atom It is preferable to contain 70 mol% or more of the above-mentioned suitable diamine residues without silicon atoms in total, more preferably 80 mol% or more of the above-mentioned suitable diamine residues without silicon atoms, and more Preferably, it contains 90 mol% or more of the above-mentioned suitable diamine residues without silicon atoms.

The diamine residue having a silicon atom in the main chain can be set as the residue after removing two amine groups in the diamine having a silicon atom in the main chain.

Examples of the diamine residue having a silicon atom in the main chain include the diamine represented by the following general formula (A).

(In the general formula (A), L independently represents a direct bond or -O- bond, and R ¹⁰ independently represents a carbon number of 1 or more and 20 or less which may have a substituent, and may also include an oxygen atom or a nitrogen atom Monovalent hydrocarbon group; R ¹¹ independently represents a divalent hydrocarbon group having a carbon number of 1 or more and 20 or less, which may have a substituent, and may also include an oxygen atom or a nitrogen atom; k is a number from 0 to 200; multiple L, R ¹⁰ And R ¹¹ can be the same or different)

Examples of the monovalent hydrocarbon group represented by R ¹⁰ include alkyl groups having 1 to 20 carbon atoms, aryl groups, and combinations thereof. The alkyl group may be linear, branched, or cyclic, or may be a combination of linear or branched and cyclic.

The alkyl group having a carbon number of 1 or more and 20 or less is preferably an alkyl group having a carbon number of 1 or more and 10 or less, and specific examples include methyl, ethyl, propyl, isopropyl, butyl, and iso Butyl, tertiary butyl, pentyl, hexyl, etc. The cyclic alkyl group is preferably a cycloalkyl group having a carbon number of 3 or more and 10 or less. Specific examples include cyclopentyl and cyclohexyl. The aryl group is preferably an aryl group having 6 or more carbon atoms and 12 or less. Specific examples include phenyl group, tolyl group, and naphthyl group. In addition, the monovalent hydrocarbon group represented by R ¹⁰ may be an aralkyl group, and examples thereof include benzyl, phenylethyl, and phenylpropyl groups.

Examples of the hydrocarbon group which may contain an oxygen atom or a nitrogen atom include at least one of ether bond, carbonyl bond, ester bond, amide bond, and imine bond (-NH-). The above-mentioned monovalent hydrocarbon group is bonded.

The substituent that the monovalent hydrocarbon group represented by R ¹⁰ may have is not particularly limited as long as the effect of the present invention is not impaired, and examples include halogen atoms such as fluorine atoms and chlorine atoms, and hydroxyl groups.

The monovalent hydrocarbon group represented by R ¹⁰ is preferably an alkyl group having a carbon number of 1 or more and 3 or less, or a carbon number of 6 or more and 10 or less in terms of the improvement of bending resistance and surface hardness. Aryl. 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 alkylene groups having 1 to 20 carbon atoms, aryl groups, and combinations of these. The alkylene group may be linear, branched, or cyclic, or may be a combination of linear or branched and cyclic.

The alkylene group having 1 to 20 carbon atoms is preferably an alkylene group having 1 to 10 carbon atoms. Examples include methylene, ethyl, various propyl groups, and various butyl groups. A group such as a combination of linear or branched linear alkylene group and cyclic alkylene group such as cyclohexyl group.

The above arylene group is preferably a C 6-12 arylene group. Examples of the arylene group include phenylene group, biphenylene group, naphthyl group, etc., and the following aromatic groups Ring substituents.

Examples of the divalent hydrocarbon group which may contain an oxygen atom or a nitrogen atom include at least one kind of ether bond, carbonyl bond, ester bond, amide bond, and imine bond (-NH-). The basis of bonding.

The substituent that the divalent hydrocarbon group represented by R ¹¹ may have may be the same as the substituent that the monovalent hydrocarbon group represented by R ¹⁰ may have.

The divalent hydrocarbon group represented by R ¹¹ is preferably an alkylene group having a carbon number of 1 or more and 6 or less, or a carbon number of 6 or more and 10 or less, in terms of improvement in bending resistance and surface hardness. The arylene group is more preferably an alkylene group having 2 to 4 carbon atoms.

k is a number from 0 to 200. The average value of k is preferably 0 or more and 6 or less, preferably 0 or more in terms of adhesion to the functional layer, suppression of interference fringes, and improvement of bending resistance and surface hardness. 4 or less. Among them, k is preferably 0 or 1.

Among them, from the viewpoint of suppressing the mobility of molecules and imparting bending resistance and improving the surface hardness, the diamine residue having a silicon atom in the main chain is preferably the second having 1 or 2 silicon atoms in the main chain Amine residues.

If a diamine residue with a large molecular weight having a large number of silicon atoms in the main chain is used, even if a relatively small amount is added, the glass transition temperature is likely to be lowered and the bending resistance or surface hardness may be deteriorated.

Examples of the diamine having one silicon atom in the main chain include the diamine represented by the following general formula (A-1) in which k = 0 among the diamines represented by the above general formula (A). Further, as the diamine having two silicon atoms in the main chain, for example, among the diamines represented by the above general formula (A), the diamine represented by the following general formula (A-2) where k = 1.

(In general formula (A-1) and general formula (A-2), L independently represents a direct bond or -O- bond, and R ¹⁰ independently represents that they may have a substituent, and may also include an oxygen atom or nitrogen A monovalent hydrocarbon group having 1 or more carbon atoms and 20 or less carbon atoms; R ¹¹ independently represents a divalent hydrocarbon group having 1 or more carbon atoms and 20 or less carbon atoms which may have a substituent, and may also include an oxygen atom or a nitrogen atom; multiple L, (R ¹⁰ and R ¹¹ may be the same or different)

The molecular weight of the diamine residue having a silicon atom in the main chain is preferably 3,000 or less, preferably 2,000 or less, preferably in terms of suppressing the mobility of the molecule, imparting bending resistance, and giving consideration to the surface hardness. It is 1000 or less, more preferably 800 or less, and even more preferably 500 or less, particularly preferably 300 or less.

Furthermore, the molecular weight of the diamine residue having 1 or 2 silicon atoms in the main chain is preferably 1,000 or less, more preferably 800 or less, still more preferably 500 or less, and particularly preferably 300 or less.

The molecular weight of the diamine residue is calculated by subtracting the molecular weight (32) of two amine groups (-NH ₂ ) from the molecular weight of the diamine.

The diamine residue having a silicon atom in the main chain can be used alone or in combination of two or more.

Further, in terms of light transmittance, and bending resistance and surface hardness, the polyimide having the structure represented by the general formula (1) is preferably R ² in the general formula (1) The diamine residue having a silicon atom in the main chain is a diamine residue having 2 silicon atoms, and from the viewpoint of the ease of acquisition or the balance between light transmittance and surface hardness, 1,3- is preferred Bis (3-aminopropyl) tetramethyldisilaxane residue, 1,3-bis (4-aminobutyl) tetramethyldisilaxane, 1,3-bis (5-amino group Amyl) tetramethyldisilaxane, etc.

When in the above general formula (1) containing the R ² backbone with the case of silicon atoms diamine residues, the total amount of R ^2, the main chain of silicon atoms having a diamine content of the residues as long as 50 mole % Or less is not particularly limited. In terms of bending resistance, it is preferably 2.5 mol% or more, preferably 2.5 mol% or more and 45 mol% or less, more preferably 3 mol% or more And below 40 mol%.

Regarding the polyimide having the structure represented by the above general formula (1), in terms of surface hardness and bending resistance in a high humidity environment, R ² in the above general formula (1) is preferred Represents at least one divalent group selected from diamine residues having no silicon atom and diamine residues having 1 or 2 silicon atoms in the main chain, and 2.5 mole% of the total amount of R ² And less than 50 mole% of the main chain has 1 or 2 silicon atoms of diamine residues. In addition, it is preferable that the remaining (100%) of the total amount of R ² (100 mol%) as the main chain of the diamine residue having 1 or 2 silicon atoms (x mol%) -x%) of 50 mol% or more and 97.5 mol% or less are diamine residues having no silicon atom.

In addition, regarding the polyimide having the structure represented by the general formula (1), in terms of improving the surface hardness, the total amount of R ^{1 and} the total amount of R ² in the general formula (1) When the total amount is set to 100 mol%, the total amount of the tetracarboxylic acid residue having an aromatic ring and the diamine residue having an aromatic ring is preferably 50 mol% or more, more preferably 60 mol% or more, Furthermore, it is more preferably 75 mol% or more.

In addition, regarding the polyimide having the structure represented by the general formula (1), in terms of surface hardness and light transmittance, and bending resistance, the tetracarboxylic acid residue of R ¹ and R At least one of ² diamine residues without a silicon atom preferably contains an aromatic ring and a fluorine atom, and more preferably a tetracarboxylic acid residue of R ¹ and a diamine without a silicon atom of R ² Both residues contain an aromatic ring and a fluorine atom.

Regarding the polyimide having the structure represented by the above general formula (1), in terms of surface hardness and light transmittance, and bending resistance, the R ¹ in the above general formula (1) When the total amount of the total amount and the total amount of R ² is set to 100 mol%, the total amount of the tetracarboxylic acid residue having an aromatic ring and a fluorine atom and the diamine residue having an aromatic ring and a fluorine atom is preferably 50 Mole% or more, more preferably 60 mole% or more, and even more preferably 75 mole% or more.

Regarding the content of fluorine atoms in the polyimide having the structure represented by the general formula (1) above, the number of fluorine atoms (F) and carbon atoms obtained by measuring the surface of the polyimide by X-ray photoelectron spectroscopy The ratio (F / C) of the number (C) is preferably 0.01 or more, and more preferably 0.05 or more. On the other hand, if the content of fluorine atoms is too high, the original heat resistance of polyimide may be reduced. Therefore, the ratio of the number of fluorine atoms (F) to the number of carbon atoms (C) (F / C ) Is preferably 1 or less, and more preferably 0.8 or less.

Here, the above ratio obtained by measurement by X-ray photoelectron spectroscopy (XPS) can be obtained from the value of atomic% of each atom measured using an X-ray photoelectron spectroscopy device (for example, Thermo Scientific's Theta Probe).

In addition, in terms of improving light transmittance and surface hardness, and bending resistance, polyimide having a structure represented by the general formula (1) can be preferably used in polyimide. More than 50% of the hydrogen atoms bonded to the carbon atoms are polyimides bonded directly to the hydrogen atoms of the aromatic ring. The ratio of hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to the carbon atoms contained in the polyimide is preferably 60% or more, more preferably 70 %the above.

In the case where more than 50% of the hydrogen atoms bonded to carbon atoms contained in the polyimide are directly bonded to the hydrogen atom of the aromatic ring, even if the heating step in the atmosphere is passed through, For example, even if the extension is performed at 200 ° C. or higher, it is preferable that the optical characteristics, especially the total light transmittance or the yellowness YI value, change little, and suppress the decrease in bending resistance. It is speculated that in the case where more than 50% of the hydrogen atoms bonded to carbon atoms contained in the polyimide are polyimides directly bonded to the hydrogen atoms of the aromatic ring, the reactivity with oxygen is low, Therefore, the chemical structure of polyimide is not easy to change, and the deterioration of the polyimide film caused by oxidation is suppressed. Polyimide film uses its high heat resistance for devices that require a processing step accompanied by heating, etc., and more than 50% of hydrogen atoms bonded to carbon atoms contained in polyimide are In the case of polyimide directly bonded to the hydrogen atom of the aromatic ring, in order to maintain transparency, there is no need to perform these subsequent steps in an inert environment, therefore, there is a cost that can suppress the cost of equipment or the cost of environmental control Advantage.

Here, the ratio of the hydrogen atoms (number) directly bonded to the aromatic ring in the total hydrogen atoms (number) bonded to the carbon atoms contained in the polyimide can use high-performance liquid chromatography, A gas chromatography mass spectrometer and NMR were used to determine the decomposition product of polyimide. For example, the sample is decomposed by alkaline aqueous solution or supercritical methanol, the obtained decomposed product is separated by high-performance liquid chromatography, and the qualitative analysis of the separated peaks is performed using gas chromatography mass spectrometry and NMR, etc., and Using a high-performance liquid chromatograph for quantification, the ratio of hydrogen atoms (number) directly bonded to the aromatic ring among the total hydrogen atoms (number) contained in the polyimide can be obtained.

In the structure represented by the general formula (1), n represents the number of repeating units and is 1 or more.

The number n of repeating units in the polyimide is not particularly limited as long as it is appropriately selected according to the structure so as to show the following preferred glass transition temperature.

The average number of repeating units is usually 10 to 2000, and more preferably 15 to 1000.

In addition, as long as the effect of the present invention is not impaired, a part of the polyimide used in the present invention may have a structure different from the structure represented by the general formula (1). The structure represented by the above general formula (1) of the polyimide used in the present invention is preferably 95% or more of the total number of repeating units of the polyimide, more preferably 98% or more, and still more preferably 100% .

As a structure different from the structure represented by the above general formula (1), for example, a structure having no aromatic ring or a polyamide structure can be cited.

Examples of the polyamidoamine structure that can be included include polyamidoamide imide structures containing tricarboxylic acid residues such as trimellitic anhydride or polyamidoamine containing dicarboxylic acid residues such as terephthalic acid. structure.

The content ratio of each repeating unit in the polyimide, and the content ratio (mol%) of each tetracarboxylic acid residue or each diamine residue can be determined based on the molecular weight added when manufacturing polyimide. In addition, the content ratio (mol%) of each tetracarboxylic acid residue or each diamine residue in the polyimide can be the same as the above, and can be directed to the polyimide obtained by decomposition of an alkaline aqueous solution or supercritical methanol. Decomposition products of amines were obtained using high-performance liquid chromatography, gas chromatography mass spectrometry, NMR, elemental analysis, XPS / ESCA and TOF-SIMS.

2. Additives

In addition to the polyimide, the polyimide film of the present invention may contain additives as needed. Examples of the above-mentioned additives include inorganic particles, silica fillers for smooth winding, and surfactants for improving film-forming properties or defoaming properties.

3. The characteristics of polyimide membrane

The above-mentioned tan δ curve, total light transmittance, yellowness, and humidity expansion coefficient in the polyimide film of the present invention have been described above, so the description here is omitted.

In terms of excellent bending resistance in a high humidity environment, when the polyimide film of the present invention is subjected to a static bending test according to the following static bending test method, the internal angle measured in the test is preferably Above 120 °, more preferably above 125 °.

[Static bending test method]

Bend the test piece of polyimide film cut into 15mm × 40mm at the position of one and a half of the long side, and use the two ends of the long side of the test piece to cut the metal piece with a thickness of 6mm (100mm × 30mm × 6mm ) It is arranged by sandwiching it from the top to the bottom, and fixed with tape in such a way that the overlap between the two ends of the test piece and the metal sheet on the top and bottom is 10mm, and in this state, a glass plate (100mm × 100 mm × 0.7 mm) clamped from above and below, and the test piece was fixed in a state of being bent with an inner diameter of 6 mm. At this time, a dummy test piece is sandwiched between the metal piece and the glass plate where the test piece does not exist, and is fixed with tape so that the glass plate becomes parallel. After the test piece fixed in the bent state as described above is allowed to stand at 60 ° C and 90% relative humidity (RH) for 24 hours, the glass plate and the fixing tape are removed, and the test piece is released and applied to the test piece. The power of the film. Thereafter, one end of the test piece was fixed, and the inner angle of the test piece 30 minutes after the release of the force applied to the test piece was measured.

In addition, in terms of more excellent bending resistance, the polyimide film of the present invention is replaced by 60 ° C. in an environment of 70 ° C. and 20% relative humidity (RH) or less in the static bending test method described above. In addition, in an environment of 90% relative humidity (RH), except for the case where the static bending test is the same as the static bending test method described above, the internal angle measured in the test is preferably 120 ° or more.

In addition, in terms of bending resistance in a high-humidity environment, the internal angle of the polyimide film of the present invention measured in a static bending test conducted in an environment of 60 ° C and 90% relative humidity (RH) and The absolute value of the difference in the internal angle measured in a static bending test conducted under an environment of 70 ° C and 20% relative humidity (RH) or less is preferably 10 ° or less, more preferably 7 ° or less, and even more preferably 5 ° Below.

In addition, in terms of surface hardness, the polyimide film of the present invention was obtained by measuring a 15 mm × 40 mm test piece with a stretching speed of 8 mm / min and a distance between jigs of 20 mm according to JIS K7127. The tensile elastic modulus at 25 ° C is preferably 1.8 GPa or more, and in terms of bending resistance, it may be 5.0 GPa or less. In terms of bending resistance and surface hardness, it is more preferably 2.0 GPa or more and 4.0 GPa or less, and still more preferably 2.0 GPa or more and 3.5 GPa or less.

The above tensile elastic modulus can use a tensile testing machine (for example, manufactured by Shimadzu Corporation: Autograph AG-X 1N, dynamometer: SBL-1KN), and a test piece with a width of 15 mm × a length of 40 mm is cut from the polyimide film. The measurement was carried out at 25 ° C at a stretching speed of 8 mm / min and a distance between clamps of 20 mm. The thickness of the polyimide film when the tensile elastic modulus is obtained is preferably 55 μm ± 5 μm.

Further, in terms of reducing optical strain, the polyimide film of the present invention has a birefringence in the thickness direction at the above wavelength of 590 nm of preferably 0.040 or less, preferably 0.020 or less, preferably 0.015 or less, and It is preferably 0.010 or less, and more preferably less than 0.008. If the optical strain of the polyimide film of the present invention is reduced, when the polyimide film of the present invention is used as a surface material for a display, it is possible to suppress a decrease in display quality of the display. In addition, when a film having a birefringence in the thickness direction of more than 0.040 at a wavelength of 590 nm is provided on the surface of the display and polarized sunglasses are worn to observe the display, there is a case where rainbow unevenness occurs and visibility deteriorates. On the other hand, if the birefringence in the thickness direction of the film provided on the surface of the display is 0.040 or less, the occurrence of rainbow unevenness when observing the display with polarized sunglasses is suppressed. Furthermore, if the birefringence in the thickness direction of the film provided on the surface of the display is 0.020 or less, the color reproducibility when the display is viewed from an oblique side is improved.

In addition, the birefringence in the thickness direction of the polyimide film of the present invention at the wavelength of 590 nm can be obtained as follows.

First, using a phase difference measuring device (for example, manufactured by Oji Measuring Instruments Co., Ltd., product name "KOBRA-WR"), the thickness-direction phase difference value (Rth) of the polyimide film is measured at 25 ° C using light with a wavelength of 590 nm ). The thickness direction phase difference value (Rth) is to measure the phase difference value at 0 degree incidence and the phase difference value at 40 degrees oblique incidence, and calculate the thickness direction phase difference value Rth according to the phase difference values. The above-mentioned phase difference value with an oblique incidence of 40 degrees is such that light with a wavelength of 590 nm enters the phase difference film from a direction inclined by 40 degrees from the normal line of the phase difference film and is measured.

The birefringence in the thickness direction of the polyimide film can be obtained by substituting the formula: Rth / d. The above d represents the film thickness (nm) of the polyimide film.

In addition, the refractive index in the direction of the late phase axis in the in-plane direction of the film (the direction in which the refractive index in the in-plane direction of the film becomes maximum) is set to nx, and the direction of the in-phase axis in the film plane (in the film plane) (The direction in which the refractive index in the direction becomes the smallest) When the refractive index in the direction is set to ny and the refractive index in the thickness direction of the film is set to nz, the phase difference in the thickness direction can be expressed as Rth [nm] = {(nx + ny) / 2-nz} × d.

In the polyimide film of the present invention, the pencil hardness may be 6B or more, but in terms of surface hardness, it is preferably 2B or more, more preferably B or more, and still more preferably HB or more.

The pencil hardness of the polyimide film can be performed as follows: after the humidity is controlled for 2 hours at a temperature of 25 ° C and a relative humidity of 60%, the test pencil specified in JIS-S-6006 is used The pencil hardness test (0.98N load) specified in JIS K5600-5-4 (1999) was performed on the film surface, and the highest pencil hardness without injury was evaluated. As the testing machine, for example, a pencil scratch coating film hardness testing machine manufactured by Toyo Seiki Co., Ltd. can be used.

In terms of light transmittance, the polyimide film of the present invention preferably has a haze value of 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. 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 above-mentioned haze value can be measured by a method according to JIS K-7105, for example, it can be measured by a haze meter HM150 manufactured by Murakami Color Technology Research Institute.

4. Composition of polyimide film

The thickness of the polyimide film of the present invention can be appropriately selected according to the application, and in terms of strength, it is preferably 1 μm or more, more preferably 5 μm or more, and still more preferably 10 μm or more. On the other hand, in terms of bending resistance, the thickness of the polyimide film is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

Furthermore, the polyimide film of the present invention may be subjected to surface treatments such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet treatment, and flame treatment.

5. Manufacturing method of polyimide film

As the method for manufacturing the polyimide film of the present invention, for example, the following method for manufacturing the polyimide film is exemplified as the first manufacturing method, which includes the following steps: a step for preparing a polyimide precursor resin composition (Hereinafter, referred to as a preparation step of a polyimide precursor resin composition), the polyimide precursor resin composition includes a polyimide precursor having a structure represented by the following general formula (1 '), And an organic solvent, the polyimide precursor contains an aromatic ring and is selected from (i) a fluorine atom, and (ii) the aromatic ring is connected to each other by a sulfonyl group or an alkylene group substituted with fluorine At least one of the group consisting of the structure; the step of applying the above polyimide precursor resin composition to the support to form a polyimide precursor resin coating film (hereinafter, referred to as polyimide) A step of forming an amine precursor resin coating film); and a step of heating to imidate the polyimide precursor (hereinafter, referred to as an imidate step).

(In the general formula (1 '), R ¹ , R ² and n are the same as the general formula (1) above)

In the above-mentioned first manufacturing method, it may further have a coating film obtained by making the polyimide precursor resin coating film and the polyimide precursor resin coating film after imidization At least one extension step (hereinafter, referred to as extension step).

Hereinafter, each step will be described in detail.

(1) Preparation steps of polyimide precursor resin composition

The polyimide precursor resin composition prepared in the above-mentioned first manufacturing method contains a polyimide precursor having the structure represented by the following general formula (1 ') and an organic solvent, and may also contain additives if necessary, The polyimide precursor includes an aromatic ring, and includes a structure selected from the group consisting of (i) a fluorine atom and (ii) aromatic rings linked to each other by a sulfonyl group or an alkylene group substituted with fluorine At least one species in the group.

<Polyimide precursor>

The polyimide precursor of the present invention suitable for manufacturing the polyimide film of the present invention and polyimide is a polyimide precursor having a structure represented by the following general formula (1 '), which contains an aromatic The group ring includes at least one selected from the group consisting of (i) a fluorine atom and (ii) a structure in which an aromatic ring is connected to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine.

The polyimide precursor having the structure represented by the above general formula (1 ') is formed by the tetracarboxylic acid component of the tetracarboxylic acid residue in R ¹ of the above general formula (1') and the above general formula Polyamide obtained by polymerization of the diamine component of the diamine residue in R ² of (1 ').

Here, R ¹ , R ² and n of the above general formula (1 ′) can be the same as R ¹ , R ² and n of the above general formula (1) described in the above polyimide.

In terms of strength and bending resistance at the time of film formation, the number average molecular weight of the aforementioned polyimide precursor is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more, and particularly preferably 50,000 the above. On the other hand, if the number average molecular weight is too large, it may become a high viscosity and the workability of filtration or the like may be reduced, preferably 10,000,000 or less, and more preferably 500,000 or less.

The number average molecular weight of the polyimide precursor can be determined by NMR (for example, manufactured by BRUKER, AVANCE III). For example, after applying a polyimide precursor solution to a glass plate and drying it at 100 ° C for 5 minutes, 10 mg of the solid content is dissolved in 7.5 mL of dimethylsulfoxide-d6 solvent and subjected to NMR measurement. The number-average molecular weight is calculated from the peak intensity ratio of hydrogen atoms bonded to the aromatic ring.

In addition, in terms of strength and bending resistance during film formation, the weight average molecular weight of the polyimide precursor is preferably 20,000 or more, more preferably 30,000 or more, and still more preferably 40,000 or more, particularly preferably It is more than 80,000. On the other hand, if the weight-average molecular weight is too large, it may become a high viscosity and the workability of filtration or the like may be reduced, preferably 10,000,000 or less, and more preferably 500,000 or less.

The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC). Specifically, the polyimide precursor is made into a 0.5% by weight concentration of N-methylpyrrolidone (NMP) solution, and the developing solvent is a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less, which is manufactured by Tosoh. The GPC device (HLC-8120, using a column: GPC LF-804 manufactured by SHODEX) was measured under the conditions of a sample injection volume 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 at the same concentration as the sample.

The polyimide precursor solution is obtained by reacting the tetracarboxylic dianhydride and the diamine in a solvent. The solvent used for the synthesis of the polyimide precursor (polyamide acid) is not particularly limited as long as it can dissolve the above-mentioned tetracarboxylic dianhydride and diamine. For example, an aprotic polar solvent or water-soluble Alcohol solvents, etc. In the present invention, among them, it is preferable to use: N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide , Hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone and other organic solvents containing nitrogen atoms; γ-butyrolactone, etc. Among them, when the above polyimide precursor solution (polyamide acid solution) is directly used to prepare the polyimide precursor resin composition, it is preferable to use an organic solvent containing a nitrogen atom, wherein, Preferably, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, or a combination of these is used. Furthermore, the so-called organic solvent is a solvent containing carbon atoms.

In addition, when the above polyimide precursor solution is prepared by combining two or more kinds of diamines, an acid dianhydride can be added to a mixed solution of two or more kinds of diamines to synthesize a polyamic acid. Two or more kinds of diamine components can be added to the reaction solution at appropriate molar ratios in stages, and the order of adding each raw material to the polymer chain can be controlled to some extent.

For example, a molar equivalent of 0.5 moles of acid dianhydride of a diamine having a silicon atom in the main chain can be put into a reaction solution in which a diamine having a silicon atom in the main chain is dissolved for reaction, thereby synthesizing the main chain The amide acid obtained by the reaction between the diamine of the silicon atom and the acid dianhydride is added with all or part of the remaining diamine, and the acid dianhydride is added to synthesize the polyamide acid. If polymerization is carried out by this method, the diamine having a silicon atom in the main chain is introduced into the polyamic acid via one acid dianhydride in a linked form.

By using this method to polymerize polyamic acid, the positional relationship of the polyamic acid having silicon atoms in the main chain is specified to some extent, and it is easy to obtain a film that maintains surface hardness and is excellent in bending resistance. good.

When the number of moles of the diamine in the polyimide precursor solution (polyamide acid solution) is X, and the number of moles of tetracarboxylic dianhydride is Y, it is preferable to set Y / X is set to 0.9 or more and 1.1 or less, more preferably 0.95 or more and 1.05 or less, further preferably 0.97 or more and 1.03 or less, particularly preferably 0.99 or more and 1.01 or less. The molecular weight (degree of polymerization) of polyamide obtained by setting to such a range can be adjusted appropriately.

The order of the polymerization reaction can be appropriately selected using known methods and is not particularly limited.

In addition, the polyimide precursor solution obtained by the synthesis reaction may be directly used, and other components may be mixed therein as necessary, or the solvent of the polyimide precursor solution may be dried and dissolved in other solvents for use.

In terms of forming a uniform coating film and a polyimide film, the viscosity of the polyimide precursor solution at 25 ° C. is preferably 500 cps or more and 200,000 cps or less.

The viscosity of the polyimide precursor solution can be measured using a viscometer (for example, TVE-22HT, Toki Industry Co., Ltd.) at 25 ° C.

<Polyimide precursor resin composition>

As the above-mentioned polyimide precursor resin composition, the above-mentioned polyimide precursor solution may be used, and additives may be contained as necessary. Examples of the above-mentioned additives include inorganic particles, silica fillers for smooth winding, and surfactants for improving film forming or defoaming properties, etc., which can be used as described in the above-mentioned polyimide film The same.

The organic solvent used for the resin composition of the polyimide precursor is not particularly limited as long as it can dissolve the polyimide precursor. For example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, Nitrogen atom-containing organic solvents such as 1,3-dimethyl-2-imidazolidinone; γ-butyrolactone, etc. Among them, it is preferable to use nitrogen atom-containing organic solvents for the above reasons.

In terms of forming a uniform coating film and a polyimide film with controllable strength, the content of the polyimide precursor in the polyimide precursor resin composition is in the solid form of the resin composition Among the material components, it is preferably 50% by mass or more, and more preferably 60% by mass or more, and the upper limit may be appropriately adjusted according to the contained components.

In terms of forming a uniform coating film and a polyimide film, the organic solvent in the resin composition of the polyimide precursor is preferably 40% by mass or more in the resin composition, and more preferably 50% by mass % Or more, and preferably 99% by mass or less.

In addition, from the viewpoint that the storage stability of the polyimide precursor resin composition becomes good and the productivity can be improved, the water content of the polyimide precursor resin composition is preferably 1000 ppm or less. If the polyimide precursor resin composition contains a large amount of water, the polyimide precursor may be easily decomposed.

In addition, the moisture content of the polyimide precursor resin composition can be determined using a Carl Fischer moisture meter (for example, a Mitsubishi Chemical Co., Ltd., trace moisture measurement device CA-200 type).

In order to set the moisture content to 1000 ppm or less as described above, it is preferable to use an organic solvent used for dehydration or moisture management, and operate in an environment with a humidity of 5% or less.

In terms of forming a uniform coating film and a polyimide film, the viscosity of the polyimide precursor resin composition at 25 ° C. is preferably 500 cps or more and 200,000 cps or less.

The viscosity of the polyimide precursor resin composition can be measured using a viscometer (for example, TVE-22HT, Toki Industry Co., Ltd.) at 25 ° C with a sample amount of 0.8 mL.

(2) Polyimide precursor resin coating film forming step

In the step of applying the above polyimide precursor resin composition to a support to form a polyimide precursor resin coating film, as the support used, as long as the surface is smooth and has heat resistance and solvent resistance There are no special restrictions on sexual materials. For example, an inorganic material such as a glass plate, a metal plate whose surface is mirror-finished, etc. may be mentioned. In addition, the shape of the support is selected according to the coating method, and may be, for example, a plate shape, a drum shape or a belt shape, or a sheet shape that can be wound around a roller.

The coating means is not particularly limited as long as it can be coated with a target film thickness, and for example, a die coater, a corner coater, a roll coater, a gravure coater, and a curtain can be used Well-known ones such as die coaters, spray coaters, die lip coaters and the like.

The coating may be performed by a single-piece coating device or a roll-to-roll coating device.

After the polyimide precursor resin composition is applied to the support and before the coating film becomes non-sticky, the coating film is applied at a temperature of 150 ° C. or less, preferably 30 ° C. or more and 120 ° C. or less. The solvent is dried. By setting the drying temperature of the solvent to 150 ° C. or lower, the imidization of the polyamic acid can be suppressed.

The drying time may be appropriately adjusted according to the film thickness of the polyimide precursor resin coating film, the type of solvent, the drying temperature, etc., and is usually set to 30 seconds to 240 minutes, preferably 1 minute to 180 minutes, more preferably It is set from 90 seconds to 120 minutes. When the upper limit value is exceeded, the production efficiency of the polyimide film is poor. On the other hand, when the value is lower than the lower limit, the rapid drying of the solvent may affect the appearance of the obtained polyimide film.

The drying method of 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 characteristics is required, the environment when the solvent is dried is preferably an inert gas environment. The inert gas environment is preferably a nitrogen environment, and the oxygen concentration is preferably 500 ppm or less, more preferably 100 ppm or less, and most preferably 50 ppm or less. If the heat treatment is performed in the atmosphere, the film may be oxidized to cause coloration or performance degradation.

(3) Amidation step

In the above-mentioned first production method, the polyimide precursor is imidized by heating.

In this manufacturing method, in the case where there is an extension step, the amide imidization step can be performed on the polyimide precursor in the above-mentioned polyimide precursor resin coating film before the extension step, and can also be performed on the extension step The polyimide precursor in the resin coating film of the polyimide precursor resin described above is also performed, and the polyimide precursor in the polyimide precursor resin coating film before the extension step and the extension step can also be performed Both of the polyimide precursors present in the latter film proceed.

The temperature of the imidate can be appropriately selected according to the structure of the polyimide precursor.

Generally, it is preferable to set the temperature increase starting temperature to 30 ° C or higher, and more preferably to 100 ° C or higher. On the other hand, the temperature increase end temperature is preferably 250 ° C. or higher.

The heating rate is preferably selected according to the film thickness of the obtained polyimide film. When the film thickness of the polyimide film is thick, it is preferable to make the heating rate slower.

In terms of the production efficiency of the polyimide film, it is preferably 5 ° C./min or more, and more preferably 10 ° C./min or more. On the other hand, the upper limit of the temperature increase rate is usually 50 ° C / min, preferably 40 ° C / min or less, and more preferably 30 ° C / min or less. In terms of suppressing poor appearance of the film or reduction in strength, and controlling whitening accompanying the amide imidization reaction, thereby improving light transmittance, it is preferable to set the above temperature increase rate.

The temperature may be continuously or intermittently increased. In terms of suppressing poor appearance of the film or a decrease in strength, and controlling whitening associated with the amide imidization reaction, it is preferably continuous. In addition, within the above-mentioned total temperature range, the temperature increase rate may be fixed, or it may be changed in the middle.

The environment when the temperature of the imidate is heated is preferably an inert gas environment. As an inert gas environment, preferably a nitrogen environment, the oxygen concentration is preferably 500 ppm or less, more preferably 200 ppm or less, and still more preferably 100 ppm or less. If the heat treatment is performed in the atmosphere, the film may be oxidized to become colored or the performance may be reduced.

However, when more than 50% of the hydrogen atoms bonded to carbon atoms contained in the polyimide are directly bonded to the hydrogen atoms of the aromatic ring, oxygen has less effect on the optical properties, even if it is not used In an inert gas environment, polyimide with high light transmittance can also be obtained.

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

Among them, it is preferable to set the imidization ratio of the polyimide precursor to 50% or more before the extending step. Since the imidization rate of the imidate is set to 50% or more before the extension step, even if the acetimilation is performed after the step and then heated at a higher temperature for a fixed period of time to perform the imidate, It can also suppress poor appearance or whitening of the film. Among them, in terms of improving the surface hardness of the polyimide film, it is preferable to set the rate of the imidate to 80% or more in the imidate step before the stretching step, preferably to proceed The reaction is up to 90% or more, and further 100%. It is presumed that by imidization and extension after the amide imidization, the rigid polymer chain is easily aligned, and thus the surface hardness is improved.

In addition, the measurement of the imidate ratio can be performed by the analysis of the spectrum obtained by infrared measurement (IR), etc.

In order to obtain the final polyimide film, it is preferable to perform the amide imidization reaction up to 90% or more, further 95% or more, and further 100%.

In order to carry out the amide imidization reaction up to 90% or more, and further to 100%, it is preferable to maintain a fixed time at the temperature-rising end temperature. The holding time is usually set to 1 minute to 180 minutes, and more preferably set to 5 minutes to 150 minute.

(4) Extension steps

The first manufacturing method described above may further include an extension step of coating the polyimide precursor resin coating film and the polyimide precursor coating film obtained by imidization of the polyimide precursor resin coating film At least one of them is extended. In the case of having this stretching step, it is preferable to include the step of stretching the coating after the imidization of the polyamide in terms of improving the surface hardness of the polyimide film.

In the above-mentioned first manufacturing method, when the initial size before stretching is set to 100%, it is preferable to perform the steps of stretching 101% or more and 10000% or less while heating at 80 ° C. or more.

The heating temperature during extension is preferably within the range of glass transition temperature of polyimide or polyimide precursor within ± 50 ° C, preferably within the range of glass transition temperature within ± 40 ° C. If the elongation temperature is too low, there is a risk that the film will not be deformed and alignment cannot be sufficiently induced. On the other hand, if the stretching temperature is too high, there is a possibility that the alignment obtained by the stretching is relaxed due to the temperature, and sufficient alignment cannot be obtained.

The extension step can be performed simultaneously with the amide imidization step. In terms of improving the surface hardness of the polyimide film, it is preferable that the rate of imidization be 80% or more, further 90% or more, further 95% or more, and especially substantially 100% acetylene After imidization, the coating film is stretched after imidization.

The stretch ratio of the polyimide film is preferably 101% or more and 10000% or less, and more preferably 101% or more and 500% or less. By extending within the above range, the surface hardness of the obtained polyimide film can be further increased.

The fixing method of the polyimide film during stretching is not particularly limited, and can be selected according to the type of stretching device and the like. In addition, the stretching method is not particularly limited. For example, an stretching device having a conveying device such as a tenter can be used, and the stretching can be performed while passing through the heating furnace. The polyimide film may be extended in only one direction (longitudinal extension or lateral extension), or it may be simultaneously extended in two directions by biaxial extension, or successive biaxial extension, oblique extension, and the like.

In terms of easily reducing the birefringence of the polyimide film, the first production method described above is preferred. According to the first manufacturing method described above, a polyimide film having a birefringence in the thickness direction at a wavelength of 590 nm of 0.020 or less, and further 0.010 or less can be preferably formed.

In addition, as the method for manufacturing the polyimide film of the present invention, the following method for manufacturing the polyimide film can be cited as the second manufacturing method, which includes the following steps: The preparation includes the formula (1) A step of a polyimide resin structure and a polyimide resin composition of an organic solvent (hereinafter, referred to as a polyimide resin composition preparation step), the polyimide contains an aromatic ring, and contains (i) at least one member of a group consisting of a fluorine atom and (ii) 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; and the above polyimide resin The step of applying the composition to the support and drying the solvent to form a polyimide resin coating film (hereinafter, referred to as a polyimide resin coating film forming step).

In an aromatic ring and at least one selected from the group consisting of a structure consisting of (i) a fluorine atom and (ii) an aromatic ring linked to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine When the polyimide having the structure represented by the above general formula (1) is well dissolved in an organic solvent, it is not used for the resin composition of the polyimide precursor, but can also be preferably used to make the above The polyimide resin composition is dissolved in an organic solvent and optionally contains additives.

In an aromatic ring and at least one selected from the group consisting of a structure consisting of (i) a fluorine atom and (ii) an aromatic ring linked to each other by a sulfonyl group or an alkylene group which may be substituted with fluorine When the polyimide having the structure represented by the above general formula (1) has solvent solubility such as 5 mass% or more dissolved in an organic solvent at 25 ° C., the production method can be preferably used.

In the preparation process of the polyimide resin composition, the polyimide can be selected from the same polyimides as described in the polyimide film and the polyimide having the above solvent solubility can be used. . As a method of imidization, it is preferable to use chemical imidization using a chemical imidate agent instead of dehydration by heating with respect to the dehydration ring-closure reaction of the aforementioned polyimide precursor. In the case of chemical imidization, known compounds such as amines such as pyridine or β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride can be used as dehydration catalysts. The acid anhydride is not limited to acetic anhydride, and examples thereof include propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride, which are not particularly limited. In this case, tertiary amines such as pyridine and β-picolinic acid may be used together. However, if these amines remain in the film, the optical properties, especially yellowness (YI value) will decrease, so it is preferable not to directly cast the reaction liquid obtained by reacting the precursor to the polyimide The membrane is purified by re-precipitation, etc., and the components other than polyimide are separately removed until it becomes 100 ppm or less of the total weight of the polyimide, and then the membrane is formed.

In the preparation step of the polyimide resin composition, as the organic solvent used as the reaction solution for chemical imidization of the polyimide precursor, for example, the above-mentioned polyimide in the first production method can be used The same as described in the preparation step of the imine precursor resin composition. In the preparation step of the polyimide resin composition, examples of the organic solvent used when redissolving the polyimide purified from the reaction solution include ethylene glycol monoethyl ether and ethylene glycol monoethyl ether acetic acid. Ester, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, o-dichlorobenzene, xylene, cresol, chlorobenzene, isobutyl acetate, isoamyl acetate , N-butyl acetate, n-propyl acetate, n-pentyl acetate, cyclohexanol, cyclohexanone, 1.4-bis Alkanes, tetrachloroethylene, toluene, methyl isobutyl ketone, methyl cyclohexanol, methyl cyclohexanone, methyl-n-butyl ketone, dichloromethane, dichloroethane, and mixed solvents of these, etc. Among them, at least one selected from the group consisting of dichloromethane, n-butyl acetate, propylene glycol monomethyl ether acetate, and mixed solvents of these can be preferably used.

The above-mentioned polyimide resin composition may contain additives as needed. As the additive, the same as described in the step of preparing the polyimide precursor resin composition in the first production method can be used.

In the second production method, as the method for setting the water content of the polyimide resin composition to 1000 ppm or less, the polyimide precursor resin used in the first production method can be used. The method described in the composition preparation step is the same.

In addition, in the polyimide resin coating film forming step in the second manufacturing method, the support or coating method may be the same as that in the polyimide precursor resin coating film forming step in the first manufacturing method. The same explanation.

In the step of forming the polyimide resin coating film in the second manufacturing method, the drying temperature is preferably 80 ° C or higher and 150 ° C or lower under normal pressure. Preferably, it is set to a range of 10 ° C or more and 100 ° C or less under reduced pressure.

In addition, the second manufacturing method may further include an extension step of extending the polyimide resin coating film after the polyimide resin coating film formation step. This stretching step may be the same as the stretching step in the first manufacturing method described above.

In terms of easily reducing the yellowness (YI value) of the polyimide film, the second production method described above is preferred. According to the second manufacturing method described above, a polyimide film having a value of 0.04 or less obtained by dividing the yellowness calculated according to JIS K7373-2006 by the film thickness (μm) can be appropriately formed.

6. Use of Polyimide Film

The use of the polyimide film of the present invention is not particularly limited, and it can be used as a substrate or surface material used for glass products such as thin plate glass and the like. Since the polyimide film of the present invention is excellent in transparency and bending resistance, it can be suitably used as a surface material for displays, especially as a surface material for flexible displays, and can also be suitably used as Surface material for folding displays.

In addition, specifically, the polyimide film of the present invention can be suitably used for, for example, thin and bendable flexible type organic EL displays, mobile terminals such as smartphones or watch-type terminals, display devices in automobiles, Flexible panels used in watches, etc. In addition, the polyimide film of the present invention can also be applied to components for image display devices such as liquid crystal display devices and organic EL display devices, components for touch panels, flexible printed substrates, surface protective films, substrate materials, and other solar devices. Components for battery panels, components for optical waveguides, other semiconductor-related components, etc.

II. Laminate

The layered system of the present invention has the laminate of the polyimide film of the present invention and a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound.

Since the laminate of the present invention uses the polyimide film of the present invention described above, it has excellent transparency and improved bending resistance under high humidity, and furthermore, the surface hardness is further improved due to the hard coat layer.

1. Polyimide film

As the polyimide film used in the laminate of the present invention, the above-mentioned polyimide film of the present invention can be used, and therefore, the description here is omitted.

2. Hard coating

The hard coat layer used in the laminate of the present invention contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound.

(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 generating a radical polymerization reaction, and examples include a group containing a carbon-carbon unsaturated double bond, etc., specific Specifically, vinyl, (meth) acryloyl and the like can be mentioned. Furthermore, in the case where the above radical polymerizable compound has two or more radical polymerizable groups, the radical polymerizable groups may be the same or different.

In terms of improving the hardness of the hard coat layer, the number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more.

As the above-mentioned radical polymerizable compound, in terms of a high degree of reactivity, among them, a compound having a (meth) acryloyl group is preferable, and 2 to 6 (methyl groups in 1 molecule) can be preferably used ) The compound called polyfunctional acrylate monomer of acryloyl or amine (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate has a number of molecules An oligomer with a molecular weight of (meth) acryloyl groups of hundreds to thousands.

In addition, in this specification, the (meth) acryloyl group means each of the acryl group and the methacryl group, and the (meth) acrylate means the each of the acrylate and methacrylate group. .

Specific examples of the radical polymerizable compound include ethylene-based compounds such as divinylbenzene; ethylene glycol di (meth) acrylate, bisphenol A epoxy di (meth) acrylate, and 9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] stilbene, alkylene oxide modified bisphenol A di (meth) acrylate (for example, ethoxylated (cyclic Oxyethane modification) bisphenol A di (meth) acrylate, etc.), trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, neopentyl alcohol Tri (meth) acrylate, neopentaerythritol tetra (meth) acrylate, di neopentaerythritol tri (meth) acrylate, di neopentaerythritol tetra (meth) acrylate, di neopentaerythritol Polyol polyacrylates such as alcohol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, bisphenol A diglycidyl ether diacrylate, hexanediol diglycidyl ether two Epoxy acrylates such as acrylates, amine acrylates obtained by the reaction of polyisocyanates with hydroxy-containing acrylates such as hydroxyethyl acrylate, and the like.

(2) Cationic polymerizable compound

The so-called cationic polymerizable compound is a compound having a cationic polymerizable group. The cationic polymerizable group possessed by the cationic polymerizable compound is not particularly limited as long as it is a functional group capable of generating a cationic polymerization reaction, and examples thereof include epoxy groups, oxetanyl groups, and vinyl ether groups. . Furthermore, in the case where the above-mentioned cationic polymerizable compound has two or more cationic polymerizable groups, the cationic polymerizable groups may be the same or different.

In terms of improving the hardness of the hard coat layer, the number of cationic polymerizable groups that the cationic polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more.

In addition, as the above-mentioned cationic polymerizable compound, among them, a compound having at least one epoxy group and oxetanyl group as a cationic polymerizable group is preferred. In terms of surface hardness, a compound having at least one of two or more epoxy groups and oxetanyl groups in one molecule is more preferable. In terms of small shrinkage accompanying the polymerization reaction, cyclic ether groups such as epoxy groups and oxetanyl groups are preferred. In addition, the compound having an epoxy group in a cyclic ether group has a compound that can easily obtain various structures, does not adversely affect the durability of the obtained hard coat layer, and is easy to control the compatibility with the radical polymerizable compound Advantage. In addition, the oxetanyl group in the cyclic ether group has a higher degree of polymerization and lower toxicity than the epoxy group, and the self-coating will be improved when the obtained hard coat layer is combined with the compound having an epoxy group The network formation speed obtained by the cationic polymerizable compound in the membrane, even in the area where it is mixed with the radical polymerizable compound, will not leave unreacted monomers in the membrane to form an independent network and other advantages.

Examples of the cationic polymerizable compound having an epoxy group include polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or by using an appropriate oxidizing agent such as hydrogen peroxide or peracid to make the cyclohexene-containing ring, ring Cycloaliphatic epoxy resins obtained by epoxidation of pentene ring compounds; polyglycidyl ethers of aliphatic polyols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polyacids, (methyl ) Aliphatic epoxy resins such as homopolymers and copolymers of glycidyl acrylate; bisphenols such as bisphenol A, bisphenol F or hydrogenated bisphenol A, or through these alkylene oxide adducts, Glycidyl ethers produced by the reaction of derivatives such as lactone adducts with epichlorohydrin, and glycidyl ether epoxy resins derived from bisphenols such as phenolic epoxy resins.

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

Moreover, as said glycidyl ether type epoxy resin, a sorbitol polyglycidyl ether (Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, Denacol EX-622), poly Glycerin polyglycidyl ether (Denacol EX-512, Denacol EX-521), neopentaerythritol polyglycidyl ether (Denacol EX-411), diglycerin polyglycidyl ether (Denacol EX-421), glycerol polyglycidyl ether (Denacol EX-313, Denacol EX-314), trimethylolpropane polyglycidyl ether (Denacol EX-321), resorcinol diglycidyl ether (Denacol EX-201), neopentyl glycol diglycidyl Ether (Denacol EX-211), 1,6-hexanediol diglycidyl ether (Denacol EX-212), hydroxybisphenol 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), butyl phenyl glycidyl ether (Denacol EX-146), phthalic acid diglycidyl ester (Denacol EX-721), hydroquinone diglycidyl Ether (Denacol EX-203), terephthalic acid diglycidyl ester (Denacol EX-711), glycidyl phthalimide (Denacol EX-731), dibromophenyl glycidyl ether (Denacol EX -147), dibromo neopentyl glycol diglycidyl ether (Denacol EX-221) (above, trade names in parentheses, manufactured by Nagase chemte X).

In addition, as other commercially available epoxy resins, trade names include Epikote 825, Epikote 827, Epikote 828, Epikote 828EL, Epikote 828XA, Epikote 834, Epikote 801, Epikote 801P, Epikote 802, Epikote 815, Epikote 815XA Epikote 816A, Epikote 819, Epikote 834X90, Epikote 1001B80, Epikote 1001X70, Epikote 1001X75, Epikote 1001T75, Epikote 806, Epikote 806P, Epikote 807, Epikote 152, Epikote 871, Epikote 154, Epikote 154, Epikote 154, Epikote 154 , Epikote YX8034, etc. (the above are trade names, manufactured by Japan Epoxy Resin).

Examples of the cationic polymerizable compound having oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101) and 1,4-bis-3-ethyloxa Cyclobutane-3-ylmethoxymethylbenzene (OXT-121), bis-1-ethyl-3-oxetanyl methyl ether (OXT-221), 3-ethyl-3-2-ethyl Hexyloxymethyloxetane (OXT-212), 3-ethyl-3-phenoxymethyloxetane (OXT-211) (above, trade names in parentheses are synthesized by East Asia Manufacturing) or trade names Eternacoll EHO, Eternacoll OXBP, Eternacoll OXTP, Eternacoll OXMA (the above are trade names, manufactured by Ube Industries).

(3) Polymerization initiator

The at least one polymer of the radical polymerizable compound and the cationic polymerizable compound contained in the hard coat layer used in the present invention can be determined, for example, by at least one of the radical polymerizable compound and the cationic polymerizable compound. It is obtained by adding a polymerization initiator and performing a polymerization reaction by a known method.

As the above-mentioned polymerization initiator, a radical polymerization initiator, a cationic polymerization initiator, a radical, a cationic polymerization initiator and the like can be appropriately selected and used. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate free radicals or cations to perform free radical polymerization and cation polymerization.

The radical polymerization initiator may be any substance that can release radical polymerization by at least one of light irradiation and heating. For example, examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, Organic peroxide, N-alkoxypyridinium salt, 9-oxysulfur Derivatives and the like; further specifically, 1,3-bis (third butyl dioxycarbonyl) benzophenone, 3,3 ', 4,4'-tetra (third butyl dioxycarbonyl ) Benzophenone, 3-phenyl-5-iso Oxazolinone, 2-mercaptobenzimidazole, bis (2,4,5-triphenyl) imidazole, 2,2-dimethoxy-1,2-diphenylethane-1-one (trade name Irgacure 651, manufactured by Ciba Japan (stock), 1-hydroxy-cyclohexyl-phenyl-one (trade name Irgacure 184, manufactured by Ciba Japan), 2-benzyl-2-dimethylamino-1- (4- Phenylphenyl) -butane-1-one (trade name Irgacure 369, manufactured by 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, manufactured by Ciba Japan Co., Ltd.), etc., but not limited to these.

In addition to the above, commercially available products can also be used, and specific examples include Irgacure 907, Irgacure 379, Irgacure 819, Irgacure 127, Irgacure 500, Irgacure 754, Irgacure 250, Irgacure 1800, Irgacure manufactured by Ciba Japan Co., Ltd. 1870, Irgacure OXE01, DAROCUR TPO, DAROCUR 1173, Speedcure MBB, Speedcure PBZ, Speedcure ITX, Speedcure CTX, Speedcure EDB, Esacure ONE, Esacure KIP150, Esacure KTO46, Japan Chemicals KAYACURE DETX-S, KAYACURE CTX, KAYACURE BMS, KAYACURE DMBI, etc.

In addition, the cationic polymerization initiator may be any substance that can release cationic polymerization by at least one of light irradiation and heating. As the cationic polymerization initiator, there can be exemplified: sulfonate, amide imine sulfonate, dialkyl-4-hydroxyammonium salt, arylsulfonic acid-p-nitrobenzyl ester, silanol-aluminum complex, (η ⁶ -benzene) (η ⁵ -cyclopentadienyl) iron (II) and the like, and more specifically, benzoin tosylate, 2,5-dinitrobenzyl tosylate, N -P-toluenesulfonyl phthalimide, etc., but not limited to these.

As a radical polymerization initiator or as a cationic polymerization initiator, there can be exemplified: aromatic iodonium salt, aromatic osmium salt, aromatic diazonium salt, aromatic phosphonium salt, three Compounds, iron-aromatic hydrocarbon complexes, etc .; further specifically, examples thereof include diphenylphosphonium, xylylphosphonium, bis (p-tertiary butylphenyl) iodide, bis (p-chlorophenyl) iodide, etc. Chloride, bromide, boron fluoride, hexafluorophosphate, hexafluoroantimonate and other iodide salts; triphenyl alkane, 4-third butyl triphenyl alkane, tris (4-methylphenyl) Chloride, bromide, boron fluoride, hexafluorophosphate, hexafluoroantimonate and other cerium salts of cerium and other cerium; 2,4,6-tris (trichloromethyl) -1,3,5-tris , 2-phenyl-4,6-bis (trichloromethyl) -1,3,5-tri , 2-methyl-4,6-bis (trichloromethyl) -1,3,5-tri Wait 2,4,6-substitute -1,3,5 three Compounds, etc .; but not limited to these.

(4) Additives

In addition to the above polymers, the hard coat layer used in the present invention may contain antistatic agents, antiglare agents, antifouling agents, inorganic or organic fine particles for improving hardness, leveling agents, various Additives such as sensitizers.

In addition, at least one polymer of the radically polymerizable compound and the cationically polymerizable compound contained in the hard coat layer used in the present invention can use Fourier transform infrared spectrophotometer (FTIR), thermal decomposition gas chromatography It can be analyzed by GC-MS, or using the combination of high-performance liquid chromatography, gas chromatography mass spectrometry, NMR, elemental analysis, XPS / ESCA and TOF-SIMS for the decomposition products of polymers.

3. Composition of laminate

The laminate of the present invention is not particularly limited as long as it has the polyimide film and the hard coat layer, and the hard coat layer may be stacked on one side of the polyimide film or on the polyimide film. Two areas of the film are coated with the above hard coat layer. In addition, the laminate of the present invention may have, for example, the above-mentioned polyimide film and the above-mentioned hard coat layer in addition to the above-mentioned polyimide film and the above-mentioned hard coat layer, as long as the effects of the present invention are not impaired. The other layers such as the primer layer of the adhesiveness, the polyimide film and the hard coating layer may be laminated via other layers such as the primer layer. In addition, the polyimide film and the hard coat layer of the laminate of the present invention may exist adjacent to each other.

The overall thickness of the layered product of the present invention may be appropriately selected according to the application, and in terms of strength, it is preferably 10 μm or more, and more preferably 40 μm or more. On the other hand, in terms of bending resistance, it is preferably 300 μm or less, and more preferably 250 or less.

In addition, in the laminate of the present invention, the thickness of each hard coat layer may be appropriately selected according to the application, preferably 2 μm or more and 80 μm or less, more preferably 3 μm or more and 50 μm or less. In addition, from the viewpoint of preventing deflection, a hard coat layer may be formed on both sides of the polyimide film.

4. Characteristics of laminate

The pencil hardness of the hard coat side surface of the laminate of the present invention is preferably H or more, more preferably 2H or more, and still more preferably 3H or more.

The pencil hardness of the laminate of the present invention can be measured in the same manner except that the load is set to 9.8 N in the above-mentioned method for measuring the pencil hardness of the polyimide film.

The laminated body of the present invention has a total light transmittance measured according to JIS K7361-1 of preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. In this way, due to the high penetration rate, the transparency becomes good and can be used as a substitute for glass.

The total light transmittance of the laminate of the present invention can be measured in the same manner as the total light transmittance of the polyimide film measured in accordance with JIS K7361-1.

The layered body of the present invention has a yellowness (YI value) calculated according to JIS K7373-2006 of preferably 20 or less, more preferably 12 or less, even more preferably 10 or less, and particularly preferably 5 or less.

In addition, in terms of suppressing the coloration of the yellow tone and improving the light transmittance, it can be suitably used as a glass substitute material, the layered product of the present invention is divided by the film thickness according to the yellowness (YI value) calculated by the above JIS K7373-2006 The value obtained (μm) (YI value / film thickness (μm)) is preferably 0.10 or less, more preferably 0.04 or less, and even more preferably 0.03 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) of the polyimide film calculated according to JIS K7373-2006.

In terms of light transmittance, the laminate of the present invention preferably has a haze value of 10 or less, more preferably 8 or less, and even more preferably 5 or less.

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 described above.

The birefringence in the thickness direction of the laminate of the present invention at a wavelength of 590 nm is preferably 0.040 or less, preferably 0.020 or less, preferably 0.015 or less, further preferably 0.010 or less, and still more preferably 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 of the polyimide film at a wavelength of 590 nm.

5. Purpose of the laminate

The use of the laminate of the present invention is not particularly limited, and for example, it can be used for the same purpose as the above-mentioned polyimide film of the present invention.

6. Manufacturing method of laminate

As a method for manufacturing the layered product of the present invention, for example, the following manufacturing method may be mentioned, which includes a step of forming at least one side of the polyimide film of the present invention containing at least a radical polymerizable compound and a cationic polymerizable compound One step of the coating film of the hard coat layer forming composition; and the step of hardening the above coating film.

The composition for forming a hard coat 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, etc., if necessary.

Here, regarding the radical polymerizable compound, the cationic polymerizable compound, the polymerization initiator and the additives contained in the composition for forming the hard coat layer, the same as described in the above hard coat layer may be used, and the solvent may be It is appropriately selected and used from known solvents.

As a method for forming the coating film of the composition for forming the hard coat layer on at least one side of the polyimide film, for example, the hard coat layer may be coated on at least one side of the polyimide film by a known coating method. The method of forming the composition.

The coating means is not particularly limited as long as it can be coated with a desired film thickness. For example, the same method as the method of applying the polyimide precursor resin composition to the support can be cited.

The coating film of the hardening resin composition for hard coat layers described above is dried to remove the solvent if necessary. Examples of the drying method include a method of drying under reduced pressure or heating, and further combining these drying methods. Moreover, when drying under normal pressure, it is preferable to dry at 30 degreeC or more and 110 degreeC or less.

For a coating film obtained by applying the above-mentioned hardening resin composition for hard coat layer and drying it as needed, the polymerizable group of the radically polymerizable compound and the cationically polymerizable compound contained in the curable resin composition , Hardening the coating film by at least any one of light irradiation and heating, whereby at least one polymer hard radical containing a radically polymerizable compound and a cationic polymerizable compound can be formed on at least one side of the polyimide film coating.

Light irradiation mainly uses ultraviolet rays, visible light, electron beams, ionizing radiation, etc. In the case of ultraviolet curing, ultraviolet rays emitted from the light of ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. are used. The irradiation amount of the energy ray source is about 50 to 5000 mJ / cm ² based on the cumulative exposure at the ultraviolet wavelength of 365 nm.

In the case of heating, the treatment is usually performed at a temperature of 40 ° C or higher and 120 ° C or lower. Alternatively, the reaction can be carried out by leaving at room temperature (25 ° C) for more than 24 hours.

III. Surface material for display

The surface material for a display of the present invention is the above-mentioned polyimide film of the present invention or the laminate of the present invention.

The surface material for displays of the present invention is arranged and used on the surface of various displays. The surface material for a display of the present invention is excellent in transparency as well as the above-described polyimide film of the present invention and the laminate of the present invention, and has improved bending resistance under high humidity, and is particularly suitable for flexibility For display.

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

Furthermore, in the case where the surface material for a display of the present invention is the laminate of the present invention described above, the surface which becomes the outermost surface after being arranged on the surface of the display may be the surface of the polyimide film side, or may be a hard coating The surface of the layer side. Among them, it is preferable to arrange the surface material for a display of the present invention such that the surface on the hard coat side further becomes the surface on the positive side. In addition, the surface material for display of the present invention may have an anti-fingerprint adhesion layer on the outermost surface.

In addition, the method of arranging the surface material for display of the present invention on the surface of the display is not particularly limited, and for example, a method via a bonding layer and the like can be cited. As the aforementioned adhesive layer, a conventionally known adhesive layer that can be used as an adhesive for surface materials for displays can be used.

Examples

In the following, unless otherwise specified, measurement or evaluation is performed at 25 ° C.

[Evaluation method]

<Weight average molecular weight of polyimide precursor>

The weight average molecular weight of the polyimide precursor is that the polyimide precursor is made into a 0.5% by weight concentration of N-methylpyrrolidone (NMP) solution, and the solution is passed through a syringe filter (pore size: 0.45 μm ) Filtration, using a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less as a developing solvent, using a GPC device (manufactured by Tosoh, HLC-8120, using a column: GPC LF-804 manufactured by SHODEX), with a sample injection volume of 50 μL, The measurement was carried out under the condition of solvent flow rate 0.5mL / min and 40 ℃. The weight average molecular weight of the polyimide precursor is measured relative to a polystyrene standard sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, 3,070) at the same concentration as the sample. Conversion value of standard polystyrene. The dissolution time is compared with the calibration curve to determine the weight average molecular weight.

<Viscosity of Polyimide Precursor Solution>

The viscosity of the polyimide precursor solution was measured using a viscometer (for example, TVE-22HT, Toki Industry Co., Ltd.) at 25 ° C with a sample volume of 0.8 mL.

<Weight average molecular weight of polyimide>

15 mg of polyimide powder was immersed in 15000 mg of N-methylpyrrolidone (NMP), while being heated to 60 ° C in a water bath, while using a stirrer at a rotation speed of 200 rpm to stir for 3 to 60 hours until the dissolution was confirmed visually So far, a NMP solution with a concentration of 0.1% by weight was obtained. This solution was filtered through a syringe filter (pore size: 0.45 μm), using a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less as a developing solvent, and using a GPC device (manufactured by Tosoh, HLC-8120, detector: differential refractive index ( RID) detector, using a column: two GPC LF-804 manufactured by SHODEX are connected in series) under the conditions of sample injection volume 50 μL, solvent flow rate 0.4 mL / min, column temperature 37 ° C, detector temperature 37 ° C Determination. The weight-average molecular weight of polyimide is set relative to the standard of the polystyrene standard sample (weight-average molecular weight: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, 3,070) at the same concentration as the sample. Conversion value of polystyrene. The dissolution time is compared with the calibration curve to determine the weight average molecular weight.

<Viscosity of polyimide solution>

The viscosity of the polyimide solution was measured using a viscometer (for example, TVE-22HT, Toki Industry Co., Ltd.) at 25 ° C with a sample volume of 0.8 mL.

<Film thickness measurement method>

Use a digital linear gauge (made by Ozaki Manufacturing Co., Ltd., model PDN12 digital gauge) to measure the film thickness of 5 points at the four corners and the center of the test piece of polyimide film cut into a size of 10cm × 10cm The average value is the film thickness of the polyimide film.

<Humidity Expansion Coefficient>

The humidity expansion coefficient was measured using water vapor TMA / S 8227A1 manufactured by Rigaku.

After drying the test piece cut into a polyimide film of 5 mm × 20 mm at 120 ° C. for 10 minutes, the test piece was set so that the distance between the clamps was 15 mm and the tensile load in the longitudinal direction became 5 g. Fix the temperature to 25 ° C and change the humidity to 15% RH, 20% RH, 50% RH. Calculate the average elongation per unit humidity of 1% based on the elongation of the 20% RH and 50% RH test pieces, and set It is the humidity expansion coefficient. In addition, the calculation formula is as follows.

Humidity expansion coefficient (ppm /% RH) = (X × 10 ⁶ ) / (Y × Z)

X: the value of the test piece length at 50% RH minus the test piece length at 20% RH

Y: Humidity change from 20% RH to 50% RH (50-20 (% RH))

Z: Length of test piece at 20% RH

In addition, the elongation of the test piece is always detected, recorded every 1 second, and measured in the following order.

In the following measurement, the fixed length of the test piece means that the change in the length of the test piece within 30 minutes is 0.1 μm or less.

1. The environment of the test piece is stable at a humidity of 15% RH. After the length of the test piece becomes fixed without change, it is maintained for more than 30 minutes

2. Then, the environment of the test piece is stabilized at a humidity of 20% RH, and the length of the test piece becomes fixed without change, and it is kept for more than 30 minutes (measure the length of the test piece)

3. Then, the environment of the test piece is stable at a humidity of 50% RH, and the length of the test piece becomes fixed without change, and it is kept for more than 30 minutes (measure the length of the test piece)

4. Calculate the difference between the length of the test piece at 20% RH and 50% RH, divide by 30 to calculate the elongation per unit humidity of 1%

<Total light transmittance>

The measurement was performed based on JIS K7361-1 and a haze meter (HM150 manufactured by Murakami Color Technology Research Institute).

<YI value (yellowness)>

The YI value is based on JIS K7373-2006, based on the use of an ultraviolet-visible near-infrared spectrophotometer (Japan Spectroscopy Co., Ltd. V-7100), using a spectrophotometric color measurement method, using an auxiliary illuminant C, a 2-degree field of view, and 250 nm at 1 nm intervals The transmittance measured in the range above and below 800 nm is measured, and the tristimulus values X, Y, and Z in the XYZ color system are obtained, and the values of X, Y, and Z are calculated according to the following formula.

YI = 100 (1.2769X-1.0592Z) / Y

<Static bending test>

Hereinafter, the method of the static bending test will be described with reference to FIG. 1.

Bend the test piece 1 of polyimide film cut into 15mm × 40mm at the position of half of the long side, and use a metal piece 2 (100mm × 30mm × 6mm) with a thickness of 6mm at both ends of the long side of the test piece 1 ) It is arranged so as to be sandwiched from the top to the bottom, and is fixed with adhesive tape so that the overlapping amounts of both ends of the test piece 1 and the top and bottom of the metal piece 2 become 10 mm, respectively. Using the glass plates (100mm × 100mm × 0.7mm) 3a, 3b, the metal piece 2 to which the test piece 1 is fixed is sandwiched from above and below, and the test piece 1 is fixed in a state where the inner diameter is bent at 6 mm. At this time, the dummy test pieces 4a, 4b are sandwiched between the metal piece 2 where the test piece 1 does not exist, and are fixed with tape so that the glass plates 3a, 3b become parallel.

After the test pieces fixed in the bent state as described above are allowed to stand for 24 hours in an environment of 60 ° C and 90% relative humidity (RH) or an environment of 70 ° C and 20% relative humidity (RH), respectively, Remove the tape used to fix the glass plate and the test piece, and release the force applied to the test piece. Thereafter, one end of the test piece was fixed, and the inner angle of the test piece was measured 30 minutes after the force applied to the test piece was released. An internal angle of 120 ° or more was evaluated as A, and an internal angle of less than 120 ° was evaluated as B.

Furthermore, when the film is completely restored to its original state without being affected by the static bending test, the internal angle becomes 180 °.

<Tensile elastic modulus>

After a test piece cut into a polyimide film of 15 mm × 40 mm was subjected to humidity control at a temperature of 25 ° C. and a relative humidity of 60% for 2 hours, the stretching speed was set to 8 mm / min according to JIS K7127, and the jig was set. The distance between them was set to 20 mm, and the tensile elastic modulus at 25 ° C was measured. The tensile testing machine was used (manufactured by Shimadzu Corporation: Autograph AG-X 1N, dynamometer: SBL-1KN).

<tanδ curve>

For the polyimide films of Examples 1 to 3 and Comparative Examples 1 to 3, a dynamic viscoelasticity measuring device DVA-225 (IT Meter. And Control, Inc.) was used, and the measurement range was set to -70 ° C or more and 400 Below ℃, choose stretching as the deformation form, with frequency 1Hz, heating rate 5 ℃ / min, static / dynamic ratio 1.5, minimum load 5cN, strain (E> 10e + 8) 0.08%, sample width 5mm, distance between clamps 15mm Perform dynamic viscoelasticity measurement to obtain a curve of tanδ (tanδ = loss elastic modulus (E ") / storage elastic modulus (E ')), and find the temperature of the peak of the peak. There are multiple cases in the peak of the tanδ curve At this time, the temperature of the apex of the peak with the maximum value of the peak is set as the glass transition temperature. The results obtained by this measurement method are shown in Table 1 and FIG. 2.

For the polyimide films of Examples 1 to 3 and Examples 4 to 8, a dynamic viscoelasticity measuring device RSA-G2 (TA Instrument Japam (share)) was used, and the measurement range was set to -150 ° C or more and 490 ° C or less , Select stretching as the deformation form, perform dynamic viscoelasticity measurement at a frequency of 1 Hz, a heating rate of 5 ° C / min, a sample width of 5 mm, and a distance between fixtures of 20 mm to obtain tanδ (tanδ = loss elastic modulus (E ") / storage elastic modulus Calculate the temperature of the peak of the peak. The measurement conditions of the device are set as follows. When there are multiple peaks of the tan δ curve, the temperature of the peak of the peak with the maximum maximum value of the peak Set to the glass transition temperature. In the analysis of the peaks and bending points, visual evaluation is not performed, but the data is digitized and analyzed based on the values. The results obtained by this measurement method are shown in Table 2 and Table 4.

<Measurement conditions of RSA-G2>

(Initial value)

Axial force: 3.0g

Sensitivity (Sensitivity): 1.0g

Proportional force Mode: Force Tracking

Axial Force> Dynamic Force: 1.5%

Minimum axial force (Minimum axial force) 2.0g

The following programmatic extension (Programmed Extension Below): 0Pa

(Auto strain)

Mode (Mode): Allowed (Enabled)

Strain adjust: 20.0%

Minimum strain: 0.01%

Maximum strain: 3.0%

Minimum force: 1.5g

Maximum force (Maximum force): 200.0g

(Test parameters)

Sampling rate (Sampling rate): 10pts / s

Strain%: 0.1%

Frequency: Single point

Frequency (Frequency) 1Hz

In addition, as a sample for measuring the tan δ curve, the following is used, which uses a razor or scalpel and uses a cutting jig formed with a slit of 5 mm width. For an environment that will be 23 ° C ± 2 ° C RH30 ~ 50% The polyimide film that was left still for 24 hours was sampled into a film made of 10 cm square or more, and then the center portion of the film was cut into a width of 5 mm × a length of 50 mm (so that the sample length becomes 20 mm when clamped). The width is determined by using a vernier caliper, recording the average value obtained by changing the position and measuring 3 times. At this time, when a part of the width measurement has a variation range of 3% or more, the sample is not used. The thickness of the polyimide film is the value measured by the above-mentioned film thickness measurement method.

<Pencil hardness>

The pencil hardness is performed by the following method: after the measurement sample is subjected to humidity control for 2 hours under the conditions of a temperature of 25 ° C and a relative humidity of 60%, a test pencil specified in JIS-S-6006 is used, and a Toyo Seiki (share ) The manufactured pencil scratch coating film hardness tester performs the pencil hardness test (0.98N load) specified in JIS K5600-5-4 (1999) on the film surface, and evaluates the highest pencil hardness without damage.

(Synthesis Example 1)

In a 5L separable flask, dissolved 2903g of dehydrated dimethylacetamide and 1,6.0g (0.07) of 1,3-bis (3-aminopropyl) tetramethyldisilaxane (AprTMOS) When the temperature of the mol) solution is controlled to 30 ℃, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) 14.6g (0.03mol ), And stir for 30 minutes using a mechanical stirrer. 400g (1.25mol) of 2,2'-bis (trifluoromethyl) benzidine (TFMB) was added to it, and after confirming complete dissolution, 4,4 '-( 565 g (1.27 mol) of hexafluoroisopropylidene diphthalic anhydride (6FDA) was synthesized to dissolve polyimide precursor solution 1 (solid content 20% by weight) in which polyimide precursor 1 was dissolved. The molar ratio (TFMB: AprTMOS) of TFMB and AprTMOS used in the polyimide precursor 1 was 95: 5. The viscosity of the polyimide precursor solution 1 (solid content 25% by weight) at 25 ° C. was 95300 cps, and the weight average molecular weight of the polyimide precursor 1 measured by GPC was 186500.

(Synthesis Example 2)

In the order of the above Synthesis Example 1, the reaction was carried out in such a way that the molar ratio of TFMB to AprTMOS (TFMB: AprTMOS) became 81:19, and a polyimide precursor solution 2 was prepared. The viscosity of the polyimide precursor solution 2 (solid content 25% by weight) at 25 ° C. was 10180 cps, and the weight average molecular weight of the polyimide precursor 2 measured by GPC was 109,000.

(Synthesis Example 3)

To a 500 mL separable flask was added 267.9 g of dehydrated dimethylacetamide, and 3,3'-bis (trifluoromethyl) -4,4 '-[(1,1,1,3 , 3,3-hexafluoropropane-2,2-diyl) bis (4,1-phenoxy)] diphenylamine (HFFAPP, manufactured by Wakayama Chemical Industry Co., Ltd.) 40.1g (61.3mmol), in When the liquid temperature of the solution in which HFFAPP is dissolved is controlled to 30 ° C, slowly add 4,4,-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) in portions so that the temperature rises below 2 ° C 27.0 g (60.8 mmol) of polyimide precursor solution 3 (solid content 20% by weight) in which polyimide precursor 3 was dissolved was synthesized. The viscosity of the polyimide precursor solution 3 (solid content 20% by weight) at 25 ° C. was 5560 cps, and the weight average molecular weight of the polyimide precursor 3 measured by GPC was 310,000.

(Comparative Synthesis Example 1)

To a 500 mL separable flask, 137.8 g of dehydrated dimethylacetamide and N, N′-bis (4-aminophenyl) p-xylylenediamine (DATA) 15.2 g (43.9 mmol) were added ), When the liquid temperature of the solution in which DATA is dissolved is controlled to 50 ° C, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride in fractions in such a way that the temperature rises below 2 ° C (6FDA) 18.3 g (41.2 mmol) of synthetic polyimide precursor solution 1 (solid content 20% by weight) in which comparative polyimide precursor 1 was dissolved. The viscosity of the comparative polyimide precursor solution 1 (solid content 20% by weight) at 25 ° C. was 1380 cps, and the weight average molecular weight of the comparative polyimide precursor 1 measured by GPC was 168,000.

(Comparative Synthesis Example 2)

In a 500mL separable flask, 174.3g of dehydrated dimethylacetamide and 4.1g of N, N'-bis (4-aminophenyl) p-xylylenediamine (DATA) were dissolved. When the solution temperature of 11.8mmol) is controlled to 30 ℃, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) 2.6g (5.9 mmol) and stirred with a mechanical stirrer for 1 hour. Add 2,2'-bis (trifluoromethyl) benzidine (TFMB) 15.0g (46.8mmol) to it, and after confirming complete dissolution, slowly add 4,4'- in portions so that the temperature rises below 2 ° C (Hexafluoroisopropylidene) diphthalic anhydride (6FDA) 23.9g (53.7mmol), synthesized with comparative polyimide precursor 2 dissolved in polyimide precursor solution 2 (solid content 20 weight%). The molar ratio (TFMB: DATA) of TFMB and DATA used in Polyimide Precursor 2 was 80:20. The viscosity of the comparative polyimide precursor solution 2 (solid content 20% by weight) at 25 ° C. was 27490 cps, and the weight average molecular weight of the comparative polyimide precursor 2 measured by GPC was 175,000.

(Comparative Synthesis Example 3)

In a 500mL separable flask, 174.5g of dehydrated dimethylacetamide and 1,3-bis (3-aminopropyl) tetramethyldisilaxane (AprTMOS) 27.9g were dissolved ( When the solution temperature of 0.11 mol) is controlled to 30 ℃, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) 50.5g in portions so that the temperature rises below 2 ℃ (0.11 mol), a comparative polyimide precursor solution 3 (solid content 30% by weight) in which the comparative polyimide precursor 3 was dissolved was synthesized. The viscosity of the comparative polyimide precursor solution 3 (solid content 30% by weight) at 25 ° C. was 4500 cps, and the weight average molecular weight of the comparative polyimide precursor 3 measured by GPC was 82,000.

(Examples 1 to 3, Comparative Examples 1 to 3)

Using the polyimide precursor solutions 1 to 3 and the comparative polyimide precursor solutions 1 to 3, the following steps (1) to (3) were carried out, whereby the thickness of the polymer shown in Table 1 was prepared respectively Acetate film.

(1) Each polyimide precursor solution was coated on glass and dried in a circulating oven at 120 ° C for 10 minutes.

(2) Under a nitrogen gas flow (oxygen concentration of 100 ppm or less), the temperature was raised to 350 ° C at a temperature increase rate of 10 ° C / min, held for 1 hour, and then cooled to room temperature.

(3) Peel off from the glass to obtain each polyimide film.

Each polyimide film was evaluated using the above evaluation method. Table 1 shows the evaluation results. As an example, the tan δ curve of the polyimide film of Example 2 is shown in FIG. 2. In addition, in the measurement of the polyimide film of Example 2, the test piece was melted in a temperature range of 350 ° C. or higher, so the correct value was not obtained.

Table 1 shows the polyimide films of Examples 1 to 3, which are equivalent to the polyimide films of the present invention, are resin films having excellent transparency and improved bending resistance in a high humidity environment.

In contrast, the polyimide films of Comparative Examples 1 to 3 have poor bending resistance in a high humidity environment. In addition, the polyimide film of Comparative Example 1 has a high yellowness (YI value) and poor transparency.

For the polyimide films of Examples 1 to 3, dynamic viscoelasticity measurement was performed using a dynamic viscoelasticity measuring device RSA-G2 (TA Instruments Japan Co., Ltd.), and the measurement range was set to -150 ° C or higher and 490 ° C or lower. Obtain the tanδ curve. Table 2 shows the measurement results.

(Synthesis Example 4)

In the order of the above Synthesis Example 1, the reaction was carried out in such a manner that the molar ratio of TFMB to AprTMOS (TFMB: AprTMOS) became 97.5: 2.5, and a polyimide precursor solution 4 was prepared. The viscosity of the polyimide precursor solution 4 (solid content 25% by weight) at 25 ° C. was 48900 cps, and the weight average molecular weight of the polyimide precursor 4 measured by GPC was 156400.

(Example 4)

In Example 1, a polyimide precursor solution 4 was used instead of the polyimide precursor solution 1, except that the polyimide film having the thickness shown in Table 4 was produced in the same manner as in Example 1. .

The obtained polyimide film was evaluated using the above evaluation method. The evaluation results are shown in Table 4.

(Example 5)

(1) Preparation of polyimide (chemical imidization)

Into a 1L separable flask was added dehydrated dimethylacetamide (466g) and 1,3-bis (3-aminopropyl) tetramethyldisilaxane (AprTMOS) (1.31 g) The solution, when controlled to a liquid temperature of 30 ° C, slowly add 4,4 ^′ -(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (1.17g) in such a way that the temperature rises below 2 ° C ), And stir for 30 minutes using a mechanical stirrer. Add 2,2'-bis (trifluoromethyl) benzidine (TFMB) (65.9g) to it, and after confirming complete dissolution, slowly add 4,4 '-(VI Fluoroisopropylidene) diphthalic anhydride (6FDA) (91.7g), a polyimide precursor solution 5 (solid content 25% by mass) in which the polyimide precursor 5 is dissolved is synthesized.

The above-mentioned polyimide precursor solution 5 (400 g) which was lowered to room temperature was added to a 5 L separable flask under a nitrogen atmosphere. Dehydrated dimethylacetamide (165.3 g) was added thereto and stirred until it became uniform. Then, pyridine (48.5 g, 613 mmol) and acetic anhydride (62.6 g, 613 mmol) as catalysts were added and stirred at room temperature for 24 hours to synthesize a polyimide solution. To the obtained polyimide solution, butyl acetate (235.3 g) was added and stirred until it became uniform. Then, methanol (1744.5 g) was slowly added to obtain a white slurry. The slurry was filtered and washed 5 times with methanol to obtain polyimide 5 (91.0 g). The weight average molecular weight of polyimide measured by GPC was 201269.

(2) Manufacture of polyimide film

The powder of polyimide 5 was dissolved in a solvent (dichloromethane) to prepare a polyimide solution 5 having a solid content of 14% by mass. The viscosity of the polyimide solution 5 (solid content 14% by mass) at 25 ° C was 4290 cps.

Using the polyimide solution 5 obtained as described above, the following steps (i) to (iii) were carried out, thereby producing a polyimide film with a thickness of 50 μm ± 5 μm.

(i) The polyimide solution 5 was applied to a glass plate, and after natural drying, the film was peeled from the glass plate.

(ii) Dry the film in a circulating oven at 50 ° C for 10 minutes.

(iii) The membrane was heated to 200 ° C at a temperature increase rate of 10 ° C / min under a nitrogen gas flow (oxygen concentration of 100 ppm or less), held at 200 ° C for 1 hour, and then cooled to room temperature to obtain a polyimide membrane.

(Example 6)

(1) Preparation of polyimide (chemical imidization)

In Example 5 above, the polyimide precursor solution 1 prepared in the same manner as in Synthesis Example 1 was used instead of the polyimide precursor solution 5, except that the implementation was obtained in the same manner as in Example 5. Example 6 of polyimide 6. Table 3 shows the weight average molecular weight of polyimide 6 measured by GPC.

(2) Manufacture of polyimide film

In Example 5, polyimide 6 was used instead of polyimide 5, and adjusted so that the solid content concentration became the concentration shown in Table 3, except that it was obtained in the same manner as in Example 5. Table 3 shows the polyimide solution 6. Table 3 shows the viscosity of polyimide solution 6 at 25 ° C.

In Example 5, the polyimide solution 6 was used instead of using the polyimide solution 5, except that the polyimide film of Example 6 was obtained in the same manner as in Example 5.

(Example 7)

(1) Preparation of polyimide (chemical imidization)

To a 5L separable flask was added dehydrated dimethylacetamide (250g) and 1,3-bis (3-aminopropyl) tetramethyldisilaxane (AprTMOS) (4.14 g) The solution, when controlled to a liquid temperature of 30 ° C, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (3.70g) in such a way that the temperature rises below 2 ° C ), And stir for 30 minutes using a mechanical stirrer. Add 2,2'-bis (trifluoromethyl) benzidine (TFMB) (21.3g) to it, and after confirming complete dissolution, slowly add 4,4 '-(VI Fluoroisopropylidene) diphthalic anhydride (6FDA) (33.3g), a polyimide precursor solution 7 (solid content 20% by mass) in which polyimide precursor 7 is dissolved is synthesized.

Add pyridine (26.3g) and acetic anhydride (34.0g) as a catalyst to the above polyimide precursor solution 7 that has dropped to room temperature under a nitrogen atmosphere, and stir at room temperature for 24 hours to synthesize a polyimide Imine solution. The obtained polyimide solution (350 g) was added to a 5 L separable flask, butyl acetate (237 g) was added and stirred until it became uniform, and then, methanol (1761 g) was slowly added to obtain a white slurry . The slurry was filtered and washed 5 times with methanol to obtain polyimide 7. The weight-average molecular weight of Polyimide 7 measured by GPC was 230,000.

(2) Manufacture of polyimide film

In Example 5, polyimide 7 was used instead of polyimide 5, and adjusted so that the solid content concentration became the concentration shown in Table 3, except that it was obtained in the same manner as in Example 5. Table 3 shows the polyimide solution 7. Table 3 shows the viscosity of polyimide solution 7 at 25 ° C.

In Example 5, the polyimide solution 7 was used instead of the polyimide solution 5, except that the polyimide film of Example 7 was obtained in the same manner as in Example 5.

(Example 8)

(1) Preparation of polyimide (chemical imidization)

Into a 1L separable flask was added dehydrated dimethylacetamide (105g) and 1,3-bis (3-aminopropyl) tetramethyldisilaxane (AprTMOS) (11.81 g) The solution, when controlled to a liquid temperature of 30 ° C, slowly add 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) (10.32g) in such a way that the temperature rises below 2 ° C ), And stir for 30 minutes using a mechanical stirrer. Add 2,2'-bis (trifluoromethyl) benzidine (TFMB) (15.14g) to it, and after confirming complete dissolution, slowly add 4,4 '-(VI Fluoroisopropylidene) diphthalic anhydride (6FDA) (31.77g), a polyimide precursor solution 8 (solid content 40% by mass) in which the polyimide precursor 8 is dissolved is synthesized.

Add pyridine (0.39g) and acetic anhydride (47.7g) as catalysts to the above polyimide precursor solution 8 that has dropped to room temperature under a nitrogen atmosphere, and stir at room temperature for 24 hours to synthesize a polyimide Imine solution. To the obtained polyimide solution, butyl acetate (362 g) was added and stirred until it became uniform, and then, methanol (3000 g) was slowly added to obtain a white slurry. The slurry was filtered and washed with methanol 10 times to obtain polyimide 8. The weight average molecular weight of polyimide measured by GPC was 78720.

(2) Manufacture of polyimide film

In Example 5, polyimide 8 was used instead of polyimide 5, and adjusted so that the solid content concentration became the concentration shown in Table 3, except that it was obtained in the same manner as in Example 5. Table 3 shows the polyimide solution 8. Table 3 shows the viscosity of the polyimide solution 8 at 25 ° C.

In Example 5, the polyimide solution 8 was used instead of the polyimide solution 5, except that the polyimide film of Example 8 was obtained in the same manner as in Example 5.

The polyimide films of Examples 5 to 8 were evaluated using the above evaluation method. The evaluation results are shown in Table 4.

Table 4 shows that the polyimide films of Examples 4 to 8 corresponding to the polyimide film of the present invention are resin films having excellent transparency and improved bending resistance in a high humidity environment.

(Example 9)

To a 40% by mass methyl isobutyl ketone solution of neopentaerythritol triacrylate, 10 mass parts of 1-hydroxy-cyclohexyl-phenyl-ketone was added with respect to 100 mass parts of neopentaerythritol triacrylate. (Manufactured by BASF, Irgacure 184), to prepare a resin composition for a hard coat layer.

The polyimide film of Example 1 was cut into 10 cm × 10 cm, and the surface of the side not in contact with the glass plate when the film was made was coated with the resin composition for a hard coat layer under a nitrogen gas flow at 200 mJ / cm ² . The exposure amount was irradiated with ultraviolet rays to harden it to form a hard coat layer as a cured film with a thickness of 10 μm, and a laminate was produced.

Claims (11)

A polyimide film containing a polyimide having a structure represented by the following general formula (1), the polyimide contains an aromatic ring, and contains a fluorine atom selected from (i), and (ii ) At least one member of 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 by fluorine, is tan δ of the value obtained by dividing the loss elastic modulus by the storage elastic modulus In the curve, the peak of the peak is only in the temperature range above 150 ° C, the total light transmittance measured according to JIS K7361-1 is 85% or more, the yellowness calculated according to JIS K7373-2006 is 12 or less, the humidity expand The coefficient is below 10.0ppm /% RH, (In the general formula (1), R ¹ represents a tetravalent residue of a tetracarboxylic acid residue, R ² represents a divalent residue of a diamine residue, and in the total amount of R ² , the diamine residue having a silicon atom in the main chain The content ratio of the base is 50 mol% or less; n represents the number of repeating units). The polyimide film according to claim 1, wherein in the above general formula (1), R ² represents a diamine residue selected from a group having no silicon atom, and the main chain has 1 or 2 silicon atoms At least one of the divalent residues in the diamine residue, and the total content of R ² , the content ratio of the diamine residue having 1 or 2 silicon atoms in the main chain is 50 mol% or less.     The polyimide film according to claim 1 or 2, wherein in the case of performing a static bending test according to the following static bending test method, the internal angle measured in the test is 120 ° or more, [static bending Test method] Bend the test piece of polyimide film cut into 15mm × 40mm at the position of one and a half of the long side, and use a metal piece (100mm × 30mm × 6mm) It is arranged by sandwiching it from the top to the bottom, and it is fixed with tape in such a way that the overlapping amounts of the two ends of the test piece and the metal sheet on the top and bottom are 10mm, and in this state, the glass plate is used (100mm × 100mm × 0.7mm) clamped from above and below, and the test piece is fixed in a state of bending with an inner diameter of 6mm; at this time, it is sandwiched between the metal piece and the glass plate where the test piece does not exist Insert the dummy test piece and fix it with tape in such a way that the glass plate becomes parallel; the test piece fixed in the state bent in the above manner will be allowed to stand at 60 ° C and 90% relative humidity (RH) for 24 After hours, remove the glass plate and the tape for fixing, and release the force applied to the test piece; then, fix one end of the test piece, and measure the test piece 30 minutes after releasing the force applied to the test piece Inner corner.     The polyimide film according to claim 1 or 2, wherein in the polyimide having the structure represented by the above general formula (1), R ¹ in the above general formula (1) contains a member selected from the group consisting of 4 , 4 '-(Hexafluoroisopropylidene) diphthalic anhydride residue, 3,4'-(Hexafluoroisopropylidene) diphthalic anhydride residue, 3,3 '-(hexa (Fluoroisopropylidene) diphthalic anhydride residues, 4,4'-oxydiphthalic anhydride residues, and 3,4'-oxydiphthalic anhydride residues At least one kind of four-valent base. The polyimide film according to claim 1 or 2, wherein in the polyimide having the structure represented by the above general formula (1), R ² in the above general formula (1) does not have The diamine residue of the silicon atom is at least one kind of divalent group selected from the group consisting of the following divalent groups, the divalent group consisting of: (i) a fluorine atom, and (ii) an aromatic ring At least one divalent group in a group consisting of a structure formed by a sulfonyl group or a fluorine-substituted alkylene group, and a divalent group represented by the following general formula (2), (In the general formula (2), R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group).     The polyimide film according to claim 1 or 2, wherein the value calculated by dividing the yellowness calculated according to the aforementioned JIS K7373-2006 by the film thickness (μm) is 0.10 or less.     The polyimide film according to claim 1 or 2, wherein in the above general formula (1), R ² represents at least one divalent group selected from diamine residues having no silicon atom, Contains a diamine residue having a hexafluoroisopropylidene skeleton in the main chain, or R ² represents a diamine residue selected from a diamine residue having no silicon atom and a main chain having 1 or 2 silicon atoms Among at least one of the divalent radicals, the total content of R ^{2 is that} the content of diamine residues having 1 or 2 silicon atoms in the main chain is 2.5 mol% or more and 50 mol% or less.     A laminate having the polyimide film according to any one of claims 1 to 7 and a hard coat layer, the hard coat layer containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound .         The laminate according to claim 8, wherein the radical polymerizable compound is a compound having two or more (meth) acryloyl groups in one molecule, and the cationic polymerizable compound is two or more in one molecule At least one compound of epoxy group and oxetanyl group.         A surface material for a display, which is a polyimide film according to any one of the above claims 1 to 7, or a laminate having the polyimide film and a hard coat layer, the hard coat layer containing free radicals At least one polymer of a polymerizable compound and a cationic polymerizable compound.         The surface material for display according to claim 10, which is for a flexible display.