JP6705583B2 - Polyimide, polyamic acid, polyamic acid solution, and polyimide film - Google Patents

Description

The present invention relates to a polyimide, a polyamic acid, a polyamic acid solution, and a polyimide film.

In the field of display devices such as displays and liquid crystal displays using organic electroluminescence elements, it has been required to develop a light and flexible material having high light transmittance as a material used for its substrate and the like. A film made of a light and flexible polyimide is attracting attention as a material used for such purposes. With respect to such a polyimide, in recent years, development of an alicyclic polyimide having sufficient light transmissivity is underway, and for example, in WO 2011/099518 (Patent Document 1), a specific general formula is used. Polyimides having the repeat units described are disclosed.

International Publication No. 2011/099518

The polyimide described in Patent Document 1 has sufficiently high transparency. However, the polyimide described in Patent Document 1 is not always sufficient from the viewpoint of exhibiting a sufficiently low yellowness and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner. As described above, the conventional polyimide is not always sufficient in that it exhibits well-balanced sufficiently high total light transmittance, sufficiently low yellowness, and sufficiently low linear expansion coefficient at a higher level. There wasn't.

The present invention has been made in view of the above problems of the prior art, and has a sufficiently high total light transmittance, a sufficiently low yellowness index, and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner. It is an object of the present invention to provide a polyimide capable of forming the polyimide, a polyamic acid capable of efficiently forming the polyimide, a solution of the polyamic acid, and a polyimide film including the polyimide.

As a result of earnest studies to achieve the above object, the inventors of the present invention have found that polyimide has a repeating unit (A) represented by the following general formula (1) and a repeating unit represented by the following general formula (2). By containing (B) and the repeating unit (A) in such a manner that the content ratio of the repeating unit (A) to the total amount of the repeating units (A) and (B) is 5 to 35 mol %, a sufficiently high total content can be obtained. The present invention has been completed by finding that it becomes possible to have a light transmittance, a sufficiently low yellowness index, and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner.

That is, the polyimide of the present invention has the following general formula (1):

[In the formula (1), R ¹ , R ² and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (A) represented by
The following general formula (2):

[In formula (2), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (A) with respect to the total amount of the repeating units (A) and (B) is 5 to 35 mol %. To do.

Further, in the polyimide of the present invention, R ¹⁰ in the general formulas (1) and (2) are both represented by the following general formula (3):

[In the formula (3), R ⁵ represents a fluoroalkyl group having 1 to 10 carbon atoms. ]
The group represented by is preferable.

Further, in the polyimide of the present invention, the content of the repeating unit (A) is preferably 5 to 25 mol% with respect to the total amount of the repeating units (A) and (B).

The polyamic acid of the present invention has the following general formula (4):

[In the formula (4), R ¹ , R ² , and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (C) represented by
The following general formula (5):

[In Formula (5), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (C) with respect to the total amount of the repeating units (C) and (D) is 5 to 35 mol %. To do.

The polyamic acid solution of the present invention is characterized by containing the polyamic acid of the present invention and an organic solvent.

Furthermore, the polyimide film of the present invention is characterized by comprising the above-mentioned polyimide of the present invention.

According to the present invention, a polyimide capable of having a sufficiently high total light transmittance, a sufficiently low yellowness index, and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner, and efficiently forming the polyimide. It is possible to provide a polyamic acid capable of being obtained, a solution of the polyamic acid, and a polyimide film made of the polyimide.

3 is a graph showing an IR spectrum of the polyimide obtained in Example 1.

Hereinafter, the present invention will be described in detail according to its preferred embodiments.

[Polyimide]
The polyimide of the present invention has the following general formula (1):

[In the formula (1), R ¹ , R ² and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (A) represented by
The following general formula (2):

[In formula (2), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (A) with respect to the total amount of the repeating units (A) and (B) is 5 to 35 mol %. To do.

Regarding the repeating unit (A), the alkyl group that can be selected as R ¹ , R ² and R ^{3 in} the general formula (1) is an alkyl group having 1 to 10 carbon atoms. When the number of carbon atoms exceeds 10, the glass transition temperature is lowered, and it becomes impossible to achieve a sufficiently high level of heat resistance, which is required when used for various substrate materials and the like. Further, the number of carbon atoms of the alkyl group that can be selected as R ¹ , R ² and R ³ is preferably 1 to 6, and preferably 1 to 5 from the viewpoint of easier purification. Is more preferable, 1 to 4 is further preferable, and 1 to 3 is particularly preferable. The alkyl group that can be selected as R ¹ , R ² and R ³ may be linear or branched. Further, as such an alkyl group, a methyl group and an ethyl group are more preferable from the viewpoint of easy purification.

Further, R ¹ , R ² , and R ^{3 in the} general formula (1) are each independently a hydrogen atom or a carbon number of 1 from the viewpoint that higher heat resistance can be obtained when a polyimide is produced. Alkyl groups of 10 to 10 are more preferable, and among them, a hydrogen atom, a methyl group, an ethyl group, and an n-propyl group are independently selected from the viewpoints of easy availability of raw materials and easier purification. Or, it is more preferably an isopropyl group, and particularly preferably a hydrogen atom or a methyl group. Further, it is particularly preferable that a plurality of R ¹ , R ² and R ³ in the formula are the same from the viewpoint of easiness of purification and the like.

R ¹⁰ in the general formula (1) is an arylene group having a fluorine-containing substituent and having 6 to 40 carbon atoms (fluorine-based arylene group). The fluorine-containing substituent referred to here is not particularly limited as long as it contains fluorine, and examples thereof include a fluorine atom itself, or an alkyl group (fluoroalkyl group) in which at least a part is substituted with a fluorine atom. Etc. Among such fluorine-containing substituents, a fluoroalkyl group having 1 to 10 carbon atoms (for example, a fluorinated methyl group, a difluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, a trifluoromethyl group, Fluoroethyl group, pentafluoroethyl group, heptafluoro-n-propyl group, heptafluoroisopropyl group, nonafluoro-n-butyl group, nonafluoro-sec-butyl group, nonafluoroisobutyl group, nonafluoro-t-butyl group, perfluoro Fluorinated alkyl groups such as a pentyl group, a perfluorohexyl group, a perfluoroheptyl group, a perfluorooctyl group, a perfluorononyl group and a perfluorodecyl group are preferable, and among them, a carbon number of 1 to 5 (more preferably 1 ~3) fluoroalkyl groups are more preferred. Further, as such a fluorine-containing substituent, a fluoroalkyl group having 1 to 5 (more preferably 1 to 3) carbon atoms is more preferable from the viewpoint of availability of raw materials. As described above, with respect to R ¹⁰ , the fluorine-containing substituent contained in the arylene group further includes a fluoroalkyl group having 1 to 3 (more preferably 1 to 2) carbon atoms (particularly preferably a perfluoroalkyl group). preferable. The term "fluoroalkyl group" as used herein refers to a group formed by substituting a part or all of hydrogen atoms of an alkyl group with a fluorine atom (such a group is a hydrogen atom of at least a part of an alkyl group). Need only be substituted with a fluorine atom, and some hydrogen atoms of the alkyl group should be further substituted with a substituent other than a fluorine atom (for example, a halogen atom other than a fluorine atom, a hydroxyl group, an alkoxy group, a phenoxy group, deuterium, etc.). The term "perfluoroalkyl group" means a group in which all the hydrogen atoms of the alkyl group are substituted with fluorine atoms.

Regarding the arylene group having a fluorine-containing substituent that can be selected as R ¹⁰ in the general formula (1), the number of carbon atoms in the arylene group (the number of carbon atoms refers to the number of carbon atoms in the arylene group itself. The number of carbon atoms in the fluorine-containing substituent is excluded from the number) is 6 to 40. Further, the carbon number of such an arylene group is preferably 6 to 30, and more preferably 12 to 20. If the number of carbon atoms exceeds the above upper limit, heat resistance tends to decrease. Examples of such an arylene group include a phenylene group, a biphenylene group, a terphenylene group, a naphthylene group, an anthracenylene group, a fluorenylene group, a phenanthrylene group, a chrysenylene group, an indenylene group, a pyrenylene group or a benzoanthracenylene group. However, among them, from the viewpoint of availability, a biphenylene group, a phenylene group, and a naphthylene group are preferable, and a biphenylene group and a phenylene group are more preferable.

Furthermore, as the arylene group having a fluorine-containing substituent that can be selected as R ¹⁰ in the general formula (1), from the viewpoint of heat resistance and availability, the following general formula (3):

[In the formula (3), R ⁵ represents a fluoroalkyl group having 1 to 10 carbon atoms (more preferably a perfluoroalkyl group). ]
And a group represented by the following general formula (3-I)

A group represented by is particularly preferable.

In the polyimide of the present invention, as the repeating unit (A), plural kinds of repeating units (A) having different kinds of R ^{10 and} the like may be used in combination.

Furthermore, the terms repeating unit (B), R ¹⁰ in the general formula (2) has the same meaning as R ¹⁰ in formula (1) (the preferred ones also in formula (1) of The same as R ^10. ). In the polyimide of the present invention, as the repeating unit (B), plural kinds of repeating units (B) having different kinds of R ^{10 and} the like may be used in combination.

Incidentally, in the polyimide of the present invention, while having a sufficient level of heat resistance, a sufficiently high total light transmittance and a sufficiently low yellowness and a sufficiently low linear expansion coefficient are balanced at a higher level. From the viewpoint of good expression, it is preferable that all the R ^{10 s} in the repeating units (A) and (B) are the same.

Further, in the polyimide of the present invention, the repeating unit (A) with respect to the total amount of the repeating unit (A) represented by the general formula (1) and the repeating unit (B) represented by the general formula (2). The content is 5 to 35 mol% based on the molar amount. When the content of the repeating unit (A) represented by the general formula (1) is less than the lower limit, a sufficiently high total light transmittance (more preferably, a total light transmittance of 83.0% or more) is obtained. It tends to be difficult to obtain, and further, it becomes difficult to have a sufficiently low linear expansion coefficient (preferably -20 ppm/K to 20 ppm/K linear expansion coefficient). It becomes impossible to have a high level of total light transmittance, a sufficiently low degree of yellowness, and a sufficiently low linear expansion coefficient in a well-balanced manner. On the other hand, when the content of the repeating unit (A) exceeds the upper limit, it should have a sufficiently low linear expansion coefficient (preferably -20 ppm/K to 20 ppm/K) in this case as well. It becomes impossible to have a sufficiently low yellowness and a sufficiently low linear expansion coefficient at a high level in a well-balanced manner.

Furthermore, in the polyimide of the present invention, while having a sufficiently high total light transmittance, from the viewpoint of having a sufficiently low yellowness index and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner. The content ratio of the repeating unit (A) to the total amount of the repeating unit (A) represented by the general formula (1) and the repeating unit (B) represented by the general formula (2) is 5 to 25 mol %. Is more preferable, 10 to 20 mol% is further preferable, and 12.5 to 17.5 mol% is particularly preferable. From the same viewpoint, the content of the repeating unit (B) with respect to the total amount of the repeating unit (A) and the repeating unit (B) needs to be 95 to 65 mol% based on the molar amount, It is more preferably 95 to 75 mol %, further preferably 90 to 80 mol %, and particularly preferably 87.5 to 82.5 mol %.

In addition, the polyimide of the present invention may contain other repeating units as long as the effects of the present invention are not impaired. Such other repeating unit is not particularly limited, and a known repeating unit capable of forming a polyimide can be appropriately used. Further, in the polyimide of the present invention, in the case of containing another repeating unit, the repeating unit (A) represented by the general formula (1) and the repeating unit (B) represented by the general formula (2) are included. The repeating units (A) and (B) are preferably contained so that the total amount is 50 mol% or more (more preferably 70 mol% or more) with respect to all the repeating units in the polyimide. Furthermore, the content ratio of the total amount of the repeating unit (A) and the repeating unit (B) to all the repeating units in such a polyimide is more preferably 80 to 100 mol %, and 90 to 100 mol %. Is more preferable. When the content ratio of the total amount of the repeating units (A) and (B) to all the repeating units in such a polyimide is less than the lower limit, it has a sufficiently low yellowness and a sufficiently low linear expansion coefficient in a well-balanced manner. Tends to be difficult to do. From the viewpoint of more efficiently forming a polyimide, the polyimide of the present invention is substantially composed of the repeating units (A) and (B) (which does not substantially contain other repeating units. , More preferably the total amount of the repeating unit (A) and the repeating unit (B) is 95 mol% or more, further preferably 98 mol% or more, particularly preferably 99 mol% or more) Is preferred.

Further, as such a polyimide, the coefficient of linear expansion is more preferably −20 ppm/K to 20 ppm/K, more preferably −10 to 10 ppm/K, and −5 to 5 ppm/K. Is more preferable. When such a linear expansion coefficient exceeds the upper limit described above, when combined with a metal or an inorganic material having a linear expansion coefficient in the range of 5 to 20 ppm/K to form a composite, peeling tends to occur due to thermal history, When used as a substrate for electronics, manufactures microelectronics final products (for example, organic EL displays, touch panels, protective films (buffer coats) for semiconductors, interlayer insulating films, photoresists, microlenses for image sensors, etc. with high yield. It becomes difficult to do. On the other hand, when the coefficient of linear expansion is less than the lower limit, peeling or curling tends to occur when inorganic substances are laminated. Incidentally, when the device is an inorganic compound in the case of manufacturing a device in the upper layer or the lower layer of a film made of polyimide, from the viewpoint of suppressing the occurrence of curl of the film and strain during manufacturing, it is sufficiently equivalent to the inorganic compound. It is preferable to use a polyimide having a low coefficient of linear expansion. From this point of view, the polyimide of the present invention preferably has a coefficient of linear expansion within the above range.

In the present invention, the following values are adopted as the value of the coefficient of linear expansion of polyimide. That is, first, with respect to the polyimide to be measured, a film made of the polyimide and having a length of 20 mm, a width of 5 mm, and a thickness of 13 μm is formed. Then, the film is vacuum dried (120° C. for 1 hour) and heat-treated at 200° C. for 1 hour in a nitrogen atmosphere to obtain a dried film. Then, using the dry film thus obtained as a sample, a thermomechanical analyzer (trade name “TMA8310” manufactured by Rigaku Corporation) was used as a measuring device, under a nitrogen atmosphere, in a pulling mode (49 mN), ascending. By adopting the condition of the temperature rate of 5°C/minute, the change in the length of the sample in the vertical direction at 50°C to 200°C was measured, and 1°C (1K) per temperature range of 50°C to 200°C was measured. Find the average value of the change in length. Then, the average value thus obtained is adopted as the value of the linear expansion coefficient of the polyimide of the present invention (the value of the linear expansion coefficient of the polyimide film when the thickness is 13 μm, Adopted as the value of linear expansion coefficient.).

Further, such a polyimide preferably has a 5% weight loss temperature (Td5%) of 400° C. or higher, more preferably 450 to 550° C. If the 5% weight loss temperature is less than the lower limit, it tends to be difficult to obtain sufficient heat resistance for use as a substrate for microelectronic products, while if it exceeds the upper limit, It tends to be difficult to produce a polyimide having such characteristics. In addition, such a 5% weight loss temperature is set to a scanning temperature of 30° C. to 550° C. under a nitrogen gas atmosphere while flowing nitrogen gas, and a heating rate is 10° C./min. It can be determined by heating under the conditions described above and measuring the temperature at which the weight of the sample used decreases by 5%. A thermogravimetric analyzer (“TG/DTA220” manufactured by SII Nano Technology Co., Ltd.), for example, can be used for such measurement.

Further, as such polyimide, those having a glass transition temperature (Tg) of 300° C. or higher are preferable, and those having a glass transition temperature (Tg) of 350 to 500° C. are more preferable. If the glass transition temperature (Tg) is less than the lower limit, it is difficult to obtain sufficient heat resistance for use as a substrate for microelectronic products (for example, solar cells, liquid crystal display devices, and organic EL displays). When polyimide is used as the substrate for the transparent electrode of the device, it becomes difficult to sufficiently suppress the deterioration of quality (cracking, etc.) of the polyimide (substrate) in the heating process in the manufacturing process of the product. On the other hand, if it exceeds the upper limit, it tends to be difficult to produce a polyimide having such characteristics. In addition, such a glass transition temperature (Tg) can be simultaneously measured by the same method as the softening temperature measurement using a thermomechanical analyzer (trade name "TMA8311" manufactured by Rigaku Corporation) as a measuring device. In addition, when measuring such a glass transition temperature, it is preferable to perform the measurement by scanning in a range of 30° C. to 550° C. under a nitrogen atmosphere under the condition of a temperature rising rate of 5° C./min.

Further, as such polyimide, those having a softening temperature (softening point) of 300 to 550° C. are preferable, those of 320 to 550° C. are more preferable, and those of 340 to 510° C. are further preferable. When the softening temperature is lower than the lower limit, the heat resistance is lowered. For example, when a film made of such a polyimide is used as a substrate for a transparent electrode of a solar cell, a liquid crystal display device or an organic EL display device, its product In the production process of, there is a tendency that it is difficult to sufficiently suppress the deterioration of the quality of the film (substrate) (occurrence of cracks, etc.), and on the other hand, when the upper limit is exceeded, polyamic acid A sufficient solid-phase polymerization reaction does not proceed simultaneously with the thermal ring-closure condensation reaction, and when a film is formed, it tends to become brittle. The softening temperature of such a polyimide can be measured as follows. That is, a film made of polyimide having a length of 5 mm, a width of 5 mm, and a thickness of 0.013 mm (13 μm) is prepared as a measurement sample, and a thermomechanical analyzer (trade name “TMA8311” manufactured by Rigaku Corporation) is used as a measuring device. In a nitrogen atmosphere, a temperature rising rate of 5° C./min is adopted, and a transparent quartz pin (tip diameter: 0.5 mm) is applied to the film under a temperature range of 30° C. to 550° C. under a pressure of 500 mN. The glass transition temperature (Tg) can be measured at the same time by inserting the needle with the needle (it can be measured by the so-called penetration (needle inserting) method). In such a measurement, the softening temperature is calculated based on the measurement data according to the method described in JIS K 7196 (1991).

Further, since it is difficult to dissolve such a polyimide in a solvent to measure the molecular weight, the molecular weight (number average molecular weight or weight average molecular weight) or molecular weight distribution of its precursor polyamic acid (polyamic acid) is used as an index. As such, it is preferable to study the suitable one. The number average molecular weight (Mn) of the polyamic acid (polyamic acid) that is a precursor of such a polyimide is preferably 1,000 to 1,000,000, and more preferably 10,000 to 500,000 in terms of polystyrene. If such a number average molecular weight is less than the lower limit, not only is it difficult to achieve sufficient heat resistance, but it tends to be difficult to obtain a polyimide efficiently, while if it exceeds the upper limit, the viscosity increases, The filtration process requires a long time and requires a large amount of a diluting solvent for adjusting the viscosity, so that the processing tends to be difficult.

The weight average molecular weight (Mw) of the polyamic acid (polyamic acid) that is a precursor of such a polyimide is preferably from 1000 to 5000000 in terms of polystyrene. The lower limit of the numerical range of the weight average molecular weight (Mw) is more preferably 5,000, further preferably 10,000, and particularly preferably 20,000. Further, the upper limit of the numerical range of the weight average molecular weight (Mw) is more preferably 5,000,000, further preferably 500000, particularly preferably 100000. If such a weight average molecular weight is less than the lower limit, not only is it difficult to achieve sufficient heat resistance, but it tends to be difficult to obtain a polyimide efficiently, while if it exceeds the upper limit, the viscosity increases, and filtration is performed. The process tends to be difficult because it requires a long time and a large amount of a diluting solvent for adjusting the viscosity.

Further, the molecular weight distribution (Mw/Mn) of the polyamic acid (polyamic acid), which is such a polyimide precursor, is preferably 1.1 to 5.0, and 1.5 to 3.0. Is more preferable. If the molecular weight distribution is less than the lower limit, it tends to be difficult to produce. On the other hand, if the molecular weight distribution exceeds the upper limit, it tends to be difficult to obtain a uniform film. The molecular weight (Mw or Mn) and the molecular weight distribution (Mw/Mn) of such polyimide are measured by gel permeation chromatography (GPC) measuring device (TOOSOH EcoSEC HLC-8320GPC, column: TOSOH GPC). Column TSKgel Super AW2500, 3000, 4000, column temperature: 40° C., developing solvent: 10 mM LiBr-added dimethylacetamide solvent (flow rate 0.5 mL/min.)), and data obtained by conversion with polystyrene be able to.

In addition, as such a polyimide, in connection with a suitable value (16 or less) of the yellowness index (YI), it can be used as a flexible transparent material for glass substitutes such as transparent displays, solar cells, touch panels, front films and transparent FPCs. From the viewpoint of ensuring a high degree of visibility required when used, a total light transmittance of 83% or more (more preferably 85% or more, particularly preferably 87% or more) is more preferable. When the total light transmittance is less than the lower limit, even if the yellowness is 16 or less, depending on the value of the yellowness, the transparency (visibility) required when used in various applications is exhibited. Becomes difficult.

Further, as such a polyimide, a polyimide having a haze (turbidity) of 5 or less (more preferably 4 or less, particularly preferably 3 or less) is more preferable from the viewpoint of obtaining higher transparency.

Further, such a polyimide has a yellowness (YI) of 16.0 or less (more preferably 11.0 or less, particularly preferably 10.5 or less) from the viewpoint of obtaining higher transparency. Is more preferable. When the yellowness exceeds the upper limit, it is difficult to secure the high hue, brightness, saturation, luminance, tone, contrast, chromaticity, and transparency (visibility) required for the application. Therefore, even if the total light transmittance is 83% or more, it is difficult to exhibit the performance required when used for various purposes.

In addition, such total light transmittance, haze (turbidity) and yellowness (YI) are used as measuring devices under the trade name “Hazemeter NDH-5000” manufactured by Nippon Denshoku Industries Co., Ltd. or Nippon Denshoku Industries Co., Ltd. The total light transmittance and the haze were measured using a trade name "Spectrocolorimeter SD6000" manufactured by the company ("Hazemeter NDH-5000" manufactured by Nippon Denshoku Industries Co., Ltd., and Nippon Denshoku Industries Co., Ltd.). The yellowness is measured with a trade name “Spectrocolorimeter SD6000” manufactured by K.K.), and a value measured by using a film made of polyimide having a thickness of 10 to 15 μm (preferably 13 μm) as a measurement sample may be adopted. it can. However, as for the yellowness (YI), as described below, a measured value of a film having a thickness of 13 μm or a converted value converted into a value of a film having a thickness of 13 μm is adopted. That is, the total light transmittance and the haze (turbidity) are the same from the same polyimide because the thickness is sufficiently thin and the measured value is not affected if the film is made of the polyimide having a thickness of 10 to 15 μm. The value can be measured. On the other hand, since the yellowness (YI) tends to be influenced by the film thickness, in the present invention, the yellowness is measured after using a film having a thickness in the above range (10 to 15 μm) as a sample for measurement. As the value of (YI), a value converted into a value of a film having a thickness of 13 μm (the measured value when using a film having a thickness of 13 μm) is adopted. As described above, in the present invention, the value of yellowness (YI) is the value measured for a film having a thickness of 13 μm or the value converted to the value for a film having a thickness of 13 μm. From such a viewpoint (the yellowness can be a value converted into the value of a film having a thickness of 13 μm), the total light transmittance, haze (turbidity) and yellowness (YI) can be measured in the above range (10). A film having a thickness of ˜15 μm can be used (note that when YI is measured using a film having a thickness other than 13 μm as a sample for measurement, a thickness of 13 μm as described above). Therefore, it is preferable to prepare and use a film made of polyimide having a thickness of 13 μm as a sample for measurement from the viewpoint that such conversion is unnecessary.) The vertical and horizontal sizes of the measurement sample may be any size as long as they can be arranged at the measurement site of the measuring device, and the vertical and horizontal sizes may be changed appropriately. In addition, such total light transmittance is calculated|required by performing the measurement based on JIS K7361-1 (issued in 1997), and haze (turbidity) is measured based on JIS K7136 (issued in 2000). The yellowness index (YI) is determined by measuring in accordance with ASTM E313-05 (published in 2005).

A method that can be suitably used for producing such a polyimide will be described later.

[Polyamic acid]
The polyamic acid of the present invention has the following general formula (4):

[In the formula (4), R ¹ , R ² , and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (C) represented by
The following general formula (5):

[In Formula (5), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (C) with respect to the total amount of the repeating units (C) and (D) is 5 to 35 mol %. To do.

Such a polyamic acid can be suitably used when producing the polyimide of the present invention (can be obtained as a reaction intermediate (precursor) when producing the polyimide of the present invention) It is something like. ^R 1 in the general formula ^{(4), R 2, R} 3, R 10 and n are the same as those in the ^{R 1, R 2, R 3} , R 10 and n in the general formula (1) And suitable ones are the same as R ¹ , R ² , R ³ , R ¹⁰ and n in the general formula (1). Further, R ¹⁰ in the general formula (5) is the same as the R ¹⁰ in the general formula (2) (i.e., is similar to the R ¹⁰ of the general formula (1) ) And the suitable ones are the same as R ¹⁰ in the general formula (2).

Further, in the polyamic acid of the present invention, the repeating unit (C) with respect to the total amount of the repeating unit (C) represented by the general formula (4) and the repeating unit (D) represented by the general formula (5). Is 5 to 35 mol% based on the molar amount. When the content of the repeating unit (C) represented by the general formula (4) is less than the lower limit described above, a sufficiently high total light transmittance (preferably, the total light transmittance (preferably, when the polyimide is produced using the polyamic acid). It tends to be difficult to have a total light transmittance of 83.0% or more) and has a sufficiently low linear expansion coefficient (preferably a linear expansion coefficient of -20 ppm/K to 20 ppm/K). Therefore, it becomes difficult to obtain a polyimide having a sufficiently high total light transmittance, a sufficiently low yellowness index, and a sufficiently low linear expansion coefficient at a high level in a well-balanced manner. On the other hand, when the content of the repeating unit (C) exceeds the upper limit, also in this case, when a polyimide is produced using such a polyamic acid, a sufficiently low linear expansion coefficient (preferably −20 ppm/K to A polyimide having a linear expansion coefficient of 20 ppm/K) cannot be obtained, and a polyimide having characteristics such as sufficiently high total light transmittance, sufficiently low yellowness, and sufficiently low linear expansion coefficient at a high level in a well-balanced manner. Can no longer be manufactured.

Furthermore, in the polyamic acid of the present invention, using the polyamic acid, from the viewpoint of obtaining a polyimide having a sufficiently low yellowness and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner, the repeating unit ( The content ratio of the repeating unit (C) to the total amount of C) and the repeating unit (D) is more preferably 5 to 25 mol%, further preferably 10 to 20 mol%, and 12.5 to Particularly preferably, it is 17.5 mol %.

Further, the polyamic acid of the present invention may contain other repeating units as long as the effects of the present invention are not impaired. Such other repeating unit is not particularly limited, and a known repeating unit capable of forming a polyamic acid can be appropriately used. Further, in the polyamic acid of the present invention, in the case of containing another repeating unit, the repeating unit (C) represented by the general formula (4) and the repeating unit (D) represented by the general formula (5) are included. It is preferable that the repeating units (C) and (D) are contained so that the total amount becomes 50 mol% or more (more preferably 70 mol% or more) based on all the repeating units in the polyamic acid. Furthermore, the content ratio of the total amount of the repeating unit (C) and the repeating unit (D) to all the repeating units in such a polyamic acid is more preferably 80 to 100 mol %, and 90 to 100 mol %. % Is more preferable. When the content ratio of the total amount of the repeating units (C) and (D) is less than the lower limit, a sufficiently high total light transmittance, a sufficiently low yellowness, and a sufficiently low linear expansion coefficient are well balanced. It tends to be difficult to produce a polyimide that has this. From the viewpoint of more efficiently forming a polyimide using such a polyamic acid, the polyamic acid of the present invention is substantially composed of repeating units (C) and (D) (substantially another repeating unit. Is not included, more preferably the total amount of the repeating units (C) and (D) is 95 mol% or more, further preferably 98 mol% or more, particularly preferably 99 mol% or more. Is preferred).

The polyamic acid preferably has an intrinsic viscosity [η] of 0.05 to 3.0 dL/g, more preferably 0.1 to 2.0 dL/g. When such an intrinsic viscosity [η] is less than 0.05 dL/g, when a film-shaped polyimide is produced using this, the obtained film tends to become brittle, while on the other hand, 3.0 dL/g When it exceeds the above range, the viscosity is too high and the processability is lowered, and it becomes difficult to obtain a uniform film, for example, when the film is produced. Moreover, such an intrinsic viscosity [η] can be measured as follows. That is, first, tetramethylurea (TMU) was used as a solvent, and the polyamic acid was dissolved in the tetramethylurea (TMU) at a concentration of 0.5 g/dL to give a measurement sample (solution). obtain. Next, the viscosity of the measurement sample is measured using a kinematic viscometer using the measurement sample under a temperature condition of 30° C., and the obtained value is adopted as the intrinsic viscosity [η]. As such a kinematic viscometer, an automatic viscosity measuring device (trade name "VMC-252") manufactured by Rikyu Co., Ltd. is used.

Hereinafter, a method that can be suitably used for producing such a polyamic acid will be described.

(Preferably available method for producing polyamic acid)
The method that can be suitably used for producing such a polyamic acid is not particularly limited, and for example, the following general formula (10):

[In the formula (10), R ¹ , R ² , and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a fluorine atom, and n is 0. Indicates an integer of -12. ]
And a compound represented by the following general formula (11):

The tetracarboxylic dianhydride containing the compound (B) represented by the formula (A) and the content of the compound (A) with respect to the total amount of the compounds (A) and (B) is 5 to 35 mol% (compound (I)),
The following general formula (12):

[In formula (12), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
By reacting a diamine compound containing a compound represented by (compound (II)) in the presence of an organic solvent,
A polyamide containing the repeating unit (C) and the repeating unit (D), and the content of the repeating unit (C) is 5 to 35 mol% with respect to the total amount of the repeating units (C) and (D). A method of obtaining an acid can be suitably used. The repeating unit (C) is formed from the compound (A) and the compound represented by the general formula (12), and the repeating unit (D) is the compound (B) and the general formula. It is formed from the compound represented by (12).

Used in the production method of such a polyamic ^{acid, R 1, R 2, R} 3 and n in the compound represented by the general formula (10) (A) is, ^R 1, R in the general formula (1) ² , R ³ and n have the same meanings (the preferred ones are also the same as R ¹ , R ² , R ³ and n in the above general formula (1)) and are represented by the above general formula (12). the ^{R 10} in the compound to be the same as ^{R 10} in the same meaning as ^{R 10} in the general formula (1) and (2) (the preferred ones also above general formula (1) and (2) .)
The method for producing the compound (A) represented by the general formula (10) is not particularly limited, and a known method (for example, the method described in International Publication No. 2011/099518) is appropriately used. Can be used.

In addition, the method for producing the compound (B) represented by the general formula (11) is not particularly limited, and a known method can be appropriately used. Further, such a compound (B) is pyromellitic dianhydride (1,2,4,5-benzenetetracarboxylic dianhydride, pyromellitic dianhydride), and as such a compound, a commercially available product is appropriately used. You may use.

Furthermore, the method for producing the compound represented by the general formula (12) is not particularly limited, and a known method can be adopted as appropriate. Further, as the compound represented by the general formula (12), a commercially available compound may be appropriately used.

Further, the tetracarboxylic dianhydride (compound (I)) is such that the content of the compound (A) is 5 to 35 mol% with respect to the total amount of the compounds (A) and (B) in the compound (I). It is necessary to use the one. When the content of the compound (A) is less than the lower limit and exceeds the upper limit, the content of the repeating unit (C) relative to the total amount of the repeating units (C) and (D) is The desired range (range of 5 to 35 mol %) cannot be achieved. In addition, in the compound (I), from the same viewpoint, the content ratio of the compound (A) to the total amount of the compounds (A) and (B) is more preferably 5 to 25 mol %, 20 mol% is more preferable, and 12.5 to 17.5 mol% is particularly preferable.

As the compound (I), a tetracarboxylic dianhydride other than the compounds (A) and (B) is mixed and used in order to contain the other repeating unit in the polyamic acid of the present invention. May be. As the tetracarboxylic acid dianhydride other than the compounds (A) and (B), other known tetracarboxylic acid dianhydrides that can be used in the production of polyimide are appropriately used. be able to. In this case, the amount of the tetracarboxylic dianhydride other than the compounds (A) and (B) used is such that the content of the repeating units (C) and (D) in the resulting polyamic acid is within the desired range ( It may be appropriately adjusted so that the above-mentioned preferable content range and the like). The tetracarboxylic acid dianhydride (compound (I)) has a sufficiently high level of heat resistance, a sufficiently high total light transmittance, a sufficiently low yellowness and a sufficiently low linear expansion. From the viewpoint of expressing the coefficient and the coefficient at a higher level in a well-balanced manner, the compound (I) substantially consists of the compounds (A) and (B) (the compound (I) is substantially a compound ( It does not contain any other tetracarboxylic acid dianhydride other than A) and (B), and in the compound (I), the total amount of the compounds (A) and (B) is more preferably 95 mol% or more. %, more preferably 98 mol% or more, particularly preferably 99 mol% or more, and most preferably 100 mol%).

Further, as the compound (II), in order to allow the polyamic acid of the present invention to contain another repeating unit, a diamine compound other than the compound represented by the general formula (12) (other aromatic diamine and It is possible to appropriately contain alicyclic diamine and the like). As such other diamine compound, other known diamine compounds that can be used in the production of polyimide can be appropriately used. As such other diamine compound, for example, amino-modified siloxane with both terminals can be preferably used. Specific examples of the amino-modified siloxane having both terminals are 1,3-bis(3-aminopropyl)tetramethyldisiloxane, amino-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. (for example, PAM-E, KF-8010). , X-22-161A, X-22-161B, KF-8012, KF-8008, X-22-1660B-3, X-22-9409 and the like), Gelest dimethylsiloxane type diamine (for example, DMS-A11). , DMS-A12, DMS-A15, DMS-A21, DMS-A31, DMS-A32, DMS-A32R, DMS-A35) and the like. The amount of the diamine compound other than the compound represented by the general formula (12) in the compound (II) is such that the content of the repeating units (C) and (D) in the obtained polyamic acid is It is necessary to appropriately adjust the content to be within a desired range (such as the above-mentioned range of suitable content). As the diamine compound (compound (II)), while having a sufficient level of heat resistance, it has a sufficiently high total light transmittance, a sufficiently low yellowness index, and a sufficiently low linear expansion coefficient. From the viewpoint of achieving balanced expression at various levels, the compound (II) is substantially composed of the compound represented by the general formula (12) (the compound (II) is substantially different from other diamine compounds). It is not contained, more preferably, in the compound (II), the total amount of the compounds represented by the general formula (12) is 95 mol% or more, further preferably 98 mol% or more, It is preferably 99 mol% or more, and most preferably 100 mol%).

The organic solvent is preferably an organic solvent capable of dissolving both the tetracarboxylic dianhydride (compound (I)) and the diamine compound (compound (II)). Examples of such an organic solvent include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, propylene carbonate, ethylene carbonate, tetramethylurea (tetramethylurea). Aprotic polar solvents such as methylurea (TMU), 1,3-dimethyl-2-imidazolidinone, hexamethylphosphoric triamide, pyridine; phenolic solvents such as m-cresol, xylenol, phenol, halogenated phenol Solvents; ether-based solvents such as tetrahydrofuran, dioxane, cellosolve and glyme; ketone-based solvents such as cyclopentanone, cyclohexanone and cycloheptanone; aromatic solvents such as benzene, toluene and xylene. Such organic solvents may be used alone or in combination of two or more.

The ratio of the tetracarboxylic dianhydride (compound (I)) to the diamine compound (compound (II)) used is 1 equivalent of the amino group contained in the diamine compound (compound (II)). The acid anhydride group in the tetracarboxylic dianhydride (compound (I)) is preferably 0.2 to 2 equivalents, more preferably 0.8 to 1.2 equivalents. If the use ratio is less than the lower limit, the polymerization reaction does not proceed efficiently, and a high molecular weight polyamic acid tends to be unobtainable. On the other hand, if the use ratio exceeds the upper limit, a high molecular weight polyamic acid is obtained in the same manner as described above. There is a tendency not to be.

Further, as the amount of the organic solvent used, the total amount of the tetracarboxylic dianhydride (compound (I)) and the diamine compound (compound (II)) is 1 to 50% by mass with respect to the total amount of the reaction solution. The amount is preferably (more preferably 10 to 30% by mass). If the amount of the organic solvent used is less than the lower limit, it is difficult to efficiently obtain the polyamic acid. On the other hand, if the amount exceeds the upper limit, the viscosity tends to be high and stirring tends to be difficult.

Further, when the tetracarboxylic dianhydride (compound (I)) is reacted with the diamine compound (compound (II)), the organic compound is used in order to improve the reaction rate and obtain a polyamic acid having a high degree of polymerization. You may add a basic compound further in a solvent. The basic compound is not particularly limited, but examples thereof include triethylamine, tetrabutylamine, tetrahexylamine, 1,8-diazabicyclo[5.4.0]-undecene-7, pyridine, isoquinoline, and α-picoline. Can be mentioned. Further, the amount of such a basic compound used is preferably 0.001 to 10 equivalents, and 0.01 to 0.1 equivalent to 1 equivalent of the tetracarboxylic dianhydride (compound (I)). More preferably, it is 1 equivalent. If the amount of such a basic compound used is less than the lower limit, the effect of addition tends to decrease, while if it exceeds the upper limit, coloring or the like tends to occur.

The reaction temperature for reacting the tetracarboxylic dianhydride (compound (I)) with the diamine compound (compound (II)) may be adjusted appropriately to a temperature at which these compounds can react. The temperature is not particularly limited, but is preferably −20° C. to 200° C. As a method for reacting the tetracarboxylic dianhydride (compound (I)) with the diamine compound (compound (II)), a polymerization reaction of the tetracarboxylic dianhydride and the diamine compound can be performed. Any known method can be used as appropriate and is not particularly limited. For example, under atmospheric pressure, under an inert atmosphere such as nitrogen, helium, or argon, the diamine compound is dissolved in a solvent, and then the tetracarboxylic acid is reacted at the reaction temperature. A method of adding an acid dianhydride (compound (I)) and then reacting for 10 to 48 hours may be appropriately adopted. If the reaction temperature or reaction time is less than the lower limit, it tends to be difficult to react sufficiently, while if the reaction temperature or reaction time exceeds the upper limit, the probability of mixing of a substance (oxygen or the like) that deteriorates the polymer increases and the molecular weight increases. It tends to decrease.

Thus, the polycarboxylic acid of the present invention is obtained by reacting the tetracarboxylic dianhydride (compound (I)) with the diamine compound (compound (II)) in the presence of an organic solvent. You can When the polyamic acid of the present invention is isolated from the organic solvent after preparing the polyamic acid in this manner, the isolation method is not particularly limited, and the known polyamic acid can be isolated. A method can be adopted as appropriate, and for example, a method of isolating as a reprecipitate may be adopted.

[Polyamic acid solution]
The polyamic acid solution of the present invention is characterized by containing the polyamic acid of the present invention and an organic solvent. As the organic solvent used in such a polyamic acid solution, the same organic solvent as that used in the above-mentioned method that can be preferably used for producing the polyamic acid can be preferably used. Therefore, the polyamic acid solution of the present invention may be prepared by carrying out a method that can be suitably used for producing the polyamic acid described above, and using the reaction solution obtained after the reaction as it is as the polyamic acid solution. Good. That is, the polyamic acid solution of the present invention reacts the tetracarboxylic dianhydride (compound (I)) with the diamine compound (compound (II)) in the presence of the organic solvent to form a polyamic acid. It may be produced by preparing and obtaining a solution containing the polyamic acid and the organic solvent.

The content of the polyamic acid in such a polyamic acid solution is not particularly limited, but is preferably 1 to 50% by mass, and more preferably 10 to 30% by mass. If the content is less than the lower limit, the molecular weight of the polyamic acid tends to decrease, while if it exceeds the upper limit, the production of polyimide tends to be difficult. In addition, such a polyamic acid solution can be suitably used for the production of the polyimide of the present invention.

When such a polyamic acid solution is used for the production of polyimide, various additives (promoters for high molecular weight and imidization, deterioration inhibitors, antioxidants, etc.) that can be used for the preparation of polyimide are used. Agents, light stabilizers, ultraviolet absorbers, modifiers, antistatic agents, flame retardants, plasticizers, nucleating agents, stabilizers, adhesion improvers, lubricants, mold release agents, dyes, foaming agents, defoamers, A surface modifier, a hard coat agent, a leveling agent, a surfactant, a filler (glass fiber, filler, talc, mica, silica, etc.) may be appropriately added and used. Further, in the case of using such an additive, the content of the additive in the polyamic acid solution is not particularly limited, but is set to about 0.0001 to 80 mass% (more preferably 0.1 to 50 mass%). Preferably.

(Preferably available method for producing polyimide)
Suitable methods for producing the polyimide of the present invention are not particularly limited, but by imidizing the polyamic acid of the present invention,
It contains the repeating unit (A) and the repeating unit (B), and the content of the repeating unit (A) is 5 to 35 mol% with respect to the total amount of the repeating units (A) and (B). It is possible to preferably use the method of obtaining a polyimide. The repeating unit (A) is formed from the repeating unit (C), and the repeating unit (B) is formed from the repeating unit (D).

Such a method for imidizing a polyamic acid is not particularly limited as long as it can imidize a polyamic acid, and a known method can be appropriately adopted. It is preferable to employ a method of imidizing by heating under a temperature condition of ~450°C (more preferably 80 to 400°C), or a method of imidizing using a so-called "imidizing agent".

In the case of adopting a method of imidization by applying such a heat treatment, if the heating temperature is lower than 60° C., the progress of the reaction tends to be delayed, while if it exceeds the upper limit, coloring or thermal decomposition occurs. The molecular weight tends to decrease. Further, the reaction time (heating time) in the case of adopting the method of imidizing by applying heat treatment is preferably 0.5 to 5 hours. If the reaction time is less than the lower limit, it tends to be difficult to sufficiently imidize, while if the reaction time exceeds the upper limit, coloring or a decrease in molecular weight due to thermal decomposition tends to occur. The polyamic acid of the present invention is a polyimide having a well-balanced low yellowness and a sufficiently low linear expansion coefficient even when it is imidized by heating under conditions containing oxygen such as in the atmosphere. Since it can be produced, the atmospheric conditions for heating are not particularly limited, and may be in an inert gas or in the air. Further, in the atmosphere, when it is produced by heating, not only the polyimide can be produced in a simpler facility, but also the polyimide can be produced without controlling the atmospheric gas, so that the production efficiency of the final product is improved. It is possible to further improve. Further, in the case of heating for imidization, a so-called accelerator (additive) may be used in order to accelerate the high molecular weight and the imidization. As such an accelerator, a known reaction accelerator (eg, imidazole compound, pyridine compound, tertiary amine compound such as triethylamine, amino acid compound, etc.) may be appropriately used. The amount of such an accelerator used is not particularly limited and is, for example, 1 to 60 parts by mass, preferably 5 to 50 parts by mass, relative to 100 parts by mass of the solid content (polyamic acid) in the polyamic acid solution. Is.

When a method of imidizing a polyamic acid using a so-called “imidizing agent” is adopted, it is preferable to imidize the polyamic acid of the present invention in a solvent in the presence of the imidizing agent. As such a solvent, those similar to the organic solvent used in the method for producing a polyamic acid of the present invention can be preferably used.

As such an imidizing agent, a known imidizing agent can be appropriately used, and examples thereof include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride, pyridine, collidine, lutidine, triethylamine, and N. Examples thereof include tertiary amines such as -methylpiperidine. Moreover, the reaction temperature at the time of imidation in the case of adding an imidizing agent and imidizing is preferably 0 to 200° C., and more preferably 30 to 150° C. The reaction time is preferably 0.1 to 48 hours. If the reaction temperature or time is less than the lower limit, it tends to be difficult to sufficiently imidize, while if the upper limit is exceeded, the probability of incorporation of a substance (such as oxygen) that deteriorates the polymer increases and the molecular weight increases. It tends to decrease or the hue deteriorates. The amount of such an imidizing agent used is not particularly limited, and is from a few millimoles to a few mols (preferably 0.1% to 1 mol of the repeating unit represented by the general formula (5) in the polyamic acid. It may be about 01 to 4.0 mol).

Further, as a method that can be suitably used for producing the polyimide of the present invention, the tetracarboxylic dianhydride (compound (I)) and the diamine compound (compound (II)) are present in the presence of an organic solvent. By reacting below, the repeating unit (C) and the repeating unit (D) are contained, and the content of the repeating unit (C) is 5 relative to the total amount of the repeating units (C) and (D). A step (I) of obtaining a polyamic acid (polyamide acid of the present invention) of about 35 mol%;
By imidizing the polyamic acid, the repeating unit (A) and the repeating unit (B) are contained, and the repeating unit (A) is contained in the total amount of the repeating units (A) and (B). A step (II) of obtaining a polyimide having a content of 5 to 35 mol% (the above-mentioned polyimide of the present invention);
It is preferable that the method includes Thus, when the method including the step (I) and the step (II) is adopted as the method for producing the polyimide of the present invention, the polyimide can be produced by a series of steps.

In the case of utilizing the method including the step (I) and the step (II) and adopting the method of imidizing by applying heat treatment in the imidization, the step (I) After carrying out I), the tetracarboxylic dianhydride (compound (I)) and the diamine compound (compound (II)) are reacted in an organic solvent without isolating the polyamic acid of the present invention. The reaction solution thus obtained (the reaction solution containing the polyamic acid of the present invention) is used as it is or with the addition of the promoter, and the solvent is removed from the reaction solution by evaporation (solvent removal). It is also possible to employ a method in which the solvent is removed by performing a treatment) and then the above-mentioned heat treatment is performed to perform imidization. By performing such a treatment for removing the solvent by evaporation, the polyamic acid of the present invention can be isolated in the form of a film or the like, and then subjected to heat treatment or the like. The temperature condition in the method of the treatment for removing the solvent by evaporation is preferably 0 to 180°C, more preferably 30 to 150°C. If the temperature condition in the process of evaporating and removing such a solvent is less than the lower limit, it tends to be difficult to sufficiently evaporate and remove the solvent, while if the temperature exceeds the upper limit, the solvent boils to form bubbles or voids. It tends to be a film containing. In this case, for example, in the case of producing a film-shaped polyimide, the reaction solution obtained may be applied as it is on a substrate (for example, a glass plate), and the treatment for removing the solvent by evaporation and the heat treatment may be performed. It becomes possible to manufacture a film-shaped polyimide by a simple method. The method of applying such a reaction solution is not particularly limited, and a known method (casting method or the like) can be appropriately adopted. When the polyamic acid of the present invention is isolated from the reaction solution and used, the isolation method is not particularly limited, and a known method capable of isolating the polyamic acid may be appropriately adopted. However, for example, a method of isolating as a reprecipitate may be adopted.

Further, in the case of utilizing the method including the step (I) and the step (II) and adopting the method of imidizing using the “imidizing agent”, the film-shaped polyimide is formed more efficiently. From such a viewpoint, the reaction solution obtained by reacting the tetracarboxylic dianhydride (compound (I)) with the diamine compound (compound (II)) in an organic solvent is used as it is (step (I) Without isolating the polyamic acid of the present invention from the reaction solution after carrying out the above), the reaction solution is used as it is), before imidization does not proceed sufficiently by adding an imidizing agent to the reaction solution, A method in which the reaction solution is applied to a substrate such as glass and imidization is carried out on the substrate can be suitably adopted.

[Polyimide film]
The polyimide film of the present invention is characterized by comprising the above-mentioned polyimide of the present invention.

The form of such a polyimide film is not particularly limited as long as it is a film shape, and can be appropriately designed into various shapes (disc shape, cylinder shape (those obtained by processing the film into a cylinder shape), etc.).

Furthermore, the thickness of the polyimide film of the present invention is not particularly limited, but it is preferably 1 to 500 μm, and more preferably 10 to 200 μm. When such a thickness is less than the lower limit, the strength tends to be low and handling becomes difficult. On the other hand, when the thickness exceeds the upper limit, coating may be required more than once or the processing becomes complicated. Tends to occur.

Such a polyimide film, while adopting the method described as a method that can be suitably used for producing the above-mentioned polyimide, a coating method so that the form of the obtained polyimide is a desired shape (film shape) It is possible to manufacture by appropriately adjusting the above.

The polyimide, polyamic acid, polyamic acid solution, and polyimide film of the present invention have been described above, but the polyimide and polyimide film of the present invention as described above have a sufficiently high total light transmittance and a sufficiently low yellowness. Since it has a sufficiently low linear expansion coefficient and a well-balanced level, it is possible to sufficiently prevent peeling of the film due to heat even when laminated on a metal substrate etc. and sufficient visibility. Since it has both, it can be used in various applications such as films for flexible wiring boards, heat-resistant insulating tapes, wire enamel, semiconductor protective coatings, liquid crystal alignment films, transparent conductive films for organic EL, display substrate materials (TFT substrates, transparent electrodes). Substrates (display substrates such as transparent electrode substrates for organic EL, transparent electrode substrates for electronic paper, etc.), transparent electrode substrates for solar cells, organic EL lighting films, flexible substrate films, flexible organic EL substrate films, Flexible transparent conductive film, transparent conductive film for organic thin film solar cell, transparent conductive film for dye-sensitized solar cell, flexible gas barrier film, substrate material for touch panel (film for touch panel etc.), front film for flexible display It is particularly useful as a material for a back film for flexible displays, a seamless polyimide belt for copying machines (so-called transfer belt), an interlayer insulating film, a sensor substrate, and the like. Further, the polyimide of the present invention is derived from its linear expansion coefficient, and among the above-mentioned applications, the substrate material of a display (a display substrate such as a TFT substrate or a transparent electrode substrate) or the substrate material for a touch panel (touch panel). It is possible to further improve the yield of the final product (for example, an organic EL element etc.) when it is used for applications such as a film for film).

Further, from the characteristics of the polyimide of the present invention, for example, microelectronics (organic EL display, liquid crystal display, touch panel, flexible display panel, high-brightness LED wafer, ultrathin silicon wafer, three-dimensional semiconductor package, semiconductor protective film). When the polyimide of the present invention is used as the material of the substrate used for products such as (buffer coat), interlayer insulating film, photoresist, microlens for image sensor, etc., not only can the device be enlarged. Due to its linear expansion coefficient, it is possible to sufficiently prevent cracks and curls in the heating process during manufacturing to achieve a high yield of the final product, and further contribute to improving production efficiency and processing capacity. It is also possible to manufacture products at low cost.

Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

First, a method for evaluating the properties of the polyimide film and the like obtained in each of the examples and each of the comparative examples will be described.

<Identification of molecular structure>
Identification of the molecular structure of the compound obtained in each Example and each Comparative Example was carried out by IR measurement using an IR measuring device (manufactured by JASCO Corporation, trade name: FT/IR-4100).

<Measurement of intrinsic viscosity [η]>
The value (unit: dL/g) of the intrinsic viscosity [η] of the polyamic acid obtained as an intermediate in each of the examples and the comparative examples is an automatic viscosity measuring device (trade name “VMC-252”) manufactured by Sogosha Co., Ltd. Was measured under a temperature condition of 30° C. using a measurement sample having a concentration of 0.5 g/dL with tetramethylurea (TMU) as a solvent.

<Measurement of glass transition temperature (Tg) and softening temperature>
The glass transition temperature (Tg) and the softening temperature value (unit: ° C.) of the polyimide obtained in each Example and each Comparative Example were measured using the polyimide film produced in each Example and each Comparative Example. A measurement sample having a size of 5 mm, a width of 5 mm, and a thickness of 0.013 mm (13 μm) was prepared, and a thermomechanical analyzer (trade name “TMA8311” manufactured by Rigaku Co., Ltd.) was used as a measuring device under a nitrogen atmosphere to raise the temperature. It was measured by inserting a transparent quartz pin (tip diameter: 0.5 mm) into the film at a pressure of 500 mN under the conditions of a temperature range (scanning temperature) of 5°C/min and 30°C to 550°C (so-called penetration ( In addition, when measuring the softening temperature, the softening temperature (softening temperature (softening temperature) is measured based on the measurement data according to the method described in JIS K7196 (1991) except that the above-mentioned measurement sample is used. Points) were calculated.

<Measurement of 5% weight loss temperature (Td5%)>
The value (unit: °C) of the 5% weight loss temperature (Td 5%) of the polyimide obtained in each Example and each Comparative Example was measured by thermogravimetric analysis using the polyimide film produced in each Example and each Comparative Example. Using a device (“TG/DTA220” manufactured by SII Nano Technology Co., Ltd.), the scanning temperature was set to 30° C. to 550° C., and the temperature was 10° C./min. It was obtained by measuring the temperature at which the weight of the sample used was reduced by 5% by heating under the conditions of.

<Measurement of total light transmittance, haze (turbidity) and yellowness (YI)>
The values of the total light transmittance (unit: %), haze (turbidity: Haze) and yellowness (YI) of the polyimides obtained in each example and each comparative example are the same as those obtained in each example. It is used as it is as a sample for measurement, and as a measuring device, a trade name “Hazemeter NDH-5000” manufactured by Nippon Denshoku Industries Co., Ltd. or a trade name “Spectrocolorimeter SD6000” manufactured by Nippon Denshoku Industries Co., Ltd. is used, respectively. It was determined by measuring. In addition, the total light transmittance and haze were measured with a trade name "Haze Meter NDH-5000" manufactured by Nippon Denshoku Industries Co., Ltd., and the yellowness was measured by a trade name "Spectrocolorimeter SD6000" manufactured by Nippon Denshoku Industries Co., Ltd. It was measured. Further, the total light transmittance is determined by performing a measurement according to JIS K7361-1 (issued in 1997), and the haze (turbidity) is determined by performing a measurement conforming to JIS K7136 (issued in 2000). , Chromaticity (YI) was determined by performing measurement according to ASTM E313-05 (published in 2005).

<Measurement of coefficient of linear expansion (CTE)>
The linear expansion coefficient was obtained by forming a film having a size of 20 mm in length, 5 mm in width, and 13 μm in thickness from the polyimide (polyimide in film form) obtained in each of Examples and Comparative Examples, and then vacuum drying the film. (120° C., 1 hour (Hr)), and heat-treated at 200° C. for 1 hour (Hr) in a nitrogen atmosphere. Samples (dry films) were used, respectively, and a thermomechanical analyzer (manufactured by Rigaku Corporation) was used as a measuring device. Trade name "TMA8310") under a nitrogen atmosphere in tension mode (49 mN) with a temperature rising rate of 5°C/min to change the length of the sample at 50°C to 200°C. It measured and measured by calculating|requiring the average value of the change of length per 1 degreeC in the temperature range of 100 degreeC-200 degreeC.

(Example 1)
<Preparation process of CpODA>
Based on the methods described in Synthesis Example 1, Example 1 and Example 2 of WO 2011/099518, the following general formula (13):

A compound represented by (norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride: CpODA) Prepared.

<Process for preparing polyamic acid>
First, a 30 ml three-necked flask was heated with a heat gun to be sufficiently dried. Next, the atmosphere gas in the sufficiently dried three-necked flask was replaced with nitrogen to create a nitrogen atmosphere in the three-necked flask. Then, in the three-necked flask, as the aromatic diamine (diamine compound), the following general formula (14):

2,2'-bis(trifluoromethyl)benzidine (TFMB) represented by 4.8035 g (15.00 mmol: manufactured by Seika Co., Ltd.) was further added, and then 33.8 g (tetramethylurea (TMU)) was added. An aromatic diamine (TFMB) was dissolved in the tetramethylurea by adding and stirring the polyamic acid in the reaction solution so that the polyamic acid concentration was 20 mass% (mass %).

Next, in a three-necked flask containing the solution, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the above general formula (13) (CpODA) as tetracarboxylic dianhydride was added under nitrogen atmosphere. A mixture with 2.7810 g (12.75 mmol) of pyromellitic dianhydride (pyromellitic dianhydride: PMDA: manufactured by Tokyo Kasei Kogyo Co., Ltd.) represented by the general formula (11) was added, and at room temperature ( It stirred at 25 degreeC for 12 hours, and obtained the reaction liquid. Thus, polyamic acid was formed in the reaction solution.

A part of the reaction solution (tetramethylurea solution of polyamic acid: polyamic acid solution) is used to prepare a tetramethylurea solution having a polyamic acid concentration of 0.5 g/dL and prepared as described above. Then, the intrinsic viscosity [η] of the polyamic acid as a reaction intermediate was measured, and the intrinsic viscosity [η] of the polyamic acid was 0.76 dL/g.

<Preparation Step of Film Made of Polyimide: Steps (i) to (iii)>
(Step (i): solvent removal treatment)
Alkali-free glass (trade name “Eagle XG” manufactured by Corning, length: 100 mm, width 100 mm, thickness 0.7 mm) is prepared as a glass substrate, and the reaction solution (polyamic acid solution) obtained as described above is prepared. A coating film was formed on the glass substrate by spin coating on the surface of the glass substrate so that the thickness of the coating film after heat curing was 13 μm. Then, the glass substrate on which the coating film was formed was placed on a hot plate at 60° C. and left standing for 2 hours to evaporate and remove the solvent from the coating film (solvent removal treatment).

(Step (ii): heating step after solvent removal treatment)
After the solvent removal treatment is performed as described above, the glass substrate on which the coating film is formed is placed in an inert oven in which nitrogen is flowing at a flow rate of 3 L/min, and the glass substrate is placed in an inert oven under a nitrogen atmosphere at 25 After being left to stand at a temperature condition of ℃ for 0.5 hours, it is heated at a temperature condition of 135 ℃ for 0.5 hours, and finally at a temperature condition of 350 ℃ (hereinafter, referred to as "final heating temperature condition" in some cases). .) for 1 hour to cure the coating film to obtain a polyimide-coated glass in which a thin film of polyimide (polyimide film) was coated on the glass substrate.

(Process (iii): Film recovery process)
Next, the polyimide-coated glass thus obtained is immersed in hot water at 90° C., and the polyimide film is peeled off from the glass substrate to give a polyimide film (length: 100 mm, width 100 mm, thickness 13 μm). Was collected to obtain a polyimide film.

In addition, in order to identify the molecular structure of the compound which forms the film obtained in this way, IR spectrum was measured using the IR measuring machine (The JASCO Corporation make, brand name: FT/IR-4100). .. An IR spectrum is shown in FIG. 1 as a result of such measurement. As is clear from the results shown in FIG. 1, C=O stretching vibration of imidocarbonyl was observed at 1715.3 cm ⁻¹ in the compound constituting the film formed in Example 1. From the molecular structure identified based on such results, it was confirmed that the obtained film was composed of polyimide.

The polyimide thus obtained has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)), based on the kind of the monomer used and the amount ratio thereof. And a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio. ([Repeating unit corresponding to repeating unit (A)]:[Repeating unit corresponding to repeating unit (B)]) is 15:85. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Example 2)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 1.1534 g (3.00 mmol) of the compound (CpODA) represented by the general formula (13) and pyromellitic represented by the general formula (11). Using a mixture with 2.6172 g (12.00 mmol) of acid anhydride (PMDA), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 34.30 g (the amount by which the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

In addition, the obtained polyimide has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)) from the type of monomer used and the amount ratio thereof, It contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio ([ The repeating unit corresponding to the repeating unit (A)]:[the repeating unit corresponding to the repeating unit (B)] is 20:80.

(Example 3)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 0.5766 g (1.50 mmol) of the compound (CpODA) represented by the general formula (13) and pyromellitic represented by the general formula (11). Using a mixture with 2.9446 g (13.50 mmol) of acid anhydride (PMDA), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 33.30 g (the amount of polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

In addition, the obtained polyimide has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)) from the type of monomer used and the amount ratio thereof, It contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio ([ The repeating unit corresponding to the repeating unit (A)]:[the repeating unit corresponding to the repeating unit (B)] is 10:90.

(Example 4)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 1.7297 g (4.50 mmol) of the compound (CpODA) represented by the general formula (13) and Pyromellit represented by the general formula (11). A polyimide was prepared in the same manner as in Example 1 except that a mixture with 2.2903 g (10.50 mmol) of acid anhydride (PMDA) was used and TMU was used in an amount such that the polyamic acid concentration in the reaction solution was 20 mass %. A thin film (polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

In addition, the obtained polyimide has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)) from the type of monomer used and the amount ratio thereof, It contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio ([ The repeating unit corresponding to the repeating unit (A)]:[the repeating unit corresponding to the repeating unit (B)] is 30:70.

(Example 5)
A polyimide thin film (polyimide film) was obtained in the same manner as in Example 1 except that the final heating temperature condition adopted in step (ii) of the polyimide film preparation step was changed from 350°C to 300°C. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Example 6)
The reaction liquid (polyamic acid solution) used in the step (i) of the process of preparing a film made of polyimide was added to 42.25 g of the reaction liquid (polyamic acid 20 mass% solution) obtained by carrying out the process of preparing the polyamic acid. Formula (15):

0.8450 g (produced by Tokyo Ohka Kogyo Co., Ltd.) of an imidazole compound represented by the formula (10 parts by mass based on 100 parts by mass of solid content (polyamic acid) in the polyamic acid solution) is dissolved. Change to the resulting solution (reaction solution (polyamic acid solution) to which the promoter is added),
Further, a polyimide thin film (polyimide film) was obtained in the same manner as in Example 1 except that the final heating temperature condition adopted in step (ii) of the polyimide film preparation step was changed from 350°C to 300°C. It was When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Example 7)
The reaction solution (polyamic acid solution) used in the step (i) of the step of preparing a film made of polyimide was added to the reaction solution 42.25 g (polyamic acid 20 mass% solution) obtained by carrying out the step of preparing the polyamic acid. The amount of the accelerator (manufactured by Tokyo Ohka Kogyo Co., Ltd.) composed of the imidazole compound represented by the formula (15) is 0.8450 g (10 parts by mass with respect to 100 parts by mass of the solid content (polyamic acid) in the polyamic acid solution). Change to a solution obtained by dissolving (a reaction solution (polyamic acid solution) to which the promoter is added),
The final heating temperature condition adopted in step (ii) of the process for preparing a film made of polyimide is changed from 350° C. to 300° C.
Furthermore, the atmosphere gas adopted in step (ii) of the step of preparing a film made of polyimide was changed from nitrogen to air (the gas flowing in the inert oven was changed from nitrogen to air, and the heating step was performed in air). Except for the above), a thin film (polyimide film) made of polyimide was obtained in the same manner as in Example 1. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Example 8)
As the aromatic diamine, instead of using 2,2′-bis(trifluoromethyl)benzidine (TFMB) represented by the general formula (14) (4.8035 g, 15.00 mmol: manufactured by Seika Co., Ltd.) alone, 4.7074 g (14.7 mmol) of the compound (TFMB) represented by the general formula (14) and amino-modified silicone oil (trade name "X-22-9409" manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4020 g (0 .3 mmol equivalent),
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 35.02 g (the amount of the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

In addition, the obtained polyimide has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)) from the type of monomer used and the amount ratio thereof, It contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio ([ The repeating unit corresponding to the repeating unit (A)]:[the repeating unit corresponding to the repeating unit (B)] is 15:85.

(Comparative Example 1)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 2.3063 g (6.00 mmol) of the compound (CpODA) represented by the general formula (13) and Pyromellit represented by the general formula (11). Using a mixture with 1.9631 g (9.00 mmol) of acid anhydride (PMDA), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 36.3 g (the amount of the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

In addition, the obtained polyimide has a repeating unit corresponding to the repeating unit represented by the general formula (1) (a repeating unit corresponding to the repeating unit (A)) from the type of monomer used and the amount ratio thereof, It contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)), and the content ratio of these repeating units is a molar ratio ([ The repeating unit corresponding to the repeating unit (A)]:[the repeating unit corresponding to the repeating unit (B)] is 40:60.

(Comparative example 2)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 3.2718 g (15.00 mmol) of pyromellitic anhydride (PMDA) represented by the general formula (11) was used alone, and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 32.3 g (the amount in which the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide. Further, the obtained polyimide contains a repeating unit corresponding to the repeating unit represented by the general formula (2) (a repeating unit corresponding to the repeating unit (B)) from the type of monomer used and the ratio thereof. The ratio is 100 mol %.

(Comparative example 3)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), the following general formula (16):

The compound (4,4′-biphthalic anhydride: BPDA: manufactured by Tokyo Chemical Industry Co., Ltd.) 4.4133 g (15.00 mmol) was used alone, and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 36.9 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative example 4)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the compound represented by the general formula (16). (4,4′-biphthalic anhydride: BPDA: manufactured by Tokyo Chemical Industry Co., Ltd.) 3.7513 (12.75 mmol) and a mixture (CpODA:BPDA molar ratio (CpODA:BPDA) is 15:85). Used,
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 37.7 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative example 5)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 3.2718 g (15.00 mmol) of pyromellitic anhydride (PMDA) represented by the general formula (11) was used alone as an aromatic diamine. Instead of using 2.80′g of 2,2′-bis(trifluoromethyl)benzidine (TFMB) represented by the above general formula (14) (15.00 mmol: manufactured by Seika Co., Ltd.), the following general formula (17) :

Using 3.1844 g (15.00 mmol) of the compound represented by (m-tolidine: m-Tol: manufactured by Tokyo Chemical Industry Co., Ltd.), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 25.8 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative example 6)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), a compound represented by the above general formula (16) (4,4′-biphthalic anhydride: BPDA: manufactured by Tokyo Chemical Industry Co., Ltd.) 4.4133 g (15) .00 mmol) alone,
As an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB) represented by the above general formula (14) (4.8035 g, 15.00 mmol: manufactured by Seika Corporation) is used instead of the above general formula. Using 3.1844 g (15.00 mmol) of the compound (m-Tol) represented by the formula (17), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 30.4 g (the amount by which the polyamic acid concentration in the reaction liquid was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative Example 7)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), the following general formula (18):

0.5044 g (2.25 mmol) of the compound (1,2,4,5-cyclohexanetetracarboxylic dianhydride: CHDA) represented by the formula (11) and the pyromellitic anhydride (PMDA) represented by the general formula (11). ) With a mixture of 2.7810 g (12.75 mmol) and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 32.4 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative Example 8)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), the following general formula (19):

0.4728 g (2.25 mmol) of the compound (1,2,3,4-cyclopentanetetracarboxylic acid dianhydride: CPDA) represented by and the pyromellitic acid anhydride represented by the general formula (11) ( PMDA) with 2.7810 g (12.75 mmol) and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 32.2 g (the amount by which the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative Example 9)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), the following general formula (20):

0.4412 g (2.25 mmol) of the compound (1,2,3,4-cyclobutanetetracarboxylic dianhydride: CBDA) represented by the formula (11) and the pyromellitic anhydride (PMDA) represented by the general formula (11). ) With a mixture of 2.7810 g (12.75 mmol) and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 32.1 g (the amount of the polyamic acid concentration in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative Example 10)
As an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB) represented by the above general formula (14) (4.8035 g, 15.00 mmol: manufactured by Seika Corporation) is used instead of the above general formula. Using 3.1844 g (15.00 mmol) of the compound (m-Tol) represented by the formula (17), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 27.3 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

(Comparative Example 11)
As the tetracarboxylic acid dianhydride, 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the pyromellitic dianhydride (PMDA) 2 represented by the general formula (11). Instead of using a mixture with 0.7810 g (12.75 mmol), 0.8650 g (2.25 mmol) of the compound (CpODA) represented by the general formula (13) and the compound represented by the general formula (16). (4,4′-biphthalic anhydride: BPDA: manufactured by Tokyo Chemical Industry Co., Ltd.) 3.7513 (12.75 mmol) and a mixture (CpODA:BPDA molar ratio (CpODA:BPDA) is 15:85). Used,
As an aromatic diamine, 2,2′-bis(trifluoromethyl)benzidine (TFMB) represented by the above general formula (14) (4.8035 g, 15.00 mmol: manufactured by Seika Corporation) is used instead of the above general formula. Using 3.1844 g (15.00 mmol) of the compound (m-Tol) represented by the formula (17), and
A thin film made of polyimide in the same manner as in Example 1 except that the amount of tetramethylurea (TMU) used was changed from 33.8 g to 31.2 g (the amount of the polyamic acid in the reaction solution was 20 mass%). (Polyimide film) was obtained. When the IR spectrum of the obtained film was measured, it was confirmed that the film was made of polyimide. Table 1 shows the evaluation results of the properties (Tg, softening temperature, etc., obtained by the above-described property evaluation method) of the obtained polyimide.

As is clear from the results shown in Table 1, the films made of the polyimides of the present invention (Examples 1 to 8) all have a total light transmittance of 85% or more, and have sufficiently high transparency. It turned out. Further, the films made of the polyimides of the present invention (Examples 1 to 8) all have a yellowness index (YI) of 16 or less (from polyimides obtained by heating in a nitrogen atmosphere (Examples 1 to 6 and 8)). The film has a CTE of −20 ppm/K to 20 ppm/K. As described above, all of the films made of the polyimide of the present invention (Examples 1 to 8) have a sufficiently high total light transmittance and a sufficiently low degree of yellowness that can be used in applications where visibility is required. In addition, it was confirmed that it has a linear expansion coefficient equivalent to that of inorganic substances such as glass and copper. That is, the films made of the polyimides of the present invention (Examples 1 to 8) all have sufficiently high total light transmittance, sufficiently low yellowness, and sufficiently low linear expansion coefficient at a higher level in a well-balanced manner. It was confirmed to be a thing. As is clear from the results shown in Table 1, the polyimides (Examples 1 to 8) of the present invention have Tg of 300° C. or higher, softening temperature (softening point) of 300° C. or higher, and 400° C. or higher (preferably It was also found that it has a Td of 5% (450° C. or higher) and has a sufficiently high level of heat resistance. Further, the polyimides of the present invention (Examples 1 to 8) each have a haze (turbidity: HAZE) of 5 or less (value of 1.1 or less), and haze may be sufficiently low. Do you get it.

On the other hand, the polyimides obtained in Comparative Examples 1 and 2 had a high linear expansion coefficient exceeding 20 ppm/K, and did not have a sufficiently low linear expansion coefficient. Further, the polyimide obtained in Comparative Example 2 also has a total light transmittance of less than 83.0, which is a very high level of light transmittance (such as that achieved by the polyimide of the present invention). It has also been found that it does not have a total light transmittance of preferably 83.0 or more, more preferably 85.0 or more).

The results and the structures of the polyimides obtained in Examples 1 to 8 and Comparative Examples 1 and 2 (the polyimide obtained in Comparative Example 1 is the repeating unit based on the total amount of the repeating units (A) and (B)). The content of (A) is 40 mol %, and the polyimide obtained in Comparative Example 2 has a content of the repeating unit (B) of 100 mol% (the content of the repeating unit (A) is 0 mol. %)), the ratio of the repeating unit (A) to the total amount of the repeating units (A) and (B) is 5 inclusive. A polyimide having a content of ˜35 mol% has a sufficiently high total light transmittance (preferably 83.0 or more, more preferably 85.0 or more) and a sufficiently low yellowness (preferably 16 or less). It has been found that YI) and a sufficiently low linear expansion coefficient (preferably CTE in the range of -20 ppm/K to 20 ppm/K) are well-balanced at a higher level.

In contrast to Example 1, BPDA (aromatic tetracarboxylic dianhydride) was used instead of PMDA (aromatic tetracarboxylic dianhydride) in the tetracarboxylic dianhydride mixture. In the case (Comparative Example 4), not only the total light transmittance cannot be made sufficiently high, but the YI value is 18.2, and the yellowness may be set to a sufficiently low value. could not. Furthermore, when BPDA (aromatic tetracarboxylic dianhydride) is used (Comparative Example 4), the linear expansion coefficient is also 60.7 ppm/K, which is a sufficiently low value. I couldn't. Thus, in the mixture of tetracarboxylic dianhydrides, when BPDA (aromatic tetracarboxylic dianhydride) was used instead of PMDA (aromatic tetracarboxylic dianhydride) (Comparative Example 4) Have found that it is not possible to achieve a sufficiently low yellowness index and a sufficiently low linear expansion coefficient. Even when the tetracarboxylic dianhydride is only BPDA (Comparative Example 3), the tetracarboxylic dianhydride is a mixture of BPDA and CpODA (Comparative Example 4). Since the yellowness (YI) value is increased, when the type of aromatic tetracarboxylic dianhydride combined with CpODA is other than PMDA, it is not always sufficiently high in total light transmittance and sufficient. It has been found that it is not possible to have a very low degree of yellowness and a sufficiently low linear expansion coefficient in a well-balanced manner.

In contrast to Example 1, in the mixture of tetracarboxylic dianhydride, instead of CpODA (aliphatic tetracarboxylic dianhydride), CHDA, CPDA or CBDA (aliphatic tetracarboxylic acid) was used. In the case of using (dianhydride) (CHDA: Comparative Example 7, CPDA: Comparative Example 8, CBDA: Comparative Example 9), the total light transmittance is less than 83%, which is a sufficiently high level of 83% or more. It was found that the total light transmittance could not be obtained.

In contrast to Example 1, when m-Tol having no fluorine-based substituent was used as the aromatic diamine instead of using TFMB having a fluorine-based substituent (Comparative Example 10). Had a YI value of 44.6, and the yellowness could not be made sufficiently low (YI of 16 or less). Furthermore, the value of total light transmittance was 75.4%, and it was found that a sufficiently high level of total light transmittance of 83% or more could not be obtained. Similarly, as the aromatic dianhydride, BPDA is used instead of PMDA, and as the aromatic diamine, TFMB having a fluorine-containing substituent is used, but m-containing no fluorine-containing substituent is used. When Tol was used (Comparative Example 11), the YI value was 23.2, and the yellowness could not be made sufficiently low (YI of 16 or less). Furthermore, the value of the total light transmittance was 79.6%, and it was found that a sufficiently high level of the total light transmittance of 83% or more could not be obtained.

Further, when comparing Comparative Example 2 and Comparative Example 5, the kind of the aromatic diamine used at the time of manufacturing the polyimide is different, but the fluorine-containing substituent (tetrafluoromethyl group) is changed from the kind of the aromatic diamine. It was confirmed that the value of the yellowness index (YI) of the polyimide was lower when the arylene group having) was introduced into the repeating unit (Comparative Example 2). Similarly, when Comparative Example 3 and Comparative Example 6 are compared, the type of aromatic diamine used in the production of the polyimide is different, but the fluorine-containing substituent (tetrafluoro) is different from the type of aromatic diamine. It was confirmed that when the arylene group having a methyl group) was introduced into the repeating unit (Comparative Example 3), the value of yellowness (YI) of the polyimide was lower. Further, when comparing Comparative Example 4 and Comparative Example 11, the kind of the aromatic diamine used at the time of producing the polyimide is different, but the fluorine-containing substituent (tetrafluoromethyl group) is changed from the kind of the aromatic diamine. It was confirmed that the value of yellowness index (YI) of the polyimide was lower when the arylene group having) was introduced into the repeating unit (Comparative Example 4).

Considering together the difference (propensity) in the effects depending on the kind of the aromatic diamine and the results of Examples 1 to 4, the repeating units (A) and (B) are contained as in the present application, Moreover, the polyimide having a ratio of the repeating unit (A) to the total amount of the repeating units (A) and (B) of 5 to 35 mol% has a sufficiently high total light transmittance, a sufficiently low yellowness and a sufficiently low yellowness. It was found to have a well-balanced low linear expansion coefficient at a higher level.

The polyimide obtained in Example 7 was obtained in the same manner as in Example 6 except that air was used as the atmospheric gas in the heating step (obtained using the polyamic acid of the present invention. Things). Here, in general, when a polyimide is produced using an aliphatic acid dianhydride and heating (calcination) at a high temperature of about 300° C. is required, it is necessary to be in air or at least 500 ppm or more (depending on the case). When a polyimide is produced by baking a polyamic acid in an atmosphere of an active gas containing 1000 ppm or more of oxygen, the polyimide is discolored yellow due to oxygen oxidation, and the molecular weight is reduced due to the breaking of the polymer main chain due to oxygen oxidation, resulting in brittleness. It is known that there is a tendency to change. Therefore, usually, when producing a highly transparent polyimide using an aliphatic acid dianhydride, under an inert gas atmosphere (for example, an inert gas It is common to obtain a polyimide by firing a polyamic acid in an atmosphere containing oxygen and having an oxygen concentration of 100 ppm or less. On the other hand, although the polyimide of the present invention obtained in Example 7 was obtained by heating (calcining) polyamic acid in air, the total light transmittance was 86% or more. It has been found that not only has a very high degree of transparency, but the yellowness (YI) of the polyimide is 16 or less. From these results, the polyamic acid of the present invention (Examples 1 to 8) is used in the fields where air calcination is indispensable in the manufacturing process, and high oxygen concentration conditions (for example, an oxygen concentration of 500 ppm or more when manufacturing or using). And conditions where it is necessary to adopt conditions such that oxygen is generated, even when a polyimide used for products such as products is manufactured, the polyimide has sufficient visibility even after manufacturing or during use. It has been proved that it can be used for the preparation of polyimides used in products in the above fields. Further, the linear expansion coefficient of the polyimide of the present invention obtained in Example 7 is about the same as those of Example 6 and Example 1 in which firing was performed in nitrogen (CTE: 1.2 ppm/K), It was also found that it has a sufficiently low coefficient of linear expansion, similar to the one baked in nitrogen. From the results shown in Table 1, although the polyimide of the present invention obtained in Example 7 was obtained by heating (calcining) polyamic acid in the air, as described above, 300 It has a Tg of ℃ or more, a softening temperature (softening point) of 300 ℃ or more, and a Td of 5% of 400 ℃ or more (preferably 450 ℃ or more), and it is also known that it has a sufficiently high level of heat resistance. It was

From such results, the polyamic acid of the present invention (Examples 1 to 8) was irrespective of the atmosphere at the time of heating (calcination), for example, when it was baked in a nitrogen atmosphere (Examples 1 to 6 and 8). Whether or not it is fired in air (Example 7), the obtained polyimide can be sufficiently suppressed from being colored, and the increase in yellowness can be sufficiently suppressed, and the transparency is high, and It was also found that it is possible to obtain a polyimide having a sufficiently low linear expansion coefficient.

<Laser peelability of the polyimide films obtained in Examples 1 to 8>
In the step of preparing a film made of polyimide, step (iii) (film recovery step: immersing the polyimide-coated glass in 90° C. hot water and peeling the polyimide film from the glass substrate to form a polyimide film. Polyimide-coated glass was prepared by employing the same steps as those described in Examples 1 to 8 except that the step of obtaining) was not performed. Next, each polyimide-coated glass was irradiated with a laser to measure whether or not it could be peeled off. That is, a product “pm848 (excimer laser XeCl, 308 nm, maximum pulse energy 320 mJ/cm ² )” manufactured by Light Machinery Co., Ltd. was used as a laser oscillator, and a laser irradiation energy density was 50 to 320 mJ/cm ² (low energy density ( From 50 mJ/cm ² ), the energy density was sequentially increased every 10 mJ/cm ² until peeling was confirmed, and the irradiation energy density at which peeling was confirmed was used.), and the pulse width was 20 to 30 ns. The overlap rate (overlap rate) was 50%, the laser repetition frequency (repetition rate) was 30 Hz, and the irradiation surface shape of the laser beam was 14 mm in length and 30 mm in width. Laser light was irradiated from the glass substrate side, and whether or not the polyimide film could be peeled off (when Newton's rings were seen, it was judged that peeling was possible), whether or not there was coloring, and whether or not there was shot unevenness was visually judged.

As a result, all of the polyimide-coated glass obtained by adopting the same steps as those described in Examples 1 to 8 have an overlap rate (overlap rate) of 50% at an irradiation energy density of 140 mJ/cm ² . It was found that the polyimide film could be peeled off without coloring or shot unevenness (newton rings could be confirmed). From these results, when the film made of the polyimide of the present invention is laminated on glass (when it is a laminate on a glass substrate), it is possible to sufficiently suppress the quality change by irradiating with a laser. It was also found that it was possible to peel it off. Further, from these results, after laminating a film made of the polyimide of the present invention on a glass substrate (so-called carrier substrate or the like), a thin film transistor or the like is directly mounted on the film, and a so-called laser lift-off process is performed from the glass substrate to polyimide. It is clear that the film made of can be peeled off, and the film made of the polyimide of the present invention was also found to be suitably applicable to a method of manufacturing a display in which a thin film transistor or the like is mounted. ..

As described above, according to the present invention, a polyimide capable of having a sufficiently high total light transmittance, a sufficiently low yellowness index and a sufficiently low linear expansion coefficient in a well-balanced manner at a high level. It is possible to provide a polyamic acid capable of efficiently forming the polyimide, a solution of the polyamic acid, and a polyimide film including the polyimide.

Since the polyimide of the present invention has a sufficiently high total light transmittance, a sufficiently low yellowness index and a sufficiently low linear expansion coefficient at a higher level in a well-balanced manner, for example, flexible wiring. Substrate film, heat-resistant insulating tape, wire enamel, semiconductor protective coating, liquid crystal alignment film, transparent conductive film for organic EL (organic electroluminescence), organic EL lighting film, flexible substrate film, substrate film for flexible organic EL , Flexible transparent conductive film, organic thin film type solar cell transparent conductive film, dye-sensitized solar cell transparent conductive film, flexible gas barrier film, touch panel film, flexible display front film, flexible display back film, It is particularly useful as a material for a flexible display TFT substrate, a semiconductor protective film (buffer coat), an interlayer insulating film, a photoresist, a microlens for an image sensor, and the like.

Claims (6)

The following general formula (1):
[In the formula (1), R ¹ , R ² and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (A) represented by
The following general formula (2):
[In formula (2), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (A) with respect to the total amount of the repeating units (A) and (B) is 5 to 35 mol %. Polyimide. R ¹⁰ in the general formulas (1) and (2) are both represented by the following general formula (3):
[In the formula (3), R ⁵ represents a fluoroalkyl group having 1 to 10 carbon atoms. ]
The polyimide according to claim 1, which is a group represented by: Content of the said repeating unit (A) with respect to the total amount of the said repeating unit (A) and (B) is 5-25 mol%, The polyimide of Claim 1 or 2 characterized by the above-mentioned. The following general formula (4):
[In the formula (4), R ¹ , R ² , and R ³ each independently represent one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, and a fluorine atom, and R ¹⁰ is It shows a C6-40 arylene group having a fluorine-containing substituent, and n represents an integer of 0-12. ]
A repeating unit (C) represented by
The following general formula (5):
[In Formula (5), R< ¹⁰ > shows a C6-C40 arylene group which has a fluorine-containing substituent. ]
And a content of the repeating unit (C) with respect to the total amount of the repeating units (C) and (D) is 5 to 35 mol %. Polyamic acid that does. A polyamic acid solution comprising the polyamic acid according to claim 4 and an organic solvent. A polyimide film comprising the polyimide according to any one of claims 1 to 3.