JP2019011452A - Polyimide film and method for producing the same - Google Patents

Abstract

To provide a polyimide film which has sufficiently low retardation (Rth) in a thickness direction and a sufficient low coefficient of thermal expansion (coefficient of linear expansion: CTE) based on an absolute value at a higher level in a good balance.SOLUTION: A polyimide film is a film made of polyimide containing a repeating unit (A) represented by a specific general formula, where in a TMA curve determined by thermomechanical analysis (TMA) of pulling the film on a condition of a load of 20 mN while raising a temperature from 50°C to 450°C at a rate of a temperature rise of 5°C/min under nitrogen atmosphere and measuring a relationship between a temperature and variation of a length of the film, an extreme value in which a ratio of the variation of the length of the film to the variation of the temperature shows from a positive value to a negative value falls within a temperature range of 200-430°C.SELECTED DRAWING: None

Description

  The present invention relates to a polyimide film and a method for producing the same.

  In recent years, the use of a film made of polyimide has been studied as an alternative material for glass for use in substrates of liquid crystal displays (LCDs) and organic EL (electroluminescence) displays (OLEDs). And, as a polyimide film used for such LCDs and OLEDs, those having a low coefficient of thermal expansion (linear expansion coefficient: CTE) and retardation in the thickness direction (Rth) are desired, but these characteristics are a trade-off. Due to the relationship, polyimide films having various structures have been studied so far.

  For example, JP-A-2006-204568 (Patent Document 1) discloses a polyimide film mainly composed of polyimide obtained by polymerizing a tetracarboxylic acid component and a diamine component, wherein the tetracarboxylic acid component and the diamine component are: It is comprised by the compound chosen from the group which consists of a compound which has an aromatic ring, and an alicyclic compound, The ratio of the compound which has an aromatic ring is 10-90 mol% in the total 200 mol% of a tetracarboxylic acid component and a diamine component. There is disclosed a polyimide film in which the ratio of the alicyclic compound is 110 to 190 mol%, and either the tetracarboxylic acid component or the diamine component is composed only of the alicyclic compound. However, such a conventional polyimide film as described in Patent Document 1 is not yet sufficient in that it has a sufficiently low CTE in a well-balanced manner while having a sufficiently low Rth. The emergence of a polyimide film having a low Rth and a sufficiently low CTE with a high level of balance is desired.

JP, 2006-204568, A

  The present invention has been made in view of the above-described problems of the prior art, and has a sufficiently low thickness direction retardation (Rth) and a sufficiently low thermal expansion coefficient (linear expansion coefficient: CTE) on the basis of absolute values. It aims at providing the manufacturing method of the polyimide film which makes it possible to have the polyimide film which can have a good balance in a higher level, and the polyimide film.

In order to use a film made of polyimide as a substrate for LCDs or OLEDs, the inventors of the present invention use a film when heated to a high temperature (for example, about 400 ° C. or higher) or when allowed to cool in the manufacturing process of the display or the like. Compared to conventional polyimide films, cracks and breakage in itself, and cracks and breakage in other layers laminated as the film expands and contracts are more advanced. From the viewpoint of suppressing at a standard level and obtaining a higher display quality when used for LCD or OLED substrates, a sufficiently low thickness direction retardation and a sufficiently low thermal expansion coefficient (linear expansion coefficient: CTE) And a specific repeating unit (A ′) represented by the following general formula (7). After forming a coating film using a resin solution containing a polyimide precursor and an organic solvent, the solvent is removed from the coating film, and the glass transition temperature (Tg) of the polyimide finally formed is determined. As a reference, a polyimide obtained by firing (heat curing) at a temperature within the range of (Tg-190) ° C. to (Tg-50) ° C. is used as a TMA curve (a graph showing the relationship between temperature and film length). ) Has an extreme value (a point at which the film changes from elongation to shrinkage in tensile TMA measurement) in a specific temperature range in which the ratio (inclination) of the change amount of the film length to the change amount of the temperature changes from positive to negative. As a result, the Rth (absolute value) of the resulting polyimide film can be made sufficiently low, while the CTE (absolute value) can be made lower. This has led to the completion of the present invention have found to be a.
That is, the polyimide film of the present invention has the following general formula (1):

[In Formula (1), A shows the tetravalent alicyclic hydrocarbon group whose number of the carbon atoms which form a cyclic structure is 4-30, ^Ra is following General formula (2)-(3). :

(In the formula (2), R ^a1 , R ^a2 , R ^a3 and R ^a4 each independently represents one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group,
In formula (3), R ^a5 and R ^a6 each independently represent one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group. )
Any one of divalent organic groups represented by the formula: ]
A film comprising a polyimide containing a repeating unit (A) represented by:
A thermal machine that measures the relationship between the temperature and the change in the length of the film by pulling the film under a load of 20 mN while raising the temperature from 50 ° C. to 450 ° C. at a temperature rising rate of 5 ° C./min in a nitrogen atmosphere. In the TMA curve obtained by analysis (TMA), an extreme value in which the ratio of the change in the length of the film to the change in the temperature changes from positive to negative exists in the temperature range of 200 to 430 ° C. Is.

  In the polyimide film of the present invention, A in the formula (1) is represented by the following general formula (4):

[In 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 n is 0 to 0. An integer of 12 is shown. ]
It is preferable that it is a tetravalent alicyclic hydrocarbon group represented by these.

  Moreover, as a polyimide film of this invention, the said polyimide is following General formula (5).

[In Formula (5), A is synonymous with A in said Formula (1), ^Rb is following General formula (6):

(In Formula (6), R ^b1 and R ^b2 each independently represent one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, and a hydroxyl group.)
The bivalent organic group represented by these is shown. ]
And the content of the repeating unit (A) with respect to the total amount of the repeating unit (A) and the repeating unit (B) in the polyimide is from 50 to 50. It is preferable that it is 100 mol%.

The method for producing a polyimide film of the present invention comprises forming a coating film using a polyimide precursor resin solution containing a polyimide precursor and an organic solvent, and then removing the solvent from the coating film and baking the polyimide film. Including a step of obtaining a film comprising:
The polyimide precursor is represented by the following general formula (7):

[In Formula (7), A shows the tetravalent alicyclic hydrocarbon group whose number of carbon atoms which forms a cyclic structure is 4-30, ^Ra is said General formula (2)-(3). Any one of the divalent organic groups represented, Y ¹ and Y ² are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms. 1 type selected. ]
And a repeating unit (A ′) represented by:
At the time of the baking, the film is made of the polyimide as a film by baking at a temperature in the range of (Tg-190) ° C. to (Tg-50) ° C., based on the glass transition temperature (Tg) of the resulting polyimide. Obtaining the polyimide film of the invention,
It is the method characterized by this.

  According to the present invention, it is possible to have a sufficiently low thickness direction retardation (Rth) and a sufficiently low thermal expansion coefficient (linear expansion coefficient: CTE) at a higher level in a well-balanced manner based on an absolute value. It becomes possible to provide the manufacturing method of the polyimide film which can be manufactured, and the polyimide film which can manufacture the polyimide film.

3 is a graph showing TMA curves of the polyimide film obtained in Example 1 and the polyimide film obtained in Comparative Example 3. FIG.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

[Polyimide film]
The polyimide film of the present invention is a film made of polyimide containing the repeating unit (A) represented by the general formula (1), and
A thermal machine that measures the relationship between the temperature and the change in the length of the film by pulling the film under a load of 20 mN while raising the temperature from 50 ° C. to 450 ° C. at a temperature rising rate of 5 ° C./min in a nitrogen atmosphere. In the TMA curve obtained by analysis (TMA), the extreme value at which the ratio (slope) of the change amount of the film length to the change amount of the temperature changes from positive to negative exists within the temperature range of 200 to 430 ° C. It is a feature.

  The polyimide contains the repeating unit (A) represented by the general formula (1). In such a repeating unit (A), A in the general formula (1) has 4 to 30 carbon atoms (more preferably 4 to 25, still more preferably 15 to 25, particularly, a cyclic structure). The tetravalent alicyclic hydrocarbon group which is preferably 16-20) is shown. The “number of carbon atoms forming the cyclic structure” as used herein refers to the number of carbon atoms forming the cyclic structure portion of the main skeleton of the alicyclic hydrocarbon (cycloaliphatic group). When has a substituent containing carbon (such as a hydrocarbon group), the number of carbons in the substituent is not included. For example, 2-ethyl-cyclohexane is cyclic because the cyclic structure portion of the main skeleton is cyclohexane (carbon number: 6) and the substituent bonded to the cyclic structure is an ethyl group (carbon number: 2). The number of carbon atoms forming the structure is 6. If the number of carbon atoms forming the cyclic structure of such a tetravalent alicyclic hydrocarbon group is less than the lower limit, the heat resistance tends to decrease and the thermal expansion coefficient (linear expansion coefficient: CTE) tends to increase. On the other hand, if the upper limit is exceeded, synthesis and purification tend to be difficult. Such an alicyclic hydrocarbon may be derived from any of a monocyclic compound, a condensed ring compound, a spiro ring compound, a polyspiro compound, and the like.

  Such a tetravalent alicyclic hydrocarbon group (A in the formula) may have a substituent bonded to the cyclic structure portion (alicyclic hydrocarbon) of the main skeleton. In addition, the alicyclic hydrocarbon (cyclic structure portion) of the main skeleton of such a tetravalent alicyclic hydrocarbon group is not particularly limited, and examples thereof include cyclobutane, cyclopentane, cyclohexane, cycloheptane, Cyclic hydrocarbons such as cyclooctane, cyclodecane, bicyclo [2.1.1] hexane, bicyclo [2.2.1] heptane, bicyclo [3.2.1] octane, bicyclo [2.2.2] octane A condensed polycyclic hydrocarbon in which these cyclic hydrocarbons are condensed; a monospiro hydrocarbon having a spiro structure in which these cyclic hydrocarbons are connected by one carbon atom (for example, spiro [4.5] decane, etc.) and Polyspirohydrocarbons (eg dispiro [4.2.4.2] tetradecane, norbornane-2-spiro-α-cyclopentanone-α′-spiro-2 ″ -no And the like. Further, the substituent that can be bonded to the cyclic structure portion (alicyclic hydrocarbon) of the main skeleton is not particularly limited, but is preferably an alkyl group or a halogen atom from the viewpoint of heat resistance and transparency. 10 alkyl groups and fluorine atoms are more preferred.

  The tetravalent alicyclic hydrocarbon group includes a tetravalent alicyclic hydrocarbon group represented by the above general formula (4), the following general formula (10) from the viewpoint of ease of film preparation. To (12):

[R ^{4 in} Formulas (10) to (12) has the same meaning as R ¹ in Formula (4). ]
Of the tetravalent alicyclic hydrocarbon group represented by the above general formula (4), the tetravalent alicyclic hydrocarbon group represented by the above general formula (10). The alicyclic hydrocarbon group is more preferable. Further, as such a tetravalent alicyclic hydrocarbon group, from the viewpoint of achieving higher heat resistance, the tetravalent alicyclic hydrocarbon group represented by the general formula (4) is Particularly preferred.

R ¹ , R ² and R ³ in the general formula (4) are each independently 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 It is an integer of ~ 12. The alkyl group that can be selected as R ¹ , R ² , or R ³ in the formula (4) 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 a sufficiently high heat resistance cannot be achieved. Moreover, as carbon number of the alkyl group which can be selected as such R < ¹ >, R < ² >, R < ³ >, it is preferable that it is 1-6 from a viewpoint that refinement | purification becomes easier, and it is 1-5. Is more preferable, it is still more preferable that it is 1-4, and it is especially preferable that it is 1-3. Further, such an alkyl group that can be selected as R ¹ , R ² , or R ³ may be linear or branched. Further, such an alkyl group is more preferably a methyl group or an ethyl group from the viewpoint of ease of purification.

R ¹ , R ² and R ³ in the formula (4) are each independently a hydrogen atom or a carbon number of 1 to 3 from the viewpoint that higher heat resistance can be obtained when a polyimide is produced. 10 alkyl groups are more preferable, and among them, from the viewpoint of easy availability of raw materials and easier purification, each independently, a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, or An isopropyl group is more preferable, and a hydrogen atom or a methyl group is particularly preferable. Moreover, it is especially preferable that several R < ¹ >, R < ² >, R < ³ > in such a formula is the same from viewpoints, such as easiness of refinement | purification.

  Moreover, n in such a formula (4) shows the integer of 0-12. If the value of n exceeds the upper limit, purification becomes difficult. Further, the upper limit of the numerical value range of n in the general formula (4) is more preferably 5 and particularly preferably 3 from the viewpoint of easier purification. Further, the lower limit of the numerical range of n in the general formula (4) is more preferably 1 and particularly preferably 2 from the viewpoint of the stability of the raw material compound. Thus, it is particularly preferable that n in the general formula (4) is an integer of 2 to 3.

Further, ^{R 4} in the general formula (10) to (12) has the same meaning as ^{R 1} in the formula (4), it is also the same as the preferable examples.

In the repeating unit (A) according to the present invention, R ^a in the general formula (1) is any one of the divalent organic groups represented by the general formulas (2) to (3) (the above The bivalent organic group represented by General formula (2) and the bivalent organic group represented by the said General formula (3) are shown. Such a polyimide film having a Tg of 350 ° C. or higher is obtained by a repeating unit including any one of the divalent organic groups represented by the general formulas (2) and (3). It is possible to have heat resistance, to express a point (pole) where the film changes from elongation to contraction between 200 to 430 ° C. when the polyimide film is heated, and to obtain a lower Rth. Become.

In addition, R ^a1 , R ^a2 , R ^a3 and R ^a4 in the general formula (2) are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group. And R ^a5 and R ^a6 in the general formula (3) are each independently one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group. is there.

Such expressions (2) - (3) an alkyl group having 1 to 10 carbon atoms which can be selected as ^R a1 ^{to R a6} in the above formula (4) carbon atoms may be selected as ^{R 1} in 10 The same as the alkyl group of (the preferred one is also the same). In addition, the halogen atom that can be selected as R ^{a1 to} R ^a6 in the formulas (2) to (3) is not particularly limited, but a chlorine atom and a fluorine atom are preferable from the viewpoint of sufficiently reducing Rth. A fluorine atom is particularly preferable.

Moreover, as groups that can be selected as R ^{a1 to} R ^a6 in the formulas (2) to (3), from the viewpoint of heat resistance, transparency, low thermal expansion, and laser releasability, a hydrogen atom, a methyl group, An ethyl group, an n-propyl group, an isopropyl group, a fluoro group, a chloro group, a bromo group, and a hydroxyl group are preferable, and a hydrogen atom, a methyl group, a fluoro group, and a chloro group are more preferable.

  Furthermore, it is said that such divalent organic groups represented by the general formulas (2) and (3) exhibit sufficiently low Rth, sufficiently low CTE, and sufficiently high heat resistance and laser peelability. From the viewpoint, the group represented by the general formula (2) is more preferable.

  Such a repeating unit (A) has the following general formula (I):

[A in the formula (I) has the same meaning as A in the above formula (1). ]
A tetracarboxylic dianhydride represented in the ^{_{formula: H 2 N-R a -NH}} 2 [R a in the formula is as defined ^{R a} in the above formula (1). ] Derived from the reaction with a diamine compound represented by the formula: The tetracarboxylic dianhydride represented by the general formula (I) is not particularly limited, and a known one can be used as appropriate, but the following general formula (I-1):

^{[R 1,} R ^{2, R} 3, n in the formula (I-1) is ^R 1 in the general formula ^(4), R ^2, the same meaning as ^R 3, n. ]
The tetracarboxylic dianhydride represented by these is preferable. Moreover, it does not restrict | limit especially as a method for manufacturing the tetracarboxylic dianhydride represented by such general formula (I), A well-known method can be employ | adopted suitably, for example, the said general formula ( When the tetracarboxylic dianhydride represented by I-1) is produced and used, a method described in International Publication No. 2011/099518 can be appropriately employed. Moreover, you may utilize a commercial item as these tetracarboxylic dianhydrides. Furthermore, these tetracarboxylic dianhydrides can be used singly or in combination of two or more.

Further, the _formula: Examples of the diamine compounds represented by _{^{H 2 N-R a -NH 2}} , as long as ^{R a} is the same as ^{R a} in the formula (1) is not particularly limited, for example, 9,9-bis (4-aminophenyl) fluorene (FDA), 9,9-bis (4-amino-3-fluorophenyl) fluorene (F-FDA), 9,9-bis (4-amino-3-) Chlorophenyl) fluorene (Cl-FDA), 9,9-bis (4-amino-3-bromophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene (Me-FDA), 9, 9-bis (4-amino-3-ethylphenyl) fluorene, 9,9-bis (4-amino-3-n-propylphenyl) fluorene, 9,9-bis (4-amino-3-isopropylphenyl) fluorene 9,9-bis (4-a Mino-3-hydroxyphenyl) fluorene, 4,4′-diaminodiphenylsulfone (4,4′-DDS), 3,3′-diaminodiphenylsulfone (3,3′-DDS), 3,7-diamino-2 , 8-dimethyldibenzothiophene sulfone, o-tolidine sulfone, bis (3-amino-4-hydroxyphenyl) sulfone, and the like. Commercial products may be used as these diamine compounds. Moreover, these diamine compounds can be used singly or in combination of two or more.

Moreover, as said polyimide, even if it contains 1 type of repeating unit (A) independently, or 2 or more types from which the kind of A in said Formula (1) and the kind of ^Ra differ. It may contain a combination of repeating units (A). Moreover, the said polyimide may contain the other repeating unit with the said repeating unit (A).

As such a polyimide, what contains the repeating unit (B) represented by the said General formula (5) with the said repeating unit (A) is preferable. That is, as said polyimide, what further contains a repeating unit (B) is preferable. A in such a general formula (5) is synonymous with A in the said Formula (1) (The suitable thing is also synonymous). R ^b in the general formula (5) is a divalent organic group represented by the general formula (6). R ^b1 and R ^b2 in the formula (6) are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, and a hydroxyl group. In addition, ^Rb1 and ^{Rb2 in} such a formula (6) are respectively synonymous with ^Ra1 in the said Formula (2) (The suitable thing is also synonymous).

Such a repeating unit (B) includes a tetracarboxylic dianhydride represented by the above general formula (I), a formula: H ₂ N—R ^b —NH ₂ [wherein R ^a is the formula (5) It is synonymous with R ^{b in} ). ] Derived from the reaction with a diamine compound represented by the formula: For the tetracarboxylic dianhydride represented by the above general formula (I), examples of the diamine compound represented by the formula: H ₂ N—R ^b —NH ₂ include 4,4′-diaminobenz Anilide (4,4′-DABAN), 2,4′-diaminobenzanilide (2,4′-DABAN), 3,4′-diaminobenzanilide, 3,3′-diaminobenzanilide, 2-methylbenzanilide Etc. Commercial products may be used as these diamine compounds. Moreover, these diamine compounds can be used singly or in combination of two or more.

  In addition, in the said polyimide, you may contain repeating units other than repeating unit (A) and (B) in the range which does not impair the effect of this invention. Such a repeating unit other than the repeating units (A) and (B) is not particularly limited, and includes known repeating units that can be used as a repeating unit of polyimide. As other repeating units other than the repeating units (A) and (B), for example, other tetracarboxylic dianhydrides other than the tetracarboxylic dianhydrides represented by the general formula (I) ( For example, a repeating unit derived from WO 2014/034760, etc. described in paragraph [0171], or a diamine other than the diamine compound (for example, paragraph WO 02/030019 paragraph [0211]). Or a repeating unit derived from the aromatic diamine described in paragraph [0157] of International Publication No. 2014/034760).

In addition, as a repeating unit other than the repeating units (A) and (B), from the viewpoint that CTE can be further reduced, the tetracarboxylic dianhydride represented by the above general formula (I) and P-phenylenediamine which may have a substituent, terphenyldiamine which may have a substituent, biphenyl diamine which may have a substituent (for example, m-tolidine, o-tolidine) 3,3 ′, 5,5′-tetramethylbenzidine, octafluorobenzidine, 2,2′-bis (trifluoromethyl) benzidine, etc.), an ester group-containing diamine which may have a substituent (for example, 4 -Aminobenzoic acid 4-aminophenyl and the like, and a diamine having a hydroxyl group (for example, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropro A repeating unit formed by reaction with at least one aromatic diamine selected from the group consisting of bread and the like (the R ^b portion of the group represented by the general formula (5) is the aromatic group) A repeating unit which is a residue obtained by removing two amino groups from a diamine can be preferably used. In addition, as a substituent of such aromatic diamine, it is preferable that it is 1 type selected from the group which consists of a C1-C10 alkyl group, a halogen atom, and a hydroxyl group. The alkyl group having 1 to 10 carbon atoms, the halogen atom and the hydroxyl group as such a substituent are the same as those which can be selected as R ^a1 in the above formula (2). is there).

  In such a polyimide, the content of the repeating unit (A) is preferably 50 to 100 mol%, more preferably 55 to 95 mol%, more preferably 60 to 90 mol based on all repeating units. % Is particularly preferable, and 65 to 90 mol% is most preferable. When the content of such a repeating unit (A) is less than the lower limit, it tends to be difficult to achieve a sufficiently low Rth, and when it is within the content range, the Rth is sufficiently low. Higher performance tends to be obtained in that the CTE has a sufficiently low CTE in a balanced manner.

  Moreover, when the said polyimide contains the said repeating unit (B) with a repeating unit (A), the total amount of the said repeating unit (A) and (B) is 80-100 mol with respect to all the repeating units. %, More preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, and particularly preferably 98 to 100 mol%. When the ratio of the total amount (content) of such repeating units (A) and (B) is less than the lower limit, it is difficult to have a sufficiently low CTE in a well-balanced manner while having a sufficiently low Rth. There is a tendency.

  Moreover, when the said polyimide contains the said repeating unit (B) with a repeating unit (A), the said repeating unit (A) with respect to the total amount of the said repeating unit (A) in this polyimide and the said repeating unit (B) ) Is preferably 50 to 99 mol% (more preferably 55 to 95 mol%, still more preferably 60 to 90 mol%, particularly preferably 65 to 90 mol%). If the content of such a repeating unit (A) is less than the lower limit, it tends to be difficult to achieve a sufficiently low Rth, whereas if it exceeds the upper limit, it is difficult to achieve a sufficiently low CTE. Tend to be. From the same viewpoint, when the polyimide contains a repeating unit (B) together with the repeating unit (A), the content ratio of the repeating unit (A) and the repeating unit (B) in the polyimide is: The molar ratio [(A) :( B)] is preferably 50:50 to 99: 1 (more preferably 55:45 to 95: 5, still more preferably 60:40 to 90:10). In addition, as said polyimide, what consists only of repeating unit (A) and (B) can be utilized suitably from a viewpoint that low Rth and low CTE are achieved in a high level with sufficient balance.

  The polyimide film of the present invention has an extreme value at which the ratio (slope) of the change amount of the film length to the change amount of the temperature changes from positive to negative in the TMA curve (CTE curve) at a temperature of 200 to 430 ° C. It exists within the range. As described above, in the TMA curve indicating the relationship between the film length and the temperature, there is an extreme value in which the ratio (slope) of the change amount of the film length to the change amount of the temperature changes from positive to negative. The polyimide film that expands due to heat up to such an extreme temperature (the length of the film is extended), and in the temperature range higher than the temperature at the position of such extreme value, basically the temperature near Tg. Until then, the film shrinks due to heat (the film length shrinks) compared to the film length at such extreme temperatures. And when the position of the extreme value exists in the said temperature range, it becomes possible to make CTE of a polyimide film into a lower value. In such a TMA curve, a polyimide having an extreme value in which the ratio (slope) of the change amount of the film length to the change amount of the temperature changes from positive to negative in the temperature range of 200 to 430 ° C. will be described later. It can manufacture efficiently by employ | adopting the manufacturing method of the polyimide of this invention. Here, a method for obtaining the “TMA curve” according to the present invention will be described below.

  For such a TMA curve, a thermomechanical analyzer (for example, a trade name “TMA8310” or “TMA8311” manufactured by Rigaku) is used as a measuring device in a tensile mode, and a film as a measurement sample is set in the measuring device. In a nitrogen atmosphere, the film (measurement sample) was pulled in the longitudinal direction under the condition of a load of 20 mN while raising the temperature from 50 ° C. to 450 ° C. at a rate of temperature rise of 5 ° C./min, and the change in temperature and length of the film It can obtain | require by the method (what is called tensile TMA measurement) which measures the relationship with quantity. In such measurement, first, the polyimide film to be measured is vacuum-dried (pressure: 0.133 kPa, 120 ° C., 1 hour), and then in a nitrogen atmosphere at a temperature of 200 ° C. A process of drying treatment for 1 hour was performed, and then a film having a size of 20 mm in length (5 mm in total grip), 5 mm in width, and 10 μm in thickness was prepared (prepared by cutting out), and a measurement sample Use as Here, when the measurement sample is set in the measurement device, in order to change the length in the longitudinal direction, the gripping portion of the measurement device (total grip portion of the film is 5 mm) Use the film so that the length between the grips (jigs) of the measuring device at the start of measurement is 15 mm (the length in the vertical direction of the film at the start of measurement is 15 mm). To use). The “TMA curve” here is a graph in which the vertical axis (Y) is the amount of change in the length of the film and the horizontal axis (X) is the measurement temperature in the above-described tensile TMA measurement. Is the point at which the ratio (slope: ΔY / ΔX) of the amount of change (ΔY) on the vertical axis to the amount of change (ΔX) on the horizontal axis turns from positive to negative, or the point where the ratio turns from negative to positive. In the tensile TMA measurement, a TMA curve having an extreme value at which the slope (ΔY / ΔX) turns from positive to negative is measured in a specific temperature range. It should be noted that such an extreme value at which the ratio (inclination) of the change amount of the film length to the change amount (increase amount) of the temperature changes from positive to negative is determined from the elongation of the film in the tensile TMA measurement. Measured as the point that changes to contraction. Therefore, the extreme value at which the ratio (ΔY / ΔX) of the film length change amount (ΔY) to the temperature change amount (ΔX) turns from positive to negative is that the film length changes from elongation to shrinkage. In other words.

  Thus, the polyimide film of the present invention has the TMA curve (CTE curve [obtained as an analysis result of tensile TMA measurement, the vertical axis (Y) is the amount of change in film length, and the horizontal axis (X) is measured. In the graph of temperature]), the extreme value at which the ratio (slope) of the change amount of the film length to the change amount (increase amount) of the temperature changes from positive to negative (in the tensile TMA measurement, the film length is increased from the elongation). The point which changes to shrinkage | contraction) exists in the temperature range (more preferably 220-420 degreeC, still more preferably 240-410 degreeC) of 200-430 degreeC. If the extreme temperature at which the slope changes from positive to negative is not within the above range, the absolute value of CTE cannot be made sufficiently small, and a sufficiently low CTE and a sufficiently low Rth can be obtained. It will not be possible to have a good balance. The upper limit of the extreme temperature range is more preferably 400 ° C., further preferably 375 ° C., particularly preferably 350 ° C., and most preferably 330 ° C.

  The reason why the present invention can provide a polyimide film having a sufficiently low Rth and a sufficiently low CTE in a balanced manner at a higher level is not necessarily clear. Thus, the structure of the polyimide film of the present invention has been found. That is, first, the present inventors have found that Rth can be made sufficiently low by the polyimide containing the repeating unit (A) according to the present invention, and further, the conditions during the production are appropriately controlled. Thus, it has been found that in the TMA curve (CTE curve), it is possible to obtain a polyimide film having an extreme value whose slope changes from positive to negative. And based on such knowledge, as a result of further studies by the present inventors, in such a TMA curve (CTE curve), the ratio (inclination) of the change amount of the film length to the change amount of the temperature. It was further found that there is a relationship between the position (temperature) of the extreme value and the value of CTE in the polyimide having an extreme value in which the value changes from positive to negative. It has been found that when the position of the extreme value is controlled to be within the specific temperature range (200 to 430 ° C.), the CTE can be lowered at a higher level. Usually, in a polyimide film, Rth and CTE are in a trade-off relationship (a relationship in which one becomes larger when one is reduced), but it is difficult to make both values sufficiently small in a balanced manner. In the present invention, since the CTE can be lowered at a higher level as described above, for example, a sufficiently small numerical range of Rth such that Rth (absolute value) is 145 nm or less. Among them, CTE (absolute value) is set to 145 nm to 50 nm, CTE (absolute value) is set to 30 ppm / K or less, and CTE (absolute value) is made sufficiently smaller in relation to the value of Rth (absolute value). Rth (absolute value) is a sufficiently small value such as less than 50 nm, CTE (absolute value) is 45 ppm / K or less, and the relationship with Rth It is a sufficiently small value of CTE; like also becomes possible. In this way, the present inventors have made it possible to provide a polyimide film having a sufficiently low Rth and a sufficiently low CTE at a higher level with a good balance. In general, when a film is pulled, the length always increases as the temperature rises as the film is pulled. Therefore, in the TMA curve, an extreme value whose slope changes from positive to negative is not confirmed. Become.

  In addition, the polyimide film of the present invention has an increased amount of film length at the extreme value (for example, an amount of length increased with respect to the length of 15 mm before measurement: 30 to 400) when measuring the TMA curve. The length elongated by the measurement at ° C.) is preferably 200 μm or less (more preferably 150 μm or less, still more preferably 0 to 100 μm). If the amount of increase in length exceeds the above upper limit, the dimensional change during heating and cooling tends to increase, leading to curling and cracking.

  Furthermore, in the polyimide film of this invention, it is preferable that the glass transition temperature (Tg) of the said polyimide is 300 degreeC or more, It is more preferable that it is 300 to 550 degreeC, It is further that it is 350 to 500 degreeC. preferable. If such a glass transition temperature (Tg) is less than the lower limit, sufficient heat resistance tends to be difficult to achieve, whereas if it exceeds the upper limit, it tends to be difficult to produce a polyimide having such characteristics. It is in. As such a Tg measurement method, a film made of polyimide having a size of 5 mm in length, 5 mm in width and 10 μm in thickness is prepared as a measurement sample, and a thermomechanical analyzer (trade name “TMA8310” manufactured by Rigaku) is used as a measurement device. Or “TMA8311”) with a transparent quartz pin (tip diameter: 0.5 mm) on the film at a pressure of 500 mN under a nitrogen atmosphere at a temperature rising rate of 5 ° C./min. A method of measuring the point at which the film is softened by heating and the quartz pin penetrates into the film as a glass transition temperature by employing a so-called penetration method (hereinafter referred to as “500 mN” for convenience). "Penetration (needle insertion) method".

  In such a polyimide film, the absolute value of retardation (Rth) in the thickness direction measured at a wavelength of 589 nm is preferably 145 nm or less, more preferably 100 nm or less, more preferably 85 nm, in terms of a thickness of 10 μm. More preferably, it is as follows. When the absolute value of the retardation (Rth) in the thickness direction exceeds the upper limit, a clear image cannot be obtained when used in a display device, and the display quality tends to deteriorate. In addition, when the absolute value of the retardation (Rth) is less than or equal to the upper limit, when used in a display device, a clear image is obtained and the display quality tends to be higher. Thus, when used in a display device, the absolute value of retardation (Rth) in the thickness direction is preferably a lower value from the viewpoints of obtaining a clear image and improving display quality.

  Such “absolute value of thickness direction retardation (Rth)” is the value of the refractive index (589 nm) of the polyimide film measured as described below using the product name “AxoScan” manufactured by AXOMETRICS as a measuring device. After input to the measuring apparatus, the retardation in the thickness direction of the polyimide film was measured using light with a wavelength of 589 nm under the conditions of temperature: 25 ° C. and humidity: 40%, and the measured value of retardation in the thickness direction thus obtained. A value (converted value) converted to a retardation value per 10 μm thickness of the film is obtained based on (measured value by automatic measurement (automatic calculation) of the measuring device), and an absolute value is calculated from the converted value. Thus, the “absolute value of retardation (Rth) in the thickness direction” can be obtained by calculating the absolute value (| converted value |) of the converted value. In addition, since the size of the polyimide film of a measurement sample should just be larger than the photometry part (diameter: about 1 cm) of the stage of a measuring device, it does not restrict | limit in particular. Further, when a measurement sample having a thickness of 10 μm is used, the “absolute value of retardation in the thickness direction (Rth)” is obtained using the measurement value obtained by the automatic measurement (automatic calculation) of the measurement apparatus as the converted value as it is. Can do.

  In addition, the value of “refractive index of polyimide film (589 nm)” used for the measurement of retardation (Rth) in the thickness direction is an unstretched film made of the same type of polyimide as the polyimide forming the film to be measured for retardation. After forming the film, such an unstretched film is used as a measurement sample (in the case where the film to be measured is an unstretched film, the film can be used as a measurement sample as it is), and measurement is performed. Using a refractive index measuring apparatus (trade name “NAR-1T SOLID” manufactured by Atago Co., Ltd.) as an apparatus, an average refractive index of a measurement sample with respect to 589 nm light is measured at a temperature condition of 23 ° C. using a light source of 589 nm. And ask. Thus, using the unstretched film, the value of “refractive index of polyimide film (589 nm)” was measured, and the obtained measurement value (average refractive index value of the measurement sample with respect to 589 nm light) was calculated as described above. This is used for the measurement of retardation (Rth) in the thickness direction. Here, the size of the polyimide film of the measurement sample is not particularly limited as long as it is a size that can be used in the refractive index measurement device, and may be 1 cm square (1 cm in length and width) and 10 μm in thickness.

  As described above, generally, the thermal expansion coefficient (linear expansion coefficient: CTE) of polyimide is in a trade-off relationship with the Rth value (absolute value). From the viewpoint of use in a display, as described above, Rth (absolute value) is preferably 145 nm or less when converted to a thickness of 10 μm. In view of such a viewpoint, the polyimide film of the present invention has a CTE absolute value of 30 ppm / K when Rth (absolute value) is in a region where the thickness is 145 nm to 50 nm when converted to a thickness of 10 μm. It is preferably below (more preferably 0 to 25 ppm / K, more preferably 0 to 20 ppm / K), and Rth is very small such that Rth (absolute value) is less than 50 nm when converted to a thickness of 10 μm. When in the region, the absolute value of CTE is preferably 45 ppm / K or less (more preferably 0 to 40 ppm / K, and still more preferably 0 to 30 ppm / K). That is, as the polyimide film of the present invention, when Rth (absolute value: converted to 10 μm in thickness) is in the range of 145 nm to 50 nm, the absolute value of CTE is 30 ppm / K or less, and Rth (absolute value: thickness of 10 μm). When the conversion is less than 50 nm, the absolute value of CTE is preferably 45 ppm / K or less. A polyimide film satisfying these conditions can be said to have a higher level and lower CTE in relation to Rth, and sufficiently low thickness direction retardation (Rth) and sufficient with respect to absolute value. It can be said that it has a very low level of thermal expansion coefficient (CTE) at a very high level. In addition, when the absolute value of such a thermal expansion coefficient exceeds the said upper limit, when it combines with a metal and an inorganic substance, it exists in the tendency for peeling, a crack, etc. to occur easily with a heat history. As a method for measuring the coefficient of thermal expansion (CTE) of such polyimide, the amount of change in the length of the sample (the length in the vertical direction) is the same as the method employed in the above-described method for obtaining the “TMA curve”. Change amount), and then, based on the data, a method of calculating an average value of changes in the length of the sample per 1 ° C. (1K) in a temperature range of 100 ° C. to 350 ° C. is adopted. . From such a measurement method, it can be said that the thermal expansion coefficient (linear expansion coefficient: CTE) of the polyimide is a value of the thermal expansion coefficient of the polyimide film when the thickness is 10 μm.

  Moreover, as a coefficient of thermal expansion (linear expansion coefficient: CTE) of the polyimide film of the present invention, the absolute value thereof is preferably in the range of 0 to 30 ppm / K from the viewpoint of obtaining more advanced characteristics. More preferably, it is in the range of 0-25 ppm / K, and still more preferably in the range of 0-20 ppm / K. Thus, as a polyimide film of the present invention, Rth (absolute value: converted to a thickness of 10 μm) is in the range of 0 to 145 nm (more preferably 0 to 110 nm) from the viewpoint of obtaining more advanced characteristics ( CTE (absolute value) is preferably 30 ppm / K or less, more preferably 0 to 25 ppm / K, and more preferably 0 to 20 ppm / K (in any case within the above range). Is more preferable.

  Moreover, as such a polyimide film, from the viewpoint of obtaining a higher degree of transparency, one having a yellowness (YI) of 20 to 0 (more preferably 10 to 0, particularly preferably 5 to 0) is more preferable. preferable. Further, such a polyimide is more preferably one having a total light transmittance of 80% or more (more preferably 85% or more, particularly preferably 87% or more) from the viewpoint of obtaining higher transparency. Moreover, as such a polyimide, the thing whose haze (turbidity) is 5-0 (more preferably 4-0, especially preferably 3-0) is more preferable from a viewpoint of obtaining higher transparency. . In addition, for measuring such yellowness (YI), a product name “Spectral Colorimeter SD6000” manufactured by Nippon Denshoku Industries Co., Ltd. is used as a measuring device, and the total light transmittance and haze (turbidity) are measured. For measurement, a trade name “Haze Meter NDH-5000” manufactured by Nippon Denshoku Industries Co., Ltd. is used as a measuring device. In addition, as a sample for measuring yellowness, total light transmittance, and haze, a film made of polyimide having a thickness of 10 μm ± 5 μm can be used (the vertical and horizontal sizes of the measurement sample are the same as those of the measuring apparatus). Any size that can be placed at the measurement site is acceptable. In addition, such yellowness (YI) is calculated | required by performing the measurement based on ASTM E313-05 (issued in 2005), and the total light transmittance is the measurement based on JIS K7361-1 (issued in 1997). The haze (turbidity) is determined by performing measurement in accordance with JIS K7136 (issued in 2000).

  Further, such a polyimide preferably has a 5% weight loss temperature of 400 ° C. or higher, more preferably 450 to 550 ° C. If such a 5% weight loss temperature is less than the lower limit, sufficient heat resistance tends to be difficult to achieve, and if it exceeds the upper limit, it tends to be difficult to produce a polyimide having such characteristics. It is in. Furthermore, such a polyimide preferably has a softening temperature of 300 ° C. or higher, more preferably 350 to 550 ° C. If the softening temperature is less than the lower limit, sufficient heat resistance tends to be difficult to achieve, and if it exceeds the upper limit, it tends to be difficult to produce a polyimide having such characteristics. Moreover, as such a polyimide, that whose thermal decomposition temperature (Td) is 450 degreeC or more is preferable, and the thing of 480-600 degreeC is more preferable. If the thermal decomposition temperature (Td) is less than the lower limit, it tends to be difficult to achieve sufficient heat resistance. On the other hand, if the thermal decomposition temperature (Td) exceeds the upper limit, a polyimide having such characteristics can be produced. It tends to be difficult. For such 5% weight loss temperature, softening temperature and thermal decomposition temperature (Td), the methods described in paragraphs [0178], [0180] and [0181] of WO2015-163314 are employed. Can be measured. Moreover, such a polyimide preferably has a hardness of 6B to 6H (more preferably HB to 4H) in pencil hardness. If the hardness is less than the lower limit, it tends to be difficult to obtain a sufficiently high level of hardness. On the other hand, if the hardness exceeds the upper limit, a colorless and transparent polyimide having such characteristics can be produced. It tends to be difficult. In addition, such a value of pencil hardness can be measured in accordance with a method defined in JIS K5600-5-4 issued in 1999.

  Furthermore, as a number average molecular weight (Mn) of such a polyimide, it is preferable that it is 1000-1 million in polystyrene conversion, and it is more preferable that it is 10000-500000. Moreover, as a weight average molecular weight (Mw) of such a polyimide, it is preferable that it is 1000-5 million in polystyrene conversion, It is more preferable that it is 5000-5 million, It is further more preferable that it is 10000-500000, 20000 Particularly preferred is 100,000. If such Mn or Mw is less than the lower limit, the film tends to be brittle and the heat resistance of the polyimide tends to decrease. On the other hand, if the upper limit is exceeded, film formation becomes difficult and the film tends to be wrinkled. It is in. Furthermore, the molecular weight distribution (Mw / Mn) of such a polyimide is preferably 1.1 to 5.0, and more preferably 1.5 to 3.0. If the molecular weight distribution is less than the lower limit, the production tends to be difficult. On the other hand, if the molecular weight distribution exceeds the upper limit, it tends to be difficult to obtain a uniform film. In addition, the molecular weight (Mw or Mn) and molecular weight distribution (Mw / Mn) of such polyimide are measured by a gel permeation chromatography (GPC) measuring device (HLC-8320GPC manufactured by Tosoh Corporation, column: manufactured by Tosoh Corporation) as a measuring device. GPC column TSK-GEL SuperAW2500 (× 4), column temperature 40 ° C., data measured using a DMAc solvent (flow rate 0.50 mL / min.) Containing lithium bromide (10 mM-LiBr) is obtained by conversion with polystyrene. be able to.

  Moreover, the form of such a polyimide film should just be a film form, and is not restrict | limited in particular, It can design suitably in various shapes (a disk shape, cylindrical shape (what processed the film into the cylinder shape) etc.). When manufactured using a polyimide precursor resin solution described later, the design can be changed more easily. Furthermore, the thickness of the polyimide film of the present invention is not particularly limited, but is preferably 0.1 to 200 μm, and more preferably 1 to 100 μm.

  Such a polyimide film of the present invention is, for example, a flexible wiring board film (FPC board), FCCL board, heat resistant insulating tape, electric wire enamel, semiconductor protective coating agent, liquid crystal alignment film, transparent conductive film for organic EL, TFT substrate for organic EL, color filter substrate, touch panel substrate, cover glass substitute film, flexible substrate film, flexible transparent conductive film, transparent conductive film for organic thin-film solar cell, transparent conductive for dye-sensitized solar cell Film, flexible gas barrier film, touch panel film, seamless polyimide belt for copying machines (so-called transfer belt), transparent electrode substrate (transparent electrode substrate for organic EL, transparent electrode substrate for solar cell, transparent electrode substrate for electronic paper, etc.), Interlayer insulation film, sensor Plate, image sensor substrate, light emitting diode (LED) reflector (LED illumination reflector: LED reflector), LED illumination cover, LED reflector illumination cover, coverlay film, high ductility composite substrate, Resist for semiconductor, lithium ion battery, organic memory substrate, organic transistor substrate, organic semiconductor substrate, color filter substrate, front film, plastic LCD TFT substrate, plastic LCD color filter substrate, plastic LCD touch panel substrate, It can use suitably suitably as a material etc. which are used for uses, such as a substrate for transparent displays.

[Production Method of Polyimide Film of the Present Invention]
The method for producing a polyimide film of the present invention comprises forming a coating film using a polyimide precursor resin solution containing a polyimide precursor and an organic solvent, and then removing the solvent from the coating film and baking the polyimide film. Including a step of obtaining a film comprising:
The polyimide precursor contains the repeating unit (A ′) represented by the general formula (7), and
At the time of the baking, the film is made of the polyimide as a film by baking at a temperature in the range of (Tg-190) ° C. to (Tg-50) ° C., based on the glass transition temperature (Tg) of the resulting polyimide. Obtaining the polyimide film of the invention,
It is the method characterized by this.

  First, a polyimide precursor, an organic solvent, and a polyimide precursor resin solution used in the method for producing a polyimide film of the present invention will be described.

Such a polyimide precursor contains the repeating unit (A ′) represented by the general formula (7). In the formula (7), A represents a tetravalent alicyclic hydrocarbon group having 4 to 30 carbon atoms forming a cyclic structure, and ^Ra represents the above general formulas (2) to (3 ), Y ¹ and Y ² each independently comprise a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms. One species selected from the group is shown. In addition, A and Ra in the said General formula (7) are synonymous with A and Ra in the said General formula (1), respectively (The suitable thing is also synonymous).

Incidentally, in such a case Y ¹ and Y ² are both hydrogen atoms (when the repeating units of the so-called polyamic acid) tend to be easy to manufacture a polyimide.

Further, the Y ¹ and Y ^2, when 1 to 6 carbon atoms (preferably having 1 to 3 carbon atoms) alkyl group, tend to be those storage stability of the polyimide precursor resin is more excellent. Also, if the Y ¹ and Y ² is a C 1 -C 6 (preferably having 1 to 3 carbon atoms) carbon alkyl group, and more preferably a methyl group or an ethyl group.

Also, if the Y ¹ and Y ² is an alkyl silyl group having 3 to 9 carbon atoms, tend to be those solubility in organic solvent for the polyimide precursor is better. Also, if the Y ¹ and Y ² is an alkyl silyl group having 3 to 9 carbon atoms, more preferably a trimethylsilyl group or t- butyldimethylsilyl group.

When Y ¹ and Y ^{2 in} such a formula are a group other than a hydrogen atom (an alkyl group and / or an alkylsilyl group), the introduction rate of the group is not particularly limited, but of Y ¹ and Y ² When at least a part is an alkyl group and / or an alkylsilyl group (at least a part of Y ¹ and Y ^{2 in} the repeating unit (A ′) contained in the polyimide precursor is an alkyl group and / or an alkylsilyl group) In the case of a group), 25% or more (more preferably 50% or more, still more preferably 75% or more) of the total amount (total number) of Y ¹ and Y ² is an alkyl group and / or an alkylsilyl group, respectively. Is preferable (in this case, Y ¹ and Y ² other than the alkyl group and / or the alkylsilyl group are hydrogen atoms). By making 25% or more of the total amount (total number) of Y ¹ and Y ² of the repeating units contained in the polyimide precursor an alkyl group and / or an alkylsilyl group, the storage stability of the polyimide precursor resin is more excellent. Tend to be. In addition, regarding the substituent represented by Y ¹ and Y ² in the general formula (7), the type of the substituent and the introduction rate of the substituent appropriately change the production conditions of the polyimide precursor. Can be changed.

Such polyimide precursors, since the production of the polyimide becomes easier, it Y ¹ and Y ² are each a hydrogen atom, i.e., is preferably a polyamic acid.

Moreover, as said polyimide precursor, even if it contains 1 type of a repeating unit (A ') independently, or of A, R ^<a> , Y < ¹ > and Y < ² > in the said Formula (7). It may contain a combination of two or more different repeating units (A ′) of at least one kind. Moreover, the said polyimide precursor may contain the other repeating unit with the said repeating unit (A ').

  As such a polyimide precursor, the following general formula (8), together with the repeating unit (A ′):

Wherein (8), A has the same meaning as A in the general formula (1) (also synonymous what its preferred), R ^b is an R ^b as defined in the general formula (5) (the preferred ones also are synonymous), respectively Y ¹ and Y ² have the same meanings as Y ¹ and Y ² in formula (7) (also synonymous what its preferred). ]
It is preferable to further contain a repeating unit (B ′) represented by

Moreover, in the said polyimide precursor, you may contain repeating units other than repeating unit (A ') and (B') in the range which does not impair the effect of this invention. Such a repeating unit other than the repeating units (A ′) and (B ′) is not particularly limited, and includes known repeating units that can be used as the repeating unit of the polyimide precursor. For example, the general formula (I) A repeating unit derived from other tetracarboxylic dianhydrides other than the tetracarboxylic dianhydride represented by) may be used as appropriate. The repeating unit other than the repeating units (A ′) and (B ′) is represented by the general formula (I) from the viewpoint that the CTE of the finally formed polyimide can be further reduced. Tetracarboxylic dianhydride, p-phenylenediamine which may have a substituent, terphenyldiamine which may have a substituent, biphenyl diamine which may have a substituent ( For example, m-tolidine, o-tolidine, 3,3 ′, 5,5′-tetramethylbenzidine, octafluorobenzidine, 2,2′-bis (trifluoromethyl) benzidine, etc.), having a substituent Ester group-containing diamines such as 4-aminophenyl 4-aminobenzoate and diamines having a hydroxyl group such as 2,2-bis (3-amino-4-hydro R ^b moiety of the groups represented by Shifeniru) hexafluoropropane, etc.) is selected from the group consisting of at least one repeating unit formed by from the reaction of an aromatic diamine (the general formula (8) Can be suitably used as a repeating unit which is a residue obtained by removing _two amino groups (—NH ₂ ) from the aromatic diamine. In addition, as a substituent of such aromatic diamine, it is preferable that it is 1 type selected from the group which consists of a C1-C10 alkyl group, a halogen atom, and a hydroxyl group. The alkyl group having 1 to 10 carbon atoms and the halogen atom as such a substituent are the same as those which can be selected as R ^a1 in the above formula (2). ).

  In such a polyimide precursor, the content of the repeating unit (A ′) is preferably 50 to 100 mol%, more preferably 55 to 95 mol%, more preferably 60 to 90 mol% is particularly preferable, and 65 to 90 mol% is most preferable. When the content of such a repeating unit (A ′) is less than the lower limit, it tends to be difficult to achieve a sufficiently low Rth, and when it is within the content range, it is sufficiently low. Higher performance tends to be obtained in that it has a sufficiently low CTE in a balanced manner while having Rth.

  Moreover, when the said polyimide precursor contains a repeating unit (B ') with a repeating unit (A'), the total amount of a repeating unit (A ') and (B') is with respect to all the repeating units. It is preferably 80 to 100 mol%, more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, and particularly preferably 98 to 100 mol%. If the ratio of the total amount (content) of such repeating units (A ′) and (B ′) is less than the lower limit, it is difficult to have a sufficiently low CTE in a well-balanced manner while having a sufficiently low Rth. It tends to be.

  Moreover, when the said polyimide contains a repeating unit (B ') with a repeating unit (A'), the said repetition with respect to the total amount of the said repeating unit (A ') and the said repeating unit (B') in this polyimide It is preferable that the content of the unit (A ′) is 50 to 99 mol% (more preferably 55 to 95 mol%, still more preferably 60 to 90 mol%, particularly preferably 65 to 90 mol%). If the content of such a repeating unit (A) is less than the lower limit, it tends to be difficult to achieve a sufficiently low Rth, whereas if it exceeds the upper limit, it is difficult to achieve a sufficiently low CTE. Tend to be. As the polyimide, those composed only of the repeating units (A ′) and (B ′) can be suitably used from the viewpoint of achieving a low Rth and low CTE in a balanced manner at a higher level.

Further, the in the case the polyimide precursor is a resin containing a repeating 'repeating with units (B units (A)'), groups other than a hydrogen atom in Y ¹ and Y ² in each formula of the repeating units When (alkyl group and / or alkylsilyl group) is included, the introduction rate of the group is not particularly limited, but is 25% or more (more preferably 50% or more, more) of the total amount (total number) of Y ¹ and Y ² Preferably, 75% or more is an alkyl group and / or an alkylsilyl group.

Moreover, when the said polyimide precursor contains a repeating unit (B ') with a repeating unit (A'), since preparation of a polyimide becomes easier, this repeating unit (A ') and (B') It is more preferable that Y ¹ and Y ² in each formula are hydrogen atoms. Thus, the polyimide precursor is more preferably a polyamic acid in which Y ¹ and Y ² in each formula are both hydrogen atoms.

  Moreover, as a polyamic acid suitable as such a polyimide precursor resin, the intrinsic viscosity [η] is preferably 0.05 to 3.0 dL / g, and preferably 0.1 to 2.0 dL / g. Is more preferable. When the intrinsic viscosity [η] is smaller than 0.05 dL / g, when a film-like polyimide is produced using the intrinsic viscosity [η], the resulting film tends to be brittle, while 3.0 dL / g is reduced. If it exceeds, the viscosity is too high and the processability is lowered. For example, when a film is produced, wrinkles approach and it is difficult to obtain a uniform film. Such intrinsic viscosity [η] can be measured as follows. That is, first, tetramethylurea (TMU) is used as a solvent, and a measurement sample (solution) in which the polyamic acid is dissolved in TMU so as to have a concentration of 0.5 g / dL is obtained. Next, using the measurement sample, the viscosity of the measurement sample is measured using a kinematic viscometer under a temperature condition of 30 ° C., and the obtained value is adopted as the intrinsic viscosity [η]. In addition, as such a kinematic viscometer, an automatic viscosity measuring apparatus (trade name “VMC-252”) manufactured by Koiso Co., Ltd. is used.

Incidentally, the polyimide precursor according to the present invention, depending on the type of Y ^1, Y ^2, 1) a polyamic acid (Y ^1, both Y ² is a hydrogen atom in the general formula of the repeating unit); 2) Polyamide Since this can be classified into acid ester (at least part of Y ¹ and Y ² is an alkyl group); 3) polyamic acid silyl ester (at least part of Y ¹ and Y ² is an alkylsilyl group); The method for manufacturing the product will be described separately for each of the above categories. In addition, the method for manufacturing such a polyimide precursor is not limited to the following manufacturing methods.

1) Polyamic acid As a method that can be suitably used for producing such a polyamic acid, for example, a tetracarboxylic dianhydride represented by the above general formula (I) and a formula: H ₂ ^N-R a -NH ₂ ^{[R a} in the formula is as defined ^{R a} in the above formula (1). The method of obtaining a polyamic acid by making it react with the diamine compound represented by this can be employ | adopted suitably.

  Thus, when making the said tetracarboxylic dianhydride and the said diamine compound react, it is preferable to make it react in presence of a polymerization solvent. Such a polymerization solvent is preferably an organic solvent capable of dissolving both the tetracarboxylic dianhydride and the diamine compound. Examples of such organic solvents include N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone. Aprotic polar solvents such as (GBL), propylene carbonate, tetramethylurea (tetramethylurea: TMU), 1,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoric triamide, pyridine; -Phenol solvents such as cresol, xylenol, phenol, halogenated phenol; ether solvents such as tetrahydrofuran, dioxane, cellosolve, glyme; aromatic solvents such as benzene, toluene, xylene; cyclopentanone, cyclohexanone, etc. Keto System solvent: acetonitrile, nitrile solvents such as benzonitrile and the like. Such organic solvents may be used singly or in combination of two or more.

  Moreover, as such a polymerization solvent, it is more preferable to use an aprotic polar solvent from the viewpoint of solubility in the tetracarboxylic dianhydride and the diamine compound, and among them, DMAc, DMI, or TMU is preferable. Particularly preferred. Thus, when DMAc, DMI, or TMU is used as the polymerization solvent, these are excellent in solubility in the tetracarboxylic dianhydride and the diamine compound. It becomes possible to proceed efficiently (the reaction is more likely to proceed), whereby a polyamic acid varnish with a high degree of polymerization can be obtained in a shorter time.

Here, when the obtained polyamic acid contains a repeating unit (B ′) in which Y ¹ and Y ² in the formula are both hydrogen atoms, together with the repeating unit (A ′), the formula: H ₂ ^N-R b -NH ₂ ^{[R b} in the formula is as defined ^{R b} in the formula (5). The diamine compound represented by the above formula: H ₂ N—R ^a —NH ₂ with respect to the tetracarboxylic dianhydride represented by the above general formula (I) And a mixture of the diamine compound represented by the above formula: H ₂ N—R ^b —NH ₂ may be reacted. Such a ^{_{formula: H 2 N-R b -NH}} 2 [R b in the formula is as defined ^{R b} in the formula (5). It is possible to contain the repeating unit (B ′) derived from the reaction between the diamine compound represented by the general formula (I) and the tetracarboxylic dianhydride represented by the general formula (I).

The tetracarboxylic dianhydride and the diamine compound (a diamine compound represented by the formula: H ₂ N—R ^b —NH ₂ together with the diamine compound represented by the formula: H ₂ N—R ^a —NH ₂ In the case of utilizing the above, the ratio of the mixture) is such that the amount of all acid anhydride groups in the tetracarboxylic dianhydride used in the reaction is 1 equivalent of amino group in the diamine compound. The amount is preferably 0.2 to 2 equivalents, and more preferably 0.3 to 1.2 equivalents. When the suitable use ratio of such a tetracarboxylic dianhydride and the diamine compound is less than the lower limit, the polymerization reaction does not proceed efficiently and a high molecular weight polyamic acid (reaction intermediate) tends to be obtained, On the other hand, when the upper limit is exceeded, high molecular weight polyamic acid (reaction intermediate) tends to be not obtained as described above.

  Further, the amount of the polymerization solvent (organic solvent) used is such that the total amount of the tetracarboxylic dianhydride and the diamine compound is 0.1 to 50% by mass (more preferably 10 to 10%) based on the total amount of the reaction solution. 30% by mass) is preferable. If the amount of the organic solvent used is less than the lower limit, the polyamic acid tends not to be obtained efficiently. On the other hand, if it exceeds the upper limit, stirring tends to be difficult due to the increase in viscosity.

  In addition, when the tetracarboxylic dianhydride and the diamine compound are reacted, a base compound is further added to the organic solvent from the viewpoint of improving the reaction rate and obtaining a polyamic acid having a high degree of polymerization. Also good. Examples of such basic compounds include, but are not limited to, triethylamine, tetrabutylamine, tetrahexylamine, 1,8-diazabicyclo [5.4.0] -undecene-7, pyridine, isoquinoline, α-picoline, imidazole. Etc. Moreover, it is preferable that the usage-amount of such a basic compound shall be 0.001-10 equivalent with respect to 1 equivalent of tetracarboxylic dianhydrides represented by the said general formula (I), 0.01- More preferably, it is 0.1 equivalent. If the amount of such a basic compound used is less than the lower limit, the effect of addition tends to be lost. On the other hand, if it exceeds the upper limit, it tends to cause coloring or the like.

Moreover, the reaction temperature at the time of making the said tetracarboxylic dianhydride and the said diamine compound react should just be suitably adjusted to the temperature which can make these compounds react, and it does not restrict | limit, According to the case. Thus, the temperature is preferably −40 to 450 ° C., more preferably −20 to 400 ° C., further preferably −20 to 200 ° C., and particularly preferably 0 to 100 ° C. Further, the tetracarboxylic dianhydride, the diamine compound (a diamine compound represented by the formula: H ₂ N—R ^a —NH ₂ , and a diamine represented by the formula: H ₂ N—R ^b —NH ₂ In the case of using a compound, a known method (conditions, etc.) capable of performing a polymerization reaction of tetracarboxylic dianhydride and an aromatic diamine is appropriately used as a method of reacting a mixture thereof) Although not particularly limited, for example, after dissolving the diamine compound in the polymerization solvent under an inert atmosphere such as nitrogen, helium, argon, etc. at atmospheric pressure, the tetra In the method of adding carboxylic dianhydride and then reacting for 10 to 48 hours, in an atmospheric pressure, inert atmosphere such as nitrogen, helium, argon, etc., the diamine After adding the compound and the tetracarboxylic dianhydride, the polymerization solvent is added, each component is dissolved in the solvent, and then reacted at the reaction temperature for 10 to 48 hours. May be. If the reaction temperature or reaction time is less than the lower limit, it tends to be difficult to cause sufficient reaction. On the other hand, if the upper limit is exceeded, the probability of mixing a substance (such as oxygen) that degrades the polymer increases and the molecular weight increases. It tends to decrease.

In this manner, the repeating unit (A ') Y ¹ and Y ² are both hydrogen atoms of the general formula by which the polyamic acid (if contained is both Y ¹ and Y ² in the general formula is a hydrogen atom And the above repeating unit (B ′) can be obtained.

2) Polyamic acid ester Next, the method which can be utilized suitably in order to manufacture the said polyamic acid ester is demonstrated. That is, first, after reacting the tetracarboxylic dianhydride represented by the general formula (I) with an arbitrary alcohol to obtain a diester dicarboxylic acid, a chlorinating reagent (for example, thionyl chloride, oxalyl chloride, etc.) Reaction is performed to obtain diester dicarboxylic acid chloride (a derivative of tetracarboxylic acid). Next, a monomer component containing at least the diester dicarboxylic acid chloride is used (in addition, as the monomer component, the diester dicarboxylic acid chloride and the tetraester represented by the general formula (I) are used. A mixture with carboxylic dianhydride), the monomer component and the diamine compound may be used in the range of -20 to 120 ° C (more preferably -5 to 80 ° C) for 1 to 72 hours. By reacting with stirring, a polyamic acid ester containing a repeating unit (A ′) in which at least a part of Y ¹ and Y ² in the formula is an alkyl group can be obtained. When the reaction is carried out at a temperature of 80 ° C. or higher during stirring, the molecular weight tends to fluctuate depending on the temperature history at the time of polymerization, and imidation may proceed due to heat. Tends to be difficult to produce stably. Moreover, the polyimide precursor which consists of the said polyamic acid ester is simply obtained also by carrying out the dehydration condensation of the diester dicarboxylic acid and the said diamine compound using a phosphorus-type condensing agent, a carbodiimide condensing agent, etc. Since the polyimide precursor comprising a polyamic acid ester obtained by such a method is stable, it can be purified by reprecipitation by adding a solvent such as water or alcohol.

3) Polyamic acid silyl ester Hereinafter, methods that can be suitably used for producing the polyamic acid silyl ester will be briefly described by dividing them into so-called indirect methods and direct methods.

<Indirect method>
The following method (indirect method) can be adopted as a method that can be suitably used for producing the polyamic acid silyl ester. That is, first, the diamine compound and a silylating agent are reacted to obtain a silylated diamine compound. In addition, you may refine | purify the diamine compound silylated by distillation etc. as needed. Next, a solution is obtained by dissolving a silylated diamine compound or a mixture of the silylated diamine compound and the diamine compound (not silylated) in a dehydrated solvent. Next, while stirring the solution, the tetracarboxylic dianhydride represented by the above general formula (I) is gradually added to the solution, and the temperature is in the range of 0 to 120 ° C (preferably 5 to 80 ° C). By stirring for ¹ to 72 hours, a polyimide precursor composed of a polyamic acid silyl ester containing a repeating unit (A ′) in which at least a part of Y ¹ and Y ² is an alkylsilyl group can be obtained. In addition, when the reaction at such a stirring temperature is 80 ° C. or higher, the molecular weight is likely to vary depending on the temperature history at the time of polymerization, and imidization may proceed due to heat, It tends to be difficult to stably produce a polyimide precursor.

  In addition, it is preferable to use the silylating agent which does not contain a chlorine atom as said silylating agent. By using a silylating agent that does not contain a chlorine atom in this way, it is not necessary to purify the silylated aromatic diamine, so that the process can be further simplified. Examples of such a silylating agent not containing a chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. The silylating agent is particularly preferably N, O-bis (trimethylsilyl) acetamide or hexamethyldisilazane because it does not contain a fluorine atom and is low in cost.

  In addition, an amine catalyst such as pyridine, piperidine or triethylamine can be used in the silylation reaction of the diamine compound in order to accelerate the reaction. Such an amine catalyst can be used as it is as a polymerization catalyst for the polyimide precursor.

<Direct method>
First, the method that can be suitably used for producing the polyamic acid described in the section of “1) Polyamic acid” described above is carried out, and the reaction solution obtained after the reaction is directly prepared as a polyamic acid solution. . Thereafter, a silylating agent is mixed with the obtained polyamic acid solution and stirred for 1 to 72 hours in the range of 0 to 120 ° C. (preferably 5 to 80 ° C.), whereby the polyimide comprising the polyamic acid silyl ester is prepared. A precursor resin can be obtained (direct method). When the reaction is carried out at a temperature of 80 ° C. or higher during stirring, the molecular weight tends to fluctuate depending on the temperature history at the time of polymerization, and imidation may proceed due to heat. Tends to be difficult to produce stably. As a silylating agent that can be used in such a direct method, a silylated polyamic acid or a silylating agent that does not contain a chlorine atom can be used because it is not necessary to purify the obtained polyimide. preferable. Examples of such a silylating agent not containing a chlorine atom include N, O-bis (trimethylsilyl) trifluoroacetamide, N, O-bis (trimethylsilyl) acetamide, and hexamethyldisilazane. Further, as such a silylating agent, N, O-bis (trimethylsilyl) acetamide and hexamethyldisilazane are particularly preferable because they do not contain a fluorine atom and are low in cost.

  As described above, any of the methods for producing the polyimide precursor described above can be carried out in an organic solvent (the polymerization solvent). Thus, when the polyimide precursor in an organic solvent is manufactured, the resin solution (varnish: polyimide precursor resin solution) of a polyimide precursor can be obtained easily.

  The polyimide precursor resin solution according to the present invention contains the polyimide precursor and an organic solvent. As such an organic solvent, the polymerization solvent described in the method for producing the polyimide precursor can be suitably used. Therefore, as a method for producing the polyimide precursor resin solution according to the present invention, from the viewpoint of ease of production, after producing a polyimide precursor in an organic solvent (the polymerization solvent), a polyimide is obtained from the reaction solution. It is preferable to employ a method in which the reaction solution is used as it is as a polyimide precursor varnish (polyimide precursor resin solution) without isolating the precursor.

  The content of the polyimide precursor resin (preferably polyamic acid) in the polyimide precursor resin solution (preferably polyamic acid resin solution) is not particularly limited, but is preferably 1 to 80% by mass. More preferably, it is -50 mass%. If such a content is less than the lower limit, it tends to be difficult to produce a polyimide film. On the other hand, if it exceeds the upper limit, stirring and film formation tend to be difficult, and it is difficult to produce a uniform polyimide film. In addition, such a polyimide precursor resin solution (preferably a polyamic acid solution) can be suitably used for producing the polyimide of the present invention, and can be suitably used for producing polyimides having various shapes.

  In addition, such a polyimide precursor resin solution (preferably a polyamide acid resin solution) may use a so-called accelerator from the viewpoint of promoting high molecular weight and imidization in the baking step described later. As such an accelerator, a known reaction accelerator (for example, an imidazole compound, a pyridine compound, a tertiary amine compound such as triethylamine, an amino acid compound, or the like) may be appropriately used. Although it does not restrict | limit especially as usage-amount of such an accelerator, It is 1-60 mass parts (more preferably 5-50 mass parts) with respect to 100 mass parts of solid content (polyamic acid) in a polyamic acid solution. It is preferable. In addition, as such an accelerator, an imidazole compound is preferable from the viewpoint of various physical properties such as optical properties, thermal properties, and mechanical properties of the film. Examples of such imidazole compounds include imidazole compounds described in International Publication No. 2017/0264448. Furthermore, as such an imidazole compound, the following general formula (X):

[In the formula (X), R ¹¹ represents one selected from the group consisting of a hydrogen atom and an alkyl group, and R ¹⁴ each independently represents a halogen atom, a hydroxyl group, a mercapto group, a sulfide group, a silyl group, a silanol group, 1 type selected from the group consisting of a nitro group, a nitroso group, a sulfonate group, a phosphino group, a phosphinyl group, a phosphonate group and an organic group, m represents an integer of 0 to 3, R ³¹ , R ³² , R ³³ R ³⁴ and R ³⁵ are each independently a hydrogen atom, hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfino group, sulfo group, sulfonate group, phosphino group, phosphinyl group, phosphono group, a phosphonate group, an amino group, an ammonio group, or an organic group, provided ^{that, R 31, R 32, R} 33, R 34 and At least one of the ³⁵ is a group other than a hydrogen atom. ]
The compound represented by these is more preferable.

R ¹¹ in the general formula (X) is preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group, and particularly a hydrogen atom from the viewpoint of the effect as an accelerator. preferable. When R ¹⁴ in the general formula (X) is an organic group, the organic group is preferably an alkyl group, an aromatic hydrocarbon group, or an aromatic heterocyclic group. When R ¹⁴ is an alkyl group, a linear or branched alkyl group having 1 to 8 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, and an isopropyl group are more preferable. Further, when R ¹⁴ is an aromatic hydrocarbon group, the aromatic hydrocarbon group is particularly preferably a phenyl group. Further, when R ¹⁴ is an aromatic heterocyclic group, a furyl group and a thienyl group are more preferable. The value of m in the general formula (X) is more preferably an integer of 0 to 2 from the viewpoint of the effect as a high molecular weight accelerator and the effect as an imidization accelerator. . Furthermore, the value of m in the general formula (X) is more preferably 0 from the viewpoint of the effect as an accelerator. In the compound represented by the general formula (X), at least one of R ³¹ , R ³² , R ³³ , R ³⁴ and R ³⁵ is represented by the formula: —O—R ³⁰ (R ³⁰ is a hydrogen atom or organic . a group) is preferably a group represented by, among others R ³⁵ has the formula: it is particularly preferably a group represented by -O-R ^30. When R ³⁵ is a group represented by the above formula: —O—R ³⁰ , R ³¹ , R ³² , R ^33, and R ³⁴ are preferably hydrogen atoms. Such R ³⁰ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 3 carbon atoms, and most preferably a methyl group.

  Furthermore, such a polyimide precursor resin solution (preferably a resin solution of polyamic acid) includes various additives (deterioration inhibitor, antioxidant, Light stabilizer, UV absorber, modifier, antistatic agent, flame retardant, plasticizer, nucleating agent, stabilizer, adhesion improver, lubricant, mold release agent, dye, foaming agent, antifoaming agent, surface modification A quality agent, a hard coat agent, a leveling agent, a surfactant, a filler (such as glass fiber, filler, talc, mica, silica, etc.) may be appropriately added and used. Moreover, regarding the case where such an additive is used, the content of the additive in the polyamic acid solution is not particularly limited, but is about 0.0001 to 80% by mass (more preferably 0.1 to 50% by mass). It is preferable.

  Next, the process of obtaining the film which consists of a polyimide employ | adopted in the manufacturing method of the polyimide film of this invention is demonstrated. This step is a step of obtaining a film made of polyimide by forming a coating film using the polyimide precursor resin solution, and then removing the solvent from the coating film and baking it.

  In such a process, a method for forming a coating film composed of the polyimide precursor resin solution is not particularly limited, and a known method can be appropriately used. For example, the polyimide precursor resin solution is formed on a substrate. The method of apply | coating and forming a coating film can be mentioned. Such a substrate is not particularly limited, and a substrate made of a known material that can be used for forming a film made of a polymer (for example, glass, depending on the shape of a film made of a target polyimide) A plate or a metal plate) can be used as appropriate.

  The method for applying the polyimide precursor resin solution on the substrate is not particularly limited. For example, spin coating, spray coating, dip coating, dropping, gravure printing, screen printing, letterpress Known methods such as a printing method, a die coating method, a slit coating method, a curtain coating method, and an ink jet method can be appropriately employed.

  The thickness of the coating film of the polyimide precursor resin solution formed on the substrate is not particularly limited, but from the viewpoint of processability and handling properties, the thickness of the cured film is 0.1 to 200 μm. It is preferable to be, and it is more preferable to be 1 to 100 μm.

  Moreover, in the said process, after forming the coating film of the said polyimide precursor resin solution, a solvent is removed from a coating film (solvent removal process). Although it does not restrict | limit especially as a method of such a solvent removal process, It is preferable to heat to 0-150 degreeC (more preferably 20-80 degreeC) and to remove a solvent from the said coating film. In addition, in such a solvent removal treatment method, the atmosphere during heating is not particularly limited and may be air, but from the viewpoint of suppressing coloration or preventing deterioration, an inert gas atmosphere ( For example, a nitrogen atmosphere is more preferable. Further, from the viewpoint of more efficient drying, the pressure condition in such solvent removal treatment is preferably 0.133 to 101.3 kPa (1 to 760 mmHg). By such solvent removal treatment, the polyimide precursor (preferably polyamic acid) can be isolated in the form of a film or the like, and then subjected to a baking treatment or the like.

  Moreover, in the said process, the coating film after the said solvent removal process is hardened by baking, and the said polyimide film of this invention is obtained. Thus, in the present invention, “baking” refers to a heating step (heat curing step) for curing the coating film after the solvent removal treatment. In such firing, it is necessary to fire at a temperature within the range of (Tg-190) ° C. to (Tg-50) ° C. based on the glass transition temperature (Tg) of the resulting polyimide. When such a baking (heating) temperature is not within the above temperature range, even if the TMA curve of the resulting polyimide is measured, the ratio of the change in the length of the film to the change in the temperature in the TMA curve The extreme value at which the (slope) turns from positive to negative cannot be confirmed within the temperature range of 200 to 430 ° C., and the polyimide of the present invention cannot be obtained. In addition, in the conventional method for producing polyimide as described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-204568), polyamic acid is based on the glass transition temperature (Tg) of the polyimide finally formed, The polyimide film is formed by baking at a temperature in the vicinity of Tg (in the example of JP-A-2006-204568, Tg ± 15 to 20 ° C.). When such conventional general polyimide firing conditions (baking conditions of about Tg ± 15 to 20 ° C.) are simply adopted, the ratio of the change in the length of the film to the change in the temperature is positive. The position (temperature) of the extreme value that turns negative cannot be controlled to 200 to 430 ° C. On the other hand, in this invention, after removing a solvent from the coating film of the said polyimide precursor (preferably polyamic acid), it baked at the temperature within the range of (Tg-190) degreeC-(Tg-50) degreeC. By preparing the polyimide, the position (temperature) of the extreme value where the ratio (slope) of the change amount of the film length to the change amount of the temperature changes from positive to negative is in the temperature range of 200 to 430 ° C. This makes it possible to lower the CTE of the resulting polyimide. If the firing (heating) temperature is not within the above temperature range, the absolute value of CTE cannot be set to a desired level (preferably 50 ppm / ° C. or less).

In addition, the firing temperature is preferably (Tg−180) ° C. to (Tg−50) ° C. from the viewpoint of expressing sufficiently low CTE in a well-balanced manner while expressing sufficiently low Rth. It is more preferable to set it as (Tg-170) degreeC-(Tg-60) degreeC, and it is still more preferable to set it as (Tg-160) degreeC-(Tg-70) degreeC. In such firing, in order to sufficiently imidize and cure the polyimide precursor (preferably polyamic acid), the firing time is preferably 0.5 to 10 hours, 0.8 to 5 More preferably, in the present invention, when the coating film after the solvent removal treatment is baked, the temperature condition is changed in multiple stages in order to heat and cure the coating film after the solvent removal treatment. You may heat it, letting it go. In such a heating process, the heating temperature may be set to a temperature within the range of the baking temperature at any stage (for example, the final heating temperature), and the baking treatment may be performed at any stage. . For example, the coating film after the solvent removal treatment is preliminarily heated at a temperature at which imidization of the polyimide precursor proceeds (in addition, imidation itself varies depending on the type of the polyimide precursor, but is heated to about 80 ° C. or more. And is heated at a temperature lower than the firing temperature (preferably 100 to 250 ° C.) for 0.5 to 10 hours to advance imidization of the polyimide precursor to some extent, and then at the firing temperature. It may be heated for 0.5 to 10 hours to further proceed with imidization to be fired (heat-cured). Further, the temperature may be changed stepwise within the range of the firing temperature. Thus, a baking process may give the heating temperature employ | adopted as the said baking temperature in the any stage of the time of heat-hardening a coating film (when imidizing and hardening).

  In addition, as an atmospheric condition in such a baking treatment, an inert gas atmosphere (for example, a nitrogen atmosphere, a low oxygen concentration atmosphere (an atmosphere having an oxygen concentration of 1 to 300 ppm) is used from the viewpoint of suppressing coloring and deterioration of physical properties due to oxygen. )). Note that heat treatment may be performed in a high oxygen concentration atmosphere (oxygen concentration: an atmosphere of greater than 300 ppm and equal to or less than 10,000 ppm) as long as it is possible to suppress coloring due to oxygen at the time of imidization by performing the baking treatment.

  Thus, by removing the solvent from the coating film and baking, the polyimide precursor (preferably polyamic acid) in the film can be efficiently closed and heat-cured, whereby the polyimide precursor It becomes possible to imidize the body (preferably polyamic acid) to efficiently form polyimide. And it becomes possible to obtain the said polyimide film of this invention by performing a baking process on specific temperature conditions in this way.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. First, a method for evaluating the characteristics of the polyimide film and the like obtained in each example and each comparative example will be described.

<Identification of molecular structure>
The film obtained in each example and each comparative example was subjected to IR measurement using an IR measuring device (trade name: FT / IR-4100, manufactured by JASCO Corporation), and imidocarbonyl was obtained in the obtained IR spectrum. It was confirmed whether or not it was made of polyimide by confirming a peak based on C═O stretching vibration.

<Measurement of intrinsic viscosity [η]>
The polyamic acid obtained as an intermediate in each Example and each Comparative Example was prepared in the same manner, and the value of intrinsic viscosity [η] (unit: dL / g) was measured. In the measurement, a solution having a concentration of 0.5 g / dL using tetramethylurea (TMU) as a solvent was prepared as a measurement sample, and an automatic viscosity measuring apparatus (trade name “VMC-252”) manufactured by Rouai Co., Ltd. was used. Was measured under the temperature condition of 30 ° C.

<Measurement of TMA curve and CTE>
The TMA curve and CTE of the polyimide film obtained in each example and each comparative example were obtained as follows. That is, first, each polyimide film was subjected to a vacuum drying process of heating for 1 hour under conditions of 0.133 kPa and 120 ° C., followed by a drying process of heat treatment for 1 hour under conditions of 200 ° C. in a nitrogen atmosphere. To obtain a dry film. Next, a measurement sample (a film having a length of 20 mm (grasping allowance 5 mm), a width of 5 mm, and a thickness of 10 μm) was prepared using the obtained dry film. Thereafter, the thermo-analytical analyzer (trade name “TMA8310” manufactured by Rigaku) as a measuring device is set with the measurement sample (film), the tensile mode (20 mN) is adopted, and under a nitrogen atmosphere, The sample to be measured was pulled in the longitudinal direction while raising the temperature from 50 ° C. to 450 ° C. at a heating rate of 5 ° C./min, and the change in the length in the longitudinal direction of the sample at 50 ° C. to 450 ° C. was measured (tensile TMA Measurement). And as a result of such tensile TMA measurement, while obtaining the TMA curve which is a graph which shows the relationship between temperature and the amount of change of the length of a longitudinal direction, 1 degreeC (1K) in the temperature range of 100 to 350 degreeC The average value of the change in the length per round was calculated, and the coefficient of thermal expansion (CTE: value of the coefficient of thermal expansion of the polyimide film having a thickness of 10 μm) was obtained. In the graph of the TMA curve, the extreme value in which the ratio (slope) of the length change amount to the temperature change amount (increase amount) changes from positive to negative (hereinafter simply referred to as “extreme value A” for convenience). ) Was observed, the temperature of the extreme value A was obtained. In addition, such temperature of the extreme value A is a temperature at which the change in the length of the measurement sample (film) changes from elongation to contraction in the tensile TMA measurement.

<Measurement of Rth>
For the polyimide films obtained in each Example and each Comparative Example, Rth was measured as follows. That is, each polyimide film was used to prepare a film having a length of 20 mm, a width of 20 mm, and a thickness of 10 μm as a measurement sample. The product name “AxoScan” manufactured by AXOMETRICS was used as a measurement device, and the polyimide film previously measured on the device was measured. The value of refractive index (589 nm) was input, and Rth was obtained as a measurement value obtained by automatic measurement using light of wavelength 589 nm under the conditions of temperature: 25 ° C. and humidity: 40% (in addition, the film Since the thickness is 10 μm, the obtained Rth is the retardation value per 10 μm thickness). Here, since the polyimide film obtained in each Example and each Comparative Example is an unstretched film, the refractive index (589 nm) of the polyimide film is 1 cm square (thickness 10 μm) from each of these polyimide films. The film was cut out to make a measurement sample, and a refractive index measurement device (trade name “NAR-1T SOLID” manufactured by Atago Co., Ltd.) was used as a measurement device, and the measurement sample was measured at a temperature of 23 ° C. using a light source of 589 nm. The value obtained in advance by measuring the average refractive index for the light of 589 nm was adopted.

<Measurement of glass transition temperature (Tg)>
Regarding the polyimide films obtained in each Example and each Comparative Example, the glass transition temperature (Tg) was measured using a thermomechanical analyzer (trade name “TMA8311” manufactured by Rigaku) as a measuring device. The measurement was performed by adopting a “penetration (needle insertion) method in which needle insertion is performed under pressure”.

<Measurement of yellowness (YI)>
Regarding the polyimide films obtained in each Example and each Comparative Example, the yellowness (YI) is measured using ASTM E313-05 (2005) using a product name “Spectral Color Meter SD6000” manufactured by Nippon Denshoku Industries Co., Ltd. as a measuring device. It was obtained by performing measurement in accordance with

(Synthesis Example 1: Adjustment of CpODA)
In accordance with the method described in Synthesis Example 1, Example 1 and Example 2 of International Publication No. 2011/099518, the following formula (21):

(Norbornane-2-spiro-α-cyclopentanone-α′-spiro-2 ″ -norbornane-5,5 ″, 6,6 ″ -tetracarboxylic dianhydride: Simply referred to as “CpODA”).

(Synthesis Example 2: Preparation of imidazole compound (reaction accelerator))
In accordance with the method described in Synthesis Example 1 of International Publication No. 2017/0264448, the following formula (22):

The represented imidazole compound was prepared.

Example 1
<Preparation process of polyamic acid resin solution>
First, a 100 ml three-necked flask was heated with a heat gun and sufficiently dried. Next, the atmosphere gas in the three-necked flask was replaced with nitrogen, and the inside of the three-necked flask was changed to a nitrogen atmosphere. In a three-necked flask, 2.7875 g (8.00 mmol) of 9,9-bis (4-aminophenyl) fluorene (manufactured by Seika Sangyo: FDA) and 4,4′-diaminobenzanilide (manufactured by Nippon Pure Chemicals Co., Ltd .: DABAN) ) 0.4545 g (2.00 mmol) was added, followed by 28.34 g of N, N, N ′, N′-tetramethylurea (TMU). The contents of the three-necked flask were stirred to obtain a slurry liquid in which diamine compounds (FDA and DABAN: aromatic diamine) were dispersed in TMU.

  Next, 3.8438 g (10.00 mmol) of CpODA prepared in Synthesis Example 1 was added to the three-necked flask, and then the contents of the flask were stirred at room temperature (25 ° C.) for 12 hours under a nitrogen atmosphere to prepare a reaction solution. Obtained. In this way, a reaction liquid (polyamic acid resin solution) in which the polyamic acid was 20 mass% (TMU solvent: 80 mass%) in the reaction liquid was obtained.

  Next, 2.1258 g of the imidazole compound prepared in Synthesis Example 2 (amount to be 30 parts by mass with respect to 100 parts by mass of the solid content of the polyamic acid) was added to the reaction solution thus obtained under a nitrogen atmosphere. It was. Next, the reaction solution was stirred at 25 ° C. for 12 hours to obtain a polyimide precursor resin solution (polyamide acid resin solution) containing an imidazole compound.

<Preparation process of polyimide film>
A polyimide precursor resin solution containing an imidazole compound obtained as described above on a glass substrate (non-alkali glass, Corning trade name “Eagle XG”, length: 100 mm, width 100 mm, thickness 0.7 mm). The coating film was formed by spin coating so that the thickness of the coating film after baking (heat curing) was 10 μm. Next, the glass substrate on which the coating film was formed was placed on a hot plate at 70 ° C. and allowed to stand for 2 hours, and the solvent was removed from the coating film by evaporation. Next, the glass substrate on which the coating film after removal of the solvent was formed was put into an inert oven in which nitrogen was flowing at a flow rate of 3 L / min. Then, in an inert oven, leave it in a nitrogen atmosphere at a temperature condition of 25 ° C. for 0.5 hours, heat at a temperature condition of 135 ° C. for 0.5 hour, and then heat at a firing temperature of 300 ° C. for 1 hour. By baking the coating film after removing the solvent and curing the coating film, a polyimide-coated glass in which a thin film (polyimide film) made of polyimide was coated on the glass substrate was obtained. 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 obtain a polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm). Got.

(Examples 2 to 6)
The firing temperature in the polyimide film preparation step is from 300 ° C. to 320 ° C. (Example 2), 340 ° C. (Example 3), 360 ° C. (Example 4), 380 ° C. (Example 5), and 400 ° C. (implementation). A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 1 except for changing to Example 6).

(Comparative Examples 1-2)
A polyimide film (100 mm length, 100 mm width) was the same as in Example 1 except that the firing temperature in the polyimide film preparation step was changed from 300 ° C. to 260 ° C. (Comparative Example 1) and 280 ° C. (Comparative Example 2), respectively. And a film having a thickness of 10 μm).

(Comparative Example 3)
In the preparation process of the polyamic acid resin solution, FDA is not used, the amount of DABAN used is changed to 2.2726 g (10 mmol), and the amount of TMU used is changed to 24.47 g. Similarly, a polyimide film (100 mm long, 100 mm wide, 10 μm thick film) was obtained.

  Table 1 shows the results obtained by measuring the characteristics of the films obtained in Examples 1 to 6 and Comparative Examples 1 to 3 based on the evaluation method described above. As a result of IR measurement, it was confirmed that all the films obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were made of polyimide. Table 1 shows the positions where peaks based on the C═O stretching vibration of imide carbonyl were confirmed in the IR spectrum. Moreover, the TMA curve of the polyimide film obtained in Example 1 and the polyimide film obtained in Comparative Example 3 is shown in FIG.

  As is clear from the results shown in Table 1, the polyimide films obtained in Examples 1 to 6 are all polyimides containing the repeating unit (A) represented by the general formula (1) from the type of monomers used. It was found that the extreme value A was confirmed in the temperature range of 200 to 430 ° C. in the TMA curve. On the other hand, the polyimide films obtained in Comparative Examples 1 and 2 are films made of polyimide containing a repeating unit represented by the general formula (1) from the type of monomer used, but the extreme value A is in the TMA curve. It was confirmed at 176 ° C. (Comparative Example 1) and 188 ° C. (Comparative Example 2) that the extreme value A was not within the temperature range of 200 to 430 ° C.

  Here, as is clear from the description of Table 1, the types of monomers used and the amounts used (molar ratio) were the same as those obtained in Examples 1-6 and Comparative Examples 1-2. In contrast to the film, when the extreme value A is in the temperature range of 200 to 430 ° C. (Examples 1 to 6), the absolute value of Rth is 85 nm or less and the absolute value of CTE is 30 ppm / It turned out that it becomes below K. On the other hand, when the extreme value A is confirmed at 176 ° C. (Comparative Example 1) and 188 ° C. (Comparative Example 2), and the extreme value A is not within the temperature range of 200 to 430 ° C. (in the case of Comparative Examples 1 and 2) In each case, it was confirmed that the absolute value of CTE was 61.2 ppm / K or more.

  From such a result, first, the film obtained in Examples 1 to 6 and the film obtained in Comparative Examples 1 and 2 were obtained using the same amount of the same monomer. In both cases, the Rth is sufficiently low (since Rth is 145 nm or less), so that a sufficiently low Rth is obtained due to the structure of the repeating unit of the polyimide constituting the film. It became clear that Moreover, even if it is polyimides (Examples 1-6 and Comparative Examples 1-2) with the same kind and usage-amount (molar ratio) of the monomer used from the result shown in Table 1, the difference in the calcination temperature at the time of manufacture Thus, the position of the extreme value A in the TMA curve becomes different, and the polyamic acid obtained based on the monomers shown in Table 1 so that the position of the extreme value A falls within a specific temperature range (the above general formula (7) The polyamic acid containing the repeating unit (A ′) represented by the formula (B) is calcined under a temperature condition of Tg-190 ° C. to Tg-50 ° C., thereby reducing Rth (absolute value) to a sufficiently low value of 145 nm or less. It was found that the CTE (absolute value) can be set to a higher value such as 30 ppm / K or less.

  As is clear from the results shown in FIG. 1, in the polyimide film obtained in Example 1, the extreme value A was confirmed within the temperature range of 200 to 430 ° C. in the TMA curve. In the first place, in the polyimide film obtained in Comparative Example 3 in which the kind of monomer is different from that in Example 1, the extreme value A in the TMA curve was obtained even if the film was baked at a temperature condition of Tg-190 ° C. to Tg-50 ° C. Was not confirmed. From this result, when the polyimide film is obtained by firing under the specific temperature condition and includes the repeating unit (A) (in the case of Examples 1 to 6), It has been found that the extreme value A can exist in the temperature range of 200 to 430 ° C. in the TMA curve.

  Thus, from the results shown in Table 1, according to the polyimide films of the present invention (Examples 1 to 6), sufficiently low thickness direction retardation (Rth) and sufficiently low thermal expansion based on absolute values. It has been confirmed that the rate (CTE) can be balanced at a higher level.

(Example 7)
In the preparation process of the polyamic acid resin solution, the usage amount of FDA was changed to 2.0906 g (6 mmol), the usage amount of DABAN was changed to 0.9090 g (4 mmol), and the usage amount of TMU was 27.37 g. A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 1 except that the thickness was changed to.

(Example 8)
In the preparation process of the polyamic acid resin solution, the usage amount of FDA was changed to 3.1360 g (9 mmol), the usage amount of DABAN was changed to 0.2273 g (1 mmol), and the usage amount of TMU was 28.83 g. A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 1 except that the thickness was changed to.

Example 9
In the preparation process of the resin solution of polyamic acid, Example 1 was used except that DABAN was not used, the amount of FDA used was changed to 3.4844 g (10 mmol), and the amount of TMU used was changed to 29.31 g. Similarly, a polyimide film (100 mm long, 100 mm wide, 10 μm thick film) was obtained.

(Example 10)
In the preparation process of the polyamic acid resin solution, the amount of FDA used was changed to 2.4391 g (7 mmol), the amount of DABAN used was changed to 0.6818 g (3 mmol), and the amount of TMU used was 27.86 g. A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 1 except that the thickness was changed to. In addition, about the polyimide film obtained by the present Example, the glass transition temperature (Tg: DMA) was measured also by what is called DMA measurement for reference. In this measurement, a dynamic viscoelasticity measuring device (trade name “DMS6100” manufactured by Seiko SII) is used as a measuring device, and a tension ( 100 mN), frequency (1 Hz, 10 Hz), DMA measurement was performed with a temperature program of 30 ° C. to 550 ° C. The glass transition temperature (Tg: DMA) measured by such DMA measurement was 470 ° C. Note that the Tg values (measured values by the penetration (needle insertion) method) shown in Table 2 described later and the measured Tg values by the DMA method were substantially equivalent.

(Examples 11 to 15)
The firing temperature in the polyimide film preparation step is from 300 ° C. to 320 ° C. (Example 11), 340 ° C. (Example 12), 360 ° C. (Example 13), 380 ° C. (Example 14), and 400 ° C. (implementation). Except having changed into Example 15), it carried out similarly to Example 10, and obtained the polyimide film (The film of the magnitude | size of length 100mm, width 100mm, and thickness 10 micrometers).

  Table 2 shows the results obtained by measuring the characteristics of the films obtained in Examples 7 to 15 based on the evaluation method described above. As a result of IR measurement, it was confirmed that all the films obtained in Examples 7 to 15 were made of polyimide. Table 2 shows the positions where peaks based on the C═O stretching vibration of imide carbonyl were confirmed in the IR spectrum. For reference, the characteristics of the film obtained in Example 1 are also shown in Table 2.

  As shown in Table 2, each of the polyimide films obtained in Examples 7 to 15 is a film made of polyimide containing the repeating unit (A) represented by the general formula (1) from the type of monomer used. And it turned out that the extreme value A is confirmed by the temperature range of 200-430 degreeC in the TMA curve. In addition, in the TMA curve of the polyimide film obtained by baking the polyamic acid obtained based on the monomer shown in Table 2 on the temperature conditions of Tg-190 degreeC-Tg-50 degreeC from the manufacturing conditions, it is extreme value A. Was found to be confirmed in the temperature range of 200-430 ° C. In addition, from the results shown in Table 2, all of the polyimide films of the present invention (Example 1 and Examples 7 to 15) had an Rth absolute value of 145 nm or less and a CTE absolute value of 30 ppm / K or less. It was confirmed that As described above, according to the polyimide film of the present invention, it is possible to make the CTE (absolute value) 30 ppm / K or less higher, while keeping Rth (absolute value) sufficiently low value of 145 nm or less. Thus, it was confirmed that it was possible to have a sufficiently low level of retardation (Rth) in the thickness direction and a sufficiently low coefficient of thermal expansion (CTE) at a higher level with an absolute value as a reference.

(Example 16)
Instead of adding FDA and DABAN in the three-necked flask by changing the type of diamine compound used in the preparation process of the polyamic acid resin solution, 4,4′-diaminodiphenylsulfone (4,4 ′) is added in the three-necked flask. -DDS) A polyimide film (length 100 mm, width 100 mm, thickness 10 μm) in the same manner as in Example 1 except that 2.4830 g (10 mmol) was added and the amount of TMU used was changed to 25.31 g. Film).

(Example 17)
Instead of adding the FDA and DABAN in the three-necked flask by changing the type of diamine compound used in the preparation process of the polyamic acid resin solution, 9,9-bis (4-amino-3-fluoro) in the three-necked flask Phenyl) fluorene (F-FDA) 3.8443 g (10 mmol) was added, and the polyimide film (100 mm in length, 100 mm in width, A film having a thickness of 10 μm was obtained.

(Example 18)
Instead of adding the FDA and DABAN in the three-necked flask by changing the type of diamine compound used in the preparation process of the polyamic acid resin solution, 9,9-bis (4-amino-3-methyl) in the three-necked flask Phenyl) fluorene (Me-FDA) 3.7650 g (10 mmol) was added and the amount of TMU used was changed to 30.44 g in the same manner as in Example 1 except that a polyimide film (length 100 mm, width 100 mm, A film having a thickness of 10 μm was obtained.

  Table 3 shows the results obtained by measuring the characteristics of the films obtained in Examples 16 to 18 based on the evaluation method described above. As a result of IR measurement, it was confirmed that the films obtained in Examples 16 to 18 were all made of polyimide. Table 3 shows the positions where peaks based on the C═O stretching vibration of imide carbonyl were confirmed in the IR spectrum.

  As shown in Table 3, each of the polyimide films obtained in Examples 16 to 18 is a film made of polyimide containing the repeating unit (A) represented by the general formula (1) from the type of the monomer used. And it turned out that the extreme value A is confirmed by the temperature range of 200-430 degreeC in the TMA curve. In addition, from the manufacturing conditions, the polyamic acid obtained based on the monomers shown in Table 3 (polyamic acid containing the repeating unit (A ′) represented by the general formula (7)) is finally obtained from the polyimide obtained. It was found that the extreme value A was confirmed in the temperature range of 200 to 430 ° C. in the TMA curve of the polyimide film obtained by firing at a temperature condition of Tg-190 ° C. to Tg-50 ° C. based on Tg. . In addition, from the results shown in Table 3, it was confirmed that all of the polyimide films of the present invention (Examples 16 to 18) had an absolute value of Rth of 145 nm or less and an absolute value of CTE of 30 ppm / K or less. According to the polyimide film of the present invention, it is possible to have a sufficiently low level of retardation (Rth) and sufficiently low coefficient of thermal expansion (CTE) at a higher level in a well-balanced manner based on absolute values. It was confirmed that In particular, in Examples 17 to 18, the absolute value of Rth is set to a value less than 50 nm, and CTE can be set to 30 ppm / K or less. The polyimide films obtained in these Examples are sufficiently It has also been found that it has a low thickness direction retardation (Rth) and a sufficiently low coefficient of thermal expansion (CTE) at a higher level in a well-balanced manner.

(Example 19)
Instead of using CpODA in the preparation process of the polyamic acid resin solution, 1.9611 g (10.00 mmol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) was used, and the amount of TMU used A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 1 except that was changed to 20.81 g.

(Comparative Example 4)
A polyimide film (a film having a length of 100 mm, a width of 100 mm, and a thickness of 10 μm) was obtained in the same manner as in Example 19 except that the baking temperature in the polyimide film preparation step was changed from 300 ° C. to 380 ° C.

  Table 4 shows the results obtained by measuring the properties of the films obtained in Example 19 and Comparative Example 4 based on the evaluation method described above. As a result of IR measurement, it was confirmed that all of these films were made of polyimide. Table 4 shows the positions where peaks based on the C═O stretching vibration of imide carbonyl were confirmed in the IR spectrum.

  As shown in Table 4, the polyimide film obtained in Example 19 is a film made of polyimide containing the repeating unit (A) represented by the general formula (1) from the type of monomer used, and It was found that the extreme value A was confirmed in the temperature range of 200 to 430 ° C. in the TMA curve. On the other hand, the polyimide film obtained in Comparative Example 4 is a film made of polyimide containing the repeating unit (A) represented by the general formula (1) from the type of monomer used, but the extreme value A in the TMA curve thereof. Could not be confirmed. In addition, from the production conditions, the polyamic acid obtained based on the monomers shown in Table 4 (polyamic acid containing the repeating unit (A ′) represented by the general formula (7)) is finally obtained from the polyimide obtained. By firing at a temperature condition of Tg-190 ° C. to Tg-50 ° C. based on Tg, the extreme value A is confirmed in the temperature range of 200 to 430 ° C. in the TMA curve of the obtained polyimide film. I understood that.

  From the results shown in Table 4, it was confirmed that the polyimide film of the present invention (Example 19) had an absolute value of Rth of less than 50 nm and an absolute value of CTE of 45 ppm / K or less. In contrast, in the polyimide film (Comparative Example 4) in which the extreme value A is not in the temperature range of 200 to 430 ° C. in the TMA curve, the absolute value of RTE is less than 50 nm, but the absolute value of CTE is 60 ppm / K, the CTE cannot be made sufficiently low in relation to the value of Rth, and has a sufficiently low retardation (Rth) and a sufficiently low coefficient of thermal expansion (CTE) in a well-balanced manner I couldn't.

  From these results, according to the polyimide film of the present invention (Example 19), a sufficiently low thickness direction retardation (Rth) and a sufficiently low coefficient of thermal expansion (CTE) are higher based on the absolute value. It was confirmed that it was possible to have a well-balanced level.

(Example 20)
In the preparation process of the polyamic acid resin solution, 1.9864 g (8 mmol) of 4,4′-diaminodiphenylsulfone (4,4′-DDS) was used instead of FDA, and the amount of TMU used was 25.14 g. Except having changed, it carried out similarly to Example 1, and obtained the polyimide film (The film of the magnitude | size of length 100mm, width 100mm, and thickness 10 micrometers).

  Table 5 shows the results obtained by measuring the properties of the film obtained in Example 20 based on the evaluation method described above. As a result of IR measurement, it was confirmed that all of these films were made of polyimide. Table 5 shows the positions where peaks based on the C═O stretching vibration of imide carbonyl were confirmed in the IR spectrum.

  As shown in Table 5, the polyimide film obtained in Example 20 is a film made of polyimide containing the repeating unit (A) represented by the general formula (1) from the type of monomer used, and its It was found that the extreme value A was confirmed in the temperature range of 200 to 430 ° C. in the TMA curve. From the results shown in Table 5, it was confirmed that the polyimide film of the present invention (Example 20) had an absolute value of Rth of 145 nm or less and an absolute value of CTE of 30 ppm / K or less. From these results, according to the polyimide film of the present invention (Example 20), a sufficiently low thickness direction retardation (Rth) and a sufficiently low coefficient of thermal expansion (CTE) are higher based on the absolute value. It was confirmed that it was possible to have a well-balanced level.

  As described above, according to the present invention, a sufficiently low thickness direction retardation (Rth) and a sufficiently low thermal expansion coefficient (linear expansion coefficient: CTE) are balanced at a higher level based on the absolute value. It is possible to provide a polyimide film that can be often included and a method for producing a polyimide film that can produce the polyimide film. Such a polyimide film of the present invention is particularly useful as a substrate for LCDs and OLEDs because of its characteristics.

Claims (4)

The following general formula (1):
[In Formula (1), A shows the tetravalent alicyclic hydrocarbon group whose number of the carbon atoms which form a cyclic structure is 4-30, ^Ra is following General formula (2)-(3). :
(In the formula (2), R ^a1 , R ^a2 , R ^a3 and R ^a4 each independently represents one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group,
In formula (3), R ^a5 and R ^a6 each independently represent one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group. )
Any one of divalent organic groups represented by the formula: ]
A film comprising a polyimide containing a repeating unit (A) represented by:
A thermal machine that measures the relationship between the temperature and the change in the length of the film by pulling the film under a load of 20 mN while raising the temperature from 50 ° C. to 450 ° C. at a temperature rising rate of 5 ° C./min in a nitrogen atmosphere. In the TMA curve obtained by analysis (TMA), an extreme value in which the ratio of the change in the length of the film to the change in the temperature changes from positive to negative exists in the temperature range of 200 to 430 ° C. Polyimide film. A in the formula (1) is the following general formula (4):
[In 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 n is 0 to 0. An integer of 12 is shown. ]
The polyimide film according to claim 1, wherein the polyimide film is a tetravalent alicyclic hydrocarbon group represented by the formula: The polyimide has the following general formula (5)
[In Formula (5), A is synonymous with A in said Formula (1), ^Rb is following General formula (6):
(In Formula (6), R ^b1 and R ^b2 each independently represent one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom, and a hydroxyl group.)
The bivalent organic group represented by these is shown. ]
And the content of the repeating unit (A) with respect to the total amount of the repeating unit (A) and the repeating unit (B) in the polyimide is from 50 to 50. It is 100 mol%, The polyimide film of Claim 1 or 2 characterized by the above-mentioned. After forming a coating film using a polyimide precursor resin solution containing a polyimide precursor and an organic solvent, the process includes removing the solvent from the coating film and obtaining a film made of polyimide by firing,
The polyimide precursor is represented by the following general formula (7):
[In Formula (7), A shows the tetravalent alicyclic hydrocarbon group whose number of carbon atoms which forms a cyclic structure is 4-30, ^Ra is following General formula (2)-(3). :
(In the formula (2), R ^a1 , R ^a2 , R ^a3 and R ^a4 each independently represents one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group,
In formula (3), R ^a5 and R ^a6 each independently represent one type selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a halogen atom and a hydroxyl group. )
And Y ¹ and Y ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and an alkylsilyl group having 3 to 9 carbon atoms. 1 type selected from ]
And a repeating unit (A ′) represented by:
Claimed as a film made of the polyimide by firing at a temperature in the range of (Tg-190) ° C. to (Tg-50) ° C., based on the glass transition temperature (Tg) of the polyimide obtained during the firing. Obtaining a polyimide film according to any one of 1 to 3,
A method for producing a polyimide film characterized by the above.