JPWO2020255890A1 - Polyimide solution and polyimide - Google Patents

Abstract

Provided are a polyimide having a small yellow index and excellent heat resistance, and a polyimide solution containing the above-mentioned polyimide. The polyimide is a mixture of a polyimide (I) composed of a repeating unit represented by a specific formula (1) and a polyimide (II) composed of a repeating unit represented by a specific formula (2). The content of I) is 5 to 95% by mass, and the content of polyimide (II) is 95 to 5% by mass.

Description

The present invention relates to a polyimide solution and a polyimide.

Currently, glass substrates are used in various display devices such as liquid crystal displays and organic EL (Electroluminescence) displays. Glass substrates are excellent in that they have high heat resistance, low coefficient of linear thermal expansion, and high transparency, while they are required to be lightweight and flexible, and resistant to impacts that can be received in daily life. From the search for alternative materials, the study of polyimide materials is underway.

Japanese Patent No. 6010533

In general, most polyimides are insoluble in solvents, and in order to obtain an industrially stable cured material, a method of converting to polyimide via a polyamic acid, which is a polyimide precursor soluble in a solvent, is widely adopted. Has been done. Since this conversion requires heating at 300 ° C. or higher, the heat load is high, which has also caused equipment failure during dehydration. Yellowing is often unavoidable in the obtained materials, and mounting on electronic devices has been limited to internal parts of the housing such as internal substrates. This yellowing (more specifically, the yellow index) could not be prevented even when the fluorene structure was introduced, which hindered the expansion of applications.

The yellowing of the polyimide material is caused by a continuous structure of a conjugated system called a CT (Charge Transfer) complex in which charge transfer can occur. Furthermore, since the structure is highly flat with a 5- or 6-membered ring as the base axis, which is characteristic of the chemical structure of polyimide, charge transfer between molecules is also considered to be a cause of yellowing.
Therefore, in general, as an effort to make polyimide transparent, a method of blending a certain amount of an aliphatic structure with a constituent raw material to suppress coloring of the material is known. On the other hand, since the glass transition point (Tg) of the material tends to decrease, it contributes to the decrease in heat resistance.

Therefore, in view of the above circumstances, it is an object of the present invention to provide a polyimide having a small yellow index and excellent heat resistance, and a polyimide solution containing the polyimide.

As a result of diligent studies on the above problems, the present inventor has found that the above problems can be solved by using two types of polyimides having a specific structure in combination, and has reached the present invention.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) It contains a polyimide (I) composed of a repeating unit represented by the formula (1) described later and a polyimide (II) composed of a repeating unit represented by the formula (2) described later.
The content of the polyimide (I) is 5 to 95% by mass, and the content of the polyimide (II) is 95 to 5% by mass with respect to the total amount of the polyimide (I) and the polyimide (II). Is a polyimide solution.
(2) A mixture of a polyimide (I) composed of a repeating unit represented by the formula (1) described later and a polyimide (II) composed of a repeating unit represented by the formula (2) described later.
A polyimide having a polyimide (I) content of 5 to 95% by mass and a polyimide (II) content of 95 to 5% by mass.
(3) The polyimide according to (2) above, wherein the glass transition point is 280 ° C. or higher.
(4) The polyimide according to (2) or (3) above, wherein the yellow index is 3 or less.
(5) A conductive film comprising the polyimide layer made of the polyimide according to any one of (2) to (4) above.

As shown below, according to the present invention, it is possible to provide a polyimide having a small yellow index (YI) and excellent heat resistance, and a polyimide solution containing the above-mentioned polyimide.

Hereinafter, the polyimide of the present invention, the polyimide solution of the present invention, and the like will be described.
In the present specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
In addition, each component may be used alone or in combination of two or more. Here, when two or more kinds of each component are used in combination, the content of the component means the total content unless otherwise specified.

In the present invention, a composition is defined in which a repeating unit that does not generate a conjugated system leading to CT complex formation and solubility in a solvent are compatible, and treatment is performed up to an imide ring closure reaction under mild conditions in a solution favorable for an intramolecular reaction. It is preferable to do so. By storing the solution containing the obtained composition individually and mixing it before use, it is possible to prevent the formation of a continuous structure of aromatic components even during long-term curing storage, and the solution is stable. It can be a technology for obtaining highly transparent materials.

[Polyimide]
The polyimide of the present invention contains a polyimide (I) composed of a repeating unit represented by the formula (1) described later and a polyimide (II) composed of a repeating unit represented by the formula (2) described later. It is a polyimide having a polyimide (I) content of 5 to 95% by mass and a polyimide (II) content of 95 to 5% by mass.

Since the polyimide of the present invention has such a structure, it is considered that the above-mentioned effects can be obtained. The reason is not clear, but it is presumed to be as follows.
As described above, the polyimide of the present invention is a mixture of polyimide (I) and polyimide (II). Here, as will be described later, both polyimide (I) and polyimide (II) are composed of repeating units having a structure in which aromatics and aliphatics are bonded, so that a conjugated system does not occur. Further, the present invention is characterized in that two types of polyimides having contrasting structures are used in combination. That is, in polyimide (I), an aromatic group having a fluorene skeleton is sandwiched between carbonyl groups, and an aliphatic group or an alicyclic group is sandwiched between nitrogen atoms. On the contrary, in polyimide (II), an aliphatic group or an alicyclic group is sandwiched between carbonyl groups, and an aromatic group having a fluorene skeleton is sandwiched between nitrogen atoms. In a mixture of these two types of polyimide, the imide groups of the two types of polyimide interact with each other to form an aromatic group of polyimide (I) and an aliphatic group or an alicyclic group of polyimide (II). It is considered that they are stacked to form a structure in which the aliphatic group or alicyclic group of polyimide (I) and the aromatic group of polyimide (II) are stacked. Therefore, in the polyimide of the present invention, it is considered that the charge transfer not only within the molecule but also between the molecules is extremely small, and as a result, coloring is suppressed.

Hereinafter, the polyimide (I) and the polyimide (II) contained in the polyimide of the present invention will be described.

<Polyimide (I)>
The polyimide (I) is a polyimide composed of a repeating unit represented by the following formula (1).

In formula (1), A ₁ represents a tetravalent aromatic group containing a fluorene skeleton. B ₁ represents a divalent, aliphatic or alicyclic group.

As described above, in formula (1), A ₁ represents a tetravalent aromatic group containing a fluorene skeleton. The tetravalent aromatic group containing the fluorene skeleton may have a substituent.

As mentioned above, B ₁ represents a divalent, aliphatic or alicyclic group. The above-mentioned "divalent, aliphatic group or alicyclic group" may have a substituent (however, does not contain a fluorene skeleton).
B ₁ is preferably a divalent alicyclic group because it has a smaller YI, better heat resistance, and a lower absolute refractive index. Hereinafter, the fact that YI is smaller and the heat resistance is more excellent is also referred to as "the effect of the present invention is more excellent".

<< Method of synthesizing polyimide (I) >>
The method for synthesizing the polyimide (I) is not particularly limited, but the obtained polyimide of the present invention has a tetracarboxylic acid or an anhydride thereof as a solvent because the YI is smaller, the heat resistance is better, and the absolute refractive index is smaller. A method of adding (acid component) and diamine (amine component) and polymerizing (method 1) is preferable. As a result, a solution containing polyimide (I) is obtained. Hereinafter, with respect to the obtained polyimide of the present invention, the fact that the YI is smaller and the heat resistance is more excellent is also referred to as "the effect of the present invention is more excellent".

(Acid component)
The acid component in the above method 1 is a compound (aromatic compound) containing a fluorene skeleton, having four carboxy groups, or an anhydride thereof. Among them, anhydrous is preferable because the effect of the present invention is more excellent, and 9,9-bis (3,4-dicarboxyphenyl) fluorene diacid anhydride (BPAF), 9,9-bis. [4- (3,4-dicarboxyphenoxy) phenyl] Fluorene diacid anhydride is more preferred, and BPAF is even more preferred.

(Amine component)
The amine component in the above method 1 is an aliphatic group or an alicyclic group and has two amino groups. Specific examples include linear or branched aliphatic diamines such as diaminobutane, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminononane, diaminodecane, diaminoundecane, diaminododecane, and 2-methyl-diaminopentane. 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 3-methyl-1,4-diaminocyclohexane, 3-methyl-3-aminomethyl-5,5-dimethyl-1- Cyclohexaneamine (isophoronediamine) (IPDA), 1,3-bisaminomethylcyclohexane, bis (4,4'-aminocyclohexyl) methane, bis (3,3'chill-4,4'-aminocyclohexyl) methane, bis (Aminomethyl) norbornan, bis (aminomethyl) -tricyclo [5,2,1,0] decane, 1,3-diaminoadamantan, 2,2'-dimethyl-4,4'-methylenebis (cyclohexane-1-ylamine) ), Diamine having an alicyclic structure such as 4,4'-methylenebis (cyclohexylamine); and the like. Among them, a diamine having an alicyclic structure is preferable, and IPDA is more preferable, for the reason that the effect of the present invention is more excellent. It may have an aromatic ring in part as long as it does not intervene in the formation of the CT complex at the imide site.

(solvent)
The solvent in Method 1 is not particularly limited as long as it can dissolve polyimide (I), but is N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-ethyl. Amido solvent such as -2-pyrrolidone; cyclic ester solvent such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone; ethylene carbonate, propylene carbonate, etc. Carbonate solvent; Glycol-based solvent such as triethylene glycol; Phenolic solvent such as m-cresol, p-cresol, 3-chlorophenol, 4-chlorophenol; Acetphenone; 1,3-dimethyl-2-imidazolidinone; Sulfolane; dimethylsulfoxide; and the like are preferably adopted. In addition, other common organic solvents such as phenol, 0-cresol, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, petit cellosolve, 2-methylcellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, Tetrahydrofuran, dimethoxyethane, diethoxyethane, dibutyl ether, diethylene glycol dimethyl ether, methyl isobutyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol and the like can also be used. A plurality of these solvents may be used in combination.

(Mole ratio)
The molar ratio of the acid component to the amine component (acid component / amine component) in the above method 1 is not particularly limited, but is preferably 0.99 to 1.10 for the reason that the effect of the present invention is more excellent. It is more preferably 0.95 to 1.05.

(Preferable Aspect of Method 1)
The polymerization temperature is not particularly limited, but is preferably 50 to 100 ° C. for the reason that the effect of the present invention is more excellent.
The polymerized polyamic acid may be imidized (thermal imidized) by a thermal method of heating the polymer as it is, but may be chemically imidized using a reactant. The "imidization by a thermal method" in the present specification is a method of imidization by heating without using a dehydrating agent and an imidization accelerator. Specifically, for example, a method of obtaining a polyimide solution by heating a polyamic acid solution can be mentioned. As the solvent for preparing the polyamic acid solution, for example, the same solvent as the solvent used at the time of polymerization can be used. Specific examples and preferred embodiments of the solvent are the same as those of the polyimide solution solvent described later.

The heating time for imidization by a thermal method varies depending on the processing amount and heating temperature of the polyimide unit that performs dehydration ring closure, but is generally 10 minutes to 5 hours after the processing temperature reaches the maximum temperature. It is preferable to carry out within the range.

Further, an azeotropic method having an azeotropic action of water may be used, and dehydration is performed by adding a solvent such as toluene or xylene that azeotropes with water to the solution containing the composition and raising the temperature to 170 to 200 ° C. The treatment may be carried out for about 1 to 5 hours while actively removing the water produced by the ring closure to the outside of the system. Decompression may be performed in order to carry out dehydration for a short time and at a low temperature.

<Polyimide (II)>
Polyimide (II) is a polyimide composed of a repeating unit represented by the following formula (2).

In formula (2), A ₂ represents a tetravalent aliphatic group or alicyclic group. B ₂ represents a divalent aromatic group containing a fluorene skeleton.
The above A ₂ is preferably a tetravalent alicyclic group for the reason that the effects of the present invention are more excellent.

As described above, in formula (2), A ₂ represents a tetravalent aliphatic group or alicyclic group. The above-mentioned "tetravalent aliphatic group or alicyclic group" may have a substituent (however, does not contain a fluorene skeleton).

As described above, in formula (2), B ₂ represents a divalent aromatic group containing a fluorene skeleton. The divalent aromatic group containing the fluorene skeleton may have a substituent.

<< Method of synthesizing polyimide (II) >>
The method for synthesizing polyimide (II) is not particularly limited, but for the reason that the effect of the present invention is more excellent, a method of adding tetracarboxylic acid or its anhydride (acid component) and diamine (amine component) to a solvent and polymerizing the polyimide (II). (Method 2) is preferable. As a result, a solution containing polyimide (II) is obtained.

(Acid component)
The acid component in the above method 2 is an aliphatic group or an alicyclic group having four carboxy groups, or an anhydride thereof. Specific examples include (1S, 2R, 4S, 5R) -cyclohexanetetracarboxylic acid dianhydride, (cis, cis, cis-1,2,4,5-cyclohexanetetracarboxylic acid dianhydride), (1S, 2S, 4R, 5R) -Cyclohexanetetracarboxylic acid dianhydride, (1R, 2S, 4S, 5R) -Cyclohexanetetracarboxylic acid dianhydride, Bicyclo [2.2.2] octane-2,3,5,6 -Tetrahydrofuran dianhydride, bicyclo [2.2.2] octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 5- (dioxotetrahydrofuryl) -3-methyl- 3-Cyclohexene-1,2-dicarboxylic acid anhydride (MCHDA), 4- (2,5-dioxotetrahydrofuran-3-yl) -tetraline-1,2-dicarboxylic acid anhydride, tetrahydrofuran-2,3,4 , 5-Tetrahydrofuran dianhydride, Bicyclo-3,3', 4,4'-Tetrahydrofuran dianhydride, Butane-1,2,3,4-Tetrahydrofuran dianhydride (BuDA), 1, , 2,3,4-Cyclopentanetetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,3-dimethyl-1,2-2,3,4-cyclobutanetetracarboxylic acid Dianoxide, 1,4-dimethyl-1,2-2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), and norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2 "-Norbornane-5,5", 6,6 "-tetracarboxylic acid dianhydride (CpODA), hexahydro-1H, 3H-4,8-methanobenzo [1,2-c: 4,5-c'] difuran -1,3,5,7-Tetrahydrofuran (BHDA), Hexahydro-1H, 3H-4,8-Etanobenzo [1,2-c: 4,5-c'] Difuran-1,3,5,7-Tetrahydrofuran (BODA), Decahydro-1H, 3H-4,10: 5,9-Dimethanonaft [2,3-c: 6,7-c'] Difran-1,3,6,8-Tetrahydrofuran (DNDA), Dodecahydro- [5,5'-Bisobenzofuran] -1,1', 3,3'-tetrahydrofuran, 5,5- (1,4-phenylene) bis (hexahydro-4,7-methanoisobenzofuran-1,3- Dione), 5,5-bi (hexahydro-4,7-methanoisobenzofuran-1,3-dione), ENEHYDE series manufactured by JXTG Energy Co., Ltd., etc. These may be used in combination of two or more.
The acid component in the above method 2 is preferably an alicyclic group having four carboxy groups or an anhydride thereof, and is preferably an alicyclic group, for the reason that the effect of the present invention is more excellent. It is more preferable that the anhydride has four carboxy groups.

(Amine component)
The amine component in the above method 2 is a compound (aromatic compound) containing a fluorene skeleton and having two amino groups. Among them, 2,7-diaminofluorene, 9,9-bis (4-aminophenyl) fluorene (BAFL), 9,9-bis (4-aminophenoxyphenyl) fluorene for the reason that the effect of the present invention is more excellent. , 9,9-bis (3-methyl-4-aminophenyl) fluorene, 9,9-bis (3-amino-4-hydroxyphenyl) fluorene, 9,9-bis (3-fluoro-4-aminophenyl) Fluorene or 9,9-bis [4- (aminophenoxy) phenyl] fluorene is preferable, and BAFL is more preferable.

(solvent)
The solvent in the above method 2 is not particularly limited as long as it can dissolve the polyimide (II), and specific examples and preferred embodiments may be selected with the expectation of the same effect as the solvent in the above method 1.

(Mole ratio)
The molar ratio of the acid component to the amine component (acid component / amine component) in the above method 2 is not particularly limited, but is preferably 0.99 to 1.10 for the reason that the effect of the present invention is more excellent. It is more preferably 0.95 to 1.05.

(Preferable Aspect of Method 2)
The preferred embodiment of the method 2 is the same as the preferred embodiment of the above-mentioned method 1.

<Content>
In the polyimide of the present invention, the content of the above-mentioned polyimide (I) is 5 to 95% by mass. Among them, for the reason that the effect of the present invention is more excellent, it is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, further preferably 30 to 70% by mass, and 35. It is particularly preferably ~ 65% by mass, and most preferably 40-60% by mass.

In the polyimide of the present invention, the content of the above-mentioned polyimide (II) is 95 to 5% by mass. Among them, for the reason that the effect of the present invention is more excellent, it is preferably 90 to 10% by mass, more preferably 80 to 20% by mass, further preferably 70 to 30% by mass, 65. It is particularly preferably ~ 35% by mass, and most preferably 60-40% by mass.

<Glass transition point>
The glass transition point of the polyimide of the present invention is preferably 280 ° C. or higher for the reason that the effect of the present invention is more excellent.

<Yellow index>
The yellow index (YI) of the polyimide of the present invention is preferably 3 or less for the reason that the effect of the present invention is more excellent.

<Production method>
The method for producing the polyimide of the present invention is not particularly limited, but the following method A or the following method B is preferable for the reason that the effect of the present invention is more excellent.

<< Method A >>
Method A is a method for obtaining the polyimide of the present invention by removing the solvent in the polyimide solution by drying the polyimide solution of the present invention described later by heating or the like.
For example, the polyimide solution of the present invention, which will be described later, is applied to a base material and dried by heating or the like to remove the solvent in the polyimide solution to obtain the polyimide of the present invention.

(Base material)
The base material may be selected so as not to be eroded by the solvent of the polyimide solution of the present invention. For example, glass; triacetate cellulose (TAC), polyethylene terephthalate (PET), diacetyl cellulose, acetate butyrate cellulose, polyether sulfone, acrylic resin, polyurethane resin, polyester, polycarbonate, polysulfone, polyether, trimethylpentene, poly. Examples thereof include films formed of various resins such as ether ketone and (meth) acrylonitrile; metals such as SUS and copper; and the like. If the base material has excellent transparency, it can be used as it is as a transparent material. If the base material is colored, it can be used without impairing its design.

Since the polyimide of the present invention has a yellow index (YI) suppressed, the substrate is an optical member or component provided with a coating layer having a defined refractive index or the like, particularly a liquid crystal display (LCD) or a cathode ray tube (CRT). ), Plasma display panel (PDP), electroluminescence display (ELD), touch panel, and other materials on the display surface of an image display device may be selected.

The film thickness accuracy can be ensured, and the cured film obtained by coating smoothly can be peeled off and handled as a film.

(Application)
As a method of applying to the base material, for example, a roll coating method, a gravure coating method, a slide coating method, a spray method, a dipping method, a screen printing method, a spray method and the like can be adopted.

(Dry)
The solvent may be volatilized and removed under temperature control, and if the time and pressure are appropriately set, the material can be obtained even under conditions below the boiling point.
Examples of the drying method include vacuum drying and hot air drying. In order to completely dry the solvent contained in the polyimide solution, vacuum drying is desirable, and the drying temperature is preferably in the range of 80 to 200 ° C. from the viewpoint of preventing decomposition of the residual solvent and deterioration of the resin due to the residual solvent.
Further, the drying time may be selected as a time during which the solvent contained in the polyimide composition can be completely dried, and is 15 hours or less from the viewpoint of the production process, more preferably 8 hours or more from the viewpoint of sufficiently drying the residual solvent. Is preferable.
When heating, the temperature is preferably 200 ° C. or lower, more preferably 100 ° C. or lower, for the reason that the effects of the present invention are more excellent. The lower limit is not particularly limited, but it is preferably 20 ° C. or higher, more preferably 30 ° C. or higher, for the reason that the effect of the present invention is more excellent.

<< Method B >>
Method B is a precipitation step in which the polyimide (I) and the polyimide (II) in the polyimide solution are precipitated by adding a poor solvent to the polyimide solution of the present invention described later, and after the precipitation step, the polyimide solution is added. This is a method including a solvent removing step of obtaining the polyimide of the present invention by removing the solvent.

Since the imide ring closure reaction is completed in the polyimide solution of the present invention, the polyimide is obtained by mixing with a poor solvent such as alcohol to precipitate the polyimide, washing the polyimide as necessary, and then drying. be able to.

That is, the reaction solution imidized as described above is dropped into a large amount of poor solvent to precipitate polyimide, and the reaction solvent, chemical imidizing agent, catalyst, etc. are removed by washing, and then the polyimide is dried. Powder can be obtained.

The poor solvent that can be used is preferably one that does not dissolve polyimide, and is not particularly limited, but water, methanol, ethanol, n from the viewpoint of compatibility with the reaction solvent and chemical imidizing agent and ease of removal by drying. -It is preferable to select propanol, isopropanol, etc.

When a polyimide solution containing polyimide, an imidization accelerator and a dehydrating agent is put into a poor solvent, the solid content concentration of the polyimide solution is not particularly limited as long as it has a viscosity that allows stirring, but the precipitated polyimide grains are not particularly limited. From the viewpoint of reducing the diameter, it is preferable that the concentration is dilute. However, if the concentration is too dilute, the amount of solvent used for precipitating the polyimide composition becomes large, which is not preferable.

From these viewpoints, it is preferable to dilute the solid content concentration of the polyimide solution to 15% by mass or less, preferably 10% by mass or less, and then add the polyimide solution to the poor solvent. The amount of the poor solvent used is preferably equal to or greater than the amount of the polyimide solution, and more preferably 2 to 3 times the amount. Since the polyimide obtained here contains a small amount of imidization accelerator and dehydrating agent, it is preferable to wash it several times with the above-mentioned poor solvent.

[Polyimide solution]
The polyimide solution of the present invention contains a polyimide (I) composed of a repeating unit represented by the above formula (1) and a polyimide (II) composed of a repeating unit represented by the above formula (2). The content of the polyimide (I) is 5 to 95% by mass, and the content of the polyimide (II) is 95 to 5% by mass with respect to the total amount of the polyimide (I) and the polyimide (II). It is a polyimide solution.

The polyimide (I) and the polyimide (II) are as described above. The solvent is not particularly limited as long as it can dissolve the polyimide (I) and the polyimide (II), and specific examples and preferred embodiments are the same as those in the above-mentioned method 1.

<Content>
In the polyimide solution of the present invention, the content of the above-mentioned polyimide (I) is 5 to 95% by mass with respect to the total amount of the above-mentioned polyimide (I) and the above-mentioned polyimide (II). Among them, for the reason that the effect of the present invention is more excellent, it is preferably 10 to 90% by mass, more preferably 20 to 80% by mass, further preferably 30 to 70% by mass, and 35. It is particularly preferably ~ 65% by mass, and most preferably 40-60% by mass.

In the polyimide of the present invention, the content of the above-mentioned polyimide (II) is 95 to 5% by mass with respect to the total amount of the above-mentioned polyimide (I) and the above-mentioned polyimide (II). Among them, for the reason that the effect of the present invention is more excellent, it is preferably 90 to 10% by mass, more preferably 80 to 20% by mass, further preferably 70 to 30% by mass, 65. It is particularly preferably ~ 35% by mass, and most preferably 60-40% by mass.

<concentration>
In the polyimide solution of the present invention, the solid content concentration of the polyimide solution is not particularly limited as long as it has a viscosity that allows stirring, but it is preferably 5 to 50% by mass. The viscosity of the solution may be appropriately set to a viscosity that does not cause any inconvenience in coating, and is preferably 0.3 to 200 Pa · s. The viscosity is a viscosity at room temperature, that is, 20 to 40 ° C.

<Production method>
The method for producing the polyimide solution of the present invention is not particularly limited. For example, the above-mentioned method 1 and the above-mentioned method 2 are used to produce the above-mentioned polyimide (I) -containing solution and the above-mentioned polyimide (II) -containing solution. , A method of mixing a solution containing polyimide (I) and a solution containing polyimide (II) can be mentioned.

[Polyimide composition]
The polyimide composition of the present invention is a composition containing the above-mentioned polyimide of the present invention.
The polyimide composition of the present invention may contain components other than the above-mentioned polyimide of the present invention. Such components include, for example, crosslinkable resins, thermosetting resins, inorganic fibers (eg, glass fibers, carbon divers, etc.), oxidation stabilizers, end sealants, fillers, silane coupling agents, photosensitizers, etc. Examples include photopolymerization initiators and sensitizers.

[Polyimide layer]
The polyimide layer of the present invention comprises the above-mentioned polyimide of the present invention or the above-mentioned polyimide composition of the present invention.

[Conducting film]
The conductive film of the present invention includes the above-mentioned polyimide layer of the present invention.
The conductive film is, for example, a wire rod layer having a high conductivity having a transmittance of 80% or more with respect to visible light formed on the polyimide layer.
Here, the polyimide layer is formed on, for example, a base material. The base material is, for example, glass, a polymer, an inorganic semiconductor material, an inorganic dielectric material, a laminate thereof, a composite material thereof, or the like. The base material constitutes components such as a touch sensor, a touch screen, a liquid crystal display (LCD), a flat panel display, an organic light emitting diode (OLED), and a solar cell.

The wire rod layer is, for example, a layer made of a wire rod arranged on the surface of the polyimide layer.
Further, the wire rod layer may be a conductive layer in which the wire rod is encapsulated in a resin. The conductive layer is formed, for example, by coating the wire while mixing it with the resin.
Examples of the wire rod constituting the wire rod layer include metals such as silver, gold, indium, tin, iron, cobalt, platinum, palladium, nickel, cobalt, titanium, copper, and alloys thereof; carbon material; and the like. , It is appropriately selected in consideration of conductivity and durability.
In order to exhibit the desired conductivity, the wire rods may be arranged linearly, or may form a mesh structure such as a mesh or a grid, if necessary.
In order to maintain good transparency, the wire is preferably fine nanowires. The average diameter of the wire is preferably 250 nm or less, more preferably 150 nm or less, and even more preferably 120 nm or less. On the other hand, the lower limit is not particularly limited, and is, for example, 10 nm or more.
In order to obtain good conductivity, the wire rod is preferably long, specifically, for example, 5 μm or more. The upper limit is not particularly limited, and is, for example, 100 μm or less.
When the wire rod is obtained by pattern formation or the like, it may be formed according to these conditions.
For the formation of the conductive layer, general coating methods such as dip coating, spray coating, knife edge coating, bar coating, Meyer rod coating, slot die, gravure, spin coating, plating, vapor deposition, printing, and transfer are appropriately selected. NS. Thermal or chemical fusion may be used to anchor the wire.

The conductive film of the present invention can, for example, impart electrical conductivity to an organic material that does not originally have conductivity, or impart antistatic properties when static electricity can be undesirable or dangerous. In the conductive film of the present invention, an optical film may be used in order to obtain various functions such as polarization, antireflection, phase shift, increase in brightness, and improvement in visibility.
In the polyimide layer of the present invention, a rigid fluorene skeleton is incorporated into the molecule to avoid excessive hybridization. As a result, it has a high affinity for the expandability of wire rods such as nanowires during a thermal response. By making the expandability of the polyimide layer close to the expandability of the wire rod layer, the polyimide layer exhibits good followability to the wire rod layer even when a load such as a temperature change is applied to the conductive film of the present invention. .. As a result, the conductive film of the present invention is reduced in distortion and deterioration, and the product life is improved.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The following physical property values were measured by the following method.
-The yellow index (YI) was measured using a color difference meter (SE7700 manufactured by Nippon Denshoku Kogyo Co., Ltd.).
-The glass transition point (Tg) was measured using a thermal analyzer (TMA-60 manufactured by Shimadzu Corporation).
The coefficient of thermal expansion (CTE) was measured using TMA-60 manufactured by Shimadzu Corporation by setting the measurement temperature range to 50 to 200 ° C. and the heating rate to 10 ° C./min.
-The surface resistivity was measured in an environment of 23 ° C. and a relative humidity of 50% using a 4-terminal 4-probe measuring device (Loresta GP manufactured by Mitsubishi Chemical Analytech).

A polyimide solution and a polyimide were produced as follows and then evaluated.

<Comparative example 1>
9,9-Bis (3,4-dicarboxyphenyl) fluorene diacid anhydride (BPAF) 19.68 g (43 mmol), isophorone diamine (IPDA) 7.34 g (43 mmol), oxalic anhydride 0.23 g, 0.59 g of triethylamine, 120 g of N-methylpyrrolidone (NMP), and 40 g of toluene were added to a three-necked flask, and the mixture was stirred at 40 ° C., and then the silicon bath temperature was raised to 180 ° C. to 200 r. p. m. The mixture was heated and stirred for 1 hour at a rotation speed of (round per minute). In order to remove 40 ml of the water-toluene fraction, the mixture was heated in a silicon bath and stirring was continued as it was. Then, the reaction was stopped after 3 hours and 30 minutes to obtain a solution (15% by mass) containing polyimide 1. Polyimide 1 corresponds to the above-mentioned polyimide (I).

The obtained solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating and drying furnace set in advance at 90 ° C. and dried for 150 minutes to try to form the coating film, but the film could not be formed.

<Comparative example 2>
Butane-1,2,3,4-tetracarboxylic acid dianhydride (BuDA) 5.15 g (26 mmol), 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1, 2.37 g (9 mmol) of 2-dicarboxylic acid dianhydride (MCHDA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2 "-norbornane-5,5", 6,6 " -Tetracarboxylic acid dianhydride (CpODA) 3.07 g (8 mmol), 9,9-bis (4-aminophenyl) fluorene (BAFL) 15.02 g (43 mmol), oxalic acid anhydride 0.23 g, triethylamine 0 Add .59 g, 120 g of N-methylpyrrolidone (NMP), and 40 g of toluene to a three-necked flask, stir at 40 ° C., raise the silicon bath temperature to 180 ° C., and rotate 200 rpm. The acid was heated and stirred for 1 hour. In order to remove 40 ml of water-toluene distillate, the mixture was heated in a silicon bath and stirred as it was. After 3 hours and 30 minutes, the reaction was stopped and the solution containing polyimide 2 (15). Mass%) was obtained.

The obtained solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating / drying furnace set in advance at 90 ° C. and dried for 150 minutes to obtain a film having a thickness of polyimide 2 of 50 μm (error ± 3 μm). YI, Tg and CTE were measured on the obtained film. The results are shown in Table 1 below.

<Example 1>
The polyimide solution of Comparative Example 1 and the polyimide solution of Comparative Example 2 are added to a three-necked flask and stirred at 40 ° C. for 60 minutes to obtain a polyimide solution (15% by mass) containing polyimide 1 and polyimide 2. rice field. The obtained solution is a mixture solution of polyimide 1 and polyimide 2. In the obtained solution, the content of polyimide 1 and the content of polyimide 2 with respect to the total amount of polyimide 1 and polyimide 2 are 41.4% by mass and 58.6% by mass, respectively.

The obtained polyimide solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating / drying furnace set in advance at 90 ° C. and dried for 150 minutes to obtain a film having a thickness of 50 μm (error ± 3 μm) of a mixture of polyimide 1 and polyimide 2. Obtained. In the obtained film (mixture), the content of polyimide 1 and the content of polyimide 2 are 41.4% by mass and 58.6% by mass, respectively. YI, Tg and CTE were measured on the obtained film. The results are shown in Table 1 below.

<Comparative example 3>
9.84 g (22 mmol) of 9,9-bis (3,4-dicarboxyphenyl) fluorendiic acid anhydride (BPAF), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) 4. 21 g (22 mmol), 9,9-bis (4-aminophenyl) fluorene (BAFL) 7.51 g (22 mmol), isophoronediamine (IPDA) 3.67 g (22 mmol), oxalic anhydride 0.23 g, triethylamine 0.59 g, 120 g of N-methylpyrrolidone (NMP), and 40 g of toluene were added to a three-necked flask, and the mixture was stirred at 40 ° C., and then the silicon bath temperature was raised to 180 ° C. to 200 r. p. m. It was heated and stirred for 1 hour at the rotation speed of. In order to remove 40 ml of the water-toluene fraction, the mixture was heated in a silicon bath and stirring was continued as it was. After 3 hours and 30 minutes, the reaction was stopped to obtain a solution (15% by mass) containing polyimide (polyimide 3) which is a copolymer of BPAF, CBDA, IPDA and BAFL.

The obtained solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating / drying furnace set in advance at 90 ° C. and dried for 150 minutes to obtain a film having a thickness of polyimide 3 of 50 μm (error ± 3 μm). YI, Tg and CTE were measured on the obtained film. The results are shown in Table 1 below.

<Comparative Example 4>
9,9-bis (3,4-dicarboxyphenyl) fluorene diacid anhydride (BPAF) 19.68 g (43 mmol), bis (aminomethyl) norbornane (NBDA) 5.65 g (36.6 mmol), 1 , 4-Diaminocyclohexane (CHDA) 0.73 g (6.4 mmol), oxalic anhydride 0.23 g, triethylamine 0.59 g, N-methylpyrrolidone (NMP) 120 g, toluene 40 g were added to a three-necked flask. After stirring at 40 ° C., the silicon bath temperature was raised to 180 ° C., and 200 r. p. m. The mixture was heated and stirred for 1 hour at a rotation speed of (round per minute). In order to remove 40 ml of the water-toluene fraction, the mixture was heated in a silicon bath and stirring was continued as it was. Then, the reaction was stopped after 3 hours and 30 minutes to obtain a solution (15% by mass) containing polyimide 1. Polyimide 1 corresponds to the above-mentioned polyimide (I).

The obtained solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating and drying furnace set in advance at 90 ° C. and dried for 150 minutes to try to form the coating film, but the film could not be formed.

<Comparative Example 5>
Butane-1,2,3,4-tetracarboxylic acid dianhydride (BuDA) 5.15 g (26 mmol), 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1, 2.37 g (9 mmol) of 2-dicarboxylic acid dianhydride (MCHDA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2 "-norbornane-5,5", 6,6 " -Tetracarboxylic acid dianhydride (CpODA) 3.07 g (8 mmol), 9,9-bis (3-methyl-4-aminophenyl) fluorene (BMAFL) 13.16 g (35 mmol), 2,7-diamino Add 1.57 g (8 mmol) of fluorene (2,7-FDA), 0.23 g of oxalic acid anhydride, 0.59 g of triethylamine, 120 g of N-methylpyrrolidone (NMP), and 40 g of toluene to a three-necked flask at 40 ° C. After stirring in, the temperature of the silicon bath was raised to 180 ° C., and the mixture was heated and stirred at a rotation speed of 200 rpm for 1 hour. The reaction was stopped after 3 hours and 30 minutes to obtain a solution containing polyimide 2 (15% by mass).

The obtained solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating / drying furnace set in advance at 90 ° C. and dried for 150 minutes to obtain a film having a thickness of polyimide 2 of 50 μm (error ± 3 μm). YI, Tg and CTE were measured on the obtained film. The results are shown in Table 1 below.

<Example 2>
The polyimide solution of Comparative Example 4 and the polyimide solution of Comparative Example 5 are added to a three-necked flask and stirred at 40 ° C. for 60 minutes to obtain a polyimide solution (15% by mass) containing polyimide 1 and polyimide 2. rice field. The obtained solution is a mixture solution of polyimide 1 and polyimide 2. In the obtained solution, the content of polyimide 1 and the content of polyimide 2 with respect to the total amount of polyimide 1 and polyimide 2 are 62.0% by mass and 38.0% by mass, respectively.

The obtained polyimide solution was applied to a 15 cm square glass plate using a doctor blade to form a coating film having a thickness of 400 μm. Next, the glass plate on which the coating film was formed was placed in a heating / drying furnace set in advance at 90 ° C. and dried for 150 minutes to obtain a film having a thickness of 50 μm (error ± 3 μm) of a mixture of polyimide 1 and polyimide 2. Obtained. In the obtained film (mixture), the content of polyimide 1 and the content of polyimide 2 are 62.0% by mass and 38.0% by mass, respectively. YI, Tg and CTE were measured on the obtained film. The results are shown in Table 1 below.

As can be seen from Table 1 above, YI was smaller in Example 1, which is a mixture of polyimide (I) and polyimide (II), as compared with Comparative Example 2 in which polyimide (II) was used alone. In addition, the heat resistance was excellent and the CTE was small. If Tg is 300 ° C. or higher, it can be said that the heat resistance is excellent. Further, the polyimide of Comparative Example 3 having a structure in which the polyimide (I) and the polyimide (II) were copolymerized had a large YI and CTE.

<Example 3>
A resin emulsion (HYTEC, SN-2002 manufactured by Toho Chemical Industry Co., Ltd.) containing a conductive metal oxide was applied to the film of Example 1 with a bar coater, and then dried with warm air at 100 ° C. or lower. In this way, the film (conductive film) of Example 3 having a conductive layer was obtained.
The surface resistivity and YI of the obtained film (conductive film) of Example 3 were measured. The surface resistivity of the film of Example 1 was also measured. The results are also shown in Table 2 below.

<Example 4>
A resin emulsion (HYTEC, SN-2002 manufactured by Toho Chemical Industry Co., Ltd.) containing a conductive metal oxide was applied to the film of Example 2 with a bar coater, and then dried with warm air at 100 ° C. or lower. In this way, the film (conductive film) of Example 4 having a conductive layer was obtained.
The surface resistivity and YI of the obtained film (conductive film) of Example 4 were measured. The surface resistivity of the film of Example 2 was also measured. The results are also shown in Table 2 below.

As shown in Table 2 above, the film of Examples 3 to 4 had a smaller surface resistivity value than the films of Examples 1 and 2, respectively, and the effect of conductivity was confirmed. YI was maintained or improved.

Claims (5)

It contains a polyimide (I) composed of a repeating unit represented by the following formula (1) and a polyimide (II) composed of a repeating unit represented by the following formula (2).
The content of the polyimide (I) is 5 to 95% by mass and the content of the polyimide (II) is 95 to 5% by mass with respect to the total amount of the polyimide (I) and the polyimide (II). Is a polyimide solution.

In formula (1), A ₁ represents a tetravalent aromatic group containing a fluorene skeleton. B ₁ represents a divalent, aliphatic or alicyclic group.
In formula (2), A ₂ represents a tetravalent aliphatic group or alicyclic group. B ₂ represents a divalent aromatic group containing a fluorene skeleton. It is a mixture of a polyimide (I) composed of a repeating unit represented by the following formula (1) and a polyimide (II) composed of a repeating unit represented by the following formula (2).
A polyimide having a polyimide (I) content of 5 to 95% by mass and a polyimide (II) content of 95 to 5% by mass.

In formula (1), A ₁ represents a tetravalent aromatic group containing a fluorene skeleton. B ₁ represents a divalent, aliphatic or alicyclic group.
In formula (2), A ₂ represents a tetravalent aliphatic group or alicyclic group. B ₂ represents a divalent aromatic group containing a fluorene skeleton. The polyimide according to claim 2, wherein the glass transition point is 280 ° C. or higher. The polyimide according to claim 2 or 3, wherein the yellow index is 3 or less. A conductive film comprising a polyimide layer made of the polyimide according to any one of claims 2 to 4.