JP3489068B2 - Cover coat ink and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover coat ink and a method for producing the same, more specifically, a cover coat ink using a polyimide resin known as a heat resistant resin, which is excellent in processability, heat resistance and low water absorption. The manufacturing method is related.

[0002]

2. Description of the Related Art Currently, flexible printed wiring boards (hereinafter referred to as FPC).
Is widely used in the field of electronic technology due to its excellent functions such as flexibility, but with the recent technological progress, FPC materials have also been required to have high characteristics and functions. .

By the way, the FPC has a basic structure in which a circuit pattern is formed on a flexible and thin base film and a cover lay or a cover coat is applied to the surface thereof. The coverlay or cover coat is an insulating film applied to the surface of the circuit pattern for the purpose of protecting and covering the circuit pattern formed on the base film,
The one in which a film-shaped cover base material is thermocompression bonded is called a cover lay, and the one in which an ink-type cover base material is applied by screen printing is called a cover coat. In general, the coverlay is responsible for electrical protection of the circuit pattern, mechanical protection as well as rust prevention, and improvement of flexibility of the FPC. On the other hand, the cover coat is used when mechanical strength is not required so much, and the electrical insulation and the mechanical protection ability are inferior to the cover lay, but the workability is excellent and the cost is low. Become. Therefore, the cover lay and the cover coat are properly used according to the purpose of use of the FPC.

As the material for the cover lay or cover coat, the same material as the base film is used. Usually, polyimide is used when heat resistance is required and polyester is used when heat resistance is not required. . In particular, the aromatic polyimide polymer is widely used as a base film or a cover substrate having excellent heat resistance for FPC due to its excellent heat resistance, mechanical strength, electrical characteristics, chemical resistance and the like.

However, in general, an aromatic polyimide polymer is insoluble or infusible, so that it is necessary to process the polyamic acid in the state of polyamic acid and thermally and chemically cyclize it to obtain a polyimide. It has poor properties and further processing is difficult. Further, for example, the water absorption rate of Apical AH (registered trademark; polyimide film, manufactured by Kaneka Kagaku Kogyo Co., Ltd.) when immersed in pure water at 20 ° C. for 24 hours is 2.5%, and the water absorption is high. I also have the problem. Therefore, the conventional aromatic polyimide polymer is often used in the form of a film, and due to its high water absorption, it has hardly been used as a solution-type cover coat ink.

On the other hand, the cover coat ink currently used is complicated because it uses a special high boiling point organic solvent, which requires solvent contamination or step curing for a long time. However, cover coat ink is desired to be used in various fields due to its processability,
With the recent technological advances, cover coat inks having further excellent workability and heat resistance are required.

[0007] Therefore, the present inventors have conducted intensive studies to use an aromatic polyimide polymer having excellent heat resistance as a cover coat ink in order to solve the above-mentioned conventional problems and meet the market demand. As a result, the inventors have come up with the present invention by contriving a cover coat ink having excellent heat resistance, low water absorption rate, and excellent processability, and a method for producing the same.

[0008]

The gist of the cover coat ink according to the present invention is that it is represented by the general formula (1):

[0009]

[Chemical 9]

(In the formula, Ar ₁ and Ar ₂ are divalent organic groups, Ar ₃
Represents a tetravalent organic group. Further, l and n represent a positive integer of 1 or more, and m represents 0 or a positive integer of 1 or more. ) It consists in the aromatic polyimide polymer represented by.

In such a cover coat ink, Ar ₁ in the general formula (1) is

[0012]

[Chemical 10]

It is a divalent organic group represented by:

Further, Ar ₂ in the general formula (1) is
1

[0015]

[Chemical 11]

It is at least one selected from the group of divalent organic groups represented by:

Further, Ar ₃ in the general formula (1) is
Two

[0018]

[Chemical 12]

It is at least one selected from the group of tetravalent organic groups represented by:

Next, the gist of the method for producing a cover coat ink according to the present invention is that represented by the general formula (2):

[0021]

[Chemical 13]

(Wherein Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. The aromatic polyamic acid polymer represented by (4) is formed into a film shape, a thread shape, or a lump shape for imidization, and then the obtained polyimide polymer is dissolved in an organic solvent which is a good solvent.

Another feature of the method for producing a cover coat ink according to the present invention is that it is represented by the general formula (2):
Four

[0024]

[Chemical 14]

(In the formula, Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. ), The aromatic polyamic acid polymer represented by the above) is imidized in a state of being dissolved in an organic solvent that dissolves the polyamic acid polymer to obtain a polyimide polymer solution, and then the solution is homogenized with the organic solvent. Is added to the poor solvent to be mixed with to obtain a filamentous or lumpy polyimide polymer, and further heated if necessary, and then the polyimide polymer is dissolved in an organic solvent that is a good solvent. .

Further, the gist of the method for producing a cover coat ink according to the present invention is that the formula (2)
Conversion 15

[0027]

[Chemical 15]

(In the formula, Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. ), An aromatic polyamic acid polymer represented by the following, in a state of being dissolved in an organic solvent that dissolves the polyamic acid polymer, by adding an appropriate amount of a catalyst and optionally a stoichiometric or more dehydrating agent Stir,
This is to raise the temperature of the solution to promote imidization, deposit a powdery polyimide polymer in the organic solvent, and then dissolve the polyimide polymer in an organic solvent that is a good solvent.

Further, the gist of the method for producing a cover coat ink according to the present invention is that the formula (2)
Conversion 16

[0030]

[Chemical 16]

(In the formula, Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. ), An aromatic polyamic acid polymer represented by the above) is imidized in a state of being dissolved in an organic solvent in which the polyamic acid polymer is dissolved to obtain a polyimide polymer solution, and the solution is an organic solvent that is a good solvent for It is to add a solvent and mix uniformly.

In addition, in the method for producing a cover coat ink, the good organic solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, triglyme, or diglyme.

[0033]

The cover coat ink of the present invention has the general formula (1)
Conversion 17

[0034]

[Chemical 17]

(In the formula, Ar ₁ and Ar ₂ are divalent organic groups, Ar ₃
Represents a tetravalent organic group. Further, l and n represent a positive integer of 1 or more, and m represents 0 or a positive integer of 1 or more. And an aromatic polyimide polymer represented by the formula (1), which is obtained as a solution of the aromatic polyimide represented by the general formula (1) in an organic solvent. The cover coat ink is a cover substrate having excellent workability that can easily form an insulating coating on an FPC by applying the cover coat ink on a circuit formed on a substrate by screen printing. Use of the aromatic polyimide polymer has enabled the use as a cover coat ink.

Since the aromatic polyimide polymer represented by the general formula (1) used in the present invention can be dissolved in an organic solvent, it can be formed by the general formula (2).

[0037]

[Chemical 18]

(In the formula, Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. ) Form an aromatic polyamic acid polymer in the form of a film, a thread, or a block and imidize it to obtain a polyimide polymer,
After that, the cover coat ink of the present invention can be easily produced by dissolving the polyimide polymer in an organic solvent to obtain a solution having an appropriate concentration (viscosity). At this time, if the film-shaped, thread-shaped, or lump-shaped polyimide polymer is pulverized with a mixer or the like to be in the form of powder or granules, it can be more easily dissolved.

When the aromatic polyamic acid polymer represented by the general formula (2) is imidized in a state of being dissolved in an organic solvent which dissolves the polyamic acid polymer, a polyimide polymer solution is obtained. To be Then, by throwing the solution into a poor solvent that is uniformly mixed with the organic solvent,
The organic solvent is transferred to the poor solvent to obtain a thread-shaped or block-shaped polyimide polymer. In addition, when imidization is not completed, imidization can be completed by further heating the obtained thread-shaped or lump-shaped polyimide polymer. Alternatively, in a state where the aromatic polyamic acid polymer represented by the general formula (2) is dissolved in an organic solvent that dissolves the polyamic acid polymer, an appropriate amount of catalyst and, if necessary, stoichiometry are added to the solution. The above dehydrating agent is added and stirred, and the imidization is completed when the temperature of the solution is raised to promote imidization, and depending on the organic solvent used for the reaction, in the organic solvent, the produced polyimide polymer is powdered. It begins to precipitate in the form of particles. The polyimide polymer thus obtained may be dissolved in an organic solvent that dissolves the polyimide polymer to obtain a solution having an appropriate concentration (viscosity), and used as a cover coat ink.

Further, the aromatic polyamic acid polymer represented by the general formula (2) is imidized in a state of being dissolved in an organic solvent which dissolves the polyamic acid polymer to obtain a polyimide polymer solution, By further adding an organic solvent to the solution and uniformly mixing the solution, a polyimide polymer solution having an appropriate concentration (viscosity) can be prepared and used as a cover coat ink.

As described above, the cover coat ink of the present invention can be made into a solution by dissolving the aromatic polyimide polymer represented by the general formula (1) in an organic solvent. Since it has a low water absorption, it can be suitably used as a solution-type cover coat ink. Further, the aromatic polyimide polymer represented by the general formula (1) can control the glass transition point between 200 ° C. and 350 ° C. depending on its composition, and is excellent in heat resistance. That is, the cover coat ink of the present invention can be a cover coat ink having excellent heat resistance, low water absorption rate, and excellent processability.

[0042]

EXAMPLES The cover coat ink of the present invention and the method for producing the same will be described below. First, the method for producing a polyamic acid polymer which is a precursor of the aromatic polyimide polymer used in the present invention will be explained.

The polyamic acid polymer is obtained by reacting an acid dianhydride component and a diamine component in an organic solvent, and is represented by the general formula (2) which is a precursor of the aromatic polyimide polymer used in the present invention. ) Conversion 19

[0044]

[Chemical 19]

(In the formula, Ar ₄ and Ar ₅ are divalent organic groups, Ar ₆
Represents a tetravalent organic group. Further, s and u represent a positive integer of 1 or more, and t represents 0 or a positive integer of 1 or more. In order to obtain the polyamic acid polymer represented by
In an atmosphere of an inert gas such as nitrogen, the general formula (3) is used.

[0046]

[Chemical 20]

The ester acid dianhydride represented by the formula (1) or the ester acid dianhydride represented by the general formula (4)

[0048]

[Chemical 21]

A mixture with an organic tetracarboxylic dianhydride represented by (hereinafter referred to as ester acid dianhydride) is dissolved or diffused in an organic solvent. By adding an aromatic diamine compound represented by the general formula (5) NH ₂ —Ar ₉ —NH ₂ (5) to this solution in the form of a solid or a solution with an organic solvent, or a slurry, and reacting it, A polyamic acid polymer solution represented by the general formula (2), which is a precursor of the cover coat ink body of the present invention, can be obtained.

In this reaction, it is not always necessary to add the aromatic diamine compound to the organic solvent solution of ester dianhydride or the like as described above, and the addition order is not particularly limited. For example, the ester dianhydride and the like may be added to the solution of the aromatic diamine compound in an organic solvent in the form of a solid, a solution in an organic solvent, or a slurry.

The reaction temperature at this time is -10 to 50 ° C, more preferably -5 to 20 ° C. Reaction time is 30 minutes to 3
It's time.

Next, in order to obtain the aromatic polyimide polymer used in the present invention from the precursor polyamic acid polymer solution, a method of thermally and / or chemically performing dehydration ring closure (imidization) is used. You can use it. Then, in order to produce the cover coat ink of the present invention, the obtained aromatic polyimide polymer may be dissolved in an organic solvent.

As an example of the method for producing the cover coat ink of the present invention, the polyamic acid polymer solution is formed into a film and imidized to obtain a film-shaped polyimide polymer, and then the film-shaped polyimide polymer is prepared. The cover coat ink of the present invention can be easily produced by dissolving a polyimide polymer in an organic solvent.

The method will be specifically described below.
In the method of thermal dehydration ring closure (imidization), a solution of the above polyamic acid polymer is cast or applied onto a support plate, an organic film such as PET, or a support such as a drum or an endless belt to form a film. Dry to obtain a self-supporting membrane. Drying is preferably performed at a temperature of 150 ° C. or lower for about 5 to 90 minutes. Then, this is heated and dried to be imidized to obtain a polyimide film made of the polyimide polymer of the present invention. The temperature during heating is 150 ℃ -350 ℃
The temperature in the range is preferable, and 300 to 350 ° C. is particularly preferable. There is no limitation on the rate of temperature increase during heating, but it is preferable to heat gradually so that the maximum temperature becomes the above temperature. The heating time varies depending on the film thickness and the maximum temperature, but is generally preferably in the range of 10 seconds to 5 minutes after the maximum temperature is reached.

The method of chemically dehydrating ring closure (imidization) is similar to the case of thermally dehydrating by adding a stoichiometric or more stoichiometric dehydrating agent and a catalytic amount of a tertiary amine to the solution of the polyamic acid polymer. It may be processed by the method. Also, a method in which a thermal method and a chemical method are used in combination may be used.

The polyimide film produced by these methods is
By dissolving in an organic solvent which is a good solvent for the polyimide film, the desired compound of the general formula (1)

[0057]

[Chemical formula 22]

(In the formula, Ar ₁ and Ar ₂ are divalent organic groups, Ar ₃
Represents a tetravalent organic group. Further, l and n represent a positive integer of 1 or more, and m represents 0 or a positive integer of 1 or more. Thus, the cover coat ink of the present invention represented by (4) can be obtained.

Further, the solubility can be improved by crushing the polyimide film with a mixer or the like and then dissolving it in the organic solvent, or by dissolving the polyimide film while crushing in the organic solvent. The polyimide polymer used in such a manufacturing method is not limited to a film-shaped polyimide polymer, and may be a thread-shaped or lump-shaped polyimide polymer.

Here, examples of the organic solvent which is a good solvent for the polyimide polymer for the cover coat ink include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-
Formamide solvents such as diethylformamide, N, N-dimethylacetamide, acetamide solvents such as N, N-diethylacetamide, pyrrolidone solvents such as N-methylpyrrolidone, and polar solvents such as ether solvents such as diglyme and triglyme. Can be mentioned. You may use these individually or as 2 or 3 or more types of mixed solvent. In particular, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, triglyme, and diglyme are preferable because of their excellent solubility in the polyimide polymer.

As another method for producing the cover coat ink according to the present invention, a method of imidizing the polyamic acid polymer in a solution state may be used.

The method will be described with reference to an example. To the polyamic acid polymer solution, an appropriate amount of a catalyst and a dehydrating agent having a stoichiometric amount or more are added and stirred, and the temperature of the solution is raised to promote imidization and stirred. However, if left unattended, powdery particles having completed imidization will be deposited. In addition, a dehydrating agent is not always necessary in such a reaction, and it is possible to promote imidization by utilizing, for example, that the boiling point of water is lower than that of the solvent. Therefore, the cover coat ink of the present invention can be obtained by drying this polyimide polymer and then adding and dissolving the above-mentioned organic solvent which is a good solvent for the polyimide polymer.

The temperature of the solution at this time is from 200 ° C. to 30 ° C.
The range of 0 ° C. is preferable, and 250 ° C. to 350 ° C. is particularly preferable. The stirring time is preferably in the range of 30 minutes to 3 hours.

In the above reaction, when imidization is carried out by stirring at room temperature for several hours, a solution of a polyimide polymer in a semi-imidized state is obtained. At this time, even if the temperature of the solution is raised, if the temperature is 200 ° C. or lower, imidization does not completely proceed, and a similar polyimide polymer solution in a semi-imidized state is obtained. Next, when the polyimide polymer solution is dropped into methanol, water, or the like, which is a poor solvent for the polyimide polymer, a thread-shaped or lump-shaped polyimide polymer is deposited. Therefore, a desired cover coat ink can be obtained by drying the deposited thread-shaped or lump-shaped polyimide polymer, further heating it to complete imidization, and dissolving it in the organic solvent which is the good solvent.

Further, the polyimide polymer in which the imidization is completed is crushed, or the deposited thread-shaped or lump-shaped polyimide polymer is dried and crushed and then heated to obtain a granular polyimide. A polymer may be obtained and the powdery or granular polyimide polymer may be dissolved in the solvent which is the good solvent. In this production method, the polyimide polymer in a semi-imidized state may be dissolved to obtain a cover coat ink without heating.

When the imidization is completed but the powder or granules do not deposit, the cover coat ink may be obtained after depositing the thread-shaped or lump-shaped polyimide polymer by the above-mentioned method. Further, to the polyimide polymer solution in which these imidizations are completed or in a semi-imidized state, the organic solvent which is the good solvent is added and uniformly mixed, so that the obtained polyimide polymer solution has an appropriate concentration ( The viscosity may be adjusted to obtain a cover coat ink.

The cover coat ink of the present invention can be produced by such a method, and various synthetic raw materials used in the present invention will be specifically described below.

As the ester dianhydride used in the present invention, ester dianhydrides having any structure can be used. Specific examples of the Ar ₇ group in the above general formula (3) include Ar ₇ group. ₇ turns into 23

[0069]

[Chemical formula 23]

Examples thereof include ester dianhydrides represented by: More specifically, from the balance of various characteristics,
Ar ₇ turns into 24

[0071]

[Chemical formula 24]

It is preferable to use as a main component.

As the organic tetracarboxylic dianhydride, organic tetracarboxylic dianhydrides having any structure can be used, but the Ar ₈ group in the general formula (4) is a tetravalent organic group. Yes, and specifically exemplifying this Ar ₈ group, Ar _8
8 groups are chemicals 25 and 26

[0074]

[Chemical 25]

[0075]

[Chemical formula 26]

An organic tetracarboxylic acid dianhydride represented by You may use these organic tetracarboxylic dianhydride individually or in combination of 2 or more types. More specifically, from the balance of various characteristics, Ar ₈ is

[0077]

[Chemical 27]

It is preferable to use at least one of the above as the main component.

Ar ₉ of the aromatic diamine compound represented by the general formula (5) may be essentially any divalent organic group, but specifically, Two
8

[0080]

[Chemical 28]

[0081]

[Chemical 29]

And the like. More specifically,

[0083]

[Chemical 30]

It is preferable to use at least one of the above as the main component.

The organic solvent used in the reaction for producing the polyamic acid polymer solution is, for example, dimethylsulfoxide or diethylsulfoxide, like the organic solvent which is a good solvent for the polyimide polymer for the cover coat ink. Sulfoxide solvents such as N, N-dimethylformamide, formamide solvents such as N, N-diethylformamide, N, N-dimethylacetamide, acetamide solvents such as N, N-diethylacetamide, N-methylpyrrolidone, etc. Examples thereof include polar solvents such as pyrrolidone solvents and ether solvents such as diglyme and triglyme.
These polar solvents are used alone or as a mixed solvent of two or more kinds. Further, these polar solvents may be mixed with a poor solvent for the polyamic acid polymer, such as acetone, methanol, ethanol, isopropanol, and benzenemethylcellosolve, or may be used as a mixed solvent with the poor solvent. .

As the tertiary amine used as a catalyst when chemically imidizing, pyridine, α-picoline, β-picoline, γ-picoline, trimethylamine,
Triethylamine, isoquinoline and the like are preferable. Further, as the dehydrating agent, for example, acetic anhydride is preferably used.

The cover coat ink according to the present invention thus obtained has the general formula (1):

[0088]

[Chemical 31]

(Wherein Ar ₁ and Ar ₂ are divalent organic groups, Ar ₃
Represents a tetravalent organic group. Further, l and n represent a positive integer of 1 or more, and m represents 0 or a positive integer of 1 or more. In the above formula, the number of repetitions l and m in the block unit is preferably 1 to 15. This is because when the number of repetitions l and m exceeds 15, the copolymerization ratio is biased and the effect of copolymerization becomes small. Further, there may be units having different values of l and m in one molecule of the polymer, but it is preferable that the values of l and m are constant.

The molecular weight of the aromatic polyimide polymer used in the present invention is not particularly limited, but when an insulating coating is applied on the FPC using the cover coating ink of the present invention, the aromatic polyimide polymer is coated on the FPC. In order to maintain the strength of the insulating film, the number average molecular weight is preferably 50,000 or more, more preferably 80,000 or more, particularly preferably 100,000 or more, further preferably 120,000 or more.

In many cases, it is difficult to directly measure the molecular weight of the polyimide polymer, but in such a case, it is estimated by an indirect method. For example, when the polyimide polymer is synthesized from polyamic acid, the value corresponding to the molecular weight of polyamic acid is the molecular weight of polyimide.

The aromatic polyimide polymer represented by the general formula (1) in the present invention thus obtained has a glass transition point between 200 ° C. and 350 ° C. depending on its composition, Water absorption of 0.3 after soaking for 24 hours
It has a low water absorption of ~ 0.5% and can be dissolved in an organic solvent. Therefore, the present invention makes it possible to use the aromatic polyimide polymer in the application as a cover coat ink which is a cover substrate having excellent processability, and the cover coat ink of the present invention has excellent heat resistance and low water absorption. It has excellent workability and shows a high rate.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the present invention is based on the knowledge of those skilled in the art without departing from the spirit of the present invention. The present invention can be implemented with various improvements, changes and modifications.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 In a 50 ml volumetric flask (1), 16.9 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as BAPP) and dimethylformamide (hereinafter referred to as D)
It is called MF. ) 25.4 g of each was taken and stirred with a stirrer to sufficiently dissolve. Further, in another 50 ml volumetric flask (2), 1.0 g of BAPP and 10.0 of DMF.
g was sampled and similarly dissolved sufficiently. On the other hand, in a 500 ml flask equipped with a stirrer, 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ', 4,4'-tetracarboxylic acid dianhydride (hereinafter referred to as ESD
It is called A. ) 11.9 g and 3,3 ', 4,4'-benzophenyl tetracarboxylic acid dianhydride (hereinafter referred to as BTDA) 6.4 g, and DMF 25.0.
g was added, and the contents in the flask were cooled with ice water and the atmosphere in the flask was replaced with nitrogen while stirring to dissolve them sufficiently.

Then, first, the BAPP solution in the 50 ml volumetric flask (1) obtained in advance was stirred at the above 50%.
Immediately charge into a 0 ml three neck flask. After allowing to stand for about 30 minutes with stirring, the BAPP solution in the 50 ml volumetric flask (2) was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask. After reaching the maximum viscosity, the addition of the BAPP solution was completed, and the mixture was left for 1 hour with stirring. Then, 78.2 g of DMF was added and stirred to obtain a polyamic acid polymer solution.

DMF18 was added to this polyamic acid polymer solution.
7.2 g, β-picoline 5.0 g, and acetic anhydride 8.0 g were added, and the mixture was stirred under ice cooling for 2 hours. Then, this solution was poured little by little into methanol stirred at high speed. Then, the filamentous polyimide polymer precipitated in methanol is dried at 150 ° C. for 30 minutes, then the filamentous polyimide polymer is crushed with a mixer, and further heated at 250 ° C. for 2 minutes to completely imidize. A polyimide powder was obtained. Thereafter, 20 g of this polyimide powder or granule was dissolved in 80 g of DMF to obtain a cover coat ink of the present invention.

The obtained cover coat ink was applied onto a supporting plate using a doctor blade and dried at 130 ° C. for 10 minutes to prepare a 25 μm-thick polyimide film, and its water absorption rate and dielectric constant were measured. For water absorption, see AS
Based on the TM D-570 standard, when the water absorption rate when immersed in pure water at 20 ° C. for 24 hours was measured, the water absorption rate was 0.4.
It was 3%. Regarding the dielectric constant, the dielectric constant (1 MHz) measured by the Q meter method was 2.89.

Example 2 40.0 g of BAPP and DM were added to a 50 ml volumetric flask (3).
F5 (1.5 g) was taken, and stirred using a stirrer to sufficiently dissolve it. In addition, add BA to another 50 ml volumetric flask (4).
1.0 g of PP and 10.0 g of DMF were taken and sufficiently dissolved. On the other hand, in a 500 ml three-necked flask equipped with a stirrer, ethylene glycol bistrimellitic acid dianhydride (hereinafter referred to as T
It is called MEG. ) 26.7 g, BTDA 11.3 g, and DMF 152.0 g were put, and the mixture was sufficiently dissolved while cooling with ice water and stirring while replacing the atmosphere in the flask with nitrogen.

50 ml volumetric flask previously obtained (3)
The BAPP solution therein was rapidly charged into the three-necked flask while stirring. After standing for about 30 minutes with stirring, the BAPP solution in the volumetric flask (4) was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask. After reaching the maximum viscosity, the addition of the BAPP solution was completed, and the mixture was left for 1 hour with stirring. afterwards,
124.5 g of DMF was added and stirred to obtain a polyamic acid polymer solution.

This polyamic acid polymer solution was applied onto a PET film and heated at 80 ° C. for 25 minutes, and then PET.
After peeling off from the film and fixing on a metal support, 150
C., 200.degree. C., 250.degree. C., and 300.degree. C. were each heated for 5 minutes for imidization to obtain a polyimide film. Further, this polyimide film was crushed with a mixer to obtain a polyimide powder. Then, this polyimide powder was dissolved in DMF in the same manner as in Example 1 to obtain a cover coat ink of the present invention.

A 25 μm-thick polyimide film was produced in the same manner as in Example 1 using the obtained cover coat ink, and its water absorption rate and dielectric constant were measured. The water absorption rate was 0.33% and the dielectric constant was It was 2.91.

From the above results, the film produced using the cover coat ink of the present invention has a dielectric constant that can be used as an insulating film, and has a water absorption rate of 0.3 to 0.5%.
And conventional aromatic polyimide polymers such as Apical A
The water absorption rate of H (registered trademark; manufactured by Kanegafuchi Chemical Industry Co., Ltd.) is 2.5%, but shows a low value, indicating that it is suitable as a cover coat ink.

[0104]

INDUSTRIAL APPLICABILITY As described above, the cover coat ink according to the present invention comprises the aromatic polyimide polymer represented by the general formula (1) and can be a cover base material excellent in heat resistance and processability. It also has the property of low water absorption. Conventionally, aromatic polyimide polymers have excellent heat resistance and other characteristics, but have a problem of poor processability, and although they are mostly used in a film form, there is a limit in their use. It is possible to realize both excellent heat resistance and processability of the aromatic polyimide polymer, and it is possible to provide a new mounting technique.

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-7-62097 (JP, A) JP-A-6-264035 (JP, A) JP-A-6-239998 (JP, A) JP-A-5- 105850 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 73/00-73/26 H05K 3/28

Claims (9)

(57) [Claims] 1. A compound represented by the general formula (1): (In the formula, Ar ₁ and Ar ₂ represent a divalent organic group, Ar ₃ represents a tetravalent organic group, l and n are positive integers of 1 or more, and m is 0 or a positive integer of 1 or more. Of the aromatic polyimide polymer represented by the formula (1). 2. Ar ₁ in the general formula (1) is represented by the following formula: The cover coat ink according to claim 1, which is a divalent organic group represented by: 3. Ar ₂ in the general formula (1) is represented by the following formula: The cover coat ink according to claim 1 or 2, which is at least one selected from the group of divalent organic groups represented by: 4. Ar ₃ in the general formula (1) is represented by the following formula: The cover coat ink according to any one of claims 1 to 3, which is at least one selected from the group of tetravalent organic groups represented by. 5. A compound represented by the general formula (2) 5: (In the formula, Ar ₄ and Ar ₅ represent a divalent organic group, Ar ₆ represents a tetravalent organic group, s and u are positive integers of 1 or more, t is 0 or a positive integer of 1 or more. Of the aromatic polyamic acid polymer represented by the formula (1) is formed into a film shape, a thread shape, or a lump shape for imidization, and then the obtained polyimide polymer is dissolved in an organic solvent that is a good solvent thereof. A method for producing a cover coat ink, comprising: 6. A compound represented by the general formula (2): (In the formula, Ar ₄ and Ar ₅ represent a divalent organic group, Ar ₆ represents a tetravalent organic group, s and u are positive integers of 1 or more, t is 0 or a positive integer of 1 or more. The aromatic polyamic acid polymer represented by the formula (1) is imidized in a state of being dissolved in an organic solvent in which the polyamic acid polymer is dissolved to obtain a polyimide polymer solution, and then the solution is added to the organic solvent. After being placed in a poor solvent that is uniformly mixed with a solvent to obtain a filamentous or lumpy polyimide polymer, further heating is performed if necessary, and then the polyimide polymer is dissolved in an organic solvent that is a good solvent thereof. A method for producing a cover coat ink, comprising: 7. A compound represented by the general formula (2): (In the formula, Ar ₄ and Ar ₅ represent a divalent organic group, Ar ₆ represents a tetravalent organic group, s and u are positive integers of 1 or more, t is 0 or a positive integer of 1 or more. The aromatic polyamic acid polymer represented by the formula (1) is imidized in a state of being dissolved in an organic solvent in which the polyamic acid polymer is dissolved to precipitate a granular polyimide polymer in the organic solvent. And then dissolving the polyimide polymer in an organic solvent that is a good solvent for the polyimide polymer. 8. A compound represented by the general formula (2): (In the formula, Ar ₄ and Ar ₅ represent a divalent organic group, Ar ₆ represents a tetravalent organic group, s and u are positive integers of 1 or more, t is 0 or a positive integer of 1 or more. The aromatic polyamic acid polymer represented by the formula (1) is imidized in a state of being dissolved in an organic solvent that dissolves the polyamic acid polymer to obtain a polyimide polymer solution, and the solution is further a good solvent thereof. A method for producing a cover coat ink, which comprises adding the organic solvent described above and mixing them uniformly. 9. The cover coat according to claim 5, wherein the good organic solvent is dimethylformamide, dimethylacetamide, N-methylpyrrolidone, triglyme, or diglyme. Ink manufacturing method.