JPS646672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paste composition comprising a polyamic acid polymer as a binder component and finely divided polyimide as a filler component.

Polyimide resins are widely used in various applications as resins with excellent heat resistance, chemical resistance, electrical properties, and toughness.

Polyimide resin with these excellent properties is formed into a film by casting a solution of its precursor, polyamic acid, onto the covered surface. However, if screen printing is performed to form a film along a pattern of a fixed shape, the polyamic acid solution cannot form an accurate pattern after printing due to non-thixotropic properties such as dripping and flow.

Another method for forming a patterned film is, for example, by applying a polyamic acid solution to the entire surface to be coated,
After drying and curing, there is a method of etching out unnecessary parts to form a patterned film, or a method of cutting the polyimide film into patterns in advance and pasting them together with an adhesive, etc. However, these methods mentioned above may be used. However, this method requires an unnecessarily complicated process, and therefore, overall, it is inferior to the screen printing method as a method for forming a patterned film.

Screen printing is the best method for forming a desired pattern accurately and easily. As a fluid capable of screen printing, it is essential that the solution has thixotropic flow characteristics.

One object of this invention is to obtain a polyamic acid solution having thixotropic properties that can be screen printed, and another object is to obtain a polyamic acid solution having thixotropic properties that can be screen printed.
The object of the present invention is to obtain a polyamic acid solution which can adhere well to glass, metal, metal oxide, etc., on which a patterned polyimide film is to be formed by screen printing. Furthermore, another object of the present invention is that the patterned polyimide film that is finally formed is free from pinholes and retains its original excellent properties such as heat resistance, chemical resistance, electrical properties, toughness, and moisture resistance. The object of the present invention is to obtain the above-mentioned polyamic acid solution.

As a result of intensive studies to achieve the above object, the inventors obtained a solution of polyamic acid modified with a specific amount of diaminosiloxane, and added powder of polyimide particles having specific particles and properties to the solution. This paste-like composition has thixotropic properties that allow it to be screen-printed, and it can be screen-printed onto glass, metals, metal oxides, etc. and finally imidized. The present invention has been made based on the discovery that when coated, it provides a pinhole-free coating that adheres well to the substrate and has excellent heat resistance, chemical resistance, electrical properties, toughness, moisture resistance, etc. This is what we have come to complete.

That is, this invention provides aromatic tetracarboxylic acid in a solution of polyamic acid modified with diaminosiloxane such that the silicon content is in the range of 1 to 4 mol% based on the total amount of diamino compounds and is 0.5% by weight or less. Maximum particle size that is infusible to heat and insoluble in organic solvents (hereinafter simply referred to as infusible and insoluble) produced by heating polymerization of acid dianhydride and aromatic polyisocyanate in an organic solvent at 100 to 160°C but
A powder of the above polyimide particles obtained by direct filtration or centrifugation from a slurry of spherical porous polyimide particles with an average particle size of 40 μm or less and an average particle diameter of 10 μm or less, and washing with the same organic solvent used during polymerization is blended. The present invention relates to a paste composition.

As described above, the first significance of this invention lies in the dispersion of a filler in order to impart thixotropic performance to a solution of polyamic acid, and in the use of a specific particulate polyimide as the filler component. . Generally, fine powder is used to impart thixotropic fluidity to varnishes, etc.
The use of inorganic powders such as SiO ₂ (trade name Aerosil) is well known. However, in this case, the amount of resin decreases accordingly, which is not preferable for applications that take full advantage of the properties of the resin, and free ions such as sodium, potassium, and halogen, and This makes it unsuitable for semiconductor applications.

In contrast, in the present invention, by using the finely divided polyimide as a filler component, the above-mentioned drawbacks when using inorganic powder are completely avoided, and the paste composition is applicable to semiconductors and other special uses. You can get things. This paste composition is characterized in that the polyimide particles are infusible and insoluble and have a specific particle size of a maximum particle size of 40 μm or less and an average particle size of 10 μm or less.
It has good thixotropic properties that can be screen printed.

Moreover, the above-mentioned polyimide particles are characterized by their spherical porosity, and this property particularly allows them to have very good adhesion or affinity with polyamic acid polymers, making it possible to form a film from this type of paste composition. It effectively prevents pinholes from forming and also gives good results to the surface appearance. That is, for example, with conventionally known polyimide powder, which is produced by precipitating polyamic acid from a general polyamic acid solution or slurry, heating it to ring-close it to imidize it, and then pulverizing it, it is difficult to obtain fine particles, and it is difficult to obtain spherical porosity. Therefore, it may lack dispersibility and adhesion with the polyamic acid polymer, which may cause minute pinholes in the film or impair the surface appearance. In contrast, the polyimide particles according to the present invention do not have such drawbacks, and therefore, when applied as a semiconductor material, good results are obtained in terms of electrical properties, moisture resistance, chemical resistance, etc., and the commercial value is also improved. do.

The second significance of this invention is that the polyamic acid polymer used as a binder is siloxane-modified, so it can be applied to surfaces such as glass, metals, and metal oxides to which conventional siloxane-modified polyamic acid polymers could not adhere. The key is to have good adhesion. The amount of siloxane modification suitable for this purpose is 1 to 4 mol%, preferably 3 to 3.5 mol%, of the total amount of diamino compounds that are the monomer components of the polyamic acid polymer, and the amount is 1 to 4 mol%, preferably 3 to 3.5 mol%. The silicon content must be 0.5% by weight or less. Excessive amount of siloxane modification inevitably leads to the introduction of excess siloxane units into the polymer skeleton, which deteriorates polyimide's original excellent heat resistance, chemical resistance,
This causes a decline in various properties such as moisture resistance, electrical properties, and toughness. Therefore, it is important to carry out the necessary minimum siloxane modification.
By using the solution of siloxane-modified polyamic acid as a binder, the film after printing the paste composition can be made to adhere sufficiently firmly to glass, metals, metal oxides, and the like.

The polyamic acid used in this invention has the following general formula (1); (R ₁ is a divalent organic group, R' is a monovalent organic group, and n is an integer from 1 to 1000.) Diaminosiloxane represented by the following general formula
(2); H ₂ N―R ₂ ―NH ₂ …(2) (R ₂ is a divalent organic group that does not contain a silicon atom.) A diamine that does not contain a silicon atom in its molecule and , the following general formula (3); (Ar is a tetravalent organic group.) It is a siloxane-modified polyimide precursor obtained by polymerization reaction with an aromatic tetracarboxylic dianhydride represented by and the silicon content contained in the final reactant is in the range of 1 to 4 mol% of
It is characterized by being 0.5% by weight or less.

In the present invention, in the diaminosiloxane represented by the general formula (1), the two R ₁ and each R' in the formula may be the same or different, and a wide variety of conventionally known diaminosiloxanes are included. Typical examples are as follows.

In this invention, diamines that do not contain a silicon atom in the molecule represented by general formula (2) (hereinafter simply referred to as silicon-free diamines) include aromatic diamines, aliphatic diamines, and alicyclic diamines, and include R ₂ therein may be the same as or different from R ₁ in the general formula (1). Particularly suitable are
Representative examples of aromatic diamines include:
For example, metaphenylenediamine, paraphenylenediamine, 4,4'-diaminophenylmethane, 4,4'-diaminodiphenyl ether, 2.
2'-bis(4-aminophenyl)propane, 3.
3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, benzidine, benzidine-
3,3'-dicarboxylic acid, benzidine-3,3'-disulfonic acid, benzidine-3-monocarboxylic acid,
Benzidine-3-monosulfonic acid, 3,3'-dimethoxy-benzidine, para-bis(4-aminophenoxy)benzene, meta-bis(4-aminophenoxy)benzene, metaxylylenediamine,
Examples include paraxylylene diamine.

In the present invention, typical examples of the aromatic tetracarboxylic dianhydride to be polymerized and reacted with the diamino compound consisting of the above-mentioned diaminosiloxane and silicon-free diamine are as follows. That is, pyromellitic dianhydride, 3.
3', 4, 4'-benzophenonetetracarboxylic dianhydride, 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride, 2, 3, 3', 4'-biphenyl tetra Carboxylic dianhydride, 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, 1, 2, 5,
6-Naphthalenetetracarboxylic dianhydride, 1.
4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride , 3・4・9・
10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 2,2'-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1 ’-screw (2.3
-Dicarboxyphenyl)ethane dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 2,3,6,7-anthracentellacarboxylic dianhydride, 1,2,7, Examples include 8-phenanthrenetetracarboxylic dianhydride.

In the present invention, it is preferable that the above diaminosiloxane and silicon-free diamine are polymerized simultaneously with an aromatic tetracarboxylic dianhydride. This is because, for example, in a method in which both diamino compounds are polymerized separately and then mixed, variations in adhesiveness, moisture resistance, etc. tend to occur.

As mentioned above, the diaminosiloxane used at this time is 1 to 10% of the total amount of the diamino compound.
4 mol %, preferably 3 to 3.5 mol %, so that the silicon atom content in the final reactant polyimide precursor is less than 0.5 mol %. If none of these quantitative relationships are satisfied, it will be difficult to achieve both adhesion and various other properties such as heat resistance, electrical properties, and moisture resistance.
The ratio of the diamine compound consisting of diaminosiloxane and silicon-free diamine to the aromatic tetracarboxylic dianhydride is usually equimolar, but one may be slightly increased if necessary.

The polymerization reaction may be carried out according to a conventionally known method, and is generally carried out in the presence of an organic solvent in a nitrogen gas stream while limiting the temperature to usually 60°C or lower, preferably 30°C or lower, in consideration of polymerization heat generation. The reaction may be carried out until a high degree of polymerization is obtained. This degree of polymerization can be easily detected by examining the intrinsic viscosity [η] of the reactant.

Examples of organic solvents include N-methyl-2-
Pyrrolidone, N-N'-dimethylacetamide,
Highly polar basic solvents such as N·N'-dimethylformamide, N·N'-dimethylsulfoxide, hexamethylphosphoramide, etc. are used. All of these types of solvents are highly hygroscopic, and absorbed water causes a decrease in molecular weight during polymerization and storage stability, so it is recommended to thoroughly dehydrate with a dehydrating agent before use. . In addition, general-purpose solvents such as glycol esters such as toluene, xylene, benzonitrile, benzene, phenol, and cellosolve can also be used together with these solvents. However, the amount used should be within a range that does not reduce the solubility of the polyamic acid produced.

The siloxane-modified polyamic acid obtained in this way has the following general formula (4):
It has a polymer structure in which the bonding units of silicon-free diamine and diaminosiloxane added to aromatic tetracarboxylic dianhydride via amide bonds are random, and there are very few siloxane bonds in the molecular chain of polyamic acid. It is characterized by having an integrated structure.

(R ₁ , R ₂ , R', n and Ar are as described above,
Both l and m are positive integers, m/l+m=
0.01-0.04).

In this invention, a paste composition is prepared by adding polyimide particles having a specific particle size and properties as a filler component to the above polyamic acid solution, but the concentration of the above polyamic acid solution is generally 5 to 40 % by weight, preferably 10-30% by weight
It is better to be at a certain level.

The polyimide particles used as a filler component are
It is infusible and insoluble, and is spherical and porous with a maximum particle size of 40 μm or less and an average particle size of 10 μm or less,
By using such specific particle diameters and properties, it is possible to impart thixotropic performance to the paste composition, and it is also possible to form a polyimide film with no pinholes and a good surface appearance.

Such polyimide particles can be obtained by heating polymerization of aromatic tetracarboxylic dianhydride and aromatic polyisocyanate in an organic solvent. The polymerization temperature at this time is 100 to 160℃, preferably
It should be 110-150℃. When the temperature is lower than 100°C, the particle size of the polyimide particles that precipitate out in the form of a slurry becomes very small, making it difficult to directly filter or centrifuge the particles from the produced slurry. In this case, the slurry containing the above particles must be poured into acetone, etc., the resulting precipitate must be filtered out, and then pulverized to form polyimide powder, but this powder is difficult to form into fine particles or spherical and porous. . In addition, the polymerization temperature is 60
If the temperature is lower than .degree. C., the polyimide particle diameter becomes too small, which makes stirring difficult and makes it impossible to obtain a sufficient reaction rate. On the other hand, 160
If it exceeds .degree. C., the particle size of the polyimide becomes too large, which is inappropriate.

The polyimide particles obtained by setting the polymerization temperature to 100 to 160°C are fine particles with a maximum particle size of 40 μm or less, an average particle size of 10 μm or less, and usually 1 to 10 μm. It has a porous structure, that is, it has spherical porous properties, and this particle size and property are inherited even after direct filtration or centrifugation from the slurry produced after polymerization.

The aromatic tetracarboxylic dianhydride and the aromatic polyisocyanate used to obtain such polyimide particles are heated to a temperature of up to 500°C, so that the polyimide produced by the polymerization reaction of both becomes infusible and insoluble. Any material can be selected and used as long as it does not melt even when heated, decomposes without melting when heated further, and does not dissolve in various solvents such as general purpose solvents as well as polar solvents. Such a selection can be easily made by a person skilled in the art based on chemical common sense regarding infusible and insoluble polyimide resins. It goes without saying that whether or not it is possible to provide an infusible and insoluble polyimide may depend on the type of aromatic tetracarboxylic dianhydride or aromatic polyisocyanate, or may depend on the combination of the two. Sometimes it is determined by the For example, thermoplastic and in some cases organic Since it provides a solvent-soluble polyimide, it must be excluded in this invention.

Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3, 3',
4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride Anhydride, 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, 1, 2, 5, 6-
Naphthalenetetracarboxylic dianhydride, 1.4.
5,8-naphthalenetetracarboxylic dianhydride,
2,2'-bis(3,4-dicarboxyphenyl)
Propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 2.
2'-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1'-bis(2,3-dicarboxyphenyl)ethane dianhydride, benzene-1.
2,3,4-tetracarboxylic dianhydride, 2.
Examples include 3,6,7-anthracenetetracarboxylic dianhydride and 1,2,7,8-phenanthrenetetracarboxylic dianhydride.

Specific examples of aromatic polyisocyanates include paraphenylene diisocyanate,
Metaphenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, diphenylpropane-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, diphenylsulfone- 3,3'-diisocyanate, diphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate,
Examples include 2,4-tolylene diisocyanate and 2,5-tolylene diisocyanate. Also, the following general formula synthesized from diphenylmethane-4,4'-diisocyanate, tolylene diisocyanate, xylylene diisocyanate, etc.; A polyisocyanate containing an isocyanurate ring represented by the following general formula; Examples include poly(methylenephenylene)polyisocyanates represented by, for example, triphenylmethane-triisocyanate.

One type or a combination of two or more of the above-mentioned aromatic tetracarboxylic dianhydrides and aromatic polyisocyanates may be used, and it is preferred that the proportions of both components used be equimolar. Of course, there is no problem even if one of the components is in an excessive amount as long as it is within a small range.

A catalyst such as a tertiary amine can be used in the polymerization reaction of aromatic tetracarboxylic dianhydride and aromatic polyisocyanate to increase the reaction rate. Specific examples include triethylamine, tri-n-butylamine, 1,8-diazabicyclo(5.4.0)undecene-7 and its acid form, dimethylbutylamine, dimethylaminotoluidyl, and the like. The amount used is usually 0.05 to 1 mole of aromatic tetracarboxylic dianhydride.
It may be about 10 mol%.

Examples of organic solvents used in the polymerization reaction include N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide,
Mention may be made of phenols such as hexamethylene phosphamide, cresol, phenol and xylenol. Further, in some cases, general-purpose solvents such as hexane, benzene, toluene, and xylene can be used together with these solvents. The amount of organic solvent to be used is such that the solid content concentration of aromatic tetracarboxylic dianhydride and aromatic polyisocyanate as main components is 5 to 80% by weight, preferably 10 to 30% by weight. It is better. If the solid concentration is too low, the reaction rate will be slow, and if it is too high, an exothermic reaction will easily cause problems in reaction control during scale-up.

The polymerization reaction is carried out by adding aromatic tetracarboxylic dianhydride, aromatic polyisocyanate, and a catalyst if necessary to an organic solvent, and heating and stirring the mixture at the predetermined temperature. In a system where each component is dissolved in an organic solvent, the solution initially becomes a homogeneous solution, and as the polymerization reaction progresses, the solution viscosity increases slightly while generating carbon dioxide gas, and then polyimide particles precipitate out in the form of a slurry. come. Thereafter, heating and stirring are continued to improve the reaction rate.

The slurry of spherical porous polyimide particles, which are infusible and insoluble and have a maximum particle size of 40 μm or less and an average particle size of 10 μm or less, is obtained by direct filtration or centrifugation from this slurry as described above. After polyimide particles having a specific particle size and properties are taken out as a powder, they are added and blended into the polyamic acid solution.

For the above-mentioned filtration or centrifugation, a general suction filter or centrifugal separator is used. The separated polyimide particles are washed with a solvent capable of dissolving them, i.e., the same organic solvent used during polymerization, to remove the terminal reactants and low molecular weight polymers that adhere to the particle surface, and then washed with a low boiling point solvent such as acetone or methanol. will be re-washed. Thereafter, by heating and drying at a predetermined temperature, a polyimide powder having the above particle size and properties is obtained. Here, the step of removing end reactants and low molecular weight polymers adhering to the particle surface using the organic solvent described above is an important step in maintaining the particle size and properties, but in addition, the step of removing end reactants and low molecular weight polymers adhering to the particle surface is If low molecular weight polymers remain, these components will thermally decompose and become impurities during the final imidization stage of the paste composition, causing problems such as adversely affecting semiconductor devices and causing discoloration. However, it is a particularly important process in that it can completely eliminate such problems.

In addition, the average particle diameter of polyimide particles described in this specification means the weight average particle diameter (), and for example, the weight can be measured using an SKN-500 light transmission particle size distribution analyzer manufactured by Seishin Enterprise Co., Ltd. The cumulative distribution is determined, and the particle size at 50% by weight of the distribution can be calculated as the average particle size.

In this invention, the amount of polyimide particles used as a filler component is usually 30 to 300 parts by weight, preferably 50 to 200 parts by weight, per 100 parts by weight of the polyamic acid polymer. If this amount is too small, sufficient thixotropic properties cannot be imparted, whereas if this amount is too large, the paste composition becomes dry and does not spread during screen printing, making it unsuitable for printing.

In this invention, the above-mentioned filler component is preferably dispersed into the polyamic acid solution by using a mixer or a roll. In particular, the dispersion method using three rolls is very effective, and it is usually good to pass through the material 5 to 10 times at high speed. of course,
Dispersion methods other than those described above are not particularly limited as long as the filler is uniformly dispersed without agglomeration.

The paste composition of the present invention produced as described above has the first characteristic that it is possible to form a thicker film than a conventional film formed only from a polyamic acid solution. That is, in general, when polyamic acid is thermally converted to polyimide, ring closure and dehydration reactions occur, but due to this condensed water, when forming a thick film, polymer precipitation occurs as well as imidization, resulting in foaming and powdering. A transparent and tough polyimide film cannot be obtained. However, in the above paste composition of the present invention, the effective thickness is determined by the filler component, so the thickness of the polyamic acid, which is the binder that undergoes ring closure and dehydration reactions, is not substantially different from that in the case of forming a thin film. Therefore, problems such as foaming and powdering do not occur. in this way,
The paste composition of the present invention is characterized in that it can be thickened.

The second feature of the paste composition of the present invention is that even when a thick film is formed as described above, its good thixotropic properties do not cause defects such as dripping or running, and therefore, pattern formation such as screen printing is possible. This means that it is easy. The third feature is that after the patterned film is formed, it is dehydrated and cyclized by high-temperature heat treatment, which allows it to adhere well to substrates such as metals, glass, and metal oxides, as shown in the following general formula. It can be converted into polyimide as shown in (5), and this polyimide film has no pinholes and has good heat resistance, chemical resistance,
It has good mechanical properties, electrical insulation properties, moisture resistance properties, etc., and also has a good appearance.

(R ₁ , R ₂ .R', Ar, n, l and m are as described above).

The paste composition having the above characteristics is
In addition to being used in the heat-resistant field of marking inks, such as printing inks for electrical and electronic equipment exposed to high temperatures, laminate marking inks, and insulating inks for printed circuit boards, they are also used as adhesives and plastics in the automobile field. It is used for various purposes such as solders, dry transformers, and shielding materials for preventing soft errors in VLSIs.

The paste composition of the present invention is particularly useful for semiconductor devices. In this case, this composition is applied to the surface of the element and then heated to undergo ring closure to form a polyimide film. The semiconductor device coated in this manner takes advantage of the above-mentioned good properties of the paste composition, and exhibits particularly good moisture resistance and excellent performance in which penetration of alpha rays is suppressed.

Examples of the present invention will be described below. In the following, the intrinsic viscosity [η] will be used as a parameter indicating the degree of polymerization (molecular weight) of polyamic acid, but this intrinsic viscosity was determined using N-methyl-2-pyrrolidone as a solvent and at a measurement temperature of 30 ± 0.01°C.
(in a constant temperature bath) according to the following formula.

[η]=ln(t/to)/C t; Falling time of polymer solution measured with Ubbelohde viscometer to; Falling time of solvent measured in the same manner as above c; Polyamic acid (polymer) concentration (0.5% by weight Example 1 <Siloxane-modified polyamic acid solution> A 500 ml flask equipped with a stirring device, a cooling tube, a thermometer, and a nitrogen purging device was fixed on a water bath.
280.90 g of purified N-methyl-2-pyrrolidone, which had been dried over phosphorus pentoxide for a day and night and then distilled under reduced pressure, was added to the flask, and nitrogen was flushed into the flask. Then 1 ml
bis(3-aminopropyl)tetramethyldisiloxane; _H2N ( _-CH2
)― ₃ Si(CH ₃ ) ₂ ―O―Si(CH ₃ ) ₂ (―CH ₂ )― ₃ NH ₂ 0.87
g (0.0035 mol), then 19.3 g (0.0965 mol) of 4,4′-diaminodiphenyl ether,
Stir until dissolved. Next 3・3′・4・4′―
Biphenyltetracarboxylic dianhydride 29.4g
(0.1 mol) was added gradually. The reaction system was stirred while maintaining the temperature below 30°C until a clear viscous solution was obtained.

The siloxane-modified polyamic acid thus obtained has an intrinsic viscosity of 1.67 and a silicon content of
It was 0.397% by weight. This solution has a solids concentration of
At 15.0% by weight, the solution viscosity was 750 poise.

<Polyimide particles> 29.4 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 223 g of N-methyl-2-pyrrolidone (hereinafter referred to as NMP)
was heated and stirred at 130°C to form a homogeneous solution. To this was added 26.4 g (0.1 mol) of 3,3'-dimethylphenyl-4,4'-diisocyanate, and further N.
When 0.2 g of N'-dimethyl-P-toluidine and 20 g of xylene were added and stirred for 10 to 12 minutes at 130±2° C., polyimide particles precipitated out in the form of a slurry. Thereafter, the polymerization reaction was further continued at the same temperature for 5 hours.

After the reaction, the polyimide particles were cooled and filtered, washed three times with NMP, and finally washed with acetone twice.
Washed twice. After washing, the powder was heated and dried at 250° C. for 3 hours to obtain 46.0 g (yield: 97.0% by weight) of spherical porous polyimide powder.

This polyimide powder had a maximum particle diameter of 20 μm and an average particle diameter of 4.5 μm, and carbonyl absorption based on imide groups was observed at 1720 cm ⁻¹ and 1780 cm ⁻¹ in the infrared absorption spectrum (by KBr method). Furthermore, this polyimide powder did not melt even when heated to 500°C, and was also insoluble in various solvents other than NMP. For reference, the magnification is shown in Figure 1.
A scanning electron micrograph of polyimide powder is shown at 5000x magnification. This photograph shows that the powder is spherical and porous.

<Paste composition> Solution of the above siloxane-modified polyamic acid 100
g and 30 g of the above polyimide powder were passed through three rolls at high speed rotation five times to disperse them. The resulting paste was thixotropic and had a viscosity of 9000 poise when measured at 10 rpm using a BH type viscometer; rotor No. 7 (the same applies hereinafter), and 5000 poise when measured at 2 rpm. This paste composition
It was diluted with cellosolve until it showed 2600 poise at 10 rpm and 2300 poise at 2 rpm.

When the paste composition thus produced was screen printed and marked on a glass bottle, the printing was smeared without dripping or running. 30 at 150℃
After curing for 6 hours at 250° C. for 6 hours, a cured print could be formed and firmly adhered to the glass bottle. No pinholes were observed in this print.

For reference, a paste composition prepared by adding 3 g of the above polyimide powder to 100 g of a solution of siloxane-modified polyamic acid did not exhibit thixotropic fluidity, and when screen printed,
Dropping and flow occurred, and the cured film showed a foaming phenomenon due to imide ring closure. Similarly, in a paste composition to which 50 g of polyimide powder was added, the thixotropic properties became too strong, and the paste became dry and did not spread during screen printing, resulting in unsuitable printability.

Example 2 <Siloxane-modified polyamic acid solution> Example 1 except that 281.46 g of purified NΓN'-dimethylacetamide was used as the solvent and 0.97 g (0.0035 mol) of bis(4-aminobutyl)tetramethyldisiloxane was used as the diaminosiloxane.
A 15% by weight solution of siloxane-modified polyamic acid was prepared in the same manner as above.

The intrinsic viscosity of the siloxane-modified polyamic acid at this time was 1.81, and the silicon content was 0.396% by weight. By heating this solution at 50±5° C. for 38 hours, the molecular weight was reduced to an intrinsic viscosity of 0.55. The viscosity of this solution was 142 poise.

<Polyimide particles> Dissolve 32.2 g (0.1 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride in 232 g of NMP, and dissolve 3,3'-dimethyldiphenyl while stirring at 130°C. -4,4'-diisocyanate 26.4
(0.1 mol), 0.2 g of N--N'-dimethyl-P-toluidine and 20 g of xylene were added. 130±2℃
When the mixture was heated and stirred for 10 to 15 minutes, polyimide particles precipitated out in the form of a slurry while vigorously generating carbon dioxide gas. Thereafter, the polymerization reaction was further continued at the same temperature for 5 hours.

Hereinafter, by the same operation as in Example 1, 45.0g
A spherical porous polyimide powder (yield: 90.4% by weight) was obtained. The maximum particle size of this powder was 12 μm and the average particle size was 2.1 μm, and carbonyl absorption based on imide groups was observed in the infrared absorption spectrum. Moreover, it was an infusible and insoluble powder similar to that of Example 1. For reference, the magnification is shown in Figure 2.
A scanning electron micrograph of polyimide powder magnified 20,000 times is shown.

<Paste composition> Solution of the above siloxane-modified polyamic acid 100
g and 20.0 g of the above polyimide powder were passed through three rolls five times at high speed rotation to obtain a thixotropic paste composition. The solution viscosity of this paste composition was 2400 poise at 10 rpm and 2800 poise at 2 rpm, showing good printability as in Example 1, and the cured film firmly adhered to the glass bottle.

Furthermore, when an LSI packaged in ceramic was similarly marked by screen printing, it also showed good printability and strong adhesion with no pinholes after curing.

[Brief explanation of drawings]

1 and 2 are scanning electron micrographs of polyimide particles as a filler component used in the paste composition of the present invention, respectively.

Claims (1)

[Claims] 1 Aromatic tetracarboxylic dianhydride and aromatic tetracarboxylic dianhydride are added to a solution of polyamic acid modified with diaminosiloxane in a range of 1 to 4 mol% of the total amount of diamino compounds and a silicon content of 0.5% by weight or less. 100~ in organic solvent with aromatic polyisocyanate
Heat-infusible and organic solvent-insoluble particles with a maximum particle size of 40 μm obtained by thermal polymerization at 160℃
A powder of the above-mentioned polyimide particles obtained by direct filtration or centrifugation from a slurry of spherical porous polyimide particles having an average particle diameter of 10 μm or less and further washing with the same organic solvent used during polymerization is blended. Paste composition.