JPH021192B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a novel polyimide powder-containing polyimide varnish that provides a heat-resistant material. Conventionally, the method for producing powder-containing polyimide varnish has been to add inorganic or organic powder to a normal polyimide varnish and mix and disperse it using a mechanical method such as stirring. However, with this method, it is difficult to uniformly disperse a large amount of powder in the varnish, and when this varnish is observed under a microscope, many secondary aggregates are seen. When this varnish is used as an ink for screen printing, for example, the ink does not easily "come through" the screen, making it impossible to print multiple times, and the resulting coating film also contains secondary aggregates, making it impossible to achieve a uniform coating film. I can't get it. An object of the present invention is to provide a method for producing a polyimide varnish in which a large amount of powder is uniformly dispersed in a varnish. In order to achieve the above object, the present invention has the following configuration:
That is, a tetraorganic carboxylic acid anhydride and a diamine are reacted in a solvent, the obtained polyimide precursor solution is heated at the imide ring closing temperature to precipitate polyimide powder, and in the suspension of the obtained polyimide powder, The present invention is characterized by a method for producing a polyimide varnish, in which a tetraorganic carboxylic acid anhydride and a diamine are reacted to form a polyimide precursor. The tetraorganic carboxylic acid anhydride applied to the present invention is represented by the general formula OCO COR ₁ CO COO, where R ₁ has a carbon number of 6 or more.
An aromatic ring or an aromatic heterocycle having 20 or less carbonyl groups bonded to the ortho or peri position. Typical examples of R ₁ include phenyl group, naphthalene group, perylene group, diphenyl group, diphenyl ether group, diphenyl sulfone group, 2,2'-diphenylpropane group, and benzophenone group. , but not limited to. Particularly preferred are phenyl and benzophenone groups. The tetraorganic carboxylic anhydride used as a raw material for the powder and the tetracarboxylic anhydride used to form the polyimide precursor in the polyimide powder suspension may be the same or different substances. Next, the diamine applied to the present invention has the general formula
It is represented by H ₂ N—R ₂ —NH, in which R ₂ consists of an aromatic ring or an aromatic heterocycle. Typical examples of R ₂ include diphenyl ether group, phenyl group, tolylene group, diphenylmethane group, and diphenyl sulfone group. Further, these groups may have substituents such as amino groups, acid groups, carboxyl groups, sulfonic acid groups, etc., as long as these groups do not adversely affect powder form performance and heat resistance. In particular, diphenyl ether group and phenyl group are preferably used. Note that the diamine used as a raw material for the powder and the diamine used to form the polyimide precursor in the suspension of polyimide powder may be the same or different substances. The solvent used for reacting the tetraorganic carboxylic acid anhydride and the diamine is preferably a polar solvent from the viewpoint of polymer solubility. As examples of polar solvents, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methyl 2-pyrrolidone, hexamethylphosphoramide, etc. are preferably used. As a method for reacting the tetraorganic carboxylic acid anhydride and diamine in a solvent, the diamine is added and dissolved in the solvent with stirring, and after dissolving, the tetraorganic carboxylic acid anhydride is added and reacted. Ratio (A) of tetraorganic carboxylic acid anhydride (A) and diamine (B)/
(B) is preferably 0.7 to 1, preferably 0.8 to 0.95.
If this ratio is less than 0.7, the varnish produced will have poor spreadability, making it difficult to print continuously when used as a screen printing ink. The concentration of the polyimide precursor in the polyimide precursor solution is preferably 20 to 35%, preferably 23 to 30%.
If it is less than 20%, the proportion of powder in the varnish is too low and the shape retention of the pattern is poor when used as a screen printing ink, and if it is more than 35%, the viscosity of the polyimide precursor solution becomes high and stirring becomes difficult. The reaction temperature for preparing the polyimide precursor solution is preferably 40 to 80°C, preferably 40 to 60°C. If the temperature is below 40°C, the polymerization rate will be slow, and if it is above 80°C, the molecular weight will decrease, which is not preferable. The imide ring-closing temperature for precipitating imide powder from a polyimide precursor solution has an upper limit of the boiling point of the solvent used and a lower limit of 100 to 200°C, preferably 110 to 170°C, although it varies somewhat depending on the polymer. In the process of making this polyimide powder suspension, condensed water generated during imide ring closure may be removed by nitrogen flow, vacuum suction, etc. in order to make the subsequent polymerization of the polyimide precursor proceed more smoothly. . The polymerization temperature when polymerizing the polyimide precursor in a suspension of polyimide powder is preferably 40°C to 80°C, preferably 40°C to 60°C. Below 40°C, the polymerization rate is slow, and above 80°C, the viscosity of the varnish decreases due to a decrease in molecular weight, which is undesirable. H ₂ N—R ₂ —NH ₂ is a diamine and is a tetraorganic carboxylic acid anhydride.

The method for adding [Formula] into a polyimide powder suspension is as follows:
Add H ₂ N―R ₂ -NH ₂ , then

Add [formula] or H ₂ N―R ₂ - NH ₂

It is preferable to mix [formula] thoroughly in a container and then add them at the same time. The weight ratio of polyimide powder/polyimide precursor is
70/30 to 40/60, preferably 65/35 to 45/55. If the polyimide powder content exceeds 70%, the film strength will decrease and the coating film will be more likely to crack. If the content is less than 40%, when the varnish is used as a screen printing ink, the shape retention of the printed pattern will be poor and good printed matter will not be obtained. Furthermore, the general formula

Polyimide powder and polyimide precursor consisting of [Formula] and H ₂ N--R ₂ --NH ₂ may be copolymerized with other monomers or organic Or/and inorganic powder may be added. The polyimide varnish manufactured by the manufacturing method described in the present invention has a solid content of 30 to 45% after drying in a hot air oven at 200°C for 2 hours, and a BS type manufactured by Tokyo Keiki Co., Ltd. with a viscosity of 700 to 2000 poise. be. A small amount of this varnish was dropped onto a cover glass and the dispersibility of the particles was examined under an optical microscope with a magnification of 150 times. As a result, no secondary aggregation of the particles was observed. In addition, the particle size distribution was measured at a microscope magnification of 150 times using a sample diluted approximately 3 to 5 times using a "Quantinet" 720 image processing analyzer manufactured by Cambridge Instrument Co., Ltd. The results showed that there were no coarse particles with a particle size of 30 μ or more. was found to be evenly distributed. This varnish was printed on a silicon wafer using an LS-150GT (manufactured by New Long Precision Industry Co., Ltd.) screen printing machine to form a soft error prevention film pattern with about 200 patterns of 3 mm x 6 mm in size and 50 μm in thickness. Screen printing cycle 3 using silicone squeegee with 150 meshes and emulsion film thickness of 100μ
min/page, squeegee angle 69 degrees, distance between screen and silicon wafer 2.8 mm, printing speed 4.6
As a result of printing at a printing pressure of 1 kg/cm ² at a printing pressure of 1 kg/cm 2 , the varnish came through the screen well, and 100 silicon wafers could be coated continuously without any part of the pattern being chipped. . Furthermore, the obtained coating film was heated at 80°C for 30 minutes + 150°C for 30 minutes + 200°C for 30 minutes + 350°C.
Cure with a 30 minute curing step,
Observation under a microscope with a magnification of 150 times confirmed that a good coating film with uniformly dispersed particles was formed. The present invention will be described in more detail in Examples below. Example 1 695.6 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) solvent was weighed into a three-necked flask. This is added to diaminodiphenyl ether (hereinafter
Add 120.1 g of DAE (abbreviated as DAE) at 50°C while stirring the solvent and dissolve completely. After DAE is completely dissolved, pyromellitic anhydride (hereinafter abbreviated as PMDA)
Add 124.3g little by little while stirring the solution.
DAE and PMDA react, and the temperature in the system increases by 5 to 10 degrees Celsius due to the heat of reaction. After reacting for 30 minutes, the system temperature was raised to 80°C and the reaction was continued for an additional 30 minutes. During this time frame, a closed system is kept under _N2 flow. After reacting at 80℃ for 30 minutes, the temperature inside the system was controlled in a closed system using a cooling tube.
The temperature is raised to 150°C to precipitate polyimide powder.
The reaction is carried out at 150°C for 1.5 to 2.0 hours to precipitate polyimide powder, and then the temperature is lowered to 70°C. When the temperature of the system reached 70°C, 94.3 g of DAE was added and immediately after that, benzophenone tetracarboxylic anhydride (hereinafter referred to as
Add 139.3g (abbreviated as BTDA) and react. Approximately 1
BC type viscometer (manufactured by Tokyo Keiki Co., Ltd.)
Measure the viscosity and adjust the viscosity to 1000 poise ± 200 poise. If the viscosity is low, add a small amount of BTDA, if it is high, dilute with NMP. Once the viscosity is equal, the mixture is allowed to react for another hour and taken out. It was confirmed using a microscope and an image processing analysis device that the varnish produced by this method had good powder dispersibility despite the powder/binder ratio being 1/1. As a result of printing this varnish with a screen printing machine, the varnish "released" well from the screen, and it was possible to print multiple times. Furthermore, as a result of curing the obtained coating film, a pattern consisting of a good polyimide film was obtained. Example 2 In Example 1, NMP was used instead of the sole solvent.
NMP/ethyl cellosolve (hereinafter abbreviated as ECS) =
A varnish was prepared in exactly the same manner as in Example 1 using an 85/15 mixed solvent system. The resulting varnish was printed with an LS-15G screen printer and had good printability, and when cured using the same curing step as in Example 1, a pattern consisting of a good polyimide film was obtained. Comparative Example 1 695.6 g of NMP was weighed into a three-necked two-flask. Add 120.1 g of DAE to this while stirring the solvent at 50°C to completely dissolve. Once DAE is completely dissolved
Add 124.3 g of PMDA little by little and react at 50°C for 30 minutes. After this, the temperature was raised to 80°C and the reaction was continued for an additional 30 minutes. Thereafter, the temperature was raised to 150°C, and a reaction was performed at 150°C for 2.0 hours to precipitate polyimide powder. This powder
Filter through a 3G glass filter and vacuum dry at 150°C for one day and night to create polyimide powder. Separately, 695.6 g of NMP was placed in a three-necked flask, and 94.3 g of DAE was added thereto while stirring at 70°C until completely dissolved. After DAE is completely dissolved, under stirring
Add 139.3g of BTDA and react for 2 hours to create polyimide acid. The polyimide powder prepared earlier was added little by little to the resulting polyamic acid solution to prepare a varnish. When this varnish was observed using a microscope image processing and analysis device, many secondary aggregates were observed, indicating that the powder was not uniformly dispersed in the binder. When I screen printed using this varnish, the varnish did not come through the screen very well.
Printing could not be performed multiple times, secondary aggregates were observed here and there in the obtained coating film, and a uniform coating film could not be obtained.

Claims (1)

[Claims] 1. React a tetraorganic carboxylic acid anhydride and a diamine in a solvent, heat the obtained polyimide precursor solution at the imide ring-closing temperature to precipitate polyimide powder, and in the suspension of the obtained polyimide powder,
A method for producing a polyimide varnish, which comprises reacting a tetraorganic carboxylic acid anhydride and a diamine to form a polyimide precursor.