WO2021227020A1 - Photosensitive polyimide resin composition and protective film applying same - Google Patents

Abstract

A photosensitive polyimide resin composition, comprising: (a) a photosensitive polyimide resin represented by formula (I), wherein in formula (I), Ar₁-Ar₄, m, n, and o are as defined in the description; (b) a photo-radical initiator; (c) a thermo-polymerizable compound, comprising an isocyanate compound; (d) a radical polymerizable compound; and (e) a solvent. A polyimide protective film having low repulsive force can be prepared from the photosensitive polyimide resin composition.

Description

Photosensitive polyimide resin composition and protective film using the same Technical field

The invention relates to a photosensitive polyimide resin composition, in particular to a photosensitive polyimide resin composition capable of producing a polyimide protective film with low resilience.

Background technique

The process technology related to the printed circuit board has developed rapidly, from the early rigid printed circuit board (PCB) design method to the structure design of the flexible printed circuit board (FPC). In this process, people's demand for lighter and thinner electronic products, especially portable electronic products, has become more obvious. Daily necessities such as mobile phones, tablet computers, health bracelets, digital cameras, etc., all use flexible printed circuit boards that can be flexed in three dimensions, which greatly reduces the volume and weight of products, and can even increase the added value of products.

Polyimide (PI) cover film is an important material used in FPC soft boards. The purpose of laminating PI cover film is to protect flexible circuits from temperature, humidity, pollution and rust in various use environments. , Greatly improve the service life of FPC soft board, and FPC soft board practitioners usually use PI cover film or ink printing to achieve their goals.

Because the traditional PI film has a certain rebound force, when the FPC soft board is flexed, it will increase the rigidity of the substrate. When the FPC soft board is connected, the rigidity of the FPC will cause residual stress after the assembly of the soft board, resulting in soft After the board is assembled, the product reliability and good rate are reduced.

PSPI (Photosensitive Polyimide) photosensitive polyimide is a photosensitive developing resin. Its main composition is polyimide with photosensitive groups and epoxy acrylic resin and other light and thermal crosslinking agents. This material is relatively soft , So it can achieve the material characteristics of lower rebound force, but most of this material is prone to shrinkage and deformation during the reflow process, which causes the FPC soft board to warp.

Summary of the invention

In view of the above technical problems, the object of the present invention is to provide a polyimide protective film. The polyimide protective film not only has good pattern formation and chemical resistance, but also has good heat shrinkability and low resilience characteristics.

To achieve the above objective, the present invention provides a photosensitive polyimide resin composition comprising: (a) a photosensitive polyimide resin represented by formula (I), which accounts for the total solids in the resin composition 33-67% by weight; (b) a photo-radical initiator, which accounts for 1-15% of the total weight of solids in the resin composition; (c) a thermally polymerizable compound, which contains an isocyanate compound, and the thermally polymerizable compound It accounts for 8-37% of the total weight of solids in the resin composition; (d) a radical polymerizable compound, which accounts for 3-27% of the total weight of solids in the resin composition; and (e) solvent:

Among them, Ar ₁ is a tetravalent organic group; Ar ₂ is a divalent organic group; Ar ₃ is a divalent organic group; Ar ₄ is a group containing

A divalent organic group of the group, wherein R is hydrogen or methyl; m, n, and o are each independently an integer selected from 10 to 600, and m>n+o.

Preferably, the isocyanate compound is selected from aromatic isocyanates, aliphatic isocyanates, alicyclic isocyanates, or a combination of any two or more of the foregoing. More preferably, the isocyanate compound is selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, two Cyclohexylmethane diisocyanate, L-lysine triisocyanate, triphenylmethane triisocyanate, phosphorothioate triphenylisocyanate, (2,4,6-trioxotriazine-1,3,5(2H, 4H,6H)-triyl)tris(hexamethylene)isocyanate or a combination of any two or more of the foregoing.

Preferably, the radically polymerizable compound is a compound having at least two (meth)acrylate groups.

Preferably, Ar _{1 is} selected from one of the following groups:

Preferably, Ar ₂ is the following group:

Wherein, p is any integer from 0-25.

Preferably, Ar _{3 is} selected from one of the following groups:

Preferably, Ar _{4 is} selected from one of the following groups:

Among them, R* means containing

An organic group of groups, where R is hydrogen or methyl.

Preferably, the solvent accounts for 35-70% of the total mass of solids in the composition.

The present invention also provides a method for preparing a polyimide protective film, which comprises the following steps: coating the resin composition according to claim 1 on a substrate to obtain a coated substrate; The coated substrate is surface-dried at 80-120°C to obtain a surface-dried substrate; and the surface-dried substrate is heated at 140-210°C to obtain the polyimide protection membrane.

Preferably, the preparation method further comprises a step of developing the surface-dried substrate before the heating step.

The present invention also provides a polyimide protective film, which is prepared by the aforementioned preparation method.

The photosensitive polyimide resin composition of the present invention adjusts the ratio of the long-chain segment organic groups of the polyimide resin, and matches the thermopolymerizable compound containing isocyanate compounds, so that the polyimide resin is combined with Isocyanate forms a special low-density cross-linked form. In addition to its developability and chemical resistance, it can meet the relevant specifications. It can also effectively improve the excessive rebound force of the traditional PI cover film and the heat of the photosensitive polyimide. Problems such as shrinkage and deformation.

Description of the drawings

Figure 1 is the FT-IR spectrum of the resin composition in Example 1.

FIG. 2 is the FT-IR spectrum of the resin composition in Comparative Example 5. FIG.

Detailed ways

The present invention provides a photosensitive polyimide resin composition. The photosensitive polyimide resin composition can produce a polyimide protective film with low resilience, and has good developability and chemical resistance. Comply with relevant regulations.

The photosensitive polyimide resin composition provided by the present invention comprises: (a) the photosensitive polyimide resin represented by formula (I), which accounts for 33-67% of the total weight of solids in the resin composition, Preferably it accounts for 35-65%; (b) a photo-radical initiator, which accounts for 1-15% of the total weight of the solids in the resin composition; (c) a thermally polymerizable compound, which contains an isocyanate compound, and the thermally polymerizable compound It accounts for 8-37% of the total weight of solids in the resin composition, preferably 10-35%; (d) free radical polymerizable compounds, which account for 3-27% of the total weight of solids in the resin composition, preferably 5 -25%; and (e) Solvent:

Among them, Ar ₁ is a tetravalent organic group; Ar ₂ is a divalent organic group; Ar ₃ is a divalent organic group; Ar ₄ is a group containing

A divalent organic group of a group, wherein R is hydrogen or methyl; m, n, and o are each independently an integer selected from 10 to 600, such as: 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, and m>n+o. In some embodiments, m is between any two of the foregoing values, n is between any two of the foregoing values, and o is between any two of the foregoing values.

In a preferred embodiment, the photo-radical initiator includes, but is not limited to: bis(2,4,6-trimethylbenzoyl)phenyl phosphorus oxide, 2,4,6-trimethylbenzoyl -At least one of diphenylphosphorus oxide.

In the present invention, the addition of the thermally polymerizable compound causes the polyimide molecular chain to form a crosslinked structure with the thermally polymerizable compound during baking. The main purpose of the thermally polymerizable compound is to cross-link with the ortho position of the -OH group on the polyimide main chain or the -OH group on the terminal through acid catalysis and heat treatment during hard baking after exposure.

The thermally polymerizable compound contains an isocyanate compound, and the isocyanate compound may be an aromatic isocyanate, an aliphatic isocyanate, or an alicyclic isocyanate. The aromatic isocyanate is preferably diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate, MDI) or toluene diisocyanate (TDI), xylene diisocyanate (Xylylene Diisocyanate, XDI), triphenyl Methyl methane triisocyanate (such as: 4,4',4"-triphenylmethane triisocyanate), phosphorothioate triphenyl isocyanate. The aliphatic isocyanate is preferably hexamethylene diisocyanate (HDI), triphenyl isocyanate Methyl hexamethylene diisocyanate (trimethylhexamethylene diisocyanate, TMDI) or L-lysine triisocyanate. The alicyclic isocyanate is preferably isophorone diisocyanate (isophorone diisocyanate, IPDI), dicyclohexylmethane diisocyanate ( 4,4'-Methylene dicyclohexyl diisocyanate, HMDI) or (2,4,6-trioxotriazine-1,3,5(2H,4H,6H)-triyl) tris(hexamethylene) isocyanate. These isocyanate compounds can be used alone, or two or more (such as: three, four, five, six, etc.) can be used in combination. In the present invention, the thermally polymerizable compound may further include isocyanate compounds. It contains epoxy resin, but preferably does not contain epoxy resin. In some embodiments, the photosensitive polyimide resin composition of the present invention does not contain epoxy resin.

In the present invention, the radically polymerizable compound generates acid after exposure to form an acid-catalyzed crosslinking mechanism. The radical polymerizable compound will absorb a certain wavelength of light energy to generate free radicals after exposure to initiate or catalyze the polymerization of the corresponding monomers or prepolymers to form crosslinks. If the amount of the radically polymerizable compound exceeds 25% of the total weight of the solids in the composition, the developability will be poor. The radically polymerizable compound is a photo-radical crosslinking agent, and its kind is not particularly limited, as long as it can achieve the aforementioned purpose. Considering properties such as developability and chemical resistance, the radically polymerizable compound is preferably a compound having at least two (meth)acrylate groups, such as a compound having two (meth)acrylate groups, and a compound having three (meth)acrylate groups. A compound having a (meth)acrylate group, a compound having four (meth)acrylate groups, a compound having five (meth)acrylate groups, or a compound having six (meth)acrylate groups. Examples of the compound having at least two (meth)acrylate groups may include, but are not limited to: ethylene glycol dimethacrylate; EO modified diacrylate of bisphenol A (n=2-50) (EO Is ethylene oxide, n is the number of moles of ethylene oxide added); EO modified diacrylate of bisphenol F; BLEMMER

(NOF Co., Ltd.); Aronix

And/or

(Manufactured by Toa Synthetic Chemical Industry Co., Ltd.); KAYARAD

And/or

(Nippon Kayaku Co.,Ltd.);

And/or

(Osaka Organic Chemical Ind., Ltd.); trimethylolpropane triacrylate (TMPTA); methylolpropane tetraacrylate; glycerol trihydroxypropyl ether triacrylate; triethoxytrimethylolpropane Triacrylate; Trimethylolpropane Trimethacrylate; Tris(2-hydroxyethyl)isocyanate Triacrylate (THEICTA); Pentaerythritol Triacrylate; Pentaerythritol Hexacrylate; Aronix

And/or

(Toa Synthetic Chemical Industry Co., Ltd.); KAYARAD

And/or

(Nippon Kayaku Co., Ltd.);

And/or

(Osaka Yuki Kayaku Kogyo Co., Ltd).

In the present invention, after the radical polymerizable compound and the thermal polymerizable compound are added at the same time, the resulting cross-linked structure can increase the developability, film-forming properties, and chemical resistance of the polyimide resin composition.

_{Ar 1} in the polyimide resin of the present invention is a tetravalent organic group, and its main chain part may contain an aliphatic ring group or an aromatic ring group. The tetravalent organic group includes but is not limited to:

_{Ar 2} in the polyimide resin of the present invention is a divalent organic group, which includes but is not limited to:

Wherein, p is any integer from 0-25.

In the present invention, p is preferably any integer from 0 to 15, such as: 3, 6, 9, 12 and so on. By adjusting p within this range, _{the chain length of Ar 2} can be adjusted within a more appropriate range. When p is in the range of 0-15, a polyimide protective film with more excellent resilience and heat shrinkability can be obtained.

_{Ar 3} in the polyimide resin of the present invention is a divalent organic group, and its branched chain portion preferably has a phenolic hydroxyl group or a carboxyl group. The content of the phenolic hydroxyl group or carboxyl group accounts for about 10-30% of the number of moles of the polyimide resin represented by formula (I). Adjusting the content of phenolic hydroxyl or carboxyl group in the branch can control the development time. When the content of phenolic hydroxyl group or carboxyl group in the branch is higher, the solubility of the polyimide resin represented by formula (I) in the alkaline developer is better, and its developability can be improved.

The divalent organic group having a phenolic hydroxyl group or a carboxyl group in the branched part is preferably the following group:

_{The Ar 4} in the polyimide resin of the present invention contains

A divalent organic group of the group, where R is hydrogen or methyl. Preferably, Ar ₄ is one selected from the following groups:

Among them, R* means containing

An organic group of groups, where R is hydrogen or methyl.

In the above structural formula, -* represents the point of attachment when other groups are attached to the group.

The synthesis step of the polyimide resin represented by formula (I) is to _{dissolve an appropriate amount of diamine monomer (containing Ar 2} ) and dianhydride monomer in N-methylpyrrolidone (NMP) at 80°C After reacting for 2 hours, xylene was added and heated to 180°C to distill it out. Then add a diamine monomer containing a phenolic hydroxyl group or a carboxyl group, react at 80°C for 2 hours, add xylene and heat to 180°C to distill it out, and cool it down after about 4 hours.

The preparation method of the photosensitive polyimide resin composition of the present invention is to take the polyimide resin (colloid) represented by the formula (I) prepared above, disperse it in a solvent, and then add light free Base initiators, radical polymerizable compounds, and thermally polymerizable compounds can be obtained.

In the present invention, the solvent is not particularly limited, as long as the components in the composition can be dispersed therein. Preferably, the solvent can dissolve the polyimide resin represented by formula (I), including but not limited to: N-methyl-2-pyrrolidone, N,N-dimethylacetamide, γ-butyrolactone , Xylene or toluene. These solvents can be used alone, or two or more (such as three, four, and five) can be used in combination.

As a further preferred solution of the present invention, the solvent accounts for 40-70% of the total mass of solids in the resin composition, such as: 45-65%, 50-65% or 50-60%.

Those familiar with the technical field of the present invention should know that the total amount of the composition does not exceed 100%. Therefore, the total amount of the photosensitive polyimide resin composition of the present invention is 100%. The photosensitive polyimide resin composition of the present invention is soluble in alkaline solutions. In addition, the photosensitive polyimide resin composition of the present invention may or may not contain other additives. In some embodiments, the resin composition does not include an oxime ester compound.

The photosensitive polyimide resin composition of the present invention can produce a polyimide protective film with low resilience. Therefore, the present invention also provides a method for preparing a polyimide protective film, which includes the following steps: The aforementioned resin composition is coated on a substrate to obtain a coated substrate; the coated substrate is heated at 80-120°C (preferably 90-120°C, such as 95°C, 100°C) , 105°C, 110°C, 115°C) to obtain a surface-dried substrate; and the surface-dried substrate is heated at 140-210°C (preferably 140-200°C, such as: 150°C, 160°C, 170°C, 180°C, 190°C) to obtain the polyimide protective film. In a preferred embodiment, the preparation method further comprises a step of developing the surface-dried substrate before the heating step.

The present invention also provides a polyimide protective film, which is prepared by the aforementioned method. The protective film can be used as a protective material in the circuit board process, and has low resilience, chemical resistance and heat resistance.

After the photosensitive polyimide resin composition of the present invention is exposed to light, several hole patterns with a minimum diameter of 50 μm can be formed in the cured resin layer.

The following examples are used to further illustrate the present invention, but they are not intended to limit the scope of the present invention. Anyone familiar with the technical field of the present invention makes changes and modifications without departing from the spirit of the present invention.

Example

Synthesis Example 1: Preparation of polyimide resin

Take a 500mL three-necked round bottom flask equipped with a mechanical stirrer and nitrogen inlet, and add 23.86g (96mmol) 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethylbis Siloxane (1,3-Bis(3-aminopropyl)tetramethyldisiloxane), 80.7g N-methylpyrrolidone (NMP), 39.68g (160mmol) bicyclo[2.2.2]oct-7-ene-2,3, 5,6-tetracarboxylic dianhydride (Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylicdianhydride). After the above solution was reacted at 50-80°C for 2 hours, 45g of xylene was added and the temperature was raised to 180°C and stirring was continued for 1.5 hours. Then 9.74g (64mmol) of 3,5-Diaminobenzoic acid (3,5-Diaminobenzoic acid) was added. acid), after reacting the above solution at 50-80°C for 2 hours, adding 45 g of xylene, raising the temperature to 180°C, and continuing to stir for 4 hours. After cooling, the PI-a1 solution can be obtained.

Take 50 g of the PI-a1 solution, add 11.38 g of glycidyl methacrylate (GMA) and stir at 70-100°C for 24 hours to obtain the photosensitive polyimide resin PSPI-a1 represented by formula (I):

Where Ar ₁ is

Ar ₂ is

p=0; Ar ₃ is

Ar ₄ is

And m=96; n+o=64.

Synthesis Example 2

Take a 500mL three-necked round bottom flask equipped with a mechanical stirrer and nitrogen inlet, and add 23.86g (96mmol) 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethylbis Siloxane (1,3-Bis(3-aminopropyl)tetramethyldisiloxane), 80.7g NMP, 26.17g (160mmol) Benzene-1,2,4,5-tetracarboxylic dianhydride (Benzene-1,2,4, 5-tetracarboxylic dianhydride), after reacting the above solution at 50-80°C for 2 hours, adding 45g of xylene, raising the temperature to 180°C, and continuing to stir for 1.5 hours, then adding 9.74g (64mmol) of 3,5-diaminobenzoic acid (3,5-Diaminobenzoic acid), after reacting the above solution at 50-80°C for 2 hours, adding 45 g of xylene, raising the temperature to 180°C, and continuing to stir for 4 hours. After cooling, the PI-a2 solution can be obtained. Take 50g of the PI-a2 solution, add 11.38g GMA, and stir at 70-100°C for 24 hours to obtain the photosensitive polyimide resin PSPI-a2 represented by formula (I):

Where Ar ₁ is

Ar ₂ is

p=0; Ar ₃ is

Ar ₄ is

And m=96; n+o=64.

Synthesis Example 3: Preparation of polyimide resin

Take a 500mL three-necked round bottom flask equipped with a mechanical stirrer and nitrogen inlet, and add 19.88g (80mmol) 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethylbis Siloxane (1,3-Bis(3-aminopropyl)tetramethyldisiloxane), 80.7g N-methylpyrrolidone (NMP), 39.68g (160mmol) bicyclo[2.2.2]oct-7-ene-2,3, 5,6-tetracarboxylic dianhydride (Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylicdianhydride). After the above solution was reacted at 50-80℃ for 2 hours, 45g xylene was added, the temperature was raised to 180℃, and stirring was continued for 1.5 hours, and then 12.172g (80mmol) 3,5-Diaminobenzoic acid (3,5-Diaminobenzoic acid) was added. acid), after reacting the above solution at 50-80°C for 2 hours, adding 45 g of xylene, raising the temperature to 180°C, and continuing to stir for 4 hours. After cooling, the PI-a3 solution can be obtained.

Take 50 g of the PI-a1 solution, add 11.38 g of glycidyl methacrylate (GMA) and stir at 70-100°C for 24 hours to obtain the photosensitive polyimide resin PSPI-a3 represented by formula (I):

Where Ar ₁ is

Ar ₂ is

p=0; Ar ₃ is

Ar ₄ is

And m=n+o=80.

Example 1-5 and Comparative Example 1-5

Mix the components according to the component composition in Table 1. The content of each component in Table 1 is the mass percentage based on the total weight of the solids in the composition. The component mixture in Table 1 was dissolved in N-methylpyrrolidone to prepare a solution with a solid content of 60% to form a photosensitive polyimide resin composition soluble in alkaline solutions, which was used as Coating liquid is used.

In Table 1, a1 represents PSPI-a1; a2 represents PSPI-a2; a3 represents PSPI-a3; b1 represents DAROCUR TPO (CIBA); c1 represents BI 7963 (hexamethylene diisocyanate, HDI, Baxenden chemicals); c2 represents BI7641 (Tolylene diisocyanate) ,TDI,Baxenden chemicals); c3 represents BI7951 (isophorone diisocyanate,IPDI,Baxenden chemicals); c4 represents NC-3000(2-[(2-methyl-1-oxo-2-propenyl)oxy]ethyl]carbamate 2-propenoate ,homopolymer,Nippon Kayaku Co., Ltd.); c5 means XD-1000 (phenol, polymer with 3a,4,7,7a-tetrahydro-4,7-methylene-1H-indene glycidyl ether, Nippon Kayaku Co., Ltd.); d1 Represents PDBE-450A (NOF).

Table 1 Photosensitive polyimide resin composition with low resilience

The detailed test method of the above resin composition is as follows:

<Pattern Formability>

The polyimide resin composition is coated on a copper foil substrate, and the surface is dried at 90°C for 6 minutes to prepare a film. After light exposure, a 1wt% sodium carbonate aqueous solution is applied to the exposed resin composition layer. Perform development for 60 seconds.

The following criteria were used to evaluate whether the film after development (ie, the polyimide protective film of the present invention) has good edge sharpness and line width. The smaller the line width of the resin composition layer, the greater the difference in solubility between the light-irradiated part and the non-light-irradiated part for the developer, indicating that a better result was obtained. In addition, the smaller the change in line width relative to the change in exposure energy, the wider the exposure latitude, indicating that better results have been achieved. After observing the formed pattern with an optical microscope, the case where a fine line pattern with line width/pitch width=75μm/75μm or less is formed is set to A; the case where a fine line pattern with line width/pitch width= more than 75μm/75μm is formed The situation is set to B.

<Chemical resistance>

The polyimide resin composition is coated on a copper foil substrate, and the surface is dried at 90°C for 6 minutes to obtain a film, and then a hard-bake procedure is performed at 200°C for 1 hour to obtain a film thickness of about 15μm. Polyimide protective film.

The following criteria were used to evaluate whether the polyimide protective film has good chemical resistance. The polyimide protective film was immersed in 10% NaOH at 25° C., and the decrease in thickness of the polyimide protective film was observed and recorded in terms of thickness. If soaking for more than 30 minutes, if the thickness of the polyimide protective film does not change and there is no color difference, the situation is set as ╳; if the thickness of the polyimide protective film is reduced or there is color difference, the situation is set to ╳.

<Heat shrinkage>

The polyimide resin composition is coated on a copper foil substrate, and the surface is dried at 90°C for 6 minutes to obtain a film, and then a hard-bake procedure is performed at 200°C for 1 hour to obtain a film thickness of about 15μm. Polyimide protective film.

The following criteria were used to evaluate whether the polyimide protective film has good heat shrinkability. The copper foil substrate coated with a polyimide protective film is heated in an oven at 270°C for 60 seconds, and then placed in an environment of 25°C for 10 seconds. Repeat three times to observe whether the copper foil substrate is warped. Evaluate. If it is heated three times and the warpage measured with a scale ≦0.5mm is judged to be ◎; if it is heated three times and the warpage measured with a scale> 0.5mm but ≦1mm, it is judged as ○; if it is heated Three times, and measuring the warpage with a ruler> 1mm, it is judged as ╳.

＜Resilience＞

The polyimide resin composition is coated on a copper foil substrate, and the surface is dried at 90°C for 6 minutes to obtain a film, and then a hard-bake procedure is performed at 200°C for 1 hour to obtain a film thickness of about 15μm. Polyimide protective film.

The following criteria were used to evaluate whether the polyimide protective film has good resilience. Cut the copper foil substrate coated with a polyimide protective film into a sample with a width of 1 centimeter (cm), fix one end with a fixture, and bend the other end back into a U shape and place it underneath When an electronic scale is pressed down until the distance between the sample and the electronic scale is 2mm, the electronic scale reading <10g/cm after standing for 3 seconds is judged as ◎; the electronic scale reading >10g/cm but ≦15g/cm is judged as ○; The electronic scale reading >15g/cm is judged as ╳.

Figure 1 is the FT-IR spectrum of the resin composition in Example 1, where 1017 cm ^-1 is the characteristic peak of Si-O in the _{Ar 2} ^{group, and 1590 cm -1} is the C=O in the polyimide group Characteristic peak, 3386cm ^-1 is the characteristic peak of NH in isocyanate. FIG. 2 is the FT-IR spectrum of the resin composition in Comparative Example 5. FIG. From the results in Table 1, it can be seen that the thermally polymerizable compound of Comparative Example 5 is an epoxy resin, which is different from the thermally polymerizable compound used in the present invention, which is an isocyanate compound. Therefore, the protective film formed in Comparative Example 5 has poor thermal shrinkage. , Will produce shrinkage and warpage problems.

In summary, after the photosensitive polyimide resin composition provided by the present invention undergoes surface drying, baking and other processes, a polyamide with heat resistance, chemical resistance, and flexibility that can meet relevant specifications can be obtained. The imine protective film also has the characteristics of low rebound force, which can effectively improve the problem of excessive rebound force of the traditional PI cover film.

The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements can be made without departing from the technical principles of the present invention. And variants, these improvements and variants should also be regarded as the protection scope of the present invention.

Claims (12)

1. A photosensitive polyimide resin composition comprising:

   (a) The photosensitive polyimide resin represented by formula (I), which accounts for 33-67% of the total weight of solids in the resin composition;

   

   Among them, Ar ₁ is a tetravalent organic group; Ar ₂ is a divalent organic group; Ar ₃ is a divalent organic group; Ar ₄ is a group containing

   

   A divalent organic group of the group, wherein R is hydrogen or methyl; m, n, and o are each independently an integer selected from 10 to 600, and m>n+o;

   (b) A photo-radical initiator, which accounts for 1-15% of the total weight of solids in the resin composition;

   (c) A thermally polymerizable compound, which contains an isocyanate compound, and the thermally polymerizable compound accounts for 8-37% of the total weight of solids in the resin composition;

   (d) A radically polymerizable compound, which accounts for 3-27% of the total weight of solids in the resin composition; and

   (e) Solvent.
2. 3. The resin composition of claim 1, wherein the isocyanate compound is selected from aromatic isocyanates, aliphatic isocyanates, alicyclic isocyanates, or a combination of any two or more of the foregoing.
3. The resin composition of claim 2, wherein the isocyanate compound is selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, Isophorone diisocyanate, dicyclohexylmethane diisocyanate, L-lysine triisocyanate, triphenylmethane triisocyanate, phosphorothioate triphenylisocyanate, (2,4,6-trioxotriazine- 1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate or a combination of any two or more of the foregoing.
4. 3. The resin composition of claim 1, wherein the radically polymerizable compound is selected from compounds having at least two (meth)acrylate groups.
5. The resin composition of claim 1, wherein Ar _{1 is} selected from one of the following groups:

   
6. The resin composition according to claim 1, wherein Ar ₂ is the following group:

   

   Wherein, p is any integer from 0-25.
7. The resin composition of claim 1, wherein Ar _{3 is} selected from one of the following groups:

   
8. The resin composition of claim 1, wherein Ar _{4 is} selected from one of the following groups:

   

   Among them, R* means containing

   

   An organic group of groups, where R is hydrogen or methyl.
9. The resin composition of claim 1, wherein the solvent accounts for 35-70% of the total mass of solids in the composition.
10. A preparation method of a polyimide protective film, which comprises the following steps:

    Coating the resin composition according to claim 1 on a substrate to obtain a coated substrate;

    Surface drying the coated substrate at 80-120°C to obtain a surface-dried substrate; and

    The surface-dried substrate is heated at 140-210°C to obtain the polyimide protective film.
11. 10. The preparation method according to claim 10, which further comprises a step of developing the surface-dried substrate before the heating step.
12. A polyimide protective film prepared by the preparation method according to claim 10 or 11.

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