TWI772796B - Photosensitive polyimide resin composition and protective film using the same - Google Patents

Abstract

The present invention provides a photosensitive polyimide resin composition comprising: (a) a photosensitive polyimide resin represented by formula (I), (b) a photo radical initiator, (c) thermal polymerizable compound, which contains an isocyanate compound; (d) a radical polymerizable compound, and (e) a solvent. The photosensitive polyimide resin composition can be used for producing a protective film of polyimide with low spring back. In formula (I), Ar₁ ~Ar₄ , m, n, and o have the meaning as defined herein.

Description

Photosensitive polyimide resin composition and protective film using the same

The present invention relates to a photosensitive polyimide resin composition, in particular to a photosensitive polyimide resin composition that can be used to prepare a low-rebound polyimide protective film.

The process technology related to printed circuit boards has developed rapidly, from the early design of rigid printed circuit boards (PCB) to the structural design of flexible printed circuit boards (FPC). In this process, people's demand for lightweight and thin electronic products, especially portable electronic products, is more obvious. Mobile phones, tablet computers, health wristbands, digital cameras, and other daily necessities all use the flexible printed circuit board's three-dimensional bending function, which greatly reduces the volume and weight of the product, and even increases the added value of the product.

Polyimide (PI) cover film is an important material used in FPC flexible boards. The purpose of laminating the PI cover film is to protect the flexible circuit from temperature, humidity, pollution and rust in various environments. Improve the service life of FPC soft board, and FPC soft board industry usually uses PI cover film or ink printing to achieve the goal.

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. Product reliability and yield after board assembly are reduced.

PSPI (Photosensitive Polyimide) photosensitive polyimide is a photosensitive developing resin. Its main composition is polyimide with photosensitive groups and light and heat crosslinking agents such as epoxy acrylic resin. This material is relatively soft. , so it can achieve the material properties of lower rebound force, but most of this material is prone to shrinkage and deformation during the reflow soldering process, causing the FPC soft board to warp.

In view of the above technical problems, the purpose 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 the characteristics of good heat shrinkage and low rebound force.

（I） 其中，Ar₁ 為四價有機基團；Ar₂ 為二價有機基團；Ar₃ 為二價有機基團；Ar₄ 為含有

基團的二價有機基團，其中R為氫或甲基；m、n及o各自獨立為選自10~600中的任一整數，且m＞n+o。In order to achieve the above object, the present invention provides a photosensitive polyimide resin composition, which comprises: (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% by weight of the total solids in the resin composition; (c) a thermally polymerizable compound, which comprises an isocyanate compound, which thermally polymerizes (d) free-radically polymerizable compounds, which constitute 3-27% of the total weight of solids in the resin composition; and (e) solvents:

(I) 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

A divalent organic group of a group, wherein R is hydrogen or methyl; m, n and o are each independently any 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 diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, Dicyclohexylmethane diisocyanate, L-lysine triisocyanate, triphenylmethane triisocyanate, phosphorothioate triphenyl isocyanate, (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:

.

，其中，p為0-25中任一整數。Preferably, Ar ₂ is the following group:

, where p is any integer from 0 to 25.

。Preferably, Ar ₃ is selected from one of the following groups:

.

其中，R*為含有

基團的有機基團，其中R為氫或甲基。Preferably, Ar ₄ is selected from one of the following groups:

Among them, R* is 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 the step of developing the surface-dried substrate before the heating step.

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

In the photosensitive polyimide resin composition of the present invention, the proportion of organic groups in the long chain segment of the polyimide resin is adjusted, and a thermally polymerizable compound including an isocyanate compound is matched, so that the polyimide resin is baked with Isocyanate forms a special low-density cross-linking type. In addition to its developability and chemical resistance, it can meet relevant specifications, and it can effectively improve the traditional PI cover film with excessive rebound force and thermal shrinkage of photosensitive polyimide. deformation, etc.

The present invention provides a photosensitive polyimide resin composition, which can prepare a polyimide protective film with low rebound force, and its developability and chemical resistance are Can meet relevant specifications.

（I） 其中，Ar₁ 為四價有機基團；Ar₂ 為二價有機基團；Ar₃ 為二價有機基團；Ar₄ 為含有

基團的二價有機基團，其中R為氫或甲基；m、n及o各自獨立為選自10~600中的任一整數，諸如：50、100、150、200、250、300、350、400、450、500、550，且m＞n+o。於一些實施態樣中，m係介於前述任兩個數值之間，n係介於前述任兩個數值之間，o係介於前述任兩個數值之間。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 solid weight of the resin composition , preferably accounting for 35-65%; (b) a photo-radical initiator, which accounts for 1-15% of the total solid weight in the resin composition; (c) a thermally polymerizable compound, which contains an isocyanate compound, The thermally polymerizable compound accounts for 8-37% of the total solid weight in the resin composition, preferably 10-35%; (d) a radically polymerizable compound, which accounts for 8-37% of the total solid weight in the resin composition 3-27%, preferably 5-25%; and (e) solvent:

(I) 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

The divalent organic group of the group, wherein R is hydrogen or methyl; m, n and o are each independently any 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 numerical values, n is between any of the foregoing two numerical values, and o is between any of the foregoing two numerical values.

In a preferred embodiment, the photo-radical initiators include but are not limited to: bis(2,4,6-trimethylbenzyl) phenylphosphonium oxide, 2,4,6-trimethyl At least one of benzalyl-diphenylphosphonium oxide.

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

The thermally polymerizable compound includes an isocyanate compound, and the isocyanate compound can be aromatic isocyanate, aliphatic isocyanate or alicyclic isocyanate. The aromatic isocyanate is preferably diphenylmethane diisocyanate (4,4'-diphenylmethane diisocyanate, MDI), tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), tris Phenylmethane triisocyanate (eg: 4,4',4''-triphenylmethane triisocyanate), phosphorothioate triphenylisocyanate. The aliphatic isocyanate is preferably hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI) or L-lysine triisocyanate. The alicyclic isocyanate is preferably isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (4,4'-Methylene dicyclohexyl diisocyanate, HMDI) or (2,4,6-trioxo) Triazine-1,3,5(2H,4H,6H)-triyl)tris(hexamethylene)isocyanate. These isocyanate compounds can be used alone or in combination of two or more (such as three, four, five, six, etc.). In the present invention, in addition to the isocyanate compound, the thermally polymerizable compound may further include an epoxy resin, but it is preferable not to include an 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. After exposure, the free radical polymerizable compound absorbs light energy of a certain wavelength and generates free radicals, which initiate or catalyze the polymerization of corresponding monomers or prepolymers to form crosslinks. If the amount of the radically polymerizable compound exceeds 25% by weight of the total solids in the composition, the developability is poor. The radically polymerizable compound is a photoradical crosslinking agent, and the type thereof is not particularly limited, as long as the aforementioned object can be achieved. Considering properties such as developability and chemical resistance, the radically polymerizable compound is preferably a compound with at least two (meth)acrylate groups, such as a compound with two (meth)acrylate groups, a compound with three (meth)acrylate groups, and a compound with three (meth)acrylate groups. A compound having one (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 PDE-100®, PDE-200®, PDE-400®, PDE-600® , PDP-400®, PDBE-200A®, PDBE-450A®, ADE-200®, ADE-300®, ADE-400A®, ADP-400® (NOF Co., Ltd.); Aronix M-210®, M-240® and/or M-6200® (manufactured by Toagosei Chemical Co., Ltd.); KAYARAD HDDA®, HX-220®, R-604® and/or R-684® (Nippon Kayaku Co., Ltd.) ; V-260®, V-312® and/or V-335HP® (Osaka Organic Chemical Ind., Ltd.); Trimethylolpropane Triacrylate (TMPTA); Methylolpropane Tetraacrylate; Triglyceride Hydroxypropyl ether triacrylate; triethoxy trimethylol propane triacrylate; trimethylol propane trimethacrylate; tris(2-hydroxyethyl) isocyanate triacrylate (THEICTA); pentaerythritol triacrylate Acrylates; Pentaerythritol Hexacrylate; Aronix M-309®, M-400®, M-405®, M-450®, M-710®, M-8030® and/or M-8060® (Toa Gosei Chemical Industry Co., Ltd.); KAYARAD DPHA®, TMPTA®, DPCA-20®, DPCA-30®, DPCA-60® and/or DPCA-120® (Nihon Kayaku Co., Ltd.); V-295®, V-300®, V-360®, V-GPT®, V-3PA® and/or V-400® (Osaka Yuki Kayaku Kogyo Co., Ltd).

In the present invention, after adding the radically polymerizable compound and the thermally polymerizable compound at the same time, the resulting cross-linked structure can increase the developability, film-forming property 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:

.

，其中，p為0-25中任一整數。Ar in the _polyimide resin of the present invention is a divalent organic group, which includes but is not limited to:

, where p is any integer from 0 to 25.

In the present invention, p is preferably any integer from 0 to 15, such as: 3, 6, 9, 12 and the like. By adjusting p within this range, the chain length of Ar ₂ can be adjusted correspondingly within a more appropriate range. When p is in the range of 0-15, a polyimide protective film with better resilience and thermal shrinkage can be obtained.

Ar ₃ in the polyimide resin of the present invention is a divalent organic group, and its branched part 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 molar number of the polyimide resin represented by formula (I). The development time can be controlled by adjusting the content of phenolic hydroxyl or carboxyl group in the branched chain. When the content of phenolic hydroxyl group or carboxyl group in the branched chain is high, the solubility of the alkaline developer solution to the polyimide resin represented by formula (I) 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:

.

基團的二價有機基團，其中R為氫或甲基。較佳地，Ar₄ 係選自下列基團中之一種：

，其中，R*為含有

基團的有機基團，其中R為氫或甲基。Ar ₄ in the polyimide resin of the present invention contains

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

, where R* is the

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

係表示其他基團連接至該基團時的連接位點。In the above structural formula,

Denotes the point of attachment at which other groups are attached to that group.

The synthesis step of the polyimide resin represented by formula (I) is to dissolve an appropriate amount of diamine monomer (which contains Ar ₂ ) and dianhydride monomer in N-methylpyrrolidone (NMP), at 80 ° C. After 2 hours of reaction, xylene was added and heated to 180°C to distill it off. A diamine monomer containing a phenolic hydroxyl group or a carboxyl group was added, and the reaction was carried out at 80° C. for 2 hours. Xylene was added and heated to 180° C. to distill it off. After about 4 hours, it was cooled.

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) obtained above, disperse it in a solvent, and then add photofree A radical initiator, a radically polymerizable compound, and a thermally polymerizable compound 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 the 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 in combination of two or more (such as three, four, and five).

As a further preferred solution of the present invention, the solvent accounts for 40-70% of the total solid mass 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 an alkaline solution. 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 prepare a polyimide protective film with low rebound force. Therefore, the present invention also provides a preparation method of a polyimide protective film, which comprises 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, Surface drying at 100°C, 105°C, 110°C, 115°C) to obtain a surface-dried substrate; and drying the surface-dried substrate at 140-210°C (preferably 140-200°C, such as : 150°C, 160°C, 170°C, 180°C, 190°C) heating to obtain the polyimide protective film. In a preferred embodiment, the preparation method further includes the step of developing the surface-dried substrate before the heating step.

The present invention further 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 manufacturing process, and has low rebound force, chemical resistance and heat resistance.

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

The present invention is further described below with examples, but it is not intended to limit the scope of the present invention, any changes and modifications made by anyone familiar with the technical field of the present invention without departing from the spirit of the present invention belong to the scope of the present invention.

Synthesis Example 1: Preparation of Polyimide Resin

Take a 500mL three-neck round bottom flask equipped with a mechanical stirrer and a nitrogen inlet, 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 (160 mmol) 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, 45 g of xylene was added, the temperature was raised to 180 °C, and stirring was continued for 1.5 hours, and 9.74 g (64 mmol) of 3,5-Diaminobenzoic acid was added. ), the above solution was reacted at 50-80 °C for 2 hours, 45 g of xylene was added, the temperature was raised to 180 °C, and the stirring was continued for 4 hours. After cooling, PI-a1 solution can be obtained.

； 其中，Ar₁ 為

；Ar₂ 為

，p=0；Ar₃ 為

，Ar₄ 為

；且m=96；n+o=64。Take 50 g of 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):

; Among them, Ar ₁ is

; Ar ₂ is

, p=0; Ar ₃ is

, Ar ₄ is

; and m=96; n+o=64.

Synthesis Example 2

； 其中，Ar₁ 為

；Ar₂ 為

，p=0；Ar₃ 為

，Ar₄ 為

；且m=96；n+o=64。Take a 500mL three-neck round bottom flask equipped with a mechanical stirrer and a nitrogen inlet, 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 the above solution was reacted at 50-80 ℃ for 2 hours, 45 g of xylene was added, the temperature was raised to 180 ℃, and the stirring was continued for 1.5 hours, and 9.74 g (64 mmol) of 3,5-diaminobenzoic acid ( 3,5-Diaminobenzoic acid), after the above solution was reacted at 50-80 °C for 2 hours, 45 g of xylene was added, the temperature was raised to 180 °C, and stirring was continued for 4 hours. After cooling, PI-a2 solution can be obtained. Take 50 g of PI-a2 solution, add 11.38 g of GMA, and stir at 70-100 ° C for 24 hours to obtain the photosensitive polyimide resin PSPI-a2 represented by formula (I):

; Among them, 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-neck round bottom flask equipped with a mechanical stirrer and a nitrogen inlet, 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 (160 mmol) 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, 45 g of xylene was added, the temperature was raised to 180 °C, and the stirring was continued for 1.5 hours, and 12.172 g (80 mmol) of 3,5-Diaminobenzoic acid was added. ), the above solution was reacted at 50-80 °C for 2 hours, 45 g of xylene was added, the temperature was raised to 180 °C, and the stirring was continued for 4 hours. After cooling, PI-a3 solution can be obtained.

； 其中，Ar₁ 為

；Ar₂ 為

，p=0；Ar₃ 為

，Ar₄ 為

；且m=n+o=80。Take 50 g of 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):

; Among them, 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

The components are mixed according to the component composition in Table 1, and the content of each component in Table 1 is the mass percentage based on the total solid weight in the composition. Each component mixture in Table 1 was dissolved in N-methylpyrrolidone to make a solution with a solid content of 60% to form a photosensitive polyimide resin composition soluble in an alkaline solution, 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 represents XD-1000 (phenol, polymer with 3a, 4, 7, 7a-tetrahydro-4,7-methylene-1H-indene glycidyl ether, Nippon Kayaku Co., Ltd.); d1 Indicates PDBE-450A (NOF).

Table 1 Photosensitive polyimide resin composition with low rebound force Photosensitive polyimide resin composition Example Comparative example 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 Formulation composition (%) photosensitive polyimide a1 45.0 65.0 45.0 45.0 60.0 45.0 45.0 70.0 30.0 45.0 45.0 45.0 45.0 a2 45.0 a3 45.0 photo free radical initiator b1 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 Thermally polymerizable compound c1 25.0 20.0 10.0 35.0 20.0 25.0 25.0 10.0 35 40.0 15.0 c2 25.0 c3 25.0 c4 25.0 c5 25.0 free radical polymerizable compound d1 20.0 5.0 20.0 20.0 20.0 10.0 25.0 20.0 20.0 10.0 25 20 20 5.0 30.0 Thickness (μm) 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 15.0 Evaluation results pattern formation A A A A A A A A A A B A A A B chemical resistance ◎ ○ ◎ ○ ○ ◎ ○ ◎ ◎ ╳ ◎ ◎ ◎ ◎ ╳ heat shrinkage ◎ ○ ◎ ◎ ○ ◎ ◎ ◎ ╳ ◎ ╳ ╳ ╳ ╳ ○ rebound ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ╳ ○ ╳ ○ ○

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

<Pattern Formability>

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

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

＜Chemical resistance＞

Coating the polyimide resin composition on the copper foil substrate, drying the surface at 90°C for 6 minutes to obtain a film, and then performing a hard bake program at 200°C for 1 hour to obtain a film thickness of about 15 μm Polyimide protective film.

The following criteria were used to evaluate whether the polyimide protective film had good chemical resistance. The polyimide protective film was soaked in 25° C. 10% NaOH, and the thickness of the polyimide protective film was observed and recorded as a thickness gauge. If soaked 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 decreases or there is color difference, the situation is set as ╳.

<Heat shrinkage>

Coating the polyimide resin composition on the copper foil substrate, drying the surface at 90°C for 6 minutes to obtain a film, and then performing a hard bake program at 200°C for 1 hour to obtain a film thickness of about 15 μm Polyimide protective film.

And using the following criteria to evaluate whether the polyimide protective film has good heat shrinkage. The copper foil substrate coated with the polyimide protective film was heated in an oven at 270°C for 60 seconds, and then placed at 25°C for 10 seconds, repeated three times to observe whether the copper foil substrate was warped. for evaluation. If it has been heated for three times, and the warpage is measured with a ruler to be ≤ 0.5mm, it is judged as ◎; if it has been heated for three times, and the warpage is measured with a ruler for more than 0.5mm but ≤ 1mm, it is judged as ○; if heated Three times, and the warpage is measured with a ruler > 1mm, it is judged as ╳.

＜Rebound force＞

Coating the polyimide resin composition on the copper foil substrate, drying the surface at 90°C for 6 minutes to obtain a film, and then performing a hard bake program at 200°C for 1 hour to obtain a film thickness of about 15 μm Polyimide protective film.

And the following criteria are used to evaluate whether the polyimide protective film has good resilience. Cut the copper foil substrate coated with polyimide protective film into samples with a width of 1 centimeter (cm), fix one end with a fixture, bend the other end back to form a U-shape, and place a sample under it. When the 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 3sec is judged as ◎; the electronic scale reading>10g/cm but ≤15g/cm is judged as ○; electronic scale The scale reading > 15 g/cm is judged as ╳.

The first figure 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 in the polyimide group. The characteristic peak of =O, and the characteristic peak of NH in isocyanate at 3386 cm ^-1 . The second graph is the FT-IR spectrum of the resin composition in Comparative Example 5. According to the results in Table 1, 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 thermal shrinkage of the protective film formed in Comparative Example 5 is not good. , will cause shrinkage warpage problem.

To sum up, after the photosensitive polyimide resin composition provided by the present invention is subjected to surface drying, baking and other processes, a polyimide can be obtained that can meet relevant specifications in terms of heat resistance, chemical resistance and flexibility. The 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 skilled in the art, some improvements can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

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The first figure is the FT-IR spectrum of the resin composition in Example 1.

The second graph is the FT-IR spectrum of the resin composition in Comparative Example 5.

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Claims (12)

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

(I) 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

A divalent organic group of a group, wherein R is hydrogen or methyl; m, n and o are each independently any integer selected from 10 to 600, and m>n+o; (b) photoradical origin A starting agent, which accounts for 1-15% of the total solid weight in the resin composition; (c) a thermally polymerizable compound, which comprises an isocyanate compound, and the thermally polymerizable compound accounts for 8% of the total solid weight in the resin composition -37%; (d) a radically polymerizable compound, which constitutes 3-27% by weight of the total solids in the resin composition; and (e) a solvent. The resin composition according to 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. The resin composition according to claim 2, wherein the isocyanate compound is selected from the group consisting of diphenylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, and trimethyl hexamethylene diisocyanate , isophorone diisocyanate, dicyclohexylmethane diisocyanate, L-lysine triisocyanate, triphenylmethane triisocyanate, phosphorothioate triphenyl isocyanate, (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. The resin composition according to claim 1, wherein the radically polymerizable compound is selected from compounds having at least two (meth)acrylate groups. The resin composition according to claim 1, wherein Ar ₁ is selected from one of the following groups:

. The resin composition of claim 1, wherein Ar ₂ is the following group:

, where p is any integer from 0 to 25. The resin composition according to claim 1, wherein Ar ₃ is selected from one of the following groups:

. The resin composition according to claim 1, wherein Ar ₄ is selected from one of the following groups:

, where R* is the

An organic group of groups where R is hydrogen or methyl. The resin composition according to claim 1, wherein the solvent accounts for 35-70% of the total solid mass in the composition. 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. The preparation method according to claim 10, further comprising the step of developing the surface-dried substrate before the heating step. A polyimide protective film, which is prepared by the preparation method described in claim 10 or 11.

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