KR20200132653A - Photosensitive soluble polyimide resin composition and protective film using the same - Google Patents

Abstract

The present invention relates to an alkali solution-soluble photosensitive polyimide resin composition including: (a) an alkali solution-soluble polyimide resin represented by chemical formula (I) and used at 45-65 wt% based on the total solid content of the composition; (b) alkali solution-soluble inorganic powder used at 25-50 wt% based on the total solid content of the composition and having a particle size of 0.1-10 micrometers; and (c) a photoinitiator used at 1-10 wt% based on the total solid content of the composition. In chemical formula (I), Ar_1 represents a tetravalent organic group; Ar_2 represents a divalent organic group; Ar_3 represents a divalent organic group; and Ar_4 represents a divalent organic group including a group represented by structural formula 1, wherein R is H or methyl, and each of m, n and o independently represents any one integer of 10-600. After the polyimide resin composition according to the present invention is subjected to processes, such as photosensitizing, baking, or the like, the photosensitive polyimide resin layer may be dissolved and removed through dipping in an alkali solvent.

Description

A photosensitive soluble polyimide resin composition and a protective film using the same TECHNICAL FIELD {PHOTOSENSITIVE SOLUBLE POLYIMIDE RESIN COMPOSITION AND PROTECTIVE FILM USING THE SAME}

The present invention relates to the technical field of a protective material for a circuit board manufacturing process, and more particularly, to a photosensitive soluble polyimide resin composition and a protective film using the same.

Printed circuit board-related process technology is rapidly developing, and it has evolved from the initial rigid printed circuit board (PCB) design method to the flexible printed circuit board (FPC) structure design. In this process, people's demand for light and thin electronic products, especially portable electronic products, has grown stronger. Everyday items such as mobile phones, tablet PCs, health bracelets, and digital cameras all use the function of a flexible printed circuit board that can be bent into a three-dimensional space, greatly reducing the volume and weight of the product and increasing the added value of the product.

Although the flexible printed circuit board has many advantages as described above, it still does not completely replace the conventional rigid printed circuit board. The main reason is that the rigid printed circuit board has excellent dimensional stability. Passive elements such as capacitors, resistors and inductors can be applied simultaneously on flexible or rigid printed circuit boards, but for more precise components such as driver ICs and camera modules, these components can be combined on rigid printed circuit boards to ensure product stability. Should be raised. Therefore, in the later period, a circuit board structure of a so-called flexible bonded board was developed. In other words, by combining the advantages of a flexible substrate and a rigid substrate, by integrating a flexible and rigid printed circuit board on the same circuit board, precise components can be mounted on the rigid substrate area and bent into a three-dimensional space of the flexible substrate. The purpose of minimizing the overall structure was implemented. The applications of flexible bonded boards are becoming more and more widespread, and the number of flexible bonded boards produced annually in the circuit board area is quite large. Therefore, there is increasing interest in problems such as yield loss and cost increase occurring in the manufacturing process of a flexible bonded substrate.

Strictly speaking, flexible and rigid printed circuit boards are two very different products, and in addition to having a large difference in final functions and features, there are also large differences in the manufacturing processes of both. This has to pay more because two different things have to be combined into one in the process of manufacturing the flexible bonded substrate. In general, in the case of a conventional manufacturing process of a flexible bonded substrate, the flexible printed circuit board portion is first completed, and then the flexible substrate must be processed in a rigid substrate manufacturing process. The manufacturing process includes processing processes such as high temperature, high pressure, acidic and alkaline solutions, in which case the already completed flexible substrate part may typically undergo some abrasion after completing this process, even in situations where it is no longer usable. You can do this.

In order to solve the above problems, a circuit board manufacturer typically covers a portion of a flexible substrate with a protective layer before manufacturing a rigid substrate, and removes the protective layer again after the entire rigid substrate manufacturing process is completed. However, since the working process of the protective layer is very cumbersome, materials such as epoxy resin adhesive, polyimide film, and release paper must be combined and the shape of the protective layer is manufactured through several processes such as hot pressing and mold molding. The protective layer has a double-layer structure, the upper layer is a polyimide film, and the lower layer is an epoxy resin adhesive layer, and the adhesive layer is distributed only around the polyimide film and forms an adhesive layer having a relatively narrow width along the edge. When this protective layer is laminated on the surface of the flexible substrate by hot pressing, the peripheral adhesive layer can be attached to the edge of the bonded flexible substrate, and the other part of the protective film is a polyimide film that is not attached by the adhesive layer and is hot pressing. Because it does not have viscosity and the Tg value reaches 300℃ or higher, it is not adhered to other parts of the flexible substrate, so it is possible to completely seal the flexible substrate area. During the manufacturing process of the rigid substrate, acid and alkali solutions penetrate into the flexible substrate area. Or the flexible substrate area sealed by the adhesive layer when passing through the tin-lead tank is not eroded or contaminated by tin, lead.

In addition to the complex fabrication process and high material cost, the flexible substrate protective layer faces quality problems at this stage. As circuit board designs become increasingly complex, standards for the volume and area of the flexible substrate protective layer are becoming smaller and more sophisticated. The adhesive layer around the protective layer should also lower the fluidity during hot pressing to prevent the epoxy resin gel from flowing into other functional areas and contaminating circuit board lines or components. However, since the protective layer is manufactured by softening the adhesive layer using hot pressing and generating adhesiveness, it is only possible to completely seal the flexible substrate region only if it has some degree of fluidity. It can be seen that the fluidity of the adhesive layer has a significant positive correlation with the sealing degree of the flexible substrate, and the protective layer at the present stage cannot take into account the functions of low fluidity and excellent sealing properties of the adhesive layer at the same time.

Photosensitive polyimide (PSPI) resin is molded using exposure to light, and after molding, the external dimension precision of the product is very high, and polyimide has high heat resistance and solvent resistance. Currently commercially available PSPI is used only for circuit board line protection functions, and PSPI resin can form a permanent protective film that cannot be removed on the line through manufacturing processes such as light exposure, development, drying and baking. In Chinese patents with application numbers 201510273707.4, 201810173588.9, 201710660813.7 and 201710634007.2, other PSPI resins are disclosed, and these resins have photosensitive or thermal conductivity, but do not have alkali solubility.

In order to solve the above technical problem, an object of the present invention is to provide a photosensitive soluble polyimide resin composition and a protective film using the same, and the polyimide resin composition of the present invention undergoes manufacturing processes such as photosensitive, baking, etc. Then, the photosensitive polyimide resin layer is dissolved and removed by immersing it in an alkaline solvent again, and through the above technical characteristics, a protective effect is realized during the electronic product manufacturing process and does not remain in the electronic product even after the manufacturing process is finished.

The first object of the present invention is to provide an alkali solution-soluble photosensitive polyimide resin composition, which is uniformly dispersed in a solvent.

(a) a polyimide resin represented by the formula (I) of alkali solution solubility and accounting for 45% to 65% of the total weight of solids in the composition;

기를 함유하는 2가 유기기이고, 여기에서 R은 수소 또는 메틸이고,Here, Ar ₁ is a tetravalent organic group, Ar ₂ is a divalent organic group, Ar ₃ is a divalent organic group, Ar ₄ is

Is a divalent organic group containing a group, wherein R is hydrogen or methyl,

m, n and o are each independently any one integer selected from the group consisting of 10 to 600,

(b) an inorganic powder soluble in an alkali solution occupying 25% to 50% of the total weight of the solid in the composition and having a particle diameter of 0.1 μm to 10 μm; And

(c) It comprises a photoinitiator which accounts for 1% to 10% of the total weight of the solid in the composition.

In a more preferred method of the present invention, the resin composition further comprises an acrylic acid resin-based photocrosslinking agent which accounts for 0% to 5%, and relatively preferably 2% to 15% of the solid weight in the composition. The photocrosslinker generates an acid after light exposure to form an acid-catalyzed crosslinking mechanism. The photocrosslinker absorbs light energy of a certain wavelength after exposure to light to generate free groups, and causes or catalyzes polymerization of a corresponding monomer or prepolymer to form a crosslink. When the dose of the photocrosslinking agent exceeds 15% of the total weight of the solid in the composition, developability is relatively poor.

In a more preferred method of the present invention, the resin composition further comprises a thermal crosslinking agent accounting for 0% to 15%, relatively preferably 2% to 15% of the total weight of the solid in the composition, and the thermal crosslinking agent is phenolic Compounds, alkoxymethylamine resins, and epoxy resins. The addition of the thermal crosslinking agent prevents the polyimide molecular chain from forming a crosslinked structure with the thermal crosslinking agent during light exposure baking. The main purpose of the thermal crosslinking agent is to crosslink with ortho of the main chain -OH group or terminal -OH group of the polyimide through acid catalyst and heat treatment during hard firing after exposure, so that the solubility difference between the exposed and unexposed areas Is to be generated so that the pattern is formed quickly. When the dosage of the thermal crosslinking agent exceeds 15% of the total weight of the solids in the composition, it becomes relatively difficult to dissolve and remove the alkali.

The crosslinked structure generated by adding a photocrosslinking agent and a thermal crosslinking agent can increase developability and film-forming properties of the polyimide resin composition.

In a more preferred method of the present invention, Ar ₁ in the polyimide resin is a tetravalent organic group, and its main chain portion may include an aliphatic cyclic group or an aromatic cyclic group, but is limited to one of the following groups. It doesn't work.

기이며, 여기에서 q는 같거나 다르고, 각각 독립적으로 0 내지 5로 이루어진 군 중 어느 하나의 정수이고, p는 0 내지 20으로 이루어진 군 중 어느 하나의 정수이다.In a more preferred method of the present invention, Ar ₂ in the polyimide resin is

Is a group, wherein q is the same or different, and each independently is an integer of any one of the group consisting of 0 to 5, and p is an integer of any one of the group consisting of 0 to 20.

More preferably, p=0 to 10, and when the Ar ₂ chain is too long, the mechanical properties and thermal performance of the polyimide resin represented by formula (I) may be destroyed.

In a more preferred method of the present invention, Ar ₃ in the polyimide resin is one of the following groups.

Ar ₃ is a divalent organic group, has a phenol group or a carboxyl group in its main chain portion, and the content of the phenol group or carboxyl group is about 10% to 30% of the number of moles of the polyimide resin represented by formula (I). The development time can be controlled by adjusting the content of the branched phenol group or carboxyl group, and if the content of the branched chain phenol group or carboxyl group is relatively high, the solubility of the alkali developer in the polyimide resin represented by formula (I) is relatively high. It becomes excellent and its developability can be improved.

In a more preferred method of the present invention, Ar ₄ in the polyimide resin is one of the following groups,

기를 포함하는 유기기이고, 여기에서 R은 수소 또는 메틸이다.Where R ^* is

It is an organic group containing a group, wherein R is hydrogen or methyl.

In the above structural formula, * indicates a linking site when another group is connected to the group.

In the synthesis step of the polyimide resin represented by formula (I), an appropriate amount of diamine monomer (containing Ar ₂ ) and dianhydride monomer are dissolved in N-methylpyrrolidone (NMP). Then, when reacting at 80° C. for 2 hours, xylene is added and heated to 180° C. for distillation. A diamine monomer containing a phenol group or a carboxyl group is added again, and when the reaction is performed at 80° C. for 2 hours, xylene is added, heated to 180° C., distilled, and cooled after about 4 hours.

The method of preparing an alkali solution-soluble photosensitive polyimide resin composition can be obtained by taking the photosensitive polyimide colloid prepared above and adding an inorganic powder, a photoinitiator, a photocrosslinking agent and a thermal crosslinking agent, wherein the photocrosslinking agent and the thermal crosslinking agent are optional. Can be added as.

In a more preferred method of the present invention, the solvent in the resin composition is N-methyl-2-pyrrolidone, N,N-dimethylacetamide (N,N-dimethylacetamide), γ-butyrolactone (γ-butyrolactone) , Xylene and toluene, but is not limited thereto.

In a more preferred method of the present invention, the photoinitiator in the resin composition is bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide), 2,4 ,6-trimethylbenzoyl-diphenylphosphine oxide (2,4,6-trimethylbenzoyl-diphenylphosphine oxide) including, but not limited to, one or more of.

In a more preferred method of the present invention, the inorganic powder in the resin composition includes, but is not limited to, one or more of aluminum oxide, aluminum hydroxide, and silicon dioxide.

In a more preferred solution of the present invention, the solvent accounts for 60% to 90% of the total mass of solids in the composition.

A second object of the present invention is to provide a method for producing an alkali solution-soluble protective film, which includes the following steps.

The alkali solution-soluble photosensitive polyimide resin composition of the present invention is coated on a substrate, surface-dried at 90°C to 120°C, and development is performed using an alkali solution after exposure to light, or from 140°C after surface drying. The alkali solution-soluble protective film can be obtained by heating at 200°C.

A third object of the present invention is to provide an alkali solution-soluble protective film prepared by the above production method.

The protective film produced by the method of the present invention can be used as a protective material in a circuit board manufacturing process, which has alkali solubility and heat resistance.

The alkali solution-soluble photosensitive polyimide resin composition of the present invention may form a plurality of pore patterns having a minimum pore diameter of 75 μm in the cured resin layer after photosensitization.

The resin composition of the present invention can be used as a protective material for any electronic product after forming the protective film, and the resin composition can be completely or partially removed during the manufacturing process or after the manufacturing process is completed, so that various application purposes of electronic products Can be implemented.

Through the above solution, the present invention has at least the following advantages.

The present invention provides an alkali solution-soluble photosensitive polyimide resin composition, wherein the composition is subjected to processes such as light exposure, development, drying and baking to obtain a cured resin layer, and the resin layer is immersed using an alkaline solvent and By dissolving, the resin layer can be removed from the surface of the protective object, and through the above technical characteristics, the electronic product can be protected during the manufacturing process, and it does not remain on the electronic product even after the manufacturing process is finished.

The above description is only a general description of the technical solution of the present invention, and in order to more clearly understand the technical means of the present invention and to be able to implement it according to the contents of the specification, the following is a comparatively preferred embodiment of the present invention and the accompanying drawings. It will be described in detail using.

1 is an FT-IR spectrum of a resin composition in Example 6.
2 is an FT-IR spectrum of a resin composition in Example 4.

Hereinafter, a specific embodiment of the present invention will be described in more detail with reference to the accompanying drawings and embodiments. The following examples are intended to illustrate the present invention and do not limit the scope of the present invention.

Example 1

Take a 500 mL 3-neck round bottom flask equipped with a mechanical stirrer and nitrogen inlet, and 19.88 g (80 mmol) bis(3-aminopropyl)]polydimethylsiloxane (Bis-(3-aminopropyl)]polydimethylsiloxane), 80.7 g 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) is added. After reacting the solution at 50° C. to 80° C. for 2 hours, 45 g of xylene was added and the temperature was raised to 180° C., followed by stirring for 1.5 hours, and then 12.172 g (80 mmol) 3,5-diaminobenzoic acid (3 ,5-Diaminobenzoic acid) was added, and the solution was reacted at 50°C to 80°C for 2 hours, and then 45g of xylene was added to raise the temperature to 180°C, followed by stirring for 4 hours. After cooling, a PIA-1 solution can be obtained. Take 50 g of the PIA-1 solution, add 11.38 g glycidyl methacrylate (GMA) and stir at 70° C. to 100° C. for 24 hours, and the photosensitive polyimide resin PSPI-A1 represented by Formula (I) Can be obtained.

이고, Ar₂는

이고, p=0이고, Ar₃은

이고, Ar₄는

이고, m=n+o=80이다.Where Ar ₁ is

And Ar ₂ is

And p=0, and Ar ₃ is

And Ar ₄ is

And m=n+o=80.

Example 2

Take a 500 mL 3-neck round bottom flask equipped with a mechanical stirrer and a nitrogen inlet, 19.88 g (80 mmol) bis(3-aminopropyl)]polydimethylsiloxane (Bis-(3-aminopropyl)]polydimethylsiloxane), 80.7 g NMP, 26.17g (160mmol) benzene-1,2,4,5-tetracarboxylic dianhydride (Benzene-1,2,4,5-tetracarboxylic dianhydride) was added, and the solution was added at 50℃ to 80℃ for 2 After reacting for a period of time, 45 g of xylene was added and the temperature was raised to 180° C., followed by stirring for 1.5 hours, and then 12.172 g (80 mmol) 3,5-diaminobenzoic acid was added, After reacting the solution at 50° C. to 80° C. for 2 hours, 45 g of xylene was added to raise the temperature to 180° C., and stirring was continued for 4 hours. After cooling, a PIA-2 solution can be obtained. 50 g of the PIA-2 solution was taken, 11.38 g of GMA was added and stirred at 70° C. to 100° C. for 24 hours to obtain a photosensitive polyimide resin PSPI-A2 represented by Formula (I).

이고, Ar₂는

이고, p=0이고, Ar₃은

이고, Ar₄는

이고, m=n+o=80이다.Where Ar ₁ is

And Ar ₂ is

And p=0, and Ar ₃ is

And Ar ₄ is

And m=n+o=80.

Example 3

Take a 500 mL 3-neck round bottom flask equipped with a mechanical stirrer and nitrogen inlet, and take 144.29 g (80 mmol) bis (3-aminopropyl)] polydimethylsiloxane (Bis- (3-aminopropyl)] polydimethylsiloxane) (the length of the chain section Is different from Example 2), 80.7g NMP, 26.17g (160mmol) benzene-1,2,4,5-tetracarboxylic dianhydride (Benzene-1,2,4,5-tetracarboxylic dianhydride) was added Then, after reacting the solution at 50°C to 80°C for 2 hours, 45g of xylene was added and the temperature was raised to 180°C, followed by stirring for 1.5 hours, and then 12.172g (80mmol) 3,5-diaminobenzoic acid. (3,5-Diaminobenzoic acid) was added, and the solution was reacted at 50°C to 80°C for 2 hours, and then 45 g of xylene was added to raise the temperature to 180°C, followed by stirring for 4 hours. After cooling, a PIA-3 solution can be obtained. 50 g of the PIA-3 solution was taken, 11.38 g of GMA was added and stirred at 70° C. to 100° C. for 24 hours to obtain a photosensitive polyimide resin PSPI-A3 represented by the formula (I).

이고, Ar₂는

이고, p=25이고, Ar₃은

이고, Ar₄는

이고, m=n+o=80이다.Where Ar ₁ is

And Ar ₂ is

And p=25, and Ar ₃ is

And Ar ₄ is

And m=n+o=80.

Examples 4 to 8 and Comparative Examples 1 to 5

Each component is mixed according to the component composition in Table 1, and the content of each component in Table 1 is a mass percentage based on the total weight of solids in the composition. Each component mixture in Table 1 was dissolved in N-methylpyrrolidone to prepare a solution having a solid content of 60% to form an alkali solution-soluble photosensitive polyimide resin composition, which was used as a coating solution.

In Table 1, A1 is PSPI-A1, A2 is PSPI-A2, A3 is PSPI-A3, B1 is aluminum hydroxide (4.0 μm), B2 is silicon dioxide (2.0 μm), C1 is Irgacure-819, D1 is PDBE-450A. (NOF), D2 stands for Resin 828 (EPON).

Table 1 Alkaline solution-soluble photosensitive polyimide resin composition

The pattern formation test method of the resin composition is as follows.

After coating the polyimide resin composition on a copper foil substrate, surface drying at 90° C. for 5 minutes to prepare a film, and after exposure to light, the photosensitive resin composition layer subjected to light exposure using 1 wt% sodium carbonate aqueous solution again was developed for 60 seconds. Let it.

Based on the following criteria, it is evaluated whether the film has excellent edge sharpness with a line width after development. The smaller the line width of the photosensitive resin composition layer means that the difference in solubility in the developer solution between the light-irradiated portion and the light-irradiated portion is large, which explains that relatively favorable results have been obtained. In addition, the smaller the change in the line width relative to the change in the light exposure energy, the wider the light exposure latitude, which explains that a relatively favorable result was obtained. After observing the pattern formed with an optical microscope, it is A when a fine line pattern of line width/interval width = 100 μm/100 μm or less is formed, and B when a fine line pattern of line width/interval width = 100 μm/100 μm or less is formed. .

The alkali solubility test method is as follows.

After coating the polyimide resin composition on a copper foil substrate, the film was prepared by surface drying at 90° C. for 5 minutes, followed by a hard firing process at 200° C. for 1 hour to obtain a soluble polyimide film having a film thickness of about 15 μm. can do.

Whether or not the polyimide film has excellent alkali solubility is evaluated based on the following criteria, the soluble polyimide film is immersed in 5% NaOH at 60° C., and the dissolution time of the soluble polyimide film is observed and recorded with an optical microscope. When the soluble polyimide film is completely removed when immersed within 1 minute, the above situation is indicated by ◎, and when the soluble polyimide film is completely removed when immersed for 1 minute or more and 3 minutes or less, the situation is indicated by ○, and 3 When the soluble polyimide film is completely removed when immersed for more than 5 minutes, the situation is indicated by △, and when the polyimide film still remains on the surface even after immersion for 5 minutes or more, the situation is indicated by X.

The heat resistance test method is as follows.

The polyimide resin composition was coated on a copper foil substrate and then surface-dried for 5 minutes at 90 to prepare a film, followed by a hard firing process at 200° C. for 1 hour to obtain a soluble polyimide film having a thickness of about 15 μm. can do.

Evaluate whether the polyimide film has excellent heat resistance based on the following criteria. After immersing the soluble polyimide film in a tin furnace at 288°C for 10 seconds, leave it in an environment at 25°C for 10 seconds, and repeat this 3 times to observe whether bubbles are formed. To evaluate. If no bubbles are observed after being immersed within 3 times, it is marked with ◎, and when bubbles are observed after being immersed within 3 times, it is marked with X.

1 is an FT-IR spectrum of a resin composition in Example 6, wherein the peak at 1019 cm ^-1 is a characteristic wavelength peak of Si-O-Si. 2 is an FT-IR spectrum of the resin composition in Example 4, where the peaks at 3526cm ^-1 , 3425cm ^-1 and 3373cm ^-1 are characteristic wavelength peaks of Al(OH) ₃ .

The above description is only a preferred embodiment of the present invention and does not limit the present invention. Those of ordinary skill in the technical field to which the present invention pertains can make minor improvements and modifications without departing from the technical spirit of the present invention, and these improvements and modifications should be regarded as the protection scope of the present invention.

Claims (10)

Evenly distributed in the solution
(a) a polyimide resin represented by the formula (I) of alkali solution solubility and accounting for 45% to 65% of the total weight of solids in the composition; (b) an inorganic powder soluble in an alkali solution occupying 25% to 50% of the total weight of the solid in the composition and having a particle diameter of 0.1 μm to 10 μm; And (c) a photoinitiator that accounts for 1% to 10% of the total weight of solids in the composition,

Here, Ar ₁ is a tetravalent organic group, Ar ₂ is a divalent organic group, Ar ₃ is a divalent organic group, and Ar ₄ is

Is a divalent organic group containing a group, wherein R is hydrogen or methyl,
m, n and o are each independently an integer selected from the group consisting of 10 to 600, an alkali solution-soluble photosensitive polyimide resin composition. The method of claim 1,
Alkaline solution-soluble photosensitive polyimide resin composition further comprising an acrylic acid resin-based photocrosslinking agent that accounts for 0% to 15% of the total weight of the solid in the composition. The method of claim 1,
Further comprising a thermal crosslinking agent occupying 0% to 15% of the total weight of the solid in the composition,
The thermal crosslinking agent is an alkali solution-soluble photosensitive polyimide resin composition comprising at least one of a phenolic compound, an alkoxymethylamine resin, and an epoxy resin. The method according to any one of claims 1 to 3,
Ar ₁ is an alkali solution-soluble photosensitive polyimide resin composition which is one of the following groups.

The method according to any one of claims 1 to 3,
Ar ₂ is

And
Here, q is each independently an integer of any one of the group consisting of 0 to 5, p is an integer of any one of the group consisting of 0 to 20, alkali solution-soluble photosensitive polyimide resin composition. The method according to any one of claims 1 to 3,
Ar ₃ is an alkali solution-soluble photosensitive polyimide resin composition which is one of the following groups.

The method according to any one of claims 1 to 3,
Ar ₄ is one of the following groups,

Where R* is

It is an organic group containing a group,
Here, R is hydrogen or methyl, an alkali solution-soluble photosensitive polyimide resin composition. The method according to any one of claims 1 to 3,
The solvent is an alkali solution-soluble photosensitive polyimide resin composition that accounts for 60% to 90% of the total mass of the solid in the composition. The alkali solution-soluble photosensitive polyimide resin composition of any one of claims 1 to 3 is coated on a substrate, surface-dried at 90°C to 120°C, and developing using an alkali solution after exposure to light, or Or after surface drying, heating at 140°C to 200°C to obtain an alkali solution-soluble protective film. An alkali solution-soluble protective film produced by the production method of claim 9.

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