JP6578295B2 - Laminated structure, dry film and flexible printed wiring board - Google Patents

Description

  The present invention relates to a laminated structure, a dry film, and a flexible printed wiring board useful as an insulating film of a flexible printed wiring board.

  In recent years, as electronic devices have become smaller and thinner due to the spread of smartphones and tablet terminals, it has become necessary to reduce the space of circuit boards. Therefore, the use of the flexible printed wiring board which can be folded and accommodated is expanded, and the flexible printed wiring board is required to have higher reliability than ever.

  On the other hand, as an insulating film to ensure the insulation reliability of flexible printed wiring boards, a cover based on polyimide with excellent mechanical properties such as heat resistance and flexibility is used for the bent part (bent part). Using a lay (see, for example, Patent Documents 1 and 2), the mounting part (non-bent part) has a mixed mounting process using a photosensitive resin composition that is excellent in electrical insulation and solder heat resistance and can be finely processed. Widely adopted.

  That is, a cover lay based on polyimide is not suitable for fine wiring because it requires processing by die punching. Therefore, it is necessary to partially use an alkali developing type photosensitive resin composition (solder resist) that can be processed by photolithography in a chip mounting portion that requires fine wiring.

Japanese Patent Laid-Open No. Sho 62-26392 Japanese Unexamined Patent Publication No. 63-110224

  As described above, the conventional flexible printed wiring board manufacturing process has to employ a mixed mounting process of bonding the coverlay and forming the solder resist, which is inferior in cost and workability. It was.

  On the other hand, in the past, it has been studied to apply an insulating film as a solder resist or an insulating film as a coverlay as a solder resist and a coverlay of a flexible printed wiring board. The material has not yet been put to practical use.

  Therefore, an object of the present invention is to provide a laminated structure, a dry film, which is excellent in flexibility and suitable for a batch forming process of an insulating film of a flexible printed wiring board, particularly a bent portion (bent portion) and a mounting portion (non-bent portion), And it is providing the flexible printed wiring board which has the hardened | cured material as a protective film, for example, a coverlay or a soldering resist.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the laminated structure of the present invention is a laminated structure having a resin layer (A) and a resin layer (B) laminated on the flexible printed wiring board via the resin layer (A), The resin layer (B) is composed of a photosensitive thermosetting resin composition containing an alkali-soluble resin, a photopolymerization initiator, and a heat-reactive compound, and the resin layer (A) is an alkali-soluble resin. And an alkali development type resin composition containing no photopolymerization initiator.

  In the laminated structure of the present invention, the resin layer (A) is preferably made of a resin composition further containing a polymerization inhibitor.

  The laminated structure of the present invention can be used for at least one of a bent portion and a non-bent portion of a flexible printed wiring board, and among the cover lay, solder resist, and interlayer insulating material of the flexible printed wiring board It can be used for at least one of the applications.

  The dry film of the present invention is characterized in that at least one surface of the laminated structure of the present invention is supported or protected by a film.

  Furthermore, the flexible printed wiring board of the present invention comprises an insulating layer formed by forming a layer of the laminated structure of the present invention on a flexible printed wiring board, patterning by light irradiation, and forming the pattern in a batch with a developer. It is characterized by having a film.

  Here, the flexible printed wiring board of the present invention is formed by sequentially forming the resin layer (A) and the resin layer (B) without using the laminated structure according to the present invention, and then patterning by light irradiation. Alternatively, the pattern may be collectively formed with a developer. In the present invention, the “pattern” means a patterned cured product, that is, an insulating film.

  According to the present invention, a laminated structure, a dry film, which is excellent in flexibility and suitable for a batch forming process of an insulating film of a flexible printed wiring board, particularly a bent portion (bent portion) and a mounting portion (non-bent portion), and It is possible to realize a flexible printed wiring board having the cured product as a protective film, for example, a cover lay or a solder resist.

It is process drawing which shows typically an example of the manufacturing method of the flexible printed wiring board of this invention. It is process drawing which shows typically the other example of the manufacturing method of the flexible printed wiring board of this invention. It is a photograph figure which shows the opening shape obtained in the Example.

Hereinafter, embodiments of the present invention will be described in detail.
(Laminated structure)
The laminated structure of the present invention has a resin layer (A) and a resin layer (B) laminated on the flexible printed wiring board via the resin layer (A), and the resin layer (B) And a photosensitive thermosetting resin composition containing an alkali-soluble resin, a photopolymerization initiator, and a heat-reactive compound, and the resin layer (A) contains an alkali-soluble resin and a heat-reactive compound. It consists of an alkali developing resin composition that does not contain a polymerization initiator.

  Such a laminated structure of the present invention has a resin layer (A) and a resin layer (B) in this order on a flexible printed wiring board in which a copper circuit is formed on a flexible substrate, and an upper resin layer ( B) is made of a photosensitive thermosetting resin composition that can be patterned by light irradiation, and the resin layer (B) and the resin layer (A) can form a pattern collectively by development. .

In such a laminated structure of the present invention, the resin layer (A) on the printed wiring board side does not contain a photopolymerization initiator and cannot be patterned by a single layer. By diffusing active species such as radicals generated from the photopolymerization initiator contained in the layer (B) into the resin layer (A) directly below, both layers can be patterned simultaneously. In particular, in a printed wiring board manufacturing method including a PEB (POST EXPOSURE BAKE) process, the effect is remarkable due to thermal diffusion of the active species.
On the other hand, when the photopolymerization initiator is contained in the resin layer (A) on the printed wiring board side, the photopolymerization initiator itself has a property of absorbing light, so that the photopolymerization initiator increases toward the deep part. Although the polymerization initiating ability is lowered and the photoreactivity in the deep part is lowered, it tends to be undercut, and high-definition pattern formation has been difficult, but the upper resin layer in the laminated structure of the present invention The present inventors considered that such a problem can be improved by the influence of the diffusion of the active species from (B). However, in spite of the diffusion of the active species, there is a problem in that the deep photoreactivity (deep curability) is still poor due to the interaction with the photopolymerization initiator and undercut occurs.
Therefore, in the structure of the laminated structure of the present invention, it is necessary that the resin layer (A) does not contain a photopolymerization initiator, and as a result, it is possible to form a pattern with excellent deep curability without undercut.
Moreover, in the laminated structure as in the present invention, the reason is not clear, but the diffusion of the active species occurs in areas other than the exposed area due to the influence of the interface. There was a new problem that so-called halation is likely to occur near the interface between A) and the resin layer (B). This problem was particularly remarkable in the PEB process. In this respect, in the laminated structure of the present invention, by further blending a polymerization inhibitor with the composition constituting the resin layer (A), unexpectedly preventing this halation, stabilizing the opening shape, and good It is possible to form a high-definition pattern excellent in resolution that can achieve both deep curability.

[Resin layer (A)]
(Alkali developable resin composition constituting the resin layer (A))
The alkali-developable resin composition constituting the resin layer (A) includes an alkali-soluble resin that contains at least one functional group of phenolic hydroxyl group and carboxyl group and can be developed with an alkali solution, and thermal reactivity. It is sufficient if the composition contains a compound and does not contain a photopolymerization initiator. Examples of the alkali-soluble resin include compounds having a phenolic hydroxyl group, compounds having a carboxyl group, compounds having a phenolic hydroxyl group and a carboxyl group, and known and commonly used resins are used.

  In particular, it contains a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, and a heat-reactive compound, which has been conventionally used as a solder resist composition, including a compound having a carboxyl group. And a resin composition containing no photopolymerization initiator.

  Here, as the carboxyl group-containing resin or the carboxyl group-containing photosensitive resin and the compound having an ethylenically unsaturated bond, known and commonly used compounds are used, and as the thermally reactive compound, a cyclic (thio) ether is used. Known and conventional compounds having a functional group capable of undergoing a curing reaction by heat, such as a group, are used.

  It is preferable that a polymerization inhibitor is further blended in the alkali developing resin composition constituting the resin layer (A). By blending this polymerization inhibitor, it is possible to minimize the influence of exposure, suppress the influence of heat in the PEB process, and stabilize the opening shape. In this case, the problem of poor curing in the deep portion does not occur. Therefore, by blending the polymerization inhibitor into the alkali developing resin composition constituting the resin layer (A), it is possible to achieve both stabilization of the opening shape and good deep part curability.

  As this polymerization inhibitor, a known and usual polymerization inhibitor can be used. As polymerization inhibitors, phenothiazine, hydroquinone, N-phenylnaphthylamine, chloranil, pyrogallol, benzoquinone, t-butylcatechol, hydroquinone, methylhydroquinone, tert-butylhydroquinone, hydroquinone monomethyl ether, catechol, pyrogallol, naphthoquinone, 4-methoxy- Examples thereof include 1-naphthol, 2-hydroxy 1,4-naphthoquinone, phosphorus-containing compounds having a phenolic hydroxyl group, and nitrosamine compounds. These polymerization inhibitors may be used individually by 1 type, and may be used in combination of 2 or more type.

  The blending amount of the polymerization inhibitor is preferably 0.01 to 100 parts by mass, and more preferably 0.03 to 50 parts by mass with respect to 100 parts by mass of the alkali-soluble resin. By making the compounding quantity of a polymerization inhibitor into the said range, halation can be prevented and it is preferable.

[Resin layer (B)]
(Photosensitive thermosetting resin composition constituting the resin layer (B))
The photosensitive thermosetting resin composition constituting the resin layer (B) includes an alkali-soluble resin, a photopolymerization initiator, and a thermoreactive compound. Among these, as the alkali-soluble resin, known and conventional resins similar to the resin layer (A) can be used, but an alkali-soluble resin having an imide ring which is superior in characteristics such as flex resistance and heat resistance is preferable. Can be used. Moreover, as a heat-reactive compound, the well-known and usual thing similar to the said resin layer (A) can be used.

(Alkali-soluble resin having an imide ring)
In the present invention, the alkali-soluble resin having an imide ring has at least one alkali-soluble group out of phenolic hydroxyl group and carboxyl group and an imide ring. For introducing the imide ring into the alkali-soluble resin, a known and usual method can be used. Examples thereof include a resin obtained by reacting a carboxylic anhydride component with an amine component and / or an isocyanate component. The imidization may be performed by thermal imidization or chemical imidization, and these may be performed in combination.

  Here, examples of the carboxylic acid anhydride component include tetracarboxylic acid anhydrides and tricarboxylic acid anhydrides, but are not limited to these acid anhydrides, and acid anhydrides that react with amino groups or isocyanate groups. Any compound having a physical group and a carboxyl group can be used, including derivatives thereof. These carboxylic anhydride components may be used alone or in combination.

  Examples of the amine component include diamines such as aliphatic diamines and aromatic diamines, polyvalent amines such as aliphatic polyether amines, diamines having carboxylic acids, and diamines having phenolic hydroxyl groups. It is not limited to. These amine components may be used alone or in combination.

  Diisocyanates such as aromatic diisocyanates and their isomers and multimers, aliphatic diisocyanates, alicyclic diisocyanates and their isomers, and other general-purpose diisocyanates can be used as the isocyanate component. It is not limited. These isocyanate components may be used alone or in combination.

  The alkali-soluble resin having an imide ring as described above may have an amide bond. This may be a polyamideimide obtained by reacting an imidized product having a carboxyl group, an isocyanate and a carboxylic acid anhydride, or may be due to other reactions. Furthermore, you may have the coupling | bonding which consists of another addition and condensation.

  In synthesizing such an alkali-soluble resin having an alkali-soluble group and an imide ring, a known and commonly used organic solvent can be used. Such an organic solvent is not particularly limited as long as it is a solvent that does not react with the carboxylic acid anhydrides, amines, and isocyanates that are raw materials and that dissolves these raw materials, and the structure is not particularly limited. In particular, aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and γ-butyrolactone are preferred because of the high solubility of the raw materials.

  An alkali-soluble resin having at least one alkali-soluble group and imide ring among phenolic hydroxyl groups and carboxyl groups as described above has an acid value of 20 to 200 mgKOH / g in order to cope with the photolithography process. And more preferably 60 to 150 mgKOH / g. When the acid value is 20 mgKOH / g or more, the solubility in alkali increases, the developability becomes good, and further, the degree of crosslinking with the thermosetting component after light irradiation becomes high, so that sufficient development contrast is obtained. be able to. Further, when the acid value is 200 mgKOH / g or less, in particular, so-called heat fogging in a PEB (POST EXPOSURE BAKE) step after light irradiation described later can be suppressed, and the process margin is increased.

  The molecular weight of the alkali-soluble resin is preferably from 1,000 to 100,000, more preferably from 2,000 to 50,000, considering developability and cured coating properties. When the molecular weight is 1,000 or more, sufficient development resistance and cured properties can be obtained after exposure and PEB. On the other hand, when the molecular weight is 100,000 or less, alkali solubility increases and developability improves.

(Photopolymerization initiator)
As the photopolymerization initiator used in the resin layer (B), known ones can be used. For example, benzoin compounds, acylphosphine oxide compounds, acetophenone compounds, α-aminoacetophenone compounds, oxime ester compounds, thioxanthones. System compounds and the like.
In particular, when used in a PEB step after light irradiation described later, a photopolymerization initiator that also has a function as a photobase generator is suitable. In this PEB step, a photopolymerization initiator and a photobase generator may be used in combination.

A photopolymerization initiator that also functions as a photobase generator is a polymer that undergoes a polymerization reaction of a thermoreactive compound, which will be described later, when the molecular structure is changed by light irradiation such as ultraviolet light or visible light, or when the molecule is cleaved. It is a compound that produces one or more basic substances that can function as a catalyst. Examples of basic substances include secondary amines and tertiary amines.
Examples of the photopolymerization initiator that also functions as a photobase generator include α-aminoacetophenone compounds, oxime ester compounds, acyloxyimino groups, N-formylated aromatic amino groups, and N-acylated aromatics. And compounds having a substituent such as a group amino group, a nitrobenzyl carbamate group, and an alkoxybenzyl carbamate group. Among these, an oxime ester compound and an α-aminoacetophenone compound are preferable, and an oxime ester compound is more preferable. As the α-aminoacetophenone compound, those having two or more nitrogen atoms are particularly preferable.

  The α-aminoacetophenone compound is not particularly limited as long as it has a benzoin ether bond in the molecule and is cleaved within the molecule when irradiated with light to produce a basic substance (amine) that exhibits a curing catalytic action.

  Any oxime ester compound can be used as long as it is a compound that generates a basic substance by light irradiation.

  Such a photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type. The blending amount of the photopolymerization initiator in the resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.3 to 20 parts by mass with respect to 100 parts by mass of the alkali-soluble resin. In the case of 0.1 parts by mass or more, the development resistance contrast of the light irradiated part / non-irradiated part can be favorably obtained. Moreover, in 40 mass parts or less, hardened | cured material characteristic improves.

  In the resin composition used in the resin layer (A) and the resin layer (B) as described above, the following components can be blended as necessary.

(Polymer resin)
As the polymer resin, known and commonly used ones can be blended for the purpose of improving the flexibility and dryness of the touch of the resulting cured product. Examples of such polymer resins include cellulose-based, polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamide-based, polyamide-imide-based binder polymers, block copolymers, and elastomers. This polymer resin may be used individually by 1 type, and may use 2 or more types together.

(Inorganic filler)
An inorganic filler can be mix | blended in order to suppress the cure shrinkage of hardened | cured material and to improve characteristics, such as adhesiveness and hardness. Examples of such inorganic fillers include barium sulfate, amorphous silica, fused silica, spherical silica, talc, clay, magnesium carbonate, calcium carbonate, aluminum oxide, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, Neuburg Sicilius Earth etc. are mentioned.

(Coloring agent)
As the colorant, known and commonly used colorants such as red, blue, green, yellow, white and black can be blended, and any of pigments, dyes and pigments may be used.

(Organic solvent)
An organic solvent can be mix | blended for the preparation of a resin composition, and the viscosity adjustment for apply | coating to a base material or a carrier film. Examples of such organic solvents include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, petroleum solvents, and the like. Such an organic solvent may be used individually by 1 type, and may be used as a 2 or more types of mixture.

(Other ingredients)
If necessary, components such as a mercapto compound, an adhesion promoter, an antioxidant, and an ultraviolet absorber can be further blended. As these, known and commonly used ones can be used. In addition, known and commonly used thickeners such as finely divided silica, hydrotalcite, organic bentonite, montmorillonite, defoamers and / or leveling agents such as silicones, fluorines and polymers, silane coupling agents, rust inhibitors Known and conventional additives such as can be blended.

  Since the laminated structure of the present invention is excellent in flexibility, it can be used for at least one of a bent portion and a non-bent portion of a flexible printed wiring board. It can be used as an application of at least one of a resist and an interlayer insulating material.

  The laminated structure of the present invention according to the configuration as described above is preferably used as a dry film in which at least one surface is supported or protected by a film.

(Dry film)
The dry film of the present invention can be produced as follows. That is, first, on the carrier film (support film), the composition constituting the resin layer (B) and the resin layer (A) is diluted with an organic solvent and adjusted to an appropriate viscosity. Apply sequentially by a known method such as a coater. Then, normally, the dry film which consists of a resin layer (B) and a resin layer (A) can be formed on a carrier film by drying at the temperature of 50-130 degreeC for 1 to 30 minutes. A peelable cover film (protective film) can be further laminated on the dry film for the purpose of preventing dust from adhering to the surface of the film. As the carrier film and the cover film, conventionally known plastic films can be used as appropriate. When the cover film is peeled off, the adhesive force between the resin layer and the carrier film may be smaller. preferable. Although there is no restriction | limiting in particular about the thickness of a carrier film and a cover film, Generally, it selects suitably in the range of 10-150 micrometers.

(Manufacturing method of wiring board)
The manufacture of a flexible printed wiring board using the laminated structure of the present invention can be performed according to the procedure shown in the process diagram of FIG. That is, a step of forming the layer of the laminated structure of the present invention on the flexible wiring board on which the conductor circuit is formed (lamination step), and a step of irradiating the layer of the laminated structure with active energy rays in a pattern (exposure step) In addition, the manufacturing method includes a step (developing step) of forming a layer of the patterned laminated structure at once by alkali developing the layer of the laminated structure. In addition, if necessary, after alkali development, further photocuring and heat curing (post-cure process) can be performed to completely cure the layer of the laminated structure to obtain a highly reliable flexible printed wiring board. .

  Moreover, the manufacture of the flexible printed wiring board using the laminated structure of the present invention can also be performed according to the procedure shown in the process diagram of FIG. That is, a step of forming the layer of the laminated structure of the present invention on the flexible wiring board on which the conductor circuit is formed (lamination step), and a step of irradiating the layer of the laminated structure with active energy rays in a pattern (exposure step) The step of heating the layer of the laminated structure (heating (PEB) step), and the step of forming the layer of the patterned laminated structure at once by developing the layer of the laminated structure with alkali (developing step) It is a manufacturing method containing. In addition, if necessary, after alkali development, further photocuring and heat curing (post-cure process) can be performed to completely cure the layer of the laminated structure to obtain a highly reliable flexible printed wiring board. . In particular, when an imide ring-containing alkali-soluble resin is used in the resin layer (B), it is preferable to use the procedure shown in the process diagram of FIG.

Hereafter, each process shown in FIG. 1 or FIG. 2 is demonstrated in detail.
[Lamination process]
In this step, a resin layer 3 (resin layer (A)) made of an alkali-developable resin composition containing an alkali-soluble resin and the like is formed on the flexible printed wiring board 1 on which the conductor circuit 2 is formed, and on the resin layer 3. And a resin layer 4 (resin layer (B)) made of a photosensitive thermosetting resin composition containing an alkali-soluble resin or the like. Here, each resin layer constituting the laminated structure forms, for example, the resin layers 3 and 4 by sequentially applying and drying the resin composition constituting the resin layers 3 and 4 on the wiring board 1. Alternatively, the resin composition that forms the resin layers 3 and 4 may be formed by laminating the resin composition in the form of a two-layer dry film on the wiring board 1.

  The application method of the resin composition to the wiring board may be a known method such as a blade coater, a lip coater, a comma coater, or a film coater. Also, the drying method is a method using a hot-air circulation type drying furnace, IR furnace, hot plate, convection oven, etc., equipped with a heat source of the heating method by steam, and the hot air in the dryer is counter-contacted and supported by the nozzle A known method such as a method of spraying on the body may be used.

[Exposure process]
In this step, the photopolymerization initiator contained in the resin layer 4 is activated into a negative pattern by irradiation with active energy rays, and the exposed portion is cured. As the exposure machine, a direct drawing apparatus, an exposure machine equipped with a metal halide lamp, or the like can be used. The patterned exposure mask is a negative mask.

As the active energy ray used for exposure, it is preferable to use laser light or scattered light having a maximum wavelength in the range of 350 to 450 nm. By setting the maximum wavelength within this range, the photopolymerization initiator can be activated efficiently. Moreover, although the exposure amount changes with film thickness etc., it can usually be set to 100-1500 mJ / cm < ² >.

[PEB process]
In this step, after exposure, the exposed portion is cured by heating the resin layer. In this step, a base generated in the exposure step of the resin layer (B) made of a composition using a photopolymerization initiator having a function as a photobase generator or a combination of a photopolymerization initiator and a photobase generator is used. By this, the resin layer (B) can be cured to a deep part. The heating temperature is, for example, 80 to 140 ° C. The heating time is, for example, 2 to 140 minutes. Since the curing of the resin composition in the present invention is, for example, a ring-opening reaction of an epoxy resin by a thermal reaction, distortion and curing shrinkage can be suppressed as compared with a case where curing proceeds by a photoradical reaction.

[Development process]
In this step, the unexposed portion is removed by alkali development to form a negative patterned insulating film, particularly a cover lay and a solder resist. The developing method can be a known method such as dipping. As the developer, sodium carbonate, potassium carbonate, potassium hydroxide, amines, imidazoles such as 2-methylimidazole, alkaline aqueous solutions such as tetramethylammonium hydroxide aqueous solution (TMAH), or a mixed solution thereof. Can be used.

[Post cure process]
In this step, after the development step, the resin layer is completely thermoset to obtain a highly reliable coating film. The heating temperature is, for example, 140 ° C to 180 ° C. The heating time is, for example, 20 to 120 minutes. Further, light irradiation may be performed before or after the post cure.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited by these Examples and a comparative example.

<Synthesis Example 1: Synthesis Example of Polyamideimide Resin Solution>
3.8 g of 3,5-diaminobenzoic acid, 2,2′-bis [4- (4-aminophenoxy) in a separable three-necked flask equipped with a stirrer, nitrogen inlet tube, fractional ring, and cooling ring 6.98 g of phenyl] propane, 8.21 g of Jeffamine XTJ-542 (manufactured by Huntsman, molecular weight 10225.64) and 86.49 g of γ-butyrolactone were charged at room temperature and dissolved.

  Next, 17.84 g of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride and 2.88 g of trimellitic anhydride were charged and held at room temperature for 30 minutes. Next, 30 g of toluene was added, the temperature was raised to 160 ° C., the mixture was stirred for 3 hours while distilling off toluene and water, and then cooled to room temperature to obtain an imidized product solution.

  To the obtained imidized product solution, 9.61 g of trimellitic anhydride and 17.45 g of trimethylhexamethylene diisocyanate were charged and stirred at a temperature of 160 ° C. for 32 hours. Thus, a polyamideimide resin solution (PAI-1) having a carboxyl group was obtained. The acid value of the obtained resin (solid content) was 83.1 mgKOH, and Mw was 4300.

<Synthesis Example 2: Synthesis of polyimide resin solution having imide ring, phenolic hydroxyl group and carboxyl group>
To a separable three-necked flask equipped with a stirrer, a nitrogen introduction tube, a fractionation ring, and a cooling ring, 22.4 g of 3,3′-diamino-4,4′-dihydroxydiphenylsulfone, 2,2′-bis [4 -(4-aminophenoxy) phenyl] propane 8.2 g, NMP 30 g, γ-butyrolactone 30 g, 4,4′-oxydiphthalic anhydride 27.9 g, trimellitic anhydride 3.8 g, The mixture was stirred at room temperature and 100 rpm for 4 hours under a nitrogen atmosphere. Next, 20 g of toluene was added, and the mixture was stirred for 4 hours while distilling off toluene and water at a silicon bath temperature of 180 ° C. and 150 rpm to obtain a polyimide resin solution (PI-1) having a phenolic hydroxyl group and a carboxyl group.
The acid value of the obtained resin (solid content) was 18 mgKOH, Mw was 10,000, and the hydroxyl equivalent was 390.

<Synthesis Example 3: Synthesis of carboxyl group-containing urethane resin>
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, 2400 g of polycarbonate diol derived from 1,5-pentanediol and 1,6-hexanediol (manufactured by Asahi Kasei Chemicals Corporation, T5650J, number average molecular weight 800) (3 mol), 603 g (4.5 mol) of dimethylolpropionic acid, and 238 g (2.6 mol) of 2-hydroxyethyl acrylate as a monohydroxyl compound were added. Next, 1887 g (8.5 mol) of isophorone diisocyanate was added as a polyisocyanate, and the mixture was stopped by heating to 60 ° C. while stirring. When the temperature in the reaction vessel began to decrease, the mixture was heated again and stirred at 80 ° C. Then, it was confirmed that the absorption spectrum (2280 cm ⁻¹ ) of the isocyanate group disappeared in the infrared absorption spectrum, and the reaction was terminated. Thereafter, carbitol acetate was added so that the solid content was 50% by mass. The acid value of the solid content of the obtained carboxyl group-containing resin was 50 mgKOH / g.

(Reference Examples 1-6, Comparative Examples 1-4)
In accordance with the composition described in the following table, the materials described in the reference example and the comparative example were respectively blended, premixed with a stirrer, and then kneaded with a three-roll mill to prepare a resin composition constituting each resin layer. . Unless otherwise specified, the values in the table are parts by mass of the solid content.

<Formation of resin layer (A)>
A flexible printed wiring board on which a circuit having a copper thickness of 18 μm was formed was prepared, and pretreatment was performed using MECBRITE CB-801Y. Then, each resin composition was apply | coated to the flexible printed wiring board which performed the pretreatment so that the film thickness after drying might be set to 25 micrometers, respectively. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, and formed the resin layer (A) which consists of a resin composition.

<Formation of resin layer (B)>
On the resin layer (A) formed above, each resin composition was applied so that the film thickness after drying was 10 μm. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, and formed the resin layer (B) which consists of a resin composition.

<Sensitivity>
Each obtained laminated structure was exposed at 500 mJ / cm ² through a 41-step step tablet (T-4105 manufactured by STOFFER) using an exposure apparatus (HMW-680-GW20) equipped with a metal halide lamp. Thereafter, for Reference Examples 3 to 6 and Comparative Examples 3 and 4, the PEB process was performed at 90 ° C. for 30 minutes, and then development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) was performed in 60 seconds. Thus, the number of remaining step tablets was used as an index of sensitivity. The greater the number of remaining stages, the better the sensitivity.

<Minimum remaining line width>
Each obtained laminated structure was exposed at 500 mJ / cm ² using an exposure apparatus (HMW-680-GW20) equipped with a metal halide lamp. As the exposure pattern, a negative mask that exposes a line having a width of 20/30/40/50/60/70/80/90/100 μm was used. Thereafter, for Reference Examples 3 to 6 and Comparative Examples 3 and 4, the PEB process was performed at 90 ° C. for 30 minutes, and then development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) was performed in 60 seconds. A pattern was drawn and heat cured at 150 ° C. for 60 minutes to obtain a cured coating film. The minimum remaining line width of the obtained cured coating film was counted using an optical microscope adjusted to 200 times. The smaller the minimum remaining line width, the better the deep curability.

<Flexibility test (mandrel test)>
Each of the obtained laminated structures was exposed at 500 mJ / cm ² using an exposure apparatus (HMW-680-GW20) equipped with a metal halide lamp. Thereafter, for Reference Examples 3 to 6 and Comparative Examples 3 and 4, the PEB process was performed at 90 ° C. for 30 minutes, and then development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) was performed in 60 seconds. The cured laminated structure was obtained by thermosetting at 150 ° C. for 60 minutes. The obtained cured laminated structure was cut into about 50 mm × about 200 mm, and the flexibility was evaluated using a cylindrical mandrel tester (BYK Gardner, No. 5710). The surface on which the resin composition was applied was placed on the outside, bent around a core rod having a diameter of 2 mm, and the presence or absence of discoloration and crack generation was evaluated. A case where no discoloration or crack occurred in the bent portion was indicated by “◎”, a case where discoloration occurred and no crack occurred, “◯”, and a case where crack occurred, ×.

<Heat resistance test>
Each obtained laminated structure was exposed to 500 mJ / cm ² through a negative mask in which an opening having a diameter of about 2 mm to 5 mm was formed on copper using an exposure apparatus (HMW-680-GW20) equipped with a metal halide lamp. Exposed. Thereafter, for Reference Examples 3 to 6 and Comparative Examples 3 and 4, the PEB process was performed at 90 ° C. for 30 minutes, and then development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) was performed in 60 seconds. The cured laminated structure was obtained by thermosetting at 150 ° C. for 60 minutes. The obtained cured laminated structure was immersed in a solder bath heated to 260 ° C. and 280 ° C., and a heat resistance test was performed. After floating in the tank for 5 seconds so that the surface to which the resin composition was applied touched the solder, it was collected and cooled to evaluate whether the resin composition floated or peeled off. Floating at 280 ° C, no peeling occurred ◎, floating at 260 ° C, no peeling occurred Floating at 280 ° C, peeling occurred ○ Floating at 260 ° C, peeling occurred X.
The evaluation results are also shown in the following table.

* 1) ZFR-1401H: acid-modified bisphenol F type epoxy acrylate, acid value 98 mgKOH / g (manufactured by Nippon Kayaku Co., Ltd.)
* 2) PAI-1: Polyamideimide resin of Synthesis Example 1 * 3) PI-1: Polyimide resin of Synthesis Example 2 * 4) BPE-900: Ethoxylated bisphenol A dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
* 5) E1001: Bisphenol A type epoxy resin, epoxy equivalent 450-500 (Mitsubishi Chemical Corporation)
* 6) E834: bisphenol A type epoxy resin, epoxy equivalent 230-270 (manufactured by Mitsubishi Chemical Corporation)
* 7) IRGACURE OXE02: Oxime-based photopolymerization initiator (BASF)
* 8) IRGACURE 379: Alkylphenone photopolymerization initiator (BASF)
* 9) Carboxyl group-containing urethane resin: Resin of Synthesis Example 3 * 10) E828: Bisphenol A type epoxy resin, epoxy equivalent 190, mass average molecular weight 380 (manufactured by Mitsubishi Chemical Corporation)

  As is clear from the evaluation results shown in the above table, it is clear that the laminated structure of each reference example is superior in sensitivity and deep curability as compared with the laminated structure of each comparative example. It is. On the other hand, in each comparative example in which the resin layer (A) contains a photopolymerization initiator, the photopolymerization initiator absorbs light, so that deep curability cannot be obtained, and fine lines are dropped during development. End up.

(Examples 1-6, Comparative Example 5)
In accordance with the composition described in the following table, the materials described in Examples and Comparative Examples were respectively compounded, premixed with a stirrer, and then kneaded with a three-roll mill, thereby forming a resin composition constituting each resin layer. The resin layer (A) and the resin layer (B) were formed in the same manner as in Reference Example 1 and the like. Unless otherwise specified, the values in the table are parts by mass of the solid content.

<Resolution (opening size and minimum remaining line width)>
Each obtained laminated structure was exposed at 500 mJ / cm ² using an exposure apparatus (HMW-680-GW20) equipped with a metal halide lamp. The exposure pattern was a pattern for drawing a line having a width of 30/40/50/60/70/80/90/100 μm and a pattern for opening an opening of 300 μm. Then, after performing a PEB process at 90 ° C. for 30 minutes, development (30 ° C., 0.2 MPa, 1 mass% Na ₂ CO ₃ aqueous solution) is performed in 60 seconds to draw a pattern, and heat curing is performed at 150 ° C. × 60 minutes A cured coating film was obtained. About the obtained cured coating film, the minimum remaining line width was counted using an optical microscope adjusted to 200 times, the opening size (design value 300 μm) was measured, and the opening shape was photographed. The smaller the minimum remaining line width, the better the deep curability. The results are shown in the table below and in FIGS. 3 (a) to (i), respectively.

<Chemical resistance (electroless gold plating resistance)>
The cured coating on the substrate is plated using a commercially available electroless gold plating bath under the conditions of nickel 0.5 μm and gold 0.03 μm. After evaluating the presence or absence, the presence or absence of peeling of the resist layer was evaluated by tape peeling. The judgment criteria are as follows. The obtained results are shown in the following table.
○: Infiltration and peeling are not seen.
Δ: Slight penetration after plating was confirmed, but peeling after tape peeling was not observed.
X: There exists peeling after a tape peel.

* 11) LUCIRIN TPO (acylphosphine oxide photopolymerization initiator, manufactured by BASF Japan)
* 12) QS-30: 4-methoxy-1-naphthol (manufactured by Kawasaki Kasei Kogyo Co., Ltd.)
* 13) HCA-HQ: phenolic hydroxyl group-containing phosphorus compound (manufactured by Sanko Co., Ltd.)

  The laminated structures of Examples 1 to 6 in which the polymerization inhibitor was blended in the resin layer (A) had little halation, a stable opening shape, and a minimum residual line width of 30 μm. On the other hand, in Reference Example 6 having the same composition as Example 6 except that the polymerization inhibitor was not blended, the opening size and the gold plating resistance were evaluated. There was a small opening size of 240 μm. In Comparative Example 5, a photopolymerization initiator is used for the resin layer (A), and halation is prevented to some extent. However, the resistance to gold plating is poor, and the minimum line width and the opening size are sufficient. It was not a thing.

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 2 Conductor circuit 3 Resin layer 4 Resin layer 5 Mask

Claims (5)

A laminated structure having a resin layer (A) and a resin layer (B) laminated on the flexible printed wiring board via the resin layer (A),
The resin layer (B) is composed of a photosensitive thermosetting resin composition containing an alkali-soluble resin, a photopolymerization initiator also having a function as a photobase generator, and a heat-reactive compound, and
The alkali developing resin composition in which the resin layer (A) includes an alkali-soluble resin, a compound having an ethylenically unsaturated bond, a heat-reactive compound, and a polymerization inhibitor, and does not include a photopolymerization initiator. Ri Do from the object,
The laminated structure characterized by the compounding quantity of the said polymerization inhibitor being 0.05-100 mass parts with respect to 100 mass parts of alkali-soluble resin contained in the said resin layer (A) .   The laminated structure according to claim 1, which is used for at least one of a bent portion and a non-bent portion of the flexible printed wiring board.   The laminated structure according to claim 1, which is used for at least one of a cover lay of a flexible printed wiring board, a solder resist, and an interlayer insulating material.   A dry film, wherein at least one surface of the laminated structure according to claim 1 is supported or protected by a film.   A flexible print comprising an insulating film formed by forming a layer of the laminated structure according to claim 1 on a flexible printed wiring board, patterning by light irradiation, and forming a pattern in a batch with a developer. Wiring board.