JP2016080921A - Dry film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry film that allows formation of a photosensitive structure excellent in flame retardancy and folding resistance of a cured product, and to provide a flexible printed wiring board having a cured product of the dry film as a protective film, for example, as a coverlay or a solder resist.SOLUTION: The photosensitive dry film includes an adhesion surface (a) to be laminated to an adherend and a protective surface (b) located on the opposite side to the adhesion surface. In an infrared absorption spectrum obtained by an ATR (attenuated total reflection) method of FT-IR (Fourier transformation infrared spectroscopy), the adhesion surface (a) shows a peak derived from a flame retardant while the protective surface (b) does not show the peak.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a dry film, and more particularly to a dry film and a flexible printed wiring board useful for forming 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.

  Currently, a polyimide-based coverlay is used for the bent part (bent part) as an insulating film to ensure the insulation reliability of the flexible printed wiring board, and the mounting part (non-bent part) is photosensitive. A mixed loading process using a conductive resin composition is widely employed (see Patent Documents 1 and 2). Polyimide is excellent in mechanical properties such as heat resistance and bendability, while the photosensitive resin composition used for the mounting portion has characteristics such as excellent electrical insulation and fine processing.

  Printed wiring boards, particularly flexible printed wiring boards (hereinafter abbreviated as FPC), are required to have high flame retardancy, and an insulating film that is one of the main components thereof is also excellent in flame retardancy. Is required. An FPC using a polyimide substrate or the like as a substrate is a thin film as compared with a printed wiring board of a glass epoxy substrate. On the other hand, since the required film thickness of the insulating film is the same for both the printed wiring board and the FPC, in the case of a thin FPC, the burden of making the insulating film flame-retardant is relatively increased.

  Therefore, various proposals have conventionally been made for flame retarding of insulating films. For example, phosphorus-containing compounds that can impart flame retardancy to resin compositions and epoxy resins with excellent heat resistance are used to obtain insulating films. Blending into a curable resin composition has been performed. For example, Patent Document 3 discloses that (a) a binder polymer such as an epoxy resin, (b) a halogenated aromatic ring such as a bromophenyl group, and a polymerizable ethylenically unsaturated bond such as a (meth) acryloyl group in the molecule. A flame-retardant photosensitive resin composition for FPC, comprising: a photopolymerizable compound having (c) a photopolymerization initiator; (d) a blocked isocyanate compound; and (e) a phosphorus compound having a phosphorus atom in the molecule. It is disclosed.

Japanese Patent Application Laid-Open No. Sho 62-263692 Japanese Unexamined Patent Publication No. 63-110224 JP 2007-10794 A

Conventional photosensitive resin compositions contain a (meth) acrylate monomer in order to adjust viscosity, improve physical properties of a cured coating film, and improve sensitivity. Since the (meth) acrylate monomer is relatively flammable and the flame retardancy of the photosensitive resin composition is impaired, it is necessary to add a large amount of a flame retardant such as a phosphorus-containing compound to compensate for it.
However, when a flame retardant such as a phosphorus-containing compound is added to the photosensitive resin composition, the crease resistance deteriorates, and cracks are likely to occur in the cured coating film at the time of cutting processing of a wiring board or a thermal shock test. There is.

  Moreover, from the point of improvement of workability | operativity, it was calculated | required to form the insulating film excellent in the flame retardance and bending resistance with the form of the dry film which is suitable for a continuous process and does not require solvent drying.

  Therefore, an object of the present invention is to provide a dry film capable of forming a photosensitive structure excellent in flame retardancy and fold resistance of a cured product, and to provide a cured film, for example, a cover, for the cured product. An object of the present invention is to provide a flexible printed wiring board having a ray or solder resist.

  In the dry film having an adhesive surface for bonding to an object to be protected and a protective surface located on the opposite side of the adhesive surface, the present inventors have studied for the purpose of achieving both flame retardancy and folding resistance. As a result, if there is no flame retardant on both the protective surface and the adhesive surface, fold resistance is obtained, but flame retardancy is not obtained, and if it has a flame retardant on the protective surface side, flame retardancy is obtained However, it was found that the folding resistance was not sufficient. Therefore, the present invention has been completed by finding that the above problems can be solved by using a dry film in which the flame retardant is collected only on the adhesive surface side without having the flame retardant on the protective surface side.

That is, the dry film of the present invention is a photosensitive dry film having an adhesive surface (a) for bonding to an object to be protected and a protective surface (b) located on the opposite side of the adhesive surface,
In an infrared absorption spectrum obtained by FT-IR (Fourier transform infrared spectrophotometer) by ATR method (total reflection method), the adhesive surface (a) has a peak derived from a flame retardant, and the protective surface (b ) Is not included.

In the dry film of the present invention, 3630~3605cm ^-1 as a peak derived from the flame retardant in an infrared absorption spectrum of the adhesive surface ^{(a), 3535~3510cm -1, 3450~3425cm} -1, the 3380～3355Cm ^-1 It is preferable that a peak is observed in any range. Moreover, in the dry film of this invention, it is preferable that the said adhesive surface (a) has the peak derived from an acryl in the said infrared absorption spectrum. Moreover, in the dry film of this invention, it is preferable in the infrared absorption spectrum of the said adhesive surface (a) that the said acryl-derived peak is a peak observed in the range of 1420-1400 cm < ^-1 >.

  It is preferable that the dry film of the present invention can be patterned by light irradiation. The dry film of the present invention has an adhesive layer (A) having the adhesive surface (a) and a protective layer (B) having the protective surface (b), and the adhesive layer (A) is a flame retardant. It is preferable that the protective layer (B) does not contain a flame retardant. The dry film of the present invention has a resin composition in which the adhesive layer (A) is made of an alkali developing resin composition, and the protective layer (B) contains an alkali-soluble resin having an imide ring or an imide precursor skeleton. It is preferable to consist of a thing. The dry film of the present invention can be suitably used for at least one of a bent portion and a non-bent portion of a flexible printed wiring board. Specifically, the flexible printed wiring board coverlay, solder resist, and interlayer insulation It is useful to be used for at least one of the materials.

  In the dry film of the present invention, at least one of the adhesive surface and the protective surface is preferably supported or protected by the film.

Furthermore, the flexible printed wiring board of the present invention is an insulating film formed by laminating the dry film of the present invention on a flexible printed wiring substrate, patterning by light irradiation, and forming the pattern in a lump with a developer. It is characterized by providing.
In the present invention, the “pattern” means a patterned cured product, that is, an insulating film.

  ADVANTAGE OF THE INVENTION According to this invention, it became possible to implement | achieve the dry film and flexible printed wiring board which can form the photosensitive structure excellent in the flame retardance and bending resistance of hardened | cured material.

It is a schematic diagram of an example of the dry film of this invention. 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 an infrared absorption spectrum of the adhesive surface (a) of the dry film of Example 1 and Comparative Examples 1-2 and the protective surface (b) of the dry film of Comparative Example 2 obtained by FT-IR by the ATR method. It is an infrared absorption spectrum of the protective surface (b) of the dry film of the comparative example 1 obtained by FT-IR by ATR method. It is the infrared absorption spectrum of the protective surface (b) of the dry film of Example 1 and the comparative example 3 obtained by FT-IR by ATR method. It is the infrared absorption spectrum of the adhesive surface (a) of the dry film of the comparative example 3 obtained by FT-IR by ATR method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Dry film)
The dry film of the present invention is a photosensitive dry film having an adhesive surface (a) for bonding to an adherend and a protective surface (b) located on the opposite side of the adhesive surface, and is an ATR method ( In the infrared absorption spectrum obtained by FT-IR (Fourier transform infrared spectroscopy) by total reflection method, the adhesive surface (a) has a peak derived from a flame retardant, and the protective surface (b) is present. It has a feature in that there is no point.

  The dry film of the present invention is formed, for example, by laminating an adhesive layer (A) having the adhesive surface (a) and a protective layer (B) having the protective surface (b) as shown in FIG. can do. In addition, when the thickness of the dry film is thin or the interface between layers is familiar, it is difficult to distinguish the adhesive layer (A) and the protective layer (B) in appearance, but by FT-IR or the like by the ATR method By analyzing the adhesive surface (a) and the protective surface (b) of the dry film, it can be determined that it is a laminated structure.

In the said infrared absorption spectrum, the peak derived from the said flame retardant will not be specifically limited if it is a peak derived from a well-known and usual flame retardant, For example, 3630-3605cm < ^-1 >, 3535-3510cm < ^-1 >, 3450-3425cm < ^-1 >, 3380. Specific peaks are observed in each range of ˜3355 cm ⁻¹ .

In the infrared absorption spectrum of the dry film of the present invention, the protective surface (b) preferably has an imide-derived peak. By including an imide structure on the protective surface, it is possible to form a flame-retardant, tough and hard-to-break coating film, and the required performance as an insulating film of a flexible printed wiring board is also improved. The imide peak derived from the ^{1785~1765cm -1, 1735~1705cm -1, 1400~1360cm -1} , but appears in the range of 740~720cm ^-1, easily among others observe peaks of 1785～1765Cm ^-1 most.

In the dry film of the present invention, the adhesive surface (a) preferably has an acrylic-derived peak blended for improving developability and photoreactivity in the infrared absorption spectrum. By including the (meth) acrylate monomer on the bonding surface side, photocurability is improved and a high-definition pattern can be easily formed. On the other hand, the protective surface (b) may or may not have an acrylic-derived peak. However, since the (meth) acrylate monomer is flammable, the protective surface ( It is preferable that b) does not have an acrylic-derived peak. Peak derived from the ^{acrylic, 1650~1610cm -1, 1420~1400cm -1,} but appears in the range of 825~795cm ^-1, inter alia the peak of 1420～1400Cm ^-1 is most observed easily.

  In the dry film of the present invention, the infrared absorption spectrum measurement by the FT-IR ATR method is not particularly limited as long as the peak derived from the flame retardant can be discriminated, and a known method can be used.

  Hereinafter, the adhesive layer (A) having the adhesive surface (a) and the protective layer (B) having the protective surface (b) will be described in detail.

(Protective layer (B))
The protective layer (B) is not particularly limited as long as it is a composition that does not substantially contain a flame retardant. For example, an alkali-soluble resin or a compound having an ethylenically unsaturated bond conventionally used as a solder resist composition A photocurable thermosetting resin composition containing a photopolymerization initiator and a thermoreactive compound can be used. In the present specification, “substantially not contained” means that it is not actively blended as a constituent component, and it is not excluded that it is contained in a small amount within a range not impairing the effects of the present invention. For example, it is preferably 5% by mass or less, more preferably 3% by mass or less in the resin composition.

  As the alkali-soluble resin, known ones can be used, and examples thereof include alkali-soluble resins that contain one or more functional groups of phenolic hydroxyl groups or carboxyl groups and can be developed with an alkaline solution. It is done. Among these, compounds having two or more phenolic hydroxyl groups, carboxyl group-containing resins, compounds having phenolic hydroxyl groups and carboxyl groups are preferred.

  As described above, known and commonly used alkali-soluble resins can be used, but an alkali-soluble resin having an imide ring or an imide precursor skeleton that is superior in characteristics such as flex resistance and heat resistance is preferably used. Can do.

(Alkali-soluble resin having imide ring or imide precursor skeleton)
The alkali-soluble resin having an imide ring or imide precursor skeleton has one or more alkali-soluble groups among phenolic hydroxyl groups or carboxyl groups and an imide ring or imide precursor skeleton. For introducing the imide ring or imide precursor skeleton into the alkali-soluble resin, a known and commonly used 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 can be used 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 or an imide precursor skeleton as described above may have an amide bond. This may be an amide bond obtained by reacting an isocyanate and a carboxylic acid, or may be caused by other reaction. Furthermore, you may have the coupling | bonding which consists of another addition and condensation.

  In synthesizing an alkali-soluble resin having such an alkali-soluble group and an imide ring or an imide precursor skeleton, 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.

  Among the phenolic hydroxyl groups or carboxyl groups as described above, an alkali-soluble resin having one or more alkali-soluble groups and an imide ring or an imide precursor skeleton has an acid value in order to correspond to the photolithography process. It is preferably 20 to 200 mg KOH / g, and more preferably 60 to 150 mg KOH / 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.

(Compound having an ethylenically unsaturated bond)
As the compound having an ethylenically unsaturated bond, known monofunctional, bifunctional and polyfunctional compounds can be used.

(Thermo-reactive compound)
As the thermoreactive compound, a known and commonly used compound having a functional group capable of curing reaction by heat such as a cyclic (thio) ether group can be used. In particular, a bifunctional epoxy resin having two epoxy groups in the molecule, a polyfunctional epoxy resin having many epoxy groups in the molecule, and the like are preferably used.

(Photopolymerization initiator)
As the photopolymerization initiator, known ones can be used, and in particular, when used in the PEB process after light irradiation described later, a photopolymerization initiator having 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 0.1 to 30 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.

(Adhesive layer (A))
The adhesive layer (A) can be formed using an alkali developing resin composition. The alkali-developing resin composition may be any composition that contains one or more functional groups of phenolic hydroxyl group and carboxyl group and contains a resin that can be developed with an alkaline solution. However, thermosetting resin compositions can also be used. Preferred examples include a resin composition containing a compound having two or more phenolic hydroxyl groups, a carboxyl group-containing resin, and a compound having a phenolic hydroxyl group and a carboxyl group, and known ones are used.

  Specifically, for example, conventionally used as a solder resist composition, a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and thermal reactivity And a photocurable thermosetting resin composition containing the compound. In addition, a resin composition containing a carboxyl group-containing urethane resin, a resin having a carboxyl group, a photobase generator, and a thermosetting component can also be used. Here, as a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and a photobase generator, known and commonly used compounds are used, and heat-reactive compounds As such, a known and commonly used compound having a functional group capable of undergoing a curing reaction by heat, such as a cyclic (thio) ether group, is used.

  In the present invention, the adhesive layer (A) preferably contains a (meth) acrylate monomer. A well-known thing can be used as a (meth) acrylate monomer.

  In the present invention, the adhesive layer (A) preferably contains a flame retardant. As the flame retardant, a known and commonly used flame retardant can be used. Known and conventional flame retardants include phosphoric acid esters and condensed phosphoric acid esters, phosphorus element-containing (meth) acrylates, phosphorus-containing compounds having phenolic hydroxyl groups, cyclic phosphazene compounds, phosphazene oligomers, phosphorus-containing compounds such as phosphinic acid metal salts, Layered layers of antimony compounds such as antimony trioxide and antimony pentoxide, halides such as pentabromodiphenyl ether and octabromodiphenyl ether, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, hydrotalcite and hydrotalcite-like compounds A double hydroxide is mentioned.

  In the resin composition used in the adhesive layer (A) and the protective 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.

  In the dry film of the present invention, the adhesive layer (A) is preferably thicker than the protective layer (B) from the viewpoint of followability to the copper circuit.

  The dry film of the present invention can be used for at least one of the bent portion and the non-bent portion of the flexible printed wiring board, preferably both, thereby providing a flexible printed wiring board having sufficient durability against bending. Can be obtained while improving cost and workability. Specifically, the dry film of the present invention can be used for at least one of a cover lay of a flexible printed wiring board, a solder resist, and an interlayer insulating material.

  At least one surface of the dry film of the present invention may be supported or protected by the film. In the production of the dry film, for example, the resin composition constituting the protective layer (B) is diluted with an organic solvent to adjust to an appropriate viscosity, and applied to the carrier film with a uniform thickness using a comma coater or the like. The coating layer is dried to form a protective layer (B) on the carrier film. Similarly, the adhesive layer (A) can be formed on the protective layer (B) with the resin constituting the adhesive layer (A), and the dry film of the present invention can be obtained. From the viewpoint of the coating film strength, the interface between the layers may be familiar. After forming the dry film on the carrier film, a peelable cover film may be further laminated on the surface of the dry film. Moreover, after forming a dry film on a cover film, you may laminate | stack the peelable carrier film on the surface of a dry film.

  The coating method of the resin composition 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, an IR furnace, a hot plate, a convection oven, or the like equipped with a heat source of a heating method using steam, and the hot air in the dryer is brought into countercurrent contact, and from a nozzle A known method such as a method of spraying on the support may be used. As the carrier film, a thermoplastic film such as a polyester film having a thickness of 2 to 150 μm is used. As the cover film, a polyethylene film, a polypropylene film, or the like can be used, but it is preferable that the adhesive force with the dry coating film is smaller than that of the carrier film.

(Manufacturing method of wiring board)
In the present invention, a flexible printed wiring board is formed by laminating the dry film of the present invention on a flexible printed wiring board, patterning by light irradiation, and forming an insulating film by collectively forming a pattern with a developer. A board can be obtained. According to the present invention, in the infrared absorption spectrum, by using a dry film having a peak derived from a flame retardant, the adhesive surface (a) but not the protective surface (b), flame retardancy and It has become possible to provide an insulating film for a flexible printed wiring board having excellent folding resistance.

  Hereinafter, as an example of a method for producing a flexible printed wiring board using the dry film of the present invention, the protective layer (B) includes a photosensitive heat containing an alkali-soluble resin, a photopolymerization initiator, and a heat-reactive compound. Regarding the case where the adhesive layer (A) is composed of a curable resin composition, and the adhesive layer (A) is composed of an alkali-developable resin composition containing an alkali-soluble resin and a heat-reactive compound and no photopolymerization initiator. The procedure is shown in the process diagram. That is, a step of laminating the dry film of the present invention on a flexible wiring board on which a conductor circuit is formed (layering step), a step of irradiating the layer with active energy rays in a pattern (exposure step), and The manufacturing method includes a step (developing step) in which the layer is alkali-developed to form a patterned layer all at once. In addition, if necessary, after alkali development, further photocuring and heat curing (post-cure process) can be performed to completely cure the patterned layer to obtain a highly reliable flexible printed wiring board. .

  Moreover, in the said protective layer (B), when using the photoinitiator which has a function as a photobase generator, or using a photoinitiator and a photobase generator together, it shows in the process drawing of FIG. A flexible printed wiring board can also be manufactured according to the procedure. That is, a step of laminating the dry film of the present invention on a flexible wiring board on which a conductor circuit is formed (lamination step), a step of irradiating the layer with active energy rays in a pattern (exposure step), It is a manufacturing method including a step of heating a layer (heating (PEB) step) and a step of developing the layer with alkali to form a patterned layer (development step). In addition, if necessary, after alkali development, further photocuring and heat curing (post-cure process) can be performed to completely cure the patterned layer to obtain a highly reliable flexible printed wiring board. . In particular, when an alkali-soluble resin containing an imide ring or an imide precursor skeleton is used in the protective layer (B), it is preferable to use the procedure shown in the process diagram of FIG.

Hereafter, each process shown in FIG. 2 or FIG. 3 is demonstrated in detail.
[Lamination process]
In this step, the resin layer 3 made of an alkali-developable resin composition containing an alkali-soluble resin or the like is laminated by laminating the dry film of the present invention on the flexible printed wiring board 1 on which the conductor circuit 2 is formed. A laminated structure comprising (adhesive layer (A)) and a resin layer 4 (protective layer (B)) made of a photosensitive thermosetting resin composition containing an alkali-soluble resin or the like on the resin layer 3. Form.

[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 photopolymerization initiator having a function as a photobase generator is used, or a base generated in the exposure step of the protective layer (B) comprising a composition in which a photopolymerization initiator and a photobase generator are used in combination. By this, the protective 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, 10 to 100 minutes. Since the curing by the PEB process 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 addition, after an image development process, you may light-irradiate an insulating film further, for example, you may heat at 150 degreeC or more.

  Hereinafter, the present invention will be described in more detail with reference to examples.

<Synthesis of an alkali-soluble resin having an imide ring>
In a separable three-necked flask equipped with a stirrer, nitrogen inlet tube, fractional ring and cooling ring, 12.2 g of 3,5-diaminobenzoic acid, 2,2′-bis [4- (4-aminophenoxy) Phenyl] propane 8.2 g, N-methyl-2-pyrrolidone (NMP) 30 g, γ-butyrolactone 30 g, 4,4′-oxydiphthalic anhydride 27.9 g, trimellitic anhydride 3.8 g In addition, 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 an alkali-soluble resin solution having an imide ring. Thereafter, γ-butyrolactone was added so that the solid content was 30% by mass. The obtained resin solution had a solid content acid value of 86 mg KOH / g and Mw of 10,000.

<Adjustment of resin composition (α1) having a peak derived from a flame retardant>
The following components were blended, premixed with a stirrer, and then kneaded with a three-roll mill.
100 parts by mass of acid-modified epoxy acrylate resin (manufactured by Nippon Kayaku Co., Ltd., ZFR-1401H)
60 parts by mass of acid-modified epoxy acrylate resin (Nippon Kayaku Co., Ltd., PCR-1170H)
24 parts by mass of trimethylolpropane EO-modified acrylate (manufactured by Toa Gosei Co., Ltd., Aronix M350
28 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, E1001)
18 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828)
30 parts by weight of aluminum hydroxide (manufactured by Showa Denko K.K., Heidilite H-42M)
10 parts by mass of alkylphenone photopolymerization initiator (BASF, Irgacure 379)
270 parts by mass in total

<Adjustment of resin composition (α2) having a peak derived from a flame retardant>
The following components were blended, premixed with a stirrer, and then kneaded with a three-roll mill.
Alkali-soluble resin having imide ring synthesized above 233 parts by mass Acid-modified epoxy acrylate resin 60 parts by mass (Nippon Kayaku Co., Ltd., PCR-1170H)
Bisphenol A epoxy resin 4 parts by mass (Mitsubishi Chemical Corporation E1001)
35 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828)
Oxime-based photopolymerization initiator 5 parts by mass (BASF Japan, OXE-02)
30 parts by weight of aluminum hydroxide (manufactured by Showa Denko K.K., Heidilite H-42M)
367 parts by mass in total

<Adjustment of resin composition (β1) having no peak derived from flame retardant>
The following components were blended, premixed with a stirrer, and then kneaded with a three-roll mill.
Alkali solubility 233 parts by mass of acid-modified epoxy acrylate resin having an imide ring synthesized above 60 parts by mass (manufactured by Nippon Kayaku Co., Ltd., PCR-1170H)
Bisphenol A epoxy resin 4 parts by mass (Mitsubishi Chemical Corporation E1001)
35 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828)
Oxime-based photopolymerization initiator 5 parts by mass (BASF Japan, OXE-02)
337 parts by mass in total

<Adjustment of resin composition (β2) having no peak derived from flame retardant>
The following components were blended, premixed with a stirrer, and then kneaded with a three-roll mill.
100 parts by mass of acid-modified epoxy acrylate resin (manufactured by Nippon Kayaku Co., Ltd., ZFR-1401H)
60 parts by mass of acid-modified epoxy acrylate resin (Nippon Kayaku Co., Ltd., PCR-1170H)
24 parts by mass of trimethylolpropane EO-modified acrylate (manufactured by Toa Gosei Co., Ltd., Aronix M350
28 parts by mass of bisphenol A type epoxy resin (Mitsubishi Chemical Corporation, E1001)
18 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER828)
30 parts by mass of barium sulfate (manufactured by Sakai Chemical Co., Ltd., B-30)
10 parts by mass of alkylphenone photopolymerization initiator (BASF, Irgacure 379)
270 parts by mass in total

<Production of dry film>
On the carrier film, the resin composition which comprises the protective layer shown in Table 1 was apply | coated so that the film thickness after drying might be set to 10 micrometers. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, and formed the protective layer (B). The resin composition constituting the adhesive layer shown in Table 1 was applied to the surface of the protective layer (B) so that the film thickness after drying was 25 μm. Then, it dried at 90 degreeC / 30 minutes with the hot-air circulation type drying furnace, the contact bonding layer (A) was formed, and the dry film was produced.

<Infrared absorption spectrum measurement by ATR method of FT-IR>
FT-IR measurement of the dry film obtained above was performed using Spectrum 100 manufactured by PerkinElmer. The measurement was performed by bringing the measured surface of the dry film into direct contact with the prism of the ATR measurement unit Dura Sample IRII and making infrared light incident.

<Determination of the presence or absence of an acrylic-derived peak>
In the infrared absorption spectrum obtained above, those having a peak in the range of 1420 to 1400 cm ⁻¹ were determined as “◯”, and those having no peak were determined as “X”.

<Determining the presence or absence of a peak derived from a flame retardant>
In the infrared absorption spectrum obtained in the ^{above, 3630~3605cm -1,} determination 3535~3510cm ^-1, 3450~3425cm ^-1, "○" and a peak is present in 3380~3355cm ^-1, those with and without "×" did.

<Flame retardance>
The dry film obtained above was laminated at 60 ° C. using a vacuum laminator on both sides of a 25 μm-thick polyimide film (manufactured by Toray DuPont, Kapton 100H (25 μm). Exposure with a metal halide lamp mounted on the resulting double-sided substrate. Using an apparatus (HMW-680-GW20), light irradiation was performed at an exposure amount of 500 mJ / cm ² and heat treatment was performed for 60 minutes at 90 ° C. Next, heat treatment was performed for 150 ° C./60 minutes using a hot-air circulating drying furnace. The test piece was subjected to a thin material vertical combustion test in accordance with the UL94 standard as a flame retardant test, and the evaluation was based on “VTM-0” to “combustion” based on the UR94 standard. expressed.

<Bendability evaluation>
After laminating the dry film obtained above on a flexible printed wiring board at 60 ° C. using a vacuum laminator, with an HMW680GW (metal halide lamp, scattered light) manufactured by ORC, with an exposure amount of 500 mJ / cm ² , a negative type The pattern was irradiated with light. Next, heat treatment was performed at 90 ° C. for 60 minutes. Thereafter, the substrate was immersed in an aqueous solution of sodium carbonate at 30 ° C. and 1% by mass and developed for 3 minutes.

  Next, heat treatment was performed at 150 ° C./60 minutes using a hot-air circulation type drying furnace to obtain an evaluation substrate on which a patterned cured coating film was formed. Using the obtained evaluation substrate, it was folded and observed visually and with an optical microscope of × 200, and the number of times before the cured coating film was cracked was recorded. The case where it was bent three times or more was marked with ◯, and the case where the number of folding was two or less was marked with ×.

  As is clear from the evaluation results shown in Table 1 above, the cured coating film obtained from the dry film of the example having no peak derived from the flame retardant on the protective surface is excellent in bendability and also has flame retardancy. VTM-0 was shown. On the other hand, the hardened | cured material obtained from the dry film of the comparative example 1 which has a peak derived from a flame retardant on both an adhesive surface and a protective surface was inferior to bendability. Further, the cured product obtained from the dry film of Comparative Example 2 in which both the adhesive surface and the protective surface have a peak derived from the flame retardant was slightly low in flame retardancy and inferior in bending resistance. The cured product obtained from the dry film of Comparative Example 3 having no flame retardant-derived peak on either the adhesive surface or the protective surface was inferior in flame retardancy.

a Adhesive surface b Protective surface A Adhesive layer B Protective layer 1 Flexible printed wiring 2 Conductor circuit 3 Resin layer 4 Resin layer 5 Mask

Claims (11)

A photosensitive dry film having an adhesive surface (a) for bonding to an adherend and a protective surface (b) located on the opposite side of the adhesive surface,
In an infrared absorption spectrum obtained by FT-IR (Fourier transform infrared spectroscopy) by ATR method (total reflection method), the adhesive surface (a) has a peak derived from a flame retardant, and the protective surface (b) A dry film characterized by not having. Dry film according to claim 1, wherein a peak derived from the flame retardant ^{3630~3605cm -1, 3535~3510cm -1, 3450~3425cm -1} , are observed in any of the range of 3380~3355cm ^-1.   The dry film according to claim 1 or 2, wherein the adhesive surface (a) has a peak derived from acrylic in the infrared absorption spectrum. The dry film according to claim 3, wherein the acrylic-derived peak is a peak observed in a range of 1420 to 1400 cm ⁻¹ .   The dry film according to claim 1, which can be patterned by light irradiation. Having an adhesive layer (A) having the adhesive surface (a) and a protective layer (B) having the protective surface (b);
The dry film according to claim 1, wherein the adhesive layer (A) contains a flame retardant and the protective layer (B) does not contain a flame retardant.   The adhesive layer (A) is made of an alkali-developing resin composition, and the protective layer (B) is made of a resin composition containing an alkali-soluble resin having an imide ring or an imide precursor skeleton. The dry film according to any one of 6.   The dry film as described in any one of Claims 1-7 used for at least any one of the bending part and non-bending part of a flexible printed wiring board.   The dry film as described in any one of Claims 1-8 used for at least any one use among the coverlay of a flexible printed wiring board, a soldering resist, and an interlayer insulation material.   The dry film according to claim 1, wherein at least one of the adhesive surface and the protective surface is supported or protected by a film.   An insulating film formed by laminating the dry film according to any one of claims 1 to 10 on a flexible printed wiring board, patterning by light irradiation, and collectively forming a pattern by a developer. A flexible printed wiring board characterized by

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