阅读说明：本技术 层叠结构体、干膜、其固化物和电子部件 (Laminated structure, dry film, cured product thereof, and electronic component ) 是由 宫部英和 小池直之 于 2019-12-27 设计创作，主要内容包括：本发明涉及层叠结构体、干膜、其固化物和电子部件。[课题]提供：满足耐热性、机械特性等、且兼顾了优异的分辨率和电路遮盖性的层叠结构体、干膜、和具有其固化物作为永久覆膜、例如覆盖层或阻焊层的电子部件。[解决方案]本发明的层叠结构体的特征在于,具有：树脂层(A)、和隔着树脂层(A)层叠在基材上的树脂层(B),树脂层(B)由单层膜厚5μm的固化膜的L*a*b*色度体系中的L值为20～40、a值为+10～-10、b值为+10～-10的感光性固化性树脂组合物形成,树脂层(A)由单层膜厚25μm的固化膜的L*a*b*色度体系中的L值为35以下、a值为+10～-10、b值为+10～-10的碱显影型固化性树脂组合物形成。(The present invention relates to a laminated structure, a dry film, a cured product thereof, and an electronic component satisfying heat resistance, mechanical characteristics, and the like, and satisfying excellent resolution and circuit hiding performance, a dry film, and an electronic component having a cured product thereof as a permanent coating film, for example, a cover layer or a solder resist [ solution ] the laminated structure of the present invention is characterized by comprising a resin layer (A) and a resin layer (B) laminated on a substrate via the resin layer (A), wherein the resin layer (B) is formed of a photosensitive curable resin composition having a L value of 20 to 40, an a value of +10 to-10, and a B value of +10 to-10 in a L a B chromaticity system of a cured film having a single layer thickness of 5 [ mu ] m, and the resin layer (A) is formed of an alkali-type curable resin composition having a L value of 35 or less, an a value of +10 to-10, and a value of +10 to-10 in a L a B chromaticity system of a cured film having a single layer thickness of 25 [ mu ] m.)

1. A laminated structure body is characterized by comprising: a resin layer (A) and a resin layer (B) laminated on a substrate with the resin layer (A) therebetween,

the resin layer (B) is formed by a photosensitive curing resin composition which has a L value of 20-40, an a value of + 10-10 and a B value of + 10-10 in a single-layer curing film with a thickness of 5 mu m and an L a B chroma system,

the resin layer (A) is formed from an alkali-developable curable resin composition having a L value of 35 or less, an a value of +10 to-10, and a b value of +10 to-10 in a color system of L a b of a cured film having a single-layer thickness of 25 [ mu ] m.

2. The laminate structure according to claim 1, wherein the resin layer (B) is formed from a photosensitive curable resin composition having a minimum value of 0.2 to 1.0 of absorbance at 450 to 700nm of a dried film having a single-layer thickness of 5 μm,

the resin layer (A) is formed from an alkali-developable curable resin composition having a minimum value of absorbance at 450-700 nm of a dried film having a single-layer thickness of 25 [ mu ] m of 0.25 or more.

3. The laminate structure according to claim 2, wherein the resin layer (B) has a film thickness of 3 to 15 μm, the resin layer (A) has a film thickness of 5 to 85 μm, and the resin layer (A) has a film thickness of 8 to 100 μm,

the cured film of the laminated structure has a color system of L aAb, wherein L value is 15-30, a value is + 5-5, b value is + 5-5,

the minimum value of absorbance at 450 to 700nm of the dried film of the laminated structure is 0.4 or more.

4. A dry film characterized in that at least one surface of the laminate structure of any one of claims 1 to 3 is supported or protected by a film.

5. A cured product comprising the laminated structure according to any one of claims 1 to 3.

6. An electronic component, comprising: a permanent coating comprising the cured product according to claim 5.

Technical Field

The present invention relates to a laminated structure useful as a permanent coating film for an electronic component such as a flexible printed wiring board, a dry film, a cured product thereof, and an electronic component.

Background

In recent years, with the miniaturization and thinning of electronic devices due to the spread of smart phones and tablet terminals, there is a growing need for a smaller space for electronic components such as circuit boards. Therefore, the flexible printed wiring board which can be stored in a bent state has been used in a wide range of applications, and the flexible printed wiring board also has been required to have a reliability as high as that of the conventional flexible printed wiring board.

In contrast, conventionally, a cover layer based on polyimide having excellent mechanical properties such as flexibility and impact resistance is used in a bent portion (flexure portion) of a flexible printed wiring board (see, for example, patent documents 1 and 2).

Such a cover layer based on polyimide having excellent mechanical properties such as heat resistance and flexibility requires punching in a die, and is therefore unsuitable for fine wiring. Therefore, in a chip mounting portion requiring fine wiring, it is necessary to partially combine and use an alkali development type photosensitive resin composition (solder resist) which can be processed by photolithography.

Disclosure of Invention

Problems to be solved by the invention

As described above, in the conventional process for manufacturing a flexible printed wiring board, a mixed mounting process of a step of die-punching a cover layer to bond the cover layer to the flexible printed wiring board and a step of forming a solder resist layer by photolithography has to be employed, and there is a problem that the cost and workability are poor.

In view of this, a photosensitive resin composition (solder resist) has been used as a cover layer, and has been studied for use over the entire surface of a flexible printed wiring board. However, materials that can sufficiently satisfy performance have not yet been put to practical use in response to the demand for a circuit board with a small space.

On the other hand, a permanent film used for a flexible printed wiring board or the like is required to have fine patterning (so-called resolution) suitable for component mounting, electrical insulation, heat resistance, and mechanical properties, and also is required to have high visual hiding properties of a circuit in terms of design or the like.

However, since a black colorant used in a conventional black photosensitive resin composition exhibits absorption capability in a wide wavelength range from an ultraviolet region to an infrared region, when excellent circuit covering properties are required, there are problems as follows: light transmittance upon irradiation with active energy rays (so-called exposure) is reduced, and light cannot reach deep, thereby deteriorating resolution.

In order to solve the problem that the circuit covering property and the resolution are in the trade-off relationship, various methods of combining coloring agents other than black have been proposed. However, in this method, the transparency of light in the ultraviolet region can be secured, and the coverage and the resolution can be partially achieved at the same time, but there is a limit in the circuit coverage, and only a limited combination of colorants can be used.

Accordingly, a primary object of the present invention is to provide: a material satisfying the required performance (excellent heat resistance, mechanical properties, etc.) of both solder resist and cover layer and having both excellent resolution and excellent circuit coverability.

Another object of the present invention is to provide: a laminated structure suitable for a process of simultaneously forming a permanent coating film, particularly a curved portion (a flexible portion) and a component mounting portion (a non-flexible portion), used for a flexible printed wiring board or the like, a dry film, a cured product thereof, and an electronic component such as a flexible printed wiring board having the cured product as a permanent coating film such as a cover layer or a solder resist layer.

Means for solving the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that a multilayer structure having both excellent resolution and circuit hiding properties while maintaining excellent resolution and circuit hiding properties can be obtained by setting the values of L, a and b in the color system of L a b of the lower layer (substrate side) and the upper layer (outer layer side) to specific values, respectively, and further preferably setting the value of absorbance of the dried coating film of each layer to a specific range.

That is, the laminated structure of the present invention is characterized by comprising: a resin layer (A) and a resin layer (B) laminated on a substrate with the resin layer (A) therebetween,

the resin layer (B) is formed of a photosensitive curable resin composition having a L value of 20 to 40, an a value of +10 to-10 and a B value of +10 to-10 in a color system of L a B of a cured film having a single layer thickness of 5 μm,

the resin layer (A) is formed from an alkali-developable curable resin composition having a L value of 35 or less, an a value of +10 to-10, and a b value of +10 to-10 in a color system of L a b of a cured film having a single-layer thickness of 25 μm.

Here, the L value, a value, and b value in the color system of L × a × b are in accordance with JIS Z8781(CIE L × a × b color space).

The resin layer (B) constituting the laminated structure of the present invention is formed from a photosensitive curable resin composition having a minimum value of absorbance at 450 to 700nm of a dried film having a single layer thickness of 5 μm of 0.2 to 1.0, and the resin layer (A) is formed from an alkali-developable curable resin composition having a minimum value of absorbance at 450 to 700nm of a dried film having a single layer thickness of 25 μm of 0.25 or more.

The laminate structure of the present invention comprising the resin layer (A) and the resin layer (B) is characterized in that the thickness of the resin layer (B) is 3 to 15 [ mu ] m, the thickness of the resin layer (A) is 5 to 85 [ mu ] m, and the thickness is 8 to 100 [ mu ] m, the cured film of the laminate structure has a value of L in the color system of L a B, a value of +5 to-5, and a value of B of +5 to-5, and the minimum value of absorbance at 450 to 700nm of the dried film of the laminate structure is 0.4 or more.

In the laminated structure of the present invention, the photosensitive curable resin composition constituting the resin layer (B) contains a black coloring agent, an alkali-soluble resin, a thermally reactive compound and a photopolymerization initiator, and the alkali-developable curable resin composition constituting the resin layer (a) contains a black coloring agent, an alkali-soluble resin and a thermally reactive compound, and preferably contains substantially no photopolymerization initiator.

In the dry film of the present invention, at least one surface of the laminated structure is supported or protected by a film.

Further, the cured product of the present invention includes the above laminated structure.

Further, an electronic component such as a flexible printed wiring board according to the present invention includes: a permanent coating film comprising the cured product.

Here, examples of the electronic component of the present invention include an electronic component having a permanent coating film formed as follows: the layer of the laminated structure is formed on a flexible printed wiring board, and the exposed portion is reacted by exposure, and the unexposed portion is dissolved by development to form a pattern. In addition, the electronic component may have a permanent coating film formed as follows: in the case where the above laminated structure is not used, the resin layer (a) and the resin layer (B) are formed in this order on the flexible printed wiring board, and then a pattern is formed by development. In the present specification, the term "pattern" refers to a patterned coating film formed by development.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided: a material satisfying the required performance (excellent heat resistance, mechanical properties, etc.) of both solder resist and cover layer and having both excellent resolution and excellent circuit coverability.

Furthermore, it is possible to realize: a laminated structure suitable for a simultaneous film forming process of a permanent film used for an electronic component such as a flexible printed wiring board, particularly a bending portion (bending portion) and a component mounting portion (non-bending portion), a dry film, a cured product thereof, and an electronic component such as a flexible printed wiring board having the cured product as a permanent film such as a cover layer or a solder resist layer.

Drawings

Fig. 1 is a process diagram schematically showing a method for manufacturing a flexible printed wiring board showing an example of an electronic component of the present invention.

Description of the reference numerals

1 Flexible printed Wiring substrate

2-conductor circuit

3 resin layer (A)

4 resin layer (B)

5 mask

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

(laminated Structure)

The laminated structure of the present invention comprises: the resin layer (A) and the resin layer (B) laminated on a substrate such as a flexible printed wiring board with the resin layer (A) therebetween. In the laminated structure of the present invention, the resin layer (a) and the resin layer (B) substantially function as an adhesive layer and a protective layer, respectively.

The laminate structure is characterized in that the resin layer (B) is formed from a photosensitive curable resin composition, the cured film having a single layer thickness of 5 [ mu ] m has a L value of 20 to 40, an a value of +10 to-10 and a B value of +10 to-10 in an L a B chromaticity system, and the resin layer (A) is formed from an alkali development type curable resin composition, and the cured film having a single layer thickness of 25 [ mu ] m has a L value of 35 or less, an a value of +10 to-10 and a B value of +10 to-10 in a L a B chromaticity system.

In order to improve circuit hiding performance, it is considered to reduce light transmittance of a resin layer on a circuit in a permanent film of a printed wiring board. In this regard, the inventors and others found that: if the permanent coating film is a laminated structure of at least 2 layers and the resin layer on the outer layer side has light transmittance to such an extent that resolution does not deteriorate, and a desired pattern can be formed by exposure and development, the light transmittance of the resin layer on the substrate surface side is extremely low, and the resin layer on the outer layer side formed by patterning functions as a coating film having development resistance even if photoreactivity is not present, and a desired pattern can be obtained.

That is, according to the laminated structure of the present invention, L a B of a cured film having a single-layer thickness of 5 μm of the resin layer (B) on the outer layer side in the laminated structure in which at least 2 resin layers are laminated has a value of L of 20 to 40, a value of +10 to-10, and a value of B of +10 to-10 in a colorimetric system, so that a desired pattern can be formed by utilizing the reaction of exposure and development, L of a L a B of a cured film having a single-layer thickness of 25 μm of the resin layer (a) on the substrate surface side has a value of 35 or less, a value of +10 to-10, and a value of B of +10 to-10 in a colorimetric system, so that the resin layer (a) has a high circuit-covering property, and even if the light transmission property is low, the resin layer (B) on the outer layer side functions as a coating film having development resistance, and the pattern can be formed by development, and as a result, it is possible to obtain a laminated structure having excellent circuit-covering property and preventing resolution and having excellent circuit-covering property.

Further, in order to achieve the above functional effects, it is preferable that the minimum value of absorbance at 450 to 700nm of a dried film having a single-layer thickness of 5 μm of the resin layer (B) on the outer layer side is 0.2 to 1.0, and the minimum value of absorbance at 450 to 700nm of a dried film having a single-layer thickness of 25 μm of the resin layer (A) on the substrate surface side is 0.25 or more.

In the laminated structure composed of the resin layer (a) and the resin layer (B), it is preferable that the resin layer (B) has a film thickness of 3 to 15 μm, the resin layer (a) has a film thickness of 5 to 85 μm, and the resin layer (B) has a film thickness of 8 to 100 μm, that the laminated structure has an excellent circuit covering property in which a value of L in a chromaticity system of L a B of a cured film of the laminated structure is 15 to 30, a value of +5 to-5, and a value of B is +5 to-5, and a minimum value of absorbance at 450 to 700nm of a dried film of the laminated structure is 0.4 or more.

When the laminate structure of the present invention is laminated on a substrate such as a flexible printed wiring board having a copper circuit formed on a flexible substrate, if the resin layer (a) on the substrate surface side can be patterned even if the photopolymerization initiator is not contained and the resin layer (B) on the outer layer side is exposed and developed, the resin layer (B) and the resin layer (a) can be simultaneously patterned by development.

[ resin layer (A) ]

The resin layer (A) is formed from an alkali-developable curable resin composition having a L value of 35 or less, a value of +10 to-10, and b value of +10 to-10 in an L a b chromaticity system of a cured film having a single thickness of 25 μm, and preferably having a L value of 30 or less from the viewpoint of circuit coverability, and the resin layer (A) is black by setting the L value, the a value, and the b value in the L a b chromaticity system to such specific ranges, and a cured coating having a thickness of 5 μm to 85 μm, preferably 5 μm to 70 μm is further formed on a circuit of a flexible printed wiring board, whereby sufficient circuit coverability can be obtained.

Further, in order to obtain excellent circuit covering properties, it is more preferable that the resin composition is formed from an alkali-developable curable resin composition having a minimum value of absorbance at 450 to 700nm of a dried film having a thickness of 25 μm per layer of the resin composition is 0.25 or more, and further that the minimum value of absorbance at 450 to 700nm is 0.3 or more.

The L value, the a value, the b value, and the absorbance in the alkali development type curable resin composition constituting the resin layer (a) can be adjusted according to the formulation of the components contained in the alkali development type curable resin composition, and preferably contains a colorant exhibiting black color, an alkali-soluble resin, a thermally reactive compound, and substantially no photopolymerization initiator, and particularly suitable is a colorant exhibiting black color, which can easily adjust the L value, the a value, the b value, and the absorbance in the alkali development type curable resin composition L a b system, and specifically, any of a black colorant, a mixture of a black colorant and another colorant, and a mixture of 2 or more colorants other than a black colorant can be used.

The substantial absence of the photopolymerization initiator means that the content of the photopolymerization initiator is such that patterning cannot be performed when the resin layer (a) is a single layer, and the photopolymerization initiator corresponds to a photopolymerization initiator described later.

(coloring agent in black)

The colorant having a black color preferably contained in the alkali-developable curable resin composition constituting the resin layer (a) may be an organic colorant or an inorganic colorant, and a pigment, a dye, or the like may be used. For example, carbon black, graphite, iron oxide, copper oxide, anthraquinone, aniline, titanium, manganese, antimony oxide, nickel oxide, perylene, molybdenum sulfide, bismuth sulfide, and the like can be used. Examples thereof include: and black colorants such as pigment black 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 18, 20, 23, 25, 26, 27, 28, 29, 30, 31, 32, and the like.

As the colorant exhibiting black color, there can be used: the above black coloring agent is suitably combined with a known and commonly used coloring agent such as blue, green, yellow, red, violet, orange, brown, white, etc.

Here, as the blue colorant, phthalocyanine-based, anthraquinone-based, and the like colorants can be used. Examples of the pigment system include: pigment blue 15, 15: 1. 15: 2. 15: 3. 15: 4. 15.6, 16, 60, etc. Examples of the dye system include: solvent blue 35, 63, 67, 68, 70, 83, 87, 94, 97, 122, 136, etc. In addition to these, phthalocyanine compounds substituted or not substituted with a metal may be used.

As the green colorant, phthalocyanine-based, anthraquinone-based, perylene-based colorants and the like can be used in the same manner. Examples thereof include: pigment green 7, 36, solvent green 3,5, 20, 28, etc. In addition to these, phthalocyanine compounds substituted or not substituted with a metal may be used.

As the yellow coloring agent, monoazo-based, disazo-based, condensed azo-based, benzimidazolone-based, isoindolinone-based, anthraquinone-based, etc. can be used. Specifically, the following substances can be mentioned. Mono-azo series: pigment yellow 1,2, 3, 4, 5, 6, 9, 10, 12, 61, 62: 1. 65, 73, 74, 75, 97, 100, 104, 105, 111, 116, 167, 168, 169, 182, 183. A bisazo system: pigment yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, 198. Condensation azo system: pigment yellow 93, 94, 95, 128, 155, 166, 180. Benzimidazolone series: pigment yellow 18, 120, 151, 154, 156, 175. Isoindolinone series: pigment yellow 109, 110, 139, 179, 185. Anthraquinone series: pigment yellow 24, 108, 147, 193, 199, 202, solvent yellow 163.

As the red colorant, monoazo-based, disazo-based, monoazo lake-based, benzimidazolone-based, perylene-based, diketopyrrolopyrrole-based, condensed azo-based, anthraquinone-based, quinacridone-based, and the like can be used. Specifically, the following substances can be mentioned. Mono-azo series: pigment red 1,2, 3, 4, 5, 6, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 112, 114, 146, 147, 151, 170, 184, 187, 188, 193, 210, 245, 253, 258, 266, 267, 268, 269. A bisazo system: pigment Red 37, 38, 41. Monoazo lakes system: pigment red 48: 1. 48: 2. 48: 3. 48: 4. 49: 1. 49: 2. 50: 1. 52: 1. 52: 2. 53: 1. 53: 2. 57: 1. 58: 4. 63: 1. 63: 2. 64: 1. 68. Benzimidazolone series: pigment red 171, 175, 176, 185, 208. Perylene series: pigment red 123, 149, 166, 178, 179, 190, 194, 224, solvent red 135, 179. Diketopyrrolopyrroles: pigment red 254, 255, 264, 270, 272. Condensation azo system: pigment red 144, 166, 214, 220, 221, 242. Anthraquinone series: pigment red 168, 177, 216, solvent red 52, l49, 150, 207. Quinacridone series: pigment red 122, 202, 206, 207, 209.

Examples of the violet colorant include pigment violet 19, 23, 29, 32, 36, 38, 42, solvent violet 13, 36, and the like.

Examples of orange colorants include pigment orange 1,5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 63, 64, 71, 73, and the like.

Examples of the brown colorant include pigment brown 23 and pigment brown 25.

Examples of the white colorant include zinc oxide represented by pigment white 4, titanium oxide represented by pigment white 6, and zinc sulfide represented by pigment white 7, and titanium oxide is particularly preferable from the viewpoints of coloring power and non-toxicity, and examples thereof include: TR-600, TR-700, TR-750, TR-840, R550, R580, R630, R820, CR50, CR60, CR90, KR270, KR310, KR380 and other rutile titanium oxides available from Fuji titanium industries, TA-100, TA-200, TA-300, TA-500, A100, A220, KA-15, KA-20, KA-35, KA-90 and other anatase titanium oxides available from Fuji titanium industries.

Further, as the colorant exhibiting black color, a colorant exhibiting black color by combining 2 or more kinds of colorants other than the black colorant may be used.

As a combination of 2 or more kinds of colorants constituting the mixture, a blue colorant, a green colorant, a red colorant, a yellow colorant, an orange colorant, and a violet colorant may be arbitrarily combined. Specifically, there may be mentioned: combinations of a blue colorant and an orange colorant, a blue colorant and a red colorant, a blue colorant and a violet colorant, a blue colorant and a yellow colorant and an orange colorant, a blue colorant and a red colorant and a yellow colorant, a blue colorant and a yellow colorant and a violet colorant, a blue colorant and an orange colorant and a violet colorant, a yellow colorant and a violet colorant, a green colorant and a violet colorant, and a green colorant and a red colorant, a green colorant and a red colorant and a blue colorant are not limited to these as long as they are black.

As these colorants, the above-mentioned known and commonly used colorants can be used.

Specifically, the amount of the black coloring agent is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, based on 100 parts by mass of the alkali-soluble resin contained in the resin layer (a), and the amount of the black coloring agent is adjusted within the above range, whereby excellent circuit hiding properties can be secured without deteriorating workability as a composition and flexibility of a cured film.

(alkali-soluble resin)

The alkali-soluble resin preferably contained in the resin layer (a) may be a resin that contains 1 or more functional groups of phenolic hydroxyl groups and carboxyl groups and is developable in an alkaline solution. Preferred examples thereof include a compound having a phenolic hydroxyl group, a compound having a carboxyl group, and a resin having a phenolic hydroxyl group and a carboxyl group. The alkali-soluble resin may have an ethylenically unsaturated double bond.

Examples thereof include a carboxyl group-containing resin and a carboxyl group-containing photosensitive resin which have been conventionally used as solder resist compositions.

Specific examples of the carboxyl group-containing resin include the following compounds (both oligomers and polymers).

(1) A carboxyl group-containing resin obtained by copolymerizing an unsaturated carboxylic acid such as (meth) acrylic acid with an unsaturated group-containing compound such as styrene, α -methylstyrene, a lower alkyl (meth) acrylate, or isobutylene.

(2) The carboxyl group-containing polyurethane resin is obtained by addition polymerization of a diisocyanate such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, an alicyclic diisocyanate, or an aromatic diisocyanate, a carboxyl group-containing diol compound such as dimethylolpropionic acid or dimethylolbutyric acid, and a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, an acrylic polyol, a bisphenol a alkylene oxide adduct diol, or a compound having a phenolic hydroxyl group and an alcoholic hydroxyl group.

(3) A carboxyl-terminated polyurethane resin obtained by addition polymerization of a diisocyanate compound such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, an alicyclic diisocyanate, or an aromatic diisocyanate with a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, an acrylic polyol, a bisphenol a alkylene oxide adduct diol, or a compound having a phenolic hydroxyl group and an alcoholic hydroxyl group.

(4) A carboxyl group-containing urethane resin obtained by addition polymerization of a diisocyanate, a (meth) acrylate ester with a 2-functional epoxy resin such as a bisphenol a epoxy resin, a hydrogenated bisphenol a epoxy resin, a bisphenol F epoxy resin, a bisphenol S epoxy resin, a bixylenol epoxy resin, a diphenol epoxy resin, or a partial acid anhydride modification thereof, a carboxyl group-containing diol compound, and a diol compound.

(5) A carboxyl group-containing urethane resin obtained by terminal (meth) acrylation of a compound having 1 hydroxyl group and 1 or more (meth) acryloyl groups in the molecule, such as hydroxyalkyl (meth) acrylate, is added to the synthesis of the resin of (2) or (4).

(6) In the synthesis of the resin of the above (2) or (4), a carboxyl group-containing urethane resin obtained by (meth) acrylating a compound having 1 isocyanate group and 1 or more (meth) acryloyl groups in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate, is added.

(7) A carboxyl group-containing resin obtained by reacting a polyfunctional epoxy resin with (meth) acrylic acid and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, or the like to a hydroxyl group present in a side chain.

(8) A carboxyl group-containing resin obtained by further epoxidizing the hydroxyl group of the 2-functional epoxy resin with epichlorohydrin to obtain a polyfunctional epoxy resin, reacting the obtained polyfunctional epoxy resin with (meth) acrylic acid, and adding a dibasic acid anhydride to the resulting hydroxyl group.

(9) A carboxyl group-containing polyester resin obtained by reacting a polyfunctional oxetane resin with a dicarboxylic acid and adding a dibasic acid anhydride to the resulting primary hydroxyl group.

(10) A carboxyl group-containing resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in 1 molecule with an alkylene oxide such as ethylene oxide or propylene oxide to obtain a reaction product, reacting the obtained reaction product with an unsaturated group-containing monocarboxylic acid, and reacting the obtained reaction product with a polybasic acid anhydride.

(11) A carboxyl group-containing resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in 1 molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate to obtain a reaction product, reacting the obtained reaction product with an unsaturated group-containing monocarboxylic acid, and reacting the obtained reaction product with a polybasic acid anhydride.

(12) A carboxyl group-containing resin obtained by reacting an epoxy compound having a plurality of epoxy groups in 1 molecule, a compound having at least 1 alcoholic hydroxyl group and 1 phenolic hydroxyl group in 1 molecule such as p-hydroxyphenylethanol, and an unsaturated group-containing monocarboxylic acid such as (meth) acrylic acid, and reacting the alcoholic hydroxyl group of the obtained reaction product with a polybasic acid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic anhydride.

(13) A carboxyl group-containing polyimide resin obtained by reacting a carboxyl group-and/or phenolic hydroxyl group-containing carboxylic anhydride with an amine such as a carboxyl group-and/or phenolic hydroxyl group-containing amine, and if necessary, reacting with another carboxylic anhydride, an amine, and an isocyanate.

(14) A carboxyl group-containing resin obtained by further adding a compound having 1 epoxy group and 1 or more (meth) acryloyl groups in the molecule, such as glycidyl (meth) acrylate and α -methylglycidyl (meth) acrylate, to the carboxyl group-containing resin described in (1) to (13) above.

Among the above carboxyl group-containing resins, the carboxyl group-containing resins described in (1), (7), (8), and (10) to (14) are preferable.

(thermally reactive Compound)

As the heat-reactive compound preferably contained in the resin layer (a), a known and commonly used compound having a functional group capable of undergoing a heat curing reaction such as a cyclic (thio) ether group is used. In particular, a compound which undergoes a thermosetting reaction with the alkali-soluble resin contained in the resin layer (a) is preferable, and an epoxy resin is suitably used.

Examples of the epoxy resin include bisphenol a type epoxy resin, brominated epoxy resin, novolac type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol a type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, trishydroxyphenylmethane type epoxy resin, bixylenol type or biphenol type epoxy resin, or a mixture thereof; bisphenol S type epoxy resins, bisphenol a novolac type epoxy resins, heterocyclic epoxy resins, biphenol novolac type epoxy resins, naphthyl-containing epoxy resins, epoxy resins having a dicyclopentadiene skeleton, and the like.

[ resin layer (B) ]

(photosensitive curable resin composition)

The resin layer (B) is formed of L A B photosensitive curable resin composition having a L value of 20 to 40, a value of +10 to-10, and B value of +10 to-10 in a single-layer cured film thickness of 5 μm and a chromaticity system, and is black in color as in the resin layer (A). by making the L value, a value, and B value in the L A B chromaticity system of the resin layer (B) in such specific ranges, a pattern having excellent resolution can be formed by exposure and development, and by laminating the resin layer (A) on top of the resin layer (A), the resin layer (A) functions as a coating film having development resistance, and further, excellent circuit-covering properties can be obtained.

Further, for the functional effects, the resin layer (B) is composed of a photosensitive curable resin composition having a minimum value of absorbance at 450 to 700nm of a dried film having a single layer thickness of 5 μm of 0.2 to 1.0. By setting the absorbance of the dried coating film in such a range, it is possible to achieve both formation of a pattern having excellent resolution and excellent circuit hiding properties.

The L value, the a value, the B value, and the absorbance in the color system L a B of the photosensitive curable resin composition constituting the resin layer (B) can be adjusted according to the formulation of the components contained in the photosensitive curable resin composition, and preferably contains a black colorant, an alkali-soluble resin, a thermally reactive compound, and a photopolymerization initiator.

(coloring agent in black)

The black colorant contained in the photosensitive curable resin composition constituting the resin layer (B) can be used, and the content can be arbitrarily adjusted as long as the cured film having a single layer thickness of 5 μm of the resin layer (B) has a color system of L a B in which the value of L is 20 to 40, the value of a is +10 to-10, and the value of B is +10 to-10.

Specifically, the amount of the black coloring agent is preferably 0.3 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the alkali-soluble resin contained in the resin layer (B). When the amount of the black colorant is in the above range, excellent resolution, development resistance of an exposed portion, and further excellent circuit covering properties as a laminated structure can be obtained.

(alkali-soluble resin)

The alkali-soluble resin may be used in the form of 1 kind alone or 2 or more kinds in combination. Further, from the viewpoint of heat resistance and mechanical properties, an alkali-soluble polyimide resin having an imide ring and containing 1 or more functional groups of a phenolic hydroxyl group and a carboxyl group can be suitably used.

(thermally reactive Compound)

As the thermoreactive compound preferably contained in the resin layer (B), the above known and commonly used compounds can be used. In particular, a compound which undergoes a thermosetting reaction with the alkali-soluble resin contained in the resin layer (B) is preferable, and the epoxy resin is suitably used.

(photopolymerization initiator)

The resin composition constituting the resin layer (B) further contains a photopolymerization initiator. As the photopolymerization initiator, known and commonly used photopolymerization initiators including a photoradical generator, a photoacid generator and a photobase generator can be used.

[ laminated Structure ]

The laminated structure of the present invention is a laminated structure having a film thickness of 8 to 100 μm, wherein the cured film of the laminated structure has a L value of 15 to 30, an a value of +5 to-5, and a B value of +5 to-5 in the L a B chromaticity system, and the minimum value of absorbance at 450 to 700nm of the dried film of the laminated structure is 0.4 or more, and has excellent circuit covering properties.

The laminated structure of the present invention has excellent flexibility, and therefore, can be used for at least either of a flexible portion and a non-flexible portion of an electronic component such as a flexible printed wiring board, and further can be used for at least either of a cover layer, a solder resist layer, and an interlayer insulating material of a flexible printed wiring board.

The laminated structure of the present invention having the above-described configuration 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, for example, as follows.

That is, first, the photosensitive curable resin composition constituting the resin layer (B) and the alkali-developable curable resin composition constituting the resin layer (a) are diluted with an organic solvent to adjust the respective viscosities to appropriate values, and the resulting solutions are sequentially applied to a support film (carrier film) by a known method such as a comma coater according to a conventional method. Then, the film is dried at a temperature of 50 to 140 ℃ for 1 to 30 minutes to produce a dry film having a coating film of the resin layer (B) and the resin layer (A) formed on the support film. A protective film (cover film) that can be peeled off may be further laminated on the dry film for the purpose of preventing dust from adhering to the surface of the coating film. As the support film and the protective film, conventionally known plastic films can be suitably used, and in the protective film, when the protective film is peeled, the adhesive force is preferably smaller than the adhesive force between the resin layer and the support film. The thickness of the support film and the protective film is not particularly limited, and is preferably selected in the range of 10 to 150 μm.

(cured product)

The cured product of the present invention is obtained by curing the above-described laminated structure of the present invention.

(electronic parts)

The laminated structure of the present invention described above can be effectively used for electronic components such as flexible printed wiring boards. Specifically, a flexible printed wiring board having a permanent film formed as follows, and the like can be given: the layer of the laminated structure of the present invention is formed on a flexible printed wiring substrate, and a pattern is formed by exposure and development.

Hereinafter, a method for manufacturing a flexible printed wiring board will be specifically described.

(method for manufacturing Flexible printed Wiring Board)

The flexible printed wiring board using the laminated structure of the present invention can be manufactured, for example, according to the steps shown in the process diagram of fig. 1. Namely, the manufacturing method comprises the following steps: a step (laminating step) of forming a layer of the laminated structure of the present invention on a flexible printed wiring substrate on which a conductor circuit is formed; a step (exposure step) of irradiating the layer of the laminated structure with an active energy ray in a pattern; and a step (developing step) of forming a patterned layer of the laminated structure by alkali-developing the layer of the laminated structure. Further, after the alkali development, if necessary, further photocuring and thermosetting (post-curing step) are performed to completely cure the layer of the laminated structure, whereby a highly reliable flexible printed wiring board can be obtained.

Hereinafter, each step in fig. 1 will be described in further detail.

[ laminating Process ]

In this step, a laminated structure including a resin layer 3 (resin layer (a)) of an alkali-developable curable resin composition and a resin layer 4 (resin layer (B)) of a photosensitive curable resin composition on the resin layer 3 is formed on the flexible printed wiring substrate 1 on which the conductor circuit 2 is formed. Here, each resin layer constituting the laminated structure can be formed, for example, by the following method: a method in which the resin compositions constituting the resin layers 3 and 4 are sequentially applied to the wiring substrate 1 and dried to form the resin layers 3 and 4, or the resin compositions constituting the resin layers 3 and 4 are formed into a dry film having a 2-layer structure, and the obtained material is laminated on the wiring substrate 1.

The method for coating the wiring substrate with the resin composition may be any known method such as a blade coater, a lip coater, a comma coater, and a film coater. The drying method may be a method of bringing hot air in a dryer into convective contact with each other by using a device having a heat source using a heating method of steam, such as a hot air circulation drying furnace, an IR furnace, a hot plate, or a convection oven; and a method of blowing the gas to the support body through the nozzle.

[ 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. In addition, after exposure, a heating step is inserted, whereby curing of a portion activated by exposure can be assisted.

As the exposure machine used in this step, a direct drawing apparatus (for example, a laser direct imaging apparatus that draws an image under direct laser light from CAD data from a computer) may be used as long as it is a device that is mounted with a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a short-arc mercury lamp, or the like and irradiates ultraviolet light. The patterned exposure mask 5 is a negative mask.

As the active energy ray for exposure, a laser beam or scattered light having a maximum wavelength in the range of 350 to 450nm is preferably used. By setting the maximum wavelength to this range, the photopolymerization initiator can be effectively activated. The exposure amount may be set to 30 to 1000mJ/cm, for example, depending on the film thickness²。

[ developing Process ]

In this step, unexposed portions are removed by alkali development, thereby forming a negative-type pattern-like permanent coating film, such as a cover layer and a solder resist layer. As the developing method, a known method such as a dipping method can be used. As the developer, an alkaline aqueous solution such as sodium carbonate, potassium hydroxide, amines, imidazoles such as 2-methylimidazole, or a tetramethylammonium hydroxide aqueous solution (TMAH), or a mixture thereof can be used.

[ post-curing step ]

This step is a step of obtaining a highly reliable coating by completely thermally curing the permanent coating after the developing step. The heating temperature is, for example, 120 ℃ to 180 ℃. The heating time is, for example, 5 minutes to 120 minutes. Further, the permanent coating film may be subjected to light irradiation before or after post-curing.