Method for producing flexible printed board

Abstract

This method for producing a flexible printed board comprises a step in which a liquid photosensitive resin composition (17) is applied to both surfaces of a substrate (11), which comprises a film-like supporting body (13) and wiring lines (14) that are provided on both surface of the film-like supporting body (13), with use of a vertical suspension type roll coater. The substrate (11) is provided with a hole (15). The liquid photosensitive resin composition (17) contains a binder polymer that has an imide group in each molecule, a radical photopolymerization initiator and a thermosetting resin. When the liquid photosensitive resin composition (17) is applied, the liquid photosensitive resin composition (17) is applied to both surfaces of the substrate (11) at the same time.

Description

Flexible printed circuit board manufacturing method

[0001] The present invention relates to a method for manufacturing a flexible printed circuit board.

[0002] As electronic components become smaller, lighter, and more multifunctional, apertures in flexible printed circuit boards incorporated into electronic devices are required to be fine enough to mount components on smaller-diameter lands, etc. (hereinafter, this may be referred to as "fine aperture capability") As a method for forming fine apertures in flexible printed circuit boards, a method is known in which a film made of a liquid photosensitive resin composition is formed on a component mounting portion of a flexible printed circuit board (hereinafter, this may be simply referred to as a "substrate") before a protective film is formed, and this film is patterned by photolithography to form a protective film with fine apertures.

[0003] Furthermore, in recent years, as the screens of mobile devices such as smartphones have become larger and thinner, flexible printed circuit boards used in the mobile devices are required to have low resilience so that they can be easily folded and installed in narrow spaces. One known method for improving the low resilience of flexible printed circuit boards is to partially apply a thermosetting resin composition known as bending ink to the bent portions of the board.

[0004] Furthermore, flexible printed circuit boards usually have through holes (through holes) and non-through holes (blind vias), and when applying a liquid photosensitive resin composition to the board, it is necessary to fill the through holes and non-through holes with the liquid photosensitive resin composition. For this reason, flexible printed circuit boards are also required to be sufficiently filled with the liquid photosensitive resin composition in the through holes and non-through holes (hereinafter, this may be referred to as "fillability"). Note that, hereinafter, through holes and non-through holes may be collectively referred to as "holes." Furthermore, hereinafter, "hole" refers to one hole or multiple holes. Furthermore, a substrate provided with holes includes a substrate provided with only through holes, a substrate provided with only non-through holes, and a substrate provided with both through holes and non-through holes.

[0005] Under these circumstances, various resin compositions for protective films (more specifically, liquid photosensitive resin compositions, etc.) and coating devices for protective film resin compositions have been investigated in order to improve the fine opening properties, low resilience, or embeddability of flexible printed circuit boards (see, for example, Patent Documents 1 to 4).

[0006] JP 2015-161764 A JP 2020-148971 A International Publication No. 2018 / 092330 JP 2015-115602 A

[0007] However, the techniques described in Patent Documents 1 to 4 still have room for improvement in terms of increasing the electrical insulation reliability of flexible printed circuit boards.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a flexible printed circuit board having excellent electrical insulation reliability.

[0009] The method for manufacturing a flexible printed circuit board according to the present invention includes a step of applying a liquid photosensitive resin composition to both sides of a substrate having a film support and wiring provided on both sides of the film support using a vertical lift-type roll coater. The substrate has holes formed therein. The vertical lift-type roll coater includes a pair of coating rolls having grooves. The surface layer of the coating roll is a rubber layer. The liquid photosensitive resin composition contains a binder polymer having an imide group in one molecule, a photoradical polymerization initiator, and a thermosetting resin. When applying the liquid photosensitive resin composition, the liquid photosensitive resin composition is simultaneously applied to both sides of the substrate.

[0010] In the method for producing a flexible printed circuit board according to one embodiment of the present invention, the film-like support has a width and a length of 200 mm or more and 600 mm or less.

[0011] In the method for producing a flexible printed circuit board according to one embodiment of the present invention, the film-like support has a thickness of 8.0 μm or more and 50.0 μm or less.

[0012] In the method for manufacturing a flexible printed circuit board according to one embodiment of the present invention, the wiring has a thickness of 8 μm or more and 50 μm or less.

[0013] In the method for manufacturing a flexible printed circuit board according to one embodiment of the present invention, the hole has a diameter of 50 μm or more and 250 μm or less.

[0014] In one embodiment of the method for producing a flexible printed circuit board according to the present invention, the film-like support contains one or more polymers selected from the group consisting of polyimide, polyamide, polyester, polycarbonate, polyarylate, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, and ethylene-chlorotrifluoroethylene copolymer.

[0015] In the method for producing a flexible printed circuit board according to one embodiment of the present invention, the liquid photosensitive resin composition further contains particles having an average particle size of 0.01 μm or more and 100 μm or less.

[0016] In the method for producing a flexible printed circuit board according to one embodiment of the present invention, the liquid photosensitive resin composition further contains a particle dispersant.

[0017] In the method for manufacturing a flexible printed circuit board according to one embodiment of the present invention, the coating roll has a plurality of independent ring-shaped grooves as the groove.

[0018] In the method for manufacturing a flexible printed circuit board according to one embodiment of the present invention, the roll diameter of the coating roll is 70 mm or more and 150 mm or less.

[0019] According to the present invention, a method for manufacturing a flexible printed circuit board having excellent electrical insulation reliability can be provided.

[0020] Fig. 1 is a cross-sectional view of a main part for explaining an example of a manufacturing method for a flexible printed circuit board according to the present invention; Fig. 2 is another cross-sectional view of a main part for explaining an example of a manufacturing method for a flexible printed circuit board according to the present invention; Fig. 3 is another cross-sectional view of a main part for explaining an example of a manufacturing method for a flexible printed circuit board according to the present invention; Fig. 4 is another cross-sectional view of a main part for explaining an example of a manufacturing method for a flexible printed circuit board according to the present invention; Fig. 5 is a cross-sectional view of a coating roll used in an example of a manufacturing method for a flexible printed circuit board according to the present invention, cut along a plane including its axis.

[0021] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0022] First, the terms used in this specification will be explained. A "roll coater" is a coating device having a pair of rotatable coating rolls. Roll coater coating methods include a vertical lifting type, in which the liquid photosensitive resin composition is applied to a substrate while the substrate is lifted vertically, and a horizontal conveying type, in which the liquid photosensitive resin composition is applied to a substrate while the substrate is conveyed horizontally. A vertical lifting type roll coater can simplify the coating device and save space compared to a horizontal conveying type roll coater. Furthermore, a vertical lifting type roll coater can dry a substrate coated with the liquid photosensitive resin composition in a suspended state, thereby suppressing the adhesion of foreign matter during the drying process of a coating film (hereinafter sometimes simply referred to as a "coating film") made of the liquid photosensitive resin composition.

[0023] The "thickness" of the film-like support is the arithmetic mean value of 10 measured values ​​obtained by randomly selecting 10 measurement points from an electron microscope image of a cross section of the film-like support cut in the thickness direction and measuring the thicknesses of the selected 10 measurement points.The "thickness" of the wiring is the arithmetic mean value of 10 measured values ​​obtained by randomly selecting 10 measurement points from an electron microscope image of a cross section of the wiring cut in the thickness direction and measuring the thicknesses of the selected 10 measurement points.

[0024] A "cured film of a liquid photosensitive resin composition" is a coating film made of the liquid photosensitive resin composition after curing. Hereinafter, a cured film of a liquid photosensitive resin composition may be simply referred to as a "cured film." In this specification, "after curing" refers to a state in which further heating no longer increases the elastic modulus of the coating film. Specifically, this refers to a state in which the increase in the elastic modulus of the coating film is less than 0.01 GPa even when the coating film is further heated at a temperature of 150°C for 60 minutes. The elastic modulus is measured by the same method as in the examples described below or a method equivalent thereto.

[0025] The term "photoradical polymerization initiator" refers to a compound that generates radicals as active species upon irradiation with light.

[0026] The "average particle size" is a volume-based median diameter (particle size at 50% of the cumulative distribution value) measured using a laser diffraction / scattering particle size distribution analyzer (for example, "LA-950V2" manufactured by Horiba, Ltd.).

[0027] Hereinafter, the compound and its derivatives may be collectively referred to by adding "based" after the compound name. When the polymer name is represented by adding "based" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, acrylic and methacrylic may be collectively referred to as "(meth)acrylic". Furthermore, acrylate and methacrylate may be collectively referred to as "(meth)acrylate". Furthermore, acryloyl groups and methacryloyl groups may be collectively referred to as "(meth)acryloyl groups". Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more types.

[0028] The drawings referred to in the following description mainly show each component in a schematic manner for ease of understanding, and the size, number, shape, etc. of each component shown may differ from the actual size, number, shape, etc. of each component due to the convenience of creating the drawings. Furthermore, for convenience of explanation, in drawings described later, the same components as those in previously described drawings may be assigned the same reference numerals, and their explanation may be omitted.

[0029] <Method for manufacturing a flexible printed circuit board> The method for manufacturing a flexible printed circuit board according to this embodiment includes a step of applying a liquid photosensitive resin composition to both sides of a substrate having a film support and wiring provided on both sides of the film support using a vertical lift-type roll coater. The substrate has holes. The vertical lift-type roll coater includes a pair of coating rolls with grooves. The surface layer of the coating roll is a rubber layer. The liquid photosensitive resin composition contains a binder polymer having an imide group in one molecule, a photoradical polymerization initiator, and a thermosetting resin. When applying the liquid photosensitive resin composition, the liquid photosensitive resin composition is applied simultaneously to both sides of the substrate.

[0030] In the method for manufacturing a flexible printed circuit board according to this embodiment, when the liquid photosensitive resin composition is applied, the liquid photosensitive resin composition is simultaneously applied to both sides of the substrate, so that the liquid photosensitive resin composition can be applied while filling holes provided in the substrate.

[0031] According to this embodiment, a method for manufacturing a flexible printed circuit board having excellent electrical insulation reliability can be provided. The reason for this is presumed to be as follows.

[0032] Generally, when a liquid photosensitive resin composition is simultaneously applied to both sides of a substrate having a film support using a vertical lifting roll coater, the thickness of the coating film at the edge of the wiring tends to be thin, resulting in reduced electrical insulation. In contrast, the vertical lifting roll coater used in this embodiment is equipped with a pair of grooved coating rolls. The surface layer of each coating roll is a rubber layer. Therefore, in this embodiment, when the liquid photosensitive resin composition is simultaneously applied to both sides of the substrate, the thickness of the coating film at the edge of the wiring tends to be relatively thick. Furthermore, because the liquid photosensitive resin composition used in this embodiment contains a binder polymer having an imide group in one molecule, the electrical insulation of the cured film obtained from this liquid photosensitive resin composition tends to be relatively high. For these reasons, this embodiment enables the production of a flexible printed circuit board with excellent electrical insulation reliability.

[0033] In this embodiment, in order to prevent the occurrence of poor appearance of the substrate on which the coating film is formed (more specifically, deformation, tearing, etc. of the substrate), the width and length of the film support are preferably both 150 mm or more and 650 mm or less, more preferably both 200 mm or more and 600 mm or less, and even more preferably both 250 mm or more and 550 mm or less. The term "width of the film support" refers to the width of the film support in a direction parallel to the axial direction of the applicator roll when applying the liquid photosensitive resin composition to the substrate. The term "length of the film support" refers to the width of the film support in a direction perpendicular to the axial direction of the applicator roll when applying the liquid photosensitive resin composition to the substrate.

[0034] In this embodiment, in order to suppress the occurrence of defective appearance of the substrate on which the coating film is formed, the thickness of the film-like support is preferably 8.0 μm or more, more preferably 10.0 μm or more, and even more preferably 12.0 μm or more. Furthermore, in this embodiment, in order to suppress the occurrence of defective appearance of the coating film (specifically, pinholes, uneven coverage of the coating film covering the wiring, groove marks of the coating roll, streaks, etc.), the thickness of the film-like support is preferably 50.0 μm or less.

[0035] In this embodiment, in order to suppress the occurrence of poor appearance of the coating film, the thickness of the wiring is preferably 8 μm or more and 50 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 15 μm or more and 50 μm or less.

[0036] In this embodiment, in order to obtain a flexible printed circuit board with excellent embeddability while ensuring electrical continuity between the wiring provided on both sides of the film-like support, the diameter (opening diameter) of the hole provided in the board is preferably 50 μm or more and 250 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0037] In this embodiment, in order to obtain a flexible printed circuit board that can suppress the occurrence of poor appearance of the coating film and the substrate on which the coating film is formed and that has excellent electrical insulation reliability, it is preferable to satisfy the following condition 1, and more preferably to satisfy the following condition 2. Condition 1: The width and length of the film-like support are both 200 mm or more and 600 mm or less, and the thickness of the film-like support is 8.0 μm or more and 50.0 μm or less. Condition 2: The above condition 1 is satisfied, and the thickness of the wiring is 8 μm or more and 50 μm or less.

[0038] This embodiment will be described below with reference to the drawings as appropriate. Figures 1 to 5 are cross-sectional views of essential parts for explaining an example of a manufacturing method for a flexible printed circuit board according to this embodiment (particularly, the coating process). In each of Figures 1 to 5, the left side of the drawing will be the upstream side of the manufacturing process, and the right side of the drawing will be the downstream side of the manufacturing process.

[0039] In the coating process of this embodiment, first, a substrate 11 suspended by a hanging jig 10 is transferred from the upstream side of the manufacturing process to above a pair of coating rolls 12a and 12b ( FIG. 1 ). In FIG. 1 , the coating roll 12a is located upstream of the manufacturing process, and the coating roll 12b is located downstream of the manufacturing process. The coating rolls 12a and 12b each preferably have a roll diameter of 70 mm or more and 150 mm or less. Furthermore, both the coating rolls 12a and 12b have a groove (for example, a ring-shaped groove 120a shown in FIG. 6 , which will be described later).

[0040] The substrate 11 also has a film-like support 13 and wiring 14 provided on both sides of the film-like support 13. Holes 15 are provided in the substrate 11. The width of the wiring 14 is, for example, 10 μm or more and 200 μm or less. The spacing (pitch) between the wiring 14 is, for example, 10 μm or more and 200 μm or less.

[0041] In the state shown in FIG. 1, a gap is provided between the application rolls 12a and 12b that allows the substrate 11 to pass through. The application roll 12a is in contact with the doctor bar 16a located upstream in the manufacturing process, and is subjected to a predetermined pressure (e.g., 0.5 kgf / cm) from the doctor bar 16a. ２ Over 3.0 kgf / cm ２ The application roll 12b is in contact with the doctor bar 16b on the downstream side of the manufacturing process, and a predetermined pressure (for example, 0.5 kgf / cm or less) is applied from the doctor bar 16b. ２ Over 3.0 kgf / cm ２ (See below) is applied.

[0042] The applicator roll 12a and the applicator roll 12b each rotate at a predetermined rotational speed (for example, 1 m / min to 10 m / min). A liquid photosensitive resin composition 17 is stored between the applicator roll 12a and the doctor bar 16a, and between the applicator roll 12b and the doctor bar 16b. The liquid photosensitive resin composition 17 is transferred to the surfaces of the applicator roll 12a and the applicator roll 12b.

[0043] 1, the hanging jig 10 is lowered, and the hanging substrate 11 passes between the coating rolls 12a and 12b and is transferred to a location (see FIG. 2) where the upper end of the substrate 11 is located between the coating rolls 12a and 12b. Then, as shown in FIG. 2, the hanging jig 10 releases the substrate 11, and the fixing jig 18 grips the lower end of the substrate 11.

[0044] Next, the rotating applicator rolls 12a and 12b sandwich the substrate 11 and press it in so as to apply pressure to the substrate 11, while the fixing jig 18 releases the lower end of the substrate 11 ( FIG. 3 ). When the substrate 11 is released from the fixing jig 18, the rotating applicator rolls 12a and 12b simultaneously apply the liquid photosensitive resin composition 17 to both sides of the substrate 11, while the substrate 11 is lifted upward. In the state shown in FIG. 3 , the amount of press-in by the applicator rolls 12a and 12b is, for example, in the range of 100 μm to 200 μm.

[0045] Next, the upper end of the substrate 11, which has been lifted upward while both sides are simultaneously coated with the liquid photosensitive resin composition 17, is gripped by a hanging jig 10 ( FIG. 4 ). As the substrate 11 is lifted, the liquid photosensitive resin composition 17 fills the holes 15 formed in the substrate 11, and a coating film 19 made of the liquid photosensitive resin composition 17 is formed on both sides of the substrate 11. By gripping the upper end of the substrate 11 with the hanging jig 10 while bringing the hanging jig 10 as close as possible to the coating rolls 12 a and 12 b, it is possible to prevent the substrate 11 from wrapping around the coating rolls 12 a and 12 b.

[0046] Next, the substrate 11 having the coating films 19 formed on both sides is transferred downstream in the manufacturing process while being suspended by the suspension jig 10 (FIG. 5). The substrate 11 transferred downstream in the manufacturing process is then placed in a drying furnace (not shown) and dried. For example, the substrate 11 is transported to the drying furnace while being suspended. The substrate 11 is then dried as it passes through the drying furnace.

[0047] Inside the drying oven, for example, hot air from which environmental foreign matter has been removed by a filter is applied to the coating film 19 formed on the substrate 11. Because the substrate 11 has a film-like support, when drying multiple substrates 11 simultaneously, if the distance between the substrates 11 is narrow, the substrates 11 will be fanned by the hot air circulation inside the drying oven, making it easier for the substrates 11 to stick together. Therefore, when drying multiple substrates 11 simultaneously, it is preferable to set the distance between the substrates 11 greater than the vertical width of the substrates 11.

[0048] The drying temperature for the substrate 11 is preferably 60°C or higher and 130°C or lower, and more preferably 70°C or higher and 120°C or lower. By setting the drying temperature for the substrate 11 to 60°C or higher, the organic solvent contained in the liquid photosensitive resin composition 17 can be sufficiently removed, thereby preventing foreign matter from adhering to the coating film 19 after drying. Furthermore, by setting the drying temperature for the substrate 11 to 130°C or lower, the curing reaction of the liquid photosensitive resin composition 17 can be suppressed, thereby preventing an increase in development time in the subsequent photolithography process. The drying temperature can be set appropriately depending on the number of substrates 11 to be put into the drying furnace and the coating speed.

[0049] The drying time for the substrate 11 is preferably 1 minute or more and 60 minutes or less, and more preferably 3 minutes or more and 40 minutes or less. By setting the drying time to 1 minute or more, the organic solvent contained in the liquid photosensitive resin composition 17 can be sufficiently removed, thereby preventing foreign matter from adhering to the coating film 19 after drying. Furthermore, by setting the drying time to 60 minutes or less, the curing reaction of the liquid photosensitive resin composition 17 can be suppressed, thereby preventing an increase in development time in the subsequent photolithography process. The drying time can be set appropriately depending on the number of substrates 11 to be put into the drying furnace and the coating speed.

[0050] Next, an example of the applicator roll 12a and the applicator roll 12b will be described. Fig. 6 is a cross-sectional view of an applicator roll 100, which is an example of the applicator roll 12a and the applicator roll 12b, cut along a plane including its axis. The applicator roll 100 shown in Fig. 6 has a metallic core 110 having a cylindrical hollow portion, and a surface layer roll 120 arranged on the outer peripheral surface of the core 110.

[0051] The surface layer roll 120 is a roll onto which the liquid photosensitive resin composition 17 (see FIG. 1) is transferred, and is made of rubber (e.g., rubber that is elastic in an atmosphere at a temperature of 25° C.). In other words, the surface layer of the application roll 100 is a rubber layer. The rubber that makes up the surface layer roll 120 is not particularly limited, but is preferably one that has chemical resistance and abrasion resistance, such as butyl rubber, ethylene propylene rubber, urethane rubber, or nitrile rubber.

[0052] The surface layer roll 120 also has a plurality of ring-shaped grooves 120a. The ring-shaped grooves 120a are independent of each other. The cross-sectional shape of the ring-shaped grooves 120a is not particularly limited, and shapes such as V-shape and U-shape can be adopted. In order to further suppress poor appearance of the coating film 19 (see FIG. 5) and the substrate 11 (see FIG. 5) on which the coating film 19 is formed, the cross-sectional shape of the ring-shaped grooves 120a is preferably V-shaped. The pitch P of the ring-shaped grooves 120a is, for example, 500 μm or more and 1000 μm or less. The opening width of the ring-shaped grooves 120a is, for example, 500 μm or more and 1000 μm or less. The depth of the ring-shaped grooves 120a is, for example, 200 μm or more and 900 μm or less. The thickness of the surface layer roll 120 (thickness of the rubber layer) is, for example, 10 mm or more and 50 mm or less. 6 has a plurality of independent ring-shaped grooves 120a, the coating roll that can be used in the present invention is not limited to this, and a coating roll provided with a single spiral groove may also be used. However, in order to suppress deformation of the substrate 11 by uniformly transmitting roll pressure to the substrate 11, it is preferable that both of the pair of coating rolls have a plurality of independent ring-shaped grooves.

[0053] The width W of the surface layer roll 120 may be appropriately selected depending on the method for hanging the substrate 11 (see FIG. 1 ). For example, as shown in FIG. 1 , when only the upper end of the substrate 11 is gripped by the hanging jig 10, it is preferable to make the width W of the surface layer roll 120 wider than the lateral width of the substrate 11, because this allows for a wider coating area of ​​the liquid photosensitive resin composition 17 on the substrate 11. On the other hand, when both left and right ends of the substrate 11 are gripped by the hanging jig (not shown), it is preferable to make the width W of the surface layer roll 120 narrower than the lateral width of the substrate 11, because this allows for an easier gripping margin for the substrate 11.

[0054] The roll diameter D of the applicator roll 100 is preferably 70 mm or more and 150 mm or less, more preferably 80 mm or more and 140 mm or less, even more preferably 90 mm or more and 130 mm or less, and particularly preferably 100 mm or more and 120 mm or less. By setting the roll diameter D to 70 mm or more, the phenomenon of excessive retention (liquid pooling) of the liquid photosensitive resin composition 17 between the applicator roll 100 and the substrate 11 tends to be less likely to occur. Therefore, by setting the roll diameter D to 70 mm or more, the occurrence of traces of grooves or streaks in the coating film 19 from the applicator roll 100 tends to be suppressed. Furthermore, by setting the roll diameter D to 150 mm or less, damage (more specifically, tearing, etc.) to the substrate 11 caused by the pressure of the applicator roll 100 can be suppressed when the liquid photosensitive resin composition 17 is applied to the substrate 11.

[0055] Next, elements of the method for manufacturing a flexible printed circuit board according to this embodiment will be described in detail.

[0056] [Film-like support] The film-like support is not particularly limited, but from the viewpoint of heat resistance, chemical resistance and dimensional stability, a film-like support containing one or more polymers selected from the group consisting of polyimide, polyamide, polyester, polycarbonate, polyarylate, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer and ethylene-chlorotrifluoroethylene copolymer is preferred, and a film-like support containing polyimide is more preferred. The film-like support may contain additives such as fillers as components other than the polymer. However, in order to obtain a film-like support with excellent flexibility, the content of the polymer in the film-like support is preferably 70 wt% or more, more preferably 80 wt% or more, even more preferably 90 wt% or more, based on the total amount of the film-like support, and may even be 100 wt%.

[0057] [Wiring] The wiring provided on the film-like support is not particularly limited, but from the viewpoint of wiring shape stability and fine wiring, wiring formed by etching electrolytic copper foil or rolled copper foil by a subtractive method, or wiring formed by screen printing a copper paste or a silver paste on the film-like support is preferred.

[0058] [Hole] The hole to be provided in the substrate is not particularly limited, but from the viewpoint of hole shape stability and interlayer connection reliability, it is preferable to form a hole in a flexible copper-clad laminate having a film-like support using a laser processing machine (more specifically, a processing machine using a carbon dioxide laser, a UV laser, a YAG laser, an excimer laser, or the like) or an NC drill processing machine, and then subject the inside of the hole to a cleaning treatment (desmear treatment) and a carbon treatment, followed by a copper plating treatment (electroless copper plating treatment, electrolytic copper plating treatment, or the like).

[0059] [Liquid Photosensitive Resin Composition] The liquid photosensitive resin composition contains a binder polymer having an imide group per molecule (hereinafter sometimes referred to as "component (A)"), a photoradical polymerization initiator (hereinafter sometimes referred to as "component (B)"), and a thermosetting resin (hereinafter sometimes referred to as "component (C)"). The liquid photosensitive resin composition may also contain, as optional components, particles having an average particle size of 0.01 μm to 100 μm (hereinafter sometimes referred to as "component (D)"), an organic solvent (hereinafter sometimes referred to as "component (E)"), and a particle dispersant (hereinafter sometimes referred to as "component (F)"). The liquid photosensitive resin composition may also contain other components described below.

[0060] {Component (A)} Component (A) is a binder polymer having an imide group per molecule. "Binder polymer having an imide group per molecule" refers to a binder polymer having at least one imide group per molecule. Component (A) is not particularly limited as long as it is a binder polymer having an imide group per molecule, but a polymer that is soluble in component (E) and has a weight-average molecular weight of 1,000 to 1,000,000 in terms of polyethylene glycol is preferred. The method for measuring the weight-average molecular weight in terms of polyethylene glycol is the same as or equivalent to the method described in the Examples below. Note that "component (A) is soluble in component (E)" means that 5 parts by weight of component (A) are added to 100 parts by weight of component (E), stirred at 40°C for 1 hour, cooled to 25°C, and left to stand for 24 hours, resulting in a solution free of insoluble matter and precipitates.

[0061] By setting the weight-average molecular weight of component (A) to 1,000 or more, the flexibility and chemical resistance of the resulting cured film can be improved, while by setting the weight-average molecular weight of component (A) to 1,000,000 or less, the viscosity of the liquid photosensitive resin composition can be prevented from becoming excessively high.

[0062] In order to improve the low resilience, crease resistance, and electrical insulation reliability of the resulting cured film, a binder polymer having a urethane bond and an imide group in one molecule (hereinafter, sometimes referred to as "component (A1)") is preferred as component (A). "A binder polymer having a urethane bond and an imide group in one molecule" means a binder polymer having at least one urethane bond and at least one imide group in one molecule.

[0063] The component (A1) can be obtained, for example, by reacting a diol compound represented by the following general formula (1) with a diisocyanate compound represented by the following general formula (2) to obtain an intermediate product having a repeating unit represented by the following general formula (3) (hereinafter, sometimes referred to as "intermediate product (3)"), and then reacting this intermediate product (3) with a tetracarboxylic dianhydride.

[0064]

[0065]

[0066]

[0067] In general formula (1), general formula (2) and general formula (3), R １ and X １ each independently represents a divalent organic group.

[0068] Examples of the diol compound represented by the general formula (1) include alkylene diols such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol; polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and tetramethylene glycol and neopentyl glycol. polyester diols obtained by reacting a polyhydric alcohol with a polybasic acid; polycarbonate diols having a carbonate skeleton; polycaprolactone diols obtained by ring-opening addition reaction of lactones such as γ-butyrolactone, ε-caprolactone, δ-valerolactone; and bisphenol A compounds such as bisphenol A, ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, hydrogenated bisphenol A, ethylene oxide adducts of hydrogenated bisphenol A, and propylene oxide adducts of hydrogenated bisphenol A, and these can be used alone or in combination of two or more.

[0069] In order to obtain a liquid photosensitive resin composition that has excellent roll pressure dispersibility during coating and to improve the low resilience and crease resistance of the resulting cured film, the diol compound represented by general formula (1) is preferably a long-chain diol such as a polyoxyalkylene diol, a polyester diol, a polycarbonate diol, or a polycaprolactone diol.

[0070] Examples of the diisocyanate compound represented by general formula (2) include diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'- Diethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4 , 4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-[2,2-bis(4-phenoxyphenyl)propane]diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate and other aromatic diisocyanate compounds; isophorone diisocyanate, norbornene diisocyanate and other alicyclic diisocyanate compounds; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate and other aliphatic diisocyanate compounds, and the like, can be used alone or in combination of two or more of these.

[0071] In particular, one or more compounds selected from the group consisting of alicyclic diisocyanate compounds and aliphatic diisocyanate compounds are preferred because, when used as the diisocyanate compound represented by general formula (2), a liquid photosensitive resin composition having excellent photosensitivity can be obtained.

[0072] When synthesizing the intermediate product (3), it is preferable to mix the diol compound and the diisocyanate compound so that the ratio of the number of hydroxyl groups to the number of isocyanate groups, isocyanate groups / hydroxyl groups, is 0.5 or more and 2.0 or less.

[0073] Furthermore, when two or more types of diol compounds are used, the reaction with the diisocyanate compound may be carried out after mixing the two or more types of diol compounds, or each diol compound may be reacted separately with the diisocyanate compound. Alternatively, after reacting the diol compound with the diisocyanate compound, the resulting terminal isocyanate compound may be further reacted with another diol compound, and the resulting reaction product may be further reacted with another diisocyanate compound. The same applies when two or more types of diisocyanate compounds are used. In this manner, the desired intermediate product (3) can be synthesized.

[0074] The reaction temperature between the diol compound and the diisocyanate compound is preferably 40°C or higher and 160°C or lower, and more preferably 60°C or higher and 150°C or lower, from the viewpoint of shortening the reaction time and suppressing gelation. The reaction time between the diol compound and the diisocyanate compound can be appropriately selected depending on the amounts of starting materials and the reaction conditions employed. If necessary, the reaction may be carried out in the presence of a catalyst such as a compound containing a metal or semimetal such as an alkali metal, alkaline earth metal, tin, zinc, titanium, or cobalt; or a tertiary amine.

[0075] The diol compound and the diisocyanate compound can be reacted without using a solvent, but in order to control the reaction, it is desirable to react them in an organic solvent. The organic solvent used here is not particularly limited, but for example, the organic solvents listed as specific examples of component (E) described below can be used.

[0076] In order to enhance the reactivity of the polymerization reaction, the amount of organic solvent used in the reaction is preferably such that the weight concentration of the solute in the reaction solution, i.e., the solution concentration, is 5% by weight or more and 90% by weight or less, more preferably 10% by weight or more and 80% by weight or less.

[0077] Examples of the tetracarboxylic dianhydride to be reacted with the intermediate product (3) include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, p-phenylenebis(trimellitate anhydride), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 4,4'-oxydiphthalic anhydride. , 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, and the like, and these can be used alone or in combination of two or more.

[0078] Furthermore, in order to improve the photosensitivity of the liquid photosensitive resin composition, a binder polymer having a urethane bond, an imide group, and a (meth)acryloyl group in one molecule may be used as component (A1). "A binder polymer having a urethane bond, an imide group, and a (meth)acryloyl group in one molecule" means a binder polymer having at least one urethane bond, at least one imide group, and at least one (meth)acryloyl group in one molecule.

[0079] A binder polymer having a urethane bond, an imide group, and a (meth)acryloyl group in one molecule can be obtained by carrying out a polymerization reaction using, for example, a diol compound, a diisocyanate compound, and a tetracarboxylic dianhydride, as well as one or more monomers selected from the group consisting of a compound represented by the following general formula (4) (hereinafter, sometimes referred to as “compound (4)”) and a compound represented by the following general formula (5) (hereinafter, sometimes referred to as “compound (5)”):

[0080]

[0081] In general formula (4), m represents an integer of 1 or more and 3 or less, R ２ represents an (m+1)-valent organic group, and R ３ represents a hydrogen atom or a methyl group.

[0082]

[0083] In the general formula (5), n represents an integer of 1 or more and 3 or less, and X ２ represents an (n+1)-valent organic group, and X ３ represents a hydrogen atom or a methyl group.

[0084] Examples of compound (4) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-1-acryloxy-3-methacryloxypropane, o-phenylphenol glycidyl ether (meth)acrylate, polyethylene glycol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 4-hydroxyphenyl (meth)acrylate, and 2-(4-hydroxyphenyl)ethyl (meth)acrylate, and these may be used alone or in combination of two or more.

[0085] Examples of compound (5) include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, and 2-(2-methacryloyloxyethyloxy)ethyl isocyanate, and these can be used alone or in combination of two or more.

[0086] Furthermore, in order to improve the alkaline developability of the liquid photosensitive resin composition, a binder polymer having a urethane bond, an imide group, and a carboxy group in one molecule may be used as the component (A1). "A binder polymer having a urethane bond, an imide group, and a carboxy group in one molecule" means a binder polymer having at least one urethane bond, at least one imide group, and at least one carboxy group in one molecule.

[0087] A binder polymer having a urethane bond, an imide group, and a carboxy group in one molecule can be obtained by carrying out a polymerization reaction using, for example, a diol compound, a diisocyanate compound, and a tetracarboxylic dianhydride, as well as a compound represented by the following general formula (6) (hereinafter, may be referred to as “compound (6)”) as a monomer.

[0088]

[0089] In general formula (6), R ４ represents a trivalent organic group.

[0090] Examples of compound (6) include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(2-hydroxyethyl)propionic acid, 2,2-bis(3-hydroxypropyl)propionic acid, 2,3-dihydroxy-2-methylpropionic acid, 2,2-bis(hydroxymethyl)butanoic acid, 2,2-bis(2-hydroxyethyl)butanoic acid, 2,2-bis(3-hydroxypropyl)butanoic acid, 2,3-dihydroxybutanoic acid, 2,4-dihydroxy-3,3-dimethylbutanoic acid, 2,3-dihydroxyhexadecanoic acid, 2,3-dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, and 3,5-dihydroxybenzoic acid. These may be used alone or in combination of two or more.

[0091] In order to enhance the photosensitivity of the liquid photosensitive resin composition, it is preferable to use an aliphatic compound (6).

[0092] The component (A) is not limited to the above-described component (A1), and can also be obtained, for example, by reacting a tetracarboxylic dianhydride (more specifically, a compound exemplified as a tetracarboxylic dianhydride for synthesizing the above-described component (A1)) with a diamine.

[0093] Examples of diamines that can be used as raw materials to obtain component (A) include p-phenylenediamine, 4,4'-diaminobenzanilide, 2,2'-bis(trifluoromethyl)benzidine, 9,9-bis(4-aminophenyl)fluorene, 4-aminophenyl-4-aminobenzoate, 1,4-diaminocyclohexane, m-phenylenediamine, 4,4'-oxydianiline, 3,4'-oxydianiline, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, N,N'-bis(4- Examples of the 4,4'-bis(4-aminophenyl)terephthalamide, 4,4'-diaminodiphenyl sulfone, m-tolidine, o-tolidine, 4,4'-bis(4-aminophenoxy)biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexaneamine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and the like can be used alone or in combination of two or more.

[0094] The method for reacting a tetracarboxylic acid anhydride with a diamine is not particularly limited, but examples thereof include the following methods 1 to 3.

[0095] Method 1: A polyamic acid solution is prepared by adding a diamine to a solution in which a tetracarboxylic dianhydride is dispersed or dissolved in an organic solvent and reacting the diamine. The total amount of diamine added is preferably adjusted so that the ratio is 0.50 to 1.50 moles per mole of tetracarboxylic dianhydride. After the reaction between the tetracarboxylic dianhydride and the diamine is complete, the resulting polyamic acid solution is heated to 100°C to 300°C, more preferably 150°C to 250°C, to carry out imidization.

[0096] Method 2: A polyamic acid solution is prepared in the same manner as in Method 1. An imidization catalyst (preferably a tertiary amine such as pyridine, picoline, isoquinoline, trimethylamine, triethylamine, or tributylamine) and a dehydrating agent (acetic anhydride or the like) are added to the prepared polyamic acid solution, and the solution is heated to 60° C. or higher and 180° C. or lower to carry out imidization.

[0097] Method 3: A polyamic acid solution is prepared in the same manner as in Method 1. The prepared polyamic acid solution is placed in a vacuum oven set at 100° C. to 250° C., and heated under reduced pressure to carry out imidization.

[0098] In order to obtain a flexible printed circuit board having excellent electrical insulation reliability while suppressing the occurrence of poor appearance of the coating film and the substrate on which the coating film is formed, the content of component (A) is preferably 10% by weight or more and 50% by weight or less, and more preferably 20% by weight or more and 40% by weight or less, based on the total amount of the liquid photosensitive resin composition.

[0099] {Component (B)} The component (B) is not particularly limited, and examples thereof include Michler's ketone, 4,4'-bis(diethylamino)benzophenone, 4,4',4''-tris(dimethylamino)triphenylmethane, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-diimidazole, acetophenone, benzoin, 2-methylbenzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-t-butylanthraquinone, 1,2-benzo-9,10-anthraquinone, methylanthraquinone, thioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, diacetylbenzyl, benzil dimethyl ketal, benzil diethyl ketal, 4,4'-diazidochalcone, 2,2 -dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl-4-dimethylaminobenzoate, 2-ethylhexyl-4-dimethylaminobenzoate, and the like, can be used alone or in combination of two or more.

[0100] In order to enhance the reactivity and resolution of the photoradical polymerization, the content of component (B) is preferably 0.5% by weight or more and 5% by weight or less, and more preferably 0.8% by weight or more and 4% by weight or less, based on the total amount of the liquid photosensitive resin composition.

[0101] {Component (C)} The component (C) is not particularly limited, but examples thereof include epoxy resins, oxetane resins, phenolic resins, isocyanate resins, blocked isocyanate resins, bismaleimide resins, bisallylnadimide resins, polyester resins (e.g., unsaturated polyester resins), diallyl phthalate resins, silicone resins, vinyl ester resins, melamine resins, polybismaleimide triazine resins (BT resins), cyanate resins (e.g., cyanate ester resins), urea resins, guanamine resins, sulfoamide resins, aniline resins, polyurea resins, thiourethane resins, polyazomethine resins, episulfide resins, benzoxazine resins, copolymer resins thereof, modified resins obtained by modifying these resins, and mixtures of these resins with each other or with other resins.

[0102] In order to impart heat resistance to the resulting cured film while also imparting adhesion to conductors such as metal foils and circuit boards, component (C) is preferably an epoxy resin, and more preferably a multifunctional epoxy resin. The term "multifunctional epoxy resin" refers to a compound containing at least two epoxy groups per molecule. Examples of epoxy resins include, but are not limited to, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, hydrogenated bisphenol A epoxy resins, biphenyl epoxy resins, phenoxy epoxy resins, naphthalene epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, trisphenolmethane epoxy resins, dicyclopentadiene epoxy resins, amine epoxy resins, flexible epoxy resins, urethane-modified epoxy resins, rubber-modified epoxy resins, chelate-modified epoxy resins, and heterocycle-containing epoxy resins. These may be used alone or in combination of two or more.

[0103] Examples of polyfunctional epoxy resins include jER (registered trademark) 828, jER (registered trademark) 1001, and jER (registered trademark) 1002 manufactured by Mitsubishi Chemical Corporation, ADEKA Resin (registered trademark) EP3100E and ADEKA Resin (registered trademark) EP3300E manufactured by ADEKA Corporation, RE-310S and RE-410S manufactured by Nippon Kayaku Co., Ltd., Epicron 840S, Epicron 850S, Epicron 1050, and Epicron 7050 manufactured by DIC Corporation, and Epotohto (registered trademark) YD-115 and Epotohto (registered trademark) YD-125 manufactured by Nippon Steel Epoxy Manufacturing Co., Ltd. 127, Epotohto (registered trademark) YD-128, and other bisphenol A type epoxy resins; jER (registered trademark) 806 and jER (registered trademark) 807 manufactured by Mitsubishi Chemical Corporation; ADEKA Resin (registered trademark) EP3901E, ADEKA Resin (registered trademark) EP3930, and ADEKA Resin (registered trademark) EP3950 manufactured by ADEKA Corporation; RE-303S, RE-304S, RE-403S, and RE-404S manufactured by Nippon Kayaku Co., Ltd.; Epiclon 830 and Epiclon 835 manufactured by DIC Corporation; and Epotohto (registered trademark) manufactured by Nippon Steel Epoxy Manufacturing Co., Ltd. Bisphenol F type epoxy resins such as Epotohto (registered trademark) YDF-170, Epotohto (registered trademark) YDF-175S, and Epotohto (registered trademark) YDF-2001; bisphenol S type epoxy resins such as Epiclon EXA-1514 (trade name) manufactured by DIC Corporation; jER (registered trademark) YX8000, jER (registered trademark) YX8034, and jER (registered trademark) YL7170 (trade name) manufactured by Mitsubishi Chemical Corporation; Adeka Resin (trade name) EP3080E (trade name) manufactured by ADEKA Corporation; Epiclon EXA-7015 (trade name) manufactured by DIC Corporation; and Epotohto (trade name) manufactured by Nippon Steel Epoxy Manufacturing Co., Ltd. hydrogenated bisphenol A type epoxy resins such as Epotohto (registered trademark) YD-3000 and Epotohto (registered trademark) YD-4000D; biphenyl type epoxy resins such as jER (registered trademark) YX4000, jER (registered trademark) YL6121H, jER (registered trademark) YL6640, and jER (registered trademark) YL6677, both manufactured by Mitsubishi Chemical Corporation, and NC-3000 and NC-3000H, both manufactured by Nippon Kayaku Co., Ltd.; phenoxy type epoxy resins such as jER (registered trademark) 1256, jER (registered trademark) 4250, and jER (registered trademark) 4275, both manufactured by Mitsubishi Chemical Corporation;Naphthalene-type epoxy resins such as Epicron HP3032, Epicron HP3700, and Epicron HP3200, manufactured by DIC Corporation, and NC-7000L, manufactured by Nippon Kayaku Co., Ltd.; jER (registered trademark) 152 and jER (registered trademark) 154, manufactured by Mitsubishi Chemical Corporation, and EPPN (registered trademark)-201-L, manufactured by Nippon Kayaku Co., Ltd.; Epicron N-740 and Epicron N-770, manufactured by DIC Corporation; and Epotohto (registered trademark) YDPN-638, manufactured by Nippon Steel Epoxy Manufacturing Co., Ltd.; phenol novolac-type epoxy resins such as EOCN (registered trademark) manufactured by Nippon Kayaku Co., Ltd. Cresol novolac epoxy resins such as EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, and Epiclon N-660, N-670, N-680, and N-695 (trade names) manufactured by DIC Corporation; trisphenol methane epoxy resins such as EPPN-501H, EPPN-501HY, and EPPN-502H (trade names) manufactured by Nippon Kayaku Co., Ltd.; dicyclo epoxy resins such as XD-1000 (trade name) manufactured by Nippon Kayaku Co., Ltd. and Epiclon HP-7200 (trade name) manufactured by DIC Corporation; Pentadiene-type epoxy resins: jER (registered trademark) 604 and jER (registered trademark) 630, manufactured by Mitsubishi Chemical Corporation; Epotohto (registered trademark) YH-434 and Epotohto (registered trademark) YH-434L, manufactured by Nippon Steel Epoxy Manufacturing Co., Ltd.; amine-type epoxy resins such as TETRAD (registered trademark)-X and TERRAD (registered trademark)-C, manufactured by Mitsubishi Gas Chemical Company, Inc.; jER (registered trademark) 871, jER (registered trademark) 872, jER (registered trademark) YL7175 and jER (registered trademark) YL7217, manufactured by Mitsubishi Chemical Corporation; and Epiclon EXA-485, manufactured by DIC Corporation. flexible epoxy resins such as ADEKA RESIN (registered trademark) EPU-6, ADEKA RESIN (registered trademark) EPU-73, and ADEKA RESIN (registered trademark) EPU-78-11, both of which are trade names; rubber-modified epoxy resins such as ADEKA RESIN (registered trademark) EPR-4023, ADEKA RESIN (registered trademark) EPR-4026, and ADEKA RESIN (registered trademark) EPR-1309, both of which are trade names; chelate-modified epoxy resins such as ADEKA RESIN (registered trademark) EP39-10 and ADEKA RESIN (registered trademark) EP39-20, both of which are trade names;Examples include heterocycle-containing epoxy resins such as TEPIC (registered trademark) manufactured by Nissan Chemical Industries, Ltd.;

[0104] The liquid photosensitive resin composition may contain a curing agent (C) as component (C). The curing agent (C) is not particularly limited, but examples thereof include phenolic resins such as phenol novolac resin, cresol novolac resin, and naphthalene-type phenolic resin; amino resins; urea resins; melamine; and dicyandiamide, which may be used alone or in combination of two or more.

[0105] The liquid photosensitive resin composition may contain a curing accelerator for component (C). The curing accelerator for component (C) is not particularly limited, but examples thereof include phosphine compounds such as triphenylphosphine; tertiary amines; alcohol amine compounds such as trimethanolamine and triethanolamine; borate compounds such as 1,8-diazabicyclo[5,4,0]-7-undecenium tetraphenylborate; imidazole compounds such as imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, and 2-phenyl-4-methylimidazole. imidazoline-based compounds such as 2-methylimidazoline, 2-ethylimidazoline, 2-isopropylimidazoline, 2-phenylimidazoline, 2-undecylimidazoline, 2,4-dimethylimidazoline, and 2-phenyl-4-methylimidazoline; and triazine-based compounds such as 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)ethyl]-1,3,5-triazine, 2,4-diamino-6-[2-(2-undecyl-1-imidazolyl)ethyl]-1,3,5-triazine and 2,4-diamino-6-(2'-ethyl-4'-methylimidazolyl)ethyl-1,3,5-triazine, and the like, which may be used alone or in combination of two or more.

[0106]

[0043] When a binder polymer having an acid value of 10 mgKOH / g or more (preferably a binder polymer having an acid value of 10 mgKOH / g or more and 160 mgKOH / g or less) is used as component (A), it is not necessary to blend the curing agent and curing accelerator of component (C) into the liquid photosensitive resin composition. The acid value of component (A) can be adjusted, for example, by changing the amount of a monomer having one or more groups selected from the group consisting of a carboxy group and a carboxylic anhydride group when synthesizing component (A).

[0107] In order to improve the flexibility and chemical resistance of the resulting cured film, the content of the component (C) is preferably from 1 to 10% by weight, and more preferably from 3 to 8% by weight, based on the total amount of the liquid photosensitive resin composition.

[0108] {Component (D)} The component (D) is not particularly limited as long as it is a particle having an average particle diameter of 0.01 μm or more and 100 μm or less, and for example, one or more particles selected from the group consisting of inorganic particles and organic particles can be used. By blending component (D) into the liquid photosensitive resin composition, the viscosity and thixotropy of the liquid photosensitive resin composition can be adjusted.

[0109] In order to improve the flexibility and chemical resistance of the resulting cured film while increasing the resolution of the liquid photosensitive resin composition, the average particle size of component (D) is preferably 0.01 μm or more and 50 μm or less, and more preferably 0.01 μm or more and 10 μm or less.

[0110] Specific examples of component (D) include inorganic particles such as silica, mica, talc, clay, barium titanate, barium sulfate, wollastonite, calcium carbonate, magnesium carbonate, aluminum oxide, titanium oxide, silicon nitride, and aluminum nitride; and organic particles such as core-shell rubber and crosslinked polymers. These may be used alone or in combination of two or more.

[0111] As the inorganic particles, silica particles are preferred from the viewpoint of suppressing cure shrinkage of the resulting cured film while increasing the hardness and adhesion of the resulting cured film. Examples of silica particles include fused silica particles, crushed silica particles, spherical silica particles, crystalline silica particles, and fumed silica particles.

[0112] As the organic particles, from the viewpoint of improving the dispersibility of roll pressure during coating while also improving the flexibility and chemical resistance of the resulting cured film, crosslinked polymer particles are preferred, and crosslinked polymer particles having an average particle size of 1 μm or more and 10 μm or less are more preferred. Specific examples of crosslinked polymer particles include Dainichiseika Color & Chemicals Mfg. Co., Ltd. products under the trade names Dimic Beads (registered trademark) UCN-8070CM Clear, UCN-8150CM Clear, UCN-5070D Clear, and UCN-5150D Clear, and Negami Chemical Industrial Co., Ltd. products under the trade names Art Pearl (registered trademark) C-100 Clear, C-200 Clear, C-300 Clear, C-300WA, C-400 Clear, C-400WA, C-600 Clear, C-800 Transparent, C-800WA, C-1000T, P300T, P-800T, U-600T, CF-600T, JB-400T, JB-800T, CE-400T, CE-800T, and MM-120T, which can be used alone or in combination of two or more.

[0113] In order to further increase the flexibility of the resulting cured film, it is preferable to use polyurethane particles as component (D).Furthermore, in order to further increase the flexibility of the resulting cured film while improving the dispersibility of roll pressure during coating, it is preferable to use crosslinked polyurethane particles, which are crosslinked polymer particles, as component (D).

[0114] In order to further suppress the occurrence of poor appearance of the coating film and the substrate on which the coating film is formed, the content of component (D) is preferably 5 parts by weight or more and 100 parts by weight or less, more preferably 5 parts by weight or more and 80 parts by weight or less, even more preferably 10 parts by weight or more and 80 parts by weight or less, and even more preferably 20 parts by weight or more and 80 parts by weight or less, relative to 100 parts by weight of component (A).

[0115] {Component (E)} Component (E) is a component used to adjust the viscosity of the liquid photosensitive resin composition. Examples of component (E) include sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide-based solvents such as N,N-dimethylformamide and N,N-diethylformamide; acetamide-based solvents such as N,N-dimethylacetamide and N,N-diethylacetamide; pyrrolidone-based solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; hexamethylphosphoramide; and γ-butyrolactone. Furthermore, if necessary, these organic solvents can be used in combination with aromatic hydrocarbons (more specifically, xylene, toluene, etc.).

[0116] Examples of the component (E) include symmetric glycol diether solvents such as 1,2-dimethoxyethane, bis(2-methoxyethyl) ether, bis[2-(2-methoxyethoxyethyl)]ether, 1,2-diethoxyethane, bis(2-ethoxyethyl) ether, and bis(2-butoxyethyl) ether; methyl acetate, ethyl acetate, isopropyl acetate, n-propyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, 3-methoxybutyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, propanediol, propylene glycol methyl ether acetate, propylene glycol methyl ether acetate, propanediol ... Acetate-based solvents such as propylene glycol diacetate and 1,3-butylene glycol diacetate; and ether-based solvents such as dipropylene glycol methyl ether, tripropylene glycol methyl ether, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, dipropylene glycol n-butyl ether, tripropylene glycol n-propyl ether, propylene glycol phenyl ether, dipropylene glycol dimethyl ether, 1,3-dioxolane, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, ethylene glycol monoethyl ether, and triethylene glycol dimethyl ether can also be used.

[0117] In order to easily adjust the viscosity of the liquid photosensitive resin composition to a range suitable for coating, the content of the component (E) is preferably 10% by weight or more and 80% by weight or less, and more preferably 20% by weight or more and 70% by weight or less, based on the total amount of the liquid photosensitive resin composition.

[0118] {Component (F)} When the liquid photosensitive resin composition contains component (D), it is preferable that the liquid photosensitive resin composition also contains component (F). Component (F) is a particle dispersant. A particle dispersant is a compound containing at least one organic group in the molecule, and is used to improve particle dispersibility. When the liquid photosensitive resin composition contains component (F), it is possible to suppress a decrease in breakdown voltage caused by detachment of particles from the coating film obtained in the coating step.

[0119] Specific examples of component (F) are listed below. Note that, in the following, "ANTI-TERRA," "BYK," "BYKJET," "DISPERBYK," "Disperlon," and "Nopcol" are all registered trademarks.

[0120] Specific examples of the component (F) include trade names ANTI-TERRA-202, ANTI-TERRA-203, ANTI-TERRA-204, ANTI-TERRA-205, ANTI-TERRA-210, ANTI-TERRA-250, ANTI-TERRA-U, ANTI-TERRA-U80, ANTI-TERRA-U100, BYK-151, BYK-153, BYK-154, BYK-155, BYK-156, BYK-220S, BYK-1160, BYK-1162, BYK-1165, and BYK-9076, manufactured by BYK Japan. BYK-9077, BYK-GO8702, BYK-GO8720, BYK-SYNERGIST2100, BYK-SYNERGIST 2105, BYK-W903, BYK-W907, BYK-W908, BYK-W909, BYK-W940, BYK-W961, BYK- W966, BYK-W969, BYK-W972, BYK-W974, BYK-W980, BYK-W985, BYK-W995, BYK -W996, BYK-W9010, BYK-W9011, BYK-W9012, BYKJET-9131, BYKJET-9132, BYK JET-9133, BYKJET-9142, BYKJET-9150, BYKJET-9151, BYKJET-9152, BYKJE T-9170, BYKJET-9171, BYLUMEN, DISPERBYK, DISPERBYK-101N, DISPERBYK-1 02, DISPERBYK-103, DISPERBYK-106, DISPERBYK-107, DISPERBYK-108, DIS PERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-115, DISPERBYK- 118, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DI SPERBYK-161, DISPERBYK-162, DISPERBYK-162TF, DISPERBYK-163, DISPERB YK-163TF, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-1 67TF, DISPERBYK-168, DISPERBYK-168TF, DISPERBYK-169, DISPERBYK-170,DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK-181, DISPE RBYK-182, DISPERBYK-184, DISPERBYK-185, DISPERBYK-187, DISPERBYK-1 90, DISPERBYK-190BF, DISPERBYK-191, DISPERBYK-192, DISPERBYK-193, D ISPERBYK-194N, DISPERBYK-199, DISPERBYK-199BF, DISPERBYK-2000, DIS PERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBYK-2010, DISPE RBYK-2012, DISPERBYK-2013, DISPERBYK-2014, DISPERBYK-2015, DISPERB YK-2015BF, DISPERBYK-2022, DISPERBYK-2023, DISPERBYK-2025, DISPERB YK-2026, DISPERBYK-2030, DISPERBYK-2050, DISPERBYK-2055, DISPERBYK -2059, DISPERBYK-2060, DISPERBYK-2061, DISPERBYK-2062, DISPERBYK- 2070, DISPERBYK-2080, DISPERBYK-2081, DISPERBYK-2096, DISPERBYK-21 18, DISPERBYK-2150, DISPERBYK-2151, DISPERBYK-2152, DISPERBYK-2155 , DISPERBYK-2155TF, DISPERBYK-2157, DISPERBYK-2158, DISPERBYK-2159 , DISPERBYK-2163, DISPERBYK-2163TF, DISPERBYK-2164, DISPERBYK-2200, DISPERBYK-2205, trade names of FLOWRENE AF-1000, FLOWRENE AF-1005, FLOWRENE D-90, FLOWRENE DOPA-15B, FLOWRENE DOPA-15BHFS, FLOWRENE DOPA-17HF, FLOWRENE DOPA-22, FLOWRENE DOPA-35, FLOWRENE DOPA-100, FLOWRENE G-100SF, FLOWRENE G-700, FLOWRENE G-820XF, manufactured by Kyoeisha Chemical Co., Ltd.FLOWLEN GW-1500, FLOWLEN KDG-2400, FLOWLEN AF-205, FLOWLEN AF-505, FLOWLEN NAF-250, FLOWLEN NAF-850, FLOWLEN G-700AMP, FLOWLEN G-700MEA, FLOWLEN GW-1640, trade names of Disparlon 201N, Disparlon 201SPN, Disparlon 1220, Disparlon 2100, Disparlon 2200, Disparlon KS-273N, Disparlon AQ-320, Disparlon AQ-330, Disparlon KS-273N, Disparlon AQ-340, Disparlon KS-273N, Disparlon AQ-350, Disparlon KS-273N, Disparlon AQ-360, Disparlon KS-273N, Disparlon AQ-370, Disparlon KS-273N, Disparlon AQ-380, Disparlon KS-273N, Disparlon AQ-390, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-390N, Disparlon KS-40 ... Examples of suitable dispersants include SN Dispersant 2060, SN Dispersant 4215, SN Dispersant 5020, SN Dispersant 5023, SN Dispersant 5027, SN Dispersant 5034, SN Dispersant 5040, SN Dispersant 5468, SN-PW-43, and Nopcol 5200, both of which are trade names manufactured by San Nopco Ltd. These may be used alone or in combination of two or more.

[0121] In order to further suppress a decrease in breakdown voltage due to detachment of particles from the coating film obtained in the coating step, the content of component (F) is preferably 0.1% by weight or more and 1% by weight or less, based on the total amount of the liquid photosensitive resin composition.

[0122] {Other Components} The liquid photosensitive resin composition may contain, as necessary, various additives such as a radical polymerizable compound, a flame retardant, an antifoaming agent, a leveling agent, a colorant, an adhesion aid, a polymerization inhibitor, etc., as other components (components different from the components (A) to (F)). The total content of the other components is, for example, 20% by weight or less, and preferably 10% by weight or less, based on the total amount of the liquid photosensitive resin composition.

[0123] The radical polymerizable compound refers to a compound containing a radical polymerizable group in one molecule, which undergoes polymerization in the presence of a radical polymerization initiator. The radical polymerizable compound is preferably a compound having a molecular weight (weight average molecular weight in the case of a polymer) of less than 1,000. Among these, a compound having at least one unsaturated double bond in one molecule is preferred, and a compound having one or more groups selected from the group consisting of a (meth)acryloyl group and a vinyl group is more preferred.

[0124] When the component (A) does not have a (meth)acryloyl group, it is preferable that the liquid photosensitive resin composition contains a radically polymerizable compound as a component capable of photoradical polymerization. That is, it is preferable that the liquid photosensitive resin composition contains a component (A) having a (meth)acryloyl group, or contains a radically polymerizable compound as another component. Furthermore, even when the component (A) has a (meth)acryloyl group, it is preferable that the liquid photosensitive resin composition contains a radically polymerizable compound in order to increase the reactivity of photoradical polymerization.

[0125] Specific examples of radical polymerizable compounds are listed below. In the following, ethylene oxide is referred to as "EO." The average number of moles of EO added is referred to as "n." Specific examples of the radical polymerizable compound include EO-modified bisphenol F diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol A diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol S diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol F dimethacrylate (n: 2 or more and 50 or less), EO-modified bisphenol A dimethacrylate (n: 2 or more and 50 or less), EO-modified bisphenol S dimethacrylate (n: 2 or more and 50 or less), 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol diacrylate, pentaerythritol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, tetramethylolpropane tetraacrylate, tetraethylene glycol diacrylate, and 1,6-hexanediol dimethacrylate. , neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, tetramethylolpropane tetramethacrylate, tetraethylene glycol dimethacrylate, methoxydiethylene glycol methacrylate, methoxypolyethylene glycol methacrylate, 3-chloro-2-hydroxypropyl methacrylate, stearyl methacrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, lauryl acrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-Hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane triacrylate, methoxydipropylene glycol methacrylate, methoxytriethylene glycol acrylate, nonylphenoxy polyethylene glycol acrylate, nonylphenoxy polypropylene glycol acrylate, isostearyl acrylate, nonylphenoxy ethylene glycol acrylate, 1,4-butanediol dimethacrylate, 3-methyl-1,5-pentanediol dimethacrylate, 1,9-nonanediol methacrylate, 2,4-diethyl-1,5- Examples of suitable acrylates include pentanediol dimethacrylate, dipropylene glycol diacrylate, 2,4-diethyl-1,5-pentanediol diacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol polyacrylate, triallyl isocyanurate, glycidyl methacrylate, glycidyl allyl ether, triallyl 1,3,5-benzenecarboxylate, triallylamine, triallyl phosphate, diallylamine, diallyldimethylsilane, diallyl disulfide, diallyl ether, diallyl isophthalate, diallyl terephthalate, 1,3-diallyloxy-2-propanol, 4,4'-isopropylidenediphenol dimethacrylate, and 4,4'-isopropylidenediphenol diacrylate, and these may be used alone or in combination of two or more.

[0126] In order to increase the solubility of the liquid photosensitive resin composition in an aqueous developer and shorten the development time, the radical polymerizable compound is preferably one or more selected from the group consisting of EO-modified bisphenol F diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol A diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol S diacrylate (n: 2 or more and 50 or less), EO-modified bisphenol F dimethacrylate (n: 2 or more and 50 or less), EO-modified bisphenol A dimethacrylate (n: 2 or more and 50 or less), and EO-modified bisphenol S dimethacrylate (n: 2 or more and 50 or less).

[0127] In order to increase the radical polymerization reactivity of the liquid photosensitive resin composition while increasing the solubility of the liquid photosensitive resin composition in an aqueous developer, the content of the radical polymerizable compound is preferably 1% by weight or more and 10% by weight or less based on the total amount of the liquid photosensitive resin composition.

[0128] Examples of the flame retardant include halogen-based flame retardants, phosphorus-based flame retardants, metal hydroxides, and antimony-based flame retardants.

[0129] A halogen-based flame retardant refers to a compound that contains at least one halogen atom in one molecule and inhibits the combustion of organic matter. Examples of halogen-based flame retardants include bromine-based compounds and chlorine-based compounds, which can be used alone or in combination of two or more.

[0130] Phosphorus-based flame retardants refer to compounds that contain at least one phosphorus atom per molecule and inhibit the combustion of organic matter. Examples of phosphorus-based flame retardants include red phosphorus, condensed phosphate ester compounds, cyclic organic phosphorus compounds, phosphazene compounds, phosphorus-containing polyol compounds, phosphorus-containing amine compounds, ammonium polyphosphate, melamine phosphate, and phosphinate, which can be used alone or in combination of two or more.

[0131] Examples of metal hydroxides that function as flame retardants include aluminum hydroxide and magnesium hydroxide, which can be used alone or in combination of two or more.

[0132] Antimony-based flame retardants are compounds that contain at least one antimony atom per molecule and inhibit the combustion of organic matter, such as antimony trioxide.

[0133] Examples of the antifoaming agent include (meth)acrylic compounds, vinyl compounds, and butadiene compounds.

[0134] Examples of the leveling agent include (meth)acrylic compounds and vinyl compounds.

[0135] Examples of colorants include phthalocyanine compounds, azo compounds, and carbon black.

[0136] Examples of the adhesion aid (also called an adhesion promoter) include silane coupling agents, triazole-based compounds, tetrazole-based compounds, and triazine-based compounds.

[0137] Examples of the polymerization inhibitor include hydroquinone and hydroquinone monomethyl ether.

[0138] [Method for Preparing Liquid Photosensitive Resin Composition] The liquid photosensitive resin composition can be prepared by grinding, dispersing, and mixing the above-mentioned components (A) to (C), and any optional components used as needed (component (D), component (E), component (F), the above-mentioned other components, etc.). The grinding and dispersion method is not particularly limited, and examples include methods using kneading devices such as a bead mill, a ball mill, and a three-roll mill. Among these, the method of grinding, dispersing, and mixing using a three-roll mill is preferred because it results in a uniform particle size distribution.

[0139] [Optional Steps] In this embodiment, the steps other than the step of applying the liquid photosensitive resin composition are optional steps, including the step of drying the substrate (drying step) described above. In addition to the drying step, the optional steps include, for example, the micro-aperture forming step and the curing step described below.

[0140] (Micro-aperture formation process) After the drying process, the coating film is irradiated with active energy rays (more specifically, ultraviolet rays, visible light, electron beams, etc.) through a negative photomask to expose a portion of the coating film. This causes photo-radical polymerizable components to polymerize in the exposed portions of the coating film. Next, the unexposed portions are washed away with a developer using a development method such as spraying, puddling, immersion, or ultrasonic waves, thereby patterning the coating film and forming micro-apertures. Note that the time until opening varies depending on the spray pressure and flow rate of the developing device and the temperature of the developer, so it is desirable to find the optimal device conditions as appropriate.

[0141] The developer is preferably an alkaline aqueous solution. The developer may contain a water-soluble organic solvent such as methanol, ethanol, 1-propanol, 2-propanol, or N-methyl-2-pyrrolidone. Examples of alkaline compounds contained in the alkaline aqueous solution include hydroxides, carbonates, or bicarbonates of alkali metals, alkaline earth metals, or ammonium ions, and amine compounds. Specific examples include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide, N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamine, triethanolamine, and triisopropylamine. Compounds other than these can also be used as long as they produce a basic aqueous solution. The concentration of the alkaline compound in the alkaline aqueous solution is preferably 0.01% by weight or more and 20% by weight or less, more preferably 0.02% by weight or more and 10% by weight or less. The temperature of the developer depends on the composition of the liquid photosensitive resin composition and the composition of the alkaline developer, but is generally from 0°C to 80°C, preferably from 10°C to 60°C.

[0142] The inside of the fine openings formed by development is preferably washed to remove unnecessary residues. Examples of the washing liquid include water and an acidic aqueous solution.

[0143] (Curing Step) Next, the coating film having micro-apertures formed therein (patterned coating film) is subjected to a heat treatment. By carrying out the heat treatment, reactive groups (e.g., reactive groups of component (C)) remaining in the molecular structure constituting the coating film are reacted, thereby obtaining a cured film with excellent heat resistance. Through the above steps, a flexible printed circuit board is obtained. The thickness of the cured film is determined taking into consideration the thickness of the wiring, etc., but is preferably 2 μm or more and 50 μm or less. The final curing temperature in the curing step is preferably low in order to prevent oxidation of the wiring, etc., and to avoid reducing the adhesion between the wiring and the film-like support. The final curing temperature is preferably 100°C or more and 250°C or less, more preferably 120°C or more and 200°C or less, and even more preferably 130°C or more and 180°C or less. The curing time at the final curing temperature is, for example, 1 minute or more and 120 minutes or less. The cured film formed according to this embodiment has excellent flexibility, flame retardancy, and electrical insulation reliability, and tends to have little warping after the curing step. Therefore, the cured film formed according to this embodiment is particularly suitable as an insulating material for flexible printed circuit boards.

[0144] When measuring the breakdown voltage of a cured film obtained using a typical photosensitive resin composition, it may frequently exhibit a low value of 200 V or less. This is due to fine surface holes formed by particles detaching from the coating film of the photosensitive resin composition during the development process. In this embodiment, the use of a binder polymer having an imide group per molecule improves the developer resistance of the exposed portion of the liquid photosensitive resin composition, tending to make it difficult for the developer to penetrate from the surface to the interior of the exposed portion. Therefore, in this embodiment, particle detachment from the coating film tends to be suppressed. Furthermore, when a liquid photosensitive resin composition containing component (F) is used, the dispersibility of the particles is improved, tending to make it difficult for particle aggregation, which is the starting point for particle detachment, to occur. In this embodiment, in order to obtain a flexible printed circuit board with superior electrical insulation reliability, it is preferable that the "ratio of films with a breakdown voltage of 200 V or less" measured by the method described in the Examples below is 20% or less.

[0145] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0146] First, methods for measuring the weight average molecular weights and acid values ​​of binder polymers P1 to P3, and the solid content concentrations of resin solutions SP1 to SP3 containing binder polymers P1 to P3, respectively, will be described.

[0147] <Method for measuring weight-average molecular weight> The weight-average molecular weight of binder polymers P1 to P3 was measured under the following conditions: Apparatus used: "HLC-8220GPC" manufactured by Tosoh Corporation Column: "TSKgel Super AWM-H" (6.0 mm I.D. x 15 cm) x 2 manufactured by Tosoh Corporation Guard column: "TSKguard column Super AW-H" x 1 manufactured by Tosoh Corporation Eluent: LiBr (concentration: 30 mmol / L) and H ３ P.O. ４ (concentration: 20 mmol / L) dissolved in N,N-dimethylformamide. Flow rate: 0.6 mL / min. Column temperature: 40°C. Detector: RI (differential refractometer). RI detection conditions: polarity (+), response (0.5 seconds). Sample concentration: 5 mg / mL. Standard: PEG (polyethylene glycol).

[0148] <Method for Measuring Acid Value> The acid values ​​of the binder polymers P1 to P3 were measured by the method described in JIS K 5601-2-1 (1999).

[0149] <Method for measuring solid content concentration of resin solution> The solid content concentrations of resin solutions SP1 to SP3 were measured by the method described in JIS K 5601-1-2 (2008). The drying conditions for the measurement were 170°C x 1 hour.

[0150] <Preparation of Resin Solutions> Hereinafter, methods for preparing resin solutions SP1 to SP3 containing binder polymers P1 to P3, respectively, as component (A) will be described. Note that although binder polymer P3 is a binder polymer that does not have an imide group in one molecule, in the following, binder polymer P3 will also be described as component (A) (more specifically, component (A) of the comparative examples). In addition, in the following, unless otherwise specified, the reaction (stirring) was carried out under a nitrogen gas flow.

[0151] [Preparation of resin solution SP1 containing binder polymer P1] A reaction vessel equipped with a stirrer, a thermometer, and a nitrogen inlet tube was charged with 35.00 g of triethylene glycol dimethyl ether (hereinafter sometimes referred to as "TEGDM") as a polymerization solvent and 10.31 g (0.050 mol) of norbornene diisocyanate, and the contents of the vessel were heated to 80 ° C. while stirring under a nitrogen stream, and norbornene diisocyanate was dissolved in TEGDM. Next, a TEGDM solution of polycarbonate diol (manufactured by Asahi Kasei Corporation, "PCDL T5652", weight average molecular weight: 2,000) was added to the contents of the vessel over 1 hour, and the resulting solution was stirred for 2 hours while being heated to 80 ° C. The polycarbonate diol TEGDM solution was prepared by dissolving 50.00 g (0.025 mol) of polycarbonate diol in 35.00 g of TEGDM. Next, 15.51 g (0.050 mol) of 4,4'-oxydiphthalic anhydride was added to the contents of the vessel, and the contents were heated to 190°C while stirring for 1 hour. The contents of the vessel were then cooled to 80°C, and 3.60 g (0.200 mol) of pure water was added to the contents of the vessel. The contents of the vessel were then heated to 110°C and refluxed for 5 hours to obtain a resin solution SP1 containing a binder polymer P1 having a urethane bond and an imide group per molecule. The solids concentration of the resulting resin solution SP1 was 53 wt%. The weight average molecular weight and acid value of the binder polymer P1 were 9,200 and 86 mgKOH / g, respectively.

[0152] [Preparation of resin solution SP2 containing binder polymer P2] A reaction vessel equipped with a stirrer, thermometer, and nitrogen inlet tube was charged with 35.00 g of TEGDM as a polymerization solvent and 10.31 g (0.050 mol) of norbornene diisocyanate, and the contents of the vessel were heated to 80 ° C. while stirring under a nitrogen stream, and norbornene diisocyanate was dissolved in TEGDM. Next, a TEGDM solution of polycarbonate diol (Asahi Kasei Corporation "PCDL T5652", weight average molecular weight: 2,000) was added to the contents of the vessel over 1 hour, and the resulting solution was stirred for 2 hours while being heated to 80 ° C. The TEGDM solution of the polycarbonate diol was a solution in which 50.00 g (0.025 mol) of polycarbonate diol was dissolved in 35.00 g of TEGDM. Next, 26.02 g (0.050 mol) of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride was added to the contents of the vessel, and the contents were stirred for 1 hour while heating to 190°C. The contents of the vessel were then cooled to 80°C, and 3.60 g (0.200 mol) of pure water was added to the contents of the vessel. The contents of the vessel were then heated to 110°C and refluxed for 5 hours to obtain a resin solution SP2 containing a binder polymer P2 having a urethane bond and an imide group per molecule. The solids concentration of the resulting resin solution SP2 was 55 wt%. The weight average molecular weight and acid value of the binder polymer P2 were 5,500 and 90 mgKOH / g, respectively.

[0153] [Preparation of resin solution SP3 containing binder polymer P3] A reaction vessel equipped with a stirrer, thermometer, and nitrogen inlet tube was charged with 30.00 g of TEGDM as a polymerization solvent and 10.31 g (0.050 mol) of norbornene diisocyanate. The contents of the vessel were heated to 80 ° C. while stirring under a nitrogen stream, and norbornene diisocyanate was dissolved in TEGDM. Next, to the contents of the vessel, polycarbonate diol (Asahi Kasei Corporation "PCDL T5652", weight average molecular weight: 2,000) and a TEGDM solution of 2,2-bis(hydroxymethyl)butanoic acid were added over 1 hour. The resulting solution was stirred for 5 hours while heating to 80 ° C. to obtain a resin solution SP3 containing binder polymer P3 having a urethane bond and a carboxy group in one molecule. The TEGDM solution of polycarbonate diol and 2,2-bis(hydroxymethyl)butanoic acid was prepared by dissolving 50.00 g (0.025 mol) of polycarbonate diol and 3.70 g (0.025 mol) of 2,2-bis(hydroxymethyl)butanoic acid in 30.00 g of TEGDM. The solids concentration of the resulting resin solution SP3 was 52 wt %. The weight average molecular weight and acid value of binder polymer P3 were 5,600 and 22 mgKOH / g, respectively.

[0154] <Preparation of Liquid Photosensitive Resin Composition> Any of the resin solutions SP1 to SP3 obtained by the above-mentioned preparation method and each of the components (specifically, components other than component (A)) listed in Tables 1 to 4 below were mixed in a stirrer equipped with a stirring blade. The resulting mixture was then passed through a three-roll mill twice and degassed in a degassing device to obtain the liquid photosensitive resin compositions used in Examples 1 to 14 and Comparative Examples 1 and 2. The average particle size of the particles in the resulting liquid photosensitive resin compositions was measured and found to be 10 μm or less in all of Examples 1 to 14 and Comparative Examples 1 and 2.

[0155] <Method for measuring physical properties of liquid photosensitive resin composition and method for evaluating liquid photosensitive resin composition> [Method for measuring elastic modulus of cured film] Each liquid photosensitive resin composition was applied to a portion (area 200 mm × 200 mm) of a 25 μm thick polytetrafluoroethylene sheet using a Baker-type applicator. At this time, the amount of the liquid photosensitive resin composition applied was adjusted so that the thickness of the cured film would be 20 μm. Next, the coating film made of the liquid photosensitive resin composition was dried under conditions of a drying temperature of 80°C and a drying time of 20 minutes, and then the cumulative exposure dose was 300 mJ / cm. ２ Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating was exposed to ultraviolet light under the conditions of: ２ Spray development was carried out for 90 seconds under the conditions of . The developed coating film was then washed with pure water and heated in an oven at 150°C for 60 minutes to form a cured film of the liquid photosensitive resin composition on the polytetrafluoroethylene sheet. The formed cured film was then peeled off from the polytetrafluoroethylene sheet and cut into a size of 200 mm in length and 15 mm in width to obtain a test piece with a thickness of 20 μm. Using the obtained test piece, the elastic modulus of the cured film was measured under the following conditions. - Apparatus used: Tensile tester (Shimadzu Corporation "Autograph S type") - Measurement temperature: 23°C - Pulling speed: 50 mm / min

[0156] [Method for evaluating micro-aperture properties] Each liquid photosensitive resin composition was applied to a portion (area 200 mm x 200 mm) of a 25 μm-thick polyimide film ("Apical (registered trademark) 25NPI" manufactured by Kaneka Corporation) using a Baker-type applicator. At this time, the amount of liquid photosensitive resin composition applied was adjusted so that the thickness of the cured film was 20 μm. Next, the coating film made of the liquid photosensitive resin composition was dried under conditions of a drying temperature of 80°C and a drying time of 20 minutes, and then exposed to an integrated exposure dose of 300 mJ / cm through a negative photomask having circular light-shielding regions with diameters of 30 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, and 200 μm. ２The coating film was exposed by irradiating it with ultraviolet light under the conditions of: Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating film was exposed to ultraviolet light under the conditions of: ２ Spray development was carried out for 90 seconds under the conditions of . The developed coating film was then washed with pure water and heated in an oven at 150°C for 60 minutes to form a cured film of the liquid photosensitive resin composition on the polyimide film. The resulting cured film was observed under an optical microscope, and the smallest diameter of the formed holes was used as an evaluation value for micro-opening property.

[0157] [Method for Measuring Repulsion Force] First, a flexible copper-clad laminate was prepared by laminating electrolytic copper foil (thickness: 12 μm) to both sides of a polyimide film ("Pixio (registered trademark) BP FRS-522#SW" manufactured by Kaneka Corporation, thickness: 12.5 μm) as a film support. The copper foil on one side of this flexible copper-clad laminate was patterned to form a comb-shaped pattern with a line width / space width of 100 μm / 100 μm on the film support. Next, the laminate with the comb-shaped pattern formed was immersed in a 10% by volume aqueous sulfuric acid solution for 1 minute and then washed with pure water. Next, each liquid photosensitive resin composition was applied onto the comb-shaped pattern using a Baker-type applicator. At this time, the amount of liquid photosensitive resin composition applied was adjusted so that the thickness of the cured film on the comb-shaped pattern was 20 μm. Next, the coating film made of the liquid photosensitive resin composition was dried under conditions of a drying temperature of 80°C and a drying time of 20 minutes, and then subjected to an integrated exposure dose of 300 mJ / cm ２ Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating was exposed to ultraviolet light under the conditions of: ２Spray development was performed for 90 seconds under the conditions of . The developed coating film was then washed with pure water and heated in an oven at 150 ° C. for 60 minutes to form a cured film of the liquid photosensitive resin composition on the comb pattern. The resulting laminate including the cured film was then cut into a size of 15 mm wide x 200 mm long to obtain a test piece. This test piece was rolled into a loop with a circumference of 50 mm and fixed to a resilience measuring device ("Loop Stiffness Tester (registered trademark)" manufactured by Toyo Seiki Seisaku-sho, Ltd.), and the looped test piece was pressed until the shortest loop diameter was 10 mm, and the resilience from the looped test piece was measured. The smaller the resilience, the more excellent the cured film's low resilience.

[0158] [Method for evaluating solder heat resistance] Each liquid photosensitive resin composition was applied to an electrolytic copper foil having a thickness of 35 μm using a Baker-type applicator. At this time, the amount of the liquid photosensitive resin composition applied was adjusted so that the thickness of the cured film would be 20 μm. Next, the coating film made of the liquid photosensitive resin composition was dried under conditions of a drying temperature of 80° C. and a drying time of 20 minutes, and then subjected to an integrated exposure dose of 300 mJ / cm. ２ Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating was exposed to ultraviolet light under the conditions of: ２ Spray development was performed for 90 seconds under the conditions of . The developed coating film was then washed with pure water and heated in an oven at 150°C for 60 minutes to form a cured film of the liquid photosensitive resin composition on the electrolytic copper foil, thereby obtaining a test piece. The obtained test piece was immersed in a solder bath at 260°C and then pulled out after 10 seconds, which was considered as one operation, and this operation was performed three times consecutively. Next, the condition of the cured film surface was visually observed, and when no blistering or peeling was observed on the cured film surface, it was evaluated as "A (excellent solder heat resistance)". On the other hand, when blistering or peeling was observed on the cured film surface, it was evaluated as "B (not excellent solder heat resistance)".

[0159] [Method for measuring breakdown voltage] Each liquid photosensitive resin composition was applied to a portion (area 200 mm × 200 mm) of a 25 μm-thick polytetrafluoroethylene sheet using a Baker-type applicator. At this time, the amount of liquid photosensitive resin composition applied was adjusted so that the thickness of the cured film would be 20 μm. Next, the coating film made of the liquid photosensitive resin composition was dried under conditions of a drying temperature of 80°C and a drying time of 20 minutes, and then subjected to an integrated exposure dose of 300 mJ / cm. ２ Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating was exposed to ultraviolet light under the conditions of: ２ Spray development was performed for 90 seconds under the conditions of . The developed coating film was then washed with pure water and heated in an oven at 150°C for 60 minutes to form a cured film of the liquid photosensitive resin composition on a polytetrafluoroethylene sheet. The formed cured film was then peeled off from the polytetrafluoroethylene sheet to obtain a 20 μm-thick test piece. Sixty such test pieces were prepared for each of Examples 1 to 14, Comparative Examples 1 and 2, and the breakdown voltage of each test piece was measured under the conditions described below. Then, for each of Examples 1 to 14, Comparative Examples 1 and 2, the number of test pieces with a breakdown voltage of 200 V or less (hereinafter referred to as the "number of pieces with a breakdown voltage of 200 V or less") was determined, and the proportion (unit: %) of test pieces with a breakdown voltage of 200 V or less was calculated according to the formula "proportion of test pieces with a breakdown voltage of 200 V or less = 100 × number of pieces with a breakdown voltage of 200 V or less / 60". Hereinafter, the ratio of dielectric breakdown voltages of 200 V or less may be referred to as "the ratio of 200 V or less."

[0160] (Conditions for measuring dielectric breakdown voltage) Pretreatment conditions for test specimen: heated at 100°C for 20 minutes, and then left in an atmosphere of 23°C and 50% relative humidity for 20 minutes. Apparatus used: Dielectric breakdown voltage tester manufactured by Yasuda Seiki Seisakusho Co., Ltd. Measurement current: AC 14 mA Voltage increase rate: 200 V / sec

[0161] <Preparation of Substrate> First, a flexible copper-clad laminate was prepared by laminating electrolytic copper foil to both sides of a polyimide film ("Pixio (registered trademark) BP FRS#SW" manufactured by Kaneka Corporation) as a film-like support. Six hundred through-holes each with diameters (opening diameters) of 30 μm, 50 μm, 80 μm, 100 μm, 130 μm, 190 μm, 240 μm, and 290 μm were provided in this flexible copper-clad laminate. Next, a cleaning treatment (desmear treatment) and a carbon treatment were performed inside the through-holes. Next, the insides of the through-holes were subjected to electrolytic copper plating, and then the electrolytic copper foils on both sides were patterned to form a comb-shaped pattern with a line width / space width of 100 μm / 100 μm on the film-like support. This resulted in a substrate having a film-like support and wiring (comb-shaped pattern) provided on both sides of the film-like support, and having through-holes. For each of Examples 1 to 14 and Comparative Examples 1 and 2, Tables 1 to 4 described below show the vertical and horizontal widths of the substrates used, the thicknesses of the film-like supports used, and the thicknesses of the wiring on the substrates used.

[0162] <Application of Liquid Photosensitive Resin Composition to Substrate and Formation of Coating Film> The substrate prepared by the above procedure was immersed in a 10% by volume aqueous sulfuric acid solution for 1 minute and then washed with pure water. Next, a liquid photosensitive resin composition (any of the liquid photosensitive resin compositions listed in Tables 1 to 4 described below) was applied to both sides of the washed substrate using a vertical lift-type roll coater equipped with a pair of coating rolls. In this case, the liquid photosensitive resin composition was simultaneously applied to both sides of the substrate. The coating conditions were as follows. In the following coating conditions, "coating roll" refers to "each of the pair of coating rolls." In the following coating conditions, the conditions regarding the "groove of the coating roll" are the conditions for Examples 1 to 14 and Comparative Example 1. In Comparative Example 2, a surface layer roll without a groove was used. Material of the surface layer of the coating roll (surface roll): ethylene propylene rubber Width of the surface roll: 680 mm Thickness of the surface roll: 20 mm Roll diameter of the coating roll: as shown in Tables 1 to 4 below Doctor bar pressure: 1.5 kgf / cm ２- Pressing amount of coating roll: 150 μm - Rotation speed of coating roll: 5 m / min - Type of grooves in coating roll: multiple independent ring-shaped grooves - Pitch of coating roll groove: 700 μm - Opening width of coating roll groove: 700 μm - Cross-sectional shape of coating roll groove: V-shaped - Depth of coating roll groove: 350 μm

[0163] Next, the substrate coated with the liquid photosensitive resin composition was dried in a hanging state at a drying temperature of 80° C. for 20 minutes. The thickness of the coating film made of the liquid photosensitive resin composition after drying (more specifically, the thickness of the coating film on the comb-shaped pattern excluding the edge portions) was 20 μm on both sides.

[0164] <Substrate Evaluation Method> [Embeddability] The through holes of each substrate after drying (specifically, 600 through holes each with a diameter of 30 μm, 50 μm, 80 μm, 100 μm, 130 μm, 190 μm, 240 μm, and 290 μm) were observed with an optical microscope, and the largest diameter of the through holes when the filling rate was 100% (when all 600 through holes were filled) was used as the embeddability evaluation value. For example, an "embeddability evaluation value of 50 μm" means that all 600 through holes with a diameter of 30 μm and 50 μm were filled, but some or all of the 600 through holes with a diameter of 80 μm were not filled. Therefore, the higher this evaluation value, the better the embeddability can be evaluated.

[0165] [Appearance of Coating Film] After drying, the coating film on each substrate was visually inspected to check for pinholes, uneven coating of the coating film covering the wiring, traces of the coating roll grooves, and streaks. The appearance of the coating film was then judged according to the following criteria. If the rating was A or B, it was evaluated as "the occurrence of poor appearance of the coating film was suppressed." On the other hand, if the rating was C, it was evaluated as "the occurrence of poor appearance of the coating film was not suppressed."

[0166] (Criteria for judging the appearance of the coating film) A: None of the following was observed: pinholes, uneven coating, groove marks, or streaks. B: At least one of the following defects was observed in one or two places in total: pinholes, uneven coating, groove marks, or streaks. C: At least one of the following defects was observed in three or more places in total: pinholes, uneven coating, groove marks, or streaks.

[0167] [Appearance of substrates on which coating films have been formed] The appearance of each substrate after drying was visually observed to check for the presence or absence of breakage and deformation of the substrate. The appearance of the substrates on which coating films have been formed was then judged according to the following criteria. If the rating was A or B, it was evaluated as "the occurrence of defects in appearance of the substrates on which coating films have been formed has been suppressed." On the other hand, if the rating was C, it was evaluated as "the occurrence of defects in appearance of the substrates on which coating films have been formed has not been suppressed."

[0168] (Evaluation criteria for the appearance of the substrate on which the coating film was formed) A: Neither breakage nor deformation of the substrate was observed. B: No breakage of the substrate was observed, but deformation of the substrate was observed. C: Both breakage and deformation of the substrate were observed.

[0169] [Electrical insulation reliability] For each substrate obtained by the above procedure after drying, an integrated exposure dose of 300 mJ / cm ２ Then, a 1.0 wt % aqueous solution of sodium carbonate (temperature: 30°C) was used as a developer, and the exposed coating was exposed to ultraviolet light under the conditions of: ２ Spray development was carried out for 90 seconds under the conditions of 1.0×10. The developed coating film was then washed with pure water and heated in an oven at 150°C for 60 minutes to form a cured film of the liquid photosensitive resin composition on the comb-shaped pattern, thereby obtaining a test piece. Next, a DC voltage of 100 V was applied to both terminals of the test piece in an environment of 85°C and 85% relative humidity, and the change in resistance value between the two terminals was observed. Then, after 1000 hours had passed since the start of application, a DC voltage of 1.0×10 ８ When the resistance value was 1.0×10 Ω or more, it was evaluated as "A (excellent electrical insulation reliability)." ８When the resistance value was less than Ω, it was evaluated as "B (not excellent in electrical insulation reliability)."

[0170] <Evaluation Results> For Examples 1 to 14 and Comparative Examples 1 and 2, the components and amounts of the liquid photosensitive resin composition used, the longitudinal and lateral widths of the substrate used, the thickness of the film-like support used, the thickness of the wiring on the substrate used, the roll diameter of the applicator roll used, the presence or absence of grooves in the applicator roll used, the physical properties and evaluation results of the liquid photosensitive resin composition used, and the evaluation results of the substrate are shown in Tables 1 to 4. In Tables 1 to 4, the numerical values ​​in the column for the composition of the liquid photosensitive resin composition indicate the amount of the component (unit: parts by weight). In Tables 1 to 4, the amount of component (E) (organic solvent) also includes the amount of organic solvent in Resin Solution SP1, Resin Solution SP2, or Resin Solution SP3. In Tables 1 to 4, "-" means that the component was not included.

[0171] In addition, in Tables 1 to 4, "369", "828", "8070", "972", "TEGDM", "903", "170", "321", and "2000" are as follows. 369: 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 as a photoradical polymerization initiator (IGM Resins' "Omnirad (registered trademark) 369") 828: Epoxy resin (Mitsubishi Chemical Corporation's "jER (registered trademark) 828") 8070: Crosslinked polyurethane particles (Dainikseika Color & Chemicals Mfg. Co., Ltd.'s "Dymic Beads (registered trademark) UCN-8070CM Clear", average particle size: 7 μm) 972: Silica particles (Nippon Aerosil Co., Ltd.'s "Aerosil (registered trademark) R-972", average particle size: 0.016 μm) TEGDM: Triethylene glycol dimethyl ether 903: Particle dispersant (BYK Japan's "BYK (registered trademark)-W903") 170: Particle dispersant (DISPERBYK (registered trademark)-170 manufactured by BYK Japan) 321: EO-modified bisphenol A dimethacrylate (FANCRYL (registered trademark) FA-321M manufactured by Showa Denko Materials, average number of moles of EO added: 10) 2000: Butadiene-based defoamer (FLOWLEN AC-2000 manufactured by Kyoeisha Chemical Co., Ltd.)

[0172]

[0173]

[0174]

[0175]

[0176] In Examples 1 to 14, the pair of coating rolls used each had a groove. In Examples 1 to 14, the surface layers of the pair of coating rolls used each were rubber layers (ethylene propylene rubber layers). In Examples 1 to 14, the liquid photosensitive resin composition used contained a binder polymer having an imide group in one molecule, a photoradical polymerization initiator, and a thermosetting resin.

[0177] In Examples 1 to 14, the electrical insulation reliability was judged to be A. Therefore, the flexible printed circuit boards obtained by the manufacturing methods of Examples 1 to 14 were excellent in electrical insulation reliability.

[0178] In Comparative Example 1, the liquid photosensitive resin composition used did not contain a binder polymer having an imide group in one molecule. In Comparative Example 2, neither of the pair of coating rolls used had a groove.

[0179] In Comparative Examples 1 and 2, the electrical insulation reliability was judged to be B. Therefore, the flexible printed circuit boards obtained by the manufacturing methods of Comparative Examples 1 and 2 did not have excellent electrical insulation reliability.

[0180] The above results demonstrate that the present invention can provide a method for producing a flexible printed circuit board with excellent electrical insulation reliability.

[0181] REFERENCE SIGNS LIST 11 Substrate 12a, 12b, 100 Coating roll 13 Film-like support 14 Wiring 15 Hole 17 Liquid photosensitive resin composition 120a Ring-shaped groove

Claims

1. A method for producing a flexible printed circuit board, comprising applying a liquid photosensitive resin composition to both sides of a substrate having a film-like support and wiring provided on both sides of the film-like support by using a vertically suspended roll coater, The substrate has a hole therein, The vertical lift roll coater includes a pair of coating rolls having grooves, the surface layer of the coating roll is a rubber layer, The liquid photosensitive resin composition contains a binder polymer having an imide group in one molecule, a photoradical polymerization initiator, and a thermosetting resin, The thickness of the film-like support is 8.0 μm or more and 50.0 μm or less, The coating roll has a plurality of ring-shaped grooves, each of which is independent from the other, as the groove, In applying the liquid photosensitive resin composition, the liquid photosensitive resin composition is applied simultaneously to both sides of the substrate.

2. The method for producing a flexible printed circuit board according to claim 1 , wherein the width and length of the film-like support are both 200 mm or more and 600 mm or less.

3. The method for producing a flexible printed circuit board according to claim 1 or 2, wherein the wiring has a thickness of 8 μm or more and 50 μm or less.

4. The method for manufacturing a flexible printed circuit board according to any one of claims 1 to 3, wherein the hole has a diameter of 50 µm or more and 250 µm or less.

5. The method for producing a flexible printed circuit board according to any one of claims 1 to 4, wherein the film-like support contains one or more polymers selected from the group consisting of polyimide, polyamide, polyester, polycarbonate, polyarylate, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluorine resin, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, and ethylene-chlorotrifluoroethylene copolymer.

6. The method for producing a flexible printed circuit board according to any one of claims 1 to 5, wherein the liquid photosensitive resin composition further contains particles having an average particle size of 0.01 µm or more and 100 µm or less.

7. The method for producing a flexible printed circuit board according to claim 6 , wherein the liquid photosensitive resin composition further contains a particle dispersant.

8. The method for producing a flexible printed circuit board according to any one of claims 1 to 7, wherein the roll diameter of the coating roll is 70 mm or more and 150 mm or less.