JP6757547B2 - Method of forming a cured coating film - Google Patents

Description

The present invention relates to a method for forming a cured coating film in which a photosensitive resin composition is applied onto a substrate by an inkjet method.

Conventionally, in forming a coating (for example, an insulating coating such as a solder resist film) on a substrate, for example, a printed wiring board having a desired circuit pattern, a photosensitive resin composition is applied and then prepared by using a screen printing method. A negative film having a pattern that is dried and has a translucent pattern other than the land of the circuit pattern is brought into close contact with the coating film of the photosensitive resin composition, and active energy rays (ultraviolet rays) are irradiated from above to correspond to the above land. The unexposed region to be exposed was removed with a dilute alkaline aqueous solution, the coating film was developed, and post-cure was performed (Patent Document 1).

However, the printed wiring board may be provided with through holes. In this case, when the screen printing method is used, the applied photosensitive resin composition escapes to the back side of the printed wiring board through the through holes, so that the applied photosensitive resin composition is rejected at the peripheral edge of the through holes. It ends up. Therefore, there is a problem that a portion where the thickness of the coating film is thin is generated in the peripheral portion of the through hole, and the thickness of the coating film cannot be made uniform sufficiently.

In particular, when the surface (back surface) of the substrate opposite to the coated surface of the photosensitive resin composition is in contact with the coating stage, the capillary force generated at the boundary surface between the front surface of the coating stage and the back surface of the substrate. This may promote the escape of the photosensitive resin composition to the back side of the printed wiring board through the through holes.

It may be required to prevent such a problem depending on the usage conditions of the substrate and the like.

JP-A-2002-293882

In view of the above circumstances, an object of the present invention is to prevent the photosensitive resin composition from coming out to the back side of the substrate through the through holes even if the substrate is provided with through holes, and to make the thickness of the coating film uniform. It is to provide a method of forming a cured coating film which can be performed.

In the aspect of the present invention, at least the through hole portion of the substrate is coated with the first photosensitive resin composition having a viscosity at 25 ° C. of 150 to 1500 mPa · s by an inkjet method, and the through hole is filled. A step of forming a coating film by applying a second photosensitive resin composition on the first main surface of the substrate and on the surface of the filler on the first main surface side. In the step of applying the first photosensitive resin composition, which comprises a step of curing the coating film to form a cured coating film, the surface of the substrate on the opposite side of the first main surface. This is a method for forming a cured coating film in which at least the peripheral edge of the through hole of the second main surface is non-contact.

In the above aspect, a desired coating method including a through hole is filled with the first photosensitive resin composition coated by the inkjet method, and the first photosensitive resin composition is filled with the through hole, and further includes the inkjet method. The second photosensitive resin composition is coated at the above, and at least the coated second photosensitive resin composition is cured. In addition, coating the second photosensitive resin composition on the first main surface of the substrate and the surface on the first main surface side of the filler means that the first main surface of the substrate and the first main surface of the filler are coated. When the second photosensitive resin composition is directly applied to the surface on the side, and on the surface on the first main surface side of the substrate and the surface on the first main surface side of the filler, other than the second photosensitive resin composition. The case includes a case where another resin composition (including the first photosensitive resin composition) is applied and then a second photosensitive resin composition is applied on the coating.

An aspect of the present invention is a method for forming a cured coating film in which the first photosensitive resin composition contains a non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C.

An aspect of the present invention is a method for forming a cured coating film in which the non-reactive diluent contains diethylene glycol diethyl ether.

In the embodiment of the present invention, the method for applying the second photosensitive resin composition is a screen printing method, an inkjet method, a roll coater method, a bar coater method, a spray coater method, a curtain flow coater method, a squeegee method, or an applicator method. , A method for forming a cured coating film, which is a blade coater method, a knife coater method, or a gravure coater method.

In the aspect of the present invention, a cured coating film is formed by applying the second photosensitive resin composition to the surface of the filler on the first main surface side by a coating method other than the inkjet method. The method.

In the embodiment of the present invention, the other coating method is a screen printing method, a roll coater method, a bar coater method, a spray coater method, a curtain flow coater method, a squeegee method, an applicator method, a blade coater method, a knife coater method or a gravure coater. It is a method for forming a cured coating film, which is a method.

An aspect of the present invention is a method for forming a cured coating film having a viscosity of the first photosensitive resin composition at 25 ° C. of 180 to 1000 mPa · s.

An aspect of the present invention is a method for forming a cured coating film having a viscosity of the second photosensitive resin composition at 25 ° C. of 120 to 60,000 mPa · s.

An aspect of the present invention is a method for forming a cured coating film, wherein the first photosensitive resin composition is the same photosensitive resin composition as the second photosensitive resin composition.

An aspect of the present invention is a method for forming a cured coating film, wherein the curing treatment is an exposure treatment and / or a heat treatment with active energy rays.

An aspect of the present invention is a method for forming a cured coating film in which the exposure amount of the exposure treatment using the active energy rays is 30 to 500 mJ / cm ² .

According to the aspect of the present invention, before coating the second photosensitive resin composition by the desired coating method, first, the viscosity at 25 ° C. is 150 to 1500 mPa · s by the inkjet method. The photosensitive resin composition of the above is applied to fill the through holes of the substrate, and at the time of filling, the peripheral portion of the through holes on the second main surface (back surface) is made non-contact, so that the surface of the coating stage and the substrate are not contacted. It is possible to prevent the generation of capillary force generated at the interface with the back surface of the. By preventing the generation of capillary force, it is possible to prevent the first photosensitive resin composition from coming out to the back surface of the substrate through the through holes, so that the through holes can be reliably filled with the first photosensitive resin composition. ..

From the above, even if the substrate to be coated is provided with through holes, the second photosensitive resin composition applied to the peripheral edge of the through holes escapes to the back surface of the substrate through the through holes and is second. It is possible to prevent the thickness of the coating film from becoming thin due to the rejection of the photosensitive resin composition of. In addition, the through holes cannot be reliably filled by the first photosensitive resin composition, and the second photosensitive resin composition applied to the peripheral edge of the through holes invades the dents remaining in the through hole traces. Can be prevented. Therefore, even with the second photosensitive resin composition applied to the peripheral edge of the through hole, the thickness of the coating film can be made uniform.

According to an aspect of the present invention, the first photosensitive resin composition contains a non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C., so that the first photosensitive resin is formed through a through hole. The first photosensitive resin composition can be reliably filled with through holes while reliably preventing the composition from coming off to the back surface of the substrate. Further, even if a coating film is formed with the first photosensitive resin composition, the thickness of the coating film can be made more uniform.

According to the aspect of the present invention, the viscosity of the first photosensitive resin composition at 25 ° C. is 150 to 1500 mPa · s, so that the through holes are surely filled and the thickness of the cured coating film is further increased. Can be made uniform.

According to the aspect of the present invention, the exposure time can be shortened by setting the exposure amount of the exposure process using the active energy rays to 30 to 500 mJ / cm ² . Therefore, even if the coating of the first photosensitive resin composition and the coating of the second photosensitive resin composition are included, the productivity can be improved.

(A) is an explanatory view in which through holes are filled by coating a first photosensitive resin composition by an inkjet method in the method for forming a cured coating film according to an embodiment of the present invention, FIG. Is an explanatory view in which the second photosensitive resin composition is applied in the method for forming a cured coating film according to an embodiment of the present invention, and FIG. 3C is a cured coating according to an example of the present invention. The explanatory view of the curing process by exposure and the figure (d) in the film forming method are explanatory views of the state of the cured coating film after development. It is explanatory drawing of the plan view of the printed wiring board which has the cured coating film formed in the method of forming the cured coating film which concerns on embodiment of this invention.

Next, an embodiment of the method for forming a cured coating film of the present invention will be described with reference to the drawings. The method for forming a cured coating film of the present invention is to form a cured coating film on a substrate provided with through holes (for example, a circuit board such as a printed wiring board or a flexible printed wiring board). In addition, FIG. 1A is an explanatory view in which through holes are filled by coating the first photosensitive resin composition by an inkjet method in the method for forming a cured coating film according to an embodiment of the present invention. The figure (b) is an explanatory view in which the second photosensitive resin composition is applied in the method for forming a cured coating film according to the embodiment of the present invention, and the figure (c) is the embodiment of the present invention. The explanatory view of the curing process by exposure and the figure (d) in the method of forming the cured coating film according to the example are explanatory views of the state of the cured coating film after development. FIG. 2 is an explanatory view of a printed wiring board having a cured coating film formed in the method for forming a cured coating film according to an embodiment of the present invention in a plan view.

As shown in FIG. 1 (a), in the method for forming a cured coating film according to the embodiment of the present invention, first, a substrate is subjected to an inkjet method (in FIG. 1, an inkjet method using a jet dispenser 4 as an example). A predetermined amount of the first photosensitive resin composition 1 is applied to the through hole 31 part of No. 3, and the first photosensitive resin composition 1 is filled in the through hole 31 part to completely fill the through hole 31. fill in.

Of both main surfaces of the substrate 3 (first main surface 21 and second main surface 22), the second main surface 22 corresponding to the back surface of the substrate 3 has a peripheral portion of the through hole 31 that is not relative to the coating stage 100. It is a contact. Therefore, a gap 101 is provided between the second main surface 22 and the surface of the coating stage 100. In FIG. 1A, the spacer 20 is installed on the surface of the coating stage 100, and the substrate 3 is placed on the spacer 20, so that the peripheral edge of the through hole 31 of the second main surface 22 is relative to the coating stage 100. It is non-contact.

By making the peripheral edge of the through hole 31 of the second main surface 22 non-contact, it is possible to prevent the generation of capillary force generated at the interface between the surface of the coating stage 100 and the second main surface 22 of the substrate 3. By preventing the generation of capillary force, it is possible to prevent the substrate 3 of the first photosensitive resin composition 1 from coming off from the first main surface 21 to the second main surface 22 through the through holes 31. The photosensitive resin composition 1 of the above can be reliably and sufficiently filled in the through hole 31. The height of the gap 101 is not particularly limited, but is, for example, 1.0 mm to 10 mm.

The viscosity of the first photosensitive resin composition 1 at 25 ° C. is adjusted to 150 to 1500 mPa · s by a non-reactive diluent. Since the lower limit of the viscosity at 25 ° C. is 150 mPa · s, when the first photosensitive resin composition 1 is applied to the through hole 31 by the inkjet method, the first photosensitive resin composition is applied at the time of coating. It is possible to prevent the object 1 from slipping out to the back surface side of the substrate 3 through the through hole 31. As a result, the through hole 31 can be filled with the first photosensitive resin composition 1. Further, since the upper limit of the viscosity at 25 ° C. is 1500 mPa · s, when the first photosensitive resin composition 1 is coated by the inkjet method, the first photosensitive resin composition 1 becomes convex. It is possible to prevent coating and, by extension, to make the thickness of the cured coating film uniform.

The viscosity of the first photosensitive resin composition 1 at 25 ° C. is not particularly limited as long as it is in the range of 150 to 1500 mPa · s, but the lower limit is the through hole 31 of the first photosensitive resin composition 1. 180 mPa · s is preferable, and 300 mPa · s is particularly preferable, from the viewpoint of surely preventing the substrate 3 from coming off to the back surface side of the substrate 3. The upper limit of the viscosity at 25 ° C. is preferably 1000 mPa · s, more preferably 900 mPa · s, and 700 mPa from the viewpoint of surely preventing the first photosensitive resin composition 1 from being coated in a convex shape. -S is particularly preferable. The size of the through hole 31 is not particularly limited, and for example, the inner diameter is 50 to 200 μm and the depth is 50 to 200 μm.

The non-reactive diluent for adjusting the viscosity of the first photosensitive resin composition 1 at 25 ° C. is not particularly limited, but is the back surface side of the substrate 3 of the first photosensitive resin composition 1 via the through hole 31. A non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C. can be filled in the through hole 31 more reliably while surely preventing the first photosensitive resin composition 1 from coming off. More preferably, a non-reactive diluent having a surface tension at 25 ° C. of 27 m N / m or less is particularly preferable. As the non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C., for example, diethylene glycol diethyl ether (surface tension of 25 m N / m at 25 ° C.) is preferable.

Next, as shown in FIG. 1 (b), the second photosensitive resin composition 2 is applied onto the first photosensitive resin composition 1 filled in the through holes 31 by a desired coating method. Paint. In FIG. 1B, the second photosensitive resin composition 2 is applied to the entire first main surface 21 of the substrate 3. The time interval from the end of coating of the first photosensitive resin composition 1 to the start of coating of the second photosensitive resin composition 2 is not particularly limited, but the first main surface 21 of the substrate 3 and the like. 72 hours or less is preferable from the viewpoint of preventing oxidation of the surface of the first photosensitive resin composition 1.

The coating method of the second photosensitive resin composition 2 is not particularly limited, and any conventionally used method can be used. Specifically, for example, a screen printing method, an inkjet method (for example, an inkjet method using a jet dispenser), a roll coater method, a bar coater method, a spray coater method, a curtain flow coater method, a squeegee method, an applicator method, and a blade. Examples include a coater method, a knife coater method, and a gravure coater method. The coating method of the second photosensitive resin composition 2 may be the same coating method as the coating method of the first photosensitive resin composition 1 (that is, the inkjet method), or may be a coating method other than the inkjet method. Good. Of these, the screen printing method is preferable from the viewpoint of ease of coating on the entire first main surface 21 of the substrate 3.

The second photosensitive resin composition 2 may be a resin composition having the same components as the first photosensitive resin composition 1 or a resin composition having different components. Further, the viscosity of the second photosensitive resin composition 2 at 25 ° C. may be the same as or different from the viscosity of the first photosensitive resin composition 1 at 25 ° C. The viscosity of the second photosensitive resin composition 2 at 25 ° C. can also be adjusted with a non-reactive diluent. The viscosity of the second photosensitive resin composition 2 at 25 ° C. depends on the coating method to be adopted. For example, the lower limit thereof is preferably 120 mPa · s from the viewpoint of coating to a predetermined film thickness, and the coating method. When the screen printing method is used as the above, 10000 mPa · s is more preferable, and 12000 mPa · s is particularly preferable from the viewpoint of reliably coating a predetermined film thickness. The upper limit of the viscosity at 25 ° C. is, for example, preferably 60,000 mPa · s from the viewpoint of coatability, and more preferably 50,000 mPa · s when the screen printing method is used as the coatability, from the viewpoint of leveling property. 30000 mPa · s is particularly preferable.

The film thickness of the second photosensitive resin composition 2 at the time of coating can be appropriately selected according to the usage situation of the substrate 3. For example, a circuit pattern of a conductor such as a copper foil is formed as the substrate 3. When coating on a circuit board, 10 to 100 μm can be mentioned.

Next, as shown in FIG. 1 (c), the coated first photosensitive resin composition 1 and the second photosensitive resin composition 2 are subjected to the curing treatment 5 to obtain the cured coating film 12. Form. Examples of the curing treatment 5 include an exposure treatment using active energy rays, a heat treatment using a heating device, and the like.

In FIG. 1 (c), on the second photosensitive resin composition 2, a negative film (photomask) 102 having a circuit pattern other than the land of the circuit pattern composed of the through hole 31 and the copper foil 32 as the conductor made transparent is formed. A curing treatment 5 is performed in which the cells are brought into close contact with each other and photocured by irradiating them with active energy rays.

The conditions for the exposure treatment using the active energy rays are not particularly limited as long as the second photosensitive resin composition 2 is photocurable, and for example, ultraviolet rays (for example, wavelength 240 to 420 nm). the lower limit of exposure, from the point to securely photocuring is preferably 10 mJ / cm ^2, more preferably ^{25mJ / cm 2, 30mJ / cm} 2 is particularly preferred. On the other hand, the upper limit of the exposure amount of ultraviolet rays is not particularly limited from the viewpoint of photocuring, but 2000 mJ / cm ² is preferable, and 500 mJ / cm ² is particularly preferable from the viewpoint of shortening the exposure time and improving productivity. preferable. The light source of ultraviolet rays is not particularly limited, and examples thereof include a metal halide lamp, an ultrahigh pressure mercury lamp, a xenon lamp, and a UV-LED.

Next, as shown in FIG. 1D, after the second photosensitive resin composition 2 is photocured, the non-exposed region corresponding to the through hole 31 and the land is removed with a dilute alkaline aqueous solution to form a coating film. To develop. As the development method, for example, a spray method, a shower method and the like are used, and the dilute alkaline aqueous solution used is not particularly limited, and examples thereof include a sodium carbonate aqueous solution of 0.5 to 5% by mass. By the development, the first photosensitive resin composition 1 filled in the through hole 31 is removed, and the through hole 31 is exposed. After development, post-cure is performed for 20 to 80 minutes in a hot air circulation type dryer or the like at 130 to 170 ° C., and as shown in FIG. 2, the target cured coating film is applied on the first main surface 21 of the substrate 3. 12 can be formed.

When the second photosensitive resin composition 2 contains a non-reactive diluent, after coating the second photosensitive resin composition 2, the non-reactive diluent is volatilized to tack. In order to obtain a free coating film, the curing treatment 5 may be carried out after pre-drying with a dryer or the like. Examples of the pre-drying condition include a heating time of about 15 to 60 minutes at a temperature of about 60 to 80 ° C.

When the curing treatment 5 is a heat treatment, the conditions thereof are not particularly limited as long as the second photosensitive resin composition 2 is thermally cured, for example, 60 to 170 ° C., 15 to 80 minutes, etc. Can be mentioned.

By performing the curing treatment 5, a cured coating film 12 having a desired pattern can be formed on the first main surface 21 of the substrate 3. In the above embodiment, the curing treatment such as exposure treatment and heat treatment was not performed after the coating of the first photosensitive resin composition and before the coating of the second photosensitive resin composition. However, if necessary, the first photosensitive resin composition is cured after the coating of the first photosensitive resin composition and before the coating of the second photosensitive resin composition. May be good. Further, in the above-described embodiment, the first photosensitive resin composition is used after the coating of the first photosensitive resin composition and before the coating of the second photosensitive resin composition, if necessary. Other resin compositions may be further applied on top, including the first photosensitive resin composition.

From the above, even if the through hole 31 is provided on the substrate 3 to be coated, the second photosensitive resin composition 2 applied to the peripheral edge of the through hole 31 can be applied to the substrate 3 through the through hole 31. It is possible to prevent the thickness of the cured coating film 12 from becoming thin due to the removal of the second photosensitive resin composition coated on the first main surface 21 through the second main surface 22. Further, the second photosensitive resin composition 2 applied to the peripheral edge of the through hole 31 is formed in the recess remaining in the trace of the through hole 31 because the through hole 31 cannot be reliably filled by the first photosensitive resin composition 1. It can be prevented from invading. Therefore, even with the second photosensitive resin composition 2 applied to the peripheral edge of the through hole 31, the thickness of the cured coating film 12 can be made uniform.

Next, the first photosensitive resin composition and the second photosensitive resin composition (hereinafter, the first photosensitive resin composition and the second photosensitive resin composition are collectively referred to as "photosensitive resin composition". ".) Will be explained. Examples of the cured coating film of the photosensitive resin composition include an insulating film (for example, a solder resist film) formed on a circuit board such as a printed wiring board. The photosensitive resin composition can contain, for example, the following components.

Photosensitive resin Examples of the photosensitive resin include a carboxyl group-containing photosensitive resin. The carboxyl group-containing photosensitive resin is not particularly limited, and examples thereof include resins having one or more, preferably two or more photosensitive unsaturated double bonds. As the carboxyl group-containing photosensitive resin, for example, acrylic acid or methacrylic acid (hereinafter referred to as "(meth) acrylic acid") is added to at least a part of the epoxy groups of the polyfunctional epoxy resin having two or more epoxy groups in one molecule. A radically polymerizable unsaturated monocarboxylic acid such as) is reacted to obtain a radically polymerizable unsaturated monocarboxylic oxide epoxy resin such as epoxy (meth) acrylate, and the generated hydroxyl group is subjected to polybasic acid or its own. Examples thereof include a polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin such as a polybasic acid-modified epoxy (meth) acrylate obtained by reacting an anhydride.

The chemical structure of the polyfunctional epoxy resin is not particularly limited as long as it is a bifunctional or higher functional epoxy resin. The epoxy equivalent of the polyfunctional epoxy resin is not particularly limited, but is preferably 3000 or less, more preferably 1000 or less, and particularly preferably 100 to 500. The polyfunctional epoxy resin includes, for example, an aralkyl type epoxy resin, a biphenyl aralkyl type epoxy resin, a biphenyl type epoxy resin, a naphthalene type epoxy resin, a dicyclopentadiene type epoxy resin, an ε-caprolactone modified epoxy resin, a bisphenol A type, and a bisphenol. Phenol novolac type epoxy resin such as F type and bisphenol AD type, cresol novolac type epoxy resin such as о-cresol novolac type, bisphenol A novolac type epoxy resin, cyclic aliphatic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy Examples thereof include resins, heterocyclic epoxy resins, bisphenol-modified novolak-type epoxy resins, polyfunctional-modified novolak-type epoxy resins, and condensate-type epoxy resins of phenols and aromatic aldehydes having phenolic hydroxyl groups. These epoxy resins may be used alone or in combination of two or more.

The radically polymerizable unsaturated monocarboxylic acid is not particularly limited, and examples thereof include (meth) acrylic acid, crotonic acid, and cinnamic acid. These radically polymerizable unsaturated monocarboxylic acids may be used alone or in combination of two or more.

The reaction method between the polyfunctional epoxy resin and the radically polymerizable unsaturated monocarboxylic acid is not particularly limited, and for example, the polyfunctional epoxy resin and the radically polymerizable unsaturated monocarboxylic acid are heated in an appropriate diluent. It can be reacted by doing so.

The polybasic acid or polybasic acid anhydride reacts with a hydroxyl group generated by the reaction of an epoxy resin and a radically polymerizable unsaturated monocarboxylic acid to introduce a free carboxyl group into the photosensitive resin. The polybasic acid or its anhydride is not particularly limited, and either saturated or unsaturated can be used. Polybasic acids include, for example, succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4- Ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydro Examples thereof include phthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid and diglycolic acid. Examples of the polybasic acid anhydride include the above-mentioned polybasic acid anhydride. These compounds may be used alone or in combination of two or more.

The above-mentioned polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin can also be used as a carboxyl group-containing photosensitive resin, but if necessary, one is added to the carboxyl group of the above-mentioned polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin. By reacting the glycidyl compound having the above radically polymerizable unsaturated group with the epoxy group, the radically polymerizable unsaturated group is further introduced into the above polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin, and the active energy ray. It may be a carboxyl group-containing photosensitive resin having further improved sensitivity to.

In the carboxyl group-containing photosensitive resin having further improved sensitivity to active energy rays, a further radically polymerizable unsaturated group is added to the side chain of the polybasic acid-modified unsaturated monocarboxylic oxide epoxy resin skeleton by the reaction of the glycidyl compound. Since they are bonded, they have high photopolymerization reactivity (photocurability) and can have excellent photosensitive characteristics. Examples of the compound having one or more radically polymerizable unsaturated group and epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether and the like. In addition, a plurality of glycidyl groups may be contained in one molecule. The above-mentioned compound having one or more radically polymerizable unsaturated groups and an epoxy group may be used alone or in combination of two or more.

Photopolymerization initiator The photopolymerization initiator is not particularly limited as long as it is generally used, and for example, etanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3. -Il] -1- (0-acetyloxime) and other oxime initiators, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2 , 2-Dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1 -[4- (Methylthio) phenyl] -2-morpholino-propane-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4, 4'-Diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-terriary butyl anthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4 -Dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, acetphenone dimethylketal, P-dimethylaminobenzoic acid ethyl ester and the like can be mentioned. These may be used alone or in combination of two or more. The blending amount of the photopolymerization initiator is not particularly limited, but is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin.

Epoxy compound The epoxy compound is for increasing the crosslink density of the cured coating film to obtain a cured coating film having sufficient strength. Examples of the epoxy compound include an epoxy resin. The epoxy resin is not particularly limited, and for example, bisphenol A type epoxy resin, aralkyl type epoxy resin, biphenyl aralkyl type epoxy resin, novolak type epoxy resin (phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, p- tert-butylphenol novolac type, etc.), bisphenol F type or bisphenol S type epoxy resin obtained by reacting bisphenol F or bisphenol S with epichlorohydrin, and fat having a cyclohexene oxide group, a tricyclodecane oxide group, a cyclopentene oxide group, etc. Triglycidyl isocyanurate having a triazine ring such as cyclic epoxy resin, tris (2,3-epoxypropyl) isocyanurate, triglycidyltris (2-hydroxyethyl) isocyanurate, dicyclopentadiene type epoxy resin, adamantan type epoxy resin Can be mentioned. These compounds may be used alone or in combination of two or more. The amount of the epoxy compound to be blended is not particularly limited, but is preferably 10 to 50 parts by mass and 20 to 40 parts by mass with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin from the viewpoint of obtaining a coating film having sufficient strength after curing. Part is particularly preferable.

Non-reactive Diluent The non-reactive diluent is for adjusting the viscosity of the photosensitive resin composition and, if necessary, the drying property. Examples of the non-reactive diluent include organic solvents. Examples of the organic solvent include ketones such as methyl ethyl ketone and cyclohexanone, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, isopropanol and cyclohexanol, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. Petroleum-based solvents such as petroleum naphtha, cellosolves such as cellosolve and butylcellosolve, carbitols such as carbitol and butylcarbitol, ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, Examples thereof include esters such as ethyl diglycol acetate and ethylene glycol acetate, and ethers such as diethylene glycol diethyl ether. Of these, a non-reactive diluent (organic solvent) having a surface tension of 35 m N / m or less at 25 ° C. is preferable, and a non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C. is more preferable. A non-reactive diluent having a surface tension of 27 m N / m or less at ° C. is particularly preferable. Examples of the non-reactive diluent having a surface tension of 35 m N / m or less at 25 ° C. include diethylene glycol diethyl ether (surface tension of 25 m N / m at 25 ° C.) and ethylene glycol acetate (surface tension of 31 m N / m at 25 ° C.). ) Is preferable. As the non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C., for example, diethylene glycol diethyl ether (surface tension of 25 m N / m at 25 ° C.) is preferable.

Further, urethane (meth) acrylate may be added to the photosensitive resin composition, if necessary. Urethane (meth) acrylate contributes to obtain a cured coating film having flexibility. Urethane (meth) acrylate is obtained by reacting a urethane compound with (meth) acrylic acid, which is a radically polymerizable unsaturated monocarboxylic acid. Urethane is obtained by reacting a compound having two or more isocyanate groups in one molecule with a polyol compound having two or more hydroxyl groups in one molecule.

The compound having two or more isocyanate groups in one molecule is not particularly limited, and for example, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diisocyanate (MDI), methylenebiscyclohexylisocyanate, and the like. Examples thereof include diisocyanate compounds such as trimethylhexamethyl diisocyanate, hexane diisocyanate, hexamethylamine diisocyanate, methylenebiscyclohexylisocyanate, toluenediisocyanate, 1,2-diphenylethanediisocyanate, 1,3-diphenylpropanediisocyanate, diphenylmethane diisocyanate and dicyclohexylmethyldiisocyanate. .. These compounds may be used alone or in combination of two or more.

The polyol compound having two or more hydroxyl groups in one molecule is not particularly limited, and is, for example, ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2. -Butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, neopentyl glycol, 1,6-hexanediol, 2,2- C ₂ − such as diethyl-1,3-propanediol, 3,3-dimethylolheptan, 2-ethyl-2-butyl-1,3-propanediol, 1,12-dodecanediol, 1,18-octadecanediol, etc. Aliphatic diols such as C ₂₂ alcan diol and alken diols such as 2-butene-1,4-diol, 2,6-dimethyl-1-octene-3,8-diol; 1,4-cyclohexanediol, 1, Alicyclic diols such as 4-cyclohexanedimethanol; glycerin, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentane, 1,2,6-hexanetriol , Trimethylol ethane, trimethyl propane, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3- (hydroxymethyl) pentane, 2,2-bis (hydroxymethyl) -3 -Adiol triols such as butanol; polyols having four or more hydroxyl groups such as tetramethylolmethane, pentaerythritol, dipentaerythritol and xylitol. These compounds may be used alone or in combination of two or more.

The blending amount of the urethane (meth) acrylate is not particularly limited, but the lower limit is preferably 5 parts by mass from the viewpoint of improving the flexibility of the cured coating film with respect to 100 parts by mass of the carboxyl group-containing photosensitive resin. 10 parts by mass is particularly preferable. On the other hand, the upper limit value is preferably 50 parts by mass from the viewpoint of preventing a decrease in photosensitivity.

Further, the photosensitive resin composition may further contain various additives such as a colorant, an extender pigment, a latent curing agent, a defoaming agent, a flame retardant, and the like, if necessary.

Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

Examples 1 to 4, Comparative Examples 1 to 4
Each component shown in Table 1 below is blended in the blending ratio shown in Table 1 below, and three rolls are used to mix and disperse at room temperature to prepare a resin composition, and a diluent solvent (diluting solvent () is further added to this resin composition. A predetermined amount of the non-reactive diluent) was added to prepare the photosensitive resin compositions used in Examples 1 to 4 and Comparative Examples 1 to 4. Then, the prepared photosensitive resin composition was applied as follows to prepare a test piece.

Substrate: Substrate with through-holes with an inner diameter of φ150 μm and a depth of 70 μm Surface of the substrate (corresponding to the first main surface) Treatment: Acid treatment (5% by mass sulfuric acid aqueous solution)
After surface treatment of the substrate, using a jet dispenser (manufactured by Nordson Advantest Technology Co., Ltd., platform body Quantum Q-6800, dispense jet valve DJ-9500), Examples 1 to 4 and Comparative Examples 2 to 4 are described above. The photosensitive resin composition prepared as described above is applied one by one, and only the through holes of the substrate are filled with the photosensitive resin composition (corresponding to the first photosensitive resin composition) to completely fill the through holes. It was. At this time, in Examples 1 to 4 and Comparative Examples 3 and 4, the back surface of the substrate (corresponding to the second main surface) is separated from the surface of the coating stage by 1.6 mm by using a spacer, and the peripheral edge of the through hole is not contacted. It was in a state. On the other hand, in Comparative Example 2, the back surface of the substrate was placed directly on the surface of the coating stage, and the peripheral edge of the through hole was brought into contact with the surface of the coating stage.

Then, with respect to Examples 1 to 4 and Comparative Examples 2 to 4, the photosensitive resin composition (corresponding to the first photosensitive resin composition) prepared as described above was further applied to the surface of the substrate by using the jet dispenser. The whole was coated with a film thickness of 50 μm, one dot at a time. Then, with respect to Examples 1 to 4 and Comparative Examples 1 to 4, the photosensitive resin composition prepared as described above (second photosensitive resin composition) was placed on the first photosensitive resin composition applied to the entire surface of the substrate. (Corresponding to the resin composition) was applied to the entire surface of the substrate by screen printing. The viscosity of the photosensitive resin compositions of Examples 1 to 4 and Comparative Examples 1 to 4 during screen printing was adjusted to 15000 mPa · s.
DRY film thickness for screen printing: 20-23 μm
Pre-drying: 80 ° C, 20 minutes exposure (curing treatment): Wavelength 250-450 nm (light source: metal halide lamp), 250 mJ / cm ² (Oak, "HMW-680GW")
Development: 1 mass% sodium carbonate aqueous solution, 60 seconds, spray pressure 0.2 MPa
Post cure: 150 ° C, 30 minutes

The DRY film thickness of screen printing was measured at a portion not coated with a jet dispenser. Further, in Comparative Example 1, the back surface of the substrate was placed directly on the surface of the coating stage without coating by the jet dispenser, and only screen printing was performed with the peripheral edge of the through hole in contact with the surface of the coating stage. ..

Evaluation items (1) Viscosity (mPa · s)
Using an E-type viscometer, the viscosities of the photosensitive resin compositions of Examples 1 to 4 and Comparative Examples 1 to 4 were measured at a temperature of 25 ° C. at 50 rpm.

(2) Through-hole filling property The 100 through-holes provided in the test piece on which the cured coating film was formed were completely filled with the photosensitive resin compositions of Examples 1 to 4 and Comparative Examples 1 to 4. It was observed with an optical microscope (× 40 times), and the number of buried through-holes was measured.
◯: 100 places Δ: 99 to 80 places ×: 79 places or less

(3) Releasability to the back side of the substrate The photosensitive resin compositions of Examples 1 to 4 and Comparative Examples 1 to 4 are placed on the back side of the substrate through 100 through holes provided in the test piece on which the cured coating film is formed. It was observed with an optical microscope (× 40 times) to see if it was missing.

(4) Film thickness uniformity The cross section of the cured coating film between the wiring patterns having through holes of the test piece on which the cured coating film was formed was sealed, polished, and then observed with a microscope at N = 9, and the jet dispenser coated portion was observed. The film thickness of was measured.
◯: The difference between the maximum and minimum film thickness is less than 3 μm.
Δ: The difference between the maximum and minimum film thickness is 3 μm or more and less than 5 μm.
X: The difference between the maximum and minimum film thickness is 5 μm or more.

(5) Void The cross section of the test piece on which the cured coating film was formed was sealed, polished, and then observed with a microscope to evaluate the presence or absence of voids.

The evaluation results are shown in Table 1 below.

As shown in Table 1, the first photosensitive resin composition having a viscosity at 25 ° C. of 200 to 800 mPa · s is applied to the through holes by an inkjet method with the peripheral edges of the through holes in non-contact state. In Examples 1 to 4 in which the through holes were filled with the first photosensitive resin composition, the through holes were excellently filled and the through holes were prevented from coming off to the back side of the substrate. Further, in Examples 1 to 4, since the film thickness uniformity of the jet dispenser coated portion was excellent, the cured coating film of the second photosensitive resin composition coated by screen printing also had a film thickness uniformity. It was excellent. Further, in Examples 1 to 4, no voids were generated and the properties of the cured coating film were excellent.

Further, from the comparison between Examples 1 and 4, when diethylene glycol diethyl ether, which is a non-reactive diluent having a surface tension of 25 m N / m at 25 ° C., is used as the diluent solvent, the surface tension at 25 ° C. is 31 m N / m. The film thickness uniformity was further improved as compared with ethylene glycol acetate, which is a non-reactive diluent of m. Further, from the comparison between Example 2 and Examples 1, 3 and 4, when the first photosensitive resin composition having a viscosity at 25 ° C. of 400 to 800 mPa · s is used, the viscosity at 25 ° C. is 200 mPa · s. Compared with the first photosensitive resin composition, it was possible to more reliably prevent the resin from coming off to the back side of the substrate.

On the other hand, in Comparative Example 1 in which only screen printing was performed, Comparative Example 2 in which the peripheral edges of the through holes were in contact with each other, and Comparative Example 4 in which the viscosity at 25 ° C. was 100 mPa · s, the through hole filling property was obtained. However, it was found that the substrate was pulled out to the back side, and the film thickness was not uniform. Further, in Comparative Example 3 in which the viscosity at 25 ° C. was 2000 mPa · s, the film thickness uniformity was not obtained and voids were also generated.

The method for forming a cured coating film of the present invention prevents the photosensitive resin composition from coming out to the back side of the substrate through the through holes even if the substrate is provided with through holes, and makes the thickness of the coating film uniform. Therefore, it has high utility value in the field of insulating coating of a circuit board provided with through holes, for example.

1 First photosensitive resin composition 2 Second photosensitive resin composition 3 Substrate 4 Jet dispenser 5 Curing treatment 12 Curing coating film

Claims (9)

By the inkjet method, at least the through hole portion of the substrate is coated with the first photosensitive resin composition containing a non-reactive diluent and having a viscosity at 25 ° C. of 150 to 1500 mPa · s, and the through hole is filled. The process of forming things and
A second photosensitive resin composition containing a non-reactive diluent is applied onto the first main surface of the substrate and the surface of the filler on the first main surface side by a screen printing method, an inkjet method, or a roll coater. The process of coating to form a coating film by the method, bar coater method, spray coater method, curtain flow coater method, squeegee method, applicator method, blade coater method, knife coater method or gravure coater method .
A step of curing the coating film to form a cured coating film,
Have,
After the coating of the first photosensitive resin composition and before the coating of the second photosensitive resin composition, the curing treatment is not performed.
In the step of applying the first photosensitive resin composition, at least the peripheral edge of the through hole of the second main surface, which is the surface opposite to the first main surface of the substrate, is made non-contact. A method for forming a cured coating film. The method for forming a cured coating film according to claim 1, wherein the first photosensitive resin composition contains a non-reactive diluent having a surface tension of 30 m N / m or less at 25 ° C. The method for forming a cured coating film according to claim 2, wherein the non-reactive diluent contains diethylene glycol diethyl ether. The method for coating the second photosensitive resin composition, a screen printing method, b Rukota method, bar coater method, a spray coating method, a curtain flow coater method, a squeegee method, applicator method, a blade coating method, a knife coating method or gravure The method for forming a cured coating film according to any one of claims 1 to 3, which is a coater method. The method for forming a cured coating film according to any one of claims 1 to 4 , wherein the viscosity of the first photosensitive resin composition at 25 ° C. is 180 to 1000 mPa · s. The method for forming a cured coating film according to any one of claims 1 to 5 , wherein the viscosity of the second photosensitive resin composition at 25 ° C. is 120 to 60,000 mPa · s. The components of the first photosensitive resin composition, a method of forming the cured coating film according to the any one of the second photosensitive claims 1 to 6 component and is the same resin composition. The method for forming a cured coating film according to any one of claims 1 to 7 , wherein the curing treatment is an exposure treatment using active energy rays and / or a heat treatment. The method for forming a cured coating film according to claim 8 , wherein the exposure amount of the exposure treatment using the active energy rays having a wavelength of 240 to 420 nm is 30 to 500 mJ / cm ² .

Images