WO2023191037A1

WO2023191037A1 - Laminate cured body, printed wiring board having same, and laminate cured body manufacturing method

Info

Publication number: WO2023191037A1
Application number: PCT/JP2023/013508
Authority: WO
Inventors: 孝典中島; 尚人小山; 悠斗小田桐
Original assignee: 太陽ホールディングス株式会社
Priority date: 2022-03-31
Filing date: 2023-03-31
Publication date: 2023-10-05
Also published as: TW202402532A

Abstract

[Problem] To provide a laminate cured body, a printed wiring board having the same, and a laminate cured body manufacturing method, wherein, even when a cured body having a large film thickness is manufactured using a photocurable resin composition, excellent curing can be performed also in the bottom portion, thereby suppressing undercut formation and achieving improved adhesion to a substrate.　[Solution] Provided are: a laminate cured body for use as a resist for a printed wiring board, the laminate cured body being characterized by comprising a lower-layer cured film made of a photocurable resin composition that has been laminated on a substrate upper surface and photocured, and one or a plurality of upper-layer cured films made of a photocurable resin composition that has been laminated on the lower-layer cured film and separately photocured, the laminate cured body being used as a resist for a printed wiring board; a printed wiring board having the same; and a laminate manufacturing method.　

Description

Cured laminate, printed wiring board including the same, and method for producing the cured laminate

The present invention relates to a cured laminate used as a resist for printed wiring boards, a printed wiring board including the same, and a method for producing the cured laminate.

Generally, in the production of printed wiring boards, a photocurable resin composition is used as a resist to protect circuit patterns in the pre-process of mounting components such as LED elements on a circuit board. For example, Patent Document 1 describes applying a solder resist made of a photocurable resin composition onto a substrate, curing the solder resist with ultraviolet rays, and then developing unexposed areas of the solder resist. As a result, a circuit protection pattern is formed using the solder resist. Various components are mounted on the substrate manufactured in this way to complete a printed wiring board.

On the other hand, in recent years, in order to improve the performance of electronic devices, there has been an increasing demand for thick copper substrates that can flow large amounts of power in a small space. In order to obtain a thick copper substrate, it is necessary to make the film thickness of the cured product of the photocurable resin composition even thicker than before. Specifically, the film thickness of the cured product of the photocurable resin composition is required to be 40 μm to 500 μm.

Additionally, in order to maximize the performance of electronic devices, it is also important to improve the connection stability between conductor circuits and mounted components.

When forming a cured product with a thick film thickness using a photocurable resin composition, when exposing the resin layer formed by coating the photocurable resin composition on a substrate and drying it, the ultraviolet light reaches the bottom of the resin layer. Because the photocuring reaction at the bottom of the resin layer does not reach the full extent, the resin layer that should remain is removed in the subsequent development process, resulting in an undercut where the bottom is thinner than the surface layer. It is more likely to occur. In such a case, sufficient adhesion between the resin layer and the substrate may not be obtained. In particular, in display applications, when forming a cured product, a photocurable resin composition containing a white colorant or a black colorant that can be used as a reflective material or a light-shielding agent is used to improve reflectance or light-shielding properties. As mentioned above, the film thickness may be increased from 40 μm to 500 μm, which is greater than the conventional thickness. In such cases, in photocurable resin compositions containing these colorants, it becomes even more difficult for ultraviolet light to reach the bottom of the resin layer, making it more likely that undercuts will occur and it will be difficult to obtain sufficient adhesion. Therefore, such concerns should be eliminated in advance.

In this regard, Patent Document 1 discloses that in the exposure process, ultraviolet light is selectively diffused through an exposure mask film consisting of a mask film on which a mask pattern is drawn and a light diffusion film laminated and bonded below the mask film. A technique has been disclosed in which a black solder resist can be cured satisfactorily. However, in the method disclosed in Patent Document 1, the ultraviolet light is diffused to form an overexposed area that does not need to be exposed, so the overexposed area remains during development, resulting in the desired shape. There is a possibility that it may not be possible to obtain the desired solder resist pattern.
Further, the cured solder resist body of Patent Document 1 does not particularly contribute to improving the connection stability between the conductor circuit and the mounted component.

Japanese Patent Application Publication No. 2012-199351

In view of the above-mentioned problems of the prior art, an object of the present invention is to suppress undercut formation by curing well even at the bottom even when forming a cured body with a thick film thickness using a photocurable resin composition. It is an object of the present invention to provide a cured laminate that has improved adhesion to a substrate, a printed wiring board equipped with the same, and a method for manufacturing the cured laminate.

As a result of intensive studies, the present inventors have found that the above-mentioned object of the present invention is a cured laminate used as a resist for printed wiring boards,
The cured laminate includes a lower cured film made of a photocurable resin composition that is laminated on one of the surfaces of the printed wiring board and photocured;
one or more upper layer cured films made of a photocurable resin composition laminated on the lower layer cured film and separately photocured;
and one or more recesses extending in the circumferential direction along the joint surface of the lower layer cured film and the upper layer cured film, or the joint surface of the plurality of upper layer cured films, on the end surface of each layered and cured cured film. It has been found that the problem can be solved by a laminated cured body characterized by having the following.

The cured laminate of the present invention is preferably laminated to surround a conductor portion provided on a printed wiring board, and the recess is preferably formed along the inner circumferential surface of the cured laminate.

It is preferable that the cured laminated body of the present invention is laminated on both sides of the conductor portion laminated on the substrate so as to face each other, and the recesses are formed on the end faces facing each other.

Further, the object of the present invention is solved by a printed wiring board characterized by comprising a cured laminated body.

Furthermore, an object of the present invention is to provide a method for producing a cured laminate used as a resist for printed wiring boards, comprising:
(1) A lower layer uncured film forming step of coating and drying a photocurable resin composition on one of the surfaces of the printed wiring board;
(2) a lower layer cured film forming step of exposing and curing the lower layer uncured film;
(3) an upper layer uncured film forming step of coating the upper surface of the lower layer cured film with a photocurable resin composition that is the same as or different from the photocurable resin composition and drying;
(4) an upper layer cured film forming step of exposing and curing the upper layer uncured film;
The problem is solved by a method for producing a cured laminate, which comprises:

The manufacturing method of the present invention includes:
After the upper layer uncured film forming step and the upper layer cured film forming step one or more times, further (5) a developing step of subjecting the laminated lower layer cured film and upper layer cured film to a development treatment,
(6) a step of thermosetting the laminated lower cured film and upper cured film after development;
It is preferable to include.

The photocurable resin composition used in the production method of the present invention includes (A) carboxyl group-containing resin, (B) photopolymerization initiator, (C) epoxy resin, (D) colorant, and (E) photopolymerizable compound. It is preferable to include.

The colorant (D) used in the production method of the present invention includes a white colorant, and the amount of the white colorant is preferably 50 to 500 parts by mass based on 100 parts by mass of the carboxyl group-containing resin (A). , more preferably 100 to 450 parts by mass.

Furthermore, the colorant (D) used in the production method of the present invention includes a black colorant, and the amount of the black colorant is 1 to 50 parts by weight based on 100 parts by weight of the carboxyl group-containing resin (A). It is preferable that

Since the cured laminate of the present invention is well cured as a whole consisting of the lower cured film and the upper cured film, the occurrence of undercuts at the bottom of the cured product is suppressed, and the adhesiveness of the cured laminate to the substrate is improved. Excellent in Furthermore, the laminated cured body having recesses at the ends can improve the connection stability of parts due to the anchor effect.
Moreover, according to the manufacturing method of the present invention, a cured laminate having the above-mentioned effects can be manufactured smoothly and reliably. Further, the printed wiring board of the present invention has excellent connection stability of mounted components by applying the cured laminate of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view for explaining a printed wiring board in which cured laminated bodies are laminated according to an embodiment of the present invention. 2 is an explanatory diagram showing a state in which components are mounted on the printed wiring board of FIG. 1. FIG. 2 is a schematic top view of the printed wiring board of FIG. 1. FIG. FIG. 1 is a schematic cross-sectional view of a cured laminate according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the shape of a cured laminate according to an embodiment of the present invention. FIG. 1 is a schematic enlarged cross-sectional view of a cured laminate according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a cured laminate obtained in Comparative Example 1 (exposed only once).

The cured laminate of the present invention is used as a resist for printed wiring boards, and includes a lower cured film made of a photocurable resin composition that is laminated on either surface of the printed wiring board and photocured. , and one or more upper layer cured films made of a photocurable resin composition that is laminated on the lower layer cured film and separately photocured. The end face of each cured film stacked and cured has one or more recesses extending in the circumferential direction along the joint surface of the lower cured film and the upper cured film or the joint surfaces of a plurality of upper layer cured films. It is characterized by

In the present invention, the lower layer refers to a layer laminated in contact with the substrate, and the upper layer refers to the upper surface of the lower layer, that is, a layer laminated apart from the substrate. When a plurality of layers exist on the upper surface of a lower layer, each of the plurality of layers becomes an upper layer. The upper layer farthest from the substrate is also called the top layer, and the upper layer between the lower layer and the top layer is also called an intermediate layer.

Hereinafter, the cured laminate of the present invention will be explained using the drawings.

FIG. 1 is a schematic cross-sectional view of a printed wiring board 10 in which a cured laminate 3 of the present invention is laminated on a circuit board 1. A conductor circuit made of copper is drawn on the surface of the circuit board 1, and the cured laminate 3 surrounds and covers the periphery 5a of the conductor portion 5, which is a part of the conductor circuit.

FIG. 2 is an explanatory diagram showing a state in which components are mounted on the printed wiring board 10 of FIG. 1. FIG. 2 shows how solder 9 is adhered to the opening 7 of the cured laminated body 3 shown in FIG. 1, and thereby a component 11 such as an LED is mounted.

FIG. 3 is a schematic top view of printed wiring board 10 of FIG. In FIG. 3, a copper conductor portion 5 (hereinafter also referred to as copper 5) is drawn in a circular shape on the circuit board 1, and the laminate cured body has a peripheral edge 5a of the copper 5 (surrounded by solid lines and broken lines in the figure). area).
In addition, in FIG. 3, the application of the laminated cured body to a circular conductor part was explained, but the shape of the conductor part may be square, rectangular, elliptical, linear, etc. as long as it is applied to patterning of a circuit board. There is no particular limitation on the shape. In addition, in Fig. 3, the conductor portion is entirely surrounded by the hardened laminated body, but it is not necessary that the entire periphery of the conductor portion is surrounded by the hardened laminated body, and the connection area between the conductor portion and other circuits is not necessarily surrounded by the hardened laminated body. etc. may have a portion that is not surrounded by the laminated cured body. Further, FIG. 3 shows how the cured laminate covers a portion of the conductor portion when viewed from above.

As will be described later in connection with the manufacturing method, the cured laminate of the present invention is a cured laminate consisting of two or more cured films, and the uncured lower film made of the photocurable resin composition is exposed to light. After being cured, an uncured upper layer film made of a photocurable resin composition is formed on the resulting lower layer cured film and is further exposed to light, so that even the bottom of each layer is exposed. The irradiation light spreads and the entire coating film is cured well even when the film is thick. For this reason, when the photocured laminate cured product is developed, the occurrence of undercuts at the bottom of the cured laminate is suppressed, and a sufficient area of the bottom surface of the cured laminate is secured. The cured product is said to have excellent adhesion to the substrate.

Furthermore, when the cured laminated body of the present invention is laminated so as to surround the periphery of the conductor portion provided on the substrate, the end face thereof corresponds to the inner periphery of the joint surface of the lower cured film and the upper cured film. Preferably, the portion has a circumferentially extending recess. In the example shown in FIG. 1, the conductor portions 5 shown in two locations are both surrounded by the laminated cured body 3. A recess 3C is formed on the end surface of the cured laminate 3, extending in the circumferential direction of the cured laminate 3, along the joint surface between the upper surface of the lower cured film 3A and the lower surface of the upper cured film 3B. When the upper layer cured film has two or more layers, recesses 3C are formed at a plurality of locations corresponding to the joints between the respective cured films on the end face of the laminated cured body 3.

According to this configuration, when mounting components near or in contact with the laminated cured body 3, the solder used enters the one or more concave portions 3C, and when the solder is fixed, it is fixed to the cured body having the concave portions. An anchor effect occurs between the solder. Further, in the printed wiring board including the laminated cured body in the form of FIG. 1, the connection stability between the printed wiring board and the mounted components is improved.

FIG. 4 shows a schematic partial cross-sectional view for explaining one embodiment of the laminated cured body 3. The laminated cured body 3 is composed of a lower cured film 3A and an upper cured film 3B formed thereon. Even if the lower layer cured film 3A is cured by coating a photocurable resin composition on the circuit board 1, drying it, and exposing it to light, the lower layer cured film 3A may be obtained by manufacturing a dry film of the photocurable resin composition in advance, An uncured film may be formed on the circuit board 1 using this dry film and then cured by exposure. Similarly, the upper cured film 3B may be a dry film of the photocurable resin composition, even if it is cured by applying a photocurable resin composition to the upper surface of the lower cured film 3A, drying it, and exposing it to light. The dry film may be produced in advance, and an uncured film may be provided on the lower cured film 3A using this dry film, and the film may be cured by exposure. After the upper layer cured film 3B is exposed, it undergoes at least a development process, and more preferably, further undergoes a heat curing process, so that it has the shape shown in the partial cross-sectional view of FIG.

In this embodiment, the ends of the lower cured film 3A and the upper cured film 3B are shaped to bulge in the extending direction of the cured film. The cross-sectional shape of the bulge at the end can be approximately arcuate as shown in FIG. 4 . In FIG. 4, the end surfaces 3Aa and 3Ba of the lower cured film 3A and the upper cured film 3B are located on the outer side of the film at thickness positions 3Ad and 3Bd, which are approximately half of the respective film thicknesses 3Ab and 3Bb (3Ab1=3Ab2, 3Bb1=3Bb2). It is configured to have an arc-shaped cross section by having the largest bulge or the largest diameter toward the center. The most swollen portions of the end surfaces 3Aa, 3Ba may be above or below the thickness positions 3Ad, 3Bd. Furthermore, the periphery of the joint surface between the upper surface of the cured film 3A (corresponding to the upper end of the arcuate end 3Aa in FIG. 4) and the lower surface of the cured film 3B that is in contact with this (corresponding to the lower end of the arcuate end 3Ba in FIG. 4) A recess 3C is formed over a part or the entire circumference of the cured laminate 3 (end surface), that is, the cured laminate 3.

The cross-sectional shape of the bulging portion of the end 3Aa of the lower cured film 3A and the end 3Ba of the upper cured film 3B is a shape other than the above-mentioned approximately arc shape, for example, an angular protruding shape or an asymmetrically protruding shape. There may be. For example, it may be bulged into a trapezoidal shape as shown in FIG.

The film thicknesses 3Ab and 3Bb of the lower cured film 3A and the upper cured film 3B are not limited, but are generally 10 to 40 μm, particularly 20 to 30 μm. By setting it to 10 μm or more, halation during exposure can be suppressed, and by setting it to 40 μm or less, undercut can be suppressed and the effects of the present invention can be better obtained. Furthermore, the thicknesses of the lower cured film 3A and the upper cured film 3B may be different from each other. Moreover, the film thickness of the entire cured laminate can be selected depending on the location where the cured laminate is laminated on the printed wiring board. In the laminated cured product of the present invention, when the total film thickness is thick, for example, even if the total film thickness exceeds 40 μm, the photocuring reaction sufficiently progresses to the bottom of the resin layer, so undercuts are suppressed. can be taken as a thing. By appropriately selecting the thicknesses of the lower cured film 3A and the upper cured film 3B and the thickness of the entire cured layer 3, the position (height) of the recess 3C relative to the overall height of the cured layer 3 can be determined in various ways. can. In addition, in the present invention, the film thickness means the average film thickness.

The position of the recess 3C in the cured multilayer body 3 is outside the vicinity of the bottom surface of the cured multilayer body 3 (the bottom surface 3A _bottom of the cured film 3A), and on the top surface of the cured multilayer body 3 (the top surface 3B _top of the cured film 3B). Preferably, the location is outside the vicinity. For example, it is preferable that the recess is formed at a position that is 5 μm or more higher than the

bottom surface

3A _bottom and 5 μm or more lower than the top surface 3B _top .

FIG. 6 shows a schematic enlarged sectional view of a cured laminate according to an embodiment of the present invention. FIG. 6 shows that, as explained using FIG. 2, a laminated cured body 3 composed of a lower cured film 3A and an upper cured film 3B provided thereon is laminated on a circuit board 1. There is. In FIG. 6, as explained using FIG. 3, the laminated cured body 3 is laminated so as to surround the conductor portion 5.
In FIG. 2, the solder 9 is in the state of a solder ball that has not yet melted, but in FIG. 6, the solder 9 is shown to be in a molten state due to the heating of the reflow process and has entered the recess 3C. It is. In this state, when the temperature decreases, the solder 9 enters into the recess 3C of the cured laminate 3 and becomes fixed, so that a so-called anchor effect is obtained, which improves the bonding state between the solder 9 and the cured laminate 3. Become. As a result, the component 11 to be mounted is stably bonded onto the circuit board 1 via the solder 9, thereby improving the reliability of the electronic component obtained.

Below, an example of setting the recess formation position in the laminated structure will be explained.
As shown in FIG. 5, the laminated cured body 300 consists of a lower cured film 300A and an upper cured film 300B, and a recess 300C is formed in the joint surface of these so as to satisfy the following conditions. First, as shown in FIG. 5, from a position P ₁ that is a distance t _t lower than the upper surface 300B _top of the laminated cured body 300 to a position P _m that is a distance t _b higher than the bottom surface 300A _bottom , the position P ₁ and the position P ₁ to each position (height) P _n at every distance t _n (for example, 5 μm) (not shown; corresponds to each height indicated by the broken line below the double-headed arrow indicating the distance t _n in FIG. ) to determine. Next, the width W _n (widths W ₁ , W ₂ , W ₃ . . . in FIG. 5) of the cured laminated body 300 is measured at the position P _n . Thereafter, two widths W _n and W _n+1 (for example, W ₆ and W ₇ ) corresponding to adjacent positions (heights) are compared. The recessed portion 300C is formed such that there is at least one location where the upper width (W _upper ) is narrower than the lower width (W _lower ) (W _upper <W _lower ). In FIG. 5, since the width _W6 is narrower than the width _W7 , a recess 300C is formed between _W6 and _W7 .
In this embodiment, the upper surface 300B _top and the bottom surface 300A _bottom are both horizontal surfaces, and the widths W _n such as the widths W ₁ and W ₂ are also parallel and horizontal surfaces to the 300B _top and the bottom surface 300A _bottom , respectively. The case is given as an example. If the film surface of the laminated cured product is not smooth and the top surface 300B _top is not horizontal, determine the position P ₁ based on the point with the largest film thickness on the top surface 300B _top , and compare W _n in the same way. .
Moreover, the distances t _b and t _t are both 5 μm.

Note that the cross-sectional shape shown in FIG. 5 is formed, for example, between any two conductor portions 5 in FIG. 3. That is, between any two adjacent conductor portions 5, the two end surfaces generally have a substantially symmetrical cross-sectional shape as in the laminated cured body shown in FIG. The inclined end face is formed around the conductor portion 5 of FIG.
On the other hand, the cured laminate extends from, for example, the periphery of the conductor portion 5 in the upper right corner of FIG. In such a case, the end face on the conductor portion 5 side and the other end face do not necessarily have a symmetrical shape in cross-sectional shape. In this case, the other end face may not be determined or may have an irregular shape that cannot be used as a reference, and it is also assumed that it will be difficult to uniformly measure the width W _n . In that case, at position _Pn in FIG. 5, an arbitrary perpendicular line drawn from the bottom surface 300A _bottom toward the upper surface 300B _top of the laminated cured body 300 is used as a reference line segment, and one end of the laminated cured body 300 and the reference The position of the concave portion 300C is determined _by determining distances W _n corresponding to a plurality of positions P _n and comparing W _n in the same manner as above.

Furthermore, as explained above, the cured laminate of the present invention includes, in addition to the above-mentioned upper cured film, further upper cured films such as second and third layers that are sequentially laminated thereon. The number of cured film layers in the cured laminate is generally 2 to 10, preferably 2 or 3. Since recesses can be formed in the cured laminated body along the bonding surfaces of two adjacent layers of cured films, the number of recesses is one less than the number of cured films.

[Method for manufacturing laminated cured body]
The laminated cured product of the present invention is
(1) A lower layer uncured film forming step (step (1)) of coating and drying a photocurable resin composition on one of the surfaces of the printed wiring board;
(2) a lower layer cured film forming step (step (2)) of exposing and curing the lower uncured film;
(3) an upper layer uncured film forming step (step (3)) of applying and drying a photocurable resin composition that is the same as or different from the photocurable resin composition on the upper surface of the lower layer cured film;
(4) Manufactured by a manufacturing method including an upper layer cured film forming step (step (4)) of exposing and curing the upper layer uncured film.

Further, in the manufacturing method of the present invention, after the above-mentioned one or more uncured upper layer film forming steps and upper layer cured film forming step, (5) the laminated lower layer cured film and upper layer cured film are subjected to a development treatment. and (6) a step of thermally curing the laminated lower cured film and upper cured film after development.
Among the above, when the combination of steps (3) and (4) is performed once, a laminated cured body consisting of two layers, the lower cured film 3A and the upper cured film 3B thereon, is formed. In addition, if the combination of steps (3) and (4) is performed two or more times, a laminated cured layer consisting of a total of three or more layers of a lower cured film 3A and two or more upper layer cured films 3B sequentially formed thereon. The body is manufactured.
In the present invention, after the upper layer (top layer) is cured, it is preferable that the step (step (5)) of subjecting the laminated lower layer cured film and upper layer cured film to a development treatment is performed. In step (5), once all the cured film has been obtained, it is exposed to a developer and treated, but in some cases, prior to this, a portion of the lower layer or upper layer may be developed in advance. You may. However, after all uncured films are exposed to light to form a cured film, the unexposed areas are developed all at once, and no development is performed before this, simplifying and smoothing the processing process. It will be done.
In the present invention, it is preferable that a step (step (6)) of thermally curing the laminated lower cured film and upper cured film after development is performed. In step (6), the cured laminate of the present invention obtained after development is further heated to a temperature of about 100 to 180° C. to thermally cure (post-cure). Heat treatment improves various properties of the cured product, such as heat resistance, chemical resistance, moisture absorption resistance, adhesion, and electrical properties.
In either case, in the manufacturing method of the present invention, after the uncured film is cured, an upper uncured film is provided on top of the uncured film and is separately exposed, thereby curing both the lower layer and the upper layer. It is possible to obtain a cured laminate in which all the films are well cured.
Steps (1) to (6) will be explained in more detail.

[Step (1)]
In the method for producing a cured laminate of the present invention, in step (1), a photocurable resin composition is used to form, for example, a lower uncured film on the circuit board 1. As the photocurable resin composition, any photocurable resin composition that is commonly used in the production of solder resists can be used without particular limitation.
In step (1), the photocurable resin composition is applied to a circuit board or the like by a method such as a screen printing method, a curtain coating method, a spray coating method, or a roll coating method, and the photocurable resin composition is coated at a temperature of, for example, 70 to 90°C. By evaporating the organic solvent contained in the composition and drying it, an uncured lower film can be formed. Alternatively, a dry film of the photocurable resin composition may be produced in advance and an uncured film may be formed on the circuit board using this dry film. The uncured lower film thus obtained is dried for 10 to 30 minutes at a temperature of 60°C to 90°C using a drying device such as a hot air circulation type drying oven, and the film thickness after drying is 10 to 30°C. The uncured film is approximately 40 μm thick.

[Step (2)]
In step (2), a photomask with a predetermined pattern is placed on the upper surface of the lower uncured film obtained in step (1), and active energy rays (light intensity: 100 to 1000 mJ/cm2) are selectively passed through the photomask. ) or by direct writing with active energy ray irradiation. The photocurable resin composition of the present invention is generally of a type that hardens at exposed areas. After step (2), it is also possible to form a patterned film by developing the unexposed areas with an alkaline aqueous solution or the like, but as will be described later, it is preferable to omit the development at this stage. At this time, it is preferable to use a direct exposure machine from the viewpoint of accuracy of alignment of the pattern to be formed. Furthermore, as a light source for irradiating active energy rays, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an LED, a xenon lamp, a metal halide lamp, or the like can be used.

[Step (3)]
In step (3), an upper uncured film made of a photocurable resin composition is further formed on the upper surface of the lower cured film obtained in step (2). The photocurable resin composition used here may be the same as or different from the photocurable resin composition in step (1), and is applied to the upper surface of the lower cured film (the opposite side of the substrate 1). Alternatively, they may be formed into a dry film and then laminated. The thus obtained laminate consisting of the lower cured film and the upper uncured film is dried to form a dry coating film. Drying conditions may be the same as or different from step (1).

[Step (4)]
In step (4), the upper surface of the upper uncured film of the laminate is exposed to light in the same manner as in step (2). The exposure conditions may be the same as or different from step (2).
Thereby, a laminated cured body having two layers of cured films is obtained.
Furthermore, the laminated cured product of the present invention can have a total of three or more cured films, and in this case, step (3) and step (4) are further applied to the upper surface of the upper cured film. By carrying out this process once, it is possible to obtain a cured laminate having three cured films: a lower layer, an upper layer (intermediate layer), and an upper layer (top layer). Further, by repeating the same method, a cured laminate having four or more cured films can also be obtained. By repeating the coating and exposure steps in this manner, a cured laminate having a desired thickness can be produced.

[Step (5)]
Furthermore, in step (5), the cured laminate body obtained as described above is developed.
As the developer, a 0.5 to 5% by weight aqueous sodium carbonate solution is generally used, but other alkaline aqueous solutions can also be used. Examples of other alkaline aqueous solutions include alkaline aqueous solutions of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, and the like. The development time varies depending on the film thickness, etc., but is generally from 70 seconds to 210 seconds, for example.
In the present invention, after the exposure of the upper layer (top layer) uncured film is completed and the upper layer (top layer) cured film is formed, it is preferable to carry out batch development, but step (2) (exposure of the lower layer uncured film) After each exposure, such as after step (4) (exposure of the upper uncured film), a development step may be performed subsequently.

[Step (6)]
The cured laminate of the present invention obtained after development can be further heated to a temperature of about 100 to 180° C. for thermal curing (post-curing). In the present invention, since exposure is performed after the formation of the uncured film, a cured laminate having relatively high hardness is already obtained even before development. However, further heat treatment improves various properties of the cured product, such as heat resistance, chemical resistance, moisture absorption resistance, adhesion, and electrical properties, so it is preferable to perform step (6). In addition, since there is no change in film thickness in steps (4) to (6), the film thickness of each cured film after step (6) is the same as that of each cured film after drying in step (1) or step (3). It is the same as the film thickness.

According to the method for producing a cured laminate of the present invention, each uncured film of the photocurable resin composition is exposed to light, that is, the whole is exposed twice or more (multiple exposures). In this regard, according to the prior art, an uncured film of a photocurable resin composition having a film thickness corresponding to the entire cured laminate is irradiated with light only once from above (on the side opposite to the substrate). It hardens, and ultraviolet light etc. irradiated from the surface of the uncured film may not fully reach the entire bottom (substrate side) of the uncured film. In that case, the photoreaction rate of the cured film after exposure monotonically decreases from the top to the bottom of the cured film. As a result, the developing process results in a cured laminate having an undercut shape. On the other hand, according to the multiple exposure in the manufacturing method of the present invention, since the uncured film is sequentially exposed to the thickness that is obtained by dividing the entire cured laminate, the uncured film is exposed from above the divided uncured film. The irradiation light reaches the entire bottom part. This suppresses the occurrence of undercuts.

Furthermore, when the lower cured film provided directly on the substrate is exposed to the upper uncured film provided above (directly above or above), the lower cured film receives the irradiation light of this exposure and is further cured. There is also. Similarly, layers other than the top layer may be affected by two or more exposures, even if the amount of light is reduced. That is, the reaction rate tends to be particularly high in layers close to the substrate, and the entire cured laminate has a good photocured state. Since the entire cured laminate has a good photocured state, the cured laminate of the present invention has excellent heat resistance. Further, the cured laminated body of the present invention can be laminated on both sides of the substrate.

Examples of components of the photocurable resin composition used in the present invention are shown below.
[Photocurable resin composition]
In the present invention, as the photocurable resin composition, any composition that is generally used in the production of solder resists and that is cured by exposure to light can be used without particular limitation. One embodiment thereof includes a composition containing (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, (D) a colorant, and (E) a photopolymerizable compound. be able to.

[(A) Carboxyl group-containing resin]
The photocurable resin composition of the present invention may contain (A) a carboxyl group-containing resin. (A) The carboxyl group-containing resin can be made into an alkali-developable photosensitive resin composition by including a carboxyl group. (A) As the carboxyl group-containing resin, a photosensitive carboxyl group-containing resin which itself has one or more photosensitive unsaturated double bonds can be used, and is not limited to a specific one. (A) The carboxyl group-containing resin may be either an oligomer or a polymer.

As examples of the carboxyl group-containing resin (A), the following can be suitably used. That is,
(1) Carboxyl group-containing resin obtained by copolymerization of an unsaturated carboxylic acid and a compound having an unsaturated double bond,
(2) A photosensitive carboxyl group-containing resin obtained by reacting a carboxyl group-containing (meth)acrylic copolymer resin with a compound having an oxirane ring and an ethylenically unsaturated group in one molecule,
(3) A copolymer of a compound having one epoxy group and an unsaturated double bond in each molecule and a compound having an unsaturated double bond is reacted with an unsaturated monocarboxylic acid. A photosensitive carboxyl group-containing resin obtained by reacting a saturated or unsaturated polybasic acid anhydride with a secondary hydroxyl group,
(4) After reacting a hydroxyl group-containing polymer with a saturated or unsaturated polybasic acid anhydride, the resulting carboxylic acid is reacted with a compound having one epoxy group and one unsaturated double bond in each molecule. It is a photosensitive hydroxyl group- and carboxyl group-containing resin obtained by

Among these, (2) photosensitive carboxyl group-containing resin, (a) a carboxyl group-containing (meth)acrylic copolymer resin, and (b) an oxirane ring and an ethylenically unsaturated group in one molecule. A copolymer resin having a carboxyl group obtained by reaction with a compound having a carboxyl group is preferred.

The carboxyl group-containing (meth)acrylic copolymer resin (a) is obtained by copolymerizing a (meth)acrylic acid ester and a compound having one unsaturated group and at least one carboxyl group in one molecule. can be obtained. Examples of the (meth)acrylic ester constituting the copolymer resin (a) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate. (meth)acrylic acid alkyl esters such as meth)acrylate, hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, etc. Containing (meth)acrylic acid esters, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, isooctyloxydiethylene glycol (meth)acrylate, phenoxytriethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, Examples include glycol-modified (meth)acrylates such as methoxypolyethylene glycol (meth)acrylate. These may be used alone or in combination of two or more. Note that in this specification, (meth)acrylate is a term that collectively refers to acrylate and methacrylate, and the same applies to other similar expressions.

In addition, examples of compounds having one unsaturated group and at least one carboxyl group in one molecule include acrylic acid, methacrylic acid, and modified unsaturated monocarboxylic acids in which the chain between the unsaturated group and the carboxylic acid is extended. , for example, β-carboxyethyl (meth)acrylate, 2-acryloyloxyethylsuccinic acid, 2-acryloyloxyethylhexahydrophthalic acid, unsaturated monocarboxylic acid having an ester bond by lactone modification, modified unsaturated having an ether bond, etc. Examples include monocarboxylic acids and those containing two or more carboxyl groups in the molecule, such as maleic acid. These may be used alone or in combination of two or more.

(b) The compound having an oxirane ring and an ethylenically unsaturated group in one molecule may be any compound having an ethylenically unsaturated group and an oxirane ring in one molecule, such as glycidyl (meth)acrylate, α -Methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 3,4-epoxycyclohexylethyl (meth)acrylate, 3,4-epoxycyclohexylbutyl (meth)acrylate, 3,4-epoxycyclohexyl Examples include methylaminoacrylate. Among them, 3,4-epoxycyclohexylmethyl (meth)acrylate is preferred. These (b) compounds having an oxirane ring and an ethylenically unsaturated group in one molecule may be used alone or in combination of two or more.
The amount of carboxyl group-containing resin (A) of the present invention is preferably 10 to 60% by mass, more preferably 15 to 55% by mass in terms of solid content of the photocurable resin composition of the present invention.

[(B) Photopolymerization initiator]
In the photocurable resin composition of the present invention, any known photopolymerization initiator can be used as a photopolymerization initiator or a photoradical generator. Examples of the photopolymerization initiator (B) used in the present invention include benzoin and benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenyl Acetophenones such as acetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone; 2-methyl-1-[4-(methylthio)phenyl]- 2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl Aminoalkylphenones such as ]-1-[4-(4-morpholinyl)phenyl]-1-butanone; Anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 1-chloroanthraquinone ; Thioxanthone such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone; Ketals such as acetophenone dimethyl ketal, benzyl dimethyl ketal; Benzophenones such as benzophenone; or Xanthone; (2,6-dimethoxybenzoyl)-2,4,4-pentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phosphine oxides such as ethyl-2,4,6-trimethylbenzoylphenylphosphinate; various peroxides, titanocene-based initiators, etc., and these include N,N-dimethylaminobenzoic acid ethyl ester , N,N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, triethanolamine, and other tertiary amines. These photopolymerization initiators can be used alone or in combination of two or more.
The amount of the photopolymerization initiator (B) of the present invention is preferably 0.01 to 30 parts by weight, more preferably 0.5 to 15 parts by weight, based on 100 parts by weight of the carboxyl group-containing resin (A). range.

[(C) Epoxy resin]
The photocurable resin composition of the present invention may contain (C) an epoxy resin in order to impart heat resistance.
(C) As the epoxy resin, various known and commonly used epoxy resins such as bisphenol S type epoxy resin, diglycidyl phthalate resin, triglycidyl isocyanurate (for example, TEPIC-H manufactured by Nissan Chemical Co., Ltd. (S-triazine ring skeleton surface β-form, which has a structure in which three epoxy groups are bonded in the same direction), and TEPIC (β-form, in which one epoxy group on the S-triazine ring skeleton surface is different from the other two epoxy groups) Epoxy resins that are poorly soluble in diluents, such as heterocyclic epoxy resins (mixtures with α-isomers that have a directional bond structure), bixylenol-type epoxy resins, biphenol-type epoxy resins, and tetraglycidyl xylenoylethane resins. Resins, bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, bisphenol F type resins, brominated bisphenol A type epoxy resins, phenol novolac type or cresol novolac type epoxy resins, alicyclic epoxy resins, bisphenol A novolacs. Soluble in diluents such as type epoxy resins, chelate type epoxy resins, glyoxal type epoxy resins, amino group-containing epoxy resins, rubber modified epoxy resins, dicyclopentadiene phenolic type epoxy resins, silicone modified epoxy resins, and ε-caprolactone modified epoxy resins. Examples include epoxy resins. These epoxy resins can be used alone or in combination of two or more.
The blending amount of the epoxy resin (C) of the present invention is preferably 0.3 to 3.0 equivalents, more preferably 0.5 to 2.0 equivalents per equivalent of carboxyl group in the carboxyl group-containing resin (A). Equivalent range.

[(D) Colorant]
The photocurable resin composition of the present invention may contain (D) a colorant in order to form a cured laminate that reflects the color of the colorant itself.
As the coloring agent (D) used in the photocurable resin composition of the present invention, conventionally known pigments or dyes such as white, black, green, blue, yellow, red, and purple may be used alone or depending on the desired use. Two or more types can be used in combination.

The white colorant is preferably a white pigment, and specific examples thereof include titanium oxide, zinc oxide, potassium titanate, zirconium oxide, antimony oxide, white lead, zinc sulfide, lead titanate, and the like. Among white pigments, it is preferable to use titanium oxide because it has a high effect of suppressing discoloration due to heat. As the titanium oxide, it is particularly preferable to use rutile type titanium oxide. Anatase titanium oxide is often used because it has higher whiteness than rutile titanium oxide. However, since anatase titanium oxide has photocatalytic activity, it may cause discoloration of the resin in the solder resist composition. On the other hand, although rutile type titanium oxide has slightly inferior whiteness compared to anatase type titanium oxide, it has almost no photoactivity, so it is possible to obtain a stable solder resist film. As the rutile-type titanium oxide, known rutile-type titanium oxides can be used. Specifically, TR-600, TR-700, TR-750, TR-840 manufactured by Fuji Titanium Industries Co., Ltd., R-550, R-580, R-630, R-820 manufactured by Ishihara Sangyo Co., Ltd. CR-50, CR-60, CR-90, KR-270, KR-310, KR-380 manufactured by Titanium Kogyo Co., Ltd., etc. can be used. White pigments can be used as a single type or as a mixture of multiple types.
Furthermore, in order to make the photocurable resin composition white after curing, it is also possible to add a pigment other than white, such as a blue pigment, to the white pigment.

Further, as the black coloring agent, black pigments are preferable, and specific examples thereof include carbon black, lamp black, bone black, graphite, iron black, copper chromium black, copper iron manganese black, cobalt iron chromium black, Examples include cobalt oxide such as tricobalt tetraoxide, ruthenium oxide, and the like.
Further, specific examples of the purple pigment include cobalt violet, manganese violet, quinacridone violet, dioxazine violet, and the like.

Specific examples of green pigments include chrome green, cobalt green, chromium oxide, phthalocyanine green, brominated green, cobalt chrome green, titanium/nickel/cobalt/zinc green, and the like. Specific examples of blue pigments include ultramarine blue, phthalocyanine blue, metal-free phthalocyanine blue, indanthrene blue, and cobalt blue.

Specific examples of yellow pigments include yellow lead, yellow iron oxide, titanium yellow, loess, antimony yellow, barium yellow, monoazo pigments, disazo pigments, polyazo pigments, isoindolinone pigments, threne pigments, metal complex pigments, and quinophthalone pigments. Examples include pigments.

Specific examples of red pigments include chrome vermilion, molybdenum red, red red, red radish, lake red 4R, carmine FB, dinitroaniline orange, pyrazolone orange, pyrazolone red, perinone orange, permanent red 2B, lake red R, bon maroon light, Examples include Bordeaux 10B, Bon Maroon Medium, Thioindigo Bordeaux, Bon Maroon L, Perylene Vermilion, Perylene Scarlet, Perylene Maroon, Benzuidazolone Orange, and the like.

When the photocurable resin composition of the present invention contains a white pigment as the colorant (D), the tendency to yellow after reflow is reduced by using the cured laminate produced by the production method of the present invention. Ru. The reason for this is as follows.
Generally, a cured laminate of a photocurable resin composition used as a solder resist etc. shows a tendency to yellow when exposed to high temperatures of, for example, 260° C. or higher during component mounting. However, according to the manufacturing method of the present invention, each uncured film is sequentially and individually exposed to light in steps (2) and (4), etc., so that the ultraviolet light sufficiently reaches each layer, resulting in good photocuring. Since it has a state, it has excellent heat resistance. When components are mounted in this state, the amount of unreacted photocuring components in each cured film, especially the underlying film, is reduced, so the degree of yellowing is reduced. Such suppression of yellowing is an extremely significant property, especially for white cured laminates that are susceptible to yellowing. In other words, if yellowing occurs in a cured laminate manufactured from a white or light-colored photocurable resin composition, it will have a greater effect on the properties than a cured laminate made of a black or dark color. When produced by the method of the present invention, since the yellowing tendency is reduced, the yellowing that occurs noticeably in white or light colors, especially white, is extremely well suppressed.

Further, even when the photocurable resin composition of the present invention contains a white pigment or a black pigment as the colorant (D), by using the cured laminate produced by the production method of the present invention, resolution, Adhesion is improved. The reason for this is as follows.
In general, a black resist containing a black pigment has the property that irradiated light during exposure is easily absorbed by the resist and difficult to transmit. Furthermore, a white resist containing a white pigment has the property that the irradiated light during exposure is easily reflected by the resist and difficult to transmit. In other words, light irradiated from the top of a black resist or white resist is absorbed or reflected within the layer before reaching the deep part of the resist, and in places where the irradiated light does not reach sufficiently, such as deep parts of the resist, photocuring occurs. The photoreaction of the resin composition may not proceed sufficiently, which may affect the undercut generation rate and resolution. However, according to the production method of the present invention, since the photocurable resin composition is subjected to two or more exposures such as steps (2) and (4) above, the entire photocurable resin composition is exposed to light more than in the case of one exposure. The reaction progresses reliably. As a result, resolution is improved and undercuts are suppressed. In other words, the black resist or white resist manufactured through the two-time exposure process of the present invention has improved adhesion to the circuit board and is difficult to peel off.
In the case of a white colorant, the blending amount of the colorant (D) of the present invention is preferably 50 to 500 parts by mass, more preferably 100 to 450 parts by mass, based on 100 parts by mass of the carboxyl group-containing resin (A). be.
In the case of a black colorant, the blending amount of the colorant (D) of the present invention is preferably 1 to 50 parts by weight based on 100 parts by weight of the carboxyl group-containing resin (A).

[(E) Photopolymerizable compound]
The photocurable resin composition of the present invention has an ethylenically unsaturated group and is photocured by irradiation with active energy rays to make the irradiated part of the photocurable resin composition insolubilized in an aqueous alkaline solution or to prevent insolubilization. (E) A photopolymerizable compound may be included. Examples of the photopolymerizable compound (E) used in the present invention include hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxybutyl acrylate; ethylene glycol, methoxytetraethylene glycol, polyethylene glycol, propylene glycol, etc. Glycol mono- or diacrylates; acrylamides such as N,N-dimethylacrylamide and N-methylolacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate; hexanediol, trimethylolpropane, pentaerythritol, di Polyhydric alcohols such as pentaerythritol, dipentaerythritol hexaacrylate (DHPA), tris-hydroxyethyl isocyanurate, or polyhydric acrylates of their ethylene oxide or propylene oxide adducts; phenoxy acrylate, bisphenol A diacrylate, and these acrylates such as ethylene oxide or propylene oxide adducts of phenols; acrylates of glycidyl ethers such as glycerin diglycidyl ether and trimethylolpropane triglycidyl ether; melamine acrylate; and/or methacrylates corresponding to the above acrylates. Examples thereof include, but are not limited to, and any known and commonly used photopolymerizable compounds may be used.
The amount of the photopolymerizable compound (E) of the present invention is preferably 0.01 to 40 parts by weight, more preferably 0.5 to 30 parts by weight, based on 100 parts by weight of the carboxyl group-containing resin (A). It is.

[Organic solvent]
The photocurable resin composition of the present invention can use an organic solvent for preparing the composition or adjusting the viscosity for coating on a substrate or carrier film. As the organic solvent, known organic solvents can be used. Moreover, one type of organic solvent may be used alone, or two or more types may be used in combination. Such organic solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, carbitol acetate, Glycol ethers such as propylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, and triethylene glycol monoethyl ether; ethyl acetate, butyl acetate, cellosolve acetate, diethylene glycol monoethyl ether acetate, and esters of the above glycol ethers Alcohols such as ethanol, propanol, ethylene glycol, and propylene glycol; Aliphatic hydrocarbons such as octane and decane; Petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha, etc. can be used.

Furthermore, a curing catalyst, a curing accelerator, a thermal polymerization inhibitor, a thickener, an antifoaming agent, a leveling agent, a coupling agent, a flame retardant aid, etc. can be used as necessary.

The photocurable resin composition of the present invention can be laminated by coating it on a substrate in a liquid or paste form and drying it.

Hereinafter, the present invention will be explained with reference to Examples, but the present invention is not limited thereto. All "parts" and "%" described below are based on mass unless otherwise specified.　

[Production example of photocurable resin composition]
[Production of composition 1 and composition 2]
A photocurable resin composition was prepared by blending the components shown in Table 1 below in the amounts shown in the table, stirring and dispersing the mixture using three rolls. The numbers in Table 1 indicate parts by mass in terms of varnish containing solvent.

Details of the components in Table 1 are as follows.
(A) Carboxyl group-containing resin Cyclomer P (ACA) Z250: Acrylic oligomer manufactured by Daicel (average molecular weight (Mw): 22000) Solid content concentration 53% by mass (solvent: dipropylene glycol monomethyl ether)
(B) Photoinitiator Omnirad 819: Manufactured by IGM Resins, bis(2,4,6-methylbenzoyl)phenylphosphine oxide (B) Photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (C) Epoxy resin jER-828: manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 184-194, liquid at room temperature (25°C), molecular weight (Mw): approximately 370
(D) Colorant CR-90: Manufactured by Ishihara Sangyo Co., Ltd., rutile type titanium oxide (D) Colorant MA-100: Manufactured by Mitsubishi Chemical Corporation, carbon black (E) Photopolymerizable compound DPHA: Dipentaerythritol hexaacrylate , Daicel Allnex Corporation Curing catalyst DICY: dicyandiamide Curing catalyst melamine

[Examples 1 to 4, Comparative Examples 1 to 4]
Using Composition 1 and Composition 2 produced as described above, a cured laminate consisting of one, two, or three layers of cured films was created.
The method for producing a cured laminate and the evaluation of the cured laminate of the present invention will be explained below. In Table 2, "-" in the treatment step means that the corresponding treatment was not performed, "-" indicates that the corresponding evaluation was not performed because Composition 2, which does not contain a white colorant, was not required to function as a reflective material.

<Creation of evaluation board>
<1. Formation of lower layer>
As described in Table 2, in Example 1, the composition was applied to a circuit board pretreated by pickling and buffing (two series of Scotch brite SF (equivalent to #600) and UEF (equivalent to #1000)). 1 was printed on the entire surface by #100 screen printing so that the film thickness after each drying was 25 μm. The uncured film of Composition 1 thus obtained was dried at 80° C. for 15 minutes using a hot air circulation drying oven (DF610 manufactured by Yamato Scientific Co., Ltd.) (precure). Then, using a direct exposure machine (manufactured by Oak Seisakusho Co., Ltd., DiIMPACT Mms60) using a metal halide as a light source, a line pattern with a width of 30 to 300 μm (in 30 μm increments) was formed on the dried uncured film. Exposure was carried out at a cumulative exposure amount of 600 mJ/cm2. Similar treatments were carried out in Examples 2 to 4 and Comparative Examples 1 to 3, but Composition 2 was used in Example 4 and Comparative Example 3. Further, in Comparative Examples 1 to 3, no exposure was performed. Thereafter, in Example 2, development was carried out for 70 seconds using a 1% by mass aqueous sodium carbonate solution at a liquid temperature of 30° C. and a spray pressure of 0.2 MPa. In Comparative Example 4, printing, drying, and exposure were performed using the same equipment and procedures as in Example 1, but the entire surface was printed using #60 screen printing so that the film thickness after drying was 50 μm. The drying time was 30 minutes, and the cumulative exposure amount was 1200 mJ/cm2.
In Table 2, the fact that the corresponding treatment step was performed is indicated by a symbol of ○ or ●.

<2. Formation of upper layer (middle layer)>
As described in Table 2, an upper layer (intermediate layer) was formed on the lower layer of Example 3 by the same operation as in Example 1, which described the formation of the lower layer, except that pickling and buffing were not performed. Formed. In Examples other than Example 3 and Comparative Examples, a cured laminate having the upper layer (top layer) in Table 2 was formed directly on the lower layer without providing an upper layer (intermediate layer).

<3. Formation of upper layer (top layer)>
Furthermore, as described in Table 2, an upper layer (top layer) was formed on the upper surface of the lower layer of Examples 1, 2, 4, and Comparative Examples 1 to 3, and on the upper surface of the upper layer (intermediate layer) of Example 3. . In each Example and Comparative Example, the same composition as the composition was used to form the lower layer, and the entire surface was printed by #100 screen printing so that the film thickness after drying was 25 μm. It was dried at 80° C. for 30 minutes using DF610 (manufactured by Kagaku Co., Ltd.) (precure). A direct exposure machine (manufactured by Oak Seisakusho Co., Ltd., DiIMPACT Mms60) using a metal halide as a light source was used to form a line pattern with a width of 30 to 300 μm (in 30 μm increments) on the dried uncured film. 1 to 4 and Comparative Examples 1 and 3, exposure was performed at an integrated exposure amount of 600 mJ/cm 2 , and Comparative Example 2 was exposed at an integrated exposure amount of 1200 mJ/cm 2 . Thereafter, Example 3 was developed for 210 seconds, and other Examples and Comparative Examples were developed for 140 seconds using a 1% by mass aqueous sodium carbonate solution at a liquid temperature of 30° C. and a spray pressure of 0.2 MPa. In Comparative Example 4, no upper layer was provided on the lower layer, and the cured product consisted of only one lower layer.

<4. Post cure＞
The cured laminated body subjected to the above treatment was post-cured by heating at 150° C. for 60 minutes in a thermal circulation box furnace. As a result, evaluation boards as the cured laminates of Examples 1 to 4 according to the present invention and the cured laminates of Comparative Examples 1 to 4 were obtained. Note that since there is no change in film thickness between exposure and post-curing, the film thickness of the cured laminate after post-curing is the same as after drying (dry state).

<Evaluation>
The following evaluation tests were conducted using each of the above evaluation boards. The results are listed in Table 2.

<1. Evaluation of resolution>
The remaining minimum line width was evaluated on each evaluation board before post-curing in <Creation of Evaluation Board> above.

<2. Peeling of evaluation board after gold plating>
The surface of the evaluation board was pretreated with acidic degreasing, soft etching, and sulfuric acid treatment, and then plated with a thickness of 3 μm of nickel and 0.03 μm of gold using an electroless nickel plating bath and an electroless gold plating bath. The gold plating process was carried out under conditions such that .
Thereafter, the gold-plated evaluation board was subjected to a tape peel test in accordance with JIS K 5600-5-6, and the minimum line width remaining on the evaluation board was evaluated.

<3. Discoloration resistance evaluation>
A substrate for discoloration resistance evaluation was created according to the same process as described above in <Creation of evaluation board>, except that instead of exposing the entire surface of the dried uncured film to light to form a line pattern. .

Using a reflow device (NIS-20-82C manufactured by Atec Techtron Co., Ltd.), the substrate for discoloration resistance evaluation was repeatedly subjected to reflow treatment five times at a maximum temperature of 285°C.
Before and after the reflow treatment, the surface of the cured film on the substrate for discoloration resistance evaluation was measured in the L*a*b* color system using a Konica Minolta spectrophotometer CM-2600d in accordance with JIS Z8781. Measure the L* value, a* value, and b* value, and use equation (1) based on the amount of change (ΔL, Δa, Δb) in the L* value, a* value, and b* value by comparing before and after reflow treatment. The ΔE calculated in was evaluated based on the following criteria.

◎: 1.5 or less 〇: More than 1.5, 2.0 or less △: More than 2.0, 2.5 or less ×: More than 2.5

<Solder ball joint evaluation>
In the above <Creation of evaluation board>, the copper circuit was exposed at the via opening by following the same process except that instead of exposing to light to form a line pattern, the via opening diameter was exposed to 500 μm. A board for bond evaluation was created.
Solder balls were formed in the via openings of each bonding evaluation substrate. The solder balls were formed by using a eutectic solder with Sn/Pb=63/37 and performing reflow treatment under the conditions of 150° C. (90 seconds) + 220° C. (10 seconds) using a reflow oven.

Next, using a universal bond tester "Series 4000" manufactured by Daiji Corporation, a heating bump pull test was conducted in the following manner.
First, the tensile probe of the bond tester is heated with a heater, and when the temperature of the tip of the tensile probe reaches 270° C., the tip of the tensile probe is vertically inserted into the center of the solder ball. Thereafter, the solder ball and the tensile probe were fixed together by cooling the inserted state until the temperature of the tip of the tensile probe reached 40°C. Next, the tensile probe was vertically pulled up at a speed of 300 μm/sec, and the strength required for the solder ball to peel off from the bonding surface (interfacial peeling) (bonding strength (N)) was determined as the bonding strength.
Evaluation was made based on the criteria below the measured bonding strength.

◎: Bonding strength is 8.5N or more 〇: Bonding strength is 7.5N or more, less than 8.5N △: Bonding strength is 6.0N or more, less than 7.5N ×: Bonding strength is less than 6.0N

FIG. 7 shows a cross-sectional view of the laminate obtained in Comparative Example 1.
In Comparative Example 1, the lower layer was printed and dried, and without exposure, the upper layer was provided on the dried lower layer, and then exposed. As a result, it was observed that significant undercutting occurred in the obtained laminate. FIG. 7 shows a schematic cross-sectional view of the cured laminated body of Comparative Example 1.

As above, the invention made by the present inventors has been specifically explained based on the embodiments, but the present invention is not limited to the above embodiments, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

1 Circuit board 3 Laminated cured body 3A Lower cured film 3Aa End face 3B of lower cured film Upper cured film 3Ba End face 3C of upper cured film Recessed part of cured laminated body 5 Conductor portion 10 Printed wiring board

Claims

A cured laminate used as a resist for a printed wiring board, wherein the cured laminate has a cured lower layer made of a photocurable resin composition that is laminated on either one of the surfaces of the printed wiring board and photocured. a membrane;
one or more upper layer cured films made of a photocurable resin composition laminated on the lower layer cured film and separately photocured;
Equipped with
One or more recesses extending in the circumferential direction along the joint surface of the lower layer cured film and the upper layer cured film, or the joint surface of the plurality of upper layer cured films, on the end face of each of the laminated and cured cured films. A laminated cured body characterized by having the following.
The cured laminate according to claim 1, wherein the cured laminate is laminated to surround a conductor portion provided on a printed wiring board, and the recess is formed along an inner circumferential surface of the cured laminate. .
The cured laminate according to claim 1, wherein the cured laminate is laminated on opposite sides of a conductor portion provided on a printed wiring board, and the recesses are formed on end faces facing each other.
A printed wiring board comprising the cured laminate according to any one of claims 1 to 3.
A method for producing a cured laminate used as a resist for printed wiring boards, the method comprising:
(1) A lower layer uncured film forming step of coating and drying a photocurable resin composition on one of the surfaces of the printed wiring board;
(2) a lower cured film forming step of exposing and curing the lower uncured film;
(3) an upper layer uncured film forming step of coating and drying a photocurable resin composition that is the same as or different from the photocurable resin composition on the upper surface of the lower layer cured film;
(4) an upper layer cured film forming step of exposing and curing the upper layer uncured film;
The method for producing a cured laminate according to any one of claims 1 to 3, comprising:
After the upper layer uncured film forming step and the upper layer cured film forming step one or more times, further (5) a developing step of subjecting the laminated lower layer cured film and upper layer cured film to a development treatment;
(6) a step of thermosetting the laminated lower cured film and upper cured film after development;
The method for producing a cured laminate according to claim 5, comprising:
Claim 5, wherein the photocurable resin composition contains (A) a carboxyl group-containing resin, (B) a photopolymerization initiator, (C) an epoxy resin, (D) a colorant, and (E) a photopolymerizable compound. A method for producing a cured laminate according to .
6. The colorant (D) includes a white colorant, and the amount thereof is 50 to 500 parts by mass based on 100 parts by mass of the carboxyl group-containing resin (A). A method for producing the above-described cured laminate.
According to claim 5, the colorant (D) includes a black colorant, and the amount thereof is 1 to 50 parts by mass based on 100 parts by mass of the carboxyl group-containing resin (A). A method for producing the above-described cured laminate.