阅读说明：本技术 印制线路基材用贴附膜 (Adhesive film for printed circuit substrate ) 是由 石冈宗悟 渡边正博 于 2019-07-05 设计创作，主要内容包括：印制线路基材用贴附膜101包括电路图形遮盖层112、与电路图形遮盖层112层叠的胶粘剂层111。其中,电路图形的遮盖层112中与胶粘剂层111相反侧的面的Rku为2.5以上、3.0以下。(The adhesive film 101 for a printed wiring board base material includes a circuit pattern cover layer 112 and an adhesive layer 111 laminated with the circuit pattern cover layer 112. Wherein the surface of the masking layer 112 of the circuit pattern opposite to the adhesive layer 111 has an Rku value of 2.5 to 3.0.)

1. A printed wiring substrate-use adhesive film, characterized by comprising:

a circuit pattern mask layer,

An adhesive layer laminated with the circuit pattern-covering layer, wherein,

and the Rku of the surface of the circuit pattern masking layer opposite to the adhesive layer is 2.5 to 3.0.

2. The adhesive film for a printed wiring substrate according to claim 1, wherein:

and Rmr of 5.3% or more and 8.5% or less when the cross-sectional height of the surface of the circuit pattern-covering layer opposite to the adhesive layer is 20%.

3. A printed wiring substrate-use adhesive film, characterized by comprising:

a circuit pattern mask layer,

An adhesive layer laminated with the circuit pattern-covering layer, wherein,

the circuit pattern cover layer has a Sku value of 1.8 to 4.0 on the surface opposite to the adhesive layer.

4. The adhesive film for a printed wiring substrate according to claim 3, wherein:

the Vmc at a load area ratio of 10% for a center portion and a projected contour crest portion separated from the surface of the circuit pattern-covering layer on the side opposite to the adhesive layer and 80% for a center portion and a projected contour trough portion separated from each other is 2.0mL/m²Above, 3.0mL/m²The following.

5. An electromagnetic wave shielding film, comprising:

the adhesive film for a printed wiring substrate according to any one of claims 1 to 4;

wherein, the adhesive layer is a conductive adhesive layer.

6. The electromagnetic wave shielding film according to claim 5, characterized in that:

and a shielding layer is also arranged between the circuit pattern covering layer and the adhesive layer.

Technical Field

The present invention relates to an adhesive film for a printed wiring board base material and an electromagnetic wave shielding film.

Background

As electronic devices become more complex, the circuit patterns of the printed wiring substrate become more complex. In addition, the design of the circuit pattern has a great influence on the performance of the electronic device, and the circuit pattern becomes important information to be protected. Therefore, the following studies have been carried out: a colored film such as a cover film is attached to the surface of a printed wiring board, so that the circuit pattern of the printed wiring board cannot be directly confirmed by eyes (see, for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-185247.

Disclosure of Invention

Technical problem to be solved by the invention

However, the surface of the printed wiring substrate has a level difference due to the circuit pattern. Therefore, even when a black colored film is attached to a printed wiring board, a circuit pattern may be projected on the surface of the film due to reflection of light or the like, and sufficient covering properties may not be obtained. Therefore, a film having further improved hiding properties is required.

The invention aims to realize a sticking film with high circuit pattern covering performance.

Means for solving the problems

The invention provides a printed wiring board adhesive film according to claim 1, comprising a circuit pattern-covering layer and an adhesive layer laminated on the circuit pattern-covering layer, wherein the Rku on the surface of the circuit pattern-covering layer opposite to the adhesive layer is 2.5 to 3.0.

In the first aspect of the adhesive film for a printed wiring board, the load length ratio (Rmr) of the circuit pattern masking layer at a cross-sectional height of 20% on the side opposite to the adhesive layer can be set to 5.3% or more and 8.5% or less.

The invention provides a printed wiring board adhesive film according to claim 2, which comprises a circuit pattern masking layer and an adhesive layer laminated on the circuit pattern masking layer, wherein the Sku on the surface of the circuit pattern masking layer opposite to the adhesive layer is 1.8 to 4.0.

In the 2 nd aspect of the adhesive film for a printed wiring board, it can be designed that the substantial volume (Vmc) of the central portion when the load area ratio of the central portion separated from the projected contour crest portion of the surface opposite to the adhesive layer in the circuit pattern masking layer is 10% and the load area ratio of the central portion separated from the projected contour trough portion is 80% is 2.0mL/m²Above, 3.0mL/m²The following.

One embodiment of the electromagnetic wave shielding film of the present invention includes the adhesive film for a printed wiring substrate of the present invention, and the adhesive layer is a conductive adhesive layer.

One form of the electromagnetic wave shielding film may further include a shielding layer between the circuit pattern covering layer and the adhesive layer.

Effects of the invention

The printed circuit substrate adhesive film can improve the covering property of circuit patterns.

Drawings

FIG. 1 is a sectional view of a printed wiring board to which a film for attaching a printed wiring board according to an embodiment is attached;

FIG. 2 is a cross-sectional view of a modified example of the adhesive film for a printed wiring board base material;

FIG. 3 is a plan view of a test substrate used in examples.

Detailed Description

The printed wiring substrate adhesive film 101 of the present embodiment (hereinafter, also simply referred to as an adhesive film) includes a circuit pattern mask layer 112 (hereinafter, also simply referred to as a mask layer), and an adhesive layer 111 formed on one surface of the mask layer 112.

The adhesive film 101 of the present embodiment can be attached to a printed wiring board 102 as shown in fig. 1. The printed wiring substrate 102 includes, for example, a base layer 121 and a circuit pattern 122 provided on a surface of the base layer 121. The circuit pattern 122 is covered with, for example, an insulating adhesive layer 123 and an insulating film 124.

The base layer 121 is formed of an insulating material. The insulating material can be an insulating resin composition, ceramic, or the like. The insulating resin composition can use, for example, at least 1 selected from the following: polyimide resins, polyamide-imide resins, polyamide resins, polyether imide resins, polyester-imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide amide resins, polyether imide resins, and polyphenylene sulfide resins.

The circuit pattern 122 is formed of a conductive material. As the conductive material, a metal foil, a conductive material obtained by printing and curing a mixture of a conductive filler and a resin composition can be used, and a copper foil is preferably used from the viewpoint of cost.

The thickness of the circuit pattern 122 is not particularly limited, but is preferably 1 to 100 μm, and more preferably 1 to 50 μm. The manufacturing cost of the printed wiring board 102 can be reduced by setting the thickness of the circuit pattern to 1 μm or more. The printed wiring board 102 can be thinned by setting the thickness to 100 μm or less.

The adhesive layer 123 is formed of an insulating material. The insulating material is preferably an insulating resin composition, and for example, at least 1 selected from the following can be used: polyimide resins, polyamide-imide resins, polyamide resins, polyether imide resins, polyester-imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide amide resins, polyether imide resins, and polyphenylene sulfide resins.

The thickness of the adhesive layer 123 is not particularly limited, but is preferably 1 μm to 50 μm.

The insulating film 124 is formed of an insulating material. The insulating material is preferably an insulating resin composition, and for example, at least 1 selected from the following can be used: polyimide resins, polyamide-imide resins, polyamide resins, polyether imide resins, polyester-imide resins, polyether nitrile resins, polyether sulfone resins, polyphenylene sulfide resins, polyethylene terephthalate resins, polypropylene resins, crosslinked polyethylene resins, polyester resins, polybenzimidazole resins, polyimide amide resins, polyether imide resins, and polyphenylene sulfide resins.

The thickness of the insulating film 124 is not particularly limited, but is preferably 1 μm to 100 μm, and more preferably 10 μm to 25 μm. The manufacturing cost of the printed wiring substrate can be reduced by setting the thickness to 1 μm or more. The printed wiring substrate can be thinned by setting the thickness to 100 μm or less.

If the masking layer 112 is colored so that the attachment film 101 is opaque, the circuit pattern 122 cannot be visually confirmed directly. For example, if the circuit pattern 122 is covered with a film having a total light transmittance of preferably 20% or less, more preferably 10% or less, and still more preferably 5% or less, the circuit pattern 122 can hardly be confirmed by the eye as it is. However, due to the circuit pattern 122, the surface of the capping layer 112 may be uneven. The general circuit pattern 122 is formed of copper wires and has a height of several μm to tens of μm. Since the difference in height between the portion where the lines exist and the portion where the lines do not exist is reduced by filling the adhesive layer 123 or the like, the height of the irregularities generated on the surface of the capping layer 112 is several μm. However, even if the irregularities are minute as described above, the presence of the irregularities can be visually confirmed on the surface that easily reflects light, and the circuit pattern 122 cannot be covered.

In order to improve the hiding property, fine irregularities may be formed on the surface of the hiding layer 112 to reduce the reflection of light by the hiding layer 112. However, the present inventors have found that the hiding property of a circuit pattern and the surface roughness as general indexes in accordance with Japanese Industrial Standards (JIS) B0601: 2001, and the three-dimensional arithmetic average height (Sa) by International Standardization Organization (ISO) 25178. On the other hand, the present inventors found that, on the surface of the cover layer 112, by adding a mask according to JISB 0601: 2001, the kurtosis (Rku) and the steepness (Sku) in accordance with ISO25178 are set to values within a certain range, and the hiding property can be improved.

Specifically, the surface (surface) of the masking layer 112 opposite to the adhesive layer 111 has an Rku of 2.5 or more, preferably 2.6 or more, more preferably 2.7 or more, 3.0 or less, preferably 2.9 or less. The Sku on the surface of the masking layer 112 is 1.8 or more, preferably 1.9 or more, more preferably 2.1 or more, and 4.0 or less, preferably 3.0 or less, and more preferably 2.5 or less. By setting at least one of Rku and Sku to the above value, the masking property of the circuit pattern 122 by the adhesive film 101 can be improved.

The relative load length ratio (Rmr) when the cross-sectional height of the surface of the cap layer 112 is 20% can be preferably 5.3% or more, more preferably 5.4% or more, further preferably 5.5% or more, preferably 8.5% or less, more preferably 8.0% or less, further preferably 7.8% or less, further preferably 7.0% or less, further preferably 6.0% or less. In addition to Rku, the hiding power can be further improved by setting Rmr to the above value.

In addition, the substantial volume (Vmc) of the central portion when the load area ratio of the center portion of the surface of the masking layer 112 to the projected contour crest portions is 10% and the load area ratio of the center portion to the projected contour trough portions is 80% can be preferably set to 1.8mL/m²More preferably 2.0mL/m or more²More preferably 2.2mL/m or more²Above, preferably 3.0mL/m²The following. By setting Vmc to the above value in addition to Sku, the hiding property can be further improved.

Also, as shown in the examples, Rku and Rmr can be obtained by the method according to JISB 0601: 2001, respectively. As shown in the examples, Sku and Vmc can be determined by the method according to ISO 25178.

The capping layer 112 can be formed of a metal, a thermoplastic resin, a thermosetting resin, an active energy ray-curable resin, or the like. As the metal, any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, and the like, or an alloy containing two or more of them can be used. The thermoplastic resin is not particularly limited, and a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, an imide resin, an acrylic resin, or the like can be used. The thermosetting resin is not particularly limited, and a phenol resin, an epoxy resin, a polyurethane resin having an isocyanate group at the end, a urea resin having an isocyanate group at the end, a polyurethane urea resin having an isocyanate group at the end, a melamine resin, an alkyd resin, or the like can be used. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least 2 (meth) acryloyloxy groups in the molecule can be used. The above resins may be used alone, or 2 or more kinds may be used in combination.

The masking layer 112 having a predetermined surface texture can be formed by applying the resin to the surface of a releasable substrate having an uneven shape by embossing or the like and drying the resin. Instead of embossing, a film provided with a matte layer having irregularities on the surface thereof can be used as the releasable substrate. The matte layer can be formed by applying a resin composition containing fine particles to the surface of the film or by embossing the surface of a resin layer formed on the surface of the film.

In addition to the use of a peelable substrate having irregularities, the masking layer 112 having a certain surface texture can be formed by a method of blasting dry ice or the like on the surface of a resin layer made of the above resin, a method of pressing a mold having irregularities, or the like.

Fine particles may be added to adjust the surface properties of the capping layer 112. The fine particles to be added to the masking layer 112 are not particularly limited, and for example, resin fine particles or inorganic fine particles can be used. The resin fine particles may be acrylic resin fine particles, polyacrylonitrile fine particles, polyurethane fine particles, polyamide fine particles, polyimide fine particles, or the like. The inorganic fine particles may be calcium carbonate fine particles, calcium silicate fine particles, clay, china clay, talc, silica fine particles, glass fine particles, diatomaceous earth, mica powder, alumina fine particles, magnesium oxide fine particles, zinc oxide fine particles, barium sulfate fine particles, aluminum sulfate fine particles, calcium sulfate fine particles, magnesium carbonate fine particles, or the like. The resin fine particles and the inorganic fine particles may be used alone or in combination.

The total light transmittance of the cover layer 112 can be designed to be preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. By setting the total light transmittance to 20% or less, it is difficult to visually confirm the circuit pattern 122 directly when the adhesive film 101 is attached to the printed wiring board 102.

From the viewpoint of making it difficult to reflect light, the capping layer 112 preferably contains a black-based colorant. The black-based colorant may be a black pigment or a mixed pigment obtained by mixing a plurality of pigments in a subtractive color to form a black color. The Black pigment may be one or a combination of carbon Black, Ketjen Black (Ketjen Black), Carbon Nanotube (CNT), perylene Black, titanium Black, iron Black, aniline Black, and the like. The mixed pigment can be used by mixing, for example, red, green, blue, yellow, violet, cyan, magenta and other pigments. The amount of the black-based colorant added is preferably 0.5% by mass or more, more preferably 1% by mass or more, per 100 parts by mass of the resin, from the viewpoint of being less likely to reflect light.

The masking layer 112 may contain at least one of a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a viscosity modifier, an anti-blocking agent, and the like, as required.

The thickness of the masking layer 112 is not particularly limited, and can be appropriately set as needed, and from the viewpoint of achieving the masking property, the ease of formation, and the securing of flexibility, it is preferably 1 μm or more, more preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less.

In the present embodiment, the adhesive layer 111 can be formed of at least one of a thermoplastic resin, a thermosetting resin, an active energy ray-curable resin, and the like.

When the adhesive layer 111 contains a thermoplastic resin, examples of the thermoplastic resin include styrene resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, imide resin, and acrylic resin. The resin can be used alone in 1, also can be combined with more than 2.

When the adhesive layer 111 contains a thermosetting resin, examples of the thermosetting resin include phenol resins, epoxy resins, urethane resins, melamine resins, polyamide resins, and alkyd resins. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least 2 (meth) acryloyloxy groups in the molecule can be used. The resin can be used alone in 1, also can be combined with more than 2.

The thermosetting resin includes, for example, a 1 st resin component containing a 1 st reactive functional group and a 2 nd resin component reactive with the 1 st functional group. The 1 st functional group can be, for example, an epoxy group, an amide group, a hydroxyl group, or the like. The 2 nd functional group may be selected according to the 1 st functional group, and for example, when the 1 st functional group is an epoxy group, the 2 nd functional group may be a hydroxyl group, a carboxyl group, an epoxy group, an amino group, or the like. Specifically, for example, when the 1 st resin component is an epoxy resin, epoxy-modified polyester resin, epoxy-modified polyamide resin, epoxy-modified acrylic resin, epoxy-modified polyurethane polyurea resin, carboxyl-modified polyester resin, carboxyl-modified polyamide resin, carboxyl-modified acrylic resin, carboxyl-modified polyurethane polyurea resin, urethane-modified polyester resin, and the like can be used as the 2 nd resin component. Among them, carboxyl-modified polyester resins, carboxyl-modified polyamide resins, carboxyl-modified polyurethane polyurea resins, and urethane-modified polyester resins are preferable. When the 1 st resin component is a hydroxyl group, an epoxy-modified polyester resin, an epoxy-modified polyamide resin, an epoxy-modified acrylic resin, an epoxy-modified polyurethane polyurea resin, a carboxyl-modified polyester resin, a carboxyl-modified polyamide resin, a carboxyl-modified acrylic resin, a carboxyl-modified polyurethane polyurea resin, a urethane-modified polyester resin, or the like can be used as the 2 nd resin component. Among them, carboxyl-modified polyester resins, carboxyl-modified polyamide resins, carboxyl-modified polyurethane polyurea resins, and urethane-modified polyester resins are preferable.

The thermosetting resin may contain a curing agent that promotes a thermosetting reaction. When the thermosetting resin contains the 1 st functional group and the 2 nd functional group, the curing agent can be appropriately selected depending on the kinds of the 1 st functional group and the 2 nd functional group. When the 1 st functional group is an epoxy group and the 2 nd functional group is a hydroxyl group, an imidazole-based curing agent, a phenol-based curing agent, a cationic curing agent, or the like can be used. The curing agent can be used alone in 1, also can be combined with more than 2. Further, an antifoaming agent, an antioxidant, a viscosity adjuster, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a colorant, a flame retardant, and the like may be contained as optional components.

The thickness of the adhesive layer 111 is not particularly limited, and is preferably 1 μm to 50 μm from the viewpoint of securing adhesiveness, flexibility, and the like.

The adhesive layer 111 may have adhesiveness at room temperature (for example, 20 ℃), that is, may have adhesiveness. Since the adhesive layer 111 has adhesiveness in an environment at normal temperature, the printed wiring board adhesive film 101 can be easily attached to any position of the printed wiring board 102.

The adhesive layer 111 may be formed of a conductive adhesive layer having conductivity by adding a conductive filler to the adhesive layer 111. The adhesive layer 111 is made conductive, and the cover layer 112 is made an insulating protective layer, whereby the adhesive film 101 can be used as an electromagnetic wave shielding film. When the adhesive film 101 is used as an electromagnetic wave shielding film, the conductive adhesive layer 111 may be connected to a ground pattern provided on the printed wiring substrate 102.

The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon-based filler, or a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. The metal powder can be produced by an electrolytic method, an atomization method, a reduction method, or the like. Among them, one of silver powder, silver-coated copper powder, and copper powder is preferable.

From the viewpoint of contact between the fillers, the average particle diameter of the conductive filler is preferably 1 μm or more, more preferably 3 μm or more, preferably 50 μm or less, and more preferably 40 μm or less. The shape of the conductive filler is not particularly limited, and may be spherical, flaky, dendritic, fibrous, or the like.

The content of the conductive filler can be appropriately selected depending on the application, and is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 95% by mass or less, and more preferably 90% by mass or less of the total solid content. From the viewpoint of embeddability, it is preferably 70% by mass or less, and more preferably 60% by mass or less. In order to realize anisotropic conductivity, the content is preferably 40% by mass or less, more preferably 35% by mass or less.

As shown in fig. 2, when the adhesive film 101 is used as an electromagnetic wave shielding film, a shield layer 113 may be provided between the cover layer 112 and the adhesive layer 111. The shield layer 113 can be formed of a metal foil, a vapor deposited film, a conductive filler, or the like.

The metal foil is not particularly limited, and may be a foil made of one or an alloy including two or more of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc.

The thickness of the metal foil is not particularly limited, but is preferably 0.5 μm or more, more preferably 1.0 μm or more. When the thickness of the metal foil is 0.5 μm or more, the attenuation of a high-frequency signal can be suppressed when a high-frequency signal of 10MHz to 100GHz is transmitted to the shield printed wiring substrate. The thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, and still more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, a good elongation at break can be secured.

The vapor deposition film is not particularly limited, and can be formed by vapor deposition of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like. The vapor deposition can be performed by an electroplating method, an electroless plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a Chemical Vapor Deposition (CVD) method, a Metal Organic Chemical Vapor Deposition (MOCVD) method, or the like.

The thickness of the vapor deposited film is not particularly limited, but is preferably 0.05 μm or more, more preferably 0.1 μm or more. When the thickness of the deposited film is 0.05 μm or more, the electromagnetic wave shielding film of the substrate for shielding a printed wiring is excellent in the electromagnetic wave shielding property. The thickness of the vapor deposited film is preferably less than 0.5. mu.m, more preferably less than 0.3. mu.m. When the thickness of the deposited film is less than 0.5. mu.m, the electromagnetic wave shielding film is excellent in flexibility and the shielding layer can be prevented from being damaged by the difference in level provided on the printed wiring substrate.

When the shielding layer 113 is formed of the conductive filler, the shielding layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the masking layer 112 and drying the solvent. As the conductive filler, a metal-coated resin filler, a carbon-based filler, or a mixture of the above fillers can be used. As the metal filler, copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, or the like can be used. The metal powder can be prepared by electrolysis, atomization and reduction. Examples of the shape of the metal powder include spherical, flaky, fibrous, and dendritic shapes.

In the present embodiment, the thickness of the shield layer 113 may be appropriately selected in accordance with the desired electromagnetic shielding effect and resistance to repeated bending and seeding.

The total light transmittance of the adhesive film 101 is preferably 20% or less, more preferably 10% or less, and further preferably 5% or less. When the total light transmittance is 20% or less, it is difficult to visually confirm the circuit pattern 122 directly when the adhesive film 101 is attached to the printed wiring board 102. In order to make the total light transmittance of the adhesive film 101 20% or less, a coloring agent, a conductive filler, or the like may be added to the masking layer 112 and/or the adhesive layer 111. Further, when the shield layer 113 made of metal foil or the like is provided, the total light transmittance can be made substantially 0. The total light transmittance can be measured according to JIS K7136.

Examples

The adhesive film is further described in detail below with reference to examples. The following examples are illustrative and not intended to limit the invention.

< production of peelable substrate >

A surface of a polyethylene terephthalate film (hereinafter referred to as a PET film) having a thickness of 25 μm was sprayed with dry ice particles to form irregularities, and then a release layer made of melamine resin was provided, thereby obtaining a releasable substrate 1.

A matte layer composition containing silica particles, melamine resin and toluene was prepared, and the composition was applied to the surface of a polyethylene terephthalate film having a thickness of 25 μm using a wire bar, followed by heating and drying to obtain a releasable substrate 2 having a matte layer having a thickness of 5 μm. By changing the particle diameter and the addition amount of the silica particles, the peeled substrates 3 to 7 having different surface states were obtained in the same manner. The surface properties of the surfaces (surfaces on which masking layers are formed) of the releasable substrates 1 to 5 are summarized in Table 1.

[ Table 1]

< production of masking layer >

A masking layer composition was prepared by mixing 100 parts by mass of a bisphenol A type epoxy resin (Mitsubishi chemical, jER 1256), 0.1 part by mass of a curing agent (Mitsubishi chemical, ST 14), and 15 parts by mass of CARBON particles (Tokai CARBON, TokaBLACK # 8300/F) as a black-based coloring agent with toluene so that the solid content became 20% by mass. The composition was applied to the surface of a releasable substrate with a wire bar and dried by heating, and a masking layer having a thickness of 5 μm was formed on the surface of the releasable substrate.

< preparation of adhesive layer >

100 parts by mass of a bisphenol a type epoxy resin (jER 1256, manufactured by mitsubishi chemical corporation) and 0.1 part by mass of a curing agent (ST 14, manufactured by mitsubishi chemical corporation) were added to toluene so that the amount of solid components became 20% by mass, and the mixture was stirred and mixed to prepare an adhesive layer composition. The obtained adhesive layer composition was applied to a PET film (hereinafter referred to as a support film) whose surface was subjected to release treatment with a wire bar, and an adhesive layer having a thickness of 5 μm was formed on the surface of the support film by heating and drying.

< making of adhesive film >

The masking layer formed on the surface of the releasable substrate and the adhesive layer formed on the surface of the support film were bonded to each other, and the resultant was heated and pressed at a pressure of 5MPa by a pair of metal rolls heated to 100 ℃. The obtained adhesive film has a total light transmittance of 5% or less.

< production of base Material for evaluation >

Using a press at a temperature: 170 ℃, time: 3 minutes, pressure: the obtained adhesive film and the printed wiring board were bonded under a pressure of 2 to 3MPa, and then the peelable substrate was peeled off to prepare a base material for evaluation.

As the printed wiring substrate, a printed wiring substrate in which a circuit pattern 122 shown in fig. 3 is formed on a base layer 121 formed of a polyimide film is used. The circuit pattern 122 was formed of a copper foil having a line width of 0.1mm and a height of 12 μm. An adhesive layer having a thickness of 25 μm and a cover film (insulating film) formed of a polyimide film having a thickness of 12.5 μm are provided on the base layer 121 so as to cover the circuit pattern 122.

< evaluation of surface State >

Using a confocal microscope (manufactured by Lasertec corporation, opterlics HYBRID, objective lens 20 times) in accordance with JISB 0601: 2001 determined at any 5 of the surface. Thereafter, the tilt was corrected by data analysis software (LMeye 7), and Rku, Rmr and Ra were measured. In addition, any 5 of the surfaces were measured according to ISO 25178. After that, the tilt of the surface was corrected by data analysis software (LMeye 7), and Sku, Vmr, Sa, Sv, and Sz were measured. The cutoff wavelength of the S filter was 0.0025mm, and the cutoff wavelength of the L filter was 0.8 mm. Each numerical value is an average value of values measured at 5 points.

< evaluation of hiding Property >

The evaluation substrate was placed on a flat table, and it was evaluated whether or not the circuit pattern could be confirmed by eyes from the masking layer side at an angle of 30cm and 45 degrees from the height of the evaluation substrate in an environment where the illuminance of the surface of the shield wiring substrate was 500 lux. When the circuit pattern was not visually confirmed, the coverage was good (o), and when the circuit pattern was visually confirmed, the coverage was poor (x).

(example 1)

An adhesive film was formed from the masking layer formed on the releasable substrate 1, and a base material for evaluation was obtained. The masking layer of the base material for evaluation after removing the releasable substrate had a surface Rku of 2.6 and a surface Sku of 2.0. Cross-sectional height of 20%Rmr of (2) was 7.7%, and Vmc was 2.8mL/m, when the load area ratio separating the center portion from the projected contour ridge portions was 10% and the load area ratio separating the center portion from the projected contour valley portions was 80%². Ra, Sa, Sv and Sz are 1.8 μm, 2.3 μm, -10.2 μm and 18.3. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern cannot be confirmed by eyes, and the covering property is very good.

(example 2)

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 2 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 2.9 and a Sku of 2.1. Rmr 5.6%, Vmc 2.9mL/m². Ra, Sa, Sv and Sz are 1.8 μm, 2.5 μm, -12.9 μm and 23.6. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern cannot be confirmed by eyes, and the covering property is very good.

(example 3)

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 3 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 3.0 and a Sku of 2.3. Rmr 5.8%, Vmc 2.5mL/m². Ra, Sa, Sv and Sz are 1.0. mu.m, 2.0. mu.m, -9.8. mu.m and 18.2. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern cannot be confirmed by eyes, and the covering property is very good.

Comparative example 1

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 4 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 2.3 and a Sku of 1.8. Rmr 8.8%, Vmc 3.5mL/m². Ra, Sa, Sv and Sz are 2.0. mu.m, 2.7. mu.m, -11.5. mu.m and 18.8. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern can be visually confirmed, and the covering property is poor.

Comparative example 2

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 5 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 2.3 and a Sku of 1.8. Rmr 10.1%, Vmc 3.5mL/m². In addition, the first and second substrates are,ra, Sa, Sv and Sz are 1.7 μm, 2.7 μm, -10.9 μm and 18.4 μm, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern can be visually confirmed, and the covering property is poor.

Comparative example 3

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 6 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 2.4 and a Sku of 1.8. Rmr 9.5%, Vmc 3.2mL/m². Ra, Sa, Sv and Sz are 1.9 μm, 2.6 μm, -10.0 μm and 16.9. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern can be visually confirmed, and the covering property is poor.

Comparative example 4

An evaluation substrate was obtained in the same manner as in example 1, except that the releasable substrate 7 was used. The masking layer of the base material for evaluation after removing the releasable substrate had an Rku of 3.1 and a Sku of 4.2. Rmr 5.1%, Vmc 1.7mL/m². Ra, Sa, Sv and Sz are 0.7 μm, 1.5 μm, -11.1 μm and 16.2. mu.m, respectively. When the circuit pattern is inspected by visual inspection, the circuit pattern can be visually confirmed, and the covering property is poor.

The results of the examples and comparative examples are summarized in Table 2.

[ Table 2]

Practicality of use

The adhesive film for a printed wiring board substrate of the present invention has high circuit pattern covering properties, and is useful as an adhesive film for covering a circuit pattern, an electromagnetic wave shielding film, and the like.

Reference numerals

101 pasting film

102 printed wiring substrate

111 adhesive layer

112 cover layer

113 shield layer

121 base layer

122 circuit pattern

123 adhesive layer

124 insulating film