JP7719607B2 - Laminated structure and method for manufacturing the laminated structure - Google Patents

Description

The present invention relates to a laminated structure and a method for manufacturing a laminated structure.

Laminated structures in which metal foil layers and resin layers are laminated are used in a variety of applications, including metal-clad laminates, insulated wires, and transparent conductive films. One method for laminating a metal foil layer and a resin layer in a laminated structure involves applying a solvent-based adhesive to the resin layer, drying it, and then thermocompressing (dry laminating) the metal foil layer (see, for example, Patent Document 1). However, lamination using this method requires the resin layer to be solvent-resistant, which creates the problem of limiting the materials that can be used for the resin layer.

In a laminated structure, when a metal foil layer and a resin layer are laminated by thermocompression bonding (dry lamination), there is a problem that curling occurs due to the difference in linear expansion coefficient between the metal foil layer and the resin layer.
To address this curling problem, an adhesive that can be applied at room temperature is used, and the adhesive layer is laminated between the metal foil layer and the resin layer, thereby avoiding the thermal processing step and preventing curling due to hot lamination. Furthermore, the use of an adhesive also makes it possible to use a material that does not have solvent resistance, such as polycarbonate (PC), as the resin layer.

Japanese Patent Application Laid-Open No. 2017-226223

The laminate structure is used by processing the metal foil layer into a desired metal pattern depending on the application. In the laminate structure, a method for processing the metal foil layer into a metal pattern includes a subtractive method in which a resist layer is provided on the metal foil layer, a resist pattern is formed by a so-called photolithography method, and then the metal foil layer is processed into a metal pattern by etching.
Here, in a laminated structure that employs an adhesive that can be applied at room temperature, the adhesive generally has a low glass transition temperature, and the etching solution easily penetrates the adhesive during the etching process, which poses a problem of impairing the transparency or durability of the laminated structure.
On the other hand, a laminate structure thermocompressed with a resin layer having a low glass transition temperature has problems of blocking and double feeding because the surface of the resin layer exposed after patterning of the metal foil layer has tackiness.

In view of the above problems, the present invention aims to provide a laminated structure and a method for manufacturing such a laminated structure that suppresses curling and has excellent transparency or durability.

As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved by using an adhesive that can be applied at room temperature when laminating a resin layer and a metal foil layer, and by providing an etching-resistant layer between the metal foil layer and the adhesive layer. In other words, the present invention provides the following [1] to [10].

[1] A laminated structure comprising: a resin layer; a pressure-sensitive adhesive layer provided on the resin layer; an etching-resistant layer provided on the pressure-sensitive adhesive layer and having resistance to an etching solution; and a metal foil layer provided on the etching-resistant layer.
[2] The laminate structure according to [1], wherein the resin layer is at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cycloolefin polymer, triacetate cellulose, fluorine-based resin, polyphenyl sulfide, polyethylene, and polypropylene.
[3] The laminate structure according to [1] or [2], wherein the adhesive forming the adhesive layer is an optically transparent adhesive.
[4] The laminate structure according to any one of [1] to [3], wherein the thickness of the pressure-sensitive adhesive layer is 5 μm or more and 50 μm or less.
[5] The laminate structure according to any one of [1] to [4], wherein the etching-resistant layer composition that forms the etching-resistant layer contains a thermosetting resin.
[6] The laminate structure according to any one of [1] to [5], wherein the etching-resistant layer composition that forms the etching-resistant layer contains a thermosetting resin having a polyester structure.
[7] The laminate structure according to any one of [1] to [6], wherein the etching-resistant layer has a thickness of 1 μm or more and 10 μm or less.
[8] The laminate structure according to any one of [1] to [7], wherein the metal foil layer is at least one selected from the group consisting of copper, stainless steel, brass, silver, aluminum, nickel, and titanium.
[9] A method for manufacturing a laminated structure, comprising the steps of: forming a first laminate by placing a pressure-sensitive adhesive on a resin layer and laminating a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive; forming a second laminate by placing an etching-resistant layer composition on a metal foil layer and drying the etching-resistant layer composition to laminate an etching-resistant layer; and arranging the pressure-sensitive adhesive layer of the first laminate and the etching-resistant layer of the second laminate so as to face each other, and bonding the pressure-sensitive adhesive layer and the etching-resistant layer at room temperature.

The present invention provides a laminated structure and a method for manufacturing a laminated structure that suppresses curling and has excellent transparency or durability.

1 is a cross-sectional view showing an embodiment of a laminated structure of the present invention. 1A to 1C are cross-sectional views showing an embodiment of a manufacturing process for a laminated structure of the present invention.

(Embodiment)
[Laminated structure]
As shown in FIG. 1 , the laminated structure 1 according to the embodiment of the present invention is characterized by comprising a resin layer 10, a pressure-sensitive adhesive layer 20 provided on the resin layer 10, an etching-resistant layer 30 provided on the pressure-sensitive adhesive layer 20 and having resistance to an etching solution, and a metal foil layer 40 provided on the etching-resistant layer 30.

<Resin layer>
The resin layer 10 preferably has transparency and durability, and is excellent in optical and mechanical performance. The resin layer 10 preferably has a total light transmittance of 80% or more, more preferably 85% or more, and even more preferably 90% or more. Here, the light transmittance is a value measured in accordance with JIS K7361-1:1997 (Test method for total light transmittance of plastic transparent materials).
In the laminate structure 1 according to the embodiment of the present invention, the resin layer 10 and the etching-resistant layer 30 can be laminated with the pressure-sensitive adhesive layer 20, and therefore curling during the manufacturing process of the laminate structure 1 can be suppressed regardless of the linear expansion coefficient of the resin layer 10. However, from the viewpoint of suppressing curling when heat is applied during storage and transportation of the laminate structure 1 after manufacturing, it is preferable that the difference in linear expansion coefficient between the resin layer 10 and the metal foil layer 40 constituting the laminate structure is small. The difference in linear expansion coefficient between the resin layer 10 and the metal foil layer 40 constituting the laminate structure is preferably 65 ppm/K or less, more preferably 60 ppm/K or less, and even more preferably 55 ppm/K or less.

The resin layer 10 is not particularly limited as long as it has transparency and mechanical strength, and is preferably at least one selected from the group consisting of polycarbonate (PC), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), triacetate cellulose (TAC), fluorine-based resins (PTFE, PFA, FEP, ETFE, PCTFE, PVDF, PVF), polyphenyl sulfide (PPS), polyethylene, and polypropylene (PP). Among these, from the standpoint of transparency and mechanical strength, it is more preferable that the resin layer 10 be at least one selected from the group consisting of polycarbonate (PC), polymethyl methacrylate (PMMA), and cycloolefin polymer (COP). Among these, from the standpoint of large thermal expansion, it is more preferable that the resin layer 10 be at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cycloolefin polymer, fluorine-based resin, polyphenyl sulfide, polyethylene, and polypropylene.

The thickness of the resin layer 10 is preferably 4 μm or more and 300 μm or less, more preferably 12 μm or more and 300 μm or less, and even more preferably 25 μm or more and 300 μm or less. By keeping the thickness of the resin layer 10 within the above range, transparency and mechanical strength can be ensured.

<Adhesive Layer>
The adhesive layer 20 does not require heat treatment and can bond the resin layer 10 and the etching-resistant layer 30 by room temperature lamination. Here, room temperature means 25°C.
The pressure-sensitive adhesive layer 20 has excellent adhesion to both the resin layer 10 and the etching-resistant layer 30. Specifically, the pressure-sensitive adhesive layer 20 has such adhesion that it can adhere to both the resin layer 10 and the etching-resistant layer 30 after being attached to them.

The adhesive used to form the adhesive layer 20 is not particularly limited as long as it can be applied at room temperature, and examples thereof include acrylic adhesives, rubber adhesives, urethane adhesives, silicone adhesives, polyvinyl ether adhesives, olefin adhesives, etc. These adhesives may be used alone or in combination of two or more.
The adhesive forming the adhesive layer is preferably an optically transparent adhesive (OCA) from the viewpoint that it is preferable that the adhesive has transparency. The adhesive layer 20 formed with the optically transparent adhesive (OCA) preferably has a total light transmittance of 80% or more, more preferably 85% or more, and even more preferably 90% or more. Here, the light transmittance is a value measured in accordance with JIS K7361-1:1997 (Test method for total light transmittance of plastic-transparent materials). As the optically transparent adhesive (OCA), for example, "Panaclean PDS1" (trade name) manufactured by Panac Corporation is available.

The thickness of the adhesive layer 20 is preferably 5 μm or more and 50 μm or less, more preferably 5 μm or more and 25 μm or less, and even more preferably 5 μm or more and 15 μm or less. By keeping the thickness of the adhesive layer 20 within the above range, sufficient adhesive strength can be obtained while maintaining transparency.

<Etching-resistant layer>
The etching-resistant layer 30 is a layer having high etching resistance, i.e., a low etching rate. By providing the etching-resistant layer 30, it is possible to prevent the etching solution from penetrating into the pressure-sensitive adhesive layer 20 in the step of etching the metal foil layer 40. In addition, the etching-resistant layer is preferably tack-free from the viewpoint of workability in steps after etching.

From the viewpoint of having high etching resistance, the etching-resistant layer 30 is preferably made of a cured product of a thermosetting resin composition.
The etching-resistant layer composition that forms the etching-resistant layer 30 preferably contains a thermosetting resin. Examples of the thermosetting resin include polyester resin, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, polyurethane resin, epoxy resin, aminoalkyd resin, melamine-urea co-condensation resin, silicon resin, and polysiloxane resin.
From the viewpoint of providing high transparency, versatile application, etching resistance, and adhesion, it is preferable to use a thermosetting resin having a polyester structure as the etching-resistant layer composition for the etching-resistant layer 30 .

From the viewpoint of achieving high etching resistance and adhesion, the etching-resistant layer 30 is preferably made of a cured product of a two-component curing thermosetting resin composition containing a base agent and a curing agent.
The two-component curing resin contained in the two-component curing resin composition as the etching-resistant layer composition is not particularly limited as long as it is a resin that is cured by adding a curing agent to a main component, and a two-component curing urethane resin in which the main component is a polyol (polyhydric alcohol) and the curing agent is an isocyanate curing agent is preferred.

Examples of polyols include polycarbonate polyols, polyether polyols, polyacrylic polyols, polyurethane polyols, polyester polyols, etc. These may be used alone or in combination of two or more.
As the isocyanate curing agent, a conventionally known compound may be used as appropriate, and examples thereof include aromatic isocyanates such as 2,4-tolylene diisocyanate (TDI), xylene diisocyanate (XDI), naphthalene diisocyanate, and 4,4'-diphenylmethane diisocyanate, and polyisocyanates such as aliphatic (or alicyclic) isocyanates such as 1,6-hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), methylene diisocyanate (MDI), hydrogenated tolylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. Adducts or polymers of these various isocyanates, such as adducts of tolylene diisocyanate and tolylene diisocyanate trimer, may also be used.

The amount of curing agent used (molar ratio) is preferably 0.2 to 5.0 moles per mole of base resin, more preferably 0.5 to 3.0 moles, and even more preferably 0.8 to 2.0 moles. When the amount of curing agent used is within the above range, a good cured state is achieved, resulting in excellent adhesion, a tack-free finish, and excellent processability with no cracks or other issues occurring during bending.

The thickness of the etching-resistant layer 30 is preferably 1 μm or more and 10 μm or less.
Furthermore, the thickness of the etching-resistant layer 30 is preferably equal to or greater than the surface roughness Rz (μm) of the metal foil layer 40 measured in accordance with JIS B0601:2001, and is preferably at least twice the surface roughness Rz of the metal foil layer 40, and more preferably at least three times the surface roughness Rz of the metal foil layer 40. Furthermore, the difference obtained by subtracting the surface roughness Rz of the metal foil layer 40 from the thickness of the etching-resistant layer 30 is preferably at least 0.5 μm, more preferably at least 1.5 μm, and even more preferably at least 2.5 μm.
When the thickness of the etching-resistant layer 30 is equal to or greater than the above lower limit, it is possible to prevent the etching solution from penetrating into the pressure-sensitive adhesive layer 20. Although there is no upper limit to the thickness of the etching-resistant layer 30, reducing the thickness can contribute to making the laminated structure 1 thinner, and can reduce the amount of material used.

<Metal foil layer>
The metal foil layer 40 is used after being processed into a desired metal pattern by etching. The etching solution used in the etching process of the metal foil layer 40 may be either acidic or alkaline, and an appropriate solution can be selected that is suitable for etching the metal foil layer 40. From the viewpoints of productivity and versatility, the etching solution is preferably ferric chloride or cupric chloride.

The metal foil layer 40 is preferably at least one selected from the group consisting of copper, stainless steel, brass, silver, aluminum, nickel, and titanium. Among these, from the perspective of versatility in various applications, it is more preferable that the metal foil layer 40 be at least one selected from the group consisting of copper, stainless steel, and brass.

The thickness of the metal foil layer 40 is preferably 3 μm or more and 50 μm or less, and more preferably 3 μm or more and 35 μm or less. By keeping the thickness of the metal foil layer 40 within this range, the strength of the metal pattern to be formed can be ensured.

《Transparency》
After the step of etching the metal foil layer 40, the laminate structure 1 preferably has high transparency at the exposed portion where the metal foil layer 40 has been removed. The exposed portion of the laminate structure 1 where the metal foil layer 40 has been removed preferably has a total light transmittance of 80% or more, more preferably 85% or more, and even more preferably 90% or more. Here, the total light transmittance is a value measured in accordance with JIS K7361-1:1997 (Test method for total light transmittance of plastic-transparent materials).

《Durability》
In the laminate structure 1, it is preferable that the pressure-sensitive adhesive layer 20 has durability of adhesive strength even after undergoing the step of etching the metal foil layer 40. Regarding the durability of adhesive strength in the laminate structure 1, it is preferable that, after undergoing the step of etching the metal foil layer 40, no lifting or peeling occurs when the exposed area where the metal foil layer 40 has been removed is visually inspected.

[Laminated structure manufacturing method]
The method for manufacturing a laminated structure of the present invention includes:
a step of forming a first laminate by disposing a pressure-sensitive adhesive on a resin layer and laminating a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive;
a step of disposing an etching-resistant layer composition on the metal foil layer and drying the etching-resistant layer composition to form a second laminate having an etching-resistant layer laminated thereon;
The method includes a step of placing the pressure-sensitive adhesive layer of the first laminate and the etching-resistant layer of the second laminate so as to face each other, and bonding the pressure-sensitive adhesive layer and the etching-resistant layer together at room temperature.

The laminated structure manufacturing method according to an embodiment of the present invention will now be described further with reference to Figure 2.

In the method for manufacturing a laminated structure according to an embodiment of the present invention, first, as shown in FIG. 2( a), an adhesive is placed on a resin layer 10, and an adhesive layer 20 made of the adhesive is laminated to form a first laminate 100.
As a method for disposing the adhesive on the resin layer 10, a transfer method can be employed in which a substrate-less adhesive sheet is laminated to transfer the adhesive onto the resin layer 10, which is the transfer target.

Next, as shown in FIG. 2( b ), an etching-resistant layer composition is placed on the metal foil layer 40 , and the etching-resistant layer composition is dried to form a second laminate 110 with an etching-resistant layer 30 laminated thereon.
The method for disposing the etching-resistant layer composition on the metal foil layer 40 is not particularly limited as long as the etching-resistant layer composition is in liquid form, and known coating methods such as gravure coating, die coating, and bar coating can be used.

Next, as shown in Figure 2 (c), the adhesive layer 20 of the first laminate 100 and the etching-resistant layer 30 of the second laminate 110 are arranged facing each other, and the adhesive layer 20 and the etching-resistant layer 30 are bonded together at room temperature.
Through the above steps, the laminated structure 1 according to the embodiment of the present invention can be obtained.

According to the laminated structure of the embodiment of the present invention, when laminating the resin layer and the metal foil layer, by using an adhesive that can be bonded at room temperature, it is possible to omit the heat treatment and suppress curling caused by the heat treatment.
Furthermore, according to the laminated structure of the embodiment of the present invention, by providing an etching-resistant layer between the metal foil layer and the adhesive layer, even when an adhesive that can be applied at room temperature is used, it is possible to prevent the etching solution from penetrating into the adhesive layer, and to prevent a decrease in transparency or durability.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples.

[Measurement and Evaluation]
The laminated structures obtained in the examples and comparative examples were subjected to the following measurements and evaluations. The results are shown in Table 1.

<Measurement of etching-resistant layer thickness>
The thickness of the etching-resistant layer of the laminated structures produced in the examples and comparative examples was measured at the relevant locations using a micrometer, and calculated from the average value of the values at 10 locations.

<Curl determination>
The test pieces (100 mm x 100 mm) of the laminated structures produced in the examples and comparative examples were evaluated for curling. The evaluation of the test pieces for curling was carried out based on the following criteria.
○: The warpage at the end of the test piece is 5 mm or less. ×: The warpage at the end of the test piece is more than 5 mm.

<Transparency>
The metal foil layer of the laminate structure produced in the examples and comparative examples was etched. The etching conditions included an aqueous solution of 37% by mass of ferric chloride (manufactured by NEP Corporation) at a temperature of 50°C and immersion for 5 minutes. The laminate structure was then rinsed with ion-exchanged water and dried for 30 minutes or more. Once the surface moisture had fully evaporated, the metal foil layer was etched and exposed. The total light transmittance was measured in accordance with JIS K7361-1:1997. Measurements were taken at 10 random locations, and the average value of the 10 measured locations was used as the total light transmittance of the laminate structure. The light incident surface was the metal foil layer side.
The total light transmittance was measured using a product named "HZ-2" manufactured by Suga Test Instruments Co., Ltd.

<Durability of Pressure-Sensitive Adhesive Layer>
The etching conditions were as follows: an aqueous solution of 37% by mass of ferric chloride (manufactured by NEP Corporation) was used as the etching solution, the solution temperature was 50° C., and the substrate was immersed for 5 minutes.
The appearance was observed before and after etching, and the occurrence of lifting or peeling was used as an index of durability.
○: No lifting or peeling ×: Lifting or peeling

[Example 1]
A polycarbonate sheet (product name "Panlite 2151" manufactured by Teijin Limited) having a thickness of 300 μm and a linear expansion coefficient of 70 ppm/K was prepared as the resin layer. An optically transparent adhesive (OCA) (product name "Panaclean PDS1-10" manufactured by Panac Corporation) was placed on the resin layer by a transfer method to form a first laminate in which an adhesive layer made of the optically transparent adhesive (OCA) was laminated.
Next, a copper foil (product name "CF-T4X-SV", manufactured by Fukuda Metal Foil Powder Co., Ltd., with a thickness of 12 μm and a linear expansion coefficient of 17 ppm/K, and a measured surface roughness Rz of 1.5 μm) was prepared as the metal foil layer. An etching-resistant layer composition (1.8 parts by mass of curing agent per 100 parts by mass of main agent) containing Elitel UE9900 (product name, manufactured by Unitika Ltd.) as the main agent and Coronate HL (product name, manufactured by Tosoh Corporation) as the curing agent was applied and arranged on the metal foil layer, and the etching-resistant layer composition was dried to form a second laminate in which an etching-resistant layer was laminated.
Next, the adhesive layer of the obtained first laminate and the etching-resistant layer of the second laminate were arranged facing each other, and the adhesive layer and the etching-resistant layer were bonded together at room temperature (25°C) to obtain the laminate structure in Example 1.
The obtained laminated structure was measured and evaluated, and the results are shown in Table 1.

[Example 2]
A laminate structure of Example 2 was obtained in the same manner as in Example 1, except that an etching-resistant layer composition was used in which Elitel UE9900 (product name, manufactured by Unitika Ltd.) was used as the base agent of the etching-resistant layer composition and Duranate MFA-75B (product name, manufactured by Asahi Kasei Corporation) was used as the curing agent (1.7 parts by mass of curing agent per 100 parts by mass of base agent). The obtained laminate structure was measured and evaluated. The results are shown in Table 1.

[Examples 3 to 6]
Except for changing the thickness of the etching-resistant layer, the laminate structures of Examples 3 to 6 were obtained in the same manner as in Example 1. The obtained laminate structures were measured and evaluated. The results are shown in Table 1.

[Comparative Example 1]
A 300 μm thick polycarbonate sheet (product name "Panlite 2151" manufactured by Teijin Limited) was prepared as the resin layer. An optically transparent adhesive (OCA) (product name "Panaclean PDS1-10" manufactured by Panac Corporation) was placed on the resin layer by a transfer method, and an adhesive layer made of the optically transparent adhesive (OCA) was laminated. The adhesive layer of the obtained first laminate was bonded to a 12 μm thick copper foil (product name "CF-T4X-SV" manufactured by Fukuda Metal Foil Powder Co., Ltd., measured surface roughness Rz: 1.5 μm) as the metal foil layer at room temperature (25°C), to obtain the laminate structure of Comparative Example 1.

[Comparative Example 2]
A 12 μm thick copper foil (product name "CF-T4X-SV", manufactured by Fukuda Metal Foil Powder Co., Ltd., with a measured surface roughness Rz of 1.5 μm) was prepared as the metal foil layer. A solvent-based adhesive was dried on the metal foil layer to form a solvent-based adhesive layer. Next, a 300 μm thick polycarbonate sheet (product name "Panlite 2151", manufactured by Teijin Limited) was heated (60°C) and bonded to the solvent-based adhesive layer as the resin layer, thereby obtaining the laminate structure of Comparative Example 2.

The results in Table 1 show that the laminate structures in Examples 1 to 6 used an adhesive that can be applied at room temperature and had an etching-resistant layer between the metal foil layer and the adhesive layer, which reduced curling and provided excellent transparency and durability.

1: Laminated structure 10: Resin layer 20: Pressure-sensitive adhesive layer 30: Etching-resistant layer 40: Metal foil layer 100: First laminate 110: Second laminate

Claims (6)

A resin layer;
a pressure-sensitive adhesive layer provided on the resin layer;
an etching-resistant layer provided on the pressure-sensitive adhesive layer and having resistance to an etching solution;
a metal foil layer provided on the etching-resistant layer,
an etching-resistant layer composition for forming the etching-resistant layer, comprising a thermosetting resin having a polyester structure;
The metal foil layer is at least one selected from the group consisting of copper, stainless steel, brass, silver, aluminum, nickel, and titanium. The laminated structure according to claim 1, wherein the resin layer is at least one selected from the group consisting of polycarbonate, polymethyl methacrylate, cycloolefin polymer, triacetate cellulose, fluorine-based resin, polyphenyl sulfide, polyethylene, and polypropylene. The laminate structure according to claim 1 or 2, wherein the adhesive forming the adhesive layer is an optically transparent adhesive. The laminate structure described in any one of claims 1 to 3, wherein the thickness of the adhesive layer is 5 μm or more and 50 μm or less. 5. The laminate structure according to claim 1 , wherein the etching-resistant layer has a thickness of 1 μm or more and 10 μm or less. a step of forming a first laminate by disposing a pressure-sensitive adhesive on a resin layer and laminating a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive;
a step of disposing an etching-resistant layer composition on the metal foil layer and drying the etching-resistant layer composition to form a second laminate having an etching-resistant layer laminated thereon;
The method includes a step of placing the pressure-sensitive adhesive layer of the first laminate and the etching-resistant layer of the second laminate so as to face each other, and bonding the pressure-sensitive adhesive layer and the etching-resistant layer at room temperature,
The etching-resistant layer composition comprises a thermosetting resin having a polyester structure.