Method for manufacturing conductive coating composites

Abstract

To provide a method for manufacturing a conductive coating film composite body which can sufficiently obtain a color difference caused by providing an overcoat layer while suppressing increase in specific resistance of a conductive film as much as possible.SOLUTION: A method for manufacturing a conductive coating film composite body coats a coating composition containing a binder resin and a solvent onto a conductive film containing a conductive filler, a binder resin, and a dye, brings a coating film in an undried state into contact with at least a part of the surface of the conductive film and laminating the coating film thereon, thereby migrates at least a part of the dye contained in the conductive film to the coating film, then dries the coating film, and forms an overcoat layer containing the dye on the conductive film.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a conductive film composite.

Background Art

[0002] Conductive compositions capable of forming circuits by printing or dispensing are increasingly being used for forming heating elements, antenna wires, etc. (for example, Patent Document 1). In a conductive film formed from a conventional conductive composition, in order to ensure a sufficient resistance value, silver powder having a low resistance value may be used as the main material as a conductive filler. In this case, the color of the formed conductive film becomes silver-white or gray. As they are, there has been an increasing demand to color the conductive film because of reasons such as aesthetics and being too conspicuous.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a method of coloring on a conductive film, it is conceivable to form an overcoat layer in which a colorant is previously blended on the conductive film. However, when the conductive film is formed on, for example, transparent glass or a film as a circuit and transparency as a whole is to be ensured, the coloring of the overcoat layer may be obstructive. If an overcoat layer colored only directly above the circuit of the conductive film can be formed, it will not be obstructive, but the technical difficulty is high. Also, as proposed in Patent Document 1, when a coloring pigment is blended in a conductive composition, if it is blended sufficiently so that the coloring can be visually discriminated, the conductivity of the conductive film will be significantly deteriorated. Furthermore, because the exposed surface of the conductive film has fine irregularities, light is scattered by these irregularities, making the overall surface appear whitish. For this reason, even when a coloring agent is added to the conductive film, it has been difficult to color the conductive film itself with the desired color.

[0005] The present invention provides a method for manufacturing a conductive coating composite that minimizes the increase in resistivity of the conductive film while enabling sufficient color difference due to the provision of an overcoat layer. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A method for manufacturing a conductive coating composite, comprising: applying a coating composition containing a binder resin and a solvent onto a conductive film containing a conductive filler, a binder resin and a dye; laminating the undried coating by bringing it into contact with at least a portion of the surface of the conductive film, thereby transferring at least a portion of the dye contained in the conductive film to the coating; and then drying the coating to form an overcoat layer containing the dye on the conductive film. [2] The method for producing a conductive coating composite according to [1], wherein, in the conductive film before applying the coating composition, the content ratio of the conductive filler to the binder resin is, on a mass basis, (conductive filler / binder resin) = (98~60 / 2~40). [3] The method for producing a conductive coating composite according to [1] or [2], wherein, in the conductive film before applying the coating composition, the content of the dye is 0.1 to 15 parts by mass per 100 parts by mass of the total of the conductive filler and the binder resin. [4] The method for producing a conductive coating composite according to any one of [1] to [3], wherein the properties of the solvent are such that the soluble mass of the dye per 100 g of the solvent is 0.10 g or more. [Effects of the Invention]

[0007] According to the present invention, it is possible to manufacture a conductive coating composite that has sufficient color difference due to the provision of an overcoat layer while minimizing the increase in resistivity of the conductive film. [Modes for carrying out the invention]

[0008] In this specification and in the claims, "(meth)acryloyl" refers to both methacryloyl and acryloyl, "(meth)acrylate" refers to both methacrylate and acrylate, and "(meth)acrylic resin" refers to both methacrylic resin and acrylic resin.

[0009] <<Method for manufacturing conductive coating composites>> A first aspect of the present invention is a manufacturing method for obtaining a conductive coating composite by laminating an overcoat layer that contacts a conductive film.

[0010] [Conductive film] The conductive film contains a conductive filler, a binder resin, and a dye. The conductive film is formed on at least a portion of the surface of the substrate. Examples of substrates include insulating substrates such as glass and plastic. The substrate may be transparent or opaque. Here, transparency refers to the property of allowing at least a portion of the incident light to pass through. The shape of the conductive film is not particularly limited; for example, it may be a conductive pattern consisting of one or more fine lines, or it may be an electrode with a geometric pattern such as a polygon, ellipse, or circle.

[0011] The thickness of the conductive film before forming the overcoat layer is not particularly limited, but examples include 0.5 to 50 μm. Here, the thickness of the conductive film is the average value measured using a magnification observation method such as an electron microscope at five or more arbitrary cross-sections where the overcoat layer is to be formed. If the value is above the lower limit of the above range, the resistivity can be sufficiently reduced, and a sufficient color difference can be obtained due to the application of the overcoat layer. If the value is below the upper limit of the above range, there is the advantage of increased adhesion to the substrate.

[0012] (Conductive filler) A conductive filler is an aggregate of conductive particles, and conductive fillers included in known conductive compositions can be used. Specifically, examples include metal powders, carbon black, and graphite. Among metal powders, silver powder is preferred from the viewpoint of lowering the resistivity of the conductive film. Carbon particles such as carbon black and graphite may be mixed with metal powders such as silver powder. The average particle size of the metal powder is, for example, 0.02 to 15 μm.

[0013] The individual particle shapes of metal powders such as silver powder can include, for example, spherical, flaky, dendritic, fibrous, and other irregular shapes (shapes that are difficult to describe as a specific shape). Among these, flaky metal powder is preferred from the viewpoint of lowering the resistivity of the conductive film and being suitable for conductive circuits, and flaky silver powder is more preferred. The conductive film may contain one or more types of conductive fillers.

[0014] (Binder resin) The binder resin is a resin component that binds conductive fillers together and adheres a conductive film to the surface of the substrate. From the viewpoint of facilitating the manufacture of conductive films, the binder resin is preferably a resin component that is soluble or dispersible in a solvent. Such binder resins can be those contained in known conductive compositions or resin compositions. Specifically, for example, resins such as polyester, polyester polyol, polyvinyl alcohol, (meth)acrylic, phenoxy, butyral, and phenol are preferred. With these preferred binder resins, the dyes contained in the conductive film can easily diffuse into the paint composition that forms the overcoat layer. The conductive film may contain one type of binder resin or two or more types.

[0015] The binder resin contained in the conductive film may be cured by a curing agent blended during the production of the conductive film. Such curing agents applicable are those contained in known conductive compositions and resin compositions. Specifically, various known isocyanates are preferred.

[0016] (Dye) A dye is generally a coloring substance that is stably soluble in an organic solvent or water. The dye contained in the conductive film may be oil-soluble or water-soluble, but oil-soluble is preferred. When it is oil-soluble, it becomes easier for the dye contained in the conductive film to diffuse into the coating composition that forms the overcoat layer. When the dye is oil-soluble, it is preferably soluble at 0.1 g or more per 100 g of an arbitrary organic solvent. Here, the organic solvent is preferably the solvent contained in the coating composition described later. When the dye is water-soluble, it is preferably soluble at 0.1 g or more per 100 g of ion-exchanged water (20 °C). The color of the dye is not particularly limited, and a desired color may be selected. The dye contained in the conductive film may be one kind or two or more kinds.

[0017] (Content ratio of each component) In the conductive film used in the production method of this aspect, the content ratio of each component before forming the overcoat layer is preferably as follows.

[0018] The content ratio of the conductive filler and the binder resin is preferably in the range of (conductive filler / binder resin) = (98 - 60 / 2 - 40) on a mass basis. The above range indicates a range of 2 - 40 parts by mass of the binder resin with respect to 98 - 60 parts by mass of the conductive filler. When it is in the above preferred range, it is easy to sufficiently lower the specific resistance of the conductive film.

[0019] With respect to 100 parts by mass in total of the conductive filler and the binder resin, the content of the dye is preferably in the range of 0.1 - 15 parts by mass, more preferably in the range of 1 - 10 parts by mass, and even more preferably in the range of 2 - 9 parts by mass. If the value is above the lower limit of the above range, sufficient dye transfer from the conductive film to the overcoat layer will occur, and a sufficient color difference due to the application of the overcoat layer will be obtained. If the value is below the upper limit of the above range, the increase in the resistivity of the conductive film can be suppressed.

[0020] The dye content is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and even more preferably 1.0 to 10 parts by mass per 100 parts by mass of conductive filler. If the value is above the lower limit of the above range, sufficient dye transfer from the conductive film to the overcoat layer will occur, and a sufficient color difference due to the application of the overcoat layer will be obtained. If the value is below the upper limit of the above range, the increase in the resistivity of the conductive film can be suppressed.

[0021] The dye content per 100 parts by mass of binder resin is preferably 2 to 200 parts by mass, more preferably 20 to 150 parts by mass, and even more preferably 30 to 100 parts by mass. If the value is above the lower limit of the above range, sufficient dye transfer from the conductive film to the overcoat layer will occur, and a sufficient color difference due to the application of the overcoat layer will be obtained. If the value is below the upper limit of the above range, the increase in the resistivity of the conductive film can be suppressed.

[0022] (Method for forming conductive films) The conductive film according to this embodiment can be formed by applying a conductive film-forming coating composition (hereinafter sometimes referred to as conductive paste) to a desired thickness over a desired area on the surface of a substrate, and then drying and curing it. Conventional methods can be used for application, drying, and curing. The temperature at which conductive paste is dried and cured is preferably 150°C or lower. If conductive paste is dried and cured at a temperature exceeding 150°C, the dye may sublimate or decompose, which may result in weaker color development when the overcoat layer is formed.

[0023] The conductive paste comprises a conductive filler, a binder resin, and a dye, and preferably further contains a curing agent and a solvent as needed. The viscosity of the conductive paste can be adjusted according to the proportions of each component, particularly the proportion of the solvent. The conductive paste is prepared by mixing each component by conventional methods.

[0024] The ratio of conductive filler to binder resin contained in the conductive paste is preferably within the mass-based range for the conductive film described above. The ratio of dye to the total amount of conductive filler and binder resin contained in the conductive paste is preferably within the mass-based range for the conductive film described above. The ratio of dye to 100 parts by mass of the total conductive filler, binder resin, and curing agent contained in the conductive paste is preferably, for example, 1.0 to 30 parts by mass, more preferably 1.0 to 20 parts by mass, and even more preferably 1.0 to 10 parts by mass. In the conductive paste, the proportion of the hardener in a total of 100 parts by mass of conductive filler, binder resin, and hardener is preferably, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5.0 parts by mass, and more preferably 1.0 to 3.0 parts by mass. The solvent content relative to 100 parts by mass of the total conductive filler, binder resin, and curing agent in the conductive paste is preferably, for example, 1.0 to 30 parts by mass, more preferably 5.0 to 20 parts by mass, and even more preferably 8.0 to 15 parts by mass, from the viewpoint of easily adjusting the paste viscosity to a applyable level.

[0025] The type of solvent included in the conductive paste is not particularly limited, and one or more of the various solvents used in conventional conductive compositions can be applied, taking into consideration compatibility with the binder resin, compatibility with the dye, compatibility with the curing agent, and dispersibility of the conductive filler. Specifically, examples include ester-based solvents, ketone-based solvents, alcohol-based solvents, glycol-based solvents, hydrocarbon-based solvents, etc.

[0026] Because the viscosity of the conductive paste can be easily adjusted, one or more solvents selected from butyl diglycol acetate (butyl carbitol acetate; abbreviation: BCA), terpineol, isophorone, γ-butyrolactone, and diethylene glycol are preferred. The conductive paste may contain one or two or more solvents.

[0027] [Formation of the overcoat layer] A coating composition for forming an overcoat layer (hereinafter sometimes referred to as "overcoat coating") contains a binder resin and a solvent, and is applied to a region on a substrate where a conductive film has been formed. At least a portion of the undried coating formed by the application is laminated in contact with at least a portion of the conductive film. In this state, at least a portion of the dye contained in the conductive film is extracted into the solvent contained in the coating. That is, at least a portion of the dye contained in the conductive film migrates to the coating and diffuses into the coating directly above the conductive film. Subsequently, by drying the coating on which the dye has migrated, an overcoat layer colored by the dye can be formed directly above the conductive film.

[0028] The overcoat paint contains a binder resin and a solvent, and preferably further contains a hardener as needed. The viscosity of the overcoat paint can be adjusted according to the proportions of each component, especially the proportion of the solvent. The overcoat paint is prepared by mixing each component by conventional methods.

[0029] The ratio of binder resin (non-volatile component) to the total mass of the overcoat paint is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and even more preferably 30 to 40% by mass. The ratio of the hardener to the total mass of the overcoat paint is preferably, for example, 1.0 to 18% by mass, more preferably 4.0 to 14% by mass, and even more preferably 7.0 to 10% by mass. The ratio of hardener to binder resin in the overcoat paint is preferably 10 to 40 parts by mass, preferably 15 to 35 parts by mass, and more preferably 20 to 30 parts by mass. The solvent content ratio relative to the total mass of the overcoat paint is preferably, for example, 40 to 70% by mass, more preferably 45 to 65% by mass, and even more preferably 50 to 60% by mass.

[0030] The type of solvent included in the overcoat paint can be one or more of the various solvents used in conventional conductive compositions, taking into consideration compatibility with the binder resin, the dye, and the curing agent. Specifically, examples include ester-based solvents, ketone-based solvents, alcohol-based solvents, glycol-based solvents, hydrocarbon-based solvents, etc.

[0031] The solvent included in the overcoat paint is preferably one or more selected from butyl diglycol acetate (BCA), butyl diglycol (butyl carbitol; abbreviation: BC), terpineol, isophorone, carbitol acetate (abbreviation: CA), N-methylpyrrolidone, and dodecane, because it facilitates the extraction of dyes contained in the conductive film. The solvent included in the overcoat paint may be one or two or more.

[0032] Preferably, at least one of the one or more solvents contained in the overcoat paint has the following property (property of the solvent alone): That is, it is preferable that the soluble mass of at least one dye contained in the conductive film to which the overcoat paint is applied is 0.10 g or more per 100 g of the solvent. Having this property makes it easier for the dye contained in the conductive film to migrate to the applied overcoat paint (making it easier to extract the dye from the conductive film).

[0033] Examples of binder resins included in overcoat paints include those the same as those included in the conductive films and conductive pastes mentioned above. Those with good adhesion to the substrate and conductive film are preferred. The binder resin contained in the overcoat paint may be the same as or different from the binder resin contained in the conductive film. The binder resin contained in the overcoat paint may be of one type or two or more types.

[0034] [Overcoat layer] The overcoat layer formed by the manufacturing method of this embodiment contains a binder resin and a dye extracted from the conductive film. The shape of the overcoat layer is not particularly limited as long as it is laminated in contact with at least a portion of the conductive film. For example, it may be a pattern consisting of one or more fine lines, or a geometric pattern such as a polygon, ellipse, or circle.

[0035] In the conductive coating composite obtained by the manufacturing method of this embodiment, it is preferable that the overcoat layer in the region where the overcoat layer and the conductive film do not overlap, when viewed in the stacking direction, be transparent. Here, transparency means the property of transmitting at least a portion of the incident light.

[0036] When viewed in the stacking direction of the conductive coating composite obtained by the manufacturing method of this embodiment, the thickness of the overcoat layer formed directly above the conductive film is preferably, for example, 1 to 100 μm, more preferably 1 to 50 μm, and even more preferably 1 to 10 μm. Here, the thickness of the overcoat layer is defined as the average value measured using a magnifying observation device such as an electron microscope at five or more arbitrary cross-sections of the overcoat layer laminated directly on top of the conductive film. If the value is above the lower limit of the above range, a sufficient color difference can be obtained due to the application of the overcoat layer. If the value is below the upper limit of the above range, there is the advantage of obtaining high insulation performance. [Examples]

[0037] <Preparation of paint composition> For each example and comparative example, the materials were mixed according to the solid content ratio (mass ratio) shown in the table below to prepare a conductive paste and an overcoat paint.

[0038] <Formation of conductive film> First, the binder resin and solvent were mixed in the mass ratios shown in Table 1, then silver powder was dispersed using a three-roller system, and finally, the dye and hardener were mixed to create a conductive paste. Next, a conductive paste was applied to the surface of a glass slide in a 3cm x 10cm strip with a thickness of 50μm, and then dried for 30 minutes under specified temperature conditions to form a conductive film. The resistivity of the formed conductive film was measured according to JIS C 2525:1999, and L*a*b* was measured using a colorimeter (Konica Minolta, model number: CM26d). The results are shown in Table 3 as "before overcoating".

[0039] <Formation of the overcoat layer> First, the binder resin, curing agent, and solvent were mixed in the mass ratios shown in Table 2 to obtain the paint composition. Next, a 3 cm long, 50 μm thick overcoat layer was applied to the area where the conductive film had been formed, and dried for 30 minutes under predetermined temperature conditions to form a light-transmitting overcoat layer. This resulted in a conductive coating composite in which the overcoat layer was laminated on at least a portion of the conductive film. The resistivity of the surface of the overcoat layer of the formed conductive coating composite was measured according to the method of JIS C 2525:1999, and L*a*b* was measured using the colorimeter. The results are shown in Table 3 as "after overcoating".

[0040] <Evaluation of conductive coating composites> The measured resistivity is 6.50-E05(6.50×10 -5 A value of Ω·m or less was considered acceptable. The color difference (△E*) of the measured color values ​​before and after the formation of the overcoat layer was calculated using the following set of formulas, and a △E* of 10 or more was considered acceptable. Equation 1… {(L* after) - (L* before)} 2 =Ls Equation 2… {(later a*)-(previous a*)} 2 =as Equation 3… {(later b*)-(previous b*)} 2 = protein Equation 4… △E* = √(Ls + as + bs)

[0041] [Table 1A]

[0042] [Table 1B]

[0043] [Table 2A]

[0044] [Table 2B]

[0045] [Table 3A]

[0046] [Table 3B]

[0047] The abbreviations and trade names in each table refer to the following compounds. • "Nikanol 1440M": Xylene resin: Manufactured by Fudo Co., Ltd. • "Kuraray Polyol F-3010": Polyester polyol: Manufactured by Kuraray Co., Ltd. • "Byron GK130": Polyester polyol: Manufactured by Toyobo Co., Ltd. • "Elitel UE-3500": Polyester polyol: Manufactured by Unitika Ltd. • "Eslec BX-5": Alkylacetalized polyvinyl alcohol: Manufactured by Sekisui Chemical Co., Ltd. • "PKHH": Phenoxy resin: Tomoe Engineering Co., Ltd. • "TPA-B80E": Hexamethylene diisocyanate: Manufactured by Asahi Kasei Corporation • "SF70M": Silver powder: Manufactured by Ames Advanced Materials Corporation • "OIL BLACK 860": Dye: Manufactured by Orient Chemical Industry Co., Ltd. • "OIL BLUE 613": Dye: Manufactured by Orient Chemical Industry Co., Ltd. • "VALIFAST RED 3304": Dye: Manufactured by Orient Chemical Industry Co., Ltd. • "VALIFAST BLACK 3870": Dye: Manufactured by Orient Chemical Industry Co., Ltd. • "WATER YELLOW 6": Dye: Manufactured by Orient Chemical Industry Co., Ltd. • "BL-100HP": Pigment: Manufactured by Titanium Industries Co., Ltd. • "BCA": Butyl diglycol acetate (butyl carbitol acetate) • "BC": Butyl diglycol (butyl carbitol) • "CA": Carbitol acetate

[0048] The "dyes" used above were dissolved in an organic solvent or deionized water. Their solubility was 0.1 g or more per 100 g of solvent. The "pigment" used above did not dissolve in the organic solvent or deionized water used as the dispersion medium. Its solubility was less than 0.1 g per 100 g of solvent.

[0049] <Consideration> The color difference (△E*) of the conductive coating composites in each example in which the conductive film contained a dye was greater than the color difference in Comparative Example 1, in which the conductive film did not contain a dye, confirming an improved coloring effect. Furthermore, the color difference in Comparative Example 2, in which a pigment was contained in the conductive film instead of a dye, was extremely small. From these results, it was found that in each example, the dye migrated to the overcoat paint applied on top of the conductive film and diffused into the overcoat layer, resulting in a larger color difference. In Example 17, in which a relatively large amount of dye was contained in the conductive film, the color difference was large, but the resistivity was high and the conductivity was inferior compared to the other examples.

Claims

1. A conductive film containing a conductive filler, a binder resin, and a dye is placed on top of the conductive film. A paint composition containing a binder resin and a solvent is applied, and the undried paint film is brought into contact with at least a portion of the surface of the conductive film and laminated, After transferring at least a portion of the dye contained in the conductive film to the coating film, A method for producing a conductive coating composite, comprising drying the coating to form an overcoat layer containing the dye on the conductive film.

2. A method for producing a conductive coating composite according to claim 1, wherein, in the conductive film before applying the coating composition, the content ratio of the conductive filler to the binder resin is, by mass, (conductive filler / binder resin) = (98-60 / 2-40).

3. A method for producing a conductive coating composite according to claim 1, wherein, in the conductive film before applying the coating composition, the content of the dye is 0.1 to 15 parts by mass relative to 100 parts by mass of the total of the conductive filler and the binder resin.

4. The method for producing a conductive coating composite according to claim 1, wherein the properties of the solvent are such that the soluble mass of the dye per 100 g of the solvent is 0.10 g or more.

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