TW202411363A - Conductive coating, and method for resin molded article having shielding layer - Google Patents

Abstract

This conductive coating contains, with respect to 100 parts by mass of a binder component (A) containing an epoxy resin: 1200-3200 parts by mass of metal particles (B); 70-200 parts by mass of a block isocyanate curing agent (C); 5-50 parts by mass of a curing agent (D) that is at least one selected from the group consisting of an amine-based curing agent and an imidazole-based curing agent; and 100-1,500 parts by mass of a solvent (E).

Description

Conductive coating, and method for producing resin molded product having shielding layer

Field of Invention The present invention relates to a method for manufacturing a conductive coating and a resin molded product having a shielding layer.

Background technology Electronic devices such as mobile phones and tablet terminals are equipped with many wireless communication electronic components for transmitting large amounts of data. Such wireless communication electronic components have the following problems: not only are they prone to generating noise, but they are also highly sensitive to noise. If exposed to external noise, they can easily cause erroneous actions.

As for this problem, it is known that, as described in Patent Documents 1 and 2, the electronic components that are noise generating sources are covered together with the package body with a shielding layer, thereby preventing the noise from being generated by the electronic components and preventing the noise from intruding, which is the so-called shielded package body.

However, when the conductive coating is cured to form a shielding layer, if the curing temperature is high, there is a risk of damaging the electronic components in the shielding package. Therefore, a conductive coating with a low curing temperature is needed. For this problem, conductive coatings such as those described in patent documents 3 and 4 have been proposed. However, their curing temperatures are all 100-120°C, and there is still room for further improvement in lowering the curing temperature.

Furthermore, it is necessary to provide a shielding layer on the resin molded product. Specifically, in order to reduce the weight of automobiles, it is currently being considered to replace the metal parts used in the past with engineering plastics, and it is necessary to make the resin molded product composed of the engineering plastics have shielding properties.

As a method for forming a shielding layer on the surface of a resin molded product, the following methods are known: laminating a conductive sheet, metal foil or metal mesh; or using an electroless plating method in which the resin molded product is immersed in a plating liquid to form a metal film to form the shielding layer.

However, the shielding layer obtained by these methods sometimes cannot obtain sufficient shielding properties or adhesion. In addition, depending on the shape of the resin molded product, there may be problems such as the inability to adhere to the conductive sheet or metal foil. The electroless plating method has the problem that the resin molded product is immersed in the plating liquid and therefore the shielding layer cannot be formed locally. Although there are methods for applying conductive coatings as described in patent documents 3 and 4, as mentioned above, since the curing temperature is 100~120℃, it cannot be applied to resin molded products with a heat resistance temperature of less than 100℃.

Prior art documents Patent documents Patent document 1: Japanese Patent Publication No. 2017-179362 Patent document 2: Japanese Patent Publication No. 2020-55977 Patent document 3: International Publication No. 2019/198336 Patent document 4: International Publication No. 2021/014964

Summary of the invention Problems to be solved by the invention The present invention is made in view of the above, and its purpose is to provide a conductive coating with a low curing temperature and excellent conductivity and adhesion, and a method for manufacturing a resin molded product with a shielding layer.

Means for Solving the Problem The present invention includes the following embodiments. [1] A conductive coating comprising: a binder component (A) comprising an epoxy resin; metal particles (B); a blocked isocyanate hardener (C); a hardener (D) selected from at least one of the group consisting of an amine hardener and an imidazole hardener; and a solvent (E); and, relative to 100 parts by mass of the binder component (A), the metal particles (B) are 1200 to 3200 parts by mass, the blocked isocyanate hardener (C) is 70 to 200 parts by mass, the hardener (D) is 5 to 50 parts by mass, and the solvent (E) is 100 to 1500 parts by mass. [2] The conductive coating of [1], wherein the metal particles (B) are at least one selected from the group consisting of silver particles, silver-coated copper particles and silver-coated copper alloy particles. [3] The conductive coating of [1] or [2], wherein the amine-based curing agent is an aliphatic amine-based curing agent having a reaction starting temperature of 60 to 100°C. [4] The conductive coating of any one of [1] to [3], wherein the reaction starting temperature of the imidazole-based curing agent is 60 to 100°C. [5] The conductive coating of any one of [1] to [4], wherein the mass ratio (C)/(D) of the blocked isocyanate curing agent (C) to the curing agent (D) is 1.4 to 40. [6] A method for manufacturing a resin molded product, comprising the following steps: A conductive coating step, comprising coating the conductive coating as described in any one of [1] to [5] on the resin molded product; and A shielding layer forming step, comprising heating the resin molded product coated with the coating at a temperature of 70 to 80°C to harden the coating to form a shielding layer.

Effect of the invention The conductive coating of the present invention can be cured at a low temperature, for example, below 80°C, and can obtain excellent conductivity and adhesion.

Forms for implementing the invention The following describes the implementation forms of the present invention in more detail.

The conductive coating of the present embodiment comprises: a binder component (A) comprising an epoxy resin; metal particles (B); a blocked isocyanate hardener (C); a hardener (D) selected from at least one of the group consisting of an amine hardener and an imidazole hardener; and a solvent (E); and, relative to 100 parts by mass of the binder component (A), the metal particles (B) are 1200 to 3200 parts by mass, the blocked isocyanate hardener (C) is 70 to 200 parts by mass, the hardener (D) is 5 to 50 parts by mass, and the solvent (E) is 100 to 1500 parts by mass.

The ratio of the epoxy resin in the adhesive component (A) is preferably 5-100% by mass, more preferably 30-100% by mass, more preferably 50-100% by mass, particularly preferably 70-100% by mass, and most preferably 90-100% by mass.

The epoxy resin may be a solid epoxy resin or a liquid epoxy resin, but it is preferred to include both. When both are included, the ratio of the solid epoxy resin in the binder component (A) is preferably 5-80% by mass, preferably 20-60% by mass. The ratio of the liquid epoxy resin in the binder component (A) is preferably 20-95% by mass, preferably 40-80% by mass. When the solid epoxy resin and the liquid epoxy resin are included in the above ratio, the conductivity, adhesion, and low-temperature curing properties of the conductive coating will be well balanced and excellent. Furthermore, the warp of the cured product after curing will be further reduced, and it is easy to produce a shielding package with better heat resistance.

Here, the so-called solid epoxy resin refers to an epoxy resin that is not fluid at room temperature (23°C) and in the absence of a solvent. The so-called liquid epoxy resin refers to an epoxy resin that is fluid at room temperature (23°C) and in the absence of a solvent.

The epoxy equivalent of the solid epoxy resin is preferably in the range of 150 to 10,000 g/eq, and the weight average molecular weight is preferably in the range of 900 to 60,000. If the epoxy equivalent is above 150 g/eq, it is easy to obtain a cured product with better adhesion of the conductive coating. If the epoxy equivalent is below 10,000 g/eq, it is easy to obtain a cured product with better conductivity and heat resistance of the conductive coating.

In this specification, "epoxide equivalent" is measured according to JIS K7236: 2009. In this specification, "weight average molecular weight" is defined as a value that can be measured by gel permeation chromatography (GPC) using tetrahydrofuran as a mobile phase and a polystyrene-converted calibration curve.

Furthermore, the solid epoxy resin is not particularly limited, and for example, bisphenol-type epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin; spirocyclic epoxy resins; naphthalene epoxy resins; biphenyl epoxy resins; terpene epoxy resins; epoxy resins such as tris(glycidoxyphenyl)methane and tetrakis(glycidoxyphenyl)ethane; Propyl ether type epoxy resin; epoxy propylamine type epoxy resin such as tetracyclyl diamino diphenylmethane; tetrabromobisphenol A type epoxy resin; cresol novolac type epoxy resin, phenol novolac type epoxy resin, α-naphthol novolac type epoxy resin, brominated phenol novolac type epoxy resin and other novolac type epoxy resins; rubber modified epoxy resin, etc. These may be used alone or in combination of two or more. In addition, the solid epoxy resin may be dissolved in the solvent (E) described later before use.

The so-called "rubber-modified epoxy resin" means a rubber component dispersed in the above-mentioned solid epoxy resin. The above-mentioned rubber component can be exemplified by butadiene rubber (BR), acrylic rubber (ACM), silicone rubber, butyl rubber (IIR), isoprene rubber (IR), chloroprene rubber (CR), nitrile rubber (NBR), styrene butadiene rubber (SBR), ethylene propylene rubber (EPR), etc. Among them, the epoxy resin modified with NBR (NBR-modified epoxy resin) is preferred. Only one kind of the above-mentioned rubber component can be used, or two or more kinds can be used.

The epoxy equivalent of the liquid epoxy resin is preferably in the range of 90 to 500 g/eq, and the weight average molecular weight is preferably in the range of 150 to 500. If the epoxy equivalent is above 90 g/eq, it is easy to obtain a cured product with better adhesion of the conductive coating. If it is below 500 g/eq, it is easy to obtain a cured product with better conductivity and heat resistance of the conductive coating.

Furthermore, the liquid epoxy resin is not particularly limited, and a liquid glycidylamine epoxy resin, a liquid glycidyl ether epoxy resin, or a liquid glycidyl ester epoxy resin, etc., can be used. These can be used alone or in combination of two or more.

The binder component (A) may contain alkyd resin, melamine resin, xylene resin, silicone resin, urethane resin, acrylic resin, etc. as components other than epoxy resin. The content of these components in the binder component (A) is preferably 30% by mass or less, and more preferably 10% by mass or less. By using these resins, the adhesion becomes good.

The content of the metal particles (B) is not particularly limited as long as it is 1200-3200 parts by mass relative to 100 parts by mass of the binder component (A), and is preferably 1500-3000 parts by mass, and more preferably 1700-2900 parts by mass.

Metal particles (B) include, for example, copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, silver-coated copper alloy particles, etc., and these particles may be used alone or in combination of two or more. The metal particles (B) are preferably at least one selected from the group consisting of silver particles, silver-coated copper particles, and silver-coated copper alloy particles. There is no particular limitation on the silver-coated copper particles as long as they have a copper particle and a silver-containing layer that coats at least a portion of the copper particle. There is no particular limitation on the silver-coated copper alloy particles as long as they have a copper alloy particle and a silver-containing layer that coats at least a portion of the copper alloy particle. The copper alloy particles may also contain 0.5-25 mass % of zinc and/or 0.5-30 mass % of nickel, and the remainder is composed of copper, and the remainder of the copper contains inevitable impurities. The content ratio of the silver-coated copper particles and the silver-containing layer in the silver-coated copper alloy particles is not particularly limited, and is preferably 4-24 mass %. The content of silver in the silver-containing layer is not particularly limited, and is preferably 90-100 mass %.

The shape of the metal particles (B) is not particularly limited, and spherical, flake (scaly), branch-shaped, and fibrous ones can be used, and spherical or flake (scaly) ones are preferred. In addition, "spherical" metal particles include not only slightly spherical ones (atomized powder), but also slightly polyhedral spheres (reduced powder) or irregular shapes (electrolytic powder) and other slightly spherical ones.

The average particle size of the metal particles (B) is preferably 1 to 20 μm. If the average particle size of the metal particles is 1 μm or more, the dispersion of the metal particles will be good, thereby preventing agglomeration. In addition, the metal particles will be less susceptible to oxidation. If the average particle size of the metal particles is 20 μm or less, when the conductive coating hardens to form a shielding layer, the connection between the package and the ground circuit will be good.

In this specification, the "average particle size of metal particles" refers to the average particle size D50 (median diameter) based on the number of particles measured by laser diffraction-scattering method.

The blocked isocyanate hardener (C) may be prepared by blocking polyisocyanate with a blocking agent.

Examples of polyisocyanates include: aliphatic diisocyanates such as hexamethylene diisocyanate (including trimer), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, etc.; alicyclic polyisocyanates such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), etc.; aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, stilbene diisocyanate, etc.; modified products of these diisocyanates (urea formate products, carbodiimide, uretdione, uretonimine, biuret and/or trimerized isocyanate, etc.). These may be used alone or in combination of two or more.

As examples of the end-capping agent, it is preferable to use: n-butyl alcohol, n-hexanol, 2-ethylhexanol, lauryl alcohol, phenol carbinol, methyl phenyl carbinol, carbinol) and other monoalkyl (or aromatic) alcohols; cellulosics such as ethylene glycol monohexyl ether and ethylene glycol mono-2-ethylhexyl ether; polyether-type double-terminated diols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol phenol; polyester-type double-terminated polyols obtained from diols such as ethylene glycol, propylene glycol, 1,4-butanediol, and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, and sebacic acid; phenols such as tert-butylphenol and cresol; oximes such as dimethyl ketone oxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, methyl amyl ketone oxime, and cyclohexanone oxime; pyrazoles such as dimethyl pyrazole; and lactamides represented by ε-caprolactam and γ-butyrolactam. These may be used alone or in combination of two or more.

The content of the blocked isocyanate hardener (C) is not particularly limited as long as it is 70 to 200 parts by mass relative to 100 parts by mass of the binder component, and is preferably 100 to 200 parts by mass.

As the hardener (D), at least one selected from the group consisting of amine hardeners and imidazole hardeners may be used, and two or more kinds may be used in combination. The hardener (D) functions as a hardening aid to assist the hardening of the blocked isocyanate hardener (C), and can promote the hardening of the conductive coating at a low temperature.

Examples of the amine-based hardener include: aliphatic amine-based hardeners (e.g., (poly)alkylene polyamines such as ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, etc.); alicyclic amine-based hardeners (e.g., monocyclic aliphatic polyamines such as menthene diamine, isophoronediamine, bis(4-amino-3-methylcyclohexyl)methane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetrahexaspiro[5.5]undecane, etc.; cross-linked cyclic polyamines such as norbornanediamine, etc.); aromatic amine-based hardeners (e.g., polyaminoaromatics (e.g., diaminoaromatics such as p-phenylenediamine and m-phenylenediamine, and ideally, diaminoC C _6-10 aromatic hydrocarbons), polyamino-alkyl aromatic hydrocarbons (e.g. diamino-alkyl aromatic hydrocarbons such as diethyltoluenediamine, and ideally diamino-mono or tri-C _1-4 alkyl C _6-10 aromatic hydrocarbons), poly(aminoalkyl) aromatic hydrocarbons (e.g. di(aminoalkyl) aromatic hydrocarbons such as xylylenediamine, and ideally di(aminoC _1-4 alkyl)C _6-10 aromatic hydrocarbons), poly(aminoaryl) alkanes (e.g. di(aminoaryl) alkanes such as diaminodiphenylmethane, and ideally di(aminoC _6-10 aryl)C _1-6 alkanes), poly(amino-alkylaryl) alkanes (e.g. di(amino-alkylaryl) alkanes such as 4,4'-methylenebis(2-ethyl-6-methylaniline), and ideally di(amino-C _1-4 alkyl C _6-10 aryl) C _1-6 alkane), bis(aminoarylalkyl)arene (for example, bis(aminoC 6-10 arylC 1-10 alkyl)C _6-10 arene such as _1,3- bis[2-(4-aminophenyl)-2-propyl]benzene and 1,4-bis[2-(4-aminophenyl)-2 _- propyl]benzene), bis(aminoaryl)ether (for example, bis(aminoC _6-12 aryl)ether such as diaminodiphenyl ether, and desirably bis(aminoC _6-10 aryl)ether), bis(aminoaryloxy)arene (for example, bis(aminoC _6-12 aryloxy)C 6-12 arene such as 1,3-bis(3-aminophenoxy)benzene, and desirably bis(aminoC _6-10 aryloxy)C _6-12 arene _6-10 aromatic hydrocarbons), di(aminoaryl)sulfones (e.g. diaminodiphenylsulfone and di(aminoC _6-12 aromatic hydrocarbons, preferably di(aminoC _6-10 aromatic hydrocarbons)sulfones, etc.); aliphatic amine curing agents are particularly preferred. Here, "C _mn " in "C _1-4 alkyl" etc. means that the number of carbon atoms is m to n, and it can be any one of those with m to n carbon atoms or a mixture of two or more.

Amine hardeners are preferably aliphatic amine hardeners with a reaction starting temperature of 60~100℃. If the reaction starting temperature is above 60℃, the storage stability of the conductive coating can be improved. If the reaction starting temperature is below 100℃, the curing property can be improved. The reaction starting temperature is preferably 60~90℃.

Examples of imidazole curing agents include: imidazoles (e.g., alkyl imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, etc.; aromatic imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-benzyl-2-phenylimidazole, etc.); salts of imidazoles (e.g., organic salts such as formates, phenol salts, phenol novolac salts, etc.; salts such as carbonates, etc.); reactants (or adducts) of epoxy compounds (e.g., polyepoxy compounds such as diglycidyl ether of bisphenol A, etc.) and imidazoles, etc.

It is preferable to use an imidazole hardener with a reaction starting temperature of 60~100℃. If the reaction starting temperature of the imidazole hardener is above 60℃, the storage stability of the conductive coating can be improved. If the reaction starting temperature is below 100℃, the curing property can be improved. The reaction starting temperature is preferably 60~90℃.

In this specification, the reaction starting temperature of the hardener is measured as follows. That is, 100 parts by weight of bisphenol A epoxy resin having an epoxy equivalent of 186 g/eq and a weight average molecular weight of 370 is mixed with 15 parts by weight of the hardener if it is an amine hardener and 10 parts by weight of the imidazole hardener, and the mixture is stirred to form a paste to prepare a sample. The sample is heated at 10°C/min using a DSC (differential scanning calorimeter), and the temperature at which the heat peak starts to rise is defined as the reaction starting temperature.

The content of the hardener (D) is not particularly limited as long as it is 5 to 50 parts by mass relative to 100 parts by mass of the binder component, and is preferably 10 to 40 parts by mass.

The total content of the hardener (the total amount of the hardener (C) and the hardener (D)) is not particularly limited, but is preferably 80 to 220 parts by mass, more preferably 100 to 200 parts by mass, relative to 100 parts by mass of the binder component.

The content ratio of hardener (C) to hardener (D) (hardener (C)/hardener (D)) is not particularly limited, and is preferably 1.4 to 40, more preferably 2 to 40, in terms of mass ratio. If the mass ratio of hardener (C)/hardener (D) is 1.4 or more, the conductivity can be improved, and if it is 40 or less, it is easy to harden at a low temperature, which can improve the adhesion. The mass ratio of hardener (C)/hardener (D) can also be 5 to 40, or 5 to 20.

Examples of the solvent (E) include alcohols such as terpineol, benzyl alcohol, 1-methoxy-2-propanol, and isobutanol; ketones such as methyl ethyl ketone, acetone, and acetophenone; ethers such as methylcellulosic acid, ethylcellulosic acid, butylcellulosic acid, methylcarbitol, ethylcarbitol, butylcarbitol, diethylene glycol dimethyl ether, and tetrahydrofuran; and esters such as methylcellulosic acid acetate, ethylcarbitol acetate, butylcarbitol acetate, methyl methoxybutyl acetate, propylene glycol monomethylethyl acetate, methoxybutyl acetate, ethyl acetate, butyl acetate, and methyl acetate. These may be used alone or in combination of two or more.

The content of the solvent (E) is not particularly limited as long as it is 100 to 1500 parts by mass relative to 100 parts by mass of the binder component, and is preferably 200 to 1500 parts by mass, more preferably 300 to 1400 parts by mass, and even more preferably 400 to 1300 parts by mass.

The conductive coating of the present invention can be obtained by blending predetermined amounts of the above components and mixing them thoroughly.

In addition, additives that have been previously added to the same conductive coatings may be added to the conductive coating of the present invention within the scope of the purpose of the present invention. Examples thereof include: curing catalysts, defoamers, thickeners, tackifiers, fillers, anti-settling agents, colorants, antioxidants, plasticizers, ultraviolet absorbers, flame retardants, etc.

Regarding the viscosity of the conductive coating of the present invention, the viscosity at a liquid temperature of 25°C is preferably 0.1~5.0Pa.s, preferably 0.3~4.5Pa.s, and more preferably 0.5~4.0Pa.s. If the viscosity of the conductive coating is 0.1Pa.s or more, when the conductive coating is hardened to form a shielding layer, the liquid on the wall of the package can be prevented from flowing down and the shielding layer can be formed in an uneven manner, and the metal particles can be prevented from settling. If the viscosity of the conductive coating is 5.0Pa.s or less, the nozzle can be prevented from being blocked when the conductive coating is sprayed, and the shielding layer can be easily formed on the surface and side wall of the package without unevenness.

In this specification, the term "viscosity of the conductive coating" refers to the viscosity measured using a BH type viscometer at a rotational speed of 10 rpm.

Next, a method for manufacturing a shielding package using the conductive coating of the present invention is described.

An example of a method for manufacturing a shielding package of the present embodiment shown below includes the following steps: (1) a package forming step; (2) a package individualizing step; (3) a conductive coating coating step; (4) a shielding layer forming step; and (5) a cutting step.

In addition, in the method for manufacturing the shielding package of the present embodiment, (2) the package individualization step is not a necessary step and can be omitted depending on the purpose.

The following diagrams are used to explain each step.

(1) Package forming step First, as shown in FIG1(a), a substrate 1 is prepared, the substrate 1 is loaded with a plurality of electronic components 2, and a grounding circuit pattern 3 is provided between the plurality of electronic components 2.

Next, as shown in FIG. 1( b ), a sealing material 4 is filled on the electronic component 2 and the ground circuit pattern 3 and cured to seal the electronic component 2 , thereby manufacturing a package body 5 .

The sealing material is not particularly limited, and metals such as iron or aluminum, resins mixed with particles of these metals, resins such as epoxy resins, ceramics, etc. can be used.

(2) Package individualization step Next, as shown in FIG. 2 , the sealing material 4 between the plurality of electronic components 2 is cut to form a groove 6. The package 5 is individualized for each electronic component 2 by the groove 6. At this time, at least a portion of the ground circuit pattern 3 is exposed from the wall surface constituting the groove 6.

By forming such grooves 6, the package 5 can be easily divided into individual pieces as described later. In the conductive coating step described later, the conductive coating can also be coated on the side surface of the package 5.

(3) Conductive coating step Next, as shown in FIG3 , a conductive coating 7 is coated on the substrate 1 on which the package 5 is formed.

There is no particular limitation on the method of applying the conductive coating, and for example, the coating may be applied by brush or sprayed using a spray gun.

When the conductive coating 7 is applied by spraying, spraying conditions such as spraying pressure, spraying flow rate, and distance from the spray nozzle of the spray gun to the surface of the package 5 should be appropriately set.

(4) Shielding layer formation step Then, after the conductive coating 7 is dried, the substrate 1 coated with the conductive coating 7 is heated to harden the conductive coating 7, thereby forming a shielding layer 7a as shown in FIG. 4. In this step, the drying and hardening of the conductive coating 7 can be performed simultaneously or separately.

The heating temperature is not particularly limited, but is preferably 70 to 80° C. Since the conductive coating 7 is the conductive coating of the present invention, the conductive coating 7 can be sufficiently cured even at such a low heating temperature.

(5) Cutting step As shown in FIG. 5 , the substrate 1 is cut along the groove 6 to separate the package 5 into individual pieces. There is no particular limitation on the cutting method of the substrate 1, and the cutting can be performed using a cutting machine or the like.

Through the above steps, a shielding package 8 having a shielding layer 7a formed on the package 5 can be obtained.

As described above, the conductive coating of the present invention can be cured at a relatively low curing temperature, thereby suppressing damage to electronic components caused by heat.

Next, a method for manufacturing a resin molded product having a shielding layer using the conductive coating of the present invention is described.

An example of a method for manufacturing a resin molded article having a shielding layer of the present invention shown below includes the following steps: (1) a conductive coating coating step; and (2) a shielding layer forming step.

(1) Conductive coating step The conductive coating of the present invention is applied to the resin molded product. There is no particular limitation on the method of applying the conductive coating, and for example, it can be applied by brush or sprayed by a spray gun. When applying the conductive coating by spraying, the spraying conditions such as the spraying pressure, spraying flow rate, and the distance from the spray gun nozzle to the surface of the resin molded product should be appropriately set.

(2) Shielding layer formation step Next, after the conductive coating is dried, it is heated to harden the conductive coating, thereby forming a shielding layer. In this step, the drying and hardening of the conductive coating can be performed simultaneously or separately.

Examples The following are examples of the present invention, but the present invention is not limited to the following examples. In addition, unless otherwise stated, the blending ratios and the like described below are based on mass.

The components were mixed according to the blending formula (parts by mass) shown in Tables 1 and 2 below to prepare a conductive coating.

． Adhesive component (A): A mixture of 40 parts by mass of solid epoxy resin (Mitsubishi Chemical Co., Ltd., trade name "JER157S70"), 30 parts by mass of liquid epoxy propylamine epoxy resin (ADEKA Co., Ltd., trade name "EP-3905S"), and 30 parts by mass of liquid epoxy propyl ether epoxy resin (ADEKA Co., Ltd., trade name "EP-4400") ． Metal particles (B) Silver-coated copper particles: a mixture of spherical silver-coated copper particles with an average particle size of 2 μm (silver content = 10% by mass) and flaky silver-coated copper particles with an average particle size of 5 μm (silver content = 10% by mass, aspect ratio = 5) (mixing ratio is 1:4 by mass ratio (spherical: flaky)) ． Metal particles (B) Silver particles: a mixture of spherical silver particles with an average particle size of 2 μm and flaky silver particles with an average particle size of 5 μm (aspect ratio = 5) (mixing ratio is 1:4 by mass ratio (spherical: flaky)) ． Metal particles (B) Silver-coated copper alloy particles: a mixture of spherical silver-coated copper alloy particles with an average particle size of 2 μm (silver content = 10 mass%) and flaky silver-coated copper alloy particles with an average particle size of 5 μm (silver content = 10 mass%, longitudinal ratio = 5) (mixing ratio is 1:4 in terms of mass ratio (spherical: flaky), and the copper alloy contains nickel at a ratio of 5 mass%. ． Blocked isocyanate hardener (C): manufactured by Tosoh (Co., Ltd.), trade name "Coronate 2554" ． Amine hardener (D): manufactured by T&K TOKA (Co., Ltd.), trade name "Fujicure-7001" (reaction starting temperature = 80°C) ． Imidazole hardener (D): manufactured by Shikoku Chemical Industries, Ltd., trade name "2MZ-H", 2-methyl-imidazole (reaction starting temperature = 75°C) ． Solvent (E): 1-methoxy-2-propanol

The curability, conductivity, storage stability, coating stability and adhesion of the obtained conductive coating were evaluated, and the results are shown in Tables 1 and 2. The evaluation method is as follows.

<Hardening 1> The conductive coating of each embodiment and each comparative example was applied to a glass plate to a thickness of 20 μm, and heated at 80°C for 120 minutes to evaluate the curing of the conductive coating. The evaluation criteria are as follows. ○: The conductive coating has been completely cured. ×: The conductive coating has not been cured or is in a semi-cured state.

<Curing property 2: Acetone friction property> Use the hardening sample prepared in the above-mentioned hardening property 1. Move the paper towel soaked with acetone back and forth on the hardening sample 10 times. Then, for the hardening sample, the hardening stripping rate (%) of the conductive coating is measured using the following formula (1). In this evaluation, the lower the hardening stripping rate of the conductive coating, the more fully the conductive coating is hardened. If it is less than 20%, it is evaluated as having excellent hardening property. Conductive coating stripping rate = {1-([area of hardened material remaining after treatment with paper towel]/[area of hardened sample before treatment with paper towel])}×100…(1)

<Conductivity> The conductive coating of each embodiment and each comparative example was applied to a 150mm×150mm square PP (polypropylene) sheet to a thickness of 20μm, and heated at 80°C for 120 minutes to obtain a cured conductive coating. The sheet resistance value was measured using a surface resistance measuring jig (mΩ HiTESTER) for the cured product. If the sheet resistance value was 50mΩ or less, the conductivity was evaluated as excellent.

<Storage stability> The viscosity of the conductive coating of each embodiment and each comparative example just manufactured was measured using a BH type viscometer rotor No. 7 (10 rpm). The measured viscosity was defined as the initial viscosity (V0). Next, the viscosity of the conductive coating of each embodiment and each comparative example after being placed at room temperature for 7 days after manufacturing was measured using a BH type viscometer rotor No. 7 (10 rpm). The measured viscosity was defined as the viscosity after 7 days of placement (V7). In addition, the viscosity change rate (%) was calculated using the following formula (2) to evaluate the storage stability of the conductive coating. If the change rate is 20% or less, the storage stability is evaluated as excellent. Change rate = {(V7-V0)/V0}×100…(2)

<Coating stability> Figures 6(a) and 6(b) are schematic diagrams showing the substrate used to evaluate coating stability. The conductive coatings prepared in each embodiment and each comparative example were sprayed on the square glass epoxy substrate (length 10 cm × width 10 cm × thickness 1 mm) shown in Figure 6(a) using a spraying device manufactured by Nordson Asymtek according to the following procedure to evaluate the coating stability of the conductive coating.

As shown in FIG6(a), four polyimide tapes 32 to 35 are respectively attached to the glass epoxy substrate 31 near each corner, and a polyimide tape 36 is attached to the center of the glass epoxy substrate 31. The area of each polyimide tape 32 to 36 is 1 cm × 1 cm (dimensions a and b in FIG6(a) are both 1 cm), and each polyimide tape 32 to 35 is attached to the inner side of each side of the glass epoxy substrate 31 1 cm in a manner that the edge of the tape is parallel to the edge of the substrate (dimensions c and d in FIG6(a) are both 1 cm).

After the conductive coating is placed in the spraying device, the glass epoxy substrate 31 is immediately sprayed with the following spraying conditions and heated at 80° C. for 120 minutes to form a cured conductive coating with a thickness of 20 μm.

Furthermore, after 20 minutes from the time the conductive coating was placed in the spraying device, spray coating was performed under the same conditions as above, and heating was performed under the same conditions, so that a cured conductive coating was formed with a thickness of about 20 μm. Hereinafter, the cured conductive coating formed immediately after the conductive coating was placed in the spraying device is recorded as "cured product A", and the cured conductive coating formed 20 minutes after the conductive coating was placed in the spraying device is recorded as "cured product B".

<Spraying conditions> "SL-940E" manufactured by Nordson Asymtek Extrusion pressure: 2.8Psi Auxiliary air (atomizing air): 5Psi Package surface temperature: 22℃ Distance from package surface to nozzle: about 150mm Nozzle moving distance: 3mm Nozzle moving speed: 250mm/sec Number of spraying times: 4 times

After the heating is completed and the film is placed at room temperature for 30 minutes, the polyimide tapes 32 to 36 are peeled off respectively. Then, a micrometer is used to measure the thickness of the peeled portion (arrow X) of the glass epoxy substrate 31 and the thickness of the portion of the glass epoxy substrate 31 adjacent to the peeled portion where the cured conductive coating 41 is formed (arrow Y), as shown in FIG. 6( b). The thickness of the cured conductive coating 41 at five locations is obtained by subtracting the thickness of the cured conductive coating from the thickness of the latter.

The coating stability was evaluated based on the thickness of the hardened material A and the thickness of the hardened material B. The evaluation criteria are as follows. The evaluation results are shown in Tables 1 and 2. ○: The thickness of all 5 hardened materials A and the thickness of all 5 hardened materials B fall within the range of 20μm±5μm. ×: There is one or more hardened materials A and/or hardened materials B whose thickness does not fall within the range of 20μm±5μm.

<Adhesion: Cross-Cut test> According to JIS K 5600-5-6:1999 (Cross-Cut method), evaluate the adhesion between the shielding layer and the package surface or the grounding circuit.

Specifically, a copper-clad laminate was prepared for evaluating the adhesion to the ground circuit, and a mold resin was prepared for evaluating the adhesion to the package surface. Polyimide tape was used to form an opening with a width of 5 cm and a length of 10 cm, and the conductive coating of each embodiment and each comparative example was sprayed with the conductive coating using a spray coating device "SL-940E" (manufactured by Nordson Asymtek). Then, the conductive coating was hardened by heating at 80°C for 120 minutes, and the polyimide tape was peeled off to form a coating film with a thickness of about 20 μm. A cross-cut test was performed on the coated copper foil and molding resin.

Adhesion is evaluated based on the following criteria. ○: The edges of the drawn lines are completely smooth, and there is no peeling in any square. ×: Slight peeling of the coating occurs at the intersection of the drawn lines. Or, the edges and intersections of the drawn lines peel off completely.

[Table 1]

[Table 2]

As shown in Table 1, Examples 1 to 10 are all excellent in curability, conductivity, storage stability, coating stability and adhesion.

According to the results shown in Table 2, Comparative Example 1 is an example in which only blocked isocyanate curing agent is used as a curing agent, and the curability 1, 2, conductivity and adhesion are poor.

Comparative Examples 2 and 3 are examples using imidazole-based hardeners or amine-based hardeners as hardeners, and their electrical conductivity and storage stability are poor.

Comparative Example 4 is an example in which the content of the blocked isocyanate hardener is less than the lower limit and the content of the imidazole hardener is greater than the upper limit, and the conductivity is poor. In terms of storage stability, the viscosity (V7) is high after 7 days of storage and cannot be measured using a measuring device.

Comparative Example 5 is an example in which the content of the blocked isocyanate curing agent is greater than the upper limit and the content of the imidazole curing agent is less than the lower limit, and the curability 1, 2 and the adhesion are poor.

Comparative Example 6 is an example in which the content of the blocked isocyanate hardener is less than the lower limit and the content of the amine hardener is greater than the upper limit, and the conductivity is poor. In terms of storage stability, the sample has gelled after being placed for 7 days.

Comparative Example 7 is an example in which the content of the blocked isocyanate hardener is greater than the upper limit and the content of the amine hardener is less than the lower limit, and the curability 1, 2 and adhesion are poor.

Comparative Example 8 is an example in which the content of metal particles is less than the lower limit and the content of solvent is less than the lower limit, and the electrical conductivity and coating stability are poor.

Comparative Example 9 is an example in which the content of metal particles is greater than the upper limit and the content of solvent is greater than the upper limit, and the hardening property is 2, and the coating stability and adhesion are poor.

1: Substrate 2: Electronic components 3: Ground circuit pattern 4: Sealing material 5: Package 6: Groove 7: Conductive coating 7a: Shielding layer 8: Shielding package 31: Glass epoxy substrate 32~36: Polyimide tape 41: Cured conductive coating a,b,c,d: Dimensions X,Y: Arrows

Figures 1(a) and (b) are schematic diagrams, which schematically show an example of a package forming step in a method for manufacturing a shielding package in an embodiment. Figure 2 is a schematic diagram, which schematically shows an example of a package individualization step in a method for manufacturing a shielding package in an embodiment. Figure 3 is a schematic diagram, which schematically shows an example of a conductive coating coating step in a method for manufacturing a shielding package in an embodiment. Figure 4 is a schematic diagram, which schematically shows an example of a shielding layer forming step in a method for manufacturing a shielding package in an embodiment. Figure 5 is a schematic diagram, which schematically shows an example of a cutting step in a method for manufacturing a shielding package in an embodiment. Figures 6(a) and (b) are schematic diagrams showing a method for evaluating coating stability.

(without)

Claims (6)

A conductive coating comprises: a binder component (A) comprising an epoxy resin; metal particles (B); a blocked isocyanate hardener (C); a hardener (D) selected from at least one of the group consisting of an amine hardener and an imidazole hardener; and a solvent (E); and, relative to 100 parts by mass of the binder component (A), the metal particles (B) are 1200-3200 parts by mass, the blocked isocyanate hardener (C) is 70-200 parts by mass, the hardener (D) is 5-50 parts by mass, and the solvent (E) is 100-1500 parts by mass. The conductive coating of claim 1, wherein the metal particles (B) are at least one selected from the group consisting of silver particles, silver-coated copper particles and silver-coated copper alloy particles. The conductive coating of claim 1 or 2, wherein the aforementioned amine hardener is an aliphatic amine hardener having a reaction starting temperature of 60-100°C. The conductive coating of claim 1 or 2, wherein the reaction starting temperature of the imidazole hardener is 60-100°C. The conductive coating of claim 1 or 2, wherein the mass ratio (C)/(D) of the blocked isocyanate hardener (C) to the hardener (D) is 1.4-40. A method for manufacturing a resin molded product comprises the following steps: A conductive coating application step is to apply the conductive coating as described in any one of claims 1 to 5 to the resin molded product; and A shielding layer forming step is to heat the resin molded product coated with the aforementioned coating at a temperature of 70-80°C to harden the aforementioned coating to form a shielding layer.

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