EMI shielding adhesive composition and use thereof

Abstract

The object of the present invention is to provide an acrylic resin-containing adhesive composition having high impact resistance, which gives an EMI shielding cured product that cures sufficiently at low temperatures and has high EMI shielding performance, and which has high tensile strength of the adhesive surface when applied to a metal surface.The present invention relates to an EMI shielding adhesive composition comprising (a) a conductive filler, (b) a (meth)acrylic resin, (c) a tackifier, (d) a bismaleimide, and (e) a radical initiator.

Description

[Technical field]

[0001] Technical Field The present invention relates to an EMI shielding adhesive composition and its use. [Background technology]

[0002] Background technology Today's compact camera modules and sensors contain many devices that generate electromagnetic waves. Electromagnetic shielding adhesives are used in these electronic components to prevent electromagnetic radiation from the equipment and protect the equipment from external electromagnetic waves. It is generally known that such electromagnetic shielding adhesives exhibit high EMI shielding performance when highly filled with filler. However, if there is too much filler, the adhesive tends to become too hard and brittle, resulting in reduced impact resistance.

[0003] Patent Document 1 discloses a compound with high EMI shielding properties, but the impact resistance is poor due to the high silver content. Patent Document 2 proposes using a preparation containing an acrylic resin to reduce the elastic modulus in order to improve the impact resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-294254 A [Patent Document 2] International Publication No. 2021 / 075265 Summary of the Invention [Problem to be solved by the invention]

[0005] Summary of the Invention technical challenges Conventional adhesive compositions containing acrylic resins with high EMI shielding performance have difficulty in exerting sufficient pull strength on metal surfaces. Furthermore, when the composition is cured at low temperatures, significant oxygen inhibition occurs, making it difficult to completely cure the composition.

[0006] An object of the present invention is to provide an acrylic resin-containing adhesive composition with high EMI shielding performance, which gives an EMI shielding cured product that has high impact resistance and cures sufficiently at low temperatures, and which provides an EMI shielding cured product that has high tensile strength (pull strength) of the adhesive surface when applied to a metal surface. [Means for solving the problem]

[0007] Solutions to the challenges The present inventors have conducted intensive research to solve the above problems, and have found that the problems can be solved by an adhesive composition containing (a) a conductive filler, (b) a (meth)acrylic resin, (c) a tackifier, (d) a bismaleimide, and (e) a radical initiator. The present invention was completed through further investigation based on the above findings, and includes the following embodiments.

[0008] Item 1: An EMI shielding adhesive composition comprising: (a) a conductive filler; (b) a (meth)acrylic resin; (c) a tackifier; (d) a bismaleimide; and (e) a radical initiator. Item 2. The EMI shielding adhesive composition according to Item 1, wherein the conductive filler (a) is present in an amount of 60 to 95% by weight based on the total weight of the adhesive composition. Item 3. The EMI shielding adhesive composition according to item 1 or 2, wherein the tackifier (c) has a softening point of 150° C. or lower. Item 4 The bismaleimide is represented by the formula (I) TIFF2024531360000001.tif31116 [wherein n represents an integer of 1 to 40, and R represents a linear or at least partially cyclic divalent hydrocarbon group having 1 to 12 carbon atoms] 4. The EMI shielding adhesive composition according to any one of items 1 to 3, represented by the formula: Item 5. The EMI shielding adhesive composition according to any one of Items 1 to 4, which is used for assembling a camera module or a sensor. Item 6. Use of the EMI shielding adhesive composition according to any one of items 1 to 4 for assembling a camera module or a sensor. Item 7. A cured product obtained by curing the EMI shielding adhesive composition according to any one of Items 1 to 4. Item 8. A method for assembling a camera module or a sensor, comprising bonding an electronic component to a substrate using the EMI shielding adhesive composition according to any one of items 1 to 4. Effect of the Invention

[0009] Advantageous Effects of the Invention By using the EMI shielding adhesive composition of the present invention, it is possible to provide an EMI shielding cured product that has higher impact resistance than conventional techniques and is sufficiently cured at low temperatures. Furthermore, when the EMI shielding cured product is applied to a metal surface, the adhesive surface exhibits high tensile strength. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a tensile strength test in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Description of the embodiments In this specification, (meth)acrylate and (meth)acrylic mean acrylate or methacrylate, and acrylic or methacrylic, respectively.

[0012] The EMI shielding adhesive composition of the present invention comprises (a) a conductive filler; (b) a (meth)acrylic resin; (c) a tackifier; (d) a bismaleimide; and (e) a radical initiator.

[0013] (a) Conductive filler The EMI shielding adhesive composition of the present invention has EMI shielding properties because it contains a conductive filler.

[0014] The conductive filler may be any that imparts EMI shielding properties and can be appropriately selected from known conductive fillers.

[0015] The conductive filler preferably comprises at least one metal selected from the group consisting of silver, copper, and nickel, and may consist essentially of one of these metals or an alloy or composite of two or more of these metals.

[0016] The conductive filler may have a core-shell structure including a core portion and a shell portion, and the core portion may include an organic material such as a resin or an inorganic material other than the above-mentioned metals, and the shell portion may include at least one metal selected from the above-mentioned group of metals.

[0017] Conductive fillers may be spherical, ellipsoidal, acicular, flaky, amorphous, etc. The conductive filler may be a mixture of two or more of these shapes.

[0018] When the conductive filler is spherical, the average particle size is preferably 0.01 to 50 μm, more preferably 0.05 to 40 μm, and even more preferably 0.1 to 20 μm, from the viewpoints of maintaining good dispersibility and suppressing clogging during dispensing.

[0019] When the conductive filler is elliptical, needle-like, scaly, or amorphous, the average particle size is preferably 0.01 to 50 μm, more preferably 0.05 to 40 μm, and even more preferably 0.1 to 20 μm, from the viewpoint of maintaining good dispersibility and suppressing clogging during dispensing.

[0020] From the viewpoint of achieving excellent EMI properties, the EMI shielding adhesive composition of the present invention preferably contains a conductive filler in an amount of 60 to 95% by weight, more preferably 65 to 90% by weight, and even more preferably 70 to 85% by weight, based on the total weight of the adhesive composition.

[0021] Examples of the conductive filler include EA-0101 (manufactured by Metalor Technologies USA), SF15 (manufactured by Ames), TC-506 (manufactured by Tokuriki Honten), and FA-DAB-283 (manufactured by DOWA Holdings).

[0022] The EMI shielding adhesive composition of the present invention may contain only one type of conductive filler, or may contain two or more types.

[0023] (b) (Meth)acrylic resin Since the EMI shielding adhesive composition of the present invention contains a (meth)acrylic resin, the cured product obtained by curing this composition has excellent impact resistance even though it contains a conductive filler.

[0024] The (meth)acrylic resin is a polymer obtained by polymerizing a monomer containing at least one hydrocarbon (meth)acrylate monomer that may be substituted with a hydrocarbon moiety. The hydrocarbon (meth)acrylate monomer may be a polyfunctional acrylate. When the (meth)acrylic resin is a copolymer of two or more hydrocarbon (meth)acrylate monomers, it is typically a random copolymer. The substitution structure that the hydrocarbon moiety may have is not particularly limited, but includes an oxygen atom, a sulfur atom, a nitrogen atom, an ester bond, an amide bond, a carbonyl group, and the like. The hydrocarbon moiety may be substituted with at least two selected from the above-mentioned substitution structure group. The hydrocarbon moiety may be saturated or unsaturated. The hydrocarbon moiety may be linear, branched, cyclic, or a combination of at least two of these.

[0025] Examples of (meth)acrylate monomers include (meth)acrylic acid alkyl esters (including polyfunctional acrylates). In this case, if the glass transition temperature (Tg) is too high, the elastic modulus becomes high and sufficient impact resistance cannot be obtained. The glass transition temperature (Tg) is preferably 50°C or less, more preferably 40°C or less, and even more preferably 30°C or less.

[0026] Examples of alkyl (meth)acrylates include n-propyl (meth)acrylate, glycidyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-methacryloxyethyl trimethoxysilane, 2-methacryloxyethyl triethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl triethoxysilane, 3-methacryloxymethyl diethoxysilane, 4-methacryloxybutyl trimethoxysilane, 4-methacryloyloxypropyl triethoxy ... Examples of the acrylates include butyl triethoxysilane, dicyclopentenyloxyethyl (meth)acrylate, pentamethyl piperidyl (meth)acrylate, tetramethyl piperidyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, stearyl (meth)acrylate, 2-methacryloyloxyethyl succinate, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

[0027] Examples of alkyl polyfunctional (meth)acrylates include dipropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol #200 di(meth)acrylate, EO modified bisphenol A di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated bisphenol A di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated polypropylene glycol di(meth)acrylate, glycerol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0028] Other examples of (meth)acrylate monomers include urethane (meth)acrylates, (poly)ester (meth)acrylates, and (poly)ether (meth)acrylates.

[0029] (Meth)acrylic resins are commercially available from many manufacturers and can be produced according to typically known methods.

[0030] Examples of (meth)acrylic resins include FA-512M manufactured by Hitachi Chemical Co., Ltd., FA-711MM manufactured by Hitachi Chemical Co., Ltd., FA-712HM manufactured by Hitachi Chemical Co., Ltd., FA-400M manufactured by Hitachi Chemical Co., Ltd., Light Ester G-201P manufactured by Kyoeisha Chemical Co., Ltd., PHE-1G manufactured by Shin-Nakamura Chemical Co., Ltd., Company S manufactured by Shin-Nakamura Chemical Co., Ltd., and SA manufactured by Shin-Nakamura Chemical Co., Ltd.

[0031] From the viewpoint of maintaining excellent electromagnetic wave shielding properties, the EMI shielding adhesive composition of the present invention preferably contains a (meth)acrylic resin in an amount of 5 to 40% by weight, more preferably 10 to 35% by weight, and even more preferably 15 to 30% by weight.

[0032] The EMI shielding adhesive composition of the present invention may contain only one type of (meth)acrylic resin, or may contain two or more types.

[0033] (c) Tackifier The EMI shielding adhesive composition of the present invention contains a tackifier and a bismaleimide described below, which improves the curing properties of the composition even when cured at low temperatures, and the adhesive surface when applied to a metal surface has high tensile strength (pull strength).

[0034] Examples of tackifiers include rosin and ester resins derived therefrom.

[0035] A tackifier having a temperature range in which it exhibits adhesiveness during curing and subsequent thermal history can be selected. In the present application, the softening point is preferably 150° C. or lower, more preferably 130° C. or lower, and even more preferably 110° C. In this specification, the softening point refers to a value measured by the ring and ball method.

[0036] Examples of the tackifier include rosin derivatives such as KE-311 (softening point 90 to 100) and D-125 (softening point 120 to 130) (both manufactured by Arakawa Chemical Industries, Ltd.).

[0037] From the viewpoints of suppressing a significant increase in viscosity and exhibiting excellent adhesion, the EMI shielding adhesive composition of the present invention preferably contains a tackifier in an amount of 1 to 15 wt %, more preferably 3 to 13 wt %, and even more preferably 5 to 11 wt %, based on the resin components excluding the filler.

[0038] The EMI shielding adhesive composition of the present invention may contain only one tackifier, or may contain two or more tackifiers.

[0039] (d) Bismaleimide Because the EMI shielding adhesive composition of the present invention contains the above-mentioned tackifier and bismaleimide, the curing properties of the composition are improved even when cured at low temperatures, and the adhesive surface when applied to a metal surface has high tensile strength (pull strength).

[0040] The bismaleimide preferably has the formula (I) TIFF2024531360000002.tif33118 [wherein n represents an integer of 1 to 40, and R represents a linear or at least partially cyclic divalent hydrocarbon having 1 to 12 carbon atoms] It is expressed as:

[0041] In the above formula (I), n is preferably 20 to 40, more preferably 30 to 40, and R preferably represents a linear or at least partially cyclic divalent hydrocarbon having 2 to 8 carbon atoms.

[0042] In the EMI shielding adhesive composition of the present invention, from the viewpoints of improving adhesion to metal surfaces and suppressing a significant increase in viscosity, the content of bismaleimide is preferably 1 to 30% by weight, more preferably 5 to 25% by weight, and even more preferably 10 to 20% by weight, based on the resin components excluding the filler.

[0043] The EMI shielding adhesive composition of the present invention may contain only one type of bismaleimide, or may contain two or more types.

[0044] (e) Radical initiator The EMI shielding adhesive composition of the present invention contains a radical initiator, which causes a polymerization reaction between the (meth)acrylic resin and the bismaleimide, and the composition has high curability even when cured at low temperatures. Furthermore, when this composition is applied to a metal surface, the adhesive surface has high tensile strength.

[0045] The radical initiator can be appropriately selected from known radical initiators.

[0046] Specific examples of radical initiators include Perbutyl O (tert-butyl peroxy-2-ethylhexanoate), Perhexyl O (tert-hexyl peroxy-2-ethylhexanoate), Perocta O (1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate), Perbutyl ND (tert-butyl peroxyneodecanoate), and Peroyl TCP (bis(4-tert-butylcyclohexyl)peroxydicarbonate) (all manufactured by NOF Corporation).

[0047] From the viewpoint of maintaining stability during use, the EMI shielding adhesive composition of the present invention contains a radical initiator in an amount of preferably 3 to 20% by weight, more preferably 5 to 17% by weight, and even more preferably 7 to 14% by weight, based on the resin components excluding the filler.

[0048] The EMI shielding adhesive composition of the present invention may contain only one radical initiator, or may contain two or more radical initiators.

[0049] Other Ingredients The EMI shielding adhesive composition of the present invention may further contain other components, or may contain two or more types of other components, as necessary.

[0050] Examples of other ingredients include adhesion promoters (eg, silanes), coupling agents (eg, titanates), and rheology modifiers (eg, fumed silica).

[0051] Purpose The EMI shielding adhesive composition of the present invention is preferably used for assembling a camera module and a sensor. The camera module is not particularly limited, but examples thereof include small camera modules used in smartphones and the like. EXAMPLES

[0052] Working Example The adhesive compositions of Examples 1 to 4 and Comparative Examples 1 and 2 were prepared by mixing the components in the composition ratios shown in Table 1 (the units of the numerical values ​​in Table 1 are weight ratios). Specifically, the components were added in any ratio, kneaded and dispersed using a planetary mixer, and vacuum degassed to obtain adhesive compositions.

[0053] The following ingredients were used: (a) Conductive filler Ag flake filler AG1 SA-0201 (Metalor Technologies USA) Ag flake filler AG2 DNS-0351P (manufactured by Daicel Corporation) Ag flake filler AG3 SF78 (manufactured by Ames)

[0054] (b) (Meth)acrylic resin M-5700 ((2-hydroxy-3-phenoxypropyl acrylate) manufactured by Toagosei Co., Ltd.) UN-7600 (urethane acrylate oligomer, manufactured by Negami Chemical Industry Co., Ltd.)

[0055] (c) Tackifier KE-311 (colorless rosin ester, softening point (ring and ball method): 90-100°C, manufactured by Arakawa Chemical Industries, Ltd.) D-125 (rosin ester, softening point (ring and ball method): 120~130℃, manufactured by Arakawa Chemical Industry Co., Ltd.)

[0056] (d) Bismaleimide 24-468A (C36 branched alkanediylbis-[6-(2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl)hexanoic acid]; manufactured by Henkel AG & Co. KGaA)

[0057] (e) Radical initiator Parkadox 16 (manufactured by Nouryon)

[0058] Each evaluation test was carried out as follows. The evaluation results are shown in Table 1. Elasticity The mixed adhesive paste was cured at 80°C for 60 minutes to a thickness of 0.3 mm and molded into a sheet. This sheet was then cut into strips with a width of 10 mm and subjected to dynamic mechanical analysis (DMA) in a tensile mode to measure the storage modulus E' at temperatures from -40°C to 250°C.

[0059] Ball drop resistance The mixed adhesive paste was applied to a Ni plate measuring 10cm x 5cm, and a SUS plate measuring 7mm x 7mm was placed on top of it. At this time, a 0.1mm spacer was inserted between the two to keep the film thickness constant. The amount of paste applied was adjusted so that the diameter after compression was 3mm. After curing for 1 hour in an 80℃ oven, a ball weighing 30g was allowed to drop vertically onto the Ni plate. Starting from a height of 10cm, the height was increased in 10cm increments. The distance until the SUS plate peeled off was defined as the ball drop resistance (cm).

[0060] EMI performance The formulated adhesive paste was used to form a cured film with a size of 250 mm x 20 mm and a thickness of 100 μm. The film was cured in an oven at 80 °C for 1 h and then measured using the dual focus flat cavity (DFFC) method. The shielding effectiveness (db) at frequencies from 1 GHz to 8.5 GHz was measured.

[0061] Pull Strength The tensile strength was measured as shown in Figure 1. Specifically, the tensile strength was measured as follows. The paste was applied to a Ni plate measuring 10 cm x 5 cm, and another Ni plate measuring 5 mm x 5 mm was placed on top of it. A 0.1 mm spacer was inserted to keep the film thickness constant. The amount of paste applied was adjusted so that the diameter after compression was 3 mm. The upper Ni plate was cured in an oven at 80°C for 1 hour, and then pulled vertically at room temperature at 10 mm / min using a tension and compression tester manufactured by Imada Seisakusho Co., Ltd. The stress during pulling was defined as the adhesive strength.

[0062] [Table 1]

[0063] This shows that when the adhesive composition of Comparative Example 2, which contains a (meth)acrylic resin instead of an epoxy resin, is cured, a cured product having higher flexibility is obtained compared to when the adhesive composition of Comparative Example 1, which contains an epoxy resin, is cured.

[0064] Furthermore, it was found that when the adhesive compositions of Examples 1 to 4 containing a (meth)acrylic resin and a tackifier were cured, not only were highly flexible cured products obtained, but the tensile resistance of the adhesive surface against the metal surface was also improved.

Claims

1. (a) a conductive filler; (b) a (meth)acrylic resin; (c) a tackifier; (d) bismaleimide; and (e) Radical initiator An EMI shielding adhesive composition comprising:

2. 2. The EMI shielding adhesive composition according to claim 1, wherein the content of the conductive filler (a) is 60 to 95% by weight of the total adhesive composition.

3. 2. The EMI shielding adhesive composition according to claim 1, wherein the tackifier (c) has a softening point of 150°C or lower.

4. The bismaleimide has the formula (I) [wherein n represents an integer of 1 to 40, and R represents a linear or at least partially cyclic divalent hydrocarbon group having 1 to 12 carbon atoms] The EMI shielding adhesive composition according to claim 1 , wherein the adhesive composition is represented by the formula:

5. The EMI shielding adhesive composition according to any one of claims 1 to 4, which is used in assembling a camera module or a sensor.

6. Use of the EMI shielding adhesive composition according to any one of claims 1 to 4 for assembling a camera module or a sensor.

7. A cured product obtained by curing the EMI shielding adhesive composition according to any one of claims 1 to 4.

8. A method for assembling a camera module or a sensor, comprising adhering an electronic component to a substrate using the EMI shielding adhesive composition according to any one of claims 1 to 4.

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