JP2018172671A - Sealant for electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the waterproofness of an electronic apparatus when used in the electronic apparatus.SOLUTION: A sheet material for electronic apparatus 10 is disposed inside an electronic apparatus so that it is sandwiched between two members 21, 22. The sheet material has a core layer 11 that allows elastic compression, and a surface layer 12 that is put on one face of the core layer 11, adsorbs one of the two members 21, 22 and can be peeled again from the member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sheet material for an electronic device that is disposed between members such as a casing and various components inside the electronic device.

In recent years, there is an increasing need for waterproofing of electronic devices such as smartphones, mobile phones, and tablet terminals. A packing made of a foam may be used as a sealing material for waterproofing a connector, an electronic board, and various components on the electronic board inside the electronic device.
Conventionally, as a foam used in an electronic device, a crosslinked polyolefin resin foam sheet obtained by foaming and crosslinking a foamable polyolefin resin sheet containing a pyrolytic foaming agent is known (for example, patents). Reference 1).
Conventionally, a vehicular seal member includes an adsorbing / removing portion having adsorbability and releasability with respect to a wall surface of a vehicle body, and an elastic compressing portion that is elastically compressible and laminated on the adsorbing / removing portion. (For example, refer to Patent Document 2).

International Publication No. 2005/007731 JP 2007-280632 A

By the way, a waterproof sealing material used in an electronic device may be processed to be thin and thin with downsizing of the electronic device. However, when a sealing material made of a conventional foam used in an electronic device is processed to be thin or narrow, the waterproof performance of the electronic device may not be sufficiently improved.
On the other hand, since the vehicle sealing member described in Patent Document 2 is formed to be thick and is not assumed to be used in a narrow width, it is used as it is as a sealing material for electronic devices. It is difficult.

  This invention is made | formed in view of the above situation, and makes it a subject to provide the sealing material for electronic devices which can make the waterproof performance of an electronic device favorable when it is used with an electronic device. .

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by providing a surface layer having specific characteristics on one surface of an elastically compressible core layer in a sealing material. Completed the invention.
That is, the present invention provides the following [1] to [11].
[1] An electronic device sheet material disposed between two members inside an electronic device, wherein the core material is elastically compressible and laminated on one surface of the core layer, A sealing material for electronic equipment, comprising a surface layer adsorbed on one of the two members and detachable from the member.
[2] The electronic device sealing material according to [1], wherein the surface layer is made of a water-impermeable material.
[3] The above-mentioned resin composition for the surface layer constituting the surface layer contains at least one selected from the group consisting of butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic resin, and styrene thermoplastic elastomer. The sealing material for electronic devices as described in [1] or [2].
[4] The electronic device sealing material according to any one of [1] to [3], wherein the core layer is made of a water-impermeable material.
[5] The electronic device sealing material according to any one of [1] to [4], wherein the core layer is made of a foam.
[6] The electronic device sealing material according to [5], wherein the resin constituting the foam is a polyolefin resin.
[7] The electronic device sealing material according to [5] or [6], wherein the foam has closed cells.
[8] The electronic device according to any one of [5] to [7], wherein the foam has an average cell diameter in the MD and TD directions of 300 μm or less and an average cell diameter of ZD is 150 μm or less. Seal material.
[9] The electronic device sealing material according to any one of [6] to [8], wherein the foam has an expansion ratio of 1.2 to 20 cm ³ / g.
[10] The electronic device sealing material according to any one of [1] to [9], wherein the thickness is 0.05 to 2.5 mm.
[11] The electronic device sealing material according to any one of [1] to [10], wherein an adhesive material is provided on the other surface of the core layer.

  By using the sealing material for electronic equipment according to the present invention for electronic equipment, it becomes possible to improve the waterproof performance of the electronic equipment.

It is a schematic cross section which shows the sealing material for electronic devices which concerns on one Embodiment of this invention. It is a schematic cross section which shows the sealing material for electronic devices which concerns on other embodiment of this invention.

Hereinafter, embodiments according to the present invention will be described in detail.
[Sealant for electronic equipment]
The electronic device sealing material 10 according to an embodiment of the present invention includes a core layer 11 and a surface layer 12 laminated on one surface of the core layer 11 as shown in FIG.
As shown in FIG. 2, the electronic device sealing material 20 according to another embodiment includes a core layer 11, a surface layer 12 stacked on one surface of the core layer 11, and the other of the core layers 11. And an adhesive material 13 laminated on the surface.
The electronic device sealing materials 10 and 20 are disposed between the two members 21 and 22 inside the electronic device.

In the electronic device sealing materials 10 and 20, the core layer 11 is elastically compressible, and the surface layer 12 is adsorbed to one member 21 of the two members, and is re-attached to the member 21. It can be peeled off. The electronic device sealing materials 10 and 20 having such a configuration can exhibit a high water-stopping property because the surface layer 12 is adsorbed to the one member 21 while being pressed by the elastic force of the core layer 11. become. Further, since the adsorbed surface layer 12 has removability, the sealing materials 10 and 20 are peeled off from the one member 21 even after the sealing material 10 is once adsorbed to the one member 21 in the electronic device. Then, it becomes possible to incorporate the sealing materials 10 and 20 into the electronic device again.
Moreover, since the sealing material 20 for electronic devices provided with the adhesive material 13 adsorb | sucks the surface layer 12 to one member 21, and the adhesive material 13 adhere | attaches on the other member 22, two members 21 inside an electronic device, It becomes possible to make the water stoppage between 22 higher.

  Inside the electronic device, the members 21 and 22 that sandwich the sealing materials 10 and 20 are an electronic component, a housing, a metal plate, a circuit board, and the like inside the electronic device. The electronic device sealing material increases the water-stopping property between the two members 21 and 22 and prevents water from entering a predetermined portion inside the electronic device. For example, the sealing material is disposed so as to surround various electronic components such as connectors or the entire electronic substrate, and prevents the electronic component and the electronic substrate from getting wet.

The thickness of the electronic device sealing material is preferably 0.05 to 2.5 mm. The sealing material for electronic devices can ensure water-stopping property by setting the thickness to 0.05 m or more. Moreover, it can use suitably for the electronic device reduced in size by setting it as 2.5 mm or less. From these viewpoints, the thickness of the electronic device sealing material is more preferably 0.1 to 2 mm, and further preferably 0.15 to 1.5 mm. Even if the sealing material for electronic devices of the present invention is thin as described above, it can sufficiently exhibit water-stopping properties.
In addition, the thickness of the sealing material for electronic devices means the thickness of the whole sealing material for electronic devices, and when the sealing material for electronic devices consists of two layers, a core layer and a surface layer, the total of these two layers. Is the thickness. Moreover, when it consists of three layers of a core layer, a surface layer, and an adhesive material, it is the total thickness of these three layers.

The electronic device sealing material is preferably narrow in width, and specifically processed into a thin line. For example, the width of the sealing material for electronic equipment may be 5 mm or less, preferably 3 mm or less, more preferably 1 mm or less. Even if the width | variety is narrowed in this way, the sealing material for electronic devices of this invention can exhibit water-stopping property. Moreover, the sealing material for electronic devices can be suitably used in the downsized electronic device by narrowing the width.
Although the lower limit of the width | variety of the sealing material for electronic devices is not specifically limited, For example, the thing of 0.1 mm or more may be sufficient, and the thing of 0.2 mm or more may be sufficient. The sealing material for electronic devices can easily increase the water-stopping property by setting a width equal to or greater than these lower limits.
Note that the planar shape of the electronic device sealing material is not particularly limited, but may be an elongated rectangular shape, a frame shape, an L shape, a U shape, or the like. However, in addition to these shapes, any other shapes such as a normal quadrangle and a circle may be used.

  The sealing material for electronic devices can be used inside various electronic devices, but is preferably used inside various portable information devices. Examples of portable information devices include mobile phones such as smartphones, tablet terminals, and notebook personal computers. Since the electronic device sealing material of the present invention is thin and can exhibit its function appropriately even if the width is small, it can be suitably used for a portable information device with a small space for arranging the electronic device sealing material. It is.

Hereinafter, each member of the sealing material for electric equipment will be described in more detail.
(Core layer)
The core layer is not particularly limited as long as it is elastically compressible, and specific examples include rubber materials and foams, with foams being preferred. By using the foam, the core layer is easily compressed in the thickness direction, so that the core layer can be easily incorporated into a miniaturized electronic device or a portion having an uneven surface.
The rubber material is made of a non-porous material, and various known rubber materials can be used.

(25% compressive strength)
The 25% compressive strength of the core layer is preferably 5 to 1500 kPa, more preferably 40 to 800 kPa, and even more preferably 50 to 700 kPa. By setting the 25% compressive strength of the core layer within these ranges, the core layer can be appropriately elastically compressed, and the water stoppage can be increased. In addition, 25% compressive strength can be measured by the measuring method shown in the Example mentioned later.

(Closed cell rate)
Moreover, it is preferable that a core layer consists of a water-impermeable material from a viewpoint of improving the sealing performance of the sealing material for electronic devices. Therefore, the foam is preferably a foam having closed cells. The foam having closed cells means that the ratio of closed cells to all bubbles (referred to as “closed cell ratio”) is 70% or more. The closed cell ratio is preferably 75% or more, more preferably 90% or more.
The closed cell ratio can be determined according to ASTM D2856 (1998). Commercially available measuring instruments include a dry automatic densitometer Accupic 1330 and the like.

More specifically, the closed cell ratio is measured in the following manner. A test piece having a flat square shape with a side of 5 cm and a constant thickness is cut out from the sheet-like foam. The thickness of the test piece is measured, the apparent volume V ₁ of the test piece is calculated, and the weight W _{1 of the} test piece is measured. Next, the apparent volume V ₂ occupied by the bubbles is calculated based on the following formula. The density of the resin constituting the test piece is 1 g / cm ³ .
Apparent volume occupied by bubbles V ₂ = V ₁ −W ₁
Subsequently, the test piece is submerged in distilled water at 23 ° C. to a depth of 100 mm from the water surface, and a pressure of 15 kPa is applied to the test piece over 3 minutes. Thereafter, the test piece is taken out of the water to remove the water adhering to the surface of the test piece, the weight W _{2 of the} test piece is measured, and the open cell rate F ₁ and the closed cell rate F ₂ are calculated based on the following formulas. To do.
Open cell ratio F ₁ (%) = 100 × (W ₂ −W ₁ ) / V ₂
Closed cell ratio F ₂ (%) = 100−F ₁

(Average bubble diameter)
The foam bubbles used in the core layer are preferably so-called fine bubbles. Specifically, the foam has an average cell diameter in the MD and TD directions of preferably 300 μm or less, more preferably 250 μm or less, still more preferably 200 μm or less, and most preferably 100 μm or less. The average cell diameter in the ZD direction is preferably 150 μm or less, more preferably 120 μm or less, still more preferably 80 μm or less, and most preferably 40 μm or less. By making fine bubbles in this way, the number of bubble walls per unit length increases. Therefore, even when the foam (sealing material for electronic equipment) has a narrow width, for example, a large number of bubble walls exist between the narrow width, and the water-stopping property is improved. In addition, a foam becomes easy to form a microbubble by making a crosslinking degree and a foaming ratio into the suitable range mentioned later.
Further, each of the average cell diameters in the MD and TD directions is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 25 μm or more, from the viewpoint of ease of production. The average cell diameter of ZD is preferably 5 μm or more, more preferably 10 m or more, and further preferably 15 μm or more.
The ratio of the average bubble diameter in the MD direction to the average bubble diameter in the ZD direction (hereinafter also referred to as “MD / ZD”) is 1 to 8, and the average bubble in the TD direction with respect to the average bubble diameter in the ZD direction. The diameter ratio (hereinafter also referred to as “TD / ZD”) is preferably 1-8. Furthermore, it is more preferable that MD / ZD is 2-7 and TD / ZD is 2-7.

The average bubble diameter is measured in the following manner.
A sheet-like foam cut into 50 mm square was prepared as a foam sample for measurement. This was immersed in liquid nitrogen for 1 minute and then cut in the thickness direction along the MD and TD directions with a razor blade. This cross section is taken with a digital microscope (Keyence Co., Ltd. “VHX-900”), and a 200 times magnified photograph is taken. All of the cross sections present in a length of 2 mm in each of the MD, TD, and ZD directions. The bubble diameter of each bubble was measured, and the operation was repeated 5 times. And the average value of all the bubbles was made into the average bubble diameter of MD direction, TD direction, and ZD direction.
In addition, MD direction means Machine direction and is a direction that coincides with the extrusion direction and the like, and TD direction means Transverse direction and is a direction orthogonal to the MD direction. The ZD direction is the thickness direction of the foam and is a direction perpendicular to both the MD direction and the TD direction.

(Crosslinking degree)
The foam is preferably a crosslinked foam, and the degree of crosslinking is preferably 20 to 70% by mass. Further, the degree of crosslinking is more preferably 25 to 65% by mass, and further preferably 30 to 60% by mass. By setting the degree of cross-linking to the lower limit value or more, it becomes easy to obtain a foam having an average cell diameter in the above range. Moreover, it becomes easy to set the compressive strength of a core layer in the above-mentioned range by making a crosslinking degree into these ranges.

(Foaming ratio)
The foaming ratio of the foam is preferably 1.2 to 20 cm ³ / g. By setting the expansion ratio within this range, the compressive strength of the core layer is easily set within the above range, and the water-stopping property is easily improved. In addition, the mechanical strength of the foam is easily improved. From these viewpoints, the foaming ratio of the foam is more preferably ³ to 15 cm ³ / g, and still more preferably 5 to 12 cm ³ / g. In the present invention, the density of the foam is obtained in accordance with JIS K7222, and the reciprocal thereof is taken as the expansion ratio.

The foam is a resin foam composed of a resin. Examples of the resin constituting the foam include polyolefin resins, various elastomers, and mixtures thereof, and among them, polyolefin resins are preferable. By using the polyolefin resin for the foam, it becomes easy to adjust the compressive strength of the core layer within the above-described range, and it becomes easy to form a thin foam having a uniform thickness.
Examples of the elastomer used for the foam include various thermoplastic elastomers such as a styrene thermoplastic elastomer and an ethylene propylene thermoplastic elastomer such as EPDM. In addition, as a styrene-type thermoplastic elastomer, what was enumerated as a styrene-type thermoplastic elastomer which can be used by the surface layer mentioned later can be selected suitably, and can be used.

[Polyolefin resin]
Examples of the polyolefin resin include a polyethylene resin, a polypropylene resin, and an ethylene-vinyl acetate copolymer. Among these, a polyethylene resin is preferable.
Examples of the polyethylene resin include a polyethylene resin polymerized with a polymerization catalyst such as a Ziegler-Natta compound, a metallocene compound, and a chromium oxide compound. Preferably, a polyethylene resin polymerized with a polymerization catalyst of a metallocene compound is used.

The polyethylene resin is preferably linear low density polyethylene. By using linear low-density polyethylene, it is possible to impart good elastic compression characteristics to the foam and to reduce the thickness of the foam. From the viewpoint of thinning, the linear low-density polyethylene is more preferably obtained using a polymerization catalyst such as a metallocene compound. The linear low density polyethylene is obtained by copolymerizing ethylene (for example, 75% by mass or more, preferably 90% by mass or more with respect to the total amount of monomers) and a small amount of α-olefin as required. More preferred is linear low density polyethylene.
Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Especially, a C4-C10 alpha olefin is preferable.
Polyethylene resin, for example the density of the linear low density polyethylene as described above is preferably 0.870~0.910g / cm ^3, more preferably 0.875~0.907g / cm ^3, 0.880~0.905g / Cm ³ is more preferable. As the polyethylene resin, a plurality of polyethylene resins can be used, and a polyethylene resin outside the above-described density range may be added.

(Metallocene compound)
Examples of the metallocene compound include compounds such as a bis (cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched between π-electron unsaturated compounds. More specifically, tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum have one or more cyclopentadienyl rings or their analogs as ligands (ligands). Can be mentioned.
Such metallocene compounds have uniform active site properties and each active site has the same activity. A polymer synthesized using a metallocene compound has high uniformity in molecular weight, molecular weight distribution, composition, composition distribution, etc., so when a sheet containing a polymer synthesized using a metallocene compound is crosslinked, the crosslinking is uniform. Proceed to. Since the uniformly cross-linked sheet is uniformly foamed, it is easy to reduce the variation in the bubble diameter. Moreover, since it can extend | stretch uniformly, it becomes easy to make the thickness of a foam thin and uniform.

Examples of the ligand include a cyclopentadienyl ring and an indenyl ring. These cyclic compounds may be substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. Examples of the hydrocarbon group include a methyl group, an ethyl group, various propyl groups, various butyl groups, various amyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups, and various decyl groups. , Various cetyl groups, phenyl groups and the like. The “various” means various isomers including n-, sec-, tert-, and iso-.
Moreover, what polymerized the cyclic compound as an oligomer may be used as a ligand.
In addition to π-electron unsaturated compounds, monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, phosphides, aryls Phosphide or the like may be used.

Examples of metallocene compounds containing tetravalent transition metals and ligands include, for example, cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethyl And silyltetramethylcyclopentadienyl-t-butylamidozirconium dichloride.
The metallocene compound exhibits an action as a catalyst in the polymerization of various olefins by combining with a specific cocatalyst (co-catalyst). Specific examples of the cocatalyst include methylaluminoxane (MAO) and boron compounds. In addition, the usage-amount of the cocatalyst with respect to a metallocene compound has preferable 10-1 million mol times, and 50-5,000 mol times is more preferable.
When the above-mentioned linear low density polyethylene is used as the polyolefin resin contained in the foam, the above linear low density polyethylene may be used alone, or may be used in combination with other polyolefin resins. For example, you may use together with the other polyolefin resin described below. When other polyolefin resin is contained, the ratio of the other polyolefin resin to the total amount of the linear low-density polyethylene and the other polyolefin resin is preferably 80% by mass or less, more preferably 50% by mass or less, and 20% by mass. % Or less is more preferable.

As for the ethylene-vinyl acetate copolymer used as polyolefin resin, the ethylene-vinyl acetate copolymer containing 50 mass% or more of ethylene is mentioned, for example. When an ethylene-vinyl acetate copolymer (EVA) is used, it is preferably used in combination with the polyethylene resin (PE) described above, and the mass ratio (EVA / PE) is preferably 10/90 to 90/10, 20 / 80-80 / 20 is more preferable, and 50 / 50-80 / 20 is more preferable.
Examples of the polypropylene resin include polypropylene and a propylene-α-olefin copolymer containing 50% by mass or more of propylene. These may be used alone or in combination of two or more.
Specific examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Octene etc. can be mentioned, Among these, C6-C12 alpha olefin is preferable.

  In the case of using a polyolefin resin as the resin for the foam, the resin contained in the foam may be a polyolefin resin alone or may contain a resin other than the polyolefin resin. In the foam, the ratio of the polyolefin resin to the total amount of the resin is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and still more preferably 70 to 100% by mass. Examples of the resin used in combination with the polyolefin resin include elastomers such as the above-described styrenic thermoplastic elastomer. The content of the elastomer is preferably 0 to 50% by mass, more preferably 0 to 40% by mass, and still more preferably 0 to 30% by mass with respect to the total amount of the resin.

(Pyrolytic foaming agent)
The foam is preferably formed by foaming a foamable composition containing a pyrolytic foaming agent in addition to the resin.
As the pyrolytic foaming agent, an organic foaming agent or an inorganic foaming agent can be used. Organic foaming agents include azodicarbonamide, azodicarboxylic acid metal salts (such as barium azodicarboxylate), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N, N′-dinitrosopentamethylenetetramine, Examples thereof include hydrazine derivatives such as hydrazodicarbonamide, 4,4′-oxybis (benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonyl semicarbazide.
Examples of the inorganic foaming agent include ammonium acid, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate, and the like.
Among these, an azo compound is preferable and azodicarbonamide is particularly preferable from the viewpoint of obtaining fine bubbles and from the viewpoints of economy and safety. These pyrolytic foaming agents can be used alone or in combination of two or more.
The amount of the thermally decomposable foaming agent in the foamable composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 7 parts by mass, and even more preferably 1.5 to 5 parts per 100 parts by mass of the resin. Part by mass.

Moreover, it is preferable that a foamable composition contains a cell nucleus regulator in addition to the said resin and a thermal decomposition type foaming agent. Examples of the cell nucleus adjusting agent include zinc compounds such as zinc oxide and zinc stearate, and organic compounds such as citric acid and urea. Among these, zinc oxide is more preferable. By using a cell nucleus modifier in addition to the above-mentioned foaming agent, it becomes easier to make the bubble diameter smaller. The blending amount of the cell core modifier is preferably 0.4 to 8 parts by mass, more preferably 0.5 to 5 parts by mass, and still more preferably 0.8 to 2.5 parts by mass with respect to 100 parts by mass of the resin. It is.
In addition to the above, the foam (foamable composition) is generally used for foams such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, fillers and the like. An additive may be contained.

  The thickness of the core layer is preferably 0.1 to 1.5 mm. By setting the thickness of the core layer to 0.1 mm or more, it becomes easy to press the electronic device sealing material against the member inside the electronic device due to the elastic force of the core layer. Moreover, it can use suitably for the portable electronic device miniaturized by setting it as 1.5 mm or less. From these viewpoints, the thickness of the core layer is more preferably 0.2 to 1.2 mm, and still more preferably 0.3 to 0.7 mm.

[Surface layer]
As described above, the surface layer may be any material that adsorbs to one of the two members sandwiching the sealing material for electronic equipment and can be re-peeled from the member, but is at least one of an elastomer and a soft resin. It is preferable that it is comprised. The surface layer can easily improve the adsorptivity and removability of the surface layer by using an elastomer or a soft resin. The elastomer and the soft resin may be collectively referred to as a main agent in the present specification.
The surface layer is preferably made of a water-impermeable material. The surface layer is made of at least one of an elastomer and a soft resin and is made of a non-porous body, thereby making it impermeable to water.

  Examples of the elastomer include acrylonitrile butadiene rubber, ethylene propylene diene rubber, ethylene propylene rubber, olefin-based thermoplastic elastomer (TPO), natural rubber, butyl rubber, polybutadiene rubber, polyisoprene rubber, and styrene-based thermoplastic elastomer. Styrene-based thermoplastic elastomers include styrene-butadiene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof. Etc. Among these, a hydrogenated product is preferable, and a hydrogenated styrene-isoprene-styrene block copolymer is more preferable. These elastomers may be used alone or in combination of two or more.

  The elastomer constituting the surface layer preferably has a Shore A hardness of 60 or less. By setting the Shore A hardness to 60 or less, the surface layer tends to have good adsorptivity and removability. 10-55 are more preferable, as for the Shore A hardness of the elastomer which comprises a surface layer, 20-50 are more preferable, and 30-45 are more preferable.

Moreover, as a soft resin, Preferably an acrylic resin is mentioned. Examples of the acrylic resin include an acrylic polymer obtained by polymerizing a polymerizable monomer containing a (meth) acrylic acid alkyl ester monomer.
In this specification, the term “(meth) acrylic acid alkyl ester” refers to a concept including both an acrylic acid alkyl ester and a methacrylic acid alkyl ester, and the same applies to other similar terms. .
The (meth) acrylic acid alkyl ester monomer is an ester of (meth) acrylic acid and an aliphatic alcohol, and is an alkyl ester derived from an aliphatic alcohol having 1 to 18 carbon atoms in the alkyl group of the aliphatic alcohol. More preferred is an alkyl ester derived from an aliphatic alcohol having 1 to 8 carbon atoms.
Specific examples of the (meth) acrylic acid alkyl ester monomer (A) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl ( (Meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) Acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, and tetradecyl (meth) Acrylate, and the like.
Moreover, it is preferable to contain the alkyl ester derived from the aliphatic alcohol whose carbon number of an alkyl group is 4-8 among (meth) acrylic-acid alkylester type monomers, The ratio is 70 on the basis of polymerizable monomer whole quantity basis. % By mass or more is preferable, 80 to 100% by mass is more preferable, and 90 to 100% by mass is further preferable. By containing many alkyl esters derived from an aliphatic alcohol having 4 to 8 carbon atoms in the alkyl group, it is possible to impart good adsorptivity and removability to the surface layer.
The (meth) acrylic acid alkyl ester monomers may be used alone or in combination of two or more.

Although a polymerizable monomer may consist of a (meth) acrylic-acid alkylester type monomer, in addition to a (meth) acrylic-acid alkylester type monomer, you may contain a polar group containing vinyl monomer. The polar group-containing vinyl monomer has a polar group and a vinyl group. Examples of polar group-containing vinyl monomers include carboxylic acid vinyl esters such as vinyl acetate, carboxylic acids containing vinyl groups such as (meth) acrylic acid and itaconic acid, and anhydrides thereof, 2-hydroxyethyl (meth) Vinyl monomers having a hydroxyl group such as acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, caprolactone-modified (meth) acrylate, polyoxyethylene (meth) acrylate, and polyoxypropylene (meth) acrylate , (Meth) acrylonitrile, N-vinylpyrrolidone, N-vinylcaprolactam, N-vinyllaurylactam, (meth) acryloylmorpholine, (meth) acrylamide, dimethyl (meth) acrylamide, N-methylol (meth) a Riruamido, N- butoxymethyl (meth) acrylamide, and nitrogen-containing vinyl monomers such as dimethylaminomethyl (meth) acrylate.
Moreover, the polymerizable monomer may contain other monomers other than the (meth) acrylic acid alkyl ester monomer and the polar group-containing vinyl monomer. Examples of other monomers include styrene monomers and polyfunctional monomers. Examples of the styrene monomer include styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene.
Moreover, as a polyfunctional monomer, the monomer which has 2 or more of vinyl groups is mentioned, Preferably the polyfunctional (meth) acrylate which has 2 or more of (meth) acryloyl groups is mentioned.
What is necessary is just to adjust suitably the kind and content of the polymerizable monomer used for an acrylic polymer so that the adsorptivity and re-peelability of a surface layer may become favorable.

  The weight average molecular weight of the acrylic polymer is preferably 100,000 to 1,500,000, more preferably 300,000 to 1,200,000, still more preferably 500,000 to 1,000,000. In addition, a weight average molecular weight is measured using a gel permeation chromatography (GPC), and is calculated as a polystyrene conversion value.

As the main agent, in the above, it is more preferable to use butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic resin, styrenic thermoplastic elastomer, or a mixture of two or more selected from these. When these elastomers or acrylic resins are used, for example, the adhesion to the core layer made of a polyolefin resin foam can be easily improved.
The resin composition constituting the surface layer (hereinafter also referred to as the surface layer resin composition) preferably contains 70% by mass or more of the above main agent with respect to the total amount of the resin composition for the surface layer, and is 80 to 99% by mass. % Is more preferable, 85 to 97% by mass is more preferable, and 87 to 97% by mass is particularly preferable.

The main agent preferably contains butyl rubber, an acrylic resin, and a styrene thermoplastic elastomer, and more preferably contains butyl rubber and an acrylic resin, from the viewpoint of making the adsorptivity better.
Butylcomb is also preferably mixed with other elastomers. For example, a mixture of butyl rubber and ethylene propylene diene rubber (EPDM) may be used as a main agent. In this case, the mass ratio of butyl rubber to EPDM is preferably 5/95 to 80/20, and more preferably 8/92 to 70/30. By setting it as such a mass ratio, it becomes easy to make the balance of adsorptivity and peelability favorable.

(Modified polymer)
A modified polymer may be further blended in the surface layer resin composition. It becomes easy to improve adsorptivity by mix | blending a modified polymer. As the modified polymer, for example, a petroleum copolymer, an ethylene-vinyl acetate copolymer, or the like is used. Coumarone-indene resin, terpene resin, terpene phenol resin, polymerized rosin, rosin ester-based rosin resin, xylene-based resin, and the like can also be used.
The modified polymer may be used alone or in combination of two or more.
The content of the modified polymer is 0.5 to 20% by mass, more preferably 1 to 15% by mass, still more preferably 1 to 10% by mass, particularly preferably 2 to 2%, based on the total amount of the resin composition for the surface layer. 10% by mass.

Examples of the ethylene-vinyl acetate copolymer used in the modified polymer include an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene, and may be modified as appropriate.
Various petroleum resins can be used as the petroleum-based copolymer, and examples thereof include C5-based petroleum resins, C9-based petroleum resins, C5C9-based petroleum resins, dicyclopentadiene resins, and hydrides thereof. Of these, hydrides are preferred. C5 petroleum resins are also preferred, and hydrides of C5 petroleum resins are more preferred.

  When the main component constituting the surface layer is an elastomer selected from butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrenic thermoplastic elastomer, or a mixture thereof, a petroleum copolymer, It is preferable to use a modified polymer selected from ethylene-vinyl acetate copolymers, and it is more preferable to use petroleum-based copolymers. By using a petroleum-based copolymer together with an elastomer, it is possible to effectively improve the adsorptivity.

  In addition, when the main component constituting the surface layer is an acrylic resin, a petroleum copolymer, coumarone-indene resin, terpene resin, terpene phenol resin, rosin resin, xylene resin should be used as the modified polymer. Of these, rosin resins are preferred. By using these modified polymers together with an acrylic resin, it is possible to effectively improve the adsorptivity.

(Other additives)
When the resin composition for surface layers contains an elastomer as a main ingredient, you may mix | blend a vulcanizing agent with the resin composition for surface layers further. Examples of the vulcanizing agent include organic peroxides, sulfur, sulfur compounds and the like. Examples of the organic peroxide include diisopropylbenzene hydroperoxide, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, t-butyl perbenzoate, cumyl hydroperoxide, t-butyl hydroperoxide, 1,1. -Di (t-butylperoxy) -3,3,5-trimethylhexane, n-butyl-4,4-di (t-butylperoxy) valerate, α, α'-bis (t-butylperoxyisopropyl) ) Benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, t-butylperoxycumene and the like. Examples of the sulfur compound include tetramethylthiuram disulfide, tetramethylthiuram monosulfide, zinc dimethyldithiocarbamate, 2-mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazolesulfenamide, Nt- Examples include butyl-2-benzothiazole sulfenamide, sulfur monochloride, sulfur dichloride and the like.
Even when the resin composition for a surface layer contains an elastomer, the resin composition for a surface layer does not contain a vulcanizing agent, and the surface layer is preferably unvulcanized. When the surface layer is unvulcanized and the above-described modified polymer is blended, the surface layer easily exhibits adsorptivity and removability.

On the other hand, when the resin composition for surface layers contains an acrylic resin as a main ingredient, you may mix | blend a crosslinking agent with the resin composition for surface layers further. The crosslinking agent is not particularly limited. For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, a peroxide crosslinking agent, a urea crosslinking agent, a metal alkoxide crosslinking agent, a metal chelate crosslinking agent. , Metal salt crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, amine crosslinking agents, polyfunctional acrylates, and the like. The above crosslinking agents may be used alone or in combination. In these, an isocyanate type crosslinking agent is preferable.
The content of the crosslinking agent is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, still more preferably 0.8 to 5% by mass, particularly preferably based on the total amount of the resin composition for the surface layer. Is 1.5-5 mass%.

In addition, the surface layer resin composition constituting the surface layer may contain other additives such as a plasticizer, a softener, a pigment, a dye, a reinforcing material, a flame retardant, and an antioxidant. When the resin composition for surface layers contains an elastomer, it is preferable that the resin composition for surface layers contains one or both of a reinforcing material and antioxidant.
As the reinforcing material, it is preferable to use carbon black. The carbon black is preferably contained in an amount of 1 to 15% by mass, more preferably 2 to 10% by mass, and further preferably 2 to 8% by mass based on the total amount of the resin composition for the surface layer.
Antioxidants include phenolic antioxidants, sulfur antioxidants, phosphorus antioxidants, amine antioxidants, etc. Among these, sulfur antioxidants, phenolic antioxidants, etc. Antioxidants are preferred. The content of the antioxidant is preferably 0.1 to 8% by mass, more preferably 0.2 to 5% by mass, and more preferably 0.5 to 3% by mass based on the total amount of the resin composition for the surface layer.

  The thickness of the surface layer is preferably 0.05 to 0.5 mm. By making the thickness of the surface layer 0.05 mm or more, it becomes easy to develop the adsorptivity. Moreover, it can use suitably for the small electronic device by setting it as 0.5 mm or less. From these points of view f, the thickness of the surface layer is more preferably 0.07 to 0.3 mm, further preferably 0.10 to 0.25 mm, and still more preferably 0.1 to 0.15 mm.

[Adhesive]
The adhesive material is laminated on the surface opposite to the surface on which the surface layer of the core layer is provided. The pressure-sensitive adhesive material includes at least a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer adheres the electronic device sealing material to other members inside the electronic device. More specifically, the adhesive material may be a single adhesive layer laminated on the other surface of the core layer, or may be a double-sided adhesive tape attached to the surface of the core layer, The pressure-sensitive adhesive layer is preferably a simple substance. When the pressure-sensitive adhesive material is made of a single pressure-sensitive adhesive layer, the thickness of the electronic device sealing material can be easily reduced.

The double-sided pressure-sensitive adhesive tape includes a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material, and adheres one pressure-sensitive adhesive layer to the core layer, and the other pressure-sensitive adhesive layer is a member inside the electronic device. It is to be adhered to.
The adhesive is preferably laminated directly on the other surface of the core layer, but may be laminated on the core layer via a primer layer formed on the other surface of the core layer. A primer layer is a layer for improving the adhesiveness of a core layer and an adhesive material, for example, and what is necessary is just to apply | coat various primers to a core layer, for example.
There is no restriction | limiting in particular as an adhesive used for an adhesive layer, For example, an acrylic adhesive, a urethane type adhesive, a rubber-type adhesive etc. can be used.
As for the thickness of an adhesive material, 5-200 micrometers is preferable, More preferably, it is 10-100 micrometers. The thickness of the pressure-sensitive adhesive means the thickness of the pressure-sensitive adhesive layer when the pressure-sensitive adhesive consists of a single pressure-sensitive adhesive layer, and the total thickness of the double-sided pressure-sensitive adhesive tape when it is a double-sided pressure-sensitive adhesive tape. To do.

[Method of manufacturing sealing material for electronic equipment]
The method for producing the sealing material for electronic devices is not particularly limited, and examples thereof include a method of laminating a surface layer on one surface of the core layer. Here, when the core layer is a foam, the foam is manufactured by the following method, and a surface layer may be laminated on one surface of the foam.

(Method for producing foam)
The method for producing the foam is not particularly limited. For example, the foam is produced by crosslinking a foamable composition containing a resin and a heat decomposable foaming agent and heating the foamable composition to foam. More specifically, the manufacturing method includes the following steps (1) to (4).
Step (1): Mixing a resin and an additive containing a thermally decomposable foaming agent to form a sheet-like foamable composition (resin sheet) Step (2): Converting the sheet-like foamable composition Step (3) of irradiating with ionizing radiation to crosslink the foamable composition: Step of heating the crosslinkable foamable composition to foam the pyrolytic foaming agent to obtain a sheet-like foam ( 4): Step of stretching the foam in one or both of the MD direction and the TD direction

In the step (1), the method of forming the resin sheet is not particularly limited. For example, the resin and additives are supplied to an extruder and melt-kneaded, and the foamable composition is extruded into a sheet form from the extruder. The resin sheet may be formed by
As a method for crosslinking the foamable composition in the step (2), a method of irradiating the resin sheet with ionizing radiation such as electron beam, α ray, β ray, γ ray and the like is used. The irradiation amount of the ionizing radiation may be adjusted so that the degree of crosslinking of the obtained foam falls within the desired range described above, but is preferably 2 to 15 Mrad, and more preferably 5 to 13 Mrad.
In the step (3), the heating temperature when the foamable composition is heated to foam the pyrolyzable foaming agent may be equal to or higher than the foaming temperature of the pyrolyzable foaming agent, preferably 200 to 300 ° C. Preferably it is 220-280 degreeC.

The stretching of the foam in the step (4) may be performed after foaming the resin sheet to obtain a sheet-like foam, or may be performed while foaming the resin sheet. In addition, when the foam is stretched after foaming the resin sheet, the foam may be stretched while maintaining the molten state during foaming without cooling the foam. After cooling the foam, the foam may be stretched again by heating it to a molten or softened state. The foam is easily thinned by stretching.
In the step (4), the draw ratio of the foam in one or both of the MD direction and the TD direction is preferably 1.1 to 5.0 times, and more preferably 1.5 to 4.0 times.
When the draw ratio is set to the above lower limit value or more, the elastic compression characteristics and compressive strength of the foam are likely to be good. On the other hand, if the value is not more than the upper limit value, the foam is prevented from breaking during stretching or the foaming gas escapes from the foam being foamed and the foaming ratio is significantly reduced. The strength is improved and the quality is easily made uniform.
Moreover, what is necessary is just to heat a foam to 100-280 degreeC at the time of extending | stretching, for example, Preferably it is 150-260 degreeC. However, the manufacturing method of a foam is not limited above, You may manufacture by methods other than the above. For example, instead of irradiating with ionizing radiation, an organic peroxide may be blended in advance in the foamable composition, and crosslinking may be performed by a method in which the foamable composition is heated to decompose the organic peroxide. Good. Further, the step (4), that is, the stretching of the foam may be omitted.

(Method for forming surface layer)
The method of forming the surface layer on one surface of the core layer is not particularly limited, but if necessary, a modified polymer and other additives may be added to and mixed with the main agent composed of at least one of an elastomer and a soft resin. The resin composition for a surface layer obtained in this manner may be processed into a sheet shape or a layer shape and laminated on a core layer such as a foam. Or you may apply | coat the resin composition for surface layers on a core layer, and may form a surface layer.

More specifically, the main agent, if necessary, a modified polymer, and other additives are supplied to an extruder and melt-kneaded, the surface layer resin composition is extruded from a die into a sheet, and a core such as a foam. What is necessary is just to laminate | stack on a layer. At this time, the resin composition for a surface layer extruded into a sheet shape and the core layer may be heat-sealed by pressing and heating between rolls. Alternatively, a resin composition for a surface layer that has been processed into a sheet shape in advance may be superposed on a core layer such as a foam, and heat-sealed by heating or pressurizing. When the vulcanizing agent and the cross-linking agent are blended, the surface layer resin composition may be vulcanized or cross-linked by being superposed on the core layer and heated in a laminated state.
Furthermore, the resin composition for the surface layer formed in a layer shape on the release treatment surface of the release sheet may be transferred onto the core layer. What is necessary is just to form the resin composition for surface layers in a layer form by apply | coating the resin composition for surface layers on a peeling sheet. Examples of the release sheet include a paper base, a release paper obtained by performing release treatment on at least one side of a resin film, and a release film.

  Application of the resin composition for the surface layer to the release sheet or the core layer may be performed using various coaters, sprays, brushes, and the like. The resin composition for the surface layer may be applied after appropriately diluting with an organic solvent to obtain a diluted solution. Moreover, after apply | coating the resin composition for surface layers or its dilution liquid, you may heat, dry, etc. as needed. The surface layer may be crosslinked by heating with a crosslinking agent or the like contained in the resin composition for the surface layer.

When the core layer is a foam, the surface layer is preferably laminated on the foamed foam. That is, the formation of the surface layer is preferably performed after the step (3) or after the step (4), but more preferably after the step (4).
However, the foamable composition may be foamed after laminating the surface layer on the sheet-like foamable composition before foaming. In this case, for example, the step of forming the surface layer may be performed between the step (1) and the step (2) described above, or may be performed between the step (2) and the step (3).

(Adhesive forming method)
The method of forming the adhesive on the other surface of the core layer may be performed by applying the adhesive to the core layer when the adhesive is made of a single adhesive layer, or on the release film. The formed pressure-sensitive adhesive layer may be transferred onto the other surface of the core layer. Moreover, when an adhesive material consists of a double-sided adhesive tape, what is necessary is just to affix one adhesive layer of a double-sided adhesive tape on the other surface of a core layer.
Although an adhesive material is not specifically limited, It is preferable to form on the other surface of a core layer, after forming a surface layer in one surface of a core layer.
The electronic device sealing material obtained as described above may be cut into a desired shape by cutting by a known method such as punching.

  Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Measuring method]
The measurement method and evaluation method of each physical property are as follows.
<25% compressive strength>
The 25% compressive strength of the core layer was measured according to JIS K6767.
<Shore A hardness>
It is a hardness measured with a type A durometer hardness meter in accordance with JIS K 6253 at 23 ° C.
<Foaming ratio>
The apparent density of the foam was measured in accordance with JISK7222, and the reciprocal thereof was taken as the expansion ratio.
<Degree of crosslinking>
A test piece of about 100 mg is taken from the foam, and the weight A (mg) of the test piece is precisely weighed. Next, this test piece was immersed in 30 cm ³ of xylene at 120 ° C. and allowed to stand for 24 hours, then filtered through a 200-mesh wire mesh to collect the insoluble matter on the wire mesh, vacuum dried, and the weight of the insoluble matter. Weigh B (mg) precisely. From the obtained value, the degree of crosslinking (% by mass) was calculated by the following formula.
Crosslinking degree (% by mass) = 100 × (B / A)
<Closed cell ratio>
It was measured according to the method described in the specification.
<Average bubble diameter>
The average cell diameter was measured by the method described in the specification.

<Waterproof>
The waterproof evaluation test is based on the IPX7 standard (JISC0920 and IEC60529), and the test sample prepared by the following method is held for a predetermined time in a state where the temperature is 23 ° C. and the relative humidity is 50%. This was done by visually confirming the presence or absence of water immersion. The case where there is no water immersion after immersion for 3 hours or more is evaluated as “S”. The case was evaluated as “B”.
The waterproof test was performed after preparing a test sample and curing for 30 minutes under the conditions of a temperature of 23 ° C. and a relative humidity of 50%.
(Creation of test sample)
Double-sided pressure-sensitive adhesive tape (“3803BH” manufactured by Sekisui Chemical Co., Ltd.) is laminated on the core layer side of the sealing material, and has a rectangular opening of 58 mm long × 38 mm wide inside, 60 mm long × 40 mm wide, 1.0 mm wide. Punched into a rectangular frame shape. However, all corners were rounded by R5 mm. The obtained sealing material was sandwiched between two 100 mm square and 10 mm thick acrylic plates and compressed by 20% of the sealing material thickness.
<Removability>
The sealing material for electronic devices obtained in Examples and Comparative Examples was cut into 25 mm × 100 mm, sandwiched between two acrylic plates, compressed by 20% of the total thickness of the sealing material, a temperature of 23 ° C., relative It was cured for 30 minutes in an environment with a humidity of 50%. Then, the peelability when peeling the sealing material for electronic devices from the acrylic board by hand was evaluated. A sample that could be easily peeled by hand was evaluated as “A”, a sample that could not be easily peeled by hand, or a sample in which the sealing material for electronic equipment was damaged during peeling was evaluated as “B”.

[Example 1]
(Production of foam)
100 parts by mass of a linear low-density polyethylene resin (manufactured by Dow Chemical Co., trade name “Affinity PL1850”, density: 0.902 g / cm ³ ) obtained by a polymerization catalyst of a metallocene compound, and azo as a pyrolytic foaming agent Extrusion of 5.0 parts by mass of dicarbonamide, 0.5 parts by mass of zinc oxide (trade name “OW-212F” manufactured by Sakai Chemical Industry Co., Ltd.) and 1.0 part by mass of antioxidant as a cell nucleus modifier It was supplied to a machine, melted and kneaded at 130 ° C., and extruded into a long resin sheet having a thickness of 300 μm.
Next, after the resin sheet is cross-linked by irradiating an electron beam with an acceleration voltage of 500 kV on both surfaces of the long resin sheet for 5 Mrad, the cross-linked resin sheet is maintained at 250 ° C. by hot air and an infrared heater. Was continuously fed and heated to be foamed to obtain a sheet-like foam having a thickness of 1000 μm.
Subsequently, after continuously feeding the obtained foam from the foaming furnace, the foam was doubled in the TD direction in a state where the temperature of the both surfaces was maintained at 200 to 250 ° C. While extending | stretching with a draw ratio, the foam was extended | stretched also to MD direction by winding up a foam with the winding speed | rate higher than the feeding speed (supply speed) of the foam to the foaming furnace. The winding speed of the foam was adjusted in consideration of the expansion in the MD direction due to foaming of the resin sheet itself.

(Formation of surface layer)
The resin composition for the surface layer obtained by putting each component shown in Table 1 into an extruder and kneading was extruded into a sheet form from a die, laminated on one surface of the foam (core layer), and pressure 0 It was pressurized at 3 MPa and heated at 80 ° C. for thermal fusion to obtain a sealing material for electronic equipment comprising a core layer / surface layer.

[Examples 2 and 3]
The same operation as in Example 1 was carried out except that the composition of the resin composition for the surface layer was changed as shown in Table 1.

[Example 4]
(Production of foam)
In the same manner as in Example 1, except that the blending number of the azodicarbonamide as the pyrolytic foaming agent was changed to 2.3 parts by mass and the thickness of the long resin sheet was 210 μm. A resin sheet was obtained.
Next, after the resin sheet was crosslinked by irradiating an electron beam with an acceleration voltage of 500 kV on both surfaces of the long resin sheet for 7 Mrad, the crosslinked resin sheet was maintained at 250 ° C. by hot air and an infrared heater. A foam was obtained in the same manner as in Example 1 except that the sheet was continuously foamed by heating and foamed to obtain a sheet-like foam having a thickness of 350 μm (before stretching).
(Adjustment of resin composition for surface layer)
Butyl acrylate and 2-ethylhexyl acrylate were added at a mass ratio of 50:40 to a reactor equipped with a thermometer, a stirrer, and a cooling tube, and 80% ethyl acetate was added to replace the nitrogen. Thereafter, the reactor was heated to start refluxing. Subsequently, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator was added to the reactor and refluxed at 70 ° C. for 5 hours to obtain an acrylic resin solution. A rosin ester-based modified polymer and a crosslinking agent were blended into the acrylic resin solution to obtain a diluted solution of the resin composition for the surface layer. The composition based on the solid content of the diluted liquid of the resin composition for the surface layer is as shown in Table 1.
(Formation of surface layer)
A release paper (thickness 150 μm) is prepared, and a diluted solution of the above surface layer resin composition is applied to the release treated surface of the release paper, and dried at 100 ° C. for 5 minutes, thereby forming a layered surface layer resin. A composition was formed. This layered resin composition for the surface layer was bonded to the surface of the foam to obtain a sealing material for electronic equipment comprising the surface layer / foam. In addition, although the release paper was affixed on the surface of the surface layer, it peeled before performing each evaluation.

[Comparative Example 1]
A foam was produced in the same manner as in Example 1 except that the amount of azodicarbonamide was changed to 7.0 parts by mass as the pyrolytic foaming agent. A surface layer was not laminated on the foam, and the foam alone was used as a sealing material for electronic devices.

[Comparative Example 2]
As the foam (core layer), a commercially available urethane foam (trade name "PORON SR-S4
0P "(manufactured by Roger Sinoac Co., Ltd.) was used, and the surface layer was not laminated on the core layer, and the foam alone was used as a sealing material for electronic devices.

[Example 5]
It was carried out in the same manner as in Example 4 except that the resin composition for the surface layer was changed to a blending ratio of 85 parts by mass of the acrylic resin, 12 parts by mass of the rosin ester-based modified polymer, and 1 part by mass of the crosslinking agent.

  In Table 1, the Shore A hardness of the elastomer means the Shore A hardness of butyl rubber and SIS in Examples 1 and 3, respectively. In Example 2, it means the Shore A hardness of an elastomer obtained by mixing butyl rubber and EPDM at a mass ratio of 1: 1.

In addition, each component in the resin composition for surface layers is as follows.
Butyl rubber: Trade name “BUTYL065”, manufactured by JSR Corporation, Shore A hardness: 20
EPDM: ethylene propylene diene rubber, trade name “EP21”, manufactured by JSR Corporation, Shore A hardness: 73
TPS: Styrenic thermoplastic elastomer (hydrogenated styrene-isoprene-styrene block copolymer), trade name “HIBLER 7311”, manufactured by Kuraray Co., Ltd., Shore A hardness: 41
Acrylic resin: Copolymer modified polymer with a weight average molecular weight of 700,000, 55.6% by weight of butyl acrylate and 44.4% by weight of 2-ethylhexyl acrylate 1: Petroleum polymer, trade name “Quintone R-100”, Nippon Zeon Co., Ltd. Company modified polymer 2: Rosin ester resin Carbon black: Carbon black antioxidant manufactured by Asahi Carbon Co., Ltd .: Mixture of sulfur antioxidant and phenolic antioxidant Crosslinker: Isocyanate crosslinking agent

Since the electronic device seals of Examples 1 to 5 have the elastically compressible core layer and the surface layer having adsorbability and removability, the waterproof performance is good. Moreover, even if it was made to adsorb | suck to the components of an electronic device once, the seal | sticker for electronic devices of Examples 1-4 could be peeled from the component again. In addition, about the structure shown in Example 2, after making it adsorb | suck to the surface layer of the punching sample used for the said waterproof evaluation, it peeled, and when this measured the waterproofness of the sample repeated 10 times, IPX7 grade was obtained. Cleared. Further, regarding the electronic device seal of Example 5, since there were many modified polymers and few crosslinking agents, the waterproof performance was good, but the removability was not as good as the other examples.
On the other hand, since the sealing material for electronic devices of Comparative Examples 1 and 2 did not have a surface layer, the waterproof performance could not be sufficiently improved.

10, 20 Sealing material for electronic equipment 11 Core layer 12 Surface layer 13 Adhesive material 21, 22 Member inside electronic equipment

Claims (11)

  An electronic device sheet material disposed between two members inside an electronic device, wherein the core material is elastically compressible, and is laminated on one surface of the core layer. A sealing material for electronic equipment, comprising a surface layer adsorbed on one of the members and capable of being peeled off from the member.   The electronic device sealing material according to claim 1, wherein the surface layer is made of a water-impermeable material.   The surface layer resin composition constituting the surface layer includes at least one selected from the group consisting of butyl rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic resin, and styrene-based thermoplastic elastomer. 2. A sealing material for electronic equipment according to 2.   The sealing material for electronic devices according to claim 1, wherein the core layer is made of a water-impermeable material.   The sealing material for electronic devices according to claim 1, wherein the core layer is made of a foam.   The electronic device sealing material according to claim 5, wherein the resin constituting the foam is a polyolefin resin.   The electronic device sealing material according to claim 5, wherein the foam has closed cells.   8. The electronic device sealing material according to claim 5, wherein each of the foams has an average cell diameter in the MD and TD directions of 300 μm or less and an average cell diameter of ZD of 150 μm or less. Expansion ratio of the foam, 1.2~20cm ³ / g electronic equipment sealing material according to any one of claims 6-8 is.   The electronic device sealing material according to any one of claims 1 to 9, wherein the thickness is 0.05 to 2.5 mm.   The sealing material for electronic devices of any one of Claims 1-10 provided with an adhesive material on the other surface of the said core layer.