JP6393052B2 - Double-sided pressure-sensitive adhesive sheet and pressure-sensitive adhesive composition - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive sheet, and more specifically, a double-sided pressure-sensitive adhesive sheet that reduces the amount of gas components that may adversely affect the operation of components incorporated in a device such as a hard disk and has excellent adhesiveness, and the double-sided pressure-sensitive adhesive sheet It is related with the adhesive composition for forming the adhesive layer with which a sheet | seat is provided.

  In this specification, “sheet” includes the concept of a tape and the concept of a film. The “component incorporated in the device” includes a component that is not directly related to the operation of the device, such as a display label. A gas component released from a double-sided PSA sheet attached to a component incorporated in a device during the manufacturing process, storage and / or use is also referred to as “outgas”.

  Devices such as hard disk drives (also referred to as “HDD” in the present specification), relays, various switches, connectors, and motors are widely used in various products. In such a device, a double-sided pressure-sensitive adhesive sheet in which both main surfaces are composed of the surface of the pressure-sensitive adhesive layer is used for the purpose of temporarily fixing at the time of assembly, fixing of the component, displaying the content of the component, and the like.

  Among the substances constituting the pressure-sensitive adhesive layer provided in such a double-sided pressure-sensitive adhesive sheet, in order to achieve the purpose of obtaining a pressure-sensitive adhesive sheet having excellent adhesiveness, the device usage environment (for example, HDD is in use) In some cases, a substance (also referred to as “low molecular weight component” in this specification) having a molecular weight small enough to volatilize may be contained. In addition, a low molecular weight component may be generated in the adhesive layer in the course of composition change of the adhesive over time. When such a low molecular weight component becomes outgas and diffuses into the device, the low molecular weight component may adhere to the surface of a component incorporated in the device.

  On the other hand, there is a case in which a part is incorporated in the device, which increases the possibility of malfunction of the part when foreign matter accumulates on the surface. Examples of such components include HDD hard disks and relay contact portions.

The adhesion of the low molecular weight component to the surface of such a component leads to malfunction of the component, and consequently malfunction of the device. Therefore, outgas is generated from the adhesive layer in the double-sided PSA sheet used in the device. It is required to be difficult to do.
Regarding the double-sided pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer, Patent Document 1 discloses a pressure-sensitive adhesive part provided with a pressure-sensitive adhesive layer on both sides of a plastic film substrate having a thickness of 20 μm or less, and both sides of the pressure-sensitive adhesive part. A double-sided pressure-sensitive adhesive sheet composed of a non-silicone release liner provided on the surface of the adhesive, wherein the pressure-sensitive adhesive portion has a thickness of 60 μm or less and an outgas amount of 1 μg / cm ² when heated at 120 ° C. for 10 minutes. The following double-sided pressure-sensitive adhesive sheet for fixing HDD components is disclosed.

JP 2009-74060 A

  However, the present inventors have confirmed that even when a double-sided pressure-sensitive adhesive sheet satisfying the conditions specified in Patent Document 1 above is used, the surface to which the double-sided pressure-sensitive adhesive sheet is attached in the housing of the HDD (in this specification, double-sided pressure-sensitive adhesive sheet). A flexible printed circuit board (also referred to as “FPC” in the present specification) through the attached double-sided pressure-sensitive adhesive sheet, including the state before the sheet is attached, including the state before the sheet is attached. ) Is attached to the housing of the HDD, it has become clear that “floating” in which the FPC peels off from the housing adherent surface together with the double-sided pressure-sensitive adhesive sheet may occur at the step portion of the HDD housing.

  This “floating” phenomenon will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view conceptually showing a housing of an HDD to which an FPC is attached via a double-sided adhesive sheet for explaining the “floating” phenomenon. As shown in FIG. 1A, when the “floating” phenomenon occurs when the laminated body 4 of the FPC 2 and the double-sided pressure-sensitive adhesive sheet 3 is attached so as to include the step portion in the housing 1 of the HDD, In the step portion, as shown in FIG. 1B, separation occurs at the interface between the double-sided pressure-sensitive adhesive sheet 3 and the HDD housing 1, and the laminate 4 is lifted from the housing at this portion. Such a phenomenon that the double-sided pressure-sensitive adhesive sheet attached to the adherend having a stepped portion partially peels off the adherend so as to include the stepped portion is referred to as “floating” (partial peeling) in the present specification. . As one means for avoiding the occurrence of the “floating” phenomenon, it is conceivable to increase the adhesiveness of the double-sided pressure-sensitive adhesive sheet 3 to the housing 1 of the HDD. However, increasing the adhesiveness of the double-sided pressure-sensitive adhesive sheet 3 is often accompanied by an increase in the amount of outgas generated from the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet 3, and cannot be said to be a preferable solution.

  Against this backdrop, the present invention is less prone to peeling even when the surface of the portion where the “floating” phenomenon is likely to occur, such as a stepped portion of the HDD housing, and the generation amount of outgas is increased. It aims at providing the adhesive composition for forming the adhesive layer with which the double-sided adhesive sheet in which this was suppressed and a double-sided adhesive sheet is provided.

  As a result of studies by the present inventors in order to achieve the above object, it is possible to reduce the amount of outgas generated by including a tackifying resin that has been avoided in the past as it may increase the amount of outgas generated. The present inventors have obtained a new finding that the occurrence of the “floating” phenomenon can be more stably suppressed while suppressing the increase.

The present invention completed based on the above findings is as follows.
(1) A double-sided pressure-sensitive adhesive sheet comprising at least one pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a tackifying resin, and the amount of outgas generated is converted to n-decane. The double-sided pressure-sensitive adhesive sheet is 1.0 μg / cm ² or less in quantity.

(2) The double-sided pressure-sensitive adhesive sheet according to (1), wherein the pressure-sensitive adhesive layer composition contains a crosslinking agent and a crosslinkable polymer, and the crosslinking agent contains an isocyanate-based crosslinking agent.

(3) The double-sided pressure-sensitive adhesive sheet according to (1) or (2), wherein the tackifying resin has a softening point of 95 ° C or higher.

(4) Both surfaces as described in said (2) or (3) whose content of the said tackifying resin in the said adhesive composition is 1 mass part or more with respect to 100 mass parts of solid content of the said crosslinkable polymer. Adhesive sheet.

(5) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (4), wherein the pressure-sensitive adhesive layer has a gel fraction of 10% to 70%.

(6) The double-sided pressure-sensitive adhesive sheet according to any one of (2) to (5), wherein the crosslinkable polymer contains an acrylic polymer.

(7) The double-sided pressure-sensitive adhesive sheet according to (6), wherein the acrylic polymer includes a structural unit based on a morpholine compound having an ethylenically unsaturated group.

(8) The double-sided pressure-sensitive adhesive sheet according to any one of (1) to (7), which is used for adhering components in a hard disk drive.

(9) A pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet described in any one of (1) to (8) above, comprising a tackifier resin Adhesive composition.

  According to the double-sided pressure-sensitive adhesive sheet according to the present invention, even when the adherend surface has a highly bent surface, it is possible to reduce the possibility of the “floating” phenomenon while suppressing an increase in the amount of outgas generated. Moreover, according to this invention, the adhesive composition for forming the adhesive layer with which said double-sided adhesive sheet is provided is provided.

It is a figure for demonstrating the "floating" phenomenon which has arisen in the double-sided adhesive sheet which concerns on a prior art, Comprising: It is a fragmentary sectional view which shows notionally the housing of HDD in which FPC was stuck via the double-sided adhesive sheet, (A) shows the state before the occurrence of the “floating” phenomenon, and (b) shows the state where the “floating” phenomenon has occurred.

Hereinafter, embodiments of the present invention will be described.
1. Double-sided pressure-sensitive adhesive sheet The other structure of the double-sided pressure-sensitive adhesive sheet according to one embodiment of the present invention is not particularly limited as long as both main surfaces thereof are constituted by a surface of a specific pressure-sensitive adhesive layer. Both main surfaces of the single pressure-sensitive adhesive layer may constitute both main surfaces of the double-sided pressure-sensitive adhesive sheet, or the double-sided pressure-sensitive adhesive sheet is composed of a laminate of a plurality of pressure-sensitive adhesive layers, The main surface may be comprised from the surface of the same kind or different kind of adhesive layer. Alternatively, the double-sided pressure-sensitive adhesive sheet may include a member other than the pressure-sensitive adhesive layer (a core material described later as a specific example), and a plurality of pressure-sensitive adhesive layers may sandwich a member such as the core material. In this case, the two main surfaces of the double-sided pressure-sensitive adhesive sheet may be composed of surfaces of the same type of pressure-sensitive adhesive layer, or may be composed of surfaces of different types of pressure-sensitive adhesive layers.

(1) Adhesive layer (1-1) composition The adhesive layer with which the double-sided adhesive sheet which concerns on this embodiment is provided is formed from the adhesive composition containing tackifying resin. The pressure-sensitive adhesive composition preferably contains a crosslinking agent and a polymer having a reactive functional group that is a functional group capable of reacting with the crosslinking agent (also referred to as “crosslinkable polymer” in the present specification). . When the pressure-sensitive adhesive composition contains a cross-linking agent and a cross-linkable polymer, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition includes a cross-linked structure formed by the reaction of the cross-linking agent and the cross-linkable polymer.

(I) Crosslinkable polymer When the adhesive layer composition of this embodiment contains a crosslinkable polymer, the kind of crosslinkable polymer is not limited. A preferable example of the crosslinkable polymer is an acrylic polymer. The structural unit of such an acrylic polymer is not particularly limited. A compound having a (meth) acryloyl group and a derivative thereof (ester, acrylonitrile, etc.) may be composed of only a structural unit based on an acrylic compound which is one or two or more compounds, or a structure based on an acrylic compound The structural unit based on compounds other than a unit and an acryl-type compound may be included. In the present specification, the “(meth) acryloyl group” means both an acryloyl group and a metalloyl group. The same applies to other similar terms. Moreover, compounds other than said acrylic compound may be comprised from one type of compound, and may be comprised from multiple types of compound.

  A preferred example of the acrylic compound is (meth) acrylic acid ester. Specific examples of (meth) acrylic acid esters include chain skeletons such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meth) acrylate having: cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) ) (Meth) acrylates having a cyclic skeleton such as acrylate, tetrahydrofurfuryl (meth) acrylate, imide acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, -(Meth) acrylate having a hydroxyl group such as hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; N-methylaminoethyl ( (Meth) acrylates having an amino group such as (meth) acrylate; (meth) acrylates having an epoxy group such as glycidyl (meth) acrylate.

  Among these, the acrylic polymer as the crosslinkable polymer may include a structural unit based on an alkyl (meth) acrylate having an alkyl group having 4 or less carbon atoms (hereinafter also referred to as “lower alkyl compound”). preferable. Specific examples of such lower alkyl compounds include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Examples include acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, and the like.

  Among these, n-butyl (meth) acrylate and methyl (meta) are preferable from the viewpoint of facilitating an appropriate balance between enhancing the adhesive properties of the pressure-sensitive adhesive layer and suppressing an increase in the amount of outgas generated. ) Acrylate is preferred. A lower alkyl compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  Monomers that give structural units based on compounds other than acrylic compounds (hereinafter also referred to as “other polymerizable compounds”) include ethylene, norbornene and other olefins, vinyl acetate and other carboxylic acid vinyl esters, and styrene and other ethylenic polymers. An aromatic compound having a saturated bond is exemplified.

  The reactive functional group possessed by the crosslinkable polymer is preferably a functional group capable of reacting with an isocyanate group since the crosslinking agent contains an isocyanate compound as described later. Examples of such functional groups include hydroxyl groups, amino groups, and amide groups.

  The kind of the compound that gives the structural unit having a reactive functional group in the crosslinkable polymer is not particularly limited. As an example, the above-mentioned (meth) acrylate having a hydroxyl group or (meth) acrylate having an amino group may be mentioned. Examples of the ethylenically unsaturated compound having such a reactive functional group (also referred to herein as “reactive compound”) include an ethylenically unsaturated compound containing an amide group and an alcohol having a vinyl group. . Specific examples of such reactive compounds include acrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, 5-hexen-1-ol, and 5-hexene-3. -Ol, 4-penten-1-ol and the like.

  The reactive functional group of the reactive compound is preferably a hydroxyl group that hardly changes color due to heat or the like. Accordingly, the reactive compound is preferably a (meth) acrylate having a hydroxyl group and / or an alcohol having a vinyl group.

  When the crosslinkable polymer includes a structural unit based on a lower alkyl compound and a structural unit based on a reactive compound, the content ratio of monomers in the crosslinkable polymer of the structural unit (lower alkyl compound: reactive compound) Is preferably 90:10 to 99.9: 0.1, and more preferably 95: 5 to 99.5: 0.5. By setting the above ratio within this range, even if an external force is applied to the adhesive layer, such as when the double-sided adhesive sheet is bent, it is difficult for stress to remain in the adhesive layer, and a “floating” phenomenon may occur. Can be reduced.

  The crosslinkable polymer may further include a structural unit based on an ethylenically unsaturated group-containing morpholine compound (hereinafter also referred to as “morpholine compound”). Since the morpholine group has a function of accelerating the reaction of the crosslinking agent described later, the crosslinkable polymer becomes a polymer having a functional group having a crosslinking accelerating function by including a structural unit based on a morpholine compound. . In this case, the crosslink density of the pressure-sensitive adhesive layer can be increased while suppressing an increase in the amount of outgas generated, compared to the case where a low molecular weight crosslinking accelerator described later is contained. Specific examples of the morpholine compound include N-vinyl morpholine, N-allyl morpholine, N- (meth) acryloyl morpholine, and the like. Among the morpholine compounds, N- (meth) acryloylmorpholine, which is also an acrylic compound, is preferable from the viewpoint of good copolymerizability with compounds relating to other structural units. One type of morpholine compound may be used, or a plurality of types may be used.

  From the viewpoint of facilitating suppressing the increase in the amount of outgas generated and obtaining a pressure-sensitive adhesive layer having appropriate tackiness, the content of the structural unit based on the morpholine compound in the crosslinkable polymer. 2 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the total amount of the lower alkyl compound based on the content of the lower alkyl compound based on the mass of the lower alkyl compound and the content of the reactive compound based on the reactive compound based on the mass of the reactive compound. It is preferably 4 parts by mass or more and 25 parts by mass or less.

  The crosslinkable polymer may include a structural unit based on a compound having an ethylenically unsaturated bond other than the structural unit based on the lower alkyl compound, the structural unit based on the reactive compound, and the structural unit based on the morpholine compound. . Specific examples of the monomer that provides such a structural unit include olefins, carboxylic acid vinyl esters, and aromatics having an ethylenically unsaturated bond, as in the case of the other polymerizable compounds described above. Or the compound which has a functional group provided with the crosslinking promotion function like a morpholine type compound like an ethylenically unsaturated group containing imidazole type compound, for example is illustrated. The content rate of the structural unit based on such a compound is not specifically limited. The content is 10 parts by mass with respect to the total of 100 parts by mass of the content of the lower alkyl compound based on the lower alkyl compound in terms of the mass of the lower alkyl compound and the content of the reactive compound based on the reactive compound in terms of mass. The upper limit is preferable, and the upper limit is more preferably 5 parts by mass.

  From the viewpoint of more stably suppressing an increase in the amount of outgas generated from the double-sided PSA sheet, the crosslinkable polymer is preferably an acrylic polymer with a reduced amount of carboxyl groups. Specifically, the content of the carboxyl group in the crosslinkable polymer is such that the structural unit having a carboxyl group is 1.0 part by mass or less with respect to 100 parts by mass of the total amount of monomers for forming the crosslinkable polymer. It is preferable that it is 0.5 mass part or less. Furthermore, the crosslinkable polymer is preferably an acrylic polymer having no carboxyl group. Similarly, it is preferable that the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet of the present embodiment has little or substantially no carboxyl group content. Examples of monomers that give structural units having a carboxyl group include acrylic acid, methacrylic acid, and itaconic acid.

(Ii) Crosslinking agent When the pressure-sensitive adhesive layer composition of the present embodiment contains a crosslinkable polymer, the crosslinking agent is one or more compounds selected from the group consisting of polyfunctional isocyanates and derivatives thereof ( In the present specification, it is also preferable to contain an “isocyanate-based crosslinking agent”. Isocyanate-based cross-linking agents were tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylylene diisocyanate (XDI) and these were subjected to addition reaction with trimethylolpropane and the like. Examples include polyisocyanate compounds, isocyanurates, burette type compounds, and urethane prepolymer type polyisocyanates obtained by addition reaction of known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, and the like. Among these, tolylene diisocyanate crosslinking agents (TDI crosslinking agents) are preferably used because they are excellent in preventing the occurrence of the “floating” phenomenon.

  The pressure-sensitive adhesive layer according to this embodiment preferably has a gel fraction of 10% to 70%, and more preferably 20% to 60%. Even if an external force is applied to the pressure-sensitive adhesive layer by adjusting the amount of the above-mentioned crosslinking agent so that the gel fraction of the pressure-sensitive adhesive layer falls within this range, internal stress can be applied. It becomes easy to obtain a pressure-sensitive adhesive layer in which the residue hardly remains. Specifically, by adjusting the content of the cross-linking agent in the pressure-sensitive adhesive composition in a range of 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the cross-linkable polymer described above, It becomes easy to set the gel fraction of the pressure-sensitive adhesive layer formed from the composition within the above range.

(Iii) Tackifying resin The pressure-sensitive adhesive composition according to this embodiment contains a tackifying resin. The specific kind of tackifying resin is not limited. Examples of tackifier resins include rosin-based tackifier resins such as rosin and derivatives thereof (specific examples include polymerized rosin, esterified rosin, polymerized rosin ester, disproportionated rosin, and hydrogenated resins thereof); α pinene resins, beta-pinene resins, terpene phenol resins, copolymers of terpenes and styrene, terpene tackifier resin of hydrogenated terpene resin is a hydrogenated product of the resin or copolymer; C ₅ petroleum resins, coumarone resins; alkylphenol resins; styrene resins; C ₉ petroleum resins, petroleum resins such as C 5 _/ C ₉ petroleum resins and hydrogenated resins and xylene resins. By containing a tackifying resin consisting of oligomers usually having a weight average molecular weight of several hundred to several thousand, the adhesiveness of the pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet according to the present embodiment increases, and a “floating” phenomenon may occur. The property can be more stably reduced. Among the above-mentioned tackifying resins, one kind selected from rosin-based tackifying resins and terpene-based tackifying resins, or a mixture of both is preferable as a material constituting the tackifying resin.

  The softening point of the tackifying resin is preferably 95 ° C. or higher, and particularly preferably 120 ° C. or higher and 160 ° C. or lower. By using a tackifying resin having a softening point of 95 ° C. or higher, it is possible to prevent the “floating” phenomenon from occurring while suppressing an increase in the amount of outgas generated.

What is necessary is just to set content of the tackifying resin in an adhesive composition so that the increase in the adhesiveness of the adhesive layer formed from tackifying resin and the generation amount of outgas may be suppressed appropriately. From the viewpoint of more stably providing tackiness to such an extent that the pressure-sensitive adhesive layer can appropriately suppress the occurrence of the “floating” phenomenon, the content of the tackifier resin in the pressure-sensitive adhesive composition is such that the pressure-sensitive adhesive composition is a crosslinkable polymer. Is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and particularly preferably 5 parts by mass or more, based on 100 parts by mass of the solid content of the crosslinkable polymer. preferable. If the generation amount of outgas of an adhesive layer is 1.0 microgram / cm < ² > or less in n-decane conversion amount, the upper limit of content of tackifying resin in an adhesive composition will not be limited. It is preferable to set it as 30 mass parts or less with respect to 100 mass parts of solid content of a crosslinkable polymer, It is more preferable to set it as 20 mass parts or less, It is especially preferable to set it as 10 mass parts or less.

(Iv) Other components The pressure-sensitive adhesive layer can contain various components as long as the amount of outgas generated is small and has suitable adhesiveness. For example, crosslinking accelerators; coloring materials such as dyes and pigments; antioxidants such as anilides and phenols; ultraviolet absorbers such as benzophenones and benzotriazoles; filler components such as talc, titanium dioxide, silica, and starch; Examples include plasticizers; antioxidants; light stabilizers; dispersants; leveling agents.

(1-2) Thickness The thickness of the pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet according to this embodiment is not particularly limited. If it is excessively thin, there is a concern that the desired adhesiveness cannot be obtained, and if it is excessively thick, there is a concern that it may be disadvantageous from the viewpoint of workability. Therefore, the thickness of the pressure-sensitive adhesive layer is generally selected in the range of 4 to 30 μm, preferably in the range of 6 to 25 μm, as the whole pressure-sensitive adhesive layer.

(2) Generated amount of outgas In the double-sided PSA sheet according to this embodiment, the generated amount of outgas is 1.0 μg / cm ² or less in terms of n-decane. When the amount of outgas generated is 1.0 μg / cm ² or less, it is used to attach a component incorporated in a device such as an HDD or a relay to another component (may be temporarily attached). In this case, it is possible to make it difficult to cause a problem of foreign matters adhering to the components in the device. From the viewpoint of more stably reducing the possibility of the above problem, the amount of outgas generated from the double-sided PSA sheet according to the present embodiment is 0.5 μg / cm ² or less in terms of n-decane. Is more preferable, 0.2 μg / cm ² or less is more preferable, and 0.1 μg / cm ² or less is particularly preferable.

(3) Core material The double-sided pressure-sensitive adhesive sheet according to the present embodiment may include a core material. In one specific example, the double-sided pressure-sensitive adhesive sheet according to this embodiment includes a core material in which a pressure-sensitive adhesive layer is laminated on each main surface.

  The material constituting the core material according to the present embodiment is not particularly limited as long as it has a basic function that should be possessed as a core material, such as higher tensile strength than the material constituting the pressure-sensitive adhesive layer. It is preferable that the organic gas is not easily generated. Specific examples of the material constituting the core material include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyimides; resin sheets such as polyamide. You may use what gave metal vapor deposition, such as aluminum, to these resin sheets. Alternatively, papers made of synthetic paper, impregnated paper, and the like, and metal foils such as aluminum foil and copper foil can also be given as specific examples of the material constituting the core material.

  When using a resin sheet as the core material, in order to improve the adhesiveness with the pressure-sensitive adhesive layer provided thereon, the surface on the side that should face the pressure-sensitive adhesive layer, such as an oxidation method or an uneven method Surface treatment can be performed. Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the unevenness method include sand blast method and solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected according to the type of the core material, but generally, the corona discharge treatment method is preferably used from the viewpoints of effects and operability. Further, primer treatment for providing a primer layer (specific examples include silane coupling treatment) can also be applied.

  The thickness of the core material according to the present embodiment is not particularly limited. If it is excessively thin, it may be difficult to handle the core material, or it may be difficult to enjoy the benefits of providing the core material (eg, the double-sided pressure-sensitive adhesive sheet is less likely to break). There is a concern to do. On the other hand, when the core is excessively thick, there is a concern that the entire double-sided PSA sheet becomes thick. Therefore, the thickness of the core is usually preferably in the range of about 2 to 50 μm, and preferably in the range of about 3 to 20 μm.

  The thickness of the entire double-sided PSA sheet is preferably about 100 μm or less, and more preferably 65 μm or less. On the other hand, from the viewpoint of ensuring handleability, the thickness of the entire double-sided PSA sheet is preferably 10 μm or more, and more preferably 20 μm or more.

(4) Release material The surfaces of the pressure-sensitive adhesive layer forming both end faces of the double-sided pressure-sensitive adhesive sheet according to this embodiment may be exposed, but usually a temporary release material is used to protect the pressure-sensitive adhesive layer until use. Stick it on.

  The release material comprises a release surface having a sheet-like support substrate and at least one surface having releasability. The release surface may be a surface opposite to the side facing the support substrate of the release agent layer provided on the surface of the support substrate that does not have releasability, or a support group having releasability. It may be one side of the material.

  Examples of the support material for the release material include paper, synthetic paper, and resin film. Examples of the paper include glassine paper and polyethylene laminated paper. Examples of the resin film include polyolefin resins such as polyethylene resin and polypropylene resin, polyester resins such as polybutylene terephthalate resin and polyethylene terephthalate resin, acetate resin, polystyrene. Examples thereof include a resin film and a vinyl chloride resin film. As a release treatment agent constituting the release agent layer, rubber containing elastomers such as olefin resins, isoprene resins, butadiene resins, long chain alkyl resins, alkyd resins, fluorine resins, silicone resins, etc. Is exemplified. The thickness of the release agent layer formed on the support substrate is not particularly limited, but is preferably 0.05 to 2.0 μm, more preferably 0 when the release agent is applied in a solution state. .1 to 1.5 μm. When the release agent layer is formed using a thermoplastic resin such as polyethylene or polypropylene, the thickness of the release agent layer is preferably 3 to 50 μm, and more preferably 5 to 40 μm.

  Examples of the support substrate having a peelable surface include polyolefin resin films such as polypropylene resin films and polyethylene resin films, and films obtained by laminating these polyolefin resin films on paper or other films.

  The thickness of the support base material of the release material is not particularly limited, but is usually about 15 μm or more and 300 μm or less.

  The double-sided pressure-sensitive adhesive sheet according to this embodiment preferably does not contain a silicone-based material because the vaporized silicone compound adversely affects the operation of the HDD. It is preferable not to contain.

  Moreover, when affixing the release surface of the release material on both sides of the double-sided pressure-sensitive adhesive sheet, the release material applied to one side of the double-sided pressure-sensitive adhesive sheet is easily peeled off from the other side of the double-sided pressure-sensitive adhesive sheet. It is possible to make the release material to be peeled off from the double-sided pressure-sensitive adhesive sheet different from each other, that is, to use a light release material and a heavy release material as the release material. Since workability | operativity at the time of sticking improves, it is preferable.

2. Adhesive composition The adhesive layer with which the double-sided adhesive sheet which concerns on this embodiment is provided is formed from an adhesive composition. In the present specification, the “pressure-sensitive adhesive composition” is a material that contains a component for forming a pressure-sensitive adhesive layer including a tackifier resin and is used in an application process for forming a pressure-sensitive adhesive layer. Means a fluid that has fluidity when placed in an environment of 23 ° C. and 50% relative humidity, and is not only a low-viscosity liquid when applied, but also a viscous material having a certain degree of viscosity. Including cases. The pressure-sensitive adhesive composition may contain a component for forming the pressure-sensitive adhesive layer as a solute or may be contained as a dispersoid. When the pressure-sensitive adhesive composition contains a solvent and / or a dispersion medium, the amount thereof may be set for the purpose of adjusting the thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

  The pressure-sensitive adhesive composition according to this embodiment contains a tackifying resin. The content is not limited, and the preferred range is as described above. In a specific example, the pressure-sensitive adhesive composition includes a crosslinkable polymer containing an acrylic polymer and an isocyanate-based crosslinker as a component for providing a cross-linked structure included in the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition. Containing. The content of the crosslinkable polymer and the isocyanate crosslinker in the pressure-sensitive adhesive composition is such that the isocyanate crosslinker is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the crosslinkable polymer. Is preferred. By preparing the pressure-sensitive adhesive composition so that the above relationship falls within this range, it becomes easy to adjust the gel fraction of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition to the above range. In addition, as long as the gel fraction of the obtained adhesive layer is the above-mentioned range, the adhesive composition may contain crosslinking agents other than an isocyanate type crosslinking agent.

  The pressure-sensitive adhesive composition may contain components such as a coloring material, an antioxidant, and an ultraviolet absorber according to the components to be contained in the pressure-sensitive adhesive layer.

  The method for preparing the pressure-sensitive adhesive composition is not limited. In some cases, it is only necessary to mix the components for forming the pressure-sensitive adhesive layer. In other cases, the components and a solvent (which may be a dispersion medium at the same time) are mixed. It may be prepared as follows. When the component for forming an adhesive layer contains what should be melt | dissolved in a solvent, you may heat a solvent so that the component may melt | dissolve appropriately.

3. Manufacturing method of a double-sided adhesive sheet The manufacturing method of the double-sided adhesive sheet which concerns on this embodiment is not specifically limited. A specific example of the method for producing a double-sided PSA sheet is as follows.

First, a first laminate and a second laminate, each of which is a laminate of a release material and an adhesive layer, are prepared.
In order to prepare a 1st laminated body, the above-mentioned adhesive composition is apply | coated on the surface at the side of the peeling surface of a 1st peeling material, and the coating film of an adhesive composition is formed on a peeling material. This coating method is not particularly limited, and conventionally known methods such as a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, and the like can be used. Next, the coating film of the pressure-sensitive adhesive composition on the release material is dried to obtain a first laminate in which the pressure-sensitive adhesive layer is laminated on the first release material. Although this drying condition is arbitrary, it is preferable to heat the above-mentioned coating film to about 100 ° C. from the viewpoint that the amount of outgas generated can be reduced. What is necessary is just to set drying time suitably according to the thickness of a coating film, drying temperature, etc. For example, when the above-mentioned coating film is heated to 100 ° C., the heating time can be set to about several minutes or less. A core material is bonded to the pressure-sensitive adhesive surface of the first laminate to obtain a single-sided pressure-sensitive adhesive sheet.

  Then, the 2nd laminated body which consists of a 2nd peeling material and the adhesive layer laminated | stacked on the peeling surface is formed. Since the formation method is the same as in the case of the first laminate, the description thereof is omitted.

  The surface on the core material side of the single-sided pressure-sensitive adhesive sheet thus obtained and the surface on the pressure-sensitive adhesive layer side of the second laminate are bonded together and laminated in the order of the pressure-sensitive adhesive layer, the core material, and the pressure-sensitive adhesive layer. The double-sided pressure-sensitive adhesive sheet is obtained in a state where the first release material and the second release material are respectively attached to the pressure-sensitive adhesive layer.

  Here, the first release material and the second release material may have the same configuration or different configurations. As described above, if one is a light release material and the other is a heavy release material, a double-sided pressure-sensitive adhesive sheet excellent in workability can be obtained.

  When either or both of the pressure-sensitive adhesive compositions for forming the pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet contain a crosslinking agent and a crosslinkable polymer, the first laminate and the second laminate By appropriately setting the drying conditions of the drying process for forming the pressure-sensitive adhesive layer in (specifically, heating the coating film to about 100 ° C. or more is exemplified), crosslinking in the coating film is performed. The reaction between the agent and the crosslinkable polymer can proceed. In order to sufficiently advance the crosslinking reaction instead of or in addition to the progress of the crosslinking reaction during the drying step for forming the pressure-sensitive adhesive layer of the laminate, for example, 23 You may provide the curing process of leaving still for several days in the environment of 50 degreeC and relative humidity after the drying process for forming the adhesive layer of a laminated body. When performing a curing process, the implementation time is arbitrary, and it may be immediately after the drying process for forming the adhesive layer of the laminate, or the first laminate and the second laminate may be directly or cored. It may be after forming the double-sided pressure-sensitive adhesive sheet by carrying out the step of laminating via.

4). Method for Using Double-Sided Adhesive Sheet The double-sided adhesive sheet according to the present embodiment is used to attach a component incorporated in a device such as an HDD (hard disk drive) or a relay to another component (may be temporary). Can be used.

  Here, it is preferable that the device includes a component that does not allow foreign matter to adhere to at least a part of its surface, such as a hard disk or magnetic head in an HDD, or an electrical contact component in a relay. In the case where the device includes such a component, when the components are pasted together using a normal double-sided PSA sheet, the substance and / or precursor thereof that forms the above foreign substance from the PSA layer of the double-sided PSA sheet (Specific examples include organic substances such as carboxylic acids and inorganic substances such as silicone compounds.) May be released as outgas and adhere to the surface of parts that do not like the adhesion of foreign substances. High nature. However, since the double-sided pressure-sensitive adhesive sheet according to the present embodiment suppresses an increase in the amount of outgas generated as a precursor of these foreign substances, it is also preferably used in a device in which a part that disposes of the above foreign substances is incorporated. can do.

  Hereinafter, the usage method of the double-sided pressure-sensitive adhesive sheet according to the present embodiment will be specifically described by taking as an example a case where the device is an HDD and an FPC is attached to a housing of the HDD (hereinafter abbreviated as “housing”). . In this case, the adhesion surface of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet is the surface of the HDD housing (housing surface) and the surface of the FPC.

  The casing is obtained by subjecting a member formed by die-casting or pressing a metal material such as an aluminum alloy to a surface treatment for improving corrosion resistance and appearance. Specific examples of the surface treatment include anodization and electrodeposition coating using a paint containing an epoxy resin. Therefore, the housing adherend surface is composed of the surface of the layer formed by this surface treatment. In many cases, the adherend surface of the housing is not a flat surface but has an uneven surface for the purpose of improving the rigidity of the housing. That is, the housing adherent surface may have a highly bent surface such as a stepped portion surface.

  On the other hand, the FPC is generally composed of a laminate (which may have an adhesive layer) of a resin film such as a polyimide film and a metal foil such as copper, and its main surface is the surface of the resin film. Often consists of Usually, the thickness of the FPC is about 10 μm to several hundred μm and has a certain degree of flexibility. Therefore, even if the housing adherend is a highly bent surface, the FPC can be deformed so as to substantially conform to the shape. However, since the FPC has a metal foil as a conductive member, when the FPC is bent so as to follow the shape of the highly bent surface of the housing adherence surface, if the minimum bending radius at the bent portion of the FPC becomes excessively small, The metal foil breaks at the part and breaks. For this reason, FPC has a bending elastic modulus of a certain degree or more to prevent the minimum bending radius from becoming too small.

  Therefore, when the laminate of the double-sided pressure-sensitive adhesive sheet and the FPC is deformed so as to conform to the shape of the highly bent surface of the case-adhered surface, the surface on the pressure-sensitive adhesive layer side of the laminate is applied to the case-adhered surface. A restoring force based on this bending elasticity is generated in the FPC, and the force causes the laminated body to be separated from the housing adherent surface at the bent portion of the laminated body of the double-sided pressure-sensitive adhesive sheet and the FPC or in the vicinity thereof. Acts as a force. When the force is large, peeling may occur between the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet and the housing.

  One of the measures for avoiding the occurrence of the above problem is to improve the adhesion between the housing surface and the surface of the pressure-sensitive adhesive layer facing the housing surface. What is necessary is just to raise the adhesiveness of the adhesive layer which makes the main surface of an adhesive sheet. However, if the composition of the pressure-sensitive adhesive layer is changed so as to increase the wettability of the housing to the adherend surface in order to increase the pressure-sensitive adhesive layer, there is a concern that the amount of outgas generated from the pressure-sensitive adhesive layer increases. .

  On the other hand, the double-sided pressure-sensitive adhesive sheet according to the present embodiment reduces the possibility of occurrence of the “floating” phenomenon on the highly bent surface or in the vicinity thereof, because the pressure-sensitive adhesive composition contains a tackifier resin, It is compatible with suppressing an increase in the amount of outgas generated from the pressure-sensitive adhesive layer. As described above, the double-sided pressure-sensitive adhesive sheet according to the present embodiment can be preferably used for attaching components in a hard disk drive (HDD) (particularly, for applying FPC to a housing).

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
Crosslinkable polymer having butyl acrylate (BA), methyl acrylate (MA), acryloyl morpholine (ACMO) and 2-hydroxyethyl acrylate (HEA) as monomer components [BA / MA / ACMO / HEA = 83.5 / 2 /14/0.5, weight average molecular weight 600,000, solid content 35% by mass] 100 parts by mass, TDI-based crosslinking agent [manufactured by Nippon Polyurethane Industry Co., Ltd., trade name “Coronate L”, solid content 75% by mass] 225 parts by mass and 3.5 parts by mass of a polymerized rosin ester having a softening point of 120 to 130 ° C. (trade name “Pencel D-125”, solid content 100%) manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier resin are mixed. An agent composition was prepared.

The coating amount after drying the pressure-sensitive adhesive composition using a knife coater on the release-treated surface of the first release material (light release material) [trade name “SP-PET 381031” manufactured by Lintec Corporation] was 25 g / m ² . The resulting coating film was heated and dried at 100 ° C. for about 2 minutes to obtain a first laminate in which an adhesive layer was formed on the first release material. Thereafter, a PET film having a thickness of 12 μm (trade name “Lumirror S10” manufactured by Toray Industries, Inc.) as a core material was laminated on the surface on the pressure-sensitive adhesive layer side of the first laminate to obtain a single-sided pressure-sensitive adhesive sheet.

Next, the adhesive composition was applied to the release treatment surface of the second release material (heavy release material) [manufactured by Lintec Corporation, trade name “SP-PET3811”] using a knife coater, and the coating amount after drying was 25 g / m. ^The resulting coating film was heated and dried at 100 ° C. for about 2 minutes to obtain a second laminate in which an adhesive layer was formed on the second release material. The 2nd laminated body was bonded to the surface at the side of the core material of the said single-sided adhesive sheet, and the double-sided adhesive tape was produced.

[Example 2]
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that the amount of the tackifying resin in the pressure-sensitive adhesive composition was changed to 1.75 parts by mass.

Example 3
Example 1 except that the type of tackifying resin in the pressure-sensitive adhesive composition was changed to a hydrogenated terpene resin having a softening point of 130 ± 5 ° C. [manufactured by Yasuhara Chemical Co., Ltd., trade name “YS Polystar TH130”, solid content: 100%]. Similarly, a double-sided adhesive tape was prepared.

Example 4
Example 1 except that the type of tackifying resin in the pressure-sensitive adhesive composition was changed to a hydrogenated terpene resin having a softening point of 115 ± 5 ° C. (trade name “YS Polystar UH115”, solid content 100%, manufactured by Yashara Chemical Co., Ltd.). Similarly, a double-sided adhesive tape was prepared.

Example 5
Similar to Example 1, except that the type of tackifying resin in the pressure-sensitive adhesive composition was changed to a styrene hydrocarbon having a softening point of 100 ° C. [trade name “FTR0100”, solid content 100%, manufactured by Mitsui Chemicals, Inc.] An adhesive tape was prepared.

Example 6
Both sides are the same as in Example 1 except that the type of tackifying resin in the pressure-sensitive adhesive composition is changed to a styrene-based hydrocarbon having a softening point of 100 ° C. [trade name “FTR8100” manufactured by Mitsui Chemicals, 100% solid content]. An adhesive tape was prepared.
Example 7
Similar to Example 2, except that the type of tackifying resin in the pressure-sensitive adhesive composition was changed to a styrene hydrocarbon having a softening point of 95 ° C. [trade name “FTR6100”, solid content 100%, manufactured by Mitsui Chemicals, Inc.] An adhesive tape was prepared.
Example 8
Example except that the type of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive composition was changed to xylylene diisocyanate (XDI) -based crosslinking agent [manufactured by Nippon Polyurethane Industry Co., Ltd., trade name “Takenate D110N”, solid content: 75 mass%] A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in 1.

[Comparative Example 1]
A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that no tackifying resin was added when preparing the pressure-sensitive adhesive composition.

[Test Example 1] <Adhesion evaluation test>
For each of the double-sided PSA sheets of Examples and Comparative Examples, the first release material was peeled off and a 25 μm-thick PET film [trade name “Lumirror” manufactured by Toray Industries, Inc.] was applied, and the resulting laminate was cut. Thus, a 25 mm × 100 mm rectangular adhesive sheet was obtained. Subsequently, the surface of the pressure-sensitive adhesive layer peeled off and exposed from the second release material of the obtained pressure-sensitive adhesive sheet was pasted onto a flat adherend comprising an epoxy electrodeposition coated plate (manufactured by Partec). Is applied in an environment of 23 ° C. and relative humidity of 50% so that the thickness becomes 25 mm × 50 mm, and in an environment of 40 ° C., it is not attached to the end of the adhesive sheet (the adhesive layer remains exposed). Then, a load of 1.96 N was applied in a direction away from the 90 ° -direction planar adherend surface with respect to the adhesion surface with the planar adherend. This state was allowed to stand for 30 minutes, and the amount of peeling (deviation amount) of the pressure-sensitive adhesive sheet from the flat adherend after 30 minutes was measured and evaluated according to the following criteria.
A: Deviation amount: 25 mm or less B: Deviation amount: more than 25 and less than 40 mm C: Deviation amount: more than 40 and less than 50 mm D: Deviation amount: 50 mm or more The evaluation results are shown in Table 1. The measured peeling amount (displacement amount) of the adhesive sheet is shown in parentheses in the evaluation result column. In addition, since the adhesive sheet of the comparative example 1 peeled from the flat adherend before 30 minutes passed after load application, it indicated that.

[Test Example 2] <Measurement of outgas generation amount>
The amount of outgas generated was measured with a purge and trap GC Mass [manufactured by JEOL Ltd., trade name “JHS-100A”]. A sample (20 cm ² ) is sealed in an ampoule bottle, and the ampoule bottle is heated at 120 ° C. for 10 minutes with a purge and trap GC Mass to collect gas, and then introduced into GCMas [PerkinElmer, product name “TurboMass”] Then, using a calibration curve created using n-decane, the amount of the collected gas was determined as an n-decane conversion amount (unit: ng / cm ² ), and the result was defined as the outgas generation amount. The evaluation results are shown in Table 1.

  As shown in Table 1, the double-sided pressure-sensitive adhesive sheet of the example satisfying the conditions of the present invention has a small amount of outgas, and the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains a tackifier resin. The double-sided PSA sheet is difficult to peel off from the adherend surface.

  Since the double-sided pressure-sensitive adhesive sheet of the present invention is excellent in adhesiveness and suppresses an increase in the amount of outgas generation, a component in which a part that dislikes adhesion of foreign matter is incorporated on the surface of a device such as an HDD or a relay. It can be suitably used as a member for adhering to a housing having a bent surface.

1 ... HDD housing 2 ... FPC
3 ... Double-sided adhesive sheet 4 ... Laminated body of FPC and double-sided adhesive sheet

Claims (5)

A double-sided pressure-sensitive adhesive sheet comprising at least one pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a crosslinkable polymer, a crosslinking agent and a tackifying resin,
The amount of outgas generated is 1.0 μg / cm ² or less in terms of n-decane,
The crosslinkable polymer contains an acrylic polymer containing a structural unit based on a morpholine compound having an ethylenically unsaturated group,
Content of the structural unit based on acrylic acid in the acrylic polymer is 1.0 part by mass or less with respect to 100 parts by mass of the total of structural units in the acrylic polymer, or the acrylic type The polymer contains no structural units based on acrylic acid ,
The double-sided pressure-sensitive adhesive sheet is used for adhering a flexible printed circuit board to a step portion of a housing of the hard disk drive in the hard disk drive .   The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the crosslinking agent contains an isocyanate-based crosslinking agent.   The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the tackifying resin has a softening point of 95 ° C or higher.   The double-sided pressure-sensitive adhesive sheet according to claim 2 or 3, wherein the content of the tackifying resin in the pressure-sensitive adhesive composition is 1 part by mass or more with respect to 100 parts by mass of the solid content of the crosslinkable polymer.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer has a gel fraction of 10% to 70%.

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