JP2014062165A - Double-sided adhesive sheet for electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double-sided adhesive sheet in which peeling is hard to be generated even in the case the face to be adhered has a highly-flexural face, and the risk of generating outgas is reduced.SOLUTION: The double-sided adhesive sheet comprises an adhesive layer including a crosslinkable structure obtained by reacting a crosslinking agent with a crosslinking polymer, and, in one example, the double-sided adhesive sheet further comprises a core material in which the respective main face is laminated with the adhesive layer, the stress residual ratio of the adhesive layer is below 40%, and the crosslinking agent comprises tolylene diisocyanate. The adhesive layer is preferably formed in such a manner that the gel fraction reaches 10 to 70%.

Description

  The present invention relates to a double-sided pressure-sensitive adhesive sheet, and more particularly, to a double-sided pressure-sensitive adhesive sheet that has a reduced possibility of releasing a gas component that may adversely affect the operation of a component incorporated in a device such as a hard disk and has excellent adhesiveness.

  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”, 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 increases the possibility of outgas generation from the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet 3, and is not a preferable solution.

  Against this backdrop, the present invention is less likely to cause peeling even when the surface of the hard-to-lift portion, such as a stepped portion of the HDD housing, is generated, and the possibility of generating outgas is reduced. It aims at providing the coating material for forming the double-sided adhesive sheet and the adhesive layer with which a double-sided adhesive sheet is provided.

  In order to achieve the above object, the present inventors have studied the above-mentioned factors that cause the float. As a result, in addition to the restoring force of the FPC when the FPC is bent along the surface of the stepped portion of the casing, It was found that the restoring force of the pressure-sensitive adhesive layer in response to the bending of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet along the surface of the stepped part is one of the factors that cause the floating.

  The present invention based on such knowledge is firstly a double-sided pressure-sensitive adhesive sheet comprising at least one pressure-sensitive adhesive layer having a residual stress ratio of less than 40%, wherein the pressure-sensitive adhesive layer comprises a crosslinking agent and a crosslinkable polymer. The double-sided pressure-sensitive adhesive sheet (Invention 1) is provided, wherein the cross-linking agent contains a tolylene diisocyanate-based cross-linking agent.

  When the stress residual value of the pressure-sensitive adhesive layer is less than 40%, the restoring force of the sheet when the double-sided pressure-sensitive adhesive sheet according to the invention is deformed to be bent can be reduced. Even if the double-sided pressure-sensitive adhesive sheet having such characteristics is affixed to a surface having a high degree of bending, such as the surface of the stepped portion of the HDD housing, the pressure-sensitive adhesive layer is difficult to peel off. Moreover, it becomes easy to control the stress residual value of an adhesive layer in said range because the crosslinking agent concerning the adhesive layer of a double-sided adhesive sheet contains a tolylene diisocyanate type crosslinking agent.

  In the said invention (invention 1), it is preferable that the gel fraction of the said adhesive layer is 10% or more and 70% or less (invention 2). By adjusting the amount of the crosslinking agent containing the tolylene diisocyanate-based crosslinking agent so that the gel fraction of the pressure-sensitive adhesive layer is in the above range, the residual stress ratio of the obtained pressure-sensitive adhesive layer is in the above range. It becomes easier to control.

  In the said invention (invention 1 and 2), it is preferable that a stress residual rate is less than 40% about all the adhesive layers with which a double-sided adhesive sheet is provided (invention 3). In this case, even if it is attached to a surface with a high degree of bending, such as the surface of the stepped portion of the HDD housing, the adhesive layer is particularly difficult to peel off.

  In the said invention (invention 1 to 3), it is preferable that the said crosslinkable polymer contains the acrylic polymer which does not have a carboxyl group (invention 4). In this case, since the possibility that outgas is generated from the adhesive layer is further reduced, it is more stable that the malfunction of the device may occur even when the double-sided adhesive sheet is stuck inside the HDD housing. Reduced to

  In the above invention (Invention 4), the acrylic polymer having no carboxyl group is an ethylenic polymer having a structural unit based on an alkyl (meth) acrylate having 4 or less carbon atoms in the alkyl group and the reactive functional group. It is preferable that the structural unit based on a saturated compound is included (invention 5). By including a structural unit based on such an ethylenically unsaturated compound, it becomes easier to improve both the adhesive properties of the pressure-sensitive adhesive layer and to reduce the outgas amount.

  In the said invention (invention 4 and 5), it is preferable that the said acrylic polymer which does not have a carboxyl group further contains the structural unit based on the morpholine type compound which has an ethylenically unsaturated group (invention 6). By including the structural unit based on such a morpholine-based compound, it becomes easier to increase both the density of cross-linking bonds existing in the pressure-sensitive adhesive layer and the amount of outgas.

  In the said invention (invention 1 to 6), it is preferable that the said double-sided adhesive sheet is equipped with the core which has two main surfaces, and the said adhesive layer is laminated | stacked on each main surface (invention 7). By having such a configuration, the pressure-sensitive adhesive layer is not easily peeled off even when the double-sided pressure-sensitive adhesive sheet is attached to a surface having a high degree of bending, and the handleability of the double-sided pressure-sensitive adhesive sheet is improved.

  In the said invention (invention 7), it is preferable that the thickness of the said core material is 2 micrometers or more and 15 micrometers or less (invention 8). When the thickness of the core material is within this range, the function of the double-sided pressure-sensitive adhesive sheet according to the above invention can be more stably exhibited while enjoying the benefits of providing the core material.

  2ndly, this invention is a coating material for forming the adhesive layer with which the double-sided adhesive sheet which concerns on the said invention (invention 1-8) is provided, Comprising: A crosslinkable polymer and a tolylene diisocyanate type crosslinking agent And a coating material having fluidity (Invention 9).

  By using such a coating material, it becomes easy to obtain the double-sided pressure-sensitive adhesive sheet according to the above inventions (Inventions 1 to 8).

  Since the double-sided pressure-sensitive adhesive sheet according to the present invention has a low stress residual ratio of the pressure-sensitive adhesive layer, the restoring force when deformed to bend the sheet is low. For this reason, when the double-sided pressure-sensitive adhesive sheet according to the present invention is applied to a surface having a high degree of bending (also referred to as “highly-bent surface” in the present specification), such as the surface of the stepped portion of the housing of the HDD. The force acting on the pressure-sensitive adhesive layer on the side facing the highly bent surface of the sheet to peel the pressure-sensitive adhesive layer from the adhesive surface of the pressure-sensitive adhesive layer is reduced. Therefore, even if the content of the low molecular weight component is not particularly increased in the composition of the pressure-sensitive adhesive layer, it is possible to reduce the possibility that the double-sided pressure-sensitive adhesive sheet is lifted off from the adherend surface on the highly bent surface or the vicinity thereof. . Therefore, according to the double-sided pressure-sensitive adhesive sheet according to the present invention, it is possible to reduce both the possibility of outgassing and the possibility of floating even when the adherend surface has a highly bent surface.

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) Pressure-sensitive adhesive layer (1-1) Stress relaxation rate At least one of the pressure-sensitive adhesive layers included in the double-sided pressure-sensitive adhesive sheet according to the present embodiment has a stress residual rate defined below of less than 40%. About all the adhesive layers with which the double-sided adhesive sheet which concerns on this embodiment is provided, it is preferable that a stress residual rate is less than 40%.

  The “stress residual ratio” in this specification is a value obtained as follows. That is, the pressure-sensitive adhesive to be measured is formed in a pressure-sensitive adhesive layer having a thickness of 50 μm, cut into 50 mm × 50 mm, and rounded into a cylindrical shape to obtain a sample for tensile test. This cylindrical tensile test sample was pulled at a tensile rate of 200 mm / min and a distance between chucks of 30 mm with a universal tensile tester in an environment of 23 ° C. and 50% relative humidity. The stress A (N) when the 30 mm portion between them is extended by 5% and the stress B (N) after 5 minutes from the extension stop are measured. B / A × 100 (%) is calculated from these measured stresses A and B, and the value is defined as a residual stress rate (%).

  When a double-sided pressure-sensitive adhesive sheet is applied to a highly bent surface such as a stepped portion of the housing of the HDD, the double-sided pressure-sensitive adhesive sheet also deforms along the highly bent surface, and the adhesive layer near the bent portion has A compressive force or tensile force based on deformation acts. However, since the pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet according to the present embodiment has a stress residual ratio of less than 40%, the pressure-sensitive adhesive layer in the vicinity of the bending point tends to be restored against deformation during application. It is hard to generate power. Since the restoring force of this pressure-sensitive adhesive layer acts as a force in the direction of separating the pressure-sensitive adhesive layer from the adherend surface, this low restoring force can cause the double-sided pressure-sensitive adhesive sheet affixed to a highly bent surface to float. It contributes to reducing. From the viewpoint of more stably reducing the possibility of floating in the double-sided PSA sheet, the stress residual rate of the PSA layer is preferably 35% or less, more preferably 30% or less, and 25% or less. It is particularly preferred.

  The lower limit of the residual stress rate is not particularly limited, but when the residual stress rate is excessively low, the density of the crosslinked structure existing in the pressure-sensitive adhesive layer (also referred to as “crosslink density” in this specification) is particularly low. Therefore, there is a concern that it is difficult to control the adhesive properties (tackiness, adhesiveness, removability, etc.). From the viewpoint of reducing the possibility that such a problem occurs, the stress residual rate of the pressure-sensitive adhesive layer is preferably 1% or more, and more preferably 10% or more.

(1-2) Composition The double-sided pressure-sensitive adhesive sheet according to this embodiment includes a cross-linking agent and a reactive functional group that is a functional group capable of reacting with the cross-linking agent. It includes a crosslinked structure formed by a reaction with a polymer (also referred to as “crosslinkable polymer” in this specification).

(I) Crosslinkable polymer From the viewpoint of further reducing the amount of outgas from the double-sided PSA sheet, the crosslinkable polymer according to the pressure-sensitive adhesive layer of this embodiment is an acrylic polymer with a reduced amount of carboxyl groups. preferable. 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 (also referred to as “carboxyl free polymer” in the present specification). Similarly, the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet of the present embodiment preferably has a low carboxyl group content, and preferably does not substantially contain a component having a carboxyl group. Examples of the structural unit having a carboxyl group include acrylic acid, methacrylic acid, and itaconic acid.

  The structural unit of the crosslinkable 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, it is preferable that a crosslinkable polymer contains the structural unit based on alkyl (meth) acrylate (henceforth a "lower alkyl compound") whose carbon number of an alkyl group is 4 or less. 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 (meth) acrylate are preferable from the viewpoint of facilitating an appropriate balance between enhancing the adhesive properties of the pressure-sensitive adhesive layer and reducing the outgas amount. . 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 according to the pressure-sensitive adhesive layer of the present embodiment is a functional group capable of reacting with an isocyanate group since the crosslinking agent contains a tolylene diisocyanate compound as described later. preferable. Examples of such functional groups other than the carboxyl group include a hydroxyl group, an amino group, and an amide group.

  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 according to the present embodiment 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, the pressure-sensitive adhesive layer including a crosslinked structure based on the obtained crosslinkable polymer can easily have the stress residual ratio within the above-described range.

  The crosslinkable polymer according to the present embodiment 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 reducing the possibility of outgassing 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.

  The content of the structural unit based on the morpholine compound in the crosslinkable polymer according to the present embodiment is the lower alkyl compound from the viewpoint of easily preventing outgassing while keeping the stress residual ratio within the above range. It is preferably 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 content of the lower alkyl compound based on the structural unit based on the reactive compound and the content of the reactive compound based on the reactive compound. More preferably, it is 4 parts by mass or more and 25 parts by mass or less.

  The crosslinkable polymer according to the present embodiment is 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. Units may be included. 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. Although the content rate of the structural unit based on such a compound is not particularly limited, when it is excessively large, there is a concern that it is difficult to control the stress residual rate within the above-described range. Therefore, the content is 10 parts by mass with respect to a total of 100 parts by mass of the content of the lower alkyl compound based on the lower alkyl compound in terms of mass of the lower alkyl compound and the content of the reactive compound based on the reactive compound in terms of mass. Is preferably the upper limit, and more preferably 5 parts by mass.

(Ii) Cross-linking agent The cross-linking agent according to the pressure-sensitive adhesive layer of the present embodiment is one or two or more compounds selected from the group consisting of tolylene diisocyanate (TDI) and derivatives thereof (in the present specification, “tolylene diisocyanate type”). It is also referred to as a “crosslinking agent” and may be abbreviated as “TDI-based crosslinking agent”. The cross-linking agent according to the pressure-sensitive adhesive layer of the present embodiment is preferably composed mainly of a TDI-based cross-linking agent, more preferably composed of a TDI-based cross-linking agent, and particularly preferably substantially composed of TDI. Specific examples of TDI-based cross-linking agents include polyisocyanate compounds, isocyanurates, burette-type compounds obtained by addition reaction with trimethylolpropane, and other known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols. And the like, and urethane prepolymer type polyisocyanate obtained by addition reaction. When the cross-linking agent contains a TDI-based cross-linking agent, the double-sided pressure-sensitive adhesive sheet is folded compared to the case where it contains other polyisocyanate compounds such as xylylene diisocyanate (XDI) or hexamethylene diisocyanate (HMDI). Even if an external force is applied to the pressure-sensitive adhesive layer, stress hardly remains in the pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer according to this embodiment preferably has a gel fraction of 10% to 70%, and more preferably 20% to 60%. By adjusting the amount of the crosslinking agent used so that the gel fraction of the pressure-sensitive adhesive layer falls within this range, the stress residual rate can be easily set within the above-described range. Specifically, the content of the cross-linking agent in the pressure-sensitive adhesive layer before the reaction for forming a cross-linked structure proceeds is 0.1 part by mass or more and 10 parts by mass with respect to 100 parts by mass of the cross-linkable polymer. By adjusting in the range below mass parts, it becomes easy to make the gel fraction of an adhesive layer into said range.

(Iii) Other components The pressure-sensitive adhesive layer can contain various components as long as the residual stress ratio is in the above-described range. 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. However, these components are preferably those which do not easily generate outgas.

(1-3) 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, it is feared that desired adhesive properties cannot be obtained. If it is excessively thick, there is a concern that it is 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) 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.

(3) 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 attached to one side of the double-sided pressure-sensitive adhesive sheet can be easily peeled off from the other side 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. The pressure-sensitive adhesive layer-forming coating material The pressure-sensitive adhesive layer provided in the double-sided pressure-sensitive adhesive sheet according to the present embodiment can be formed using a pressure-sensitive adhesive layer-forming coating material described below. In the present specification, the “pressure-sensitive adhesive layer-forming coating material” is a material that contains a component for forming the pressure-sensitive adhesive layer and is used in the coating process for forming the 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. Moreover, the component for forming an adhesive layer may be contained as a solute, and may be contained as a dispersoid.

  The coating material for forming an adhesive layer according to the present embodiment has a particularly limited composition as long as the stress residual ratio is in the above-described range and contains a component for forming an adhesive layer including a crosslinked structure. Not. For the purpose of adjusting the thickness of the pressure-sensitive adhesive layer, a solvent (which may be a dispersion medium at the same time) may be contained.

  In a specific example, the pressure-sensitive adhesive layer-forming coating material according to this embodiment does not have a carboxyl group as a component for providing a cross-linked structure included in the pressure-sensitive adhesive layer formed by the coating material. It contains a cross-linkable polymer including an acrylic polymer (carboxyl group-free acrylic polymer) and a TDI cross-linking agent. The relationship between the content of the crosslinkable polymer and the TDI crosslinker in the coating material for forming the adhesive layer is such that the TDI crosslinker is 0.1 parts by mass or more and 10 parts by mass with respect to 100 parts by mass of the crosslinkable polymer. The following is preferable. By preparing the coating material so that the above relationship falls within this range, the gel fraction of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive layer-forming coating material is likely to be within the above-described range. It becomes easy to control the stress residual ratio of the pressure-sensitive adhesive layer formed of the material to less than 40%. The pressure-sensitive adhesive layer-forming coating material may contain a crosslinking agent other than the TDI-based crosslinking agent as long as the residual stress ratio of the obtained pressure-sensitive adhesive layer is in the above range.

  The coating material for forming the pressure-sensitive adhesive layer may contain components such as a coloring material, an antioxidant, and an ultraviolet absorber depending on the components to be contained in the pressure-sensitive adhesive layer.

  The method for preparing the coating material for forming the pressure-sensitive adhesive layer is not limited, and it may be only necessary to mix the components for forming the pressure-sensitive adhesive layer, or the component and the solvent (there may be a dispersion medium at the same time). In some cases. 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 the first laminate, the above-mentioned pressure-sensitive adhesive layer-forming coating material is applied onto the surface on the release surface side of the first release material, and the coating film of the pressure-sensitive adhesive layer-forming coating material Is formed on the release 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 adhesive layer-forming coating material on the release material is dried to obtain a first laminate in which the adhesive layer is laminated on the first release material. This drying condition is arbitrary and may be left at room temperature, or the above-mentioned coating film may be heated to about 80 ° C., for example. What is necessary is just to set drying time suitably according to the thickness of a coating film, drying temperature, etc. For example, when heating the coating film to 80 ° 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.

  Moreover, the drying conditions of the drying process for forming the adhesive layer in the first laminate and the second laminate are appropriately set (specifically, the coating film is heated to about 60 ° C. or more). The reaction between the crosslinking agent in the coating film and the crosslinkable polymer can be advanced. In order to sufficiently advance the cross-linking reaction instead of or in addition to the progress of the cross-linking reaction during the drying step for forming the pressure-sensitive adhesive layer of each laminate as described above, for example, You may provide the curing process of leaving still in the environment of 23 degreeC and relative humidity 50% for several days after the drying process for forming the adhesive layer of each laminated body. When performing a curing process, the implementation time is arbitrary and may be immediately after the drying process for forming the adhesive layer of each laminated body, or the first laminated body and the second laminated body may be directly or cored. It may be after carrying out the process of laminating via a material and forming a double-sided adhesive sheet.

4). 2. Usage method of double-sided pressure-sensitive adhesive sheet The double-sided pressure-sensitive adhesive sheet according to the present embodiment is used to attach a component incorporated in a device such as an HDD or a relay to another component (may be temporarily attached). .

  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 thereof include organic substances such as carboxylic acids, inorganic substances such as silicone compounds, etc.) that are released as outgas and adhere to the surface of parts that do not like the adhesion of foreign substances. Probability is high. However, the double-sided pressure-sensitive adhesive sheet according to the present embodiment is suitable for a device in which a part that dislikes the adhesion of foreign matter is incorporated because the possibility that these foreign matters and the outgas as a precursor thereof are released is reduced. Can be used for

  The method for using the double-sided pressure-sensitive adhesive sheet according to the present embodiment will be specifically described by taking as an example the case where such a device is an HDD and an FPC is attached to a housing of the HDD (hereinafter abbreviated as “housing”). To do. 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 from the pressure-sensitive adhesive layer increases.

  On the other hand, a restoring force similar to that of the FPC is generated in the adhesive layer constituting the double-sided adhesive sheet disposed between the housing and the FPC, and this restoring force also acts as a force that separates the FPC from the housing adherend surface. If the double-sided pressure-sensitive adhesive sheet according to this embodiment provided with a pressure-sensitive adhesive layer whose stress residual ratio is less than 40% is disposed between the housing and the FPC, the double-sided pressure-sensitive adhesive according to this embodiment will be described. It is possible to weaken the force acting on the laminate composed of the sheet and the FPC in the direction of separating the laminate from the housing adherend surface. Therefore, even if the composition of the pressure-sensitive adhesive layer is not changed so that the wettability with respect to the case-adhered surface is increased, the peeling between the case-adhered surface and the double-sided pressure-sensitive adhesive sheet on a highly bent surface such as the surface of the stepped portion. It has been realized to reduce the possibility of occurrence. In this way, the double-sided pressure-sensitive adhesive sheet according to the present embodiment reduces the possibility of floating on a highly bent surface or in the vicinity thereof, and reduces the possibility of outgassing from the pressure-sensitive adhesive layer. Both are compatible.

  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, polymerization average molecular weight 600,000, solid content 35% by mass] to 100 parts by mass, tolylene diisocyanate crosslinking agent [manufactured by Toyo Ink Co., Ltd., trade name “BHS-8515”, solid content 37.5 mass %] 0.45 parts by mass were mixed to prepare an adhesive layer-forming coating material.

The application amount after drying the adhesive forming coating material using a knife coater on the release treatment surface of the first release material (light release material) [trade name “SP-PET381031” manufactured by Lintec Corporation] is 25 g / the coating is m ^2, obtained by the coating film was dried by heating at 100 ° C. for about 2 minutes to obtain a first laminate adhesive layer formed on a first release liner. 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, a coating material for forming an adhesive using a knife coater is applied to the release treatment surface of a second release material (heavy release material) [trade name “SP-PET3811”, manufactured by Lintec Co., Ltd.]. It was applied so as to be 25 g / m ^2, and the obtained coating film was dried by heating at 100 ° C. for about 2 minutes to obtain a second laminate in which an adhesive layer was formed on the second release material. It was. 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]
Implemented except that 0.3 parts by mass of tolylene diisocyanate cross-linking agent [trade name “BHS-8515”, solid content 37.5 mass%] manufactured by Toyo Ink Co., Ltd.] was mixed to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as in Example 1.

Example 3
Implemented except that 0.6 parts by mass of tolylene diisocyanate crosslinking agent [trade name “BHS-8515”, solid content 37.5% by mass] manufactured by Toyo Ink Co., Ltd.] was mixed to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as in Example 1.
Example 4
Implemented except that 1.2 parts by mass of tolylene diisocyanate crosslinking agent [trade name “BHS-8515”, solid content 37.5% by mass] manufactured by Toyo Ink Co., Ltd. was mixed to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as in Example 1.

Example 5
Crosslinkable polymer [BA / MA / AA / ACMO] containing butyl acrylate (BA), methyl acrylate (MA), acrylic acid (AA), acryloyl morpholine (ACMO) and 2-hydroxyethyl acrylate (HEA) as monomer components /HEA=83/2/0.5/14/0.5, polymerization average molecular weight 600,000, solid content 35% by mass] and 100 parts by mass of a tolylene diisocyanate-based crosslinking agent [manufactured by Toyo Ink Co., Ltd., trade name “BHS −8515 ”, solid content 37.5% by mass] A double-sided pressure-sensitive adhesive tape was prepared in the same manner as in Example 1 except that 0.4 part by mass was mixed to prepare a coating material for forming an adhesive layer.
[Comparative Example 1]
Example 1 except that 2.0 parts by mass of a xylene diisocyanate-based cross-linking agent [manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BXX5640”, solid content: 35.0 mass%] was mixed to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as described above.
[Comparative Example 2]
Example 1 except that 3.0 parts by mass of a xylene diisocyanate-based cross-linking agent [manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BXX5640”, solid content 35.0% by mass] was prepared to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as described above.
[Comparative Example 3]
Implemented except that 3.0 parts by mass of tolylene diisocyanate-based crosslinking agent [trade name “BHS-8515”, solid content 37.5% by mass] manufactured by Toyo Ink Co., Ltd.] was mixed to prepare a coating material for forming an adhesive. A double-sided adhesive tape was prepared in the same manner as in Example 1.

[Test Example 1] <Measurement of gel fraction>
A second release material was applied to the pressure-sensitive adhesive layer side surface of the first laminate obtained in the examples or comparative examples to obtain a laminate for measuring gel fraction. This laminate for gel fraction measurement was left for 7 days in an environment of 23 ° C. and a relative humidity of 50%. Thereafter, the laminate for measuring gel fraction was cut into 50 mm × 90 mm, and the first release agent and / or the second release material adhered to the laminate was peeled off to obtain only the pressure-sensitive adhesive layer. After measuring the mass of this pressure-sensitive adhesive layer as a gel fraction measurement sample, it was wrapped in a Teflon (registered trademark) mesh (# 380) and immersed in 200 ml of ethyl acetate for 48 hours. Subsequently, the Teflon mesh and the gel fraction measurement sample contained therein were taken out from ethyl acetate and dried in an oven at 80 ° C. for 2 hours. The Teflon mesh and the gel fraction measurement sample contained therein were taken out of the oven, and the mass of the gel fraction measurement sample in the Teflon mesh was measured. The gel fraction was calculated from the measured sample mass based on the following formula. The results are shown in Table 1.
Gel fraction (%) = (sample weight after drying / sample weight before immersion) × 100
The calculation result of the gel fraction is shown in Table 1.

[Test Example 2] <Measurement of residual stress rate>
Using the knife coater on the release treatment surface of the first release material (light release material) [trade name “SP-PET 381031” manufactured by LINTEC Co., Ltd.], the adhesive-forming coating materials of each Example and Comparative Example were used. The coated film was dried so that the coating amount was 50 μm, and the obtained coating film was dried by heating at 100 ° C. for about 2 minutes to obtain a first laminate comprising a first release material and an adhesive layer. It was. This laminate was left for 7 days in an environment of 23 ° C. and 50% relative humidity. Next, the second release material (heavy release material) was bonded to the surface of the first laminate on the pressure-sensitive adhesive layer side, and then these release materials were removed to obtain only the pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was rolled into a cylindrical shape to prepare a sample for a tensile test. The tensile test sample was pulled with a universal tensile tester at a pulling speed of 200 mm / min and a chuck-to-chuck distance of 30 mm, and the stress A (when the measurement target portion of the tensile test sample (30 mm between the chucks) was extended by 5% N) and stress B (N) after 5 minutes from the stop of elongation. B / A × 100 (%) was calculated from these measured stresses A and B, and the value was defined as the residual stress rate (%).
Table 1 shows the calculation results of the stress residual ratio.

[Test Example 3] <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 attached in an environment of 23 ° C. and a relative humidity of 50% so as to be 25 mm × 50 mm, and in the environment, the end of the adhesive sheet that is not attached (the adhesive layer remains exposed) A load of 0.49 N was applied in the 90 ° direction with respect to the bonding surface with the flat adherend. This state was allowed to stand for 24 hours, and the amount of peeling (displacement amount) of the pressure-sensitive adhesive sheet from the flat adherend after 24 hours was measured and evaluated according to the following criteria.
A: Deviation amount: 10 mm or less B: Deviation amount: more than 10 and less than 40 mm C: Deviation amount: 40 mm or more 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 is stuck in a state where the double-sided pressure-sensitive adhesive sheet is bent because the residual stress ratio of the pressure-sensitive adhesive layer included in the sheet is less than 40%. Even if it is done, the force which tries to restore | restore a double-sided adhesive sheet from the bent state in the bending part or its vicinity does not work easily. Therefore, the bent double-sided pressure-sensitive adhesive sheet is difficult to peel from the adherend surface.

  Since the printing sheet of the present invention has a low possibility of outgas generation and is excellent in adhesiveness, a part 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, and a highly bent surface is used. It can be suitably used as a member for adhering to a housing or the like having it.

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

Claims (9)

A double-sided pressure-sensitive adhesive sheet comprising at least one pressure-sensitive adhesive layer having a stress residual ratio of less than 40%,
The pressure-sensitive adhesive layer includes a crosslinked structure formed by a reaction between a crosslinking agent and a crosslinkable polymer,
The double-sided pressure-sensitive adhesive sheet, wherein the crosslinking agent contains a tolylene diisocyanate crosslinking agent.   The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a gel fraction of 10% to 70%.   The double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein a stress residual ratio is less than 40% for all the pressure-sensitive adhesive layers provided in the double-sided pressure-sensitive adhesive sheet.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the crosslinkable polymer contains an acrylic polymer having no carboxyl group.   The acrylic polymer having no carboxyl group includes a structural unit based on an alkyl (meth) acrylate having an alkyl group having 4 or less carbon atoms and a structural unit based on an ethylenically unsaturated compound having the reactive functional group. The double-sided pressure-sensitive adhesive sheet according to claim 4.   The double-sided pressure-sensitive adhesive sheet according to claim 4 or 5, wherein the acrylic polymer having no carboxyl group further comprises a constituent unit based on a morpholine compound having an ethylenically unsaturated group.   The double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the double-sided pressure-sensitive adhesive sheet includes a core material having two main surfaces, and the pressure-sensitive adhesive layer is laminated on each main surface.   The double-sided pressure-sensitive adhesive sheet according to claim 7, wherein the core material has a thickness of 2 µm to 15 µm.   It is a coating material for forming the adhesive layer with which the double-sided adhesive sheet as described in any one of Claims 1-8 is equipped, Comprising: A crosslinkable polymer and a tolylene diisocyanate type crosslinking agent are contained. A fluid coating material.

Images