WO2017195899A1

WO2017195899A1 - Pressure-sensitive adhesive sheet and process for producing adherend laminate

Info

Publication number: WO2017195899A1
Application number: PCT/JP2017/018089
Authority: WO
Inventors: 美和子坂井
Original assignee: ソマール株式会社
Priority date: 2016-05-12
Filing date: 2017-05-12
Publication date: 2017-11-16
Also published as: KR20190008283A; CN109072022A; CN109072022B; KR102312787B1; JPWO2017195899A1; TWI739833B; TW201809181A; JP6884141B2

Abstract

Provided is a heat-peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer which, even when heated under severe conditions (for example, 100°C, 3 hours), can retain the expanded state without shrinking and can thereafter be easily peeled from the adherend. The pressure-sensitive adhesive sheet 1 includes a first pressure-sensitive adhesive layer 33, which comprises a heat-expandable pressure-sensitive adhesive composition comprising a thermally expanding agent and a pressure-sensitive adhesive. The pressure-sensitive adhesive sheet 1 is characterized in that the first pressure-sensitive adhesive layer 33 has been formed so as to satisfy relationships 1 and 2 and requirement a, wherein "S₀" is the surface area of the first pressure-sensitive adhesive layer 33, "Ra" is the arithmetic average roughness of the surface of the first pressure-sensitive adhesive layer 33a which was heated at 100°C for 3 hours, "H1" is the upper-limit height which is the highest point in the recesses and protrusions of said surface, "H5" is the lower-limit height which is the lowest point in the recesses and protrusions of said surface, and "S_H1-H5" is the area of said surface ranging from H1 to H5. Relationship 1: (H1-H5)≥50 µm Relationship 2: S_H1-H5/S₀≥2.5 Requirement a: Ra=4 to 8 µm

Description

Adhesive sheet and method for producing adherend laminate

The present invention relates to a heat-peelable pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer in which the adhesive strength of the contact surface with the adherend changes before and after heating at a predetermined temperature or more, and production of an adherend laminate using the pressure-sensitive adhesive sheet With respect to methods.

Adhesive layer containing thermally expandable microspheres as a re-peelable adhesive sheet that can be attached to an adherend with an appropriate adhesive force and can be easily peeled off after the intended purpose is no longer needed There is known a pressure-sensitive adhesive sheet provided with a base material (Patent Document 1).

JP 11-302614 A

When the pressure-sensitive adhesive sheet disclosed in Patent Document 1 is heated, the heat-expandable microspheres expand to generate irregularities on the surface of the pressure-sensitive adhesive layer. Is reduced, and the adhesive strength is reduced to facilitate the peeling of the adherend.

The reason why the adherend can be easily peeled is that the unevenness generated on the surface during the peel of the adherend is maintained and the expanded state of the adhesive layer is maintained. Therefore, even if the heat-expandable microspheres contained in the adhesive layer are expanded and then partially contracted, the expanded state of the adhesive layer is not maintained, resulting in partial adhesion with the adherend, The adherend may not be easily peeled from the adhesive sheet. It has been found that such a phenomenon is likely to occur particularly when the heating time (the time from the start of heating to the start of peeling of the adherend) is long.

However, after adhering the adhesive layer of the adhesive sheet to the adherend, the adherend is removed from the adhesive layer after being heated at a relatively low temperature (eg, 100 ° C.) for a long time (eg, 3 hours). It may be required to peel off. When subjected to heating for a long time even at a relatively low temperature, the expansion state of the adhesive layer that has been maintained until about 30 minutes have passed since the start of heating is maintained at the start of peeling of the adherend at the end of heating. It may not be possible. This is because the heat-expandable microspheres were expanded in the adhesive layer by heating and then partially contracted without being able to maintain the state, and as a result, the expanded adhesive layer was once deflated. Seem. As a result, partial adherence to the adherend was caused, and the adherend could not be easily peeled from the adhesive sheet. Therefore, even when the heating conditions are severe (for example, 100 ° C., 3 hours), it is desired to develop a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer that can maintain an expanded state without deflating the pressure-sensitive adhesive layer.

The object of the present invention is to provide a thermal exfoliation type having an adhesive layer that can maintain an expanded state without being deflated even after severe heating conditions (for example, 100 ° C., 3 hours), and then easily peeled off from the adherend. The pressure-sensitive adhesive sheet and a method for producing an adherend laminate using the pressure-sensitive adhesive sheet are provided.

The present inventor earnestly observed and investigated the surface state of the post-heating adhesive layer in which the expanded state is maintained without being deflated even under severe heating conditions (for example, 100 ° C., 3 hours). As a result, it has been determined that an adhesive layer may be formed so as to satisfy predetermined conditions after heating, and the present invention has been completed.

That is, according to the present invention, a heat-peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having the following constitution is provided. This pressure-sensitive adhesive sheet is suitably used, for example, for the production of an adherend laminate in which a cover material is adhered via an adhesive layer cured on the upper surface of the adherend. That is, according to this invention, the manufacturing method of the adherend laminated body shown below using the adhesive sheet is also provided.

The pressure-sensitive adhesive layer (pressure-sensitive adhesive layer before heating) of the present invention is thermally foamable and satisfies the following two points.
First, it is formed of a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition is thermally foamable, and includes a thermal foaming agent (preferably thermally expanded microspheres) and a pressure-sensitive adhesive.
Secondly, the surface area of the heat-foamable pressure-sensitive adhesive layer (before heating) is “S ₀ ”, and the surface of the heat-foamable pressure-sensitive adhesive layer (heat-foamable pressure-sensitive adhesive layer after heating) surface when heated at 100 ° C. for 3 hours. The arithmetic average roughness is “Ra”, the upper limit height that is the highest point of the unevenness is “H1”, the lower limit height that is the lowest point of the unevenness is “H5”, and the surface area in the range of H1 to H5 is “ when the S _H1-H5 ", that is formed such that it satisfies the following formulas 1 and 2 and the following conditions a.
Formula 1: (H1-H5) ≧ 50 μm,
Formula 2: S _H1-H5 / S ₀ ≧ 2.5, and Condition a: Ra is 4 to 8 μm.

The method for producing an adherend laminate according to the present invention includes an adherend laminate (for example, a display substrate) in which a cover material is bonded to an upper surface of an adherend (for example, a display substrate) via a cured adhesive layer. Display material having a layer structure of adhesive / post-curing layer / cover material), wherein the heat-foamable pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is bonded to the lower surface using the pressure-sensitive adhesive sheet having the above structure. The cover material is overlaid on the adherend so that the upper surface of the adherend and the adhesive layer before curing of the cover material face each other, and the whole is then subjected to predetermined heating conditions (90 to 110 ° C., 1 to 10 hours). After heating and curing the adhesive layer before curing, the pressure-sensitive adhesive sheet is peeled off from the lower surface of the adherend.

Since the heat-peelable pressure-sensitive adhesive sheet according to the present invention has a heat-foamable pressure-sensitive adhesive layer formed so as to satisfy predetermined conditions after heating, even if the heating conditions are severe (for example, 100 ° C., 3 Time), the expanded state is maintained without the adhesive layer being deflated after heating. Therefore, it can be said that it is particularly suitable for the production of an adherend laminate under the specific heating conditions.

The adherend laminate is not particularly limited. For example, a display substrate is used for the adherend, and a cover material is attached to the upper surface of the adherend via a cured adhesive layer. Examples thereof include display materials having an adhesive layer / cover material layer structure. As the display material, for example, the surface material of a head-mounted wearable display (or head-mounted display) equipped with a small liquid crystal panel for a user to view images, videos, etc. Examples thereof include a flexible display that can be used to view images and videos in a folded state.

It is sectional drawing which shows the adhesive sheet as an example of this invention. It is sectional drawing which shows the display material as an example of the adherend laminated body manufactured by this invention method. It is sectional drawing which shows one state of the 1st process which manufactures the display material of FIG. It is sectional drawing of the 1st laminated body prepared at a 1st process. It is sectional drawing which shows one state of a 2nd process. It is sectional drawing of the 2nd laminated body prepared at a 2nd process. It is sectional drawing of the 3rd laminated body prepared at a 3rd process. It is sectional drawing which shows the mode of the 4th laminated body prepared at a 4th process, and its heat processing. It is sectional drawing which shows the display material obtained at a 5th process. It is a figure explaining the measurement range of a surface area.

Hereinafter, the pressure-sensitive adhesive sheet of the present invention will be described in detail.
The pressure-sensitive adhesive sheet of the present invention is an adherend in which a heat-foamable pressure-sensitive adhesive layer is bonded to the lower surface in the production of an adherend laminate in which a cover material is bonded via an adhesive layer cured on the upper surface of the adherend. The cover material is overlaid on the adherend so that the upper surface of the body and the adhesive layer before curing of the cover material face each other, and then the whole is heated to cure the adhesive layer before curing, It is a heat-peelable pressure-sensitive adhesive sheet used in the step of peeling the heat-foamable pressure-sensitive adhesive layer from the lower surface of the adherend. The surface area of the heat foamable adhesive layer is "S _0", the thermally foamable adhesive layer surface when heated 3 hours at 100 ° C., the arithmetical mean roughness as a "Ra", the upper limit height is the highest point of the concave-convex When the thickness is “H1”, the lower limit height which is the lowest point of the unevenness is “H5”, and the surface area in the range from H1 to H5 is “S _H1-H5 ”, the thermally foamable pressure-sensitive adhesive layer has the following formula: 1, 2 and the following conditions are satisfied.
Formula 1: (H1-H5) ≧ 50 μm,
Formula 2: S _H1-H5 / S ₀ ≧ 2.5,
Condition: Ra is 4 to 8 μm

It is important that the pressure-sensitive adhesive sheet of the present invention has the thermally foamable pressure-sensitive adhesive layer. The heat-foamable pressure-sensitive adhesive layer contains a heat-foamable pressure-sensitive adhesive composition containing a heat-foaming agent and a pressure-sensitive adhesive. The pressure-sensitive adhesive sheet of the present invention may further include a base material layer formed on the lower surface of the thermally foamable pressure-sensitive adhesive layer and a slightly pressure-sensitive adhesive layer formed on the lower surface of the base material layer.

As shown in FIG. 1, an adhesive sheet 1 as an example of the adhesive sheet of the present invention is used for manufacturing a display material (an example of a surface material of a flexible display), has an adhesive layer 3, In the example, the pressure-sensitive adhesive layer 3 is disposed between the first separator 5 and the second separator 7.

In this example, the pressure-sensitive adhesive layer 3 is configured to have two pressure-sensitive adhesive layers on both the front and back surfaces of the substrate. Specifically, as the heat-foamable pressure-sensitive adhesive layer, one surface of the substrate 31 is thermally foamable. A first adhesive layer 33 is formed, and a slightly adhesive second adhesive layer 35 is formed on the other surface of the substrate 31 (the surface opposite to the surface on which the first adhesive layer 33 is provided) as the slightly adhesive layer. And at least a three-layer structure.

The substrate 31 is not particularly limited. For example, polyethylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate, triacetyl cellulose, polyimide, polyamide, polyethersulfone, polyetherimide, aromatic polyamide Various synthetic resin films such as polysulfone, acrylic, polyvinyl chloride, and fluororesin can be used.

The thickness of the substrate 31 is not particularly limited, and is generally about 10 μm to 250 μm, preferably about 25 μm to 125 μm.

The first adhesive layer 33 corresponds to the pre-heating foaming adhesive layer referred to in the present invention, and in this example, the physical properties thereof are appropriately adjusted. In the following, “first adhesive layer 33” means “before heating”, and “first adhesive layer 33a” means “after heating”. And
First, the surface area of the first adhesive layer 33 is _{"S 0".} This value is obtained by using a pressure-sensitive adhesive sheet sample in which the first pressure-sensitive adhesive layer 33 is formed on one side of a transparent polyethylene terephthalate film having a thickness of 50 μm, for example, and using the shape analysis laser microscope (VK− 9510: Keyence Corporation).

Next, the arithmetic average roughness of the surface of the first adhesive layer 33a when the entire adhesive sheet sample including the first adhesive layer 33 is heated at 100 ° C. for 3 hours is defined as “Ra”. In this example, the maximum height of the surface of the first adhesive layer 33a is “Ry”, and the ten-point average roughness is “Rz”. Ra, Ry, and Rz here can be measured, for example, with the same shape analysis laser microscope as described above.
Next, the upper limit height that is the highest point of the unevenness present on the surface of the first adhesive layer 33a is set to “H1”, and the lower limit height that is the lowest point is set to “H5”. Further, the surface area in the range from H1 to H5 is defined as “S _H1-H5 ”. In this example, the height at a position 10 μm lower is “H2”, the height at a position 20 μm lower is “H3”, and the height at a position 30 μm lower is “H4”. To do. Furthermore, the surface area in the range from H1 to H2 is “S _H1-H2 ”, the surface area in the range from H1 to H3 is “S _H1-H3 ”, and the surface area in the range from H1 to H4 is “S _H1-H4”. "

In the case of the above definition, in this example, the first adhesive layer 33 is formed so as to satisfy at least the above expressions 1, 2 and condition a.

Equation 1 is a condition that makes the difference between H1 and H5 (H1-H5) equal to or greater than a predetermined value. In this example, this value may be 50 μm or more, preferably 55 μm or more. This parameter (H1-H5) is for determining the degree of unevenness of the unevenness present on the surface of the first adhesive layer 33a.

In Formula 2, the value (S _H1−H5 / S ₀ ) obtained by dividing the surface area (S _H1−H5 ) in the range from H1 to H5 by the surface area (S ₀ ) of the first adhesive layer 33 is a predetermined value or more. It is a condition. In this example, this value may be 2.5 or more, preferably 3.0 or more. The upper limit is not particularly limited, but is preferably about 3.8 or less, for example. This parameter (S _H1-H5 / S ₀ ) is for determining the peelability from the adherend.

The condition a is a condition where the arithmetic average roughness (Ra) of the surface of the first adhesive layer 33a is within a predetermined value range. In this example, this value may be 4 μm or more, preferably 6 μm or more and 8 μm or less. This parameter (Ra) is for determining the roughness of the unevenness present on the surface of the first adhesive layer 33a.

In this example, the first pressure-sensitive adhesive layer 33 before heating is formed so that the surface of the first pressure-sensitive adhesive layer 33a after heating becomes a predetermined one, so that the heating conditions are strict (for example, 100 ° C., 3 hours). It has been found that the expanded state of the first pressure-sensitive adhesive layer 33a after heating can be maintained, and as a result, peeling from the adherend (described later) can be facilitated.

The first adhesive layer 33 of the present example satisfies all of the above-described formula 1, formula 2, and condition a, and at least one of formula 3, formula 4, formula 5, condition b, and condition c described later ( It is also possible to adjust so that most preferably all of these are satisfied.

Formula 3, the surface area _{(S H1-H2)} in the range of H1 through to H2, divided by the surface area of the first adhesive layer _{_{33 (S 0) (S H1}} -H2 / S 0) becomes a predetermined value range It is a condition. In this example, this value is 0.13 or more, preferably 0.17 or more, and is 0.25 or less, preferably 0.23 or less.

Equation 4, the surface area _{(S H1-H3)} in the range of H1 through to H3, divided by the surface area of the first adhesive layer _{_{33 (S 0) (S H1}} -H3 / S 0) becomes a predetermined value range It is a condition. In this example, this value is 0.90 or more, preferably 1.00 or more, 1.72 or less, preferably 1.50 or less.

In Formula 5, a value (S _H1−H4 / S ₀ ) obtained by dividing the surface area (S _H1−H4 ) in the range from H1 to H4 by the surface area (S ₀ ) of the first adhesive layer 33 is a predetermined value range. It is a condition. In this example, this value is 2.28 or more, preferably 2.40 or more, and is 3.00 or less, preferably 2.90 or less.

Condition b is a condition in which the maximum height (Ry) of the surface of the first adhesive layer 33a is within a predetermined value range. In this example, this value is 50 μm or more, preferably 53 μm or more and 65 μm or less, preferably 63 μm or less.

Condition c is a condition in which the ten-point average roughness (Rz) of the surface of the first adhesive layer 33a is within a predetermined value range. In this example, this value is 45 μm or more, preferably 50 μm or more and 65 μm or less, preferably 61 μm or less.

Each parameter of the formula 3-5 as well as the conditions b and c described above _{_{_{(S H1-H2 / S 0}}} ), (S H1-H3 / S 0), (S H1-H4 / S 0), Ry and Rz are both Is also for determining the peelability from the adherend after heating and foaming.

The first adhesive layer 33 having the above physical properties is formed of an adhesive composition containing a thermal foaming agent and an adhesive as essential components.

The thermal foaming agent is not particularly limited, and for example, a known thermal foaming agent (a pyrolytic type, an expanded graphite, a microencapsulated one, etc.) can be appropriately selected and used. Those obtained (hereinafter referred to as “thermally expandable microspheres”) can be preferably used.

As a heat-expandable microsphere, a microsphere having a structure in which a foaming agent is enclosed inside an elastic outer shell and exhibiting a heat expandability (a property that the whole expands when heated) is given as a preferable example. Can do. Examples of elastic outer shells include hot-melt materials and materials that are destroyed by thermal expansion, such as vinylidene chloride-acrylonitrile copolymers, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, etc. What was formed in (1) can be mentioned as a suitable example. Examples of the foaming agent include substances such as hydrocarbons such as isobutane, propane, and pentane that are easily gasified by heating and expand. Commercially-available products of thermally expandable microspheres include, for example, the trade name “Matsumoto Microsphere” series (Matsumoto Yushi Seiyaku Co., Ltd.), Advancel EM series (Sekisui Chemical Co., Ltd.), Expansel (Nihon Ferrite Co., Ltd.) And the like.

The size of the thermally expandable microspheres may be appropriately selected depending on the application of the pressure-sensitive adhesive sheet 1, and specifically, the mass average particle diameter is preferably 10 to 20 μm. By setting the size of the thermally expandable microspheres to be used in such a range, the initial adhesive force can be easily adjusted, and the surface shape of the adhesive layer after heat peeling can be easily controlled.

Thermally expandable microspheres can be used after adjusting their particle size distribution. The particle size distribution may be adjusted by classifying and removing particles having a relatively large particle size contained in the heat-expandable microspheres to be used with a centrifugal air classifier, dry classifier, sieving machine, or the like. By removing particles having a larger particle size than the average particle size and sharpening the particle size distribution, the surface smoothness of the first adhesive layer 33 to be formed is improved and the surface shape when heated is made uniform. can do. Specifically, the standard deviation of the particle size distribution of the heat-expandable microspheres is desirably 5.0 μm or less, preferably 4.5 μm or less, and more preferably 4.0 μm or less. When the standard deviation is 5.0 μm or less, the surface shape of the adhesive layer after heat peeling can be easily controlled.

Further, when using the thermally expandable microspheres, it is easy to adjust the thickness of the first adhesive layer 33 to be formed by classifying in advance. For example, when the thickness of the first adhesive layer 33 before heating is about 25 to 35 μm, in addition to using thermally expandable microspheres having a mass average particle diameter of about 10 to 20 μm, the mass average particle diameter is 10 μm. Thermally expandable microspheres obtained by classifying and removing those having a particle size of less than that and particles having a large particle size (for example, a particle size exceeding 20 μm) can be used. Thus, according to the method of classifying thermally expandable microspheres, the thermally expandable microspheres used so far can be used as they are. Therefore, it is not necessary to newly grasp expansion characteristics, behavior, etc., and development time can be shortened and development efficiency can be improved.

In the above, “particle size distribution” and “mass average particle size” are values measured by a laser diffraction particle size distribution measuring apparatus.

The expansion ratio of the thermally expandable microspheres may be 1.5 times or more, preferably 5 times or more, and more preferably 7 times or more. On the other hand, it is preferably 15 times or less, and more preferably 12 times or less. When the expansion ratio of the thermally expandable microspheres used in this example is preferably in the range of 5 to 15 times, the adhesive force of the first adhesive layer 33a can be efficiently reduced by heat treatment. . The outer shell of the thermally expandable microsphere preferably has an appropriate strength that does not rupture even when the thermally expandable microsphere expands to the predetermined expansion ratio.

Examples of other thermal foaming agents include pyrolytic foaming agents and expanded graphite. Pyrolytic foaming agents are classified into inorganic and organic types.
Examples of the inorganic foaming agent include ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, azides and the like. Examples of the organic foaming agent include water, fluorinated alkanes (for example, trichloromonofluoromethane, dichloromonofluoromethane, etc.), azo compounds (for example, azobisisobutyronitrile, azodicarbonamide (ADCA), Barium azodicarboxylate), hydrazine compounds (eg, paratoluenesulfonyl hydrazide, diphenylsulfone-3,3′-disulfonylhydrazide, 4,4′-oxybis (benzenesulfonylhydrazide), allylbis (sulfonylhydrazide), etc.) Semicarbazide compounds (eg, ρ-toluylenesulfonyl semicarbazide, 4,4′-oxybis (benzenesulfonyl semicarbazide), etc.), triazole compounds (eg, 5-morpholyl-1,2,3,4-thiatriazol) Etc.), N- nitroso compounds (e.g., N, N'-dinitrosopentamethylenetetramine, N, N'-dimethyl -N, N'-dinitrosoterephthalamide, etc.), and the like.
These thermal foaming agents can be used alone or in combination.

When heat-expandable microspheres are used as the thermal foaming agent, the blending amount is preferably 10 parts by mass or more, more preferably 13 parts by mass or more, and preferably 50 parts by mass with respect to 100 parts by mass of the adhesive described later. Part or less, more preferably 40 parts by weight or less. If the amount of thermally expandable microspheres is too small, the peelability after heating may be insufficient. On the other hand, when there are too many compounding quantities, the initial adhesive force may fall too much.

The blending ratio of the thermal foaming agent may be appropriately selected so that the unevenness on the surface of the first pressure-sensitive adhesive layer 33a after heating can be sufficiently formed. Usually, the pressure-sensitive adhesive described later: 10 to 50 parts by mass with respect to 100 parts by mass Range. In the experiment, when the blending ratio of the thermal foaming agent is less than 10 parts by mass, the convex part of the surface layer of the first adhesive layer 33a after heating tends to be less likely to be peeled off. Since unevenness is formed on the surface of the first pressure-sensitive adhesive layer 33, the substrate before heating with the adherend (in this example, the display substrate 21 described later. The same applies to the case of “adherend” hereinafter). This is not preferable because the adhesiveness tends to decrease. A preferable blending ratio is 13 to 40 parts by mass, more preferably 15 to 30 parts by mass, from the viewpoints of adhesion before heating with the adherend and releasability after heating from the adherend.

In this example, the thermal foaming agent used has a thermal foaming temperature of 80 ° C. or higher, particularly 90 ° C. or higher, and 110 ° C. or lower, particularly 100 ° C. or lower. By using a thermal foaming agent having a thermal foaming temperature in a predetermined range, it is possible to easily maintain the state in which the thermal foaming agent is optimally foamed. The thermal foaming temperature corresponds to the thermal expansion temperature when using thermally expandable microspheres as the thermal foaming agent, and corresponds to the thermal decomposition temperature when using a pyrolytic foaming agent. Here, the “thermal expansion temperature” is synonymous with the foaming start temperature, and in this example means the thermal expansion start temperature in the TMA measurement, and does not mean the maximum expansion temperature at which the volume expands to the maximum. If the thermal foaming temperature belongs to a predetermined range, two or more kinds may be used in combination.
When thermally expandable microspheres are used as the thermal foaming agent, the maximum expansion temperature is 120 ° C. or higher, particularly 125 ° C. or higher, and 140 ° C. or lower, particularly 135 ° C. or lower.

The pressure-sensitive adhesive may be appropriately selected from pressure-sensitive adhesives conventionally used when forming a pressure-sensitive adhesive layer containing a thermal foaming agent. However, it is preferable to use an acrylic pressure-sensitive adhesive in view of the uneven shape formed on the surface of the first pressure-sensitive adhesive layer 33a when the thermal foaming agent is foamed, the initial adhesive force, and the removability. There is no restriction | limiting in particular in the composition of an acrylic adhesive. However, it is preferable to use an acrylic pressure-sensitive adhesive having an acid value of 30 or more. By setting the acid value of the acrylic pressure-sensitive adhesive to 30 or more, it is possible to obtain a sufficient cross-linking density when cross-linking is performed using a cross-linking agent. It is because it is convenient at the point which becomes easy to peel. The “acid value” refers to the amount (mg) of potassium hydroxide required to neutralize free fatty acids and resin acids contained in 1 g of a sample (acrylic adhesive), and conforms to JIS K0070. And can be calculated by the neutralization titration method from the following formula (1).

Acid value A = B × F × 5.661 / S (1)

[B: amount of 0.1 ml / l potassium hydroxide ethanol solution used for measurement,
F: factor of ethanol solution of 0.1 mol / l potassium hydroxide,
S: the mass of the sample (g),
5.611: Formula weight of potassium hydroxide (56.11 × 1/10)]

The weight average molecular weight of the acrylic pressure-sensitive adhesive is not particularly limited, but is preferably 10,000 to 2,000,000, more preferably 100,000 to 1,500,000, and particularly preferably 200,000 to 1,000,000. By setting the weight-average molecular weight of the acrylic pressure-sensitive adhesive within the above range, the adhesive has sufficient adhesive force to perform higher-precision processing, and has better peelability without remaining adhesive on the adherend. Easy to make things.

The acrylic pressure-sensitive adhesive is preferably one that can react with the crosslinking agent. The acrylic pressure-sensitive adhesive includes a copolymer of an acrylic acid alkyl ester and / or a methacrylic acid alkyl ester and a monomer having a functional group capable of reacting with a crosslinking agent. Examples of the “alkyl esters” of acrylic acid alkyl esters and methacrylic acid alkyl esters include, for example, methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester Hexyl ester, heptyl ester, octyl ester, isooctyl ester, 2-ethylhexyl ester, isodecyl ester, dodecyl ester, tridecyl ester, pentadecyl ester, octadecyl ester, nonadecyl ester, eicosyl ester, etc. . Examples of the functional group capable of reacting with the crosslinking agent include a carboxyl group and a hydroxyl group.

Examples of the monomer whose functional group capable of reacting with the crosslinking agent is a carboxyl group include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. . Moreover, as a monomer whose functional group is a hydroxyl group, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, hydroxyhexyl acrylate, Examples include hydroxyhexyl methacrylate, hydroxyoctyl acrylate, hydroxyoctyl methacrylate, hydroxydecyl acrylate, hydroxydecyl methacrylate, hydroxylauryl acrylate, and hydroxylauryl methacrylate.

Monomers having a functional group capable of reacting with a crosslinking agent can be used alone or in combination of two or more. The ratio of the (meth) acrylic acid alkyl ester to the monomer having a functional group capable of reacting with the crosslinking agent is preferably in the range of 85:15 to 98: 2 in terms of mass ratio. If the blending ratio of the monomer having a functional group capable of reacting with the crosslinking agent is less than this range, when the thermally expandable microspheres expand, the peelability from the adherend tends to be impaired. On the other hand, when there are many compounding ratios of the monomer which has a functional group which can react with a crosslinking agent than this range, it exists in the tendency for the adhesive force to a to-be-adhered body to become scarce. From the viewpoint of improving the adhesion to the adherend and the peelability from the adherend, the ratio between the (meth) acrylic acid alkyl ester and the monomer having a functional group capable of reacting with the crosslinking agent is The ratio is more preferably 88:12 to 93: 7.

If desired, other monomers other than the (meth) acrylic acid alkyl ester and the monomer having a functional group capable of reacting with the crosslinking agent may be used in combination. Examples of other monomers include styrene, vinyl acetate, acrylonitrile, acrylamide, polyethylene glycol acrylate, N-vinyl pyrrolidone, and tetrafurfuryl acrylate.

The acrylic pressure-sensitive adhesive can be obtained by radical copolymerization of monomer components. The copolymerization method in this case is conventionally known, and examples thereof include an emulsion polymerization method, a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method. The glass transition temperature of the acrylic pressure-sensitive adhesive is preferably −50 to −15 ° C. If the glass transition temperature exceeds -15 ° C, the adhesion to the adherend tends to decrease. On the other hand, when the glass transition temperature is less than −50 ° C., adhesive residue is liable to occur at the time of peeling from the adherend, and the peelability tends to be difficult. From the viewpoint of improving the adhesion to the adherend and the peelability from the adherend, the glass transition temperature of the acrylic pressure-sensitive adhesive is more preferably −40 ° C. to −20 ° C.

Next, the crosslinking agent will be described. The crosslinking agent may be appropriately selected according to the acrylic pressure-sensitive adhesive to be used, and is not particularly limited. Specific examples of the crosslinking agent include an isocyanate crosslinking agent, a metal chelate crosslinking agent, and an epoxy crosslinking agent. Among these, an epoxy-based cross-linking agent is used from the viewpoint of improving the peelability from the adherend after heating to a temperature at which the heat-expandable microspheres expand and preventing adhesive residue on the adherend. It is preferable. Examples of the epoxy-based crosslinking agent include bisphenol-based epoxy resins (for example, bisphenol A type, bisphenol F type, bisphenol AD type), phenol novolac type epoxy resins, ethylene glycol diglycidyl ether, 1,6-hexanediol glycidyl ether, Trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane Etc.

Further, in terms of adhesiveness to the adherend at normal temperature and releasability from the adherend after expansion of the heat-expandable microspheres, a polyfunctional epoxy crosslinking agent is preferable, and a tetrafunctional epoxy crosslinking agent. Is more preferable. Specific examples include N, N, N ′, N′-tetraglycidyl-m-xylenediamine and 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane. However, since these epoxy-based crosslinking agents tend to slow the crosslinking reaction rate, when the crosslinking reaction is insufficient, (1) a catalyst such as amine is added to promote the crosslinking reaction. (2) It is desirable to use a monomer having an amine functional group as a constituent of the pressure-sensitive adhesive, and (3) to use an aziridine-based crosslinking agent in combination with the crosslinking agent. In particular, it is preferable to add a tertiary amine having a catalytic effect to a crosslinking agent such as N, N, N ′, N′-tetraglycidyl-m-xylenediamine.

A crosslinking agent may be used independently or may be used in combination of 2 or more type. If the blending ratio of the crosslinking agent is appropriately selected so that the first adhesive layer 33 has a preferable elastic modulus together with the above-described thermally expandable microspheres, the acrylic pressure-sensitive adhesive, and a tackifier resin to be used as required. Well, there are no particular restrictions. However, the ratio of the crosslinking agent contained in the pressure-sensitive adhesive composition is preferably 0.5 equivalent or less with respect to the acrylic pressure-sensitive adhesive because the adhesion to the base material 31 is improved. When the ratio of the cross-linking agent exceeds 0.5 equivalent in terms of the acrylic pressure-sensitive adhesive, the adhesive force to the adherend tends to decrease, and before the thermally expandable microspheres are heated and expanded, the adherend is This is not preferable because it tends to be peeled off. From the viewpoint of adhesion between the base material 31 and the adherend, the ratio of the crosslinking agent contained in the pressure-sensitive adhesive composition is 1 × 10 ⁻³ to 0.3 equivalent in terms of the acrylic pressure-sensitive adhesive. Is more preferable.

The elastic modulus at 20 ° C. of the first adhesive layer 33, 1.0 × ¹⁰ 4 Pa or more, when the range of less than 1.0 × ¹⁰ 6 Pa, for initial peel strength tends to decrease, the adherend In some cases, the adhesion of the resin may deteriorate. For this reason, the case where the processing accuracy of a to-be-adhered body and a process yield fall is also assumed. Therefore, it is preferable that the pressure-sensitive adhesive composition for forming the first pressure-sensitive adhesive layer 33 contains a tackifier resin as a tackifier because it is easy to adjust the adhesion to the adherend near room temperature.
As the tackifier resin, those having a softening point of 120 ° C. or higher are preferable. Specific examples of tackifying resins include α-pinene-based, β-pinene-based, dipentene-based, terpene-phenol-based terpene-based resins; gum-based, wood-based, tall oil-based natural rosins; Examples thereof include rosin resins such as rosin derivatives obtained by treating rosin with hydrogenation, disproportionation, polymerization, maleation, esterification, etc .; petroleum resins; coumarone-indene resins.

Among these, those having a softening point in the range of 120 to 160 ° C. are more preferable, and those having a softening point in the range of 140 to 160 ° C. are particularly preferable. When a tackifying resin having a softening point within the above range is used, not only is there little contamination and adhesive residue on the adherend, but it is also possible to further improve the adhesion to the adherend in the work environment. Become. Moreover, it is easy to adjust the elastic modulus of the first pressure-sensitive adhesive layer 33 within a desired predetermined range, and even if the elastic modulus of the first pressure-sensitive adhesive layer 33 is less than 1.0 × 10 ⁶ Pa, the initial peeling force is reduced. Since it can be made high, it is preferable. Furthermore, when a terpene phenol type tackifying resin is used as the tackifying resin, not only the adherend is contaminated and the adhesive residue is small, but also the tackiness to the adherend in an environment of 50 to 90 ° C. is improved. At the same time, after expansion of the thermally expandable microspheres, peeling from the adherend becomes easier.

The blending ratio of the tackifier resin may be appropriately selected so that the elastic modulus of the first adhesive layer 33 can be adjusted within a desired predetermined numerical range, and is not particularly limited. However, from the viewpoint of the elastic modulus and the initial peeling force of the first adhesive layer 33, the amount is preferably 10 to 100 parts by mass with respect to 100 parts by mass of the acrylic adhesive. When the blending ratio of the tackifying resin is less than 10 parts by mass with respect to 100 parts by mass of the acrylic pressure-sensitive adhesive, the adhesion to the adherend during operation tends to decrease. On the other hand, if it exceeds 100 parts by mass, the adhesion to an adherend at room temperature will deteriorate. From the viewpoint of adhesion to the adherend and stickability at normal temperature, the blending ratio of the tackifying resin is more preferably 15 to 50 parts by mass with respect to 100 parts by mass of the acrylic adhesive. Moreover, it is preferable that the hydroxyl value of tackifying resin is 30 mg / KOHg or more. By setting the hydroxyl value of the tackifying resin to 30 mg / KOHg or more, it is difficult to cause adhesive residue on the adherend upon peeling after the heat treatment.

The first adhesive layer 33 has a reaction accelerator, a surfactant, a pigment, a lubricant, a colorant, an antistatic agent, a flame retardant, an antibacterial agent, as long as it does not impair the function of the adhesive composition. Various additives such as an antifungal agent, an ultraviolet absorber, a light stabilizer, an antioxidant, a leveling agent, a flow regulator, and an antifoaming agent can be included.

The pressure-sensitive adhesive composition is obtained by adding the above-mentioned pressure-sensitive adhesive, thermal foaming agent, and further, if necessary, a crosslinking agent, a tackifier, a solvent, and an additive in any order, and dissolving or dispersing them. Can do. The raw materials can be mixed using a mixer or a kneader such as a dissolver, planetary mixer, butterfly mixer. Although mixing temperature changes with compositions, it is necessary to carry out below the thermal foaming temperature (T1) of a thermal foaming agent.

The first pressure-sensitive adhesive layer 33 can be obtained by applying the above-mentioned pressure-sensitive adhesive composition to one surface of the substrate 31 and drying it as necessary.

In this example, the thickness of the first adhesive layer 33 is preferably 15% or more, more preferably 20% or more, based on the size (mass average particle diameter) of the thermal foaming agent to be selected. , Preferably 75% or less, more preferably 60% or less. For example, when a thermal foaming agent having a mass average particle diameter of 9 μm to 15 μm is used, the thickness of the first adhesive layer 33 is preferably 20 μm or more, more preferably 35 μm or more, and the upper limit is 60 μm or less. Furthermore, it is preferable to be 50 μm or less. By setting the thickness of the first adhesive layer 33 to 20 μm or more, it is easy to make the initial adhesive force sufficient. By setting the thickness of the first adhesive layer 33 to 60 μm or less, cohesive failure does not easily occur at the time of peeling after the heat treatment, and it is easy to obtain better peelability. Moreover, since the energy for sufficiently foaming the thermal foaming agent during the heat treatment is likely to spread throughout the adhesive layer, it is more difficult for the adhesive residue to remain when peeling after the heat treatment.

In addition, depending on the amount of volatile matter remaining in the first adhesive layer 33 (residual volatile matter amount), the peelability from the adherend after heat treatment and the adhesive residue may be affected. Accordingly, the residual volatile content in the first adhesive layer 33 is preferably 4% by mass or less, and more preferably 2% by mass or less.

Since the first adhesive layer 33 is formed so as to satisfy predetermined conditions (at least Formula 1, Formula 2, and Condition a) after heating, it is severe at 90 to 110 ° C. for 1 to 10 hours. Even if it is subjected to heating under conditions, the first pressure-sensitive adhesive layer 33a (described later) that has expanded after heating is not deflated, and the expanded state is maintained.

The second adhesive layer 35 has a peel strength before heat treatment (to a polyethylene terephthalate film) adjusted to about 0.4 N / 25 mm or less, preferably about 0.1 to 0.4 (N / 25 mm). The composition (adhesive composition) is not particularly limited. However, the second adhesive layer 35 does not include the thermal foaming agent included in the first adhesive layer 33 in this example.
The second pressure-sensitive adhesive layer 35 is obtained by applying a pressure-sensitive adhesive composition having a predetermined composition to the other surface of the substrate 31 (the surface opposite to the surface on which the first pressure-sensitive adhesive layer 33 is provided) and drying it as necessary. Obtainable.

The thickness of the second adhesive layer 35 is not particularly limited. For example, the lower limit is preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is preferably 15 μm or less, more preferably 10 μm or less. If the thickness of the second adhesive layer 35 is too thick, inconveniences such as reattachment and removal after processing are difficult to occur, and if it is too thin, it is difficult to obtain the effect of providing this.

The first separator 5 and the second separator 7 are not particularly limited. For example, polyethylene laminated paper, polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, triacetyl cellulose, polyvinyl chloride, acrylic, A plastic film such as polystyrene, polyamide, polyimide, vinylidene chloride-vinyl chloride copolymer, or the like obtained by subjecting one surface of the plastic film to a mold release treatment can be used.

The thickness of the first separator 5 and the second separator 7 is not particularly limited, but is generally 10 μm to 250 μm, preferably 25 μm to 125 μm.

The pressure-sensitive adhesive sheet 1 of this example includes a pressure-sensitive adhesive layer 3 including a heat-foamable first pressure-sensitive adhesive layer 33 formed so as to satisfy predetermined conditions (at least Formula 1, Formula 2, and Condition a) after heating. Therefore, even when subjected to heating under severe conditions such as 1 to 10 hours at 90 to 110 ° C., the first adhesive layer 33a that has expanded after heating is not deflated and the expanded state is maintained. Therefore, it can be applied to an adherend (display substrate 21 in the following description) with an appropriate adhesive force before heating, and various operations (as a releasable adhesive sheet that can be easily peeled off from the adherend after heating) It can be used for the production of an adherend laminate, etc. Especially for the production of the display material 20 of FIG.

Next, the method for producing the adherend laminate of the present invention will be described in detail.
The method for producing an adherend laminate of the present invention is a method for producing an adherend laminate in which a cover material is bonded via an adhesive layer cured on the upper surface of an adherend. And a heat-foamable pressure-sensitive adhesive layer comprising a heat-foamable pressure-sensitive adhesive composition containing the pressure-sensitive adhesive, the surface area of the heat-foamable pressure-sensitive adhesive layer is “S ₀ ”, and the heat when heated at 100 ° C. for 3 hours. The arithmetic average roughness of the surface of the foamable adhesive layer is “Ra”, the upper limit height that is the highest point of unevenness is “H1”, and the lower limit height that is the lowest point of unevenness of the thermally foamable adhesive layer before heating was as "H5", when the surface area in the range from H1 H5 as "S _H1-H5", using the adhesive sheet to form a pressure-sensitive layer so that it satisfies the following formulas 1 and 2 and the following conditions, The upper surface of the adherend in which the thermally foamable adhesive layer of the adhesive sheet is bonded to the lower surface, and before the cover material is cured The cover material is overlaid on the adherend so that the adhesive layer faces, and then the whole is heated at 90 to 110 ° C. for 1 to 10 hours to cure the pre-curing adhesive layer. It consists of peeling the said adhesive sheet from a lower surface.
Formula 1: (H1-H5) ≧ 50 μm,
Formula 2: S _H1-H5 / S ₀ ≧ 2.5,
Condition: Ra is 4 to 8 μm.

The adherend laminate produced by the production method of the present invention is not particularly limited. For example, a display base material is used for the adherend, and a cover material is affixed via an adhesive layer cured on the upper surface thereof. And display materials having a layer structure of display substrate / adhesive layer after curing / cover material. As the display material, for example, the surface material of a head-mounted wearable display (or head-mounted display) equipped with a small liquid crystal panel for a user to view images, videos, etc. Examples thereof include a flexible display that can be used to view images and videos in a folded state.

FIG. 2 is a cross-sectional view showing a display material as an example of an adherend laminate. In this example, the case where the display material 20 shown in FIG. 2 as an example of an adherend laminate is manufactured using the pressure-sensitive adhesive sheet 1 shown in FIG.

First, the structure of the display material 20 to be manufactured will be described. As shown in FIG. 2, the display material 20 is configured by adhering a cover material 25 to the upper surface of the display substrate 21 via a cured adhesive layer 23 a. In the following description, “adhesive layer 23a” means “after curing”, and “adhesive layer 23” means “before curing”.
Examples of the display substrate 21 include glass and plastic substrates.
The adhesive layer 23a is obtained by curing the adhesive layer 23 (before curing) having a predetermined thickness formed from the adhesive composition by heating.
Examples of the cover material 25 include glass and plastic materials.

Next, the detail of the manufacturing method of the display material 20 is demonstrated. First, as shown in FIGS. 3 and 4, the first separator 5 is pulled away from the adhesive sheet 1 of FIG. 1, and one side (second adhesive layer 35) side of the adhesive layer 3 is exposed on the second separator 7. The 1st laminated body 50 is prepared by overlapping on the 1 to-be-adhered body 40 (1st process). Examples of the first adherend 40 include a glass substrate.
Next, as shown in FIG. 5 and FIG. 6, the second separator 7 is pulled away from the first laminated body 50, and the other side (first adhesive layer 33) side of the adhesive layer 3 is exposed on the first adherend 40. The second laminated body 52 is prepared so as to overlap the display substrate 21 as the second adherend (second step).

Next, as shown in FIG. 7, the second stacked body 52 is punched into a predetermined shape, and unnecessary portions are removed to prepare a third stacked body 54 (third step).
Next, as shown in FIG. 8, the adhesive layer 23 of the cover material 25 is overlapped on the display substrate 21 of the third laminated body 54 to prepare the fourth laminated body 56, and then heat treatment is performed ( (4th process). The heating conditions are 100 ° C. and 3 hours in this example.
By such heat treatment, as shown in FIG. 9, the first adhesive layer 33 expands to become the first adhesive layer 33a, and the tack on the display substrate 21 side is reduced. At the same time, the adhesive layer 23 of the cover material 25 is cured to form the adhesive layer 23a, whereby the display material 20 shown in FIG. 2 is obtained (fifth step).

According to the method of this example using the pressure-sensitive adhesive sheet 1, even when the fourth laminate 56 shown in FIG. 8 is heated under severe conditions of 100 ° C. and 3 hours, the first pressure-sensitive adhesive layer 33 a in contact with the display substrate 21 is formed. There is no wilting and the expanded state is maintained. As a result, as shown in FIG. 9, the display material 20 can be easily peeled off, and a reduction in the manufacturing yield of the display material 20 can be suppressed.

Hereinafter, the present invention will be specifically described based on experimental examples (including examples and comparative examples), but the present invention is not limited to these examples.

1. Preparation of adhesive sheet [Experimental Examples 1 to 7]
Baker-type applicators were prepared by applying heat foamable adhesive layer-forming coating liquids a1 and b prepared by uniformly mixing and dissolving the following components at a solid content ratio shown in Table 1 on one side of a transparent PET film having a thickness of 50 μm. Was applied. Table 1 shows the solid content ratio (mass conversion) of the adhesive and the like of each coating solution. The total solid content in each coating solution was adjusted to 40%. Then, after forming a heat-foamable pressure-sensitive adhesive layer by sufficiently drying at 80 ° C., a PET film (separator) having a thickness of 38 μm whose one surface was subjected to silicone release treatment on the surface of the heat-foamable pressure-sensitive adhesive layer The adhesive sheet of each example was produced by arrange | positioning.

<< Constituent Components of Adhesive Layer Forming Coating Liquids a1 and b >>
-Adhesive (solid content 34%): 294 parts by mass (solid content 100)
(Nissetsu PE-121, acrylic acid-butyl acrylate copolymer (AA / BA = 10/90), molecular weight: 500,000, glass transition temperature: -20 ° C., acid value: 78, manufactured by Nippon Carbide)
-Thermally expandable microspheres: types and solid content ratios listed in Table 1-Epoxy crosslinking agents: solid content ratios listed in Table 1 (Tetrad X, N, N, N ', N'-tetraglycidyl-m-xylenediamine , Epoxy equivalent 100, manufactured by Mitsubishi Gas Chemical Company)
-Tackifier (solid content 100%): Table 1 type and solid content ratio-Toluene: 226 parts by mass

In Table 1, “Y1” as the tackifier is a terpene phenol tackifier resin (YS Polystar K125, terpene phenol, softening point 125 ° C., molecular weight 1000, manufactured by Yasuhara Chemical Co., Ltd.), and “Y2” is terpene phenol. Type tackifier resin (YS Polystar G150, terpene phenol type, softening point 150 ° C., molecular weight 700, manufactured by Yasuhara Chemical Co., Ltd.).
“Z1” of thermally expandable microspheres is a thermally expanded particle (Matsumoto) having a mass average particle size of 13 μm, a thermal expansion temperature (synonymous with thermal foaming temperature; the same shall apply hereinafter) of 80 ° C., and an expansion ratio of 1.5 to 5 times. Microsphere, F-36D (manufactured by Matsumoto Yushi Seiyaku Co., Ltd.), “Z2” is a thermally expanded particle having a mass average particle diameter of 12 μm, a thermal expansion temperature of 100 ° C., and an expansion ratio of 1.5 to 5 times (Matsumoto Micro Sphere, F-48D, manufactured by Matsumoto Yushi Seiyaku Co., Ltd.).

2. Measurement, calculation and evaluation of physical properties (2-1) Measurement of S ₀ , Ra, Ry and Rz For the pressure-sensitive adhesive sheet obtained in each example, the separator was peeled off, and then a shape analysis laser microscope (VK-9510: Keyence Corporation) The surface area (S ₀ ) of the exposed adhesive layer was measured at a magnification of 50. Then, after heating for 3 hours in an oven at 100 ° C. with the adhesive layer exposed (heating conditions are as shown in Table 3), the adhesive layer was thermally expanded (sample after heating), and then S ₀ was measured. Using the shape analysis laser microscope used for the above, the arithmetic average roughness (Ra), maximum height (Ry) and ten-point average roughness (Rz) of the adhesive layer surface after being heated and expanded under the following conditions Was measured. The results are shown in Table 2.

(2-2) Calculation of (H1-H5) and (S _H1-H2 / S ₀ ) to (S _H1-H5 / S ₀ ) Similarly to the above 2. In using a shape analysis laser microscope was used to measure such S _0, the irregularities present on the adhesive layer surface, on which the upper limit height (the highest point H1) and a lower limit height (lowest point H5) were measured, H1 And the difference between H5 and H5 (H1-H5) was calculated. In addition, after measuring the surface area (S _H1-H5 ) in the range from H1 to H5 (see, for example, FIG. 10), The value of (S _H1-H5 / S ₀ ) was calculated by dividing by the measured value of the surface area (S ₀ ) of the adhesive layer (before heating) obtained in ( ₁ ). Furthermore, with reference to the above-mentioned H1, when the height of the position 10H lower (H2), the height 20H lower (H3), and the height 30H lower (H4), respectively, from H1 to H2 The surface area in the range of (S _H1-H2 ), the surface area in the range from H1 to H3 (S _H1-H3 ), and the surface area in the range from H1 to H4 (S _H1-H4 ) are measured. The values are the same as those described in 2. Each value of (S _H1-H2 / S ₀ ) to (S _H1-H4 / S ₀ ) was also calculated by dividing by the measured value of the surface area (S ₀ ) of the adhesive layer (before heating) obtained in . The results are shown in Table 2.
The unit of each surface area is μm ² .

3. Evaluation About the adhesive sheet obtained by each example, the thickness of the adhesion layer and heat peelability (peelability after heat processing) were measured or evaluated by the following methods.

(3-1) [Adhesive layer thickness]
Using a micrometer, the thickness including the two PET sheets was measured and calculated by subtracting the thickness of the two PET sheets from the measured value. The results are shown in Table 2.

(3-2) [Peelability after heat treatment]
The pressure-sensitive adhesive sheet obtained in the experimental example of 2 cm × 10 cm was prepared, and the pressure-sensitive adhesive layer peeled off and exposed was bonded to a glass plate (thickness 1.0 mm, 15 cm × 10 cm) and heated in an oven. The heating conditions were as shown in Table 3. After standing to cool, at room temperature (23 ° C.), whether or not the adhesive layer of the adhesive sheet was peeled off from the glass plate was visually evaluated according to the following criteria. The results are shown in Table 3.
“◎”: All were peeled off (very good).
“◯”: All were peeled off, but the surface was slightly tacky (good).
“Δ”: almost peeled off, but partly not peeled off slightly (not so good).
“×”: not peeled off (defect).

The above 2. The following physical property evaluation based on the calculated value of (2-2) is also shown in Table 3.
It was evaluated whether each of Formula 1 ((H1-H5) ≧ 50 μm), Formula 2 (S _H1-H5 / S ₀ ≧ 2.5), and Condition a (Ra is 4 to 8 μm) is satisfied. . Further, Formula 3 ((S _H1−H2 / S ₀ ) = 0.13 to 0.25), Formula 4 ((S _H1−H3 / S ₀ ) = 0.90 to 1.72), Formula 5 (( S _H1-H4 / S ₀ ) = 2.28 to 3.00), condition b (Ry = 50 to 65 μm), and condition c (Rz = 45 to 65 μm) Evaluated by criteria.
“O”: I was satisfied. “×”: Not satisfied.

4). Consideration The surface of the heat-foamable adhesive layer when heated at 100 ° C. for 3 hours has predetermined conditions ((H1-H5) ≧ 50 μm, S _H1-H5 / S ₀ ≧ 2.5, Ra is 4 to 8 μm, and so on. In Experimental Examples 1 to 4 which are pressure-sensitive adhesive sheets satisfying the above (Table 2), the peelability after the heat treatment is good even under other heating conditions (100 ° C. for 1 hour, 3 hours, 5 hours, 7 hours). (Table 3).
On the other hand, Experimental Examples 5 and 6 that are adhesive sheets that do not satisfy all of the predetermined conditions (Table 2) are inferior in peelability after heat treatment as compared with Experimental Examples 1 to 4 that satisfy all of the predetermined conditions. (Table 3).

1 ... Adhesive sheet,
3 ... Adhesive layer,
31 ... base material,
33 ... 1st adhesion layer (before heating), 33a ... 1st adhesion layer (after heating),
35 ... second adhesive layer,
5 ... 1st separator,
7 ... second separator,
20: Display material (an example of an adherend laminate),
21 ... Display substrate,
23 ... Adhesive layer (before curing), 23a ... Adhesive layer (after curing),
25 ... cover material,
40 ... first adherend,
50 ... 1st laminated body, 52 ... 2nd laminated body, 54 ... 3rd laminated body, 56 ... 4th laminated body.

Claims

When manufacturing an adherend laminate in which a cover material is bonded via an adhesive layer cured on the upper surface of the adherend, the upper surface of the adherend having a thermally foamable adhesive layer bonded to the lower surface, and the cover material The cover material is overlaid on the adherend so that the adhesive layer before curing is opposed, and then the whole is heated to cure the adhesive layer before curing, and then the heat is applied from the lower surface of the adherend. A heat-peelable pressure-sensitive adhesive sheet used in the step of peeling the foamable pressure-sensitive adhesive layer,
The heat-peelable pressure-sensitive adhesive sheet has the heat-foamable pressure-sensitive adhesive layer,
The heat-foamable pressure-sensitive adhesive layer comprises a heat-foamable pressure-sensitive adhesive composition containing a heat-foaming agent and a pressure-sensitive adhesive,
The surface area of the heat-foamable pressure-sensitive adhesive layer is “S 0 ”, the arithmetic average roughness of the surface of the heat-foamable pressure-sensitive adhesive layer when heated at 100 ° C. for 3 hours is “Ra”, and the upper limit is the highest point of unevenness When the thickness is “H1”, the lower limit height which is the lowest point of the unevenness is “H5”, and the surface area in the range from H1 to H5 is “S H1-H5 ”, the thermally foamable pressure-sensitive adhesive layer has the following formula: A pressure-sensitive adhesive sheet is formed so as to satisfy the following conditions.
Formula 1: (H1-H5) ≧ 50 μm,
Formula 2: S H1-H5 / S 0 ≧ 2.5,
Condition: Ra is 4 to 8 μm.
The pressure-sensitive adhesive sheet according to claim 1, wherein a thickness of the heat-foamable pressure-sensitive adhesive layer is 15% to 75% of an average particle diameter of the heat-foaming agent before heating.
The pressure-sensitive adhesive sheet according to claim 1, wherein the thickness of the heat-foamable pressure-sensitive adhesive layer is 20 μm to 60 μm.
The pressure-sensitive adhesive sheet according to claim 2, wherein the heat-foamable pressure-sensitive adhesive layer has a thickness of 20 μm to 60 μm.
A base material layer formed on the lower surface of the thermally foamable adhesive layer;
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, further comprising a slightly pressure-sensitive adhesive layer formed on the lower surface of the base material layer and having a peeling force before heating of 0.4 N / 25 mm or less.
A method for producing an adherend laminate in which a cover material is adhered via an adhesive layer cured on the upper surface of an adherend,
It has a heat-foamable pressure-sensitive adhesive layer comprising a heat-foamable pressure-sensitive adhesive composition containing a heat-foaming agent and a pressure-sensitive adhesive. The surface area of the heat-foamable pressure-sensitive adhesive layer is “S 0 ” and heated at 100 ° C. for 3 hours. In this case, the arithmetic average roughness of the surface of the heat-foamable pressure-sensitive adhesive layer is “Ra”, the upper limit height that is the highest point of unevenness is “H1”, and the lower limit height that is the lowest point of unevenness is “H5”. When the surface area in the range of H1 to H5 is “S H1-H5 ”, a pressure-sensitive adhesive sheet formed using a pressure-sensitive adhesive layer so as to satisfy the following formulas 1 and 2 and the following conditions is used. The cover material is overlaid on the adherend so that the upper surface of the adherend having the adhesive adhesive layer bonded to the lower surface and the adhesive layer before curing of the cover material face each other. After heating the whole for 10 hours to cure the adhesive layer before curing, A method for producing an adherend laminate, comprising peeling an adhesive sheet.
Formula 1: (H1-H5) ≧ 50 μm,
Formula 2: S H1-H5 / S 0 ≧ 2.5,
Condition: Ra is 4 to 8 μm.