TW202022074A - Release film and adhesive sheet laminate using same - Google Patents

Abstract

The objective of the present invention is to provide a release film wherein the tightness of contact between a base material (support layer) and a release layer is excellent. In order to achieve the objective, this release film has the following constitution. Namely, the release film has at least a support layer and a release layer, wherein the release layer contains a low density polyethylene (A) with a density of 0.940 g/cm3 or less, the support layer includes a low density polyethylene (D) with a density of 0.940 g/cm3 or less and at least one selected from the group consisting of polypropylene (B) and a high density polyethylene (C) with a density of 0.941 g/cm3 or more.

Description

Release film and adhesive sheet laminate using it

The present invention relates to a release film. Specifically, it relates to a release film suitable for an adhesive sheet laminate.

As for the release film used in the adhesive sheet, a silicone-based release agent having excellent releasability is generally used. However, the silicone compound contained in the silicone-based release agent may have adverse effects on electronic equipment such as hard disk drive devices, such as corrosion and malfunction.

Therefore, in the case of adhesive sheets used in electronic devices such as hard disk drive devices, in order to prevent silicone contamination, it has been proposed that a release layer containing polyethylene is laminated on polyester through a primer layer and a pull-down layer. Release films for base materials such as films and polyolefin films (Patent Documents 1 and 2). [Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Publication No. 2005-350650 Patent Document 2: International Publication No. 2009/060924

[The problem to be solved by the invention]

However, a release film including a release layer containing polyethylene on a base material such as a polyester film or a polyolefin film has insufficient adhesion between the base material and the release layer.

Therefore, the object of the present invention is to provide a release film with good adhesion between the substrate (support layer) and the release layer. [Means to solve the problem]

The above-mentioned object of the present invention is achieved by the following invention. [1] A release film comprising at least a support layer and a release layer, the release layer contains low-density polyethylene (A) with a density of 0.940 g/cm ³ or less, and the support layer contains At least one selected from the group of polypropylene (B) and high-density polyethylene (C) having a density of 0.941 g/cm ³ or more, and low-density polyethylene (D) having a density of 0.940 g/cm ³ or less. [Effect of invention]

According to the present invention, it is possible to provide a release film with good adhesion between the support layer and the release layer.

[Form to implement the invention]

The release film of the present invention has at least a support layer and a release layer. The release layer contains low-density polyethylene (A) with a density of 0.940 g/cm ³ or less. By using such a release layer, better peelability can be obtained.

The support layer contains at least one selected from the group consisting of polypropylene (B) and high-density polyethylene (C) with a density of 0.941 g/cm ³ or more, and low-density polyethylene with a density of 0.940 g/cm ³ or less (D). By laminating such a support layer and the above-mentioned release layer, the adhesion between the release layer and the support layer is improved. In addition, since the support layer contains at least one selected from the group consisting of polypropylene (B) and high-density polyethylene (C) with a density of 0.941 g/cm ³ or more, the rigidity of the release film (the middle section) Strengthened), the handling and peeling workability of the release film are improved.

[Release Layer] The release layer in the present invention contains low-density polyethylene (A) having a density of 0.940 g/cm ³ or less. Low-density polyethylene (A), so that releasability from the adhesive sheet and improve such a viewpoint, preferably the density 0.935g / cm ³ or less, more preferably 0.930g / cm ³ or less, and particularly preferably 0.928g /cm ³ or less. In addition, the aforementioned density is preferably 0.850 g/cm ³ or higher, more preferably 0.860 g/cm ³ or higher, and particularly preferably 0.870 g/cm ³ or higher.

In the following description, low-density polyethylene (A) having a density of 0.940 g/cm ³ or less may be referred to as "low-density polyethylene (A)".

As for low-density polyethylene, there are branched low-density polyethylene and linear low-density polyethylene. Generally speaking, if low-density polyethylene is mentioned, it means branched low-density polyethylene other than linear low-density polyethylene. As for the release layer in the present invention, any one can be used. From the viewpoint of further improving the releasability from the adhesive sheet, the low-density polyethylene (A) in the release layer preferably contains at least linear low-density polyethylene, and more preferably contains at least a density of 0.850 to 0.940g/cm ³ linear low-density polyethylene.

Straight-chain low-density polyethylene is a copolymer of α-olefin with ethylene monomer as its main component. Here, the main component means a component containing 50 mol% or more of the entire monomer component constituting the linear low-density polyethylene.

As the α-olefin, an α-olefin having 3 to 12 carbon atoms is preferred, and an α-olefin having 4 to 10 carbon atoms is more preferred. Specifically, examples include 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1- Decene etc. These α-olefins can be used alone or in combination. Among the α-olefins, α-olefins having a carbon number of 4 to 8 are more preferred. In particular, from the viewpoint of polymerization productivity, 1-butene, 1-hexene, and 1-octene can be preferably used.

From the viewpoint of improving the releasability from the adhesive sheet, the content of the low-density polyethylene (A) in the release layer is 100% by mass relative to the total solid content of the release layer, preferably 50% by mass Above, it is more preferably 60% by mass or more, and particularly preferably 70% by mass or more. The upper limit is 100% by mass.

In the release layer, linear low density polyethylene and branched low density polyethylene can be used together as low density polyethylene (A). In this case, with respect to 100 parts by mass of linear low-density polyethylene, it is preferable to contain 1-50 parts by mass of branched low-density polyethylene, more preferably 3-40 parts by mass, and particularly preferably 5-30 parts by mass.

Further, the release layer preferably having a density of 0.900g / cm ³ or more 0.940g / cm ³ or less linear low density polyethylene, and a density of 0.850g / cm ³ or more is less than 0.900g / cm ³ linear Low-density polyethylene, as a linear low-density polyethylene with a density of 0.850 to 0.940 g/cm ³ . This further improves the releasability from the adhesive sheet.

In addition, a linear low-density polyethylene having a density of 0.850 g/cm ³ or more and less than 0.900 g/cm ³ may be referred to as "linear ultra-low density polyethylene".

Hereinafter, linear low-density polyethylene with a density of 0.900 g/cm ³ or more and 0.940 g/cm ³ or less is sometimes referred to as "LLDPE", and the density is 0.850 g/cm ³ or more and less than 0.900 g/cm ³ The linear ultra-low density polyethylene is called "VLDPE".

LLDPE and VLDPE-based copolymers of ethylene and α-olefin have a tendency to decrease in density as the content of α-olefin increases. The content of the α-olefin in the LLDPE is preferably 0.5-15 mol% of the entire monomer component, more preferably 1-10 mol%, particularly preferably 2-7 mol%. The content of the α-olefin in the VLDPE is preferably 4-30 mol% of the entire monomer component, more preferably 7-25 mol%, particularly preferably 10-20 mol%.

LLDPE is preferably a copolymer of ethylene and an α-olefin having a carbon number of 3 to 12, more preferably a copolymer of ethylene and an α-olefin having a carbon number of 4 to 10, and particularly preferably ethylene and a carbon number of 4 to 8 alpha-olefin copolymer. Among the aforementioned α-olefins having 4 to 8 carbon atoms, 1-butene, 1-hexene, and 1-octene are preferred.

The density of LLDPE is preferably 0.910 g/cm ³ or more, more preferably 0.915 g/cm ³ or more, and particularly preferably 0.917 g/cm ³ or more. Further, the density was 0.940g / cm ³ or less, preferably 0.935g / cm ³ or less, more preferably 0.930g / cm ³ or less, particularly preferably 0.928g / cm ³ or less.

VLDPE is preferably a copolymer of ethylene and an α-olefin having a carbon number of 3 to 12, more preferably a copolymer of ethylene and an α-olefin having a carbon number of 4 to 10, and particularly preferably ethylene and a carbon number of 4 to 8 alpha-olefin copolymer. Among the aforementioned α-olefins having 4 to 8 carbon atoms, 1-butene, 1-hexene, and 1-octene are preferred. By including such VLDPE in the release layer, it becomes easy to suppress the increase in the peeling force after heating. In particular, when VLDPE is a copolymer of ethylene and 1-octene, the effect of suppressing the increase in peel force after heating becomes greater.

³ density of the VLDPE preferred, particularly preferably less than 0.885g / cm ³ of less than 0.895g / cm ^3, more preferably less than 0.890g / cm. Further, the preferred density of 0.855g / cm ³ or more, more preferably 0.860g / cm ³ or more, particularly preferably 0.865g / cm ³ or more.

As the content ratio of LLDPE and VLDPE, from the viewpoint of further improving the releasability from the adhesive sheet, the release layer system preferably contains 2-30 parts by mass of VLDPE relative to 100 parts by mass of LLDPE, and more preferably contains 4-20 parts by mass, particularly preferably 6-15 parts by mass.

In addition, the release layer may contain polyolefins other than low-density polyethylene (A) (hereinafter, it may be referred to as "other polyolefins"). Examples of other polyolefins include polypropylene, polybutene, poly(4-methyl-1-pentene), propylene-α-olefin copolymers, copolymers of ethylene and α-olefin components other than Wait.

Examples of the α-olefin in the above propylene-α-olefin copolymer include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1 -Decene, 3-methyl-1-butene, 4-methyl-1-pentene, etc.

Examples of copolymers of components other than ethylene and α-olefin include ethylene-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA); Ionomer; ethylene-(meth)acrylate copolymers such as ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), etc. ; Ethylene-vinyl acetate copolymer (EVA); ethylene-vinyl alcohol copolymer and so on.

The above-mentioned other polyolefin can be used individually or in combination of 2 or more types.

When the release layer contains other polyolefin, the content of other polyolefin is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the low-density polyethylene (A).

From the viewpoint of further improving the releasability from the adhesive sheet, the release layer preferably has a large surface roughness. Specifically, the arithmetic average roughness Ra of the surface of the release layer is preferably 0.5 μm or more, more preferably 1.0 μm or more, and particularly preferably 1.5 μm or more. If the arithmetic average roughness Ra of the release layer becomes too large, the uneven shape of the release layer may be transferred to the adhesive sheet, and the adhesion between the adhesive sheet and the adhered body such as the hard disk drive may decrease. Therefore, the above arithmetic The average roughness Ra is preferably 7.0 μm or less.

The surface roughness of the above-mentioned release layer can be controlled by forming fine irregularities on the surface of the release layer.

The uneven shape on the surface of the release layer is not particularly limited, and the same uneven pattern is arranged regularly or irregularly, and different uneven patterns are arranged regularly or irregularly. As the uneven pattern, for example, a grid pattern, a cloth pattern, a pear pattern, a dot pattern, etc. are mentioned.

In addition, in the case of forming fine irregularities on the surface of the release layer, the maximum height roughness Rz is preferably 5.0 μm or more, more preferably 10.0 μm or more, still more preferably 15.0 μm or more, and particularly preferably 21.0 μm or more. The upper limit of the above-mentioned maximum height roughness Rz is about 50 μm. When the maximum height roughness Rz of the surface of the release layer is 5.0 μm or more, and preferably 10.0 μm or more, it becomes easy to suppress an increase in the peeling force from the adhesive sheet after heating.

As a method of forming fine irregularities on the surface of the release layer, for example, there can be mentioned: embossing (emboss) treatment, sandblasting treatment, chemical treatment, or forming with concave and convex engraving in the film forming step of the release layer Rolling against the release layer in the molten state.

Among the above-mentioned uneven forming methods, embossing is preferable. As the embossing treatment, for example, a method of pressing a heated embossing roll against the release layer of the release film is preferable. The heating temperature and pressure of the embossing roll can be adjusted to control the formation on the release layer. The uneven shape of the layer. The heating temperature of the embossing roll is preferably 80°C to 160°C, more preferably 100°C to 140°C.

[Support layer] The support layer in the present invention contains at least one selected from the group consisting of polypropylene (B) and high-density polyethylene (C) having a density of 0.941 g/cm ³ or more, and a density of 0.940 g/ cm ³ or less low density polyethylene (D). In the following description, high-density polyethylene (C) with a density of 0.941 g/cm ³ or higher is sometimes referred to as "high-density polyethylene (C)". In addition, the density is 0.940 g/cm ³ or lower. The low density polyethylene (D) is called "low density polyethylene (D)".

As the polypropylene (B) that can be contained in the support layer, a propylene homopolymer, a copolymer of propylene and other α-olefin, or a mixture thereof can be mentioned.

As other α-olefins in the copolymer of propylene and other α-olefins, ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1- Nonene, 1-decene, 3-methyl-1-butene, 4-methyl-1-pentene, etc. As the copolymer of propylene and other α-olefins, any of random copolymers and block copolymers can be used. The content of the α-olefin in the copolymer of propylene and another α-olefin is preferably 20% by mass or less, and more preferably 10% by mass or less. If the content of α-olefin exceeds 20% by mass, the degree of crystallinity may decrease.

In polypropylene (B), from the viewpoint of increasing the rigidity of the release film (making the middle part stronger), the higher the degree of crystallinity, the better. Specifically, the degree of crystallinity of the polypropylene (B) contained in the support layer is preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more. The upper limit of the degree of crystallinity is 100%.

The degree of crystallinity of polypropylene can be adjusted by controlling the cooling temperature and cooling rate after melt extrusion in the film forming step of the support layer by melt extrusion. For example, by slowing the cooling rate, the crystallinity of polypropylene becomes higher. In addition, the degree of crystallinity can be improved by using a crystal nucleating agent in combination.

The crystal nucleating agent is not particularly limited, and a known compound can be used. For example, inorganic substances such as talc, carboxylic acid metal salts, phosphoric acid metal salts, sorbitol derivatives, rosin metal salts, and the like can be mentioned.

The high density polyethylene (C) that can be contained in the support layer is preferably polyethylene having a density of 0.941 to 0.980 g/cm ³ , more preferably polyethylene having a density of 0.945 to 0.975 g/cm ³ , and particularly preferably Polyethylene with a density of 0.950 to 0.970 g/cm ³ .

As the support layer, polypropylene (B) and high-density polyethylene (C) may be used alone, or polypropylene (B) and high-density polyethylene (C) may be used in combination. When polypropylene (B) and high-density polyethylene (C) are used in combination, the content ratio (B:C) is not particularly limited. For example, in terms of mass ratio, it is preferably 98:2 to 2:98, and more Preferably, it is 95:5 to 5:95.

Low-density polyethylene (D) contained in the support layer, preferably a density of 0.935g / cm ³ or less, more preferably 0.930g / cm ³ or less, particularly preferably 0.928g / cm ³ or less. Further, the preferred density of 0.870g / cm ³ or more, more preferably 0.890g / cm ³ or more, particularly preferably 0.900g / cm ³ or more.

The low density polyethylene (D) may be linear low density polyethylene or branched low density polyethylene. In addition, the above two types can be used in combination.

The low-density polyethylene (D) can use the same type or a different type of low-density polyethylene as the low-density polyethylene (A) used in the aforementioned release layer. From the standpoint of adhesion and productivity, it is better It is preferably the same kind of low density polyethylene. Here, the linear low-density polyethylene and the branched low-density polyethylene are of different types. When the density difference is 0.005 g/cm ³ or more, they are different types, and the case that does not meet the above range is Same kind.

The total content of polypropylene (B) and high-density polyethylene (C) in the support layer, from the viewpoint of increasing the rigidity of the release film, is preferably 100% by mass relative to the total solid content of the support layer 50% by mass or more, more preferably 60% by mass or more, particularly preferably 70% by mass or more. On the other hand, if the total content of polypropylene (B) and high-density polyethylene (C) becomes too large, the adhesion to the release layer may decrease, so the total content is preferably 97% by mass or less , More preferably 95% by mass or less.

The content of the low-density polyethylene (D) in the support layer, from the viewpoint of improving the adhesion between the release layer and the support layer, is preferably 3% relative to the total solid content of the support layer 100% by mass. Mass% or more, more preferably 5 mass% or more, particularly preferably 7 mass% or more. On the other hand, if the content of low-density polyethylene (D) becomes too large, the rigidity of the release film may decrease. Therefore, the above content is preferably 40% by mass or less, more preferably 30% by mass or less, particularly preferred It is 25% by mass or less.

In the support layer, in terms of mass ratio, the total (B+C) of polypropylene (B) and high-density polyethylene (C) and the content ratio of low-density polyethylene (D) ﹛(B+C): (D )﹜ Preferably it is 97:3～60:40, more preferably 95:5～70:30, particularly preferably 93:7～75:25. By containing in the above-mentioned ratio, the adhesiveness can be further improved while ensuring the rigidity of the release film.

The support layer can contain additives such as coloring pigments and antioxidants.

[Release film] The release film of the present invention has at least a support layer and a release layer. The release layer can be disposed on the support layer directly or through another layer. From the viewpoint of the adhesion between the release layer and the support layer, it is preferable that the release layer be directly laminated on the support layer.

The release film of the present invention can be used with silicone-based release agents or release agents other than silicone-based release agents, such as long-chain alkyl release agents, alkyd resin release agents, and fluorine-based release agents Wait for surface treatment on the surface of the release layer. However, considering that the release film of the present invention has better releasability from the adhesive sheet and transfer of the release agent to the adhesive sheet, the above-mentioned surface treatment with the release agent is preferably not implemented.

In addition, in the release film of the present invention, the back layer can be provided on the surface of the support layer opposite to the surface on which the release layer is provided. Such a back layer can be composed of the same type or different types of compositions. The details of the back layer will be described later.

The thickness of the release film is not particularly limited, but is preferably 30 to 150 μm, more preferably 40 to 120 μm, and particularly preferably 50 to 100 μm.

The thickness of the support layer is preferably 20 to 130 μm, more preferably 30 to 120 μm, still more preferably 40 to 100 μm, particularly preferably 50 to 80 μm.

The thickness of the release layer is preferably 5 to 40 μm, more preferably 10 to 35 μm, and particularly preferably 15 to 30 μm.

From the viewpoint of the peelability from the adhesive sheet and the rigidity of the release film, the ratio (Rt/St) of the thickness (Rt) of the release layer to the thickness (St) of the support layer is preferably 0.05 to 0.50, more preferably It is 0.10 to 0.40, particularly preferably 0.15 to 0.40.

The release film of the present invention can be produced by a known method such as a melt extrusion method and a melt extrusion lamination method. In particular, it is preferable to form the support layer, the release layer, and the back layer provided as needed into a film by a melt coextrusion method. Thereby, the adhesion between the release layer and the support layer can be improved. In addition, the melt coextrusion method is also preferable from the viewpoint of productivity.

The release film of the present invention is preferably composed of a three-layer release layer/support layer/back layer. These layers are preferably all made of polyolefin as the main component. In addition, the melt coextrusion method is preferably used as described above. To make a film. That is, the release film of the present invention is preferably a multi-layer (3-layer) co-extruded film containing polyolefin.

The release film of the present invention can reduce the peeling force with the adhesive sheet by heating. The heating temperature is preferably 70°C or higher, more preferably 75°C or higher, and particularly preferably 80°C or higher. The upper limit is about 130°C. The heating time can be appropriately set according to the heating temperature and the form of the release film.

In the case of heating in the film transport step such as the film forming step of the release film, for example, at a temperature of 75 to 130°C, the heating is preferably for 30 seconds or more, and more preferably for 60 seconds or more. Preferably, it is heated for more than 100 seconds. On the other hand, when the release film is in the form of a roll, for example, at a temperature of 70-100°C, heating is preferably for 1 hour or more, more preferably for 2 hours or more, and particularly preferably for 5 hours. the above.

The peeling force reduction effect of the release film due to heating tends to be greater when the release layer contains LLDPE and VLDPE. For a release film having a release layer containing LLDPE and VLDPE, by applying the above-mentioned heat treatment, even if the surface of the release layer is not embossed to form irregularities on the surface of the release layer, the peeling force can be reduced.

That is, a release film having a release layer containing LLDPE and VLDPE can reduce the peeling force with the adhesive sheet even if the arithmetic average roughness Ra of the surface of the release layer is less than 0.5 μm.

In the release film of the present invention, the peeling force (normal peeling force) of the surface of the release layer to the adhesive tape (normal peeling force) is preferably 7.0N/50mm or less, more preferably 4.0N/50mm or less, and still more preferably 2.0 N/50mm or less, particularly preferably 1.0N/50mm or less. The lower limit of the aforementioned peeling force is about 0.05 N/50 mm. In addition, the difference between the heated peeling force and the normal peeling force (the value obtained by subtracting the normal peeling force from the heated peeling force) is preferably 2.0N/50mm or less, more preferably 1.0N/50mm or less, and still more preferably 0.7N/50mm Below, it is particularly preferably 0.3N/50mm or less.

Here, the peeling force of the surface of the release layer to the adhesive tape is measured in the form of peeling force (B) in the examples described later. The details of the measurement method will be described later. In addition, the normal peeling force and heating peeling force also follow the measuring method of peeling force (B).

[Back layer] The release film of the present invention preferably has a back surface layer on the surface of the support layer opposite to the surface having the release layer. The back layer can be provided in order to protect the support layer or to improve the slidability of the release film.

The back layer preferably contains polyolefin, and more preferably contains polyolefin as a main component. Here, containing polyolefin as the main component means containing 50% by mass or more of polyolefin relative to 100% by mass of the total solid content of the back layer, more preferably 60% by mass or more of polyolefin, and still more preferably containing 70% by mass or more, particularly preferably 80% by mass or more. The upper limit is 100% by mass.

Examples of polyolefins include homopolymers of ethylene, propylene, and α-olefins having 4 to 10 carbon atoms, and copolymers of these. Examples of α-olefins having 4 to 10 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1- Decene, 3-methyl-1-butene, 4-methyl-1-pentene, etc.

As the above-mentioned copolymers, for example, copolymers of ethylene and propylene, copolymers of ethylene and α-olefins having 4 to 10 carbons, copolymers of propylene and α-olefins having 4 to 10 carbons, Copolymer of ethylene, propylene, and α-olefin having 4 to 10 carbon atoms.

The above-mentioned polyolefins may be used alone or in combination of two or more kinds.

The back layer preferably contains at least one selected from the group consisting of polyethylene and polypropylene. As the polyethylene, the aforementioned low-density polyethylene (A) can be preferably used. As polypropylene, a homopolymer of propylene can be preferably used.

The back layer may be composed of the same type of composition as the release layer, or may be composed of a different type of composition from the release layer.

The back surface layer is preferably a relatively rough surface from the viewpoint of ensuring the slidability of the release film. In particular, when the surface of the release layer is relatively smooth (when no unevenness is formed due to embossing, etc.), specifically, the arithmetic average roughness Ra on the surface of the release layer is less than 0.5μm When it is further smaller than 0.3 μm, the back layer is preferably a relatively rough surface. For example, the arithmetic average roughness Ra of the surface of the back layer is preferably 0.1 to 0.5 μm, more preferably 0.2 to 0.4 μm. Similarly, the maximum height roughness Rz of the surface of the back layer is preferably 1.0 to 7.0 μm, more preferably 1.5 to 6.0 μm, and particularly preferably 2.0 to 5.0 μm.

In order to roughen the back layer, the back layer preferably contains a propylene homopolymer and a polyolefin other than the propylene homopolymer. As polyolefins other than propylene homopolymers, it is preferable to use polyethylene, a homopolymer of α-olefin having 4 to 10 carbons, copolymers of propylene and ethylene, and ethylene and carbon 4 to 10 At least one selected from the group of α-olefin copolymers. Among them, propylene-ethylene is preferred. Random copolymer.

The thickness of the back layer is preferably 2 to 40 μm, more preferably 5 to 40 μm, still more preferably 10 to 35 μm, particularly preferably 15 to 30 μm.

When the release film is a release layer/support layer/back layer, from the viewpoint of ensuring the rigidity of the release film to suppress curling, the thickness of the support layer is less than the total thickness of the release layer and the back layer The ratio {(support layer thickness)/(total thickness of release layer and back layer)} is preferably 1.0 or more and less than 4.0, more preferably 1.2 or more and less than 3.5, and particularly preferably 1.5 or more and less than 3.0.

[Application example] The release film of the present invention is suitable as a release film of an adhesive sheet. That is, the release film of the present invention is suitable as a release film laminated on an adhesive layer of an adhesive sheet having an adhesive layer on a base film.

In particular, the release film of the present invention is suitable as a release film of an adhesive sheet for hard disk drives. The adhesive sheet is preferably a non-silicone adhesive sheet containing no silicone compound.

[Adhesive sheet] The adhesive sheet to which the release film of the present invention is applied is not particularly limited. As far as the adhesive layer constituting the adhesive sheet is concerned, it can be preferably used: acrylic adhesive, polyester adhesive, urethane adhesive Non-silicone adhesives such as rubber adhesives and rubber adhesives. In particular, an acrylic adhesive is preferable.

Examples of the base film constituting the pressure-sensitive adhesive sheet include plastic films such as polyolefin films, polyester films, and polystyrene films, metal foils such as aluminum foil and copper foil, and laminated films of plastic films and metal foils.

The adhesive sheet laminate (adhesive sheet with a release film) of the present invention is an adhesive sheet laminate formed by laminating the release film of the present invention and an adhesive sheet, and the aforementioned adhesive sheet is provided with an adhesive layer on a base film The adhesive sheet is laminated so that the release layer of the release film and the adhesive layer of the adhesive sheet are in contact with each other.

The above-mentioned adhesive sheet laminate is preferably an adhesive sheet laminate for hard disk drives. The adhesive sheet is preferably a non-silicone adhesive sheet. [Example]

Hereinafter, the present invention will be described in detail through examples, but the present invention is not limited to these examples.

[Measurement method and evaluation method] (1) Determination of the density of polyethylene According to JIS K7112 (1999), it is measured by the density gradient tube method (23°C).

(2) Measurement of the degree of crystallinity of polypropylene contained in the support layer The produced release film was measured by the following method using a differential scanning calorimeter (DSC) (DSC-60Plus manufactured by Shimadzu Corporation).

>Measurement method> The temperature was increased from 0°C to 250°C at a temperature increase rate of 10°C/min, and the heat of fusion was determined. Based on the obtained heat of fusion ΔH (J/g), the degree of crystallinity was obtained from the equation (ΔH/resin fraction/209)×100 (%). Here, the so-called resin fraction indicates the polymer fraction in the material, and if the resin component is 100%, it is 1.0. The heat of fusion (J/g) when 100% of 209-series polypropylene is crystallized.

(3) Evaluation of adhesion On the surface of the release layer of the release film, add 100 1mm ² cross cuts, stick the Cellotape made by Nichiban (strand) on it, and press it firmly with your fingers. It peels off rapidly in the 90-degree direction. From the number of cross cuts remaining on the release layer after the Cellotape was peeled off, the adhesion was evaluated according to the following criteria. A: 100 pieces B: 80 to 99 pieces C: 50 to 79 pieces D: Less than 50 pieces.

(4) Measurement of peeling force (A) Attach it so that the surface of the release layer of the release film faces the adhesive surface of the following adhesive sheet, press it with a rubber roller weighing 5 kg, and make it back and forth to make an adhesive sheet. Laminated body (adhesive sheet with release film).

Prepare a sample in which the adhesive sheet laminate is left at room temperature (23±2°C) for 24 hours, and a sample in which the adhesive sheet laminate is heated at 40°C for 10 days. For each sample, a tensile testing machine (Shimadzu The "EZ-SX" model made by Mfg. Co., Ltd.), and the peeling force when the adhesive sheet side was torn off at a speed of 300 mm/min at 180° was measured.

The peeling force of the sample left at room temperature (23±2°C) for 24 hours was defined as the normal peeling force, and the peeling force of the sample heated at 40°C for 10 days was defined as the heating peeling force.

>Adhesive sheet> In ethyl acetate, in the presence of a polymerization initiator (azobisisobutyronitrile), 93 parts by mass of n-butyl acrylate and 7 parts by mass of acrylic acid are subjected to solution polymerization by a common method to obtain a mass average molecular weight of 1.5 million acrylic polymer solution (solid content concentration 25% by mass). To 100 parts by mass of the acrylic polymer solution, 2 parts by mass of trimethylolpropane-modified toluene diisocyanate ("Coronate L" manufactured by Japan Urethane Co., Ltd.) as a crosslinking agent was added to prepare acrylic acid Department of adhesive composition.

This acrylic adhesive composition was coated on a 50-μm-thick polyethylene terephthalate film ("Lumirror (registered trademark)" S-105 manufactured by Toray Co., Ltd.) so that the dry thickness became 25μm , Dried at 140°C for 3 minutes to obtain an acrylic adhesive sheet.

(5) Measurement of peeling force (B) While overlapping the release layer surface of the release film with the adhesive surface of the acrylic adhesive tape (No. 31B manufactured by Nitto Denko Co., Ltd.) facing each other, press it with a 5kg rubber roller while making It is laminated back and forth to make a sample placed at room temperature (23±2°C) for 24 hours and a sample heated at 70°C for 24 hours. For each sample, a tensile tester ("EZ-SX" model manufactured by Shimadzu Corporation) was used to measure the peeling force when the adhesive sheet side was torn off at a speed of 300 mm/min at 180°.

The peeling force of the sample left at room temperature (23±2° C.) for 24 hours was regarded as the normal peel force, and the peeling force of the sample heated at 70° C. for 24 hours was regarded as the heating peeling force.

(6) Determination of the arithmetic average roughness Ra and the maximum height roughness Rz of the release layer (back layer) surface According to JIS B0601 (2001), the measurement was performed using a surface roughness measuring machine ("Surftest SJ-400" manufactured by Mitsutoyo Co., Ltd.).

>Measurement conditions> . The tip radius of the contact pin: 2μm . Measuring power: 0.75mN . Cut-off value: λs=2.5μm, λc=0.8mm (Cut-off value after embossing treatment: λs=2.5μm, λc=2.5mm).

[Example 1] The following raw materials were used to produce a release film composed of a three-layer laminate of release layer/support layer/back layer by a three-layer melt co-extrusion method. The mold temperature of each layer is set as follows: the release layer is 225°C, the support layer is 250°C, and the back layer is 220°C. On the casting drum maintained at 60°C, the thickness of the release layer becomes 20μm. It extruded so that the thickness became 60 micrometers, and the thickness of the back layer became 20 micrometers, and the release film with a total thickness of 100 micrometers was produced.

The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 made by Prime Polymer (stock); density 0.903g/cm ³ ). Supporting layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 90 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 10 parts by mass mixture. Raw material for the back layer: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer (Stock); density 0.903 g/cm ³ ).

[Example 2] Except for changing the raw material of the support layer in the following manner, the same procedure as in Example 1 was carried out to produce a release film composed of a three-layer buildup of a release layer/support layer/back layer. The crystallinity of polypropylene in the support layer of the release film is 70%. . Supporting layer raw materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 97 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 3 parts by mass mixture.

[Example 3] Except for changing the raw material of the support layer in the following manner, the same procedure as in Example 1 was carried out to produce a release film composed of a three-layer buildup of a release layer/support layer/back layer. The crystallinity of polypropylene in the support layer of the release film is 70%. . Supporting layer raw materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 93 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 7 parts by mass mixture.

[Example 4] Except for changing the raw material of the support layer in the following manner, the same procedure as in Example 1 was carried out to produce a release film composed of a three-layer buildup of a release layer/support layer/back layer. The crystallinity of polypropylene in the support layer of the release film is 70%. . Supporting layer raw materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 80 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 20 parts by mass mixture.

[Example 5] Except for changing the raw material of the support layer in the following manner, a release film consisting of a three-layer buildup of a release layer/support layer/back layer was produced in the same manner as in Example 1. The crystallinity of polypropylene in the support layer of the release film is 70%. . Supporting layer raw materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 70 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 30 parts by mass mixture.

[Example 6] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: linear low-density polyethylene ("Evolue (registered trademark)" SP2540 made by Prime Polymer (stock); density 0.924g/cm ³ ). Supporting layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 90 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP2540; density 0.924g/cm ³ ) 10 parts by mass mixture. Raw material for the back layer: linear low-density polyethylene ("Evolue (registered trademark)" SP2540 manufactured by Prime Polymer; density 0.924 g/cm ³ ).

[Example 7] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: branched low-density polyethylene ("Sumikasen (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd.; density 0.924g/cm ³ ). Support layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro, Japan) 90 parts by mass and branched low-density polyethylene ("Sumikasen (registered trademark)" manufactured by Sumitomo Chemical Co., Ltd. CE3059; density 0.924g/cm ³ ) 10 parts by mass mixture. Material of the back layer: branched low-density polyethylene ("Sumikasen (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd.; density 0.924 g/cm ³ ).

[Example 8] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: 80 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer; density 0.903g/cm ³ ) and branched low-density polyethylene (Sumitomo Chemical (Stock) system "Sumikasen (registered trademark)"CE3059; density 0.924g/cm ³ ) a mixture of 20 parts by mass. Supporting layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 90 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 10 parts by mass mixture. Material of the back layer: 80 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer; density 0.903g/cm ³ ) and branched low-density polyethylene (Sumitomo Chemical Stock) "Sumikasen (registered trademark)"CE3059; density 0.924 g/cm ³ ) 20 parts by mass mixture.

[Example 9] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer raw materials: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer; density 0.903g/cm ³ ) 75 parts by mass, branched low-density polyethylene (Sumitomo Chemical "Sumikasen (registered trademark)" CE3059 manufactured by Co., Ltd.; density 0.924g/cm ³ ) 15 parts by mass and ethylene-propylene copolymer ("Tafuma P (registered trademark)" P0180, manufactured by Mitsui Chemicals Co., Ltd.) 10 mass Parts of the mixture. Supporting layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 90 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 10 parts by mass mixture. Raw material for the back layer: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer (Stock); density 0.903 g/cm ³ ).

[Example 10] Using the following raw materials, a release film composed of a two-layer laminate of a release layer/support layer was produced by a two-layer melt coextrusion method. The mold temperature of each layer is set as follows: the release layer is 225°C, the support layer is 250°C, and the thickness of the release layer becomes 25μm and the thickness of the support layer becomes 75μm on the casting drum maintained at 60°C. Finally, a release film with a total thickness of 100 μm was produced.

The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 made by Prime Polymer (stock); density 0.903g/cm ³ ). Supporting layer materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 90 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP0540; density 0.903g/cm ³ ) 10 parts by mass mixture.

[Example 11] The following raw materials were used to produce a release film composed of a three-layer laminate of release layer/support layer/back layer by a three-layer melt co-extrusion method. The mold temperature of each layer is set as follows: the release layer is 225°C, the support layer is 250°C, and the back layer is 250°C. On the casting drum maintained at 60°C, the thickness of the release layer is 15μm. It extruded so that the thickness became 40 micrometers, and the thickness of the back layer became 5 micrometers, and the release film with a total thickness of 60 micrometers was produced. The obtained release film was heat-treated at 90°C for 60 seconds.

In addition, the arithmetic average roughness Ra of the surface of the back layer was 0.3 μm, and the maximum height roughness Rz was 2.6 μm.

>Raw materials of each layer>． Release layer raw materials: 90 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP2540 made by Prime Polymer; density 0.924g/cm ³ ) and linear ultra-low density polyethylene (ethylene -1-octene copolymer; "AFFINITY (registered trademark)" KC8852G manufactured by Dow Chemical; density 0.875g/cm ³ ) a mixture of 10 parts by mass. Supporting layer raw materials: high-density polyethylene ("Novatec (registered trademark)" HF562 manufactured by Japan Polyethylene (Stock); density=0.961g/cm ³ ) 75 parts by mass and linear low-density polyethylene (Prime Polymer (stock) ) "Evolue (registered trademark)"SP2540; density 0.924g/cm ³ ) 25 parts by mass mixture. Back layer raw materials: polypropylene ("NOBRENE (registered trademark)" FLX80E4 manufactured by Sumitomo Chemical Co., Ltd.) 80 parts by mass and propylene-ethylene. A mixture of 20 parts by mass of random copolymer (ethylene content 5 mass%).

[Example 12] Except for changing the raw material of the release layer in the following manner, the same operation as in Example 11 was carried out to produce a release film composed of a three-layer buildup of release layer/support layer/back layer, and the same heat treatment was performed . In addition, the arithmetic average roughness Ra of the surface of the back layer was 0.3 μm, and the maximum height roughness Rz was 2.6 μm. . Raw materials of the release layer: 85 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP2540 manufactured by Prime Polymer; density 0.924g/cm ³ ) and linear ultra-low density polyethylene (ethylene -1-butene copolymer; "Tafuma P (registered trademark)" P1070S manufactured by Mitsui Chemicals Co., Ltd.; density 0.870 g/cm ³ ) 15 parts by mass mixture.

[Example 13] Except for changing the raw material of the support layer in the following manner, a release film consisting of a three-layer buildup of a release layer/support layer/back layer was produced in the same manner as in Example 11, and the same heat treatment was performed. The crystallinity of polypropylene in the support layer of the release film is 70%. In addition, the arithmetic average roughness Ra of the surface of the back layer was 0.3 μm, and the maximum height roughness Rz was 2.6 μm. . Support layer raw materials: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Japan)) 75 parts by mass and linear low-density polyethylene ("Evolue (registered trademark)" manufactured by Prime Polymer (Prime Polymer) SP2540; density 0.924g/cm ³ ) 25 parts by mass mixture.

[Example 14] Except for changing the support layer raw material in the following manner, a release film consisting of a three-layer buildup of a release layer/support layer/back layer was produced in the same manner as in Example 11, and the same heat treatment was performed. The crystallinity of polypropylene in the support layer of the release film is 70%. In addition, the arithmetic average roughness Ra of the surface of the back layer was 0.3 μm, and the maximum height roughness Rz was 2.6 μm. . Supporting layer material: high-density polyethylene ("Novatec (registered trademark)" HF562 made by Japan Polyethylene Co., Ltd.; density=0.961g/cm ³ ) 60 parts by mass, polypropylene ("NOBRENE" made by Sumitomo Chemical Co., Ltd.) (Registered trademark) "FLX80E4) 15 parts by mass and 25 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP2540 manufactured by Prime Polymer; density 0.924 g/cm ³ ).

[Comparative Example 1] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer material: branched low-density polyethylene ("Sumikasen (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd.; density 0.924g/cm ³ ). Supporting layer material: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Stock) in Japan). Material of the back layer: branched low-density polyethylene ("Sumikasen (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd.; density 0.924 g/cm ³ ).

[Comparative Example 2] The release film was produced in the same manner as in Example 1 except that the raw materials of each layer were changed in the following manner. The crystallinity of polypropylene in the support layer of the release film is 70%.

>Raw materials of each layer>． Release layer raw materials: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer; density 0.903g/cm ³ ) 75 parts by mass, branched low-density polyethylene (Sumitomo Chemical "Sumikasen (registered trademark)" CE3059 manufactured by Co., Ltd.; density 0.924g/cm ³ ) 15 parts by mass and ethylene-propylene copolymer ("Tafuma P (registered trademark)" P0180, manufactured by Mitsui Chemicals Co., Ltd.) 10 mass Parts of the mixture. Supporting layer material: polypropylene ("Novatec PP (registered trademark)" FL4 manufactured by Polypro (Stock) in Japan). Raw material for the back layer: linear low-density polyethylene ("Evolue (registered trademark)" SP0540 manufactured by Prime Polymer (Stock); density 0.903 g/cm ³ ).

[Comparative Example 3] On a polyethylene terephthalate film ("Lumirror (registered trademark)" S-105 manufactured by Toray (stock)) with a thickness of 50 μm, in a tandem arrangement, first, at a mold temperature of 325 The branched low-density polyethylene ("Sumikasen (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd.; density 0.924g/cm ³ ) was extruded and laminated at ℃ to form a primer layer (UC layer; dry thickness) 10μm). Then, on this undercoat layer, the following release layer raw material was extruded at a mold temperature of 273°C to laminate the release layer (dry thickness 10 μm).

>Raw material of the release layer> 75 parts by mass of linear low-density polyethylene ("Evolue (registered trademark)" SP0540 made by Prime Polymer; density 0.903g/cm ³ ), branched low-density polyethylene (Sumitomo "Sumikasen (registered trademark)" CE3059 manufactured by Chemical Co., Ltd.; density 0.924 g/cm ³ ) 15 parts by mass and ethylene-propylene copolymer ("Tafuma P (registered trademark)" manufactured by Mitsui Chemicals Co., Ltd. P0180) 10 The mixture of parts by mass.

[Evaluation] The release films of the examples and comparative examples produced above were evaluated in accordance with the above-mentioned measurement methods and evaluation methods. The results are shown in Table 1.

[Table 1]

[Examples 21 to 31] The following embossing rolls were used to apply embossing treatment to each of the release films produced in Example 1 and Examples 6 to 11, to obtain a release film having fine irregularities formed on the surface of the release layer. The embossing process is performed by pressing an embossing roll heated to 140°C against the release layer of the release film. Table 2 shows the relationship between the release film before embossing and the embossing roll.

>Embossing Roll> . Embossing roller 1: An embossing roller processed into a relatively deep pear pattern . Embossing roller 2: An embossing roller processed into a relatively shallow pear pattern . Embossing roller 3: Embossing roller processed into cloth pattern [Evaluation] The release film of the example produced above was evaluated in accordance with the above-mentioned measuring method and evaluation method. The results are shown in Table 2.

[Table 2]

no

no.

no.

Claims (14)

A release film, a release film having at least a support layer and a release layer, the release layer contains low-density polyethylene (A) with a density of 0.940 g/cm ³ or less, and the support layer contains polypropylene ( B) and at least one selected from the group of high-density polyethylene (C) having a density of 0.941 g/cm ³ or more, and low-density polyethylene (D) having a density of 0.940 g/cm ³ or less. The release film of claim 1, wherein the low-density polyethylene (A) in the release layer contains at least a linear low-density polyethylene with a density of 0.850 to 0.940 g/cm ³ . The requested item from the film 2, wherein the release layer comprises a density of 0.900g / cm ³ or more 0.940g / cm ³ or less linear low density polyethylene, and a density of 0.850g / cm ³ or more is less than 0.900g /cm ³ linear low-density polyethylene is a linear low-density polyethylene with a density of 0.850 to 0.940 g/cm ³ . The release film of claim 3, wherein the release layer contains 2-30 parts by mass relative to 100 parts by mass of linear low-density polyethylene with a density of 0.900g/cm ³ or more and 0.940g/cm ³ or less The density is 0.850g/cm ³ or more and less than 0.900g/cm ³ linear low-density polyethylene. The release film according to any one of claims 1 to 4, wherein the polypropylene (B) contained in the support layer has a crystallinity of 40% or more. The release film according to any one of claims 1 to 5, wherein the arithmetic average roughness Ra of the surface of the release layer is 0.5 to 7.0 μm. The release film according to any one of claims 1 to 6, wherein in the support layer, the total (B+C) and low density of polypropylene (B) and high-density polyethylene (C) in terms of mass ratio The content ratio of polyethylene (D) {(B+C): (D)} is 97:3 to 60:40. The release film according to any one of claims 1 to 7, wherein the ratio (Rt/St) of the thickness (Rt) of the release layer to the thickness (St) of the support layer is 0.05 to 0.50. The release film according to any one of claims 1 to 8, wherein the support layer has a back layer on the surface opposite to the surface having the release layer. The release film of claim 9, wherein the back layer contains polyolefin. The release film of claim 9 or 10, wherein the arithmetic average roughness Ra of the surface of the back layer is 0.1 to 0.5 μm. The release film according to any one of claims 1 to 11, which comprises a multi-layer co-extruded film of polyolefin. An adhesive sheet laminate, which is an adhesive sheet laminate formed by laminating a release film and an adhesive sheet according to any one of claims 1 to 12, and the adhesive sheet is an adhesive sheet having an adhesive layer on a base film, It is laminated so that the release layer of the release film and the adhesive layer of the adhesive sheet are in contact with each other. Such as the adhesive sheet laminate of claim 13, which is used in a hard disk drive.