WO2020050037A1

WO2020050037A1 - Release film and adhesive sheet laminate using same

Info

Publication number: WO2020050037A1
Application number: PCT/JP2019/032749
Authority: WO
Inventors: 大谷博志; 田崎竜幸; 谷尚樹
Original assignee: 東レフィルム加工株式会社
Priority date: 2018-09-07
Filing date: 2019-08-22
Publication date: 2020-03-12
Also published as: CN112638647A; TW202022074A; JP2020075509A; TWI816873B; CN112638647B; KR102627147B1; KR20210057007A

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 pressure-sensitive adhesive sheet laminate using the same

The present invention relates to a release film. Specifically, the present invention relates to a release film suitable for a pressure-sensitive adhesive sheet laminate.

シリコーン Since the release film used for the pressure-sensitive adhesive sheet is generally made of a silicone release agent having excellent releasability. However, the silicone compound contained in the silicone-based release agent may adversely affect electronic devices such as hard disk drives, such as corrosion and malfunction.

Therefore, in order to prevent silicone contamination, a release layer containing polyethylene is applied to a base material such as a polyester film or a polyolefin film on an adhesive sheet used for an electronic device such as a hard disk drive device. Release films laminated via a pull layer have been proposed (Patent Documents 1 and 2).

JP 2005-350650 A International Publication No. 2009/060924

However, the release film in which the polyethylene-containing release layer was provided on a substrate such as a polyester film or a polyolefin film did not have sufficient adhesion between the substrate and the release layer.

Accordingly, it is an object of the present invention to provide a release film having good adhesion between a substrate (support layer) and a release layer.

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

According to the present invention, a release film having good adhesion between the support layer and the release layer can be provided.

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) having a density of 0.940 g / cm ³ or less. By using such a release layer, relatively good releasability can be obtained.

The support layer comprises 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 low-density polyethylene (D) having a density of 0.940 g / cm ³ or less. ). By laminating such a support layer and the release layer, the adhesion between the release layer and the support layer is improved. In addition, when the support layer 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, the rigidity of the release film is increased ( The stiffness is increased), and the handleability and release workability of the release film are improved.

[Release layer]
The release layer in the present invention contains a low-density polyethylene (A) having a density of 0.940 g / cm ³ or less. The low-density polyethylene (A), from the viewpoint of improving the peeling property between the pressure-sensitive adhesive sheet preferably has a density 0.935 g / cm ³ or less, more preferably 0.930 g / cm ³ or less, 0.928 g / cm Particularly preferred is ³ or less. Further, the density is preferably from 0.850 g / cm ³ or more, more preferably 0.860 g / cm ³ or more, 0.870 g / cm ³ or more is particularly preferable.

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)”.

The low-density polyethylene includes a branched low-density polyethylene and a linear low-density polyethylene. Generally, low-density polyethylene means a branched low-density polyethylene other than linear low-density polyethylene. Any of the release layers in the present invention can be used. From the viewpoint of further improving the releasability from the pressure-sensitive adhesive sheet, the low-density polyethylene (A) in the release layer preferably contains at least a linear low-density polyethylene, and has a density of at least 0.850 to 0.940 g /. More preferably, it contains cm ³ linear low density polyethylene.

Linear low-density polyethylene is a copolymer of an ethylene monomer as a main component and an α- olefin. Here, the main component means a component contained in 50% by mole or more of the entire monomer components constituting the linear low-density polyethylene.

The α-olefin is preferably an α-olefin having 3 to 12 carbon atoms, and more preferably an α-olefin having 4 to 10 carbon atoms. Specific examples include 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene and the like. These α-olefins can be used alone or in combination. Among the α-olefins, α-olefins having 4 to 8 carbon atoms are more preferable, and 1-butene, 1-hexene and 1-octene are particularly preferably used from the viewpoint of polymerization productivity.

From the viewpoint of improving the releasability from the pressure-sensitive adhesive sheet, the content of the low-density polyethylene (A) in the release layer is preferably 50% by mass or more based on 100% by mass of the total solid content of the release layer, and is 60% by mass. % Or more, more preferably 70% by mass or more. The upper limit is 100% by mass.

直鎖 In the release layer, as the low-density polyethylene (A), a linear low-density polyethylene and a branched low-density polyethylene can be used in combination. In this case, the content of the branched low-density polyethylene is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the linear low-density polyethylene. It is particularly preferred to do so.

Further, the release layer, as linear low density polyethylene having a density of 0.850 ~ 0.940g / cm ^3, density of 0.900 g / cm ³ or more 0.940 g / cm ³ or less of a linear low-density It is preferable to contain polyethylene and a linear low-density polyethylene having a density of 0.850 g / cm ³ or more and less than 0.900 g / cm ³ . Thereby, the releasability from the adhesive sheet is further improved.

Note that 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, density may say 0.900 g / cm ³ or more 0.940 g / cm ³ or less linear low density polyethylene as "LLDPE", a density of 0.850 g / cm ³ or more 0.900 g / cm ³ A linear ultra-low-density polyethylene of less than may be referred to as “VLDPE”.

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

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

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

VLDPE is preferably a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, more preferably a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, Particularly preferred is a copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms. Among the above 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, an increase in the peeling force after heating is easily suppressed. In particular, when VLDPE is a copolymer of ethylene and 1-octene, the effect of suppressing an increase in the peeling force after heating increases.

Density of VLDPE is preferably less than 0.895 g / cm ^3, more preferably less than 0.890 g / cm ^3, less than 0.885 g / ^{m 3} is especially preferred. Further, the density is preferably from 0.855 g / cm ³ or more, more preferably 0.860 g / cm ³ or more, 0.865 g / cm ³ or more is particularly preferable.

As for the content ratio of LLDPE and VLDPE, the release layer preferably contains 2 to 30 parts by mass of VLDPE with respect to 100 parts by mass of LLDPE from the viewpoint of further improving the releasability from the pressure-sensitive adhesive sheet. It is more preferably contained by mass part, particularly preferably from 6 to 15 parts by mass.

The release layer may contain a polyolefin other than the low-density polyethylene (A) (hereinafter, may be referred to as “other polyolefin”). Examples of the other polyolefin include polypropylene, polybutene, poly (4-methyl-1-pentene), a propylene-α-olefin copolymer, and a copolymer of ethylene and a component other than α-olefin.

Examples of the α-olefin in the propylene-α-olefin copolymer include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 3-methyl-1- Butene, 4-methyl-1-pentene and the like.

Examples of the copolymer of ethylene and a component other than α-olefin include ethylene-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymer (EAA) and ethylene-methacrylic acid copolymer (EMAA). Copolymers; ionomers; ethylene- (meth) acrylate copolymers such as ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer (EEA), and ethylene-methyl methacrylate copolymer (EMMA); Ethylene-vinyl acetate copolymer (EVA); and ethylene-vinyl alcohol copolymer.

The other polyolefins described above can be used alone or in combination of two or more.

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

から From the viewpoint of further improving the releasability from the pressure-sensitive adhesive sheet, the release layer preferably has a relatively 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 is excessively large, the adhesiveness between the pressure-sensitive adhesive sheet and the adherend such as a hard disk drive may be reduced by transferring the unevenness of the release layer to the pressure-sensitive adhesive sheet, The arithmetic average roughness Ra is preferably 7.0 μm or less.

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

The uneven shape of the release layer surface is not particularly limited, and one having the same uneven pattern arranged regularly or irregularly, one having different uneven patterns arranged regularly or irregularly, or the like is employed. can do. Examples of the concavo-convex pattern include a lattice pattern, a silk pattern, a satin pattern, and a dot pattern.

When fine irregularities are formed 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, and further preferably 15.0 μm or more. It is particularly preferable that the thickness be 21.0 μm or more. The upper limit of the maximum height roughness Rz is about 50 μm. When the maximum height roughness Rz of the release layer surface is 5.0 μm or more, preferably 10.0 μm or more, an increase in the peeling force from the pressure-sensitive adhesive sheet after heating is easily suppressed.

As a method of forming fine irregularities on the surface of the release layer, for example, embossing, sand blasting, chemical treatment, or a forming roll in which irregularities are engraved on the release layer in a molten state in a film forming process of the release layer. There is a pressing method.

エン Embossing is preferred among the above-mentioned unevenness forming methods. As the embossing treatment, for example, a method in which a heated embossing roll is pressed against the release layer of the release film is preferable, and the unevenness formed on the release layer is controlled by adjusting the heating temperature and the pressing pressure of the embossing roll. be able to. The heating temperature of the embossing roll is preferably from 80 ° C to 160 ° C, more preferably from 100 ° C to 140 ° C.

[Support layer]
The support layer in the present invention includes 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 low density having a density of 0.940 g / cm ³ or less. Polyethylene (D). In the following description, high-density polyethylene (C) having a density of 0.941 g / cm ³ or more may be referred to as “high-density polyethylene (C)”, and low-density polyethylene having a density of 0.940 g / cm ³ or less. Polyethylene (D) may be referred to as "low density polyethylene (D)".

(4) Examples of the polypropylene (B) that can be contained in the support layer include a propylene homopolymer, a copolymer of propylene and another α-olefin, or a mixture thereof.

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

The polypropylene (B) preferably has a higher degree of crystallinity from the viewpoint of increasing the rigidity (strengthening) of the release film. Specifically, the 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 crystallinity is 100%.

結晶 The crystallinity of the polypropylene can be adjusted by controlling the cooling temperature and the cooling rate after the melt extrusion in the film forming process by melt extrusion of the support layer. For example, by lowering the cooling rate, the crystallinity of polypropylene increases. Further, the crystallinity can be increased by using a crystal nucleating agent in combination.

The crystal nucleating agent is not particularly limited, and a known compound can be used. Examples include inorganic substances such as talc, metal carboxylate, metal phosphate, sorbitol derivatives, metal salts of rosin, and the like.

As the high-density polyethylene (C) that can be contained in the support layer, polyethylene having a density of 0.941 to 0.980 g / cm ³ is preferable, and polyethylene having a density of 0.945 to 0.975 g / cm ³ is more preferable. Preferably, polyethylene having a density of 0.950 to 0.970 g / cm ³ is particularly preferred.

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

The low-density polyethylene (D) contained in the support layer, preferably the density is 0.935 g / cm ³ or less, more preferably 0.930 g / cm ³ or less, 0.928 g / cm ³ or less is particularly preferred. The density is preferably 0.870 g / cm ³ or more, more preferably 0.890 g / cm ³ or more, and particularly preferably 0.900 g / cm ³ or more.

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

The low-density polyethylene (D) may be the same or different from the low-density polyethylene (A) used for the release layer, but is preferably the same from the viewpoint of adhesion and productivity. Here, the linear low-density polyethylene and the branched low-density polyethylene are different types, and when the difference in density is 0.005 g / cm ³ or more, they are different types, and when they do not fall within the above range, they are the same type.

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

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

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

The support layer can contain additives such as a coloring pigment and an antioxidant.

[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 directly on the support layer or via another layer, but from the viewpoint of adhesion between the release layer and the support layer, the release layer is directly laminated on the support layer. Is preferred.

The release film of the present invention, on the surface of the release layer, a silicone-based release agent or a release agent other than the silicone-based release agent, for example, a long-chain alkyl release agent, an alkyd resin release agent, a fluorine-based release agent Surface treatment with an agent or the like is possible. However, the release film of the present invention is not subjected to the above-described surface treatment with the release agent in consideration of the relatively good releasability from the pressure-sensitive adhesive sheet and the transfer of the release agent to the pressure-sensitive adhesive sheet. Is more preferred.

In addition, in the release film of the present invention, a 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 or different composition as the release layer. Details of the back layer will be described later.

厚み 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.

(4) The thickness of the support layer is preferably from 20 to 130 μm, more preferably from 30 to 120 μm, further preferably from 40 to 100 μm, and particularly preferably from 50 to 80 μm.

厚み 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 releasability from the pressure-sensitive 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 0.05 to 0.50. It is preferably 0.10 to 0.40, more preferably 0.15 to 0.40.

離 The release film of the present invention can be manufactured by a known method such as a melt extrusion method or a melt extrusion lamination method. In particular, it is preferable that the support layer, the release layer, and the optional back layer are formed by a melt coextrusion method. This enhances the adhesion between the release layer and the support layer. Further, the melt coextrusion method is preferable from the viewpoint of productivity.

The release film of the present invention preferably has a three-layer structure of a release layer / a support layer / a back layer, and all of these layers preferably contain a polyolefin as a main component. The film is preferably formed by an extrusion method. That is, the release film of the present invention is preferably composed of a polyolefin multilayer (three-layer) coextruded film.

離 The release film of the present invention can reduce the peeling force from the pressure-sensitive 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 is appropriately set depending on the heating temperature and the form of the release film.

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

(4) The effect of reducing the release force by heating the release film tends to increase when the release layer contains LLDPE and VLDPE. By subjecting the release film having a release layer containing LLDPE and VLDPE to the above-described heat treatment, the release force can be reduced without forming irregularities on the surface of the release layer by embossing or the like.

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

In the release film of the present invention, the release force (normal release force) of the release layer surface to the pressure-sensitive adhesive tape is preferably 7.0 N / 50 mm or less, more preferably 4.0 N / 50 mm or less, and further 2.0 N / 50 mm. Or less, and particularly preferably 1.0 N / 50 mm or less. The lower limit of the peeling force is about 0.05 N / 50 mm. Further, the difference between the heat peeling force and the normal peeling force (the value obtained by subtracting the normal peeling force from the heat peeling force) is preferably 2.0 N / 50 mm or less, more preferably 1.0 N / 50 mm or less, and further more preferably 0.7 N / 50 mm. It is preferably at most 50 mm, particularly preferably at most 0.3 N / 50 mm.

Here, the peeling force of the release layer surface with respect to the pressure-sensitive adhesive tape was measured as the peeling force (B) in Examples described later. Details of the measuring method will be described later. Further, the normal peeling force and the heating peeling force are in accordance with the measuring method of the peeling force (B).

[Back layer]
The release film of the present invention preferably has a back layer on the surface of the support layer opposite to the surface having the release layer. The back layer can be provided for protecting the support layer or improving the slipperiness of the release film.

The back layer preferably contains a polyolefin, and more preferably contains a polyolefin as a main component. Here, containing a polyolefin as a main component means that the polyolefin is contained in an amount of 50% by mass or more based on 100% by mass of the total solid content of the back layer, and that the polyolefin is contained in an amount of 60% by mass or more. More preferably, the content is more preferably 70% by mass or more, particularly preferably 80% by mass or more. The upper limit is 100% by mass.

Polyolefins include homopolymers of ethylene, propylene and α-olefins having 4 to 10 carbon atoms, and copolymers thereof. Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 3-methyl-1-butene , 4-methyl-1-pentene and the like.

Examples of the copolymer include a copolymer of ethylene and propylene, a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and a copolymer of propylene and an α-olefin having 4 to 10 carbon atoms. Copolymers include copolymers of ethylene, propylene and an α-olefin having 4 to 10 carbon atoms.

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

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) is preferably used. As the polypropylene, a homopolymer of propylene is preferably used.

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

The back layer is preferably relatively rough from the viewpoint of ensuring the slipperiness of the release film. In particular, when the surface of the release layer is relatively smooth (when unevenness due to embossing or the like is not formed), specifically, the arithmetic average roughness Ra of the surface of the release layer is less than 0.5 μm, When it is less than 0.3 μm, the back layer is preferably relatively rough. 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 more preferably 2.0 to 5.0 μm. It is particularly preferred that there is.

背面 In order to roughen the back layer, the back layer preferably contains a propylene homopolymer and a polyolefin other than the propylene homopolymer. Polyolefins other than propylene homopolymer include polyethylene, homopolymers of α-olefins having 4 to 10 carbon atoms, copolymers of propylene and ethylene, and α-olefins having 4 to 10 carbon atoms of ethylene. It is preferable to use at least one member selected from the group consisting of Among these, a propylene-ethylene random copolymer is preferred.

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

When the release film has a configuration of a release layer / a support layer / a back layer, the thickness of the support layer relative to the total thickness of the release layer and the back layer is from the viewpoint of securing the rigidity of the release film and suppressing curling. {(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 1.5 or more and 3 or less. Is especially preferred.

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

Particularly, the release film of the present invention is suitable as a release film for an adhesive sheet for a hard disk drive. This pressure-sensitive adhesive sheet is preferably a non-silicone pressure-sensitive adhesive sheet containing no silicone compound.

[Adhesive sheet]
The pressure-sensitive adhesive sheet to which the release film of the present invention is applied is not particularly limited, but the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet includes an acrylic pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, and the like. Non-silicone adhesives are preferably used. In particular, an acrylic pressure-sensitive adhesive is preferable.

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

The pressure-sensitive adhesive sheet laminate (pressure-sensitive adhesive sheet with a release film) of the present invention is a pressure-sensitive adhesive sheet laminate obtained by laminating the release film of the present invention and a pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive on a base film. A pressure-sensitive adhesive sheet having a layer, wherein the release layer of the release film and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet are laminated so as to be in contact with each other.

The pressure-sensitive adhesive sheet laminate is preferably a pressure-sensitive adhesive sheet laminate for a hard disk drive. This pressure-sensitive adhesive sheet is preferably a non-silicone pressure-sensitive adhesive sheet.

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

[Measurement method and evaluation method]
(1) Measurement of density of polyethylene The density was measured by a density gradient tube method (23 ° C.) according to JIS K7112 (1999).

(2) Measurement of Crystallinity of Polypropylene Contained in Supporting Layer Using a differential scanning calorimeter (DSC) (DSC-60Plus, manufactured by Shimadzu Corporation), measurement was performed on the produced release film by the following method.

<Measurement method>
The temperature was raised from 0 ° C. to 250 ° C. at a rate of 10 ° C./min, and the heat of fusion was determined. From the obtained heat of fusion ΔH (J / g), the crystallinity was determined from the formula of (ΔH / resin fraction / 209) × 100 (%). Here, the resin fraction indicates the polymer fraction in the material, and is 1.0 if the resin component is 100%. 209 is the heat of fusion (J / g) at the time of 100% crystallization of polypropylene.

(3) Evaluation of Adhesion 100 cross cuts of 1 mm ² were put on the surface of the release layer of the release film, and a cellophane tape manufactured by Nichiban Co., Ltd. was adhered thereon and pressed strongly with a finger. It peeled off rapidly in the degree direction. Based on the number of crosscuts remaining on the release layer surface after the cellophane tape was peeled off, the adhesion was evaluated according to the following criteria.
A; 100 B; 80 to 99 C; 50 to 79 D; less than 50.

(4) Measurement of peeling force (A) Affix the adhesive sheet to the release layer surface of the release film so that the adhesive surface of the following adhesive sheet faces each other, hold down with a 5 kg rubber roller and make a single reciprocation to laminate the adhesive sheet. A body (adhesive sheet with release film) was prepared.

This adhesive sheet laminate was left at room temperature (23 ± 2 ° C.) for 24 hours, and a sample heated at 40 ° C. for 10 days was prepared. For each sample, a tensile tester (“EZ-SX” manufactured by Shimadzu Corporation) was used. ) At a speed of 300 mm / min, the peeling force when the adhesive sheet side was peeled at 180 ° was measured.

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

<Adhesive sheet>
93 parts by mass of n-butyl acrylate and 7 parts by mass of acrylic acid were subjected to solution polymerization in ethyl acetate in the presence of a polymerization initiator (azobisisobutyronitrile) by a conventional method to give a mass average molecular weight of 1.5 million. An acrylic polymer solution (solid content concentration: 25% by mass) was obtained. To 100 parts by mass of this acrylic polymer solution, 2 parts by mass of trimethylolpropane-modified tolylene diisocyanate ("Coronate L" manufactured by Nippon Polyurethane Co., Ltd.) was added as a crosslinking agent to prepare an acrylic pressure-sensitive adhesive composition.

The acrylic pressure-sensitive adhesive composition was applied on a 50 μm-thick polyethylene terephthalate film (“Lumirror (registered trademark)” S-105, manufactured by Toray Industries, Inc.) so that the dry thickness was 25 μm, and at 140 ° C. After drying for 3 minutes, an acrylic pressure-sensitive adhesive sheet was obtained.

(5) Measurement of peeling force (B) A rubber having a weight of 5 kg is superimposed on the release layer surface of the release film such that the adhesive surface of an acrylic adhesive tape ("No. 31B" manufactured by Nitto Denko Corporation) faces each other. The sample was bonded by being reciprocated once while being held by a roller, and a sample left at room temperature (23 ± 2 ° C.) for 24 hours and a sample heated at 70 ° C. for 24 hours were produced. With respect to each sample, the peeling force when the pressure-sensitive adhesive sheet side was peeled to 180 ° at a speed of 300 mm / min was measured by a tensile tester (product number of “EZ-SX” manufactured by Shimadzu Corporation).

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

(6) Measurement of Arithmetic Average Roughness Ra and Maximum Height Roughness Rz of Surface of Release Layer (Back Layer) A surface roughness measuring machine (“Surftest” manufactured by Mitutoyo Corporation) in accordance with JIS B0601 (2001). SJ-400 ”).

<Measurement conditions>
・ Stylus tip radius: 2 μm
・ Measurement force: 0.75mN
Cutoff value: λs = 2.5 μm, λc = 0.8 mm
(Cutoff value after embossing; λs = 2.5 μm, λc = 2.5 mm).

[Example 1]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was prepared by a three-layer melt coextrusion method using the following raw materials. The die temperature of each layer was set at 225 ° C. for the release layer, 250 ° C. for the support layer, and 220 ° C. for the back layer, and the thickness of the release layer was 20 μm on the casting drum maintained at 60 ° C. It extruded so that thickness might be set to 60 micrometers and the thickness of a back layer might be set to 20 micrometers, and the release film whose total thickness was 100 micrometers was produced.

ポリプロピレン The crystallinity of polypropylene in the support layer of this release film was 70%.

<Raw material for each layer>
Releasing layer material; linear low density polyethylene (KK Prime Polymer "Evolue (registered trademark)"SP0540; density 0.903 g / ^cm 3)
-Supporting layer raw material: 90 parts by mass of polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low density polyethylene ("Evolu (registered trademark)" SP0540 manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) A mixture with 10 parts by mass of a back layer material; linear low-density polyethylene (“Evolu (registered trademark) SP0540; manufactured by Prime Polymer Co., Ltd .; density 0.903 g / cm ³ ).

[Example 2]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was produced in the same manner as in Example 1 except that the support layer raw materials were changed as follows. The crystallinity of polypropylene in the support layer of this release film was 70%.
-Raw material for support layer: 97 parts by mass of polypropylene ("Novatec PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low-density polyethylene ("Evolu (registered trademark)" SP0540 manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) a mixture with 3 parts by mass.

[Example 3]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was produced in the same manner as in Example 1 except that the support layer raw materials were changed as follows. The crystallinity of polypropylene in the support layer of this release film was 70%.
-Supporting layer raw material: 93 parts by mass of polypropylene ("Novatech PP (registered trademark)" FL4, manufactured by Nippon Polypropylene Co., Ltd.) and linear low-density polyethylene ("Evolu (registered trademark)" SP0540, manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) a mixture with 7 parts by mass.

[Example 4]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was produced in the same manner as in Example 1 except that the support layer raw materials were changed as follows. The crystallinity of polypropylene in the support layer of this release film was 70%.
-Supporting layer raw material: 80 parts by mass of polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low-density polyethylene ("Evolu (registered trademark)" SP0540 manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) a mixture with 20 parts by mass.

[Example 5]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was produced in the same manner as in Example 1 except that the support layer raw materials were changed as follows. The crystallinity of polypropylene in the support layer of this release film was 70%.
-Supporting layer raw material: 70 parts by mass of polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low density polyethylene ("Evolu (registered trademark)" SP0540 manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) a mixture with 30 parts by mass.

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

<Raw material for each layer>
Releasing layer material; linear low density polyethylene (KK Prime Polymer "Evolue (registered trademark)"SP2540; density 0.924 g / ^cm 3)
-Supporting layer raw material: 90 parts by mass of polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low density polyethylene ("Evolu (registered trademark)" SP2540 manufactured by Prime Polymer Co., Ltd.) 0.924 g / cm ³ ) A mixture with 10 parts by mass of a back layer material; linear low-density polyethylene (“Evolu (registered trademark)” SP2540 manufactured by Prime Polymer Co., Ltd .; density 0.924 g / cm ³ ).

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

<Raw material for each layer>
Release layer material: branched low-density polyethylene (“Sumikacene (registered trademark)” CE3059, manufactured by Sumitomo Chemical Co., Ltd .; density: 0.924 g / cm ³ )
-Supporting layer raw material: 90 parts by mass of polypropylene ("Novatec PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and branched low density polyethylene ("Sumikacene (registered trademark)" CE3059 manufactured by Sumitomo Chemical Co., Ltd .; density 0) .924 g / cm ³ ) A mixture with 10 parts by mass of a back layer material; branched low-density polyethylene (“Sumikacene (registered trademark)” CE3059 manufactured by Sumitomo Chemical Co., Ltd .; density 0.924 g / cm ³ ).

Example 8
A release film was produced in the same manner as in Example 1, except that the raw materials of each layer were changed as follows. The crystallinity of polypropylene in the support layer of this release film was 70%.

<Raw material for each layer>
Releasing layer material; linear low density polyethylene (Co. Prime Polymer Co. "Evolue (registered trademark)"SP0540; density 0.903 g / ^cm 3) 80 parts by mass branched low density polyethylene (Sumitomo Chemical (Co. ) Manufactured by Sumikasen (registered trademark) CE3059; density: 0.924 g / cm ³ ) mixture with 20 parts by mass of raw material for support layer; polypropylene (Novatech PP (registered trademark) FL4 manufactured by Nippon Polypro Co., Ltd.) 90 mass Of a low-density polyethylene and 10 parts by mass of a linear low-density polyethylene (“Evolu (registered trademark)” SP0540 manufactured by Prime Polymer Co., Ltd .; density 0.903 g / cm ³ ); Ltd. Prime polymer "Evolue (registered trademark)"SP0540; density 0.903 g / ^cm 3) 80 parts by mass branched low density po Ethylene (Sumitomo Chemical Co., Ltd. "Sumikathene (registered trademark)"CE3059; density 0.924 g / ^cm 3) mixture of 20 parts by weight.

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

<Raw material for each layer>
Material for release layer: 75 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP0540 manufactured by Prime Polymer Co., Ltd .; density: 0.903 g / cm ³ ) and branched low-density polyethylene (Sumitomo Chemical Co., Ltd.) 15 parts by mass of “Sumikacene (registered trademark) CE3059; density 0.924 g / cm ³ ” and 10 parts by mass of an ethylene-propylene copolymer (“Tuffmer P (registered trademark)” P0180 manufactured by Mitsui Chemicals, Inc.) 90 parts by mass of polypropylene (“Novatec PP (registered trademark) FL4” manufactured by Nippon Polypropylene Co., Ltd.) and linear low-density polyethylene (“Evolu (registered trademark)” SP0540 manufactured by Prime Polymer Co., Ltd.) ; mixture & backside layer material with a density 0.903 g / ^cm 3) 10 parts by weight; linear low density polyethylene (Co. Prime polymer Ltd. "Evolue (registered trademark)"SP0540; Density 0.903g / ^cm 3).

[Example 10]
A release film having a two-layer laminated structure of a release layer and a support layer was produced by a two-layer melt coextrusion method using the following raw materials. The die temperature of each layer was set at 225 ° C. for the release layer and 250 ° C. for the support layer, and the thickness of the release layer was 25 μm and the thickness of the support layer was 75 μm on a casting drum maintained at 60 ° C. To produce a release film having a total thickness of 100 μm.

<Raw material for each layer>
Releasing layer material; linear low density polyethylene (KK Prime Polymer "Evolue (registered trademark)"SP0540; density 0.903 g / ^cm 3)
-Supporting layer raw material: 90 parts by mass of polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low density polyethylene ("Evolu (registered trademark)" SP0540 manufactured by Prime Polymer Co., Ltd.) 0.903 g / cm ³ ) a mixture with 10 parts by mass.

[Example 11]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was prepared by a three-layer melt coextrusion method using the following raw materials. The die temperature of each layer was set at 225 ° C. for the release layer, 250 ° C. for the support layer, and 250 ° C. for the back layer, and the thickness of the release layer was 15 μm on the casting drum maintained at 60 ° C. Extrusion was performed so that the thickness was 40 μm and the thickness of the back layer was 5 μm, to produce a release film having a total thickness of 60 μm. The obtained release film was heat-treated at 90 ° C. for 60 seconds.

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 material for each layer>
Material for release layer: 90 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP2540, manufactured by Prime Polymer Co., Ltd .; density: 0.924 g / cm ³ ) and linear ultra-low-density polyethylene (ethylene- 1-octene copolymer; mixture with 10 parts by mass of “Affinity (registered trademark)” KC8852G (density 0.875 g / cm ³ ) manufactured by Dow Chemical Co., Ltd .; raw material for supporting layer; high-density polyethylene (manufactured by Nippon Polyethylene Corporation) Novatec (registered trademark) "HF562; density = 0.961g / ^cm 3) 75 parts by weight of linear low density polyethylene (KK Prime polymer" Evolue (registered trademark) "SP2540; density 0.924 g / cm ³ ) 25 parts by mass of mixture / back layer material; polypropylene (“Noblen (registered trademark)” FLX manufactured by Sumitomo Chemical Co., Ltd.) 0E4) 80 parts by weight of propylene - ethylene random copolymer (ethylene content 5 mass%) mixture of 20 parts by weight.

[Example 12]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was prepared in the same manner as in Example 11, except that the release layer raw material was changed as follows, and heat-treated similarly. The arithmetic average roughness Ra of the back layer surface was 0.3 μm, and the maximum height roughness Rz was 2.6 μm.
Release layer raw material; 85 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP2540, manufactured by Prime Polymer Co., Ltd .; density: 0.924 g / cm ³ ) and linear ultra-low-density polyethylene (ethylene- A mixture of 1-butene copolymer and 15 parts by mass of “Tuffmer P (registered trademark)” P1070S (manufactured by Mitsui Chemicals, Inc .; density: 0.870 g / cm ³ ).

Example 13
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was prepared in the same manner as in Example 11 except that the raw material of the support layer was changed as described below, and heat-treated similarly. The crystallinity of polypropylene in the support layer of this release film was 70%. The arithmetic average roughness Ra of the back layer surface was 0.3 μm, and the maximum height roughness Rz was 2.6 μm.
-Supporting layer raw material: 75 parts by mass of polypropylene ("Novatec PP (registered trademark) FL4" manufactured by Nippon Polypropylene Co., Ltd.) and linear low density polyethylene ("Evolu (registered trademark)" SP2540 manufactured by Prime Polymer Co., Ltd.); 0.924 g / cm ³ ) a mixture with 25 parts by mass.

[Example 14]
A release film having a three-layer laminated structure of a release layer / a support layer / a back layer was prepared in the same manner as in Example 11 except that the raw material of the support layer was changed as described below, and heat-treated similarly. The crystallinity of polypropylene in the support layer of this release film was 70%. The arithmetic average roughness Ra of the back layer surface was 0.3 μm, and the maximum height roughness Rz was 2.6 μm.
· Support layer material; high density polyethylene (Nippon Polyethylene Co., Ltd. "Novatec (registered trademark)"HF562; density = 0.961g / ^cm 3) 60 parts by weight of polypropylene (Sumitomo Chemical Co., Ltd. "Noblen (trademark ) A mixture of 15 parts by mass of “FLX80E4” and 25 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP2540, manufactured by Prime Polymer Co .; density 0.924 g / cm ³ ).

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

<Raw material for each layer>
Releasing layer material; branched low density polyethylene (Sumitomo Chemical Co., Ltd. "Sumikathene (registered trademark)"CE3059; density 0.924 g / ^cm 3)
-Support layer material: polypropylene ("Novatech PP (registered trademark) FL4" manufactured by Nippon Polypro Co., Ltd.)
- back layer material; branched low density polyethylene (Sumitomo Chemical Co., Ltd. "Sumikathene (registered trademark)"CE3059; density 0.924 g / ^cm 3).

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

<Raw material for each layer>
Material for release layer: 75 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP0540 manufactured by Prime Polymer Co., Ltd .; density: 0.903 g / cm ³ ) and branched low-density polyethylene (Sumitomo Chemical Co., Ltd.) 15 parts by mass of “Sumikacene (registered trademark) CE3059; density 0.924 g / cm ³ ” and 10 parts by mass of an ethylene-propylene copolymer (“Tuffmer P (registered trademark)” P0180 manufactured by Mitsui Chemicals, Inc.) Mixture / support layer raw material; polypropylene (“Novatech PP (registered trademark) FL4” manufactured by Nippon Polypropylene Co., Ltd.)
Back layer material: linear low-density polyethylene (“Evolu (registered trademark)” SP0540, manufactured by Prime Polymer Co., Ltd .; density: 0.903 g / cm ³ ).

[Comparative Example 3]
First, on a 50 μm-thick polyethylene terephthalate film (“Lumilar (registered trademark) S-105” manufactured by Toray Industries, Inc.) in a tandem method, first, branched low-density polyethylene (“Sumikasen (registered trademark)” manufactured by Sumitomo Chemical Co., Ltd.) ) "CE3059; density 0.924 g / cm ³ ) was extruded and laminated at a die temperature of 325 ° C to form an undercoat layer (UC layer; dry thickness 10 µm). Subsequently, on this undercoat layer, The following release layer raw materials were extruded at a die temperature of 273 ° C. to laminate a release layer (dry thickness 10 μm).

<Roll release layer material>
75 parts by mass of linear low-density polyethylene (“Evolu (registered trademark)” SP0540, manufactured by Prime Polymer Co., Ltd .; density: 0.903 g / cm ³ ) and branched low-density polyethylene (Sumitomo Chemical Co., Ltd., “Sumikacene (registered) A mixture of 15 parts by mass of a trademark (trademark) “CE3059; density of 0.924 g / cm ³ ) and 10 parts by mass of an ethylene-propylene copolymer (“ Tuffmer P (registered trademark) ”P0180 manufactured by Mitsui Chemicals, Inc.).

[Evaluation]
The release films of the examples and the comparative examples produced above were evaluated according to the above-described measurement methods and evaluation methods. Table 1 shows the results.

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

<Emboss roll>
Embossing roll 1: Embossing roll processed into a relatively deep satin-like shape Embossing roll 2: Embossing roll processed into a relatively shallow satin-like shape Embossing roll 3: Embossing roll processed into a silk-like shape [Evaluation] ]
The release films of the examples prepared above were evaluated according to the above-described measurement methods and evaluation methods. Table 2 shows the results.

Claims

A release film having at least a support layer and a release layer, wherein the release layer contains a low-density polyethylene (A) having a density of 0.940 g / cm 3 or less, wherein the support layer is polypropylene (B) and A release film containing at least one member selected from the group consisting 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 according to claim 1, wherein the low-density polyethylene (A) in the release layer contains at least a linear low-density polyethylene having a density of 0.850 to 0.940 g / cm 3 .
The release layer is a linear low density polyethylene having a density of 0.850 ~ 0.940g / cm 3, density of 0.900 g / cm 3 or more 0.940 g / cm 3 or less linear low density polyethylene The release film according to claim 2, comprising a linear low-density polyethylene having a density of 0.850 g / cm 3 or more and less than 0.900 g / cm 3 .
The release layer, wherein the density of 0.900 g / cm 3 or more 0.940 g / cm 3 or less the density with respect to the linear low-density polyethylene 100 parts by weight of 0.850 g / cm 3 or more 0.900 g / The release film according to claim 3, comprising 2 to 30 parts by mass of a linear low-density polyethylene having a size of less than 3 cm3.
The release film according to any one of claims 1 to 4, wherein the crystallinity of the polypropylene (B) contained in the support layer is 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.
In the support layer, the content ratio (B + C) :( D) of the total (B + C) of the polypropylene (B) and the high-density polyethylene (C) and the low-density polyethylene (D) is from 97: 3 by mass ratio. The release film according to any one of claims 1 to 6, wherein the ratio is 60:40.
The release film according to any one of claims 1 to 7, wherein a ratio (Rt / St) of a thickness (Rt) of the release layer to a thickness (St) of the support layer is 0.05 to 0.50. .
離 The release film according to any one of claims 1 to 8, further comprising a back layer on a surface of the support layer opposite to a surface having the release layer.
型 The release film according to claim 9, wherein the back layer contains a polyolefin.
11. The release film according to claim 9, wherein the arithmetic mean 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, comprising a multi-layer co-extruded film of polyolefin.
A pressure-sensitive adhesive sheet laminate obtained by laminating the release film according to any one of claims 1 to 12 and a pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a base film, A pressure-sensitive adhesive sheet laminate, wherein the release layer of the release film and the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet are laminated so as to be in contact with each other.
The pressure-sensitive adhesive sheet laminate according to claim 13, which is used for a hard disk drive.