JP2023027221A - Adhesive resin composition, and laminated film comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition which has sufficient adhesive force when stuck to an adherend having fine surface ruggedness, and prevents acceleration of the adhesive force even when exposed to high temperature during its conveyance and storage.

SOLUTION: An adhesive resin composition contains the following block copolymer. The block copolymer is a block copolymer containing the following polymer block A and the following polymer block B. Polymer block A: polymer block having a continued aromatic alkenyl compound unit as a main component. Polymer block B: aromatic alkenyl-conjugated diene copolymer block randomly containing a conjugated diene unit and an aromatic alkenyl compound unit.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to an adhesive composition and a laminated film having such an adhesive layer. More specifically, it relates to a pressure-sensitive adhesive composition having excellent adhesion to an adherend and releasability, and a laminated film having such a pressure-sensitive adhesive layer.
Background technology

Conventionally, protective films are used for stacking and storing members such as prism sheets used for optical applications, synthetic resin plates, stainless steel plates, aluminum plates, decorative plywood, steel plates, and glass plates used for building materials. It has been used to protect against scratches during transportation and secondary operations such as bending and pressing. It has also been used to protect household appliances, precision instruments and automobile bodies from scratches during transportation in the manufacturing process.
Such a protective film should have good adhesiveness and be easily peeled off after use without contaminating the surface of the adherend with the adhesive.

In recent years, the variety of adherends has progressed, and a large number of adherends ranging from those with smooth surfaces to those with uneven surfaces can be seen.
The back surface of the prism sheet is smoother than the prism surface, which has large surface irregularities. It has functions such as interference prevention and making appearance defects such as scratches less noticeable.

Therefore, the back surface of the prism sheet is protected by a protective film when stacked and stored or transported.
However, when time elapses after the protective film is attached to the adherend, there arises a problem of an increase in adhesive strength (so-called increased adhesion), which makes it difficult to peel off. It is known that this becomes more conspicuous when the product to which the surface protection film is attached is exposed to high temperatures during transportation, storage, or the like. This problem is likely to occur particularly when the surface of the product (adherend) is uneven.

As a protective film used for adherends having fine surface irregularities, aromatic alkenyl compound units are continuous, polymer blocks mainly composed of aromatic alkenyl compound units, conjugated diene (butadiene) units and aromatic alkenyl compound units Randomly containing aromatic alkenyl-conjugated diene copolymer block, the content of the aromatic alkenyl compound unit is 35 to 55% by mass, and the adhesive layer uses a copolymer ( For example, Patent Document 1.) did not achieve both adhesive strength and ease of peeling after the passage of time.

JP 2014-169347 A

An object of the present invention is to have sufficient adhesive strength when applied to an adherend having fine surface irregularities, such as the back surface of a prism sheet, and to withstand exposure to high temperatures during transportation and storage. Also, since the adhesive strength is not easily increased and the protective film is easily peeled off from the adherend, no adhesive residue is left on the adherend even after the protective film is peeled off.

The present invention is an adhesive resin composition that contains a block copolymer and satisfies the following conditions (1), (2), (3), (4), and (5).
(1) The block copolymer is
It is a block copolymer containing the following polymer block A and the following polymer block B.
Polymer block A: A polymer block composed mainly of aromatic alkenyl compound units having consecutive aromatic alkenyl compound units Polymer block B: Aromatic alkenyl-conjugated diene containing conjugated diene units and aromatic alkenyl compound units randomly The content of the copolymer block (2) aromatic alkenyl compound unit in the block copolymer is 50% by mass or more.
(3) The content of polymer block A in the block copolymer is 15% by mass or more.
(4) The hydrogenation rate of double bonds derived from the conjugated diene units in the polymer block B is 90 mol % or more.
(5) The mass average molecular weight (Mw) of the block copolymer is 180,000 or less.

In this case, the block copolymer preferably comprises the following copolymer (I) and/or copolymer (II).
Copolymer (I): including the following polymer block A and the following polymer block B, represented by the general formula [AB]n (wherein A is polymer block A, B is polymer block B, n is 1 Represents an integer of up to 3.) It consists of a hydrogenated copolymer having a structure represented by
Copolymer (II): A copolymer containing the following polymer block A and the following polymer block B and having a structure represented by the general formula ABA (wherein the symbols have the same meanings as above) It consists of a hydrogenated polymer.
Polymer block A: A polymer block composed mainly of aromatic alkenyl compound units having consecutive aromatic alkenyl compound units Polymer block B: Aromatic alkenyl-conjugated diene containing conjugated diene units and aromatic alkenyl compound units randomly copolymer block

In this case, the adhesive resin composition according to claim 1 or 2, wherein the content of the adhesive aid in the adhesive resin composition is 1 to 50% by mass.

Moreover, in this case, it is preferable that the adhesion aid is a hydrogenated terpene phenol resin. The adhesive resin composition according to claim 3.

Furthermore, in this case, the content of the organic lubricant in the adhesive resin composition is preferably 0.1 to 2% by mass.

Furthermore, in this case, the organic lubricant is preferably ethylenebisstearic acid amide and/or calcium stearate.

Furthermore, in this case, a laminated film having a substrate layer mainly composed of a polypropylene-based resin and an adhesive layer composed of the adhesive resin composition on one side thereof is preferable.

Furthermore, in this case, a laminated film having a substrate layer mainly composed of a polypropylene resin, an adhesive layer composed of the adhesive resin composition on one side thereof, and a release layer on the opposite side to the adhesive layer is preferred.

Furthermore, in this case, the laminated film is suitable for protecting the back surface of the prism sheet.

When the adhesive resin composition of the present invention is applied to an adherend having fine surface irregularities, such as the back surface of a prism sheet, it has sufficient adhesive strength and can withstand high temperatures during transportation and storage. Since the protective film does not easily increase its adhesive strength even when exposed to water and is easily peeled off from the adherend, it does not leave an adhesive residue on the adherend even after the protective film is peeled off, and its function can be maintained.

(Block copolymer)
The block copolymer in the present invention is a block copolymer containing polymer block A and polymer block B below.
Polymer block A: A polymer block composed mainly of aromatic alkenyl compound units having consecutive aromatic alkenyl compound units Polymer block B: Aromatic alkenyl-conjugated diene containing conjugated diene units and aromatic alkenyl compound units randomly Copolymer Block Herein, the term "randomly" is interpreted broadly and a chain distribution of conjugated diene units and tetra-aromatic alkenyl compound units is obtained by simultaneously polymerizing mixed conjugated diene and aromatic alkenyl compounds. It means being in a state that obeys certain statistical laws.

The content of aromatic alkenyl compound units (St(A+B)) in the block copolymer is required to be 50% by mass or more. If the content of the aromatic alkenyl compound unit is less than 50% by mass, the initial adhesive strength may be too strong, or the adhesive strength may easily increase. On the other hand, the content of aromatic alkenyl compound units is preferably 80% by mass or less. If it exceeds 80% by mass, the initial adhesive strength may not be recognized. More preferably, it is 55% by mass or more, and still more preferably 60% by mass or more.

The content of aromatic alkenyl compound units (St(A+B)) in the block copolymer represents a numerical value defined by the following formula.
Such aromatic alkenyl compound unit content is determined by 1H-NMR. In addition, such an aromatic alkenyl compound unit content can also be determined by an infrared spectroscopy method, and a value approximately equivalent to 1H-NMR is obtained.

St(A+B)=
[(mass of units derived from aromatic alkenyl compound monomer units in block copolymer)/(mass of all units derived from monomers in block copolymer)] × 100 (% by weight)

The content of the polymer block A in the block copolymer must be 15% by mass or more. If the content of the polymer block A is less than 25% by mass, the initial adhesive strength may be too strong, adhesive residue may occur, and the adhesive strength may increase easily. More preferably, it is 30% by mass or more.
On the other hand, the content of polymer block A is preferably 50% by mass or less. If it exceeds 50% by mass, the initial adhesive strength may not be recognized. More preferably, it is 45% by mass or less, and still more preferably 40% by mass or less.

Since the hydrogenated product of the block copolymer B in the present invention can obtain excellent heat resistance and weather resistance, 90% or more, preferably 95% or more of the double bonds derived from the conjugated diene monomer units, More preferably, 98% or more is a hydrogenated product in which unsaturated bonds become saturated bonds due to hydrogenation. If it is less than 90%, the adhesive strength to an adherend having fine unevenness cannot be obtained, and there is concern about heat resistance and weather resistance.

The block copolymer preferably has a weight average molecular weight of 30,000 to 180,000. If the weight-average molecular weight is less than 30,000, the polymer may adhere to production equipment or the like in the process of desolvating and drying the polymer, making industrial production difficult. On the other hand, if the weight-average molecular weight exceeds 180,000, not only is the adhesive strength to an adherend having fine surface irregularities not obtained, the solubility in solvents and heat-melting properties deteriorate, and the industrial use of pellets is impaired. Film production by mechanical processing and melt coextrusion may also be difficult. It is more preferably 60,000 to 180,000, still more preferably 100,000 to 180,000, and particularly preferably 150,000 to 180,000.

The block copolymer preferably has a melt flow rate (MFR) value in the range of 0.1 to 20 g/min, more preferably 1 to 15 g/min. By setting the melt flow rate value in the range of 0.1 to 20 g/min, not only does it facilitate industrial production of the aromatic vinyl block copolymer, but also excellent processing is achieved during film formation. can provide sexuality. When the melt flow rate value is less than 0.1 g/min, the solubility in the solvent during polymerization is deteriorated, the heat meltability is lowered, and it may be difficult to remove the polymer from the production equipment. This difficulty becomes a problem that may reoccur during film formation.
On the other hand, if the melt flow rate value is more than 20 g/min, the polymer adheres and remains inside the manufacturing equipment in the step of desolvating and drying the polymer, making it difficult to remove the polymer. This difficulty becomes a problem that may reoccur during film formation.

The block copolymer of the present invention preferably comprises the following copolymer (I) and/or copolymer (II).
Copolymer (I): including the following polymer block A and the following polymer block B, represented by the general formula [AB]
n (Wherein, A represents polymer block A, B represents polymer block B, and n represents an integer of 1 to 3.)
It consists of a hydrogenated copolymer having a structure represented by
Copolymer (II): A copolymer containing the following polymer block A and the following polymer block B and having a structure represented by the general formula ABA (wherein the symbols have the same meanings as above) It consists of a hydrogenated polymer.
Polymer block A: A polymer block composed mainly of aromatic alkenyl compound units having consecutive aromatic alkenyl compound units Polymer block B: Aromatic alkenyl-conjugated diene containing conjugated diene units and aromatic alkenyl compound units randomly copolymer block

(Polymer block A)
The polymer block A in the present invention is a polymer block having continuous aromatic alkenyl compound units and mainly composed of aromatic alkenyl compound units. Examples of aromatic alkenyl compound units include, but are not limited to, styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, Aromatic vinyl monomeric units such as vinylanthracene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene and vinylpyridine may be mentioned. Among them, the "aromatic vinyl monomer unit" is preferably a styrene unit.
The repeating unit other than the aromatic alkenyl monomer unit is a repeating unit derived from a compound copolymerizable with the aromatic alkenyl monomer unit, such as a repeating unit derived from a conjugated diene compound or a (meth)acrylic acid ester compound. can be mentioned. Among them, 1,3-butadiene and isoprene are preferable because they are highly copolymerizable with aromatic alkenyl monomer units.
Polymer block A must be composed of aromatic alkenyl monomer units as main repeating units. Specifically, the content of aromatic alkenyl monomer units is preferably 80% by mass or more, more preferably 90% by mass or more. By setting the content of the aromatic alkenyl monomer unit within this range, it is possible to further improve the adhesive strength, the conformability to the surface irregularities of the adherend, and the unrolling property from the roll state.

(Polymer block B)
Polymer block B in the present invention is an aromatic alkenyl-conjugated diene copolymer block randomly containing conjugated diene units and aromatic alkenyl compound units. By randomly containing units derived from conjugated diene units and units derived from aromatic alkenyl compound units, the protective film using the adhesive resin composition of the present invention can be attached to an adherend having fine surface irregularities. After attachment, even when exposed to high temperatures during transportation and storage, adhesion is less likely to increase.
The conjugated diene monomer unit constituting the polymer block B in the present invention is a repeating unit derived from a conjugated diene monomer. Conjugated diene monomer units are not particularly limited, but examples include 1,3-butadiene, 1,2-butadiene, isoprene, 2,3-dimethyl-butadiene, 1,3-pentadiene, 2-methyl-1, 3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene and chloroprene. Among them, at least one repeating unit selected from 1,3-butadiene units and isoprene units, which have high polymerization reactivity and excellent adhesiveness and weather resistance, is preferable. Furthermore, it is more preferable to select 1,3-butadiene units in order to obtain high mechanical strength.
In addition, polymer block B is preferably an aromatic vinyl-conjugated diene copolymer block containing conjugated diene monomer units and aromatic vinyl monomer units randomly.

Since the hydrogenated product of the block copolymer B in the present invention can obtain excellent heat resistance and weather resistance, 90% or more, preferably 95% or more of the double bonds derived from the conjugated diene monomer units, More preferably, 98% or more is a hydrogenated product in which unsaturated bonds become saturated bonds due to hydrogenation. If it is less than 90%, the adhesive strength to an adherend having fine unevenness cannot be obtained, and there is concern about heat resistance and weather resistance.

(Adhesive resin composition)
The adhesive resin composition of the present invention is characterized by containing a block copolymer satisfying the following conditions (1), (2), (3), (4), and (5).
(1) The block copolymer is a block copolymer containing polymer block A and polymer block B below.
Polymer block A: A polymer block composed mainly of aromatic alkenyl compound units having continuous aromatic alkenyl compound units Polymer block B: Aromatic alkenyl randomly containing conjugated diene (butadiene) units and aromatic alkenyl compound units - The content of the conjugated diene copolymer block (2) aromatic alkenyl compound unit in the block copolymer is 50% by mass or more.
(3) The content of polymer block A in the block copolymer is 25% by mass or more.
(4) The hydrogenation rate of double bonds derived from the conjugated diene units in the polymer block B is 90 mol % or more.
(5) The mass average molecular weight (Mw) of the block copolymer is 180,000 or less.

The adhesive resin composition of the present invention contains, in addition to the above block copolymer, if necessary, an adhesive aid, an organic lubricant, an antioxidant, a light stabilizer, an ultraviolet absorber, a filler, a pigment, a styrene-based Known additives such as a block phase reinforcing agent, a softening agent, an anti-adhesion agent, an olefin resin, a silicone resin, a liquid acrylic copolymer, and a phosphoric acid ester compound may be appropriately contained.

(adhesion aid)
In the present invention, an adhesion aid can be added for the purpose of increasing the adhesive strength of the adhesive resin composition. Examples of adhesive aids include petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic/aromatic copolymers and alicyclic copolymers; coumarone-indene resins. terpene-based resins; terpene-phenolic resins; rosin-based resins such as polymerized rosin; phenol-based resins; be able to.
It is preferable to use an adhesive agent having a glass transition temperature of 30° C. or higher. If the temperature is less than 30°C, there is concern about exudation at room temperature, resulting in poor handleability. The glass transition temperature of the tackifier is preferably 65° C. or higher in consideration of high temperature acceleration. Among the adhesive aids, terpene phenol resins are preferred, and hydrogenated terpene phenols are particularly preferred. When the adhesion aid has a phenol group, it has an electrical affinity with the adherend, and it is expected that the adhesive force will be improved more independently of the temperature. In addition, the addition of hydrogen can reduce concerns about discoloration due to high temperature or aging.
The adhesion aid may be used alone or in combination of two or more. When the adhesive aid is a hydrogenated resin, the releasability, weather resistance, etc. are further enhanced. The adhesive aid in the adhesive layer is preferably a hydrogenated resin.

The content of the adhesive aid in the adhesive resin composition is preferably 1 to 50% by mass. Adhesive aids are expected to improve adhesive strength and progress due to the effect of plasticizing the adhesive resin composition and the effect of inhibiting the molecular movement of the adhesive. When the content of the adhesion aid exceeds 50% by mass, the compatibility with the adhesive resin composition is deteriorated, and the initial adhesive strength may be lowered. More preferably, it is 40% by mass or less, and still more preferably 30% by mass or less.

(organic lubricant)
The organic lubricant used in the present invention is preferably saturated fatty acid bisamide or fatty acid metal salt, considering excessive exudation at room temperature or high temperature. Specific examples include ethylenebisstearic acid bisamide and stearic acid metal salts. These may be used alone or in combination of two or more.

The content of the organic lubricant in the adhesive resin composition is preferably 0.1 to 2% by mass. An organic lubricant can be expected to have the effect of suppressing the increase in adhesive strength. However, if the organic lubricant exceeds 2% by mass relative to the adhesive resin composition, there is a concern that the organic lubricant will bleed out excessively at high temperatures or over time, and may stain the adherend. The organic lubricant used in the present invention preferably has a high melting point in view of bleeding out at high temperatures and over time, and specific examples thereof include ethylenebisstearic acid amide and calcium stearate.

(Antioxidant)
Antioxidants used in the present invention are not particularly limited, and include, for example, commonly used phenolic (monophenolic, bisphenolic, polymeric phenolic), sulfur, and phosphorus antioxidants.

(light stabilizer)
The light stabilizer used in the present invention includes hindered amine compounds.

(Ultraviolet absorber)
The UV absorber used in the present invention is not particularly limited, and examples thereof include salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based.

(Softener)
In the present invention, a softening agent can be added for the purpose of lowering the hardness of the adhesive resin composition. Softeners are also effective in improving adhesion. Softening agents include, for example, low molecular weight diene polymers, polyisobutylene, hydrogenated polyisobutylene, hydrogenated polybutadiene, paraffinic process oils, naphthenic process oils, aromatic process oils, castor oil, tall oil, natural oils, Liquid polyisobutylene resin, polybutene, hydrogenated products thereof, and the like, which are generally used for pressure-sensitive adhesives, can be used without particular limitation. These softeners may be used alone or in combination of two or more.

(filler)
Examples of fillers include calcium carbonate, magnesium carbonate, silica, zinc oxide and titanium oxide.

(Laminated film)
The laminated film according to the present invention is obtained by laminating an adhesive layer made of the adhesive resin composition on a substrate layer. Furthermore, a release layer may be provided on the substrate layer on the side opposite to the adhesive layer.
A detailed description will be given below.

(Adhesive layer)
The pressure-sensitive adhesive layer in the present invention is made of the pressure-sensitive adhesive composition described above, and has a thickness of usually about 1 to 30 μm, preferably 2 to 10 μm.

The initial adhesive strength of the laminated film of the present invention is preferably 2 cN/25 mm or more and 20 cN/25 mm or less. When it is 2 cN/25 mm or more, it does not peel off or float during handling and transportation, and when it is 20 cN/25 mm or less, excessive force is not required when peeling it off. More preferably, it is 3 cN/25 mm or more and 15 cN/25 mm or less. More preferably, it is 3 cN/25 mm or more and 10 cN/25 mm or less. Particularly preferably, it is 3 cN/25 mm or more and 8 cN/25 mm or less.
The initial adhesive strength was measured as follows.
23±2° C. and a relative humidity of 50±5% RH so that the surface of the adhesive layer of the laminated film is in contact with the back surface of the prism sheet. H. , a linear pressure of 15 kN/m was applied from the opposite side of the adhesive layer surface of the laminated film, and the laminate film was adhered at a speed of 2 m/min.
The resulting specimens were subjected to a temperature of 23±2° C. and a relative humidity of 50±5% RH. H. After being left in a room for 30 minutes, the 180-degree peel strength (unit: cN) at a width of 25 mm was measured at a peel speed of 300 mm/min according to JIS Z0237, and was defined as the initial adhesive strength.

The adhesive strength over time of the laminated film of the present invention is preferably 2 cN/25 mm or more and 80 cN/25 mm or less. When it is 2 cN/25 mm or more, it does not peel off or float during handling and transportation, and when it is 80 cN/25 mm or less, excessive force is not required when peeling. More preferably, it is 3 cN/25 mm or more and 70 cN/25 mm or less. More preferably, it is 3 cN/25 mm or more and 60 cN/25 mm or less. Particularly preferably, it is 3 cN/25 mm or more and 45 cN/25 mm or less.
The adhesive strength over time was measured as follows.
A test piece was prepared under the same conditions as those for the prism sheet used to measure the adhesive strength over time. After being left for one week in an atmosphere of 65°C ± 2°C and a load of 6 kg/400 cm 2 , the 180° peel strength at a width of 25 mm was measured at a peel speed of 300 mm/min according to JIS Z0237, and was taken as the adhesive strength over time.

It is preferable that the laminated film of the present invention has an adhesion enhancement rate of 1000% or less. When the adhesion rate is 1000% or less, working conditions for peeling the film from the adherend become more constant, and working efficiency improves. More preferably, it is 800% or less, still more preferably 600% or less, and particularly preferably 500% or less.
The adhesion rate was calculated by the following formula using the initial adhesive strength and the time-dependent adhesive strength.
Adhesion rate = (adhesive strength over time/initial adhesive strength) x 100 (%)

The peeling force between the surface of the adhesive layer and the surface opposite to the adhesive layer of the present invention is in the range of 200 cN/25 mm or less at 23 ° C., from the viewpoint of the film feeding property when the laminated film is rolled. preferable. When the peel force exceeds 200 cN/25 mm, problems such as partial elongation and deformation of the film occur when the laminated film is rolled out. In addition, the lower limit of the peeling force between the surface of the adhesive layer of the laminated film and the surface opposite to the adhesive layer is about 1 cN/25 mm, more preferably about 5 cN/25 mm as a realistic value. More preferably, it is 2 to 100 cN/25 mm, and even more preferably 3 to 50 cN/25 mm.

(Base material layer)
The substrate layer in the present invention can be formed from a polyolefin resin. A polyolefin resin is a polymer using an olefin monomer such as ethylene, propylene, or α-olefin, and the ratio of the olefin monomer to the total monomers constituting the polyolefin resin is 70 mol% or more. refers to the Polyolefin resins contained in the substrate include ethylene homopolymer, ethylene-α-olefin copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester copolymer, and ethylene - polyethylene resins such as vinyl acetate copolymers; polypropylene resins such as propylene homopolymers, propylene-α-olefin copolymers, and propylene-ethylene copolymers; butene homopolymers; conjugates such as butadiene and isoprene Examples thereof include diene homopolymers and copolymers. Further, examples of the polyethylene-based resin include high-density polyethylene, medium-density polyethylene, and low-density polyethylene. The form of copolymerization may be random, block, or terpolymer form.
The above polyolefin-based resins may be used alone, or two or more of them may be used in combination.

The polyethylene-based resin is obtained using ethylene as a main component. The proportion of structural units derived from ethylene is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more in 100% by mass of all structural units in the polyethylene-based resin.

The polypropylene-based resin is obtained using propylene as a main component. The proportion of structural units derived from propylene is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more in 100% by mass of all structural units of the polypropylene-based resin. The substrate layer of the present invention is preferably composed mainly of a polypropylene-based resin in terms of heat resistance, weather resistance, or adhesion to the adhesive layer.

The thickness of the substrate layer in the present invention is preferably 10 μm or more, more preferably 100 μm or less. When the thickness of the substrate is 10 μm or more and 100 μm or less, the laminated film can be handled even more easily.

When the laminated film according to the present invention is composed only of a substrate layer and an adhesive layer made of the adhesive composition, the surface is provided with unevenness in order to suppress the peeling force between the surface of the substrate layer and the surface of the adhesive layer. It is preferable to reduce the contact area with the adhesive layer.
In this case, considering the resin composition of the adhesive layer of the present invention, the average surface roughness SRa of the surface of the release layer is preferably 0.40 μm or more. It is more preferable that the average surface roughness of the surface is 0.850 μm or less in SRa, and more preferably 0.500 μm or more and 0.700 μm or less.
By setting the average surface roughness SRa of the adhesive layer surface and the opposite surface of the adhesive layer of the base material layer to 0.40 μm or more, the adherend protection performance and peeling force can be improved. When the surface roughness of the release layer is less than 0.40 μm, the unreeling property of the film is deteriorated when the film is rolled. If the surface roughness of the base material layer is higher than 0.850 μm, the surface unevenness of the base material layer may be transferred to the surface of the adhesive layer, resulting in a significant decrease in adhesive strength.

In order to make the average surface roughness SRa 0.40 μm or more, as the resin used for the base material layer, it is preferable to add a resin incompatible with homopropylene or random polypropylene, or to use a propylene-ethylene block copolymer. can be used for When a propylene-ethylene block copolymer is used, the uneven state is less likely to change due to changes in production equipment and melt-kneading conditions during film formation, and stable production is possible.
The average surface roughness SRa can be increased by increasing the molecular weight of the ethylene-propylene rubber in the propylene-ethylene block copolymer or by increasing the amount of ethylene. Further, by mixing an incompatible resin into the propylene-ethylene block copolymer, the average surface roughness SRa can be increased.
The average surface roughness SRa can also be increased by lowering the shear rate applied to the resin or lengthening the residence time in the extrusion step, which will be described later.
On the other hand, in order to reduce the average surface roughness SRa, it is effective to mix a propylene-ethylene block copolymer with a homopolypropylene resin.

As the resin incompatible with the propylene-ethylene block copolymer, 4-methylpentene-1 polymer or 4-methyl-1-pentene/α-olefin copolymer can be preferably used. The α-olefin is not particularly limited as long as it can be copolymerized with ethylene, propylene, 4-methyl-1-pentene. Examples include ethylene, propylene, 1-butene, 1-hexene, 4-methyl- Mention may be made of 1-pentene, 1-octene, 1-pentene, 1-heptene.
In addition, low-density polyethylene, high-density polyethylene, copolymer of ethylene and a small amount of α-olefin, copolymer of ethylene and vinyl acetate, polystyrene, alicyclic olefin resin, polyester resin, polyamide resin, etc. is mentioned. In particular, 4-methylpentene-1 polymer or 4-methyl-1-pentene/α-olefin copolymer not only roughens the surface like a mat, but also lowers the surface free energy of the film surface, further reducing the release force. is expected, so it is preferable.

The amount of 4-methylpentene-1 polymer or 4-methyl-1-pentene/α-olefin copolymer having 4 or more carbon atoms in the substrate layer (resin component constituting the substrate layer) is 0 mass. % or more and 35 mass % or less. When the amount of the α-olefin (co)polymer having 4 or more carbon atoms exceeds 35% by mass, when the base material layer and the adhesive layer raw materials are co-extruded using a T-die or the like to laminate, the base material The film formability of the layer deteriorates.

(release layer)
The release layer in the present invention is provided on the substrate layer on the side opposite to the adhesive layer. As a result, by distributing the functions to the substrate layer and the release layer respectively, it is possible to respond to a wider range of applications.

In this case, it is preferable to reduce the contact area with the adhesive layer by imparting unevenness to the surface in order to suppress the peeling force between the surface of the release layer and the surface of the adhesive layer.
Considering the resin composition of the adhesive layer of the present invention, the average surface roughness SRa of the surface of the release layer is preferably 0.40 μm or more. It is more preferable that the average surface roughness of the surface is 0.850 μm or less in SRa, and more preferably 0.500 μm or more and 0.700 μm or less.

By setting the average surface roughness SRa of the surface of the release layer to 0.40 μm or more, it is possible to improve the protection performance of the adherend and the release force. When the surface roughness of the release layer is less than 0.40 μm, the unreeling property of the film is deteriorated when the film is rolled. If the surface roughness of the release layer is higher than 0.850 μm, the unevenness of the surface of the release layer may be transferred to the surface of the adhesive layer, resulting in a significant decrease in adhesive strength.

In order to make the average surface roughness SRa 0.40 μm or more, as the resin used for the release layer, it is preferable to add a resin incompatible with homopropylene or random polypropylene, or to use a propylene-ethylene block copolymer. can be used for When a propylene-ethylene block copolymer is used, the uneven state is less likely to change due to changes in production equipment and melt-kneading conditions during film formation, and stable production is possible.
The average surface roughness SRa can be increased by increasing the molecular weight of the ethylene-propylene rubber in the propylene-ethylene block copolymer or by increasing the amount of ethylene. Further, by mixing an incompatible resin into the propylene-ethylene block copolymer, the average surface roughness SRa can be increased.
The average surface roughness SRa can also be increased by lowering the shear rate applied to the resin or lengthening the residence time in the extrusion step, which will be described later.
On the other hand, in order to reduce the average surface roughness SRa, it is effective to mix a propylene-ethylene block copolymer with a homopolypropylene resin.

As the resin incompatible with the propylene-ethylene block copolymer, α-olefin (co)polymers having 4 or more carbon atoms such as 4-methylpentene-1 (co)polymers can be suitably used. Other examples include low-density polyethylene, high-density polyethylene, copolymers of ethylene and a small amount of α-olefin, copolymers of ethylene and vinyl acetate, polystyrene, polyester resins, polyamide resins, and the like. In particular, a 4-methylpentene-1 (co)polymer is preferable because it not only roughens the surface in a matt state, but also lowers the surface free energy of the film surface, thereby further reducing the peeling force.

The content of the α-olefin (co)polymer having 4 or more carbon atoms in the release layer (resin component constituting the release layer) is in the range of 0% by mass or more and 35% by mass or less. When the content of the α-olefin (co)polymer having 4 or more carbon atoms exceeds 35% by mass, the film formability of the base layer deteriorates when the base layer and the adhesive layer are laminated by co-extrusion.
The thickness of the release layer is not particularly limited. The thickness of the release layer is preferably 2 μm or more and preferably 10 μm or less. When the release layer has a thickness of 2 μm or more and 10 μm or less, the laminated film can be handled even more easily.

The method for producing the laminated film of the present invention includes, for example, putting the adhesive composition and the polyolefin resin for the base layer into separate extruders and, if necessary, the polyolefin resin for the release layer, melting, A method of co-extrusion from a T-die and laminating, or a method of laminating another layer on the layer obtained by inflation molding by a lamination method such as extrusion lamination or extrusion coating, each layer being independently formed into a film. After that, there is a method of laminating each obtained film by dry lamination, but from the viewpoint of productivity, each material of the release layer, the base layer, and the pressure-sensitive adhesive layer is used in a multilayer extruder Co-extrusion molding is preferable, and T-die molding is more preferable from the viewpoint of thickness accuracy.

The surface protective film of the present invention is used to protect the surface of an adherend having a smooth surface or fine irregularities, especially when the surface roughness is about 0.1 to 0.3 μm. It is valid.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
The measurement method is shown below.

(1) Initial Adhesive Strength The surface protective film obtained above was adhered so that the adhesive layer surface was in contact with the back surface of the prism sheet to prepare a test piece. Application was performed at 23±2° C. and 50±5% R.H. H. , a linear pressure of 15 kN/m was applied from the outside of the surface protection film (that is, the side opposite to the pressure-sensitive adhesive layer surface), and the film was adhered at a speed of 2 m/min. The following laminator was used for lamination.
Laminator manufacturer: Tester Sangyo Co., Ltd.
Model: SA-1010-S
Roll: Heat-resistant silicone rubber roll Roll diameter: Φ200
The resulting specimens were stored at 23±2° C. and 50±5% R.H. relative humidity. H. After being left in a room for 30 minutes, the 180-degree peel strength (unit: cN) at a width of 25 mm was measured at a peel speed of 300 mm/min according to JIS Z0237, and was defined as the initial adhesive strength.

(2) Adhesive strength over time The resulting surface protective film was attached under the same conditions as the prism sheet used in the evaluation of the initial adhesive strength in (1), and subjected to an atmosphere of 65°C ± 2°C and a load of 6 kg/400 cm ² . After allowing to stand for one week, the 180 degree peel strength at a width of 25 mm was measured at a peel rate of 300 mm/min according to JIS Z0237, and was taken as the adhesive strength over time.

(3) Rate of Adhesion Rise Using the initial adhesive strength and the time-dependent adhesive strength obtained in (1) and (2) above, the rate of change from the initial adhesive strength to the time-dependent adhesive strength (adhesion rate) was calculated by the following formula. .
Rate of change (adhesion rate) = (adhesive strength over time/initial adhesive strength) x 100

(4) Peeling force The obtained surface protective film is laminated with two films so that the adhesive layer of one film and the peeling layer of the other film face each other to a thickness of 110 mm (winding direction at the time of film production). A test piece cut out to a size of 40 mm (perpendicular to the winding direction at the time of film production) was cut out, sandwiched between copy papers at the top and bottom, a weight of 60 kg was placed on it, and left to stand in a room at a temperature of 40°C for 72 hours. bottom. After that, it was cooled to 23±2° C. and 50±5% R.H. H. Leave it for 1 hour in the room of (
Using "Autograph (registered trademark)" (AGS-J) manufactured by Shimadzu Corporation, the resistance value when peeled 180 degrees at a speed of 300 mm/min was taken as the peel force [cN/25 mm].
When measuring, prepare a polyester sheet with a thickness of 190 μm and a size of 40 mm × 170 mm as a gripping margin for the measurement sample, and attach it to the end of the 110 mm × 40 mm test piece with a cellophane tape with a width of 15 mm. It was used as a catch fee. The measurement was performed three times for one sample, and the average value was taken as the peel strength of that sample.

(5) Surface roughness Evaluation of the surface roughness on the side opposite to the adhesive layer of the obtained laminated film was performed using a three-dimensional roughness meter (manufactured by Kosaka Laboratory Co., Ltd., model number ET-30HK), with a stylus pressure of 20 mg. Measured with a measurement length of 1 mm in the X direction, a feed speed of 100 μm/sec, a feed pitch of 2 μm in the Y direction, 99 recorded lines, a magnification of 20000 times in the height direction, and a cutoff of 80 μm. It was calculated according to the definition of arithmetic mean roughness described in .
Arithmetic mean roughness (SRa) was evaluated by the average value of three trials.

(6) Content of Aromatic Alkenyl Compound Unit in Block Copolymer Each raw material resin and mixed resin sample was dissolved in CDCl3, and 1H-NMR was measured under the following conditions.
Apparatus: Fourier transform nuclear magnetic resonance apparatus (AVANCE500 manufactured by Bruker Biospin)
Measurement solution: 10 to 30 mg of sample was dissolved in 0.6 ml of deuterated chloroform. 5 to 10 vol % of trifluoroacetic acid was added thereto.
1H resonance frequency: 500.13MHz
Flip angle of detection pulse: 45°
Data acquisition time: 4.0 seconds Delay time: 1.0 seconds Accumulation times: 20 to 100 times Measurement temperature: 25 to 40°C

(7) Content of polymer block A in block copolymer The spectrum of homopolystyrene was compared with the infrared spectrum of each starting resin and mixed resin sample, and the content of polymer block A was calculated.

(8) Weight Average Molecular Weight Each raw material resin and mixed resin sample were dissolved in tetrahydrofuran (sample concentration: 0.05% by mass). After filtration through a 0.20 μm membrane filter, GPC analysis of the resulting sample solution was performed under the following conditions. The molecular weight was calculated in terms of standard polystyrene.
GPC apparatus Conditions Apparatus: High performance liquid chromatograph HLC-8220 (TOSOH)
Column: TSKgel SuperHZM-H + SuperHZM-H + SuperHZ2000 (TOSOH)
Solvent: THF (tetrahydrofuran)
Flow rate: 0.35mL/min
Injection volume: 10 μL
Temperature: 40°C
Detector: RI
Data processing: GPC data processing system (TOSOH)

Raw material resins used in the following examples and comparative examples are shown below.

1) S1605: Product name “S1605”, hydrogenated styrene-butadiene copolymer, manufactured by Asahi Kasei Corporation, MFR = 3.5 g/10 min, double bond hydrogen derived from conjugated diene unit of polymer block B Addition rate = 100%, weight average molecular weight = 180700, density = 1.00 g/cc, content of aromatic alkenyl compound units = 66% by mass, content of polymer block A = 31% by mass, structural formula AB -A and a mixture of copolymers of structural formula AB.

2) L613: Product name “L613”, hydrogenated styrene-butadiene copolymer, manufactured by Asahi Kasei Corporation, MFR = 5.0 g/10 min, double bond hydrogen derived from conjugated diene unit of polymer block B Addition rate = 100%, weight average molecular weight = 138200, density = 1.00 g/cc, content of aromatic alkenyl compound units = 32% by mass, content of polymer block A = 35% by mass, structural formula AB -A and a mixture of copolymers of structural formula AB.

3) S1606: Product name "S1606", hydrogenated styrene-butadiene copolymer, manufactured by Asahi Kasei Corporation, MFR = 4.0, hydrogenation rate of double bonds derived from conjugated diene units in polymer block B = 100%, weight average molecular weight = 169900, density = 0.96 g/cc, content of aromatic alkenyl compound units = 50% by mass, content of polymer block A = 25% by mass, structural formula ABA copolymer.

4) H1221: Product name "H1221", hydrogenated styrene-butadiene copolymer, manufactured by Asahi Kasei Corporation, MFR = 4.5/10 min, double bond hydrogen derived from conjugated diene unit of polymer block B Addition rate = 100%, weight average molecular weight = 147600, density = 0.89 g/cc, content of aromatic alkenyl compound units = 12% by mass, content of polymer block A = 12% by mass, polymer block B No copolymer.

5) UH115: trade name "UH115", hydrogenated terpene phenol resin, manufactured by Yasuhara Chemical Co., glass transition temperature = 65 ° C.

6) TH130: Product name "TH130", terpene phenol resin, manufactured by Yasuhara Chemical Co., Ltd., glass transition temperature = 80°C

7) EB-P (trade name “EB-P”, ethylenebisstearic acid amide, manufactured by Kao Corporation)

(Comparative Example 4)
A pressure-sensitive adhesive composition containing 100 parts by weight of S1606 and a polyolefin resin (trade name “WF836DG3”, propylene-ethylene random copolymer, manufactured by Prime Polymer Co., Ltd., MFR = 4.5/10 min, melting point = 164°C, ethylene copolymerization amount = 0.3% by mass), and a polyolefin resin (trade name “BC3HF”, polypropylene-ethylene block copolymer, manufactured by Prime Polymer Co., Ltd., melting point = 171°C, as a raw material for the release layer). ethylene content = 9% by mass), the pressure-sensitive adhesive layer resin is extruded at a rate of 6 kg/h using a 40 mmφ single-screw extruder, and the substrate layer resin is extruded at a rate of 30 kg/h using a 90 mmφ single-screw extruder. , The release layer resin is co-extruded using a 60 mmφ single screw extruder at a discharge rate of 4 kg / hour, using a three-layer T die (lip width 850 mm, lip gap 1 mm), cooled with a cooling roll, and adhesive A laminate film having a thickness of 6 μm, 30 μm, and 4 μm for the layer, base layer, and release layer, and a length of 650 mm in the width direction was obtained. Table 1 shows the above results.

(Comparative Examples 5-7, Examples 5-7, Comparative Example 8, Comparative Examples 1-3)
A laminated film was obtained in the same manner as in Example 1 except that the content of the raw material resin and additives of the adhesive layer, and the thickness and content of the adhesive layer were changed as shown in Table 1. Table 1 shows the above results.

The laminated films of Examples 5 to 7, when attached to the back surface of the prism sheet, have sufficient adhesive strength with the back surface, and the adhesive strength does not easily increase even after one week in high humidity. , blocking with the release layer was also less.
On the other hand, the laminated films of Comparative Examples 1 and 2 had too strong adhesion to the back surface and were difficult to peel off from the back surface.

The laminate film of Comparative Example 3 had increased adhesion to the back surface after one week of exposure to high humidity, and was difficult to peel off from the back surface.

The pressure-sensitive adhesive composition of the present invention is industrially useful as the surface protective film of the present invention is suitably used for surface protection of prism sheets and the like, particularly for the back surface thereof.

Claims (7)

A substrate layer mainly composed of a polypropylene resin, containing a block copolymer on one side thereof, and the following (1), (2), (3), (4), (5), and (6) A laminated film having an adhesive layer made of an adhesive resin composition that satisfies the conditions.
(1) The block copolymer consists of the following copolymer (I) and copolymer (II).
Copolymer (I): including the following polymer block A and the following polymer block B, represented by the general formula [AB]n (wherein A is polymer block A, B is polymer block B, n is 1 Represents an integer of up to 3.) It consists of a hydrogenated copolymer having a structure represented by
Copolymer (II): A copolymer containing the following polymer block A and the following polymer block B and having a structure represented by the general formula ABA (wherein the symbols have the same meanings as above) It consists of a hydrogenated polymer.
Polymer block A: A polymer block in which the aromatic alkenyl compound units are continuous and the content of the aromatic alkenyl compound units is 80% by mass or more Polymer block B: Conjugated diene units and aromatic alkenyl compound units are randomly contained. Aromatic alkenyl-conjugated diene copolymer block (2) The content of aromatic alkenyl compound units in the block copolymer is 55 % by mass or more and 61% by mass or less.
(3) The content of polymer block A in the block copolymer is 25% by mass or more.
(4) The hydrogenation rate of double bonds derived from the conjugated diene units in the polymer block B is 90 mol % or more.
(5) The mass average molecular weight (Mw) of the mixture of block copolymers is 180,000 or less.
(6) Contains terpene phenolic resins and/or organic lubricants. The laminated film according to claim 1, wherein the content of the terpene phenol resin in the adhesive resin composition is 1 to 50% by mass. The laminated film according to claim 2, wherein the terpene phenol resin is a hydrogenated terpene phenol resin. The laminated film according to any one of claims 1 to 3, wherein the content ratio of the organic lubricant in the adhesive resin composition is 0.1 to 2% by mass. 5. The laminated film according to claim 4, wherein the organic lubricant is ethylenebisstearic acid amide and/or calcium stearate. 6. The laminated film according to any one of claims 1 to 5, wherein the laminated film has a release layer on the side opposite to the adhesive layer of the substrate layer. 7. The laminated film according to claim 6, which is used for protecting the back surface of the prism sheet. ”.