JP2003113354A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film developing excellent adhesive force and workability of attachment also to a material to be protected having unevenness on the surface in a wide temperature area from a low temperature to a normal temperature. SOLUTION: In this surface protective film, a adhesive layer composed of an adhesive comprising 100 pts.wt. rubber-based polymer and 25-60 pts.wt. tackiness-imparting resin which is solid at a normal temperature and 0.5-50 pts.wt. tackiness-imparting resin which is liquid at a normal temperature is formed on either one surface of a support composed of a thermoplastic resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to, for example, a metal plate,
The present invention relates to a surface protection film suitable for surface protection of various materials such as coated steel plates, synthetic resin plates, decorative plywood, name plates, and glass plates. Incidentally, the surface protective film referred to in the present invention,
A surface protective sheet and a surface protective tape are also included.

[0002]

2. Description of the Related Art Conventionally, the surface of various materials (objects to be protected) such as metal plates, coated steel plates, synthetic resin plates, decorative plywood, name plates, and glass plates is protected (coated) with a so-called surface protection film. Therefore, it is widely practiced to prevent surface contamination and surface damage that tend to occur during transportation, processing, construction, etc.

Such a surface protective film is generally composed of
Support (base material) made of thermoplastic resin film or paper
It has a structure in which a pressure-sensitive adhesive layer made of various pressure-sensitive adhesives is formed on one surface, and when in use, the pressure-sensitive adhesive layer of the surface protection film is temporarily attached to the surface of the protected object, thereby protecting it. It has the function of protecting the surface of the body and preventing surface contamination and surface damage.

As the method for forming the pressure-sensitive adhesive layer, for example, a method of forming a pressure-sensitive adhesive layer by applying a solvent-type pressure-sensitive adhesive on a predetermined surface of a support and then removing the solvent in a drying step, or a hot method A method in which a melt-type pressure-sensitive adhesive is heat-melted and applied to a predetermined surface of a support and then the temperature is returned to room temperature to form a pressure-sensitive adhesive layer is widely used.

However, in the case of the former method using a solvent-type pressure-sensitive adhesive, it is necessary that each component constituting the pressure-sensitive adhesive is soluble in the organic solvent, and it is necessary to remove a large amount of the organic solvent in the drying step. Therefore, the equipment scale is large, and when the support is made of a polyolefin resin, the adhesive force (adhesion) of the solvent-based adhesive to the support is generally weak, so that for example, corona discharge is applied to a predetermined surface of the support in advance. There is a problem that it is necessary to perform surface treatment such as treatment or primer coating. Further, in the case of the latter method using a hot-melt adhesive, the hot-melt adhesive having a high cohesive force (elastic modulus) has a high melt viscosity, which makes coating difficult, and the support is a polyolefin. When the hot-melt pressure-sensitive adhesive is made of a system resin, the adhesive force of the hot-melt type adhesive to the support is generally weak, so that there is a problem in that a predetermined surface of the support needs to be subjected to the above-mentioned surface treatment in advance.

Various attempts have been made to address the above problems. For example, Japanese Patent Publication No. 58-30911 discloses a compound represented by the general formula -ABA- (where A is a homopolymer at 20 ° C). A styrene polymer block having the above glass transition temperature, and B is a conjugated diene polymer block), a block copolymer rubber alone or the rubber 100
An adhesive (adhesive) component having a specific adhesive force in a normal state obtained by adding 30 parts by weight or less of a tackifying resin to parts by weight and a heat capable of forming a film by melt extrusion, such as a polyolefin resin. Disclosed is a method for producing a surface protection film, which is obtained by melt-extruding a plastic resin to composite a film layer (support) and an adhesive layer (adhesive layer).

Further, Japanese Patent Publication No. 1-26389 discloses that
A styrene-diene block such as a styrene-butadiene block copolymer or a styrene-isoprene block copolymer in a composition containing a support resin made of polyethylene or polypropylene, an ethylene copolymer, a tackifying resin and a stabilizer. A method for producing a surface protective film is disclosed, in which a resin compound for a pressure-sensitive adhesive layer prepared by blending a copolymer is coextruded.

Further, in Japanese Unexamined Patent Publication (Kokai) No. 1-129085, a block copolymer of the general formula ABA (where A is styrene is provided on one side of a support made of a thermoplastic resin such as a polyolefin resin. A polymer block, B represents a butadiene polymer block, an isoprene polymer block or an olefin polymer block obtained by hydrogenating these), a tackifier resin, and a polyethyleneimine having a higher alkyl group introduced therein. Disclosed is a surface protective film having a pressure-sensitive adhesive layer formed by mixing and.

However, each of the surface protective films disclosed in the above publications has a low adhesive force to an object to be protected having unevenness (for example, center line average roughness Ra: 2 μm or more) on the surface, and particularly at low temperature (0 Since the adhesive strength at the time of application at around (° C.) is low, there is a problem that peeling easily occurs from a protected object having unevenness on the surface and the workability of application deteriorates especially in winter. As a method for dealing with the above problems, there is also a method of increasing the layer thickness of the pressure-sensitive adhesive layer to improve the anchoring property (anchor property) to the irregularities on the surface of the protected body,
This method is not a preferable method because the manufacturing cost is high.

[0010]

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide excellent adhesive force and sticking work even for a protected object having irregularities on its surface in a wide temperature range from low temperature to room temperature. The object is to provide a surface protective film exhibiting properties.

[0011]

The surface protective film of the present invention comprises, on one side of a support made of a thermoplastic resin, a tackifying resin 25- It is characterized in that a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive containing 60 parts by weight and 0.5 to 50 parts by weight of a tackifying resin which is liquid at room temperature is formed.

The thermoplastic resin constituting the support of the surface protective film of the present invention may be various thermoplastic resins conventionally used for the support of the surface protective film, such as low density polyethylene and medium density. Polyethylene resin such as polyethylene, high-density polyethylene, linear low-density polyethylene; ethylene-α-other than ethylene
Olefin copolymer; ethylene-ethyl acrylate copolymer, ethylene-n-butyl acrylate copolymer,
Examples thereof include ethylene-alkyl (meth) acrylate copolymers such as ethylene-methyl methacrylate copolymers; ethylene-vinyl acetate copolymers; polypropylene resins; α-olefin copolymers other than propylene-propylene. The copolymer may be a random copolymer or a block copolymer. Further, these thermoplastic resins may be used alone or in combination of two or more kinds.

Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 1-
Hexene, 4-methyl-1-pentene, 1-heptene,
1-octene etc. are mentioned. These α-olefins may be used alone or in combination of two or more kinds.

The thermoplastic resin constituting the support may be a crystalline nucleating agent such as benzylidene sorbitol or the like, if necessary, for example, in order to improve transparency and glossiness, as long as the object of the present invention is not hindered. , Filler, extender, softener (plasticizer), surfactant, coupling agent, antioxidant (aging inhibitor), heat stabilizer, light stabilizer, UV absorber, colorant, lubricant, antistatic One kind or two or more kinds of various additives such as agents and flame retardants may be added.

As a method for molding the support, for example, a thermoplastic resin composition comprising a thermoplastic resin and various additives added as necessary is prepared in advance by a conventional method,
This thermoplastic resin composition is melt-kneaded and extruded by an extruder, and is formed into a film (including a sheet) by using a T die, a circular die, or the like, or the thermoplastic resin composition is an organic solvent or the like. After dissolving or dispersing in the solvent of, the method of molding into a film by the cast method,
Examples include a method in which the thermoplastic resin composition and a pressure-sensitive adhesive used to form the pressure-sensitive adhesive layer described below are coextruded to simultaneously form the support and the pressure-sensitive adhesive layer at the same time. Any method may be adopted, but it is preferable to adopt the coextrusion method because it is excellent in productivity.

The support thus obtained may have a single-layer structure or a multi-layer structure of two or more layers.

The thickness of the support is not particularly limited, but is preferably 20 to 100 μm. When the thickness of the support is less than 20 μm, the strength of the obtained surface protection film and the peelability after use may be insufficient, and conversely, when it exceeds 100 μm, the flexibility of the obtained surface protection film and The conformability to the irregularities on the surface of the protected object may be insufficient.

The pressure-sensitive adhesive layer constituting the surface protective film of the present invention comprises 25 to 60 parts by weight of a tackifying resin which is solid at room temperature and 100% by weight of a rubber-based polymer and a tackifying resin which is liquid at room temperature. It is formed from a pressure-sensitive adhesive containing 0.5 to 50 parts by weight.

As the rubber-based polymer, various rubber-based polymers conventionally used for the pressure-sensitive adhesive layer of the surface protective film may be used, for example, natural rubber; styrene-
Synthetic rubber such as butadiene copolymer rubber, polyisoprene rubber, and butyl rubber; AB type block copolymer, AB
Examples thereof include block copolymers such as -A type block copolymers and ABC type block copolymers, and hydrogenated products thereof. These rubber-based polymers may be used alone or in combination of two or more kinds.

In the present invention, among the above rubber-based polymers, a group consisting of an AB type block copolymer, an ABA type block copolymer and an ABC type block copolymer is selected. At least one selected block copolymer which may be hydrogenated is preferably used,
Above all, ABC type block copolymers and hydrogenated products thereof are particularly preferably used. These block copolymers may be used alone or in combination of two or more kinds.

The above block copolymer has the general formula (AB)
n, (A-B) m-X, (A-B-A), (A-B-
A) m-X, (A-B-C), or (A-B-C) m-X.

In the above general formula, A is a vinyl aromatic compound polymer block, B is a random copolymer block of a vinyl aromatic compound and a conjugated diene, and C is a vinyl aromatic compound of the vinyl aromatic compound and a conjugated diene. A taper block with increasing amounts of compound is shown. In addition, n represents an integer of 1 or more,
m represents an integer of 2 or more, and X represents a coupling residue.

Examples of the vinyl aromatic compound include styrene, α-methylstyrene, vinyltoluene,
Examples include 1,1-diphenylethylene and the like, and among them, styrene and α-methylstyrene are preferably used.
These vinyl aromatic compounds may be used alone or in combination of two or more kinds.

The conjugated diene is a structure in which two ethylene bonds are directly bonded by a single bond (C = C-C =
Hydrocarbons having C), such as butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-
1,3-Butadiene and the like can be mentioned, but among them, butadiene and isoprene are preferably used. These conjugated dienes may be used alone or in combination of two or more.

In the present invention, the constitutional ratio (weight ratio) of the vinyl aromatic compound and the conjugated diene in the block copolymer is preferably 3/97 to 50/50, more preferably 5/95. -40 to 60/60, particularly preferably 5/95 to 25/75.

If the composition ratio (weight ratio) of the vinyl aromatic compound and the conjugated diene is less than 3/97, the cohesive force of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) will be insufficient, and after use. When the surface protection film is peeled off from the protected object, cloudiness or adhesive residue may occur on the surface of the protected object. On the contrary, when the above composition ratio (weight ratio) exceeds 50/50, the resulting pressure-sensitive adhesive (adhesive The adhesiveness (tack) or adhesive force of the agent layer) may be insufficient, and the workability of sticking the surface protective film to a protected object having irregularities on the surface may be impaired.

The total content of vinyl aromatic compounds in the vinyl aromatic compound polymer blocks (A) and (C) constituting the above block copolymer is preferably 2 to 20% by weight.

The hydrogenation rate of the double bond of the conjugated diene moiety in the random copolymer block (B) is preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95. ~ 100 mol%.

If the hydrogenation rate is less than 80 mol%, the resulting pressure-sensitive adhesive (pressure-sensitive adhesive layer) may have insufficient thermal stability and weather resistance.

The above block copolymer preferably has a polystyrene equivalent weight average molecular weight of 50,000 to 400,000, more preferably 80,000 to 200,000.

When the weight average molecular weight is less than 50,000,
The cohesive force of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) becomes insufficient, and when the used surface protection film is peeled from the protected object, clouding or adhesive residue may occur on the protected object surface, On the other hand, when the weight average molecular weight exceeds 400,000, the adhesiveness (adhesive layer) of the resulting pressure-sensitive adhesive (adhesive layer) becomes insufficient, and in particular, the sticking of the surface protective film to a protected object having irregularities on the surface. Workability may be hindered.

The tackifying resin which is solid at room temperature and is contained in the pressure-sensitive adhesive used in the present invention includes, for example, aliphatic petroleum resin, alicyclic petroleum resin, aromatic petroleum resin, rosin resin, Examples thereof include terpene-based resins, phenol-based resins, xylene-based resins, coumarone-indene-based resins and hydrogenated products thereof. These tackifying resins that are solid at room temperature may be used alone or in combination of two or more.

The tackifying resin which is solid at room temperature preferably has a softening point of 100 to 150 ° C. When the softening point is less than 100 ° C, the heat resistance of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) may be insufficient, and conversely, when it exceeds 150 ° C, the glass of the pressure-sensitive adhesive (pressure-sensitive adhesive layer) obtained. The transition point may increase, and the adhesive strength and the workability of sticking of the surface protective film to the object to be protected at low temperatures may become insufficient.

In the pressure-sensitive adhesive used in the present invention, it is necessary that 25 to 60 parts by weight of the tackifying resin which is solid at room temperature is contained with respect to 100 parts by weight of the rubber-based polymer. Is 30 to 50 parts by weight.

When the above content is less than 25 parts by weight, the adhesiveness (adhesive layer) of the resulting adhesive (adhesive layer) may be insufficient in adhesiveness or adhesive force to the object to be protected, and conversely exceeds 60 parts by weight. If so, the elastic modulus of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) becomes too high, and the adhesive force and sticking workability of the surface protection film to the object to be protected at low temperature may become insufficient.

Examples of the tackifying resin which is liquid at room temperature contained in the pressure-sensitive adhesive used in the present invention include, for example, liquid rosin resin, liquid terpene resin, liquid xylene resin,
Examples include liquid alicyclic petroleum resins and hydrogenated products thereof. These tackifying resins that are liquid at room temperature may be used alone or in combination of two or more.

Examples of the liquid rosin resin include
Examples of the liquid include gum rosin, wood rosin, dimerized rosin, polymerized rosin, disproportionated rosin, and hydrogenated products thereof.

As the liquid terpene resin,
Examples thereof include terpene resins, terpene-phenol copolymers, terpene-styrene copolymers, and hydrogenated products thereof.

The tackifying resin which is liquid at room temperature is 25
The viscosity at 0 ° C. is preferably 5 to 100 Pa · s, more preferably 10 to 50 Pa · s. If the viscosity of the tackifying resin that is liquid at room temperature is less than 5 Pa · s, the tackifying resin has too low a molecular weight, and the tackifying resin bleeds from the resulting tackifier (tack layer) over time. Out and may contaminate the surface of the protected object,
On the other hand, when it exceeds 100 Pa · s, the elastic modulus of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) at a low temperature does not sufficiently decrease, and the adhesive strength and sticking workability of the surface protective film to a protected object at a low temperature are poor. May be sufficient.

The pressure-sensitive adhesive used in the present invention must contain 0.5 to 50 parts by weight of the tackifying resin which is liquid at room temperature with respect to 100 parts by weight of the rubber-based polymer. , Preferably 1 to 40 parts by weight.

When the above content is less than 0.5 part by weight,
The adhesiveness of the obtained pressure-sensitive adhesive (pressure-sensitive adhesive layer) or the pressure-sensitive adhesive force to the object to be protected at low temperature may be insufficient. On the contrary, when it exceeds 50 parts by weight, the pressure-sensitive adhesive obtained (pressure-sensitive adhesive layer)
Therefore, the tackifying resin may remarkably bleed out over time, resulting in a decrease in the adhesive force with respect to the object to be protected or the cohesive force of the adhesive layer, or contamination of the surface of the object to be protected.

In the pressure-sensitive adhesive used in the present invention, in addition to the rubber-based polymer which is an essential component, the tackifying resin which is solid at room temperature, and the tackifying resin which is liquid at room temperature, the range which does not hinder the achievement of the object of the present invention. If necessary, for example, a peelability adjusting agent, a filler, a filler, a softening agent (plasticizer), a surfactant, a coupling agent, an antioxidant (antiaging agent), a light stabilizer, an ultraviolet absorber. One or more kinds of various additives such as a colorant, a lubricant, an antistatic agent, and a flame retardant may be added.

The form of the above-mentioned pressure-sensitive adhesive is not particularly limited, and may be any form such as solvent-type pressure-sensitive adhesive, emulsion-type pressure-sensitive adhesive, hot melt-type pressure-sensitive adhesive and the like. Further, the above-mentioned pressure-sensitive adhesive may be a non-crosslinking type pressure-sensitive adhesive, may be a cross-linking type pressure-sensitive adhesive, may be a one-pack type pressure-sensitive adhesive, or is a multi-liquid pressure-sensitive adhesive of two or more liquids. May be

As the method for producing the surface protective film of the present invention, for example, an ordinary coating machine such as a roll coater is used to directly coat an adhesive on a predetermined surface of the support,
A direct coating method in which after the steps such as drying and cooling are formed as necessary, the pressure-sensitive adhesive layer is formed, and then the release-treated surface of the release material such as release paper or release film is laminated on the pressure-sensitive adhesive layer, if necessary. After forming a pressure-sensitive adhesive layer on the release-treated surface of the release material in the same manner as described above, this pressure-sensitive adhesive layer is laminated on a predetermined surface of the support, and the pressure-sensitive adhesive layer is formed on the predetermined surface of the support. Transfer method for transferring, extrusion laminating method for forming a pressure-sensitive adhesive layer by extruding and laminating a pressure-sensitive adhesive on a predetermined surface of a support, co-extrusion of a thermoplastic resin for a support and a pressure-sensitive adhesive for a pressure-sensitive adhesive layer Examples of the method include a co-extrusion method in which molding of the support and formation of the pressure-sensitive adhesive layer are simultaneously performed. Either method may be adopted, but the co-extrusion method is adopted because of excellent productivity. It is preferable. The predetermined surface of the support may be subjected to surface treatment such as corona discharge treatment, plasma discharge treatment, and primer coating in advance in order to enhance the adhesiveness of the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer constituting the surface protective film of the present invention preferably has a shear storage elastic modulus at a frequency of 10 Hz of 15 MPa or less at 0 ° C. When the shear storage elastic modulus exceeds 15 MPa, the adhesive strength of the surface protective film to a protected object having irregularities on the surface at low temperature may be insufficient. Further, the pressure-sensitive adhesive layer preferably has a shear storage elastic modulus at a frequency of 10 Hz of 0.2 to 0.9 MPa at 23 ° C.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 3 to 50 μm. When the thickness of the pressure-sensitive adhesive layer is less than 3 μm, the obtained surface protection film may have insufficient tackiness or tackiness,
On the other hand, when it exceeds 50 μm, when the obtained surface protection film is used and peeled from the protected object, clouding or adhesive residue may occur on the surface of the protected object.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION The following examples are given to illustrate the present invention in more detail, but the present invention is not limited to these examples.

Example 1 A polyethylene resin (trade name "Mirason 16", melt flow rate: 3.7 g / 10 minutes, manufactured by Mitsui Chemicals, Inc.) was prepared as a thermoplastic resin for a support. Further, as a rubber-based polymer, an ABC type block copolymer (total styrene bond content: 10% by weight, styrene bond content of block A and block C: 4.5% by weight, a conjugated diene moiety in block B Vinyl bond content: 80% by weight, weight average molecular weight: 250,000) 100 parts by weight, alicyclic hydrogenated petroleum resin (trade name "ALCON P100", manufactured by Arakawa Chemical Industry Co., Ltd.) as a tackifying resin that is solid at room temperature. 40 parts by weight, tackifying resin that is liquid at room temperature (trade name "Clearon LH", viscosity at 25 ° C: 13 Pa
s, manufactured by Yasuhara Chemical Co., Ltd.) and 5 parts by weight of an antioxidant (trade name “Irganox 1010”, manufactured by Ciba Specialty Chemicals Co., Ltd.) were prepared to prepare an adhesive pellet for a pressure-sensitive adhesive layer.

Then, using a co-extruder (T-die method),
Two-layer coextrusion of the polyethylene resin "Mirason 16" for the support and the pressure-sensitive adhesive pellets for the pressure-sensitive adhesive layer obtained above was carried out to obtain a support having a thickness of 50 μm and a pressure-sensitive adhesive layer having a thickness of 1
A surface protection film having a thickness of 0 μm and a total thickness of 60 μm was produced.

(Examples 2 and 3) and (Comparative Examples 1 to 3) In the same manner as in Example 1 except that the adhesive pellets for the adhesive layer had the composition shown in Table 1. A surface protection film was produced.

Frequency 1 of the pressure-sensitive adhesive layer of the surface protective films obtained in Examples 1 to 3 and Comparative Examples 1 to 3
The shear storage elastic modulus at 0 ° C. at 0 Hz was determined by the following method. The results are shown in Table 1. [Method of measuring shear storage modulus] Using a dynamic viscoelasticity spectrum measuring instrument (manufactured by Iwamoto Seisakusho), frequency: 10 Hz,
Temperature rising rate: 3 ° C / min, temperature range: -50 ° C to + 120 ° C
The shear storage elastic modulus was measured under the conditions of, and the shear storage elastic modulus at 0 ° C. was obtained.

The performance of the surface protective film (0
The adhesive strength at 0 ° C and the adhesive strength at 23 ° C) were measured by the following methods. The results are shown in Table 1.

Adhesive strength at 0 ° C .: PVC laminate steel sheet-I (center line average roughness Ra: 7.4 μ) as a protected object
m, surface gloss: 4%) and PVC laminated steel sheet-I
I (center line average roughness Ra: 4.2 μm, surface gloss: 7)
%), And in a 0 ° C. atmosphere, a surface protection film having a width of 25 mm is applied to the above-mentioned two types of protected objects.
After sticking with a pressure roller of 300 kg at a speed of 300 mm / min and left for 60 minutes, JIS Z 0237
18 in accordance with "Adhesive tape / adhesive sheet test method"
The 0 degree angle peel strength was measured.

Adhesive strength at 23 ° C .: The same operation as in the case of 23 ° C.-65% RH was carried out to obtain 18
The 0 degree angle peel strength was measured.

[0055]

[Table 1]

[0056]

The surface protective film of the present invention has a pressure-sensitive adhesive layer formed on one surface of a support made of a thermoplastic resin, and the pressure-sensitive adhesive layer has a specific amount of a rubber-based polymer. As the tackifying resin, a tackifying resin that is solid at room temperature and a tackifying resin that is liquid at room temperature are used in combination, and since it is formed from a pressure-sensitive adhesive containing each specific amount thereof,
In a wide temperature range from low temperature to room temperature, excellent adhesive force and sticking workability are exhibited even for a protected object having irregularities on the surface.

At least one selected from the group consisting of an AB type block copolymer, an ABA type block copolymer and an ABC type block copolymer as the rubber-based polymer. Of the optionally hydrogenated block copolymer, a tackifying resin having a specific viscosity at 25 ° C. as a liquid tackifying resin at room temperature, or 0 ° C. of the adhesive layer. The above-mentioned performance is further improved by setting the shear storage elastic modulus (frequency: 10 Hz) in 1 to a specific value.

As described above, the surface protective film of the present invention exhibits excellent adhesive strength and workability for sticking to a protected object having irregularities on its surface in a wide temperature range from low temperature to room temperature. Therefore, for example, it is suitably used for surface protection (surface coating) of various materials (objects to be protected) such as metal plates, coated steel plates, synthetic resin plates, decorative plywood, name plates, and glass plates.

Continued front page    F term (reference) 4F100 AK01A AK04 AK11B AK11J                       AK12J AK28B AK28J AL02B                       AN02B BA02 BA07 CA06                       CA16B EH20 JA06B JB16A                       JK07B JL00 JL13B YY00B                 4J004 AA05 AA17 AB01 AB03 CA03                       CA04 CC03 CD01 CD08 FA04                       FA08                 4J040 BA202 CA011 CA081 CA091                       DA141 DB051 DK012 DM011                       DN032 EB031 JA09 JB09                       KA26 NA12 NA20 PA23

Claims (4)

[Claims] 1. A tackifying resin which is solid at room temperature and 25 to 60 parts by weight and a liquid tackifying resin at room temperature with respect to 100 parts by weight of a rubber polymer on one surface of a support made of a thermoplastic resin. A surface protective film comprising a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive containing 0.5 to 50 parts by weight. 2. The rubber-based polymer comprises an AB type block copolymer, an ABA type block copolymer and an AB type block copolymer.
C-type block copolymer (where A is a vinyl aromatic compound polymer block, B is a random copolymer block of a vinyl aromatic compound and a conjugated diene, and C is a vinyl aromatic compound and a conjugated diene). Group compound showing a gradually increasing tapered block), which is at least one optionally hydrogenated block copolymer selected from the group consisting of vinyl aromatic compounds in the block copolymer before hydrogenation. The surface protection film according to claim 1, wherein the composition ratio (weight ratio) of the group compound and the conjugated diene is 3/97 to 50/50. 3. The surface protective film according to claim 1, wherein the tackifying resin which is liquid at room temperature has a viscosity at 25 ° C. of 5 to 100 Pa · s. 4. The surface protective film according to claim 1, wherein the pressure-sensitive adhesive layer has a shear storage elastic modulus at a frequency of 10 Hz of 15 MPa or less at 0 ° C.