JP3116110B2 - Surface protection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film to be temporarily attached to a surface of a resin plate, a metal plate or the like. In particular, there is no change in the adhesive function such as an increase in the adhesive strength when subjected to a high temperature (for example, 100 to 160 ° C.) processing or an ultraviolet curing processing, or a decrease in the adhesive strength. Has the feature of stably protecting the adherend without contaminating it. In addition, it has a feature that it has an appropriate adhesive strength to a non-smooth adherend having an uneven surface and also protects the adherend similarly without causing contamination.

[0002] Surface protective films are exposed to various environments and conditions following processing steps such as coating and thermoforming in addition to surface protection during transport and transportation. Among them, high temperature conditions,
In particular, the temperature is often higher than the melting point of the surface protective film. Perform surface processing such as coating on a base material such as a resin plate,
Treat in a drying oven to evaporate the solvent and dispersant. At this time, the substrate surface that is not coated is processed with the surface protective film in close contact with it to prevent damage. In addition, UV-irradiated cured paints are used for environmental protection. The surface protective film of the present invention can withstand such a load applied during processing.

In some cases, the surface of a resin plate or a metal plate has a predetermined three-dimensional shape from the viewpoint of handling properties, surface appearance, optical functions (scattering and transmission), and the like. It is very difficult to apply the surface protective film to such rough or uneven surfaces. If the viscosity and plasticity of the adhesive layer are increased so as to follow the three-dimensional space, the cohesive force of the adhesive layer decreases, and contamination due to layer destruction (glue) The rest) occur. In addition, slip between the adhesive layer and the base layer is reduced,
Causes blocking. The surface protective film of the present invention stably adheres to such a non-smooth adherend, and has the characteristics of not causing contamination, slip reduction and blocking.

[0004]

2. Description of the Related Art A surface protective film is required to have a light adhesive strength that can easily be peeled off after finishing the surface protective function while maintaining an adhesive function that can withstand severe use conditions. Moreover, it is required that the adherend should not be contaminated, and that no trace of the surface protective film should be left on the plate. When used for optical purposes, it is strictly required not to contaminate. Contamination is mainly caused by material transition (including compound transition and cohesive failure transition) of the surface protective film. The surface protective film must simultaneously satisfy active and inactive functions as material properties. When the base layer and the adhesive layer are manufactured by an extrusion process, especially in the co-extrusion process, materials are limited and a high level of technology is required. Various contrivances are required to fulfill the contradictory performance requirements. The surface protective film must be tightly adhered to the adherend in order to fulfill the protective function, and when affixed to the adherend, the planar shape of the surface protective film must not be deformed. Take measures to prevent the adhesive layer and substrate layer from blocking and to provide an appropriate degree of slipperiness so that the shape when rolled is not distorted and the film can be easily rewound from the roll. . In order to simultaneously satisfy both the active function and the inactive function as materials, the surface protective film has been repeatedly devised by using a non-polar material mainly composed of polyolefin to maintain stable adhesive strength.

For application to rough surfaces and uneven surfaces, various rubbers or elastomers are used for the adhesive layer. For example, natural rubber, acrylate copolymers, styrene butadiene copolymers (SBR, SBS, SEBS, etc.) ),
Ethylene copolymers (EPR, EBR, etc.) are available, but have problems such as contamination of the adherend due to cohesive failure of the adhesive layer, blocking between the adhesive layer / substrate layer, and reduction in slip.

The use of an ethylene-α-olefin copolymer (linear low-density polyethylene) for improving the function of the pressure-sensitive adhesive layer of a surface protective film has been conventionally proposed. -47886, 4-
55488, 5-229080, 5-239420, 5
-30068. The properties of the ethylene-α-olefin copolymers described in these articles are density and viscosity (M
I, MFR) are specified, but nothing is mentioned about the melting point and melting behavior, which are the material constituent requirements of the present invention. In addition, ethylene-
α-olefin copolymer, compared to the material used in the present invention,
The melting point is relatively high for the same density contrast, and the constituent requirements are different, such as showing a plurality of peaks in the melting curve. Therefore, there is a limit in the expression of functions, and the features intended by the present invention cannot be achieved.

[0007]

Since the surface protective film simultaneously satisfies the contradictory functions, it is difficult to fulfill the required functions with a unique material constitution. The prior art remains in a one-sided area in the search for constituent materials. For this reason, only a part of the required function is achieved, and the function that is opposite to the achieved function remains unfinished. A plurality of intersecting properties cannot be satisfied simultaneously.

[0008] The surface protective film has various use conditions in practical use, and the purpose can be achieved only when it can be industrially smoothly and easily handled in each practical condition. For this purpose, it is necessary to take measures not only for the function relating to the adhesion but also for the performance relating to the handling of the surface protective film, for example, the interrelation between the adhesion layer and the back layer, for example, the slipperiness and the blocking property. However, if an attempt is made to improve the performance related to handling, the original adhesive function is impaired. In particular, when the function under high temperature processing conditions, that is, the function to prevent contamination and deformation during molding, is satisfied, the handling properties of the film, the slipperiness between the adhesive layer and the back layer, the blocking property and the retention of the form of the film, the maintenance of the flatness are maintained. Can not be satisfied. When the film is wound around the surface protection film roll, a distortion is generated, and a part of the roll is deformed, so that the surface protection film is deformed or an extra force is required when the film is pulled out from the roll, resulting in deformation of the film.

An object of the present invention is to optimize and consolidate the constitutional requirements of a surface protective film having an adhesive layer made of an ethylene-α-olefin copolymer from various aspects, and to cover a wide range of use conditions, for example, heating, ultraviolet irradiation. In thermoforming,
To provide a surface protection film that satisfies the characteristics that the adhesive strength does not increase and does not contaminate the adherend, is easy to handle, does not distort the film, and makes the most of its functions. is there.

[0010]

The present invention solves such a problem.
To solve the problem, the following means are adopted. Sand
Chi, surface protective film of the present invention consists of a composite form of the adhesive layer and the substrate layer, the adhesive layer, density from 0.860 to 0.9
20, melting point 6 from 0 to 115 ° C., the melting curve was obtained a single peak by differential scanning calorimetry - ethylene -α- olefin copolymer showing a click, a range tackifier following 40 wt%
It is characterized by being composed of a compound that contains it
Things.

[0011]

Next, the present invention will be described in more detail. (1) Adhesive Layer (1) In order to exhibit the effects aimed at by the present invention, the adhesive layer must be chemically and physically aggregated and satisfy the performance. The relationship between the function of the adhesive layer and the material properties is summarized as follows. a. Chemical interaction between adherend and adhesive layer (adhesive element, etc.)
To control the chemical composition of the material is defined. The ethylene-α-olefin copolymer used in the present invention is chemically inert and hardly causes an increase in adhesion to an adherend. b. An appropriate physical interaction exists between the adherend and the adhesive layer, and a predetermined adhesive force must be maintained. For rough surface adherends variable塑的behavior of the polymer in room temperature it is important.

The physical properties of the polymer are related to viscoelasticity, crystallinity, and thermodynamic properties (such as transition properties in the vicinity of room temperature under practical conditions). In particular, uniformity of the composition distribution and molecular weight distribution of the polymer is important. It is important that the ethylene-α-olefin copolymer used exhibits a distinct single melting peak.

In the ethylene-α-olefin copolymer, the molecular structure (molecular weight, molecular weight) such as the length and distribution of the main chain and side chains (the status of short-chain and long-chain branching species and their degree of branching), and the composition distribution. , Composition distribution.) Form the properties of the polymer.

In the present invention, it has been found that density, melting point, and melting behavior are effective for defining a preferable physical interaction of the ethylene-α-olefin copolymer. The melting point is the melting point of the crystalline substance, but ethylene-α-
In the case of the olefin copolymer, if the density and the melting point are specified, the behavior of the polymer at room temperature using a surface protective film can be controlled. (2) Density 0.860-0.920, melting point 60-115
° C, melting curve obtained by differential scanning calorimetry
It has been found that the use of an ethylene-α-olefin copolymer exhibiting the effect of the present invention achieves the desired effects of the present invention, but the density and melting point of the copolymer fall below the lower limits of the preferred ranges. If the surface of the adherend is contaminated and exceeds the upper limit of the preferred range, the adhesion to the adherend decreases, or the ability to follow thermoforming deteriorates. (3) The ethylene-α-olefin copolymer used in the present invention is a polymer having a lower melting point at the same density versus the same density as polymers conventionally introduced as an adhesive layer of a surface protective film. The relationship between density (D) and melting point (Tm)
Density 0.860 to satisfy Tm ≦ 400D-256
A polymer having a melting point of 0.920 and a melting point of 60 to 112 ° C can be more preferably used.

When the relationship between the density and the melting point is compared with that of the prior art, the ethylene-α-olefin copolymer of the prior art has a melting point of a plurality of peaks, so that the highest melting point among the main peaks is representative. And (4) The ethylene-α-olefin copolymer having the properties used in the present invention can be synthesized by using a single-site catalyst having a single active site. Although synthesis is possible with a multi-site catalyst, a single-site catalyst is easier to control the polymer structure.

An example of a single-site catalyst is a metallocene. A compound having a structure in which a transition metal is sandwiched between π-electron unsaturated cyclic compounds, such as a combination of zirconocene dichloride and methylaluminoxane (a Kaminski catalyst). In some cases, a boron compound is used as a promoter. On the other hand, a multi-site catalyst represented by a Ziegler catalyst has a plurality of active sites, so that the polymer structure is distributed and dispersed, and the ethylene-α-olefin copolymer having the polymer structure defined in the present invention is used. It is difficult to get. The polymer synthesized by the present catalyst generally shows a plurality of melting peaks. The Ziegler catalyst is a catalyst comprising a system in which a metal organic compound of Groups I, II, and III (excluding boron) is used as one component and a metal compound of Groups IV to VIII is used as another component. A typical example is a system composed of a trialkylaluminum and titanium (IV) chloride.

The ethylene-α-olefin copolymer used in the present invention has a highly linear and homogeneous polymer structure, and the branches are composed of a homogeneous short chain. However, a polymer in which a small amount of long-chain branching is introduced into the linear structure under control may have excellent melt fluidity and may be preferably used. Various processes can be used for synthesizing the ethylene-α-olefin copolymer that can be used in the present invention. One example is shown in, for example, Published Patent Publication 7-500622.

The chemical structure of the α-olefin which is a comonomer of the copolymer is not particularly limited.
1, hexene-1, 4-methylpentene-1 and octene-1.

The properties of the desired polymer can be adjusted by the type of copolymer and the copolymerization amount. For example, in the case of octene-1, the desired properties can be obtained in a copolymerization amount of 7 to 30 wt%. (5) The present invention relates to a method in which the ethylene-α-olefin copolymer is combined with a tackifier.
Prevention of contamination of body and prevention of blocking of film roll
It is important in terms of gender. Such tackifiers, terpene compounds and rosins are preferably used. Take
The amount to ethylene -α- olefin copolymer tackifier, pollution and film B adherend - over Le antiblocking, preferably within 40 wt%, further
Particularly preferably, the content is 6 to 40% by weight . Such Te Lupe <br/> emission compound, with oligomers of isoprene, a glass transition temperature of 30 to 100 ° C., a softening temperature of 30 to 150 ° C.
Of and polyterpenes, its hydrogenated product (hydrogenated terpene resin), further as a modified product, terpene styrene resin, terpene phenol - can be used like Le resin. What
Incidentally, structural units of such polyterpenes include α-pinene, β-pinene, dipentene and the like .

[0020] As the rosins, rosin, polymerized rosin, and hydrogenated rosin, its modified product, a derivative, glycerin esters of rosin or hydrogenated rosin, pentaerythritol esters and the like can be used. (6 ) Other components include the following elastomers and pseudo-elastomer
May be contained. For example, styrene butadi
Ene styrene (SBS), styrene isoprene stainless
Tylene (SIS), styrene / ethylene / butylene /
Styrene-based thermoplastic elastomer such as styrene (SEBS)
Toma, butadiene rubber, styrene-butadiene rubber,
Olefin rubbers such as 1,2-polybutadiene,
In addition, ethylene-α-olefin copolymer, multi-component (ternary
Etc.) Contains copolymer elastomers and pseudo-elastomer
It may be. Here, examples of the α-olefin include
Ebae styrene, propylene, butene-1, pentene -
1, hexene-1, octene-1 etc. can be used
it can. Examples of the copolymer include ethylene
Pyrene (random) copolymer, ethylene butene-1
(Random) copolymers and the like can be used.

Further, such other components may include other polyolefins, polymers of olefin copolymers, aliphatic compounds or cyclic compounds.

When the density and melting point of the ethylene-α-olefin copolymer of the present invention are in the lower limit range, other polyolefins and olefin copolymers can be blended to adjust the adhesion and roll blocking. A material having good compatibility and a small swell ratio for maintaining the adhesive function can be preferably used. (7) When using low-molecular compounding agents, keep the amount to the minimum necessary. Unnecessary mixing causes undesired contamination of the adherend. The amount of the antioxidant to be compounded for the extrusion process is limited to the minimum necessary for maintaining the surface shape specified in the present invention as a primary purpose. Low-density polyethylene often has good thermal stability of the polymer and does not require the addition of an antioxidant. However, ethylene-α-olefin copolymers have low viscosity loss under shear load and have poor thermal stability. However, it becomes rougher than the specified surface shape. The content of the stabilizer is 500 to 3,000 for the antioxidant.
0 ppm is preferred. If the lower limit is exceeded, the prescribed surface shape cannot be maintained due to polymer crosslinking, and if the upper limit is exceeded, the adherend is contaminated. In addition, a neutralizing agent is required to contain the catalyst residue, but the amount is preferably 1,000 ppm or less. Antioxidants act to scavenge radicals and decompose peroxides, but their structures are phenol-based, aromatic amine-based, thioether-based, phosphorus-based, etc. These may be used in combination. For example, there is a combination of a phenol type and a phosphorus type. (8) The addition of a so-called organic lubricant to the pressure-sensitive adhesive layer is not preferable because it makes the adhesion to the adherend unstable or causes contamination. From this point of view, attention must be paid to the neutralizing agent for the synthesis catalyst residue. As the neutralizing agent, calcium stearate is generally used, but tends to be a source of adherend contamination. Magnesium chloride / aluminum hydrocarbonate (hydrotalcite) is preferred. (9) The surface shape of the pressure-sensitive adhesive layer has a center line average roughness of 0 . Preferably, it is less than 10 microns and the maximum roughness is less than 0.50 microns. (2) Base material layer (1) The material of the base material layer is not particularly limited, but polyethylene and / or ethylene-α-olefin copolymer can be preferably used. When an ethylene-α-olefin copolymer is used, it is preferable that the copolymer has a smaller amount of comonomer and a higher density than those used for the adhesive layer. The same product as the ethylene-α-olefin copolymer used in the adhesive layer can be blended, but the blending amount is preferably within 30% by weight in view of surface characteristics such as slippage. The blending of the ethylene-α-olefin copolymer is effective for improving the fluidity during extrusion and adjusting the stiffness. (2) It is preferable to adjust the function of the base material layer by mixing two or more materials. Density: 0.
If polyethylene having a swell ratio of 1.6 or less is used, the surface of the base material layer has an appropriate rough surface shape, which is preferable for blocking and sliding. The swell ratio is the ratio of the extrudate diameter to the nozzle diameter when the polymer is extruded from a nozzle having a constant diameter in a molten state under a constant pressure and cooled and solidified. The swell ratio is determined by the molecular weight distribution and the state of branching of the polymer, and for example, a large swell ratio can be obtained when there are many long-chain branches and the molecular weight distribution is wide. In the process of producing polyethylene, a polymer having such characteristics can be obtained by an autoclave method under high pressure. The swell ratio affects the physical properties of the film during film formation (such as draft orientation) and affects the behavior during melting of the film (such as melt tension). Therefore, it is preferable to control and use the polymer having the selected swell ratio. (3) It is important to keep the amount of organic low-molecular compounding agents in the substrate layer to the minimum necessary. If it is added more than necessary, it causes contamination of the adherend. The surface conditions involved in slipping and blocking are largely determined by the polymer requirements. As a compounding agent that can be preferably used for fine adjustment, there are fine particles of an inorganic compound, such as silicon dioxide, calcium carbonate, and zeolite. Such particles obtained industrially are in a dispersed state, but preferably have a maximum diameter of 10 μm or less and an average diameter of 2 to 5 μm. (4) The base layer has a center line average roughness of 0.02 to 0.30 μ,
In addition, it is preferable to satisfy a surface shape having a maximum roughness of 0.30 to 1.50 μm from the viewpoint of excellent film handling function and suppression of blocking. (5) In the present invention, the various functions of the base layer are not expressed as effects of the base layer alone, but are expressed in connection with the function of the adhesive layer. (3) Viscosity of Polymer The viscosity of the polymer used in the present invention is not particularly limited, but is preferably in the range of 1 to 20 in melt index (MI) or melt flow rate (MFR). (4) Film-forming method The film-forming method of the present invention is not particularly limited, but an extrusion method (single-layer extrusion, multiple-layer extrusion), an extrusion laminating method and the like can be adopted, but a multilayer-layer extrusion method is preferable. . The extrusion method includes a T-die method and an inflation method, but the T-die method is preferred from the viewpoint of controlling the surface shape.

In the case of the T-die method, when the air knife or air chamber casting method is adopted, a prescribed surface shape can be achieved by adjusting the following conditions. B.Optimal combination of extrusion temperature / extrusion amount / drawing speed b.Casting drum temperature c.Distance between die and casting drum / atmospheric temperature of draft path d.Air-temperature / air flow / wind speed e. (Smooth, rough surface) (5) Measurement and evaluation method of material properties and surface protective film properties (1) Melting curve of ethylene-α-olefin copolymer Differential scanning calorimeter (Shimadzu Corporation, thermal analyzer DT-4
0) under the following conditions. The melting peak employs the measurement of the second stage. First stage: The temperature is raised to 150 ° C. at a rate of 10 ° C./min. Then, it is air-cooled to 25 ° C. at room temperature (23 ° C.) in the measurement chamber. Second stage: The temperature is raised to 150 ° C. at a rate of 10 ° C./min, and the melting curve is measured. The AMP-RANGE of the recording is 10 mj / s. (2) Attachment of sample film A sample film was put on a plastic plate with a rubber roll (3 kg /
(50 mm). After pasting, the film is cut to have the same dimensions as the board.

After being left in a constant temperature room at 23 ° C. for 24 hours, it is used for each measurement and evaluation. (3) Adhesive Properties As the plastic plate, a mirror plate having a thickness of 0.5 mm was used as a polycarbonate plate (Ra: 0.03 μ, Rt: 0.36 μ). As the rough plate, a polycarbonate plate having Ra: 0.9 μ and Rt: 2.2 μ was used. A, Adhesive Strength Under normal temperature conditions, the sample prepared by the above method was peeled 180 ° at a tensile speed of 300 m / min using a tensile tester, and the peel strength was determined as the adhesive strength. For the high-temperature characteristics, the sample prepared by the above method is suspended by clipping one end in an oven set at 120 ° C., left for 30 minutes, taken out, and then subjected to a peeling test in the same manner. The unit is g / 50 mm. B. Adhesion The sample prepared by the above method was subjected to the conditions of 23 ° C. and 12
The following observation was made on the condition left in the oven set at 0 ° C., and the condition was evaluated.

The following judgment is made by visually observing the adhesion between the plastic plate and the film. ：: Completely adhered △: Very small part of poor adhesion and part of film floating (within area ratio, within 30%) ×:
The film floats at a portion of 70% or more. (4) Thermal processing model test A, Observation of contamination of adherend The test piece on which the sample film was attached was placed at 120 ° C for 30 minutes.
The sample film is peeled off after standing for minutes. A spot light is applied to the surface of the adherend in a dark room, and the state of contamination on the surface is visually observed. Judgment ○: No contamination, △: Slight contamination, ×:
Contaminated B, thermoforming A film is stuck by the above method using an acrylic plate having a thickness of 2 mm.

The prepared sample was suspended in an oven set at 140 ° C. with one end clipped, left for 5 minutes, and then taken out. After peeling off the sample film, the surface of the adherend is exposed to light in a dark room, and the deformation state (such as a dent) of the plate is visually observed at an angle of 45 degrees. Judgment ○: No deformation, △: Slight deformation, ×:
Deformation C, blocking property Two sample films were laminated with a base material layer and an adhesive layer and 42 g /
A load of 2 cm was applied, left under a condition of a temperature of 40 ° C. and a relative humidity of 84% for 24 hours, taken out, and peeled off by a tensile tester at a tensile speed of 300 mm / min. The unit is g
/ 12cm {2}. The following judgment is made based on the value of the peeling force. Judgment ：: peeling force 300 or less, Δ: 300 to 700,
X: 700 or more However, even when the peeling force is within each of the judgment values of ○ or △, if the substrate layer or the adhesive layer is damaged due to cohesive failure or the like, ×.
And (5) Surface roughness The surface roughness is a three-dimensional representation of the surface shape, and can be obtained by analyzing a roughness profile (roughness curve) measured by a commonly used surface shape measuring instrument.

Center line average roughness: A portion having a measurement length 1 is extracted from the roughness curve in the direction of the center line (Ra). The center line of the extracted portion is defined as the X axis, and the direction of the longitudinal magnification is defined as the Y axis. When the roughness curve is represented by Y = f (x), Ra given by Expression 1 is represented in micron units.

[0028]

(Equation 1)

Maximum roughness: The distance between the maximum peak and the deepest valley within the measured length of the roughness curve, expressed in (Rt) microns. (6) Adherend As the adherend, a wide range of materials such as a resin plate and a metal plate can be used .
Can be used . Here, the term “ mirror plate ” as used in the present invention means that the center line average roughness is less than 0.1 μm and the maximum roughness is 0.1 μm.
An adherend having a surface shape of less than 5 μ is shown, and a rough surface plate is an adherend having a surface shape having a center line average roughness of 0.1 μ or more and a maximum roughness of 0.5 μ or more.

The mirror plate from the balance of the adhesive force and release force in the present invention, density 0. 860 to 0.920, melting point 6
Adhesive layer composed of 0 to 115 ° C. ethylene -α- olefin copolymer are preferably used, particularly preferably Density
0 . 880 to 0.920, an adhesive layer consisting of melting point 6 five to one hundred and fifteen ° C. ethylene -α- olefin copolymer used
You .

[0031] The rough surface plate, density 0. 860 to 0.92
0, the adhesive layer is preferably used consisting Melting point 6 from 0 to 115 ° C. ethylene -α- olefin copolymer and a tackifier
It is, for mild rough surface plate, density 0. 880-0.9
20, the adhesive layer comprising a blend of a melting point 6 5 to 115 ° C. ethylene -α- olefin copolymer and a tackifier is particularly preferred <br/> was rather used.

[0032]

EXAMPLES Next, examples will be described together with comparative examples, but the present invention is not limited to these examples. Examples 1-2, Comparative Examples 1-6 Adhesive layer raw materials were extruded from an extruder having a diameter of 35 mm, and raw materials for a base layer were extruded from an extruder having a diameter of 40 mm. A film having a total thickness of 50 μ was obtained with a configuration of a layer thickness of 15 μ / a back layer thickness of 35 μ.
Extrusion temperature conditions are as shown in Table 1.

[0033]

[Table 1]

The material composition and composition of the adhesive layer and the base layer are as shown in Tables 2 and 3. The melting curves of the main components of the adhesive layer are shown in FIGS.

[0035]

[Table 2]

[0036]

[Table 3]

The properties of the obtained surface protective film are as shown in Tables 4 and 5. As is clear from Tables 4 and 5, the surface protective film according to the present invention satisfies all of the functions of adhesiveness, adhesion, suitability for thermal processing (particularly non-staining), and blocking ability. In addition, various functions can be satisfied both for the mirror surface plate and the rough surface plate.

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

According to the present invention, viscosity force application, adhesion, thermal workability can be processed without generating contamination, also satisfies any surface characteristics of (blocking), and adopted roughened plate <br / > Provide a surface protection film that can be provided .

[Brief description of the drawings]

FIG. 1 shows a melting curve of a main material of an example.

FIG. 2 shows a melting curve of a main material of a comparative example.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Utaro Sakamoto 1-5 Sakuramachi, Takatsuki City, Osaka Prefecture Toray Gosei Film Co., Ltd. Takatsuki Plant (56) References JP-A-8-157792 (JP, A) (58) ) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 C09J 7/02

Claims (3)

(57) [Claims] 1. A consists conjugate form of the adhesive layer and the substrate layer, the viscosity <br/> adhesive layer, density from 0.860 to 0.920, melting point 6 0-11
5 ° C , adhesion to ethylene-α-olefin copolymer whose melting curve obtained by differential scanning calorimetry shows a single peak.
In a compound containing the imparting agent in the range of 40 wt% or less
A surface protective film characterized by being constituted . 2. A tackifier is a terpene compound Oyobiro
The surface protective film according to claim 1, wherein the surface protective film is at least one selected from gin . Wherein the ethylene -α- olefin copolymer,
In the relationship between the density (D) and the melting point (Tm), Tm ≦ 40
0D-256 is satisfied.
Or the surface protective film according to 2.