JPH1095959A - Surface protection film - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a surface protection film by a co-extrusion method,
Provided is a surface protective film that solves the problem of the increase in adhesive force due to the above-described heating and does not cause problems such as dent of a protected object and entrapment of bubbles due to generation of fish eyes. SOLUTION: In a surface protection film formed by coextruding an adhesive layer on one surface of a base layer made of a polyethylene resin, 10% by weight of the polyethylene resin of the base layer was eluted by a cross separation method. 10 from the current temperature
The temperature range at the end of 0% by weight elution is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1.5 to
3.5, the density is 0.84 to 0.92 g / cm ³ , and the pressure-sensitive adhesive layer has a vinyl acetate content of 10 to 47% by weight.
And a mixture of an ethylene-vinyl acetate copolymer of the above and a polyethylene resin of the same type as that used for the base layer, so that the total vinyl acetate content in the whole mixture is 8 to 20% by weight. A surface protective film, characterized in that:

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 which is used for protecting a surface of a synthetic resin plate or the like, and is particularly suitable for protecting components of a liquid crystal display such as a polarizing plate and a retardation plate.

[0002]

2. Description of the Related Art In order to prevent the surface of a liquid crystal display member such as a synthetic resin plate, especially a polarizing plate or a retardation plate from being damaged or adhered during processing or transportation, various surface protective films have been used. I have. These surface protective films are peeled off and removed after use after processing or transportation.

In such a surface protective film,
Generally, a pressure-sensitive adhesive layer is formed on one surface of a base material layer made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or a mixture thereof.

As one method of producing such a surface protective film, a method in which a pressure-sensitive adhesive composition dissolved in a solvent is applied on a base film, and then the solvent is removed in a drying step to obtain a surface protective film. is there. However, this method has a disadvantage that a large amount of solvent needs to be removed in the drying step, and the equipment scale becomes large. Further, in the drying step, it is impossible to completely remove the solvent, and when the solvent remaining in the adhesive is adhered to the protected object, it has a disadvantage that the surface of the protected object is attacked. I have.

As a method for producing a surface protective film which solves the above-mentioned problem of the solvent, there is a method of applying a heat-melted adhesive composition to a base film. However, according to this method, a pressure-sensitive adhesive composition having a high cohesive force has a high melt viscosity, and thus has a drawback that application becomes difficult. Furthermore, in this method, the adhesive strength between the substrate and the adhesive is weak as it is to the polyolefin substrate, and the adhesive remains on the surface of the protected object when the surface protective film is peeled from the protected object after use. A phenomenon, so-called glue residue occurs.

As a method for producing a surface protective film that solves this adhesive residue, there is a method in which a substrate layer is hot-melted together with a pressure-sensitive adhesive composition and co-extruded (hereinafter abbreviated as co-extrusion method). In this method, since no solvent is used, there is no contamination to the protected object, and further, the base material composition and the pressure-sensitive adhesive composition are melted and adhered in the mold, so that the adhesive force between the base material and the pressure-sensitive adhesive is strong, Will not remain.

In recent years, a surface protection film formed by a co-extrusion method has been used as a surface protection film used for a synthetic resin plate for the reasons described above. In such a surface protective film, the adhesiveness at the initial stage of application is good, but after being attached to a protected object, when placed in a high-temperature environment, the adhesive force tends to increase sharply.
There is a problem that peeling off from the protected object becomes extremely difficult after use and adhesive residue remains.

[0008] In particular, in the field of synthetic resin plates, various processes are performed with the surface protective film adhered to prevent the plates from being scratched and dust from adhering. At that time, heat treatment at a relatively high temperature is often involved.

Further, in the case of protecting the surface of a liquid crystal display member such as a polarizing plate, a heat treatment is carried out at 50 to 120 ° C. for about 5 to 240 minutes after a surface protective film is adhered to correct the orientation of the liquid crystal. Further, in order to enhance the adhesion to the glass cell, an autoclave treatment is performed at 50 to 100 ° C., 2 to 20 atm, and about 10 to 60 minutes.

In general, the surface protective film that has been subjected to such a heat treatment has a significantly increased adhesive strength, making it very difficult to peel it off from the object to be protected. As a method for suppressing an increase in adhesive strength after heat treatment, Japanese Patent Application Laid-Open No. 59-75974 is disclosed.
As described in the publication, an ethylene-vinyl acetate copolymer (EVA) is liquefied at normal temperature at a temperature of 100 to 200 ° C., and bleeds from the pressure-sensitive adhesive layer, specifically, a melting point of 20 ° C. or lower. Of α-olefin oxides and the like are known. However, the surface protective film obtained by this method has a sufficient initial adhesiveness so that the organic compound which is liquid at room temperature and bleeds from the pressure-sensitive adhesive layer bleeds to the surface of the pressure-sensitive adhesive layer before being applied to the protected object. And has the drawback that it is difficult to adhere to an object to be protected. In addition, there is a disadvantage that the bleed organic compound migrates to the surface of the object to be protected and contaminates the object to be protected.

A number of techniques relating to the above-described surface protective film formed by the coextrusion method are known. For example, in JP-A-54-133578, in a resin film composed of a polyethylene resin layer and an adhesive resin layer, the polyethylene resin layer is 0.91 to 0.93 g / cm ^3.
A low-density polyethylene of 50 to 90 parts by weight, a weight average molecular weight of 4 × 10 ⁴ to 10 × 10 ⁴ , and a ratio (Mw / Mn) of weight average molecular weight Mw to number average molecular weight Mn of 9 to 15,
And a surface protective film comprising 10 to 50 parts by weight of a high-density polyethylene having a density of 0.955 to 0.962 g / cm ³ and an adhesive resin layer comprising an ethylene-unsaturated ester copolymer.

As the surface protective film used for the synthetic resin plate, a surface protective film formed by a co-extrusion method is particularly preferable because the adhesive residue is disliked or the object to be protected is weak to a solvent. As the resin extruded as the base material, a polyethylene resin is used from the viewpoint of being inexpensive and easy to mold.

[0013]

However, the conventional polyethylene resin has a problem that unmelted fish eyes are liable to occur during film formation. Due to the presence of the fish eyes, when the surface protection film was stacked and stored with the surface protection film attached to the object to be protected, there was a problem that the object to be protected was dented.

In recent years, the demand for resin plates for optical applications has increased. A polarizing plate or the like used for a liquid crystal display material is one type of a resin plate. If such a resin plate for optical use has a dent due to fish eyes, the image is distorted and cannot be used.

In addition to dents, the entrapment of air bubbles generated between the resin plate and the film with fish eyes as nuclei may be regarded as poor appearance, and may be erroneously recognized as a surface abnormality of the resin plate itself.

FIG. 1 is a cross-sectional view for explaining a state in which bubbles are entrained by fish eyes as described above. On the polarizing plate 4 which is a resin plate, a surface protection film composed of the base material layer 2 and the pressure-sensitive adhesive layer 1 is attached. The fisheye 3 as described above is present in the pressure-sensitive adhesive layer 1, and the presence of the fisheye 3 causes the air bubbles 5 to be caught in the vicinity thereof. Thus, the generation of the fish eyes 3 causes the air bubbles 5 to be caught between the polarizing plate 4 and the pressure-sensitive adhesive layer 1.

An object of the present invention is to solve the above-mentioned problem of an increase in adhesive force due to heating in a co-extrusion surface protective film, and to prevent problems such as dent of a protected object and entrapment of bubbles due to generation of fish eyes. It is to provide a surface protective film which does not cause any problem.

[0018]

The surface protection film of the invention according to claim 1 is a surface protection film formed by coextruding an adhesive layer on one side of a base layer made of a polyethylene resin. The polyethylene resin of the base layer is
The temperature range from the temperature at which 10% by weight was eluted by the cross fractionation method to the temperature at which 100% by weight was eluted was 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight was 1.
5 to 3.5 and a density of 0.84 to 0.92 g / cm
³ , wherein the pressure-sensitive adhesive layer is composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 47% by weight and a polyethylene resin of the same type as that used for the base material layer in the entire mixture. It is characterized by being mixed so that the vinyl acetate content is 8 to 20% by weight.

The surface protection film according to the second aspect of the present invention is a surface protection film in which an adhesive layer is coextruded on one surface of a base material layer made of a polyethylene resin. The resin is polymerized using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and the pressure-sensitive adhesive layer has a vinyl acetate content of 10 to 4
7% by weight of an ethylene-vinyl acetate copolymer and the same kind of polyethylene resin as that used for the base layer are mixed so that the total vinyl acetate content in the whole mixture is 8 to 20% by weight. It is characterized by having been done.

[0020] The surface protective film according to the third aspect of the present invention is a surface protective film in which an adhesive layer is coextruded on one side of a base layer made of a polyethylene resin. The resin is polymerized using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and a temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. And the value of weight average molecular weight / number average molecular weight is 1.5 to 3.5, and the density is 0.84 to 0.9.
2 g / cm ³ , and the pressure-sensitive adhesive layer has a vinyl acetate content of 1
The ethylene-vinyl acetate copolymer of 0 to 47% by weight and the same kind of polyethylene resin as that used for the base layer are mixed so that the total vinyl acetate content in the whole mixture becomes 8 to 20% by weight. It is characterized by being mixed.

Hereinafter, the invention according to claims 1 to 3 (hereinafter, referred to as the invention)
Each configuration of the present invention will be described in detail.
Examples of the polyethylene resin used as the base layer in the present invention include ethylene alone or a resin containing ethylene and an α-olefin as structural units. Examples of the α-olefin include propylene, 1-butene,
Examples include 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene and the like. The polyethylene resin used for the base layer needs to have flexibility in order to reduce entrapment of air bubbles.
Therefore, the temperature range from the temperature at which 10% by weight is eluted by the cross separation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1.5 to 3. 5 and a density of 0.84 to 0.9
It is limited to those of 2 g / cm ³ or those polymerized using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst.

First, the cross sorting method of the present invention will be described below. Polyethylene resin at 140 ° C
Alternatively, the temperature at which the polyethylene resin completely dissolves
After dissolving in dichlorobenzene, the solution is cooled to 0 ° C. at a constant rate to form a thin polymer layer on the surface of a previously prepared inert carrier in order of crystallinity and molecular weight. Next, the temperature is raised continuously or stepwise, the concentration of the components eluted sequentially is detected, and the composition distribution (crystallinity distribution) is measured. It is measured by type GPC. In the present invention, the above-mentioned temperature rise elution fractionation (TREF = Temperatur
e Rising Elution Fractionation) part and high temperature GPC
(SEC = Size Exclusion Chromatograph) The above data was measured using a cross-separation chromatograph <CFC-T150A: manufactured by Mitsubishi Chemical Corporation> equipped with a system.

The polyethylene resin used in the present invention has a temperature range from the temperature at which 10% by weight is eluted to the temperature at which 100% by weight is eluted is 30 by the above-mentioned cross fractionation method.
° C or lower, preferably 28 ° C or lower. If the temperature range exceeds 30 ° C., a high crystalline component and a low crystalline component will be present simultaneously in the polyethylene resin,
The viscosity of the resin becomes uneven, and a film having a uniform appearance cannot be obtained.

The polyethylene resin used in the present invention has a weight-average molecular weight / number-average molecular weight value measured by the above-mentioned cross fractionation method in the range of 1.5 to 3.5. Preferably, it is 1.7-3.0. If this value is less than 1.5, the resin will not easily flow during melting, and molding will be difficult. On the other hand, when this value exceeds 3.5, the abundance ratio of low molecular weight molecules and high molecular weight molecules increases, and the low molecular weight components remain on the surface of the protected object when peeled from the protected object and become contaminated. The portion becomes unmelted fish eyes when the film is formed, and after being attached to the object to be protected, when heated while being attached, dents occur in the object to be protected.

The polyethylene resin used in the present invention can be obtained by polymerization using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. Examples of the tetravalent transition metal include titanium, zirconium, nickel, palladium, hafnium, and platinum. Compounds in which one or more cyclopentadienyl rings and their analogs exist as ligands in these tetravalent transition metals are generally called metallocene compounds.

Specific examples of the ligand include a cyclopentadienyl ring, a cyclopentadienyl ring, a cyclopentadienyl oligomer ring substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group, Examples include an indenyl ring and an indenyl ring substituted by a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group, and one or more of these ligands are present. Other ligands include
Examples thereof include monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylalkoxides, aryloxides, amides, arylamides, phosphides, arylphosphides and the like.

Representative of the above hydrocarbon groups are methyl, ethyl, propyl, butyl, amyl, isoamyl,
Hexyl, isobutyl, heptyl, octyl, nonyl,
Decyl, cetyl, 2-ethylhexyl and phenyl.

Examples of the metallocene compound to which these ligands are coordinated are cyclopentadienyl titanium tris (dimethylamide), methylcyclopentadienyl titanium tris (dimethylamide), bis (cyclopentadienyl) titanium dichloride, dimethylsilyltetrachloride. Methylcyclopentadienyl-tert-butylamidozirconium dichloride, dimethylsilyltetramethylcyclopentadienyl-tert-butylamidohafnium dichloride, dimethylsilyltetramethylcyclopentadienyl-pn-butylphenylamidozirconium chloride, methylphenyl Silyltetramethylcyclopentadienyl-tert-butylamidohafnium dichloride, indenyl titanium tris (dimethylamide), indenyl Titanium tris (diethylamide), indenyl titanium tris (di -n- propyl amide), indenyl titanium bis (di -n- butylamide) (di -n- propyl amide) and the like.

The polymerization is usually carried out on these metallocene compounds,
The reaction is carried out in a catalyst system to which methylaluminoxane (MAO), a boron compound or the like is added as a cocatalyst. The use ratio of the cocatalyst to the metallocene compound is 10 to 1000
It is 000 mol times, usually 50 to 5000 mol times.

The polymerization conditions are not particularly limited, and a solution polymerization method using an inert medium, a bulk polymerization method using substantially no inert medium, or a gas phase polymerization method can be used. Generally, the polymerization temperature is from -100 ° C to 300 ° C, and the polymerization pressure is from normal pressure to 100 kg / cm ² .

The polyolefin polymerized with these metallocene catalysts has a narrow molecular weight distribution, and in the case of a copolymer, the copolymer component is introduced at almost the same ratio in all molecular weight components. Commercial products of such a polyethylene resin include CGCT manufactured by Dow Chemical Company, Affinity, Engage, and EXACT manufactured by Exxon Chemical Company.
Etc. are known.

EV used in the pressure-sensitive adhesive layer in the present invention
A has a vinyl acetate content (VAC) of 10% to 47%.
And more preferably 15-20% EVA. 10
% Of EVA with a VAC of less than 0.1%, the initial adhesive strength is too low and does not adhere to the protected object. Also, there is no EVA with a VAC higher than 47%.

In the present invention, the above EVA is mixed with a polyethylene resin, and the total VAC in the whole mixture is from 8 to 8.
The pressure-sensitive adhesive layer is prepared at a mixing ratio of 20%, more preferably 10 to 15%. At this time, the total V in the mixture
When the AC becomes VAC lower than 8%, the initial adhesive strength becomes too low and does not adhere to the protected object. On the other hand, if the VAC is higher than 20%, the adhesive strength increases after the heat treatment, and peeling becomes difficult.

In the present invention, as the polyethylene resin used for the pressure-sensitive adhesive layer, the same kind of polyethylene resin as that used for the base layer is used. The polyethylene-based resin does not need to be exactly the same as that used for the base material layer, and is appropriately selected and used in consideration of temporary attachment performance to an adherend. The polyethylene resin has a molecular chain of C
Since it is composed only of H, CH ₂ , and CH ₃ and has no carbonyl group or the like, the adhesive strength does not increase even if it is placed in a high-temperature environment after being attached to a protected object.

The above-mentioned polyethylene resin used in the pressure-sensitive adhesive layer in the present invention needs to have flexibility in order to obtain initial tackiness to an object to be protected and to reduce entrapment of air bubbles. Therefore, the density of the resin is 0.84 to
Must be 0.92 g / cm ³ . 0.8 density
If it is less than 4 g / cm ³ , the crystallinity of the resin decreases, and the heat resistance of the pressure-sensitive adhesive layer deteriorates. If it exceeds 0.92 g / cm ³ , the flexibility of the pressure-sensitive adhesive layer comprising the resin composition will be insufficient, and not only will not sufficient initial adhesion to the protected object be obtained, but also fisheye will form as a core. The reduction of entrained bubbles cannot be expected.

The constitution of the resin composition in the present invention is as described above, but various antioxidants, flame retardants, pigments and the like may be added as long as the physical properties are not impaired. As a method for producing the surface protective film in the present invention, the above resin is melt-kneaded using a single screw extruder or a twin screw extruder, and is heated using a blow mold and a T-die mold as a base material. It is common to form a film together with a plastic resin by a co-extrusion method.

The pressure-sensitive adhesive layer of the surface protective film of the present invention comprises:
Since it is formed by mixing a predetermined EVA and a polyethylene-based resin, it has an initial tackiness to the object to be protected and has sufficient flexibility to reduce the entrapment of bubbles. The molecular chains are CH, CH ₂ , C
Since it consists only of H ₃ and has no carbonyl group or the like,
The initial tackiness is expected, and there is no increase in tackiness due to heating.

Further, since the polyethylene resin and EVA are mixed so that the total VAC in the whole mixture is 8 to 20%, the same initial tackiness as EVA alone is exhibited, and EVA alone cannot be expected. In addition, it is possible to form a pressure-sensitive adhesive layer having a small increase in pressure-sensitive adhesive strength due to heating.

In the present invention, the polyethylene resin used for the pressure-sensitive adhesive layer has a low ratio of molecules having a low molecular weight and a high molecular weight, so that contamination at the time of peeling from a protected object and unmelted fish at the time of forming a film. Eye generation is reduced.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Metallocene as a polymerization catalyst
Polyethylene resin obtained using the compound (Exxon
Chemical Company, trade name "EXACT3027", density
0.900 g / cm ^Three, Weight average molecular weight / number average molecular weight
= 2.0, the measurement results of the cross fractionation method are as shown in Table 1.
You. ) As a base material layer, on one side of which EVA of VAC 14%
(Mitsui Dupont Polychemical Co., Ltd., product name "Evafre
X 560 ") 100 parts by weight and used in the base material layer
Mixed with 40 parts by weight of the same polyethylene resin as
The pressure-sensitive adhesive layer having a total VAC of 10% was coated with a base material layer having a thickness of 40%.
μm and the thickness of the adhesive layer is 20 μm.
Melt adhesion by two-layer coextrusion method by a
Was made.

Example 2 Metallocene as a polymerization catalyst
Polyethylene resin obtained using the compound (Exxon
Chemical company, trade name "EXACT4011", density
0.885 g / cm ^Three, Weight average molecular weight / number average molecular weight
= 2.1, the measurement results of the cross fractionation method are as shown in Table 1.
You. ) As a substrate layer, and the same EV as that used in Example 1
A100 parts by weight and the same po
40 parts by weight of ethylene resin, and the total VAC is 1
0% pressure-sensitive adhesive layer, base material layer thickness 40 μm, pressure-sensitive adhesive
Two layers by an inflation die so that the layer thickness becomes 20 μm
Melt adhesion by co-extrusion method to produce surface protection film
Was.

(Comparative Example 1) The polyethylene resin used in Example 2 was used as a base material layer, and one surface of the polyethylene resin was VAC 28% EV.
A (100 parts by weight, manufactured by DuPont Mitsui Polychemicals, trade name "Evaflex 270") and 12 parts by weight of the same polyethylene resin used for the base layer were mixed, and the total VAC was 25%. Was melt-adhered by a two-layer coextrusion method using an inflation die so that the thickness of the base material layer was 40 μm and the thickness of the pressure-sensitive adhesive layer was 20 μm to prepare a surface protective film.

(Comparative Example 2) The polyethylene resin used in Example 2 was used as a base material layer, and one surface of the polyethylene resin was used.
A (used in Examples 1 and 2) 100 parts by weight and the same polyethylene resin 13 used for the base material layer
0 parts by weight, and a pressure-sensitive adhesive layer having a total VAC of 6% is melt-adhered by a two-layer coextrusion method using an inflation die so that the thickness of the base material layer becomes 40 μm and the thickness of the pressure-sensitive adhesive layer becomes 20 μm. A surface protection film was produced.

Comparative Example 3 Linear low-density polyethylene resin (trade name "1044D", manufactured by Idemitsu Petrochemical Co., Ltd., density 0.925 g / c) obtained using a titanium trichloride catalyst
m ³ , weight average molecular weight / number average molecular weight = 4.0, and the results of measurement by the cross fractionation method are as shown in Table 1. ) Is used as a base material layer, and 100% by weight of EVA (used in Example 1 and Example 2) of 14% VAC is mixed on one side with 40 parts by weight of the same polyethylene resin used for the base material layer. And
The pressure-sensitive adhesive layer having a total VAC of 10% was coated with a base material layer having a thickness of 40%.
μm and a thickness of the pressure-sensitive adhesive layer of 20 μm were melt-contacted by a two-layer coextrusion method using an inflation die to prepare a surface protective film.

The initial adhesive strength and the adhesive strength after the heat treatment of the surface protective film obtained as described above were measured by the methods described below. Further, the surface state of the polarizing plate after the heat treatment was visually observed, and the number of indentations and bubbles entrained on the polarizing plate was counted. Table 2 shows the results.

Measurement method (Initial adhesive strength) A surface protective film was 150 mm long and 1 mm wide.
After affixed to a 00 mm polarizing plate with a laminator and allowed to stand at 23 ° C. for 30 minutes, a force required for peeling at a peel width of 25 mm and a peel angle of 180 ° is measured.

(Adhesive force after heat treatment) A surface protective film was adhered to a polarizing plate having a length of 150 mm and a width of 100 mm with a laminator, left in a hot-air circulation oven preheated to 90 ° C. for 30 minutes, and taken out. After cooling, the force required for peeling at a peel width of 25 mm and a peel angle of 180 ° is measured.

(Number of indentations on the polarizing plate after heat treatment, number of bubbles involved) The surface protective film was 150 mm long and 100 mm wide.
To the polarizing plate with a laminator, and count the number of bubbles entrained at that time. Then, after leaving it for 30 minutes in a hot-air circulation oven preheated to 90 ° C., take it out, cool it to room temperature, peel off the surface protective film, observe the surface condition of the polarizing plate with a 20-power loupe, and make an impression. Count the number of.

Tables 1 and 2 are shown below. In Table 1, Mw indicates the weight average molecular weight, and Mn indicates the number average molecular weight. T1 is ₁ of the total resin by cross separation.
Indicates the temperature of 0 wt% is eluted, T ₂ represents the elution termination temperature of the whole resin by cross fractionation. In Table 2, the number of bubbles involved and the number of indentations were 150 mm × 10
The number per 0 mm is shown.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

According to the surface protective film of the present invention, the adhesive strength does not increase even after the heat treatment, and the dents of the protected object and the entrapment of air bubbles when stored in a stack are stored. Generation of unmelted fish eyes during molding of the resulting surface protective film.

Accordingly, it can be suitably used for protecting the surface of a liquid crystal display component such as a resin plate, particularly a polarizing plate or a retardation plate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which bubbles are trapped by fish eyes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Adhesive layer 2 ... Base layer 3 ... Fish eye 4 ... Polarizing plate 5 ... Air bubbles

Claims (3)

[Claims] 1. In a surface protective film formed by coextruding an adhesive layer on one side of a base layer made of a polyethylene resin, 10% by weight of the polyethylene resin of the base layer is eluted by a cross separation method. 10 from the temperature when
The temperature range at the end of 0% by weight elution is 30 ° C. or less, and the value of weight average molecular weight / number average molecular weight is 1.5 to
3.5, the density is 0.84 to 0.92 g / cm ³ , and the pressure-sensitive adhesive layer has a vinyl acetate content of 10 to 47% by weight.
And a mixture of an ethylene-vinyl acetate copolymer of the above and a polyethylene resin of the same type as that used for the base layer, so that the total vinyl acetate content in the whole mixture is 8 to 20% by weight. A surface protective film, characterized in that: 2. A surface protective film formed by coextruding an adhesive layer on one side of a base layer made of a polyethylene resin, wherein the polyethylene resin of the base layer is a tetravalent transition metal as a polymerization catalyst. Wherein the pressure-sensitive adhesive layer has an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 47% by weight, and a polyethylene of the same type as that used for the base layer. And the total amount of vinyl acetate in the whole mixture is 8 to 20.
A surface protective film characterized by being mixed so as to be in a weight%. 3. A surface protective film formed by extruding an adhesive layer on one side of a base layer made of a polyethylene resin, wherein the polyethylene resin of the base layer is a tetravalent transition metal as a polymerization catalyst. Is polymerized using a metallocene compound containing, and a temperature range from the temperature at which 10% by weight is eluted by the cross fractionation method to the temperature at which 100% by weight is eluted is 30 ° C. or less, and the weight average molecular weight / number average The molecular weight is 1.5-3.5 and the density is 0.84
0.92 g / cm ³ , wherein the pressure-sensitive adhesive layer is composed of an ethylene-vinyl acetate copolymer having a vinyl acetate content of 10 to 47% by weight and a polyethylene resin of the same type as that used for the base layer. The total vinyl acetate content in the whole mixture is 8 to 2;
A surface protective film which is mixed so as to be 0% by weight.