KR102416740B1 - surface protection film - Google Patents

Abstract

Provided is a surface protection film excellent in releasability at the time of peeling again after adhering adhesion layers, and re-adhesiveness to an adherend. Consists of an adhesive layer and a base layer, and the adhesive layer contains at least one of ethylene/vinyl acetate copolymer and low-density polyethylene as main components, and 5 to 25% by weight of a styrene-based elastomer having a glass transition temperature of -40°C or more and more than 70% by weight It is a surface protection film which contains.

Description

surface protection film

The present invention relates to a surface protection film.

A liquid crystal display used in a liquid crystal television, a personal computer, or the like is usually composed of a liquid crystal cell sandwiched by a polarizing plate, a light diffusion film, and a light source unit on the back side. In the light source unit, in a structure in which a light source such as an LED is located at the edge of the display surface, the edge becomes bright but becomes dark in the center. And a light guide plate is used for the purpose of uniform contrast of the display by adjusting the amount of scattering.

In general, when a scratch or dust is attached to the surface of the light guide plate, the reflection of incident light becomes non-uniform on the entire surface, so that there is a problem that a part of the display is bright or dark. For this reason, in the production line of the light guide plate, for the purpose of preventing the adhesion of scratches and dust, the surface protection film is attached immediately after discharge and molding of resin such as acrylic. When the purpose of protection was completed and became unnecessary, the method of use was that it was peeled off and discarded. Therefore, the surface protection film is required to have a suitable adhesive strength that it does not peel during storage or transport of the light guide plate and is easily peeled off when unnecessary, and an ethylene/vinyl acetate copolymer (hereinafter referred to as EVA) is required for the adhesive layer of the surface protection film. It was common to add a tackifier in order to stabilize the adhesive force to a resin composition, such as .

However, in the manufacturing process of the light guide plate, there is a step of drying the light guide plate after processing such as dot printing on the surface of the light guide plate. . However, in the case of a surface protection film in which a tackifier is added to a resin composition such as an ethylene/vinyl acetate copolymer in the pressure-sensitive adhesive layer, the adhesive strength increases due to an increase in drying temperature, which makes peeling of the surface protection film difficult. has been burned Therefore, regarding the adhesive layer of the surface protection film, for example, Patent Document 1 discloses a surface protection film in which the adhesive layer consists of 30 parts by weight or less of a tackifying resin with respect to 100 parts by weight of styrene/butadiene or styrene/isoprene copolymer rubber. there is In addition, Patent Document 2 discloses a method of adjusting adhesive strength by extruding a mixture comprising a styrene/butadiene block copolymer and an ethylene/vinyl acetate copolymer as an adhesive layer at a temperature of 140 to 180°C. In addition, Patent Document 3 discloses a surface protection film of an adhesive layer comprising 10 to 200 parts by weight of a tackifying resin and 10 to 200 parts by weight of a polyolefin resin with respect to 100 parts by weight of a styrenic elastomer. Moreover, in patent document 4, the proposal of the surface protection film whose sum of the ethylene component and polyethylene-type resin in the styrene-type elastomer in an adhesion layer is 35 mass % or more and less than 70 mass % is made|formed.

In addition, conventionally, the surface protection film is peeled off during random extraction in the middle of the light guide plate manufacturing process, and is discarded together with the light guide plate after inspection. There is an increasing number of usages, such as folding and storing with facing each other, and unfolding and reusing the folded surface protection film after the inspection is completed. However, in the surface protection film as shown in Patent Documents 1 to 4, the content of the styrene-based elastomer is large, the adhesive layer is very soft, and when the adhesive surfaces are joined and then peeled again by hand, there is a problem that a large force is required for peeling. there was. Moreover, when the adhesive surfaces of a surface protection film were peeled, there also existed a problem that the adhesive surface became cloudy and re-adhesion to a to-be-adhered body became impossible.

Japanese Patent Publication No. 58-30911 Publication Japanese Patent Publication No. Hei 7-59689 Japanese Patent Laid-Open No. 5-194923 Japanese Patent Laid-Open No. 2013-234321

An object of the present invention is to solve the above problems and suppress the rise in adhesive strength while having sufficient adhesiveness to protect the adherend, and when the re-adhesiveness when the surface protection film is reused or when peeling off after the adhesive layers come into contact with each other , to provide a surface protection film in which there is no or slight clouding of the adhesive layer, and the adhesive layers can be easily peeled off.

MEANS TO SOLVE THE PROBLEM This inventor discovered that the objective could be achieved by setting it as the following structure, as a result of repeating earnest research and development in order to solve the said subject.

(1) The adhesive layer is a surface protection film having a base layer, wherein the adhesive layer contains at least one selected from the group consisting of ethylene/vinyl acetate copolymer and low-density polyethylene as a main component, and has a glass transition temperature of greater than 70% by weight - A surface protection film, which is a composition comprising 5 to 25% by weight of a styrene-based elastomer at 40°C or higher.

(2) The surface protection film according to (1), wherein the styrene-based elastomer is a styrene/ethylene/butylene/styrene copolymer.

(3) The surface protection film according to (1) or (2), wherein the main component of the pressure-sensitive adhesive layer contains a low-density polyethylene, and the low-density polyethylene is a linear low-density polyethylene having a density of 0.90 to 0.93 g/cm 3 .

(4) The surface protection film in any one of said (1)-(3) whose peeling force at the time of bonding adhesion layers is 0.75 N/15 mm or less.

(5) in any one of (1) to (4) above, wherein the adhesive force of the adhesive layer after heating adjustment for an adhesion temperature of 50 ° C. and 70 ° C. x 15 minutes to the acrylic plate is in the range of 0.2 to 5.0 N/50 mm The surface protection film.

(6) The surface protection film according to any one of (1) to (5), which is for protecting a light guide plate.

(Effects of the Invention)

The surface protection film of the present invention has the following effects.

(1) As for the surface protection film of this invention, rise of the adhesive force by heating is suppressed, and peeling of a surface protection film becomes easy.

(2) The surface protection film of this invention is excellent in the peelability of adhesive layers, and does not require large force for peeling of adhesive layers.

(3) In the surface protection film of the present invention, there is no cohesive fracture trace on the surface of the adhesive surface after peeling, or even if there is a fracture trace, reattachment to the adherend can be easily performed.

The surface protection film of this invention is a laminated|multilayer film which has a base material layer and an adhesion layer. The base layer can express mechanical strength, such as elastic strength and tensile strength, to facilitate handling as a surface protection film, and the adhesive layer can be designed independently of the base layer based on its adhesive properties.

As the base layer of the surface protection film of the present invention, any resin capable of coextrusion and lamination with the pressure-sensitive adhesive layer by an inflation method or a T-die method is sufficient. Since the main component of the adhesive layer used in the surface protection film of the present invention is an ethylene/vinyl acetate copolymer or low-density polyethylene (hereinafter sometimes referred to as LDPE), polyolefin resins such as low-density polyethylene, high-density polyethylene, and polypropylene are used. It is used particularly suitably.

In addition, the number of the base material layers in this invention may be one, or it may be comprised by the multilayer of two or more layers. For example, it is preferable to set the base material layer as a two-layer lamination having a back surface layer on the opposite side to the pressure-sensitive adhesive layer from the viewpoint of facilitating a design that prevents blocking with the pressure-sensitive adhesive layer when wound in a roll shape.

The thickness of the surface protection film of the present invention is preferably 50 to 90 µm from the viewpoint of handling, and the ratio of the thickness of the substrate layer to the thickness of the surface protection film is in the range of 70 to 90% from the balance of mechanical properties and adhesive properties. Preferably, it is 75-85% more preferably.

The surface protection film of the present invention is first adhered to the surface of the adherend, then cut, peeled for one more inspection, folded and stored with the adhesive surfaces facing each other, and the folded surface protection film after the inspection is finished For the usage method of unfolding and then bonding to an adherend again, it is necessary to have adhesive strength and cutability, as well as performance for securing the peeling force after bonding the adhesive layers and the state of the adhesive surface after peeling.

The adhesive layer in the surface protection film of the present invention contains, as a main component, at least one selected from the group consisting of ethylene/vinyl acetate copolymer (EVA) and low-density polyethylene, and a styrene-based elastomer having a glass transition temperature of -40°C or higher. It consists of a composition containing

The ratio of the main component of the adhesion layer in this invention is more than 70 weight%. The ethylene/vinyl acetate copolymer alone may be more than 70% by weight, and the low-density polyethylene alone may be more than 70% by weight. Further, the total amount of the ethylene/vinyl acetate copolymer and the low-density polyethylene may exceed 70% by weight.

The ethylene/vinyl acetate copolymer (EVA) used for the adhesive layer is not particularly limited, but the surface protection film is often attached to the adherend in a high temperature state during the manufacturing process of the adherend, and also dot printing on one side of the light guide plate It is preferable to use a resin whose adhesive strength is not increased by heat because it is often heated in the drying process after . Specifically, the content of vinyl acetate is 5% by weight or more and less than 20% by weight, preferably the content of vinyl acetate is 5% by weight or more and less than 15% by weight, More preferably, the content of vinyl acetate is 7% by weight or more and 13% by weight The following ethylene/vinyl acetate copolymers (EVA) are preferably used. If the content rate of vinyl acetate is less than 5 weight%, adhesiveness may become difficult to express and it may become difficult to stick a surface protection film to a light-guide plate. Conversely, if the content rate of vinyl acetate is 20 weight% or more, adhesive force rises by heat, and it may become impossible to peel a surface protection film rather than a to-be-adhered body.

For the low-density polyethylene (LDPE) used for the adhesive layer, it is preferable to use a resin whose adhesive strength does not increase by heat for the same reason.

The low-density polyethylene is not particularly limited, but linear low-density polyethylene (hereinafter sometimes referred to as LLDPE) has good malleability, and the adhesive surface is smooth and adhesive properties are easily expressed. Therefore, it is preferable to use linear low-density polyethylene. do. Specific examples of the linear low-density polyethylene include an ethylene/butene copolymer, an ethylene/pentene copolymer, an ethylene/hexene copolymer, an ethylene/4-methylpentene-1 copolymer, and an ethyleneoctene copolymer.

It is preferable that a density is the range of 0.90-0.93 g/cm<3> about a linear low-density polyethylene. When the density of linear low-density polyethylene is more than 0.93 g/cm<3>, adhesiveness may become difficult to express and it may become difficult for a surface protection film to adhere to a to-be-adhered body. Conversely, when the density of the linear low-density polyethylene is less than 0.90 g/cm 3 , the adhesive strength is easily increased by heat, and the surface protection film cannot be peeled from the adherend in some cases. In addition, when the adhesive layers of the surface protection film are bonded once and then peeled, the peeling force becomes greater than 0.75 N/15 mm to cause cohesive failure, which causes cloudiness in the adhesive layer of the surface protection film, and the adhesive layer on the adherend. It may become impossible to attach.

For the styrene-based elastomer used in the adhesive layer, styrene/conjugated diene copolymers such as styrene/butadiene copolymer (SBR), styrene/isoprene/styrene copolymer (SIS), styrene/butadiene/styrene copolymer (SBS), and Hydrogenated substances thereof, for example, hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylene-butylene-styrene copolymer (hereinafter sometimes referred to as SEBS), styrene-isobutylene copolymer such as styrene - An isobutylene-styrene triblock copolymer (SIBS), a styrene-isobutylene diblock copolymer (SIB), or these mixtures, etc. are mentioned. These styrenic elastomers may use only 1 type, and may use 2 or more types together.

The weight average molecular weight of the styrenic elastomer is preferably in the range of 50,000 to 400,000, more preferably in the range of 50,000 to 300,000. When the weight average molecular weight is less than 50,000, the cohesive force of the pressure-sensitive adhesive layer is lowered, and when it is peeled off from the adherend, a glue residue may be generated. When the weight average molecular weight exceeds 400,000, the viscosity may increase and productivity may decrease.

The styrene-based elastomer used in the present invention has a glass transition temperature of -40°C or higher as measured in JIS K7121 (1987). Preferably they are -35 degreeC or more and 30 degrees C or less, More preferably, they are -30 degreeC or more and 0 degrees C or less. For the determination of the glass transition temperature, it is determined by differential scanning calorimetry (DSC).

A styrenic elastomer is composed of a styrene-based structural moiety and other structural moieties, but the magnitude of the glass transition temperature is greatly influenced by the structural moiety. For example, in a styrene/ethylene/butylene/styrene copolymer, styrene In addition to a tendency for the glass transition temperature to increase as the ratio of the content increases, the glass transition temperature decreases when the ratio of ethylene-based structural moieties in the molecular chain increases, and the glass transition temperature increases when the ratio of butylene-based structural moieties increases. . Adjustment of the adhesive force and the glass transition temperature can be easily adjusted by adjusting the ratio of these styrenic structural sites. From this point of view, as the styrene-based elastomer, a styrene/ethylene/butylene/styrene copolymer is preferable.

When the glass transition temperature of these styrenic elastomers is less than -40°C, the adhesive layer becomes very soft, and the sticky component increases, and the molecular chains of the resin are easily entangled on the surface of the adhesive layer. For this reason, when the adhesive surfaces of the surface protection film are pressed and peeled, the peeling force becomes larger than 0.75 N/15 mm, and cohesive failure occurs within the adhesive layers, not the interfacial peeling between the adhesive layers of the surface protection film, and surface protection. There exists a possibility that a film may become cloudy and it may become impossible to re-attach to a to-be-adhered body.

In the present invention, the mixing ratio of at least one main component selected from the group consisting of ethylene/vinyl acetate copolymer and low-density polyethylene used in the adhesive layer and the styrene-based elastomer is appropriately determined by the desired adhesive strength, but the styrene-based elastomer is 5 to 25% by weight, preferably 5 to 20% by weight. When the amount of the styrene-based elastomer is less than 5% by weight, the adherend is at a high temperature and a surface protection film is attached, and when the adherend is cut after that, the adhesive force becomes less than 0.20N/50mm, so that the surface protection film is peeled from the cut surface and dust from the cut surface may be mixed. In addition, when the amount of the styrenic elastomer exceeds 25% by weight, the adhesive strength increases by heat, and in some cases, it is not possible to peel the surface protection film from the adherend, which is not preferable. Moreover, when the adhesive layers of a surface protection film are pressed and peeled, the peeling force becomes larger than 0.75 N/15 mm, cohesive failure may generate|occur|produce, the surface protection film may become cloudy, and it may become impossible to re-attach to a to-be-adhered body.

The styrenic elastomer used for the adhesive layer of the surface protection film of the present invention is not particularly limited with respect to the durometer hardness defined by ASTM: D2240, but the lower the hardness, the higher the adhesive strength. It is preferable that it is the range of 20-50.

The surface protection film of this invention sticks at 50 degreeC, and it is preferable that the range of the adhesive force with respect to the acrylic plate after heating adjustment for 70 degreeC x 15 minutes is 0.2-5.0N/50mm. When the adhesive force to an acrylic plate exceeds 5.0 N/50 mm, since a great force is required for peeling of a surface protection film, it may become difficult to peel, and a surface protection film may crack at the time of peeling. Moreover, when the adhesive force with respect to an acrylic plate is less than 0.2 N/50 mm, since adhesive force runs short when cutting an acrylic plate, a surface protection film may peel from the cut point. Therefore, 0.2-5.0N/50mm is preferable as for the adhesive force with respect to an acrylic board, More preferably, it is 0.3-3.0N/50mm, More preferably, it is 0.3-1.5N/50mm.

In addition, the surface protection film of the present invention has a tackifier and a glass transition temperature in the pressure-sensitive adhesive layer within a range that does not impair the peeling force when the adhesive surfaces of the surface protection film are pressed together and peeled for the purpose of making the adhesive strength desired. It is also possible to add a styrene-based elastomer having a value of less than -40°C. Examples of the tackifier include commercially available resin groups such as rosin-based, terpene-based, coumaron-indene-based, and the like. As the styrene-based elastomer, the hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-isobutylene copolymer, for example, styrene-isobutylene-styrene triblock copolymer a copolymer (SIBS), a styrene/isobutylene diblock copolymer (SIB), or a mixture thereof. However, it is preferable not to add the tackifier because it leads to contamination such as residues of glue on the surface of the adherend. In addition, with respect to the addition of a styrene-based elastomer having a glass transition temperature of less than -40°C, since the peel force after bonding the adhesive layers once and the shape of the surface of the adhesive layer after peeling deteriorate, the amount added to the adhesive layer is 10% by weight. It is preferable to set it as below.

In addition, the surface protection film of the present invention is an antistatic agent for preventing static electricity generated when peeling the surface protection film within the range that does not impair the adhesive strength or peeling force when the adhesive layers of the surface protection film are pressed and peeled. , it is also possible to add a release agent that reduces friction between the surface protection film base layer and the adhesive layer.

Example

Hereinafter, the surface protection film of the present invention will be described in detail based on specific examples, but the present invention is not limited to these examples. In addition, it measured and evaluated by the method shown below.

(1) Adhesion

After creating the surface protection film, store it under an atmosphere of room temperature 23°C and humidity 50RH% for 3 days or more, and after that, it was heated to 50°C in advance to have a thickness of 20 mm and a width of 50 mm, manufactured by Mitsubishi Rayon Co., Ltd. “ACRYLITE S” " It was affixed to an acrylic board with an adhesion pressure of 9,100 N/m, and an adhesion speed of 300 cm/min. After that, it is stored for 15 minutes in a hot-air dryer pre-heated at 70°C, the sample is taken out from the hot-air dryer, and stored for 24 hours in an atmosphere of 23°C. °, the surface protection film was peeled, and adhesive force was measured.

(2) re-adhesiveness

After measuring the adhesive force in said (1), the peeled surface protection film was again crimped|bonded to an acrylic board with a finger, and it visually observed whether QN bonding was carried out, and the following judgment was performed.

(double-circle): Adhesive spontaneously from the part pressed with a finger toward the periphery

○: The portion pressed with the finger is adhered

x: It does not stick even if it crimps|bonds strongly with a finger|finger.

(3) Peeling force when bonding adhesive layers together

After measuring the adhesive force in said (1), the adhesion layers of the peeled surface protection film were affixed by the adhesion pressure of 9,100 N/m, and the adhesion rate of 300 cm/min. Then, after storage for 24 hours at 23° C., the sample width is cut to 15 mm, and the surface protection films are peeled off at a tensile rate of 300 mm/min and a peeling angle of 90° using a tensile tester, and the adhesive layers are separated from each other. The peeling force at the time of bonding was measured.

<Example 1>

A composition comprising 93 wt% of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10 wt% and 7 wt% of a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -27°C (SEBS) was used as an adhesive layer. and 85% by weight of high-density polyethylene having a density of 0.97g/cm3 and a melt flow rate of 40g/10min at 230℃, 12% by weight of an ethylene/propylene random copolymer having a melting point of 145℃, and a melt flow rate of 2g/10min at 190℃ A composition composed of 3% by weight of low-density polyethylene is used as a base layer, and the surface is co-extruded using a T-die composite film making machine so that the base layer thickness ratio is 80%, the adhesive layer thickness ratio is 20%, and the total thickness is 70 μm. A protective film was created.

<Example 2>

93 wt% of a linear low-density polyethylene resin (LLDPE-1) obtained using a single site catalyst (metallocene catalyst) having a density of 0.91 g/cm 3 as an adhesive layer and styrene/ethylene/butyl having a glass transition temperature of -27°C A surface protection film was prepared by co-extrusion in the same manner as in Example 1 except for using a composition comprising 7% by weight of a ren-styrene copolymer (SEBS).

<Example 3>

In the composition of the adhesive layer, 90 wt% of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10 wt% and a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -21°C (SEBS) of 10 wt% Except having set it as it, it carried out similarly to Example 1, and created the surface protection film.

<Example 4>

A surface protection film was created in the same manner as in Example 2, except that in the composition of the pressure-sensitive adhesive layer, a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -27°C was 10% by weight.

<Example 5>

80 wt% of a linear low-density polyethylene resin (LLDPE-2) obtained by using a multi-site catalyst (Ziegler-Natta catalyst) having a density of 0.92 g/cm 3 as an adhesive layer and a glass transition temperature of -27 ° C. A composition composed of 20% by weight of butylene/styrene copolymer (SEBS) was used, the same high-density polyethylene as in Example 1 was used as the base layer, and 80% by weight of homopolypropylene was used on the opposite side to the adhesive layer, 230°C A two-layered configuration having a back layer composed of a melt flow rate of 40 g/10 min under the bottom, 16 wt% of an ethylene/propylene random copolymer having a melting point of 145°C, and 4 wt% of a low-density polyethylene having a melt flow rate of 2 g/10 min at 190°C It co-extruded so that the base material layer thickness ratio might be 80%, the adhesion layer thickness ratio might be 20%, and the total thickness might be 70 micrometers, and the surface protection film was created.

Here, the thickness ratio of the layer which consists of high-density polyethylene of a base material layer, and the back layer which consists mainly of homopolypropylene was made into 90/10.

<Example 6>

As the adhesive layer, 55% by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10% by weight, 20% by weight of low-density polyethylene having a density of 0.92g/cm 3 , and styrene/isobutylene/styrene having a glass transition temperature of -20°C Except for using the composition which consists of 25 weight% of triblock copolymer (SIBS), it co-extruded similarly to Example 5, and created the surface protection film.

<Example 7>

In the composition of the adhesive layer, 55 wt% of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10 wt%, 40 wt% of a low-density polyethylene, and a styrene/isobutylene/styrene triblock copolymer having a glass transition temperature of -20°C Except having made (SIBS) into 5 weight%, it carried out similarly to Example 6, and created the surface protection film.

<Example 8>

30% by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10% by weight as an adhesive layer, 50% by weight of a linear low-density polyethylene having a density of 0.92g/cm3 by a multi-site catalyst, and a glass transition temperature of -27°C A surface protection film was created in the same manner as in Example 6 except that the styrene/ethylene/butylene/styrene copolymer (SEBS) was 20% by weight.

<Example 9>

73 wt% of a linear low-density polyethylene resin (LLDPE-2) having a density of 0.92 g/cm 3 and 20 wt% of a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -27°C, and a glass transition temperature A composition comprising 7% by weight of a hydrogenated styrene-butadiene copolymer (HSBR) having a value of -50°C was used as the pressure-sensitive adhesive layer, and the substrate layer had the same constitution as in Example 5 to prepare a surface protection film.

<Comparative Example 1>

The surface protection film was created similarly to Example 1 except that the composition which consists of the ethylene-vinyl acetate copolymer whose content rate of vinyl acetate is 10 weight% sets it as an adhesive layer.

<Comparative Example 2>

A surface protection film was prepared by co-extrusion in the same manner as in Example 1, except that a composition composed of 95% by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10% by weight and 5% by weight of a rosin ester was used as an adhesive layer. .

<Comparative Example 3>

A composition composed of 93 wt% of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10 wt% and 7 wt% of a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -50°C is adhered Except setting it as a layer, it co-extruded similarly to Example 5, and created the surface protection film.

<Comparative Example 4>

A composition comprising 85 wt% of a linear low-density polyethylene resin (LLDPE-1) having a density of 0.91 g/cm 3 and 15 wt% of a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -50°C A surface protection film was created in the same manner as in Example 5, except that it was used as an adhesive layer.

<Comparative Example 5>

A composition comprising 80 wt% of a linear low-density polyethylene (LLDPE-2) having a density of 0.92 g/cm 3 and 20 wt% of a styrene/ethylene/butylene/styrene copolymer (SEBS) having a glass transition temperature of -54°C is adhered Except using it as a layer, the surface protection film was created similarly to Example 5.

<Comparative Example 6>

A composition comprising 60% by weight of an ethylene/vinyl acetate copolymer having a vinyl acetate content of 10% by weight and 40% by weight of a hydrogenated styrene-butadiene copolymer (HSBR) having a glass transition temperature of -50°C as an adhesive layer Except that, it co-extruded similarly to Example 5, and created the surface protection film.

The evaluation results of Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Tables 1 and 2.

All of the surface protection films obtained in Examples 1 to 9 have an adhesive force of 0.20 N/50 mm or more and 5.0 N/50 mm or less, and when the surface protection film is peeled from the light guide plate, there is no concern that the surface protection film will peel when the light guide plate is cut. There is nothing difficult to peel off or not to peel off. In addition, there is no problem in the re-adhesiveness to the acrylic plate, and the peeling force at the time of bonding the adhesive layers together is 0.75 N/15 mm or less, and there is almost no cohesive failure of the adhesive layer, and it is suitable for the re-adhesion of a surface protection film.

The surface protection film obtained in Comparative Example 1 has no problem with regard to re-adhesiveness and peeling force when bonding the adhesive layers, but the adhesive strength is less than 0.20 N/50 mm and it is very easy to peel, in the step after bonding the surface protection film It had the problem that a surface protection film peels.

The surface protection film obtained in Comparative Example 2 has no problem with respect to re-adhesiveness and peeling force when the adhesive surfaces are bonded, but the adhesive strength exceeds 5.0 N/50 mm and is very difficult to peel, so that in the inspection step of the adherend In addition to the extremely poor working efficiency, there was a problem in that the surface protection film did not peel off in the final step.

The surface protection films obtained in Comparative Examples 3 and 4 did not have any problems in adhesive strength and re-adhesiveness, but since the peeling force when bonding the adhesive layers was greater than 0.75 N/15 mm, the adhesive layers of the surface protection film were bonded together. In addition, when peeling surface protection films again, it took a lot of effort and had the problem that the work efficiency in the inspection process of a to-be-adhered body worsened very much.

Although the surface protection film obtained in Comparative Example 5 does not have a problem in adhesive strength, the peeling force when the adhesive surfaces are bonded to each other exceeds 0.75 N/15 mm, and re-adhesiveness to an adherend is not expressed. When bonding adhesion layers and peeling back surface protection films again, much effort was required, the work efficiency in the inspection process of a to-be-adhered body worsened very much, and it was not able to adhere to a to-be-adhered body again.

The surface protection film obtained in Comparative Example 6 has an adhesive force of 5.0 N/50 mm or more, which is extremely difficult to peel, and the working efficiency in the inspection step of the adherend is extremely poor. In addition, since the peeling force when the adhesive surfaces are bonded exceeds 0.75 N/15 mm, and re-adhesiveness to an adherend is not expressed, the adhesive surfaces of the surface protection film are bonded together, and the surface protection films are again separated from each other. When peeling, an enormous amount of effort is required, the working efficiency in the inspection step of the adherend is extremely poor, and further adhesion to the adherend is not possible again.

As described above, by using at least one of the ethylene/vinyl acetate copolymer and low-density polyethylene in the present invention and a styrene-based elastomer having a glass transition temperature of -40°C or higher for the adhesive layer of the surface protection film, a surface suitable as a light-guide plate protective film A protective film may be provided.

Claims (6)

A surface protection film having an adhesive layer and a base layer, comprising:
The adhesive layer contains, as a main component, at least one selected from the group consisting of ethylene/vinyl acetate copolymer and low-density polyethylene, and 5 to 25% by weight of a styrenic elastomer having a glass transition temperature of -40°C or higher A surface protection film, characterized in that it is a composition. The method of claim 1,
A surface protection film wherein the styrene-based elastomer is a styrene/ethylene/butylene/styrene copolymer. 3. The method of claim 1 or 2,
A surface protection film comprising low-density polyethylene as a main component of the adhesive layer, wherein the low-density polyethylene is a linear low-density polyethylene having a density of 0.90 to 0.93 g/cm 3 . 3. The method of claim 1 or 2,
The surface protection film whose peeling force at the time of bonding adhesive layers together is 0.75 N/15 mm or less. 3. The method of claim 1 or 2,
The surface protection film whose adhesive force of the adhesion layer after heating adjustment for 50 degreeC and 70 degreeC x 15 minutes with respect to an acrylic board is the range of 0.2-5.0N/50mm. 3. The method of claim 1 or 2,
A surface protection film for protecting the light guide plate.