KR100597111B1 - Self-adhesive surface protective film - Google Patents

Abstract

In the present invention, the tensile modulus of the two-layer film is measured according to ASTM D882 as a coextruded two-layer film in which the supportive outer layer is formed of a polyolefin resin and the self-adhesive inner layer is formed of a resin containing 5 to 30% by weight of vinyl acetate units. Is 200 to 1,000 MPa, outer layer thickness is 60 to 90% of the total thickness, inner layer thickness is 10 to 40% of the total thickness, the flexural modulus for the outer layer resin measured according to ASTM D790 is X, It is a self-adhesive surface protection film, characterized in that the X / Y value is in the range of 5 to 25 when the flexural modulus of the resin is Y. It is adhesive, peelable, economical, cutable and anti-curl. )) It is useful for surface protection film of products such as film, sheet, plate plastic, metal, glass, etc., especially products requiring ultra-cleanness.

Cutting, anti-curling, self-adhesive, surface protection film

Description

Self-adhesive Surface Protective Film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film having excellent adhesiveness, peelability, economical efficiency, and excellent cutting property and anti-curl property, and more particularly, to a surface protective film suitable for an adhesive requiring ultra-cleanness. .

The surface protection film is used for the purpose of preventing scratches, contamination, corrosion, etc. of the surface generated during processing, transportation or storage of products such as film, sheet, plate plastic, metal, glass, etc. After temporarily adhering to the surface and achieving the above object, a property that can be easily peeled off is required. It also has a one-time product characteristic, so it is required to be as cheap as possible.

Conventionally, as a surface protection film, a product in which adhesives such as acrylic, urethane, and rubber are applied to a base film mainly composed of very inexpensive polyethylene, polypropylene, polyvinyl chloride, and the like have been widely used. However, such a surface protection film has seriously raised a problem that components such as an adhesive or an undried residual solvent are transferred to the adherend and remain when peeled from the adherend. In particular, this is a serious problem in the case of an adherend that requires ultra-cleanness such as a light guide plate and a polarizing plate for liquid crystal display (LCD), which are rapidly expanding in demand.

In contrast, a two-layer structure produced by a coextrusion method using an ethylene-vinylacetate copolymer, a polyolefin-based elastomer, a styrene-based elastomer or the like as a self-adhesive inner layer resin, and a polyethylene-based resin as a supportable outer layer resin. The self-adhesive surface protective film provides various tackiness according to the composition of the inner layer resin, and there is no problem remaining after being transferred to the adherend during peeling, and thus the demand for the surface protective film for the adherend requiring ultra-cleanness is expanding.

On the other hand, the film, sheet, and plate-like adherends are often peeled off part of the surface protection film at the edges during many processing processes such as cutting, cutting, and lamination. There is a serious problem of a so-called curl phenomenon that is difficult to make, and also the cutting is cut in the form of a slack edge, or sometimes the shape is cut into fine saw blade shape after cutting and the fine powder generated at this time is the surface of the adherend There is a serious problem of cutting, such as attached to the. In particular, the adherends that require extremely high purity such as LCD glass, light guide plate, and polarizing plate are more serious and occur even when all the expensive adherends have to be discarded due to such defects. All are satisfied, and there is an urgent need for the appearance of a surface protection film that completely solves these problems.

MEANS TO SOLVE THE PROBLEM In order to solve the said problem, the present inventors earnestly studied and came to this invention.

That is, the present invention is to provide a surface protection film using a specific resin, to be suitable for specific physical properties, having excellent adhesiveness, peelability, economical efficiency and excellent cutting properties and anti-curlability.

In order to solve the above problems, the present invention is ASTM D882 as a coextruded two-layer film formed of a polyacetate resin, the self-adhesive inner layer is formed of a vinyl acetate resin containing 5 to 30% by weight of vinyl acetate units. Tensile modulus of the two-layer film measured in accordance with 200 ~ 1,000MPa, the outer layer thickness is 60 ~ 90% of the total thickness, the inner layer thickness is 10 ~ 40% of the total thickness, the outer layer resin measured in accordance with ASTM D790 When the flexural modulus for X and the flexural modulus for the resin for the inner layer is Y to provide a self-adhesive surface protective film, characterized in that the X / Y value satisfies the range of 5-25.

The polyolefin resin in the present invention is any one homopolymer selected from low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, or a copolymer composed mainly of ethylene, a polypropylene homopolymer, or propylene as a main component. Copolymers, polybutenes, and the like, and the polyolefin resin may be prepared by a polymerization method using a Ziegler catalyst, a chromium catalyst, a metalocene catalyst, and the like, and the copolymer may be a random copolymer or a block copolymer. It may be in the form, the molecular structure may be any of atactic, isotactic or syndiotactic, and the polymerization method may be any of low pressure method, medium pressure method or high pressure method. It is possible to mix | blend additives, such as a heat stabilizer, a ultraviolet absorber, an antistatic agent, a fluorescent agent, with such polyolefin resin by a well-known method.

The vinyl acetate resin containing 5 to 30% by weight of the vinyl acetate unit in the present invention is a total vinyl acetate contained in the resin as a mixture of an ethylene-vinylacetate copolymer or an ethylene-vinylacetate copolymer and the polyolefin resin. It means that the content is 5 to 30% by weight. More specifically, the vinyl acetate content is a ethylene-vinylacetate copolymer having a vinyl acetate content of 5 to 30% by weight alone or a mixture of the ethylene-vinylacetate copolymer containing 5 to 30% by weight of vinyl acetate and the polyolefin resin. It is more preferable to use this 10-20 weight% thing. Usually, the higher the vinyl acetate content, the higher the adhesive strength to the adherend, and if the adhesive strength is too high, the peelability may be poor. On the contrary, if the adhesive strength is too low, there is a problem of easy peeling. It is important to select the content level. The appropriate vinyl acetate content may vary greatly depending on the adhesion characteristics such as surface characteristics, adhesion temperature, and pressure of the adherend, and when the vinyl acetate content is less than 5% by weight, it is difficult to secure desired adhesiveness, and when it exceeds 30% by weight. It is difficult to secure peelability.

The inventors of the present invention used a polyolefin-based resin as a supportive outer layer raw material as described above, and a vinyl acetate-based resin containing 5 to 30% by weight of vinyl acetate unit as a self-adhesive inner layer raw material. As well as ensuring excellent adhesiveness and peelability aimed at the present invention it can be seen that the constituent resins are very inexpensive to ensure excellent economic efficiency.

In the present invention, the core of the technology introduced in order to maintain excellent adhesiveness, peelability and economy while at the same time securing excellent cutting properties and anti-curlity is tensile elasticity rate and thickness composition for the two-layer film, and the flexural modulus of the resin constituting each layer. With the idea that the ratio is closely related to the cleavage and anti-calcule, the new attempt was successful.

First, the cutability was evaluated for the two-layer film prepared according to the various resins and thickness compositions according to the present invention. In addition, the tensile modulus of elasticity of the obtained two-layer film was measured in accordance with ASTM D882, and the correlation was obtained. As a result, it may be different depending on the cutting means, but the tensile modulus was found to be excellent when the tensile modulus of 200 ~ 1,000MPa, more preferably 300 ~ 800MPa. If the tensile modulus of elasticity is less than 200MPa, it is too flexible to cut the film at the cutting part neatly, and if it exceeds 1,000MPa, it is cut like a saw blade to generate fine fragments and contaminate the adherend. Scratch frequency is increased.

In addition, in the two-layer film according to the present invention, the outer layer thickness is 60 to 90% of the total thickness, and the inner layer thickness is preferably 10 to 40% of the total thickness. If the outer layer thickness is less than 60% and the inner layer thickness is more than 40%, the flexibility of the obtained two-layer film is so increased that the tensile modulus is difficult to meet the desired range, resulting in high possibility of cutting failure, and the outer layer thickness is more than 90%, inner layer thickness If it is less than 10%, it is difficult to secure sufficient adhesive strength, and considering the thickness deviation of a very thin inner layer of less than 10% due to the characteristics of the co-extrusion facility, it is not preferable because of high quality accidents for poor adhesion.

However, it was found that the above two means did not have a large relationship with the anti-curlity, and new means for solving the above problems were related to the flexural modulus of the self-adhesive inner layer resin and the flexural modulus of the supportable outer layer resin. That is, when the flexural modulus of the outer layer resin measured according to ASTM D790 is X and the flexural modulus of the inner layer resin is Y, it is found that excellent anti-curling property is secured when the X / Y value is within the range of 5 to 25. Could. In other words, when the X / Y value is 5 to 25, more preferably 10 to 20 has an excellent anti-curlability. If the X / Y value is less than 5, curling tends to occur in the outer layer direction, and if it exceeds 25, the film is too hard and there is a high possibility that the scratch frequency on the adherend becomes high. This is because the self-adhesive inner layer resin, which has a relatively high elasticity compared to the outer layer resin, is strongly adhered by the secondary bonding force by heat and pressure in the adhesion process with the adherend, and then peels off by any external force. If the flexural modulus of the supportable outer layer resin is weak in the process of dissipating the force to the supportable outer layer as the molecules of the resin are rearranged, the curling phenomenon that occurs in the direction of the curling in the direction becomes unstable, and conversely occurs. If the flexural modulus of the outer layer resin is large, it is inferred to be caused by being able to absorb and prevent this force, thereby preventing curling.

Introducing a method of carrying out the present invention more specifically and easily, first, the resin for the inner layer and the thickness ratio of the inner layer are determined according to the surface properties of the adherend. In other words, the vinyl acetate content and the inner layer thickness ratio of the inner layer resin having appropriate adhesive strength and peelability are first determined. Of course, the inner layer thickness ratio satisfies 10 to 40% of the total thickness. After measuring the flexural modulus (Y) for the resin for the inner layer determined as described above, and measuring the flexural modulus (X) for the various candidate candidate resins for the outer layer, the two layers obtained at the same time while satisfying the range of 5-25 What is necessary is just to select the resin for outer layers which satisfy | fills the tensile elasticity modulus with respect to a film 200-1,000 Mpa. For example, when the inner resin having a low vinyl acetate content is suitable for adhesiveness and peelability, a resin having a low vinyl acetate content generally has a relatively high flexural modulus. Polyolefin resin with high flexural modulus can be used as a supportive outer layer resin to ensure excellent anti-curlity.

The self-adhesive surface protective film of the two-layer structure according to the present invention may be obtained by a conventional inflation method or a casting method, which will be described in more detail. First, a pellet state obtained through dry branding or melt branding of a pellet state resin The resin for each layer was weighed and introduced into each hopper, followed by melt extrusion through two conventional single or twin screw extruders, and finally the self-adhesive surface protective film having a two-layer structure by air or water cooling. Can be obtained. When manufacturing a self-adhesive surface protection film suitable for LCD glass, light guide plate, polarizing plate, etc., which is particularly aimed at the ultra-cleanness, which is aimed at the present invention, ultra-class that is almost zero in a clean room in a class range of 1,000 to 10,000. It is necessary to produce using clean air as blowing air.

As described above, in the self-adhesive surface protection film according to the present invention, the support outer layer is made of polyolefin resin, and the self-adhesive inner layer is coextruded two layers made of vinyl acetate resin containing 5 to 30% by weight of vinyl acetate unit. As the film, the tensile modulus of the two-layer film is 200 to 1,000 MPa, the outer layer thickness is 60 to 90% of the total thickness, the inner layer thickness is 10 to 40% of the total thickness, and the flexural modulus for the outer layer resin is X, When the flexural modulus of the resin for the inner layer is Y, the X / Y value is in the range of 5 to 25, and it is a breakthrough that ensures excellent adhesiveness, peelability, economical efficiency, cutting property, and anti-curlity. The two-layer film thus obtained can be usefully used in the surface protection film of products such as plastic, metal, glass in the form of film, sheet or plate, especially products requiring ultra-cleanness.

Through the following examples will be described in more detail the present invention. The following examples are merely examples and are not limited to the examples.

Flexural modulus and adhesive strength, peelability, tensile modulus, cutability, and anti-curl property of the resin specimens prepared according to the following Examples and Comparative Examples were measured as follows.

Flexural Modulus

Using a universal testing machine (Instron, Inc., USA) was measured the flexural modulus of the injection specimen of the resin according to ASTM D790.

(Adhesive strength)

Laminate the film specimen (size: 100mm x 400mm) to the adherend at 40 ℃ and 2atm pressure, and then stick it at 23 ℃ and 65% RH for 2 hours, then pull out at 300mm / min using the universal testing machine. Adhesion strength (mN / 25mm) was measured as peeling force with.

(Peelability)

The film specimen was adhered to the adherend under the same conditions as when the adhesive strength was measured, and peeled after standing, while the peelability was visually observed and the contamination caused by the transition to the adherend was observed. Good, ○ Good, △ Normal, X Poor)

Tensile Modulus

Tensile modulus for the film specimens was measured according to ASTM D882 using a universal testing machine (manufactured by Instron, USA) (sample size: 100 mm length x 25 mm width, tensile speed 500 mm / min, measurement temperature 23 ° C.). Tensile modulus was measured in the running direction and the width direction, respectively, and was taken as the average value.

(Cleavability)

While sticking the film specimen to the adherend and cutting it to a certain size, cut in the form of edges when cutting, cut into fine saw blade shape, and observe the contamination of the adherend due to the generation of fine powder after cutting. (◎ good, good, good, good, bad).

(Antique)

The film specimen was adhered to the adherend, left at 23 ° C. and 65% RH for 2 hours, and then peeled off. Then, the film was observed to dry. The anti-curability was evaluated in four steps. (◎ Excellent, Good, Good, Good X bad)

Example 1

As the resin for the inner layer, an ethylene-vinylacetate copolymer (resin A) containing 15 wt% of vinyl acetate having a melt index of 1.2 g / 10 min (190 DEG C and 2.16 kg) and a density of 0.938 g / cm &lt; 3 &gt; was used. As a result of evaluating the flexural modulus of the inner resin A, 55 MPa was obtained. Low-density polyethylene (resin B) with a melt index of 1.0 g / 10 min (190 ° C. and 2.16 kg) and a density of 0.924 g / cm 3 as the resin for the outer layer, and a melt index of 0.9 g / 10 min (190 ° C. and 2.16 kg) with a density of 0.956. The resin mixture which mix | blended g / cm <3> of high density polyethylene (resin C) by 75:25 weight ratio was used. As a result of evaluating the flexural modulus of the resin mixture for the outer layer, the flexural modulus was shown to be 435 MPa (see Table 1). Each layer of the prepared pellets was weighed and introduced into each hopper and melt-extruded through two twin-screw extruders. After inflation of the laminated film, a two-layer film specimen having a total thickness of 100 μm having a thickness of 75% of the outer layer and 25% of the inner layer was finally obtained. Film molding was made using a class zero ultra clean air as blowing air in a clean room of class 10,000. An acrylic LCD light guide plate (Sehwa Polytech, 10T) was used as the adherend, and adhesive strength, peelability, tensile modulus, cutability, and anti-curlity of the obtained film specimens were measured, and the results are shown in Table 2.

[Examples 2 and 3]

As in Table 1, only the composition of the resin raw material for the outer layer was changed, and the same procedure as in Example 1 was carried out. The adhesive strength, peelability, tensile modulus, cutting property, and anti-curling property of the obtained film specimens were measured and the results are shown in Table 2.

Example 4

As the resin for the inner layer, an ethylene-vinylacetate copolymer (resin D) containing 12 wt% of vinyl acetate having a melt index of 1.0 g / 10 min (190 DEG C and 2.16 kg) and a density of 0.936 g / cm 3 was used. As a result of evaluating the flexural modulus of the inner resin D, the result was 70 MPa. As resin for outer layer, resin mixture containing high density polyethylene (resin C) and melt index 5.0 g / 10 minutes (190 ° C, 2.16 kg) and medium density polyethylene (resin E) having a density of 0.937 g / cm 3 at a 70:30 weight ratio. Was used. As a result of evaluating the flexural modulus of the resin mixture for the outer layer, the flexural modulus was shown to be 850 MPa (see Table 1). The prepared resin was carried out in the same manner as in Example 1 to obtain a total thickness of 90 μm having a thickness of 70% for the outer layer and 30% for the inner layer. Two-layer film specimens were obtained. The adhesive was used in the same manner as in Example 1, and the adhesive strength, peelability, tensile modulus, cutting property, and anti curl property of the obtained film specimens were measured, and the results are shown in Table 2.

Example 5

As the resin for the inner layer, an ethylene-vinylacetate copolymer (resin F) containing 18 wt% of vinyl acetate having a melt index of 2.0 g / 10 min (190 DEG C and 2.16 kg) and a density of 0.940 g / cm &lt; 3 &gt; was used. As a result of evaluating the flexural modulus of the inner resin F, the result was 50 MPa. Outer layer resins are high density polyethylene (resin C), medium density polyethylene (resin E), polypropylene homopolymer (resin G) of 1.5 g / 10 min (230 ° C., 2.16 kg), and a density of 0.910 g / cm 3. Was used in a 30:60:10 weight ratio. As a result of evaluating the flexural modulus of the resin mixture for the outer layer, the flexural modulus was 935 MPa (see Table 1). The prepared resin was carried out in the same manner as in Example 1 to obtain a total thickness of 70 μm having a thickness of 70% for the outer layer and 30% for the inner layer. Two-layer film specimens were obtained. The adhesive was used in the same manner as in Example 1, and the adhesive strength, peelability, tensile modulus, cutting property, and anti curl property of the obtained film specimens were measured, and the results are shown in Table 2.

Comparative Example 1

It carried out similarly to Example 4 except having used ethylene-vinylacetate copolymer (resin D) alone as an inner layer resin, and using low density polyethylene (resin B) alone as an outer layer resin (refer Table 1). The adhesive strength, peelability, tensile modulus, cutting property, and anti-curling property of the obtained film specimens were measured and the results are shown in Table 2.

Comparative Example 2

It carried out similarly to Example 5 except having used the resin mixture which mix | blended resin C, resin E, and resin G by 10:10:80 weight ratio as resin for outer layers (refer Table 1). The adhesive strength, peelability, tensile modulus, cutting property, and anti-curling property of the obtained film specimens were measured and the results are shown in Table 2.

Table 1 Raw Material Composition, Flexural Modulus and Film Thickness Composition for Each Layer for Examples and Comparative Examples

TABLE 2 Film property evaluation results obtained according to Examples 1 to 5 and Comparative Example 1

As can be seen in Examples 1 to 3, it can be seen that the adhesiveness and the peelability are satisfied, and both the cutting property and the anti-curling property are excellent, and in particular, as the X / Y value increases, the anti-curling property becomes more excellent. This phenomenon can also be observed in Examples 4 and 5 modified in the type and thickness of the resin. On the other hand, when looking at Comparative Example 1, the cutability and anti-curlability is very poor, it is considered that the film tensile elasticity modulus has a very low flexibility, due to too small X / Y value. In addition, referring to Comparative Example 2, the same inner layer and outer layer resins as in Example 5 were used, but were prepared by varying the mixing ratio of the resins constituting the outer layer. The X / Y value exceeded 25 and the tensile modulus of the film was 1,000 MPa. In case of exceeding the anti-curling property is somewhat good, but the cutting property is very poor. This is due to the fact that the film is so hard that it cuts like a saw blade, causing fine chips to contaminate the adherend as well as an increase in the frequency of scratches on the adherend.

The present invention is a coextruded two-layer film formed of a polyolefin resin and a self-adhesive inner layer of a vinyl acetate resin containing 5 to 30% by weight of vinyl acetate units. By adjusting the thickness composition and appropriately adjusting the X / Y value, which is the ratio of the flexural modulus of the outer layer resin to the flexural modulus of the inner layer resin, it can be seen that satisfactory adhesiveness and peelability can be satisfied, and excellent cutting property and anti-curlability can be secured. .

Claims (7)

Tensile modulus of the two-layer film formed according to ASTM D882 as a coextruded two-layer film formed of a polyolefin resin and a self-adhesive inner layer made of a vinyl acetate resin containing 5 to 30% by weight of vinyl acetate units. Is 200 to 1,000 MPa, outer layer thickness is 60 to 90% of the total thickness, inner layer thickness is 10 to 40% of the total thickness, the flexural modulus for the outer layer resin measured according to ASTM D790 is X, A self-adhesive surface protective film, characterized in that the flexural modulus of the resin is Y when the X / Y value satisfies the range of 5 ~ 25. The method of claim 1, The polyolefin-based resin is any one homopolymer selected from low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, or a copolymer based on ethylene, a polypropylene homopolymer, or a copolymer based on propylene, and a polybutene Self-adhesive surface protective film, characterized in that at least one compound selected from the group consisting of. The method of claim 1, The vinyl acetate-based resin is a self-adhesive surface protective film, characterized in that the mixture of ethylene-vinylacetate copolymer or ethylene-vinylacetate copolymer and the polyolefin resin. The method of claim 3, wherein The vinyl acetate-based resin is a self-adhesive surface protective film, characterized in that the vinyl acetate content of 5 ~ 30% by weight of ethylene-vinylacetate copolymer. The method of claim 3, wherein The vinyl acetate-based resin is a self-adhesive surface protective film, characterized in that the mixture of the ethylene-vinylacetate copolymer having a vinyl acetate content of 5 to 30% by weight and the polyolefin resin. A molded article selected from the group consisting of plastic, metal and glass in the form of a film, sheet or plate comprising the surface protection film of any one of claims 1 to 5. The method of claim 6, Molded article, characterized in that the molded article is any one selected from glass for LCD, light guide plate, polarizing plate.