JP2019001856A - Low elastic film - Google Patents

Abstract

To provide a low elastic film, especially a low elastic film capable of being suitably used for a surface protective sheet, a decorative sheet, a transfer sheet or the like.SOLUTION: There is provided a film capable of being extended with a small force such as about 300%, having no necking when extended at about 300% and large contraction strain after extension. Such low elastic film is obtained by arranging an ultra-thin skin layer mainly containing a polyolefin resin (B) on a substrate layer mainly containing a polyethylene resin (A) having density of less than 910 kg/m.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a low elastic film. More specifically, the present invention relates to a low-elasticity film that can be used for a surface protective sheet, a decorative sheet, a transfer sheet, and the like and is easy to stretch and hardly returns to its original shape.

Since the surface protective sheet for protecting the surface of a metal plate or the like to be deep drawn is deep drawn together with the metal plate or the like, it is required to have a property of not being distorted or wrinkled during the deep drawing. Further, there is a demand for the property that the dimension does not change over time after deep drawing. If the surface protection sheet changes in size over time, the surface protection sheet may be lifted or peeled off from the surface of the adherend such as a metal plate.
Similar properties are also required for a decorative sheet for making up the surface of a molded product having a curved surface, a transfer sheet for transferring a design layer to the surface of the molded product, and the like. When covering a molded product having a curved surface with a decorative sheet or a transfer sheet, the sheet is usually stretched along the curved surface. If the sheet does not have the property of being stretched without distortion by a small force, the molded product may be deformed or the design (decorative layer or design layer) may be wrinkled or distorted. Further, if the dimensions change after the sheet covers the molded product, the design may be distorted.

  In Patent Document 1, necking (constriction occurs at a certain limited point of the sample film when the sample is stretched, and the constricted portion grows longer with stretching) during stretching (tensile operation) occurs. This invention relates to a difficult polyolefin-based soft film. A surface protective sheet (surface protective adhesive sheet) having a pressure-sensitive adhesive layer formed on one side of the film is bonded to the surface of a metal plate or the like at the time of deep drawing processing of various metal plates or the like. Protect from scratches.

  The polyolefin-based soft film has a weight average molecular weight in the range of 100,000 to 450,000, and the resin elution amount at 0 ° C. or more and 20 ° C. or less by the cross fractionation method is 20 to 50% of the total polyolefin resin amount. %, And the resin elution amount at 20 ° C. to 75 ° C. or less is 5 to 25% by weight, and the resin elution amount at 75 ° C. to 125 ° C. is 35 to 70% by weight. And The polyolefin-based resin is generally a polymer alloy material in which a low polyolefin polymer is uniformly dispersed in a propylene-based polyolefin upon polymerization.

  The polyolefin-based soft film or surface protective sheet disclosed in Patent Document 1 is a film formed of polypropylene or a polypropylene blended with polypropylene or an EPR rubber because a copolymer component such as ethylene is uniformly present in the polymer chain. Compared to, necking is less likely to occur during elongation. In addition, the film has a low dimensional recoverability (tensile deformation recovery rate) after 100% elongation. Therefore, when the surface protective sheet using the film is used for deep drawing, the phenomenon that the surface protective sheet floats from the metal plate or the like with time is unlikely to occur.

  However, since the film contains propylene-based polyolefin as a main component, it seems that a greater force is required for elongation (tensile operation) than a polyethylene-based film. In particular, it seems that a high load is required for the work of stretching at a high magnification exceeding 100%. In addition, no consideration has been given to problems such as necking or tearing of the film when stretched at a high magnification.

  Patent Document 2 discloses a polyethylene-based laminated film excellent in uniform stretchability. Specifically, the layer (A) has an amount of propylene and / or butene-1 of 50% by weight or more, and the amount of boiling n-heptane unnecessary component is 60% by weight or less. And (B) layer is made of polyethylene produced with a metallocene catalyst, and (A) layer and (B) layer are laminated. A polyethylene-based laminated film is disclosed.

  Although the film has been confirmed with respect to stretchability (uniform stretchability), no consideration has been given to the load necessary to stretch the film and the dimensional recoverability of the film after stretching. In addition, since the amorphous polyolefin is blended in the (A) layer of the film, the film sticks to a transporting roll or the like during film formation, or the film is deformed when the film wound in a roll shape is fed out. There is a fear.

JP-A-7-90091 JP 2000-218745 A

  An object of the present invention is to provide a low elastic film. Specifically, it is an object to provide a low elastic film that can be suitably used for a surface protective sheet, a decorative sheet, a transfer sheet, and the like.

The present inventors have a film that can be stretched by about 300% with a small force, does not neck when stretched by about 300%, and has a large stretch distortion after stretching. It has been found that it can also be used for a surface protective sheet covering a plate or the like, a decorative sheet used for a molded product having a curved surface, a transfer sheet, and the like.
In addition, in such a low elastic film, a skin layer mainly composed of a polyolefin resin (B) is provided on a base material layer mainly composed of a polyethylene resin (A) having a density of less than 910 kg / m ^3. It was found that However, if the skin layer becomes too thick, the film may be necked when stretched. Therefore, it has been found that by selecting a resin having a high MFR as the skin layer and making the skin layer as thin as possible, it is possible to easily obtain a film that can be uniformly stretched without necking and hardly return to its original shape after stretching. .

That is, according to the present invention, as a means for solving the above-mentioned problems, in a low elastic film made of polyolefin resin, 300% elongation load in the expansion and contraction test described later is 5 N / 15 mm or less in both MD direction and TD direction. There is provided a low elastic film characterized in that the strain is 100% or more and the test piece does not neck while being stretched by 300%.
The skin density mainly a substrate layer mainly composed of polyethylene resin (A) of less than 910 kg / ^{m 3,} a polyolefin resin having a density excluding polyethylene resin of less than 910 kg / ^{m 3} and (B) The low-elasticity film characterized by comprising a layer is provided.
Further, the low elastic film is characterized in that the polyolefin resin (B) excluding the polyethylene resin having a density of less than 910 kg / m ³ is a polyethylene resin, a polypropylene resin or a cyclic olefin resin. .

Furthermore, the low elastic film is characterized in that the skin layer has a thickness of 0.5 to 10 μm.
Furthermore, the low-elasticity film includes the skin layer, the base material layer, and the skin layer in order, and the thickness ratio of each layer is 1: 6: 1 to 1: 30: 1. The low elastic film is provided.
Furthermore, the density of 910 kg / ^{m 3} than polyethylene test temperature 190 ° C. of the resin (A) of the melt flow rate at a load 2.16kg Ma (g / 10min), polyethylene the density is less than 910 kg / ^{m 3} When the melt flow rate at a test temperature of 190 ° C. and a load of 2.16 kg of the polyolefin-based resin (B) excluding the resin is Mb, the low elastic film is 1.5Ma ≦ Mb ≦ 5.0Ma. Provided.

Furthermore, according to this invention, the surface protection sheet characterized by using the said low elastic film is provided.
Furthermore, according to this invention, the decorative sheet characterized by using the said low elastic film is provided.
Furthermore, according to the present invention, there is provided a transfer sheet using the low elastic film.

  The low elastic film of the present invention stretches by about 300% with a small force, and does not neck when it stretches by about 300%. Therefore, the surface protective sheet using the low elastic film of the present invention can protect the surface of the adherend without being distorted or wrinkled even when deep drawing is performed together with the adherend. Further, the decorative sheet or transfer sheet using the low-elasticity film of the present invention may be extended as necessary to follow the curved surface even if the decorative layer or the molded product to which the design layer is transferred has a curved surface. it can. Therefore, a beautiful makeup layer or design layer free from distortion and wrinkles can be formed on the surface of the molded product.

  In addition, the low elastic film of the present invention has a large stretch distortion after stretching. Therefore, even if deep drawing is performed together with the adherend or the surface of the adherend is covered in an extended state, the residual stress is small and the dimension does not change over time. Therefore, the surface protection sheet, the decorative sheet, the transfer sheet, etc. using the low-elasticity film do not naturally lift or peel off from the adherend until the sheet is intentionally peeled off. .

It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of Example 1. FIG. It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of Example 2. FIG. It is a hysteresis loop figure at the time of an expansion-contraction test of the low elastic film of Example 3. It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of Example 4. FIG. It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of the comparative example 3. It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of the comparative example 4. It is a hysteresis loop figure at the time of carrying out the expansion-contraction test of the low elastic film of the comparative example 5.

[About elastic properties]
The low elastic film of the present invention comprises a polyolefin-based resin. In the following stretch test, (1) 300% elongation load is 5 N / 15 mm or less in both MD and TD directions, and (2) stretch strain is 100% or more. (3) It has an elastic property that the test piece does not neck during 300% elongation. In the present invention, the MD direction means the length direction of the film, and the TD direction means the width direction of the film. When the film is rolled, the MD direction is the film winding direction (circumferential direction), and the TD direction is the direction perpendicular to it (width direction).

<Extension test>
The expansion / contraction test in the present invention is performed as follows.
First, a film is cut into a rectangle having a width of 15 mm to prepare a test piece. When performing a stretching test in the MD direction of the film, the TD direction of the film is the length direction of the test piece when performing a stretching test in the TD direction so that the MD direction of the film is the length direction of the test piece. To be. Next, the test piece is mounted on a tensile tester. At this time, the distance between chucks is set to 40 mm.
Further, the test piece is stretched 300% at a speed of 200 mm / min (until the distance between chucks reaches 160 mm), and then the test piece is stretched at a speed of 200 mm / min until the distance between chucks returns to 40 mm.
In the present invention, the load applied to the tensile tester when it is elongated by 300% (until the distance between chucks reaches 160 mm) is set to a 300% elongation load (N / 15 mm). Further, when returning the extension of the test piece, the load applied to the tensile tester is almost 0, strictly speaking, the distance between chucks when the load becomes 0.01 N / 15 mm is L1 (mm), and 100 × (L1-40) / 40 is defined as stretching strain (%).

FIG. 1 is a hysteresis loop diagram showing the results of the film stretching test of Example 1. FIG. The upper curve in FIG. 1 shows the relationship between strain and load when the test piece is extended, and the lower curve shows the relationship between strain and load when returning the test piece to elongation.
The low elastic film of the present invention has (1) 300% elongation load (value of X in FIG. 1) of 5 N / 15 mm or less. If the 300% stretching load exceeds 5 N / 15 mm, the load when stretching the film at a high magnification becomes high, and stretching work becomes difficult. The value is preferably 4 N / 15 mm or less, particularly preferably 3.5 N / 15 mm or less. When the low elastic film having a value exceeding 5 N / 15 mm is used as a decorative sheet or a transfer sheet, the adherend may be deformed.

  In the low elastic film of the present invention, (2) stretch distortion (value of Y in FIG. 1) is 100% or more. If the stretching strain is less than 100%, when the film is used for a surface protective sheet, a decorative sheet, a transfer sheet or the like, the sheet may be lifted from the surface of a metal plate or a molded product. In addition, when used for a decorative sheet, a transfer sheet, or the like, there is a risk that the design (decorative layer or design layer) is distorted. The value is preferably 120% or more, particularly preferably 150% or more.

Further, the low elastic film of the present invention is characterized in that (3) the test piece does not neck during 300% elongation (the upper curve in FIG. 1 does not decrease between 0% and 300% strain). . If necking occurs while the low elastic film of the present invention is stretched by 300%, the film cannot be used for a surface protection sheet such as a metal plate that is deep drawn at a high magnification. At the time of deep drawing, there is a possibility that the thickness difference of the sheet is caused by necking, the sheet is cut, or the surface of the protected plate is scratched by the sheet. When the film is used for a decorative sheet or a transfer sheet, there is a risk that the pattern may be distorted or wrinkled when the sheet is stretched along the adherend.
Necking means that when a sample is stretched, necking occurs at a certain limited point of the sample film, and the necked portion grows longer with stretching. The cross section of the constricted portion is much smaller than the cross section of the remaining portion.

A low-elasticity film having such stretch properties includes a base material layer mainly composed of a polyethylene resin (A) having a density of less than 910 kg / m ^3, and a skin layer mainly composed of a polyolefin resin (B); Can be achieved.

[Substrate layer]
The base layer of the low elastic film of the present invention contains a polyethylene resin (A) having a density of less than 910 kg / m ³ as a main component. Polyethylene resins (A) having a density of less than 910 kg / m ³ are roughly classified into plastomers polymerized with metallocene catalysts and ultra-low density polyethylenes (hereinafter abbreviated as VLDPE) polymerized with Ziegler catalysts. . As for these, the ethylene-alpha olefin copolymer is common.

Plastomer has a narrow molecular weight distribution and composition distribution, and has excellent performance in impact strength, transparency, and extraction resistance, and is high in strength and heat resistance in spite of being flexible. The layer containing plastomer as a main component is more soft in the thickness direction than the layer containing VLDPE as a main component. Therefore, when using a low elastic film as a surface protection sheet, impact resistance can be imparted to the film by using plastomer as the main component of the base material layer.
VLDPE retains good physical properties even when highly filled with filler, and has excellent stress cracking resistance. The layer mainly composed of VLDPE has more flexibility in the plane direction than the layer mainly composed of plastomer. Therefore, when using a low elastic film as a decorative sheet or a transfer sheet, the extensibility of the film can be further enhanced by using VLDPE as the main component of the base material layer.
In addition, these resins can be blended and used as the polyethylene resin (A) having a density of less than 910 kg / m ^{3 according to} the present invention.

The low elastic film of the present invention can be uniformly stretched with a low load by the polyethylene-based resin (A) having a density of less than 910 kg / m ³ , and the dimensional recoverability can be kept low. The polyethylene resin (A) preferably has a density of less than 900 kg / m ^{3 and} particularly preferably less than 890 kg / m ³ .
The polyethylene-based resin (A) having a density of less than 910 kg / m ³ in the base material layer is a main component (mixing ratio is 50% by weight or more), but the mixing ratio of the polyethylene-based resin (A) is 70 to 100% by weight. Is preferable, and 90 to 100% by weight is particularly preferable.

[About skin layer]
The base material layer described above has a polyethylene resin (A) having a density of less than 910 kg / m ³ as a main component and stretches with a very weak force. Therefore, when the base material layer alone is used to transport or wind a film. In addition, the dimensional change is remarkably lacking in handling properties.
Therefore, it is desirable that the low elastic film of the present invention includes a skin layer. The skin layer preferably contains a polyolefin resin (B) as a main component in consideration of adhesion to the base material layer. As polyolefin resin (B), homopolymers of α-olefins such as polyethylene, polypropylene, poly (1-butene), poly (4-methyl-1-pentene), copolymers of ethylene and α-olefins, Examples include copolymers of ethylene and vinyl acetate, block copolymers and random copolymers of propylene and ethylene, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene. One or more of these resins may be appropriately selected and used.
In addition, when employ | adopting crystalline polyethylene-type resin (B) as a main component of a skin layer, it is necessary to select a thing with a density of 910 kg / m < ³ > or more. A polyethylene resin having a density of less than 910 kg / m ³ is poor in improving the handling properties of the base material layer. In the case where the skin layer and the base material layer both employ a polyethylene resin as a main component, the density difference between these polyethylene resins is preferably 40 kg / m ³ or more, particularly 50 kg / m ³ or more. desirable.

In view of the coextrusion moldability with the base material layer among the above-mentioned resins, it is desirable to employ a polyethylene resin, a polypropylene resin, or a cyclic olefin resin as the polyolefin resin (B). It is desirable to use high density polyethylene of 942 kg / m ³ or more. When the skin layer contains the high-density polyethylene as a main component, the effect of improving the handleability of the film is high, the adhesion with the base material layer is good, and the blocking resistance of the film is also good.
The polyolefin resin (B) in the skin layer is the main component (the blending ratio is 50% by weight or more), but the blending ratio of the polyolefin resin (B) is preferably 70 to 100% by weight, particularly 90 to 100% by weight. preferable.

  If the skin layer can improve the handleability of the film, it is desirable that the skin layer is thin. Specifically, the thickness of the skin layer in the low elastic film is preferably about 0.5 to 10 μm, particularly about 1 to 5 μm. If the skin layer is less than 0.5 μm, it is difficult to improve the handling property of the low-elasticity film, and even if the skin layer exceeds 10 μm, no further improvement in the handling property of the film is seen, and the low elasticity of the film is lowered. Only. In addition, when a low elastic film is provided with two or more skin layers, it is desirable that the thickness of each skin layer is the said range.

[About low elastic film]
The low-elasticity film of the present invention is preferably composed of the above-described base material layer and skin layer. For example, the low elastic film may be a two-layer film of skin layer / base material layer. Skin layer / base material layer / skin layer May be a three-layer film, and may be a four-layer or more film including another resin layer between the skin layer and the base material layer. However, considering the blocking properties of the film, it is desirable to provide skin layers on both sides of the base material layer. In order to maximize the low elasticity of the base material layer, it is desirable not to include layers other than the base material layer and the skin layer.

  The ratio of the thickness of the skin layer to the base material layer is not particularly limited, but in the case of two layers of skin layer / base material layer, it is preferably about 1: 3 to 1:30, and particularly 1: 5 to 1:25. In the case of three layers of skin layer / base material layer / skin layer, the ratio is preferably about 1: 6: 1 to 1: 30: 1, particularly about 1: 10: 1 to 1: 25: 1. Is desirable. If the thickness of the base material layer is less than 3 times the thickness of the skin layer (the total thickness when there are two or more skin layers), the resulting film may not have sufficient low elasticity. In addition, the film may cause necking. Moreover, when the thickness of a base material layer exceeds 30 times of a skin layer, it will become difficult to form the skin layer of a uniform film thickness on the surface of a base material layer.

In order to make the thickness of the skin layer significantly thinner than the thickness of the base material layer, MFR (JIS K7210) at a test temperature of 190 ° C. and a load of 2.16 kg of the polyolefin resin (B) as the main component of the skin layer. Mb (based on JIS K7210) at a test temperature of 190 ° C. and a load of 2.16 kg of a polyethylene resin (A) having a density of less than 910 kg / m ^{3 as} a main component of the base material layer. Then, it is desirable that 1.5 Ma ≦ Mb ≦ 5.0 Ma, and it is particularly desirable that 2.0 Ma ≦ Mb ≦ 4.0. By increasing the MFR of the resin that is the main component of the skin layer by 1.5 times or more of the MFR of the base material layer, a thin skin layer (0.5 to 10 μm) having a uniform thickness can be formed. However, if the MFR of the resin that is the main component of the skin layer becomes too high, the thickness of the skin layer becomes difficult to stabilize.

  The film thickness of the low elastic film of the present invention is not particularly limited, but in order to make the 300% elongation load 5 N / 15 mm or less, it is preferably 200 μm or less, and particularly preferably 100 μm or less. . If it is too thin, it may be broken when used as a surface protective sheet or the like. Therefore, the film thickness is desirably 20 μm or more, and particularly desirably 30 μm or more.

  The low elasticity film of this invention may contain arbitrary appropriate other components in the range which does not impair the effect of this invention. Examples of such other components include mold release agents, UV absorbers, heat stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, anti-smudge agents, and anti-blocking agents. It is done.

[Production method of low elasticity film]
The low-elasticity film of the present invention may be produced by separately forming the above-described skin layer and base material layer and then laminating them via an adhesive for dry lamination or the like. However, it is difficult to form the base material layer alone. Therefore, for example, a co-extrusion method in which a resin composition for a skin layer and a resin composition for a base layer are supplied from one extruder to a single die to form a film, or after a skin layer is formed in advance The extrusion laminating method in which the resin composition for the base material layer is extruded on the skin layer, after the two skin layers are formed in advance, the resin composition for the base material layer is extruded between the skin layers, and laminated The film may be formed by a sand lamination method or the like.
In consideration of the productivity of the film, it is desirable to use the co-extrusion method, and it is particularly desirable to adopt the T-die co-extrusion method in consideration of the film thickness accuracy.

[Surface protection sheet]
In this invention, a surface protection sheet is proposed as a use of the low elastic film mentioned above. The manufacturing method of this surface protection sheet is not specifically limited, What is necessary is just to employ | adopt a conventionally well-known method. For example, primer treatment may be performed on one surface of the low elastic film, and an adhesive layer may be provided on the treated surface. The pressure-sensitive adhesive is not particularly limited as long as it is a commonly used pressure-sensitive adhesive. For example, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, or the like can be employed.
Since the surface protective sheet of the present invention has low elasticity, even when deep drawing is performed together with a metal plate or the like, the metal plate or the like is not damaged or scratched.

[Decorative sheet]
In the present invention, a decorative sheet is further proposed as an application of the above-described low elastic film. The manufacturing method of the decorative sheet may be a conventionally known method. For example, surface treatment such as corona discharge treatment, plasma treatment, ozone treatment, etc. is applied to a low-elasticity film to form a pattern layer (solid ink layer, pattern ink layer, etc.), and a functional coat layer is provided if necessary. Can be manufactured.
The decorative sheet is laminated on the adherend using a known adhesive or the like. Since the decorative sheet of the present invention has low elasticity, even if the adherend is a R-processed wood material or a plastic molded product having a gentle curved surface, it can follow the R-processed surface or curved surface. You can make beautiful makeup on the external surface.

[Transfer sheet]
In the present invention, a transfer sheet is further proposed as an application of the above-described low elastic film. The transfer sheet can also be produced by a conventionally known method. For example, it can be produced by treating the surface of a low elastic film with a silicone-based release agent or the like and then providing a design layer on the treated surface by printing.
The method for transferring the design layer is not particularly limited. For example, using a vacuum forming apparatus, an article (adherent) to which the design is to be transferred and a transfer sheet are placed in the apparatus, and the inside of the apparatus is decompressed. Good. Since the transfer sheet of the present invention uses a low elastic film as a base material, the transfer sheet is stretched along the adherend in the apparatus and can transfer a beautiful design layer.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all.

Evaluation methods in Examples and Comparative Examples are as follows. In addition, Shimadzu Corporation autograph AG-IS was used as a tensile tester.
<300% elongation load>
The load applied to the tensile tester when the test piece is stretched by 300% (distance between chucks: 40 mm → 160 mm) is set to 300% stretch load (N / 15 mm) by the above-described stretching test.
<Elastic strain>
By the above-described stretching test, the distance between the chucks (L1 (mm)) was measured when the load applied to the tensile testing machine was 0.01 N / 15 mm when the specimen was stretched by 300% and then returned to stretch. Stretching strain (%) is calculated from equation (1).
Formula 1: 100 * (L1-40) / 40
<Necking>
About the test piece after an expansion-contraction test, the presence or absence of necking is confirmed visually.

Resins used in Examples and Comparative Examples are as follows.
Plastomer resin (PR): ethylene-α olefin copolymer (density 886 kg / m ³ , MFR 4.0 g / min (190 ° C., 2.16 kg)) by metallocene catalyst
Elastomer resin (ER): Propylene-ethylene random copolymer with a metallocene catalyst (density 862 kg / m ³ , MFR 3.0 g / min (230 ° C., 2.16 kg), ethylene content 16% by weight)
High density polyethylene (HDPE): ethylene homopolymer (density 960 kg / m ³ , MFR 8.0 g / min (190 ° C., 2.16 kg))
Propylene-ethylene random copolymer (r-PP) (density 910 kg / m ³ , MFR 12.8 g / 10 min (190 ° C., 2.16 kg))

[Example 1]
Using PR as the base material layer and HDPE as the skin layer, a three-layer low-elasticity film (40 μm) composed of skin layer / base material layer / skin layer was obtained by a T-die coextrusion method. The thickness ratio of each layer is shown in Table 1. The low elastic film was checked for the presence of 300% elongation load, stretching strain, and necking. The results are also shown in Table 1.

[Examples 2 to 4]
The low-elasticity films of Examples 2 to 4 are the same as Example 1 except that the resin for forming the base material layer, the resin for forming the skin layer, and the thickness ratio of each layer are changed as shown in Table 1. 40 μm) was obtained. Each film was checked for 300% elongation load, stretching strain, and the presence or absence of necking, and the results are also shown in Table 1.

[Comparative Example 1]
An attempt was made to form a single layer film (40 μm) of PR. However, the film could not be transported and could not be formed.

[Comparative Example 2]
A low elastic film was formed in the same manner as in Example 1 except that the thickness ratio was changed as shown in Table 2. However, the skin layer was partially interrupted at the edge of the film, and the film stuck to the transport roll at that portion and could not be formed.

[Comparative Examples 3 to 5]
The low-elasticity films of Comparative Examples 3 to 5 were the same as in Example 1 except that the resin for forming the base material layer, the resin for forming the skin layer, and the thickness ratio of each layer were changed as shown in Table 2. 40 μm) was obtained. Each film was checked for the presence of 300% elongation load, stretching strain, and necking. The results are also shown in Table 2.

The films of Examples 1 to 4 using PR for the base material layer had a low 300% elongation load, a large stretching strain, and no necking occurred.
On the other hand, the film of Comparative Example 3 in which the thickness ratio of skin layer / base material layer / skin layer was 1/4/1 and the film of Comparative Example 5 using LLDPE as the base material had large stretching strain, This is probably because the film was stretched beyond the yield point. Further, the film of Comparative Example 4 using ER as the base material layer was a highly elastic film having a small stretch strain, although the 300% elongation load was small.

In the present invention, the surface protective sheet, the decorative sheet, and the transfer sheet have been exemplified and described in detail as the use of the low elastic film, but the use of the low elastic film of the present invention is not limited thereto. Since the elasticity of the low elasticity film of the present invention is extremely low, it is suitably used for applications that are stretched while being bonded to a specific article, or those that are bonded to a specific article while being stretched. be able to.

Claims (9)

In low elastic film made of polyolefin resin,
Low elasticity, characterized in that the 300% elongation load in the following stretching test is 5 N / 15 mm or less in both the MD and TD directions, the stretching strain is 100% or more, and the test piece does not neck during 300% stretching. the film.
[Extension test]
The film is cut into a rectangle with a width of 15 mm, a test piece is prepared, the test piece is mounted on a tensile tester so that the distance between chucks is 40 mm, and the distance between chucks is 160 mm at a speed of 200 mm / min. Until the distance between chucks returns to 40 mm at a speed of 200 mm / min.
The load applied to the tensile tester when the distance between chucks is 160 mm is assumed to be a 300% elongation load (N / 15 mm). When the load applied to the tensile tester when returning to elongation is 0.01 N / 15 mm and the distance between chucks is L1 (mm), 100 × (L1-40) / 40 is expansion / contraction strain (%) And A substrate layer density mainly composed of polyethylene resin (A) of less than 910 kg / ^{m 3,} a skin layer having a density as a main component a polyolefin resin (B) excluding the polyethylene resin of less than 910 kg / ^{m 3} The low-elasticity film according to claim 1, comprising: The low-elasticity film according to claim 2, wherein the polyolefin resin (B) excluding the polyethylene resin having a density of less than 910 kg / m ³ is a polyethylene resin, a polypropylene resin, or a cyclic olefin resin. The low elasticity film according to claim 2 or 3, wherein the skin layer has a thickness of 0.5 to 10 µm. The low-elasticity film includes the skin layer, the base material layer, and the skin layer in order, and a ratio of thicknesses of the layers is 1: 6: 1 to 1: 30: 1. The low elasticity film of any one of 2 thru | or 4. The polyethylene resin (A) having a density of less than 910 kg / m ³ has a melt flow rate of Ma (g / 10 min) at a test temperature of 190 ° C. and a load of 2.16 kg, and the density is less than 910 kg / m ^3. 6. Any one of claims 2 to 5, wherein when the melt flow rate at a test temperature of 190 ° C. and a load of 2.16 kg of the polyolefin resin (B) is Mb, 1.5 Ma ≦ Mb ≦ 5.0 Ma. 2. The low elastic film according to claim 1. A surface protective sheet comprising the low-elasticity film according to claim 1. A decorative sheet using the low-elasticity film according to claim 1. A transfer sheet using the low-elasticity film according to claim 1.

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