JP2022073171A - Heat-shrinkable multilayer film - Google Patents

Abstract

[Problem] To provide a heat-shrinkable multilayer film capable of preventing trapping defects during overprinting and reducing ink splashes, and a method for producing the same. [Solution] The heat-shrinkable multilayer film according to the present invention comprises a substrate having a first surface and a second surface and containing a thermoplastic resin, an intermediate layer laminated on at least one of the first surface and the second surface of the substrate, and a surface layer laminated on the intermediate layer and containing a thermoplastic resin, the intermediate layer comprising a thermoplastic resin and fine particles held by the thermoplastic resin, and the surface layer has projections and recesses formed thereon to conform to the fine particles of the intermediate layer. [Selected Figure] Figure 1

Description

The present invention relates to a heat-shrinkable multilayer film capable of preventing trapping defects during overprinting and reducing ink skipping.

In recent years, many containers such as PET bottles and metal cans are equipped with a heat-shrinkable label obtained by printing or the like on a heat-shrinkable film made of a thermoplastic resin. The heat-shrinkable film is required to have various performances such as heat resistance, solvent resistance, and perforation-cutting property in addition to low-temperature shrinkage.

Generally, a heat-shrinkable film is made by winding a film into a roll, cutting it into a predetermined size, printing, sealing with a solvent, and attaching it to a container by heat-shrinking. As a result, there is a problem that the films are torn during feeding and the films cannot be peeled off from each other. Further, when the label is attached to the container due to heat shrinkage or when the label is stored in the state of being attached to the container, there is a problem that the labels adhere to each other and cannot be peeled off, or the label is peeled off from the container.

Therefore, in order to prevent the slipperiness of the films and the adhesion between the films, a method of adding an anti-blocking agent such as silica or talc is used. However, although these anti-blocking agents can exhibit slipperiness and blocking resistance by roughening the surface of the film, there is a problem that the film becomes dirty and causes poor appearance.

On the other hand, Patent Document 1 proposes a shrink film containing rubber-modified styrene, lubricant, organic fine particles and the like in order to improve blocking resistance and natural shrinkage resistance under long-term storage.

Japanese Unexamined Patent Publication No. 2002-161147.

Here, when the label of the shrink film is overprinted, the next ink is transferred onto the ink printed first, so that the ink layer printed first needs to catch the ink printed later. However, the ink printed later may not be transferred to the ink printed earlier due to the viscosity of the ink, the smoothness of the film, the wettability, etc., and such a phenomenon is called a trapping defect. Ink skipping is a state in which the ink is not transferred due to poor trapping and the color is lost. Especially in the case of gradation printing, since the plate depth of the plate to be printed later is shallow in the portion where the gradation level is low (the portion where the color is light), the amount of ink transferred is small and the ink skips due to poor trapping. In addition to ink skipping, poor trapping also causes color unevenness. The shrink film described in Patent Document 1 has a problem that such ink skipping cannot be sufficiently prevented.

The present invention has been made to solve the above problems, and to provide a heat-shrinkable multilayer film capable of preventing trapping defects during overprinting and reducing ink skipping, and a method for manufacturing the same. With the goal.

Item 1. A base material having a first surface and a second surface and containing a thermoplastic resin,
An intermediate layer laminated on at least one of the first surface and the second surface of the base material,
A surface layer laminated on the intermediate layer and containing a thermoplastic resin,
Equipped with
The intermediate layer comprises a thermoplastic resin and fine particles held by the thermoplastic resin.
A heat-shrinkable multilayer film in which irregularities are formed on the surface layer along the fine particles of the intermediate layer.

Item 2. Item 2. The heat-shrinkable multilayer film according to Item 1, wherein the thickness of the surface layer is smaller than the mode diameter of the fine particles.

Item 3. Item 2. The heat-shrinkable multilayer film according to Item 1 or 2, wherein the surface layer has a thickness of 0.1 to 3 μm.

Item 4. Item 2. The heat-shrinkable multilayer film according to any one of Items 1 to 3, wherein the intermediate layer and the surface layer contain a cyclic olefin resin.

Item 5. The intermediate layer is laminated on the first surface and the second surface of the base material, respectively.
Item 2. The heat-shrinkable multilayer film according to any one of Items 1 to 4, wherein the surface layer is laminated on each of the intermediate layers.

Item 6. A base material having a first surface and a second surface,
A surface layer laminated on at least one of the first surface and the second surface of the base material, and
Equipped with
The base material comprises a thermoplastic resin and fine particles held by the thermoplastic resin.
A heat-shrinkable multilayer film in which irregularities are formed on the surface layer along the fine particles of the base material.

Item 7. A first material for a substrate containing a thermoplastic resin, a second material for an intermediate layer containing a thermoplastic resin and fine particles held by the thermoplastic resin, and a surface layer containing a thermoplastic resin. Steps to prepare the third material and
In order to form an intermediate film in which the intermediate layer is laminated on at least one surface of the base material and the surface layer is further laminated on the intermediate layer, the first material, the second material, and the third material are used. The step of co-extrusion and
The step of stretching the intermediate film and
A method for manufacturing a heat-shrinkable multilayer film.

According to the heat-shrinkable multilayer film according to the present invention, it is possible to prevent trapping defects during reprinting and reduce ink skipping.

It is sectional drawing which shows an example of the heat shrinkable multilayer film of this invention. It is sectional drawing which shows an example of the heat shrinkable multilayer film of this invention. It is sectional drawing which shows an example of the heat shrinkable multilayer film of this invention.

Hereinafter, an embodiment of the heat-shrinkable multilayer film according to the present invention will be described. This heat-shrinkable multilayer film is formed on a sheet-like base material having a first surface and a second surface, an intermediate layer laminated on at least one of the first surface and the second surface of the base material, and the intermediate layer. It has a surface layer to be laminated. Therefore, as shown in FIG. 1, in the heat-shrinkable multilayer film according to the present embodiment, the intermediate layer 2 is laminated on both surfaces of the base material 1, and the surface layer 3 is laminated on each of the intermediate layers 2. As shown in FIG. 2, the intermediate layer 2 is laminated on one surface of the base material 1, and the surface layer 3 is laminated on the intermediate layer 2. Hereinafter, each member will be described in detail.

<1. Base material>
The base material 1 contains a thermoplastic resin, for example, a propylene-based resin, an ethylene-based resin, or an olefin-based elastomer. In addition, at least one of a petroleum resin and a cyclic olefin resin can be contained, if necessary. This will be described below. As the thermoplastic resin, those made from biomass can also be used.

<1-1. Propene resin>
As the propylene-based resin, a binary or ternary random copolymer containing propylene as a main component and α-olefin as a copolymerization component is preferable from the viewpoint of exhibiting heat shrinkage. Specifically, as the α-olefin, those composed of ethylene, 1-butene, 1-hexene, 1-octene and the like are preferable, and two or more kinds of α-olefins may be contained. The ratio of α-olefin as a copolymerization component is preferably 1 to 10 mol%. Further, the propylene-based resin may be a mixture of different propylene-α-olefin random copolymers.

The Vicat softening temperature of the propylene-based resin is preferably 100 ° C. or higher, and preferably 130 ° C. or higher. When this propylene-based resin is a mixed resin containing two or more kinds of propylene-based resins having different Vicat softening temperatures, the Vicat softening temperature of the propylene-based resin is the Vicat softening temperature of each propylene-based resin and the blending ratio (weight). It means the apparent vicut softening temperature calculated by summing the product with the ratio).

The content of the propylene-based resin with respect to 100% by weight of the resin component constituting the base material 1 is preferably 10% by weight or more, more preferably 15% by weight or more, and preferably 65% by weight or less. It is preferably 60% by weight or less, more preferably 60% by weight or less.

<1-2. Ethylene resin>
Examples of the ethylene-based resin include a branched low-density polyethylene resin, a linear low-density polyethylene resin, an ethylene-vinyl acetate copolymer, an ionomer resin, or a mixture thereof. Further, a copolymer of ethylene and α-olefin can be mentioned. Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and the like. The above-mentioned copolymer may be a random copolymer or a block copolymer. Of these, an ethylene-butene copolymer is preferably used.

The density of the ethylene resin is preferably 880 kg / m ³ or more, and preferably 950 kg / m ³ or less.

The Vicat softening temperature of the ethylene resin is preferably 50 ° C. or higher, and preferably 60 ° C. or lower. Further, it is preferable that the Vicat softening temperature of the ethylene resin is lower than the Vicat softening temperature of the propylene resin described above. The difference between the Vicat softening temperature of the ethylene resin and the Vicat softening temperature of the propylene resin is preferably 45 ° C. or higher, more preferably 55 ° C. or higher, preferably 75 ° C. or lower, and preferably 65 ° C. The following is more preferable.

The content of the ethylene-based resin with respect to 100% by weight of the resin component constituting the base material 1 is, for example, preferably 10% by weight or more, more preferably 15% by weight or more, and 60% by weight or less. It is preferably 50% by weight or less, and more preferably 50% by weight or less.

<1-3. Petroleum resin>
Examples of the petroleum resin include an alicyclic petroleum resin from cyclopentadiene or a dimer thereof, an aromatic petroleum resin from a C9 component, and the like.

The Vicat softening temperature of the petroleum resin is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, preferably 150 ° C. or lower, and more preferably 130 ° C. or lower. When the Vicat softening temperature of the petroleum resin is within the above range, good heat shrinkage can be exhibited. The difference between the Vicat softening temperature of the propylene resin and the Vicat softening temperature of the petroleum resin is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, and more preferably 30 ° C. or lower. It is more preferably 25 ° C. or lower.

The content of the petroleum resin with respect to 100% by weight of the resin component constituting the base material 1 can be, for example, 5% by weight or more, 50% by weight or less, preferably 8% by weight or more, and 45% by weight. The following is more preferable. When the content is in this range, high shrinkage can be imparted to the heat-shrinkable multilayer film, and a high-rigidity film can be obtained. When it is not more than the above upper limit, it is possible to suppress the decrease in elongation at low temperature and the peeling between layers.

The base material 1 may contain a hydrocarbon resin other than a petroleum resin such as a terpene resin and a rosin resin. Examples of the terpene resin include terpene resin from β-pinene, terpene-phenol resin and the like. Examples of the rosin-based resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin and pentaerythritol.

<1-4. Olefin elastomer>
As the olefin-based elastomer, it is preferable to use a propylene / α-olefin random copolymer elastomer and an ethylene / α-olefin random copolymer elastomer. The α-olefin random copolymer elastomer is an elastomer having a copolymerization component of α-olefin having 3 or more carbon atoms in an amount of 15 mol% or more. Here, examples of the α-olefin include propylene, butene-1, pentene-1, hexene-1, octene-1, 4-methylpentene-1, and the like.

The content of the olefin-based elastomer with respect to 100% by weight of the resin component constituting the base material 1 is preferably 60% by weight or less. If it exceeds 60% by weight, the waist strength of the heat-shrinkable multilayer film may decrease.

<1-5. Cyclic olefin resin>
It can contain a cyclic olefin resin. Examples of commercially available products of the cyclic olefin resin include ZEONOR (manufactured by ZEON Corporation), Apel (manufactured by Mitsui Chemicals Co., Ltd.), TOPAS (manufactured by Polyplastics Co., Ltd.) and the like. Specifically, for example, it can be the same as the cyclic olefin resin contained in the intermediate layer 2 described later.

<1-6. Base material thickness>
The thickness of the base material 1 is preferably, for example, 10 to 60 μm, more preferably 15 to 50 μm.

<2. Middle class>
The intermediate layer 2 is a layer that exhibits anti-blocking performance, and contains a thermoplastic resin and fine particles. By containing the fine particles, unevenness can be formed on the surface of the intermediate layer 2 as shown in the enlarged views of FIGS. 1 and 2. The thermoplastic resin may contain a cyclic olefin resin as a main component, and may also contain at least one of a polyolefin resin and a petroleum resin, if necessary. The details of these components are as described for the base material, but the differences from the base material 1 will be described below. The enlarged views of FIGS. 1 and 2 are schematic views exaggerated to explain the role of the fine particles. This point is the same as in FIG. 3, which will be described later.

<2-1. Thermoplastic resin>
<2-1-1. Cyclic olefin resin>
Examples of the cyclic olefin resin include (a) a copolymer of ethylene or propylene and a cyclic olefin (for example, norbornene and its derivative, tetracyclododecene and its derivative, etc.), and (b) a ring-opening polymer of the cyclic olefin. Alternatively, a copolymer with α-olefin, (c) a hydrogenated product of the polymer of (b) above, (d) a graft-modified product of (a) to (c) above with an unsaturated carboxylic acid and a derivative thereof, etc. Can be mentioned. Examples of commercially available products of the cyclic olefin resin include ZEONOR (manufactured by ZEON Corporation), Apel (manufactured by Mitsui Chemicals Co., Ltd.), TOPAS (manufactured by Polyplastics Co., Ltd.), and the like, as in the case of the above-mentioned base material 1. .. By using the cyclic olefin resin as a main component, the crystallinity of the thermoplastic resin can be lowered, the heat shrinkage rate can be increased, and the stretchability during film formation can be improved.

The cyclic olefin is not particularly limited, and specifically, for example, norbornene, 6-methylnorbornene, 6-ethylnorbornene, 5-propylnorbornene, 6-n-butylnorbornene, 1-methylnorbornene, 7-methylnorbornene, etc. 5,6-dimethylnorbornene, 5-phenylnorbornene, 5-benzylnorbornene and the like can be mentioned. Examples of tetracyclododecene and its derivatives include 8-methyltetracyclo-3-dodecene, 8-ethyltetracyclo-3-dodecene, 5,10-dimethyltetracyclo-3-dodecene and the like.

The number average molecular weight of the cyclic olefin resin measured by the GPC (gel permeation chromatography) method is preferably 1000 or more, and preferably 1 million or less. Within the above range, the film can be easily formed.

The glass transition temperature of the cyclic olefin resin is preferably 20 ° C. or higher, more preferably 50 ° C. or higher, preferably 130 ° C. or lower, and more preferably 100 ° C. or lower. When the glass transition temperature is 20 ° C. or higher, the heat resistance of the film surface is made good, the occurrence of blocking between containers on the mounting line can be suppressed, and the natural shrinkage rate is in a good range. can do. When the temperature is 130 ° C. or lower, the heat shrinkage rate in the lateral direction can be sufficiently increased.

The density of the cyclic olefin resin is preferably 1000 kg / m ³ or more, more preferably 1010 kg / m ³ or more, preferably 1050 kg / m ³ or less, and 1040 kg / m ³ or less. Is more preferable.

The content of the cyclic olefin resin with respect to 100% by weight of the resin component constituting the intermediate layer 2 can be, for example, 30% by weight or more and 85% by weight or less, and more preferably 40% by weight or more and 80% by weight or less. Below, it is more preferably 55% by weight or more and 75% by weight or less. Within the above range, the handleability and transparency of the heat-shrinkable multilayer film can be improved.

<2-1-2. Polyolefin resin>
Examples of the polyolefin resin constituting the intermediate layer 2 include the above-mentioned <1-1. Propene resin> and <1-2. The same material as in the section of Ethylene resin> can be used, and the content of the polyolefin resin with respect to 100% by weight of the resin component of the intermediate layer 2 can be, for example, 1% by weight or more and 50% by weight or less. It is more preferably 10% by weight or more and 40% by weight or less.

<2-1-3. Petroleum resin>
As the petroleum resin constituting the intermediate layer 2, the same petroleum resin contained in the above-mentioned base material layer can be used, and the content of the petroleum resin with respect to 100% by weight of the resin component is, for example, 1% by weight or more. , 50% by weight or less, more preferably 10% by weight or more and 40% by weight or less.

<2-2. Fine particles>
As the fine particles contained in the intermediate layer 2, either organic fine particles or inorganic fine particles can be used. As the organic fine particles, organic fine particles such as acrylic resin fine particles, styrene resin fine particles, styrene-acrylic resin fine particles, urethane resin fine particles, and silicone resin fine particles can be used. These may or may not be crosslinked, but it is desirable that they are crosslinked in order to increase the heat resistance of the fine particles. Among them, acrylic resin fine particles are preferable, and polymethyl methacrylate-based crosslinked fine particles are more preferable, from the viewpoint of compatibility with the cyclic olefin resin. Among the above organic fine particles, commercially available products include, for example, Techpolymer (manufactured by Sekisui Plastics Co., Ltd.), Finesphere (manufactured by Nippon Paint Co., Ltd.), Ganz Pearl (manufactured by Aica Kogyo Co., Ltd.), and Art Pearl (manufactured by Negami Kogyo Co., Ltd.). (Manufactured by the company) and the like.

As the inorganic fine particles, for example, silica, zeolite, alumina and the like can be used.

The most frequent particle size of the fine particles is, for example, preferably 1.0 to 7.0 μm, preferably 1.2 to 6.7 μm, and even more preferably 1.5 to 6.5 μm. , 2.0 to 6.3 μm is particularly preferable. When the mode particle size is in the above range, aggregation can be suppressed and ink skipping due to poor trapping can be effectively suppressed. The most frequent particle size was measured by a known laser diffraction / scattering method or the like.

The content of the fine particles is preferably 0.01 to 0.10 parts by weight, preferably 0.03 to 0.08 parts by weight, based on 100 parts by weight of the resin component constituting the intermediate layer 2. Is even more preferable. When the content is in the above range, as described above, the unevenness formed on the surface of the intermediate layer 2 can suppress ink skipping due to poor trapping in addition to the blocking resistance of the heat-shrinkable multilayer film. .. Further, it is preferable that the fine particles have a higher hardness than the surface layer 3 described later.

<2-3. Thickness>
The thickness of the thermoplastic resin of the intermediate layer 2 is preferably, for example, 1 to 5 μm, more preferably 1.5 to 4.5 μm.

<3. Surface layer>
The surface layer 3 is made of a thermoplastic resin. As the thermoplastic resin, for example, a cyclic olefin resin, polyethylene terephthalate, a styrene resin, or the like, or a mixture of at least one of these can be used. As the styrene-based resin, for example, a styrene-butadiene copolymer and a hydrogenated styrene-based thermoplastic elastomer can be used. The details of the cyclic olefin resin are as described above. Further, when a cyclic olefin resin is used, the glossiness is increased and the surface texture can be improved. If the cyclic olefin resin is contained in the adjacent member of the base material 1, the intermediate layer 2, and the surface layer 3, the interlayer adhesion can be improved.

The thickness of the surface layer 3 is, for example, preferably 0.1 to 3 μm, more preferably 0.2 to 2 μm, and even more preferably 0.3 to 1 μm. Further, the thickness of the surface layer 3 is preferably smaller than the mode particle diameter of the fine particles of the intermediate layer 2 described above. By doing so, as shown in the enlarged views of FIGS. 1 and 2, the surface layer 3 is formed with irregularities on the surface of the surface layer 3 along the irregularities due to the fine particles of the intermediate layer 2. Due to this unevenness, anti-blocking performance is exhibited. For anti-blocking performance, the surface roughness Rz of the surface layer 3 is, for example, preferably 1 to 5 μm, more preferably 1.5 to 4.5 μm, and 1.8 to 4 μm. It is more preferably 2 to 3.5 μm, and particularly preferably 2 to 3.5 μm.

<4. Thickness of heat-shrinkable multilayer film>
The thickness of the entire heat-shrinkable multilayer film of the present invention is, for example, preferably 20 μm or more, more preferably 25 μm or more, preferably 80 μm or less, and even more preferably 70 μm or less. When the thickness of the entire heat-shrinkable multilayer film is within the above range, excellent heat-shrinkability, excellent converting property such as printing or center sealing, and excellent wearability can be obtained.

The surface layer 3 has <2-2. Fine particles> may be contained. Further, the surface layer 3 can be composed of a single layer or a plurality of layers.

<5. Other ingredients>
The base material 1, the intermediate layer 2, and the surface layer 3 may have an antioxidant, a heat stabilizer, an ultraviolet absorber, a light stabilizer, a lubricant, an antistatic agent, a flame retardant, an antibacterial agent, and a fluorescent agent, if necessary. Additives such as a whitening agent and a coloring agent may be contained.

<6. Heat shrinkage performance of heat shrinkable multilayer film>
The heat shrinkage rate when the heat-shrinkable multilayer film of the present invention is immersed in warm water at 70 ° C. for 10 seconds is preferably 5% or more, and preferably 30% or less. Further, the heat shrinkage rate when immersed in warm water at 80 ° C. for 10 seconds is preferably 30% or more, and preferably 60% or less. Further, the heat shrinkage rate when immersed in warm water at 100 ° C. for 10 seconds is preferably 60% or more, and preferably 76% or less. When the heat shrinkage rate is within the above range, problems such as poor shrinkage do not occur, and the film can be suitably used as a heat shrinkable multilayer film.

<7. Method for manufacturing heat-shrinkable multilayer film>
The method for producing the heat-shrinkable multilayer film of the present invention is not particularly limited, but a method in which each layer is simultaneously molded by a coextrusion method is preferable. When the coextrusion method is coextrusion with a T-die, the laminating method may be a feed block method, a multi-manifold method, or a method in which these are used in combination.

Specific examples of the method for producing the heat-shrinkable multilayer film of the present invention include, for example, corresponding to the raw materials constituting the base material, the intermediate layer, and the surface layer (corresponding to the first, second, and third materials, respectively). ) Is put into an extruder, extruded into a sheet with a die (corresponding to an intermediate film), cooled and solidified by a take-up roll, and then stretched to one or two axes. As the stretching method, for example, a roll stretching method, a tenter stretching method, or a combination thereof can be used. The stretching temperature varies depending on the softening temperature of the resin constituting the film, the shrinkage characteristics required for the heat-shrinkable multilayer film, etc., but is preferably 65 ° C. or higher, more preferably 70 ° C. or higher. It is preferably 120 ° C. or lower, and more preferably 115 ° C. or lower.

The stretching ratio in the main shrinkage direction varies depending on the resin constituting the film, the stretching means, the stretching temperature, etc., but is preferably 3 times or more, more preferably 4 times or more, preferably 7 times or less, and 6 times or less. Is more preferable.

By setting such a stretching temperature and stretching ratio, in particular, the stretching of the surface layer 3 and the intermediate layer 2 causes the resin around the fine particles to become thin, and unevenness due to the fine particles can be generated in the intermediate layer 2 and the surface layer 3. can.

<8. Applications for heat-shrinkable multilayer films>
The use of the heat-shrinkable multilayer film of the present invention is not particularly limited, but the heat-shrinkable multilayer film of the present invention has excellent perforation cutability, drop impact resistance, and transparency. For example, it is suitably used as a base film for a heat-shrinkable label attached to a container such as a PET bottle or a metal can.

<9. Other aspects of heat shrinkable multilayer film>
In the above description, the heat-shrinkable multilayer film is composed of the base material 1, the intermediate layer 2, and the surface layer 3, but a second base material in which the base material 1 and the intermediate layer 2 are integrated is formed. As shown in FIG. 3, a heat-shrinkable multilayer film can be formed by forming a surface layer 3 having the same structure as the above on both surfaces of the second base material 4. It is also possible to form the surface layer 3 only on one surface of the second base material 4.

The second base material 4 of this heat-shrinkable multilayer film can be formed of the same material as the intermediate layer 2 described above. The manufacturing method is substantially the same as the above-mentioned method, and can be formed by co-extruding two materials (material for a second base material and a material for a surface layer), cooling the material, and stretching the material. The thickness of the second base material 4 can be, for example, 10 to 60 μm. Further, a configuration including a second base material layer 4 in which fine particles are unevenly distributed on the surface layer 3 side and a surface layer 3 is also within the scope of the present invention. Specifically, the base material and <1. It can be produced by coextruding a layer composed of a resin composition having the same composition as described in the section of> Substrate> and fine particles, and a surface layer. In such a case, it is observed as two layers in the cross-sectional photograph.

<10. Features>
According to the present invention, since the intermediate layer 2 contains fine particles, the fine particles can form irregularities on the intermediate layer 2. Since the unevenness of the intermediate layer 2 is also formed on the surface layer 3 covering the surface thereof, the anti-blocking performance can be exhibited by the unevenness of the surface layer 3.

Since the intermediate layer 2 is covered with the surface layer 3, it is possible to prevent the fine particles of the intermediate layer 2 from detaching from the heat-shrinkable multilayer film, and it is possible to reduce the surface roughness Rz. This makes it possible to prevent trapping defects during overprinting and reduce ink skipping. Further, for example, when the fine particles are aggregated, the aggregate tends to protrude from the intermediate layer 2, but since such a protrusion is also covered by the surface layer 3, the degree of protrusion can be alleviated.

Hereinafter, examples of the present invention will be described in detail. However, the present invention is not limited to these examples.

<1. Preparation of Examples and Comparative Examples>
As described below, heat-shrinkable multilayer films according to Examples 1 to 6 and Comparative Example 1 were produced. Examples 1 to 3 have a five-layer structure shown in FIG. 1, and Examples 4 to 6 have a three-layer structure shown in FIG. Comparative Example 1 has a structure having a base material and an intermediate layer and no surface layer.

By using the components shown in Table 1 as raw materials constituting the base material, the intermediate layer, and the surface layer and mixing them in the ratio shown in Table 1, the base material and the intermediate according to Examples 1 to 6 and Comparative Example 1 are mixed. A raw material composition constituting the layer and the surface layer was obtained.

Subsequently, using another extruder, the raw material composition constituting the base material, the intermediate layer, and the surface layer is subjected to a barrel temperature of 180 ° C. for the base material, a barrel temperature of 210 ° C. for the intermediate layer, and a barrel temperature for the surface layer. It was melted at 210 ° C., extruded from a T-die, and cooled and solidified with a roll cooled to 30 ° C. to prepare an unstretched sheet. This was stretched 5 times in the TD direction with a tenter type stretching machine having a temperature of 90 ° C. to prepare a heat-shrinkable multilayer film having the thickness shown in Table 1.

表面層、中間層、及び基材を構成する各材料の単位は、質量％である。

The unit of each material constituting the surface layer, the intermediate layer, and the base material is mass%.

<2. Evaluation>
The following evaluations were made for Examples 1 to 6 and Comparative Example 1.

<2-1. Gloss>
The glossiness at an incident angle of 45 ° was measured with respect to Examples 1 to 6 and Comparative Example 1 using a VG-2000 type manufactured by Nippon Denshoku Kogyo Co., Ltd. by a method according to ASTM D523.

<2-2. Surface roughness>
Examples 1 to 6 and Comparative Example 1 were set on Surfcom 570A manufactured by Tokyo Seimitsu Co., Ltd., and the ten-point average roughness Rz was measured in accordance with the ISO13565-1 standard. The measurement conditions were as follows.
・ Cutoff: 0.8mm
・ Measurement terminal drive speed: 0.3 mm / sec ・ Measurement length: 20.0 mm
-Measurement magnification: Vertical magnification x 10,000, horizontal magnification x 5

<2-3. Blocking>
2 measuring samples having a size of 100 mm in length × 30 mm in width (samples were cut out with the flow direction of the film as the vertical direction and the width direction as the horizontal direction) from arbitrary locations of Examples 1 to 6 and Comparative Example 1. I cut it out one by one. Next, the two measurement samples were overlapped with each other on the same surface (the surface in contact with the cooling roll) in an area of 40 mm in length × 30 mm in width. Subsequently, the overlapping measurement samples were sandwiched between two glass plates, and a weight of 5 kg was placed on the overlapping portion of the samples. The sample set in this way was placed in a constant temperature bath at 40 ° C. and left for 48 hours. Then, the sample taken out from the constant temperature bath was set in a peeling tester (Peeling TESTER HEIDON-17) manufactured by Shinto Kagaku Co., Ltd., and the blocking strength was measured at a tensile speed of 200 mm / min.

The lower the block king strength, the better, and if it is 2.0 N / cm or more, a manufacturing problem will occur. On the other hand, the inventor has confirmed that if the blocking strength is 1.5 N / cm or less, there is no problem in manufacturing, and if the blocking strength is 1.3 N / cm or less, blocking does not occur.

<2-4. Trapping (printability)>
The surface layers of Examples 1 to 6 and Comparative Example 1 were printed under the following conditions using a five-color gravure printing machine. The printing conditions were as follows.
-Film width: 900 mm
-Printing ink: OSM type made by Dainichiseika Kogyo Co., Ltd. Ink, red, yellow, blue, white (base part)
・ Ink viscosity: 15 seconds with Zahn cup method # 3 ・ Plate: Color chart plate created by engraving plate ・ Printing speed: 150 m / min

After printing, the number of ink drops per 1 m ² of Examples 1 to 6 and Comparative Example 1 was measured using a defect detector (manufactured by FUTEC), and evaluated according to the following criteria.
・ A: 5 or less ・ B: 6 to 10 ・ C: 11 or more

<2-5. Go board peeling test (interlayer adhesion)>
In an environment of a temperature of 23 ° C. and a relative humidity of 53%, a cut line was made on the surface layer side so as to have a length of 1 mm, a width of 1 mm, and 25 squares, and then a cellophane tape was attached to perform 90 ° peeling. The evaluation of the grid peeling test was based on the number of peeled cells in 25 cells as follows.
・ A: 0 to 3
・ B: 4-11
・ C: 12 or more

<2-6. Evaluation result>
The evaluation results are as follows.

According to the above results, although Examples 1 to 6 have a surface layer, the surface roughness is about the same as that of Comparative Example 1. As a result, it was found that the blocking strength was 1.5 N / cm or less in each case, and there was no problem in manufacturing. However, it was found that the blocking strength of Examples 1 to 5 in which the surface layer was formed by one kind of compound was lower than that in Example 6 in which the surface layer was formed by two kinds of compounds. Further, since Comparative Example 1 does not have a surface layer, there is a possibility that fine particles in the intermediate layer may have come off, and it is considered that the number of ink drops increased due to the larger surface roughness Rz as compared with Examples. Be done. Further, in Examples 1 to 3 and 6, since the surface layer and the intermediate layer contain the cyclic olefin resin, the layers are different from those in Examples 4 and 5 in which the cyclic olefin resin is contained only in the intermediate layer. Adhesion is improved.

1 Base material 2 Intermediate layer 3 Surface layer

Claims (7)

A base material having a first surface and a second surface and containing a thermoplastic resin,
An intermediate layer laminated on at least one of the first surface and the second surface of the base material,
A surface layer laminated on the intermediate layer and containing a thermoplastic resin,
Equipped with
The intermediate layer comprises a thermoplastic resin and fine particles held by the thermoplastic resin.
A heat-shrinkable multilayer film in which irregularities are formed on the surface layer along the fine particles of the intermediate layer. The heat-shrinkable multilayer film according to claim 1, wherein the thickness of the surface layer is smaller than the mode diameter of the fine particles. The heat-shrinkable multilayer film according to claim 1 or 2, wherein the surface layer has a thickness of 0.1 to 3 μm. The heat-shrinkable multilayer film according to any one of claims 1 to 3, wherein the intermediate layer and the surface layer contain a cyclic olefin resin. The intermediate layer is laminated on the first surface and the second surface of the base material, respectively.
The heat-shrinkable multilayer film according to any one of claims 1 to 4, wherein the surface layer is laminated on each of the intermediate layers. A base material having a first surface and a second surface,
A surface layer laminated on at least one of the first surface and the second surface of the base material, and
Equipped with
The base material comprises a thermoplastic resin and fine particles held by the thermoplastic resin.
A heat-shrinkable multilayer film in which irregularities are formed on the surface layer along the fine particles of the base material. A first material for a substrate containing a thermoplastic resin, a second material for an intermediate layer containing a thermoplastic resin and fine particles held by the thermoplastic resin, and a surface layer containing a thermoplastic resin. Steps to prepare the third material and
In order to form an intermediate film in which the intermediate layer is laminated on at least one surface of the base material and the surface layer is further laminated on the intermediate layer, the first material, the second material, and the third material are used. The step of co-extrusion and
The step of stretching the intermediate film and
A method for manufacturing a heat-shrinkable multilayer film.

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