JP6094619B2 - Surface treatment method for biaxially stretched polyester film - Google Patents

Description

  The present invention relates to a method of performing surface treatment on a film such as biaxially oriented polyester to impart heat sealability, a film imparted with heat sealability, a packaging bag using the film, and a method for producing the packaging bag.

  Biaxially oriented polyester films such as a biaxially oriented polyethylene terephthalate film are useful as various packaging materials because they are excellent in strength, heat resistance, dimensional stability, chemical resistance, fragrance retention and the like. Thus, packaging bags such as flexible pouches formed by heat-sealing such films are expected.

  However, a film having orientation is poor in heat sealability. Thus, for example, Patent Document 1 discloses a method of imparting heat sealability by irradiating electromagnetic waves with a short pulse on the surface of a biaxially oriented polyester film and modifying the surface.

Japanese Patent Publication No. 4-26339

  In the short pulse irradiation method disclosed in Patent Document 1, it is necessary to generate a short pulse with high output using a xenon gas lamp or the like in order not to impair the internal orientation of the biaxially oriented polyester film. . Such a high-powered device has low energy efficiency and it is difficult to ensure safety. Therefore, a method using such a device has not been put into practical use.

  Therefore, an object of the present invention is to provide a surface treatment method for imparting heat sealability to a biaxially oriented polyester film having high efficiency and high safety.

One aspect of the invention, in some regions of the film biaxially oriented polyester monolayer thickness 50 mu m, or thickness is a laminate comprising a surface biaxially oriented polyester layer of 12 [mu m, 2 By irradiating an infrared laser beam to the axially stretched polyester layer so that the energy to be irradiated is ² J / cm ² or more and 15 J / cm ² or less, heat sealability is achieved in a part of the biaxially stretched polyester layer. This is a surface treatment method to be applied.

  According to the present invention, it is possible to provide a surface treatment method for imparting heat sealability to a biaxially oriented polyester film having high efficiency and high safety.

The figure which shows the method which concerns on embodiment of this invention The top view of the film concerning the embodiment of the present invention The figure which shows the method which concerns on embodiment of this invention The top view which shows the modification of the fine structure of the film which concerns on embodiment of this invention The top view which shows the modification of the fine structure of the film which concerns on embodiment of this invention The top view of the film which concerns on embodiment of this invention, and a packaging bag

  Hereinafter, a method for imparting heat sealability to a biaxially oriented polyester film according to an embodiment of the present invention will be described. This method can be applied to both a film composed of a single layer of biaxially oriented polyester and a film composed of a laminate comprising a biaxially oriented polyester layer on the surface. The biaxially oriented polyester is, for example, biaxially oriented polyethylene terephthalate, but is not limited thereto. Further, it can be applied to a film having another thermoplastic resin instead of the biaxially oriented polyester layer.

(First embodiment)
FIG. 1 is a diagram for explaining a method according to the first embodiment. FIG. 1 shows, as an example, a plan view of a film 1 made of a laminate including biaxially oriented polyethylene terephthalate layers (hereinafter referred to as PET layers) on both surfaces (front and back surfaces) and along the line AA ′. FIG. The film 1 includes an aluminum layer 4 that reflects laser light laminated between two PET layers 31 and 32.

  When heat sealability is imparted to a part of the region 2 on the surface of the film 1, the region 2 is irradiated while scanning with laser light. In the example shown in FIG. 1, the irradiation spot S of the laser beam is irradiated so as to draw a plurality of parallel linear trajectories at a predetermined interval. As the laser beam, it is preferable to use a carbon dioxide laser beam having an infrared wavelength whose energy is easily absorbed by the PET layer. Other laser beams can be used as long as the laser beam has an infrared wavelength.

  The PET layer 31 irradiated with the laser light is altered by being temporarily melted by the energy of the laser light. Due to the irradiation of the laser light, the region 2 loses flatness according to, for example, the locus of irradiation, and a fine structure having a concave portion or a convex portion is formed. In the example shown in FIG. 1, as shown in the cross-sectional view, a plurality of continuous linear ridges are formed in parallel at predetermined intervals as a fine structure. The fine structure can take various forms according to the output of the laser beam, the energy density in the irradiation spot, the shape of the scanning locus, the scanning speed, and the like. In addition, such a fine structure may not occur. In addition to the formation of the fine structure or instead of the formation of the fine structure, the irradiated portion may be whitened, for example, and the light reflectance may be larger than that of other regions.

  As described above, heat sealability is exhibited by the alteration in the portion irradiated with the laser beam. As the content of the alteration, for example, at least partial reduction or disappearance of the molecular orientation of the PET layer 31 can be considered. It is also possible that other factors are involved. And the provision of the heat sealability to the region 2 is completed by irradiating the entire region 2 with scanning. In FIG. 2, the top view and sectional drawing of the film 1 which complete | finished provision of heat-sealability are shown.

  The aluminum layer 4 is a layer formed using, for example, an aluminum foil of about 9 μm, and functions to prevent the PET layers 31 and 32 from melting and shrinking and being unable to maintain a film state due to laser light irradiation. Have

  In general, when biaxially oriented polyethylene terephthalate is a relatively thin single film having a thickness of about 20 μm or less, for example, the irradiated portion may be melted and contracted by the temperature rise accompanying laser light irradiation to maintain the film state. It tends to be difficult. However, by laminating the aluminum layer 4, the shrinkage of the PET layer 31 irradiated with the laser light can be suppressed. In addition, since the aluminum layer 4 reflects laser light, the temperature does not easily rise compared to a material that absorbs laser light such as black. Therefore, even if the aluminum layer 4 is provided, the PET layers 31 and 32 can be prevented from being heated more than necessary. In addition, since the aluminum layer 4 blocks the laser beam, the PET layer 32 on the side opposite to the side irradiated with the laser beam is not altered, and heat sealability can be imparted only to one side of the film 1.

  In the film 1, the PET layers 31 and 32 were directly formed on both surfaces of the aluminum layer 4, but instead of the aluminum layer 4 and the PET layer 31 or 32, or instead of the aluminum layer 4, for example, polyethylene or the like, One or more resin layers that are easy to transmit laser light and are not easily heated may be included. Further, although aluminum is used as the material for the layer that reflects the laser beam, other materials can be appropriately used as long as the laser beam can be reflected. The layer opposite to the side irradiated with the laser beam is not limited to the PET layer, and may include one or more other layers instead of the PET layer 32.

The type of laser light, irradiation energy, irradiation spot diameter, scanning trajectory, scanning speed, and the like may be appropriately set according to the material of the PET layer 31 and the aluminum layer 4 so that the heat-sealing property is suitably developed. As an example of suitable conditions for developing heat sealability, the irradiation energy (density) of laser light is ² J / cm ² or more and 15 J / cm ² or less.

  As described above, according to the method according to the first embodiment, the predetermined region of the film 1 made of the laminated body including the aluminum layer 4 that reflects the laser light laminated between the two PET layers 31 and 32. In the above, by irradiating the laser beam while scanning, heat sealability can be imparted to a predetermined region of one PET layer 31 while preventing melting, shrinkage, etc. due to the irradiation of the laser beam.

  In addition, according to the method according to the first embodiment, since the laser beam having a constant output is continuously drawn and irradiated, the energy efficiency is higher than that in the case of irradiating a high-power electromagnetic wave with a short pulse, Safety can be easily ensured, and for example, practical use of a packaging bag formed by heat-sealing biaxially oriented polyester films can be promoted.

(Second Embodiment)
FIG. 3 is a diagram for explaining a method according to the second embodiment. The film 5 according to the present embodiment is composed of the PET layer 33 alone. In FIG. 3, the top view of the film 5 and sectional drawing along the BB 'line | wire are shown. In the following description, the description overlapping with the first embodiment will be omitted as appropriate.

  Also in the second embodiment, similarly to the first embodiment, when heat sealability is imparted to a part of the region 2 on the surface of the film 5, the region 2 is irradiated while scanning with laser light. The PET layer 33 irradiated with the laser light is altered by at least the surface on the laser light incident side being temporarily melted by the energy of the laser light, thereby forming a fine structure and exhibiting heat sealability.

  Thus, according to the method according to the second embodiment, in the region 2 of the film 5, at least one surface side is given heat sealability by irradiating the laser beam while scanning from the one surface side. Can do. One or more other layers may be provided on the other surface side of the film 5.

(Modification)
4 and 5 are plan views showing modifications of the fine structure. The fine structure described in the first and second embodiments can be a structure other than a continuous line in which a plurality of ridges are formed in parallel at a predetermined interval as shown in FIGS. . Examples of the fine structure include a structure in which a plurality of at least one convex shape or concave shape having a continuous line shape, an intermittent line shape, and a dot shape are formed. For example, an intermittent line-shaped convex shape ((a), (b) in FIG. 4), a dotted convex shape ((c) in FIG. 4), or an intermittent linear shape and a dotted convex shape (( d)) may be formed. Such fine structure patterns can be variously formed according to the output, the scanning trajectory, and the like when the laser beam is irradiated while scanning. Alternatively, the fine structure may be a structure in which planar shape units such as squares are arranged as shown in FIG. Such a structure can be formed by appropriately setting the spot diameter and spot shape of the laser beam and irradiating the laser beam on the surface. The shape unit is not limited to a quadrangle, and may be an arbitrary shape such as a triangular shape, a circular shape, or a band shape.

  Laser light irradiation may be performed by overlapping pulse irradiation instead of continuous irradiation. In this case, the irradiation energy of each pulse is preferably 0.1 J or more and 1 J or less, for example. Alternatively, the pulse speed (frequency) is preferably 1000 pulses / second or more and 500000 pulses / second or less, for example. Within such a range, energy irradiation can be performed stably and sufficiently using a general carbon dioxide laser device.

(Packaging bag)
For example, a packaging bag can be manufactured using the film which consists of a laminated body to which the heat-sealing property was provided by the method which concerns on 1st-3rd embodiment. The manufacturing method of a packaging bag includes the process of providing heat-sealability to one or more films, and the process of heat-sealing the area | regions provided with the heat-sealability of one or more films. FIG. 6 shows an example of a film and a packaging bag. In the films 11, 12, and 13, heat sealing properties are imparted by the present method at locations indicated by hatching at the peripheral edge. The packaging bag 20 can be manufactured by sandwiching the folded film 13 between the films 11 and 12 and performing a heat sealing process. The packaging bag is not limited to the packaging bag 20 and can be variously configured using one or more films. Since such a packaging bag uses a polyester film excellent in heat resistance, chemical resistance, fragrance retention and the like for the innermost layer, the contents can be suitably stored.

Example 1
The film according to the present example is a film composed of a laminate having a layer structure of biaxially oriented polyethylene terephthalate (thickness 12 μm) / aluminum (thickness 9 μm) / biaxially oriented polyethylene terephthalate (thickness 12 μm) from the surface. . Irradiation of infrared laser light was performed from one surface side of this film using a carbon dioxide laser device ML-Z9510 manufactured by Keyence Corporation. The irradiation energy was ² J / cm ² . Heat sealing was performed by applying heat and pressure at a temperature of 140 ° C. and a pressure of 0.2 MPa between the regions on the incident surface side irradiated with the laser light for 2 seconds. It was 10N / 15mm as a result of measuring the seal strength of the sample which cut out the heat seal area | region into 15 mm width.

(Example 2)
This example differs from Example 1 only in that the irradiation energy is 10 J / cm ² . The seal strength was 15 N / 15 mm.

(Example 3)
This example differs from Example 1 only in that the irradiation energy is 15 J / cm ² . The seal strength was 15 N / 15 mm.

Example 4
The film according to this example has a layer structure of biaxially oriented polyethylene terephthalate (thickness 12 μm) / aluminum (thickness 9 μm) / polyethylene (thickness 20 μm) / biaxially oriented polyethylene terephthalate (thickness 12 μm) from the surface. It is a film made of a laminate. The film was irradiated with infrared laser light from the back side using the same apparatus as in Example 1. The irradiation energy was ² J / cm ² . Further, the regions on the back surface where the laser light irradiation was performed were heat-sealed under the same conditions as in Example 1. The seal strength in the heat seal region was measured in the same manner as in Example 1. As a result, it was 10 N / 15 mm.

(Example 5)
This example differs from Example 4 only in that the irradiation energy is 10 J / cm ² . The seal strength was 15 N / 15 mm.

(Example 6)
This example differs from Example 4 only in that the irradiation energy is 15 J / cm ² . The seal strength was 15 N / 15 mm.

(Example 7)
The film according to this example is a monolayer film of biaxially oriented polyethylene terephthalate (thickness 50 μm). The film was irradiated with infrared laser light from the one surface side using the same apparatus as in Example 1. The irradiation energy was ² J / cm ² . In addition, the regions on the incident surface side where the laser light irradiation was performed were heat-sealed under the same conditions as in Example 1. As a result of measuring the seal strength in the heat seal region in the same manner as in Example 1, it was 11 N / 15 mm.

(Example 8)
This example differs from Example 7 only in that the irradiation energy is 10 J / cm ² . The seal strength was 15 N / 15 mm.

Example 9
This example differs from Example 8 only in that the irradiation energy is 15 J / cm ² . The seal strength was 15 N / 15 mm.

(Comparative Example 1)
This comparative example differs from Example 1 only in that the irradiation energy is 1 J / cm ² . The seal strength was 1 N / 15 mm.

(Comparative Example 2)
This comparative example differs from Example 1 only in that the irradiation energy is 16 J / cm ² . The PET layer on the side irradiated with laser light was evaporated by heat and disappeared, and heat sealing could not be performed.

(Comparative Example 3)
This example differs from Example 4 only in that the irradiation energy is 1 J / cm ² . The seal strength was 1 N / 15 mm.

(Comparative Example 4)
This comparative example differs from Example 4 only in that the irradiation energy is 16 J / cm ² . The PET layer on the side irradiated with laser light was evaporated by heat and disappeared, and heat sealing could not be performed.

(Comparative Example 5)
This comparative example differs from Example 7 only in that the irradiation energy is 1 J / cm ² . The seal strength was 1 N / 15 mm.

(Comparative Example 6)
This comparative example differs from Example 7 only in that the irradiation energy is 16 J / cm ² . The PET layer was evaporated by heat and disappeared, and could not be heat sealed.

  The above results are summarized in Table 1 below. As shown in Table 1, a sufficient seal strength of 10 N / 15 mm or more was obtained in each example (determination ◯). On the other hand, in each comparative example, the PET layer disappeared and heat sealing could not be performed, or even if it could be heat sealed, only a seal strength of 1 N / 15 mm was obtained (determination ×). Thereby, the effect of the present invention could be confirmed.

  The present invention is useful for improving the heat sealability of films used for packaging bags and the like.

1, 5, 11, 12, 13 Film 2 Region to impart heat sealability 31, 32, 33 Biaxial polyethylene terephthalate layer (PET layer)
4 Aluminum layer 20 Packaging bag

Claims (3)

In some areas of thick biaxially oriented polyester monolayer of 50 mu m, or thickness is a laminate comprising a surface biaxially oriented polyester layer of 12 [mu m film, the layer of the biaxially oriented polyester The surface that imparts heat sealability to the partial region of the biaxially stretched polyester layer by irradiating with infrared laser light so that the energy to be irradiated is ² J / cm ² or more and 15 J / cm ² or less. Processing method. The laser light is a pulse light, the total irradiation energy of each pulse is less than 0.1 J 1 J, surface treatment method according to claim 1.   The surface treatment method according to claim 2, wherein a maximum pulse rate of the pulsed light is 1000 pulses / second or more and 500000 pulses / second or less.

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