JP2017190169A - Film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having effective heat-sealability by use of a high-efficiency and high-safety method.SOLUTION: A film is composed of a laminate not containing a layer single body of biaxial drawing polyester or a metal foil layer including a layer of the biaxial drawing polyester on a surface. The surface of the layer of the biaxial drawing polyester includes a seal part which is an area having a fine uneven structure and having heat sealability and an unsealed part which is an area having no heat sealability. An L* value of the seal part is greater by 5 or more than an L* value of the unsealed part when colors of the seal part and the unsealed part are measured by placing a black color chart printed with rich black behind the film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biaxially stretched polyester film provided with heat sealability.

  Biaxially stretched polyester films such as a biaxially stretched 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 the surface of a biaxially oriented polyester film with a short pulse to modify the surface.

Japanese Patent Publication No. 4-26339

  The short pulse irradiation method disclosed in Patent Document 1 needs to generate a high-output short pulse 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-power device has low energy efficiency and it is difficult to ensure safety. For this reason, the approach for providing heat sealability to a biaxially oriented polyester film has not been made for practical use.

  This invention is made | formed in view of such a subject, and it aims at providing the film which provided heat-sealability by the highly efficient and highly safe method, and a packaging bag using the same.

  One aspect of the present invention is a film composed of a single layer of a biaxially stretched polyester or a laminate not including a metal foil layer that includes a layer of a biaxially stretched polyester on the surface, and the surface of the layer of the biaxially stretched polyester Is equipped with a black chart printed in rich black on the back of the film, including a seal part that has a fine concavo-convex structure and a heat sealability and a non-seal part that does not have heat sealability. When the color of the seal part and the non-seal part is measured, the L * value of the seal part is 5 or greater than the L * value of the non-seal part.

  According to the present invention, it is possible to provide a film provided with heat sealability effectively by a highly efficient and safe method and a packaging bag using the film.

The top view and sectional view of the film concerning one embodiment of the present invention A plan view and a cross-sectional view showing a film manufacturing method The top view and sectional drawing of the laminated body film which concern on one Embodiment of this invention The top view of the packaging bag which concerns on one Embodiment of this invention, a side view, and the top view of the film used for manufacture of a packaging bag

(the film)
In FIG. 1, the top view of the film 10 which concerns on one Embodiment, and sectional drawing along the AA 'line | wire are shown. The film 10 is composed of a biaxially stretched polyester layer 30 alone. In a predetermined region 20 of the film 10, a seal portion 40 to which heat sealability is imparted by reducing crystallinity is formed.

  In FIG. 2, the manufacturing method of the film 10 is shown. In order to form the seal portion 40 in the region 20, the laser beam is continuously irradiated while scanning. In the example shown in FIG. 2, 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 light, it is preferable to use carbon dioxide laser light having an infrared wavelength whose energy is easily absorbed by the biaxially stretched polyester layer 30. Other laser beams can be used as long as the laser beam has an infrared wavelength.

  The region 20 of the biaxially stretched polyester layer 30 irradiated with the laser beam is heated to the melting point or higher by the laser beam irradiation, and cooled to the melting point or lower after the irradiation, whereby the crystallinity is lowered and the heat sealing property is exhibited. To do. The region 20 after the scanning irradiation with the laser beam only needs to have a lowered crystallinity, and a plurality of linear protrusions as shown in the cross-sectional view of FIG. The fine structure formed in is formed. Further, the shape of the irradiation spot of the laser beam and the scanning locus can be appropriately selected from arbitrary ones. The fine structure can take various forms depending on the form of laser light irradiation and the thickness of the biaxially stretched polyester layer 30, but generally the surface is rough due to the uneven structure and whitening due to diffuse reflection is observed.

  Thus, the method of imparting heat sealability by laser light irradiation can increase energy efficiency compared with the method of imparting heat sealability by irradiating high-power electromagnetic waves with short pulses, It is possible to ensure safety.

  The thickness of the biaxially stretched polyester layer 30 is not particularly limited as long as the polyester can be formed into a film. Such thickness is generally 2 to 3 μm or more, but is not limited thereto. When the thickness is too large, it takes time to transmit sufficient heat to the bonding interface during heat sealing, which may not be practical for use as a packaging bag. In general, a thickness of 1000 μm or less is desirable, but not limited thereto. The thickness of the biaxially stretched polyester layer 30 can be appropriately set according to the purpose of use.

(Laminated film)
The laminate film containing biaxially stretched polyester on the surface can be irradiated with laser light to impart heat sealability. In FIG. 3, the top view of the laminated body film 11 and sectional drawing along the BB 'line | wire are shown. The laminate film 11 is a laminate including a biaxially stretched polyester layer 31 and other layers 50 and 32. In a predetermined region 21 of the laminate film 11, a seal portion 41 to which heat sealability is imparted is formed by irradiating the biaxially stretched polyester layer 31 with laser light to lower the crystallinity. As the other layers 50 and 32, for example, an aluminum layer and a biaxially stretched polyester layer can be used, respectively, but the material and the number of layers are not particularly limited.

(polyester)
The polyester used for the biaxially stretched polyester layers 30, 31, 32 of the film 10 and the laminate film 11 is formed from a polymer containing an ester group obtained by a condensation method of a dicarboxylic acid and a diol component. Acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimer acid, 1,4-cyclohexene Α, β-unsaturated dicarboxylic acids such as xanthenedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid and its anhydride, fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, etc. 2,5-norbornene dicarboxylic acid anhydride, tet Examples include lahydrophthalic anhydride and 2,5-norbornene dicarboxylic acid anhydride.

  Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3- Methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, dipropylene glycol, 2,2-bis ( Examples thereof include 4-hydroxyethoxyphenyl) propane, ethylene glycol-modified bisphenol A, polyethylene glycol, and the like. Of course, a copolymer obtained from two or more kinds of dicarboxylic acids or diols, or a copolymer obtained by copolymerizing another monomer or polymer may be used.

  Specific examples include polyethylene terephthalate composed of terephthalic acid and ethylene glycol, polybutylene terephthalate composed of terephthalic acid and 1,4-tandiol, polyethylene naphthalate composed of 2,6-naphthalenedicarboxylic acid and ethylene glycol, 2 , 6-Naphthalenedicarboxylic acid and 1,4-butanediol polybutylene naphthalate, or those copolymerized or blended therewith are not particularly limited.

(Relationship between heat sealability and whitening)
As described above, the surface of the biaxially stretched polyester layer irradiated with laser light exhibits a fine structure due to a decrease in crystallinity, imparts heat sealability, and increases the diffuse reflectance of light and whitens. It has been found that the degree may be high. That is, in a biaxially stretched polyester film, heat sealability can be evaluated by evaluating the change in the degree of whitening of the surface after laser light irradiation.

  The degree of whitening of the film can be measured using, for example, a colorimeter. Color measurement is performed using an SCE (regular reflection light removal) type colorimeter in a region irradiated with laser light and a region not irradiated, and L * in the CIE (L * a * b *) color system. When the value is measured and the L * value in the region irradiated with laser light is larger than the L * value in the region not irradiated, it can be determined that whitening has occurred in the region irradiated with the laser light. If the film does not contain a metal layer such as an aluminum layer, the portion that is not irradiated with laser light has high transparency, so the entire film is placed on a predetermined color chart of one color, and the background color is unified. It is preferable to measure and suppress variations in the measured values. In order to easily evaluate the degree of whitening, the color chart preferably has a dark color, particularly black.

  Note that the measurement can be performed using a digital camera or the like instead of the colorimeter. For example, under a white light source, film is shot with a digital camera with the exposure adjusted appropriately, and the RAW data of the image is converted to a gray scale adjusted to correspond linearly to the L * value, and laser light is emitted. The L * value may be calculated by calculating the average value of the gray scale of each pixel in the region and other regions. In this case, pixel data of, for example, 100 pixels or more from a 5 mm square area may be used as the gray scale value of each area.

(Packaging bag)
In FIG. 4, the top view of the packaging bag 100 which concerns on one Embodiment, the side view, and the top view of the film 12 used for manufacture of the packaging bag 100 are shown. The packaging bag 100 is a four-side sealed bag manufactured by stacking two films 12 so that regions 22 to be described later face each other and performing a heat sealing process on the peripheral edge. The region 22 indicated by hatching at the peripheral edge of the film 12 is given heat sealability by the above-described method. The film 12 may be a single layer film such as the film 10 or a laminate film such as the film 11.

  The shape of the packaging bag 100 is not limited to the four-sided seal bag, and any shape can be adopted. For example, a film 12 is folded in half, and a three-sided seal bag formed by heat-sealing the combined peripheral edge portion or a film 12 folded in two between the two films 12 is sandwiched, A flexible packaging bag or the like having a self-supporting property formed by sealing the peripheral edge can be used.

  Three types of films were prepared, laser irradiation was performed under different conditions, and the relationship between the seal strength and the degree of whitening was investigated.

Laser irradiation was performed on each region 1 to 5 of a polyethylene terephthalate (PET) layer having a thickness of 50 μm under the following conditions using a laser irradiation apparatus with an output of 30 W.
Area 1: Output 10%, scan speed 1000 mm / sec Area 2: Output 30%, scan speed 1000 mm / sec Area 3: Output 50%, scan speed 4000 mm / sec Area 4: Output 75%, scan speed 6000 mm / sec Area 5 : Output 90%, scan speed 12000mm / sec

Laser irradiation is performed on each region 6 to 10 of a laminate composed of a PET layer with a thickness of 12 μm / aluminum layer with a thickness of 7 μm / PET layer with a thickness of 12 μm using a laser irradiation device with an output of 30 W under the following conditions. went.
Area 6: Output 10%, scan speed 1000 mm / sec Area 7: Output 30%, scan speed 1000 mm / sec Area 8: Output 50%, scan speed 4000 mm / sec Area 9: Output 75%, scan speed 6000 mm / sec Area 10 : Output 90%, scan speed 12000mm / sec

Laser irradiation with an output of 30 W is applied to each region 11 to 15 of the laminate composed of a first PET layer having a thickness of 12 μm / aluminum layer having a thickness of 7 μm / a polyethylene layer having a thickness of 30 μm / a second PET layer having a thickness of 12 μm. Using the apparatus, laser irradiation was performed from the first PET layer side under the following conditions.
Area 11: Output 10%, scan speed 1000 mm / sec Area 12: Output 30%, scan speed 1000 mm / sec Area 13: Output 50%, scan speed 4000 mm / sec Area 14: Output 75%, scan speed 6000 mm / sec Area 15 : 90% output, scan speed 6000mm / sec

  Each area of each film and the unirradiated area of the laser beam were measured using a colorimeter under the conditions of a D65 light source, 45 ° / 0 ° ring arrangement illumination, and an SCE method with a measurement diameter of 5 mm. When measuring the PET layer single film having no aluminum layer, a black chart printed with rich black (C40, M40, Y40, K100) was placed behind the film.

  The same region was heat sealed, the seal strength was measured, and the heat sealability was evaluated. The heat sealing conditions were as follows: load: 0.2 MPa, load time: 1.0 second, temperature: 160 ° C.

  The results are shown in Table 1. A region where the heat seal strength is 0 N / 15 mm, that is, a region where heat seal cannot be performed is indicated by “−”. When heat sealability is exhibited, a region where the heat seal strength is greater than 0 N / 15 mm and less than 10 N / 15 mm is indicated by “+”, and a region where 10 N / 15 mm or more is indicated by “++”. When the laser beam output is small or large, but the scan speed is too fast, the crystallinity of the film surface is not sufficiently lowered, and heat sealability is not exhibited. In addition, when the output of the laser beam is large, the portion where the degree of crystallinity has decreased is immediately evaporated, leaving only a small amount on the film, and it is also conceivable that the heat sealability is not exhibited.

  As shown in Table 1, when the L * value in the laser irradiation region was larger than the L * value in the non-irradiation region and the difference was 5 or more, heat sealability could be confirmed. Moreover, when the difference was 17 or more, it was confirmed that the heat seal strength was particularly favorable.

  The present invention is useful for a packaging bag manufactured by heat-sealing a film.

10, 12 Film 11 Laminated film 20, 21, 22 Region 30, 31, 32 Biaxially stretched polyester layer 40, 41 Sealing part 50 Aluminum layer 100 Packaging bag

Claims (2)

A biaxially stretched polyester layer alone or a film comprising a laminate not including a metal foil layer containing the biaxially stretched polyester layer on the surface,
The surface of the biaxially stretched polyester layer includes a seal portion that is a region having a fine concavo-convex structure and heat sealability and a non-seal portion that is a region not having heat sealability,
When a black chart printed in rich black is placed behind the film and the color of the seal part and the non-seal part is measured, the L * value of the seal part is 5 or more than the L * value of the non-seal part Big film. A film comprising a laminate comprising a biaxially stretched polyester layer on the surface and having an aluminum layer laminated on the biaxially stretched polyester layer,
The surface of the biaxially stretched polyester layer includes a seal portion that is a region having a fine concavo-convex structure and heat sealability and a non-seal portion that is a region not having heat sealability,
A film in which the L * value of the seal part is 5 or more larger than the L * value of the non-seal part when the color of the seal part and the non-seal part is measured.

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