JP2002316360A - Heat-shrinkable film with cutting line and method for forming cutting line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a cutting line showing superb cutting properties on a transverse uniaxially oriented heat-shrinkable polyester film to be used for a cap seal or a shrink label of a bottle or the like and thereby achieve the easy opening of the cap seal or the easy release of the label after their use (separate recovery of a container and the label). SOLUTION: This heat-shrinkable film is of such a construction that the cutting line (11) which is positioned intersecting an orientation direction is formed on the transverse uniaxially oriented polyester film molded in the form of a tube in the orientation direction as a peripheral direction and a thick walled part (13) is formed on both sides of the film along the cutting line (11). The wall thickness of the thick walled part (13) is preferably 1 to 5 tF (tF is the wall thickness of a film). The cutting line (11) is preferably a row of linearly arranged through holes (hole diameter <= about 0.5 mm and pitch <=about 2.0 mm). The cutting line (11) with the thick walled part is efficiently formed by scanning the film with a carbon dioxide gas laser in a direction intersecting the film orientation direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a cut line of a heat-shrinkable film tube attached to a container such as a bottle as a cap seal or a shrink label, and more particularly to a cut of a heat-shrinkable tube made of a polyester film. This makes it possible to easily open the cap seal and cut off the label when separating the label from the used container.

[0002]

2. Description of the Related Art Conventionally, heat-shrinkable tubes have been used as cap seals, shrink labels, and the like to be attached to containers such as bottles. This is formed into a cylindrical shape with the stretching direction of the transversely uniaxially stretched film as the circumferential direction, and is fitted to the mouth or the body of a container (plastic bottle, glass bottle, etc.) and subjected to a heat treatment (steam heater, etc.). ) Is attached in close contact by heat shrinking. Polyvinyl chloride has been widely used as the heat-shrinkable tube so far. However, in recent years, a polyester film has been replaced with a polyester film having excellent surface characteristics (gloss, printability, etc.), dimensional stability, weather resistance, and the like. The amount of harmful substances generated at the time of disposal after use is increasing because it is advantageous for environmental protection and the like.

As shown in FIG. 7, a heat-shrinkable tube is used to open a cap seal and separate a label from a used container (separate collection of a bottle / label).
1) is often provided. The cut line is a tube (1
It is formed in the vertical direction (direction intersecting with the stretching direction of the film) for the peeling of 0). For the purpose of facilitating the cutting operation, a method in which two cutting lines (11) are provided in parallel and cut in a tape shape as shown in FIG. 8 may be adopted. Conventionally, these cut lines are formed as a row of slits (cutting marks of the blade) by pressing a blade (Thomson blade, rotary blade, etc.) against the film with a punching machine (die roll, punching sewing machine, etc.).

[0004]

As described above, the use of a uniaxially stretched polyester film as a heat-shrinkable tube material has been increasing in recent years. In the vertical direction = direction crossing the film stretching direction). When the cap seal or shrink label is attached to a bottle or the like as shown in FIG. 11, when the cap seal is opened or the label is peeled off (separated from the bottle), the cap seal is easily broken in the horizontal direction during the cutting as shown in FIG. It is difficult to smoothly cut the entire length of (11). Even in a system in which two cut lines are provided and cut in a tape shape as shown in FIG. 8, a problem such as tearing of the tape in the middle of the cut is often caused.

[0005] As a countermeasure, it is conceivable to increase the length of the slit (cutting mark of the blade) of the cut-off line and increase the slit interval. However, even if the slit configuration is changed in such a manner, it is difficult to provide good cutability with a heat shrinkable tube made of polyester. In addition, due to the change in the slit form, a problem arises that a film crack, a tube distortion, and the like starting from the slit are easily generated in a heat shrinking step of a tube mounted on a bottle or the like. The present invention aims to solve the above-mentioned problems related to the tube of the heat-shrinkable polyester film,
The cut line is cut well, and the cap seal or label attached to the bottle or the like can be opened and separated smoothly.

[0006]

SUMMARY OF THE INVENTION The heat-shrinkable film with cutout lines of the present invention is substantially uniaxially stretched polyester film formed into a tube with the stretching direction of the film being the circumferential direction. The cutout line is formed in the direction of the cutout, and thick portions are formed on both sides along the cutout line.

As an effect of increasing the thickness of both sides of the cut line, lateral tearing during cutting is suppressed and suppressed. Therefore, the tube is easily cut when the tube is mounted on a bottle or the like. Since it is possible to smoothly cut from the start end to the end, conventional difficulties in opening the cap seal and peeling the label (separate collection of bottle / label, etc.) are eliminated. This cut line can be efficiently formed by applying a laser beam irradiation method as described later.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing embodiments. 1 to 4 show a form of a cut line formed on the film (F) (FIG. 1: a plan view, FIG. 2: a cross section taken along the line AA, FIG. 3: a cross section taken along the line BB,
(Fig. 4: CC section). Film (F) is a transversely uniaxially stretched heat-shrinkable polyester film.
Are formed by scanning a laser beam in a direction (vertical direction) crossing the film stretching direction (circumferential direction of the tube to be formed).

The perforated line (11) is formed as a row of through-holes or recessed thin portions. Fig. 2 (cross section taken along the line AA in Fig. 1)
Shows an example in which the perforated line (11) is composed of a row of through-holes ( _12a ) (lined at appropriate intervals). The thick portions (13) on both sides of the cut line (11) bulge out on both front and back surfaces of the film and extend in a bank shape along the cut line. Chain line (13 _T) denotes the top of the thick portion (13), the broken line (13 _B) shows the Susoen.

FIG. 5 (cross section taken along the line AA in FIG. 1) shows another form of the cut line. The cut-out line (11) is formed in a recessed thin portion (1) different from FIG. 2 (the row of the through holes 12).
_2b ) (formed in a line at appropriate intervals), and the thick portions (13) extend on both sides thereof.

Thick portions (13) extending on both sides of the cut line
The thickness of _{(t 13)} (thickness of the top 13 _T), in order to makes it clear the cut-improving effect (cut middle liable to occur transverse direction of tearing prevention), about 1.1t _F ~5t _F (t _F : film thickness). More preferably, 1.
It is a 3t _F ~5t _F. The thick portion (1) shown in FIGS.
3) has an uneven shape in which the height changes repeatedly along the cut line direction, which depends on the laser beam irradiation conditions. If it extends along the cut line, such an uneven shape may be used. In addition, the through hole (1
The thickness before and after 2) (in the direction of the cutting line) is the thick portion (13)
Thinner wall thickness.

If the thick portion (13) extends on both sides, the cut line (11) may be a perforated cut line (FIG. 2), which is a row of the through holes (12a) as described above, or a thin line. Any of the half-cut cutting lines composed of the row of recesses (12b) (FIG. 5) may be used, but when comparing the cutting performance of both, the perforated cutting line (row of through holes) is more excellent. The shape of the opening of the through hole (12a) may be a true circle or a deformed oval shape (a through hole formed by laser beam scanning may extend in the scanning direction = vertical direction depending on irradiation conditions). Oval shape).

The cut line (11) and the thick portion (13)
A specific example of the original size will be described with reference to FIG.
Hole diameter (d) of hole (12a): about 0.5 mm or less (vertical direction
In the case of an oval shape, the average hole in the vertical and horizontal directions
Diameter), hole pitch (center-to-center distance) (p): about 2.0 mm or less
And the thickness (t) of the thick portion (13)₁₃): About 1.1 to 5
t _F(t_FIs the film thickness), thick portions on both sides of the cut line
Spacing (W₁₃): About 1.5 mm or less. Cut out again
Film thickness when the line is a row of thin recesses (12b)
Part) is about × 1/3 (t_F: Film thickness) or less (thin
The film surface of the film may be partially defective.) What
Depending on the conditions for forming the cut line, the through hole (12
The edge (14) such as a) is the original thickness of the film (t)._F)
Although it is slightly thicker, the degree of thickening depends on both sides of the cut line.
Less than the thick part (13) of
And not.

The cutting line (11) is formed as a single cutting line or a double cutting line for cutting into a tape shape (FIGS. 7 and 8). In addition, as shown in FIG. 9, for the purpose of further improving the cutability, it is formed as a double line composed of two adjacent cut lines. The figure shows two cut lines (1
1) Although each of (11) is a double line, one cut line (FIG. 7) may be formed as a double line.
The gap between the double lines (interval between cut lines) is, for example, 1 mm
It is about. Laser irradiation makes it easy to form such a double line.

The cut line (11) is formed at a uniform pitch over the entire length. For example, as shown in FIG. 10, a portion (A) on the cut start end side when peeling from the bottle (20) is formed. (The hole diameter d is 0.3 mm and the hole pitch p of the part A is about 0.5)
mm, the hole pitch of the B portion is about 1.5 mm), and the like, so that the sharpness at the start of cutting can be further improved by adjusting the shape according to the shape of the container and the mounting mode of the tube. In addition, as a supplementary measure to improve the cutting performance, a notch (length from the edge) about the starting edge of the tube (the upper and lower ends of the tube in FIGS. 7 to 9 and the portion A in FIG. 10) is used. 1-10mm, preferably 2-6mm) along (or overlapping) the cut line (11)
It may be provided.

Regarding the stretching process of the heat-shrinkable film (F) of the present invention, the term “substantially uniaxially stretched” means not only a film uniaxially stretched in the horizontal direction of the film (circumferential direction of the tube) but also It includes films that have been biaxially stretched in the horizontal / vertical directions. The biaxially stretched film preferably has a stretching ratio of about 2 times or more (for example, 2 to 7 times) in the horizontal direction (the circumferential direction of the tube) and about 1.5 times or less in the vertical direction.

The heat-shrinkable film (F) preferably has a heat-shrinkage rate (horizontal direction) of 30% or more (90 ° C. hot water × 10 seconds). This is because the laser beam irradiation (scanning in the vertical direction) for forming the cutout line (12) effectively forms the thick portion (13) as a function of the heat shrinkage stress. The heat shrinkage is more preferably at least 50%.

The cut line (11) of the present invention is formed efficiently by laser irradiation. When a small area of the film is irradiated with a laser beam, the small area instantaneously dissolves or evaporates to form a fine hole or a recessed thin portion. By the beam scanning in the direction (vertical direction) crossing the stretching direction of the transverse uniaxially stretched film, the cut line (11) and the thick portions (13) on both sides thereof are simultaneously formed. The thick portion (13) is formed because a local thermal contraction stress (lateral direction) is generated near both sides of the cut line (extending in the vertical direction) due to the thermal effect when the beam is irradiated. It depends.

The laser may be an argon laser, a YAG laser, or the like as long as it is absorbed by the polyester film. However, the carbon dioxide laser is easy to obtain a high output (energy) and easily absorbed by the polyester film. It is suitable for forming the cut line (11) and the thick portion (13) in the present invention.

The forming direction (laser scanning direction) of the cut line (11) is 45 degrees with respect to the film stretching direction (horizontal direction).
It is preferably at least (45-90 °), and most preferably 90 °. Setting the crossing angle of the cut line with respect to the stretching direction of the film in this manner is effective in promoting the formation of the thick portion (13).

The laser irradiation is performed, for example, at the center seal line of the film (a long strip-shaped film is rolled out from a roll and formed into a tube, and both edges are adhered to form a long tube-shaped body).
In the above, it can be carried out under continuous transfer of the film. Irradiation conditions (laser output, depth of beam focus, scanning speed
= Film transfer speed, beam ON / OFF cycle, etc.), the hole diameter (d), pitch (p), form of thick portion (thickness t ₁₃ , facing width w ₁₃ etc.) of the cut line can be arbitrarily set. Can be adjusted. It should be noted that printing (product name, design, etc.) on the film does not hinder the laser irradiation, and either the printing surface or the non-printing surface may be the irradiation surface.

Since the cut line in the present invention is formed by the thermal energy of a laser, unlike a conventional mechanical method (cutting a knife), a defect such as a micro crack (a heat shrinking step of attaching a tube to a bottle or the like). (Which is likely to be a starting point of film breakage), and the tube mounting property is improved. Further, the cut line formed of the through-holes and the like of the present invention does not have a sharp edge (likely a starting point of film breakage due to stress concentration) like a cut line (rows of linear slits) by a cutting tool, and thus, when the tube is mounted. The stress concentration is reduced and avoided, and the breakage resistance is excellent. For this reason, the minute holes of the cut line can be formed densely (with a small pitch), and the cutability can be further improved as an effect of densification.

It is also easy to form the cut line as a through-hole having an extremely fine diameter of sub-millimeter (for example, 200 to 100 μm) depending on the laser irradiation conditions. With such an extremely fine hole, the sealability when the tube is attached to a beverage bottle or the like as a cap seal is high, and it is possible to prevent an unexpected trouble (for example, invasion of a fine insect) in a product distribution process. It is possible, which is advantageous in terms of safety and health and quality assurance.

As the heat-shrinkable film of the present invention, those having various compositions known as polyester films are used. For example, JP-A-62-91555, JP-A-63-23662
No. 3, JP-A-7-311547, JP-A-11-115133, various ones disclosed in JP-A-2000-318105, etc., as the dicarboxylic acid component of the raw material, terephthalic acid, isophthalic Acids, aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and azelaic acid; diol components such as ethylene glycol, diethylene glycol, butylene glycol, neopentyl glycol, and 1,4 -Cyclohexanedimethanol and the like. As a specific example,
Space Clean S7570, S7553, S7561
(Manufactured by Toyobo Co., Ltd.), "Hishipet LX-10S" (manufactured by Mitsubishi Plastics, Inc.), "Fancy Wrap TAS" (Gunze Co., Ltd.)
And BPT5A (manufactured by BONSET).

[0025]

[Example] (1) Preparation of test tube Using a heat-shrinkable polyester film, a test tube A (shrink label for bottle mounting) having two cut lines (tape cut lines) by the following steps: And a test tube B (cap seal for milk bottle) was prepared.

First, a product name, design, and the like were printed (gravure printing, using a urethane-based ink) on the back surface of the heat-shrinkable polyester film, and finally, solid white printing was performed on substantially the entire surface. While a strip obtained by slitting the film to a predetermined width was fed out from a film roll, formation of a cut line and subsequent center sealing were performed under continuous transfer of the film to obtain a long tubular body.

The cut line of the strip is formed by irradiating two carbon dioxide gas laser beams to a predetermined position with the front surface of the film as an irradiation surface. This was performed by bonding with an organic solvent-based adhesive. The obtained long cylindrical bodies were cut at a predetermined pitch to obtain test tubes A and B. The film material type of each test tube, the laser irradiation conditions for forming the cut line, and the form of the formed cut line are as follows.

[Test tube A] (Shrink label for bottle mounting) Film "Space Clean S755" manufactured by Toyobo Co., Ltd.
3) Heat shrinkage: 68% in the horizontal direction, 4% in the vertical direction (90 ° C hot water x 10
Seconds), Thickness: 50μm Laser beam irradiation conditions Output: 20W Frequency (ON / OFF cycle): 1360Hz Scanning speed (= film transfer speed): 40m / min Form of cut line Through hole (12a): Diameter (d) approx. 250μm (beam scanning direction about 300
μm) Pitch (p) about 500 μm (hole spacing about 200 μm) Thick part (13): thickness (T ₁₃ ) about 180 μm, facing width (W ₁₃ ) about 40
0μm

[Test tube B] (Cap seal for milk bottle) Film "Space Clean S757" manufactured by Toyobo Co., Ltd.
0 ”Thermal shrinkage: 58% in horizontal direction, 3% in vertical direction (90 ° C hot water x 10
Seconds), Thickness: 45μm Laser beam irradiation condition Output: 16W, Frequency (ON / OFF cycle): 2500Hz Scanning speed (= Film transfer speed): 100m / min Form of cut line Through hole (12a): Diameter (d) Approx. 320 μm (Approx. 350 in beam scanning direction
μm) Pitch (p) about 650 μm (hole spacing about 300 μm) Thick part (13): thickness (T ₁₃ ) about 200 μm, facing width (W ₁₃ ) about 45
0μm

(2) Attaching and Cutting to Container (2.1) Test Tube A A 500 ml PET bottle filled with tea was covered as a shrink label on a body portion, and heated and attached by a steam heater (50 bottles). Book). After being attached in this manner, a finger was pinched between the two cut lines, and pulled off in the cut line direction to cut off the bottle. All the labels had good cut lines, and the entire length of the tube could be cut off smoothly without causing horizontal tearing or tearing during cutting.

(2.2) Test tube B A cap glass was placed on the mouth of a capped milk glass bottle as a cap seal, and heated with a steam heater and attached in a tight contact state (50 bottles). After being attached in this manner, the space between the two cut lines was picked up with a finger, pulled in the cut line direction, and cut off to separate from the mouth of the bottle. Each of the cap seals had a good cut line, and the entire length could be cut off smoothly without causing horizontal tearing or tearing during cutting.

[0032]

The heat-shrinkable polyester film of the present invention has a good cutting line, and can be suitably used as a cap seal or label for bottles, etc., cutting at opening, label separation after use, etc. Is easy, and the usefulness of the polyester film is enhanced.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a cut line of a heat-shrinkable film of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along the line BB of FIG. 1;

FIG. 4 is a sectional view taken along the line CC of FIG. 1;

FIG. 5 is a view showing another example of a cross section taken along the line BB of FIG. 1;

FIG. 6 is an explanatory sectional view of the form of a cut line (FIG. 1 (1):
FIG. 2B is a view in the direction of the arrow BB, and FIG.

FIG. 7 is an external perspective view showing an example of a cut line forming mode of a tube.

FIG. 8 is an external perspective view showing another example of the cut line forming mode of the tube.

FIG. 9 is an external perspective view showing another example of the cut line forming mode of the tube.

FIG. 10 is an external perspective view illustrating an example of a mounting mode of a tube to a container.

FIG. 11 is an external perspective view showing a problem of tearing in a horizontal direction when a tube is cut off.

[Explanation of symbols]

 10: heat-shrinkable tube 11: cut-out line 12a: through hole 12b: thin-film recess 13: thick portion 20: bottle F: heat-shrinkable film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E068 AE00 DB10 4F210 AA24 AE01 AG01 RC02 RG13 RG15

Claims (6)

[Claims] 1. A substantially uniaxially stretched polyester film formed into a tube with the stretching direction of the film being a circumferential direction, wherein a cut line is formed in a direction crossing the stretch direction, and the cut line is formed along the cut line. A heat-shrinkable film with cutout lines, characterized in that thick portions are formed on both sides. 2. The heat-shrinkable film with a cut-off line according to claim 1, wherein the cut-out line comprises a row of through holes arranged in a line. 3. The thickness of the thick portion is 1.1 t _{F to} 5 t.
_{F (t F} is the film thickness) heat-shrinkable film with cut lines according to claim 1 or 2 is. 4. A cut line and thick portions on both sides thereof are formed by scanning a carbon dioxide gas laser beam in a direction crossing a stretching direction of a film.
13. The method for forming a cut line of a heat-shrinkable film according to the above item. 5. The method for forming a cut line of a heat-shrinkable film according to claim 5, wherein the cut line comprising a row of through holes is formed by interrupting the irradiation of the laser beam or by repeatedly controlling the intensity of the irradiation. 6. The heat shrinkage of the film is 30% or more (90 ° C.
The method for forming a cut line of a heat-shrinkable film according to claim 4 or 5, wherein the method is hot water x 10 seconds.