JP4243085B2 - Heat shrinkable film with tear line, method for forming tear line and continuous film body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-shrinkable film with a tear line attached to a container such as a bottle as a shrink tube, and a method for forming the tear line, and in particular, a bag-breaking resistance for ensuring a stable state of the tube attached to the container. And a cutting line having a good cutting property for facilitating separation from the container.
[0002]
[Prior art]
Shrink tubes (heat-shrinkable tubes) formed with the stretching direction of a laterally uniaxially stretched plastic film as a circumferential direction are used as product display labels for containers such as beverages, sealing cap seals for container mouths, and the like. The shrink tube generally has a perforated cut line (1) as shown in FIG. The tear line (1) separates the shrink tube (10) attached to the container from the container (such as removing the cap seal when opening the container mouth, separating and collecting the container and label after use). is necessary.
[0003]
The cut line (1) is formed as a perforation composed of slit-shaped minute holes, which are blade punch marks, by pressing a blade (Thomson blade, rotary blade, etc.) against the film with a punching machine. As another method, it has also been proposed to irradiate a film surface with a laser beam using a laser beam to form a perforation composed of a row of minute holes having a constant hole pitch as an irradiation mark of the beam (Japanese Patent Laid-Open No. 2002-2002). -179029).
[0004]
The cut line of the tube (10) is excellent in breakage resistance in the process of attaching the tube to the container and in the distribution process of the container (beverage filling bottle, etc.) equipped with the tube, in addition to having good cutting properties. It takes a thing. In the process of attaching to the container (the heat shrinking process of the tube 10), stress (tensile stress) tends to concentrate on the cut line (1) with the heat shrinking deformation of the tube. In this case, a large tensile stress acts on the tear line due to a momentary bulge and deformation due to a drop impact, which may result in a broken bag (rupture of the tube starting from the tear line).
[0005]
[Problems to be solved by the invention]
The bag-breaking resistance and the cutting property of the tube in which the tear line (1) is formed are contradictory properties. The cutting performance is enhanced by increasing the hole pitch of the micro holes, but the bag resistance is reduced accordingly. On the contrary, if the hole pitch is increased, the bag breaking resistance is improved, but the cutting property is deteriorated.
[0006]
In view of the above, the present invention satisfies both cutting performance and bag breaking resistance at the same time, prevents bag breaking starting from a tear line in the mounting process and distribution process, and separates the shrink tube (opens the container mouth, The present invention provides a tear-line heat-shrinkable film having good cutting properties required for the separate collection of used containers and labels, and an efficient method for forming the tear lines.
[0007]
[Means for Solving the Problems]
The present invention relates to a heat-shrinkable film with a tear line in which a tear line composed of a row of micro holes is formed in the heat-shrinkable film, and the hole pitch of the micro holes where the tear line functions with respect to the tear property is p. ₀ The hole pitch of the micropores that function for the dense part and the resistance to bag breaking is p _a It is characterized in that it has a dense and dense array pattern constituted by repeating unit patterns composed of rough parts in the cut line direction. Period T of repeated unit pattern _m Is the hole pitch p ₀ of 2 or more consecutive N ₀ Including the same hole pitch p ₀ N is a holeless portion where no micropore exists. _a As including
T _m = p ₀ × (n ₀ + N _a )
The pitch p of the micropores in the rough portion is given by _a Is p _a = (N _a +1) p ₀ The cut line of the dense and dense array pattern formed by repeating the unit pattern has a characteristic of simultaneously satisfying the desired cut property and resistance to bag breakage. In this way, it is possible to improve the cutting performance in the portion where the hole pitch of the minute hole is dense, while ensuring the resistance to bag breakage in the portion where the hole pitch of the minute hole is rough, and thus the cut line cutting property. It is possible to simultaneously satisfy two contradictory properties of bag-breaking resistance.
[0008]
The tear line may be Dense array pattern But Different Cut line A form in which two or more types are arranged in a column is given. According to this configuration, it is possible to add different characteristics to each part by using an arrangement pattern according to the shape and mounting mode of a container such as a bottle to which the shrink tube is mounted.
In the present specification, the “hole pitch” of the micro holes refers to the distance between the centers of the adjacent micro holes, and the “column” of the micro hole columns is a column of micro holes having a different unit pattern. It means that it is continuous in the column direction.
[0009]
The formation of the tear line of the present invention is typically performed by applying laser beam irradiation. This is a cut line forming method in which a heat shrinkable film that moves relative to a laser beam is irradiated with a laser beam to form a cut line composed of a row of microholes, in a basic oscillation pulse of a predetermined period of the laser beam. By performing intermittent pulse oscillation in which a predetermined pulse oscillation is periodically stopped, a cut line composed of a row of microholes configured by repeating unit patterns arranged with the pitch of the microholes changing coarsely and densely is formed, The hole pitch of the micropores that function for cutting performance is p ₀ The hole pitch of the minute holes that function for the dense part and the resistance to bag breaking is p _a = (N _a +1) p ₀ It is characterized in that it has a dense and dense arrangement pattern formed by repeating unit patterns composed of rough portions in the direction of the cutoff line, and has the characteristics of satisfying desired cutability and bag breaking resistance at the same time. Here, p is the hole pitch corresponding to the fundamental oscillation pulse. ₀ And n ₀ The 2 or more The number of continuous oscillation pulses, n _a 1 to the number of continuous oscillation pause pulses,
T _m = p ₀ × (n ₀ + N _a )
The period T given by _m Are repeatedly formed in the cut line direction. According to this configuration, the waveform of the intermittent pulse oscillation can be easily changed by the pulse signal processing, and a cut line composed of a row of micro holes having a desired arrangement pattern can be easily obtained.
[0010]
In the above cut line forming method, pulse oscillation control is performed such that two or more types of cut lines having different arrangement patterns are cascaded by switching the intermittent pulse oscillation to a different waveform, if desired.
Further, the continuous film body according to the present invention is a long film in which cut lines made of rows of micro holes are formed in the heat-shrinkable film, and cutting positions for cutting into a plurality of products are provided in a direction intersecting the direction of the cut lines. In the continuous film body, the cut line has a fine hole pitch p which functions against the cutting property. ₀ The hole pitch of the micropores that function against the bag breaking resistance is p _a A unit pattern having a coarse / dense arrangement pattern formed by repeating a unit pattern composed of rough portions in the direction of the cut-off line, and a period T of the repeated unit pattern _m Is the hole pitch p ₀ of 2 or more consecutive N ₀ Including the same hole pitch p ₀ N is a holeless portion where no micropore exists. _a As including
T _m = p ₀ × (n ₀ + N _a )
The pitch p of the micropores in the rough portion is given by _a Is p _a = (N _a +1) p ₀ The cut line of the dense and dense array pattern formed by repeating this unit pattern has a characteristic that satisfies the desired cutability and bag-breaking resistance at the same time, and the micropores of the unit pattern at the cutting start portion close to the cutting position The arrangement density is higher than the arrangement density of the micropores of the unit pattern in the portion other than the cut start portion.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments.
FIG. 1 exemplifies an arrangement pattern of micro-holes of a cut line configured as a repetition of unit patterns arranged with the pitch of micro-holes changing roughly and densely. A mark indicates a micropore (2) formed in the heat-shrinkable film, and a ₂ Have no micropores at that position (same hole pitch p in the figure) ₀ The position where the micropores are formed is indicated by a chain mark ◯. This cut line (1) has a hole pitch p ₀ Unit pattern U having two micro holes (2) and including a hole-free portion corresponding to one micro hole ₁ Is the period T ₁ [= p ₀ × (2 + 1) = 3p ₀ ] Has an arrangement pattern that repeats in the direction of the cut line, and the hole pitch of the micro holes (2) is p. ₀ And the pitch of the micropores is p _a (= 2p ₀ ) And a rough portion.
[0012]
The cut line in the present invention is formed as a perforation composed of a row of slit-like microholes that are punch marks of a blade, or formed as a perforation composed of a row of microholes by pulse irradiation of a laser beam. In the case of laser beam pulse irradiation, by setting arbitrary / various pulse patterns including intermittent pauses of pulses by pulse waveform conversion processing, a cut line composed of repeated unit patterns or different unit patterns 2 It is possible to efficiently form a cut line in which rows of micropores of seeds or more are vertically arranged.
[0013]
Next, formation of a cut line by pulse irradiation of a laser beam will be described.
When the surface of the film is irradiated with a laser beam, the beam irradiation point dissolves and evaporates instantaneously, and micropores (2) are formed as irradiation marks. By irradiating the laser beam with pulses while transporting the film at a constant speed, perforated cut lines that are rows of micro holes (2) aligned in the beam scanning direction are formed. Hole pitch p of micropore (2) ₀ The expansion / contraction (increase / decrease) can be adjusted by the oscillation cycle of the beam and the scanning speed (film transfer speed). According to the present invention, various arrangements in which unit patterns are arranged in the direction of the cut line are repeated in a manner that the hole pitch changes coarsely and densely, unlike the conventional cut line, by the conversion process of the pulse waveform to insert the pulse pause. A cut line with a pattern is obtained.
[0014]
[A] and [b] in FIGS. 2 to 4 show examples of the pulse waveform pattern of the laser beam and the arrangement pattern of the micropores to be formed ([a]: waveform pattern of the pulse Pls, [b] : Arrangement pattern of micropores 2). The chain line in [a] in each figure shows the pause of the pulse (no pulse oscillation). T added to each figure _m Is the unit pattern U shown by the following equation _m It is a cycle.
T _m = p ₀ × (n ₀ + N _a )
[Where n ₀ : 1 to the number of continuous oscillation pulses
n _a : 1 to the number of continuous oscillation pause pulses]
[0015]
FIG. 2 shows a basic oscillation pulse (continuous oscillation pulse, hole pitch p). ₀ ), An intermittent pulse pattern of “3 oscillation-1 pause (= 3 strokes 1 pause)” in which one pulse pause (microhole omitted) is inserted every 3 pulse oscillations (microhole formation) is expressed as a unit pattern U. ₂ FIG. 3 shows an example in which a row of micropores (2) is formed by converting into a pulse waveform of “4 oscillations” in which two continuous pulse pauses (microholes omitted) are inserted for every four pulse oscillations (microhole formation). -2 pause (= 4 strokes, 2 breaks) "is used as the unit pattern U ₃ This is an example in which a row of micro holes (2) is formed with a pulse waveform as follows. FIG. 4 shows an example of a cut line composed of a row of two kinds of micro holes having different unit patterns. This cut line is "3 oscillations-1 pause (= 3 strokes 1 pause)" unit pattern U ₄ The unit pattern U is a row of micropores (left half of the figure) and “2 oscillation-1 pause (2 strokes 1 pause)” ₅ The row of micropores (right half of the figure) is arranged in a column.
[0016]
2 to 4 are compared with each other, the cut line in FIG. 2 (pulse oscillation pattern = 3 strokes 1 rest) shows the hole pitch p. ₀ Unit pattern U having three micro-holes and including a non-hole portion equivalent to one micro-hole ₂ Is the period T ₂ [= p ₀ × (3 + 1) = 4p ₀ ] Has an arrangement pattern that repeats in the direction of the cut line, and the cut line in FIG. ₀ Unit pattern U having four micro-holes and including a non-hole portion equivalent to two micro-holes ₃ Is the period T ₃ [= p ₀ × (4 + 2) = 6p ₀ ] Has an arrangement pattern that repeats in the direction of the cut line. Also, the cut line in FIG. 4 (pulse oscillation pattern = left half area “3 strokes 1 rest” —right half area “2 strokes 1 rest” in the figure) is the hole pitch p ₀ Unit pattern U having three micro-holes and including a non-hole portion equivalent to one micro-hole ₄ Is the period T ₄ [= p ₀ × (3 + 1) = 4p ₀ ], The arrangement pattern (left half area) that repeats in the direction of the cut line and the hole pitch p ₀ Unit pattern U having two micro-holes and including a hole-free portion corresponding to one micro-hole ₅ Is the period T ₅ [= p ₀ × (2 + 1) = 3p ₀ ] Is configured as a combination with an array pattern (right half area) that repeats in the direction of the cut line.
[0017]
FIG. 5 shows a calculation flow for generating a continuous pulse signal and converting the pulse signal into a desired waveform pattern for pulsed irradiation of a laser beam in a continuous film transfer line. First, the film transfer speed of the continuous transfer line is read by the rotary encoder (f1) as the rotation speed of the film feed roller, converted to analog by the P / A converter (f2), and then a signal generator such as a function generator (pulse Generator) (f3). In the signal generator (f3), a pulse signal corresponding to the film feed speed in the transfer line (hole pitch p) is used as the basic oscillation pulse signal. ₀ A continuous oscillation waveform in which a row of minute holes is formed using a logic circuit such as a flip-flop.
[0018]
The basic oscillation pulse signal created by the signal generator (f3) is input to the P / A converter (f4) and the calculator (f5). From the P / A converter (f4), the irradiation control voltage is input to the laser controller (f6). The arithmetic unit (f5) performs processing of the pulse waveform by the logic circuit (conversion to a waveform including pulse pause), and the processed pulse signal is gate-input from the arithmetic unit (f5) to the laser controller (f6). A laser oscillator (f6) controls the laser oscillator to irradiate the film in the continuous transfer line with a controlled pulse waveform and output.
[0019]
FIG. 6A shows an example of the logic circuit of the arithmetic unit (f5) in the above arithmetic flow. This logic circuit is configured such that the circuit (C1) and the circuit (C2) can be arbitrarily switched in parallel. FIG. 7B shows an input signal of the logic circuit (a continuous pulse signal generated by the signal generator f3) (S _I ) And processed output signal (S _O1 ) (S _O2 ) Shows each waveform. Input signal (S _I ) Is processed by the circuit (C1), the pulse waveform “S” in FIG. _O1 "(In the figure, the pattern of" 3 strokes-1 rest "), when processed by the circuit (C2), the pulse waveform" S "in FIG. _O2 "(" 2 strokes-1 rest "pattern in the figure) and output. Switching of the circuits (C1) and (C2) (switching of the waveform conversion pattern) is arbitrary. Therefore, as illustrated in FIG. 4, the arrangement pattern of the micro-holes (2) of the cut line is changed for each portion in the cut line direction. You can switch freely.
[0020]
FIG. 7 illustrates a tube (10) in which a cut line (1) is formed by laser beam irradiation with a processed pulse waveform. This tube is attached to a body portion such as the bottle (20) of FIG. When comparing the arrangement pattern of the micro holes in the A and C parts (opening edge area of the tube) of the cut line (1) and the micro holes in the B part (inside area excluding the A and B parts), the A part (the tube The density of the micropores in the portion that becomes the cutting start end when removing) is high, and the density of the portion B (portion that easily causes bag breakage due to the drop impact of the container) is relatively low. If this is shown by the “oscillation-pause pattern” of the pulse waveform, for example, the A part and the C part have an array pattern of micro holes formed by the pulse waveform of “3 strikes-1 rest”, and the B part is “2”. It has an array pattern formed with a pulse waveform of “Strike-1 break”. Note that part D (the part facing the neck part 21 of the bottle in FIG. 15) has a lower arrangement density, if desired, in order to further improve the bag breaking resistance. A pattern is given.
[0021]
FIG. 9 shows a cut line forming line (L ₁ ) And a center seal (tube forming) line (L ₂ ) Are performed as a continuous process. Center seal line (L ₂ ) Has a conventional general configuration in which an adhesive application device (applying an adhesive to an edge portion to be an overlap bonding margin of a film), a pressing roll for crimping the overlap bonding margin, and the like are arranged. The long film (F) unwound from the film roll (31) is continuously transferred (arrows) at a predetermined speed controlled by the feed roller (33), and a cut line is formed by pulse irradiation by the laser oscillator (32). Is done. The film on which the cut line is formed is the center seal line (L ₂ ) Is formed into a long cylindrical body (10 ′) using the right and left end edges of the film as an adhesive allowance, and then wound on a roll (36).
[0022]
FIG. 10 shows a long cylindrical body (10 ′) obtained through the center sealing process. The chain line (CL) indicates the cutting position. By cutting the cylindrical body (10 ') at the chain line (CL) part, the product tube (tube length l ₁₀ ) (10) is obtained. The cut line (1) of the cylindrical body (10 ') is connected to each product tube (tube length l ₁₀ ), The arrangement pattern of the micropores (2) in each part in the longitudinal direction of the cut line (each part of A, B, C in the example of the figure) is changed, and each arrangement pattern is changed to the tube length ( l ₁₀ ) Is repeated at a period corresponding to. The arrangement pattern of the micro holes (2) can be freely changed by the conversion / switching of the pulse waveform of the laser beam described with reference to FIGS.
[0023]
In the pulse irradiation of the laser beam, the cut line (1) formed by scanning the beam in the direction orthogonal to the stretching direction of the transverse uniaxially stretched heat-shrinkable film has a unique form as shown in FIGS. . Perimeter of micropore (2) (2 ₁ ) Is slightly thicker (FIGS. 12 and 13), and a bank-like thick part (3) extends along the rows of micro holes (2) on both sides thereof. The thick portion (3) bulges on both the front and back sides of the film, and the bulge thickness has undulations with a period substantially matching the hole pitch of the micropores (2). It takes such a form as a thermal effect accompanying beam irradiation (scanning in a direction perpendicular to the film stretching direction) as a local heat shrinkage stress (film stretching direction) generated in the vicinity of the micropores (2) and This is thought to be due to the effect of surface tension.
[0024]
The above form is effective for enhancing the function of the tear line. Periphery of micropore (2) (2 ₁ ) Is thickened to increase the resistance to bag breakage in the tube attachment process and the distribution process of the attached products, and also to the embankment-like thick part extending on both sides of the row of micro holes (2) ( 3,3) plays a guiding function when separating the tube (10) from the container (20), prevents a shift in the cutting direction (lateral tearing of the tube), and is smooth over the entire length of the cutting line (1). It has the effect of facilitating cutting.
[0025]
The bulging thickness of the thick part (3) on both sides of the micro hole (2), the opposing width of the bulging part (3) (the distance between the left and right thick parts facing each other across the row of micro holes 2) The thickness of the thick portion (3) (t ₃ ) Is about 1.1t _F ~ 5t _F (T _F Is the thickness of the film), the opposing width of the thick part (3) (w ₃ ) Is about 1.5 mm or less, and the hole diameter (d) of the micropores (2) is about 1 mm or less. The hole diameter of the minute hole (2) is controlled by increasing or decreasing the output. Depending on the laser beam irradiation conditions, the hole shape of the microhole (2) may be a slightly long oval shape in the scanning direction (cut line direction). In this case, the hole diameter (d) is perpendicular to the diameter of the cut line in the cut line direction. It is displayed as an arithmetic average of the passing diameter in the direction. In addition, regarding the hole pitch (p) of the micro holes (2) (the distance between the centers of the adjacent micro holes), the continuous pulse waveform before processing (the input signal S of FIG. 6A). _I The hole pitch (p) of the micro holes (2) formed by the waveform is, for example, 0.1 to 1.0 mm.
[0026]
The heat-shrinkable film (F) is a laterally uniaxially stretched film made of a general material type as a shrink tube material, for example, a polyester film, a polystyrene film, or a polypropylene film. The wall thickness is, for example, 10 to 150 μm. The term “lateral uniaxial stretching” includes not only a transverse process (circumferential direction of the tube) but also a horizontal / vertical bi-directional stretched film that can be substantially regarded as a lateral uniaxially stretched material. In the horizontal / vertical bi-directional stretching, if the stretching ratio in the horizontal direction is 2 times or more (for example, 2 to 7 times) and the vertical direction is about 1.5 times or less, the film can be used without any trouble as a shrink tube molding film. .
[0027]
The laser oscillator used for forming the cut line may be any one that oscillates a laser beam absorbed by the film, such as carbon dioxide, YAG, or semiconductor. A laser is preferably used because its output can be easily controlled, and a laser beam has good absorbability with respect to a polyester film which is a typical material of a shrink tube. In general, the front or back surface of the film is printed for display or decoration of product information (product name, ingredients, usage, name of manufacturer / seller, etc.). Laser pulse irradiation may be performed on either the printing surface or the non-printing surface of the film.
Further, the form of the cut line (1) is formed as a single perforation illustrated in FIG. 15, and as shown in FIG. 14, the two cut lines are separated by an appropriate interval (for example, 5-10 mm). It can also be formed as parallel lines and cut into a tape shape.
[0028]
【Example】
Under the continuous film transfer line (Fig. 9), under the continuous transfer of the film, the cutting line is formed by the laser beam irradiation of the carbon dioxide laser oscillator, the long cylindrical body (10 ') (Fig. 10) is formed by the center seal, the cylinder The product shrink tube (10) is obtained through the step of cutting the shaped body.
[0029]
(1) Film
"Space Clean S7553" (polyester film manufactured by Toyobo Co., Ltd.)
Heat shrinkage: 68% in the horizontal direction, 4% in the vertical direction (90 ° C hot water x 10 sec) Wall thickness: 50 μm
(2) Micro-hole arrangement pattern of cut lines
The arrangement pattern of the micropores in each part of the tubes A, B, and C (FIG. 7) was adjusted as follows.
[0030]
[Test tube (1)] (Invention example 1)
Part A-Part C ... (Pulse waveform: 3 oscillations-1 pause = 3 strokes 1 pause)
[Test tube (2)] (Invention example 2)
Part A: 3 strokes 1 rest (pulse waveform: 3 oscillations-1 pause = 3 strokes 1 rest)
Part B: 2 strokes, 1 break (pulse waveform: 2 oscillations-1 pause = 2 strokes, 1 break)
Part C: 3 strokes 1 rest (pulse waveform: 3 oscillations-1 pause = 3 strokes 1 rest)
[Test tube (3)] (Comparative example)
Part A-Part C: Continuous pulse (no pulse pause)
[0031]
The hole pitches (see FIG. 8) of the micro holes in each test tube are as follows (the figure [a]: 3 strokes 1 rest pattern, [b]: 2 strokes 1 rest pattern).
Hole pitch p ₀ (Continuous pulse oscillator): 1.0mm
Hole pitch p _a (1 pulse pause): 2.0mm (= p ₀ × 2)
[0032]
In addition, the diameter of the microhole (2) of each test tube and the form of the microhole array (see FIGS. 10 to 12) are as follows.
Diameter of micropore (d) ^{* 1} : 0.5mm
Thick part thickness (t ₃ : 70μm
Opposite width of thick part (w ₃ ): 0.7mm
* 1… The hole diameter (d) (= 0.5mm) is the arithmetic mean value of the passing diameter in the cut line direction and the passing diameter in the direction perpendicular thereto.
[0033]
(3) Attaching to a bottle and an evaluation test for resistance to bag breakage
(3.1) Attaching to the bottle
Attached to the body of the bottle by heat treatment.
(3.2) Fracture resistance test (drop impact test)
After dropping the bottle with the test tube (beverage filling) from a height of 1.5 m so that the bottom of the bottle collides with the concrete floor surface, inspect whether there is a break in the tear line of the label.
[0034]
(4) Evaluation of resistance to breakage and tearability
In any of the test tubes (1) to (3), there is no bag breakage in the tube mounting step, the mounting operability is good, and there is no substantial difference in the cutting ability to remove the tube from the bottle. However, in the tear resistance evaluation test, in the test tube (3) (comparative example), tearing of the tear line was observed near the center of the trunk, whereas the test tubes (1) and (2) ( The invention example) has no such abnormality and maintains a healthy tube form.
[0035]
Note that the cut line formed according to the present invention is not limited to the arrangement pattern of each of the above-described embodiments, and may be formed by repeating unit patterns that are arranged with finely varying hole pitches. Another arrangement pattern may be used. For example, a coarse and dense arrangement pattern may be formed by gradually increasing or decreasing the hole pitch of the micropores.
[0036]
【The invention's effect】
According to the present invention, by forming a row of minute holes constituting a tear line by repeating unit patterns arranged with the hole pitch changing in a coarse and dense manner, both characteristics of the shrink resistance and tear resistance of the shrink tube can be achieved. The cutting line which fills can be formed efficiently. In the case of applying laser beam pulse irradiation to the formation of microholes, various array patterns according to the type and form of the container can be efficiently formed by various and flexible processing of the pulse waveform.
[Brief description of the drawings]
FIG. 1 is an explanatory plan view showing an example of an array pattern of micro holes forming a cut line.
FIG. 2 is an explanatory diagram ([a]: pulse waveform, [b]: microhole distribution) showing an example of correspondence between a pulse waveform of a laser beam and an arrangement pattern of micropores.
FIG. 3 is an explanatory diagram ([a]: pulse waveform, [b]: microhole array pattern) showing an example of correspondence between a pulse waveform of a laser beam and a microhole array pattern.
FIG. 4 is an explanatory diagram ([a]: pulse waveform, [b]: microhole array pattern) showing an example of correspondence between a pulse waveform of a laser beam and a microhole array pattern.
FIG. 5 is a diagram illustrating an example of a calculation flow of pulse waveform conversion of a laser beam.
6 is a diagram illustrating an example of a logic circuit and an input / output signal for pulse waveform conversion ([a]: logic circuit, [b]: pulse signal). FIG.
FIG. 7 is an explanatory diagram of a tear line formed in the shrink tube.
FIG. 8 is an explanatory diagram of a hole pitch of minute holes.
FIG. 9 is a diagram showing a film cut line formation and tube forming (center seal) process by laser beam irradiation.
FIG. 10 is an explanatory diagram of a cut line of the long cylindrical body obtained in the center sealing step.
FIG. 11 is a plan view showing a form of a cut line formed by laser beam irradiation.
12 is a cross-sectional view taken along arrow XX in FIG.
13 is a cross-sectional view taken along arrow YY in FIG.
FIG. 14 is a front view showing another form of the cut line.
FIG. 15 is a front view showing an example of attaching a shrink tube to a container.
[Explanation of symbols]
1: Cut line
2: Micropore
2 ₁ : Hole edge
3: Thick part
10: Shrink tube
10 ': Long cylindrical body
20: Bottle
21: Bottle constriction
31: Film roll
32: Laser beam oscillator
33: Film feed roller
34: Tube roll
F: Heat shrinkable film
L ₁ : Laser beam irradiation (cut line formation) process
L ₂ : Center seal (tubular body formation) process
CL: Cutting position of cylindrical body
p ₀ , p _a : Hole pitch

Claims (5)

A heat-shrinkable film with a tear line in which a tear line composed of a row of micro holes is formed in the heat-shrinkable film,
The cut line is formed by cutting out _a unit pattern consisting of a dense portion having a fine hole pitch p ₀ functioning for cutability and a coarse portion having a fine hole pitch pa functioning for bag breaking resistance pa. It has a dense and dense arrangement pattern that is repeated in the line direction,
The period T _m of a unit pattern repeated includes n ₀ or two or more consecutive micropores hole pitch p _0, including without hole portion with the same hole pitch p ₀ no micropores n _a number,
_{T m = p 0 × (n} 0 + n a)
Given in
Hole pitch p _a of micropores in the coarse portion, p a ₌ given by _(n a ₊₁₎ p _0, cut lines of the arrangement pattern of density made of repetition of the unit pattern, a desired cutting property and rupture A heat-shrinkable film with a tear line, characterized by having the characteristics of simultaneously satisfying bag characteristics.   The heat-shrinkable film with a cut line according to claim 1, wherein two or more kinds of cut lines having different dense and dense arrangement patterns are arranged in tandem. A cut line forming method of forming a cut line composed of a row of micropores by irradiating a laser beam to a heat-shrinkable film that moves relative to the laser beam,
By performing intermittent pulse oscillation in which the predetermined pulse oscillation in the basic oscillation pulse of the predetermined period of the laser beam is periodically paused,
As basic hole pitch corresponding to the oscillation pulses as p _0, a n ₀ 2 or more consecutive a number of oscillation pulses, n _a 1 to oscillation-stopping number of pulses contiguous,
_{T m = p 0 × (n} 0 + n a)
The unit pattern repeatedly formed in the cut-line direction with a period T _m given by,
Forming a cut line having an arrangement pattern in which unit patterns arranged by changing the pitch of the micro holes in a coarse and dense manner are repeated in the cut line direction;
It consists of a dense portion where the hole pitch of the micropores functioning for cutting property is p ₀ and a rough portion where the hole pitch of the microholes functioning for resistance to bag breakage is p _a = (n _a +1) p _0. A method of forming a cut line having a dense and dense arrangement pattern configured by repeating unit patterns in a cut line direction, and having a characteristic that simultaneously satisfies a desired cut property and resistance to bag breaking. .   The cut line forming method according to claim 3, wherein two or more types of cut lines having different coarse and dense arrangement patterns are arranged in tandem by switching the intermittent pulse oscillation to different waveforms. The heat-shrinkable film is a continuous continuous film body in which a cut line composed of a row of micro holes is formed, and a cutting position for cutting into a plurality of products is provided in a direction intersecting the direction of the cut line,
Cut lines, cut the unit pattern hole pitch of the fine holes with a hole pitch of micropores which functions to cut resistance serves to rupture bag with in a dense part of the p ₀ consists rough parts of p _a It has a dense and dense arrangement pattern that is repeated in the line direction,
The period T _m of a unit pattern repeated includes n ₀ or two or more consecutive micropores hole pitch p _0, including without hole portion with the same hole pitch p ₀ no micropores n _a number,
_{T m = p 0 × (n} 0 + n a)
Given in
Hole pitch p _a of micropores in the coarse portion is given by _{p a = (n a +1)} p 0, cut lines of the arrangement pattern of density made of repetition of the unit pattern, a desired cutting property and rupture bag Have the characteristics to satisfy
A continuous film body, wherein the arrangement density of micropores in a unit pattern in a cutting start portion near the cutting position is higher than the arrangement density of micropores in a unit pattern in a portion other than the cutting start portion.

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