JP6634815B2 - Laminated body and heat seal inspection sheet comprising the same - Google Patents

Description

  The present invention relates to a laminate, a heat seal inspection sheet made of the laminate, and an inspection method using the same.

In recent years, for the production of packaging bags and packaging containers, the stacked packaging materials are sandwiched between hot plates of a heat sealer or between a hot plate and a pedestal, and heat-pressed at a predetermined temperature, pressure and time, and heat-sealed. (Heat fusion) technology is often used (Patent Document 1).
The heat-sealed seal portion is required to have a good seal state in order to prevent leakage of the packaged object and to prevent intrusion of foreign matter, oxygen, and moisture from the outside. That is, it is required that there is no unintended unsealed portion, weakly sealed portion, etc., and that a sufficient sealing property is secured uniformly with a desired sealing strength.
The quality of the sealing state varies depending on various parameters such as the state of the hot plate (the state of attachment to the heat sealer main body, the influence from the surrounding environment, etc.) and the heat sealing temperature, pressure, time and the like. Therefore, every time the heat sealing conditions are changed or a hot plate is re-installed in response to a failure, etc., before the production line is put into operation, a preliminary inspection is performed to determine whether the heat sealing is performed well. (Heat seal inspection) must be performed.

In such a heat seal inspection, conventionally, a heat seal inspection sheet made of pressure-sensitive paper has been used. In other words, in order to stop the production line that had been operating up to that point and restart it under new conditions, the hot plate was cooled once, the pressure-sensitive paper was interposed between the cooled hot plates, and the device was temporarily operated, Observe the color development state of the pressure-sensitive paper and check whether the pressure is applied uniformly.
However, since the metal of the hot plate actually heated to the heat sealing temperature thermally expands, the pressure is not necessarily applied in the same manner as in the case of a cooled state, and a sealing defect occurs and it is necessary to set again. Further, in that case, it takes time until the hot plate is cooled down again and the inspection becomes possible, during which time the production line cannot be operated.

JP-A-2-296630

  The present invention solves the above-described problems, and reliably and efficiently performs a heat seal inspection. A laminate, a heat seal inspection sheet including the laminate, and an inspection method using the inspection sheet are provided. The purpose is to provide.

  The present inventors have conducted intensive studies and as a result, a laminate having a first heat-resistant sheet, a heat-sensitive ink layer, a non-heat-sensitive ink layer, an adhesive layer or an adhesive layer, and a second heat-resistant sheet in this order, and It has been found that the above-mentioned problems are solved by a heat seal inspection sheet comprising the above and an inspection method using the same.

That is, the present invention has the following features.
(1) A laminate having a first heat-resistant sheet, a heat-sensitive ink layer, a non-heat-sensitive ink layer, an adhesive layer or an adhesive layer, and a second heat-resistant sheet in this order.
(2) The laminate according to the above (1), wherein the first heat-resistant sheet is a heat-resistant transparent resin film.
(3) The method according to the above (1) or (2), wherein the non-thermosensitive ink layer is a layer formed by solid printing a toluene-based solvent-type ink containing no ester-based solvent, ketone-based solvent and alcohol-based solvent. Laminate.
(4) A heat seal inspection sheet comprising the laminate according to any one of (1) to (3).
(5) An inspection method using the heat seal inspection sheet described in (4) above to confirm temperature unevenness of the hot plate of the heat sealer or uneven pressure of the hot plate.

The laminate of the present invention is a heat-sensitive laminated sheet that develops color by heat. Therefore, by using the heat seal inspection sheet made of the laminate of the present invention, the heat seal inspection can be performed under the same heat sealing conditions as when the actual production line is operating. Therefore, reliable inspection is possible, and the risk of occurrence of a seal failure is reduced during the actual operation after the inspection. In addition, since it does not respond to pressure, it does not apply pressure during production, transportation, storage, etc., and the ink does not develop color.It is excellent in productivity and handling, and after storing the results of heat seal inspection, It is also possible to compare and examine various conditions.
Further, since it is not necessary to cool the hot plate before the heat seal inspection, the inspection can be performed quickly and efficiently without stopping the machine.
Still further, the laminate of the present invention can detect sharply, and unlike the case of pressure sensitivity, the degree of color development is proportional to the actual seal strength, so that the accurate sealing state can be clearly displayed in a vivid color image. Can be grasped visually.

It is a schematic sectional view showing an example about the layer composition of a layered product of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a use state of the heat seal inspection sheet of the present invention. It is a reference photograph which shows the state of discoloration of a heat seal inspection sheet after performing a heat seal inspection under heat seal conditions which cause a seal failure. It is a reference photograph which shows the state of discoloration of the heat seal inspection sheet after performing the heat seal inspection under the heat seal conditions which can obtain a favorable sealing state.

The laminate of the present invention will be described in detail below.
Hereinafter, as the resin name used in the present invention, those commonly used in the industry are used.

<1> Layer Configuration of Laminate FIG. 1 is a schematic sectional view showing an example of the layer configuration of the laminate of the present invention.
As shown in FIG. 1, the laminate of the present invention comprises a first heat-resistant sheet 1, a heat-sensitive ink layer 2 printed on the first heat-resistant sheet, and a non-heat-sensitive ink layer (protective layer) 3. , An adhesive layer or an adhesive layer 4, and a second heat-resistant sheet 5 as a basic configuration. Here, the first heat-resistant sheet 1 is a transparent resin film. In the present invention, “transparent” means having a visible light transmittance such that discoloration of the heat-sensitive ink inside can be visually recognized. On the other hand, the second heat-resistant sheet 4 may be a transparent sheet or an opaque sheet.
Next, materials constituting the laminate of the present invention, a method for producing the same, and the like will be described.

<2> Heat Resistant Sheet In the present invention, the first and second heat resistant sheets are known as long as they have a smooth surface and a heat resistance capable of maintaining a shape under heat sealing conditions. Can be widely used. Examples of such a heat-resistant sheet include polyester films such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate, and polyarylate, and nylon films. These may be uniaxially stretched or biaxially stretched. Also, uniaxially or biaxially oriented polypropylene films can be used. From the viewpoint of excellent heat resistance, a PET film can be particularly preferably used.

In one embodiment of the present invention, each of the first and second heat-resistant sheets is a transparent resin film.
In another aspect of the present invention, the second heat-resistant sheet may be an opaque sheet. As the heat-resistant opaque sheet, various papers such as high-quality paper, pure white paper, single-art paper, mozo paper, bleached kraft paper, and any heat-resistant colored film can be used.
When paper is used as the opaque sheet, heat from one of the two hot plates can be cut off due to the thermal barrier properties of the paper, and the inspection can be conducted mainly on the state of the other hot plate. it can. That is, by blocking the heat from one hot plate to some extent or completely, it prevents the thermal ink in the inspection sheet from reacting excessively, and discovers abnormalities such as partial pressure of the other hot plate and foreign matter mixing. easy.
The thickness of the heat-resistant sheet is preferably about 10 to 100 μm, and more preferably 20 to 70 μm. When the thickness is less than 10 μm, the stiffness of the sheet is weak, resulting in poor handling. On the other hand, if the thickness is more than 100 μm, the cost is increased and the way of transmitting heat is weakened.

<3> Thermal ink layer In the laminate of the present invention, the thermal ink layer is a layer formed by partially or solid printing the thermal ink on the first heat-resistant sheet.
As the thermal ink, any irreversible thermal ink that undergoes irreversible discoloration above a predetermined temperature is used. In the present invention, the thermosensitive ink is a thermochromic ink containing a combination of a color former (leuco dye) and a developer as a main component, a thermochromic ink that changes color by thermal decomposition or sublimation of an organic substance, and a thermochromic ink that changes color by thermal decomposition. It includes a thermosetting paint composed of a pigment (inorganic compound) and a varnish.

  A thermochromic ink containing a combination of a leuco dye and a color developer as a main component is particularly preferable because high density, high contrast before and after color development, and good thermal sensitivity can be obtained. As such a thermochromic ink, a thermochromic ink obtained by adding a leuco dye and a developer to a binder resin and kneading the mixture with a solvent is preferably used. Here, a toluene-based solvent is used as the solvent. Organic solvents containing esters, ketones, alcohols, etc. are not preferred because they promote the color development reaction between the developer and the leuco dye.

In the present invention, as the color former (leuco dye), a conventional one can be used. For example, 3,6-dimethoxyfluoran, 3,6-dibutoxyfluoran, 3-diethylamino-6,8-dimethyl Examples include, but are not limited to, fluoran, 3-chloro-6-phenylaminofluoran, and the like.
As the developer, any component capable of developing a leuco dye can be used, and examples thereof include benzotriazoles, phenols such as bisphenol A and β-naphthol, aliphatic carboxylic acids, aromatic carboxylic acids, and acidic phosphoric acid. Examples include esters, but are not limited thereto.
In addition to the color former and the color developer, a color change temperature regulator may be included. As the discoloration temperature regulator, those conventionally known can be used, and examples thereof include esters, ethers, ketones, amides, azomethines, fatty acids, hydrocarbons, and alcohols. However, the present invention is not limited to these.

The binder resin may be any of an aqueous resin and an oily resin, but an oily binder resin such as an acrylic resin is preferable from the viewpoints of adhesion to a film and drying during coating.
The discoloration temperature of the thermal ink can be appropriately determined by those skilled in the art according to the set heat sealing temperature and the like, but a thermal ink that discolors at about 120 ° C, for example, 100 to 250 ° C is preferably used. If the discoloration temperature is lower than 100 ° C., discoloration occurs due to frictional heat or the like in an environment such as storage, which is not preferable. Conversely, if the temperature is higher than 250 ° C., it is necessary to increase the heat resistance of the film, and the material of the heat-resistant film is limited.
Using the above-described heat-sensitive ink, a heat-sensitive ink layer having a thickness of about 0.1 to 2 μm can be formed on the surface of the first heat-resistant sheet by, for example, a gravure printing method or a flexographic printing method. . If the thickness of the heat-sensitive ink layer is less than 0.1 μm, sufficient density discoloration cannot be obtained. Conversely, if the thickness is more than 2 μm, the strength between the aggregations of the heat-sensitive ink is weakened, and the lamination strength is reduced, so that the ink tends to peel off due to impact or rubbing, which is not preferable.

<4> Non-heat-sensitive ink layer In the laminate of the present invention, the non-heat-sensitive ink layer is a layer obtained by solid printing of the non-heat-sensitive ink on the heat-sensitive ink layer, and prevents the heat-sensitive ink from coming into contact with the adhesive layer. Has a function as a protective layer.
As a non-thermal ink, a conventional white ink obtained by adding an organic pigment or an inorganic pigment, for example, titanium oxide, and various additives to a binder resin such as a urethane resin, an acrylic resin, and an olefin resin, and kneading using a solvent. And color inks. The white ink is preferably used in that the difference in lightness is large with respect to the color development (for example, black) of the heat-sensitive ink and the color is more easily recognized.
The solvent of the non-thermosensitive ink is excellent in volatility and does not affect the thermal ink layer, so it consists only of a toluene-based solvent and does not include other organic solvents such as ester-based solvents, ketone-based solvents, and alcohol-based solvents. Absent.
The thickness of the non-thermosensitive ink layer is preferably about 0.1 to 2 μm. When the non-thermosensitive ink layer is thinner than 0.1 μm, it does not function as a protective layer, and the thermosensitive ink layer and the adhesive layer react with each other, and discoloration of the thermosensitive ink may proceed. On the other hand, when the thickness is more than 2 μm, the strength between the cohesion of the non-thermosensitive ink is weakened, and the lamination strength is reduced.

<5> Adhesive Layer and Adhesive Layer In the present invention, the adhesive constituting the adhesive layer is not particularly limited, and any adhesive can be used. Specifically, a thermosetting resin such as a urethane-based adhesive, a vinyl-based adhesive, an acrylic-based adhesive, and an epoxy-based adhesive is preferably used.
As the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, a general pressure-sensitive adhesive can be used, and examples thereof include an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a urethane-based pressure-sensitive adhesive.
Examples of the method of applying the above-mentioned adhesive or pressure-sensitive adhesive include a gravure coating method, a reverse roll coating method, a knife coating method, a kiss coating method and other methods. It is desirable that the coating amount is, for example, about 0.5 to 4 μm in a dry state.
For example, the adhesive or pressure-sensitive adhesive is applied on a first heat-resistant sheet provided with a heat-sensitive ink layer and a non-heat-sensitive ink layer by printing, and a second heat-resistant sheet is laminated and wound up. The laminate of the present invention can be obtained by curing at a temperature of, for example, an oven at 35 to 40 ° C. for a certain period of time, for example, about 24 hours.

<6> Heat seal inspection sheet and heat seal inspection method The laminate of the present invention can be suitably used as a heat seal inspection sheet.
Specifically, before forming various packaging bags with a bag making machine, or before heat-sealing a lid material to a packaging container with a filling machine, temperature unevenness of the hot plate of the heat sealer and unevenness of the hot plate. As shown in FIG. 2, a heat seal inspection sheet of the present invention was placed between two hot plates to check the pressure and the degree of contact, and the heat sealer was operated under actual heat seal conditions (temperature, pressure, time). Activate.
Next, the inspection sheet is taken out, the state of discoloration of the thermal ink is observed, and the heat sealing conditions are examined based on whether discoloration has occurred at a uniform and sufficient density.

The heat sealer may be a single-sided heater including a single hot plate and a heat-resistant rubber pedestal. In the case of single-sided heating, the heat transmitted to the thermal ink is weakened, and the color density due to discoloration is reduced.
According to the present invention, three-sided seal type, four-sided seal type, standing pouch, gusset type, envelope pasting seal type, heat sealing of various packaging bags such as pillow type, and filling machine for packaging containers such as cup ramen and milk portion. In the ring seal in the above, it is possible to prevent leakage of contents due to poor heat sealing, and to ensure good sealing performance.
Next, the present invention will be specifically described with reference to examples.

[Example 1]
As a white ink, a titanium oxide pigment was used, and a urethane resin and an additive were kneaded as a binder resin using toluene to prepare a white ink.
As a thermal ink, LG-LS Indication Agent F (acrylic resin, developer, manufactured by Tokyo Ink Co., Ltd.), LG-LS Indication Agent G (acrylic resin, leuco dye, manufactured by Tokyo Ink Co., Ltd.) and toluene were used. It was blended at a mass ratio of 3/2 to prepare a thermochromic ink.
A 16 μm-thick biaxially stretched PET film having one surface corona-treated was used, and the thermochromic ink was printed on the corona-treated surface with a thickness of 1 μm by a gravure method to provide a heat-sensitive ink layer.

Then, the above white ink was printed at a thickness of 0.5 μm on the obtained heat-sensitive ink layer to provide a non-heat-sensitive ink layer.
Next, a solvent-type two-component curable polyurethane-based adhesive was applied on the obtained non-thermosensitive ink layer, and an adhesive layer was formed by dry lamination (2.0 μm in dry state).
Next, a biaxially-stretched PET film (second heat-resistant sheet) having a thickness of 25 μm and having one surface subjected to corona treatment is laminated on the adhesive layer so that the corona-treated surface faces the adhesive layer. A laminate of the present invention was manufactured.
Biaxially stretched PET film (first heat resistant sheet) / thermal ink layer / non-thermal ink layer / adhesive layer / biaxially stretched PET film (second heat resistant sheet)
In the present specification, “/” means an interface between layers.

[Example 2]
As a second heat-resistant sheet, except that a high-quality paper having a basis weight of 52.3 g / m ² was laminated.
In the same manner as in Example 1, a laminate of the present invention having the following layer constitution was produced.
Biaxially stretched PET film (first heat-resistant sheet) / thermal ink layer / non-thermal ink layer / adhesive layer / quality paper (second heat-resistant sheet)

[Heat seal inspection]
The upper and lower heat dies of the bag making machine are heated to a heat sealing temperature (180 ° C.), and a heat seal inspection sheet made of the laminate manufactured in Example 1 is sandwiched between them, for 0.4 second. The bag making machine was operated at a sealing pressure of 490 kPa. Next, the test sheet was taken out from between the hot dies and the discoloration of the thermal ink was confirmed. As shown in FIG. 3, unevenness in the temperature of the hot plate was observed, and the density of black due to the discoloration of the thermal ink was low. Was. Under these conditions, when the packaging material was actually heat-sealed, there was a weak seal portion in part, and sufficient sealing properties could not be obtained.

  Next, the hot mold was set again, and the bag making machine was operated again under the same conditions as above (heat sealing time: 0.4 seconds, sealing pressure: 490 kPa). When the inspection sheet was taken out and the discoloration of the thermal ink was confirmed, as shown in FIG. 4, coloration of a uniform and sufficient density was observed. Under these conditions, when the packaging material was actually heat-sealed, uniform sealing strength was obtained over the entire surface of the sealing portion, and a packaging bag having excellent sealing properties was obtained.

1. 1. First heat-resistant sheet 2. Thermal ink layer 3. Non-thermal ink layer Adhesive layer5. Second heat-resistant sheet 6. Hot plate

Claims (4)

A laminate having a first heat-resistant sheet, a heat-sensitive ink layer, a non-heat-sensitive ink layer, an adhesive layer or an adhesive layer, and a second heat-resistant sheet in this order ,
The above laminate, wherein the non-thermosensitive ink layer is a layer obtained by solid printing a toluene-based solvent-type ink containing no ester-based solvent, ketone-based solvent and alcohol-based solvent.   The laminate according to claim 1, wherein the first heat-resistant sheet is a heat-resistant transparent resin film.   A heat seal inspection sheet comprising the laminate according to claim 1.   An inspection method using the heat seal inspection sheet according to claim 3, wherein the temperature unevenness of the hot plate of the heat sealer or the bias of the hot plate is confirmed.

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