JPH03202341A - Heat shrinkable film - Google Patents

Abstract

PURPOSE:To prevent the generation of bending in the transparent part at the end part of a heat shrinkable label in a cylindrical or bag-shaped heat shrinkable film to which printing is applied so as to leave a transparent part at the open end part thereof by laminating or applying a membrane to the single surface and/or both surfaces of a part of the transparent part or applying an org. resin thereto. CONSTITUTION:A membrane is laminated or applied to at least a part of transparent parts 4 or an org. resin is applied thereto in order to minimize the shrinking speed difference between the transparent parts 4 and a printed part to form transparent coating layers 3. The transparent coating layers 3 are formed for the purpose of reducing the shrinking speed difference and, as the org. resin, nitrocellulose, a polyamide resin, a polyester resin, a polyurethane resin, a vinyl chloride resin, a rubbery resin or an acrylic resin can be designated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-shrinkable film, in particular a container, a bottle, etc.
Protection and bundling of cans, stick-shaped objects, etc. (hereinafter simply referred to as containers),
For the purpose of pasting labels, etc., on the caps of the above containers,
The present invention relates to a heat-shrinkable film used as a packaging material for covering or binding part or all of shoulders, body parts, etc.

[Prior Art] Heat-shrink packaging is a method in which a product is relatively roughly wrapped in a heat-shrinkable film in the form of a tube or bag, for example, and then the film is heat-shrinked to tightly adhere the film to the outer circumferential surface of the product. Since it is possible to obtain a beautiful packaging appearance relatively easily even when packaging irregularly shaped containers, demand for heat-shrinkable film is expected to increase in the future as a material suitable for automation.

However, when the heat-shrinkable film is printed to form a cylindrical body and attached as an annular label to the shoulder of a plastic bottle, for example, the following problems occur. When labeling plastic bottles, etc., first, label printing is applied intermittently at regular intervals on one side of a sheet-shaped heat-shrinkable film, and then the sheet-shaped heat-shrinkable film is attached to the unprinted transparent part. Separate each unit label individually by cutting with This is done by heat-shrinking the label by placing it over a plastic bottle in a predetermined position, but currently, as shown in Figure 3, the transparent parts left at the top and bottom edges of the label curl inward and bend, spoiling the appearance. .

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances. Another object of the present invention is to provide a heat-shrinkable film that does not cause bending in the transparent portion at the end of the heat-shrinkable label in a bag-shaped heat-shrinkable label.

[Ninth Means for Solving the Problems] The present invention that solves the above problems is a heat-shrinkable film in the form of a cylinder or bag, which is printed with a transparent portion left at the end of the heat-shrinkable film. In the transparent film, a thin film is laminated or coated on one side and/or both sides of at least a part of the transparent part, or an organic polymer resin is applied, or at least one of the parts of the film from the transparent part to the printed part is coated with a thin film. The gist is that one and/or both sides are laminated or coated with a thin film or coated with an organic polymer resin.

[Function] As a result of intensive research, the present inventors found that the curl that occurs during heat shrinkage is due to the difference in heat shrinkage speed between the transparent part and the printed part, and came up with the present invention. It became a thing. Therefore, the following description will be given with reference to FIGS. 4 and 5.

When printing is applied to a heat-shrinkable film, the printed part where the printing ink is laminated is reinforced by the printing ink, and since the printing ink itself does not exhibit heat-shrinkability, there is a gap between the printed part and the plain transparent part. Differences in thermal behavior occur. That is, on the same label made from the above-mentioned heat-shrinkable film, a fast-shrinking part [hereinafter referred to as transparent part (4)] and a slow-shrinking part [hereinafter referred to as printed part (5)] are formed. becomes. Therefore, in Figure 's4, the state of the label after the heat shrinkage time ■ seconds has elapsed is that the transparent part (4) has shrunk in advance as shown in Figure 5 (■). This results in bending as shown in (2).

Therefore, the present inventors conducted repeated studies to minimize the difference in shrinkage speed between the transparent part (4) and the printed part (5), and found that at least part of the transparent part (4) should be laminated or covered with a thin film. Alternatively, if a transparent coat layer [(3) in Figure 1] (hereinafter abbreviated as transparent coat layer) is formed by coating an organic polymer resin, the transparent portion (
It was found that the shrinkage speed of 4) could be suppressed, and folding after heat shrinkage could be prevented.

The heat-shrinkable film in the present invention is not limited by type, and includes heat-shrinkable films such as polyamide film, polyethylene film, polypropylene film, polystyrene film, polyvinyl chloride film, polyvinylidene chloride film, polyester film, and hydrochloric acid rubber film. Compatible film is applicable.

In addition, the transparent coat layer in the present invention is formed for the purpose of reducing the difference in shrinkage speed, and the resin used for the transparent coat layer may be appropriately selected depending on conditions such as the type and thickness of the heat-shrinkable film and printing ink. However, any resin that can be laminated, coated, or adhered to the above heat-shrinkable film can be used; nitrocellulose,
Examples include organic polymer resins such as polyamide resin, polyester resin, polyurethane resin, vinyl chloride resin, rubber resin, and acrylic resin.

Examples of the method for forming the transparent coat layer include laminating or covering the heat-shrinkable film with the organic polymer resin film, or coating the heat-shrinkable film with the molten organic polymer resin.

Furthermore, various forms of forming the transparent coat layer can be considered.In addition to the method of forming the transparent coat layer on the entire transparent part as shown in Fig. 1, there is also a method of forming it on a part of the transparent part as shown in Fig. 2. However, in addition to this, many methods are possible by combining the printing part and the transparent part, for example, by forming it on part or all of the part. In addition to forming the transparent coat layer on the inner circumferential side, it is also possible to form it on a part or all of the outer circumferential side.

[Example: 45 μm polyester film with a heat shrinkage rate of 60%
Printed on one side with a thickness of 2.5 μm, and on both the top and bottom edges with 3
A label having a transparent part of width (1) was prepared to obtain a cylindrical comparative example test piece.

Next, the transparent portion of the printed side of the label was coated with a transparent polyamide resin to a thickness of 1.5 μm to form a cylindrical shape to obtain a test piece of the present invention. The above test piece was heated at 140° C. for 6 seconds to undergo heat shrinkage, and then the transparent portion was checked for curl. Curl in the transparent portion was evaluated by visual inspection, and if even one bend was observed at the tip in the circumferential direction, it was determined that curl had occurred. The results are shown in Table 1.

On the other hand, the above label before being formed into a cylindrical shape was heated at 140°C, and the heat shrinkage rates of the transparent part and the printed part were measured by the following method 1 second, 3 seconds, and 6 seconds after the start of heat shrinkage. The difference in thermal shrinkage rate was determined. The results are shown in the 'tS2 table.

[Heat shrinkage rate When the length of Collabelle in a cylindrical shape is measured in the circumferential direction, and the length before heating is 11 and the length after heat shrinkage is 12, u, -IL2 × 100 1 was taken as the heat shrinkage rate (%).

In the Examples shown in Table 's1, the heat shrinkage rates of the printed part and the transparent part are almost the same, so the difference in heat shrinkage rate between 1 second and 3 seconds after the start of heat shrinkage is small, and no curl is observed in the transparent part. On the other hand, in Comparative Example 1, which is a conventional heat-shrinkable label, complete bending occurred because the difference in heat-shrinkage rate was particularly large 1 second after the start of heat-shrinkage.

The curl state of the transparent portion was examined in the same manner as in Example 1, except that the printed portion was coated with the transparent resin to a width of 3.5 mm, and no inward curling was observed.

When the curl state of the transparent portion was examined in the same manner as in Example 1 except that the transparent resin was coated with a thickness of 5 μm, there was no inward curl. However, it was slightly curled outward.

i-Kiri 1 The curling condition of the transparent portion was examined in the same manner as in Example 1 except that the transparent resin was coated with a thickness of 3 μm. There was no inward curling, and outward curling was almost good.

From Example 3.4, it can be considered as follows.

The present invention prevents curling due to differences in heat shrinkage speed by forming a transparent coat layer on at least a part of the transparent portion, and is not particularly limited by the thickness of the transparent coat layer. If it is too thick, the shrinkage speed of the transparent part will be too slow and it will tend to curl outward. That is, it can be seen that the formation of the transparent coat layer greatly contributes to eliminating the curling property of the thermal AIM shrinkable film by controlling the heat shrinkage rate.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to prevent the transparent part from folding inward, which occurs when labeling a bottle, thereby improving the aesthetic appearance of the product and increasing the product value. was able to increase

[Brief explanation of drawings]

Fig. 1 is a reference sectional view of a heat-shrinkable film showing the main embodiment of the present invention, Fig. 2 is a reference sectional view of a heat-shrinkable film showing an embodiment other than Fig. 1, and Fig. 3 is a reference sectional view of a heat-shrinkable film showing a main embodiment of the present invention. A reference external view showing the curled state when labeling a heat-shrinkable film. Figure 4 is a graph showing the difference in heat shrinkage speed between the transparent part and the printed part. Figure 5 is a reference diagram showing the change in heat shrinkage over time. It is a diagram. l... Heat shrinkable film 2... Printing ink 3.
...Transparent coat layer 4...Transparent part 5...Printed part Fig. 1 Fig. 3 Fig. 4 Fig. 2 (a) (b) (C) (d) (e) (f) ■ ■ Heat Shrinkage time (sec) Figure 5 ■ ■ 1. Display of the case 1999 Patent No. 344390 2. Name of the invention Heat-shrinkable film 3. Person making the amendment Interaction with the case

Claims (2)

[Claims] (1) In a cylindrical or bag-shaped heat-shrinkable film that is printed leaving a transparent part at the open end of the cylindrical or bag-shaped heat-shrinkable film, at least one of the transparent parts A heat-shrinkable film characterized in that one and/or both sides are laminated or coated with a thin film or coated with an organic polymer resin. (2) In a cylindrical or bag-shaped heat-shrinkable film in which printing is applied while leaving a transparent portion at the open end of the cylindrical or bag-shaped heat-shrinkable film, the film extends from at least the transparent portion to the printed portion. A heat-shrinkable film characterized in that it is formed by laminating or coating a thin film on one side and/or both sides, or coating an organic polymer resin.