JP7850200B2 - Adhesive tape - Google Patents

Description

This invention relates to an adhesive tape that uses environmentally friendly paper as a base material, has no problems with wear or peeling of the printed layer, and has no restrictions on the ink used in the printed layer. It is particularly suitable for bundling vegetables or fresh flowers, sealing food containers or packaging bags, or for product identification.

Conventionally, adhesive tapes have been used for bundling vegetables or fresh flowers, sealing food containers or packaging bags, or for product identification. Such adhesive tapes have traditionally included a printed layer with ink-printed characters, symbols, or designs representing the names of vegetable or flower suppliers, brand names, retailers, barcodes, QR codes (registered trademarks), etc. (see, for example, Patent Documents 1 and 2). Such adhesive tapes generally consist of a base material, an adhesive layer, and a printed layer, with paper or plastic film used as the base material. The problems with such conventional adhesive tapes will be explained below with reference to Figures 1 and 2.

Figure 1 shows an example of a conventional adhesive tape in which an adhesive layer and a printed layer are arranged on each side of the base material. While paper is commonly used as the base material for this type of adhesive tape, the printed layer is exposed on the surface. For example, when used to bundle vegetables such as green onions, friction between adjacent vegetables during display in stores can cause the letters, symbols, and designs on the printed layer to wear away, making it difficult for consumers to read information such as the shipper's name or brand name. Furthermore, excessive friction could cause the printed layer to peel off, making it impossible for consumers to read this information at all. Additionally, this type of adhesive tape is intended for applications that may come into contact with food, but the ink used in the printed layer that may come into direct contact with food must comply with the Food Sanitation Act. Furthermore, since this type of adhesive tape is generally sold in a wound roll form, a release layer is formed on top of the printed layer to facilitate dispensing during use. However, when the release agent for this release layer is applied, the ink in the printed layer may dissolve, potentially causing the printed layer to peel off when the adhesive tape is dispensed.

To overcome the problems of the adhesive tape type shown in Figure 1, the adhesive tape type shown in Figure 2 has been proposed. Figure 2 shows an example of a conventional adhesive tape in which a printed layer is placed between the adhesive layer and the substrate. While transparent plastic is commonly used as the substrate material for this type of adhesive tape, unlike the type shown in Figure 1, the printed layer is not exposed on the surface of the adhesive tape and is covered by the substrate, thus avoiding the drawbacks and problems seen in the type shown in Figure 1. However, in the case of the type shown in Figure 2, because the printed layer is in direct contact with the adhesive layer, if the adhesion between the adhesive and the adherend is higher than the adhesion between the substrate and the printed layer, the printed layer can detach from the substrate during tape removal, remaining on the adherend along with the adhesive layer. Furthermore, this type of adhesive tape, using plastic as the substrate, is not environmentally friendly.

Japanese Unexamined Patent Publication No. 56-26968 Japanese Patent Publication No. 2016-35071

This invention was devised to solve the problems of the prior art described above. Its objective is to provide an adhesive tape using an environmentally friendly paper substrate that eliminates problems of wear and peeling of the printed layer, has no restrictions on the ink used in the printed layer, and eliminates problems of the printed layer detaching.

The inventors, through diligent research to achieve the above objectives, have discovered that in an adhesive tape having a paper substrate as shown in Figure 1, by placing another transparent substrate on the side where the printed layer's paper substrate is absent, and covering the surface of the printed layer with this other transparent substrate, it is possible to maintain the visibility of the printed layer while avoiding problems of wear and peeling of the printed layer, as well as limitations on the ink used for the printed layer. Furthermore, by using highly transparent "glassine paper" instead of transparent plastic as this other transparent substrate, environmental considerations can be taken into account. In particular, "glassine paper," unlike conventional papers such as crepe paper and Japanese paper commonly used as paper substrates for adhesive tapes, does not contain sealing resin, making it more recyclable and environmentally friendly than ordinary paper. Additionally, because "glassine paper" does not contain sealing resin, it has high heat resistance and is less prone to thermal shrinkage, making it suitable for pitch printing where the same design is repeatedly printed. Moreover, "glassine paper" is processed under high pressure during manufacturing, resulting in superior smoothness compared to ordinary paper, thus providing excellent adhesion between adjacent layers.

The present invention was completed based on the above findings and has the following configurations (1) to ( 3 ).
(1) An adhesive tape comprising a first substrate, a second substrate, an adhesive layer, and a printed layer, wherein the printed layer is disposed between the first substrate and the second substrate, the adhesive layer is disposed on the side of the first substrate where the printed layer is absent , the first substrate and the second substrate are made of glassine paper , and the adhesive tape is used for bundling vegetables or fresh flowers, or for sealing food containers or packaging bags .
( 2 ) The adhesive tape according to (1), characterized in that a primer layer is disposed between the adhesive layer and the first substrate, an adhesive layer is disposed between the printed layer and the second substrate, and a release agent layer is disposed on the side of the second substrate where the adhesive layer is absent.
( 3 ) The adhesive tape according to (1), characterized in that a primer layer is disposed between the adhesive layer and the first substrate, an adhesive layer is disposed between the first substrate and the printed layer, and a release agent layer is disposed on the side of the second substrate where the printed layer does not exist.

The adhesive tape of this invention covers the surface of the printed layer with highly transparent "glassine paper," thus maintaining the visibility of the printed layer while avoiding problems with wear and peeling of the printed layer, as well as limitations on the inks used for the printed layer. Furthermore, unlike ordinary papers such as crepe paper and Japanese paper, "glassine paper" does not contain sealing resins, making it more recyclable and environmentally friendly than these papers. In addition, because the adhesive tape of this invention uses "glassine paper" which has high heat resistance and is less prone to heat shrinkage, it is suitable for pitch printing where the same design is printed repeatedly. Moreover, because the adhesive tape of this invention uses "glassine paper" which is smoother than ordinary paper, it exhibits excellent adhesion to adjacent layers.

Figure 1 shows a schematic diagram of an example of the layer structure of a conventional adhesive tape. Figure 2 shows a schematic diagram of another example of the layer structure of a conventional adhesive tape. Figure 3 shows a schematic diagram of an example of the layer structure of the adhesive tape of the present invention. Figure 4 shows a schematic diagram of another example of the layer structure of the adhesive tape of the present invention. Figure 5 shows a schematic diagram of an example of the manufacturing procedure for the adhesive tape of the present invention. Figure 6 shows an example of the use of the adhesive tape of the present invention.

The adhesive tape of the present invention will be described below with reference to the drawings, but the present invention is not limited to these. Note that the drawings are schematic for illustrative purposes, and therefore the ratios of the thicknesses of each layer may differ from the actual dimensions.

The adhesive tape of the present invention comprises two base materials, an adhesive layer, and a printed layer as its basic structural layers. Specifically, it is suitably used for purposes such as bundling vegetables like spinach or fresh flowers like chrysanthemums, sealing containers or packaging bags for food products like prepared foods, identifying purchased goods for the purpose of preventing shoplifting, or identifying goods for the purpose of detecting when they have been opened.

An example of the layer configuration of the adhesive tape of the present invention is shown in Figure 3. The adhesive tape in Figure 3 has a basic structure in which a printed layer is placed between a first substrate and a second substrate, and an adhesive layer is placed on the side of the first substrate where the printed layer is absent. The adhesive tape in Figure 3 may further optionally have a primer layer between the adhesive layer and the first substrate, an adhesive layer between the printed layer and the second substrate, and a release agent layer on top of the second substrate. In summary, the adhesive tape of the present invention has a basic structure in which, in order from the side intended to face the adherend, the adhesive layer, the first substrate, the printed layer, and the second substrate are arranged. Optionally, a primer layer may be placed between the adhesive layer and the first substrate, an adhesive layer between the printed layer and the second substrate, and a release agent layer may be placed on the side of the second substrate where the adhesive layer is absent.

In this invention, the adhesive layer is provided for the adhesion of the adhesive tape to the substrate. As the constituent material of the adhesive layer, conventionally known adhesives such as acrylic adhesives, rubber adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives can be used. It is preferable to select an adhesive layer that has sufficient adhesive strength for the adhesion of the adhesive tape to the substrate. Furthermore, it is preferable to select an adhesive layer that does not leave any adhesive residue when peeled off and has sufficient adhesive strength when reapplied as needed. Specifically, it is preferable to select an adhesive layer with an adhesive strength of, for example, 0.5 to 6.0 N/10 mm, preferably 1.0 to 5.0 N/10 mm, at the time of initial application, and for example, 0.3 to 5.0 N/10 mm, preferably 0.5 to 4.0 N/10 mm, at the time of reapplication. The thickness of the adhesive layer is, for example, 2 to 70 μm, preferably 10 to 50 μm.

In this invention, the first substrate serves as a support for the adhesive tape. Furthermore, the first substrate is positioned between the adhesive layer and the printed layer, preventing the printed layer from directly contacting the adhesive layer, thereby preventing the printed layer from detaching.

In this invention, the first base material is preferably made of glassine paper for recyclability, but it can also be made of transparent plastic. Glassine paper is a high-density paper manufactured by using sulfurous acid pulp, which has been finely beaten for a long time, as the raw material, and applying high pressure using a smooth roller called a supercalender. Unlike conventional papers such as crepe paper and Japanese paper, which are commonly used as paper base materials for adhesive tapes, glassine paper does not contain a sealing resin, making it more recyclable and environmentally friendly than conventional paper. Furthermore, because glassine paper does not contain a sealing resin, it has high heat resistance and is less prone to thermal shrinkage, making it suitable for forming printed layers by pitch printing, which involves repeatedly printing the same design. In addition, glassine paper is processed under high pressure during manufacturing, resulting in superior smoothness and high transparency compared to conventional paper.

The thickness of the glassine paper constituting the first substrate is preferably 5 to 50 μm, and more preferably 10 to 40 μm, considering the balance between strength as a support and flexibility during handling. Since various types of glassine paper constituting the first substrate are commercially available, those skilled in the art can appropriately select a suitable one from among them.

In this invention, the first substrate is not necessarily made of glassine paper; it can also be made of transparent plastic. As the transparent plastic, conventionally used substrates for adhesive tapes can be used, such as PET film, polypropylene film, or polyethylene film. The thickness of these films is preferably 5 to 50 μm, and more preferably 10 to 40 μm, considering the balance between strength as a support and flexibility during handling. Since various types of these films are commercially available, those skilled in the art can appropriately select suitable ones from among them.

In this invention, the printed layer is a layer on which characters, symbols, patterns, etc., are printed with ink. For example, it can represent information such as the name of a vegetable or flower supplier, brand name, store name, barcode, or QR code (registered trademark). In this invention, the printed layer is not exposed on the surface of the adhesive tape and is covered by a second substrate. Therefore, in the adhesive tape of this invention, since the printed layer does not have the potential to come into direct contact with food, inks other than those compliant with the Food Sanitation Law can be used, and there are no restrictions on the ink used for the printed layer. The printed layer can be formed by conventionally known methods. For example, the printed layer can be formed by gravure printing a solvent-based colored ink, followed by drying and curing. In particular, it can be formed by pitch printing, which involves repeatedly printing the same design. The thickness of the printed layer is, for example, 0.1 to 5 μm, preferably 0.3 to 3 μm.

This invention is characterized in that the second base material is composed of glassine paper. Glassine paper is semi-transparent and has higher transparency compared to crepe paper and Japanese paper, which are conventionally used as paper base materials for adhesive tapes. Therefore, glassine paper can be used as a substitute for transparent plastic base materials to cover the printed layer without causing any visibility problems. Furthermore, glassine paper has superior recyclability compared to ordinary paper, making it even more environmentally friendly. In addition, glassine paper has superior smoothness compared to ordinary paper, resulting in excellent adhesion between adjacent layers. The thickness of the glassine paper constituting the second base material is preferably 5 to 50 μm, and more preferably 10 to 40 μm, considering the balance between strength as a cover for the printed layer and flexibility during handling. As with the first base material, suitable glassine paper can be appropriately selected from various commercially available products as the glassine paper constituting the second base material.

In the adhesive tape of the present invention, a primer layer may be placed between the adhesive layer and the first substrate, if necessary. The primer layer serves to improve the adhesion between the adhesive layer and the first substrate. The constituent material of the primer layer can be appropriately selected according to the constituent material of the adhesive layer; for example, resins such as acrylic, rubber, urethane, and epoxy resins can be used. The thickness of the primer layer is, for example, 0.08 to 5 μm, preferably 0.5 to 3 μm.

In the adhesive tape of the present invention, an adhesive layer may be placed between the printed layer and the second substrate, or between the first substrate and the printed layer, as needed. The adhesive layer serves to improve the adhesion between the printed layer and the substrate. As the adhesive constituting the adhesive layer, conventionally known adhesives such as solution-type urethane resin adhesives, epoxy resin adhesives, and polyester resin adhesives can be used. The thickness of the adhesive layer is, for example, 0.1 to 10 μm, preferably 1 to 5 μm.

In the adhesive tape of the present invention, a release agent layer may be placed on the second substrate as needed. The release agent layer serves to facilitate the unwinding of the adhesive tape when it is wound in a roll. As the constituent material of the release agent layer, known release agents such as long-chain alkyl release agents and silicone release agents can be used. The basis weight of the release agent layer is, for example, 0.1 to 10 g/ ^m² , preferably 0.1 to 3 g/ ^m² .

Next, Figure 4 shows another example of the layer structure of the adhesive tape of the present invention. The adhesive tape in Figure 4 has the same layer structure as the adhesive tape in Figure 3, except that the position of the adhesive layer differs from that of the adhesive tape in Figure 3. That is, in Figure 3, the adhesive layer is positioned between the printed layer and the second substrate, whereas in Figure 4, the adhesive layer is positioned between the first substrate and the printed layer. This difference in position stems from the fact that Figure 3 corresponds to a type where the printed layer is printed on the front, while Figure 4 corresponds to a type where the printed layer is printed on the back. Because the second substrate of the adhesive tape of the present invention is made of highly transparent glassine paper, fine information such as barcodes and QR codes (registered trademarks) can be easily read even in the back-printed type as shown in Figure 4.

Next, the manufacturing procedure for the adhesive tape of the present invention will be described with reference to Figure 5. The adhesive tape of the present invention can be manufactured using conventionally known methods. For example, in the case of the type shown in Figure 3, the adhesive tape can be manufactured using the following procedure.

First, a printed layer is formed on one side of the first base material, glassine paper, by printing letters, symbols, or designs with ink. Next, a primer is applied to the side of the glassine paper opposite the printed layer to form a primer layer, creating a laminate (1) as shown in the upper left of Figure 5. Meanwhile, a release agent is applied to one side of the second base material, glassine paper, to form a release agent layer. Next, an adhesive is applied to the side of the glassine paper opposite the release agent layer to form an adhesive layer, creating a laminate (2) as shown in the upper right of Figure 5. Then, laminates (1) and (2) are bonded together so that the printed layer of laminate (1) contacts the adhesive layer of laminate (2), creating a laminate (3) as shown in the lower left of Figure 5. Finally, an adhesive is applied to the primer layer of this laminate (3) to form an adhesive layer, completing the adhesive tape as shown in the lower right of Figure 5.

In the case of the type shown in Figure 4, adhesive tape can be manufactured in a similar manner by changing the formation procedure of laminate (1) and laminate (2) according to the differences in the layer structure.

The adhesive tape of the present invention, manufactured in this manner, can be provided in a roll form by winding it around a core for ease of handling. In the case of rolled adhesive tape, it can be used by unwinding and cutting the required length.

Next, Figure 6 shows specific examples of the adhesive tape of the present invention. In Figure 6, Example 1 is an example of its use in bundling vegetables such as spinach; Example 2 is an example of its use in sealing food containers and packaging such as prepared foods; Example 3 is an example of its use in identifying purchased items for the purpose of preventing shoplifting; and Example 4 is an example of its use in identifying items for the purpose of detecting tampering with products. Furthermore, in addition to these examples, the adhesive tape of the present invention can be used as an industrial tape, taking advantage of its excellent heat resistance and low heat shrinkage.

The effects of the adhesive tape of the present invention are demonstrated by the following examples, but the present invention is not limited to these examples.

As an example of the present invention , an adhesive tape was prepared by laminating the layers in the order shown in Figure 3. The constituent materials and layer thicknesses of each layer of the adhesive tape are as shown in Table 1 below.

[Table 1]
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Layer Constituent Material Thickness (μm)
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Release agent layer: Long-chain alkyl release agent 0.5

Second base material: Glassine paper 31.5

Adhesive layer: Polyester resin 3.0

Printing layer: Printing ink (solvent type) 1.0

First base material: Glassine paper 31.5

Primer layer: Rubber-based resin 1.0

Adhesive layer: Rubber-based adhesive 25.0
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Specifically, first, a barcode was repeatedly pitch-printed onto one side of the first substrate, glassine paper, using a solvent-based printing ink to form a printed layer. Next, a rubber-based resin was applied as a primer to the side of the glassine paper opposite to the printed layer to form a primer layer, creating a laminate (1) as shown in the upper left of Figure 5. Meanwhile, a long-chain alkyl-based release agent was applied as a release agent to one side of the second substrate, glassine paper, to form a release agent layer. Next, a polyester-based resin adhesive was applied as an adhesive to the side of the glassine paper opposite to the release agent layer to form an adhesive layer, creating a laminate (2) as shown in the upper right of Figure 5. Finally, these laminates (1) and (2) were bonded together so that the printed layer of laminate (1) was in contact with the adhesive layer of laminate (2), creating a laminate (3) as shown in the lower left of Figure 5. Finally, a rubber-based adhesive was applied as an adhesive layer to the primer layer of this laminate (3) to form an adhesive layer, completing the adhesive tape shown in the lower right of Figure 5.

The visibility and readability of the barcode on the printed layer of the manufactured adhesive tape were checked and found to be at a level that posed no practical problems. Furthermore, the pitch printing was performed without issue, and despite the thinness of the primer and adhesive layers, the adhesion to adjacent layers was excellent.

Comparative Example As a comparative example, an attempt was made to produce an adhesive tape in the same manner as the present invention example, except that the constituent materials of the first and second substrates were changed to 31.5 μm thick Japanese paper, which is commonly used as a paper substrate for adhesive tapes. However, at the stage of pitch printing of the printing layer, the Japanese paper of the first substrate underwent thermal shrinkage due to the sealing resin contained therein, making it impossible to perform proper pitch printing.

Furthermore, when the visibility and readability of the barcode on the printed layer of the manufactured adhesive tape were checked, the barcode was almost invisible and could not be read by the reader. Also, because the Japanese paper has an uneven surface, its adhesion to adjacent layers was poor, requiring a greater thickness for both the primer and adhesive layers.

The adhesive tape of the present invention can overcome conventional problems such as wear and peeling of the printed layer and limitations on the ink used for the printed layer, while maintaining the visibility of the printed layer. Furthermore, the adhesive tape of the present invention is highly recyclable, making it more environmentally friendly, suitable for pitch printing where the same design is printed repeatedly, and exhibits excellent adhesion between adjacent layers. Therefore, the adhesive tape of the present invention can be suitably used for bundling various materials, sealing various containers and bags, or for product identification.

Claims (3)

An adhesive tape comprising a first substrate, a second substrate, an adhesive layer, and a printed layer, wherein the printed layer is disposed between the first substrate and the second substrate, the adhesive layer is disposed on the side of the first substrate where the printed layer is absent , the first substrate and the second substrate are made of glassine paper , and the adhesive tape is used for bundling vegetables or fresh flowers, or for sealing food containers or packaging bags . The adhesive tape according to claim 1, characterized in that a primer layer is disposed between the adhesive layer and the first substrate, an adhesive layer is disposed between the printed layer and the second substrate, and a release agent layer is disposed on the side of the second substrate where the adhesive layer is absent. The adhesive tape according to claim 1, characterized in that a primer layer is disposed between the adhesive layer and the first substrate, an adhesive layer is disposed between the first substrate and the printed layer, and a release agent layer is disposed on the side of the second substrate where the printed layer is absent.