JPH0371277B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a transfer material, and more specifically, it provides a beautiful metallic luster to containers and packaging for microwave foods that are heated and cooked in a microwave oven. This invention relates to a transfer material for microwave food containers and packaging that does not cause electrical discharge or thermal shrinkage even when microwaved and irradiated with microwaves. (Prior art and its problems) Conventionally, paper and plastic have been used for microwave food containers and packaging, but conventionally known metal vapor deposition such as Al has been used for microwave food containers and packaging. When a transfer material having a layer is completely or partially transferred to give it a metallic luster and then heated and cooked in a microwave oven, electric charge generated by the microwaves in the metal vapor deposited layer generates a discharge.
The heat generated may cause the plastic container to shrink, or the electrical discharge may cause the paper or plastic to burn. In order to improve this, it is possible to generate cracks in the metal deposited layer of the transfer material by applying physical or mechanical stress, or to remove the metal deposited layer in a lattice pattern. When used as a direct current, it exhibits a large surface resistance like an insulator, but it is difficult to process it into a surface area so fine as to eliminate the amount of charge caused by microwaves, so it is not used for microwave food containers and packaging. is not enough. In addition, such products have cracks in the metal deposited layer, or the metal deposited layer is removed in a grid pattern, and the many curved lines or straight lines are unsightly, and are far from completely beautiful metallized products. It doesn't feel luxurious. The present invention relates to a transfer material for microwave food containers and packaging which eliminates the above-mentioned drawbacks, and uses a microwave food container and packaging onto which the transfer material of the present invention has been transferred and is heated in a microwave oven. It is an object of the present invention to provide an optimal container/packaging for microwave foods that has microwave transparency and beautiful continuous metallic luster when cooked, and does not cause electrical discharge, combustion, heat shrinkage, etc. I can do it. (Means for Solving the Problems) The present invention provides a transfer material in which a release layer, a protective layer, a metal vapor deposited layer, and an adhesive layer are sequentially laminated on one side of a base material, in which the metal of the metal vapor deposit layer is Sn, Either Sn-Al alloy or Sn-Si alloy is used and the metal vapor deposited layer is formed with an island size of 200 Å to 1 μm and an island spacing of 100.
It is characterized by having an island-like structure of Å to 5000 Å,
This is a transfer material for microwave food containers and packaging that has microwave transparency and metallic luster. As the base material, materials conventionally used as base materials for transfer materials such as plastic films such as polyester film, cellophane, metal foil, and paper can be used, and of course materials with uneven processing such as hairline processing can also be used. . Note that, if necessary, the base material may be coated with a silicone resin or the like to provide better releasability to the base material itself. For the release layer, all the materials conventionally used for the release layer of transfer materials, such as modified phenolic resin, acrylic resin such as polymethyl methacrylate, epoxy resin, nitrocellulose, silicone resin, rosin resin, and wax, can be used. Can be used. For the protective layer, all materials conventionally used for the protective layer of transfer materials, such as acrylic resin, nitrocellulose, urethane resin, polyamide resin, polyester resin, melamine resin, urea resin, epoxy resin, and rosin resin, can be used. Further, the protective layer may be colored with a suitable dye, pigment, etc., but even in this case, the protective layer is transparent or semitransparent. Furthermore, the protective layer may also serve as a release layer in some cases, and in this case, one layer serves as both the release layer and the protective layer. The metal vapor deposition layer is formed by a conventionally known thin film forming method such as vacuum evaporation, sputtering, or ion plating. In terms of the thin film production process, the metal vapor deposition layer is provided so as to form an island-like structure after passing through "nucleation", "nuclear bonding", and "initial island-like structure". The major feature of this invention is that by forming the metal vapor deposited layer into an island-like structure, it has microwave transparency and beautiful metallic luster even though the metal vapor deposited layer is used. It is something that you have. The size of the island in the island-like structure is 200 Å to 1 μm.
degree. If the island size is smaller than 200 Å, beautiful metallic luster cannot be obtained. When the size of the islands exceeds 1 μm, the islands come into contact with each other and become a single unit, making it impossible for microwaves to pass through. When microwaves are irradiated onto the metal vapor deposited layer, it becomes electrically charged, causing discharge, combustion, or heat generation. Plastic heat shrinks,
Unable to heat or cook food. The spacing between the islands is 100 Å to 5000 Å. If the distance between the islands is less than 100 Å, a tunnel current of charged charges flows, causing discharge, combustion, or thermal contraction.
If the spacing between the islands is larger than 5000 Å, the overall amount of metal will be small and a beautiful metallic luster will not be obtained. Furthermore, if the spacing between the islands exceeds 5000 Å, the density of the metal vapor deposited layer in the plane direction will become coarse and the wear resistance will decrease, and at the same time, when an adhesive layer is later formed on the metal vapor deposition layer, the solvent will penetrate through this gap. This causes an adverse effect between the protective layer and the metal vapor deposited layer, reducing the heat resistance during transfer, resulting in abnormal appearance due to so-called heat discoloration during transfer, reducing the reflective gloss, and further reducing the pencil hardness of the metal vapor deposited layer. This makes it extremely susceptible to scratches. To obtain the island-like structure of the metal vapor deposited layer of this invention,
It is necessary to control the evaporation rate, the thickness of the deposited film, etc. Controlling the size and spacing of the islands in this invention may be difficult depending on the metal used. Roughly speaking, metals with low melting points and noble metals are relatively easy to control, especially Sn, Pb, Zn, Bi, etc. However, considering the toxicity when used for food, Pb, Zn , Bi, etc. are not preferred, and Sn, Sn-Al
Alloys or Sn-Si alloys are optimal. In addition, Ti,
Transition metals such as Cr, Fe, Co, and Ni are relatively difficult to control. The generation of the metal vapor deposited layer with the island-like structure of this invention replaces the control of the relationship between the cohesive energy and adsorption energy of the metal, and therefore requires the control of various vapor deposition conditions. The faster the speed, the smaller the island tends to be. However, the influence of the deposited layer thickness is particularly large, and when the deposited layer thickness is converted into light transmittance, the light transmittance is 1%.
~15% is optimal for obtaining the island-like structure of the metallized layer of this invention. Of course, this range also varies depending on the metal, and while this is fine for Sn, this range may not necessarily be optimal for other metals. In the case of Sn, which is a typical metal used in this invention, if the light transmittance of the Sn vapor deposited layer is less than 1%, the Sn vapor deposited layer will be charged by microwaves and discharged.
It may undergo heat shrinkage, and if the light transmittance exceeds 15%, no discharge or heat shrinkage will occur, but a beautiful metallic luster will not be obtained. In order to obtain beautiful metallic luster, a Sn vapor deposited layer generally requires a gloss level of 350 or higher, but if the light transmittance of the Sn vapor deposited layer is 15% or less, the gloss level will be 350 or higher. The adhesive layer is made of acrylic resin, vinyl chloride resin,
All materials conventionally used for adhesive layers of transfer materials, such as polyvinyl butyral resin, vinyl acetate resin, and vinyl acetate-vinyl chloride copolymer resin, can be used. (Example) On one side of a 25 μm thick transparent long polyester film, a 1 μm thick release layer was applied using a gravure coater using an acrylic resin mainly composed of methyl methacrylate. A protective layer of 1.5 μm thick is coated on the mold layer using an acrylic-urethane resin using a gravure coater, and then Sn is deposited on the protective layer using a semi-continuous vacuum evaporator.
Examples 1 to 7 are obtained by providing a vapor deposition layer by vacuum vapor deposition under the following vapor deposition conditions, and furthermore, each of these Examples
An adhesive layer of 2.5 μm thick was formed on the Sn vapor-deposited layer using an acrylic-vinyl chloride-vinyl acetate copolymer resin using a reverse coater to obtain transfer materials for microwave food containers and packaging of Examples 1 to 7.

[Table] Next, each of the transfer materials of Examples 1 to 7 was transferred to microwave food container paper using a hot stamp machine, and the microwave food container paper with a beautiful metallic luster was transferred to
I got the kind. Next, the seven types of microwave food container paper mentioned above were measured for gloss, island size, island spacing, and surface resistance, and then each microwave food container paper was heated in a microwave oven (SHARP.RE-11 (voltage 100V).
Microwave oven suitability was investigated by applying a high frequency output of 400W)). The results of these measurements and investigations were as follows.

【table】

[Table] (Comparative example) Instead of the Sn vapor deposition layer in the above example, the thickness was 100 mm.
Comparative Example 1, Comparative Example 2, and Comparative Example 3 were prepared in the same manner as in the Example except that Al vapor deposited layers with thicknesses of 200 Å, 200 Å, and 500 Å were used, and the results of measurement and investigation of these in the same manner as in the Example are shown in the following table. It was hot on the street.

[Table] (Effects of the Invention) The transfer material for microwave food containers and packaging according to the present invention has a metal vapor deposition layer having an island-like structure as described above, and has microwave transparency and metallic luster. If you use a microwaveable food container or packaging that has been transferred to it and heat and cook it directly in the microwave, the microwave will pass through and there will be no discharge, combustion, or heat shrinkage.
Additionally, the entire piece exhibits a beautiful continuous metallic luster.

Claims (1)

[Claims] 1. A transfer material in which a release layer, a protective layer, a metal vapor deposited layer, and an adhesive layer are sequentially laminated on one side of a base material,
The metal of the metal vapor deposition layer is Sn, Sn-Al alloy or Sn-Si.
A microwave oven having microwave transparency and metallic luster, characterized in that the metal vapor deposited layer has an island-like structure with an island size of 200 Å to 1 μm and an island spacing of 100 Å to 5000 Å. Transfer material for food containers and packaging. 2. The transfer material for microwave food containers and packaging having microwave transmittance and metallic luster according to claim 1, wherein the metal vapor deposited layer has a light transmittance of 1% to 15%.