JPH0453700B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a lid material for a container for packaging foods and the like. (Prior Technology) Conventionally, A1 vapor-deposited film and A1 foil, which have a beautiful metallic luster that is continuous in the plane direction, have been used as lids for plastic containers that are filled and packaged with various foods. (Jikko Sho 60-
(See Publication No. 26986, Publication No. 1986-2040). (Problems to be Solved by the Invention) However, with conventional lids, when food is heated and cooked in a microwave oven with the lid attached,
Because the metal of the A1 vapor deposition layer and A1 foil forms a conductive layer or film that is continuously connected in the plane direction,
Electric charge generated by microwaves in the A1 vapor deposited layer or A1 foil causes discharge, heat generation and thermal contraction, and if there is flammable material such as paper or plastic, combustion may occur due to discharge. In order to eliminate these defects, physical stress may be applied to form cracks in the A1 deposited layer, or A1
It is also conceivable to remove the deposited layer in a grid pattern. However, in this case, although the A1 vapor deposited layer exhibits a large surface resistance like an insulator on the entire lid material of the container, it is necessary to process the A1 vapor deposited layer to a fine surface area that eliminates charging by microwaves. is difficult, so it is not sufficient for use in microwave ovens. Also, if you do it like this, A1
The deposited layer does not have a beautiful metallic luster that is continuous in the plane direction, and many curves and straight lines due to cracks and lattices are noticeable. Therefore, as a result of intensive research, the present inventor discovered that a metal vapor deposited layer with a specific structure among metal vapor deposited layers has all of microwave transmittance, insulation properties, and metallic luster. This invention eliminates the various drawbacks mentioned above, and
It has a beautiful metallic luster that is continuous in the plane direction, and also has microwave permeability and insulation properties, and provides a lid material for a container that is most suitable for use in a microwave oven. (Means for Solving the Problems) The present invention provides a lid material for a container comprising at least a plastic film and a metal vapor deposited layer, in which the size of the islands of the metal vapor deposited layer is 200 Å to 1 μm, and the spacing between the islands is 100 Å to 1 μm. This is a lid material for containers that is characterized by a 5000 Å island-like structure and has microwave transparency, insulation properties, and metallic luster. The simplest structure of this invention consists of a two-layered structure in which a plastic film and a metal vapor deposited layer having an island-like structure with an island size of 200 Å to 1 μm and an island spacing of 100 Å to 5000 Å are laminated. However, of course, other plastic films, paper, cellophane, etc. may be appropriately laminated on this two-layer structure by bonding, etc., and an appropriate resin layer may also be laminated by coating. Further, in this invention, appropriate layers may be colored. Furthermore, in this invention, it is free to perform appropriate printing at appropriate locations. As the plastic film, polyester film, polypropylene film, polyethylene film, polyvinyl chloride film, and other various plastic films can be used. Plastic film has hairline processing,
It may be processed with unevenness such as matte processing, or suitably colored or printed. The plastic film may be heat-sealable or non-heat-sealable. The metal deposited layer having an island-like structure is formed on the surface of the plastic film by a conventionally known thin film forming method such as vacuum deposition, sputtering, or ion plating. A protective layer may be provided on the metal vapor deposited layer having an island-like structure, and a base layer as a pretreatment may be provided below the metal vapor deposited layer having an island structure. Further, in the present invention, the metal vapor deposited layer having an island-like structure may be formed partially, and in this case, the parts where the metal vapor deposited layer having the island-like structure exists and the parts where it does not exist coexist. Appropriate patterns, designs, etc. can be made to appear. 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. The size of the island in the island-like structure of the metal vapor deposited layer is
If it is smaller than 200 Å, the islands are too small and a beautiful metallic luster that is continuous in the plane direction cannot be obtained. If the size of the islands is larger than 1 μm, the islands are too large and will come into contact with each other and become one piece, resulting in a decrease in insulation and impermeability of microwaves, and when microwaves are irradiated to the metal vapor deposited layer, electric charges will be generated. is charged, causing electrical discharge, thermal contraction, combustion, etc. The spacing between islands in the island-like structure of the metal vapor deposited layer is 100
If it is smaller than Å, a tunnel current of charged charges flows, causing discharge, thermal contraction, combustion, etc. If the spacing between the islands is greater than 5000 Å, the overall amount of metal will decrease, making it impossible to obtain a beautiful metallic luster that is continuous in the plane direction. The metal vapor deposited layer with island-like structure contains Sn, Sn-Al.
Alloy, Sn-Si alloy, Pb, Zn, Bi, Ti, Cr, Fe,
Various metals and alloys such as Co, Ne, Si, and Ge can be used. The metal vapor deposition layer having an island-like structure according to the present invention can be formed by controlling the evaporation rate, the thickness of the vapor deposition layer, etc. in vacuum vapor deposition or the like. In terms of the thin film production process, control in vacuum evaporation, etc., varies from ``nucleation'' to ``nuclear bonding'' to ``initial island structure.''
control so that it forms an island-like structure. Control is difficult depending on the metal used. Generally speaking, metals with low melting points and noble metals are relatively easy to control, especially Sn, Sn-Al alloy, Sn-
Si alloys, Pb, Zn, Bi, etc. are particularly easy to use, but considering the toxicity when used for food, Pb,
Zn, Bi, etc. are not so preferred, and Sn, Sn-Al alloy, and Sn-Si alloy are optimal. Also, Ti, Cr,
Control of transition metals such as Fe, Co, and Ne, and semiconductor metals such as Si and Ge is relatively difficult. In controlling the formation of a metal vapor deposited layer having an island-like structure, generally speaking, the faster the evaporation rate, the smaller the size of the islands tends to be. However, the influence of the thickness of the vapor deposited layer is particularly large, and when the thickness of the vapor deposited layer is converted into light transmittance, a light transmittance of about 1% to 15% is optimal for obtaining the island-like structure of the metal vapor deposited layer of this invention. . Of course, this also varies depending on the metal; Sn, Pb,
This range is fine for Zn, Bi, etc., but 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 lower than 1%,
Microwaves charge the Sn vapor deposited layer,
Discharge and thermal shrinkage may occur, and if the light transmittance is higher than about 15%, discharge and thermal shrinkage will not occur, but a beautiful metallic luster that is continuous in the plane direction will not be obtained. In order to obtain a beautiful metallic luster that is continuous in the plane direction, the Sn vapor deposited layer requires a gloss level of approximately 350 or higher, but the light transmittance of the Sn vapor deposited layer is approximately 350 or higher.
If it is 15% or less, the gloss level will be approximately 350 or higher. The container lid material of the present invention can be used by being attached to a container as a lid material by heat sealing, using an adhesive, or the like. (Examples and Comparative Examples) Example 1 One side of a wide and long polyethylene terephthalate film with a thickness of 25 μm was coated on one side using a semi-continuous vacuum evaporator, with an evaporation rate of 0.4 g/min and a film winding speed of 250 m/min. While controlling Sn
A vapor deposition layer was formed to obtain a lid material for a container of the present invention. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 1000 Å, and the spacing between the islands was 100 Å. The size of the islands can be determined using an electron microscope.
Observe the Sn deposition layer and display the average size.
Regarding the spacing between the islands, the Sn vapor deposition layer was observed with an electron microscope and the average spacing was displayed (Example 2 to
The same applies to Example 6 and Comparative Examples 1 to 4). Incidentally, the total light transmittance of the Sn vapor deposited layer of the lid material of the obtained container was measured by the method of JISK-6714 (Examples 2 to 6 and Comparative Examples 1 to 4).
(Same as above) However, the light transmittance was 16%. Example 2 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the film winding speed was 180 m/min. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 1000 Å, and the spacing between the islands was 100 Å. Incidentally, the light transmittance of the Sn vapor-deposited layer of the lid material of the obtained container was 10%. Example 3 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the film winding speed was 150 m/min. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 2000 Å, and the spacing between the islands was 100 Å. Incidentally, the light transmittance of the Sn vapor-deposited layer of the lid material of the obtained container was 6%. Example 4 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the film winding speed was 70 m/min. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 7000 Å, and the spacing between the islands was 500 Å. Incidentally, the light transmittance of the Sn vapor-deposited layer of the lid material of the obtained container was 1%. Example 5 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the evaporation rate was 0.6 g/min and the film winding speed was 200 m/min. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 600 Å, and the spacing between the islands was 100 Å. Incidentally, the light transmittance of the Sn vapor-deposited layer of the lid material of the obtained container was 12%. Example 6 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the evaporation rate was 0.6 g/min and the film winding speed was 180 m/min. The size of the islands in the Sn vapor deposited layer of the lid material of the obtained container was 1600 Å, and the spacing between the islands was 300 Å. Incidentally, the light transmittance of the Sn vapor deposited layer of the lid material of the obtained container was 8%. Comparative Example 1 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the film winding speed was 30 m/min. The Sn vapor deposited layer of the lid material of the obtained container did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the Sn vapor-deposited layer of the lid material of the obtained container was 0.1%. Comparative Example 2 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor deposition layer was replaced with an Al vapor deposition layer and the film winding speed was 400 m/min. The Al vapor-deposited layer of the lid material of the obtained container did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the Al vapor deposited layer of the lid material of the obtained container was 63%. Comparative Example 3 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor deposition layer was replaced with an Al vapor deposition layer and the film winding speed was 350 m/min. The Al vapor-deposited layer of the lid material of the obtained container did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the Al vapor-deposited layer of the lid material of the obtained container was 48%. Comparative Example 4 A lid material for a container of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor-deposited layer was replaced with an Al-deposited layer and the film winding speed was 40 m/min. The Al vapor-deposited layer of the lid material of the obtained container did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the Al vapor-deposited layer of the lid material of the obtained container was 0.2%. The surface resistance and gloss of each container lid material obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were measured, and the film side of each container lid material was An unstretched polypropylene film with a thickness of 30 μm and a polyethylene terephthalate film with a thickness of 50 μm were pasted on the Sn vapor deposited layer side of the lid material of each container using a urethane adhesive, and the unstretched polypropylene film and polyethylene terephthalate film were attached. Six types of container lid materials and four types of container lid materials of the present invention were obtained. The above six types of container lid materials and four types of container lid materials of the present invention are reattached as lid materials by heat sealing to a container containing food, and then the thus-formed material is heated and cooked in a microwave oven. We investigated its suitability for use in microwave ovens. The results of these measurements and investigations are shown in the table below.

[Table] The surface resistance in the above table was measured according to the method of JIS K-6911. The glossiness in the table above was measured according to the method of JIS Z-874. Microwave suitability in the table above was determined based on the presence or absence of electrical discharge and thermal contraction, and whether heating and cooking were possible. (Effects of the Invention) This invention provides a metal vapor deposition layer with an island size of 200 Å.
Since the island-like structure with a diameter of ~1 μm and an island spacing of 100 Å to 5000 Å has microwave permeability, insulation, and metallic luster, this invention can be used as a lid material for a container to create a container with a lid material. Even if you heat and cook food in a microwave oven, the microwaves will pass through and there will be no electrical discharge, heat shrinkage, or combustion, and the entire product has a beautiful metallic luster that continues in the plane direction. It is something.

Claims (1)

[Claims] 1. In a lid material for a container comprising at least a plastic film and a metal vapor deposited layer, the metal vapor deposited layer has an island size of 200 Å to 1 μm and an island spacing of 100 μm.
It is characterized by having an island-like structure of Å to 5000 Å,
Container lid material with microwave transparency, insulation, and metallic luster. 2 The metal of the metal vapor deposition layer is Sn, Sn-Al alloy or Sn
-The container lid material according to claim 1, which is made of a Si alloy. 3. The lid material for a container according to claim 2, wherein the metal vapor deposited layer has a light transmittance of 1% to 15%.