JPH0448346B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention is a molding sheet that has beautiful metallic luster and is continuous in the plane direction, and is used to form molded objects such as food containers such as food plates and lunch boxes, and molded objects such as toys. It is related to. (Prior Art) Conventionally, moldable films such as polypropylene films have been used as molding sheets that are continuous in the plane direction and have beautiful metallic luster for forming molded objects such as food containers by vacuum forming or the like. It is known that an A1 vapor deposited layer is provided between a moldable sheet such as a polystyrene sheet, and a moldable sheet such as a polystyrene sheet. (Problem to be solved by the invention) However, when the conventional molding sheet is molded into a food container and the container is heated and cooked in a microwave oven, the A1 vapor deposition layer is continuously connected in the plane direction. Since it is a conductive layer or film, electric charges generated by microwaves in the A1 vapor deposition layer may cause discharge, heat generation and thermal contraction, and there may be combustible materials such as paper or plastic. Combustion may occur due to electrical discharge. In order to eliminate these defects, physical stress may be applied to form cracks in the A1 deposited layer, or A1
There is also one in which the deposited layer is removed 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 forming sheet, it is not possible to process the A1 vapor-deposited layer into a surface area so fine as to eliminate charging by microwaves. Because of the difficulty, it is not suitable for use in microwave ovens. Also, if you do this,
The A1 vapor 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
The present invention provides a moldable sheet that has beautiful metallic luster that is continuous in the plane direction, and also has microwave transparency and insulation properties, making it ideal for use in microwave ovens. (Means for Solving the Problems) The present invention provides a molding sheet in which a metal vapor deposited layer is provided between a moldable film and a moldable sheet, in which the metal vapor deposited layer has an island size of 200 Å.
This is a sheet for molding that has microwave transmittance, insulation properties, and metallic luster, and is characterized by an island-like structure of ~1 μm and an island spacing of 100 Å to 5000 Å. The simplest structure of this invention is that between the formable film and the formable sheet, the size of the island is
It consists of a three-layer structure in which a metal vapor deposited layer is provided with an island-like structure of 200 Å to 1 μm and an island spacing of 100 Å to 5000 Å. However, of course, other plastic films, paper, cellophane, etc. can be laminated to this three-layer structure by laminating them as appropriate, and
An appropriate resin layer may 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 moldable film, polypropylene film, polyester film, polyethylene film, vinyl chloride film, polystyrene film, and various other moldable plastic films can be used. As the moldable sheet, a sheet of the same type or a different type from the moldable film 1 described above can be used. Both the moldable film and the moldable sheet may be textured such as hairline processing or matte processing, or may be appropriately colored or printed. Further, both the moldable film and the moldable sheet may be a single film or sheet, or the moldable film or sheet may be laminated by laminating other appropriate materials. It may be a physical object. The metal deposited layer having an island-like structure is formed on the surface of a moldable film or sheet 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. After forming a metal vapor deposited layer having an island-like structure on the surface of a formable film or sheet, a formable film or sheet is formed by laminating, extrusion molding, etc. on the metal vapor deposited layer having an island structure. Form a moldable sheet. The metal vapor deposited layer has an island-like structure with an island size of 200 Å to 1 μm and an island spacing 5 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 on 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−A1
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. is from ``nucleation'' to ``nuclear bonding'' to the initial island-like 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-A1 alloy, Sn-
Si alloys, Pb, Zn, Bi, etc. are particularly easy to use, but when using them as food containers, considering their toxicity, Pb, Zn, Bi, etc. are not so preferred, and Sn,
Sn-A1 alloy and Sn-Si alloy are optimal. Also,
Transition metals such as Ti, Cr, Fe, Co, Ne, Si, Ge
It is relatively difficult to control semiconductor metals such as 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 molding sheet of the present invention can be used to form molded objects such as food containers and toys by vacuum forming or the like. (Examples and Comparative Examples) Example 1 One side of a wide and long unstretched polypropylene film with a thickness of 30 μm was coated with a semi-continuous vacuum evaporator at an evaporation rate of 0.4 g/min and a film winding speed of 250 m/min. A Sn vapor deposition layer was formed while controlling the temperature to be at min. When the size and spacing of the islands in the Sn vapor deposited layer were measured, the island size was 1000 Å and the spacing between the islands was 100 Å.
It was 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). By the way, the total light transmittance of the Sn vapor deposited layer is JISK
-6714 (the same applies to Examples 2 to 6 and Comparative Examples 1 to 4), the light transmittance was 18%. Furthermore, the surface resistance and gloss of the Sn vapor-deposited layer were also measured. Next, a polystyrene sheet having a thickness of 400 μm was adhered onto the Sn vapor-deposited layer using an acrylic-vinyl chloride-vinyl acetate copolymer resin to obtain a molding sheet of the present invention. Example 2 A sheet for molding 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 deposition layer is 1000Å, and the spacing between the islands is
It was 100Å. Incidentally, the light transmittance of the Sn vapor-deposited layer was 12%. Example 3 A sheet for molding 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 deposition layer is 2000Å, and the spacing between the islands is
It was 100Å. Incidentally, the light transmittance of the Sn vapor-deposited layer was 7%. Example 4 A molded sheet 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 deposition layer is 7000Å, and the spacing between the islands is
It was 500Å. Incidentally, the light transmittance of the Sn vapor-deposited layer was 2%. Example 5 A sheet for molding 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 is 600Å, and the spacing between the islands is
It was 100Å. Incidentally, the light transmittance of the Sn vapor-deposited layer was 14%. Example 6 A sheet for molding 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 deposition layer is 1600Å, and the spacing between the islands is
It was 300Å. Incidentally, the light transmittance of the Sn vapor deposited layer was 9%. Comparative Example 1 A sheet for molding 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 obtained molding sheet 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 was 0.1%. Comparative Example 2 A sheet for molding of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor deposition layer was the A1 vapor deposition layer and the film winding speed was 400 m/min. The A1 vapor deposited layer of the obtained molding sheet did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the A1 vapor deposited layer was 65%. Comparative Example 3 A sheet for molding of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor deposition layer was the A1 vapor deposition layer and the film winding speed was 350 m/min. The A1 vapor deposited layer of the obtained molding sheet did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the A1 vapor deposited layer was 50%. Comparative Example 4 A sheet for molding of the present invention was obtained in the same manner as in Example 1, except that the Sn vapor deposition layer was the A1 vapor deposition layer and the film winding speed was 40 m/min. The A1 vapor deposited layer of the obtained molding sheet did not have an island-like structure, but formed a continuous layer in the plane direction. Incidentally, the light transmittance of the A1 vapor deposited layer was 0.2%. The molding sheets obtained in Examples 1 to 6 and Comparative Examples 1 to 4 above were vacuum formed to form the main body and lid of a bento box, and frozen foods were placed therein and electronically They were heated and cooked in a microwave oven, and their suitability for use in a microwave oven was investigated. The results of the measurement and investigation of surface resistance, glossiness, and microwave oven suitability in Examples 1 to 6 and Comparative Examples 1 to 4 are shown in the following table.

[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 we created an island-like structure with a diameter of ~1 μm and an island spacing of 100 Å to 5000 Å, it has microwave transparency, insulation properties, and metallic luster, so it can be molded into a food container and placed in a microwave oven to store food. Even when heated or cooked, microwaves pass through and cause discharge,
Heat shrinkage and combustion do not occur, and the entire surface exhibits a beautiful metallic luster that continues in the plane direction.

Claims (1)

[Scope of Claims] 1. A sheet for forming formed by providing a metal vapor deposited layer between a formable film and a formable sheet, the metal vapor deposited layer having an island size of 200 to 1 μm and an island spacing of 100 μm. A sheet for molding having microwave permeability, insulation properties, and metallic luster, characterized by having an island-like structure of 〓~5000〓. 2 The metal of the metal vapor deposition layer is Sn, Sn-A1 alloy or Sn
-The molding sheet according to claim 1, which is a Si alloy. 3. The molding sheet according to claim 2, wherein the metal vapor deposited layer has a light transmittance of 1% to 15%.