JPS5910305B2 - Metal-deposited resin sheet as a material for microwave oven containers and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal-deposited resin sheet as a material for microwave oven containers and a method for manufacturing the same.

Metal-deposited resin sheet, i.e., base material resin sheet 1 (Fig. 1)
A metal vapor-deposited layer 2, generally made of aluminum, is uniformly formed on one or both sides of the metal vapor-deposited layer 2 according to a conventional method (the thickness of the vapor-deposited layer 2 is generally about 0.05 μm), or 5. In addition, the metal vapor-deposited layer 2 Laminated with resin 3 (top coat layer) on the surface (in this case, one or both of layers 1 and 3 are transparent, colored transparent,
Translucent) has a beautiful metallic luster on either one or both sides, and is therefore widely used in decorative materials, packaging materials, building materials, and other applications. For example, packaging containers for various foods such as fresh foods, cooked foods, and semi-cooked foods, station lunches,
Disposable lunch boxes for caterers, various types of disposable tableware used in simple cafeterias, food stalls, mock shops, etc.
5 When made from metal-deposited resin sheets, it is possible to obtain a solid, elegant metalware-like, tasteful and clean product, which increases the commercial value and quality of the container itself or the food contained therein. In addition, since it is possible to obtain tableware that has a good appearance and does not feel strange or resistant, 20 simple lightweight resin containers for food are made of ordinary synthetic resin filled sheets, the same foam sheets, and the same various laminated sheets. In addition to those made from the metal vapor-deposited resin sheet mentioned above, those made from the metal vapor-deposited resin sheet are also manufactured in large quantities and used for prizes.

25 By the way, the popularity of microwave ovens for cooking has become remarkable these days.
Its popularity and usage are increasing even in ordinary households.
Various cooking methods using microwave ovens have also been developed.

Under these circumstances, the connection between packaged foods and microwave ovens is inevitable. Cook stuffed in the microwave,
A rational system is established in which the pack containers can be used as tableware and served at the dining table. 35 Currently, for example, some retailers of packaged lunches offer a service in which the packaged lunches are heated in a microwave oven and handed to customers, and simple restaurants also use disposable tableware. Some places put food in simple containers and put the container in the microwave to cook.

However, in such a case, a problem arises when the pack container or simple tableware is made of the metal vapor-deposited resin sheet as described above.

In other words, this type of container or tableware can be used in a microwave oven even if the metal vapor deposited layer 2 is covered with a resin top coat layer 3, or even if the entire container is wrapped in an insulating bag or sheet. Microwaves can cause electrical discharge (sparks), and containers that are not suitable for microwave ovens include general metal containers, woven wire mesh, metal skewers with rings, and containers coated with gold or silver powder. It is recommended to avoid using it in the microwave. The present invention was proposed in view of the above, and has developed a metal-deposited resin sheet that does not generate discharge even when exposed to microwaves, and by using this as a material, it does not generate discharge even when used in a microwave oven. The purpose is to enable the production of safe, simple, lightweight containers made of metal vapor-deposited resin sheets, and the metal vapor-deposited layer 2 is a small-area divided layer 2' that is discontinuous in the plane direction and has a length and width of about 5 TWL or less. The subject matter is a metal-deposited resin sheet as a material for containers for microwave ovens, which is characterized by being composed of a set of .

That is, as a result of various experimental studies, the present inventor has found that if the metal vapor deposited layer 2 is not formed into a continuous layer that is uniform throughout, but is formed into a subdivided layer structure as described above, the reason for this is not clear, but at least The present invention was completed by discovering that no discharge occurs even when receiving microwaves with an intensity comparable to that of a microwave oven.

The area limitation of each divided layer 22 was found experimentally by conducting the following tests.

That is, a base material resin sheet 1 with a continuous layer 2 (thickness approximately 0.05 μm) of metal vapor deposited, such as aluminum, uniformly formed on one side by a conventional method is used as the original material, and the second side of the metal vapor deposited layer of the material is used as the tip. In this case, the evaporated metal on the 2'5 part of the line is completely scraped off and marked with a fine scribing needle to make the metal evaporated layer 2 discontinuous in the plane direction. Make it into two small layers. And what are the grid dimensions of that grid pattern? We make a variety of products with different units, and use each material in a general microwave oven (for example, high frequency output 600W,
The oscillation frequency is 2450MHz, power consumption is 1.25KW), and the presence or absence of discharge is observed by applying microwaves.As a result, the grid size is approximately 5Trrf.
It has been found that those with a grid size larger than n will cause discharge, but anything smaller than that will not cause discharge. In this case, one of the vertical and horizontal grid dimensions is 5WfL.
The other layer is a rectangular grid pattern on top of 5a.
Similar discharge observations were made for various types of divided specimens, and in this case discharge was observed. From this, the presence or absence of discharge due to microwaves in each divided layer 2' is not only related to the size of its area, but also to its length dimension. Approximately 5 wrIn vertically and horizontally as described above, the range that does not cause discharge even when receiving microwaves with the strength of the output of a general microwave oven.
This is below the range. The shape of each divided layer 2' is arbitrary as long as the area range is less than or equal to the above range, and is irrelevant to the discharge. Further, the deposition thickness of each divided layer γ is also irrelevant to the discharge, at least within the deposition thickness range that is usually used to obtain a beautiful metallic luster. In addition to the above-mentioned marking method using a scribing needle, the metal vapor deposition layer 2 can be obtained by performing the metal vapor deposition 2 on the base material resin sheet 1 through a mesh screen. It is also effective to form a uniform continuous metal vapor deposited layer on the base resin sheet surface and then remove the vapor deposited metal portion corresponding to the parting line 25 by an corrosion method.

However, none of the above methods are suitable as industrial means.

Therefore, the present inventor has separately developed a method that can easily and inexpensively mass-produce the metal vapor-deposited resin sheet of the present invention as described above. It is characterized in that the material on which the layer 2 is formed, or the material in which the metal evaporated surface 2 is further laminated with a resin 3, is stretched by about 5% or more in each direction. That is, when the resin sheet on which the metal vapor deposited continuous layer 2 has been applied is stretched by about 5% or more in the vertical and horizontal directions, the metal vapor deposit layer 2 of the resin sheet has microscopic microscopic particles all over the surface as shown in the example in FIG. As a result, the vapor deposited layer 2 is divided into a large number of fine irregularly shaped small area layers 7 (for example, in the range of 20 to 30 μ in the vertical and horizontal directions) that are discontinuous in the plane direction. It has been found that a metal vapor deposited sheet in which the metal vapor deposited layer 2 is fragmented in this manner does not cause discharge even when exposed to microwaves.

In order to easily stretch the resin sheet, and also to generate cracks almost uniformly over the entire surface of the metal vapor deposited sheet even if the metal vapor deposited sheet has a large area, the metal vapor deposited sheet to be stretched is prepared in advance. The resin sheet is heated to an appropriate temperature below its melting point to soften it appropriately, and then stretched.

If the amount of stretching in the vertical and horizontal directions is small, that is, below 5(f) above, network cracks will not occur in the deposited layer, or even if they occur, most of them will be split layers with a large area of 5 Trm or more in both the vertical and horizontal directions, or is not preferable because it gets crowded.

If it is stretched only in one direction, vertically and horizontally, or by more than 5(f) in one direction and less than 5% in the other direction, it will split into elongated vertical or horizontal stripes as shown in the example in Figure 5, that is, cracks. The sheet should be stretched by more than about 5 (f) in both the length and width so that a substantially continuous layer morphology is maintained that still produces a discharge. By increasing the amount of stretching in the vertical and horizontal directions, the areas of the individual divided layers produced can be reduced. On the other hand, since the width of the network crack lines 2'5 also increases, the reflectance of the metal vapor deposited layer 2 as a whole decreases, and the gloss also decreases. Therefore, it is better to avoid increasing the amount of stretching to an extremely large extent (generally 5 to 10
The amount of vertical and horizontal stretching should be about 0 (Ft), especially about 7 to 50%. According to the above-described stretching method, it is possible to easily and inexpensively mass-produce the metal-deposited resin sheet of the present invention, which does not generate electric discharge due to microwaves.

By using the sheet, it is possible to manufacture simple, lightweight containers made of metal-deposited resin sheets that are safe and do not generate electrical discharge even when used in a microwave oven. In addition to applying the metal vapor deposition layer 2 over the entire surface of the base resin sheet 1, it is also possible to partially coat the base resin sheet 1 with letters, symbols, figures, decorative patterns, etc. such as trademarks, etc. When expressed by vapor deposition, such vapor-deposited characters, patterns, etc. can be formed into an aggregated form of small-area divided layers of less than about 50 cm in length and width, which are mutually discontinuous in the plane direction, using the above-mentioned stretching method, for example, to create the same (discharge) It is possible to eliminate the phenomenon, and the present invention also includes such a method.

Example 1 A polystyrene resin sheet with a thickness of 0.4 wm was used as the base resin sheet 1, and aluminum with a purity of 99.98% was coated on one side of the sheet to a thickness of about 0.05 μm according to a conventional method.

When the positive and negative electrode needles of a tester are brought into contact with the surface of the vapor-deposited layer 2 at intervals of, for example, 1 cm, this metal-deposited resin sheet becomes electrically conductive and forms a continuous layer over the entire surface. Place the cut pieces (10 cm square, same hereinafter) in a microwave oven (high frequency output 600 W, oscillation frequency 2450 MHz, power consumption 1.25 KW) and watch for discharge (sparks) when exposed to microwaves. On the other hand, the metal vapor-deposited sheet was heated and softened at about 140° C. and then stretched by about 30% in the length and width.

When the metal-deposited surface of this stretched sheet was observed under a microscope, fine mesh-like cracks were formed on the surface of the deposited layer, and the entire layer was finely divided. The area size of each split layer was in the range of 20 to 30 μm in length and width. Further, although the positive and negative electrode needles of the tester were brought as close as possible to the surface of the vapor-deposited layer and brought into contact (below the distance 1a), there was no continuity. In addition, there was no significant decrease in the reflectance or gloss of the metal-deposited surface as a whole.
Then, the cut pieces of the stretched sheet were placed in a microwave oven and exposed to microwaves in the same manner as described above, but no discharge was observed. Example 2 A polypropylene resin sheet with a thickness of 0.4 TmL was used as the base resin sheet 1, and one side of the sheet was coated with purity 99.98 in accordance with a conventional method.
% aluminum to a thickness of about 0.05 μm, and then a transparent low-density polyethylene resin layer of about 50 μm thick was formed on the entire surface of the vapor deposited layer 2 as a tobu coat layer 3 by extrusion lamination. A metal vapor-deposited sheet was obtained in which the vapor-deposited layer 2 was interposed in the sandwich trench.

When the cut piece (10 cm square) was placed in a microwave oven and exposed to microwaves in the same manner as in Example 1, discharge was observed penetrating the exposed portion of the vapor deposited layer on the cut end face of the cut piece or the Tobucoat layer. On the other hand, the metal vapor-deposited sheet was heated and softened at about 140° C. and then stretched by about 30% in the length and width.

When the metal vapor-deposited surface of this stretched sheet was observed under a microscope through the transparent top coat layer 3, fine mesh-like cracks were formed on the entire surface of the vapor-deposited layer, as in Example 1, and the entire layer was fine. It was divided. The area size of each split layer is the same as in Example 1, from 20 to 20
It was in the 30μ range. In addition, there was no significant decrease in the reflectance or gloss of the metal-deposited surface as a whole. Then, as in Example 1, the cut pieces of the stretched sheet were placed in a microwave oven and exposed to microwaves, but no discharge was observed. Zhou, Example 1,
In step 2, the sheet stretching process is performed industrially by, for example,
By using a combination of so-called stretching rollers in the longitudinal direction and a so-called sheet tenter in the lateral direction, long pieces can be processed continuously.

In addition, as in Example 2, the sandwich type in which the metal vapor deposited layer 2 is present as an intermediate layer is manufactured using the base resin sheet 1.
Alternatively, the metal may be deposited on one or both sides of the substrate, stretched according to the method of the present invention, and then a top coat layer may be laminated on the metal deposited surface. Application Examples The metal vapor-deposited sheets according to the present invention obtained in Examples 1 and 2 were used as raw materials, and the width was 120wn and the length was 200mm.
wn, a simple bento box with a height of 35 wwft is vacuum formed using a vacuum forming machine equipped with a mold that can take 35 pieces within a molding area of about 1 d, and each integrally connected molded product is made into individual pieces using a trimming press. A simple bento box was manufactured by punching and separating.

In the bento box obtained above, (1) put about 8 minutes of cold rice in it, (2) put 3 pieces of raw fish in it, (3) put 6 pieces of halved potatoes in each ( Heat treatment was performed in a general household microwave oven (2450 MHz) at settings 1) for 3 minutes, (2) for 6 minutes, and (3) for 10 minutes.

Although monitoring was carried out throughout the set time, no abnormalities such as swark phenomenon or deformation of the container were observed, and the contents of (1) to {3) were all successfully heat-treated.

Furthermore, when the lunch box was covered with a lid made of a metallized sheet made of the same material as the bento box, no sparking occurred and the contents were heated well.

Yes, this type of container is preferably made of a relatively heat-resistant resin that does not easily deform when the contents are heated in a microwave oven.For example, as the base material sheet 1, Polypropylene, polyester, polycarbonate, etc. are effective, and as the top coat resin, polypropylene, polyethylene, etc. are effective.

The polystyrene sheet that has conventionally been generally used as the base material sheet 1 is inferior to the above-mentioned example in terms of heat resistance. However, there is no problem if it is used while heating within its heat resistance limit.

[Brief explanation of the drawing]

Fig. 1 is a layer structure diagram of →1 of the metal vapor deposited resin sheet, Fig. 2 is a plan view of the sheet with the metal vapor deposited layer surface divided into a grid pattern,
Fig. 3 is a cross-sectional view of the same, Fig. 4 is an enlarged plan view of the fine network crack pattern that occurs on the surface of the metal vapor-deposited layer when the metal-deposited resin sheet is stretched by more than 5% vertically and horizontally, and Fig. 5 is an enlarged plan view of one of the vertical and horizontal directions. An enlarged plan view of the same crack pattern when stretched by about 5% or more and the other by 5 (!) or less. 1 is a base resin sheet, 2 is a metal vapor deposited layer, 3 is a top coat layer, 2' is a dividing layer of the vapor deposited layer, and 2'' is a dividing line or crack thereof.

Claims (1)

[Scope of Claims] 1. The metal vapor deposited layer applied to the surface of the base resin sheet in order to obtain metallic luster consists of a collection of small-area divided layers having a range of about 5 mm or less in length and breadth that are mutually discontinuous in the surface direction. A metal-deposited resin sheet as a material for containers for microwave ovens. 2. A metal vapor deposited layer is formed on one or both sides of the base resin sheet by a conventional method, and the base resin sheet is heated and softened at a temperature below the melting point, and then stretched by 5 to 100% in the vertical and horizontal directions. A method for producing a metal-deposited resin sheet as a material for containers for microwave ovens, characterized in that: 3 A metal vapor deposited layer is formed on one or both sides of a base resin sheet by a conventional method, and a resin is further laminated on the metal vapor deposited surface, and the base resin sheet and the laminate resin are heated and softened at a temperature below the melting point. Approximately 5~
A method for producing a metal-deposited resin sheet as a material for microwave oven containers, characterized by subjecting it to 100% stretching treatment.