JPH0535067B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention is directed to packaging films for fresh foods, processed foods, pharmaceuticals, medical devices, etc., particularly those that are considered to have important properties in these applications, such as gas barrier properties, moisture proofing properties, light blocking properties, etc. The present invention relates to a film or sheet with good quality and a method for manufacturing the same. [Conventional technology] In recent years, food packaging formats have changed significantly due to changes in food distribution formats and eating habits themselves, and the required characteristics of packaging films and sheets (hereinafter referred to as "film") have been increasing. It's getting tougher. In particular, there is a growing demand for films that have low gas and moisture permeability and that do not lose their value as food products even when subjected to freezing, boiling, retorting, and other treatments. i.e. fish meat,
When packaging meat, shellfish, etc., it is important to suppress oxidation and deterioration of proteins, oils, etc. and maintain taste and freshness. It is necessary to prevent penetration. Furthermore, packaging with a gas barrier film retains the unique odor and aroma of the contents, and
Since moisture permeation is also prevented, dry products are prevented from deteriorating due to moisture absorption, and moisture-containing products are prevented from deterioration and solidification due to moisture volatilization, allowing them to retain their original fresh flavor for a long time. . Many foods are also susceptible to deterioration due to light (ultraviolet rays, etc.), and deterioration can be further suppressed by packaging with a light-shielding film. For these reasons, pastry products such as kamaboko, dairy products such as butter and cheese,
The gas barrier properties (including moisture resistance) and light blocking properties are considered to be extremely important properties for packaging films for miso, tea, coffee, ham/sausages, instant foods, and confectionery such as castella and biscuits. These characteristics are not limited to films for food packaging, but are also extremely important for films for packaging medical products, medical devices, etc. that require sterile handling. From this point of view, much research is being carried out with the aim of improving gas barrier properties and light shielding properties.
The most commonly used films with the above properties are vapor-deposited films in which metals such as aluminum or metal compounds such as SiO ₂ are vapor-deposited on one side of a synthetic resin film such as polyester, polyolefin, or polyvinylidene chloride. It is. In other words, since metals and metal compounds themselves have excellent gas barrier properties and light blocking properties, by forming a vapor-deposited layer of these on one side of the synthetic resin, the gas barrier properties and light blocking properties that are lacking in the synthetic resin film can be improved. Light blocking properties can be significantly improved. [Problems to be solved by the invention] As mentioned above, metal or metal compound vapor-deposited films have superior gas barrier properties and light-shielding properties compared to ordinary synthetic resin films, and are used as a variety of packaging films. has been done. However, as safety standards for packaged foods become stricter and consumers become more conscious of hygiene, the gas barrier and light shielding properties required of packaging films have become even more stringent. Compound vapor deposited films are becoming unsatisfactory. The present invention was made in view of these circumstances, and its purpose is to develop a film (or sheet) that can exhibit gas barrier properties and light shielding properties that are even better than conventional metal or metal compound vapor-deposited films. ), and another object of the present invention is to provide a method for producing a film (or sheet) with high productivity that exhibits excellent gas barrier properties and light blocking properties as described above. That is. [Means for Solving the Problems] The structure of the gas barrier film (or sheet) according to the present invention is such that at least one outer surface has a maximum height roughness of 0.8 μm or more and the thickness of the outer surface forming film or sheet is 0.8 μm or more. A vapor-deposited layer of a metal or metal compound is formed on either one of the two outer surfaces of the multilayer synthetic resin film or sheet formed with a rough surface having a roughness of 60% or less and one or more laminated interfaces. The manufacturing method according to the present invention is characterized in that the manufacturing method according to the present invention is characterized in that a metal or A synthetic resin film or sheet having a first vapor deposited layer of a compound, and a synthetic resin film or sheet having a second vapor deposited layer of a metal or metal compound formed thereon, with the first vapor deposited layer on the surface side and the second vapor deposited layer. The gist is that the layers are stacked so that the vapor deposited layers are at the interface between the layers. [Function] A metal or metal compound vapor-deposited film combines the excellent flexibility of a synthetic resin film with the high level of gas barrier and light-shielding properties of a metal or metal compound vapor-deposited layer (hereinafter simply referred to as a metal vapor-deposited layer). This combination makes it an extremely excellent packaging film. Therefore, the present inventors began research to further improve gas barrier properties and light shielding properties based on the combination of the above two types of base materials.
First of all, we conducted research in the direction of increasing the thickness of the metal vapor deposited layer, and found that making the metal vapor deposit layer thicker not only increased the material cost, but also significantly reduced productivity, and furthermore, the flexibility of the vapor deposited film decreased. I learned that there are problems such as the product becoming scarce and becoming unsuitable for packaging. As a result of further research to find other improvement measures, we found that a single-layer or multi-layer synthetic resin film with metal vapor deposited layers formed on both sides simply combined the gas barrier and light shielding properties of each metal vapor deposited layer. They discovered that the two metal vapor deposited layers act synergistically to dramatically improve gas barrier properties and light shielding properties, and filed a separate patent application. However, as mentioned above, a film with vapor-deposited layers formed on both sides has extremely superior gas barrier properties compared to a single-sided vapor-deposited film; It became clear that the following problems would occur. The term "smooth surface" as used herein is opposed to a rough surface described later, and refers to a surface having a maximum height roughness of less than 0.8 μm as defined in JIS B-0601. In other words, when manufacturing and processing double-sided vapor-deposited films, they are wound around a suitable core material in the same way as ordinary synthetic resin films, but in the case of double-sided vapor-deposited films, if both surfaces of the film are smooth, the vapor deposition surface will also be Because they are smooth, when microscopically observing the contact area between the vapor-deposited surfaces, the contact area becomes very large, which may cause blocking at the contact area. Moreover, since the close contact surface has poor slippage (due to the large microscopic contact area as mentioned above), for example, once air is caught between double-sided vapor deposited films F and F, the vapor deposition surface becomes slippery, as shown in FIG. 2A. The function of opening and discharging air cannot be expected, and the film F remains partially swollen and stable. In this state, when the next winding layer G is further piled up from the outer circumferential side,
Film F is bent while leaving air inside,
As the film G is layered on top of it, Figure 2B
As shown in the figure, wrinkles 1 are formed on films F and G. If this happens, not only will the appearance of the film be significantly impaired, but the vapor deposited layer at the folded portion will break and crack, and the gas barrier properties will also be adversely affected. Therefore, as a result of further research to improve this problem, it was found that if one side was left as a synthetic resin, there would be no direct contact between the deposited layers during winding, and blocking would be prevented. In addition, if at least one of the outer surfaces is roughened, the microscopic contact area during winding will be reduced, and the slippage will be further improved, and as described above, the slippage between the films during winding will be maintained well. Even if air is caught in the winding process, the winding pressure of the next layer pushes the air toward the side edges, and the films F and G are wound neatly over each other, eliminating the "wrinkles" shown in Figure 2B above. It has become clear that this does not occur at all. As a result of further research aimed at clarifying the degree of roughness to further improve slippage, we found that the maximum height roughness (JIS B-0601) of the deposited film forming surface of the synthetic resin film was It has been found that by roughening the surface to a thickness of 0.8 μm or more, the occurrence of the aforementioned “wrinkles” and cracks can be reliably prevented. However, the maximum height roughness above is based on the thickness of the synthetic resin film (or sheet) on which the vapor deposited film is formed.
If it exceeds 60%, the strength of the synthetic resin film as a base material becomes poor and it becomes unsuitable for packaging purposes. From this point of view, in the present invention,
The rough surface formed on the vapor deposited film forming side of the synthetic resin film (or sheet) on which the vapor deposited film is formed has a maximum height roughness of 0.8 μm or more and the thickness of the film.
It was set to 60% or less. When a vapor deposited film is formed on such a roughened synthetic resin film, the rough surface becomes slightly homogenized, but the outer surface of the vapor deposited film has a rough surface that roughly corresponds to the roughness of the synthetic resin film. As a result, the slippage of the film winding surface can be significantly improved. In addition, the above-mentioned slippage improvement effect due to surface roughening is sufficient as long as at least one of the vapor deposited films in contact with the film during winding is exerted. It includes both those that have been roughened on one side and those that have been roughened on only one side. As for other vapor deposited layers for synergistically enhancing gas barrier properties, the purpose was achieved by providing them on the laminated boundary surfaces of the synthetic resin layers formed in multiple layers. In addition, when a vapor-deposited layer is provided on the outermost surface, the vapor-deposited layer may be damaged or peeled off due to bending fatigue, etc., and if this happens, the gas barrier properties will deteriorate rapidly, which is a problem. If a vapor-deposited layer is formed at the laminated interface, both sides will be sandwiched between synthetic resin films (or sheets), which may cause cracks or peeling due to bending fatigue during use. It becomes a gas barrier film (or sheet) with excellent durability without fear. The synthetic resin film that serves as the base of the film of the present invention serves as a support base for the metal vapor deposited layer and ensures the strength and flexibility considered necessary for packaging applications. Conventional packaging materials include polyolefins such as polyester, nylon, polypropylene and polyethylene, ethylene-vinyl acetate copolymer, polyethersulfone, polyimide, fluororesin, polystyrene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, and regenerated cellulose. All synthetic resins known for commercial use can be used, and these resin films may of course be used unstretched or uniaxially or biaxially stretched. The thickness of the resin film (or sheet) can be determined arbitrarily depending on the application, but it is approximately 2 to 500 μm when used in a film form such as a packaging bag, or approximately 2 to 500 μm when used in a sheet form such as a packaging box material. In this case, it is generally about 100 to 1000 μm. On the other hand, examples of metals for vapor deposition include aluminum, zinc, copper, platinum, indium, tin, gold, silver, and silicon, and examples of metal compounds include silicon oxide. Common. The type of these vapor deposition materials may be appropriately selected depending on the purpose (type of packaged contents, etc.). Further, the basic cross-sectional structure of the film according to the present invention is as schematically shown in FIGS. 1A to 1L [A ₁ , A ₂
B 1 and B 2 are synthetic resin layers, B ₁ and B ₂ are vapor deposited layers, C is a roughened surface, and D is an adhesive (including heat sealing material) layer], two sheets laminated with adhesive layer D interposed therebetween. One or both of the synthetic resin layers A ₁ and A ₂ (A ₁ and A ₂ may be of the same type or different types) are roughened, and one of the outer surfaces of the two is coated with a vapor deposited layer B. ₁ is formed, and a vapor deposited layer B ₂ (B ₁ and B ₂ may be of the same type or different types) is formed at the laminated interface of the synthetic resin layers A ₁ and A ₂ via an adhesive layer D. has been done. Although the laminated interface may be smooth, it is preferable to roughen one or both sides of the laminated interface to further increase the interlayer adhesion. FIGS. 1 M to 0 show application examples of the present invention, in which at least one synthetic resin layer A ₁ to _{A 3} (of course, four or more layers may be used) is laminated. In the figure, vapor deposited layers B ₂ and B ₃ are formed at the lamination interface of 1 or 2),
This shows an example in which one or both of the outermost surfaces are subjected to surface roughening treatment. In particular, when a vapor deposited layer is formed at the interface of two (or three or more) laminated layers as shown in Figure 1 O, a total of three layers ( (or more) are formed, and their synergistic effect can further improve gas barrier properties. Furthermore, if necessary, a release agent, adhesive, heat sealer, etc. can be applied to part or the entire surface of the film of the present invention, and it is also possible to print upon use. It is. Various methods can be considered for producing the film of the present invention as described above, but the most industrially advantageous are two types of synthetic resin films (or sheets) in which a vapor deposited layer is formed on a roughened surface or a smooth surface. This is a method of stacking the vapor-deposited layers so that one of the vapor-deposited layers is located on the outer surface side, the other vapor-deposited layer is located at the lamination interface, and the roughening treatment is located on at least one of the outermost surfaces. For example, FIGS. 3A and 3B are explanatory diagrams schematically illustrating the manufacturing method of the gas barrier film according to the present invention. As shown in FIG. 3A, each synthetic resin film A ₁ (or A ₂ ) Vapor deposited layer B ₁ (or
B ₂ ) is formed, and then, as _shown in FIG _.
If a method is adopted in which the films A ₁ and A ₂ are laminated so that the lamination interface becomes the lamination interface, it is possible to obtain a film having vapor deposited layers B ₁ and B ₂ by simply preparing a relatively small-scale vacuum facility. . In this case, it is a matter of course that one or both surfaces (either the vapor-deposited surface or the non-vapor-deposited surface) of the synthetic resin film should be subjected to surface roughening treatment. Moreover, in the lamination step of each film A ₁ , A ₂ after forming the vapor deposited layers B ₁ , B ₂ , other synthetic resin films, vapor deposited films, etc. may be inserted between the laminated layers as necessary. It is also easy to obtain a film (or sheet) with a multilayer structure as shown in F. The gas barrier film (or sheet) of the present invention obtained in this way can be used as a flexible packaging material for various foods, medicines, medical instruments, etc., or as a hard container such as a box-shaped bottle, or as a laminate material thereof. It can be used widely. [Example] Example 1 One side of biaxially stretched nylon-6 (containing 0.15% silicon dioxide by weight) with a thickness of 12 μm was roughened to a thickness of 1.1 μm, and then aluminum vapor-deposited with a thickness of 400 μm was applied to this surface. The single-sided roughened vapor-deposited film is laminated in accordance with the method shown in FIG. (using an isocyanate adhesive), a gas barrier film was obtained. A bag was made using this film, filled with spherical particles having a diameter of 2.8 mm, and vacuum packaged, and the gas barrier properties of the filled bag were evaluated based on the change in hardness over time. For comparison, a bag was made using a single-sided vapor-deposited film alone and its gas barrier properties were examined in the same manner as above. Furthermore, each film was subjected to bending treatment 100 times, and the amount of oxygen permeation before and after the treatment was examined. The results are shown in Table 1. However, the evaluation criteria for gas barrier properties in vacuum packaging are as follows. ◎: Feels like a hard plate when touched with the hand. ○: The plate-like appearance can be slightly softened when touched by hand, but it still exhibits a hard plate-like appearance. △: It is soft to the touch, and the degree of vacuum is clearly lowered. ×: Particulate matter can be easily grabbed from outside the bag and moved, and the degree of vacuum is extremely low. In other words, as long as the internal vacuum level is maintained, the granules are tightly clamped and the bag remains in a hard plate shape, but as the vacuum level decreases, the filled bag becomes soft due to air intrusion, and the bag becomes plate-shaped. becomes impossible to hold.
Therefore, the quality of the gas barrier property can be evaluated based on this feel.

[Table] As is clear from Table 1, not only is the gas barrier property of the single-sided vapor deposited film poor before bending, but the gas barrier property is further deteriorated by the bending process. shows a declining trend after 3 months and worsens after 6 months. In contrast, the film of the present invention maintains excellent gas barrier properties both before and after the bending process, and the vacuum packaging condition remains unchanged even after 6 months.
It maintains a good vacuum condition even after many years. All of the above films have one side left as a synthetic resin layer, and one of the outer surfaces has been roughened, so it has very good slippage during winding and prevents blocking and "wrinkling". , cracks, etc. did not occur at all. [Effects of the Invention] The present invention is configured as described above, and gas barrier properties are achieved by forming one or more metal or metal compound vapor-deposited layers on one outer surface of the multilayer synthetic resin film and the lamination interface. can be dramatically increased, and the shelf life of the contents can be significantly extended. Moreover, this vapor-deposited film has at least one vapor-deposited layer located at the laminated interface, so it can maintain a high level of gas barrier property even when subjected to bending force, and furthermore, the metal vapor-deposited layers are in direct contact with each other. Since at least one outer surface is roughened, slippage during winding is maintained well, preventing blocking, cracking, and "wrinkling."
etc. will not occur. Further, by employing the manufacturing method of the present invention, a film with excellent gas barrier properties can be obtained using relatively small vapor deposition processing equipment, and production costs including manufacturing equipment costs can be kept low.

[Brief explanation of the drawing]

Figures 1 A to O are schematic cross-sectional views illustrating the gas barrier film of the present invention, Figures 2 A and B are cross-sectional explanatory views showing how wrinkles occur, and Figures 3 A and B.
FIG. 1 is a schematic explanatory diagram illustrating the manufacturing method of the present invention. A, A ₁ ~ _{A 3} ...Synthetic resin layer (film), B ₁ ~
B ₃ ... Metal or metal compound vapor deposited layer, D, D ₁ , D ₂ ...
Adhesive (or heat seal) layer, C... roughened surface.

Claims (1)

[Claims] 1. At least one outer surface has a maximum height roughness.
One or more outer surfaces of a multilayer synthetic resin film or sheet formed with a rough surface of 0.8 μm or more and 60% or less of the thickness of the outer surface constituent film or sheet. 1. A multilayer gas barrier film or sheet, characterized in that a vapor-deposited layer of a metal or metal compound is formed on the interface. 2. A synthetic resin film or sheet having a first vapor-deposited layer of a metal or metal compound on the rough surface with a maximum height roughness of 0.8 μm or more and 60% or less of the thickness of the film or sheet, and a metal or metal second compound
A multilayer gas barrier film or sheet, characterized in that synthetic resin films or sheets on which vapor deposited layers are formed are laminated such that the first vapor deposited layer is on the surface side and the second vapor deposited layer is on the lamination interface. Method of manufacturing sheets.