JPS6046363A - Formation of transparent thin film having moistureproofness - Google Patents

Abstract

PURPOSE:To obtain a transparent thin film high in moistureproofness, by evaporating metal magnesium while supplying oxygen gas into a vacuum tank to form a magnesium oxide thin film on a base material. CONSTITUTION:A film like base material comprising polyvinyl chloride is arranged in a vacuum tank and oxygen gas is introduced into the vacuum tank while said tank is evacuated and metal magnesium is heated. Magnesuim vapor is generated by heating and reacted with the introduced oxygen gas to form a thin magnesium oxide film on the base material. The supply amount of the oxygen gas is controlled so as to bring oxygen partial pressure during vapor deposition to 1X10<-4>-1X10<-3> Torr and the film thickness of the thin magnesium oxide film is pref., set to about 0.01-0.5mum. By this method, a transparent thin film high in moistureproofness is obtained regardless of the kind of the base material and can be utilized as a packing material of food or medicine.

Description

[Detailed description of the invention] Technical field: The present invention relates to a method for forming a transparent thin film having moisture-proof properties.

In particular, it relates to a method for forming transparent and highly moisture-proof thin films regardless of the type of substrate.

Prior Art: Packaging materials, especially packaging materials used for packaging foods, medicines, chemical products, etc., must have a moisture-proof function to prevent the contents from deteriorating.

To this end, conventionally, for example, aluminum foil has been bonded to a base plastic film to utilize the moisture-proofing properties of the aluminum foil. Although this packaged packaging material has good moisture resistance, the transparency of the base plastic film is impaired and the contents cannot be seen through. Furthermore, since the flexibility is reduced at the end of the surface, there is a risk of bottle holes occurring. Another example of the packaging material is a vinylidene chloride/fluorocarbon resin film which itself has moisture-proof properties. These films must be thick for applications where moisture resistance is strictly required, and various problems arise in manufacturing operations.

Attempts have still been made to improve the moisture resistance by vapor-depositing a metal film on the surface of plastic. However, the AY4 vapor barrier film is opaque, making it difficult to see the contents when used as packaging material. I can't see it at first glance. Moreover, since the adhesion strength between the vapor-deposited plate fc atv minium and the pace film is relatively low, there is a possibility that peeling may occur at the interface.

In order to improve these shortcomings of conventional packaging materials.

For example, Japanese Patent Publication No. 51-48511 proposes providing a vapor-deposited layer of silicon oxide on the surface of a plastic film to obtain a transparent moisture-proof film.

Since the silicon oxide of this silicic oxide vapor-deposited film dissolves in water to a small extent, its moisture-proof performance deteriorates over time. Further, JP-A-54-152089 discloses a polyester p-film A-film on which metals, metal oxides, and silicon oxides are vapor-deposited.

This vapor-deposited film can only exhibit its moisture-proof performance when a polyester film is used as the base material.

In recent years, in the field of electronics industry, transparent films with high moisture resistance are increasingly required as protective films for EL elements, solar cells, and the like.

OBJECT OF THE INVENTION: An object of the present invention is to provide a method for forming a thin film that is transparent and has high moisture resistance regardless of the type of substrate. Another object of the present invention is to provide a method for forming a thin film with excellent adhesion to a substrate.

Summary of the invention: The thin film forming method of the present invention involves heating and evaporating metallic magnesium while introducing oxygen gas into a vacuum chamber to form a transparent magnesium oxide thin film on a substrate. The above objective is achieved.

The base material to be used is not particularly limited, but transparent and flexible films such as polyvinyl chloride, polypropylene, polyethylene, polyester/1/1/2, polyvinylitine chloride, nylon, and polyvinyl alcohol base resin are used. Note that the base material may be plate-shaped or may be a lens-shaped plastic molded body. There is no particular limit to the thickness of the film, considering workability. 5 μm ~
300 μm is preferred. Oxygen gas is supplied to this transparent film and a magnesium oxide thin film is formed by reactive vapor deposition. Specifically, the film described above is placed inside a vacuum chamber, and while the vacuum chamber is evacuated using a vacuum pump, oxygen gas is introduced and metal magnesium is heated by resistance.

Heating is performed by a known heating method such as electron beam heating. This heating generates magnesium vapor. This magnesium vapor reacts with the introduced oxygen gas to form a magnesium oxide thin film on the substrate.

The amount of free element Ganu to be introduced is usually in a vacuum metallurgy container. It is determined appropriately depending on the evacuation capacity of the vacuum pump, the evaporation rate of magnesium, etc., but the oxygen partial pressure during deposition is I x 10-' ~
It is preferable to adjust it so that it becomes Ix10-8)-ru. When the oxygen partial pressure is I x 10 ) -p, the formed magnesium oxide thin film has a small amount of oxygen and is colored, resulting in loss of transparency. When the oxygen partial pressure is higher than IXIOI, the quality of the formed magnesium oxide thin film becomes Beauhune, and the moisture proofing property decreases.

The magnesium oxide thin film can be formed not only by reactive vapor deposition but also by reactive ion blasting. The thin film obtained by this method does not have the same performance as the thin film obtained by the above-mentioned reactive vapor deposition method.

The thickness of the magnesium oxide thin film is 0.01p1n.
~0.5 μm is preferred. When the film thickness is 0.01 μm or less, it is difficult to form a uniform continuous film. As a result, moisture resistance is significantly reduced. If the thickness is 0.5 μm or more, cracks are likely to occur in the formed magnesium oxide thin film, resulting in a decrease in moisture resistance.

Example: The present invention will be explained below with reference to Examples.

Example 1 A polyethylene terephthalate (OPE) film with a thickness of 1 5 71 F 71 was used as a P-7 film, and this was placed in a metal fittings station cypress. After evacuating the inside of the phase to 1xlO-5 to/h, the partial pressure of oxygen gas in the tank becomes 3x10-41.
--Oxygen gas was introduced to a pressure of #. Metallic magnesium, which is 99% pure, is heated by applying a resistance of 2 and a microwave.
Vapor deposition was performed to obtain K. And the film thickness is 1000
Two types of deposited thin films, A and 2000A, were obtained. The water vapor permeability of the transparent vapor-deposited films thus selected is shown in the table together with the transparency. Moisture permeability is 40° based on JIS Z0208.
The water vapor transmission rate at 90% RH is shown. Transparency was measured by visual observation, and excellent transparency is indicated by 1, good by +, and opaque by -.

Example 2 The same as Example 1 except that the oxygen gas partial pressure was adjusted to 5×10 −4 Torr. The results are shown in the table.

Example 3 The same as Example 2 except that a biaxially stretched polypropylene film was used as the base film. The results are shown in the table.

Comparative Example 1 Under a vacuum degree of 5×10 )-tv, P with a 1γ thickness of 15μ7n
SiO on ET film at about looo, A and 200
OA +7) Deposited to two different thicknesses. The moisture permeability and transparency are shown in the table.

Comparative Example 2 Under vacuum degree 5 x 1O-5), thickness 15 μm 0P
Approximately 1000 people and U 20 of 5i02 on ET film
The film was deposited to a film thickness of 0. The moisture permeability and transparency are shown in the table.

Comparative Example 3 Everything was the same as in Example 1 except that the oxygen partial pressure during vapor deposition was 5 x lo-5).

The results are shown in the table.

Effects of the invention: The thin film obtained by the method of the invention is transparent and moisture-proof regardless of the type of base film. It is.

Moreover, its moisture resistance is significantly improved compared to conventional vapor-deposited silicon 19) films. The adhesion of the magnesium oxide film according to the present invention to the base film was also good, and passed the illumination test according to JISD-0202.

The transparent rubber film with the transparent thin film of the present invention has an unprecedented superior N-preventing ability, so it is used as packaging materials for foods, medical products, certain chemical products, etc., and in the electronic industry field. Ideal for protecting EL elements and solar cells.

that's all

Claims (1)

[Scope of Claims] 1. A method for forming a transparent thin film having moisture-proof properties, which comprises heating and evaporating synthetic magnesium while supplying oxygen gas into a vacuum chamber to form a transparent thin film of magnesium oxide on a substrate. 2. By controlling the supply amount of the oxygen gas, the oxygen partial pressure in the vaporized magnesium can be adjusted to I
)--The method according to claim 1. 3. The method according to claim 1, wherein the substrate is a transparent adhesive or film.