Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
1999-08-19
2001-09-25
Mayekar, Kishor (Department: 1741)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S238000, C118S7230ER
Reexamination Certificate
active
06294226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing a plastic container which is provided with high barrier property and returnable property, especially relates to an apparatus and a method for forming a diamond-like carbon (DLC) film on an inner surface of a plastic container so that the film is uniform in its thickness, or an apparatus and a method for mass-producing plastic containers where the DLC film is formed on an inner wall of the container so as to be uniform in its condition in the whole of the container.
2. Description of the Related Art
Generally, a plastic container is used in various fields such as foods, medical supplies or the like, because of its various properties. Namely, for example, it is easy to form and is light in weight. And furthermore, the cost of producing the plastic container is low.
However, it is well known that plastic has undesirable properties of permitting low molecular gas such as oxygen or carbon dioxide to permeate through it, or permitting bringing sorption of low molecular organic compound (a property of absorbing molecular organic compound into a plastic composition). Therefore, the purposes of plastic container or the cases where the container can be used are widely limited in comparison with other container formed of glass or the like.
For instance, when the plastic container is used for holding a beverage which is apt to deteriorate by oxidization, there is some possibility that the beverage in the container deteriorates with age because oxygen can permeate plastic and reach the inside of the container. And when the plastic container is used for holding a carbonated drink such as beer, there is a fault that time in which can be spent on a distribution of the drink unfortunately comes to be shorter as compared with the other containers such as glass containers or the like because there is the possibility that the drink goes flat by releasing of carbon dioxide gas through the plastic wall of the container.
When the plastic container is used for holding a beverage, such as orange juice, including aroma compositions, the balance of the plural aroma compositions is broken and quality of the beverage is spoiled because low molecular organic compounds as the aroma compositions such as limonene included in the orange juice are absorbed in plastic. So, cases where the plastic container can be used as a container for beverages including such an aroma composition is unfortunately restricted.
And, the plastic container may deteriorate purity of material held in the container by elution of low molecular compound, such as plasticizer, residual monomer or other addition agent, included in the plastic compositions. Therefore, the plastic container is not used as a container for holding a substance specially in a case where purity of the substance held within the container should be maintained.
On the other hand, in recent years, making good use of resources is specially asserted and recycling of spent containers is a subject of study at present. However, if the plastic container is used as a returnable container, various low molecular compositions, for example, compositions causing a smell such as an odor of mold, are absorbed into plastic. Since these compositions absorbed into plastic are remained after washing of the plastic container, it is not sanitary to recycle it. There is also the possibility that the low molecular compositions as heterogeneity gradually soaks into contents held in the container to deteriorates the contents.
Therefore, in a case where the plastic container is used as a returnable container, it is necessary to inspect the plastic container which has been collected for the purpose of checking whether there is any residual heterogeneity. So, it is extremely rare to use the plastic container as a returnable container at present because the inspecting operation as to residual heterogeneity is a time-consuming job.
However, since the plastic container has the merits that it is easy to form, is light in weight, and is low-cost, it is very convenient to be able to use the plastic container for holding beverages such as carbonated drinks, beverages including flavor composition or material whose purity has to be maintained. And it is also greatly convenient to be able to use the plastic container as a returnable container.
The applicant of the present invention proposed an invention by which the plastic container can be used as a returnable container in the previous patent application (Japanese Patent Application No. 189224 of 1994), paying attention to convenience of the plastic container.
The invention of the previous application is related to an apparatus for forming DLC (Diamond Like Carbon) film on the inner surface of the plastic container so as to improve the property of gas barrier of the wall and prevent from absorbing of low molecular compound into the plastic container.
The DLC film mentioned above is hard carbon film also called “i carbon” or “amorphous hydrocarbon”, and is amorphous carbon film mainly consisting of SP
3
bond. The DLC film, which is extremely hard, has good electrical insulating property and high refractive index.
In the previous application, an apparatus for manufacturing the above plastic container coated with the carbon film is proposed. By the apparatus, the DLC thin film is formed on the inner surface of the plastic container to produce the plastic container which can be used as a returnable container through preventing permeating of gas via plastic and absorbing low molecular organic compound by forming the DLC film.
As shown in
FIG. 25
, the above apparatus for manufacturing the plastic container coated with the carbon film is provided with ceramic insulating plate
2
attached on a base
1
, an outer electrode
3
attached on the insulating plate
2
, and an inner electrode
4
inserted into a chamber formed in the outer electrode
3
.
The outer electrode
3
composes a vacuum chamber in its inner space. The vacuum chamber is prepared for plasma discharge. By a vacuum pump not shown, the vacuum chamber is exhausted via a exhaust tube
5
until the chamber comes to be evacuated, after a plastic container B is inserted into a body part
3
A and the chamber is sealed by a lid part
3
B.
After spouting out the raw gas which has been supplied via a providing tube
6
into the chamber of the electrode
3
from spouting holes
4
A formed in the inner electrode
4
so that a raw gas is diffused uniformly in the evacuated chamber, electric power is given to the outer electrode
3
by a high frequency power source
8
through a matching circuit
7
. In this way, plasma is generated between the outer electrode
3
and the inner electrode
4
connected to ground earth, and then the DLC film is formed on the inner surface of the plastic container B by plasma.
In this apparatus for manufacturing the plastic container coated with the DLC film, the chamber of the outer electrode
3
is formed in a shape almost similar to the outer surface of the plastic container B, and the outer surface of the inner electrode
4
is formed in a shape almost similar to the inner surface of the wall of the plastic container B, therefore, the gap between these electrodes is made uniform. And the DLC film is formed only on the inner surface of the wall of the plastic container B because the raw gas is spouted into the inside of the plastic container B.
Furthermore, in the apparatus, since the outer electrode composes the vacuum chamber, the time required for evacuating the vacuum chamber can be remarkably shorten, and therefore, the mass production of the plastic returnable container comes to be realizable.
As mentioned above, the DLC film is restrictively formed only on the inner surface of the wall of the container B for the purpose of avoiding deteriorating quality of the plastic container B. If the DLC film is also formed on the outer surface of the wall of the plastic container B, there is the possibility that the thin and hard DLC film formed o
Kirin Beer Kabushiki Kaisha
Mayekar Kishor
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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