Plastic container coated with carbon film

Details Plastic container coated with carbon film Plastic container coated with carbon film

2003-06-03

2004-10-19

Nolan, Sandra M. (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C428S216000, C428S218000, C428S408000, C428S421000, C428S454000, C428S457000, C428S458000, C428S474400, C428S480000, C428S500000, C428S524000

Reexamination Certificate

active

06805931

ABSTRACT:

TECHNICAL FIELD
This invention relates to a plastic container, the inner surface of which is coated with a hard carbon film.
BACKGROUND ART
In general, plastic containers are widely used as packaging materials in various kinds of fields such as a food field and a medicine field because plastic containers have various benefits which are easy to mold, light in weight and low in cost. However, as is well known, plastic permits low molecular gas, such as oxygen and carbon dioxide, to permeate therethrough, and furthermore, plastic sorbs (i.e., both of absorption and adsorption occur simultaneously) inside therein low molecular organic compound, namely, low molecular organic compound infiltrates into the plastic composition and diffuses therein in such a manner that the low molecular organic compound is absorbed inside the plastic. Therefore, plastic containers are restricted in many aspects to specific objects and forms in use in comparison with other containers such as a glass container.
For example, in case that a carbonated beverage such as beer is filled into a plastic container, oxygen in the atmosphere permeates the wall of the plastic container to reach inside the plastic container, thus gradually oxidizing and deteriorating the beverage contained therein. In addition,carbon dioxide gas in the carbonated beverage permeates, in reverse, the wall of the plastic container and is released off toward outside, thus the carbonated beverage loses its savor.
Further, in case that beverages having aroma component such as orange juice are filled into a plastic container, aroma component (such as limonene in the case of the orange juice) which is a low molecular organic compound is sorbed inside the plastic. Consequently, chemical composition of the aroma components in the beverages may lose its balance to deteriorate the beverages in quality.
In addition, a plastic container may have a problem that low molecular compound contained in the plastic container dissolves in a liquid content contained in the container. More specifically, in case that content (especially, liquid) requiring a high purity is filled into the container, plasticizer, residual monomer or other additives dissolves out of the container into the liquid content, thus deteriorating purity of the content.
Furthermore, at present, how the large numbers of the used containers are to be treated has become a social issue, and collecting the used containers for the sake of recycling of the resources is in progress. However, when the used plastic containers are to be used as the recycled containers, if the used plastic containers are left in the environment before being collected, various low molecular organic compounds such as mold odor is sorbed in the plastic container, unlike glass containers. The low molecular organic compound thus sorbed in the container remains in the plastic even after being washed. Therefore, thus sorbed low molecular organic compound gradually dissolves out of the plastic into the content in the plastic container as impurity, thereby deteriorating the content in quality and causing a hygienic problem. This results in that the plastic containers can be hardly used as returnable containers, namely, the containers collected to be reused.
In order to suppress the above-mentioned features of the plastic, namely, the feature of permitting low molecular gas to permeate therethrough or the feature of sorbing low molecular organic compound therein, crystals in the plastic have been oriented to enhance crystallinity or thin sheets of plastic having a lower sorption or thin films of aluminum have been laminated. In either methods, however, problems of gas barrier property and the sorption of low molecular organic compound cannot be perfectly solved while maintaining the basic properties of the plastic container.
Recently, there has appeared a thin film forming technology for a DLC (Diamond like carbon) film and it is known that laboratory tools such as beakers and flasks are coated with the DLC film. The DLC film comprises amorphous carbon including mainly SP
3
bond between carbons. The DLC film is a hard carbon film which is very hard, and has a good insulation, a high index of refraction and a smooth morphology.
Japanese Patent Provisional Publication No. 2-70059 discloses an example in which the DLC film forming technology is applied to laboratory tools for coating thereof. An apparatus for forming the DLC film disclosed in the above publication comprises the followings. As shown in
FIG. 16
, a cathode
2
is disposed in a reaction chamber
1
having an inlet
1
A for carbon resource gas which generates carbon or is converted to carbon and an outlet
1
B, and a laboratory tool
3
such as a beaker is accommodated in a space
2
A formed in the cathode
2
. The reaction chamber
1
is decompressed by discharging air from the outlet
1
B after an earthed anode
4
is inserted into an inner space of the laboratory tool
3
. After the carbon resource gas is led into the reaction chamber
1
from the inlet
1
A, a high frequency is impressed on the cathode
2
from a high frequency power source
5
to excite the carbon resource gas, thus generating plasma to form the DLC film on the surfaces of the laboratory tool
3
.
However, in the above DLC film forming apparatus, the reaction chamber
1
accommodates the cathode
2
and the anode
4
, so that the volume of the reaction chamber
1
is remarkably large in comparison with that of the laboratory tool
3
to be coated. Therefore, it causes wastes of time and energy for a vacuum operation of the reaction chamber. Furthermore, since the film forming speed (rate) in the above DLC film forming apparatus is 10 to 1000 Å per minute, which speed is slow, there is a problem in which it is difficult to continuously form the film at a low cost.
The conventional DLC film forming apparatus described above is applied to laboratory tools such as beakers and flasks so as to mainly further increase their qualities, so that the manufacturing cost and time thereof is not much considered. However, containers used for beverages such as beer and orange juice must be manufactured in large quantities at low cost. Accordingly, the DLC film forming apparatus cannot be applied to the containers used for beverages.
In the above DLC film forming apparatus, since the carbon resource gas moves into the space between the inner surface of the cathode
2
and the outer surface of the laboratory tool
3
to be coated, it is impossible to coat only the inner surface of the laboratory tool
3
.
Containers for beverages are often collided and weared with each other in a manufacturing process in a factory or a selling process in a selling route, unlike the laboratory tool such as a beaker and a flask. Therefore, in case that the DLC film is formed on the outer surface of a container for beverages, the DLC film itself is damaged to decrease the value of merchandise of containers because the film is thin and hard. Accordingly, it is required that the DLC film is formed only on the inner surface of the container.
It is an object of this invention to provide a plastic container coated with carbon film which can solve the problems of gas barrier property and sorption inherently owned by the plastic while maintaining basic properties of plastic, which can be returnably used to extend the fields and the forms in which plastic containers can be used, which can be continuously manufactured at a low cost, and which is not damaged during handling of the containers.
DISCLOSURE OF INVENTION
In order to attain the above object, a plastic container of this invention comprises a bottle for beverage made of a plastic material with a hard carbon film formed only on a inner surface thereof. In addition, the hard carbon film comprises a diamond like carbon film.
According to the above plastic container of the invention, permeability of the container against low molecular inorganic gas such as oxygen and carbon dioxide can be remarkably lowered, and furthermore, the sorption in the plastic of various low molecula

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