JP2009190747A - Plastic container coated with thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic container having excellent gas barrier properties, low adsorptivity, excellent recyclability, and excellent transparency while being capable of avoiding considerable degradation of the gas barrier properties even when, for example, neutral tap water is filled and preserved at a high temperature of 40°C or more. <P>SOLUTION: In the plastic container coated with thin film having a plurality of layers of thin films being coated on an inner surface thereof, the plurality of layers of thin films include at least one carbon film 2 and at least one silicon oxide film 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a plastic container such as a plastic bottle or a plastic cup, and relates to a plastic container having improved gas barrier properties, contents adsorbability and the like by forming a thin film on the inner surface thereof.

  Plastic containers are lightweight, easy to use, safe and relatively low cost, so they are used in various fields including food and pharmaceutical fields. On the other hand, however, it has disadvantages such as poor gas barrier properties compared to metal containers and glass containers, and easily adsorbs the components of the contents.

  Therefore, for the purpose of improving the gas barrier property of the plastic container or imparting low adsorptivity, a method of forming a silicon oxide thin film or a carbon film on the container surface has been proposed. For example, as described in Patent Document 1, an organic silicon compound polymer layer containing 15% or more of silicon, 20% or more of carbon, and the rest containing oxygen is provided as a first layer on the surface of a plastic substrate. A plastic container provided with a silicon oxide layer as the second layer has been proposed. The plastic container having the structure as described in this patent document is excellent in gas barrier property and low adsorptivity, and the formed silicon oxide film is a colorless and transparent film, so that no thin film is formed in appearance. It has the characteristics that it is not different from the container at all and is excellent in the recyclability of the container.

  However, when the organosilicon compound polymer layer is filled assuming that a liquid content having a high hydrogen ion concentration (pH), for example, neutral tap water, is used, adhesion can be maintained. The gas barrier property may be deteriorated because it is difficult or the silicon oxide thin film itself is always in contact with tap water. This tendency was particularly noticeable when stored at a high temperature of 40 ° C. or higher, not at normal temperature. Therefore, the contents that can be accommodated in the container are limited to non-aqueous contents such as oil and alcohol, or low pH contents such as carbonated drinks.

Further, as described in Patent Document 2, a plastic container having a gas barrier property has been proposed in which an amorphous carbon material layer is provided on the surface of the plastic substrate to ensure adhesion with the plastic substrate. . However, if this amorphous carbon material film is made to have a film thickness that can exhibit a practical gas barrier property, the color of the film will be brown, so the use is limited due to problems in appearance compared to a container in which a thin film is not formed. There was a problem. Further, it was not preferable in terms of recycling.
Japanese Patent No. 2526766 Special table 2002-509845 gazette

The present invention has been made to solve the above-described problems, and is a liquid content, such as neutral, which has excellent gas barrier properties, low adsorptivity, recyclability, and high hydrogen ion concentration (pH). Even when filled with tap water and stored at a high temperature of 40 ° C. or higher, a significant decrease in gas barrier properties can be avoided and a plastic container excellent in transparency can be provided.

According to a first aspect of the present invention, there is provided a plastic container having a plurality of thin films formed on an inner surface, wherein the plurality of thin films are at least one carbon film and one or more layers. A thin film-coated plastic container characterized by comprising a silicon oxide film.

  The invention according to claim 2 is characterized in that a carbon film is present as a first layer on the inner surface, and a silicon oxide film is formed as a second layer thereon. Coated plastic container. It is.

  The invention described in claim 3 is characterized in that a silicon oxide film is present as a first layer on the inner surface, and a carbon film is formed as a second layer thereon. It is a coated plastic container.

  In the invention according to claim 4, a carbon film is present as the first layer on the inner surface, a silicon oxide film is present as the second layer thereon, and a carbon film is formed as the third layer thereon. 2. The thin film-coated plastic container according to claim 1, wherein the plastic container is coated with a thin film.

  According to the present invention, the contents to be filled are not limited to non-aqueous contents or low-pH contents, and the contents having a higher hydrogen ion concentration (pH) than conventional ones, for example, neutral Filling a certain tap water can solve the problems described so far.

  Specifically, when the first layer in contact with the plastic substrate is a carbon film, and a silicon oxide film is provided as a second layer on the carbon film, the carbon film is not applied to either the plastic substrate or the silicon oxide film. However, since the adhesiveness is excellent, even if the contents are in direct contact with the silicon oxide film, the adhesiveness is not lowered and the gas barrier property is maintained. Further, since the carbon film may be thin, the film is not colored brown, and transparency can be ensured.

  In addition, when the first layer is a silicon oxide film and a carbon film is provided thereon as the second layer, the water repellency of the carbon layer is high, so that the hydrogen ion concentration (pH) such as tap water is high. Even if the liquid content comes into contact, it is possible to avoid a significant decrease in gas barrier properties.

  Also, when the first layer is a carbon film, a silicon oxide film is provided as a second layer thereon, and a carbon film is provided as a third layer thereon, these three layers are firmly integrated, In addition to being in close contact with the plastic substrate, the contents do not come into direct contact with the silicon oxide film, so stable adhesion and gas barrier properties are ensured even with high hydrogen ion content such as tap water. Can be demonstrated.

  Since these carbon films can be made to a film thickness of about 15 nm or less without impairing transparency, the carbon barrier itself is not sufficient in gas barrier properties, but the silicon oxide film in contact with the carbon film exhibits gas barrier properties. As a whole, sufficient gas barrier properties and transparency can be achieved. In this way, the liquid content, for example, neutrality, which is excellent in gas barrier property, low adsorptivity, recyclability and high hydrogen ion concentration (pH) while ensuring high transparency that is difficult to be obtained by a single carbon film. Even when filled with tap water and stored at a high temperature of 40 ° C. or higher, the adhesion between the thin film and the plastic substrate is sufficient, and it is possible to provide a plastic container capable of avoiding a significant decrease in gas barrier properties.

Embodiments of the present invention will be described in detail with reference to the drawings. 1 to 3 are schematic cross-sectional views showing an example of an embodiment of a plastic container of the present invention. In FIGS. 1 and 3, a carbon film 2 is formed on the surface (inner surface of the container) of the plastic substrate 1, and a silicon oxide film 3 is formed thereon. In FIG. 3, a carbon film 4 is further formed on the silicon film 3.
Is formed. In FIG. 2, a silicon oxide film 3 is formed on the surface of a plastic substrate 1, and a carbon film 2 is formed thereon.

  As the plastic substrate 1, a general plastic resin material usually used as a plastic container can be used. For example, polyolefin resins such as low density polyethylene (LDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. Synthetic resins such as polyester resins, polymethyl methacrylate (PMMA) resins, polyamide resins, polystyrene resins (PS), polyvinyl chloride resins (PVC), polycarbonate resins (PC), and the like. Among these, polyethylene terephthalate (PET) resin is most preferably used for the purpose of the present invention in consideration of various characteristics such as transparency, mechanical properties, processability, and gas barrier properties.

As the carbon film 2 and the carbon film 4, an amorphous carbon film or a diamond-like carbon film having carbon as a main skeleton is preferable because it has excellent adhesion to the plastic substrate 1 and flexibility. An amorphous carbon film having a CH ₃ group is also excellent in adhesion to the plastic substrate 1 and the silicon oxide film 3 and when located in the innermost layer of the container as shown in FIGS. Even when it comes into contact, it has a feature of excellent water repellency. The carbon film 2, the carbon film 4, and the silicon oxide film 3 can all be directly formed on the inner surface of the plastic container by plasma CVD.

  FIG. 6 is a schematic view showing an apparatus for forming a thin film on the inner surface of a plastic container by plasma CVD. This film forming apparatus is installed so as to cover a metal resonator a and a plastic container b for film formation, and introduces a process gas into the vacuum chamber c and the plastic container b for evacuating the inside. A gas supply pipe d for the purpose, a microwave power source e for supplying microwave energy to the resonator a, an impedance matching unit f for impedance matching, and a rectangular waveguide g for transmitting the microwave energy.

  In the actual film forming process, the vacuum chamber c is evacuated to a constant pressure (1 to 10 Pa), the process gas is introduced into the plastic container b from the gas supply pipe d, and the microwave is oscillated from the microwave power source e. By doing so, the process gas in the plastic container b is turned into plasma, and a thin film is formed on the inner surface of the plastic container b.

  Examples of the process gas used to form the carbon films 2 and 4 include alkanes such as methane, ethane, propane, butane, pentane and hexane, alkenes such as ethylene, propylene, butene, pentene and butadiene, Alkynes such as acetylene, aromatic hydrocarbons such as benzene, toluene, xylene and naphthalene, cycloparaffins such as cyclopropane and cyclohexane, cycloolefins such as cyclopentene and cyclohexene, oxygen-containing carbon such as methyl alcohol and ethyl alcohol Compounds, nitrogen-containing carbon compounds such as methylamine, ethylamine, aniline, and the like can be used. These gases may be used alone, or may be used by mixing with a rare gas such as argon or helium.

Process gases used to form the silicon oxide film 3 include 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, vinyltrimethylsilane, methyltrimethoxysilane, and hexamethyldisilane. , Methylsilane, dimethylsilane, trimethylsilane, diethylsilane, propylsilane, phenylsilane, vinyltriethoxysilane, vinyltrimethoxysilane, tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, octamethylcyclotetra It can be selected from siloxane and the like, and 1,1,3,3-tetramethyldisiloxane, hexamethyldisiloxane, and octamethylcyclotetrasiloxane are particularly preferable. However, it is not limited to these, and aminosilane, silazane, etc. can also be used. A gas obtained by vaporizing the organosilicon compound, which is liquid, and mixed with oxygen or a gas having an oxidizing power (for example, N ₂ O, CO _2, etc.), or helium which is an inert gas in the mixed gas and / or It is also possible to add a gas mixed with argon as appropriate.

As described above, the film thickness of the carbon film 2 is preferably 15 nm or less in terms of transparency, but is not limited thereto depending on the application. The film thickness of the carbon film 2 is preferably in the range of 10 nm to 15 nm. The same applies to the film thickness of the carbon film 4.
The film thickness of the silicon oxide film 3 is preferably 10 nm to 50 nm, more preferably 20 nm to 40 nm.

Hereinafter, the plastic container of the present invention will be specifically described based on examples.
Using the film forming apparatus shown in FIG. 6, a polyethylene terephthalate resin bottle having a capacity of 500 ml and a weight of 32 g was used as a plastic container substrate, and this inner surface was formed by plasma CVD under the conditions shown below. . Then, the tap water of the obtained plastic container, oxygen barrier property after 40 degreeC accelerated | stimulated preservation | save, adhesiveness, and transparency were evaluated. The evaluation results are shown in Table 1. The oxygen barrier property was measured with Oxitran 2/20 manufactured by Mocon. Tap water, oxygen barrier property after accelerated storage at 40 ° C., and adhesion are evaluated by measuring the oxygen barrier property after filling a plastic container with 500 ml of tap water and storing it at 40 ° C. for 3 months. The degree of was investigated. Transparency was evaluated by visual observation, and when the color change was not recognized or small compared with the non-film-formed product, the case where the color change was recognized was rated as ◯, and the color change was recognized as x.

<Example 1>
In order to make the layer structure of the embodiment shown in FIG. 1, acetylene gas 100SCCM (Standard CC / min) is first introduced as a process gas, and the first layer carbon is applied by applying 300 watts of microwave power for 1 second. A film 2 was formed. Subsequently, 3 SCCM and 100 SCCM of hexamethyldisiloxane and oxygen gas were respectively introduced, and a 300 watt microwave power was applied for 3 seconds to form a second silicon oxide film 3. However, this silicon oxide film, which is the second layer film, changes the gas flow rate of hexamethyldisiloxane during 3 seconds, so that even if it is a single film, the gas barrier property is not filled with tap water as the contents. In order not to deteriorate, the film quality to be compatible with each other is formed so that the adhesion to the polyethylene terephthalate container and the gas barrier property are improved.

<Example 2>
In order to make the layer structure of the embodiment shown in FIG. 2, hexamethyldisiloxane and oxygen gas are introduced as process gases at 3 SCCM and 100 SCCM, respectively, and microwave power of 300 watts is applied for 3 seconds to thereby form the first layer. A silicon oxide film 3 was formed. Subsequently, acetylene gas 100 SCCM was introduced, and a 300 watt microwave power was applied for 1 second to form a second carbon film 2. The conditions for forming the silicon oxide film 3 are the same as those in Example 1.

<Example 3>
In order to make the layer configuration of the embodiment shown in FIG. 3, acetylene gas 100SCCM was introduced as a process gas, and 300 watts of microwave power was applied for 1 second to form the first carbon film 2. Next, hexamethyldisiloxane and oxygen gas were introduced at 3 SCCM and 100 SCCM, respectively, and a 300 watt microwave power was applied for 3 seconds to form a second silicon oxide film 3. Subsequently, acetylene gas 100 SCCM was introduced, and 300 watts of microwave power was applied for 1 second to form a third-layer carbon film 4. The conditions for forming the silicon oxide film are the same as in Example 1.

  The comparative example of the present invention is shown below.

<Comparative Example 1>
In order to make the layer structure shown in FIG. 4, hexamethyldisiloxane and oxygen gas are introduced as process gases at 3 SCCM and 100 SCCM, respectively, and 300 watts of microwave power is applied for 3 seconds to form the first silicon oxide film. 3 was deposited. The conditions for forming the silicon oxide film are the same as in Example 1.

<Comparative Example 2>
In order to make the layer structure shown in FIG. 5, acetylene gas 100SCCM was introduced as a process gas, and 300 watts of microwave power was applied for 5 seconds to form the first carbon film 2. In order to develop gas barrier properties, the initial value of oxygen barrier properties is made equal by increasing the power application time from 1 second to 5 seconds.

  The results are shown in Table 1. In the comprehensive evaluation, ◯ indicates that both transparency and oxygen barrier properties are good, ◎ indicates particularly excellent, and X indicates that either is inferior.

以上によると、比較例２で作成した酸素ガスバリア性の発現する炭素膜単体（推定膜厚み60ｎｍ）の褐色と比べて実施例１、２、３の透明性は比較例１の酸化ケイ素膜単体と比べても透明性は同等といえる。

According to the above, the transparency of Examples 1, 2 and 3 is the same as that of the silicon oxide film alone of Comparative Example 1 as compared with the brown color of the carbon film alone (estimated film thickness 60 nm) which is produced in Comparative Example 2 and exhibits oxygen gas barrier properties. In comparison, the transparency is equivalent.

For evaluation of oxygen barrier property and adhesion after accelerated storage at 40 ° C. for 3 months, the silicon oxide film produced in Comparative Example 1 was significantly deteriorated, and Examples 1, 2, 3 and Comparative Example 2 The deterioration of the carbon film alone was good. Among them, Example 3 and Comparative Example 2 were even better.
Overall, the layer structure of Example 3 had a well-balanced result including both transparency, oxygen barrier property after accelerated storage at 40 ° C. × 3 months, and adhesion.

It is a cross-sectional schematic diagram which shows an example of embodiment of the plastic container of this invention. It is a cross-sectional schematic diagram which shows an example of embodiment of the plastic container of this invention. It is a cross-sectional schematic diagram which shows an example of embodiment of the plastic container of this invention. It is a schematic diagram which shows the cross-sectional structure of the plastic container of the comparative example 1. 10 is a schematic diagram showing a cross-sectional configuration of a plastic container of Comparative Example 2. FIG. It is a schematic diagram which shows the example of the apparatus for manufacturing the plastic container of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plastic base material 2 ... Carbon film 3 ... Silicon oxide film 4 ... Carbon film a ... Resonator b ... Plastic container c ... Vacuum chamber d ... Gas supply Tube e ... Microwave power supply f ... Impedance matching device g ... Rectangular waveguide

Claims (4)

  A plastic container having a plurality of thin films formed on an inner surface thereof, wherein the plurality of thin films include at least one carbon film and one or more silicon oxide films.   2. The thin film-coated plastic container according to claim 1, wherein a carbon film is present as a first layer on the inner surface, and a silicon oxide film is formed thereon as a second layer.   2. The thin film-coated plastic container according to claim 1, wherein a silicon oxide film is present as a first layer on the inner surface, and a carbon film is formed thereon as a second layer.   2. A carbon film as a first layer on the inner surface, a silicon oxide film as a second layer thereon, and a carbon film as a third layer formed thereon. A thin film coated plastic container as described.

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