U.S. patent application number 13/557737 was filed with the patent office on 2013-07-25 for dlc film coated plastic container, and device and method for manufacturing the plastic container.
This patent application is currently assigned to KIRIN BEER KABUSHIKI KAISHA. The applicant listed for this patent is Hideyasu ANDO, Akira SHIRAKURA, Teruyuki YAMASAKI. Invention is credited to Hideyasu ANDO, Akira SHIRAKURA, Teruyuki YAMASAKI.
Application Number | 20130189448 13/557737 |
Document ID | / |
Family ID | 29706439 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130189448 |
Kind Code |
A1 |
YAMASAKI; Teruyuki ; et
al. |
July 25, 2013 |
DLC FILM COATED PLASTIC CONTAINER, AND DEVICE AND METHOD FOR
MANUFACTURING THE PLASTIC CONTAINER
Abstract
The present invention provides method of DLC film coating a
plastic container by DLC film coating the container in an
apparatus, where the apparatus comprises a container side electrode
which forms one portion of a pressure-reducing chamber and a facing
electrode, where the container side electrode is formed so that the
average inner hole diameter (R2) of the inner wall surrounding a
neck portion is smaller than the average inner hole diameter (R1)
of the inner wall surrounding the body portion, and the average
distance (d2) between the outer wall of the container and the inner
wall of the container side electrode in a horizontal cross section
with respect to the vertical direction of the container at the neck
portion becomes longer than the average distance (d1) between the
outer wall of the container and the inner wall of the container
side electrode.
Inventors: |
YAMASAKI; Teruyuki; (Tokyo,
JP) ; SHIRAKURA; Akira; (Tokyo, JP) ; ANDO;
Hideyasu; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
YAMASAKI; Teruyuki
SHIRAKURA; Akira
ANDO; Hideyasu |
Tokyo
Tokyo
Tokyo |
|
JP
JP
JP |
|
|
Assignee: |
KIRIN BEER KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
29706439 |
Appl. No.: |
13/557737 |
Filed: |
July 25, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12749175 |
Mar 29, 2010 |
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13557737 |
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10514728 |
Jul 27, 2005 |
7754302 |
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PCT/JP03/06528 |
May 26, 2003 |
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12749175 |
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Current U.S.
Class: |
427/577 ;
118/723I |
Current CPC
Class: |
C23C 16/045 20130101;
B65D 23/0814 20130101; Y10T 428/1352 20150115; C23C 16/26 20130101;
B65D 1/0215 20130101; C23C 16/505 20130101 |
Class at
Publication: |
427/577 ;
118/723.I |
International
Class: |
C23C 16/26 20060101
C23C016/26 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2002 |
JP |
2002-154697 |
Claims
1-23. (canceled)
24. A method of DLC film coating a plastic container, comprising:
DLC film coating said container in an apparatus, wherein said
apparatus comprises: a container side electrode which forms one
portion of a pressure-reducing chamber which houses a container
formed from plastic in which the cross-sectional area of an opening
of said container is smaller than the cross-sectional area of a
horizontal cross section at a body portion of said container and a
neck portion is provided between said opening and said body
portion, and a facing electrode which faces said container side
electrode and is arranged inside said container or above said
opening, wherein said container side electrode and said facing
electrode are made to face each other via an insulating body which
forms a portion of said pressure-reducing chamber, source gas
supply means which supply a source gas that is converted to plasma
for coating the inner wall surface of said container with a diamond
like carbon (DLC) film includes a supply gas inlet pipe provided in
said pressure-reducing chamber to introduce said source gas
supplied to said pressure-reducing chamber to the inside of said
container, exhaust means which exhaust gas inside said
pressure-reducing chamber from above the opening of said container
are provided, and high frequency supply means which supply a high
frequency is connected to said container side electrode; wherein
said container side electrode is formed so that the average inner
hole diameter (R2) of the inner wall surrounding said neck portion
is smaller than the average inner hole diameter (R1) of the inner
wall surrounding said body portion, and the average distance (d2)
between the outer wall of said container and the inner wall of said
container side electrode in a horizontal cross section with respect
to the vertical direction of said container at said neck portion
becomes longer than the average distance (d1) between the outer
wall of said container and the inner wall of said container side
electrode in a horizontal cross section with respect to the
vertical direction of said container at said body portion.
25. The method of claim 24, wherein said average distance d2 is
formed to be a distance which suppresses the rise in plasma density
accompanying the rise in pressure of the source gas converted to
plasma at said neck portion inside said container in order to form
a roughly uniform plasma density inside said container.
26. The method of claim 24, wherein said average distance d2 is
formed to be the same as or shorter than the distance at which the
strength of ionic impacts due to collisions of the ions of the
source gas converted to plasma with the inner wall surface of said
container forms an ionic impact strength capable of forming a DLC
film having a prescribed lower limit oxygen barrier property, and
said average distance d2 is formed to be the same as or longer than
the distance at which the entire wall surface of said container has
a roughly uniform color by suppressing coloration of a specific
part of said container from said neck portion to said opening
caused by plasma damage or plasma etching of the inner wall surface
of said container due to the increase in plasma density
accompanying the increase in pressure of the source gas converted
to plasma in said neck portion inside said container.
27. The method of claim 24, wherein said average distance d2 is
formed to be a distance at which the DLC film coated plastic
container secures a prescribed oxygen barrier property and the
entire wall surface of said DLC film coated plastic container has a
roughly uniform color.
28. The method of claim 24, wherein the average diameter of said
body portion of said container is made D1, the average diameter of
said neck portion is made D2, and in the case where K is made an
offset coefficient that satisfies the relationship of Equation 1,
the offset coefficient K satisfies the relationship of Equation 2
or Equation 3, and said average distance d2 forms the d2 determined
from Equation 1: d2=K.times.(D1-D2)/2+d1 Equation 1
0.29.ltoreq.K.ltoreq.0.79 where 0.2 mm.ltoreq.d1.ltoreq.2.0 mm
Equation 2 0.11.ltoreq.K.ltoreq.0.51 where 2.0 mm<d1.ltoreq.4.0
mm. Equation 3
29. The method of claim 24, wherein the average diameter of said
body portion of said container is made D1, the average diameter of
said neck portion is made D2, an offset coefficient that satisfies
the relationship of Equation 4 is made K, and when a of Equation 4
is a container compensation coefficient that takes into account the
container shape dependency satisfying Equation 5, the offset
coefficient K satisfies the relationship of Equation 2 or Equation
3, and said average distance d2 forms the d2 determined from
Equation 4: 0.29.ltoreq.K.ltoreq.0.79 where 0.2
mm.ltoreq.d1.ltoreq.2.0 mm Equation 2 0.11.ltoreq.K.ltoreq.0.51
where 2.0 mm<d1.ltoreq.4.0 mm Equation 3
d2=.alpha.K.times.(D1-D2)/2+d1 Equation 4
.alpha.=(D1/D2).sup.2/3.54. Equation 5
30. The method of claim 24, wherein said container has an axial
symmetrical shape with respect to the central axis of the vertical
direction, and the inner wall shape of said container side
electrode is formed to be an axial symmetrical shape with respect
to said central axis when said container is housed.
31. The method of claim 24, wherein when said container is housed
in said container side electrode, the inner wall of said container
side electrode surrounding said body portion of said container is
formed to have a cylindrical shape, the inner wall of said
container side electrode surrounding said neck portion of said
container is formed to have a truncated cone shaped cylindrical
shape in which the diameter becomes smaller toward the container
opening, and the inner wall of said container side electrode is
formed to have a continuous shape.
32. The method of claim 31, wherein the inner wall of said
container side electrode surrounding the opening of said container
is formed to have a cylindrical shape.
33. The method of claim 24, wherein said body portion of said
container has a square tube shape, the inner wall of said container
side electrode surrounding said body portion of said container is
formed to have a square tube shape, the inner wall of said
container side electrode surrounding said neck portion of said
container is formed to have a truncated pyramid shaped square tube
shape in which the diameter becomes smaller toward the container
opening, a square tube shape or a shape which is a combination of
these, and the inner wall of said container side electrode is
formed to have a continuous shape.
34. The method of claim 33, wherein the inner wall of said
container side electrode surrounding the opening of said container
is formed to have a square tube shape.
35. The method of claim 24, wherein said container side electrode
is formed so that d1 is greater than 0 mm and less than or equal to
4 mm.
36. The method of claim 24, wherein said container is a container
for beverages.
Description
TECHNOLOGICAL FIELD
[0001] The present invention is related to a plastic container
having an inner wall surface coated with a diamond like carbon
(DLC) film, a manufacturing method thereof and a manufacturing
apparatus therefor.
PRIOR ART TECHNOLOGY
[0002] Japanese Laid-Open Patent Application No. HEI 8-53117
discloses an apparatus for manufacturing a carbon film coated
plastic container which coats the inner wall surface of the plastic
container with a carbon film, and a manufacturing method thereof.
As shown in FIG. 11, this apparatus is equipped with a hollow
external electrode 112 which is formed to house a container and
includes a space having a shape roughly similar to the external
shape of the housed container 120, an insulating member 111 which
insulates the external electrode and makes contact with a mouth
portion of the container when the container is housed inside the
space of the external electrode, a grounded internal electrode 116
which is inserted into the inside of the container housed inside
the space of the external electrode from the mouth portion 120A of
the container, exhaust means 115 which communicate with the inside
of the space of the external electrode to exhaust the inside of the
space, supply means 117 which supply a source gas to the inside of
the container housed inside the space of the external electrode,
and a high frequency power source (RF power source) 114 which is
connected to the external electrode.
[0003] The manufacturing method of the same laid-open patent
application forms a carbon film by a plasma CVD method which
generates plasma between the external electrode and the internal
electrode in the same apparatus. Namely, in the method of
manufacturing a carbon film coated plastic container, a space
having a shape roughly similar to the external shape of a housed
container is formed in the external electrode, the external
electrode is insulated by an insulating member which makes contact
with the mouth portion of the container housed inside this space,
an internal electrode is inserted into the inside of the container
housed inside the space from the mouth portion of the container and
this internal electrode is grounded, the inside of the space of the
external electrode is exhausted, a source gas is supplied to the
inside of the container housed inside the space of the external
electrode, and then a high frequency is applied to the external
electrode.
SUMMARY OF THE INVENTION
[0004] According to research conducted by the inventors of the
present invention, a DLC film coated plastic container manufactured
by electrodes similar to those disclosed in the laid-open patent
application described above had a satisfactory oxygen barrier
property (the oxygen permeability was reduced to less than one
tenth compared to the base material) but the color of the neck
portion was dark. Further, when the container was recycled, there
were cases where the coloration of the neck portion caused problems
such as coloration of the recycled items.
[0005] In the laid-open patent application described above, plasma
is created after a prescribed film forming pressure is achieved by
balancing the exhaust of the inside of the space housing the
plastic container and the supply of source gas to the inside of the
plastic container. Accordingly, when plasma is created and before
and after this, the source gas normally flows through the inside of
the plastic container, and this forms a source gas flux. In the
case where a container having a container shape in which the neck
portion is narrow relative to the body portion is made the object,
the cross-sectional area of a horizontal cross section at the neck
portion of the container with respect to a central axis of the
vertical direction of the container becomes smaller suddenly
compared to the body portion. Due to this kind of sudden decrease
of cross-sectional area, the present inventors discovered that the
gas pressure of the source gas flowing through the inside of the
container rises at the neck portion which causes the plasma density
to also rise. In this way, because the DLC film formed on the inner
wall surface of the neck portion of the container exposed to high
density plasma receives more plasma damage or a stronger plasma
etching effect, there is considerably more coloring of dark
yellowish brown at the neck portion than there is at the body
portion.
[0006] In this regard, it is an object of the present invention to
provided an apparatus for manufacturing a DLC film coated plastic
container which has the same degree of oxygen barrier property as a
prior art DLC film coated plastic bottle, and can prevent the
coloring of the DLC film formed on the neck portion of the
container. Namely, it is an object to mitigate plasma damage or
plasma etching of the DLC film at the neck portion by adjusting the
relationship between the space (neck portion offset distance)
between the container outer wall at the neck portion of the
container and the container side electrode inner wall and the space
(body portion offset distance) between the container outer wall at
the body portion of the container and the container side electrode
inner wall under conditions in which a desired oxygen barrier
property is obtained. Further, it is an object to prevent irregular
color of the container and solve recycling problems due to the
coloring described above by providing a manufacturing apparatus
that makes it possible to form a transparent film roughly the same
as that of the body portion on the neck portion. Further, by
adjusting the neck portion offset distance and the body portion
offset distance, it is possible to prevent the occurrence of
irregular color in the rotation direction of the container central
axis.
[0007] Further, it is an object of the present invention to
regulate the neck portion offset distance in more detail in the
manufacturing apparatus according to the present invention. Namely,
an optimum neck portion offset is regulated with the plasma density
distribution, the oxygen barrier property (oxygen permeability) or
the coloration degree of the container as an indicator.
[0008] Further, it is an object of the present invention to provide
a manufacturing apparatus which has a container side electrode
having an inner wall structure suited to a container having an
axial symmetrical shape with respect to the central axis of the
vertical direction of the container. At this time, combined
concrete and simple shapes of the inner wall structure of the
container side electrode are proposed.
[0009] Further, it is an object of the present invention to propose
combined concrete and simple shapes of the inner wall structure of
an optimum container side electrode for containers having an
angular tube-shaped body portion.
[0010] Further, it is an object of the present invention to
concretely regulate the body portion offset distance for obtaining
a container coloration degree (which changes depending on plasma
density distribution shifts and the like) below a prescribed value,
and a required oxygen barrier property in the manufacturing
apparatus according to the present invention.
[0011] Further, as an object of both securing a required oxygen
barrier property and preventing coloration, it is an object of the
present invention to provide a plurality of manufacturing methods
which prevent coloration of the container by controlling the
increase of source gas pressure inside the container at the neck
portion so as to form a uniform plasma density distribution.
Further, it is an object of the present invention to also propose
an optimum manufacturing apparatus when executing these
manufacturing methods.
[0012] Further, it is an object of the present invention to provide
a manufacturing apparatus which solves the problems described above
and at the same time makes it possible to prevent the adherence of
dust to a source gas inlet pipe.
[0013] Further, it is an object of the present invention to provide
an optimum manufacturing method and an optimum manufacturing
apparatus for manufacturing containers for beverages.
[0014] In this way, it is an object of the present invention to
provide a recyclable plastic container which has an oxygen gas
barrier property and can prevent coloration of the neck
portion.
[0015] An apparatus for manufacturing a DLC film coated plastic
container according to the present invention includes a container
side electrode which forms one portion of a pressure-reducing
chamber which houses a container formed from plastic in which the
cross-sectional area of an opening of said container is made
smaller than the cross-sectional area of a horizontal cross section
at a body portion of said container and a neck portion is provided
between said opening and said body portion, and a facing electrode
which faces said container side electrode and is arranged inside
said container or above said opening, wherein said container side
electrode and said facing electrode are made to face each other via
an insulating body which forms a portion of said pressure-reducing
chamber, source gas supply means which supply a source gas that is
converted to plasma for coating the inner wall surface of said
container with a diamond like carbon (DLC) film includes a supply
gas inlet pipe provided in said pressure-reducing chamber to
introduce said source gas supplied to said pressure-reducing
chamber to the inside of said container, exhaust means which
exhaust gas inside said pressure-reducing chamber from above the
opening of said container are provided, and high frequency supply
means which supply a high frequency is connected to said container
side electrode, wherein said container side electrode is formed so
that the average inner hole diameter (R2) of the inner wall
surrounding said neck portion when the container is housed becomes
smaller than the average inner hole diameter (R1) of the inner wall
surrounding said body portion, and the average distance (d2)
between the outer wall of said container and the inner wall of said
container side electrode in a horizontal cross section with respect
to the vertical direction of said container at said neck portion
becomes longer than the average distance (d1) between the outer
wall of said container and the inner wall of said container side
electrode in a horizontal cross section with respect to the
vertical direction of said container at said body portion.
[0016] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, preferably said average distance d2
is formed to be a distance which suppresses the rise in plasma
density accompanying the rise in pressure of the source gas
converted to plasma at said neck portion inside said container in
order to form a roughly uniform plasma density inside said
container.
[0017] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, preferably said average distance d2
is formed to be the same as or shorter than the distance at which
the strength of ionic impacts due to collisions of the ions of the
source gas converted to plasma with the inner wall surface of said
container forms an ionic impact strength capable of forming a DLC
film having a prescribed lower limit oxygen barrier property, and
said average distance d2 is formed to be the same as or longer than
the distance at which the entire wall surface of said container has
a roughly uniform color by suppressing coloration of a specific
part of said container from said neck portion to said opening
caused by plasma damage or plasma etching of the inner wall surface
of said container due to the increase in plasma density
accompanying the increase in pressure of the source gas converted
to plasma in said neck portion inside said container.
[0018] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, preferably said average distance d2
is formed to be a distance at which the DLC film coated plastic
container secures a prescribed oxygen barrier property and the
entire wall surface of said DLC film coated plastic container has a
roughly uniform color.
[0019] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, preferably the average diameter of
said body portion of said container is made D1, the average
diameter of said neck portion is made D2, and in the case where K
is made an offset coefficient that satisfies the relationship of
Equation 1, the offset coefficient K satisfies the relationship of
Equation 2 or Equation 3, and said average distance d2 forms the d2
determined from Equation 1.
d2=K.times.(D1-D2)/2+d1 (Equation 1)
0.29.ltoreq.K.ltoreq.0.79 where 0.2 mm.ltoreq.d1.ltoreq.2.0 mm
(Equation 2)
0.11.ltoreq.K.ltoreq.0.51 where 2.0 mm<d1.ltoreq.4.0 mm
(Equation 3)
[0020] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, preferably the average diameter of
said body portion of said container is made D1, the average
diameter of said neck portion is made D2, an offset coefficient
that satisfies the relationship of Equation 4 is made K, and when a
of Equation 4 is a container compensation coefficient that takes
into account the container shape dependency satisfying Equation 5,
the offset coefficient K satisfies the relationship of Equation 2
or Equation 3, and said average distance d2 forms the d2 determined
from Equation 4.
d2=.alpha.K.times.(D1-D2)/2+d1 (Equation 4)
.alpha.=(D1/D2).sup.2/3.54 (Equation 5)
[0021] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, 2, 3, 4, 5 or 6, preferably said
container has an axial symmetrical shape with respect to the
central axis of the vertical direction, and the inner wall shape of
said container side electrode is formed to be an axial symmetrical
shape with respect to said central axis when said container is
housed.
[0022] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, 2, 3, 4, 5, 6 or 7, preferably when
said container is housed in said container side electrode, the
inner wall of said container side electrode surrounding said body
portion of said container is formed to have a cylindrical shape,
the inner wall of said container side electrode surrounding said
neck portion of said container is formed to have a truncated cone
shaped cylindrical shape in which the diameter becomes smaller
toward the container opening, and the inner wall of said container
side electrode is formed to have a continuous shape that does not
have different stages.
[0023] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 8, preferably the inner wall of said
container side electrode surrounding the opening of said container
is formed to have a cylindrical shape.
[0024] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, 2, 3, 4, 5 or 6, preferably said
body portion of said container has a square tube shape, the inner
wall of said container side electrode surrounding said body portion
of said container is formed to have a square tube shape, the inner
wall of said container side electrode surrounding said neck portion
of said container is formed to have a truncated pyramid shaped
square tube shape in which the diameter becomes smaller toward the
container opening, a square tube shape or a shape which is a
combination of these, and the inner wall of said container side
electrode is formed to have a continuous shape that does not have
different stages.
[0025] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 10, preferably the inner wall of said
container side electrode surrounding the opening of said container
is formed to have a square tube shape.
[0026] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11,
preferably said container side electrode is formed so that d1 is
greater than 0 mm and less than or equal to 4 mm.
[0027] Further an apparatus for manufacturing a DLC film coated
plastic container according to the present invention includes a
container side electrode which forms one portion of a
pressure-reducing chamber which houses a container formed from
plastic, and a facing electrode which faces said container side
electrode and is arranged inside said container or above said
opening, wherein said container side electrode and said facing
electrode are made to face each other via an insulating body which
forms a portion of said pressure-reducing chamber, source gas
supply means which supply a source gas that is converted to plasma
for coating the inner wall surface of said container with a DLC
film includes a supply gas inlet pipe provided in said
pressure-reducing chamber to introduce said source gas supplied to
said pressure-reducing chamber to the inside of said container,
exhaust means which exhaust gas inside said pressure-reducing
chamber from above the opening of said container are provided, and
high frequency supply means which supply a high frequency is
connected to said container side electrode, wherein exhaust
conductance adjustment means are provided to carry out adjustment
by freely restricting the amount of gas exhaust that is exhausted
from a horizontal cross section of said pressure-reducing chamber
above the opening of said container.
[0028] In the apparatus for manufacturing a DLC film coated plastic
container described in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
or 13, preferably said container is a container for beverages.
[0029] Further a method of manufacturing a DLC film coated plastic
container according to the present invention includes the steps of
exhausting the inside of a container formed from plastic to a
pressure less than or equal to a prescribed pressure, then
introducing a source gas which will be converted to plasma to the
inside of said container while continuing to exhaust the inside of
said container so that the inside of said container is replaced
with said source gas and a prescribed equilibrium pressure is
formed inside said container, then stopping most of the exhaust of
the inside of said container and making the introduction rate of
said source gas smaller than the introduction rate at the time of
replacement so that the flow of said source gas inside said
container is slowed and the pressure distribution inside said
container is made roughly uniform, and then generating source gas
type plasma inside said container to form a DLC film on the inner
wall surface of said plastic container.
[0030] Further, a method of manufacturing a DLC film coated plastic
container according to the present invention includes the steps of
exhausting the inside of a container formed from plastic to a
pressure less than or equal to a prescribed pressure, then making
the exhaust rate inside said container smaller or zero and
introducing a source gas which will be converted to plasma to the
inside of said container, and then generating source gas type
plasma inside said container to form a DLC film on the inner wall
surface of said plastic container at the point in time when the
pressure distribution inside said container is roughly uniform and
a prescribed pressure has been reached.
[0031] In the method of manufacturing a DLC film coated plastic
container described in claim 15 or 16, preferably said container is
a container for beverages.
[0032] A DLC film coated plastic container according to the present
invention is a plastic container having a DLC film formed on the
inner wall surface thereof in which the cross-sectional area of an
opening of said container is made smaller than the cross-sectional
area of a horizontal cross section at a body portion of said
container and a neck portion is provided between said opening and
said body portion, wherein the DLC film formed on said neck portion
has a lower graphite mixing proportion than the DLC film formed on
said body portion, and the oxygen permeability of said container is
less than or equal to 0.0050 ml/container (500 ml PET
container)/day (23.degree. C. and RH90%, measurement values after
20 hours from the start of nitrogen gas replacement). At this time,
preferably the amount of graphite mixing of the DLC film formed on
said neck portion is 5.about.18% of the amount of graphite mixing
of said body portion. In this regard, the amount of mixing is
compared for the same film thickness.
[0033] Further, the oxygen permeability of the container is given
for a 500 ml container prescribed as a standard, but this can be
applied to containers having other capacities by carrying out ratio
conversion. For example, in a 1000 ml container, oxygen
permeability is less than or equal to 0.0100 ml/container/day.
[0034] Further, a DLC film coated plastic container according to
the present invention is a plastic container having a DLC film
formed on the inner wall surface thereof in which the
cross-sectional area of an opening of said container is made
smaller than the cross-sectional area of a horizontal cross section
at a body portion of said container and a neck portion is provided
between said opening and said body portion, wherein the DLC film
formed on said neck portion has a higher hydrogen atom content than
the DLC film formed on said body portion, and the oxygen
permeability of said container is less than or equal to 0.0050
ml/container (500 ml PET container)/day (23.degree. C. and RH90%,
measurement values after 20 hours from the start of nitrogen gas
replacement). At this time, preferably the composition proportion
of carbon and hydrogen (carbon atom/hydrogen atom) of the DLC film
formed on said neck portion is 37/63.about.48/52, and the
composition proportion of carbon and hydrogen (carbon atom/hydrogen
atom) of the DLC film formed on said body portion is
55/45.about.75/25.
[0035] Further, a DLC film coated plastic container according to
the present invention is a plastic container having a DLC film
formed on the inner wall surface thereof in which the
cross-sectional area of an opening of said container is made
smaller than the cross-sectional area of a horizontal cross section
at a body portion of said container and a neck portion is provided
between said opening and said body portion, wherein the DLC film
formed on said neck portion has a lower graphite mixing proportion
and a higher hydrogen atom content than the DLC film formed on said
body portion, and the oxygen permeability of said container is less
than or equal to 0.0050 ml/container (500 ml PET container)/day
(23.degree. C. and RH90%, measurement values after 20 hours from
the start of nitrogen gas replacement). At this time, preferably
the amount of graphite mixing of the DLC film formed on said neck
portion is 5.about.18% of the amount of graphite mixing of said
body portion, the composition proportion of carbon and hydrogen
(carbon atom/hydrogen atom) of the DLC film formed on said neck
portion is 37/63.about.48/52, and the composition proportion of
carbon and hydrogen (carbon atom/hydrogen atom) of the DLC film
formed on said body portion is 55/45.about.75/25.
[0036] In the apparatus for manufacturing a DLC film coated plastic
container of the present invention, it is possible to prevent
coloration of the DLC film at the neck portion of a container
manufactured to have the same level of oxygen barrier property as a
prior art DLC film coated plastic bottle. This is achieved by
adjusting the relationship between the neck portion offset length
and the body portion offset length to mitigate plasma damage or
plasma etching of the DLC film at the neck portion. In this way,
irregular color of the container can be prevented by forming a
transparent film roughly the same as that of the body portion on
the neck portion, and this makes it possible to solve the recycling
problem due to coloration.
[0037] Further, in the present invention, an optimum offset is
determined by indicating the plasma density distribution, the
oxygen barrier property (oxygen permeability) or the coloration
level of the container.
[0038] Further, the present invention shows concrete and simple
embodiments of a manufacturing apparatus suited to a container
having an axial symmetrical shape with respect to the central axis
of the vertical direction of the container or a container having a
square tube shaped body portion. In this way, instead of preparing
a separate container side electrode to match each of the various
shapes of beverage containers, for example, the container side
electrode can be used for all applications.
[0039] The present invention concretely shows the body portion
offset length in the manufacturing apparatus according to the
present invention, and in this way a container coloration level at
or below a prescribed value and a required oxygen barrier property
were obtained.
[0040] Further, in the manufacturing method of the present
invention, coloration of the container is prevented by suppressing
the rise in source gas pressure at the neck portion inside the
container and carrying out control so that the plasma density
distribution becomes uniform, whereby both a required oxygen
barrier property is secured and coloration is prevented. Further,
the present invention proposes an optimum manufacturing apparatus
when this manufacturing method is carried out.
[0041] Further, the present invention is designed to solve the
problems described above and at the same time prevent the adherence
of dust to the source gas inlet pipe.
[0042] Further, because both an oxygen barrier property and
transparency are obtained, the present invention is ideally suited
to the manufacture of beverage containers which require
transparency and recyclability.
[0043] Further, the DLC film of the container manufactured by the
apparatus of the present invention is a fine DLC film having a
small number of graphite like carbon sp.sup.2 bonding structures
and a high proportion of sp.sup.3 bonding structures (diamond
structures and the like). This DLC film makes it possible to
achieve a light uniform color over the entire container while
securing an oxygen barrier property.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a schematic drawing which shows one embodiment of
the present manufacturing apparatus.
[0045] FIG. 2 is a drawing which shows the meaning of the symbols
in the present invention.
[0046] FIG. 3 is a schematic drawing which shows a second
embodiment of the present manufacturing apparatus.
[0047] FIG. 4 is a schematic drawing which shows a third embodiment
of the present manufacturing apparatus.
[0048] FIG. 5 is a schematic drawing which shows another embodiment
of a source gas inlet pipe in the apparatus of FIG. 1.
[0049] FIG. 6 is a schematic drawing which shows another embodiment
of a source gas inlet pipe in the apparatus of FIG. 3.
[0050] FIG. 7 is a conceptual drawing which shows the flow of gas
from the container opening to the exhaust port using the apparatus
of FIG. 3 as an example.
[0051] FIG. 8 is a drawing which shows the names of each part of a
beverage container.
[0052] FIG. 9 is a schematic drawing of an apparatus in the case
where exhaust conductance adjustment means are provided using the
apparatus of FIG. 3 as an example.
[0053] FIGS. 10(a).about.10(c) are conceptual drawings which show
details of the exhaust conductance adjustment means, wherein FIG.
10(a) is a schematic drawing showing one embodiment of the exhaust
conductance adjustment means 50 in a cross section taken in the
plane formed by the axial direction of the source gas inlet pipe 9
and the insertion direction of a restrictor 51 of the exhaust
conductance adjustment means 50. FIG. 10(b) is a cross-sectional
schematic drawing taken along X-X in FIG. 9, and is the case where
the restrictor 51 is open. FIG. 10(c) is a cross-sectional
schematic drawing taken along X-X in FIG. 9, and is the case where
the restrictor 51 is closed.
[0054] FIG. 11 is a drawing which shows a conceptual drawing of a
prior art apparatus for manufacturing a DLC film coated plastic
container.
[0055] FIG. 12 is a schematic drawing of the case where the
container side electrode is given an electrode structure having a
shape similar to the container in the apparatus of FIG. 1.
[0056] FIG. 13 is a graph which shows the body portion offset
length dependence of the oxygen permeability.
[0057] FIG. 14 is a graph which shows the neck portion offset
length dependence of the oxygen permeability.
[0058] FIG. 15 is a graph which shows the body portion offset
length dependence of the b* value.
[0059] FIG. 16 is a graph which shows the neck portion offset
length dependence of the b* value.
[0060] FIG. 17 is a drawing which shows the relationship of the
optimum offset length.
[0061] FIG. 18 is a picture which shows a comparison of a DLC film
container (mentioned as present invention) obtained by the
manufacturing apparatus of the present invention and a DLC film
container obtained by a prior art manufacturing apparatus in which
the inner wall of the space of the container side electrode housing
the container has a shape similar to the container outer wall.
[0062] FIG. 19 is a drawing which shows the relationship between
the film thickness of the DLC film and the b* value.
[0063] FIG. 20 is a graph which shows the difference in
transmittance spectrum properties of DLC film containers which
depend on the electrode structure.
[0064] FIG. 21 is a graph which shows a comparison of the Raman
spectrums of the container of the present invention and the
container of Comparative Example 2 (prior art technology).
[0065] FIG. 22 shows enlarged views of the DLC related portions
after the effects due to fluorescence are eliminated in FIG.
21.
[0066] FIG. 23 is a drawing which shows the sequence of
Manufacturing Method 3.
[0067] FIG. 24 is a schematic drawing of the case where the
container side electrode is given an electrode structure having a
shape similar to the container in the apparatus of FIG. 4.
[0068] The meaning of the symbols is as follows. 1 shows an upper
electrode, 2 shows a lower electrode, 3 shows a container side
electrode, 4 shows an insulating body, 5 shows a facing electrode,
5a shows a tubular body, 5b shows a tubular body end, 5c shows an
internal electrode, 6 shows a pressure-reducing chamber, 7 shows a
plastic container, 8 shows an O-ring, 9 shows a source gas inlet
pipe, 9a shows a blowout hole, 10 shows an opening, 11 shows an
annular portion of the facing electrode, 12 shows a matching box,
13 shows a high frequency power source, 14 shows high frequency
supply means, 16 shows a pipeline, 17 shows a source gas generating
source, 18 shows source gas supply means, 19 shows a vacuum valve,
20 shows an exhaust pump, 21 shows exhaust means, 23 shows an
exhaust port, 50 shows exhaust conductance adjustment means, 51
shows a restrictor, 52 shows a through hole, and 53 shows a
restrictor opening/closing mechanism.
PREFERRED EMBODIMENTS OF THE INVENTION
[0069] Detailed descriptions showing embodiments of the present
invention are given below, but it should not be interpreted that
the present invention is limited to these descriptions.
[0070] First, the structure of an apparatus for manufacturing a DLC
film coated plastic container according to the present invention
will be described with reference to FIGS. 1.about.12. Further, the
same symbols are used for the same members in the drawings. FIG. 1
is a schematic drawing showing one embodiment of the present
manufacturing apparatus. FIGS. 1, 3.about.7, 9 and 12 are
cross-sectional schematic drawings of a pressure-reducing chamber
taken along the vertical direction of a container. As shown in FIG.
1, the manufacturing apparatus has a container side electrode 3
which forms one portion of a pressure-reducing chamber 6 which
houses a container 7 formed from plastic in which the
cross-sectional area of an opening 10 of the container 7 is made
smaller than the cross-sectional area of a horizontal cross section
at a body portion of the container 7 and provided with a neck
portion between the opening 10 and the body portion, and a facing
electrode 5 which faces the container side electrode 3 and is
arranged inside the container 7 or above the opening 10, wherein
the container side electrode 3 and the facing electrode 5 are made
to face each other via an insulating body 4 which forms a portion
of the pressure-reducing chamber 6, source gas supply means 18
which supply a source gas that is converted to plasma for coating
the inner wall surface of the container 7 with a DLC film includes
a supply gas inlet pipe 9 provided in the pressure-reducing chamber
6 to introduce the source gas supplied to the pressure-reducing
chamber 6 to the inside of the container 7, exhaust means 21 which
exhaust gas inside the pressure-reducing chamber 6 from above the
opening 10 of the container 7 are provided, and high frequency
supply means 14 which supply a high frequency is connected to the
container side electrode 3.
[0071] The container side electrode 3 is constructed from an upper
electrode 1 and a lower electrode 2 which can be attached to and
removed from the upper electrode 1. An O-ring 8 is arranged between
the upper electrode 1 and the lower electrode 2 to ensure
airtightness. The upper electrode 1 and the lower electrode 2 form
a conducting state so as to form one body as a container side
electrode. The container side electrode 3 has a structure that is
divided into the upper electrode 1 and the lower electrode 2 to
provide a housing opening for housing the plastic container 7
inside the container side electrode 3. In FIG. 1, the container
side electrode 3 is divided to form the two upper and lower
portions, but it may be divided to form three upper, middle and
lower portions for housing the container, or it may be divided
vertically.
[0072] The container side electrode 3 shown in FIG. 1 is given a
shape which houses the container 7 excluding the mouth portion of
the container 7. The reason for this is that it reduces the
formation of a DLC film on the inner wall surface of the mouth
portion. Accordingly, in the case where a DLC film is formed on the
inner wall surface of the mouth portion, a shape may be formed to
house the entire container. Further, in order to adjust the film
forming region, a shape may be formed to house the container
excluding the mouth portion of the container and one portion of the
neck portion.
[0073] Further, as shown in FIG. 2, the container side electrode 3
is formed so that the average inner hole diameter (R2) of the inner
wall surrounding the container neck portion when the container is
housed becomes smaller than the average inner hole diameter (R1) of
the inner wall surrounding the body portion. At the same time, the
container side electrode 3 is formed so that the average distance
(d2; defined as the average neck portion offset length) between the
container outer wall and the inner wall of the container side
electrode in a horizontal cross section with respect to the
vertical direction of the container at the neck portion becomes
smaller than the average distance (d1; defined as the average body
portion offset length) between the container outer wall and the
inner wall of the container side electrode in a horizontal cross
section with respect to the vertical direction of the container at
the body portion. Further, d1 is preferably made sufficiently small
so that the self bias produced at the container body portion wall
surface at the time of plasma generation is not lowered more than
necessary, and to avoid plasma concentration at the neck portion.
Even though d1 will change depending on the container capacity and
the film forming conditions, it is preferably greater than 0 mm and
less than or equal to 4 mm. The relationship R2<R1 is
established because in the relationship R2.gtoreq.R1, the neck
portion offset length is too long, and it is not possible to secure
a required oxygen barrier property as described later. Further,
when there is the relationship R2=R1, the inner wall of the
container side electrode 3 forms a cylindrical shape. On the other
hand, the relationship d2>d1 is established to suppress increase
of the plasma density at the neck portion by providing a moderate
neck portion offset, and to mitigate plasma damage or a plasma
etching effect to the DLC film. Further, the relationship d2=d1 is
the case where the outer wall of the container and the inner wall
of the space of the container side electrode have similar shapes
which almost touch.
[0074] When (R2<R1) and (d2>d1) are satisfied, the average
neck portion offset length d2 preferably forms a distance that
suppresses the increase of plasma density accompanying the increase
in pressure of the source gas converted to plasma at the neck
portion inside the container in order to form a roughly uniform
plasma density inside the container. By making the plasma density
uniform, degradation due to plasma damage or plasma etching of the
DLC film formed on the neck portion is mitigated.
[0075] When (R2<R1) and (d2>d1) are satisfied, the average
neck portion offset length d2 is formed to be the same as or
shorter than the distance at which the strength of ionic impacts
due to collisions of the ions of the source gas converted to plasma
with the inner wall surface of the container forms an ionic impact
strength capable of forming a DLC film having a prescribed lower
limit oxygen barrier property. At the same time as this, the
average neck portion offset length d2 is preferably formed to be
the same as or shorter than the distance at which the entire wall
surface of the container has a roughly uniform color by suppressing
coloration of a specific part of the container from the neck
portion to the opening caused by plasma damage or plasma etching of
the inner wall surface of the container due to the increase in
plasma density accompanying the increase in pressure of the source
gas converted to plasma in the neck portion inside the
container.
[0076] In the apparatus of the present invention, the formation of
a DLC film on the inner wall surface of the container 7 is carried
out by a plasma CVD method. Namely, discharging is produced by the
high frequency applied between the container side electrode 3 and
the facing electrode 5, plasma is generated, and if the conditions
for continuing discharge are satisfied, the plasma discharge is
stabilized. Then, the source gas is decomposed by the plasma to
form various kinds of radicals (most of which are ionized to
positive). On the other hand, the electrons produced by discharging
accumulate on the inner wall surface, and a prescribed potential
drop (the application of a self bias voltage) is created, whereby a
potential well (called a sheath potential) is possible. Then, the
energy of the kinds of radicals ionized at the inner wall surface
of the container 7 are accelerated by the sheath potential created
on the container wall surface, and these randomly collide with the
entire inner surface of the inner wall surface. At this time, the
undecomposed radicals and ions are finally decomposed on the inner
wall surface of the container, and if the source gas is a
hydrocarbon gas, there is bonding between adjacent carbon atoms and
between carbon atoms and hydrogen atoms, and the release of
temporarily bonded hydrogen atoms (a spattering effect) occurs.
When the above processes are carried out, a very fine DLC film is
formed on the inner wall surface of the container 7. By applying a
moderate high frequency output and selecting a suitable gas flow
rate, plasma discharge will continue between the container side
electrode 3 and the facing electrode 5.
[0077] In this regard, if the strength of ionic impacts due to
collisions of the ions of the source gas converted to plasma with
the inner wall surface of the container is weak, a fine DLC film
will not be obtained, and an oxygen barrier property will not be
obtained. As the average neck portion offset length d2 becomes
larger, the self bias voltage becomes smaller and the strength of
the ionic impacts becomes weaker. Accordingly, the average neck
portion offset length d2 must be an average neck portion offset
length d2 that obtains an ionic impact strength greater than or
equal to an ionic impact strength capable of forming a DLC film
having a prescribed lower limit oxygen barrier property. Namely,
the average neck portion offset length d2 needs to be formed to be
the same as or shorter than the distance at which the strength of
ionic impacts due to collisions of the ions of the source gas
converted to plasma with the inner wall surface of the container
forms an ionic impact strength capable of forming a DLC film having
a prescribed lower limit oxygen barrier property. In this regard,
the prescribed lower limit oxygen barrier property is an oxygen
permeability of 0.0050 ml/container (500 ml PET container)/day
(23.degree. C. and RH90%, measurement values after 20 hours from
the start of nitrogen gas replacement).
[0078] When the average neck portion offset length d2 becomes
shorter, the self bias voltage becomes higher. Then, with regard to
the shoulder portion in comparison with the body portion, because
an increase in plasma density occurs accompanying the increase in
pressure of the source gas converted to plasma at the neck portion
inside the container, there is more exposure to excessive plasma
than there is at the body portion, whereby coloration at a specific
part of the container from the neck portion to the opening is
created by degradation (bonding state and the like) due to plasma
damage or plasma etching. In order to make the entire wall surface
of the container have a roughly uniform color, the average neck
portion offset length d2 needs to be made sufficiently long so that
this coloration does not occur.
[0079] To summarize the above, the average neck portion offset
length d2 is preferably formed to be a distance at which the DLC
film coated plastic container secures a prescribed oxygen barrier
property and the entire wall surface of the DLC film coated plastic
container has a roughly uniform color. Further, the prescribed
oxygen barrier property is an oxygen permeability which is less
than or equal to 0.0050 ml/container (500 ml PET container)/day
(23.degree. C. and RH90%, measurement values after 20 hours from
the start of nitrogen gas replacement).
[0080] Further, the average neck portion offset length d2 is
calculated from Equation 1. As indicated by the symbols in FIG. 2,
the average diameter of the body portion of the container is made
D1, the average diameter of the neck portion is made D2, and in the
case where K is made the offset coefficient that satisfies the
relationship of Equation 1, the offset coefficient K satisfies the
relationship of Equation 2 or Equation 3.
d2=K.times.(D1-D2)/2+d1 (Equation 1)
0.29.ltoreq.K.ltoreq.0.79 where 0.2 mm.ltoreq.d1.ltoreq.2.0 mm
(Equation 2)
0.11.ltoreq.K.ltoreq.0.51 where 2.0 mm<d1.ltoreq.4.0 mm
(Equation 3)
[0081] In this regard, the average diameter of the body portion is
the diameter of a cylinder in the case where the container body
portion is approximated by a cylindrical shape having the same
height and the same volume. The average diameter of the neck
portion is the diameter of a cylinder in the case where the
container neck portion is approximated by a cylindrical shape
having the same height and the same volume.
[0082] In this regard, the offset coefficient K is a parameter used
at the time the average neck portion offset length d2 is determined
using D1, D2 and d1, and when K=0, this forms d2=d1, and the inner
wall of the space housing the container of the container side
electrode 3 forms a similar shape that almost touches the
container. On the other hand, when K=1, this forms d2=(D1-D2)/2+d1,
and the inner wall of the space housing the container of the
container side electrode 3 forms a cylindrical shape. The average
neck portion offset length d2 at the time of forming a distance at
which the DLC film coated plastic container secures a prescribed
oxygen barrier property and the entire wall surface of the DLC film
coated plastic container has a roughly uniform color is determined
by the offset coefficient K given by Equation 2 or Equation 3.
[0083] Further, in order to compensate the container shape
dependency of Equation 1, the average neck portion offset length d2
may be determined from Equation 4 by introducing the container
compensation coefficient .alpha. shown in Equation 5. At this time,
the offset coefficient K satisfies the relationship of Equation 2
or Equation 3.
d2=.alpha.K.times.(D1-D2)/2+d1 (Equation 4)
.alpha.=(D1/D2).sup.2/3.54 (Equation 5)
[0084] In the case where the container has an axial symmetrical
shape with respect to the central axis of the vertical direction,
the inner wall shape of the container side electrode 3 is
preferably formed to be an axial symmetrical shape with respect to
the container central axis when the container is housed. In this
case, because a horizontal cross section of the container with
respect to the central axis forms a circular shape, the inner wall
of the container side electrode 3 also forms a circular shape
concentric with this. In this way, the offset length on a
horizontal cross section of the container with respect to the
central axis becomes the same everywhere. Accordingly, it is
possible for the distribution of the self bias voltage created on
the container wall surface to be made uniform on a horizontal cross
section of the container with respect to the central axis.
[0085] In the case where the container has an axial symmetrical
shape with respect to the central axis of the vertical direction,
when the container is housed in the container side electrode, the
inner wall of the container side electrode surrounding the body
portion of the container may be formed to have a cylindrical shape,
the inner wall of the container side electrode surrounding the neck
portion of the container may be formed to have a truncated cone
shaped cylindrical shape in which the diameter becomes smaller
toward the container opening, and the inner wall of the container
side electrode may be formed to have a continuous shape that does
not have different stages. The present inventors call the container
side electrode having this shape a "cone compound electrode", and
instead of preparing a separate container side electrode to match
each of the various shapes of beverage containers, for example,
this structure provides a container side electrode that can be used
for all applications. This corresponds to the fact that the mouth
portion of the container has a cylindrical shape.
[0086] In the cone compound electrode, the shape of the inner wall
of the space can be constructed from two members comprising a
cylindrical base portion and a cylindrical upper portion having a
truncated cone shape. By forming a truncated cone shape, the body
portion offset length and the neck portion offset length can be
controlled independently by a relatively simple structure. Further,
an optimum electrode structure can be searched easily for various
containers having different shapes.
[0087] In the cone compound electrode, the inner wall of the
container side electrode surrounding the opening of the container
may be formed to have a cylindrical shape.
[0088] On the other hand, in the case of so-called square bottles
where the body portion of the container has a square tube shape,
the inner wall of the container side electrode surrounding the body
portion of the container may be formed to have a square tube shape,
the inner wall of the container side electrode surrounding the neck
portion of the container may be formed to have a truncated pyramid
shaped square tube shape in which the diameter becomes smaller
toward the container opening, a square tube shape or a shape which
is a combination of these, and the inner wall of the container side
electrode (hereafter referred to as a "pyramid compound electrode")
may be formed to have a continuous shape that does not have
different stages. A DLC film coating can be obtained even when a
film is formed on a square tube shaped container using the cone
compound electrode described above, but the pyramid compound
electrode is preferably applied in order to apply a uniform self
bias voltage to the wall surface of the square bottle.
[0089] In the pyramid compound electrode, the shape of the inner
wall of the space can be constructed from two members comprising a
square tube base portion and a square tube upper portion having a
truncated pyramid shape, and the body portion offset length and the
neck portion offset length can be controlled independently by a
relatively simple structure. Further, an optimum electrode
structure can be searched easily for various containers having
different shapes.
[0090] In the pyramid compound electrode, the inner wall of the
container side electrode surrounding the opening of the container
may be formed to have a square tube shape. This corresponds to the
fact that the mouth portion of the container has a cylindrical
shape. Further, the inner wall of the container side electrode
surrounding the opening of the container may be formed to have a
cylindrical shape, but in this case, stages will be created in the
inner wall of the space of the container side electrode housing the
container.
[0091] In the case where a pyramid compound electrode is used, in
particular in the case of a 90.degree. rotation object container,
by substituting the length of one side in a horizontal cross
section with respect to the container central axis at the body
portion for D1 of Equation 4 and Equation 5, and by substituting
the average length of one side in a horizontal cross section with
respect to the container central axis at the neck portion for D2 of
Equation 4 and Equation 5, K satisfies Equation 2 and Equation 3,
and based on that, d2 can be calculated from Equation 4.
[0092] Next, a description will be given for the facing electrode
5. The facing electrode 5 is an electrode that faces the container
side electrode 3. Accordingly, because the facing electrode 5 and
the container side electrode 3 need to form an insulating state,
the insulating body 4 is provided between these electrodes. The
facing electrode 5 is arranged so as to be positioned above the
opening 10 of the container. At this time, the entire facing
electrode 5 or a portion thereof is preferably arranged near the
opening 10 of the container. This shortens the distance to the
container side electrode 3, and makes the plasma distribution
become a uniform distribution inside the container. Further, the
shape of the facing electrode 5 can be freely formed, but as shown
in FIG. 1, the facing electrode is preferably equipped with an
annular portion 11 having roughly the same inner hole diameter as
the opening diameter of the plastic container 7. This facing
electrode is formed so that the opening of the end of the annular
portion 11 is aligned on the same axis for the opening 10 of the
plastic container 7 and arranged near the opening 10 of the plastic
container 7. The reason for forming an annular shape is because
this makes it possible to prevent an increase of the exhaust
resistance caused by the facing electrode. Further, the facing
electrode 5 is preferably grounded.
[0093] In the present invention, as shown in FIG. 3, the facing
electrode 5 is formed to have a tubular portion 5a which hangs down
from the top portion of the pressure-reducing chamber to a position
above the opening 10 of the plastic container 7, the source gas
supplied by the source gas supply means 18 is introduced to the
inside of the tubular portion 5a, and the end 5b of the tubular
portion 5a may be connected to the source gas inlet pipe 9. At this
time, the end 5b of the tubular portion 5a is preferably arranged
near the opening 10 of the plastic container 7. In the case of FIG.
3, the end 5b forms splicing means for connecting the tubular
portion and the source gas inlet pipe. By forming this kind of
structure, it is possible to eliminate the lowering of exhaust
conductance as the facing electrode is brought near the opening 10.
Accordingly, the plasma discharge is easily stabilized.
[0094] The facing electrode or the end of the annular portion 11 of
FIG. 1 or the end of the tubular portion of FIG. 3 preferably makes
contact with the gas flow formed from a position near the opening
10 of the plastic container 7 to an exhaust port 23 of the
pressure-reducing chamber 6 by the exhaust means 21. This makes it
possible to easily generate plasma and stabilize the discharge.
[0095] Further, by providing the facing electrode with the annular
portion 11 of FIG. 1 or the tubular portion of FIG. 3, it is
possible to reduce the unevenness of plasma distribution inside the
plastic container in the circumferential direction of the container
side, and this makes it possible to reduce the unevenness of the
film distribution.
[0096] In the manufacturing apparatus of the present invention, in
addition to the apparatus shown in FIG. 1 or FIG. 3, a facing
electrode 5c may be formed to have a shape that is arranged inside
the plastic container 7, namely, the facing electrode 5c may be
formed as an internal electrode having an electrode shape that is
inserted inside the container. At this time, the source gas inlet
pipe is also used as the facing electrode 5c which is a conducting
body.
[0097] Further, the material of the container side electrode and
the facing electrode is preferably stainless steel (SUS) or
aluminum.
[0098] The insulating body 4 serves the role of forming an
insulating state between the facing electrode 5 and the container
side electrode 3, and also serves the role of forming one portion
of the pressure-reducing chamber 6. The insulating body is formed
by a fluororesin, for example. The pressure-reducing chamber 6 is
formed by assembling the container side electrode 3, the insulating
body 4 and the facing electrode 5 to be mutually airtight. Namely,
an O-ring is arranged between the container side electrode 3 and
the insulating body 4 to ensure airtightness. Further, an O-ring
(not shown in the drawings) is also arranged between the insulating
body 4 and the facing electrode 5 to ensure airtightness. In the
apparatus of FIG. 1, a structure is formed in which the facing
electrode 5 is provided above the insulating body 4, but when the
facing electrode 5 forms a facing electrode that faces the
container side electrode 3, because the size thereof can be freely
set, the size of the member formed from the insulating body 4 and
the facing electrode 5 shown in FIG. 1 may be fixed, and the
insulating body may be formed large with the facing electrode being
made smaller by just that size portion. Alternatively, the
insulating body may be formed small enough to serve the role of
only a rough insulator with the facing electrode being made larger
by just that size portion. A space 40 is formed inside the member
formed from the insulating body 4 and the facing electrode 5, and
the space 40 together with the space inside the plastic container 7
form a pressure-reducing space. The pressure-reducing chamber 6
forms this pressure-reducing space.
[0099] The source gas inlet pipe 9 is formed to have a hollow
(cylindrical) shape. The material in the case where the apparatus
is constructed so that the facing electrode is arranged outside the
container as in FIG. 1 or FIG. 3 is preferably formed from a resin
material having an insulating property and heat resistance
sufficient to endure plasma. In this regard, fluororesin,
polyamide, polyimide, and polyether ether ketone can be used as
examples of a resin material. Alternatively, the source gas inlet
pipe 9 is preferably formed from a ceramic material having an
insulating property. Alumina, zirconia, titania, silica and quartz
glass can be used as examples of a ceramic material. Further, in
the case where the apparatus is constructed so that the facing
electrode 5c is inserted inside the container as in FIG. 4, the
source gas inlet pipe 9 is formed by stainless steel or aluminum.
The source gas inlet pipe 9 is provided inside the
pressure-reducing chamber 6 so as to be arranged inside the plastic
container 7 by being freely inserted and removed through the
opening 10 of the container. At this time, the source gas inlet
pipe 9 is supported on the pressure-reducing chamber 6. As for the
method of support, the source gas inlet pipe 9 can be supported on
the facing electrode 5 as shown in FIG. 1, for example, or the
source gas inlet pipe 9 can be supported on the tubular portion 5a
via the splicing means as shown in FIG. 3. Further, one blowout
hole (9a) which communicates the inside and the outside of the
source gas inlet pipe 9 is formed on the lower end of the source
gas inlet pipe 9. Further, instead of providing a blowout hole at
the lower end, a plurality of blowout holes (not shown in the
drawings) may be formed to pass through the inside and the outside
of the source gas inlet pipe 9 in radial directions. The source gas
inlet pipe 9 is connected to the end of a pipeline of the source
gas supply means 18 which communicates with the inside of the
source gas inlet pipe 9. Further, the apparatus is constructed so
that the source gas sent into the inside of the source gas inlet
pipe 9 via the pipeline can be blown into the inside of the plastic
container 7 via the blowout hole 9a. Further, by forming the source
gas inlet pipe 9 by an insulating material, it is possible to
reduce the adherence of source gas type dust to the external
surface of the source gas inlet pipe 9.
[0100] By inserting the tip portion of the source gas inlet pipe 9
through the opening of the plastic container to a position near the
mouth portion as shown in FIG. 5 or FIG. 6, it becomes possible to
supply source gas to the entire inside of the plastic container. In
this regard, the tip of the source gas inlet pipe shown in FIG. 1,
FIG. 3 or FIG. 4 is more preferably arranged to be freely inserted
to and removed from a deep position reaching the bottom portion
from the body portion through the opening of the plastic container.
The reason for this is that it makes it possible to form a
turbulence-free source gas flow from the bottom portion of the
container to the opening as shown in FIG. 7, and this makes it
possible to form a DLC film more uniformly on the inner wall
surface of the container.
[0101] Further, in the apparatus of the present invention, the
source gas inlet pipe is inserted inside the plastic container at
the time a source gas is introduced, and source gas inlet pipe
insertion/removal means (not shown in the drawings) may be provided
to place the source gas inlet pipe in a removed state from the
plastic container at the time plasma is generated. The source gas
inlet pipe insertion/removal means make it possible to distribute
source gas and form a DLC film over the entire inside of the
plastic container, and there is absolutely no adherence of dust
because the source gas inlet pipe make it possible to remove the
source gas inlet pipe from the plasma region at the time a film is
formed. Further, in the case where source gas inlet pipe
insertion/removal means are provided to place the source gas inlet
pipe in a removed state from the plastic container when plasma is
generated, a valve (shutter) (not shown in the drawings) which can
be freely opened and closed for the purpose of controlling the
exhaust rate of the source gas is preferably provided near the
opening 10.
[0102] Further, dust incineration means (not shown in the drawings)
may be provided to incinerate dust adhering to a ceramic material
type source gas inlet pipe 9 in the present apparatus. Two or more
source gas inlet pipes which can be arranged in an alternating
manner are prepared, and after a film is formed a prescribed number
of times, the arrangement of the source gas inlet pipes are
switched, and the dust adhering to the source gas inlet pipe in
standby is incinerated by operating the dust incineration
means.
[0103] The source gas supply means 18 introduces the source gas
supplied from a source gas generating source 17 to the inside of
the plastic container 7. Namely, one side of a pipeline 16 is
connected to the facing electrode 5 or the insulating body 4, and
the other side of the pipeline 16 is connected to one side of a
mass flow controller (not shown in the drawings) via a vacuum valve
(not shown in the drawings). The other side of the mass flow
controller is connected to the source gas generating source 17 via
a pipeline. The source gas generating source 17 generates a
hydrocarbon gas or the like such as acetylene or the like.
[0104] Aliphatic hydrocarbons, aromatic hydrocarbons,
oxygen-containing hydrocarbons, nitrogen-containing hydrocarbons
and the like which form a gas or liquid at room temperature are
used as a source gas. In particular, benzene, toluene, o-xylene,
m-xylene, p-xylene, cyclohexane and the like having a carbon number
of 6 or higher are preferred. Ethylene type hydrocarbons and
acetylene type hydrocarbons represent examples of aliphatic
hydrocarbons. These materials may be used separately or as a gas
mixture or two or more types. Further, these gases may be used in a
way in which they are diluted by a noble gas such as argon or
helium. Further, in the case where a silicon-containing DLC film is
formed, a Si-containing hydrocarbon type gas is used.
[0105] The DLC film in the present invention refers to an amorphous
carbon film containing sp.sup.3 bonding which is a carbon film that
is also called an i-carbon film or a hydrogenated amorphous carbon
film (a-CH). The amount of hydrogen contained in the DLC film which
sets the film quality from hardness to softness (polymer like) is
in the range from 0 atom % to 70 atom %.
[0106] The exhaust means 21 is constructed from a vacuum valve 19
and an exhaust pump 20 as well as a pipeline that connects these.
The space 40 formed inside the member formed from the insulating
body 4 and the facing electrode 5 is connected to one side of an
exhaust pipeline. For example, in FIG. 1, an exhaust pipeline is
connected to the exhaust port 23 provided in the facing electrode
5. The other side of the exhaust pipeline is connected to the
exhaust pump 20 via the vacuum valve 19. The exhaust pump 20 is
connected to an exhaust duct (not shown in the drawings). By
operating the exhaust means 21, pressure is reduced in a
pressure-reducing space formed from the space 40 and the space
inside the container inside the pressure-reducing chamber 6.
[0107] The high frequency supply means 14 is formed from a matching
box 12 which is connected to the container side electrode 3, and a
high frequency power source 13 which supplies a high frequency to
the matching box 12. The matching box 12 is connected to the output
side of the high frequency power source 13. In FIG. 1, the high
frequency supply means 14 is connected to the lower electrode 2,
but it may also be connected to the upper electrode 1. Further, the
high frequency power source 13 is grounded. The high frequency
power source 13 generates a high frequency voltage between itself
and the ground potential, and in this way a high frequency voltage
is applied between the container side electrode 3 and the facing
electrode 5. In this way, the source gas inside the plastic
container 7 is converted to plasma. The frequency of the high
frequency power source is 100 kHz.about.1,000 MHz, and the
industrial frequency of 13.56 MHz is used, for example.
[0108] The container according to the present invention includes a
container that uses a cover or a stopper or is sealed, or a
container used in an open state that does not use these. The size
of the opening is determined in accordance with the contents. The
container shape is especially preferred to be a container shape
having a neck portion in which the cross-sectional area of the
opening of the container is made smaller than the cross-sectional
area of a horizontal cross section at the body portion of the
container. This is because in a container having this shape, the
pressure increases at the neck portion when the source gas flows,
and this also increases the plasma density, whereby the DLC film
receives plasma damage or plasma etching. Further, the plastic
container includes a plastic container having a moderate stiffness
and a prescribed thickness, and a plastic container formed from a
sheet material that does not have stiffness. The substance that is
filled into the plastic container according to the present
invention can be a beverage such as a carbonated beverage or a
fruit juice beverage or a soft drink or the like, as well as a
medicine, an agricultural chemical, or a dried food which hates
moisture absorption. Further, the container may be either a
returnable container or a one-way container.
[0109] Further, in the present invention, each part of a beverage
container or a container having a shape similar to this is named as
shown in FIG. 8.
[0110] The resin used when forming the plastic container 7 of the
present invention can be polyethylene terephthalate (PET) resin,
polybutylene terephthalate resin, polyethylene naphthalate resin,
polyethylene resin, polypropylene (PP) resin, cycloolefin copolymer
(COC, annular olefin copolymer) resin, ionomer resin,
poly-4-methylpentene-1 resin, polymethyl methacrylate resin,
polystyrene resin, ethylene-vinyl alcohol copolymer resin,
acrylonitrile resin, polyvinyl chloride resin, polyvinylidene
chloride resin, polyamide resin, polyamide-imide resin, polyacetal
resin, polycarbonate resin, polysulfone resin, or ethylene
tetrafluoride, acrylonitrile-styrene resin,
acrylonitrile-butadiene-styrene resin, for example. Of these, PET
is particularly preferred.
[0111] In the present invention, in a manufacturing apparatus in
which the facing electrode 11 or 5a is arranged above the container
opening taking FIG. 1 or FIG. 3 as an example, or in a
manufacturing apparatus in which a so-called internal electrode is
arranged by arranging the facing electrode 5c inside the container
taking FIG. 4 as an example, exhaust conductance adjustment means
50 are preferably provided to carry out adjustment by restricting
the amount of gas exhaust that is exhausted from a horizontal cross
section of the pressure-reducing chamber 6 above the opening 10 of
the plastic container 7 as shown in FIG. 9, for example.
[0112] In order to describe the exhaust conductance adjustment
means 50 in detail, a description will be given using FIG. 10. FIG.
10(a) is a schematic drawing showing one embodiment of the exhaust
conductance adjustment means 50 in a cross section taken in the
plane formed by the axial direction of the source gas inlet pipe 9
and the insertion direction of a restrictor 51 of the exhaust
conductance adjustment means 50. FIG. 10(b) is a cross-sectional
schematic drawing taken along X-X in FIG. 9, and is the case where
the restrictor 51 is open. FIG. 10(c) is a cross-sectional
schematic drawing taken along X-X in FIG. 9, and is the case where
the restrictor 51 is closed. Further, the object shown by the
symbol 52 in FIG. 10 is a horizontal cross section of the
pressure-reducing space inside the pressure-reducing chamber above
the container opening, and is a through hole of the
pressure-reducing chamber that allows exhaust gas to flow. At this
time, in order to adjust the flow of gas exhausted from the
container, the exhaust conductance adjustment means 50 is provided
above the container opening.
[0113] The exhaust conductance adjustment means 50 (a special gate
valve) is formed from the restrictor 51 and a restrictor
opening/closing mechanism 53 which opens and closes the restrictor
51. The restrictor 51 is instantly moved toward the source gas
inlet pipe by the restrictor opening/closing mechanism 53 to cover
the through hole 52 of the pressure-reducing chamber. FIG. 10(c)
shows the case where the restrictor 51 is moved completely to the
end. In this way, it becomes possible to adjust the amount of
exhaust gas exhausted from the container. Further, in the exhaust
conductance adjustment means 50 shown in FIG. 10, an insertion
guide 53 for the source gas inlet pipe 9 is cut into the restrictor
51, and due to the existence of the insertion guide 53, the through
hole 52 of the pressure-reducing chamber is not completely covered
even when the restrictor 51 is restricted as in FIG. 10(c).
Accordingly, the exhaust conductance adjustment means 50 shown in
FIG. 10 does not completely shut off the flow of gas exhausted from
the container.
[0114] Instead of the embodiment shown in FIG. 10, the exhaust
conductance adjustment means 50 may be constructed to open and
close the through hole 52 by moving two restrictors having the same
shape as the restrictor 51 of FIG. 10 toward each other in a
symmetrical arrangement with respect to the source gas inlet pipe.
When this structure is formed, because the insertion guide
described above is mutually covered by the two restrictors, it
becomes possible to almost completely shut off the flow of gas
exhausted from the container.
[0115] Further, the shut off degree of the flow of gas exhausted
from the container may be adjusted by a restricting mechanism that
is the same as a light quantity restricting mechanism of a camera
in which the source gas inlet pipe forms a centripetal axis for the
purpose of opening and closing the through hole 52 of the
pressure-reducing chamber.
[0116] The above-mentioned three embodiments of the exhaust
conductance adjustment means 50 were described, but other
embodiments of a restrictor may be formed for the purpose of
opening and closing the through hole 52 of the pressure-reducing
chamber.
[0117] It becomes possible to adjust the flow of gas exhausted from
the container over a wide range by operating the separate opening
and closing of the exhaust conductance adjustment means 50, or
operating the opening and closing of the vacuum valve 19, or
operating the opening and closing of the exhaust conductance
adjustment means 50 and the vacuum valve 19 by the exhaust
conductance adjustment means 50 provided above the container
opening.
[0118] In the present embodiment, an apparatus of the type in which
the opening of the container faces upward is shown, but it is also
possible to form a pressure-reducing chamber in which the top and
bottom are reversed.
[0119] Further, in the present embodiment, a DLC film is the thin
film formed by the manufacturing apparatus, but it is also possible
to use the film forming apparatus described above when forming a
Si-containing DLC film or other thin film.
[0120] Next, with reference to FIG. 1, a description will be given
for a process in the case where a DLC film is formed on the inner
wall surface of the plastic container 7 using the present
apparatus.
[0121] (Manufacturing Method 1)
[0122] (Loading Container in Manufacturing Apparatus)
[0123] First, a vent (not shown in the drawings) is opened, and the
inside of the pressure-reducing chamber 6 is opened to the
atmosphere. In this way, air enters the space 40 and the space
inside the plastic container 7, and the inside of the
pressure-reducing chamber 6 reaches atmospheric pressure. Next, the
lower electrode 2 of the container side electrode 3 is removed from
the upper electrode 1, and the plastic container 7 is set so that
the bottom portion thereof makes contact with the top surface of
the lower electrode 2. A PET bottle is used as the plastic
container 7, for example. Then, by raising the lower electrode 2,
the plastic container 7 is housed in the pressure-reducing chamber
6. At this time, the source gas inlet pipe 9 provided in the
pressure-reducing chamber 6 is passed through the opening 10 of the
plastic container 7 and inserted inside the plastic container 7,
and the facing electrode 5 is arranged above the opening of the
container. Further, the container side electrode 3 is sealed by the
O-ring 8.
[0124] (Operation to Reduce Pressure in Pressure-Reducing
Chamber)
[0125] When the lower electrode 2 is raised to a prescribed
position and the pressure-reducing chamber 6 is sealed, a state is
formed in which the periphery of the plastic container 7 makes
contact with the inner surface of the lower electrode 2 and the
upper electrode 1. Next, after closing the vent, the exhaust means
21 is operated to exhaust the air inside the pressure-reducing
chamber 6 through the exhaust port 23. Then, the pressure inside
the pressure-reducing chamber 6 is reduced until a required vacuum
level of 4 Pa, for example, is reached. This is because there will
be too many impurities inside the container when the vacuum level
is allowed to exceed 4 Pa.
[0126] (Introduction of Source Gas)
[0127] Then, the source gas (e.g., a carbon source gas such as an
aliphatic hydrocarbon, an aromatic hydrocarbon or the like) sent
from the source gas supply means 18 which controls the flow rate is
introduced inside the plastic container 7 from the blowout hole 9a
of the source gas inlet pipe 9. The source gas supply rate is
preferably 20.about.50 ml/min. The concentration of the source gas
becomes fixed, and a prescribed film forming pressure is stabilized
at 7.about.22 Pa, for example, by balancing the controlled gas flow
rate and the exhaust capacity.
[0128] (Plasma Film Formation)
[0129] By operating the high frequency power source 13, a high
frequency voltage is applied between the facing electrode 5 and the
container side electrode 3 via the matching unit 12, and source gas
type plasma is generated inside the plastic container 7. At this
time, the matching unit 12 matches the impedance of the container
side electrode 3 and the facing electrode 5 by the inductance L and
the capacitance C. In this way, a DLC film is formed on the inner
wall surface of the plastic container 7. Further, the output (e.g.,
13.56 MHz) of the high frequency power source 13 is approximately
200.about.500 W.
[0130] Namely, the formation of a DLC film on the inner wall
surface of the plastic container 7 is carried out by a plasma CVD
method. Namely, as described above, a self bias voltage is applied
to the container wall surface, and the ions of the source gas
converted to plasma are accelerated in accordance with the strength
of the self bias voltage and spattered on the container inner wall
surface, whereby a DLC film is formed. By carrying out a CVD
process, a very fine DLC film is formed on the inner wall surface
of the plastic container 7. By applying a moderate high frequency
output, plasma discharge is continued between the container side
electrode 3 and the facing electrode 5. The film formation time is
several seconds which is short.
[0131] At this time, by providing a neck portion offset like that
in the apparatus of FIG. 1 or FIG. 3, the self bias voltage of the
neck portion is lowered moderately, and degradation of the film
quality of the DLC film due to plasma damage or plasma etching
caused by a concentration of plasma density at the neck portion is
mitigated.
[0132] Further, after the concentration of source gas becomes fixed
and stabilization at a prescribed film formation pressure is
achieved by balancing the controlled gas flow rate and the exhaust
capacity, the source gas inlet pipe may be removed from the plastic
container before plasma generation by operating the source gas
inlet pipe insertion/removal means, and then source gas type plasma
may be generated inside the plastic container 7 by applying a high
frequency voltage between the facing electrode 5 and the container
side electrode 3 via the matching unit 12 by operating the high
frequency power source 13. At this time, because the source gas
inlet pipe is not inside the plastic container during plasma
discharge, it is possible to almost completely suppress the
adherence of dust.
[0133] (Termination of Film Formation)
[0134] The RF output from the high frequency power source 13 is
stopped, and the supply of source gas is stopped. Then, the
hydrocarbon gas inside the pressure-reducing chamber 6 is exhausted
by the exhaust pump 20. Then, the vacuum valve 19 is closed, and
the exhaust pump 20 is stopped. Then, the vent (not shown in the
drawings) is opened to open the inside of the pressure-reducing
chamber 6 to the atmosphere, and by repeating the above-described
film formation method, a DLC film is formed on the inside of the
next plastic container. The film thickness of the DLC film is
formed to be 10.about.80 nm.
[0135] The plastic container manufactured in this way had an oxygen
permeability the same as or lower than the carbon film coated
plastic container mentioned in Japanese Laid-Open Patent
Application No. HEI 8-53117. In the case where a 30 nm (average for
the entire container) DLC film was formed on a plastic container
having a capacity of 500 ml, a container height of 200 mm, a
container body portion diameter of 71.5 mm, a mouth portion opening
inner diameter of 21.74 mm, a mouth portion opening outer diameter
of 24.94 mm, a container body portion thickness of 0.3 mm, and a
resin weight of 32 g/container, the oxygen permeability was 0.0040
ml/container (500 ml PET container)/day (23.degree. C. and RH90%,
measurement values after 20 hours from the start of nitrogen gas
replacement).
[0136] In the present embodiment, a PET bottle for beverages was
used as the container having a thin film formed on the inside, but
it is also possible to use containers used for other uses.
[0137] (Manufacturing Method 2)
[0138] With reference to FIG. 9, a description will be given for a
film formation method that roughly fixes the gas pressure inside
the container and suppresses the rise of plasma density at the neck
portion by adjusting the exhaust of source gas inside the plastic
container at the time of film formation. The special feature of
this manufacturing method is the structure in which the space of
the container side electrode has a shape similar to the outer wall
of the container, namely, it is a manufacturing method which can
eliminate coloration of the container neck portion while having an
oxygen barrier property even when coating is carried out using an
apparatus in which the mouth portion offset length d3, the neck
portion offset length d2 and the body portion offset length d1 are
roughly the same.
[0139] The process of loading the container in the manufacturing
apparatus is the same as the process described in Manufacturing
Method 1 (loading a container in the manufacturing apparatus).
[0140] (Operation to Reduce Pressure in Pressure-Reducing
Chamber)
[0141] The process of reducing the pressure in the
pressure-reducing chamber is the same as the process described in
Manufacturing Method 1 (operation to reduce pressure in the
pressure-reducing chamber).
[0142] (Introduction of Source Gas)
[0143] Then, while continuing to exhaust the inside of the
pressure-reducing chamber 6, namely, the inside of the plastic
container, the source gas (e.g., a carbon source gas such as an
aliphatic hydrocarbon, an aromatic hydrocarbon or the like) sent
from the source gas supply means 18 which controls the flow rate is
introduced inside the plastic container 7 from the blowout hole 9a
of the source gas inlet pipe 9. At this time, the introduction rate
of the source gas is 20.about.50 ml/min, for example. Then, the
inside of the plastic container 7 is replaced by the source gas and
the source gas concentration becomes fixed, and a prescribed film
forming pressure is stabilized at 7.about.22 Pa, for example, by
balancing the controlled gas flow rate through the inside of the
plastic container 7 and the exhaust capacity.
[0144] Then, the exhaust of the inside of the plastic container 7
is almost completely stopped. The stopping of the exhaust is
carried out by shutting the vacuum valve 19 of FIG. 9 or
restricting the restrictor 51 of the exhaust conductance means 50
shown in FIG. 9 and FIG. 10 to the closed position. At the same
time the exhaust is stopped, the introduction rate of the source
gas is made smaller than the introduction rate at the time of
replacement by the mass flow controller (not shown in the drawings)
of the source gas supply means. At this time, the introduction rate
of the source gas is 5.about.20 ml/min, for example. By carrying
out this operation, the flow of source gas inside the plastic
container 7 is slowed, and the pressure distribution inside the
container is made roughly uniform.
[0145] (Plasma Film Formation)
[0146] After the source gas and the source gas pressure inside the
plastic container form the state described above, a DLC film is
formed on the inner wall surface of the plastic container 7 by
carrying out the operations described in Manufacturing Method 1
(plasma film formation). Further, the output (e.g., 13.56 MHz) of
the high frequency power source 13 is approximately 200.about.500
W.
[0147] The film thickness of the DLC film is formed to be
10.about.80 nm.
[0148] As described above, after the flow of source gas inside the
plastic container 7 is slowed and at the same time the pressure
distribution inside the container is made roughly uniform, the flow
of source gas inside the container is made smaller by the
generation of plasma. In this way, there is almost no constriction
of source gas accompanying the sudden decrease of cross-sectional
area of a horizontal cross section of the container vertical axis
at the container shoulder portion, the pressure distribution inside
the container is uniform, and there is no increase of plasma
density at specific parts. In this way, it is possible to prevent
the DLC film at specific parts from receiving plasma damage or
plasma etching. The DLC film coated plastic container does not have
coloration at the shoulder portion, and is almost transparent with
a uniform color.
[0149] (Termination of Film Formation)
[0150] A process for terminating the film formation is carried out
by carrying out the operations described in Manufacturing Method 1
(termination of film formation).
[0151] A plastic container having a capacity of 500 ml, a container
height of 200 mm, a container body portion diameter of 71.5 mm, a
mouth portion opening inner diameter of 21.74 mm, a mouth portion
opening outer diameter of 24.94 mm, a container body portion
thickness of 0.3 mm, and a resin weight of 32 g/container was used
as the plastic container. The film thickness of the DLC film in
this case was 25 nm (average for the entire container).
[0152] (Manufacturing Method 3)
[0153] With reference to FIG. 9, a description will be given for
another embodiment of a film formation method that roughly fixes
the gas pressure inside the container and suppresses the rise of
plasma density at the neck portion by adjusting the exhaust of
source gas inside the plastic container 7 at the time of film
formation. The special feature of this manufacturing method is that
it is a manufacturing method which can eliminate coloration of the
container neck portion while having an oxygen barrier property even
when coating is carried out using an apparatus in which the space
of the container side electrode has a shape similar to the outer
wall of the container.
[0154] The process of loading the container in the manufacturing
apparatus is the same as the process described in Manufacturing
Method 1 (loading a container in the manufacturing apparatus).
[0155] (Operation to Reduce Pressure in Pressure-Reducing
Chamber)
[0156] The process of reducing the pressure in the
pressure-reducing chamber is the same as the process described in
Manufacturing Method 1 (operation to reduce pressure in the
pressure-reducing chamber).
[0157] (Introduction of Source Gas)
[0158] Then, the exhaust rate inside the plastic container 7 is
made smaller or made zero. The adjustment of exhaust is an
adjustment of the vacuum valve 19 of FIG. 9 or an adjustment
carried out by restricting the restrictor 51 of the exhaust
conductance means 50 shown in FIG. 9 and FIG. 10 to the closed
position. Together with this operation, the source gas (e.g., a
carbon source gas such as an aliphatic hydrocarbon, an aromatic
hydrocarbon or the like) sent from the source gas supply means 18
which controls the flow rate is introduced inside the plastic
container 7 from the blowout hole 9a of the source gas inlet pipe
9. At this time, the introduction rate of the source gas is
5.about.40 ml/min, for example.
[0159] (Plasma Film Formation)
[0160] Then, at the point in time when the pressure distribution
inside the plastic container 7 is roughly uniform and a prescribed
pressure is reached, a DLC film is formed on the inner wall surface
of the plastic container 7 by carrying out the operations described
in Manufacturing Method 1 (plasma film formation). Further, the
output (e.g., 13.56 MHz) of the high frequency power source 13 is
approximately 200.about.500 W, and the prescribed pressure inside
the container is approximately 10.about.50 Pa.
[0161] The film thickness of the DLC film is formed to be
10.about.80 nm.
[0162] In this way, by adjusting the exhaust, after the flow of
source gas inside the plastic container 7 is slowed and at the same
time the pressure distribution inside the container is made roughly
uniform, it is possible to obtain results that are the same as
those of Manufacturing Method 2, namely, it is possible to prevent
rises in plasma density at specific parts by the generation of
plasma. The DLC film coated plastic container does not have
coloration at the shoulder portion, and is almost transparent with
a uniform color.
[0163] (Termination of Film Formation)
[0164] A process for terminating the film formation is carried out
by carrying out the operations described in Manufacturing Method 1
(termination of film formation).
[0165] A plastic container having a capacity of 500 ml, a container
height of 200 mm, a container body portion diameter of 71.5 mm, a
mouth portion opening inner diameter of 21.74 mm, a mouth portion
opening outer diameter of 24.94 mm, a container body portion
thickness of 0.3 mm, and a resin weight of 32 g/container was used
as the plastic container. The film thickness of the DLC film in
this case was 25 nm (average for the entire container).
[0166] In Manufacturing Method 2 or Manufacturing Method 3, the
manufacturing apparatus of FIG. 9 in which the facing electrode is
provided outside the container was described as an example, but a
manufacturing apparatus in which the internal electrode 5c is
arranged inside the container as a facing electrode like the
manufacturing apparatus of FIG. 4 may be used, or a manufacturing
apparatus in which exhaust conductance means (the same as the
exhaust conductance means 50 of FIG. 9) are provided in the
apparatus of FIG. 4 may be used.
[0167] In Manufacturing Method 2 or Manufacturing Method 3, a
manufacturing apparatus in which the container side electrode is a
similar shaped electrode like that shown in FIG. 24 may be used. A
manufacturing apparatus in which exhaust conductance means (the
same as the exhaust conductance means 50 of FIG. 9) are provided in
the apparatus of FIG. 24 may be used.
[0168] Further, in Manufacturing Method 2 or Manufacturing Method
3, the processes up to the point before plasma generation are
carried out while the source gas inlet pipe is in an inserted state
in the plastic container, and then after the source gas inlet pipe
is removed from the plastic container by operating the source gas
inlet pipe insertion/removal means directly before plasma
generation, source gas type plasma may be generated inside the
plastic container 7 by applying a high frequency voltage between
the facing electrode 5 and the container side electrode 3 via the
matching unit 12 by operating the high frequency power source 13.
At this time, because the source gas inlet pipe is not inside the
plastic container during plasma discharge, it is possible to almost
completely suppress the adherence of dust.
Specific Embodiments
Examination of Optimum Offset Length
[0169] A PET bottle having an axial symmetrical shape with respect
to the central axis of the vertical direction of the container was
used as the plastic container. The plastic container used in the
present embodiments is a PET container having a capacity of 500 ml,
a container height of 200 mm, a container body portion diameter of
71.5 mm, a mouth portion opening inner diameter of 21.74 mm and
outer diameter of 24.94 mm, a container body portion thickness of
0.3 mm, and a resin weight of 32 g/container of polyethylene
terephthalate resin (PET resin RT553 manufactured by Nihon Yunipet
(Inc.)).
[0170] The apparatus used in the present embodiments is the
apparatus shown in FIG. 3 or FIG. 4. FIG. 3 shows a manufacturing
apparatus in the case where a tube made of fluororesin is used as
the source gas inlet pipe in an apparatus in which a mouth side
electrode 5a is arranged outside the container. FIG. 4 shows a
manufacturing apparatus in the case where SUS is used for the
internal electrode 5c which also functions as a gas inlet pipe. A
plurality of cone compound electrode type container side electrodes
is prepared for examination by changing the standards of the offset
lengths. The offset lengths of the electrodes are shown in Table 1
and Table 2. Further, because the electrode is a cone compound
electrode, the average opening offset length d3, the average neck
portion offset length d2 and the average body portion offset length
d1 are listed respectively as the opening offset length d3, the
neck portion offset length d2 and the body portion offset length
d1. Because a container manufactured using the apparatus of either
FIG. 3 or FIG. 4 will obtain roughly the same results under the
same conditions, the coatings of specific embodiments 1.about.16
were carried out by establishing the conditions of Table 1 and
Table 2 in the apparatus of FIG. 3. The coatings were carried out
in accordance with Manufacturing Method 1.
[0171] A DLC film was coated by an apparatus (not shown in the
drawings) provided with a cylindrical electrode as Comparative
Example 1, and by an apparatus provided with a similar shaped
electrode in which the container outer wall and the inner wall of
the space of the container side electrode are almost touching as
Comparative Example 2. The coatings were carried out in accordance
with Manufacturing Method 1. The conditions of the apparatus are
shown in FIG. 3.
TABLE-US-00001 TABLE 1 Cone Compound Electrode Type Specific
Specific Specific Specific Specific Specific Specific Specific
Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Offset 1 2 3 4 5 6 7 8 Length type 1 type 2
type 3 type 4 type 5 type 6 type 7 type 8 Opening 2.0 5.0 8.0 12.0
8.0 2.0 2.0 2.0 offset length (d3)mm Neck 6.2 8.5 10.5 13.4 10.0
6.4 6.2 6.2 portion offset length (d2)mm Body 3.75 3.75 3.75 3.75
0.75 0.75 0.75 3.75 portion offset length (d1)mm Material Al Al Al
Al Al Al Al Al
TABLE-US-00002 TABLE 2 Cone Compound Electrode Type Specific
Specific Specific Specific Specific Specific Specific Specific
Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment
Embodiment Embodiment Offset 9 10 11 12 13 14 15 16 Length type 9
type 10 type 12 type 13 type 14 type 15 type 16 type 17 Opening 2.0
2.0 2.0 2.0 2.0 5.0 8.0 12.0 offset length (d3)mm Neck 6.2 6.2 7.1
6.8 6.2 8.5 10.5 13.4 portion offset length (d2)mm Body 1.75 2.75
2.75 1.75 2.75 2.75 2.75 2.75 portion offset length (d1)mm Material
Al Al Al Al Al Al Al Al
TABLE-US-00003 TABLE 3 Cylindrical Similar Shaped Electrode
Electrode Comparative Comparative Offset Length Example 1 Example 2
Opening offset length (d3) 2.0 1.5 mm Neck portion offset length
15.8 1.0 (d2)mm Body portion offset length 1.0 1.0 (d1)mm Material
Al Al
[0172] Eight standards of the neck portion offset are prepared from
6.2 mm to 13.4 mm, and four standards of the body portion offset
are prepared. The electrodes formed with these standard offset
lengths were assembled to form container side electrodes. Further,
in the present embodiments, Al is used as the material of the
electrodes, but it is clear that the same electrode improvement
results can be obtained using SUS or another metal.
[0173] The method of evaluating the DLC film is as follows. The
oxygen permeability of the container was measured under the
conditions 23.degree. C. and 90% RH using an Oxtran 2/20
manufactured by Modern Control Company, and measurement values were
recorded after 20 hours from the start of nitrogen gas
replacement.
[0174] The film thickness of the DLC film was measured using a
DEKTAK 3 made by Veeco Company.
[0175] The evaluation of the color of the plastic container is
indicated by the coloration degree b* value. The b* value is the
color difference of JISK 7105-1981, and is calculated by Equation 6
from the tristimulus values X, Y and Z.
b*=200[(Y/Y.sub.0).sup.1/3-(Z/Z.sub.0).sup.1/3] (Equation 6)
[0176] A U-3500 Model automatic recording spectrophotometer
manufactured by Hitachi provided with a 600 integrating sphere
attached apparatus (for infrared near visible infrared)
manufactured by the same company was used. An ultrahigh sensitivity
photomultiplier (R928: for visible ultraviolet) and a cooling type
PbS (for the near infrared region) were used. As for the
measurement wavelengths, the transmittance was measured in the
range from 240 nm to 840 nm. By measuring the transmittance of the
PET container, it is possible to calculate the transmittance
measurement of only the DLC film, but the b* value of the present
embodiments as is shows a calculation in a form that includes the
absorptance of the PET container. The correlation with b* in the
present invention that depends on a visual observation is
approximately as shown in Table 4. The b* value of an unprocessed
PET container is within the range 0.6.about.1.0. Further, when the
b* value is 2 or less, the container can be said to be colorless
and transparent. The approximate correlation with the b* value
difference (.DELTA.b* value) that depends on the visual observation
is shown in Table 5. In order to satisfy the recycle standard, it
has been determined that b* should be 6 or less, and preferably 5
or less.
TABLE-US-00004 TABLE 4 b* Value 0-2 2-4 4-6 6-8 8- Expression
Colorless Very light Light Slightly Dark by Visual yellowish
yellowish yellowish yellowish Observation brown brown brown brown
color color color color
TABLE-US-00005 TABLE 5 .DELTA.b* Value 0-1 1-1.5 1.5-3 3-6 6-12
Expression Almost Very little Small Different Very by Visual No
difference defference different Observation difference
[0177] In the present embodiments, the film forming conditions of
the DLC film were set in accordance with Manufacturing Method 1. At
this time, except when specifically stated otherwise, the high
frequency power source output was 400 W, the flow rate of acetylene
which was the source gas was 40 ml/min, and the film forming time
was set at 2 seconds. The film thickness of the DLC film was
approximately 30 nm (average for the entire container).
[0178] By assembling the 16 types shown in Table 1 and Table 2, a
film was formed under the conditions described above. The body
portion offset length dependence of the oxygen permeability that
depends on the difference in electrode structure is shown in FIG.
13, the neck portion offset length dependence of the oxygen
permeability that depends on the difference in electrode structure
is shown in FIG. 14, the body portion offset length dependence of
the b* value that depends on the difference in electrode structure
is shown in FIG. 15, and the neck portion offset length dependence
of the b* value that depends on the difference in electrode
structure is shown in FIG. 16.
[0179] (Oxygen Barrier Property of Container)
[0180] With reference to FIG. 13, under the same film forming
conditions, the oxygen permeability becomes higher (the oxygen
barrier property becomes lower) as the body portion offset length
becomes shorter. This is due to an increase in plasma damage caused
by stronger ionic collisions due to the fact that the plasma
density distribution that concentrates at the neck portion
increases the plasma damage due to the working of the small
distribution at the body portion side and makes the sheath
potential become large and deep. However, a prescribed oxygen
barrier property was satisfied. The container manufactured by the
cylindrical electrode of Comparative Example 1 had a low oxygen
barrier property compared with the containers manufactured by the
present invention. With regard to the neck portion offset length
dependence, with reference to FIG. 14, under the same film forming
conditions, the oxygen barrier property becomes lower as the body
portion offset length becomes shorter. However, for all the body
portion offset lengths, the oxygen barrier property of the entire
container satisfied a prescribed standard for neck portion offset
lengths up to 13.4 mm. In the case of the cylindrical electrode of
Comparative Example 1, the barrier property was low, and the
prescribed standard was not satisfied. Further, from the results of
Raman analysis, it was understood that the DLC film of the neck
portion of Comparative Example 1 was a sparse film having few
diamond structures, and the DLC film of the neck portion of
Specific Embodiment 1 was a fine film that included a relatively
large number of diamond structures. Accordingly, in order to form a
fine DLC film, the neck portion offset length needs to be adjusted
to an optimum length to change the self bias and form an optimum
sheath potential. To summarize the above, ranges in which the body
portion offset length is 5.75 mm or less and the neck portion
offset length is 13.4 mm or less are obtained from the oxygen
permeability.
[0181] (Coloration of Container)
[0182] On the one hand, with regard to the color degree b* value of
the film, with reference to the body portion offset length
dependence of FIG. 15, except for one portion of data, there is a
tendency for the b* value to increase as the body portion offset
length increases. From this fact, at the least the body portion
offset length needs to be 4 mm or less. The reason for this
dependency is that because the effective potential applied to the
body portion of the container and the facing electrode is lowered
when the body portion offset length is increased, the plasma
distribution undergoes further movement to the neck portion from
the body portion, and because the plasma distribution becomes more
concentrated at the neck portion, it is assumed that the conditions
approach the conditions of the prior art technology, whereby the
color of the film becomes dark. Further, when the data of the neck
portion offset length dependency of FIG. 16 is examined, the color
degree b* value becomes larger as the neck portion offset length is
reduced in the range where the neck portion offset length is short.
This is because plasma concentration at the neck portion becomes
more remarkable as the electrode structure approaches Comparative
Example 2. On the other hand, when the neck portion offset length
at the place where the b* value shows a minimum value is exceeded,
the b* value increases, and before long shows a tendency to become
saturated. This is assumed to be caused by degradation of the film
quality (bonding structure and the like) due to the lowering of the
self bias which makes the ionic collisions at the time of film
formation become smaller when the effective voltage applied to the
container and the facing electrode is reduced accompanying the
increase of the neck portion offset length.
[0183] (Examination of Relationship between Oxygen Barrier Property
of Container and Coloration of Neck Portion)
[0184] From the data of the oxygen barrier property and the
coloration given above, the range of the body portion offset length
and the neck portion offset length forms the range (blackened
portion) shown in FIG. 17. Namely, when the body portion offset
length is less than or equal to 4 mm from the color data, the neck
portion offset length changes depending on the body portion offset
length. For example, in the case where the body portion offset
length is 0.2 mm, the neck portion offset length is greater than or
equal to 8.0 mm and less than or equal to 13.4 mm, and in the case
where the body portion offset length is 4.0 mm, the neck portion
offset length becomes 5.9 mm.
[0185] In order to represent this mathematically, an offset
coefficient K is introduced. In the case of the containers of the
present embodiments, the correlation between the neck portion
offset length and the body portion offset length can be prescribed
by the equation given below.
d2=K.times.(D1-D2)/2+d1 (Equation 1)
[0186] When K is zero, this represents the cylindrical electrode of
Comparative Example 1, and when K is 1, this represents the similar
electrode of Comparative Example 2. By introducing this kind of
offset coefficient K, it is possible to obtain the electrode design
value of the present invention.
[0187] The offset coefficient from FIG. 17 and Equation 1 is as
follows.
0.29.ltoreq.K.ltoreq.0.79 where 0.2 mm.ltoreq.d1.ltoreq.2.0 mm
(Equation 2)
0.11.ltoreq.K.ltoreq.0.51 where 2.0 mm<d1.ltoreq.4.0 mm
(Equation 3)
[0188] (Introduction of Container Compensation Coefficient
.alpha.)
[0189] The present invention can be applied even in the case of a
container in which the body portion and the neck portion have
different dimensions. With regard to the shape of the container, in
order to show that the present invention can be applied to other
shapes, the constant .alpha. is introduced to give container
dependence to Equation 1. In view of the change in plasma density
that depends on the change in size of the neck portion, the degree
of plasma concentration at the neck portion is represented by the
ratio of the body portion average cross-sectional area and the neck
portion average cross-sectional area of the container.
.alpha.=(D1/D2).sup.2/3.54 (Equation 5)
[0190] By introducing this equation in Equation 1, the following is
obtained.
d2=.alpha.K.times.(D1-D2)/2+d1 (Equation 4)
[0191] In the present embodiments, (D1/D2).sup.2=3.54, and because
this gives .alpha.=1, Equation 4 becomes the same equation as
Equation 1.
[0192] (Comparison of Prior Art DLC Film Having Large b* Value and
DLC Film Having Small b* Value Obtained by Apparatus of Present
Invention)
[0193] The DLC film of the shoulder portion obtained by the
manufacturing apparatus of the present invention has a small b*
value compared with the DLC film of the shoulder portion obtained
by a prior art manufacturing apparatus in which the inner wall of
the space of the container side electrode housing the container has
a similar shape, and there is clearly a difference even when a
comparison is carried out by visual observation. In order to show
this comparison, FIG. 18 shows a picture in which both containers
are compared. Further, the case of the manufacturing apparatus of
the present invention is mentioned as present invention, and the
case of the manufacturing apparatus having a similar shaped
electrode is mentioned as prior art technology. In the container of
the present invention, the body portion and the neck portion appear
to have roughly the same color, there is little irregular color,
and such color is light. On the other hand, in the container of the
prior art technology, the color of the neck portion is darker than
the color of the body portion, and there is irregular color.
[0194] It became clear that the light color of the DLC film formed
on the neck portion of the present invention is not due a thin film
thickness. The correlation of the film thickness and the b* values
is shown in FIG. 19. Places having a dark color formed the
measurement places. The container of the present invention was
shown to have small b* values regardless of the film thickness. In
this regard, FIG. 20 shows the optical transmittance property at
the same portions. The data of the graph is the optical
transmittance property of only the DLC film in which the effects of
the PET base material were eliminated. It was understood that the
container of the present invention has a slightly higher optical
transmittance property than the container of Comparative Example 1.
Further, in contrast with the container of the present invention
which has a prescribed oxygen barrier property, the container of
Comparative Example 1 did not achieve the prescribed oxygen barrier
property. From the results of Raman analysis, it was understood
that the film quality is degraded (the proportion of diamond
bonding is very small).
[0195] Further, a comparison of the Raman spectrums of the
container of the present invention and the container of Comparative
Example 2 (prior art technology) is shown in FIG. 21, and enlarged
views of the DLC related portions after the effects due to
fluorescence were eliminated are shown in FIG. 22. As for the Raman
spectrum, a Super Labram manufactured by Jobin Yvon Company was
used.
[0196] FIG. 21 shows the Raman scattering spectrums (in which the
peak of the PET base is subtracted) of Specific Embodiment 1 and
Comparative Example 2. The writing of DLC in the graph represents a
graphite structure peak. Because there is almost no observation of
a diamond structure peak by Raman, a form in which evaluation is
indirectly carried out from the intensity of the graphite band or
the like is formed. From the spectrum of Specific Embodiment 1 of
the present invention, it is understood that Comparative Example 2
is the one in which the graphite peak intensity is large and the
graphite mixing proportion or the proportion of carbon (hereafter
written as C) double bonds is large. This is assumed to form the
cause of coloration.
[0197] FIG. 22 shows enlarged views of the spectrums. As for the
graphite band, the G band and the D band are observed, and the D
band of the lower wave number side is a band that signifies
Disorder and reveals the graphite crystal property will be
destroyed. The appearance of the D band is believed to correspond
to the fact that DLC exists in the film and the graphite crystal
property is being destroyed. In the DLC film, there exists a mixing
of sp.sup.2 structures and sp.sup.3 structures. The D band
described above does not appear in the composition region where the
proportion of DLC is very small in contrast with the graphite
described above, and conversely when the proportion of DLC
increases, there is a tendency for the intensity to be reduced
again accompanying the increase in the abundance ratio of sp.sup.3
structures (diamond bonding and C--H bonding) in the DLC film. In
the regions of Specific Embodiment 1 and Comparative Example 2, the
intensity of the D band is weak, but the proportion of sp.sup.3
structures is high, and this represents a high proportion of
diamond bonding and C--H bonding. In the enlarged views, the
graphite bands (G band and D band) appear even in the present
embodiments, but from an intensity comparison of the vertical axis,
and from the fact that noise is included in the shape of the
spectrum and the fact that both the G band and the D band are weak,
it is understood that the graphite mixing proportion is low and the
ratio of sp.sup.3 bonding is high.
[0198] Conversely, in Comparative Example 2, it is understood that
the peak intensity of the G band is 5.3 times higher compared to
the DLC film of Specific Embodiment 1, and the graphite mixing
proportion is high.
[0199] Accordingly, this increase in the proportion of graphite
mixing and carbon double bonds is assumed to make the coloration of
the container neck portion darker.
[0200] From the b* value and the results of the Raman spectrums, it
became clear that the DLC film formed on the container neck portion
of the present invention and the DLC film formed on the container
neck portion of the prior art technology are DLC films having
different film qualities (C bonding states and the like). In the
apparatus of the present invention, there are few graphite type
carbon sp.sup.2 bonding structures, and because it is possible to
form a fine DLC film having a high proportion of sp.sup.3 bonding
structures (diamond structures and the like) on the container neck
portion (and body portion), it is possible to manufacture a
container having a light uniform color over the entire container
while securing an oxygen barrier property.
[0201] (Examination of Carbon Atom Content, Hydrogen Atom Content
and Amount of Graphite Type Bonding of Film)
[0202] The carbon atom content and the hydrogen atom content in the
container neck portion of specific embodiments 1, 2, 3 and 5 and
comparative examples 1 and 2 are shown in Table 6. In this regard,
scaling is carried out so that the carbon atom content and the
hydrogen atom content form a total of 100. The measurement device
used a RBS (Rutherford backward scattering analyzer) and a HFS
(hydrogen forward scattering measurement apparatus). The
accelerator was a 5SDH2 manufactured by National Electronics
Corporation, the measurement system was a RBS400 manufactured by
Charls Evans and Associates, and the RBS and the HFS were used
together.
TABLE-US-00006 TABLE 6 Specific Specific Specific Specific
Comparative Comparative Embodiment 1 Embodiment 2 Embodiment 3
Embodiment 5 Example 1 Example 2 Carbon 37 48 39 43 48 55 Content
of Neck portion (atom %) Hydrogen 63 52 61 57 52 45 Content of Neck
portion (atom %)
[0203] The composition proportion of carbon and hydrogen (carbon
atom/hydrogen atom) of the DLC film formed on the neck portion was
37/63.about.48/52. In this regard, there is no difference between
the specific embodiments and the comparative examples with regard
to the body portion carbon content and the body portion hydrogen
content, wherein the body portion carbon content was 55.about.75
atom %, and the body portion hydrogen content was 25.about.45 atom
%. Accordingly, in the present embodiments, it is possible for the
DLC film formed on the neck portion to have higher hydrogen atom
content than the DLC film formed on the body portion.
[0204] Further, in Comparative Example 1, the carbon atom content
and the hydrogen atom content in the container neck portion were
the same as those of Comparative Example 2, but the oxygen barrier
property was low as described above, and a prescribed standard was
not satisfied.
[0205] Next, comparisons of the content of graphite type bonding
(SP.sup.2) in the container neck portion and the container body
portion of specific embodiments 1, 2, 3 and 5 and comparative
examples 1 and 2 are shown in Table 7. The comparisons were carried
out by conversion to the amount of graphite type bonding per each
film thickness. The amount of graphite type bonding was measured
using an ESR (electron spin resonance analyzing apparatus,
JES-FE2XG, manufactured by JEOL).
[0206] As is understood from Table 7, the DLC film formed on the
neck portion has a lower graphite mixing proportion than the DLC
film formed on the body portion. Namely, the graphite mixing
proportion of the DLC film formed on the neck portion is
5.about.18% of the graphite mixing proportion of the body
portion.
[0207] In Comparative Example 2, the amount of graphite type bond
mixing of the neck portion and the body portion are the same level.
Accordingly, there is more coloration of the neck portion as the
thickness of the neck portion becomes larger. In the embodiments,
because the amount of graphite type bond mixing is small, it is
possible to prevent coloration even when the thickness of the neck
portion becomes large.
TABLE-US-00007 TABLE 7 Specific Specific Specific Specific
Comparative Comparative Embodiment 1 Embodiment 2 Embodiment 3
Embodiment 5 Example 1 Example 2 Amount of 0.38 0.31 0.38 0.12 0.14
1.00 Graphite like bonding of Neck portion Film thickness 62.9 62.7
67.2 64.0 47.4 53.0 of Neck portion (nm) A: Amount of 0.0060 0.0049
0.0057 0.0019 0.0030 0.0019 Graphite like bonding/film thickness
Amount of -- -- -- 0.40 -- 0.25 Graphite like bonding of Body
portion Film thickness 12.3 10.9 11.6 11.5 11.8 15.0 of Body
portion (nm) B: Amount of -- -- -- 0.0348 -- 0.0167 Graphite like
bonding/film thickness A/B, where B 17.4 14.2 16.3 5.4 -- -- is
Data of Specific Embodiment 5 A/B, where B -- -- -- -- 8.5 113.2 is
Data of Comparative Example 2
[0208] As described above, in the DLC film coated plastic
containers of the present embodiments, the DLC film formed on the
neck portion has a lower proportion of graphite mixing and a higher
hydrogen atom content than the DLC film formed on the body portion.
Moreover, the oxygen permeability of the container was ensured to
be less than or equal to 0.0050 ml/container (500 ml PET
container)/day (23.degree. C. and RH90%, measurement values after
20 hours from the start of nitrogen gas replacement).
[0209] (Examination of Container Manufactured by Manufacturing
Method 3)
[0210] A PET bottle having an axial symmetrical shape with respect
to the central axis of the vertical direction of the container was
used as the plastic container. The plastic container used in the
present embodiments is a PET container having a capacity of 500 ml,
a container height of 200 mm, a container body portion diameter of
71.5 mm, a mouth portion opening inner diameter of 21.74 mm and
outer diameter of 24.94 mm, a container body portion thickness of
0.3 mm, and a resin weight of 32 g/container of polyethylene
terephthalate resin (RT553, PET resin manufactured by Nihon Yunipet
(Inc.)).
[0211] The apparatus used by the present embodiments is the
apparatus shown in FIG. 24. This is a manufacturing apparatus which
uses a similar shaped electrode. FIG. 24 shows a manufacturing
apparatus in the case where SUS is used as an internal electrode
which also functions as a gas inlet pipe.
[0212] Coating was carried out according to the conditions
described in Manufacturing Method 3. The sequence of Manufacturing
Method 3 is shown in FIG. 23. In FIG. 23(a), the air inside the
container is sufficiently exhausted by the vacuum pump in the state
where a butterfly valve is open 100% to secure a vacuum level of 2
Pa. Next, in FIG. 23(b), the opening of the butterfly valve is made
0% or is made smaller, and source gas is introduced. The inside of
the container is sufficiently filled with source gas, and the
pressure is made uniform at 20.about.50 Pa. Next, in FIG. 23(c), a
high frequency is applied, the source gas is converted to plasma,
and the container inner wall surface is coated with a DLC film.
Next (not shown in the drawing), the supply of source gas is
stopped, the butterfly valve opening is returned to 100%, the
vacuum valve is stopped, and air is introduced inside the
container. This formed Specific Embodiment 17.
[0213] In the container of Specific Embodiment 17 manufactured by
the processes described above, the average thickness (average for
the entire container) of the DLC film was 25 nm, and the b* value
of the container neck portion was 3.8, and this made it possible to
manufacture a container having a light uniform color over the
entire container. Further, the same results were obtained even when
the electrode (an electrode in which the neck portion offset length
is larger than the body portion offset length) of the present
invention shown in FIG. 4 was used.
[0214] Further, using the apparatus of FIG. 4, a container was
manufactured according to Manufacturing Method 2. This forms
Specific Embodiment 18. In the container of Specific Embodiment 18,
it was possible to form a light color DLC film on the container
neck portion in the same way as in Specific Embodiment 17. It was
possible to manufacture a container having a light uniform color
over the entire container while ensuring an oxygen barrier
property. Further, the same results were obtained by the apparatus
shown in FIG. 24.
[0215] A container was manufactured in accordance with
Manufacturing Method 3 using the manufacturing apparatus in the
case where a tube made of fluororesin is used as the source gas
inlet pipe 9 in the apparatus shown in FIG. 3 in which the mouth
side electrode 5 is arranged outside the container. This forms
Specific Embodiment 19. In the container of Specific Embodiment 19,
it was possible to form a light color DLC film on the container
neck portion in the same way as in Specific Embodiment 17. It was
possible to manufacture a container having a light uniform color
over the entire container while ensuring an oxygen barrier
property. Further, the same results were obtained even by the
apparatus in which the container side electrode in the apparatus of
FIG. 3 is formed as a similar shaped electrode.
[0216] A container was manufactured in accordance with
Manufacturing Method 2 using the manufacturing apparatus in the
case where a tube made of fluororesin is used as the source gas
inlet pipe 9 in the apparatus shown in FIG. 3 in which the mouth
side electrode 5 is arranged outside the container. This forms
Specific Embodiment 20. In the container of Specific Embodiment 20,
it was possible to form a light color DLC film on the container
neck portion in the same way as in Specific Embodiment 17. It was
possible to manufacture a container having a light uniform color
over the entire container while ensuring an oxygen barrier
property. Further, the same results were obtained even by the
apparatus in which the container side electrode in the apparatus of
FIG. 3 is formed as a similar shaped electrode.
[0217] A container was coated with a DLC film to form Specific
Embodiment 21 in accordance with the conditions described in
Manufacturing Method 2 by the manufacturing apparatus shown in FIG.
12 in which a so-called similar shaped electrode is arranged.
Further, a container was coated with a DLC film to form Specific
Embodiment 22 in accordance with the conditions described in
Manufacturing Method 3 by the manufacturing apparatus shown in FIG.
12 in which a so-called similar shaped electrode is arranged. In
the container of either Specific Embodiment 21 or Specific
Embodiment 22, it was possible to form a light color DLC film on
the container neck portion in the same way as in Specific
Embodiment 17. It was possible to manufacture a container having a
light uniform color over the entire container while ensuring an
oxygen barrier property. Further, the same results were obtained by
the apparatus shown in FIG. 1.
[0218] A container was coated with a DLC film to form Comparative
Example 3 in accordance with the conditions described in
Manufacturing Method 1 by the manufacturing apparatus shown in FIG.
12 in which a so-called similar shaped electrode is arranged. The
container of Comparative Example 3 had a film thickness (average
for the entire container) of 27 nm. The oxygen permeability was
0.0045 ml/container (500 ml PET container)/day (23.degree. C. and
RH90%, measurement values after 20 hours from the start of nitrogen
gas replacement), and the b* value was 9.2. Accordingly, the
container secured an oxygen barrier property but had irregular
color that created coloration in the neck portion.
[0219] When specific embodiments 17.about.22 and Comparative
Example 3 are compared, Manufacturing Method 2 and Manufacturing
Method 3 are manufacturing methods which make it possible to
manufacture a container having a light uniform color over the
entire container while securing an oxygen barrier property by
reducing degradation due to plasma damage or plasma etching of the
DLC film at the neck portion even when applied to either the
apparatus in the present invention or the prior art apparatus in
which a similar shaped electrode is arranged.
* * * * *