Process for the manufacture of deposition films and apparatus therefor

An apparatus for use in a process for the substantially continuous manufacture of a silicon oxide deposition film by evaporating a deposition material composed mainly of a combination of silicon and silicon oxide or silicon oxide alone by heating the material to continuously form a deposition layer composed mainly of silicon oxide and having a thickness of from 100 to 3,000 .ANG. on the surface of a travelling flexible plastic film. The apparatus comprises a vacuum chamber and, within the vacuum chamber, a means to allow a flexible plastic film to travel continuously, a heat evaporation member having a means to hold a shaped deposition material and a means to evaporate the shaped deposition material, the holding means having a supply port for the shaped deposition material, an outlet for evaporation residue and an opening for evaporation of the deposition material, and the means to substantially continuously supply the shaped deposition material being connected to the supply port to the heat evaporation member and to substantially continuously discharge evaporation residue from the heat evaporation member.

FIELD OF THE INVENTION 
This invention relates to a process for the manufacture of a flexible 
plastic film having a deposition layer comprising a silicon oxide as a 
main component, and an apparatus usable therefor. 
PRIOR ARTS OF THE INVENTION 
Japanese Patent Publication No. 12953/1978 proposes a transparent plastic 
film comprising a transparent flexible film and a silicon oxide deposition 
layer formed thereon as one which has high gas barrier properties. And, 
Japanese Patent Publication No. 48511/1976 describes that silicon monoxide 
is usually used as a deposition material to give such a deposition layer, 
that silicon and silicon dioxide are also used depending upon requirement 
for use and these components are in the form of powders, particles or 
rods, that the deposition is carried out in a continuous vacuum 
evaporation coater, and that the heating method in a vacuum evaporation 
coater is preferably a high frequency induction heating method, however, 
the other methods such as resistance heating and electron beam heating may 
be used. 
In general, this continuous vacuum evaporation coater is of a batch type 
which uses, as a heat evaporating portion, a crucible 1 shown in FIG. 1 
and a boat 2 shown in FIG. 2. As described in "Thin Film Handbook" 
(published by OHM-sha in December 1983), there are also other proposals of 
(1) a method which comprises continuously supplying a deposition material, 
which is shaped into small particles having a suitable size, from a hopper 
3 through a shooter 4 to a crucible 1 (FIG. 3), (2) a method which 
comprises continuously supplying an aluminum wire from a supply portion 6 
to a boat 2 (FIG. 4), and (3) a method which comprises placing, below a 
crucible 1, a container 8 containing an replenishing deposition material 7 
and continuously supplying the replenishing material 7 into the crucible 1 
by using a driving shaft 9 (FIG. 5). 
According to the present inventors' study, however, it was found that when 
a combination of silicon and silicon oxide or silicon oxide alone is 
deposited, none of the above deposition methods succeed in continuously 
forming, on a travelling film, a deposition layer free from non-uniformity 
in gas barrier properties, i.e., a deposition layer with stable gas 
barrier properties. That is, the gas permeability of a deposition film so 
obtained varies depending upon courses of time in forming deposition 
layer, and the non-uniformity in its gas barrier properties markedly 
appears, particularly, after retort treatment in the case of use as a food 
packaging material. 
The present inventors assiduously investigated causes for the above 
defects. As a result, it was found that the composition of silicon 
monoxide or a mixture of silicon and silicon dioxide is likely to change 
at the time of depositing it. Namely, although silicon monoxide can be 
obtained by oxidation of silicon, reduction of silicon dioxide or reaction 
between silicon and silicon dioxide, it is very difficult to obtain a 
stoichiometric compound having an SiO compositional ratio of 1:1, and 
there are only obtained compounds represented by formula of SiO.sub.x 
(wherein x represents about 1, generally 0.9 to 1.1). Usually, such 
compounds are called silicon monoxide. That is, commercially available 
"silicon monoxide" consists of Si, SiO, Si.sub.2 O.sub.3, Si.sub.3 O.sub.4 
and SiO.sub.2. Further, so-called silicon monoxide above is a considerably 
unstable, subliming material under deposition conditions exceeding 
1,000.degree. C. For example, it undergoes decomposition into silicon and 
oxygen gas, undergoes oxidation by a very small amount of oxygen, or the 
like. 
Further, another large cause for non-uniformity in the gas barrier 
properties of the deposition film is that easiness of evaporation varies 
among the components of the above mixture. For example, silicon monoxide 
is evaporated at a temperature of 1,000.degree. to 1,100.degree. C., 
whereas silicon dioxide and silicon show difficulty in evaporation under 
the above conditions. 
When a mixture of silicon and silicon dioxide is used as a deposition 
material, silicon monoxide is formed and deposited. However, the 
composition of this formed silicon monoxide is not constant, either, and 
the composition and thickness of deposition layer vary from the beginning 
to the end during the deposition. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a process for the manufacture 
of a deposition film which is free from any change in its gas barrier 
properties caused depending upon the course of times in forming a 
deposition layer on a travelling flexible plastic film from a material of 
a combination of silicon and silicon oxide or silicon oxide alone and 
which exhibits excellent gas barrier properties. 
It is another object of this invention to provide an apparatus capable of 
manufacturing a deposition film which is free from any change in its gas 
barrier properties caused depending upon the course of times in forming a 
deposition layer on a travelling flexible plastic film from a material of 
a combination of silicon and silicon oxide or silicon oxide alone and 
which exhibits excellent gas barrier properties. 
It is still another object of this invention to provide a process for the 
manufacture of a deposition film in which the thickness of the deposition 
layer formed on the flexible plastic film does not change from the 
beginning to the end during the deposition, and an apparatus usable for 
said process. 
It is yet another object of this invention to provide a process for the 
manufacture of a deposition film of which the gas barrier properties are 
scarcely deteriorated even after retort treatment, and an apparatus usable 
for said process. 
This invention provides a process for the manufacture of a deposition film 
which comprises evaporating a deposition material composed mainly of 
silicon and silicon oxide or silicon oxide alone by heating to 
continuously form a deposition layer composed mainly of silicon oxide and 
having a thickness of from 100 to 3,000 .ANG. on the surface of a 
travelling flexible plastic film; wherein a material shaped from the above 
deposition material is evaporated by heating while said material is being 
supplied to a heat evaporating portion substantially continuously, and a 
evaporation residue is discharged from the heat evaporating portion 
substantially continuously. 
This invention provides an apparatus usable in the above process for the 
manufacture of a deposition film, which comprises a vacuum chamber and, 
within the vacuum chamber, means to allow a flexible plastic film to 
travel continuously, a heat evaporation member having means to hold a 
shaped deposition material and means to evaporate the shaped deposition 
material, said holding means having a supply port of said shaped 
deposition material, an outlet of evaporation residue and an opening for 
evaporation of the deposition material, and means to substantially 
continuously supply the shaped deposition material connected to said 
supply port to the heat evaporation member and to substantially 
continuously discharge evaporation residue from the heat evaporation 
member.

DETAILED DESCRIPTION OF THE INVENTION 
The present inventors have made further studies and as a result, found 
that, by evaporating the deposition material under heat such that 
evaporation residue does not remain in the heat evaporating portion, the 
composition and thickness of a deposition layer on a travelling film 
unexpectedly become uniform from the beginning to the end during the 
deposition and the gas barrier properties of the deposition film are 
excellent. Thus, this finding has led to this invention. 
In this invention, no special limitation is imposed on the flexible plastic 
film. Examples of the materials therefor include polyester, polyamide, 
polypropylene, fluorine polymer, polycarbonate, polyimide, polyethylene, 
polyvinyl chloride, saponified ethylene-vinyl acetate copolymer, etc., and 
these materials may be used by applying a silane coupling agent, primer or 
the like on the surface thereof or subjecting these materials to surface 
treatment by corona discharge, low temperature plasma, etc. Plastic films, 
which are monoaxially or biaxially stretched, may also be used. 
In general packaging, the use of a biaxially stretched polypropylene film 
is preferred in terms of gloss and strength. In the field of electronic 
materials, a fluorine polymer film and a polyester film are used. In the 
case where the deposition films are used for food packaging which are 
subjected to a retorting or a sterilizing by boiling, it is desirable to 
use a polyester film or polyamide film of which the surface on the 
deposition side is not subjected to corona discharge treatment, low 
temperature plasma treatment, etc. When the deposition is effected on the 
surfaces of the polyester film and polyamide film which are subjected to 
such surface treatment, the resultant deposition layer is in some cases 
detached at the time of retorting or boiling. The reason therefor is not 
clear. Presumably, however, the hydrophilic nature of the film surface is 
increased by the surface treatment and therefore, the effect of water 
increases at the retorting or boiling time. The thickness of the plastic 
film is preferably 5 to 300 .mu.m in terms of easiness of taking-in and 
prevention of occurrence of stretching, shrivelling, cracking, etc., at 
the time of taking the film in. In addition, it is preferable to use a 
preliminarily dried plastic film in order to enhance the uniformity of the 
thickness of the deposition layer and the adhesion strength between the 
deposition layer and the plastic film. 
The above flexible plastic film is provided, on its one surface or both 
surfaces, with a transparent deposition layer mainly composed of silicon 
oxide and having a thickness of 100 to 3,000 .ANG.. When the thickness of 
the transparent deposition layer is less than 100 .ANG., the gas barrier 
properties of the resulting deposition film are insufficient. When the 
thickness of the transparent deposition layer is more than 3,000 .ANG., 
the resulting deposition layer is likely to undergo cracking. 
The transparent deposition layer is formed on the flexible plastic film by 
supplying a shaped material, which is obtained by shaping material 
containing silicon and silicon oxide or silicon oxide alone to the heat 
evaporating portion continuously and evaporating the material by heating 
in the heat evaporating portion. 
There is used a combination of silicon and silicon oxide or silicon oxide 
alone as the deposition material, and at least one member selected from 
the group consisting of SiO, Si.sub.2 O.sub.3, Si.sub.3 O.sub.4 and 
SiO.sub.2 is used as the silicon oxide. These silicon compounds may be 
crystalline or amorphous. In order to improve the durability, strength, 
etc., of the deposition layer, not more than 10%, based on the above 
deposition material, of silicon compounds other than the above-specified 
silicon oxides, or of alloys or compounds such as oxides, silicides, 
silicates, fluorides, nitrides, carbides, etc., of metals other than 
silicon or a mixture of these may be incorporated to the above deposition 
material. Examples of these metals include tin, magnesium, aluminum, 
indium, manganese, silver, etc. The use of a small amount of metal in 
combination gives an effect of improving the degree of vacuum further 
owing to a reaction thereof with residual oxygen in a vacuum chamber. 
Among these metals, tin and indium show good stability in deposition and 
give a desirable result. 
The deposition material made of these components is prepared into a shaped 
material by optionally adding a binder, lubricant, degrading agent, etc., 
in order to ease its continuous supply and discharge and prevent its 
splashing during the deposition, and shaping the mixture, in wet or dry 
condition, into a cylindrical, cubic, rectangular parallelopiped-like, 
tablet-like, pellet-like, rod-like or wire-like form by granulation, 
compression molding, extruding or other method. In order to increase the 
strength of the shaped material and remove water, gas, impurities, etc., 
contained in the shaped material, it is preferable to dry or sinter the 
material in air, inert gas or vacuum during or after the shaping. The 
cylindrical or pillar-like, especially, cylindrical or tablet-like form of 
the shaped article is preferable in terms of easiness of handling and 
shaping. In the case when the deposition material is in the cylindrical 
form, it is desirable that the so-shaped deposition material has a 
diameter of not more than 300 mm at the most, preferably 10 to 100 mm, in 
terms of prevention of its breakage and prevention of splashing during the 
deposition. And, in the case when the deposition material is in powder 
form and the shaping is carried out by compression molding, it is 
preferable to use a powder having a particle size of smaller than 100 
mesh, especially smaller than 200 mesh, in terms of moldability and 
reactivity during the deposition. Further, the shaped deposition material 
may be subjected to sintering treatment as required in order to improve 
its physical properties. 
In this invention, the heat evaporating portion comprises a heat 
evaporation member having means to hold the shaped deposition material and 
means to evaporate the shaped deposition material by heating, said holding 
means having a supply port of the shaped deposition material, an outlet of 
evaporation residue and an opening for evaporation of the deposition 
material. 
As means for evaporation by heating in this invention, there are used 
conventionally known heating methods such as resistance heating method, 
electron beam heating method, and high frequency induction heating method. 
FIGS. 6 to 12 show embodiments of the heat evaporation members of this 
invention. 
FIGS. 6 to 8 show a heat evaporation member having a holding means 12 which 
is circular in the inner cross section and which has a deposition material 
supply port 10 and an evaporation residue outlet 11, one openin 13 on the 
surface thereof along a major axis of the holding means 12 and heating 
means which is a high frequency induction coil 14. FIG. 6 is a plan view 
of said heat evaporation member, FIG. 7 is a cross sectional view taken 
from A--A' and FIG. 8 is a side view of said member. 
FIG. 9 is a perspective view of an heat evaporation member which has a 
holding means having an opening 13 extending along the entire length of 
the holding means and a U letter-shaped inner cross section and in which 
heating means is a resistance heating having electrodes 15 at the vicinity 
of both end portions of the holding means 12. A cooling water is 
circulating within the electrodes so as to dissipate a heat built up 
during the deposition. 
FIGS. 10 to 12 show a heat evaporation member having two openings 13 along 
the upper surface of a holding means 12 of which the inner cross section 
is circular and heating means which is a resistance heating by an 
electrode 15. FIG. 10 is a plan view of said heat evaporation member, FIG. 
11 is a front view of said member and FIG. 12 is a side view of said 
member. 
A heat evaporation member having a preliminary heating portion, which can 
heat the upper side portion of the shaped deposition material, between the 
supply port 10 and the opening 13 as shown in FIGS. 6 to 8 or FIGS. 10 to 
12 is more preferably usable than a heat evaporation member which is cut 
open all along the upper side thereof as shown in FIG. 9. 
The heat evaporation member may be provided with means to preliminarily 
heat the shaped evaporation material or means for gas removal. The 
material for the holding means depends on the heating methods, and said 
material is selected from alumina, graphite, titanium diboride, boron 
nitride composite sintered body, aluminum nitride, berylium oxide, and the 
like, and, preferably, those having less reactivity with the deposition 
material are used. 
In terms of producibility and universality, high frequency induction 
heating and resistance heating are preferably used as the heating method. 
An auxiliary heater may be used in combination in order to make the 
temperature distribution in the heating portion uniform or to 
intentionally make the same nonuniform. 
In this invention, there is no limitation on means to supply and discharge 
the shaped deposition material substantially continuously. For example, it 
is possible to use a device shown in FIG. 13 in which the shaped 
deposition material 17 is continuously supplied by using an endless belt 
16, and another device shown in FIG. 14 in which conveyor rolls 18 are 
used to continuously supply the shaped deposition material. 
A device in which the supply is partially intermittent as shown in FIG. 15 
may also be used since such a supply substantially has an effect identical 
to that of the continuous supply. In FIG. 15, the shaped material 17 is 
placed in a supply member 19 having a U letter-shaped holder connected to 
the shaped deposition material supply port 10 of the heat evaporating 
portion, and the right end of a feeding rod 20, which is driven to the 
right and left, is connected to the left side of the shaped material 17. 
This feeding rod 20 moves rightward by a length of the shaped material 17 
at a pre-determined slow constant speed (e.g., 5 mm/minute) to supply 
shaped material to the heat evaporating portion. After the rod 20 moves to 
the predetermined position, it is allowed to move leftward by a length of 
the shaped material 17 at a comparatively high speed (e.g., 50 cm/minute) 
whereby shaped material 17 (pellet) is allowed to fall from a replenishing 
means 21 to the supply member 19. Immediately thereafter, the feeding rod 
20 again moves rightward at the previous slow speed to supply shaped 
material to the heating member. In this way, the supply of the shaped 
material 17 to the heating member is seemingly intermittent, but is 
substantially continuous. 
The direction in supply of the shaped deposition material may be the same 
as, or different from, the direction in travel of the flexible plastic 
film. 
In this invention, there is no limitation on means to discharge deposition 
residue from the heating portion. Even without any special means, the 
deposition residue can be continuously discharged through the holding 
means 12 by said means to continuously supply the shaped deposition 
material 17. 
FIG. 16 is a schematic view showing an apparatus for the manufacture of a 
deposition film in this invention. Said apparatus has vacuum chambers 
22,22' connected to vacuum means (not shown). Within the vacuum chamber 
22, there are a feeding roll 24 which allows a flexible plastic film 23 to 
travel, a taking-in roll 25 having actuating means (not shown) and a chill 
roll 26 which projects the lower portion into the vacuum chamber 22' side 
and is placed between the above two rolls. Within the vacuum chamber 22', 
there are a heat evaporation member 27 below the deposition roll 26 and 
means to substantially continuously supply the shaped deposition material 
17 to the heat evaporation member 27 and discharge evaporation residue. 
Opposite to a heat evaporation means 27 of the supply discharge means 29, 
there is placed the replenishing means 21 which sequentially replenishes 
the supply member 19 with the shaped deposition material 17. The shaped 
deposition material 17 is substantially continuously supplied to the heat 
evaporation means 27 by forward and backward movement of the feeding rod 
20, and the evaporation residue 28 is substantially continuously 
discharged to a pan 30. The heat evaporation member 27 uses a direct 
resistance heating method using an electrode 15. 
The number of each of the heat evaporation member 27 and the supply 
discharge means 29 of shaped deposition material may be suitably selected 
depending upon the width of travelling flexible plastic films. Usually, 
one set of heat evaporation member and supply discharge means are placed 
every 10 to 20 cm. 
The degree of vacuum of the vacuum chamber 22, 22' is not more than 
10.sup.-3 Torr, preferably 10.sup.-4 Torr. The thickness of the deposition 
layer can be suitably controlled by a film thickness sensor 31 which 
detects the thickness of the deposition layer. 
According to this invention, there are provided a process for the 
manufacture of a deposition film having a deposition layer mainly composed 
of silicon oxide, having uniform composition and thickness of a deposition 
layer from beginning to end during the deposition and having excellent gas 
barrier properties, and an apparatus usable for said process. 
According to this invention, there are provided a process for manufacturing 
the above deposition film very effectively in producibility and an 
apparatus usable for said process. 
EXAMPLES 
This invention will be illustrated more in detail according to Examples 
herein below. 
EXAMPLE 1 
An equimolar mixture of silicon and silicon dioxide was compression molded 
to obtain a tablet-shaped material having a diameter of 40 mm and 
thickness of 35 mm. A heat evaporation member shown in FIGS. 6 to 8 was 
used in an apparatus shown in FIG. 16. The above shaped material was 
continuously supplied to a supply port of a heat evaporation member made 
of boron nitride composite sintered body at a speed of 5 mm/minute, and 
heated to 1,350.degree. C. with a high frequency induction heating device 
under vacuum of 0.7.times.10.sup.-4 Torr to carry out deposition on a 
polyethylene terephthalate film having a thickness of 12 .mu.m and 
travelling at a speed of 30 m/minute. In addition, the thickness of the 
deposition layer was controlled by using an optical intensity monitor. 
Measurement of the thickness of the deposition layer on the resultant 
deposition polyethylene terephthalate film by taking an electron 
photomicrograph of the cross section of the film showed that the thickness 
of the deposition layer was constant, i.e., about 1,000 .ANG., regardless 
of points of time after the deposition was started, as is shown in FIG. 
17. 
The measurement of the bond energy of 2 p orbital of silicon atom in the 
deposition layer of the resultant deposition polyethylene terephthalate 
film by X ray photoelectron spectroscopic analysis showed that the bond 
energy is nearly constant and the composition of the deposition layer was 
nearly constant regardless of points of time after the deposition was 
started, as is shown in FIG. 18. 
The bond energies of 2 p orbitals of silicon atoms in silicon dioxide and 
silicon are 103.4 eV and 98.6 eV, respectively. 
COMATIVE EXAMPLE 1 
The procedure of Example 1 was repeated except that 2 pieces of the 
tablet-shaped material obtained in Example 1 were charged into a usual 
crucible made of graphite shown in FIG. 1, that the above shaped material 
was not replenished and that the travelling speed of a polyethylene 
terephthalate film was set at 10 m/minute, and the high frequency 
induction heating was carried out to give a deposition on polyethylene 
terephthalate film. Incidentally, the volume of evaporation residue 70 
minutes after the deposition was started was 26 cm.sup.3. 
It was found that the thickness of the deposition layer of the resultant 
deposition polyethylene terephthalate film decreased with passage of time 
after the deposition was started, as is shown in FIG. 19. 
The 2 p orbital bond energy of silicon atom in the deposition layer of the 
resultant deposition polyethylene terephthalate film changed as shown in 
FIG. 20, and it was found that the composition of the deposition layer 
shifted toward silicon dioxide with passage of time after the deposition 
was started. 
It is thought that the causes for the gradual decrease in thickness of the 
deposition layer, the change in its composition and occurence of 
evaporation residue are that the volume of the shaped deposition material 
decreased with passage of time, and that since, due to a long stay of the 
shaped deposition material in the crucible, it reacted with residual 
oxygen and oxygen emitted from the film and silicon was eluted toward the 
surface of the shaped deposition material to change the silicon/silicon 
dioxide compositional ratio, the proceeding of a reaction to form SiO was 
difficult. 
EXAMPLE 2 
The deposition layer surface of the deposition polyethylene terephthalate 
film obtained in Example 1 was bonded to the surface of a casted 
polypropylene film having a thickness of 70 .mu.m by using a polyurethane 
adhesive "Adcote 900" (trade name, made by Toyo Morton Co., Ltd.) and a 
pouch was prepared therefrom according to customary method. The pouch was 
filled with distilled water as contents and sealed. Then the pouch was 
subjected to retort sterilization treatment at 125.degree. C. for 30 
minutes. Then, the pouch was opened and the oxygen permeability (OP) was 
measured according to ASTM-D-3985-81 to show 1.4 ml/m.sup.2 -24 hrs-1 
atm-25.degree. C.-100% RH. In addition, the OP before the retort 
sterilization treatment was 1.0 ml/m.sup.2 -24 hrs-1 atm-25.degree. 
C.-100% RH. Thus, it was found that there was little decrease in the OP 
after retort sterilization treatment. 
COMATIVE EXAMPLE 2 
Pouches were prepared by repeating Example 2 except for the use of those 
three portions of the deposition polyethylene terephthalate film obtained 
in Comparative Example 1 which had deposition layer thicknesses of 1,400 
.ANG., 1,000 .ANG. and 700 .ANG., respectively. Then these pouches were 
subjected to retort sterilization treatment and the OPs were measured 
before and after the retort sterilization treatment. 
Table 1 shows the results of the above measurement. 
TABLE 1 
______________________________________ 
OP* 
Thickness of Before retort 
After retort 
deposition sterilization 
sterilization 
layer (.ANG.) treatment treatment 
______________________________________ 
1,400 0.7 1.0 
1,000 1.1 2.5 
700 1.3 4.5 
______________________________________ 
*OP: unit ml/m.sup.224 hrs1 atm25.degree. C. 100% RH 
EXAMPLE 3 
A silicon/silicon monoxide/silicon dioxide mixture having a molar ratio of 
35/30/35 was compression-molded to obtain pillar-shaped deposition 
material having a length of 25 mm, width of 25 mm and thickness of 15 mm. 
A heat evaporation member shown in FIG. 9 was used in an apparatus shown in 
FIG. 16. The resultant shaped material was supplied to a supply port of a 
heat evaporation member made of graphite at a speed of 5 mm/minute, and 
heated to 1,300.degree. C. under vacuum of 0.7.times.10.sup.-4 Torr using 
a resistance heating method to carry out deposition on a polyethylene 
terephthalate film travelling at a speed of 30 m/minute. 
The thickness of the resultant deposition layer was nearly 1,000 .ANG., 
i.e., constant, regardless of points of time after the deposition was 
started. 
Pouches were prepared by using the deposition polyethylene terephthalate 
film obtained above in the same way as in Example 2. Then, along the 
procedures mentioned in Example 2, and retort sterilization treatment was 
carried out, and OPs were measured before and after the retort 
sterilization treatment. Table 2 shows results of the measurement. 
COMATIVE EXAMPLE 3 
Example 3 was repeated except that the supply of the pillar-shaped 
deposition material was stopped during the course of time, and pouches 
were prepared by using deposition films obtained 10 minutes, 30 minutes 
and 60 minutes after the supply was stopped. Retort sterilization 
treatment was carried out, and OPs were measured before and after the 
retort sterilization treatment. Table 2 shows results of the measurement. 
TABLE 2 
______________________________________ 
OP* 
Before After 
Thickness retort retort 
of deposi- sterili- sterili- 
tion zation zation 
layer (.ANG.) 
treatment 
treatment 
______________________________________ 
Ex. 3 1,000 1.0 1.2 
CEx. 3 (**) 
10 minutes 
850 1.1 2.0 
30 minutes 
700 1.3 4.0 
60 minutes 
400 1.8 10.0 
______________________________________ 
*OP: Unit ml/m.sup.224 hrs1 atm25.degree. C. 100% RH. 
**: Time after the supply was stopped. 
EXAMPLE 4 
A silicon/tin/silicon dioxide mixture having a molar ratio of 10/1/10 was 
compression-molded to obtain a tablet-shaped material having a diameter of 
15 mm and thickness of 25 mm. A heat evaporation member shown in FIG. 10 
was used in an apparatus shown in FIG. 16. The resultant shaped material 
was supplied to the supply port of a heating evaporation member made of 
graphite shown at a speed of 5 mm/minute in a supply method as shown in 
FIG. 10. The shaped material was heated to 1,350.degree. C. under vacuum 
of 0.4.times.10.sup.-4 by using a direct resistance heating device to 
carry out a deposition in the same way as in Example 1. Then, the 
thickness of the deposition layer was measured to show that the thickness 
was about 1,000 .ANG. or nearly constant regardless of the points of time 
during the deposition and the presence of tin. It was possible to maintain 
the atmosphere of high degree of vacuum and stably carry out the 
deposition.