JP4144705B2 - Gas barrier film forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic material and a method of forming a thin film having a gas barrier function with respect to oxygen, water vapor and the like on a plastic film material.
[0002]
[Prior art]
A gas barrier sheet used for packaging food and drink, pharmaceuticals, chemicals, daily necessities, miscellaneous goods, and various articles is configured by coating a gas barrier film on a plastic film. Conventionally, in order to prevent deterioration of the contents and to allow confirmation of foreign matters in the contents by visual inspection or a metal detector, for example, various kinds of materials that are particularly transparent to oxygen and water vapor are cut off. Gas barrier films have been proposed and developed. Examples of the gas barrier film of the inorganic material for such purpose include, for example, an electron beam evaporation method, a sputtering method, and plasma CVD (CVD is an abbreviation for Chemical Vapor Deposition, and may be called chemical vapor deposition or chemical vapor deposition. The silicon oxide film and the aluminum oxide film are generally used by the above method.
[0003]
In recent years, a display using organic electroluminescence (EL), liquid crystal, or the like has been proposed in which a plastic thin plate or a plastic film is used as a substrate from the viewpoint of weight reduction, thinning, and flexibility. A gas barrier film that is transparent and has a high barrier property against oxygen and water vapor from the viewpoint of preventing the oxidative deterioration of the element portion formed on the substrate surface while maintaining the visibility of the display portion even for this plastic substrate. Need to be coated. As a high-performance gas barrier film of an inorganic material for such a purpose, a configuration in which a silicon nitride film or a silicon oxynitride film is coated by a sputtering method or a CVD method has been proposed.
[0004]
In the formation of the silicon nitride film, for example, a silane (SiH ₄ ) gas and an ammonia (NH ₃ ) gas are supplied as source gases to a heating element made of a tungsten wire heated to about 1600 to 1800 ° C., for example. The chemical vapor deposition method (that is, the catalytic CVD (abbreviated as Cat CVD) method or the CVD method such as Hot Wire CVD method) that deposits a silicon nitride film on the substrate by being decomposed and activated is transparent, oxygen and In recent years, it has attracted attention as one of the methods for forming a gas barrier film having a water barrier property.
[0005]
In order to form the gas barrier film on the surface of the plastic film, it is desired to improve the film forming speed from the viewpoint of reducing the cost. In order to increase the deposition rate of the gas barrier film by chemical vapor deposition such as plasma CVD and catalytic CVD, it is necessary to increase the input energy for generating the deposition active species. The heating energy for the film increases, and the substrate temperature of the plastic film rises as the growth time elapses. Since the heat resistance temperature of the plastic film is low, the input energy for generating the film-forming active species is reduced so that the heat resistance temperature of the plastic film is not exceeded within the film formation time to obtain the desired film thickness of the gas barrier film. And the deposition rate of the gas barrier film must be compatible.
[0006]
When a silicon nitride film is formed on a plastic film at high speed using a silane gas and ammonia gas or nitrogen gas by plasma CVD, aminosilane, which is a precursor, is formed in the silicon nitride film formed as a gas barrier film. Of hydrogen atoms remain without desorption. As a result, the denseness of the silicon nitride film is lowered, and it becomes easy to oxidize, which causes a problem that the gas barrier performance is lowered. This problem is particularly serious when the film is formed at a relatively low temperature so as not to exceed the heat resistance temperature of the plastic film. The reason is that at such a low temperature, the desorption of hydrogen from the surface of the silicon nitride film is slow, and even when the film formation rate is increased, the desorption of hydrogen is not in time. This is because the hydrogen concentration in the silicon nitride film is remarkably increased.
[0007]
When a silicon nitride film is formed on a plastic film at a high speed using a silane gas and an ammonia gas by a catalytic CVD method, aminosilane which is a precursor in the above-mentioned plasma CVD method is not generated, but plasma CVD is performed. Similar to the method, there is a problem that the hydrogen concentration in the silicon nitride film is high due to the low substrate temperature and high-speed film formation, the denseness is lowered, the oxidation is easy, and the gas barrier performance is lowered.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a gas barrier film forming method in which a silicon nitride film, which is a gas barrier film, can be densely formed on the surface of a plastic substrate at a relatively low temperature and at a high film formation rate. Is to provide.
[0009]
[Means for Solving the Problems]
In this specification, the term “substrate” refers to an object on which a gas barrier film is to be formed, and may be a film having a thickness of, for example, 10 to 500 μm, or thicker than the film and, for example, less than 5 mm. It may be a plate-like body having a relatively large thickness, may be flexible, may be rigid, may have other shapes, and may be formed on at least a part of the surface. It is an object on which a gas barrier film is to be formed. This base material is made of synthetic resin.
[0010]
The present invention relates to a gas barrier film forming method for forming a gas barrier film on a plastic substrate.
A first gas containing a halogen atom and a silicon atom in the gas molecule;
Using a second gas containing nitrogen atoms,
A gas barrier film forming method, wherein a silicon nitride film is formed on the surface of the substrate by chemical vapor deposition.
[0011]
In the present invention, the chemical vapor deposition method is
It is a catalytic chemical vapor deposition method in which a film is formed on the surface of the substrate by active species generated by catalytic decomposition of the first and second gases with the heating element.
[0012]
In the present invention, the first gas is chlorosilane or fluorinated silane,
The second gas is nitrogen, ammonia or hydrazine.
[0013]
According to the present invention, the first and second gases are used as the source gas, and the first gas is, for example, silane chloride (SiH _n Cl _4-n (n = 0,1,2,3)) or fluorinated silane. (SiH _n F _4-n (n = 0,1,2,3)), etc., the gas molecules contain halogen atoms and silicon atoms, and the second gas is nitrogen, ammonia, hydrazine, etc. Includes a nitrogen atom. As the second gas, ammonia is preferable from the viewpoint of high decomposition efficiency and easy handling. Instead of the first and second gases, a gas containing a halogen atom, a silicon atom, and a nitrogen atom in a single gas molecule may be used. A silicon nitride film is formed on the surface of the substrate by chemical vapor deposition such as plasma CVD or catalytic CVD. In the catalytic CVD method, since a relatively transparent silicon nitride film can be obtained as compared with the plasma CVD method, the catalytic CVD method is preferable.
[0014]
In the catalytic CVD method, the heating element is preferably a tungsten wire, for example, but may be other materials and shapes. The heating element is a material in which the heating element itself is not melted and volatilized at the temperature at which the first gas and the second gas are catalytically decomposed, further silicidation is suppressed, and corrosion due to halogen is suppressed, For example, the above-mentioned tungsten is preferable. The shape of the line of the heating element may be a straight line, or may be a right cylindrical coil, may have other shapes, and may have a structure other than a line. The temperature of the heating element is a temperature at which the first and second gases are catalytically decomposed as described above, and is preferably a temperature that does not cause thermal damage to the plastic substrate. 2000 ° C. is preferred.
[0015]
Examples of the plastic substrate used in the present invention include polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polysulfone, polyethersulfone, polyester, polymethyl methacrylate, polycarbonate, polyarylate, polyacetate, polyamide, poly-4. -It may be a resin having transparency such as methylpentene-1, cellulose, polyvinyl chloride, polyacrylonitrile resin, phenoxy resin, polyphenylene oxide resin, but may not have transparency.
[0016]
One embodiment of the present invention is a vacuum vessel having a space for storing a plastic substrate on which a gas barrier film is to be formed,
A first gas source for supplying a first gas containing halogen atoms and silicon atoms in gas molecules into the space of the vacuum vessel;
A second gas source for supplying a second gas containing nitrogen atoms into the space of the vacuum vessel;
A gas barrier film formation comprising: a heating element that catalytically decomposes the first and second gases from the first and second gas sources to generate active species and forms a silicon nitride film on the surface of the substrate Device.
[0017]
In addition, further comprising an inlet means having an inlet opening in the space of the vacuum vessel,
First and second gases from the first and second gas sources are led to the inlet means,
The heating element is arranged between the surface of the base material and the introduction port.
[0018]
In the gas barrier film forming apparatus of the catalytic CVD method, the first and second gases from the first and second gas sources are mixed and simultaneously, or the first gas and the second gas are individually guided to the heating element. As a result, catalytic decomposition occurs to generate active species. These active species reach a plastic substrate such as a plastic film, and a silicon nitride film as a gas barrier film is formed on the surface thereof. The ratio (= Q1 / Q2) between the flow rate Q1 of the first gas and the flow rate Q2 of the second gas is, for example, 1/1 to 1/100, and may be simultaneously supplied into the space of the vacuum vessel, or The first and second gases may be individually supplied to the space of the vacuum vessel at a volume ratio equal to the flow rate ratio.
[0019]
The film thickness of the gas barrier film made of a silicon nitride film formed on the surface of the plastic substrate may be determined to an optimum value depending on the gas barrier property, light transmittance, and bending resistance that does not cause cracks when bent, preferably 5 ˜200 nm, more preferably 20˜100 nm.
[0020]
The present invention may be a so-called batch-type apparatus which will be described later with reference to FIGS. 1 to 3, but the manufacturing cost is reduced particularly when the plastic substrate is a long strip-shaped plastic film. From a viewpoint, a mechanism for feeding a roll-shaped film, a mechanism for forming a silicon nitride film on the surface of the film by the above-described catalytic CVD method, and a mechanism for winding the formed film into a roll It is desirable as a mass production facility to use a configured film forming apparatus, that is, a so-called roll-to-roll continuous film forming apparatus.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view showing a simplified overall configuration of a gas barrier film forming apparatus 13 according to an embodiment of the present invention. The gas barrier film forming apparatus 13 deposits and forms a silicon nitride film, which is a gas barrier film, on the surface of the plastic film 4 held in the space 14 of the vacuum vessel 1 facing downward in FIG. 1 by catalytic CVD.
[0022]
In the space 14 in the vacuum vessel 1, the inlet means 2 having the inlet 15 for supplying the source gas is arranged. The introduction port 15 opens to the space 14 toward the upper side of FIG. 1 and faces the plastic film 4. A plastic film 4 is held above the space 14 by a holding mechanism 5 that functions as a substrate holder. The holding mechanism 5 has a surface on which a silicon nitride film that is a gas barrier film of the film 4 is to be formed. The surface on the opposite side (that is, the upper surface of FIG. 1) contacts.
[0023]
The holding mechanism 5 is provided with a temperature adjusting mechanism 6 that heats or cools the film 4, thereby maintaining the temperature at which the silicon nitride film is optimally deposited below the heat-resistant temperature of the film 4. The temperature adjusting mechanism 6 is a heating means such as an electric heater, for example, which is a jacket for heating the film 4 or supplying cooling water, and a silicon nitride film is densely and optimally formed on the surface of the film 4. It keeps the temperature at a certain temperature.
[0024]
Within the space 14, the heating element 3 made of a tungsten wire is disposed between the inlet 15 of the inlet means 2 and the film 4. Electric power is supplied to the heating element 3 from the power supply 16, and thereby, catalytic decomposition of the gas guided to the heating element 3 is performed.
[0025]
A shielding member 17 that is an openable / closable shutter that partitions the space 14 is provided between the heating element 3 and the film 4 in the space 14 of the vacuum container 1. The shielding member 17 is driven to open and close by the driving means 18.
[0026]
Silane chloride gas from the first gas source 21 and ammonia gas from the second gas source 22 are supplied to the inlet means 2 via the pipe lines 23 and 24, respectively. Flow control valves 7 and 8 and on-off valves 25 and 26 are interposed in the pipelines 23 and 24, respectively. The exhaust pump 19 evacuates the space 14 to a pressure of 2 × 10 ⁻⁴ Pa or less, for example.
[0027]
FIG. 2 is a block diagram showing an electrical configuration in the embodiment of FIG. An input means 29 for performing an input operation by an operator is connected to the processing circuit 28 realized by a microcomputer or the like. The processing circuit 28 controls the driving means 18 for the shielding member 17 and the on-off valves 25 and 26, keeps the heating element 3 at, for example, 1800 ° C. by the power source 16, and further evacuates the space 14 by the exhaust pump 19. To do. Thus, by the operation of the processing circuit 28, a silicon nitride film as a gas barrier film can be automatically and continuously formed on the surface of the film 4.
[0028]
FIG. 3 is a timing chart for explaining the operation of the processing circuit 28. 3 (1) shows the open / close state of the shutter, FIG. 3 (2) shows the open / close state of the on / off valve 25 for the first gas, and FIG. 3 (3) shows the open / close state of the on / off valve 26 for the second gas. First, at time t1, the on-off valve 26 is opened, and a second gas such as ammonia gas is introduced. Then, the power source 16 is turned on to start heating the heating element 3, preferably at a desired temperature, and the on-off valve 25 is opened at time t2 to introduce a first gas such as silane chloride gas. The shielding member 17 is opened at time t3 when the temperature and pressure are stabilized. The ratio (= Q1 / Q2) between the flow rate Q1 of the first gas and the flow rate Q2 of the second gas by the flow rate control valves 7 and 8 is set in a range of 1/1 to 1/100, for example.
[0029]
As a result, the active species 11 and 12 in which the first gas molecules 9 and the second gas molecules 10 are contact-decomposed by the heating element 3 reach the surface of the film 4, and a silicon nitride film as a gas barrier film is formed on the surface. The Thus, the period from time t1 to time t3 before time t3 is the period until the state of the active species 11 and 12 generated by catalytic decomposition by the first and second gas heating elements 3 in the space 14 is stabilized. And before the time t3, the shielding member 17 is closed. At time t4 after the silicon nitride film is formed on the surface of the film 4 in this way, the shielding member 17 is closed by the driving means 18 and the on-off valves 25 and 26 are closed, thus completing a series of operations.
[0030]
In this way, in the batch type gas barrier film forming apparatus using the catalytic CVD method, the first gas containing halogen atoms and silicon atoms and the second gas containing nitrogen atoms are used as the source gas, and the first control is performed by the flow rate control valves 7 and 8. The flow rate of the second gas is adjusted, and the second gas is discharged from the inlet means 2 into the space 14 of the vacuum vessel 1 in a mixed gas state. The gas molecules 9 of the first gas and the gas molecules 10 of the second gas supplied from the introduction port 15 change into the active species 11 and 12 by passing through the heating element 3 in contact with each other. 12 reach the surface of the film 4 as a substrate, and a silicon nitride film as a gas barrier film is formed on the surface.
[0031]
【Example】
Examples of the present invention are shown below. In the apparatus as shown in FIGS. 1 to 3, after a polyethylene terephthalate (abbreviated as PET) film 4 having a thickness of 125 μm is brought into close contact with the holding mechanism 5 as a substrate holder and installed in the space 14 of the vacuum vessel 1. The vacuum vessel 1 was evacuated to 2 × 10 ⁻⁴ Pa or less by the exhaust pump 19, and then the holding mechanism 5, which is a substrate holder, was cooled to 0 ° C. by the temperature adjustment mechanism 6. With the temperature adjustment mechanism 6 holding the temperature of the holding mechanism 5, and hence the film 4, at 0 ° C., the on-off valve 26 is opened at time t 1 in FIG. 3 (3), and the second gas source 22 serves as the second gas. Ammonia gas was introduced into the space 14 of the vacuum vessel 1, and the heating element 3 was heated to 1800 ° C. in order to catalytically decompose and activate the second gas. The heating element 3 is formed in a linear shape made of tungsten. Subsequently, as illustrated in FIG. 3B, the first gas that is silane chloride SiH ₂ Cl ₂ is introduced into the space 14 from the first gas source 21 through the on-off valve 25 at time t ₂ . As shown in FIG. 3A, the shielding member 17 is opened by the driving means 18 at time t3. A film was formed on the surface of the film 4 at a film formation rate of 150 nm / min for 20 seconds, and a silicon nitride film having a thickness of 50 nm was formed on the film 4.
[0032]
When the oxygen gas permeability of the film 4 on which the silicon nitride film was formed was evaluated at a temperature of 23 ° C. and a relative humidity of 0% by the Japanese Industrial Standard differential pressure method, it was 1.0 cc / m ² · day · Pa. The water vapor transmission rate of the film 4 on which the silicon nitride film was formed was evaluated at a temperature of 40 ° C. and a relative humidity of 100% by the Japanese Industrial Standard Mocon method, and found to be 0.5 g / m ² · day. Further, the film 4 on which the silicon nitride film was formed had a total light transmittance in the visible light region of 82%, and was visually colorless and transparent.
[0033]
[Comparative example]
Comparative Example, in place of the second gas in which silane SiH ₂ Cl ₂ gas chloride in the foregoing embodiments, using the SiH ₄ gas, the procedure of other catalytic CVD method is the same as in the above embodiment. That is, in the apparatus as shown in FIGS. 1 to 3, a polyethylene terephthalate (abbreviated as PET) film 4 having a thickness of 125 μm is placed in close contact with a holding mechanism 5 that is a substrate holder and installed in the space 14 of the vacuum vessel 1. After that, the vacuum vessel 1 was evacuated to 2 × 10 ⁻⁴ Pa or less by the exhaust pump 19, and then the holding mechanism 5 as a substrate holder was cooled to 0 ° C. by the temperature adjusting mechanism 6. With the temperature adjustment mechanism 6 holding the temperature of the holding mechanism 5, and hence the film 4, at 0 ° C., the on-off valve 26 is opened at time t 1 in FIG. 3 (3), and the second gas source 22 serves as the second gas. Ammonia gas was introduced into the space 14 of the vacuum vessel 1, and the heating element 3 was heated to 1800 ° C. in order to catalytically decompose and activate the second gas. The heating element 3 is formed in a linear shape made of tungsten. Subsequently, at time t <b> 2 shown in FIG. 3B, the first gas that is silane SiH ₄ is introduced from the first gas source 21 into the space 14 through the on-off valve 25. As shown in FIG. 3 (1), the shielding member 17 is opened by the driving means 18 at time t3, and film formation is performed on the surface of the film 4 at a film formation rate of 150 nm / min for 20 seconds. Film formation was performed on film 4.
[0034]
When the oxygen gas permeability of the film 4 on which the silicon nitride film was formed was evaluated at a temperature of 23 ° C. and a relative humidity of 0% by the Japanese Industrial Standard differential pressure method, it was 9.8 cc / m ² · day · Pa. When the water vapor transmission rate of the film 4 on which the silicon nitride film was formed was evaluated at a temperature of 40 ° C. and a relative humidity of 100% by the Mokon method of Japanese Industrial Standard, it was 3.5 g / m ² · day.
[0035]
Therefore, in the Example of this invention, it was confirmed that oxygen gas permeability is small compared with a comparative example, and gas barrier property is improved.
[0036]
【The invention's effect】
As is apparent from the above description, according to the present invention, a dense transparent silicon nitride film can be formed at a low film formation temperature and at a high film formation speed, and is excellent in mass productivity. The gas barrier film has a high gas barrier performance particularly against oxygen and water vapor.
[Brief description of the drawings]
FIG. 1 is a simplified cross-sectional view showing the overall configuration of a gas barrier film forming apparatus 13 according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an electrical configuration in the embodiment of FIG. 1;
FIG. 3 is a timing chart for explaining the operation of the processing circuit 28;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Inlet means 3 Heat generating body 4 Plastic film 5 Holding mechanism 11, 12 Active species 13 Gas barrier film forming apparatus 14 Space 15 Inlet 17 Shielding member 21 First gas source 22 Second gas sources 25, 26 On-off valve

Claims (3)

In a gas barrier film forming method for forming a gas barrier film on a plastic substrate,
A first gas containing a halogen atom and a silicon atom in the gas molecule;
Using a second gas containing nitrogen atoms,
A gas barrier film forming method, comprising: forming a silicon nitride film on the surface of the substrate by chemical vapor deposition. Chemical vapor deposition is
2. The gas barrier film according to claim 1, wherein the gas barrier film is a catalytic chemical vapor deposition method in which a film is formed on the surface of the base material by active species generated by catalytic decomposition of the first and second gases with the heating element. Forming method. The first gas is chlorosilane or fluorinated silane,
The gas barrier film forming method according to claim 1, wherein the second gas is nitrogen, ammonia, or hydrazine.

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