JP2005248255A - Method for depositing fluororesin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for depositing a fluororesin film having both excellent antifoulancy and scratch resistance in combination. <P>SOLUTION: A target 14 composed of a fluororesin is irradiated with ion beams of inert gas in a gas atmosphere containing gaseous fluorine or a compound comprising fluorine atoms so as to be sputtered, and a fluororesin film is deposited on a film substrate 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a fluororesin coating.

In recent years, a fluororesin film such as polytetrafluoroethylene (PTFE) has been applied to plastics, glass, etc., or a base material provided with a functional film on them for the purpose of imparting antifouling functions such as oil repellency. A film is formed.
As the film forming method, for example, a method of forming a film by high frequency (RF) sputtering using a fluororesin as a target is disclosed (for example, refer to Patent Documents 1 and 2).
However, such a fluororesin film has a certain degree of antifouling property but is not sufficient. In addition, there is a problem that the film is soft and the scratch resistance is poor.

In order to solve such a problem, for example, Patent Document 3 discloses a method of providing a composite film of a fluororesin and a metal oxide on a plastic substrate. In this method, a metal oxide-fluorine resin composite film is formed on a plastic substrate by performing high-frequency sputtering using a composite target in which a metal oxide target is partially coated with a fluororesin. It is a method of providing the property and scratch resistance.
However, even the metal oxide-fluororesin composite film cannot simultaneously satisfy excellent antifouling properties and scratch resistance. For example, increasing the proportion of the metal oxide in the composite film to improve the scratch resistance significantly decreases the antifouling property, and increases the proportion of the fluororesin in the composite film to improve the antifouling property. As a result, the scratch resistance is significantly reduced.
Furthermore, since the antifouling property and the scratch resistance are worsened as the sputtering output is higher, it is said that high-frequency sputtering using a fluororesin as a target needs to be performed at a low output, and the productivity is poor.
Moreover, even if the output is low, it is difficult to obtain a dense film, which is inferior to conventional wet film formation in terms of surface mechanical properties such as scratch resistance. However, in the wet process, it is necessary to form the film again in the air after the functional film is formed in vacuum, and there is a disadvantage that the productivity is low and the cost is high.
Furthermore, continuous productivity is low, and it is difficult to stably manufacture products of similar quality over a long period of time.
JP-A-56-98475 JP 56-98469 A JP-A-3-153589

  The present invention provides a method for forming a fluororesin film having both excellent antifouling properties and scratch resistance.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention replaced the conventional high-frequency sputtering method with irradiation of an ion beam to a fluororesin target and sputtered particles containing fluorine or fluorine atoms. It is found that a fluororesin film having both excellent antifouling property and scratch resistance can be obtained by forming a film through a gas atmosphere composed of the compound to be completed, and the present invention is completed based on the knowledge. It came to.
That is, the present invention provides a fluororesin coating film characterized by performing sputtering by irradiating an ion beam of an inert gas onto a target composed of a fluororesin in a gas atmosphere composed of a fluorine gas or a compound containing a fluorine atom. A film forming method is provided.

  By the method for forming a fluororesin film of the present invention, a fluororesin film having both excellent antifouling properties and scratch resistance can be obtained.

Hereinafter, the present invention will be described in detail.
The present invention performs sputtering by irradiating an ion beam of an inert gas onto a target made of a fluororesin in a gas atmosphere made of a fluorine gas or a compound containing a fluorine atom to form a fluororesin coating on a substrate. It is characterized by doing.
In the present invention, ion beam sputtering is performed on a substrate by performing in an atmosphere of a gas composed of a fluorine gas or a compound containing a fluorine atom (hereinafter, both may be collectively referred to as a fluorine-containing gas). It is considered that a decrease in the fluorine content in the fluororesin film is suppressed, and a fluororesin film having excellent antifouling properties and scratch resistance can be formed.

  The compound having a fluorine atom in the present invention is a fluorinated hydrocarbon having 1 to 10 carbon atoms (hereinafter referred to as fluorinated hydrocarbons) which may have a halogen atom other than a fluorine atom and / or an etheric oxygen atom. ), At least one compound selected from the group consisting of sulfur hexafluoride and nitrogen trifluoride. Examples of halogen atoms other than fluorine atoms include chlorine atoms and bromine atoms.

Fluorinated hydrocarbons include hydrofluorocarbon (HFC), hydrofluoroether (HFE), chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), perfluorocarbon (PFC), perfluoroether (PFE), and the like. . These may be linear, branched or have an aliphatic ring structure. Further, even a saturated compound may have an unsaturated carbon-carbon bond.
As the fluorinated hydrocarbons, those having a large ratio of fluorine to carbon (F / C (molar ratio)), for example, those having F / C of 2 or more are preferable, and PFC or PFE is preferable. .
The fluorinated hydrocarbons preferably have 1 to 4 carbon atoms. In particular, a PFC having 1 to 4 carbon atoms is preferable. PFC having 1 to 4 carbon atoms means perfluoroalkane, perfluoroalkene, perfluorocycloalkane, and the like, specifically, CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₃ F ₆ , C such as _{4 F 10, C 4} F ₈ and the like.

  In the present invention, the fluorine-containing gas is particularly preferably at least one selected from the group consisting of fluorine gas, PFC having 1 to 4 carbon atoms, and sulfur hexafluoride. Further, PFC having 1 to 4 carbon atoms is most preferable.

  The concentration of the fluorine-containing gas is preferably 3 to 10% by volume, and more preferably 4 to 6% by volume. When the concentration of the fluorine-containing gas is within this range, a fluorine resin film having excellent antifouling properties and scratch resistance can be formed. In addition, the film formation rate of the fluororesin coating is sufficient.

  Examples of the fluororesin used for the target include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), and tetrafluoro. Examples thereof include ethylene / ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene, and polyvinyl fluoride. Among these, a perfluoro resin is preferable, and at least one selected from the group consisting of PTFE, PFA, and FEP is particularly preferable. These may be used alone or in combination of two or more.

  Examples of the inert gas used for the ion beam include argon, helium, neon, krypton, and xenon.

In the present invention, the fluororesin coating is usually formed on the surface of the substrate.
Examples of the substrate include glass, ceramics, metal, and plastic. Among these, a film-like substrate is preferable because continuous film formation is easy, and a plastic film is more preferable because it is easy to handle.
Moreover, a fluororesin film can be formed on the surface of the base material on which a functional film such as an antireflection film, an electromagnetic wave shielding film, a near infrared shielding film, a color tone correction film, or an optical interference film is formed.
By forming a fluororesin film on the surface of the base material or a functional film formed on the surface of the base material (hereinafter collectively referred to as a base material) using the method of the present invention, A fluororesin film having good adhesion to the material and having excellent antifouling properties and scratch resistance can be obtained. In particular, by forming a fluororesin film on the functional film as described above by the method of the present invention, antifouling performance with excellent durability can be imparted to the surface of an optical filter or the like of various display devices. .

The present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an example of a film forming apparatus used in the method for forming a fluororesin film according to the present invention. The film forming apparatus 11 includes two substrate holding rolls 13a and 13b arranged at a predetermined interval for holding a film-like substrate (film substrate) 12, and the substrate holding roll 13a. , 13b between the plate-like target 14 that is diagonally opposed to each other at a predetermined interval below the base material 12, the target holder 15 with a cooling mechanism for placing the target 14, and the target 14 The ion source 16 is arranged mainly on the side so that the ion beam is irradiated toward the target 14.

The film forming apparatus 11 is housed in a vacuum chamber (not shown) that can be evacuated, and can hold the periphery of the film substrate 12 in a vacuum atmosphere.
Further, an atmospheric gas supply source such as a gas cylinder is connected to the vacuum chamber, and the inside of the vacuum chamber is made of fluorine gas or a compound containing fluorine atoms while maintaining a vacuum state of, for example, 0.5 Pa or less. Gas can be supplied.

The target 14 is attached to the target holder 15.
The tilt angle of the target holder 15 can be adjusted, and the incident angle of the ion beam to the target 14 can be adjusted.
The ion source 16 irradiates the target 14 with an ion beam.

Hereinafter, in the present invention, an example of forming a fluororesin film on the surface of a film substrate using the film forming apparatus 11 having the configuration shown in FIG. 1 will be described.
First, using the film forming apparatus 11, the target 14 made of a fluororesin is placed on the target holder 15, and the film base 12 is placed on the base material holding rolls 13a and 13b.
Next, the inside of the container containing these is evacuated to create a reduced pressure atmosphere. As a vacuum state at this time, a vacuum atmosphere of about 0.5 Pa or less is preferable. In such a vacuum atmosphere, glow discharge is likely to occur.
When the ion source 16 is activated and the target 14 is irradiated with an ion beam, the constituent particles of the target 14 are knocked out by the ion beam and fly and deposit on the film substrate 12. Then, a fluororesin film having a desired film thickness is formed.

  The film thickness of the fluororesin film is preferably thick in order to obtain high scratch resistance, but if it becomes too thick, the film itself tends to warp or peel off from the substrate due to the stress of the film itself, Preferably it is 2-20 nm, More preferably, it is 3-10 nm.

  In the present invention, the functional film may be formed in advance on the surface of the film substrate. The method for forming the functional film is not particularly limited, and a known thin film forming method such as a sputtering method can be used. The functional film and the fluororesin film are formed in the same manner. The film forming apparatus 11 is preferably used in a vacuum atmosphere of 0.5 Pa or less. In this case, after the functional film is formed in a vacuum atmosphere, the functional film can be subsequently formed in the same vacuum atmosphere, so that productivity is high and costs can be reduced.

  The fluororesin film formed by such a film forming method has both excellent antifouling properties and scratch resistance, and can be used as an optical filter of a display device such as a plasma display.

The reason why a fluororesin film having both excellent antifouling properties and scratch resistance can be obtained by the present invention is not clear, but sputtered fluororesin particles (hereinafter sometimes referred to as fluorocarbon particles) and the like. It is conceivable that decomposition of the fluorine-containing gas is suppressed.
That is, in the conventionally used high frequency sputtering, there is plasma for ionizing an inert gas such as argon between the substrate and the target. Therefore, it is considered that the fluorocarbon particles and the fluorine-containing gas are exposed to plasma and decomposed, which deteriorates the antifouling property and scratch resistance.
On the other hand, in the present invention, since the film is formed by irradiating the target generated outside the ion beam source with the ions generated in the ion beam source, the fluorocarbon particles and the fluorine-containing gas are hardly affected by the plasma, Therefore, it is considered that the antifouling property can be exhibited and at the same time the scratch resistance is improved.
Moreover, the fluororesin coating in the present invention is excellent in adhesion to the substrate, productivity, continuous productivity, and the like.

Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
An antireflection film 1 (hereinafter, referred to as an antireflection film with an antifouling function) having a structure shown in FIG. 2 and having a fluororesin coating 9 formed on the outermost surface was prepared by the following procedure.
Polyethylene terephthalate (hereinafter referred to as PET) having a thickness of 188 μm was used as the substrate 2, and the acrylic hard coat layer 3 was provided on the surface of the substrate 2 with a film thickness of 6 μm.
Next, dry cleaning using an ion beam source for cleaning the surface of the hard coat layer 3 was performed. That is, about 30% oxygen was mixed in Ar gas, 100 W electric power was applied, and Ar ions and oxygen ions ionized by an ion beam source were irradiated on the surface of the hard coat layer 3. Thereafter, an antireflection film 4 was formed on the surface of the hard coat layer 3 by the following method.

Using an ITO target (indium: tin = 90: 10) on the treated surface, 2% oxygen gas was mixed and introduced into argon, and the pressure was 0.35 Pa, the frequency was 100 kHz, and the power density was 1. Pulse sputtering with 5 w / cm ² and inversion pulse width of 1 μsec was performed to form an ITO layer 5 (n = 2.00) with a film thickness of 20 nm as an intermediate refractive index layer and a conductive film.
Next, using Asahi Glass ceramics SiC target (trade name SC), 40% oxygen gas was mixed with argon gas and introduced at a frequency of 100 kHz and a power density of 4.0 w / cm ² at a pressure of 0.35 Pa. Pulse sputtering with a pulse width of 4.5 μsec was performed to form a 30 nm-thickness SiO ₂ layer 6 (n = 1.46) as a low refractive index layer.
Next, using a ZnO target doped with 5% by mass of aluminum, 3% of oxygen gas was mixed with argon gas, introduced at a pressure of 0.35 Pa, a frequency of 100 kHz, and a power density of 4.0 w / cm ² , inversion. Pulse sputtering with a pulse width of 1 μsec was performed to form an AZO layer 7 (n = 1.93) having a thickness of 120 nm as a high refractive index layer.
Next, using Asahi Glass ceramics SiC target (trade name SC), argon gas was mixed with 40% oxygen gas, introduced at a pressure of 0.5 Pa, frequency 100 kHz, power density 3.25 w / cm ² , inversion. Pulse sputtering with a pulse width of 4.5 μsec was performed to form a SiO ₂ layer 8 (n = 1.46) having a thickness of 85 nm as a low refractive index layer.

After the antireflection film 4 composed of the ITO layer 5, the SiO ₂ layer 6, the AZO layer 7, and the SiO ₂ layer 8 was formed as described above, the fluororesin film 9 was continuously formed in a vacuum apparatus.
As a polytetrafluoroethylene (hereinafter referred to as PTFE) material, a PTFE sheet (“Fluon (registered trademark)”, manufactured by Asahi Glass Co., Ltd.) containing PTFE as a main component was used. As an ion source, an ion beam source “LIS-38” manufactured by Advanced Energy was used. The Ar gas amount is adjusted so that the Ar partial pressure becomes 0.19 Pa and introduced into the ion beam source to generate Ar ions, and at the same time, tetrafluoromethane (CF ₄ ) is simultaneously added so that the CF ₄ partial pressure becomes 0.01 Pa. It was introduced into the sputtered particle path in the tank.
The ion beam sputtering power was 80 W, and the fluororesin film 9 was formed to a thickness of 5 nm. The pressure during film formation was 0.25 Pa.

Comparative Example 1
In Example 1, an antireflection film with an antifouling function was produced in the same manner as in Example except that the fluororesin coating was changed to RF magnetron sputtering.
The RF power frequency of RF sputtering was 13.56 MHz, the RF power density was 1.1 W / cm ² , Ar partial pressure was 0.25 Pa, CF 4 was 0.01 Pa, and the total pressure during sputtering was 0.26 Pa. It was.

About the antireflection film with an antifouling function produced in Example 1 and Comparative Example 1, five items were tested to evaluate the characteristics.
The characteristic evaluation method is shown below.
"Abrasion"
[Steel wool rubbing test]
Steel wool of # 0000 was used, and a load of 3.0 N / cm ² was applied to rub the fluororesin coating side of the antireflection film with an antifouling function.
[Ethanol rubbing test]
Ethanol was wetted on the cotton cloth, a load of 9.8 N / cm ² was applied, and the fluororesin coating side of the antireflection film with an antifouling function was rubbed.

"Adhesion"
[Cross-cut test]
100 squares were made at intervals of 1 mm using a cutter in the range of 10 mm × 10 mm on the fluororesin coating side of the antireflection film with antifouling function. “Nichiban cello tape” (manufactured by Nichiban Co., Ltd.) was applied to the entire area where the cells were formed and peeled off at once, and the number of cells remaining was measured.

“Anti-fouling”
[Contact angle]
As evaluation of antifouling property, the contact angle of Nujol on the fluororesin coating side of the antireflection film with antifouling function was measured by FACE CA-X type manufactured by Kyowa Interface Science Co., Ltd. For reference, the water repellency was also evaluated by measuring the water contact angle.
The contact angle of Nujol before film formation of the fluororesin coating of the antireflection film with antifouling function, that is, the contact angle of Nujol on the surface of the antireflection film 4 was 20 degrees or less, and could not be measured accurately. The water contact angle was 20 degrees.

  The evaluation results are shown in Table 1.

Comparative Example 2
In Example 1, an antireflection film with an antifouling function was produced in the same procedure as in Example 1 except that the fluororesin film was formed without introducing CF ₄ . As a result, the contact angle of Nujol measured by the same method as described above was 30 degrees or less, and the water contact angle was 50 degrees.

  As is clear from these results, the antireflection film with an antifouling function of Example 1 was excellent in various mechanical property evaluations while maintaining the antifouling property.

It is a schematic block diagram of the film-forming apparatus 11 used in one Embodiment of this invention. It is a typical schematic sectional drawing which shows the layer structure of the antireflection film 1 with an antifouling function manufactured in the Example.

Explanation of symbols

1 ... laminate 2 ... substrate, 3 ... hard coat layer, 4 ... antireflection film, 5 ... ITO layer, 6 ... SiO ₂ layer, 7 ... AZO layer, 8 ... SiO ₂ layer, 9 ... fluororesin film, DESCRIPTION OF SYMBOLS 11 ... Film-forming apparatus, 12 ... Film base material, 13a, 13b ... Base material holding roll, 14 ... Target, 15 ... Target holder, 16 ... Ion source

Claims (5)

  A method for forming a fluororesin film, comprising performing sputtering by irradiating a target made of a fluororesin with an ion beam of an inert gas in a gas atmosphere made of a fluorine gas or a compound containing a fluorine atom.   The method for forming a fluororesin film according to claim 1, wherein the fluororesin is a perfluororesin.   The perfluoro resin is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene / hexafluoropropylene copolymer. A method for forming a fluororesin film.   The compound containing a fluorine atom is composed of a fluorinated hydrocarbon having 1 to 10 carbon atoms which may have a halogen atom and / or an etheric oxygen atom other than the fluorine atom, sulfur hexafluoride and nitrogen trifluoride. The method for forming a fluororesin film according to any one of claims 1 to 3, wherein the film is at least one compound selected from the group. The method for forming a fluororesin coating according to any one of claims 1 to 3, wherein the compound containing a fluorine atom is sulfur hexafluoride and / or a perfluorocarbon having 1 to 4 carbon atoms.

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