Patent Publication Number: US-2011052891-A1

Title: Gas barrier film and method of producing the same

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a gas barrier film for use in displays. The present invention more specifically relates to a gas barrier film having organic layers and one or more inorganic layers stacked on a surface of a flexible film and capable of being produced with high efficiency and a method of producing the gas barrier film. 
     A gas barrier film which has a layer exhibiting gas barrier properties on a surface of a plastic film such as polyethylene terephthalate (PET) film is used not only in such positions or parts that require moisture resistance in various devices including optical devices, displays such as liquid-crystal displays and organic EL displays, semiconductor devices, and thin-film solar cells, but also in packaging materials used to package food, clothing, electronic components, and the like. 
     A layer made of any of various inorganic materials (inorganic compounds) such as silicon nitride, silicon oxide and aluminum oxide is known as the layer exhibiting gas barrier properties that may be used in such a gas barrier film. 
     Also known is a laminate type gas barrier film (gas barrier laminate film) that has a plurality of layers including organic layers (organic compound layers) and an inorganic layer (inorganic compound layer) stacked on a surface of a flexible film to achieve still higher gas barrier properties. 
     For example, JP 2003-341003 A describes a gas barrier film comprising a first resin thin film layer having a mean surface roughness of 4 nm or less and made of an epoxy compound which is formed on a surface of a flexible film; a vapor deposition layer of an inorganic oxide formed by vapor-phase deposition on the first resin thin film layer; and a second resin thin film layer of the same type as the first resin thin film layer formed on the vapor deposition layer. 
     U.S. Pat. No. 6,420,003 describes a gas barrier film comprising a first crosslinked acrylate layer formed on a surface of a thermoplastic flexible film; an oxygen barrier layer of an inorganic material such as silicon oxide or aluminum oxide formed on the first crosslinked acrylate layer; and a second crosslinked acrylate layer of the same type as the first crosslinked acrylate layer formed on the oxygen barrier layer. 
     These gas barrier films can have excellent gas barrier properties by forming an organic layer on a surface of a flexible film to cover fine topographic features at the surface of the flexible film to thereby give a highly smooth surface and forming an inorganic layer (gas barrier film) made of an inorganic oxide on the highly smooth surface. 
     The inorganic layer mainly exhibiting gas barrier properties is protected by forming another organic layer on the inorganic layer. In addition, a plurality of layers including organic layers and inorganic layers can be stacked on top of each other to achieve still higher gas barrier properties while releasing the stress of the inorganic layer and ensuring the flexibility of the gas barrier film. 
     The inorganic layer is generally formed by vapor-phase deposition techniques (vacuum deposition techniques) such as plasma-enhanced CVD, sputtering and vacuum evaporation. 
     On the other hand, flash evaporation is advantageously used to form the organic layer as described in JP 2003-341003 A and U.S. Pat. No. 6,420,003. 
     As described above, the organic layer is formed to ensure the smoothness of the surface on which the inorganic layer is to be formed, and the organic layer obtained has a very high surface smoothness by using flash evaporation. 
     What is more, flash evaporation is a technique in which film deposition is performed in vacuum, and therefore formation of the first organic layer by flash evaporation, formation of the inorganic layer by vapor-phase deposition and formation of the second organic layer by flash evaporation can be continuously performed in a single vacuum chamber, thus also preventing dust or foreign matter from adhering to the film deposition surface. 
     For example, JP 2003-341003 A and U.S. Pat. No. 6,420,003 each describe a device in which a drum is disposed in a vacuum chamber and the first organic layer, the inorganic layer and the second organic layer are sequentially formed by a first flash evaporation unit, a CVD unit (vacuum evaporation unit) and a second flash evaporation unit each disposed so as to face a peripheral surface of the drum as the flexible film travels on the drum in a longitudinal direction. 
     In such a gas barrier film having organic layers and inorganic layers stacked on top of each other, the organic layers formed have a larger thickness than the inorganic layers. 
     In other words, the surface topographic features of the flexible film can be covered to obtain a sufficiently smooth surface by forming the organic layer having a certain degree of thickness. 
     For example, according to JP 2003-341003 A, the organic layer thickness is preferably from 5 to 2000 nm and the inorganic layer thickness is preferably from 5 to 500 nm. 
     In addition, JP 2003-341003 A describes in Examples a gas barrier film comprising a flexible film (PET film); a first organic layer (transparent epoxy layer) with a thickness of 500 nm formed on the flexible film; and an inorganic layer (silicon oxide layer) with a thickness of 100 nm formed on the first organic layer, and another gas barrier film further comprising a second organic layer of the same type as the first organic layer formed on the inorganic layer of the above-described gas barrier film. 
     The difference between the thickness of the organic layer and that of the inorganic layer may hinder the improvement of the productivity. For example in cases where the inorganic layer has a thickness of 50 nm, the film deposition rate is 500 nm/min and the organic layer has a thickness of 500 nm, the organic layer must be formed at a film deposition rate of 5000 nm/min so that the organic layer may be formed in time before the formation of the inorganic layer is started. 
     Therefore, as described in JP 2003-341003 A and U.S. Pat. No. 6,420,003, in cases where a gas barrier film is produced by continuously performing the formation of the first organic layer by flash evaporation, the formation of the inorganic layer by vapor-phase deposition and optionally the formation of the second organic layer as a long flexible film travels in a longitudinal direction, the travel speed of the flexible film is determined by the organic layer-forming step and the flexible film cannot travel at a higher speed. 
     In other words, in a conventional gas barrier film production method which uses flash evaporation and with which an organic layer and an inorganic layer are stacked on top of each other, the inorganic layer is formed on a highly smooth film deposition surface to enable a gas barrier film having excellent gas barrier properties to be produced, but the formation of the organic layer becomes a rate-determining factor to hinder high productivity or high-speed production. 
     SUMMARY OF THE INVENTION 
     In order to solve the aforementioned prior art problems, an object of the present invention is to provide a gas barrier film exhibiting excellent gas barrier properties and capable of high-speed production. 
     Another object of the present invention is to provide a gas barrier film production method capable of producing such a gas barrier film. 
     A gas barrier film according to the present invention comprises: a flexible film; a first organic layer formed at atmospheric pressure on a surface of the flexible film; a second organic layer formed in vacuum on a surface of the first organic layer; and an inorganic layer formed in vacuum on a surface of the second organic layer. 
     A method of producing a gas barrier film according to the present invention comprises the steps of: making a flexible film in strip form travel in a longitudinal direction thereof; forming a first organic layer at atmospheric pressure on a surface of the flexible film which is traveling; forming a second organic layer in vacuum on a surface of the first organic layer; and forming an inorganic layer in vacuum on a surface of the second organic layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  schematically shows the layout of an organic deposition device used to produce a gas barrier film according to an embodiment of the present invention; 
         FIG. 1B  schematically shows the layout of a vacuum deposition device used to produce the gas barrier film according to this embodiment; 
         FIG. 2  is a partial cross-sectional view showing a gas barrier film according to this embodiment; 
         FIG. 3A  is a partial cross-sectional view showing a gas barrier film in a modified embodiment; and 
         FIG. 3B  is a partial cross-sectional view showing a gas barrier film in another modified embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     On the following pages, the gas barrier film and the method of producing the gas barrier film according to the present invention are described in detail with reference to the preferred embodiments shown in the accompanying drawings. 
       FIGS. 1A and 1B  show schematic layouts of an organic deposition device  24  and a vacuum deposition device  26  used to produce a gas barrier film according to this embodiment, respectively. 
     The organic deposition device  24  forms a first organic layer  12  on a surface of a long strip of flexible film Z (film base) as it travels in a longitudinal direction. 
     On the other hand, the vacuum deposition device  26  forms a second organic layer  14  on the first organic layer  12 , then an inorganic layer  16  on the second organic layer  14 , and a third organic layer  18  on the inorganic layer  16  as the flexible film Z having the first organic layer  12  formed on its surface travels in the longitudinal direction. 
     Then, the organic deposition device  24  forms a fourth organic layer  20  on the third organic layer  18  as the flexible film Z having the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  formed thereon travels in the longitudinal direction. 
     The devices shown in  FIGS. 1A and 1B  are used to produce a gas barrier film  10  as shown in  FIG. 2 . The gas barrier film produced may be used as an intermediate product. 
     The material of the flexible film Z is not particularly limited and various types of film in strip form used to produce gas barrier films may be used. 
     Specific examples of the flexible film Z that may be advantageously used include plastic films (resin films) in sheet form made of organic materials such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene, polypropylene, polystyrene, polyamide, polyvinyl chloride, polycarbonate, polyacrylonitrile, polyimide, polyacrylate, and polymethacrylate. 
     The flexible film Z used may be one obtained by forming one or more than one layer to impart various functions on a plastic film base or other base. Exemplary layers include a protective layer, an adhesion layer, a light-reflecting layer, a light-shielding layer, a planarizing layer, a buffer layer, and a stress-relief layer. 
     A film having the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and optionally the third organic layer  18  may be used as the flexible film Z. The three or four layers are also hereinafter collectively referred to as “gas barrier laminate.” In other words, the gas barrier film of the present invention (gas barrier film having the gas barrier laminate in the present invention) is formed as an intermediate, which is used as the flexible film Z to form an organic layer and an inorganic layer thereon according to the present invention to produce a final gas barrier film of the present invention. 
     This point will be described later in further detail. 
     The organic deposition device  24  shown in  FIG. 1A  is a device where an organic material (organic compound) is deposited by a film deposition method at atmospheric pressure to form the first organic layer  12  on the surface of the flexible film Z. In addition, the organic deposition device  24  deposits an organic material to form the fourth organic layer  20  on the flexible film Z on which the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  have been formed by the vacuum deposition device  26  to be described later, thereby completing the gas barrier film  10  as shown in  FIG. 2 . 
     The organic deposition device  24  in the illustrated embodiment forms the first organic layer  12  and optionally the fourth organic layer  20  by a coating method, and includes a rotary shaft  28 , a take-up shaft  30 , a coating means  32 , a drying means  34 , a curing means  36 , and guide rollers  38   a  and  38   b . The coating means  32 , the drying means  34 , and the curing means  36  are disposed so as to face the travel path of the flexible film Z between the guide rollers  38   a  and  38   b.    
     The organic deposition device  24  is a so-called roll-to-roll film deposition device in which the flexible film Z is fed from a film roll  40  having a long strip of flexible film Z wound into a roll, the first organic layer  12  or the fourth organic layer  20  (the fourth organic layer  20  is hereinafter omitted unless the fourth organic layer  20  is particularly necessary to distinguish or illustrate) is formed on the flexible film Z traveling in a longitudinal direction and the flexible film Z having the first organic layer  12  formed thereon is rewound on the take-up shaft  30 . 
     In addition to the illustrated members, the organic deposition device  24  may also have various members of a device for continuously depositing a film by a coating method including various sensors, and various members (transport means) for making the flexible film Z travel along a predetermined path, as exemplified by a transport roller pair and a guide member for regulating the position in the width direction of the flexible film Z. 
     The flexible film Z fed from the film roll  40  is guided by the guide roller  38   a  to reach the coating means  32 . 
     The coating means  32  applies to a surface of the flexible film Z on which a gas barrier laminate is to be deposited, a coating material containing an organic material making up the first organic layer  12  such as a coating material prepared by dissolving or dispersing an organic material in a solvent, a coating material prepared by dissolving an organic monomer in a solvent, or a coating material prepared by dissolving an organic monomer and a polymerization initiator in a solvent. 
     The coating method used in the coating means  32  is not particularly limited and various known methods used to form a coating can be used, as exemplified by roll coating, gravure coating, knife coating, dip coating, curtain flow coating, spray coating, bar coating, and spin coating. 
     The drying means  34  evaporates the solvent from the coating or coating material applied to the surface of the flexible film Z in the coating means  32  to dry the coating. The drying means  34  is not particularly limited and known drying means suitable to the coating applied such as drying with a heater or hot air drying may be used. 
     In cases where the coating is sufficiently viscous and thixotropic to enable the first organic layer  12  to be formed by merely curing the coating in the downstream curing means  36 , it is not necessary to provide the drying means  34 . 
     The curing means  36  cures the dried coating to form the first organic layer  12 . In cases where the coating material contains an organic monomer as described above, the curing means  36  polymerizes the monomer to form the first organic layer  12 . 
     The curing means  36  is not particularly limited and curing means suitable to the organic material used to form the first organic layer  12  may be appropriately selected and used, as exemplified by plasma irradiation means (plasma curing), ultraviolet (UV) irradiation means (UV curing), electron beam irradiation means (electron beam curing), light irradiation means (light curing), and heating means (thermal curing). 
     The curing means  36  may not be provided in cases where the coating can be fully cured to form the first organic layer  12  by merely drying. Alternatively, if drying and curing can be performed in a single means, only one of the drying means and the curing means may be provided to serve as a drying/curing means. 
     In the organic deposition device  24 , the film roll  40  is mounted on the rotary shaft  28 . Once the film roll  40  has been mounted on the rotary shaft  28 , the flexible film Z is fed from the film roll  40  and travels on a predetermined travel path as it is guided by the guide rolls  38   a  and  38   b  to be wound on the take-up shaft  30 . 
     Once the coating means  32 , the drying means  34  and the curing means  36  are ready to start the treatments, the flexible film Z starts to travel. Feeding of the flexible film Z from the film roll  40  and winding of the flexible film Z on the take-up shaft  30  are performed in synchronism so that during the travel of the flexible film Z in the longitudinal direction, the coating means  32  applies a coating material to form the first organic layer  12 , the drying means  34  dries the applied coating material and the curing means  36  cures the coating to form the first organic layer  12  on the surface of the flexible film Z. 
     In the present invention, the method of forming the first organic layer  12  is not limited to the coating method, and various film deposition methods including a transfer method in which the first organic layer  12  formed into a sheet shape is transferred to the flexible film can be all used as long as the method applied is capable of forming a layer or a film of an organic material at atmospheric pressure. 
     However, the coating method is used with advantage in consideration of the film deposition rate and the covering of the surface topographic features of the flexible film. 
     The first organic layer  12  is not limited to an organic monolayer formed at atmospheric pressure and a plurality of organic sublayers may be formed at atmospheric pressure to serve as the first organic layer  12 . In other words, the first organic layer  12  in the present invention may include a plurality of organic sublayers formed by a film deposition method at atmospheric pressure such as the coating method. 
     In this regard, the same holds true for the second organic layer  14 , the inorganic layer  16 , the third organic layer  18 , and the fourth organic layer  20  to be described later. For example, the second layer  14  may include a plurality of organic sublayers formed by flash evaporation. Alternatively, the inorganic layer  16  may include a plurality of inorganic sublayers formed by plasma-enhanced CVD. 
     The plurality of sublayers making up the first organic layer  12  and the inorganic layer  16  may be made of the same material or different materials. 
     The material used to form the first organic layer  12  is not particularly limited and various organic materials capable of film deposition or film formation at atmospheric pressure as in the coating method can be used. 
     Exemplary materials include epoxy resins, (meth)acrylic resins, polyesters, methacrylic acid/maleic acid copolymers, polystyrenes, transparent fluororesins, polyimides, fluorinated polyimides, polyamides, polyamideimides, polyetherimides, cellulose acylates, polyurethanes, polyetherketones, polycarbonates, fluorene ring-modified polycarbonates, alicyclic ring-modified polycarbonates, and fluorene ring-modified polyesters. 
     The flexible film Z on which the first organic layer  20  has been thus formed is guided by the guide roller  38   b  on the predetermined path to be wound on the take-up shaft  30  into a roll. 
     The flexible film Z wound on the take-up shaft  30  is supplied to the vacuum deposition device  26  as a film roll  42 . 
     The vacuum deposition device  26  forms the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  on the flexible film Z having the first organic layer  12  formed thereon. 
     The vacuum deposition device  26  is also the same type roll-to-roll device as the organic deposition device  24 . The second organic layer  14 , the inorganic layer  16  and the third organic layer  18  are sequentially formed on the first organic layer  12  of the flexible film Z fed from the film roll  42  as it travels in the longitudinal direction, and the flexible film Z having these layers formed thereon is then rewound into a roll. 
     The vacuum deposition device  26  includes a feed chamber  46 , a vacuum deposition chamber  48  and a take-up chamber  50 . 
     In addition to the illustrated members, the vacuum deposition device  26  may also have various members of a device in which film deposition by a coating method, film deposition by flash evaporation and film deposition by vapor-phase deposition are continuously carried out on a long strip of flexible film Z, including various sensors, and various members (transport means) for making the flexible film Z travel along a predetermined path, as exemplified by a transport roller pair and a guide member for regulating the position in the width direction of the flexible film Z. 
     The feed chamber  46  includes a rotary shaft  52 , a guide roller  54   a  and a vacuum evacuation means  55 . 
     The film roll  42  is mounted on the rotary shaft  52  of the feed chamber  46 . Upon mounting of the film roll  42  on the rotary shaft  52 , the flexible film Z travels along a predetermined travel path starting from the feed chamber  46  and passing through the vacuum deposition chamber  48  to reach a take-up shaft  106  of the take-up chamber  50 . 
     In the vacuum deposition device  26 , feeding of the flexible film Z from the film roll  42  and winding of the flexible film Z on the take-up shaft  106  of the take-up chamber  50  are carried out in synchronism so that the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  may be sequentially formed in the vacuum deposition chamber  48  on the first organic layer  12  having already been formed on the surface of the flexible film Z as the long strip of flexible film Z travels on the predetermined travel path in the longitudinal direction. 
     The travel speed of the flexible film Z in the vacuum deposition device  26  is not particularly limited and a travel speed of at least 10 m/min is preferred. 
     As described above, in a conventional gas barrier film having an organic layer formed by flash evaporation and an inorganic layer formed by vapor-phase deposition, the organic layer has a larger thickness and therefore may not be deposited by flash evaporation to a desired thickness before the formation of the inorganic layer is started. In such a case, since the travel speed of the flexible film cannot be improved, gas barrier films cannot be produced at high speed with high efficiency. 
     In contrast, the present invention in which film deposition at atmospheric pressure as by the coating method is combined with film deposition in vacuum (at reduced pressure) as by flash evaporation to form two organic layers and an inorganic layer is formed thereon is capable of considerably improving the organic layer film deposition rate. Therefore, the present invention considerably improves the travel speed of the flexible film Z in the production of gas barrier films and is capable of obtaining gas barrier films at high speed with high production efficiency. 
     In other words, by setting the travel speed of the flexible film Z to 10 m/min or more, the characteristic feature of the present invention that the travel speed of the flexible film can be improved is fully achieved to enable the gas barrier films with high gas barrier properties to be produced with high productivity or at a high speed. 
     In consideration of this point, the travel speed of the flexible film Z is more preferably set to at least 30 m/min. 
     The vacuum evacuation means  55  is provided in a preferred embodiment to evacuate the feed chamber  46  to reduce the pressure to a predetermined value. 
     In other words, the feed chamber  46  communicates with the vacuum deposition chamber  48  through a slit  58   a  to be described later and therefore the feed chamber  46  can be prevented from adversely affecting the pressure of the vacuum deposition chamber  48  by keeping the feed chamber  46  at a predetermined pressure or degree of vacuum by the vacuum evacuation means  55 . 
     In the present invention, the feed chamber  46  and the take-up chamber  50  to be described later are not limited to a structure having a vacuum evacuation means, and may be used at atmospheric pressure. 
     The vacuum evacuation means  55  is not particularly limited, and exemplary means that may be used include vacuum pumps such as a turbo pump, a mechanical booster pump, a rotary pump and a dry pump, an assist means such as a cryogenic coil, and various other known (vacuum) evacuation means employed in vacuum deposition devices and using means for adjusting the ultimate degree of vacuum or the amount of air discharged. 
     In this regard, the same holds true for the other vacuum evacuation means described later. 
     The flexible film Z is guided by the guide roller  54   a  to travel from the feed chamber  46  to the vacuum deposition chamber  48  separated from the feed chamber  46  by a partition wall  56   a . The partition wall  56   a  has the slit  58   a  through which the flexible film Z passes. 
     The vacuum deposition chamber  48  sequentially forms the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  on the flexible film Z having the first organic layer  12  formed thereon. 
     In the present invention, the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  are all formed by film deposition in vacuum (under reduced pressure). 
     In the illustrated case, the vacuum deposition chamber  48  includes a second organic layer deposition unit  60  for forming the second organic layer  14 , an inorganic layer deposition unit  62  for forming the inorganic layer  16 , a third organic layer deposition unit  64  for forming the third organic layer  18 , a drum  68 , guide rollers  54   b  and  54   c , and a vacuum evacuation means  70 . 
     The second organic layer deposition unit  60 , the inorganic layer deposition unit  62  and the third organic layer deposition unit  64  are respectively separated from the other regions (other spaces) in a substantially air-tight manner by the drum  68  and partition walls  72   a  and  72   b  extending from the wall surface of the vacuum deposition chamber  48  to the vicinity of the drum  68 , by the drum  68  and partition walls  72   b  and  72   c , and by the drum  68  and partition walls  72   c  and  72   d.    
     The vacuum evacuation means  70  is used to keep the space separated from the film deposition units in a substantially air-tight manner by the drum  68  and the partition walls  72   a  and  72   d  at a predetermined degree of vacuum. 
     The space in the vacuum deposition chamber  48  communicates with the feed chamber  46  and the take-up chamber  50  through the slits  58   a  and  58   b , respectively. Therefore, the vacuum evacuation means  70  adjusts the degree of vacuum in this space based on the film deposition pressure in the second organic layer deposition unit  60  and the third organic layer deposition unit  64  for forming the organic layers in vacuum, whereby the pressure in the upstream and downstream chambers can be prevented from adversely affecting the film deposition pressure in the second organic layer deposition unit  60  and the third organic layer deposition unit  64 . 
     In the illustrated vacuum deposition chamber  48 , the space evacuated by the vacuum evacuation means  70  and the second organic layer deposition unit  60 , the second organic layer deposition unit  60  and the inorganic layer deposition unit  62 , the inorganic layer deposition unit  62  and the third organic layer deposition unit  64 , and the third organic layer deposition unit  64  and the space evacuated by the vacuum evacuation means  70  are separated from each other in a substantially air-tight manner by the partition walls  72   a ,  72   b ,  72   c ,  72   d , respectively. 
     However, this is not the sole case of the present invention and a differential unit serving as the space for substantially air-tight isolation and provided with a pressure adjusting means such as a vacuum evacuation means to keep the pressure at a predetermined degree of vacuum may be disposed between the space evacuated by the vacuum evacuation means  70  and its adjacent film deposition unit and/or between the adjacent film deposition units so that the respective spaces may be more reliably separated (isolated) from each other. 
     The guide rollers  54   b  and  54   c  are of an ordinary type guiding the flexible film Z on the predetermined travel path. 
     The drum  68  is a cylindrical member which is rotatable about a rotary shaft disposed in the width direction of the flexible film Z which is perpendicular to the direction of travel. The flexible film Z is guided by the guide roller  54   b  on the predetermined path, passes over a predetermined region of the peripheral surface of the drum  68  and sequentially travels through the second organic layer deposition unit  60 , the inorganic layer deposition unit  62  and the third organic layer deposition unit  64  before reaching the guide roller  54   c.    
     The drum  68  also serves as a counter electrode of a shower head electrode  90  in the inorganic layer deposition unit  62  to be described later. To this end, the drum  68  is connected to a bias power source or grounded (connection is not shown in both the cases). Alternatively, the drum  68  may be capable of switching between connection to the bias power source and grounding. 
     The drum  68  may also serve as a temperature adjusting means of the flexible film Z for aggregation of an organic liquid in the second organic layer deposition unit  60  or the third organic layer deposition unit  64  or suppressing the temperature increase of the flexible film during the film deposition. Therefore, the temperature adjusting means is preferably built into the drum  68 . The temperature adjusting means of the drum  68  is not particularly limited and various types of temperature adjusting means including one in which a refrigerant is circulated and a cooling means using a piezoelectric element can be all used. 
     The second organic layer deposition unit  60  is a unit where an organic material is deposited by a vacuum deposition method on the surface of the first organic layer  12  formed on the flexible film Z to form the second organic layer  14  thereon. In a preferred embodiment, the illustrated second organic layer deposition unit  60  forms the second organic layer  14  by flash evaporation and includes a vapor deposition section  74 , a curing means  76 , an organic material supply section  78  and a vacuum evacuation means  80 . 
     In flash evaporation, as is well known, a film material is evaporated and the vapor is deposited on the flexible film, and cooled/condensed to form a liquid film, which is then cured by exposure to ultraviolet light or electron beams to finally form a film. 
     The vacuum evacuation means  80  evacuates the second organic layer deposition unit  60 , that is, the closed spaced defined by the partition walls  72   a  and  72   b  and the peripheral surface of the drum  68  to adjust the pressure to a degree of vacuum (film deposition pressure) suitable to the flash evaporation in the second organic layer deposition unit  60 . 
     The film deposition pressure in the flash evaporation is not particularly limited and is, for example, from about 0.1 to about 100 Pa. 
     The organic material supply section  78  vaporizes an organic monomer in liquid form or a coating material obtained by dissolving an organic monomer and optionally a polymerization initiator in a solvent by application of heat or ultrasound and supplies the vaporized monomer through a pipe  74   a  to the vapor deposition section  74 . In the illustrated embodiment, the organic monomer in liquid form is used as the material of the second organic layer  14 . 
     The vapor deposition section  74  ejects and deposits the vaporized organic monomer supplied from the organic material supply section  78  onto the first organic layer which has already been formed on the surface of the flexible film Z traveling on the drum  68 . The organic monomer is thus deposited to form the second organic layer  14 . 
     For example, the differential pressure between the inside of the organic material supply section  78  and the inside of the second organic layer deposition unit  60  may be used to move the vaporized material from the organic material supply section  78  to the vapor deposition section  74  and to eject the vaporized material from the vapor deposition section  74 . 
     Although not shown, the vapor deposition unit  74  is provided with a heat control means and heating nozzles for heating the environment to a temperature which is not less than the aggregation temperature but not more than the evaporation temperature of the material used. 
     The vaporized monomer supplied from the organic material supply section  78  passes through the heating nozzles to form a certain amount of deposits on the first organic layer  12  of the flexible film Z. The drum  68  is preferably cooled to improve the aggregation efficiency of the monomer. 
     The curing means  76  cures the organic material deposited on the first organic layer  12  to form the second organic layer  14 . A UV irradiation means for irradiating the flexible film Z on the drum  68  with UV light may be used for the curing means  76 . 
     An electron beam irradiation means for emitting electron beams, a microwave irradiation means for emitting microwaves and a plasma irradiation means for plasma irradiation may be advantageously used as the curing means  76  for curing the deposited organic materials. 
     In the present invention, the method of forming the second organic layer  14  is not limited to flash evaporation and various methods capable of forming the organic layer in vacuum may be used, as exemplified by plasma polymerization. 
     However, flash evaporation is more advantageously used in terms of the surface smoothness of the second organic layer  14 , the quality (e.g., purity) of the film to be formed, film deposition rate, long-term stability and ease of maintenance. 
     The material used to form the second organic layer  14  is not particularly limited and various materials capable of film deposition or film formation in vacuum or at reduced pressure as by flash evaporation can be used. 
     Exemplary materials include (meth)acrylic resins, epoxy resins, polyesters, methacrylic acid/maleic acid copolymers, polystyrenes, transparent fluororesins, polyimides, fluorinated polyimides, polyamides, polyamideimides, polyetherimides, cellulose acylates, polyurethanes, polyetherketones, polycarbonates, fluorene ring-modified polycarbonates, alicyclic ring-modified polycarbonates, and fluorene ring-modified polyesters. 
     The material of the first organic layer  12  may be the same as or different from that of the second organic layer  14 , but both the layers are preferably made of the same type of material and more preferably the same material in terms of the surface smoothness and the adhesion. 
     The same type of material refers to a material in which the functional group or the binding group characterizing the organic material used is of the same type and the main component is the same. For example, when the first organic layer  12  is made of acrylic resin, the second organic layer  14  is also made of acrylic resin, and when the first organic layer  12  is made of polyimide, the second organic layer  14  is also made of polyimide. The materials which contain the same main component are deemed as those of the same type even if there are differences in various additives (auxiliary components) used such as an adhesion promoter and the amounts thereof. 
     The inorganic layer deposition unit  62  is a unit where an inorganic material or inorganic compound is deposited on the surface of the second organic layer  14  by vacuum vapor-phase deposition to form the inorganic layer  16  thereon. 
     The inorganic layer deposition unit  62  in the illustrated embodiment forms the inorganic layer  16  by capacitively coupled plasma CVD (hereinafter abbreviated as “CCP-CVD”) and includes the shower head electrode  90 , a material gas supply section  92 , an RF power source  94 , and a vacuum evacuation means  96 . 
     The shower head electrode  90  is of a known type used in film deposition by means of CCP-CVD. 
     In the illustrated embodiment, the shower head electrode  90  is in the form of a hollow and substantially rectangular solid and is disposed so that its largest surface faces the peripheral surface of the drum  68  and the perpendicular from the center of the largest surface coincides with the normal of the drum  68  with respect to its peripheral surface. A large number of through holes are formed at the whole surface of the shower head electrode  90  facing the drum  68 . In a preferred embodiment, the surface of the shower head electrode  90  facing the drum  68  is so curved as to contour the peripheral surface of the drum  68 . 
     In the illustrated embodiment, one shower head electrode (film deposition means using CCP-CVD) is provided in the inorganic layer deposition unit  62 . However, this is not the sole case of the present invention and a plurality of shower head electrodes may be disposed in the direction of travel of the flexible film Z. In this regard, the same holds true when using plasma-enhanced CVD of other type than CCP-CVD. For example, when the inorganic layer  16  is formed by ICP-CVD, a plurality of coils for forming an induced electric field (induced magnetic field) may be provided along the direction of travel of the flexible film Z. 
     The present invention is not limited to the case in which the inorganic layer  16  is formed by ICP-CVD using the shower head electrode  90 ; the inorganic layer  16  may be formed by using a common electrode in plate form and a gas supply nozzle. 
     The material gas supply section  92  is of a known type used in vacuum deposition devices such as plasma CVD devices, and supplies material gases into the shower head electrode  90 . For example, in cases where the inorganic layer  16  formed is a silicon nitride layer or film, material gases including silane gas, ammonia gas and optionally an inert gas are supplied to the shower head electrode  90 . 
     As described above, a large number of through holes are formed at the surface of the shower head electrode  90  facing the drum  68 . Therefore, the material gases supplied into the shower head electrode  90  pass through the through-holes to be introduced into the space between the shower head electrode  90  and the drum  68 . 
     The RF power source  94  is one for supplying plasma excitation power to the shower head electrode  90 . Known RF power sources used in various plasma CVD devices can be all used for the RF power source  94 . 
     In addition, the vacuum evacuation means  96  evacuates the inorganic layer deposition unit  62 , i.e., the closed space defined by the partition wall  72   b , the partition wall  72   c , and the peripheral surface of the drum  68 , to keep it at a predetermined film deposition pressure in order to form the gas barrier film by plasma-enhanced CVD. 
     In the present invention, the method of forming the inorganic layer  16  is not limited to the foregoing CCP-CVD, and vapor-phase deposition methods carried out in vacuum are all applicable as long as the inorganic layer  16  can be formed. Examples thereof include other types of plasma-enhanced CVD such as inductively coupled plasma CVD (ICP-CVD) and microwave plasma CVD, catalytic CVD (Cat-CVD), thermal CVD, sputtering, vacuum evaporation, and ion plating. 
     The material of the inorganic layer  16  formed is not particularly limited and various inorganic materials used to form gas barrier films exhibiting good gas barrier properties can be used. 
     Illustrative examples include metal oxides such as aluminum oxide, magnesium oxide, tantalum oxide, zirconium oxide, titanium oxide and indium tin oxide (ITO); metal nitrides such as aluminum nitride; metal carbides such as aluminum carbide; silicon oxides such as silicon oxynitride, silicon oxycarbide and silicon oxynitrocarbide; silicon nitrides such as silicon nitride and silicon carbonitride; silicon carbides such as silicon carbide; hydrides thereof; mixtures of two or more thereof; and those materials containing hydrogen. 
     In the production method of the present invention, the first organic layer  12  is formed by a film deposition method at atmospheric pressure such as the coating method, then the second organic layer  14  is formed by vacuum film deposition such as flash evaporation, and the inorganic layer  16  mainly exhibiting gas barrier properties is formed on the second organic layer  14  by vacuum vapor-phase deposition, thereby forming a gas barrier laminate to produce a gas barrier film. 
     Laminate-type gas barrier films as also described in JP 2003-341003 A and U.S. Pat. No. 6,420,003 are known in which a flexible film such as a plastic film is coated with an organic layer, which is then coated with an inorganic layer, which is optionally coated with another organic layer. 
     In such a laminate-type gas barrier film, the organic layer underlying the inorganic layer is formed to cover the surface topographic features of the flexible film to thereby form a highly smooth surface, and the inorganic layer made of, for example, an inorganic oxide and exhibiting gas barrier properties is formed on the highly smooth surface to obtain a gas barrier film having excellent gas barrier properties. 
     Flash evaporation is a preferred method used to form the organic layer because the organic layer obtained has a highly clean and smooth surface. 
     On the other hand, the inorganic layer is typically formed by vapor-phase deposition techniques such as plasma-enhanced CVD. 
     The organic layer formed as the underlayer of the inorganic layer needs to have a considerably larger thickness than the inorganic layer to reliably cover topographic features of the flexible film Z to thereby achieve high surface smoothness. The difference between the thickness of the organic layer and that of the inorganic layer may hinder the improvement of the productivity. More specifically, in the illustrated case where the organic layer and the inorganic layer are continuously formed as the flexible film Z travels, the thicker organic layer cannot be deposited by flash evaporation to a predetermined thickness before starting the deposition of the thinner inorganic layer by vapor-phase deposition to a predetermined thickness, thus giving rise to a need to decrease the film deposition rate of the inorganic layer. 
     Therefore, in the production of a gas barrier film which involves forming a first organic layer by flash evaporation, forming an inorganic layer on the first organic layer and optionally forming a second organic layer on the inorganic layer by flash evaporation, the gas barrier film obtained has excellent gas barrier properties by taking advantage of the characteristics of flash evaporation, but the flash evaporation is a rate-limiting factor which makes it difficult to improve the productivity. 
     Therefore, in the production method in which the organic layer and inorganic layer are sequentially formed as the flexible film travels in the longitudinal direction as in the illustrated roll-to-roll film deposition device, the flexible film Z cannot travel at high speed, which hinders the improvement of the productivity and the production efficiency. 
     In contrast, in the embodiment under consideration, the first organic layer  12  is first formed on the surface of the flexible film Z by a film deposition method at atmospheric pressure such as the coating method, and the second organic layer  14  is formed on the first organic layer  12  by a vacuum film deposition method such as the flash evaporation; the two organic layers are then used as the underlayer to form the inorganic layer  16  thereon by vacuum vapor-phase deposition. 
     As is well known, the film deposition rate of the organic layer formed at atmospheric pressure by such a typical method as the coating method is higher than that of the inorganic layer formed by a vapor-phase deposition method such as plasma-enhanced CVD to enable a thick film to be formed in a short period of time. On the other hand, the organic layer formed by flash evaporation has excellent surface smoothness and also has high surface cleanness because it is formed in vacuum. 
     In addition, the inorganic layer  16  formed on the second organic layer  14  is also formed in vacuum in this embodiment, and therefore the treatments from the formation of the second organic layer  14  to the end of the formation of the inorganic layer  16  can be performed in vacuum as shown in the embodiment of  FIG. 1B . Therefore, after the end of the formation of the second organic layer  14 , adhesion of dust and foreign matter is advantageously prevented to enable the inorganic layer  16  to be formed with the surface kept clean, the surface cleanness being one of the characteristics of flash evaporation. In other words, there is no dust or foreign matter on the surface of the second organic layer  14  on which the inorganic layer  16  is to be formed, thereby preventing the reduction of the gas barrier properties. 
     In view of this, in the present invention, after the end of the formation of the second organic layer  14 , the inorganic layer  16  is preferably formed with no member (solid surface thereof) contacting the surface of the second organic layer  14  (particularly the region used for a product) as in the vacuum deposition device  26  shown in  FIG. 1B . Such a configuration can suppress adhesion of dust and foreign matter while preventing damage to the second organic layer  14  due to contact with a member and its surface deformation, thus enabling the inorganic layer  16  to be formed on the surface having higher smoothness and cleanness. 
     In addition, the first organic layer  12  and the second organic layer  14  are each made of an organic film and are therefore highly compatible with each other. Particularly in cases where the same type of material is used, the first organic layer  12  and the second organic layer  14  have good adhesion and can be deemed as a monolayer film. 
     In addition, according to the embodiment under consideration, the first organic layer  12  substantially covers large topographic features of the flexible film Z, and then the second organic layer  14  can cover topographic features that may be inevitably caused somewhat by the subsequent handling of the flexible film including its traveling (e.g., flaws that may occur during the winding of the flexible film Z into a roll and topographic features due to foreign matter that may adhere during the traveling of the flexible film Z in vacuum). 
     Therefore, the second organic layer  14  formed in vacuum just before the formation of the inorganic layer  16  can also have a reduced thickness. 
     In other words, the organic layer having a sufficiently large thickness can be formed at a rate fully matching the film deposition rate of the inorganic layer  16  formed by vapor-phase deposition, and the inorganic layer  16  can be formed on the organic layer by taking advantage of favorable characteristics of the organic layer formed in vacuum as by flash evaporation (e.g., surface smoothness and cleanness). 
     Therefore, according to the embodiment under consideration, in the production method in which the organic layer and the inorganic layer are formed as the flexible film travels in the longitudinal direction as in the production device shown in  FIGS. 1A and 1B  in which film deposition is performed by a roll-to-roll system, the flexible film Z can be made to travel at high speed to achieve high productivity and production efficiency and the inorganic layer  16  can be formed on the organic layer having high surface smoothness and cleanness to obtain a gas barrier film having excellent gas barrier properties. 
     There is no particular limitation on the thickness of the first organic layer  12  and the second organic layer  14  formed so as to be adjacent to each other but the total thickness of the two layers is preferably from 0.3 to 5 μm. 
     In addition, the second organic layer  14  preferably has a thickness which is not more than 0.5 μm or not more than 50% of the total thickness of the first organic layer  12  and the second organic layer  14 . The second organic layer  14  preferably has a thickness which is at least 0.1 μm or at least 20% of the total thickness of the two layers. 
     Such a configuration yields favorable results in that a sufficiently high thickness to cover topographic features of the flexible film Z can be ensured and that the flexible film Z can be made to travel at high speed to achieve higher productivity and production efficiency. 
     The thickness of the inorganic layer  16  is also not particularly limited and may be appropriately set according to the required gas barrier properties and productivity. However, the inorganic layer  16  preferably has a thickness of 10 to 300 nm. 
     At a thickness of the inorganic layer  16  within the above-defined range, favorable results can be obtained in that excellent gas barrier properties can be achieved, good flexibility can be achieved, good transparency can be achieved, and sufficiently high durability (environmental resistance) can be achieved. 
     The third organic layer deposition unit  64  is a unit where an organic film is deposited on the inorganic layer  16  to form the third organic layer  18  thereon. 
     In the illustrated embodiment, the third organic layer deposition unit  64  forms the third organic layer  18  by flash evaporation as in the second organic layer deposition unit  60 . Therefore, a vapor deposition section  98 , a curing means  100 , an organic material supply section  102 , and a vacuum evacuation means  104  in the third organic layer deposition unit  64  are the same as the vapor deposition section  74 , the curing means  76 , the organic material supply section  78  and the vacuum evacuation means  80  in the second organic layer deposition unit  60 , respectively. 
     As in the second organic layer  14 , the method of forming the third organic layer  18  is not limited to flash evaporation and various methods capable of forming an organic layer in vacuum may be all used. 
     However, flash evaporation is also used with advantage to form the third organic layer  18  for the same reason as the second organic layer  14 . 
     The third organic layer  18  is formed in a preferred embodiment. 
     Also as a preferred embodiment, the gas barrier film  10  shown in  FIG. 2  has a fourth organic layer  20  formed as the uppermost layer by a film deposition method at atmospheric pressure such as the coating method. As will be described later in detail, the gas barrier film of the present invention may have a plurality of gas barrier laminates, each gas barrier laminate including the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and optionally the third organic layer  18 . 
     That is, the presence of the third organic layer  18  enables the first organic layer  12  and the fourth organic layer  20  to be formed on the surface made of an organic material by a film deposition method in the air such as the coating method. In other words, the underlying layer on which the organic layer is to be formed at atmospheric pressure is made of an organic material. Such a configuration enables the adhesion of the first organic layer  12  and the fourth organic layer  20  to be considerably improved compared to the case where the first organic layer  12  or the fourth organic layer  20  is directly formed on the inorganic layer  16 , and the gas barrier film  10  can have considerably improved strength. 
     The third organic layer  18  is also formed by a vacuum film deposition method such as flash evaporation. Therefore, the first organic layer  12  and the fourth organic layer  20  can be formed on the underlying layer having a highly smooth surface to achieve higher adhesion. 
     The treatments from the formation of the inorganic layer  16  to the end of the formation of the third organic layer  18  can be performed in vacuum. In other words, the gas barrier film is discharged to the atmosphere after the formation of the inorganic layer  16  and the third organic layer  18 , and therefore is not exposed to atmospheric pressure. Therefore, adhesion of dust and foreign matter to the surface of the inorganic layer  16  and damage to the inorganic layer  16  can be advantageously prevented from occurring. Accordingly, the gas barrier properties can be prevented from being reduced by the adhesion of dust or foreign matter to the inorganic layer  16 . 
     In view of this, after the formation of the inorganic layer  16 , the third organic layer  18  is preferably formed with no member contacting the surface of the inorganic layer  16  (particularly the region used for a product) as in the vacuum deposition device  26  shown in  FIG. 1B . Such a configuration can more reliably suppress adhesion of dust and foreign matter while preventing damage to the inorganic layer  16  due to contact with a member and its surface deformation, thereby achieving good gas barrier properties. 
     The material used to form the third organic layer  18  in the present invention is not particularly limited and various organic materials capable of film formation in vacuum as by flash evaporation can be used. 
     Exemplary materials include epoxy resins, (meth)acrylic resins, polyesters, methacrylic acid/maleic acid copolymers, polystyrenes, transparent fluororesins, polyimides, fluorinated polyimides, polyamides, polyamideimides, polyetherimides, cellulose acylates, polyurethanes, polyetherketones, polycarbonates, fluorene ring-modified polycarbonates, alicyclic ring-modified polycarbonates, and fluorene ring-modified polyesters. 
     The thickness of the third organic layer  18  is also not particularly limited and is preferably from about 0.1 to about 0.5 μm. 
     In cases where a plurality of gas barrier laminates are formed as described above, the third organic layer  18 , the first organic layer  12  and the second organic layer  14  formed so as to be adjacent to each other (see the third organic layer  18   a , the first organic layer  12   b  and the second organic layer  14   b  in  FIG. 3A ) preferably have a total thickness of 0.3 to 5 μm. In addition, the second organic layer  14  and the third organic layer  18  preferably have a thickness which is not more than 0.5 μm or not more than 25% of the total thickness of the third organic layer  18 , the first organic layer  12  and the second organic layer  14 . 
     Such a configuration yields favorable results in that a sufficiently high thickness to cover topographic features of the flexible film Z can be ensured and that the flexible film Z can be made to travel at high speed to achieve higher productivity and production efficiency. 
     The flexible film Z having the third organic layer  18  formed in the third organic layer deposition unit  64  is then guided by the guide roller  54   c  to reach the take-up chamber  50  which is separated from the vacuum deposition chamber  48  by a partition wall  56   b . The partition wall  56   b  has the slit  58   b  through which the flexible film Z passes. 
     The flexible film Z having reached the take-up chamber  50  travels to the take-up shaft  106  as it is guided by a guide roller  54   d  and is wound on the take-up shaft  106  to form a film roll  110  into which the flexible film Z having the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  formed thereon is wound. In a preferred embodiment, the take-up chamber  50  also includes a vacuum evacuation means  108  as in the above-described feed chamber  46 , and is evacuated to a predetermined pressure based on the pressure of the vacuum deposition chamber  48  to prevent the take-up chamber  50  from adversely affecting the pressure of the vacuum deposition chamber  48 . 
     The operation of the vacuum deposition device  26  is described below. 
     As described above, upon mounting of the film roll  42  on the rotary shaft  52 , the flexible film Z is let out from the film roll  42  to travel on the predetermined travel path. More specifically, the flexible film Z travels in the feed chamber  46  and is guided by the guide roller  54   a  to reach the vacuum deposition chamber  48 , where the flexible film Z is guided by the guide roller  54   b  to travel on the predetermined region of the peripheral surface of the drum  68  and is then guided by the guide roller  54   c  to reach the take-up chamber  50 , where the flexible film Z reaches the take-up shaft  106  as it is guided by the guide roller  54   d.    
     The vacuum evacuation means  80  evacuates the second organic layer deposition unit  60  to a predetermined degree of vacuum suitable to the formation of the second organic layer  14  by flash evaporation, the vacuum evacuation means  104  evacuates the third organic layer deposition unit  64  to a predetermined degree of vacuum suitable to the formation of the third organic layer  18  by flash evaporation, and the vacuum evacuation means  70  evacuates the region communicating with the feed chamber  46  and the take-up chamber  50  to a predetermined degree of vacuum suitable to the flash evaporation. 
     In addition, in the inorganic layer deposition unit  62 , the material gas supply section  92  supplies to the shower head electrode  90  material gases suitable to the inorganic layer  16  to be formed, and the vacuum evacuation means  96  evacuates the inorganic layer deposition unit  62  to a predetermined degree of vacuum suitable to the formation of the inorganic layer  16  by CCP-CVD. 
     Furthermore, the vacuum evacuation means  55  and  108  evacuate the feed chamber  46  and the take-up chamber  50  to predetermined degrees of vacuum based on the pressure of the vacuum deposition chamber  48 , respectively. 
     Once the amounts of material gases supplied and the pressure in all the film deposition units have stabilized, the flexible film Z starts traveling from the feed chamber  46  toward the take-up chamber  50 , and the second organic layer deposition unit  60  starts ejecting a vaporized monomer for use in forming the second organic layer  14  from the organic material supply section  78  to the vapor deposition section  74  and irradiating UV light from the curing means  76 . The inorganic layer deposition unit  62  starts supplying plasma excitation power from the RF power source  94  to the shower head electrode  90 . The third organic layer deposition unit  64  starts ejecting a vaporized monomer for used in forming the third organic layer  18  from the organic material supply section  102  to the vapor deposition section  98  and irradiating UV light from the curing means  100 . 
     The flexible film Z fed from the feed chamber  46  and guided by the guide roller  54   a  on the predetermined path first travels to the vacuum deposition chamber  48 . 
     The flexible film Z having reached the vacuum deposition chamber  48  travels on the drum  68  as it is guided by the guide roller  54   b  on the predetermined path, and the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  are sequentially formed on the flexible film Z in the second organic layer deposition unit  60 , the inorganic layer deposition unit  62  and the third organic layer deposition unit  64 , respectively, and the flexible film Z is then guided by the guide roller  54   c  on the predetermined path to reach the take-up chamber  50 . 
     The flexible film Z having reached the take-up chamber  50  is guided by the guide roller  54   d  to be wound on the take-up shaft  106  to obtain the film roll  110  into which the flexible film Z having the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and the third organic layer  18  formed thereon is wound. The film roll  110  is fed again to the organic deposition device  24 . Alternatively, the film roll  110  may be used in the next step as a gas barrier film or an intermediate product of gas barrier film. 
     The film roll  110  is fed again to the organic deposition device  24  to produce the gas barrier film  10  shown in  FIG. 2  which has the fourth organic layer  20  formed on the third organic layer  18 . 
     In the organic deposition device  24 , upon mounting of the film roll  110  on the rotary shaft  28 , the same treatments as for the first organic layer  12  are repeated: the coating means  32  applies a coating material for the fourth organic layer  20  and the coating material is dried by the drying means  34  and is then cured by the curing means  36  to form the fourth organic layer  20 . 
     The flexible film Z having the fourth organic layer  20  formed thereon, that is, the gas barrier film  10  is wound on the take-up shaft  30  and fed to the next step as a gas barrier film or an intermediate product of gas barrier film. 
     In a preferred embodiment, the fourth organic layer  20  is an uppermost organic layer. 
     Favorable results can be obtained in that the fourth organic layer  20  can protect the gas barrier laminate including the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and optionally the third organic layer  18  against damage to obtain a gas barrier film having excellent strength and durability. 
     The thickness of the fourth organic layer  20  is not particularly limited and may be appropriately set according to the strength and thickness required for the gas barrier film  10 . However, the fourth organic layer  20  preferably has a thickness of 0.3 to 5 μm. 
     At a thickness of the fourth organic layer  20  within the above-defined range, favorable results can be obtained in terms of the durability and mechanical strength of the gas barrier film  10 . 
     The material used to form the fourth organic layer  20  is not particularly limited and various organic materials capable of film deposition at atmospheric pressure as in the coating method can be used. 
     Exemplary materials include epoxy resins, (meth)acrylic resins, polyesters, methacrylic acid/maleic acid copolymers, polystyrenes, transparent fluororesins, polyimides, fluorinated polyimides, polyamides, polyamideimides, polyetherimides, cellulose acylates, polyurethanes, polyetherketones, polycarbonates, fluorene ring-modified polycarbonates, alicyclic ring-modified polycarbonates, and fluorene ring-modified polyesters. 
     The gas barrier film of the present invention may have a plurality of gas barrier laminates each including the first organic layer  12 , the second organic layer  14  and the inorganic layer  16 , and optionally the third organic layer  18 . 
     More specifically, as an example is shown in  FIG. 3A , the gas barrier film may have a gas barrier laminate including a first organic layer  12   a , a second organic layer  14   a , an inorganic layer  16   a  and a third organic layer  18   a  which is overlaid with another gas barrier laminate including a first organic layer  12   b , a second organic layer  14   b , an inorganic layer  16   b  and a third organic layer  18   b , and then with a fourth organic layer  20 . Alternatively, the gas barrier film may have three or more such gas barrier laminates. 
     For example, such a gas barrier film may be produced as follows: From the second organic layer  14   a  to the third organic layer  18   a  are formed in the vacuum deposition device  26 , after which the first organic layer  12   b  is formed in the organic deposition device  24 ; then, from the second organic layer  14   b  to the third organic layer  18   b  are formed in the vacuum deposition device  26  before the fourth organic layer  20  is formed in the organic deposition device  24 . 
     As described above, the third organic layer  18  is formed in a preferred embodiment and therefore a film structure shown in  FIG. 3B  is also possible in which a gas barrier laminate including the first organic layer  12   a , the second organic layer  14   a  and the inorganic layer  16   a  is overlaid with another gas barrier laminate including the first organic layer  12   b , the second organic layer  14   b  and the inorganic layer  16   b , and then the fourth organic layer  20 . Alternatively, the gas barrier film may have three or more such gas barrier laminates. 
     As described above, the fourth organic layer  20  is also formed in a preferred embodiment. 
     The gas barrier film may have one or more gas barrier laminates each including the first organic layer  12 , the second organic layer  14  and the inorganic layer  16 , and one or more another gas barrier laminates each including the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and the third organic layer  18 . 
     In other words, the gas barrier film shown in  FIG. 2  may also have another set of the first organic layer  12 , the second organic layer  14 , the inorganic layer  16  and optionally the third organic layer  18 , or a plurality of gas barrier laminates each composed of such organic layers and inorganic layer may be formed. 
     The above-described production device includes the organic deposition device  24  for forming the organic layer by coating and the vacuum deposition device  26  for vacuum film deposition as separate entities. However, this is not the sole case of the present invention and a gas barrier film may be formed by using a roll-to-roll film deposition device for forming from the first organic layer  12  to the fourth organic layer  20 . 
     In this case, the device shown in  FIG. 1B  may be provided with a film deposition chamber similar to the organic deposition device  24  shown in  FIG. 1A  between the feed chamber  46  and the vacuum deposition chamber  48 , and between the vacuum deposition chamber  48  and the take-up chamber  50 . 
     However, as shown in  FIGS. 1A and 1B , the film deposition device for forming the organic layer by coating and the film deposition device for film formation in vacuum are preferably provided as separate entities in terms of a higher degree of flexibility in the operating conditions of the manufacturing facility and the facility layout; for example, the film travel speed in the film deposition device by coating in which the film deposition rate is very high is made higher than that of the device in which vacuum film deposition is performed; and one device is used for film deposition by coating at a very high film deposition rate, whereas three devices are used for vacuum film deposition. 
     While the gas barrier film and the gas barrier film production method according to the present invention have been described above in detail, the present invention is by no means limited to the foregoing embodiments and it should be understood that various improvements and modifications may of course be made without departing from the scope and spirit of the invention. 
     The present invention is advantageously applicable to gas barrier films for use in manufacturing plasma displays and organic EL displays.