Abstract:
A method for forming multiple coating layers produces a coating construction that has flexibility corresponding to the number of layers of multiple coating layers, by which a multilayer coating film can be produced with small film thickness without adherence of dust to a film surface, a drying fault such as unevenness induced by drying-wind on the film surface, or a coating fault such as a level variation and a streak. The multilayer coating film has a coating surface state of high quality with coating thickness deviation of 3% or less. In the method, a belt-like substrate is continuously fed. A coating/drying step follows, with multiple steps performed in a single unit. A plurality of coating layers are formed by sequentially performing the coating/drying step by multiple units. Finally, the belt-like substrate with the multiple coatings is continuously wound.

Description:
[0001]     This application is a division of co-pending application Ser. No. 10/341,245, filed on Jan. 14, 2003, the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a production apparatus of a multilayer coating film, and particularly to a production apparatus of a multilayer coating film which produces function films such as a wide view angle film and an antireflection film that are used for liquid crystal displays.  
         [0004]     2. Description of the Related Art  
         [0005]     Recently, various kinds of function films such as a wide view angle film and an antireflection film are widely used for a liquid crystal display. This function film needs to have a small film thickness, no adherence of dust to a coating surface, no coating fault such as a level variation and a streak, and no drying fault such as unevenness on the surface induced by drying-wind, and it further needs to have a high quality coating surface with a coating thickness deviation of 3% or less. The function film comprises multiple coating layers, and the multiple coating layers are made by applying coating solutions with organic solvents a plurality of times to a flexible substrate (hereinafter referred to as a web).  
         [0006]     Since the above-described high quality is demanded, the function film with the high quality coating surface cannot be efficiently produced with an ordinary coating device. For example, with a coating device equipped with one coater and a dryer, a web has to be repeatedly passed through the coating device as many times as the number of layers to perform multilayer coating, thus causing the disadvantage that a large variation occurs to the quality, and production efficiency becomes extremely low. Only in terms of quality, it is considered to perform multilayer coating with a spattering device, but the production speed is extremely low with 1 m/min, and the production cost is too high, thus making it difficult to be adopted. There is a multilayer coating apparatus for performing multilayer coating by placing a plurality of sets of coating devices including coaters and dryers in layers, where a web is continuously transferred from the coating device on the upper layer to the coating device in the lower layer to perform multilayer coating. However, the multilayer coating apparatus is limited to three layer coating at the maximum in terms of operability because a delivery device and a winder for the web should not be far from the coater. This apparatus has the disadvantage that a burden of cleaning the coating devices, an operation of passing the web through the devices and the like is too large, and too much loss of time concerning the maintenance is required.  
         [0007]     From the viewpoint of efficient multilayer coating, a gravure printing apparatus having three sets to ten sets or more at the maximum of coaters and dryers for one printing apparatus is the most efficient apparatus.  
         [0008]     However, in the gravure printing apparatus, it is difficult to build a preferable and flexible coating construction corresponding to the number of layers of the multiple coating layers, and the gravure printing apparatus is insufficient as a multilayer coating film production apparatus for a function film which is demanded to have the above-described high quality in terms of coating, drying, dust prevention and handling. Accordingly, the fact is that there is no production apparatus of the multilayer coating films, especially, no preferable production apparatus of the multilayer coating films which efficiently produces high quality function films such as wide view angle films and antireflection films used for liquid crystal displays.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is achieved in view of the above-described circumstances, and has its object to provide a production apparatus of a multilayer coating film preferable for producing various kinds of function films such as a wide view angle film, and an antireflection film, since it is capable of easily building a coating construction with flexibility according to the number of layers of the multiple coating layers, and is capable of producing a multilayer coating film with small film thickness, without adherence of dust to the film surface, a drying fault such as unevenness induced by drying-wind on the film surface, and a coating fault such as a level variation and a streak, and further with a high quality coating surface state with a small coating thickness deviation.  
         [0010]     In order to attain the aforementioned object, the present invention is directed to an apparatus for producing a multilayer coating film in which a plurality of coating layers are formed on a web, comprising: a production chamber; a delivery device and a winder of the web which are placed on a floor surface of the production chamber; and a plurality of coating devices which are arranged between the delivery device and the winder of the web, a number of the plurality of coating devices being equal to a number of the plurality of coating layers, each of the plurality of coating devices being constructed to be a unit by integrally incorporating at least a feed roller for transferring the web along a transfer path, a coater provided at the transfer path to form one of the plurality of coating layers on the web, and a dryer for drying the one of the plurality of coating layers inside a casing having an inlet port and an outlet port for the web.  
         [0011]     According to the present invention, the coating device is constructed as a unit which makes it easy to provide a plurality of the same devices and combine it with other devices by integrally incorporating at least the feed roller, the coater and the dryer in the casing, and the coating device is given a unit function as an independent device, whereby the production apparatus of the multilayer coating film can be constructed by only suitably placing as many coating devices as the number of layers of the multiple coating layers which are formed on the web between the delivery device and the winder. This makes it possible to build the production apparatus of the multilayer coating film which corresponds to production of the multilayer coating film with any number of layers with one transfer from the delivery of the web to the winding. Accordingly, the production efficiency can be improved, and the production cost can be reduced.  
         [0012]     Preferably, the production apparatus of the multilayer coating film further comprises: a dust removing device which is constructed as a unit by integrally incorporating at least a feed roller for transferring the web along a transfer path, and a dust remover provided at the transfer path to remove dust on the web inside a casing having an inlet port and an outlet port for the web; a heat treatment device which is constructed as a unit by integrally incorporating at least a feed roller for transferring the web along a transfer path, and a heat treatment machine provided at the transfer path to thermally treat the web inside a casing having an inlet port and an outlet port for the web; and a surface inspection machine which is constructed as a unit by integrally incorporating at lease a feed roller for transferring the web along a transfer path, and a surface inspection machine provided at the transfer path to inspect a coating surface state of the web, wherein: the dust removing device is placed between the delivery device and the plurality of coating devices; and the heat treatment device and the surface inspection device are placed in order from an upstream side in a transfer direction of the web between the plurality of coating devices and the winder.  
         [0013]     According to the present invention, a series of function film production route from delivery of the web to winding is formed. Accordingly, the production apparatus of the multilayer coating film, which produces a function film such as a wide view angle film and an antireflection film, is easily constructed. By providing a UV treatment machine for performing UV treatment for the coating layer after drying at the position after the dryer, the apparatus can suitably correspond to the case in which the cured resin contained in the coating solution is a UV cure resin, and in the case in which it is a thermosetting resin.  
         [0014]     Concerning handling of the web which is important to prevent the coating fault such as a level variation and a streak, the feed roller is provided at each device to make tension of the web cut at each device. Hence, even if tension variation occurs to one of the devices, an adverse influence of the tension variation is not given to the devices before and after the device.  
         [0015]     Concerning dust prevention, which is important to prevent dust adhering to the film surface, a fan filter unit is provided at an air inlet port formed at a ceiling surface of a casing of each device, an air exhaust port is formed at a bottom surface of the casing, and clean air blown into the casing from the fan filter unit is exhausted from the air exhaust port. As a result, a down flow of clean air can be formed in the casing of each device, and cleanliness inside the casing can be improved. In addition, the fan filter unit is provided at each casing, and therefore cleanliness according to the treatment of each device such as dust removing, coating, surface inspection and the like can be formed inside the casing.  
         [0016]     Further, a transfer path in each device is enclosed by a transfer path case, which has an inlet port and an outlet port for the web and has an air introduction port and an air exhaust port, along the transfer path, and clean air is supplied into the air introduction port. As a result, the transfer path in which the web is exposed to dust the most easily can be made a slim transfer path case with a small volumetric capacity, which is corresponding to the transfer path, therefore making it possible to prevent the wind speed of the clean air supplied into the transfer path case from decreasing, and a dead zone where clean air does not flow from occurring. As a result, dust prevention for the web can be performed with a small amount of clean air, and an air amount supplied into the casing can be reduced, and the total air amount can be made small.  
         [0017]     As for the dryer important to prevent a drying fault such as unevenness induced by drying-wind on the film surface, the dryer is divided into three or more drying zones along the transfer direction of the web, a supply device which supplies dry air and an exhaust device are provided at each drying zone, and micro-differential pressure gauges to perform static pressure management between the dry zones are provided. As a result, it is possible to individually set the dry air amount and temperature and relative humidity for each drying zone, and a drying condition corresponding to a film surface strength of the coating layer can be selected, thus making it possible to prevent unevenness induced by drying-wind. By performing static pressure management between the drying zones, coming and going of drying air from and to each of the zones can be eliminated as much as possible, the precision of set condition of each zone can be enhanced.  
         [0018]     The coater which is important to form a suitable layer for each layer in the multiple coating layer is any one of a direct gravure coater, a reverse coater, a kiss coater, a microgravure coater, a bar coater, and an extrusion coater, and the coater is provided to be replaceable. As a result, even when the coating condition of each layer constructing a multilayer, for example, kinds of solution, coating amount, coating method (kind of coater) differ, the apparatus can easily correspond to it.  
         [0019]     Further, the coater inside the coating device is placed to be located on a floor surface of the casing of the coating device or near the floor surface. As a result, since all of the delivery device, coater, and the winder can be arranged on the same floor, operability in attaching required a raw roll of the web to the delivery machine, winding handling of the multilayer coating film being the produced product to the winder, replacing operation of the coater, transportation of the coating solution and the like according to the types of the multilayer coating film to be produced can be extremely improved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein:  
         [0021]      FIG. 1  is an entire block diagram of a production apparatus of a multilayer coating film of the present invention;  
         [0022]      FIG. 2  is a block diagram of a coating device constructed as a unit;  
         [0023]     FIGS.  3 ( a ),  3 ( b ) and  3 ( c ) are explanatory views explaining switching of coaters;  
         [0024]      FIG. 4  is an explanatory view explaining a dancer roller;  
         [0025]      FIG. 5  is a side sectional view explaining a dryer;  
         [0026]      FIG. 6  is an explanatory view explaining relationship between a nozzle plate and a backup roller of the dryer;  
         [0027]      FIG. 7  is a sectional side view explaining a dust prevention measure for a transfer path; and  
         [0028]      FIG. 8  is a sectional front view explaining the dust prevention measure for the transfer path. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     A preferred embodiment of a production apparatus of a multilayer coating film according to the present invention will be explained in detail below with reference to the attached drawings.  
         [0030]      FIG. 1  is a block diagram of an entire production apparatus of a multilayer coating film according to the present invention and is an example of the production apparatus which produces function films such as a wide view angle film and an antireflection film. The apparatus in  FIG. 1  is constructed to produce a multilayer coating film of five layers.  
         [0031]     As shown in  FIG. 1 , the production apparatus  10  is entirely housed in a production chamber  12 , and clean conditioned air is supplied into the production chamber  12  from an air conditioner (not shown) through an air duct  13 . A floor surface  14  of the production chamber  12  is formed by a grating floor, and an underfloor space  16  is formed under the floor surface  14 . Consequently, the conditioned air supplied into the production chamber  12  flows down inside the production chamber  12  to the underfloor space  16  from the floor surface  14  and is discharged through an exhaust duct  18 .  
         [0032]     Inside the production chamber  12 , a delivery device  22  for letting out a web  20  wound like a roll, a dust removing device  24  which removes dust on the web  20  and is constructed as a unit, five coating devices  26  which form coating layers on the web  20  in order and are constructed as units, a heat treatment device  28  which thermally treats the coating layers formed by coating on the web  20  and is constructed as a unit, a surface inspection device  30  which checks whether there are a coating fault and a drying fault such as level irregularity, streak, and unevenness induced by drying-wind on a surface of the coating layers and is constructed as a unit, and a winder  32  which rolls a product of the produced multilayer coating film around on a core, are laterally placed in line from the left end side to the right end side in  FIG. 1 . This constructs a route of a series of function film production of: delivery of the web  20 →feeding into the first device→(dust removal)→(the first coating→drying→UV treatment)→intermediate feeding between the devices→(the second coating→drying UV treatment)→intermediate feeding between the devices→ . . . →(the fifth coating→drying→UV treatment)→heat treatment→surface inspection→feeding out of the device winding. In  FIG. 1 , five of the coating devices  26  are shown, but the coating devices  26  as many as the number of layers of the multiple coating layers to be formed are placed.  
         [0033]     The dust removing device  24  is constructed by integrally including at least a feed roller  36  for transferring the web  20  along a transfer path and a dust remover  38  provided at the transfer path in a casing  34  having an inlet port and an outlet port of the web  20 . The dust remover  38  is not especially limited, if only it can effectively remove dust from the web  20 , and an air dust removing method and an ultrasonic wave cleaner can be suitably used. As the feed roller  36 , a nip method of transferring the web  20  by nipping it with two rollers, or a suction method of transferring the web  20  by sucking it to a roller can be suitably used. The dust removing device  24  arrests dust of the web  20  at a time just before the first coating is applied, and as to dust prevention after the dust removing device  24 , a static electricity eliminator (not shown) is placed as necessary to prevent dust from adhering to the web  20 , or dust prevention is performed by cleaning air blowing into the production chamber  12  and a transfer path case  98  (see  FIGS. 7 and 8 ) covering the transfer path, which will be described later.  
         [0034]     As shown in  FIGS. 1 and 2 , the coating device  26  is constructed by integrally including at least a feed roller  36  for transferring the web  20  along the transfer path, a dancer roller  37  which is provided at the transfer path and eliminates a tension variation of the web  20 , a coater  40  which forms one coating layer on the web  20 , and a dryer  42  which dries the coating layer, in the casing  34  having an inlet port  34   a  and an outlet port  34   b  of the web  20 . In this case, if a UV treatment device  43 , which performs UV (ultraviolet ray) treatment for the coating layer after drying, is provided, the apparatus can correspond to the case in which a cured resin contained in the coating solution is a UV cured resin and the case in which it is a thermosetting resin as necessary.  
         [0035]     The coater  40  is constructed to be switchable to any one of a direct gravure coater, a reverse coater, a kiss coater, a micro-gravure coater, a bar coater, and an extrusion coater so that the kind of the coater  40  can be changed according to a coating method and coating conditions of each layer of the multiple coating layers, for example, the kind of a coating solution, coating amount, tension of the web  20 , drying temperature, air flow and so on. Of the above coaters, as to three types of coaters which are the direct gravure coater, the reverse coater, and the kiss coater, pass rollers  44  placed at an upstream side and a downstream side of the coater are made swingable in the A-B direction in  FIG. 3 ( a ) around swing devices  46 , and an impression roller  50  is constructed to be movable in the C-D direction in  FIG. 3 ( a ) with a moving device  52  so that an printing roller  48  rotatable forwardly and reversely and the impression roller  50  can move close to or away from each other as shown in  FIG. 3 ( a ). The swing devices  46  and the moving device  52  are made to be operated with an operating panel  54 . According to this structure, it is preferable to perform switching of the direct gravure coater in  FIG. 3 ( a ), the kiss coater in  FIG. 3 ( b ) and the reverse coater in  FIG. 3 ( c ) by one-touch control on the operating panel  54 . As for three types of coaters which are the micro-gravure coater, the bar coater, and the extrusion coater, it is preferable to unitize a set of coater device and make it possible to attach and detach the entire device to and from the casing  34 .  
         [0036]     Since coating of high quality with coating thickness deviation being 3% or less without coating fault such as level variations and streak is demanded in production of the function film such as a wide view angle film and antireflection film, it is preferable to construct the coating device  26  as follows.  
         [0037]     In the case of the coater  40  using the printing roller  48  and the impression roller  50 , the rotational speed variations of the printing roller  48  and the impression roller  50  are made 0.2% or less. For this purpose, it is preferable to use an AC vector inverter motor, a planetary roller reducer, a form flexible joint, and high precision bearing in a driving system. As the feed roller  36 , a nip type and a suction type can be suitably used as the dust removing device  24 .  
         [0038]     In the case of any kind of coater  40 , it is preferable to make the variation ratio of the transferring speed of the web  20  to be 0.5% or less. For this purpose, it is preferable to adopt a sectional drive method, and it is suitable to provide the feed roller  36  at an end of a downstream of the transfer path of the web  20  at each coating device  26 . Consequently, the feed rollers  36  are individually driven to make it possible to transfer the web  20  to the coating devices  26 , and the tension in the transfer direction of the web  20  is cut for each coating device  26 , therefore making it possible to prevent a tension variation occurring to one of the coating device  26  from being consecutively transmitted to the other coating devices  26 . In the driving system for the feed rollers  36 , it is preferable to use an AC vector inverter motor, a planetary roller reducer, a form flexible joint and a high precision bearing.  
         [0039]     Further, it is suitable to place the dancer roller  37  at an upstream side of the coater  40 . This not only makes it possible to eliminate the transfer speed variation and the tension variation of the web  20  in each of the coating devices  26 , but also makes it possible to prevent the transfer speed variation and the tension variation of the web  20  in the coating device  26  at the upstream side from influencing on the coating device  26  at the downstream side. As the dancer roller  37 , the one with the construction as shown in  FIG. 4  can be suitably used. In the dancer roller  37 , a swing plate  60 , which swings in the E-F direction around a shaft  58 , is placed under a plurality of pass rollers  56  fixedly placed, and a plurality of moving rollers  62  are rotatably supported in a longitudinal direction of the swing plate  60 . The web  20  is alternately passed around the pass rollers  56  and the moving rollers  62 . Consequently, if there is the transfer speed variation and/or the tension variation in the web  20 , the swing plate  60  swings in the E-F direction, and the variation is thereby eliminated.  
         [0040]     Harmony of the transfer speed and the tension of the web  20  between the plurality of coating devices  26  may be attained by controlling the feed rollers  36  and the dancer rollers  37  as follows. Namely, the feed roller  36  of the coating device  26  at the uppermost stream position out of the plurality of coating devices  26  placed between the delivery device  22  and the winder  32  is made a reference roller to control the transfer speed of the web  20 , and the feed rollers  36  of the second coating device  26  and the following coating devices  36  are controlled with a speed signal derived from the reference roller as the reference. The dancer roller  37  of the coating device  26  at the uppermost stream position out of the plurality of coating devices  26  is made as the reference dancer roller, and the dancer rollers  37  of the second coating device  26  and the following coating devices  26  are controlled with a positional signal showing a swing amount of the reference dancer roller  37  as the reference. In this case, as the dancer roller  37 , the large-capacity dancer roller  37  is preferable. This is to control a long-period variation that has a large influence on the coating fault, though ignoring a short-period variation of the tension variation to some extent.  
         [0041]     As shown in  FIG. 5 , in the dryer  42 , a device casing  64  is formed into an arch shape, and is divided into three dry zones  42 A,  42 B and  42 C by partition plates  69  having passage ports  66  for the web  20 , and an air supply fan  68  for supplying dry air and an exhaust fan  70  for exhausting air are provided at each of the dry zones  42 A,  42 B and  42 C. Each of an air supply duct  72  and an exhaust duct  74 , which are provided with the air supply fan  68  and the exhaust fan  70 , is provided with a damper device  76 , and by controlling the damper opening degree, supply and exhaust air amounts in each of the dry zones  42 A,  42 B and  42 C are individually controlled. As a result, it is possible to control dry temperature and relative humidity, and air quantity independently for each of the dry zones  42 A,  42 B and  42 C, and dry conditions corresponding to the film surface strength of the coating layer formed on the web  20  can be set. Accordingly, the drying fault such as unevenness induced by drying-wind on the coating surface during drying can be prevented.  
         [0042]     In the device casing  64 , a number of backup rollers  78  are arranged on an arch line along the transfer path of the web  20 , and an arch-shaped nozzle plate  80  is placed at an opposite side of the backup rollers  78  across the web  20 . An air supply chamber  82  is formed in a space enclosed by the nozzle plate  80  and the device casing  64 , and an arch-shaped supply side current plate  84  which is parallel with the nozzle plate  80  is placed in the air supply chamber  82 . Further, an air suction chamber  88  is formed in a space enclosed by an arch-shaped suction plate  87  and the device casing  64  at an opposite side of the air supply chamber  82  across the backup rollers  78 , and an arch-shaped suction side current plate  90  is placed inside the air suction chamber  88 . A number of holes are formed in a punched metal form in the suction plate  87  and the current plates  84  and  90 , and dry air supplied into the device casing  64  by the supply air fan  68  is formed into a laminar flow from the air supply chamber  82  to the air suction chamber  88  by the action of the current plates  84  and  90  at the supply side and the suction side. As a result, disturbance of dry air at the coating layer surface can be prevented, and therefore drying fault such as unevenness induced by drying-wind can be further reduced.  
         [0043]     As shown in  FIG. 6 , the nozzle plate  80  is formed into a continuous corrugated plate form, which is parallel with the backup rollers  78  (in a direction perpendicular to the sheet of  FIG. 6 ) and has alternating raised portions  80 A and recessed portions  80 B, and nozzle holes  80 C are provided in the raised portions  80 A. As known from  FIG. 6 , the backup rollers  78  and the raised portions  80 A are constructed to be placed to face each other, so that dry air, which is blown from the nozzle holes  80 C, blows against the backup rollers  78 . As a result, the web  20  transferred on the backup rollers  78  is pressed against the backup rollers  78  to be gripped securely, and therefore flapping of the web  20  and occurrence of a scratch on the web  20  by a slip can be prevented.  
         [0044]     Further, as shown in  FIG. 5 , micro-differential pressure gauges  86  for managing static pressure differences are provided between the respective adjacent dry zones  42 A,  42 B, and  42 C, and according to measurement values of the micro-differential pressure gauges  86 , air supply and exhaust amount is managed so that the static pressure of each of the dry zones  42 A,  42 B and  42 C becomes the same. Consequently, air of the adjacent dry zones  42 A,  42 B and  42 C does not go back and forth via the passage ports  66  for the web  20 , which are formed at the partition plates  69 , and therefore drying condition for each of the dry zones  42 A,  42 B and  42 C can be set with high precision.  
         [0045]     The heat treatment device  28  is constructed by integrally incorporating at least a heat treatment machine  51  for thermally treating the coating layer inside the casing  34  having an inlet port and an outlet port for the web  20  as shown in  FIG. 1 . As the heat treatment machine  51 , for example, a machine with a method of heating the web  20  to be transferred by supplying hot air into the casing  34  can be suitably used as shown in  FIG. 1 , but the heat treatment machine  51  is not limited to this. In  FIG. 1 , the feed roller  36  is not provided in the heat treatment device  28 , but it may be provided therein.  
         [0046]     The surface inspection device  30  is constructed by integrally incorporating at least the feed roller  36  for transferring the web  20  along the transfer path, and a surface inspection machine  55 , which is provided at the transfer path and inspects the state of the coating surface of the coating layer, inside the casing  34  having an inlet port and an outlet port for the web  20  as shown in  FIG. 1 . Since the surface inspection device  30  is constructed as the device having an independent function, an optional number of them can be placed at an optional position of the production apparatus  10 , and by placing it in front of the winder  32  as shown in  FIG. 1  and carrying out the following usage, the surface inspection of each layer of the multiple coating layers can be performed with one surface inspection device  30 . Namely, at the time of starting operation of the production apparatus  10 , or when a defect in coating and the like is found in an end product, coating and surface inspection are performed for each layer from the coater  40  at the upstream side, then if this is acceptable, coating and surface inspection are performed for the following coaters  40  in order, and the final coating and surface inspection are performed. As a result, it can be determined which layer has the coating defect. During normal operations, the surface inspection device  30  is used for surface inspection of the end products.  
         [0047]     Next, a dust prevention measure on the transfer path of the above-described devices  24  to  30  is explained with the example of the coating device  26  in  FIG. 2 .  
         [0048]     As shown in  FIG. 2 , air inlets  92  are formed in a ceiling surface of the casing  34 , and a plurality of fan filter units  96  are provided in a space  94  in the ceiling (see  FIG. 1 ) of the casing  34 , which corresponds to the air inlets  92 . The conditioned air is supplied to the space  94  in the ceiling from the air conditioner (not shown). The fan filter unit  96  is a unit in which a fan  96 A and a HEPA filter  96 B are integrally incorporated, and the number of the fan filter units  96  provided can be easily increased or decreased according to cleanliness demanded according to the kind of the unit. Meanwhile, an air exhaust port  97  is formed in the bottom surface of the casing  34 , and the casing  34  is placed on the floor surface  14  formed by the grating floor, whereby the casing  34  is allowed to communicate with the underfloor space  16  (see  FIG. 1 ). As a result, the conditioned air which is supplied to the space  94  in the ceiling is further purified in the HEPA filter  96 B and blown into the casing  34 , flows down inside the casing  34 , then flows into the underfloor space  16  from the floor surface  14 , and is exhausted through the exhaust duct  18 .  
         [0049]     The transfer path from the inlet port  34   a  to the outlet port  34   b  of the casing  34  is enclosed by a box-shaped or tube-shaped transfer path case  98  along the transfer path. An air introduction port  100  and air exhaust ports  102  are formed at the transfer path case  98 , and the air introduction port  100  is connected to one of the fan filter units  96 . The parts enclosed by the transfer path case  98  are an area around the dancer roller  37 , an area around the coater  40 , an area around the UV treatment machine  43 , and an area around a passage  104  from the UV treatment machine  43  to the outlet port  34   b.    
         [0050]      FIGS. 7 and 8  show the passage  104  part from the UV treatment machine  43  to the outlet port  34   b  in detail, wherein a number of pass rollers  106  which transfer the web  20  are arranged in a vertical direction, and the tube-shaped transfer path case  98  is provided along this passage  104 . As a result, as known from  FIG. 8 , the passage  104  is formed to be a doubly enclosed structure by the casing  34  and the transfer path case  98 . As shown in  FIG. 8 , the relationship between the casing  34  and the transfer path case  98 , and a pass roller  106  is constructed so that roller journal portions  110  supported by bearings  108  fixed to the inner wall surface of the casing  34  are placed outside the transfer path case  98 , and only a roller shell portion  112  of the pass roller  106  and the web  20  are enclosed by the transfer path case  98 . In this manner, out of the pass roller  106 , only the roller shell portion  112  with which the web  20  is in contact is enclosed by the transfer path case  98 , whereby the transfer path case  98  can be made slim and small in volumetric capacity corresponding to the passage  104 , and therefore a wind speed of clean air supplied into the transfer path case  98  can be maintained and dead zone where clean air does not flow can be prevented from occurring. The bearings  108  and the roller journal parts  110  where dust easily occurs and dust easily settles are located outside the transfer path case  98 , whereby cleanliness inside the transfer path case  98  can be kept further higher. In such construction, gaps  114  not to hinder rotation are formed between the transfer path case  98  and the roller journal parts  110 . However, a flow of air from an inside of the transfer path case  98  to an outside thereof always occurs through the gaps  114 , and therefore dust which occurs at the bearings  108  and the roller journal parts  110  do not enter the transfer path case  98 . Further, as shown in  FIG. 8 , a plurality of micro-differential pressure gauges  116  for detecting pressure difference between the inside and the outside of the transfer path case  98  are provided inside and outside the transfer path case  98 , and according to the detection result of the micro-differential pressure gauge  116 , the inside pressure of the transfer path case  98  is kept higher than the outside pressure, whereby it is made further possible that air in the casing  34  side does not enter the transfer path case  98 . Further, it is more preferable to provide a micro-differential gauge  118  for detecting the pressure difference between an inside and an outside of the casing  34  to keep the inside pressure of the casing  34  higher than the outside pressure.  
         [0051]     The above-described dust prevention measure of the transfer path is the explanation of the transfer path of the passage  104  part from the UV treatment machine  43  to the outlet port  34   b , and it is suitable to construct the dancer roller  37 , the coater  40  and the UV treatment machine  43  so that the drive parts where dust easily occurs are placed outside the transfer path case  98  and perform pressure management with the micro-differential pressure gauges  116  and  118 .  
         [0052]     As explained thus far, according to the production apparatus of the multilayer coating film of the present invention, coating construction with flexibility according to the number of layers of the multiple coating layers can be easily constructed, and the multilayer coating film with small film thickness, without dust attaching to the film surface, dry fault such as unevenness induced by drying-wind on the film surface and coating fault such as level variation and a streak, and further with coating surface state with high quality with coating thickness deviation of 3% or less can be produced. Accordingly, the present invention is preferable to produce various kinds of function films such as wide view angle films and antireflection films.  
         [0053]     It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the invention is to cover all modifications, alternate constructions and equivalents falling within the spirit and scope of the invention as expressed in the appended claims.