Abstract:
The present invention relates to a calender roll cleaning apparatus for smoothing a surface of a magnetic layer of a magnetic recording medium passed through a plurality of calender rolls. The cleaning apparatus comprises a wiping cloth feeding apparatus that feeds a calender roll surface wiping cloth at a definite rate and tension. A cleaning liquid supplying apparatus supplies a controlled amount of cleaning liquid such that the cleaning liquid permeates into the wiping cloth fed from the wiping cloth feeding apparatus. A wiping cloth pressing apparatus presses the permeated wiping cloth at a controlled pressing load.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a calender roll cleaning apparatus for smoothing a surface of a magnetic layer of a magnetic recording medium. 
     2. Description of the Related Art 
     During production of a magnetic recording medium, after coating a magnetic coating material on a non-magnetic support, a calender apparatus for smoothing a surface of a magnetic layer is used. The calender apparatus includes a plurality of calender rolls, that is, metal rolls and elastic rolls, alternately disposed. After placing the side of the magnetic layer of the magnetic recording medium next to the metal roll, the magnetic recording medium is fed into a nip portion located between the metal roll and the elastic roll, whereby the surface of the magnetic layer is smoothened. 
     However, in the calender apparatus, a binder, a hardening agent and a lubricant of the magnetic coating material coated on the magnetic recording medium are released, whereby the surfaces of the metal rolls or the elastic rolls are stained. Also, the stains on the surfaces of rolls are transferred onto the magnetic layer, etc. of the magnetic recording medium, thereby causing drop-out of the magnetic recording medium and spoiling the recording and reproducing qualities. 
     In order to remove the stains from the surfaces of the metal rolls of the calender apparatus, there has hitherto been proposed a roll cleaning apparatus that brings a cleaning tape into sliding contact with the surfaces of the metal rolls. 
     However, in this conventional roll cleaning apparatus, the cleaning tape is brought into sliding contact with the surfaces of the metal rolls in a dry system, and therefore, the stains on the roller surfaces cannot be adequately removed. As a result, production is interrupted every hour or two, and the stains on the surfaces of the metal rolls are wiped off by hand, resulting in poor productivity. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to adequately remove the stains from the surfaces of the calender rolls and improve productivity of the calender treatment. 
     A first aspect of the present invention relates to a calender roll cleaning apparatus for smoothing a surface of a magnetic layer of a magnetic recording medium passed through a plurality of calender rolls. The cleaning apparatus comprises a wiping cloth feeding apparatus that feeds a calender roll surface wiping cloth at a definite rate and tension. A cleaning liquid supplying apparatus supplies a controlled amount of cleaning liquid such that the cleaning liquid permeates into the wiping cloth fed from the wiping cloth feeding apparatus. A wiping cloth pressing apparatus presses the permeated wiping cloth at a controlled pressing load. 
     Incidentally, the term “definite” of “definite tension” and “definite feeding rate” means a tension and a feeding rate, respectively, generated under a mechanically definite control. For example, not only does “definite feeding rate” include the case of setting the feeding rate to a definite rate of 10 cm/minute but also the case of varying the feeding rate by from 5 to 15 cm/minute by control rollers. The same logic is also applicable to the “definite tension.” 
     A second aspect of the present invention relates to the calender roll cleaning apparatus according to the first aspect, wherein the cleaning liquid supplying apparatus is equipped with a porous member that oozes the cleaning liquid and is brought into contact with the wiping cloth. 
     A third aspect of the present invention relates to a calender roll cleaning apparatus according to the first or the second aspect, wherein the cleaning liquid supplying apparatus controls the cleaning liquid supply amount to the amount at which the cleaning liquid applied to the calender roll from the wiping cloth is vaporized before reaching a magnetic recording medium nip portion located between the rolls. 
     Still another aspect of the present invention relates to a calender roll cleaning apparatus according to any aspects above, wherein the feeding rate of the wiping cloth is from 3 to 60 cm/minute and the pressing load is from 5 to 7 kgf. 
     According the first aspect of the present invention, the following advantageous effects are obtained. The use of a fresh wiping cloth fed at a proper feeding rate from the wiping cloth feeding apparatus. The use of a wet wiping cloth permeated with a cleaning liquid is supplied at a proper amount controlled by the cleaning liquid supply apparatus. The use of a wiping cloth pressed against the calender rolls at a proper pressing load controlled by the wiping cloth pressing apparatus so as to adequately remove stains from the surfaces of the calender rolls. 
     According to the second aspect of the present invention, the following advantages are obtained. The cleaning liquid supply apparatus is equipped with a porous member that oozes a cleaning liquid. By contacting the porous member with the wiping cloth, the cleaning liquid is uniformly distributed throughout the entire wiping cloth, whereby the stains on the surfaces of the calender rolls are adequately removed. 
     According to the third aspect of the present invention, the following advantages are obtained. The cleaning liquid supply apparatus controls the cleaning liquid supply amount to the amount at which the cleaning liquid applied to the calender rolls from the wiping cloth is vaporized before reaching the magnetic recording medium nip portion of the rolls. Thus, the cleaning liquid applied to the calender rolls disappears immediately after acting to remove the stains from the surfaces of the calender rolls, whereby the cleaning liquid is not brought into contact with a magnetic recording medium in the nip portion of the calender rolls to dissolve the magnetic coating material coated thereon. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view showing a calender roll cleaning apparatus. 
     FIG. 2 is a schematic view showing a cleaning liquid supplying apparatus of the calender roll cleaning apparatus of FIG.  1 . 
     FIG. 3 is a schematic view showing a calender apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The calender apparatus  10  of FIG. 3 has, for example, three metal rolls  11 A to  11 C and two elastic rolls  12 A and  12 B alternately disposed in parallel. Nip portions  13 A to  13 D are formed between the adjacent metal roll  11 A and elastic roll  12 A, between the adjacent elastic roll  12 A and metal roll  11 B, between the adjacent metal roll  11 B and elastic roll  12 B, and between the adjacent elastic roll  12 B and metal roll  11 C, respectively. In the metal rolls  11 A to  11 C, for example, a chromium plating is applied to a surface of a steel roll, and the surface thereof is polished. The surfaces of the elastic rolls  12 A and  12 B are each provided with cotton, etc. Guide rolls  14  are also provided. 
     The calender apparatus  10  feeds a magnetic recording medium  1  while holding the medium using each of the nip portions  13 A to  13 D of the metal rolls  11 A to  11 C and the elastic rolls  12 A and  12 B. The magnetic layer side of the magnetic recording medium  1  faces the metal rolls  11 A to  11 C, and pressure and heat are applied to the magnetic layer of the magnetic recording medium  1 , whereby the magnetic layer surface is smoothed. 
     However, in the calender apparatus  10 , as shown in FIG. 1, a roll cleaning apparatus  20  is provided in each of the metal rolls  11 A to  11 C. In this case, the roll cleaning apparatus  20  can also be provided in each of the elastic rolls  12 A and  12 B. The roll cleaning apparatus  20  provided in the metal roll  11 A (the same as the roll cleaning apparatus  20  provided in other metal rolls  11 B, etc.) is hereinafter explained. 
     The roll cleaning apparatus  20  has a wiping cloth feeding apparatus  21 , a cleaning liquid supply apparatus  22 , and a wiping cloth pressing apparatus  23 . 
     The wiping cloth feeding apparatus  21  has a brake-equipped unwinding reel  21 A, a motor-equipped winding reel  21 B, and feeding gears  21 C. The wiping cloth feeding apparatus  21  feeds a wiping cloth  24  for wiping the surface of the metal roll  11 A at a definite feeding rate while maintaining a definite tension. The feeding gears  21 C are composed of a pair of adjustable driving spur gears holding the wiping cloth  24  and apply a feeding force to the wiping cloth  24 . 
     The cleaning liquid supply apparatus  22  has a pump  22 A and a supply head  22 B. The cleaning liquid supply apparatus  22  supplies a cleaning liquid so that the cleaning liquid is permeated into the wiping cloth  24  fed from the wiping cloth feeding apparatus  21 , and the supply amount thereof can be controlled by controlling the discharge amount of the pump  22 . 
     The wiping cloth pressing apparatus  23  has two press rolls  23 A,  23 A and pressing apparatuses  23 B,  23 B for pressing the press rolls  23 A,  23 A against the metal roll  11 A. The wiping cloth  24  fed from the unwinding reel  21 A of the wiping cloth feeding apparatus  21  is wound around the press rolls  23 A,  23 A to regulate the feeding route of the wiping cloth  24  around the metal roll  11 A. The wiping cloth  24  permeated with the cleaning liquid by the cleaning liquid supply apparatus  22  is pressed against the metal roll  11 A, and the pressing load is controlled by press controlling the pressing apparatus  23 B. 
     As the wiping cloth  24 , for example, “SAVINA” (a Japanese Registered Trade Mark) “MINIFMAX” (a Japanese Registered Trade Mark) grade using super fine fibers made by Kanebo, Ltd., can be used. Also, as the cleaning liquid, a solvent for cleaning, for example, methyl ethyl ketone, can be used. 
     Also, in the cleaning liquid supply apparatus  22 , the supply head  22 B can be equipped with a porous member  22 C made of, for example, a fluorocarbon resin sintered material. The porous member  22 C is contacted with the wiping cloth  24  that is made to back up to the press roll  23 A and can ooze the cleaning liquid into the wiping cloth  24 . 
     Further, the cleaning liquid supply apparatus  22  controls the cleaning liquid supply amount by controlling the discharge amount of the pump  22 A to the amount at which the cleaning liquid applied to the metal roll  11 A from the wiping cloth  24  is vaporized before reaching the nip portion  13 A located between the metal roll  11 A and the elastic roll  12 A. 
     The roll cleaning apparatus  20  performs the cleaning process in the following manner. 
     The fresh wiping cloth  24  unwound from the unwinding reel  21 A of the wiping cloth feeding apparatus  21  is wound around the press rolls  23 A,  23 A and fed via the feeding route around the metal roll  11 A at a definite tension and a definite rate. The cleaning liquid oozed from the porous member  22 C of the supply head  22 B of the cleaning liquid supply apparatus  22  is permeated into the wiping cloth  24 . In this case, the supply amount of the cleaning liquid supplied to the wiping cloth  24  is controlled to the amount at which the cleaning liquid applied to the metal roll  11 A from the wiping cloth  24  is vaporized before reaching the nip portion  13 A located between the metal roll  11 A and the elastic roll  12 A. Finally, the wiping cloth  24  permeated with the cleaning liquid is pressed against the metal roll  11 A by the wiping cloth pressing apparatus  23 . In this case, the pressing load is controlled by the pressing apparatus  23 B. 
     There are many advantages obtained by the present invention. The use of a fresh wiping cloth  24  fed at a proper feeding rate from the wiping cloth feeding apparatus  21 . The use of a wet wiping cloth  24  permeated with a proper amount of cleaning liquid controlled by the cleaning liquid supply apparatus  22 . The use of a wiping cloth  24  pressed against the calender roll  11 A, etc. at a proper pressing load controlled by the wiping cloth pressing apparatus  23  so as to ensure that stains are removed from the surfaces of the calender roll  11 A, etc. 
     The cleaning liquid supply apparatus  22  is equipped with the porous member  22 C that oozes a cleaning liquid. By contacting the porous member  22 C with the wiping cloth  24 , the cleaning liquid is uniformly distributed throughout the entire wiping cloth  24 , whereby the stains on the surfaces of the metal roll  11 A, etc. are adequately removed. 
     The cleaning liquid supply apparatus  22  controls the cleaning liquid supply amount such that the cleaning liquid applied to the metal roll  11 A, etc. from the wiping cloth  24  is vaporized before reaching the magnetic recording medium nip portion  13 A, etc. of the roll  11 A, etc. Thus, the cleaning liquid applied to the metal roll  11 A, etc., disappears immediately after removing stains from the surfaces of the metal roll  11 A, etc., such that the cleaning liquid is not brought into contact with a magnetic recording medium in the nip portion  13 A, etc. of the metal roll  11 A, etc. to dissolve the magnetic coating material coated thereon. 
     EXAMPLES 
     Preferred values of the cleaning working conditions of the roll cleaning apparatus  20  provided in the above-described calender apparatus  10  were as follows. 
     (A) Feeding Rate of the Wiping Cloth  24   
     A preferred value of the feeding rate of the wiping cloth  24  was from 3 cm/min. to 60 cm/min., and more preferably from 5 cm/min. to 40 cm/min. 
     (B) Supply Amount of the Leaning Liquid 
     Preferred values of the common values (gf/min) in the case of using methyl ethyl ketone as the cleaning liquid are shown in Table 1 with respect to the roll temperature of the metal roll  11 A, etc. and the line speed of the magnetic recording medium  1 . 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Line speed 
                 Roll temperature 
                 Supply amount of 
               
               
                 m/min. 
                 ° C. 
                 Cleaning liquid gf/min. 
               
               
                   
               
             
             
               
                 100 
                 70 
                 2.5 
               
               
                   
                 80 
                 4.4 
               
               
                   
                 90 
                 6.8 
               
               
                 200 
                 80 
                 6.5 
               
               
                   
                 90 
                 8.2 
               
               
                   
               
             
          
         
       
     
     (C) Pressing Load of the Wiping Cloth  24   
     A preferred value of the pressing load of the wiping cloth  24  was from 5 to 7 kgf. 
     A specific embodiment of the present invention has been described in detail with reference to the attached drawings. However, the invention is not limited thereto. Variations may be made without deviating from the spirit and scope of the invention.