JP5203497B2 - Method for heat-sealing and joining films, joining apparatus, and method for producing optical film - Google Patents

Description

  The present invention relates to a method for thermally welding and bonding films, a bonding apparatus, and a method for manufacturing an optical film.

  The demand for polarizing films is rapidly increasing with the spread of liquid crystal display devices (hereinafter, LCDs). In the polarizing film, a protective film is generally bonded to both surfaces or one surface of a polarizing layer having polarizing ability via an adhesive layer. As a material for the polarizing layer, a PVA (polyvinyl alcohol) -based film is generally used, and a film tip from a raw roll obtained by winding the PVA-based film into a roll is sent to a stretching device, It is manufactured by stretching while being treated (see, for example, Patent Documents 1 and 2).

  In this case, in order to efficiently perform the stretching process, it is preferable to perform the stretching process continuously, instead of performing the stretching process in a batch manner for each of the plurality of raw fabric rolls. In order to perform continuous stretching treatment on a plurality of raw rolls, the film rear end of the raw roll (hereinafter referred to as “old roll”) that is being stretched and the original roll (hereinafter referred to as “new roll”) to be stretched next. )) Is required to be joined.

  As a device for joining the rear end portion and the front end portion of the films, there is a web butt joining device and a joining method described in Patent Document 3, for example. In this joining method, the rear end and the front end of the films are cut while being held on the suction drum and joined with a joining tape.

  However, the method of joining with a joining tape has a problem that only the joined portion is different in thickness and rigidity from other film portions, and thus the joined portion is peeled off or broken during the stretching treatment.

  For this reason, as described in Patent Document 4, for example, the rear end portion and the front end portion of the films are overlapped and heat-sealed (heat-sealed).

JP 2008-122988 A JP 2008-250326 A JP 2007-55704 A JP 2004-160665 A

  However, in the conventional heat welding joining method, there exists a problem that the joining part by which the films were overlapped and heat-welded easily becomes wrinkles, and air pockets are easily generated inside the wrinkles. In particular, the PVA film, which is a film suitable for manufacturing a polarizer, is soft and thin, and wrinkles are generated at the time of heat welding due to the recent widening of the film width (for example, 3 m or more). easy. Moreover, since the manufactured PVA-type film is wound and stored in a medium-high roll shape, the film tends to become wrinkles when the film is rewound. The middle-high roll is wound so that the roll diameter at the center is larger than the roll diameter at the end, and the film elongation differs between the center and the end in the film width direction.

  And if wrinkles are generated in the joints and air is trapped inside the wrinkles, sufficient bonding strength cannot be obtained. As a result, the actual situation is that the problem that the joint portion still peels off or breaks during the stretching process has not been solved.

  In addition, if the tail end part (the end part of the rear end part or the front end part) is large at the rear end part or the front end part after the rear end part and the front end part of the films are overlapped and thermally welded, Stress concentration occurs at the boundary, and the film is easily broken.

  The present invention has been made in view of such circumstances, and it is possible to prevent wrinkles from occurring after heat-sealing the rear end portion and the front end portion of the films, and to prevent the tail portion from becoming long. It is an object of the present invention to provide a method for heat-welding and bonding a film to each other, and a method for manufacturing an optical film, in which a bonded portion is not peeled off or broken during processing.

  In order to achieve the above object, the method for heat-sealing and bonding films according to claim 1 of the present invention is a method in which the rear end portion of the strip-shaped first film and the leading end portion of the strip-shaped second film are overlapped and heat-welded and joined together. In the heat welding joining method, by overlapping the joining region portion of the first film and the second film, sandwiched between the flat suction surfaces of the suction boxes disposed opposite to both sides of the joining region portion, A surface pressure applying step for applying surface pressure to both surfaces of the overlapped portion, and after applying the surface pressure, the first and second films are sucked and held on the suction surfaces of the respective suction boxes. A separation movement step of moving the boxes in a direction in which the overlapping portion is separated, and the first and second films by cutting each film in a state in which the first and second films are separated from each other. A cutting step of forming the rear end portion and the front end portion in the joining region portion of the rumm; and a rear end portion and a second strip shape of the first belt-shaped film formed by moving the suction boxes closer to each other. It is characterized by comprising at least a heat welding step of joining the films together by thermally welding a joining portion where the leading ends of the films are overlapped.

  According to claim 1 of the present invention, the surface pressure is applied to both sides of the joining region portion of the first film and the second film before the first and second films are heat-welded and joined together. That is, the joining region portion is sandwiched between suction boxes having a flat suction surface disposed opposite to each other so as to apply a surface pressure to the joining region portion, so that the wrinkles of the joining region portion can be extended and eliminated. Therefore, wrinkles do not occur after the rear end portion and the front end portion of the films are heat-welded, so that the joint portion is not peeled off or broken during the stretching process, for example. In addition, since the suction box for holding the rear end portion and the front end portion of the first and second films can be used for eliminating wrinkles when heat-welding, no special device for eliminating wrinkles is required. . Thereby, the apparatus can be made compact.

  In order to achieve the above-described object, the method for heat-sealing and bonding films according to claim 2 of the present invention is a method in which the rear end portion of the strip-shaped first film and the leading end portion of the strip-shaped second film are overlapped and thermally welded to each other. In the heat welding joining method, the first film and the second film are overlapped with each other, and the first and second surfaces are sucked by suction surfaces of suction boxes disposed opposite to each other on both sides of the joint area. A suction holding step for sucking and holding the film, a separation moving step for moving the suction boxes in a direction for separating the overlapping portions, and cutting the respective films in a state in which the first and second films are separated from each other. Then, the cutting step of forming the rear end portion and the tip end portion in the joining region portion, and moving the suction boxes in the film longitudinal direction to move the first belt-like film The overlap width adjusting step for adjusting the overlap width for overlapping the rear end portion and the front end portion of the second strip-shaped film, and the first formed by moving the suction boxes closer to each other after adjusting the overlap width. And a heat-welding step of joining the films together by heat-welding a joining portion in which the rear end portion of the belt-like film and the tip portion of the second belt-like film are overlapped with each other.

  Claim 2 of the present invention is another major feature of the present invention, wherein the overlap width of the joint portion obtained by superimposing the rear end portion of the first film and the front end portion of the second film on the joint region portion is adjusted. Therefore, it is possible to reduce a tail portion (an end portion of the rear end portion or the front end portion) which is not welded at the rear end portion or the front end portion. As a result, the tail portion does not flutter or get caught by the conveyance roller during film conveyance, so that the joint portion is not peeled off or broken. Further, since the suction box itself is slid in the film conveyance direction to adjust the overlap width of the joint portion, no wrinkle is generated on the film during the adjustment of the overlap width. Incidentally, the method of transporting and sliding the film itself in a state where the suction force of the suction box is released tends to cause the film to become wrinkled because the transport tension tends to vary in the film width direction. In particular, in the case of a wide film having a film width exceeding 3 m as in recent years, it tends to be wrinkled.

  In the present invention, it is preferable to perform both the surface pressure applying step which is the main feature of claim 1 and the overlap width adjusting step which is the main feature of claim 2. Thereby, the film which eliminated wrinkles in the surface pressure applying step does not have a problem that wrinkles are generated again when adjusting the overlap width of the joint portion.

  In the heat welding and bonding method of the present invention, the first film is subjected to a desired treatment from the first reel that winds and supports the old roll in use through the pair of suction boxes. A first film transporting process for transporting to a film stretching unit, a second film pulling process for drawing the second film from a second reel that supports a new roll to be used next to the suction box, and The first film is provided between the suction box and the film stretching section, and stores a first film having a length corresponding to the time required for heat-welding and joining the first and second films, and transports the first film. It is preferable to provide a reservoir step that enables the first film to be supplied to the film stretching processing unit while stopping the heat treatment and performing thermal welding.

  The heat welding joining method of this invention can be used in the state which stopped the production line incorporating the heat welding joining apparatus for joining. However, by providing the above configuration, the first and second films can be joined to each other without stopping the production line.

  In the heat welding and bonding method of the present invention, the suction surface of the suction box may have a friction coefficient of 4 or less, preferably 2 or less, particularly preferably 1 or less. For example, polytetrafluoroethylene can be suitably used. .

In the heat welding joining method of the present invention, the auxiliary suction box having a coefficient of friction of the suction surface that is flush with the suction surface of the suction box on both sides of the joint region portion and smaller than the friction coefficient of the suction surface of the suction box Are fixedly arranged, and in the step between the cutting step and the thermal welding step, the vicinity of the cut ends of the cut first film and the second film is sucked and held so as not to inhibit the thermal welding. Is preferred.

  Thereby, it can prevent that the cutting edge vicinity of the cut | disconnected 1st film and 2nd film hangs down with dead weight. Further, the suction surface of the auxiliary suction box has a smaller coefficient of friction and better slipperiness than the suction surface of the suction box. Therefore, even if the first and second films are slid in the overlap width adjusting process, the suction surface is rubbed. Does not cause wrinkles or scratches. Therefore, the accuracy of heat welding joining can be improved.

  In the heat welding joining method of this invention, it is preferable that the said overlap width adjustment process is performed in the state which made the distance of the said suction boxes arrange | positioned opposite approached rather than the said cutting process. Thereby, it can prevent more reliably that the cutting edge vicinity of the cut | disconnected 1st film and 2nd film hangs down with dead weight.

  In this invention, it is preferable that the said 1st and 2nd film is a PVA-type film for optical film manufacture. Of course, the present invention can perform heat-welding and bonding of films other than PVA-based films, but when the material is soft as in PVA-based films and the film thickness is extremely thin as for optical film production, This is because it tends to become soot and an air pocket caused by soot weakens the bonding strength.

  In the heat welding joining method of this invention, it is preferable to pressurize the said joining area | region part at 0.2-0.8 Mpa in the said surface pressure provision process. More preferably, it is the range of 0.4-0.8 MPa. When the pressure is less than 0.2 MPa, the effect of stretching the wrinkles is hardly observed, and when the pressure exceeds 0.8 MPa, there is a possibility that a pressure spot is generated on the film surface.

  In the heat welding joining method of the present invention, in the heat welding step, the unwelded area that is not heat welded is 1.5 mm or less in the respective ends of the first and second films of the joint. It is preferable to perform heat welding so that

  This is because if the unwelded area (tail part) that is not thermally welded is larger than 1.5 mm among the first and second films of the joint part, the tail part may flutter when the film is transported, or the transport roller There is a risk of being caught on the film, and the film is easily peeled off or broken.

  In the heat welding and bonding method of the present invention, in the heat welding step, it is preferable to heat-weld the film at an inclination angle of 20 ° or more and 60 ° or less with respect to a direction orthogonal to the film longitudinal direction. Thereby, the fracture | rupture tolerance of the junction part at the time of an extending | stretching process etc. can be improved, for example.

  In the heat welding and bonding method of the present invention, in the heat welding step, the film width direction both ends of the bonded portion before the heat welding or the bonded portion after the heat welding are circularly arranged before or after the heat welding step. It is preferable to have a cutting step of cutting in an arc shape. Thereby, the fracture | rupture tolerance of the junction part at the time of an extending | stretching process etc. can be improved, for example.

  In order to achieve the above object, the film-to-film heat welding and bonding apparatus according to claim 14 of the present invention is a method in which the rear end portion of the belt-like first film and the tip portion of the belt-like second film are superposed and heat-welded. In the heat welding bonding apparatus, the suction box having a flat suction surface disposed opposite to both sides of the bonding region portion where the first film and the second film are overlapped, and the suction boxes disposed opposite to each other Are moved toward and away from each other, and the first moving means for moving the joining region portion toward and away from each other in accordance with the movement of the suction boxes, and the suction boxes arranged opposite to each other in the longitudinal direction of the film. A second moving means for moving, a suction force generating means for applying a suction force to the suction surface of the suction box disposed opposite to each other; A cutting blade that cuts each of the two films to form the rear end portion and the front end portion in the joining area portion, and a superposition of the rear end portion of the first film and the front end portion of the second film. A heat welding means for heat-welding the part, and a control means for performing ON-OFF control of the first and second moving means, the suction force generating means, the cutting blade, and the heat welding means. It is characterized by that.

  In the present invention, the present invention is configured as an apparatus, and it is possible to prevent wrinkles from occurring and a tail portion from becoming long after heat-sealing the rear end portion and the front end portion of films. Therefore, for example, the joint portion is not peeled off or broken during the stretching process.

  In the heat welding and bonding apparatus of the present invention, the suction surface of the suction box may have a friction coefficient of 4 or less, preferably 2 or less, particularly preferably 1 or less. For example, polytetrafluoroethylene can be suitably used. .

  In the heat welding bonding apparatus according to the present invention, the cutting blades have suction surfaces that are flush with the suction surface of the suction box and smaller than the coefficient of friction of the suction surface of the suction box on both sides of the bonding region portion. It is preferable to fix and arrange auxiliary suction boxes for sucking and holding the vicinity of the cut ends of the first film and the second film cut in step 1 so as not to inhibit the thermal welding.

  Thereby, it can prevent that the cutting edge vicinity of the cut | disconnected 1st film and 2nd film hangs down with dead weight. Further, the suction surface of the auxiliary suction box has a smaller coefficient of friction and better slipperiness than the suction surface of the suction box. Therefore, even if the first and second films are slid in the overlap width adjusting process, the suction surface is rubbed. Does not cause wrinkles or scratches. Therefore, the accuracy of heat welding joining can be improved.

  In the heat welding joining apparatus of the present invention, it is preferable that the first moving means has an adjusting mechanism for adjusting the distance of the approaching movement and the distance of the separation movement.

  Thereby, it can prevent more reliably that the cutting edge vicinity of the cut | disconnected 1st film and 2nd film hangs down with dead weight.

  In the heat welding and bonding apparatus according to the present invention, the first reel for winding and supporting the first film in a roll shape, the second reel for winding and supporting the second film in a roll shape, and the first film as described above First film transporting means for transporting the first film from the first reel to the film stretching unit for performing a desired process on the first film through the suction boxes disposed opposite to each other, and the second film on the second reel A second film drawing means for drawing between the suction boxes arranged opposite to each other, and a requirement to heat-weld the first and second films provided between the suction box and the film stretching unit The first film having a length corresponding to the time is stored, and the first film can be supplied to the film stretching processing unit while the conveyance of the first film is stopped and heat welding is performed. Preferably comprises a reservoir device.

  Thereby, it becomes possible to join 1st and 2nd films, without stopping a production line.

  In order to achieve the above object, the optical film manufacturing method according to claim 20 of the present invention includes at least a stretching process step of stretching the film in a production line for manufacturing the optical film by performing various treatments on the film. In the film manufacturing method, the process of performing the heat welding joining method of the films of any one of Claims 1-9 in the upstream position of the said manufacturing line was provided.

  According to the method for producing an optical film of the present invention, since the above-described heat welding joining method is performed, the joining portion of the film is not peeled off or broken in the stretching treatment step of stretching the film. Thereby, the production efficiency of the optical film can be dramatically improved.

  In the method for producing an optical film of the present invention, the film is preferably a PVA film. This is because the PVA film is soft and has a very thin film thickness for optical use, so that it easily becomes wrinkles and the heat welding method of the present invention is particularly effective.

  According to the method and apparatus for thermally welding and bonding films of the present invention, it is possible to prevent wrinkles from occurring and the tail portion from becoming long after the film is thermally welded between the rear end portion and the front end portion of the films. Therefore, if this heat welding joining method is applied to the manufacturing method of an optical film, for example, the joining part will not be peeled off or broken during the stretching treatment.

Schematic configuration diagram incorporating a heat welding and bonding device into the optical film production line Side view along the film transport direction of the thermal welding device Step diagram showing steps (A) to (E) of the thermal welding method Step diagram showing steps (F) to (J) of the thermal welding method Step diagram showing steps (K) to (M) of the thermal welding method Diagram explaining the slipperiness and holding force of the suction surface of the suction box Explanatory drawing explaining the length of the tail part of a junction Explanatory drawing explaining oblique joining Explanatory drawing which cuts off the both ends of the film width direction of a junction part in circular arc shape Explanatory diagram of problems that are likely to occur when an auxiliary suction box is not provided Explanatory drawing explaining the effect by having provided the auxiliary suction box

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for thermally bonding and bonding films according to the present invention and a method for producing an optical film are described in detail below with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram in which a thermal welding joining apparatus according to an embodiment of the present invention is incorporated in a production line for producing an optical film. In addition, although this Embodiment demonstrates by the example of a polarizing film as an optical film, it is not limited to this.

  A PVA (polyvinyl alcohol) -based film can be suitably used as the belt-like film used for the polarizing film. Examples of the PVA film include a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film, and a polyvinyl alcohol dehydration film.

  The degree of polymerization of the PVA film is generally 500 to 10,000, preferably in the range of 1000 to 6000, and more preferably in the range of 1400 to 4000. Furthermore, in the case of a partially saponified polyvinyl alcohol film, the degree of saponification is preferably 75 mol% or more, more preferably 98 mol% or more, for example, from the viewpoint of solubility in water, and 98.3 to 99.8. More preferably in the range of mol%.

  As a method for producing a PVA-based film, a film formed by an arbitrary method such as a casting method in which a stock solution dissolved in water or an organic solvent is cast, a casting method, an extrusion method, or the like can be appropriately used. A film having a retardation value of 5 nm to 100 nm is preferably used. In order to obtain a polarizing film having a uniform in-plane, it is preferable that the in-plane retardation variation in the PVA-based film is as small as possible, and the in-plane retardation variation in the PVA-based film is 10 nm or less at a measurement wavelength of 1000 nm. Preferably, it is 5 nm or less.

  As shown in FIG. 1, the optical film production line 1 mainly includes a film supply unit 2, a film stretching processing unit 3, a film drying unit 14, a bonding unit 16, a drying unit 17, and a film winding unit 18. The heat welding and joining device 26 is incorporated in the film supply unit 2.

  The film supply unit 2 mainly includes a turret device 24 that holds a plurality of film rolls, a thermal welding joining device 26 that thermally welds and joins a first film 36a in use and a second film 40a to be used next, and a reservoir. The device 28 is configured.

  A turret arm 30 is provided on the support column 32 of the turret device 24 so as to be rotatable by a rotation drive source (not shown) with a shaft 34 as a fulcrum. At one end of the turret arm 30, a first film roll 36 b obtained by winding the first film 36 a in use in a roll shape is rotatably supported by the first reel 38. And the 1st film roll 36b in use is set to a film supply position.

  A second film roll 40 b obtained by winding the second film 40 a to be used next in a roll shape is rotatably supported on the second reel 42 at the other end of the turret arm 30. Then, the second film 40a is pulled out from the second film roll 40b to the heat welding joining device 26 after the remaining amount of the first film 36a in use is reduced and joined to the second film 40a. That is, when the remaining amount of the film 36a on the first film roll 36b decreases, the turret arm 30 rotates, and thereby the second film roll 40b moves to the film supply position. And the front-end | tip part of the 2nd film 40a is pulled out from the 2nd film roll 40b, and it joins with the rear-end part of the 2nd film 40a in the heat welding joining apparatus 26. FIG. When the joining is completed, a new film roll is attached to the first reel 38 of the turret arm 30. A film is continuously supplied from the film supply unit 2 by repeatedly executing the above-described operation.

  Although FIG. 1 does not describe an automatic drawing means for pulling out the leading end portion of the second film 40 a from the second film roll 40 b, for example, between the film supply position of the turret device 24 and the heat welding bonding device 26. Thus, it is possible to employ a reciprocating means for reciprocating by clamping the film leading end. It can also be performed manually by an operator.

  Further, the thermal welding joining apparatus 26 and the thermal welding joining method using the apparatus 26 according to the embodiment of the present invention will be described in detail after explaining the optical film production line 1.

  The film stretching processing unit 3 includes, for example, a swelling tank 4, a dyeing tank 6, a dura mater tank 8, a stretching tank 10, and a washing tank 12. After the treatment, the drawing tank 10 is drawn. Here, an example in which processing is performed on the first film 36a will be described.

  The first film 36 a conveyed to the film stretching processing unit 3 swells the first film 36 a in the swelling tank 4 and dyes the first film 36 a in the dyeing tank 6. Next, after the film-forming polymer is cross-linked in the hardening tank 8, the first film 36a is longitudinally stretched in the stretching tank 10. Although an example of longitudinal stretching will be described here, lateral stretching using a tenter device or the like can also be employed. Finally, the 1st film 36a is wash | cleaned in the washing tank 12, and the process in the film extending process part 3 is complete | finished.

  In the swelling tank 4, the surface of the first film 36 a is cleaned of dirt and an anti-blocking agent by transporting the first film 36 a while being immersed in water. Furthermore, non-uniformity such as uneven dyeing is prevented by swelling the first film 36a.

  In the swelling tank 4, you may add glycerol, potassium iodide, etc. suitably. The addition concentration of glycerin is preferably 5% by mass or less, and the addition concentration of potassium iodide is preferably 10% by mass or less. The temperature of the swelling tank 4 is preferably in the range of 20-50 ° C, more preferably 25-45 ° C. The immersion time in the swelling tank 4 is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 60 to 120 seconds. The first film 36 a may be stretched in the swelling tank 4. The stretching ratio is preferably about 1.1 to 3.5 times including stretching due to swelling.

  In the dyeing tank 6, the dichroic substance is adsorbed to the first film 36a by transporting the first film 36a while being immersed in a liquid containing a dichroic substance such as iodine. As the dichroic material, conventionally known materials can be used, and examples thereof include iodine and organic dyes. Organic dyes include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. These dichroic substances may be used alone or in combination of two or more. When using the said organic dye, it is preferable to combine 2 or more types from the point which aims at neutralization of visible region, for example. Specific examples include a combination of Congo Red and Splat Blue G, Splat Orange GL and Direct Sky Blue, or a combination of Direct Sky Blue and First Black.

  As the solution in the dyeing tank 6, a solution in which the above dichroic substance is dissolved in a solvent can be used. As the solvent, water can be generally used, but an organic solvent compatible with water may be further added and used. The concentration of the dichroic substance is preferably in the range of 0.010 to 10% by mass, more preferably in the range of 0.020 to 7% by mass, and the range of 0.025 to 5% by mass. It is particularly preferable to do this.

  Further, when iodine is used as the dichroic substance, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.010 to 10% by mass, and more preferably 0.10 to 5% by mass in the dyeing bath. Among these, it is preferable to add potassium iodide, and the ratio (mass ratio) of iodine and potassium iodide is preferably in the range of 1: 5 to 1: 100, and 1: 6 to 1:80. Is more preferable, and a range of 1: 7 to 1:70 is particularly preferable.

  Although the immersion time of the 1st film 36a in the dyeing tank 6 is not specifically limited, 1-5 minutes are preferable and 2-4 minutes are more preferable. Moreover, it is preferable to make the temperature of the dyeing tank 6 into the range of 5-42 degreeC, and it is more preferable to set it as the range of 10-35 degreeC. Moreover, you may extend | stretch the 1st film 36a in this dyeing tank 6, and it is preferable that the total draw ratio accumulate | stored at this time shall be about 1.1 to 4.0 times.

  In addition to the method of immersing in the dyeing tank 6 as described above, for example, a method of applying or spraying an aqueous solution containing a dichroic substance to the first film 36a may be employed. Moreover, in this invention, you may employ | adopt the film formed by the polymer raw material with which the dichroic substance was mixed beforehand as the 1st film 36a, without performing a dyeing | staining process.

  In the dura mater tank 8, it bridge | crosslinks by conveying the 1st film 36a, immersing it in the solution containing a crosslinking agent. A conventionally known substance can be used as the crosslinking agent. For example, boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde can be used. These may be used alone or in combination of two or more. When two or more types are used in combination, for example, a combination of boric acid and borax is preferable, and the addition ratio (molar ratio) is preferably in the range of 4: 6 to 9: 1. A range of 5: 4.5 to 7: 3 is more preferable, and a range of 6: 4 is most preferable.

  As a solution of the dura mater 8, a solution in which the cross-linking agent is dissolved in a solvent can be used. For example, water can be used as the solvent, but an organic solvent compatible with water may be used in combination. Although the density | concentration of a crosslinking agent is not specifically limited, It is preferable to set it as the range of 1-10 mass%, and it is more preferable to set it as 2-6 mass%.

  Iodide may be added to the dura mater tank 8 in order to obtain in-plane uniform characteristics of the polarizing film. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. When added, the iodide content is preferably 0.05 to 15% by mass, more preferably 0.5 to 8% by mass. As a combination of the crosslinking agent and iodide, a combination of boric acid and potassium iodide is preferable, and a ratio (mass ratio) of boric acid and potassium iodide is in a range of 1: 0.1 to 1: 3.5. It is preferable that the range is 1: 0.5 to 1: 2.5.

  The temperature of the dura tank 8 is usually preferably in the range of 20 to 70 ° C., and the immersion time of the first film 36a is usually 1 second to 5 minutes, preferably 5 seconds to 4 minutes. Note that the first film 36 a may be stretched in the hardening tank 8. The accumulated total draw ratio at this time is preferably about 1.1 to 5.0 times. As in the dyeing, a method of applying or spraying a solution containing a crosslinking agent may be used instead of the treatment of immersing the first film 36a in the dura mater 8.

  In the stretching tank 10, the first film 36a is longitudinally stretched by a so-called roll stretching method. That is, the first film 36a is nipped and conveyed by a pair of nip rollers 39a provided on the upstream side and the downstream side in the film conveying direction, respectively. Then, the film 36a is stretched in the longitudinal direction by making the roller rotation speed on the downstream side higher than that on the downstream side. FIG. 1 shows an example in which a nip roller 39a is arranged so that each tank can be stretched.

  In this case, the film is stretched so that the accumulated total stretching ratio is, for example, about 2 to 7 times while being immersed in the stretching tank 10. Although it does not necessarily limit as a solution of the extending | stretching tank 10, For example, the solution to which the compound of various metal salts, iodine, boron, or zinc was added can be used. As a solvent of this solution, water, ethanol, or various organic solvents can be appropriately used. In particular, it is preferable to use a solution to which about 2 to 18% by mass of boric acid and / or potassium iodide is added. When boric acid and potassium iodide are used simultaneously, the content ratio (mass ratio) is about 1: 0.1 to 1: 4, more preferably about 1: 0.5 to 1: 3. It is preferable to use in. As temperature of the extending | stretching tank 10, it is preferable to set it as the range of 40-67 degreeC, for example, and it is more preferable to set it as 50-62 degreeC.

  In the washing tank 12, unnecessary residues such as boric acid attached in the previous treatment are washed away by passing the first film 36a through water. It is preferable to add iodide to water, for example, it is preferable to add sodium iodide or potassium iodide. When potassium iodide is added to the water in the washing tank 12, the concentration is usually 0.1 to 10% by mass, preferably 3 to 8% by mass. Furthermore, the temperature of the washing tank 12 is preferably 10 to 60 ° C, and more preferably 15 to 40 ° C. Further, the number of cleaning processes is not particularly limited, and may be plural. The cleaning step may be performed by storing water having different types and concentrations of additives in the plurality of cleaning tanks 12 and passing the first film 36a through them.

  When pulling up the first film 36a from the tank in each step, a conventionally known liquid breaker roll such as a pinch roll is used or the liquid is scraped off by the air knife 60 in order to prevent the occurrence of dripping. The excess water may be removed by a method such as

  In addition to the nip roller 39a, the film stretching processing unit 3 includes a plurality of guide rollers 39b that regulate the film transport path of the first film 36a in each tank.

  The first film 36a processed by the film stretching unit 3 is then sent to the film drying unit 14 and dried. As a drying method, an appropriate method such as natural drying, hot air drying, heat drying using infrared rays or the like can be adopted, but hot air drying is usually preferable. The hot air drying conditions are preferably a heating temperature of about 20 to 80 ° C. and a drying time of about 1 to 10 minutes.

  The dried film 36 a is then sent to the bonding unit 16. The bonding unit 16 includes a pair of feeders 66 and 66 that supply a film roll 64 b in which the protective film 64 a is rolled, and a pair of rollers 68. In the bonding part 16, the protective film 64a is affixed on both surfaces or one side of the 1st film 36a. TAC (triacetyl cellulose) can be suitably used as the protective film 64a. A drying unit 17 is provided after the bonding unit 16 and dried.

  Finally, the 1st film 36a is wound up by the film winding part 18 at roll shape, and, thereby, a polarizing film is manufactured.

  In order to improve the manufacturing efficiency of such a polarizing film, the rear end portion of the first film 36a in use and the front end portion of the second film 40a to be used next are thermally welded with the heat welding joining device 26. It is necessary to always supply a film to the production line 1 by joining them together. In this case, wrinkles are not generated in the thermally welded joint portion A, and the length (L1) of the tail portion, which will be described later, is prevented from becoming long. In the stretching process, it is important to perform heat-weld bonding so that the bonded portion does not peel off or break. Therefore, in the present embodiment, such a problem is achieved by the heat welding joining device 26 described below.

  FIG. 2 is a side view along the film conveying direction of the thermal welding joining apparatus 26 according to the embodiment of the present invention.

  As shown in FIG. 2, the heat welding and bonding apparatus 26 mainly includes an upper unit 70 and a lower unit 71. On both sides of the film conveyance direction with the upper unit 70 interposed therebetween, a pair of raising / lowering rollers 73 involved in the raising / lowering movement of the first film 36a in use is provided. An engagement roller 74 that engages with the second film 40a is provided on the left side of the lower unit 71, and the tip of the second film 40a drawn from the second film roll 40b of the turret device 24 is provided on the right side. A pinch roller 75 is provided that holds the portion between a pair of rollers 75A and 75B. Thereby, the conveyance path | route of the 1st film 36a and the drawing | extracting path | route of the 2nd film 40a are formed between the upper unit 70 and the lower unit 71.

  The pair of lifting rollers 73 described above is configured to be vertically movable by a cylinder device 73A.

  In the upper unit 70, an elevating part 78 is supported by being suspended from a ceiling frame, and an elevating mechanism is mounted on the elevating part 78. As this lifting mechanism, for example, a hydraulic or hydraulic cylinder mechanism can be suitably used.

  Further, a support portion 91 and a slide portion 92 are provided at the lower end portion of the elevating portion 78. The support portion supports the suction box 88A of the pair of suction boxes 88A and 88B, the thermal welding head 85, and the upper cutting blade 89. Further, a suction box 88B located on the downstream side in the transport direction of the first film 36a is supported by the slide portion 92. The slide portion 92 is mounted with a slide mechanism (not shown) that moves the suction box 88B along the transport direction of the first film 36a. This slide mechanism preferably has a movement accuracy of about 0.1 mm. For example, a mechanism that controls the feed screw mechanism with a servo heater can be suitably used. Note that the suction box 88A located on the upstream side in the transport direction of the first film 36a is also supported via the slide portion, and in the transport direction of the first film 36a in a state independent of the suction box 88B on the downstream side. You may enable it to move along.

  Further, the pair of suction boxes 88A and 88B and the thermal welding head 85 are formed long in the front and back direction of FIG. 2, and the thermal welding width is about 10 mm wide at the tip (lower end) of the thermal welding head 85. A linear heater 85A longer than the film width is provided.

  Here, the upstream suction box viewed from the film transport direction (from left to right in FIG. 2) is referred to as an upstream suction box 88A, and the downstream suction box is referred to as a downstream suction box 88B. In addition to the filament heater 85A, an upper cutting blade 89 that cuts the first film 36a in the width direction is disposed between the downstream suction box 88A and the upstream suction box 88B. The upper cutting blade 89 is attached to a moving mechanism (not shown) that moves in the film width direction along the side surface of the thermal welding head 85. The moving mechanism positions the cutting blade 89 outside the film width when the film is not cut, and moves the cutting blade from one side to the other side in the film width direction when the film is cut. Thereby, the 1st film 36a can be cut | disconnected in the width direction, and it is comprised so that the cutting blade 89 may not become obstructive at the time of the surface pressure process mentioned later or heat welding.

  In addition, suction surfaces 88C having a large number of suction holes are formed on the lower surfaces of the suction boxes 88A and 88B on the upstream side and the downstream side, and the suction surfaces 88C are formed as mirror-level flat surfaces. The suction surfaces 88C of the upstream and downstream suction boxes 88A and 88B and the tips of the filament heaters 85A are substantially flush with each other, and excessive pressure is applied to the filament heaters 85A in the press processing described later. When applied, the linear heater 85 </ b> A (width 0.1 to 0.5 mm) is configured to be immersed in the heat welding head 85.

  On the other hand, in the lower unit 71, a support block 95 is erected on the floor 93 surface, and a support portion 98 and a slide portion 96 are provided on the support block 95 as in the case of the upper unit 70. The supporting portion 98 is provided with a lower main member including a suction box 101B of the pair of suction boxes 101A and 101B, a receiving base 97 (made of rubber tube) of the heat welding head 85, and a lower cutting blade 102. . In addition, the slide unit 96 supports a suction box 101A located on the upstream side in the transport direction of the second film 40a. The slide unit 96 is mounted with a slide mechanism (not shown) that moves the suction box 101A along the transport direction of the second film 40a.

  As the slide mechanism, a mechanism similar to that described in the upper unit 70 can be employed. Note that the suction box 101B located downstream in the transport direction of the second film 40a is also supported through the slide portion, and in the transport direction of the second film 40a in a state independent of the upstream suction box 101A. You may enable it to move along.

  Here, the upstream suction box viewed from the film transport direction (from left to right in FIG. 2) is referred to as an upstream suction box 101A, and the downstream suction box is referred to as a downstream suction box 101B.

  In addition to the cradle 97, a lower cutting blade 102 that cuts the second film 40a in the width direction is disposed between the downstream suction box 101A and the upstream suction box 101B. Here, the upper cutting blade 89 of the upper unit 70 is disposed on the left side of the filament heater 85 </ b> A in FIG. 2, while the lower cutting blade 102 of the lower unit 71 is disposed on the right side of the cradle 97. In other words, the cutting blade 89 of the upper unit 70 and the cutting blade 102 of the lower unit 71 are not completely opposed to each other, but are arranged in a slightly shifted state.

  Further, the lower cutting blade 102 of the lower unit 71 is located outside the film width when not being cut by a moving mechanism (not shown), like the upper cutting blade 89 of the upper unit 70, When the film is cut, the film moves from one side to the other side in the film width direction. Thereby, the second film 40a can be cut in the width direction, and the lower cutting blade 102 is configured not to be in the way at the time of press processing or heat welding described later.

  A suction surface 101C having a number of suction holes is formed on the upper surfaces of the upstream and downstream suction boxes 101A and 101B, and the suction surface 101C is formed as a flat surface at a mirror surface level.

  Further, a dancer mechanism 107 is provided at a downstream position of the upper unit 70 in the transport direction of the second film 40 a, and a pinch roller type that feeds the second film 40 a to the film stretching processing unit 3 on the downstream side of the dancer mechanism 107. A feed roller 108 is provided.

  The driving devices, the dancer mechanism 107, and the feed roller 108 constituting the upper unit 70 and the lower unit 71 are connected to the control means 106 by a signal cable or wirelessly, and are ON / OFF controlled by the control means 106. FIG. 2 shows the case of wireless control. Each suction box 88A, 88B, 101A, 101B is connected to a suction force generator (not shown).

  Next, with reference to FIGS. 3A to 3C, a method for thermally welding and bonding the first film 36 a and the second film 40 a with the heat welding and bonding apparatus 26 configured as described above will be described. If there is an arrow in the suction box, it means that a suction force is applied to the suction box.

  The first film 36a in use sent out from the first reel 38 of the turret arm 30 shown in FIG. 1 passes between the upper unit 70 and the lower unit 71 as shown in FIG. 3A (A). 1 is conveyed to the film stretching unit 3 in FIG.

  When the remaining roll amount of the first film 36a decreases, the turret arm 30 rotates and the second film roll 40b to be used next moves to the film supply position. Further, the leading end of the second film 40 a is pulled out from the second film roll 40 b, passes between the upper unit 70 and the lower unit 71, and is sandwiched between the pinch rollers 75. The remaining amount of the first film roll 36b can be detected, for example, by measuring the roll thickness of the first film roll 36b with a sensor (not shown) or the like. In this state, the reservoir device 28 (see FIG. 1) is driven, and the driving of the feed roller 108 that supplies the first film 36a to the film stretching unit 3 is stopped, so that the first film 36a on the upstream side of the reservoir device 28 is stopped. Stop conveyance.

  Next, as shown in FIG. 3A (B), the pair of elevating rollers 73 and 73 are lowered. Thereby, the joining area | region part of the 1st film 36a and the 2nd film 40a is piled up.

  Here, the joining region portion is not the joining portion A (see FIG. 4) in which the rear end portion of the first film 36a and the leading end portion of the second film 40a are finally overlapped and heat-welded and joined. The film part which is located between the unit 70 and the lower unit 71 and is the object of each step described later is said.

  Next, as shown in FIG. 3A (C), the elevating mechanism of the elevating unit 78 is driven to lower the upper unit 70. And the joining area | region part of 1st and 2nd film 36a, 40a is pinched | interposed with suction box 88A, 88B of upstream and downstream, and suction box 101A, 101B of the upstream and downstream of the lower unit 71. Press. During the pressing, no suction force is applied to the four suction boxes 88A, 88B, 101A, 101B. Thereby, surface pressure is applied to both surfaces of the joining region portion by the flat suction surfaces 88C and 101C of the suction boxes 88A, 88B, 101A and 101B of the upper unit 70 and the lower unit 71. Therefore, even if there is a wrinkle in the joining region portion, the wrinkle can be extended by the ironing effect.

  As the first and second films 36a and 40a wound and supported by the turret device 24, it is usual to use those wound and stored in a medium-high roll shape, and the first and second films are used. When the films 36a and 40a are rewound, the film tends to become wrinkles. The press pressure is preferably in the range of 0.2 to 0.8 MPa, more preferably in the range of 0.4 to 0.8 MPa.

  Next, as shown in FIG. 3A (D), suction force is applied to the four suction boxes 88A, 88B, 101A, 101B, so that the joining region portions of the first and second films 36a, 40a that are free from wrinkles are formed. Hold by suction.

  Next, as shown in FIG. 3A (E), the pair of elevating rollers 73 and 73 are moved up, and the elevating mechanism of the elevating unit 78 is driven to move the upper unit 70 up. The joining region portions of the two films 36a and 40a are separated from each other.

  Next, as shown in FIG. 3B (F), the first and second films 36a and 40a are cut in the film width direction by the cutting blades 89 and 102 of the upper unit 70 and the lower unit 71, respectively. Thus, a rear end part for joining the first film 36a in use and a front end part for joining the second film 40a to be used next are formed.

  Next, as shown in FIG. 3B (G), the suction force of the upstream suction box 88A of the upper unit 70 is released, and the first reel 38 of the turret device 24 is reversely rotated to cut the first film. Wind up the turret side portion of 36a. Further, the suction force of the downstream suction box 101B of the lower unit 71 is released and the pinch roller 75 is rotated to remove the cut film piece 40c of the second film 40a.

  Next, as shown in FIG. 3B (H), the slide mechanisms 92 and 96 of the upper unit 70 and the lower unit 71 are driven, and the downstream suction box 88B and the lower unit 71 of the upper unit 70 are driven. By moving the upstream suction box 101A in the direction of the arrow along the film conveyance direction and adjusting the overlap width for overlapping the rear end portion of the first film 36a and the front end portion of the second film 40a. The joining width of the joining part A to be adjusted is adjusted. This reduces the length (L1) of the tail portion that is not thermally attached at the rear end portion of the first film 36a, and the length of the tail portion that is not thermally attached at the front end portion of the second film 40a. (L1) is reduced. The length (L1) of the tail portion will be described in detail later.

  Since the suction widths of the joint portion A are adjusted by sliding the suction boxes 88B and 101A themselves as described above, wrinkles are generated in the first and second films 36a and 40a during the adjustment. There is nothing. Incidentally, the method of transporting and sliding the film itself in a state where the suction force of the suction boxes 88B and 101A is released tends to cause the film to become wrinkled because the transport tension easily varies in the film width direction. In particular, in the case of a wide film having a film width exceeding 3 m as in recent years, it tends to be wrinkled. As a method for conveying the film itself, the first film can be driven by driving the feed roller 108, and the second film can be performed by rotating the second reel 42 in the reverse direction.

  In the above-described steps from (A) in FIG. 3A to (H) in FIG. 3B, for example, in (A) in FIG. 3A, the first and second suction boxes 88A, 88B, 101A, and 101B are in the OFF state without applying suction. It is necessary to transport the second films 36a and 40a and set the first and second films 36a and 40a in flat positions without wrinkles at predetermined positions of the suction boxes 88A, 88B, 101A, and 101B. Therefore, the conveyed first and second films 36a and 40a may rub against the suction surfaces 88C and 101C of the suction boxes 88A, 88B, 101A and 101B. In this contact, if the friction coefficient of the suction surfaces 88C and 101C is large, the first and second films 36a and 40a may be damaged such as scratches. Therefore, the slipperiness of the suction surfaces 88C and 101C should be improved. Is preferred.

  On the other hand, in (H) of FIG. 3B, the suction boxes 88B and 101A securely hold the first and second films 36a and 40a on the suction surfaces 88C and 101C in a state where a tensile tension is applied in the film longitudinal direction. However, it is necessary to adjust the overlap width of the first and second films 36a and 40a by sliding the suction boxes 88B and 101A. That is, the first film 36a is kept in tension between the suction box 88B and the reservoir device 107, and tension is applied to the suction surface 88C. The second film 40a is maintained in a tension state between the suction box 101A and the second reel 42, and tension is applied to the suction surface 101C.

  The magnitude of the tensile tension is about 4.9 N (Newton) when tested with a film width of 220 mm. Therefore, the suction surfaces 88C and 101C are required to have a holding force of 4.9 N or more per film width (220 mm) at a suction pressure of −1 to −2 kPa.

  That is, the suction surfaces 88C, 101C of the suction boxes 88A, 88B, 101A, 101B are required to have both slipperiness and holding force. As the characteristics of the suction surfaces 88C and 101C that satisfy both the slipping property and the holding force, the friction coefficient is preferably 4 or less, more preferably 2 or less, and particularly preferably 1 or less.

  As a material satisfying such a friction coefficient, for example, polytetrafluoroethylene (PTFE) can be preferably used.

  FIG. 4A shows a comparison of the coefficient of friction between the adsorption surface formed with SUS304 and the adsorption surface formed with PTFE, and SUS304 was about 8 and PTFE was about 0.5. And as a result of conveying a PVA film so that each adsorption | suction surface may be contacted, it turned out that the adsorption | suction surface of SUS304 has bad slipperiness, and a wrinkle and a damage | wound are easy to generate | occur | produce in a PVA film. On the other hand, the PTFE adsorption surface had good slipperiness, and no wrinkles or scratches were generated on the PVA film.

  FIG. 4B shows a prototype of a suction box (with a width of 280 mm in the film conveyance direction) formed of SUS304 and a suction box (with a width of 280 mm in the film conveyance direction) formed of PTFE. In addition, the holding power when the 220 mm-wide PVA film is held by the respective suction surfaces is compared. In the holding force test, when the PVA film held on the adsorption surface was pulled along the adsorption surface, the tensile force immediately before the PVA film moved was defined as the holding force. Then, the relationship between the suction pressure on the suction surface and the holding force is plotted and shown in FIG.

  As can be seen from FIG. 4B, the holding force of the suction surface formed with PTFE is inferior to that of the suction surface formed with SUS304, but 10 kPa can be secured when the suction pressure is -1 kPa. As a result, the holding force of 4.9 N or more was sufficiently satisfied.

  In addition, in the film (for example, 3 m or more width | variety) actually used, when calculating | requiring required holding force, holding force can be calculated | required by relationship with the width of 220 mm of the tested film.

  Next, as shown in FIG. 3B (I), the pair of elevating rollers 73 and 73 are lowered, and the elevating mechanism of the elevating part 78 is driven to lower the upper unit 70 so that the rear of the first film 36a. The joining portion A is formed by overlapping the end portion with the leading end portion of the second film 40a. Then, the linear heater 85A of the heat welding head 85 is turned on, and the joining portion A is heat-welded and joined. Thereby, the rear-end part of the 1st film 36a and the front-end | tip part of the 2nd film 40a are joined. In the description of the present embodiment, the term “joint portion A” is used for both before and after joining, and when it is important to be before joining or after joining, this will be explained.

  A temperature range of 160 to 280 ° C. is preferable as a condition for heat welding. When the temperature is lower than 160 ° C., welding is not sufficient, and when the temperature exceeds 280 ° C., bubbles are mixed into the joined portion A and the strength of the joined portion A cannot be maintained sufficiently. The required time including the cooling time after heating is preferably 2 seconds to 10 seconds. The pressing force for pressing the filament heater 85A against the cradle 97 (rubber tube) is preferably in the range of 0.1 to 0.6 MPa.

  Next, as shown in FIG. 3B (J), the suction force of the downstream suction box 88B of the upper unit 70 is applied as it is, and the suction forces of the remaining suction boxes 88A, 101A, 101B are released.

  Next, as shown in FIG. 3C (K), the pair of elevating rollers 73 and 73 is raised, and the elevating mechanism of the elevating part 78 is driven to raise the upper unit 70. Then, as shown in FIG. 3C (L), the linear heater 85A is turned OFF and the suction force of the downstream suction box 88B of the upper unit 70 is released. Thereby, one heat welding joining is performed to the junction part A which piled up the rear-end part of the 1st film 36a, and the front-end | tip part of the 2nd film 40a.

  3A to 3C have been described with an example in which one thermal welding is performed on the joint A, the thermal welding may be performed multiple times (for example, twice) on the joint A.

  In this case, the downstream suction box 88B of the upper unit 70 is slid in the film transport direction to change the position of the filament heater 85A in the joining portion A to perform heat welding joining.

  Then, when the thermal welding is finished, the driving of the reservoir device 28 is stopped, and the feed roller 108 that supplies the first film 36a to the film stretching unit 3 is driven, so that the first film 36a in use is continued. Next, the second film 40 a to be used is continuously supplied to the film stretching unit 3.

  According to the embodiment of the present invention, flaws are generated after the rear end portion and the front end portion of the films 36a and 40a are thermally welded by performing the above-mentioned heat welding joining method using the heat welding joining device 26. And the length (L1) of the tail portion is not increased. As a result, no air pool is generated in the joining portion A, so that the joining strength can be increased, and the tail portion does not flutter during film conveyance. For example, the joining portion A is also formed during the stretching process in the stretching tank 10. It will not peel off or break.

  FIG. 5 shows the length (L1) of the tail portion when performing one thermal welding (FIG. 5A) and when performing two thermal welding (FIGS. 5B and 5C). Is shown. This is a case where the width of the linear heater 85A, that is, the width D of the heat welding wire B is set to 10 mm.

  As shown in FIGS. 5A to 5C, the length (L1) of the tail portion at the rear end of the first film 36a and the length (L1) of the tail portion at the front end of the second film 40a are as follows. , 1.5 mm or less is preferable. If the length (L1, L2) of the unwelded tail portion is greater than 1.5 mm, the tail portion tends to flutter or get caught on the transport roller during film transport, and the joint A is easily peeled off.

  Further, as shown in FIGS. 5B and 5C, in the case of performing the two-time heat welding, it is preferable to perform heat welding so that the heat welding wire B partially overlaps in the width direction. In this case, the overlap amount (L2) is preferably more than 0 mm and not more than 1.5 mm.

  Further, in the thermal welding, as shown in FIG. 6, the angle (θ) formed by the orthogonal line 110 orthogonal to the arrow conveying direction (film conveying direction) and the center line 112 of the thermal welding line B is 20 ° or more. It is preferable to perform oblique joining so as to be 60 ° or less.

  The deformation in the film width direction in the bonding portion A and the vicinity thereof in the stretching process of the PVA-based film (nonuniformity of the film width), in particular, the breaking property of the bonding portion A due to the nonuniformity has the following phenomenon. That is, when the PVA-based film is stretched 3 to 8 times in the transport direction, the film shrinks in the width direction, but the joint A hardly shrinks in the film width direction. For this reason, when heat welding and joining in the direction orthogonal to the film transport direction, on the film, the difference in expansion and contraction in the film width direction becomes large between the joined film part and the other film part, which causes unevenness or breakage of the film width. Cause.

  Therefore, by performing oblique joining as described above, the joining portion A also easily expands and contracts when longitudinally stretched, so that it is difficult to break. In this case, the film width direction component (vector) of the bonded portion A at the time of longitudinal stretching becomes smaller as the angle (θ) of the oblique bonding becomes smaller. Therefore, the larger the angle (θ), the more uneven the film width. And the effect of suppressing breakage of the film are increased. That is, theoretically, it may be less than 90 °. On the other hand, if the angle (θ) is too large, the equipment and the like for forming the joint A will be too large. Therefore, the upper limit of the angle (θ) for oblique joining is preferably 60 ° or less. Further, if the angle (θ) is less than 20 °, the effect is not sufficiently exhibited. Therefore, the angle (θ) is preferably 20 ° or more and 60 ° or less, and more preferably 30 ° or more and 60 ° or less.

  In addition, a film cutter (not shown) is disposed before the heat welding and bonding device 26 or between the heat welding and bonding device 26 and the film stretching unit 3. And it is preferable to cut off the both ends of the joining part A before heat welding or the joining part A after heat welding in the shape of a circular arc.

  In this way, by cutting off both ends in the film width direction of the joint portion A in an arc shape, even when a breaking force is applied to the joint portion A in a stretching process or the like, the fracture resistance can be improved.

  The reason will be described with reference to FIG. As shown in FIG. 7A, when the rear end portion of the film 36a and the front end portion of the film 40a are heat-welded and joined in a state of being shifted in the film width direction, stress is concentrated on the shifted portion. However, as shown in FIG. 7B, the film width direction misalignment between the rear end portion of the film 36a and the front end portion of the film 40a is eliminated by cutting out both ends of the joint portion A in the film width direction in an arc shape. The Thereby, it can prevent that stress concentrates on the gap part of joined part A. Therefore, when the first and second films 36a and 40a before joining are cut in an arc shape, the curvature may be such that a step (displacement) can be eliminated in the film width direction after the heat welding joining.

  Moreover, as shown to FIG. 7 (B), it is preferable that the relationship between the film width W0 and the film width (L) of the part cut out circularly satisfy | fills the following formula | equation.

0.01 (%) ≦ (1- (L / W0)) × 100 ≦ 29 (%)
In this case, if it exceeds 29%, the film may be broken during the stretching treatment, and if it is less than 0.01%, the effect of arcuate cutting cannot be substantially exhibited.

  In addition, although this Embodiment demonstrated in the example which manufactures a polarizing film, it is not limited to this, It can apply also when manufacturing another optical film.

[Second Embodiment]
In the second embodiment, the suction surfaces 88C, 101C of the suction boxes 88A, 88B, 101A, 101B are flush with the suction surfaces 88C, 101C of the suction boxes 88A, 88B, 101A, 101B on both sides of the joining region portion. The auxiliary suction boxes 110A and 110B having suction surfaces smaller than the friction coefficient are fixedly arranged, and the cut ends of the cut first film 36a and second film 40a in the step between the cutting process and the thermal welding process. The vicinity 36x, 40x was sucked and held so as not to inhibit the thermal welding.

  That is, in the step (I) of FIG. 3B, the rear end portion of the first film 36a is overlapped with the front end portion of the second film 40a to form the joined portion A, and the linear heater 85A of the heat welding head 85 is turned on. Then, the joining portion A is heat-welded and joined. Thereby, the rear-end part of the 1st film 36a and the front-end | tip part of the 2nd film 40a are joined.

  In such a heat welding joining step, the unwelded portions (tail portions) formed on both sides of the joining portion A during the heat welding are not subjected to a tensile tension in the film longitudinal direction. The film width does not shrink (necking) during the stretching process. Therefore, if the tail portion is too long, the stress concentration becomes strong and causes the film to break. Therefore, the length (L1) of the tail portion needs to be about 0.5 to 1.5 mm.

  However, due to the structure of the heat welding and joining device 26, in the upper unit 70, the distance between the cutting blade 89 and the suction box 88B needs to be about 100 mm apart. Similarly, in the lower unit 71, the distance between the cutting blade 102 and the suction box 101A needs to be about 100 mm apart. Thereby, the length of the cutting end vicinity 36x which is not attracted | sucked by the suction box 88B among the rear-end parts of the 1st film 36a cut | disconnected by the cutting blade 89 becomes long with about 100 mm. Similarly, the length of the vicinity of the cutting end 40x that is not sucked by the suction box 101A out of the tip of the second film 40a cut by the cutting blade 102 is as long as about 100 mm.

  Therefore, in (F), (H), and (I) of FIG. 3B described in the first embodiment, the vicinity of the cutting end 36x of the first film 36a and the vicinity of the cutting end 40x of the second film 40a hang down due to their own weight. It becomes easy. As a result, in the thermal welding step of (I) in FIG. 3B, folds occur in the vicinity of the cutting end 36x of the first film 36a and in the vicinity of the cutting end 40x of the second film 40a, and the accuracy of the thermal welding joining tends to deteriorate. .

This will be further explained with reference to FIG. 8. As shown in FIG. 8 (F ₁ ), the cut end vicinity 36x of the cut first film 36a hangs down by its own weight.

Further, as shown in (H ₁ ) of FIG. 8, when the suction box 88B and the suction box 101A are slid in the direction of the arrow in order to adjust the bonding width, the vicinity of the cut end of the second film 40a that has been cut. 40x hangs down due to its own weight between the cradle 97 and the suction box 101A and is likely to be broken.

Then, as shown in (I ₁ ) of FIG. 8, the vicinity of the cut end 36x of the first film 36a that hangs down when the wire heater 85A is lowered toward the pedestal 97 at the time of heat welding is easily bent.

  Accordingly, there is a tendency that the vicinity of the cutting end 36x of the first film 36a and the vicinity of the cutting end 40x of the second film 40a are not overlapped with a predetermined bonding width or are not overlapped at all. Such a defect hardly occurs in a film having a large rigidity, but tends to occur when the film is soft and thin like a PVA film.

  Therefore, in the second embodiment, the auxiliary suction box 110 </ b> A is provided between the suction box 88 </ b> B of the upper unit 70 and the thermal welding head 85 at a position that does not hinder the lifting / lowering operation of the thermal welding head 85. Similarly, the auxiliary suction box 110B is provided between the suction box 101A of the lower unit 71 and the cradle 97. The auxiliary suction boxes 110A and 110B are fixedly disposed so as not to slide together with the suction boxes 88B and 101A when adjusting the joining width. In this case, it is preferable that the auxiliary suction box 110 </ b> A is fixedly disposed close to the thermal welding head 85 as long as it does not hinder the elevation of the thermal welding head 85. Further, it is preferable that the auxiliary suction box 110 </ b> B is fixedly disposed in the vicinity of the cradle 97.

  The auxiliary suction boxes 110A and 110B are formed to have suction surfaces that are flush with the suction surfaces 88C and 101C of the suction boxes 88B and 101A and are smaller than the friction coefficients of the suction surfaces 88C and 101C of the suction boxes 88B and 101A. Is done.

  FIG. 9 is a diagram illustrating an operational effect obtained by providing the auxiliary suction boxes 110A and 110B.

As shown in FIG. 9 (F ₁ ), the cut end vicinity 36x of the cut first film 36a is sucked and held by the auxiliary suction box 110A, so that it is prevented from sagging due to its own weight.

Further, as shown in (H ₁ ) of FIG. 9, when the suction box 88B and the suction box 101A are slid in the direction of the arrow to adjust the bonding width, the vicinity of the cut end of the cut second film 40a 40x is sucked and held by the auxiliary suction box 110B. Thereby, it is prevented that the cutting end vicinity 40x hangs down due to its own weight between the cradle 97 and the suction box 101A and is not bent.

  In this case, the suction surfaces of the auxiliary suction boxes 110A and 110B have a smaller coefficient of friction and better slipperiness than the suction surfaces 88C and 101C of the suction boxes 88B and 101A, so the first and second films 36a and 36a, Even if it rubs on the suction surface when sliding 40a, it does not cause wrinkles or scratches. Therefore, the accuracy of heat welding joining can be improved.

Further, as shown in (I ₁ ) of FIG. 9, the cut end of the first film 36 a when the linear heater 85 </ b> A is lowered toward the receiving base 97 and comes into contact with the cut end vicinity 36 x at the time of heat welding joining. Since the vicinity 36x does not hang down, the cutting end vicinity 36x is not bent.

  Thereby, heat welding can be performed with high accuracy so that the set joining width and the set tail portion length are obtained.

  Since the auxiliary suction boxes 110A and 110B do not slide when adjusting the joining width, when the suction boxes 88B and 101A are slid, the cutting end vicinity 36x or the cutting end vicinity 40x is sucked and held along the suction surface. It is necessary to slide the vicinity 36x or the cutting edge vicinity 40x.

  Therefore, the suction surfaces of the auxiliary suction boxes 110A and 110B need to have a smaller friction coefficient than the suction surfaces of the suction boxes 88B and 101A, and the friction coefficient is 2 or less, particularly preferably 1 or less. Further, the holding force of the auxiliary suction boxes 110A and 110B only needs to prevent the vicinity of the cutting end vicinity 36x of the first film 36a or the cutting end vicinity 40x of the second film 40a from drooping under its own weight. Power is not necessary.

  For example, when an auxiliary suction box (the width in the film conveyance direction is 20 mm) is prototyped and a PVA film having a film width of 220 mm is held at a suction pressure of -1.0 kPa, the holding force is in the range of 0.3 to 0.5 kPa. If it is.

  Thus, when adjusting the bonding width, the first and second films 36a and 40a do not get wrinkles or scratches even if they run while contacting the suction surfaces of the auxiliary suction boxes 110A and 110B, and the first film It is possible to prevent the vicinity of the cutting edge 36x of 36a or the cutting edge vicinity 40x of the second film 40a from sagging due to its own weight.

In this case, when adjusting the bonding width of (H ₁ ) in FIG. 9, as can be seen from the comparison with (H ₁ ) in FIG. 8, the suction boxes 88 A and 88 B of the upper unit 70 and the suction box of the lower unit 71. It is preferable to adjust the bonding width in a state where the distances from 101A and 101B are close to each other. Thereby, the auxiliary suction boxes 110A and 110B are not sucked and held, but can be received by the pedestal 97 depending on the sag of the end protruding into the space, so that the accuracy of the thermal welding and bonding can be further improved.

  Therefore, it is preferable that the cylinder device that raises and lowers the pair of raising and lowering rollers 73 and the raising and lowering unit 78 that raises and lowers the suction boxes 88A and 88B have an adjustment mechanism that adjusts the lifting distance.

  DESCRIPTION OF SYMBOLS 1 ... Production line of a polarizing film, 2 ... Film supply part, 3 ... Film stretching process part, 14 ... Film drying part, 16 ... Bonding part, 17 ... Drying part, 18 ... Film winding part, 24 ... Turret apparatus, DESCRIPTION OF SYMBOLS 26 ... Thermal welding joining apparatus, 28 ... Reservoir apparatus, 30 ... Turret arm, 32 ... Support | pillar, 36a ... 1st film, 36b ... 1st film roll, 38 ... 1st reel, 39a ... Nip roller, 39b ... Guide roller, 40a ... second film, 40b ... second film roll, 64a ... protective film, 64b ... film roll, 68 ... laminating roller, 70 ... upper unit, 71 ... lower unit, 73 ... lifting roller, 74 ... engaging roller, 75 ... Pinch roller, 76 ... Ceiling frame, 78 ... Elevating part (first moving means), 85 ... Thermal welding head, 85A ... Line heater, 8A ... Upstream suction box of the upper unit, 88B ... Downstream suction box of the upper unit, 88C ... Suction surface, 89 ... Upper cutting blade, 92 ... Slide part (second moving means), 93 ... Floor, 95 ... Column block 96 ... Slide part (second moving means) 97 ... Stand (made of rubber tube), 101A ... Upstream suction box of the lower unit, 101A ... Downstream suction box of the lower unit, 102 ... Lower cutting blade, 106 ... Control means, 107 ... Tamper mechanism, 108 ... Feed roller, 110A, 110B ... Auxiliary suction box

Claims (21)

In the heat welding joining method between the films in which the rear end portion of the belt-like first film and the tip portion of the belt-like second film are superposed on each other,
By superimposing the joining region portions of the first film and the second film and sandwiching them between the flat suction surfaces of the suction boxes disposed opposite to both sides of the joining region portion, A surface pressure applying step for applying surface pressure;
A separation moving step in which, after applying the surface pressure, the first and second films are sucked and held on the suction surfaces of the respective suction boxes, and the suction boxes are moved in a direction in which the overlapping portions are separated from each other; ,
A cutting step of cutting the respective films in a state of separating the first and second films to form the rear end portion and the front end portion in the joining region portion of the first and second films;
A thermal welding step of joining the films together by thermally welding a joint portion where the rear end portion of the formed first film and the leading end portion of the second film are overlapped by moving the suction boxes closer to each other; A method for heat-welding and bonding films to each other. In the heat welding joining method between the films in which the rear end portion of the belt-like first film and the tip portion of the belt-like second film are superposed on each other,
Suction that holds the first film and the second film with the suction surfaces of the suction boxes disposed opposite to each other on both sides of the joining region portion by superimposing the joining region portions of the first film and the second film. Holding process;
A separation movement step of moving the suction boxes in a direction of separating the overlapping portions;
A cutting step of cutting each film in a state of separating the first and second films to form the rear end portion and the front end portion in the joining region portion,
An overlap width adjusting step of adjusting the overlap width of overlapping the rear end portion of the first film and the front end portion of the second film by moving the suction boxes in the film longitudinal direction;
After adjusting the overlap width, the suction boxes are moved closer to each other, and the films are formed by heat-welding a joint where the rear end portion of the formed first film and the front end portion of the second film are overlapped. And a heat-welding step for joining the films. Between the cutting step and the thermal welding step, the overlapping width of the joint portion in which the suction boxes are moved in the film longitudinal direction and the rear end portion of the first film and the front end portion of the second film are overlapped. The method for heat-welding and joining films according to claim 1, further comprising an overlap width adjusting step for adjusting the thickness. First film transport for transporting the first film from a first reel that winds and supports an old roll in use to a film stretching processing section that performs a desired process on the first film through a pair of suction boxes. Process,
A second film drawing step of drawing the second film from the second reel supporting the new roll to be used next to the space between the suction boxes;
The first film is provided between the suction box and the film stretching section, and stores a first film having a length corresponding to the time required for heat-welding and joining the first and second films, and transports the first film. And a reservoir step that allows the first film to be supplied to the film stretching section while performing thermal welding while stopping the film, and the films according to any one of claims 1 to 3 Thermal welding joining method.   The method for heat welding and bonding films according to any one of claims 1 to 4, wherein the suction surface of the suction box has a friction coefficient of 4 or less.   6. The method for heat-welding and bonding films according to claim 5, wherein the suction surface of the suction box is made of polytetrafluoroethylene. Auxiliary suction boxes that are flush with the suction surface of the suction box and have a friction coefficient of the suction surface smaller than the suction surface of the suction box are fixedly arranged on both sides of the joining region portion, respectively, from the cutting step In the step between the heat welding steps, the cut ends of the cut first film and second film are sucked and held so as not to inhibit the heat welding. The heat welding joining method of the films of any one. The method for heat-sealing and bonding films according to claim 2 or 3, wherein the overlap width adjusting step is performed in a state in which the distance between the suction boxes arranged to face each other is closer than that of the cutting step.   The method for heat-welding and bonding films according to any one of claims 1 to 8, wherein the first and second films are PVA-based films for producing an optical film. 2. The method for heat-welding and bonding films according to claim 1, wherein in the surface pressure applying step, the bonding region portion is pressurized at 0.2 to 0.8 MPa.   In the heat welding step, heat welding is performed so that an unwelded region that is not heat welded is 1.5 mm or less among the end portions of the first and second films of the joint portion. The heat welding joining method of the films of any one of Claims 1-10 to do. The thermal welding step is performed by thermal welding by inclining an inclination angle in a range of 20 ° or more and 60 ° or less with respect to a direction orthogonal to the longitudinal direction of the film. The method for heat-sealing and bonding films as described in 1.   The cutting step of cutting out both ends in the film width direction of the bonded portion before the heat welding or the bonded portion after the heat welding in an arc shape before or after the heat welding step. The heat welding joining method of the films of any one of 1-12. In the heat welding joining apparatus between the films, in which the rear end portion of the belt-like first film and the tip portion of the belt-like second film are superposed on each other,
A suction box having a flat suction surface, oppositely disposed on both sides of the joining region portion where the first film and the second film are overlapped;
A first moving means for moving the opposingly arranged suction boxes toward and away from each other, and moving the joining region portion toward and away from each other according to the movement of the suction boxes;
A second moving means for moving the suction boxes arranged opposite to each other in the film longitudinal direction;
A suction force generating means for applying a suction force to the suction surface of the suction box disposed oppositely;
A cutting blade that cuts each of the first and second films to form the rear end portion and the front end portion in the joining region portion;
Heat welding means for heat-welding a joint portion where the rear end portion of the first film and the front end portion of the second film are overlapped;
The first and second moving means, the suction force generating means, the cutting blade, and a control means for performing ON-OFF control of the thermal welding means, are provided. Joining device.   The apparatus of claim 14, wherein the suction surface of the suction box has a friction coefficient of 4 or less.   The apparatus for thermally welding and bonding films according to claim 15, wherein the suction surface of the suction box is made of polytetrafluoroethylene.   The first film and the second film that have suction surfaces that are flush with the suction surface of the suction box and smaller than the friction coefficient of the suction surface of the suction box and are cut by the cutting blade on both sides of the joining region portion. The apparatus for thermally welding and bonding films according to any one of claims 14 to 16, wherein auxiliary suction boxes each holding and holding the vicinity of the cut end of the film so as not to inhibit the thermal welding are fixedly arranged. .   The apparatus for heat welding and bonding films according to any one of claims 14 to 17, wherein the first moving means includes an adjustment mechanism that adjusts the distance of the approaching movement and the distance of the separation movement. . A first reel that winds and supports the first film in a roll;
A second reel for supporting the second film in a roll shape;
A first film transporting means for transporting the first film from the first reel to the film stretching unit for performing a desired process on the first film through the opposing suction boxes;
Second film pulling means for pulling out the second film from the second reel between the opposingly arranged suction boxes;
The first film is provided between the suction box and the film stretching section, and stores a first film having a length corresponding to the time required for heat-welding and joining the first and second films, and transports the first film. And a reservoir device capable of supplying the first film to the film stretching unit while performing thermal welding while stopping the heat treatment. In a production line for producing an optical film by performing various treatments on the film, in an optical film production method comprising at least a stretching treatment step for stretching the film,
The manufacturing method of the optical film provided with the process of performing the heat welding joining method of the films of any one of Claims 1-9 in the upstream position of the said manufacturing line.   The method for producing an optical film according to claim 20, wherein the film is a PVA-based film.

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