JP2004130797A - Solution film-forming method, protective film for polarizing plate, and optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize, concerning a thin film, the carrying of the film in the connection section in which the film is taken off from the support and carried to the tenter. <P>SOLUTION: A dope is cast onto the support 20. The formed film 25 is taken off with the take-off roller 24 while being supported. The guide apparatuses 83 are installed in the connection section 82 between the take-off roller 24 and the tenter drier 81. The guide plates 84, 85 are installed on both the sides of the edges 25a, 25b of the film 25. In carrying the film 25, floating wind is delivered to the guide plates 84, 85 from the blowers 86, 87 thereby to float the film 25 and convey by non-contact. The film 25 conveyed by the guide plates 84, 85 is immediately sandwiched in both the edges 25a, 25b by the tenter clips 88, 89, and this stabilizes the carrying. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a solution film forming method and a polarizing plate protective film and an optical film using a film formed by the method.

As a method for producing a film, a melt extrusion method and a solution casting method are conventionally known. For example, cellulose triacetate film is generally produced by a solution casting method. The solution casting method can produce a film having excellent optical properties (optical isotropy), physical properties, and thickness uniformity as compared with other production methods such as a melt extrusion method, and having few foreign matters. Films formed using cellulose acylate, especially cellulose triacetate (hereinafter referred to as TAC), as a polymer are photographic film base film, polarizing plate protective film, retardation film, transparent conductive film, and antiglare reflection. It is used for optoelectronic products such as prevention films.

FIG. 13 shows a film forming facility (hereinafter referred to as a film film forming line) 150 used for carrying out the conventional solution film forming method. A polymer solution 151 (hereinafter referred to as “dope”) in which a polymer is dissolved in a solvent is sent from a mixing tank 152 to a filtration device 154 by a pump 153, and after removing impurities, a support (for example, casting) is cast from a casting die 155. A cast film (hereinafter also referred to as a gel film) 157 is formed by casting on a belt 156 (which may be a belt or a rotating drum). After drying and having a self-supporting property, the film is peeled off from the support 156 while being supported by the peeling roller 158 to obtain a soft film (hereinafter, a film containing a large amount of solvent may be referred to as a soft film) 159.

Soft film 159 contains a large amount of solvent, and soft film 159 needs to be dried to volatilize the solvent. Therefore, in the solution casting method, the peeled soft film 159 is usually dried with a tenter dryer 160 capable of transporting and drying in a contactless manner at the center of the film, which is the product of the film formed. In the space 161 from the peeling roller 158 to the tenter dryer 160 (referred to as a crossing section), the soft film 159 is conveyed by a large number of crossing rollers 162. The soft film 159 dried by the tenter dryer 160 is sent out as a film 163, passes through the drying chamber 164 and the cooling chamber 165, and is wound up by the winder 166. However, since the volatilization rate from each part of the buffy coat 159 is different when the solvent volatilizes, there is a case where a phenomenon called a curl, where the edge of the buffy coat is curved, may occur. Further, since the tenter dryer 160 sandwiches and conveys the edge of the soft membrane 159, if a curl (hereinafter also referred to as an ear curl) occurs on the edge of the soft membrane 159, the tenter dryer 160 on the tenter dryer inlet side 160a This has caused a problem of biting and has caused problems during continuous film formation of the film. In particular, as the film thickness decreases, curling is more likely to occur. When the ear curl increases, the buffy coat (film) 159 may not be conveyed.

Therefore, a method of installing a curl correction device (see, for example, Patent Document 1 and Patent Document 2) during the period from the peeling position from the support until it is transported to the tenter dryer (hereinafter referred to as a transition part). There is known a method of suppressing the occurrence of curling at the crossing portion and providing a non-contact conveyance zone with the film (for example, see Patent Document 2).

JP 11-090944 A JP 2001-277267 A

However, as the film thickness is reduced, a large curl is generated on the soft film peeled off from the support, resulting in unstable conveyance.

The present invention provides a solution film-forming method that stabilizes the conveyance of the crossing portion even when the film is thin, suppresses the occurrence of curling, and prevents the poor biting when inserted into a tenter dryer and the method It is an object of the present invention to provide a polarizing plate protective film and an optical film constituted by using the film formed by the above method.

The present inventor has provided a guide plate on both sides of the soft film (meaning a film containing a large amount of solvent) at the crossover portion, and by providing floating air so that the guide plate and the soft film do not contact each other. The present inventors have found that curling can be suppressed without increasing the size of the apparatus. In addition, the surface (surface) of the guide plate facing the soft film is subjected to grooves and unevenness processing, or the surface energy is lowered by coating with fluorine as a raw material, so that the soft film becomes the surface of the guide plate. It has also been found that even if it comes into contact with the film, it is possible to reduce adhesion failure by suppressing adhesion. Furthermore, it has also been found that by arranging the guide plate just before the film biting portion of the tenter dryer, it is possible to further reduce the conveyance failure of the soft film at the transition portion.

The first solution casting method of the present invention is a solution casting in which a dope containing a polymer and a solvent is cast on a support, the formed soft film is peeled off, and transported to a tenter dryer to form a film. In the method, at the time of the conveyance, the guide portion is provided with guide portions on both sides of the edge of the buffy coat, and the guide portion blows a first wind on the surface of the buffy coat opposite to the support, And the contact opposite surface are conveyed in a non-contact manner.

The second solution casting method of the present invention is a solution casting in which a dope containing a polymer and a solvent is cast on a support, the formed soft film is peeled off, and transported to a tenter dryer to form a film. In the method, the guide portions provided on both sides of the edge of the buffy coat at the time of the conveyance are provided such that the tips thereof are provided to at least a part of the tenter dryer, A first wind is blown on the support contact opposite surface, and the guide portion and the contact opposite surface are conveyed in a non-contact manner. It is preferable to use a guide that expands / contracts in conjunction with expansion / contraction of the biting portion of the tenter dryer and does not interfere with the clamping means of the tenter dryer.

It is preferable that second air is blown onto the support contact surface of the buffy coat with the guide portion, and the guide portion and the buffy coat are conveyed in a non-contact manner. It is preferable that an outlet for blowing the first wind is provided in the guide portion, and the temperature of the first wind at the outlet is 20 ° C. or less. It is preferable that the surface of the guide portion on the buffy coat side has a contact angle with pure water of 45 ° or more. It is preferable to use a surface of the guide portion on the buffy face side coated with a material containing fluorine.

It is preferable to provide a groove having an angle between 0 ° to 45 ° between the soft film transport direction and a direction in which the soft film is stretched from the edge of the soft film on the surface of the guide portion on the soft film surface side. . It is preferable to use a surface roughness (Ra) of the guide portion on the soft membrane surface side of 50 μm ≦ Ra ≦ 500 μm. The guide portion provided on the support contact surface side and the support contact opposite surface side of the buffy coat has an interval L1 between the support contact surface surface and the support contact opposite surface surface in a range of 1 mm ≦ L1 ≦ 20 mm. It is preferable to use those.

It is preferable that the spray angle α of the first wind against the buffy coat is in the range of 5 ° to 85 °. It is preferable that the spray angle α of the second wind with respect to the buffy coat is in the range of 5 ° to 85 °. The first wind and the second wind are in any direction between a direction from the upstream side to the downstream side in the conveyance direction of the buffy coat and a direction from the central part of the buffy coat to the edge of the buffy coat side It is preferably directed to. It is preferable that the step β in the vertical direction between the upper edge and the lower edge of the first and second wind outlets is in the range of −10 mm ≦ β ≦ 10 mm.

It is preferable to use cellulose acylate for the polymer, more preferably cellulose acetate, and most preferably cellulose triacetate. The present invention also includes a polarizing plate protective film and an optical film that are formed using a film formed by the solution casting method.

According to the first solution casting method of the present invention, a dope containing a polymer and a solvent is cast onto a support, the formed soft film is peeled off, and the solution is transported to a tenter dryer to form a film. In the film forming method, at the time of the conveyance, using a guide portion provided on both sides of the edge of the buffy coat, the guide portion blows a first wind on the surface of the buffy coat opposite to the support, Since the guide portion and the contact opposite surface are conveyed in a non-contact manner, the buffy coat can be stably conveyed at the transition portion.

According to the second solution film-forming method of the present invention, a dope containing a polymer and a solvent is cast onto a support, the formed soft film is peeled off, and transported to a tenter dryer to form a film. In the film forming method, the guide portions provided on both sides of the edge of the buffy coat at the time of the conveyance are provided such that the tips thereof are provided to at least a part of the tenter dryer, Since the first wind is blown to the surface of the soft membrane that is opposite to the support, and the guide portion and the surface that is opposite to the contact are transported in a non-contact manner, the transport of the soft membrane at the transition portion can be stabilized. It is possible to prevent a biting failure when inserting the. Further, since the guide portion is expanded and contracted in conjunction with the expansion and contraction of the biting portion of the tenter dryer and does not interfere with the holding means of the tenter dryer, it is easy to change the width of the film to be formed. Yes.

When performing the first and second solution film-forming methods of the present invention, the guide portion blows a second wind onto the support contact surface of the buffy coat and conveys the guide portion and the buffy coat in a non-contact manner. As a result, the conveyance height of the buffy coat becomes constant, and the conveyance can be further stabilized. Further, the curling of the ear end portion of the buffy coat can be suppressed, and when the curling occurs, the curling can be corrected while the crossing portion is being conveyed.

When performing the solution casting method of the present invention, the surface of the guide portion on the buffy coat side 1) having a contact angle with pure water of 45 ° or more is used.
2) Use a material coated with fluorine.
3) A groove having an angle between 0 ° to 45 ° formed between the buffy coat conveyance direction and the direction in which the buffy coat is stretched from the edge of the buffy coat is positive.
4) A surface roughness (Ra) of the surface of the guide portion on the soft film surface side is 50 μm ≦ Ra ≦ 500 μm.
By using the guide plate subjected to at least the above treatments 1) to 4), adhesion of the buffy coat can be suppressed.

When performing the solution casting method of the present invention, a floating wind that floats the buffy coat on the buffy coat insertion part of the guide part or an adjustment wind that blows wind from the upper surface of the buffy coat to bring the conveyance height to a desired position By blowing, when the buffy coat is inserted into the guide portion, an accident that contacts the edge of the guide portion can be prevented.

When carrying out the solution casting method of the present invention, if cellulose acylate is used as the polymer, it becomes possible to form a film suitable for a polarizing plate protective film or an optical film. In addition, since the transfer of the soft film at the crossing portion is stable, it can be used for so-called thin film film formation in which the film thickness after drying is thin. In particular, the range of 15 μm to 125 μm is preferable, the range of 25 μm to 105 μm is more preferable, and the most preferable is application to film formation of a film of 35 μm to 85 μm.

[solvent]
Any known solvent can be used as the solvent for preparing the dope used in the solution casting method of the present invention. In particular, halogenated hydrocarbons such as methylene chloride (dichloromethane), esters such as methyl acetate, ethers, alcohols (eg, methanol, methanol, n-butanol, etc.), ketones (eg, acetone, etc.), etc. Although used preferably, it is not limited to these. It is also possible to prepare a dope from a solvent in which a plurality of these solvents are mixed (hereinafter referred to as a mixed solvent) and to form a film from the dope. In the present invention, a mixed solvent containing dichloromethane as a main solvent is referred to as a dichloromethane solvent, and a mixed solvent containing methyl acetate as a main solvent is referred to as a methyl acetate solvent.

[polymer]
The polymer used in the present invention is not particularly limited. Examples include cellulose acylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, but are not limited thereto. Cellulose acylate is preferably used as the polymer, and cellulose triacetate (TAC) having an acetylation degree of 59.0% to 62.5% is particularly preferable. Moreover, when using TAC, the raw material has the thing of a cotton linter and the thing of a wood pulp, TAC which used them independently may be used, and TAC which mixed them may be used.

[Additive]
Any of known additives can be added to the dope. Examples of additives include plasticizers (triphenyl phosphate (hereinafter referred to as TPP), biphenyl diphenyl phosphate (hereinafter referred to as BDP), etc.), ultraviolet absorbers (for example, 2,4-bis- (n-octylthio)- 6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5 Chlorobenzotriazole, etc.), matting agents such as silicon dioxide, thickeners, oil gelling agents and the like, but are not limited thereto. These additives can also be mixed with the polymer when preparing the dope. Further, after the dope is prepared, it can be mixed in-line using a static mixer or the like when transferred. In the present invention, the polymer and the additive are collectively referred to as a solid content.

[Preparation of dope]
The above-described solid content (polymer and additive) is charged into the above-described solvent (may be a mixed solvent), and then dissolved by any known dissolution method to prepare a dope. This dope generally removes foreign matters by filtration. For filtration, various known filter media such as filter paper, filter cloth, non-woven fabric, metal mesh, sintered metal, and perforated plate can be used. By filtering, foreign substances and undissolved substances in the dope can be removed, and defects due to foreign substances in the product film can be reduced.

It is also possible to improve the solubility by heating the dope once prepared. For heating, there are a method of heating while stirring in a stationary tank, and a method of heating while transferring the dope using various heat exchangers such as a multi-tube type and a jacket pipe with a static mixer. Moreover, a cooling process can also be implemented after a heating process. It is also possible to heat the apparatus to a temperature higher than the boiling point of the dope by pressurizing the inside of the apparatus. By performing these treatments, it is possible to completely dissolve the fine undissolved material, and it is possible to reduce the load of filtration and reduce foreign matters in the film.

In the present invention, the weight percentage (dope solid content concentration) of the dope is preferably 15 to 30% by weight, more preferably 18 to 25% by weight. If it is less than 15% by weight, the solid content concentration of the dope is too low, so it may take time for the gel film formed from the dope to have a preferable film stress, which may cause a problem in terms of cost. . On the other hand, if the solid concentration is too low, a gel film may not be formed when the dope is cast. On the other hand, if it exceeds 30% by weight, the viscosity of the dope becomes too high, and the bead leveling effect (smoothing) becomes difficult to be exhibited, and it may be difficult to form a uniform film.

[Solution casting method]
FIG. 1 shows a schematic view of a film casting line 10 used for carrying out the solution casting method according to the present invention. In the mixing tank 11, the dope 12 prepared by the above-described method is charged and stirred by the stirring blade 13 to be uniform. The dope 12 is sent to the filtration device 15 by the pump 14 to remove impurities. Then, it is sent to the casting die 16 at a constant flow rate. The casting die 16 is disposed on the casting belt 20. The casting belt 20 travels endlessly as the rotating rollers 21 and 22 are rotated by a rotation driving device (not shown). The dope 12 is cast on the casting belt 20 from the casting die 16. The dope 12 becomes a gel film 23 on the casting belt 20. After the gel film 23 has self-supporting properties, the soft film 25 is obtained by peeling off the gel film 23 while being supported by the peeling roller 24. In addition, although the form which used the casting belt for the support body is demonstrated, the support body used for this invention is not limited to it, For example, you may use a casting drum (rotary drum) etc.

A period until the peeled soft film 25 is conveyed to the tenter dryer 30 is referred to as a transition portion 31 in the present invention, and a guide device (hereinafter referred to as a first type guide device) installed in the transition portion 31. 32) will be described with reference to FIG. The guide device 32 is provided with guide plates 33 and 34 on both edges 25a and 25b of the buffy coat, and further blowers 35 and 36 are connected. In FIG. 2, the guide device 32 and the tenter dryer 30 are shown with their respective upper lids removed.

3 shows a cross-sectional view taken along line III-III in FIG. The guide plate 33 includes an upper guide plate main body 37 disposed to face the support contact surface 25c of the buffy coat 25 and a lower guide plate main body 38 disposed to face the support contact opposite surface 25d. ing. The soft film 25 is conveyed between the guide plate bodies 37 and 38. The piping 39 is attached to the lower guide plate main body 38 so that the soft film 25 and the surface on the soft film surface side of the lower guide plate main body 38 (hereinafter, the surface facing the soft film surface is referred to as the surface) 38a do not contact. The soft film 25 can be conveyed without contact by flowing the floating air (first air) 40 blown from the blower 35 between the lower guide plate main body surface 38a and the soft film surface 25d from the pipe 39. It becomes possible. Further, the characteristics of the buoyant wind 40 are not particularly limited. However, when the temperature at the buoyant wind outlet 39a is 20 ° C. or less, rapid volatilization of the solvent from the soft film 25 is suppressed, and the generation of the curl 25e is suppressed. This is preferable. In the present invention, the distance L1 between the lower guide plate body surface 38a and the upper guide plate body surface 37a is not particularly limited, but is preferably in the range of 1 mm ≦ L1 ≦ 20 mm.

Also, the buffy coat 25 may have a curl 25e on the edge 25a side due to the volatilization of the solvent being conveyed. At this time, if the floating air 40 is blown only between the lower guide plate main body surface 38a and the soft film surface 25d to float the soft film 25, the curl 25e may come into contact with the upper guide plate main body surface 37a. Therefore, the pipe 41 is also attached to the upper guide plate body 37, and an adjustment wind (second wind) 42 for positioning the soft membrane 25 is caused to flow between the support contact surface 25c and the upper guide plate body surface 37a. The occurrence of the curl 25e can be suppressed, and the generated curl 25e can be corrected. The conveyance height of the buffy coat 25 can be kept constant, and the buffy coat 25 can be conveyed stably at the transition portion 31. be able to. In addition, the ventilation of the adjustment wind 42 may use the air blower 35 which blows the floating air 40, and may use the other air blower which is not shown in figure. In the present invention, the guide plate 34 and the blower 36 attached to the other edge 25b of the buffy coat 25 are also preferably configured in the same manner, and description thereof is omitted.

The blowing angle α of the floating air 40 against the soft film 25 is not particularly limited. However, it is preferably in the range of 5 ° or more and 85 ° or less so as not to cause deformation of the soft film 25 and displacement of the transfer position. Similarly, the spray angle α of the adjustment air 40 against the soft film is preferably 5 ° or more and 85 ° or less. Further, the pipes 39 and 40 are attached to the lower guide plate main body 38 and the upper guide plate main body 37, and blowout ports for the respective winds 40 and 42 are formed. The step β between the upper edge portion and the lower edge portion of the outlet is preferably in the range of −10 mm to 10 mm. This is because when the step β is smaller than −10 mm or larger than 10 mm, the edges of the pipes 39 and 40 may come into contact with the soft film 25. The step β is positive in the direction from the lower guide plate main body 38 toward the upper guide plate main body 37 as shown in FIG.

The soft film 25 peeled off while being supported from the casting belt 20 by the peeling roller 24 is conveyed to the tenter dryer 30 in a non-contact manner by the guide device 32 provided in the transfer section 31 as described above (FIG. 2). reference). The tenter dryer 30 is provided with a large number of tenter clips 45 and 46 connected by endless chains 43 and 44. The soft film 25 from the biting portion 30a of the tenter dryer 30 is transported and dried with the edges 25a and 25b sandwiched between tenter clips 45 and 46. In addition, X in FIG. 2 means the positive direction of the direction in which the buffy coat is stretched, and Y means the conveyance direction of the buffy coat. Since the present invention enables non-contact conveyance, it is preferably used for so-called thin film formation in which the film after drying is thin. The thickness of the film after drying is not particularly limited, but is preferably in the range of 15 μm to 125 μm, more preferably in the range of 25 μm to 105 μm, and most preferably applied to film formation of a film of 35 μm to 85 μm.

As shown in FIG. 3, in the present invention, the buffy coat 25 is transported between the upper guide plate body surface 37a and the lower guide plate body surface 38a. For this reason, when the soft film 25 has irregularities or undulates, it may come into contact with the surfaces 37a and 38a and stable conveyance cannot be performed. Therefore, it is more preferable to apply a process that hardly adheres to the surfaces 37a and 38a so that the soft film 25 does not adhere to the surfaces 37a and 38a when contacted. Moreover, it is preferable to use the thing to which the location adjacent to the soft film 25 of the piping 39 and 41 which ventilates the buoyant wind 40 and the adjustment wind 42 was similarly difficult to adhere. These will be described with reference to the drawings.

FIG. 4 shows a cross-sectional view of the guide plate body 60. The guide plate body 60 is preferably made of a base material 60a and a coating layer 60b coated on the base material 60a. The base material 60a is made of SUS304, SUS316, SS material + HCr plating (hard chrome plating) or the like such that the guide plate body 60 has durability. Further, it is preferable to select a coating layer 60b having a large surface tension so that it does not easily adhere when the soft film 25 (see FIG. 3) comes into contact. As such an example, it is preferable to coat a material containing fluorine such as polyperfluoroethylene. In addition, when pure water 61 is dropped on the guide plate body surface 60c, it is preferable that the contact angle D1 be 45 ° or more. In order to make the contact angle D1 within the above-described range, a coating layer 60b may be provided as shown in FIG. 4, or the base material 60b having such characteristics is used and the coating layer is omitted. May be. The guide plate main body 60 shown in FIG. 4 can be used for both the upper guide plate main body 37 and the lower guide plate main body 38 as shown in FIG. It is. The guide plate main body (not shown) provided in the guide plate 34 is preferably of the same form as the above-described guide plate main body 60 (including guide plate main bodies of other embodiments described later). .

FIG. 5 (a) shows a plan view of a guide plate body 65 of still another embodiment. A groove 65 b is formed on the surface 65 a of the guide plate 65. The groove angle D2 defined by the X direction and the Y direction described in FIG. 2 is preferably 0 ° ≦ D2 ≦ 45 °. The groove 65b also serves as a flow path for levitation air and adjustment air, and can suppress adhesion between the guide plate body surface 65a and the soft film. Any known method may be used as a method of forming the groove 65b. If the groove angle D2 exceeds 45 °, the force that stretches the attached soft membrane increases, which may cause the soft membrane to wrinkle. In severe cases, the guide device may become clogged, making continuous operation difficult. There is also. The cross-sectional shape of the groove is not particularly limited, but the cross-section may be a concave shape so that it can be easily processed like the groove 66a of the guide plate main body 66 shown in FIG. 5B, or FIG. The cross section of the guide plate main body 67 shown in FIG. In FIG. 5, the grooves and the like are exaggerated. The width L2 of the groove is not particularly limited, but is preferably in the range of 0.1 mm to 3.0 mm, and the depth d is preferably in the range of 30 μm to 800 μm with respect to the average value of the surface of the guide plate body. .

Further, in the present invention, the surface roughness Ra of the surfaces 37a, 38a (see FIG. 3) of the guide plate bodies 37, 38 is preferably in the range of 50 μm ≦ Ra ≦ 500 μm, and it is preferable to have some unevenness. It is not limited to. If it is less than 50 μm, the effect of suppressing adhesion of the buffy coat may not be exhibited. On the other hand, when the thickness exceeds 500 μm, the soft film adheres to the soft film when it comes into contact with the film, and the conveyance becomes unstable. May be difficult.

As described above, by using the solution casting method of the present invention, it is possible to stably carry the soft film 25 in the transfer section 31 from the peeling roller 24 to the tenter dryer 30 (FIG. 2). reference). In the present invention, it is preferable to dry 0.2 to 5 minutes in the range of 20 to 200 ° C. with the tenter dryer 30, but is not limited to these ranges. Hereinafter, the dried buffy coat 25 is referred to as a film 70 (see FIG. 1). The film 70 is preferably sent from the tenter dryer 30 and further sent to the drying chamber 71. In the drying chamber 71, it is conveyed and dried while being wound around a number of rollers 72. In the present invention, the temperature of the drying chamber 71 is preferably adjusted to a range of 20 ° C. to 200 ° C. and dried for 5 minutes to 25 minutes, but is not limited to these ranges. Further, it is preferable that the film 70 is sent out to the cooling chamber 73 and is cooled by a winder 74 after being cooled (preferably to room temperature but not particularly limited). In addition, before winding up the film 70, an ear-cut process may be performed or knurling may be performed.

FIG. 6 shows and describes a film deposition line 80 of another embodiment used in the solution casting method of the present invention. FIG. 7 is a main part schematic diagram of the crossover part 82 and will be described. A guide device (hereinafter also referred to as a second type guide device) 83 is provided with guide plates 84 and 85 on both edges 25a and 25b of the buffy coat 25, and blowers 86 and 87 are connected to the guide plates 84 and 87, respectively. , 87 blows wind.

The downstream end portion 83 a of the guide device 83 is disposed in the tenter dryer 81. The soft film 25 has a transfer position (height) of the edges 25a and 25b of the guide plates 84 and 85 at the crossing portion 82, and the upstream side of the biting portion 81a of the tenter dryer 81 while maintaining the transfer position. It is conveyed without contact until just before. Thereby, conveyance of the soft film 25 in the transfer part 82 can be performed more stably. Thereafter, both edges 25a and 25b are held between the tenter clips 88 and 89 and conveyed. Hereinafter, the form is demonstrated using FIG.8 and FIG.9.

FIG. 8 is a cross-sectional view taken along line VIII-VIII. The clip 88 a of the tenter clip 88 is lifted upward by the opening member 90 of the guide plate 84. Although not shown in FIG. 7, the opening member 90 is provided at the curvature portion of the conveying path of the tenter clip 88. The tip end portion 84a (see FIG. 7) of the guide plate 84 can be inserted between the lower portion 88b of the clip 88a and the tenter clip lower portion 88c, and the guide plate 84 and the clip 88a can be prevented from interfering with each other. Further, when the tenter clip 88 moves downstream from the opening member 90, the clip 88a is released from the structure where the clip 88a is lifted upward, and the cross section of the IX-IX line is shown in FIG. Is conveyed. Moreover, it is preferable that the guide plate 85 and the air blower 87 attached to the other edge 25b of the soft membrane 25 have the same configuration, and the description thereof is omitted. In the present invention, the form of the opening member 90 is not limited to the illustrated one.

It is preferable that shift mechanisms 91 and 92 are respectively attached to the guide device 83 and the tenter dryer 81 so that the width of the film can be changed according to the product (see FIG. 7). When the width of the biting portion 81a is enlarged or reduced by the shift mechanism 92, the guide plates 84 and 85 no longer interfere with the tenter clips 88 and 89 when the width of the guide plate 85 is enlarged or reduced by the shift mechanism 91 in conjunction therewith. . In the present invention, the mounting form of the shift mechanism is not limited to the illustrated one. Further, the shift mechanisms 91 and 92 can be omitted.

As shown in FIG. 10, it is preferable that pipes 93 and 94 are attached to the upstream side of the guide plate 85 and connected to the blower 87 because the soft film 25 is inserted without contacting the guide plate 85. In order to prevent the soft film 25 from coming into contact with the lower guide plate main body 85c, the floating air 95 is blown from the blower 87 through the pipe 94. Further, it is more preferable that the adjustment air 96 is blown from the blower 87 through the pipe 93 so that the height of the soft film 25 becomes a desired position and is not brought into contact with the upper guide plate main body 85b. Similarly, the guide plate 84 can be connected to the inlet side of the guide plate 84 via the pipe 97 to blow air, thereby preventing a soft film contact accident at the inlet.

As shown in FIG. 11, by using the guide plates 100 and 101 according to another embodiment, it is possible to adjust the direction in which the floating air and the adjustment air are blown between the guide plate body and the soft membrane 25. The direction of the levitation wind and the adjustment wind is a direction between the wind direction 103a in the conveyance direction of the buffy coat 25 and the wind direction 103b in the direction from the center of the buffy coat 25 to the edge of the buffy coat 25, so that the conveyance of the buffy coat 25 is stabilized. Therefore, it is preferable. In the above description, the wind direction is adjusted by directing the supply pipe of the wind (floating wind, adjusted wind) in a desired blowing direction, but the present invention is not limited to these forms. For example, a guide plate such as a fin may be provided to adjust the wind direction.

FIG. 12 is a schematic diagram showing a crossover portion 131 of a film deposition line 130 of still another embodiment used in the solution casting method of the present invention and an apparatus provided before and after that. In addition, the same code | symbol is attached | subjected about the same location as the film forming line 80 of FIG. 6, and description is abbreviate | omitted. When the gel film 23 has self-supporting property on the casting belt 20, it is peeled off as the soft film 25 while being supported by the peeling roller 24. The soft film 25 is conveyed to the second type guide device 136 by the first type guide device 132, the transition roller 133, the first type guide device 134, and the transition roller 135 provided in the transition portion 131. As shown in FIG. 7, the second guide transport device 136 is provided with a guide plate until just before the biting portion 81 a of the tenter dryer 81 to stabilize the transport. As shown in FIG. 12, the tenter dryer 81 and the drying chamber 71 cannot be installed in the vicinity of the support (FIG. 12 shows the casting belt 20 but the same applies to the casting drum). Even in such a case, by using the guide plate device, it is possible to stably carry the buffy coat. That is, in the present invention, a guide device is used to stabilize the conveyance of the buffy coat 25. However, the guide device can convey the buffy coat and suppress the occurrence of curling as described above, and correct the generated curl. Is also possible. For this reason, it is possible to stably carry even if a crossover roller is used for the crossover portion. In FIG. 12, the first type guide devices 132 and 134 and the two crossing rollers 133 and 135 are used alternately and arranged alternately. However, the present invention is not limited to the illustrated form, and the crossing roller 131 is placed in the crossing unit 131. It is also possible not to use. Moreover, although the example which provided the 2nd type guide apparatus 136 in the upstream of the tenter dryer 81 was illustrated, it is also possible to use a 1st type guide apparatus (refer FIG.1 and FIG.2).

The film 70 formed by the solution casting method of the present invention can be used as an optical film (optical film) such as a polarizing plate protective film. A polarizing plate can be formed by sticking this polarizing plate protective film (polarizing plate protective film) on both surfaces of a polarizing film formed of polyvinyl alcohol or the like. Furthermore, it can also be used as an optical functional film such as an optical compensation film in which an optical compensation sheet is attached to the above film, or an antireflection film in which an antiglare layer is formed on the film. A liquid crystal display plate which is a part of the liquid crystal display device can also be configured from these products.

Hereinafter, the present invention will be described in detail with reference to Example 1 and Example 2, but the aspects of the present invention are not limited thereto. First, Experiment 1 to Experiment 7 will be described as Example 1, and are collectively shown in Table 1 later. The description will be described in detail in Experiment 1, and the description of the other experiments where the conditions are the same as in Experiment 1 will be omitted. Then, Experiment 8 to Experiment 14 will be described as Example 2, and are summarized in Table 2 later. In the description of the second embodiment, the description of the same parts as those in Experiment 1 is omitted. Further, it will be described in detail in Experiment 8, and description of the other experiments will be omitted for the same conditions as in Experiment 8.

The dope A used in Experiment 1 of Example 1 according to the present invention uses a dichloromethane-based mixed solvent composed of dichloromethane (64 parts by weight), methanol (16 parts by weight), and n-butanol (0.4 parts by weight). It was. As the polymer, cellulose acetate (20 parts by weight) synthesized from wood pulp and having an acetylation degree of 62% was used. Using 2.2 parts by weight of a plasticizer (TPP: BDP = 2: 1) as an additive, it is further an ultraviolet absorber (2,4-bis- (n-octylthio) -6- (4-hydroxy-3) , 5-di-tert-butylanilino) -1,3,5-triazine (0.4 part by weight) and silica (0.05 part by weight) as a matting agent, dichloromethane was mainly used for dope preparation. This was performed by a known method when used as a solvent, and the solid content concentration of the obtained dope A was 22% by weight.

The film was deposited using the film deposition line 80 shown in FIG. As the casting die 16, a coat hanger type die was used. The temperature was adjusted so that the temperature of the casting belt 20 was 20 ° C. Further, the rotational driving of the rotating rollers 21 and 22 was controlled so that the film forming speed was 60 m / min. A dope A at 34 ° C. was cast on the casting belt 20 at a film forming speed of 60 m / min to form a gel film 23. Casting was carried out so that the average film thickness T0 in the product after drying was 80 μm and the average film thickness T1 at the outer ear end of the product was 123 μm (hereinafter referred to as film forming condition 1). After the gel film 23 became self-supporting, the gel film 23 was peeled off while being supported by the peeling roller 24, and a soft film 25 was obtained.

The surfaces of the guide plates 84 and 85 of the guide device 83 were used so that the contact angle D1 was 50 ° and the groove angle D2 was 0 °. Pipes were attached to the upper and lower guide plate bodies, respectively. The attachment angle α was 45 ° in all cases, and the step β was 0.5 mm (absolute value). And 20 degreeC wind was blown at 5 m / s, respectively, and the wind was also blown to the buffy coat insertion side (see FIG. 11). Thereby, the soft film 25 is conveyed to the biting part 81a of the tenter dryer 81 without contact. The both edges 25a and 25b of the buffy coat 25 are conveyed while being held between tenter clips 88 and 89. The film 70 was obtained by conveying the tenter dryer 81 maintained at 100 ° C. for 1 minute.

The stability of biting of the buffy coat 25 in the biting part 81a is visually confirmed, and there is no failure in biting the tenter of the film ear (◯), continuous conveyance is possible, but failure is sporadic (△), and cannot be conveyed (×) 3 Evaluation was performed in stages. In addition, the state of occurrence of biting flaws (film powder) in the biting portion 81a was also confirmed visually, and no biting flaws were generated (◎). Evaluation was performed in three stages, (◯), where biting flaws occurred and it was impossible to use the formed film as a product (×). If biting material (film powder) is generated in the biting portion 81a, it adheres to the film surface and causes defects. In Experiment 1, the biting stability was excellent (◯) and no biting occurred (◎), and it was possible to continuously form a film.

Further, the film 70 was sent to a drying chamber 71 maintained at 120 ° C., dried for 10 minutes, cooled in a cooling chamber 73 at 25 ° C. and then wound up by a winder 74. There was no abnormality in the surface shape of the obtained film 70, and it was possible to continuously form a film.

In Experiment 2 according to the present invention, the film after drying was formed such that the average film thickness T0 in the product was 40 μm and the product outer ear end average film thickness T1 was 98 μm (hereinafter referred to as film forming condition 2). The conditions were the same as in Experiment 1 except for the above. As a result, it was possible to obtain a film 70 that was excellent in biting stability (◯) and slightly bitten (O) but could be used as a product.

In Experiment 3 to Experiment 5 according to the present invention, the same conditions as in Experiment 2 except that the floating air temperature was 0 ° C. in Experiment 3, the contact angle D1 was 70 ° in Experiment 4, and the groove angle D2 was 20 ° in Experiment 5. Experiments were conducted under film forming conditions 2). As a result, in any of Experiments 3 to 5, the biting stability was excellent (◯), and no biting was generated (◎). The films formed from these experiments were of good quality.

In Experiment 6, which is a comparative experiment, the guide unit 83 is not provided in the transfer section 82, but three driven rollers (also referred to as transfer rollers) used in a known solution casting method are provided, and the soft film is used as the transfer roller. Used and sent to the tenter dryer 81. Other conditions were the same as in Experiment 1 (film formation condition 1) to form a film. Although it was possible to carry out the biting with the tenter dryer 81, the biting failure occurred sporadically (Δ), and it was necessary to make adjustments by stopping the operation of the film forming line 80 each time. Further, the occurrence of biting flaws was noticeable (×), and a film that could be used as a product could not be obtained.

Also in Experiment 7, which is a comparative experiment, as in Experiment 6, the guide device 83 was not provided, three transfer rollers were provided, and the soft film was sent to the tenter dryer 81 using the transfer rollers. Other conditions were the same as in Experiment 2 (film formation condition 2) to form a film. The tenter dryer 81 failed to bite continuously and could not be conveyed (×). In addition, the occurrence of biting flaws was also noticeable (×).

Dope B used in Experiment 8 of Example 2 according to the present invention is methyl acetate (64 parts by weight), ethanol (12 parts by weight), acetone (4 parts by weight), and n-butanol (0.4 parts by weight). A methyl acetate mixed solvent was used. As the polymer, cellulose acetate (20 parts by weight) synthesized from wood pulp and having an acetylation degree of 59.6% was used. The same additive as dope A was used under the same conditions. The dope was prepared by a known method using methyl acetate as the main solvent. The solid content concentration of the obtained dope B was 22% by weight.

In Experiment 8, a film was formed using the film forming line 80 shown in FIG. 6 under the same conditions as in Experiment 1 (film forming condition 1) except that dope B was used. When the biting stability in the biting portion 81a was visually confirmed, it was found that the biting stability was excellent (◯) and there was no biting flaws (◎), and it was possible to continuously form a film. It was.

In Experiment 9 according to the present invention, a film was formed under the same conditions as in Experiment 2 (film formation condition 2) except that dope B was used. As a result, it was possible to obtain a film 70 having excellent biting stability (◯) and a good biting generation (ブ).

In Experiment 10 to Experiment 12 according to the present invention, the same conditions as in Experiment 9 except that the floating air temperature was 0 ° C. in Experiment 10, the contact angle D1 was 70 ° in Experiment 11, and the groove angle D2 was 20 ° in Experiment 12. Experiments were conducted under film forming conditions 2). As a result, in any of Experiments 10 to 12, the biting stability was excellent (◯), and no biting was generated (◎). The films formed from these experiments were of good quality.

In Experiment 13, which is a comparative experiment, the experiment was performed under the same conditions as in Experiment 6 (film formation condition 1) except that dope B was used. Although it was possible to bite the tenter dryer 81, the biting failure occurred sporadically (.DELTA.), And it was necessary to make adjustments by stopping the operation of the film forming line 80 each time. Further, the occurrence of biting flaws was noticeable (×), and a film that could be used as a product could not be obtained.

Experiment 14, which is a comparative experiment, was performed under the same conditions as in Experiment 7 (film forming condition 2) except that dope B was used. The tenter dryer 81 failed to bite continuously and could not be conveyed (×). In addition, the occurrence of biting flaws was also noticeable (×).

It is the schematic of the film film forming line used for the solution film forming method of this invention. It is a principal part schematic plan view of the film film-forming line shown in FIG. It is sectional drawing of the III-III line | wire of FIG. It is sectional drawing of other embodiment of the guide plate used for the solution casting method of this invention. It is sectional drawing of other embodiment of the guide plate used for the solution casting method of this invention. It is the schematic of other embodiment of the film film forming line used for the solution film forming method of this invention. It is a principal part schematic plan view of the film film-forming line shown in FIG. It is sectional drawing of the VIII-VIII line of FIG. It is sectional drawing of the IX-IX line of FIG. It is sectional drawing of the XX line of FIG. It is the principal part schematic of other embodiment of the film film forming line used for the solution film forming method of this invention. It is the principal part schematic of other embodiment of the film film forming line used for the solution film forming method of this invention. It is the schematic of the film forming line used for the conventional solution casting method.

Explanation of symbols

10, 80, 130 Film forming line 24 Stripping roller 25 Soft film 25a, 25b Edge 25e Curl 30, 81 Tenta dryer 30a Biting part 31 Transition part 32, 83 Guide device 33, 34 Guide plate 35, 36 Blower 40 Floating Wind 42 Adjusting wind 70 Film 88 Tenter clip 90 Opening member L1 Surface spacing

Claims (17)

In a solution casting method in which a dope containing a polymer and a solvent is cast on a support, the soft film formed is peeled off, and transported to a tenter dryer to form a film.
At the time of conveyance, using what provided guide parts on both sides of the edge of the buffy coat,
A first wind is blown on the surface of the buffy coat that is opposite to the support body in the guide portion,
A solution casting method comprising transporting the guide portion and the contact opposite surface in a non-contact manner. In a solution casting method in which a dope containing a polymer and a solvent is cast on a support, the soft film formed is peeled off, and transported to a tenter dryer to form a film.
During the conveyance, the guide portions provided on both sides of the buffy coat edge are provided with at least a part of the tip of the tenter dryer,
A first wind is blown on the surface of the buffy coat that is opposite to the support body in the guide portion,
A solution casting method comprising transporting the guide portion and the contact opposite surface in a non-contact manner. 3. The solution casting method according to claim 2, wherein the guide portion is expanded and contracted in conjunction with expansion and contraction of the biting portion of the tenter dryer and does not interfere with the clamping means of the tenter dryer. A second wind is blown to the support contact surface of the buffy coat at the guide portion,
The solution casting method according to claim 1, wherein the guide portion and the buffy coat are conveyed in a non-contact manner. An outlet for blowing the first wind is provided in the guide part,
5. The solution casting method according to claim 1, wherein the temperature of the first wind at the outlet is 20 ° C. or less. The solution casting method according to any one of claims 1 to 5, wherein a surface having a contact angle with pure water of 45 ° or more is used for the surface of the guide portion on the buffy coat side. The solution casting method according to any one of claims 1 to 6, wherein a surface of the guide portion on the soft membrane surface side is coated with a material containing fluorine. A groove having an angle between 0 ° to 45 ° formed between the soft film transport direction and a direction in which the soft film is stretched from the edge of the soft film is provided on the surface of the guide portion on the soft film surface side. The solution casting method according to any one of claims 1 to 7. The surface roughness (Ra) of the surface of the guide portion on the buffy coat side is:
9. The solution casting method according to claim 1, wherein a film having a thickness of 50 μm ≦ Ra ≦ 500 μm is used. Guide portions provided on the support contact surface side and the support contact opposite surface side of the buffy coat,
10. The solution casting method according to claim 1, wherein a distance L1 between the support contact surface and the support contact opposite surface is in the range of 1 mm ≦ L1 ≦ 20 mm. . 11. The solution casting method according to claim 1, wherein the spray angle α of the first wind against the soft film is in the range of 5 ° to 85 °. The solution casting method according to any one of claims 4 to 11, wherein a spray angle α of the second wind to the soft film is in a range of 5 ° to 85 °. The first wind and the second wind are either between a direction from the upstream side to the downstream side in the conveyance direction of the buffy coat and a direction from the central part of the buffy coat to the edge side of the buffy coat side 13. The solution casting method according to claim 4, wherein the solution casting method is directed in a direction. 5. The step β in the vertical direction between the upper and lower edges of the first and second wind outlets is in the range of −10 mm ≦ β ≦ 10 mm. 14. The solution casting method according to any one of 13 to 13. The solution casting method according to claim 1, wherein cellulose acylate is used for the polymer. A polarizing plate protective film comprising a film formed by the solution casting method according to any one of claims 1 to 15. An optical film using the film formed by the solution casting method according to any one of claims 1 to 15.

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