JP5970117B1 - Polarizing film manufacturing method and manufacturing apparatus - Google Patents

Abstract

The present invention provides a polarizing film production method capable of efficiently draining water by a simple method. A method for producing a polarizing film 23 comprising producing a polarizing film 23 from a polyvinyl alcohol-based resin film 10, wherein a treatment liquid 13, 15, 17, 19 is contacted with the polyvinyl alcohol-based resin film 10 for processing. And a treatment liquid removal step of removing the treatment liquid adhering to the surface of the polyvinyl alcohol resin film 10 by bringing the liquid draining members 71 and 72 into contact with the polyvinyl alcohol resin film 10 after the treatment process. The manufacturing method of the polarizing film 23 provided with this order, and the surface roughness Ra of the surface which the liquid cutting members 71 and 72 contact the polyvinyl alcohol-type resin film 10 are 0.5 micrometer or less. [Selection] Figure 1

Description

  The present invention relates to a method for producing a polarizing film that can be used as a constituent member of a polarizing plate.

  Conventionally used is a polarizing film obtained by adsorbing and orienting a dichroic dye such as iodine or a dichroic dye on a uniaxially stretched polyvinyl alcohol resin film. A polarizing film is usually a polarizing plate obtained by laminating a protective film on one or both sides with an adhesive, and used for liquid crystal display devices such as liquid crystal televisions, monitors for personal computers and mobile phones. It is used.

  In general, a polarizing film is produced by subjecting a long polyvinyl alcohol resin film to be continuously conveyed to a swelling process, a dyeing process, a stretching process, a crosslinking process and a washing process, and finally drying. In JP 2014-109740 A (Patent Document 1), defects are caused on the surface of the polarizing film due to crystal foreign matter or the like by blowing air on the polyvinyl alcohol resin film after the cleaning treatment. It is described that this can be suppressed.

JP 2014-109740 A

  The polarizing film and the polarizing plate are required to be further thinned as compared with the conventional film. In Patent Document 1, draining without breaking the thin polyvinyl alcohol resin film by adjusting the tension of the polyvinyl alcohol resin film at the time of air blowing, the air volume, and the distance from the tip of the air outlet to the film surface. It is described that it can be performed (see Table 1 of Patent Document 1).

  The method of draining water by air blowing is complicated as described above. An object of this invention is to provide the manufacturing method of a polarizing film which can drain water efficiently by a simple method.

This invention provides the manufacturing method of the polarizing film shown below.
[1] A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film,
A treatment step of bringing a treatment liquid into contact with the polyvinyl alcohol-based resin film for treatment;
A treatment liquid removing step of contacting the liquid draining member to the polyvinyl alcohol resin film after the treatment step and removing the treatment liquid adhering to the surface of the polyvinyl alcohol resin film is provided in this order,
The liquid draining member is a method for producing a polarizing film, wherein the surface roughness Ra of the surface in contact with the polyvinyl alcohol-based resin film is 0.5 μm or less.

  [2] The method for producing a polarizing film according to [1], wherein the liquid draining member has a water contact angle of 60 ° or less on a surface in contact with the polyvinyl alcohol-based resin film.

[3] The liquid draining member is plate-shaped,
In the treatment liquid removing step, the liquid draining member is brought into contact so that an angle formed between the polyvinyl alcohol resin film and the liquid draining member becomes an acute angle on the upstream side in the transport direction of the polyvinyl alcohol resin film. The manufacturing method of the polarizing film as described in [1] or [2].

  [4] In the treatment liquid removal step, the liquid drainage member is configured such that an angle formed between the polyvinyl alcohol resin film and the liquid drainage member is 45 ° or less on the upstream side in the transport direction of the polyvinyl alcohol resin film. The manufacturing method of the polarizing film as described in [3] which is made to contact.

  [5] In the treatment liquid removing step, the polyvinyl alcohol-based resin film between the polyvinyl alcohol-based resin film and the liquid draining member, with a position contacting the polyvinyl alcohol-based resin film and the liquid draining member as a boundary. The upstream space formed on the upstream side in the transport direction of the production of the polarizing film according to [1] to [4], which is narrower than the downstream space formed on the downstream side in the transport direction of the polyvinyl alcohol-based resin film. Method.

  [6] In the treatment liquid removing step, the treatment member adhering to both surfaces of the polyvinyl alcohol resin film is removed by bringing the liquid draining member into contact with both surfaces of the polyvinyl alcohol resin layer. ] The manufacturing method of the polarizing film as described in [5].

  [7] The treatment step includes a swelling treatment step using a swelling solution as the treatment solution, a dyeing treatment step using a dye solution as the treatment solution, a crosslinking treatment step using a crosslinking solution as the treatment solution, or a cleaning solution as the treatment solution. The manufacturing method of the polarizing film as described in [1]-[6] which is the washing process process using this.

[8] The method further includes a drying step of drying the polyvinyl alcohol-based resin film,
The said process liquid removal process is a manufacturing method of the polarizing film as described in [1]-[7] performed before the said drying process, after the said process process just before the said drying process is complete | finished.

  According to the method of the present invention, it is possible to efficiently drain water by a simple method, and it is possible to produce a polarizing film in which generation of defects is suppressed.

It is sectional drawing which shows typically an example of the manufacturing method of the polarizing film which concerns on this invention, and a polarizing film manufacturing apparatus used for it. FIG. 2 is a perspective view schematically showing a liquid draining member shown in FIG. 1. It is sectional drawing orthogonal to the length direction of the glass plate after chamfering. It is sectional drawing orthogonal to the length direction of the glass plate after chamfering. It is sectional drawing which shows the angle which the liquid cutting member shown in FIG. 1 and a film make. It is sectional drawing which shows the angle which the liquid cutting member of another shape and a film make.

<Production method of polarizing film>
In the present invention, the polarizing film is one in which a dichroic dye (iodine or dichroic dye) is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. The polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is usually obtained by saponifying a polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, more preferably about 99 mol% or more. The polyvinyl acetate resin can be, for example, a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000.

  These polyvinyl alcohol resins may be modified. For example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used.

  In the present invention, an unstretched polyvinyl alcohol-based resin film (raw fabric) having a thickness of 65 μm or less (for example, 60 μm or less), preferably 50 μm or less, more preferably 35 μm or less, and even more preferably 30 μm or less is used as a starting material for manufacturing a polarizing film. Film). As a result, it is possible to obtain a thin polarizing film whose market demand is increasing. The width of the raw film is not particularly limited and can be, for example, about 400 to 6000 mm. The original fabric film is prepared, for example, as a roll (raw fabric roll) of a long unstretched polyvinyl alcohol resin film.

  The polarizing film, while unwinding the above-described long original film from the original roll, is continuously conveyed along the film conveying path of the polarizing film manufacturing apparatus, and the processing liquid (hereinafter, It can be continuously produced as a long polarizing film by carrying out a drying step after carrying out a predetermined treatment step that is drawn after being immersed in a “treatment bath”. The treatment process is not limited to the method of immersing the film in the treatment bath as long as the treatment solution is brought into contact with the film, and the treatment solution is adhered to the film surface by spraying, flowing down, dropping, or the like. And a method of processing the film.

  Examples of the treatment liquid include swelling liquid, dyeing liquid, crosslinking liquid, and cleaning liquid. And as said process process, the swelling process process which makes a swelling liquid contact a raw fabric film, performs the swelling process, the dyeing process process which makes a dyeing liquid contact the film after swelling process, and a dyeing process Examples include a crosslinking treatment step in which a crosslinking solution is brought into contact with the subsequent film and a washing treatment step in which the washing solution is brought into contact with the film after the crosslinking treatment to perform the washing treatment. In addition, a uniaxial stretching process is performed in a wet or dry manner between these series of processing steps (that is, before and after any one or more processing steps and / or during any one or more processing steps). Other processing steps may be added as necessary.

  In the present invention, after one of the above processing steps is completed, all the processing steps for processing in the transport path for transporting the film to the next processing step or by bringing the processing liquid into contact with the film are completed. After that, the treatment liquid removing step is performed in the conveyance path for conveying the film to the drying step. The treatment liquid removing step is a step of removing the treatment liquid used in the treatment step immediately before adhering to the film surface by bringing the liquid draining member into contact with the film that has been treated with the treatment liquid. Since defects such as crystal foreign matter are likely to occur when the treatment liquid remains on the surface of the film in the drying process, after all the treatment processes for processing by bringing the treatment liquid into contact with the film are completed, the drying process In the transport path before the film is introduced into the film, it is preferable to perform the treatment liquid removing step from the viewpoint of suppressing defects generated in the polarizing film. The treatment liquid removing step is not limited to one time and may be performed a plurality of times. You may make it perform a process liquid removal process after all the process processes using a process liquid.

In the treatment liquid removing step of the present invention, a liquid draining member having a surface roughness Ra of 0.5 μm or less, preferably 0.3 μm or less, on the surface in contact with the polyvinyl alcohol-based resin film is used as the liquid cutting member. If the surface roughness Ra of the surface of the liquid cutting member that contacts the polyvinyl alcohol-based resin film exceeds 0.5 μm, the treatment liquid adhering to the film surface may not be sufficiently removed. When the surface roughness Ra exceeds 0.5 μm, it is considered that the treatment liquid adhering to the film enters the irregularities on the surface of the liquid draining member and the liquid drainability is lowered. Moreover, it can suppress that the surface of a film produces a damage | wound by contact by using the liquid cutting member whose surface roughness is 0.5 micrometer or less. Here, the surface in contact with the liquid draining member is the farthest distance from the polyvinyl alcohol resin film surface on the downstream side in the transport direction of the polyvinyl alcohol resin film, with the position where the polyvinyl alcohol resin film and the liquid draining member are in contact with each other. Is the surface of the liquid draining member. As the liquid draining member, it is preferable to use a member having a length equal to or greater than the length in the width direction of the film. When the liquid draining member is in contact with the film, the entire width direction of the film is in contact with the liquid draining member. It is preferable. Details of the liquid draining member will be described later.

  When the nip roll is disposed on the conveyance path where the treatment liquid removing step is performed, the liquid draining member is preferably disposed on the upstream side of the nip roll. The treatment liquid adhering to the surface of the polyvinyl alcohol resin film may be spread by passing through the nip roll or may move to the inside of the polyvinyl alcohol resin film, so the treatment liquid is removed before passing through the nip roll. By performing the process, the treatment liquid can be effectively removed, and the occurrence of defects due to the attached treatment liquid can be further suppressed.

  Hereinafter, an example of the manufacturing method of the polarizing film which concerns on this invention is demonstrated in detail, referring FIG. Drawing 1 is a sectional view showing typically an example of the manufacturing method of the polarizing film concerning the present invention, and the polarizing film manufacturing device used for it. The polarizing film manufacturing apparatus shown in FIG. 1 transports a raw fabric (unstretched) film 10 made of polyvinyl alcohol resin along a film transport path while continuously unwinding from a raw fabric roll 11. A swelling bath (swelling liquid accommodated in the swelling tank) 13, a dyeing bath (staining liquid accommodated in the dyeing tank) 15, and a crosslinking bath (crosslinking liquid accommodated in the crosslinking tank) 17 provided on the conveyance path. , And a cleaning bath (cleaning liquid contained in a cleaning tank) 19 are sequentially passed, and finally, a drying furnace 21 is passed. The obtained polarizing film 23 can be conveyed, for example, to the next polarizing plate production step (step of bonding a protective film on one or both sides of the polarizing film 23) as it is. The arrow in FIG. 1 has shown the conveyance direction of the film.

  FIG. 1 shows an example in which one bath is provided for each of the swelling bath 13, the dyeing bath 15, the crosslinking bath 17, and the washing bath 19, but if necessary, one or more treatment baths are provided in two or more baths. It may be provided. In the description of FIG. 1, “treatment tank” is a generic name including a swelling tank, a dyeing tank, a crosslinking tank, and a washing tank, and “treatment liquid” is a generic name that includes a swelling liquid, a staining liquid, a crosslinking liquid, and a washing liquid. The “treatment bath” is a generic term including a swelling bath, a dyeing bath, a crosslinking bath and a washing bath.

  The film transport path of the polarizing film manufacturing apparatus includes guide rolls 30 to 41, 60, 61 that can support the film to be transported or can further change the film transport direction in addition to the processing bath, and the film to be transported. Can be constructed by placing nip rolls 50 to 55 at appropriate positions, which can press and hold the film and apply a driving force by rotation thereof to the film, or can further change the film conveyance direction. Guide rolls and nip rolls can be arranged before and after each treatment bath or in the treatment bath, whereby the film can be introduced and immersed in the treatment bath and drawn out from the treatment bath (see FIG. 1). For example, by providing one or more guide rolls in each treatment bath and transporting the film along these guide rolls, the film can be immersed in each treatment bath.

In the polarizing film manufacturing apparatus shown in FIG. 1, nip rolls are arranged before and after each treatment bath (nip rolls 50 to 54), and thereby, nip rolls arranged before and after any one or more treatment baths. It is possible to perform inter-roll stretching in which longitudinal uniaxial stretching is performed with a difference in peripheral speed between them.

  In the polarizing film manufacturing apparatus shown in FIG. 1, a pair of liquid draining members 71 and 72 are arranged on the conveyance path downstream of the cleaning bath 19 so as to contact the film, and are dried after the cleaning process. A treatment liquid removal step is performed before the step. Hereinafter, each step will be described.

(Swelling process)
The swelling treatment step is performed for the purpose of removing foreign matter on the surface of the original film 10, removing the plasticizer in the original film 10, imparting easy dyeability, and plasticizing the original film 10. The processing conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme dissolution and devitrification of the raw film 10 do not occur.

  Referring to FIG. 1, in the swelling treatment step, the raw film 10 is continuously unwound from the original roll 11 and conveyed along the film conveying path, and the original film 10 is immersed in the swelling bath 13 for a predetermined time. And then withdrawing. In the example of FIG. 1, the raw film 10 is conveyed along the film conveyance path constructed by the guide rolls 60 and 61 and the nip roll 50 until the original film 10 is unwound and immersed in the swelling bath 13. Is done. In the swelling process, the film is conveyed along the film conveyance path constructed by the guide rolls 30 to 32.

  As the swelling liquid of the swelling bath 13, in addition to pure water, boric acid (JP-A-10-153709), chloride (JP-A-06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol It is also possible to use an aqueous solution to which a kind or the like is added in the range of about 0.01 to 10% by weight.

  The temperature of the swelling bath 13 is, for example, about 10 to 50 ° C., preferably about 10 to 40 ° C., and more preferably about 15 to 30 ° C. The immersion time of the raw film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. Moreover, when the raw fabric film 10 is a polyvinyl alcohol-based resin film previously stretched in gas, the temperature of the swelling bath 13 is, for example, about 20 to 70 ° C, preferably about 30 to 60 ° C. The immersion time of the raw film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

  In the swelling treatment, the problem that the original film 10 swells in the width direction and the film is wrinkled easily occurs. As one means for conveying the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 30, 31 and / or 32, a cross guider, a bend bar. Or using other widening devices such as tenter clips. Another means for suppressing the generation of wrinkles is to perform stretching. For example, the uniaxial stretching process can be performed in the swelling bath 13 by utilizing the peripheral speed difference between the nip roll 50 and the nip roll 51.

In the swelling treatment, the film swells and expands in the film conveyance direction. Therefore, when the film is not actively stretched, for example, it is disposed before and after the swelling bath 13 in order to eliminate the sag of the film in the conveyance direction. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51. Further, for the purpose of stabilizing the film conveyance in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, or an EPC device (Edge Position).
It is also useful to use a Control device: a device that detects the end of the film and prevents the film from meandering).

  In the example shown in FIG. 1, the film drawn from the swelling bath 13 passes through the guide roll 32 and the nip roll 51 in this order and is introduced into the dyeing bath 15.

(Dyeing process)
The dyeing treatment step is performed for the purpose of adsorbing and orienting the dichroic dye on the polyvinyl alcohol resin film after the swelling treatment. The processing conditions are determined within a range in which the object can be achieved and in a range in which defects such as extreme dissolution and devitrification of the film do not occur. Referring to FIG. 1, the dyeing process is carried along a film carrying path constructed by guide rolls 33 to 35 and nip roll 51, and the film after swelling treatment is dyed in bath 15 (process accommodated in a dyeing tank). (Liquid) for a predetermined time and then withdrawing. In order to enhance the dyeability of the dichroic dye, the film subjected to the dyeing treatment step is preferably a film subjected to at least some uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, Alternatively, in addition to the uniaxial stretching process before the dyeing process, it is preferable to perform the uniaxial stretching process during the dyeing process.

  When iodine is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, iodine / potassium iodide / water = about 0.003-0.3 / about 0.1-10 / weight by weight. An aqueous solution of 100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment described later in terms of containing iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, the dyeing bath 15 Can be considered. The temperature of the dyeing bath 15 when dipping the film is usually about 10 to 45 ° C., preferably 10 to 40 ° C., more preferably 20 to 35 ° C., and the dipping time of the film is usually 30 to 600 seconds. Degree, preferably 60 to 300 seconds.

  When a water-soluble dichroic dye is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, dichroic dye / water by weight ratio of about 0.001 to 0.1 / 100. An aqueous solution can be used. This dyeing bath 15 may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. Only one dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The temperature of the dyeing bath 15 when dipping the film is, for example, about 20 to 80 ° C., preferably 30 to 70 ° C., and the dipping time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds. is there.

  As described above, in the dyeing process, the film can be uniaxially stretched in the dyeing bath 15. Uniaxial stretching of the film can be performed by a method of making a peripheral speed difference between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 15.

  Also in the dyeing process, the widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 33, 34 and / or 35 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling process. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  In the example shown in FIG. 1, the film drawn from the dyeing bath 15 passes through the guide roll 35 and the nip roll 52 in this order and is introduced into the crosslinking bath 17.

(Crosslinking process)
The crosslinking treatment step is a treatment performed for the purpose of water resistance and hue adjustment (such as preventing the film from being bluish) by crosslinking. With reference to FIG. 1, the crosslinking treatment is carried along the film conveyance path constructed by the guide rolls 36 to 38 and the nip roll 52, and is subjected to the dyeing treatment in the crosslinking bath 17 (crosslinking liquid accommodated in the crosslinking tank). It can be carried out by immersing the film for a predetermined time and then withdrawing it.

  The crosslinking liquid of the crosslinking bath 17 can be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking liquid preferably contains iodide in addition to boric acid. The amount is, for example, 1 to 30 parts by weight with respect to 100 parts by weight of water. It can be. Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

  In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, when the purpose of the crosslinking treatment is water resistance by crosslinking, and the polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment and crosslinking treatment in this order, the crosslinking agent-containing liquid in the crosslinking bath has a concentration by weight ratio. It can be an aqueous solution of boric acid / iodide / water = 3 to 10/1 to 20/100. As needed, it may replace with boric acid and may use other crosslinking agents, such as a glyoxal or glutaraldehyde, and may use boric acid and another crosslinking agent together. The temperature of the crosslinking bath when dipping the film is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the dipping time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably. Is 20 to 200 seconds. Moreover, when performing the dyeing | staining process and the crosslinking process in this order with respect to the polyvinyl alcohol-type resin film previously extended | stretched before the swelling process, the temperature of the crosslinking bath 17 is about 50-85 degreeC normally, Preferably it is 55-80 degreeC. .

  In the crosslinking treatment for the purpose of adjusting the hue, for example, when iodine is used as the dichroic dye, the concentration of boric acid / iodide / water is 1 to 5/3 to 30/100 in terms of weight ratio. Liquid can be used. The temperature of the crosslinking bath when dipping the film is usually about 10 to 45 ° C., and the dipping time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

  The crosslinking treatment may be performed a plurality of times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath used may be the same or different as long as they are within the above range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment may be performed in a plurality of steps, respectively.

  A uniaxial stretching process can also be performed in the crosslinking bath 17 by utilizing the peripheral speed difference between the nip roll 52 and the nip roll 53.

  In the cross-linking treatment, a widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 36, 37 and / or 38 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling treatment. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  In the example shown in FIG. 1, the film drawn from the crosslinking bath 17 passes through the guide roll 38 and the nip roll 53 in this order and is introduced into the cleaning bath 19.

(Washing process)
The example shown in FIG. 1 includes a cleaning process after the crosslinking process. The washing treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol resin film. The cleaning process is performed, for example, by immersing the crosslinked polyvinyl alcohol resin film in the cleaning bath 19. In addition, instead of the step of immersing the film in the cleaning bath 19, the cleaning treatment step is performed by spraying the cleaning liquid on the film as a shower, or by using both immersion in the cleaning bath 19 and spraying of the cleaning liquid. It can also be done.

  FIG. 1 shows an example in which a polyvinyl alcohol resin film is immersed in a cleaning bath 19 to perform a cleaning process. The temperature of the washing bath 19 in the washing treatment is usually about 2 to 40 ° C., and the immersion time of the film is usually about 2 to 120 seconds.

  In the cleaning process, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 39, 40 and / or 41 for the purpose of conveying the polyvinyl alcohol resin film while removing wrinkles. Or other widening devices such as cross guiders, bend bars, tenter clips can be used. In the film cleaning process, a stretching process may be performed in order to suppress generation of wrinkles.

(Stretching process)
As described above, the raw film 10 is uniaxially stretched wet or dry during the series of processing steps (that is, before and after any one or more processing steps and / or during any one or more processing steps). It is processed. A specific method of the uniaxial stretching process is, for example, between rolls that perform longitudinal uniaxial stretching with a peripheral speed difference between two nip rolls (for example, two nip rolls arranged before and after the treatment bath) constituting the film conveyance path. Stretching, hot roll stretching as described in Japanese Patent No. 2731813, tenter stretching, and the like, and inter-roll stretching is preferred. The uniaxial stretching treatment step can be performed a plurality of times before the polarizing film 23 is obtained from the raw film 10. As described above, the stretching treatment is also advantageous for suppressing the generation of wrinkles on the film.

  The final cumulative draw ratio of the polarizing film 23 on the basis of the original fabric film 10 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching treatment step may be performed in any processing step, and when the stretching treatment is performed in two or more processing steps, the stretching treatment may be performed in any processing step.

(Processing liquid removal process)
In the example shown in FIG. 1, a processing liquid removal step for removing the cleaning liquid is performed after the cleaning processing step. In FIG. 1, the example in the case of performing a process liquid removal process using a pair of liquid cutting members 71 and 72 arrange | positioned at the front and back of a film is shown. In the treatment liquid removing step, the cleaning liquid adhered to the surface of the film passing therethrough by the liquid cutting members 71 and 72 is arranged by contacting the liquid cutting members 71 and 72 respectively with the surface of the film to be conveyed. Removed from the surface of the film. As shown in FIG. 1, the pair of liquid draining members 71 and 72 are preferably arranged so as to be slightly shifted in the transport direction so that the two liquid draining members 71 and 72 do not contact the film at the same position. . By arrange | positioning in this way, the burden concerning a film by the contact of the liquid cutting members 71 and 72 can be suppressed.

The treatment liquid removing step is preferably performed such that the cleaning liquid is removed from the surface of the film by the liquid draining members 71 and 72 and the removed cleaning liquid is collected in the cleaning bath 19. For example, in the example shown in FIG. 1, the removed cleaning liquid can be collected in the cleaning bath 19 by disposing the liquid draining members 71 and 72 above the opening of the cleaning bath 19. In addition, even when a liquid draining member is provided after other processing steps other than the cleaning processing step, similarly, it is preferable that the processing liquid is collected in the immediately preceding processing tank. By collecting the treatment liquid in the treatment tank, a decrease in the treatment liquid in the treatment tank can be suppressed.

  FIG. 2 is a perspective view schematically showing the liquid draining member 71 shown in FIG. The liquid cutting member 71 has a plate-like shape having a length equal to or greater than the length of the film 10 in the width direction. It is preferable that the liquid cutting member 71 is arranged so that the length direction substantially coincides with the width direction of the film and contacts the film, and by arranging in this way, the entire width direction of the film becomes the liquid cutting member 71. Will be in contact. The liquid draining member 71 is disposed such that the side surface 71a in the length direction contacts the film. The surface roughness Ra of the side surface 71a is 0.5 μm or less, and more preferably 0.3 μm or less. When the surface roughness Ra exceeds 0.5 μm, the treatment liquid adhering to the film surface may not be sufficiently removed. The surface roughness Ra of the side surface 71a of the liquid cutting member 71 can be adjusted by, for example, the degree of polishing of the side surface 71a. The side surface 71a is preferably polished after a chamfering process such as chamfering or round chamfering. As a polishing method, a known method such as grinding with a grindstone, mirror cutting, lapping polishing, buffing, or flame polishing can be used. The surface roughness Ra that can be reached by normal polishing is 0.001 μm.

  Moreover, it is preferable that the water contact angle of the side surface 71a which contacts the liquid cutting member 71 is 60 degrees or less, and it is more preferable that it is 45 degrees or less. When the water contact angle exceeds 60 °, the amount of the processing liquid held in the space between the liquid draining member and the film decreases, and thus the liquid drainage may decrease. The water contact angle of the liquid cutting member 71 can be adjusted by the material used for the liquid cutting member 71, for example. Examples of the material capable of adjusting the liquid draining member having a water contact angle of 60 ° or less include glass, ceramics, metals (stainless steel, aluminum, iron, etc.), and resins. In order to set the water contact angle to the above desired value, these materials may be subjected to a hydrophilic treatment. Glass and hydrophilic ceramics are preferably used because they have good polishing properties and corrosion resistance, and glass is preferably used because they have good hydrophilic sustainability. Any glass that is usually used may be used, and examples thereof include quartz glass, soda-lime glass, potash glass, and borosilicate glass. Moreover, what laminated | stacked the several glass plate for the intensity | strength improvement may be used. In general, the water contact angle of glass is in the range of 3 to 45 °.

  In addition, since the above-mentioned water contact angle in the liquid drainage member is limited only to the surface in contact with the film in the liquid drainage member, the surface of the surface in contact with the film of the liquid drainage member formed of a corrosion-resistant material Further, a thin film of a material having a desired water contact angle may be formed. Although the thickness of the liquid cutting member 71 is not specifically limited, For example, it is 1-20 mm.

  The liquid cutting member 71 can be manufactured by chamfering the side surface 71a in the length direction using, for example, a glass plate. Further, the side surface 71b facing the side surface 71a may also be chamfered. 3 and 4 represent cross-sectional views orthogonal to the length direction of the glass plate after chamfering. The chamfering method is not limited, and for example, as shown in FIG. 3, the chamfering can be performed by chamfering the chamfer so that the apex in the cross section perpendicular to the length direction becomes an obtuse angle. The chamfer dimension r1 at the time of chamfering is 0.5 to 2 mm, for example. Further, for example, as shown in FIG. 4, it can be produced by performing a round chamfering process so that a vertex in a cross section orthogonal to the length direction has a round shape. The curvature radius r2 of round chamfering is, for example, 0.5 to 2 mm.

In the apparatus shown in FIG. 1, the angle formed between the polyvinyl alcohol-based resin film 10 and the liquid draining member 71 is preferably an acute angle on the upstream side in the transport direction of the polyvinyl alcohol-based resin film 10, and is 45 ° or less. More preferred is 30 ° or less. FIG. 5 shows an angle formed between the polyvinyl alcohol resin 10 film and the liquid cutting member 71. An angle formed on the upstream side in the transport direction of the polyvinyl alcohol-based resin film 10 is indicated by an angle θ1, and an angle formed on the downstream side in the transport direction is indicated by an angle θ2. That is, the angle θ1 is preferably an acute angle, more preferably 45 ° or less, and further preferably 30 ° or less.

  As described above, when the angle θ1 is an acute angle, that is, when the angle θ1 <the angle θ2, the liquid cutting property can be further improved. This is because the space formed between the film 10 and the liquid draining member 71 is the upstream space formed on the upstream side in the film transport direction with the position where the film and the liquid draining member are in contact with each other. Since it becomes narrower than the downstream space formed on the downstream side in the transport direction, when the liquid draining member 71 moves relative to the film surface, the capillary is more than the processing liquid moving to the downstream space of the liquid draining member 71. This is thought to be because the force tends to stay in the upstream space. 2 to 5, the liquid draining member 71 has been described, but the liquid draining member 72 disposed on the other surface side of the film is also as described above for the liquid draining member 71. In the treatment liquid removing step, as shown in FIG. 1, the method is not limited to the method in which the two liquid cutting members 71 and 72 are arranged to face each other, and the liquid cutting member is arranged only on one surface of the film. There may be a plurality of liquid draining members disposed on one surface of the film. For example, in a case where the film transport path is inclined with respect to the vertical direction and the processing liquid is likely to adhere only to the upper surface of the film, the liquid draining member is disposed only on the upper surface of the film. There may be. From the viewpoint of improving liquid drainage, a configuration in which liquid drainage members are arranged on both surfaces of the film is preferable.

  1 to 5, the plate-shaped liquid draining member 71 is shown. However, the liquid draining member used in the processing liquid removing step may be a plate as long as it can remove the processing liquid adhered to the surface of the film by contact. For example, it may be a prismatic liquid draining member such as a triangular prism or a quadrangular prism, or a cylindrical liquid draining member. Even for a liquid draining member having a shape other than a plate shape, the desired surface roughness, desired water contact angle, and material of the surface in contact with the film are as described above for the plate-like liquid draining member 71. is there. FIG. 6 is a cross-sectional view showing the relationship between the film 10 and the liquid draining member 73 when the triangular columnar liquid draining member 73 is used. The liquid draining member 73 improves the liquid drainability by contacting the film 10 so that the space formed on the upstream side in the transport direction with respect to the contact position becomes narrower than the space formed on the downstream side in the transport direction. It is preferable from the point which can be made. That is, the angle formed between the surface of the liquid draining member 73 and the film 10 is preferably such that the angle θ1 on the upstream side is smaller than the angle θ2 on the downstream side.

  A member similar to the treatment liquid member described above can also be disposed above the downstream side of the swelling bath 13, above the downstream side of the dyeing bath 15, or above the downstream side of the cross-linking bath 17. The step of removing the swelling liquid adhering to the film surface after the treatment step, the step of removing the dye liquor adhering to the film surface after the dyeing treatment step, and the step of removing the cross-linking liquid adhering to the film surface after the crosslinking treatment step it can.

(Drying process)
It is preferable to perform the process which dries a polyvinyl alcohol-type resin film after a washing process process. The drying of the film is not particularly limited, but can be performed using a drying furnace 21 as in the example shown in FIG. The drying temperature is, for example, about 30 to 100 ° C., and the drying time is, for example, about 30 to 600 seconds. The thickness of the polarizing film 23 obtained as described above is, for example, about 5 to 30 μm.

(Other processing steps for polyvinyl alcohol resin film)
Processing other than the processing described above can also be added. Examples of treatments that can be added include immersion treatment (complementary color treatment) in an aqueous iodide solution that does not contain boric acid, and immersion treatment in an aqueous solution that does not contain boric acid and contains zinc chloride, etc. Zinc treatment).

<Polarizing plate>
A polarizing plate can be obtained by bonding a protective film via an adhesive on at least one surface of the polarizing film produced as described above. As the protective film, for example, a film made of an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose; a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate resin film, a cyclo Examples include olefin resin films; acrylic resin films; and films made of polypropylene-based chain olefin resins.

  Surfaces such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. on the polarizing film and / or protective film bonding surface in order to improve the adhesion between the polarizing film and the protective film Processing may be performed. As an adhesive used for laminating a polarizing film and a protective film, an active energy ray curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of a polyvinyl alcohol resin, or an aqueous solution in which a crosslinking agent is blended. And water-based adhesives such as urethane emulsion adhesives. The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photo radical polymerization initiator, a mixture of an epoxy compound and a photo cationic polymerization initiator, or the like. Alternatively, a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound may be used in combination, and a photo cationic polymerization initiator and a photo radical polymerization initiator may be used in combination as an initiator.

  Hereinafter, the liquid drainage was evaluated using various plate-shaped liquid drainage members similar to the liquid drainage member shown in FIG. Note that the present invention is not limited to these examples. In the following examples, the surface roughness and water contact angle of the surface in contact with the polyvinyl alcohol resin film of the liquid draining member were measured by the following methods.

[Measurement of surface roughness]
By a method based on JIS B 0601, the surface roughness Ra of the surface in contact with the film of the liquid draining member was measured using a surface roughness measuring machine (Handy Surf E-35A, manufactured by Tokyo Seimitsu Co., Ltd.). The measurement conditions (cutoff length, evaluation length) for measuring Ra were set as appropriate according to the surface roughness Ra determined by JIS B0633. That is, when the surface roughness Ra is more than 0.006 μm and not more than 0.02 μm, the cutoff length is 0.08 mm and the evaluation length is 0.4 mm, and the surface roughness Ra is more than 0.02 μm and not more than 0.1 μm. In this case, when the cut-off length is 0.25 mm and the evaluation length is 1.25 mm, and the surface roughness Ra is more than 0.1 μm and 2 μm or less, the cut-off length is 0.8 mm and the evaluation length is 4 mm. When the surface roughness Ra is more than 2 μm and not more than 10 μm, the cut-off length is 2.5 mm and the evaluation length is 12.5 mm.

(Measurement of water contact angle)
Using an image processing contact angle meter (FACE CA-X, manufactured by Kyowa Interface Science Co., Ltd.), 1 microliter of pure water was dropped onto the surface of the liquid draining member, and the water contact angle was measured.

[Liquid drainage evaluation test 1]
The plate-shaped liquid draining members of Examples 1 to 8 and Comparative Examples 1 to 3 having different degrees of polishing on the material and the surface in contact with the film were prepared and evaluated as follows. The material of each liquid draining member is as shown in Table 1, and Table 1 shows the measured values obtained by measuring the surface roughness and the water contact angle of the surface of each liquid cutting member in contact with the film.

  40 microliters of pure water was dropped onto the surface of a polarizing film (width 30 mm, thickness 22 μm) held horizontally at a tension of 35 N / m. Next, a liquid cutting member brought into contact with the surface of the polarizing film on which pure water was dropped at an angle shown in Table 1 (an angle formed by the polarizing film and the liquid cutting member on the upstream side with respect to the relative movement direction of the polarizing film) was 6 m. The liquid was drained by moving at a speed of / min. The state of the surface of the polarizing film after draining was visually observed to evaluate the drainage. Liquid drainage was evaluated according to the following criteria in three stages from “1” to “3”. Table 1 shows the evaluation results. In this evaluation test, evaluation was performed by moving the liquid draining member with respect to the polarizing film, but even if the polarizing film was moved with the liquid draining member fixed (the relationship in the apparatus shown in FIG. 1 was implemented). Even so, it can be considered that the same evaluation result is obtained.

1: No water is observed on the polarizing film after draining,
2: A thin film of water is observed on the polarizing film after draining.
3: Water droplets are observed on the polarizing film after draining.

[Liquid drainage evaluation test 2]
As Examples 9 and 10, a liquid drainage member similar to the liquid drainage member prepared in Example 2 of the liquid drainage evaluation test 1 was prepared, and the following evaluation was performed. In the process of continuously producing a polarizing film as shown in FIG. 1, the angle shown in Table 2 (upstream with respect to the polarizing film transport direction) is removed from the cleaning bath and transported to the film. In this case, the liquid film was drained by contact at an angle formed by the polarizing film and the liquid draining member. In addition, the conveyance speed of the film was 10 m / min. The state of the film surface after draining was visually observed to evaluate the drainage. Liquid drainage was evaluated according to the following criteria in three stages from “1” to “3”. Table 2 shows the evaluation results.

1: No water is observed on the polarizing film after draining,
2: A thin film of water is observed on the polarizing film after draining.
3: Water droplets are observed on the polarizing film after draining.

As shown in Examples, the present invention can be suitably used for the production of a polarizing film produced from a polyvinyl alcohol-based resin. In addition, the liquid cutting member which concerns on this invention is a functional resin including the process of making a polymer resin film contact a process liquid similarly to the process liquid removal process of the polyvinyl alcohol-type resin film in the manufacturing method of a polarizing film. It can be used suitably also for the process liquid removal process of manufacture of a film, for example, manufacture of the separator film for lithium secondary batteries.

  10 Raw film made of polyvinyl alcohol resin, 11 Raw roll, 13 Swelling bath, 15 Dye bath, 17 Cross-linking bath, 19 Washing bath, 21 Drying furnace, 23 Polarizing film, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 60, 61 Guide roll, 50, 51, 52, 53, 54, 55 Nip roll, 71, 72, 73 Liquid draining member.

Claims (7)

A method for producing a polarizing film for producing a polarizing film from a polyvinyl alcohol-based resin film,
A treatment step of bringing a treatment liquid into contact with the polyvinyl alcohol-based resin film for treatment;
A treatment liquid removing step of contacting the liquid draining member to the polyvinyl alcohol resin film after the treatment step and removing the treatment liquid adhering to the surface of the polyvinyl alcohol resin film is provided in this order,
The liquid switching member, the polyvinyl alcohol-based surface roughness Ra of the surface in contact with the resin film is 0.5μm or less and the water contact angle of Ri der 60 ° or less,
In the treatment liquid removing step, the liquid drainage member is brought into contact with each other so that an angle formed between the polyvinyl alcohol resin film and the liquid drainage member is 60 ° or less on the upstream side in the transport direction of the polyvinyl alcohol resin film. A method for producing a polarizing film. The liquid switching member Ru plate der, method for producing a polarizing film according to claim 1. In the treatment liquid removing step, the liquid drainage member is brought into contact so that an angle formed by the polyvinyl alcohol resin film and the liquid drainage member is 45 ° or less on the upstream side in the transport direction of the polyvinyl alcohol resin film. The manufacturing method of the polarizing film of Claim 1 or 2 . In the treatment liquid removing step, said both surfaces are brought into contact with the liquid switching member of the polyvinyl alcohol-based resin film, removing the processing solution adhering to both sides of the polyvinyl alcohol resin film, according to claim 1 to 3 The manufacturing method of the polarizing film of any one of these. The treatment step includes a swelling treatment step using a swelling liquid as the treatment liquid, a dyeing treatment step using a staining liquid as the treatment liquid, a crosslinking treatment step using a crosslinking liquid as the treatment liquid, or a washing using a washing liquid as the treatment liquid. The manufacturing method of the polarizing film of any one of Claims 1-4 which is a process process. A drying step of drying the polyvinyl alcohol resin film;
The said process liquid removal process is a manufacturing method of the polarizing film of any one of Claims 1-5 performed before the said drying process, after the said process process just before the said drying process is complete | finished. A polarizing film production apparatus for producing a polarizing film from a polyvinyl alcohol-based resin film,
A treatment means for treating the polyvinyl alcohol-based resin film by bringing a treatment liquid into contact therewith, and
A treatment liquid removing means for removing the treatment liquid adhering to the surface of the polyvinyl alcohol resin film by bringing a liquid draining member into contact with the polyvinyl alcohol resin film after passing through the treatment means in this order. Prepared,
The liquid switching member, the polyvinyl alcohol-based surface roughness Ra of the surface in contact with the resin film is 0.5μm or less and the water contact angle of Ri der 60 ° or less,
In the treatment liquid removing means, the liquid draining member is brought into contact with the polyvinyl alcohol resin film so that an angle formed between the polyvinyl alcohol resin film and the liquid draining member is 60 ° or less on the upstream side in the transport direction of the polyvinyl alcohol resin film. A polarizing film manufacturing apparatus.

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