JP5914452B2 - Method for producing optical laminate - Google Patents

Description

  The present invention relates to a method for producing an optical laminate having a polarizing film.

  In a liquid crystal display device which is a typical image display device, polarizing films are arranged on both sides of a liquid crystal cell due to the image forming method. As a method for producing a polarizing film, for example, there is a method in which a laminate having a resin base material and a polyvinyl alcohol (PVA) resin layer is stretched and then subjected to a dyeing treatment to obtain a polarizing film on the resin base material. It has been proposed (for example, Patent Document 1). According to such a method, a polarizing film having a small thickness can be obtained, and thus has been attracting attention as being able to contribute to the recent thinning of image display devices.

  However, the polarizing film produced using the above resin base material may have appearance problems such as irregularities.

JP 2000-338329 A

  The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to provide a method for producing a polarizing film in which appearance problems such as irregularities are improved.

  When the present inventors examined about the said uneven | corrugated defect, the generation | occurrence | production mechanism was estimated as follows. That is, the polarizing film is produced by stretching and dyeing a laminate having a resin base material and a PVA-based resin layer, typically washing with a cleaning solution containing iodide, and finally drying. . Here, when drying is performed in a state where a cleaning solution containing iodide remains on the surface of the laminate, iodide is formed on the surface of the resin substrate having a higher hydrophobicity than the surface of the PVA resin layer (polarizing film). Precipitate with a relatively large particle size. Next, when the laminated body in such a state is wound and collected in a roll shape, the thickness of the polarizing film is thin, so that the shape of the precipitate is easily transferred to the polarizing film, and it is assumed that the unevenness defect occurs.

  As a result of further investigation based on the above estimation, the present inventors have further investigated the unevenness defect and the like by further washing the resin substrate side surface of the laminate after washing with a washing solution containing iodide to remove the iodide. It has been found that problems in appearance can be improved and the present invention has been completed.

The method for producing an optical laminate in which a polarizing film is laminated on a resin base material of the present invention includes stretching and dyeing a laminate having a resin base material and a polyvinyl alcohol resin layer formed on one side of the resin base material. Then, a step of producing a polarizing film on the resin substrate, a first cleaning step of immersing and cleaning the laminate in a cleaning solution containing iodide, and a resin substrate side surface of the laminate are only included. A second cleaning step of cleaning, and a step of drying the laminate.
In one embodiment, the cleaning in the second cleaning step is performed by bringing the resin substrate side surface of the laminate into contact with the cleaning liquid.
In one embodiment, the cleaning in the second cleaning step is provided with a liquid dam that holds the cleaning liquid so that the resin substrate side surface sequentially contacts the cleaning liquid while transporting the laminate in the longitudinal direction. Is done by.
In one embodiment, the liquid dam faces the laminated body from the laminated body that is conveyed in the longitudinal direction, a blade that is arranged so that the tip is in sliding contact with the surface of the resin base material, and the blade. And both ends in the width direction are open.
In one embodiment, the width of the blade is wider than the width of the laminate.
In one embodiment, the cleaning in the second cleaning step is performed by spraying a cleaning liquid on the surface of the resin base material while transporting the laminate in the longitudinal direction.
In one embodiment, the stretching includes underwater stretching.
In one embodiment, the liquid adhering to the surface of the laminate is drained after the second cleaning step.
According to another aspect of the present invention, an optical laminate is provided. The optical layered body of the present invention is obtained by the above production method.
According to still another aspect of the present invention, a blade disposed so that the front end is in sliding contact with one surface of the long sheet conveyed in the longitudinal direction; There is provided an apparatus comprising: a wall; and a liquid supply means for supplying a liquid to a liquid dam defined by a long sheet, a blade, and a water shielding wall.

  According to the present invention, the laminate in which the polarizing film is laminated on the resin substrate is washed with a cleaning solution containing iodide, and then the resin substrate side surface of the laminate is further washed, Precipitation can be suppressed, and as a result, appearance problems such as irregularities can be improved.

It is a fragmentary sectional view of the laminated body by preferable embodiment of this invention. It is the schematic explaining an example of a 2nd washing | cleaning process. It is the schematic explaining another example of a 2nd washing | cleaning process. It is a principal part schematic perspective view of embodiment shown to FIG. 3A. It is a graph which shows the number of uneven | corrugated defects in Example 1 and Comparative Example 1.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

  In the method for producing an optical laminate of the present invention, a laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate is stretched and dyed, and a polarizing film is formed on the resin substrate. A first cleaning step in which the laminate is cleaned by immersing the laminate in a cleaning solution containing iodide, a second cleaning step in which only the resin substrate side surface of the laminate is cleaned, and the lamination Drying the body. Hereinafter, each process will be described.

A. Production process of polarizing film A-1. Laminate FIG. 1 is a partial cross-sectional view of a laminate according to a preferred embodiment of the present invention. The laminate 10 includes a resin base material 11 and a polyvinyl alcohol resin layer 12. The laminate 10 is produced by forming a polyvinyl alcohol-based resin layer 12 on a long resin base material 11. Any appropriate method can be adopted as a method of forming the polyvinyl alcohol-based resin layer 12. Preferably, a PVA-based resin layer 12 is formed by applying a coating liquid containing a polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) on the resin base material 11 and drying it.

  Any appropriate thermoplastic resin can be adopted as the material for forming the resin base material. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, preferred are norbornene resins and amorphous polyethylene terephthalate resins.

  In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among these, amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol as a glycol.

  When an underwater stretching method is adopted in the stretching described later, the resin base material absorbs water, and the water can be plasticized by acting as a plasticizer. As a result, the stretching stress can be greatly reduced, the film can be stretched at a high magnification, and the stretchability can be superior to that during air stretching. As a result, a polarizing film having excellent optical characteristics can be produced. In one embodiment, the resin base material preferably has a water absorption rate of 0.2% or more, and more preferably 0.3% or more. On the other hand, the water absorption rate of the resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, it is possible to prevent problems such as a significant decrease in dimensional stability during production and deterioration of the appearance of the resulting polarizing film. Moreover, it can prevent that a base material fractures | ruptures at the time of extending | stretching in water, or a PVA-type resin layer peels from a resin base material. The water absorption rate of the resin base material can be adjusted, for example, by introducing a modifying group into the forming material. The water absorption is a value determined according to JIS K 7209.

  The glass transition temperature (Tg) of the resin base material is preferably 170 ° C. or lower. By using such a resin base material, the stretchability of the laminate can be sufficiently ensured while suppressing crystallization of the PVA-based resin layer. Furthermore, considering the plasticization of the resin base material with water and the good stretching in water, the temperature is more preferably 120 ° C. or lower. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 ° C. or higher. By using such a resin base material, it is possible to prevent problems such as deformation of the resin base material (for example, generation of unevenness, tarmi, wrinkles, etc.) when applying and drying the coating solution containing the PVA resin. Thus, a laminate can be manufactured satisfactorily. In addition, the PVA-based resin layer can be satisfactorily stretched at a suitable temperature (for example, about 60 ° C.). In another embodiment, a glass transition temperature lower than 60 ° C. may be used as long as the resin base material does not deform when applying and drying a coating solution containing a PVA-based resin. The glass transition temperature of the resin substrate can be adjusted by, for example, heating using a crystallization material that introduces a modifying group into the forming material. The glass transition temperature (Tg) is a value obtained according to JIS K7121.

  The thickness of the resin base material before stretching is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it exceeds 300 μm, for example, in stretching in water, it takes a long time for the resin base material to absorb water, and an excessive load may be required for stretching.

  Arbitrary appropriate resin may be employ | adopted as PVA-type resin which forms the said PVA-type resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

  The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. Average polymerization degree is 1000-10000 normally, Preferably it is 1200-5000, More preferably, it is 1500-4500. The average degree of polymerization can be determined according to JIS K 6726-1994.

  The coating solution is typically a solution obtained by dissolving the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferable. The concentration of the PVA resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the resin substrate can be formed.

  You may mix | blend an additive with a coating liquid. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. By using the easy-adhesion component, the adhesion between the resin base material and the PVA-based resin layer can be improved. As a result, for example, problems such as peeling of the PVA-based resin layer from the substrate can be suppressed, and dyeing and underwater stretching described later can be performed satisfactorily.

  As the easily adhesive component, for example, modified PVA such as acetoacetyl-modified PVA is used. As the acetoacetyl-modified PVA, a polymer having at least a repeating unit represented by the following general formula (I) is preferably used.

  In the above formula (I), the ratio of n to l + m + n (degree of modification) is preferably 1% to 10%.

  The saponification degree of acetoacetyl-modified PVA is preferably 97 mol% or more. The pH of the 4% by weight aqueous solution of acetoacetyl-modified PVA is preferably 3.5 to 5.5.

  The modified PVA is preferably added so as to be 3% by weight or more, more preferably 5% by weight or more of the total weight of the PVA resin contained in the coating solution. On the other hand, the amount of the modified PVA added is preferably 30% by weight or less.

  Any appropriate method can be adopted as a coating method of the coating solution. Examples thereof include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method and the like).

  The coating / drying temperature of the coating solution is preferably 50 ° C. or higher.

  The thickness of the PVA resin layer before stretching is preferably 3 μm to 40 μm, more preferably 5 μm to 20 μm.

  Before forming the PVA-based resin layer, the resin substrate may be subjected to surface treatment (for example, corona treatment), or an easy-adhesion layer may be formed on the resin substrate. Among these, it is preferable to form an easy-adhesion layer (coating treatment). As a material for forming the easy adhesion layer, for example, an acrylic resin, a polyvinyl alcohol resin, or the like is used, and a polyvinyl alcohol resin is particularly preferable. Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a modified product thereof. Examples of the modified product of the polyvinyl alcohol resin include the acetoacetyl-modified PVA. In addition, it is preferable that the thickness of an easily bonding layer shall be about 0.05-1 micrometer. By performing such a treatment, the adhesion between the resin substrate and the PVA resin layer can be improved. As a result, for example, problems such as peeling of the PVA-based resin layer from the substrate can be suppressed, and dyeing and underwater stretching described later can be performed satisfactorily.

  The water contact angle on the resin substrate side surface of the laminate is usually 60 ° to 80 °, for example, 65 ° to 75 °. The water contact angle is measured by the droplet method.

A-2. Stretching of laminated body Any appropriate method may be adopted as a stretching method of the laminated body. Specifically, it may be fixed end stretching or free end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Preferably, it is free end stretching.

  The extending direction of the laminate can be appropriately set. In one embodiment, it extends | stretches in the longitudinal direction of an elongate laminated body. In this case, typically, a method of stretching the laminate between rolls having different peripheral speeds is employed. In another embodiment, it extends | stretches in the width direction of an elongate laminated body. In this case, typically, a method of stretching using a tenter stretching machine is employed.

  The stretching method is not particularly limited, and may be an air stretching method or an underwater stretching method. The underwater stretching method is preferable. According to the underwater stretching method, the resin base material and the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 ° C.), and the crystallization of the PVA resin layer is suppressed. However, it can be stretched at a high magnification. As a result, a polarizing film having excellent optical characteristics can be produced.

  The stretching of the laminate may be performed in one stage or in multiple stages. When performing in multiple stages, for example, the free end stretching and the fixed end stretching may be combined, or the underwater stretching method and the air stretching method may be combined. Moreover, when performing by multistep, the draw ratio (maximum draw ratio) of the laminated body mentioned later is a product of the draw ratio of each step.

  The stretching temperature of the laminate can be set to any appropriate value depending on the resin base material, the stretching method, and the like. When adopting the air stretching method, the stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10 ° C., and particularly preferably Tg + 15 ° C. That's it. On the other hand, the stretching temperature of the laminate is preferably 170 ° C. or lower. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin, and to suppress problems due to the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). it can.

  When employing the underwater stretching method, the temperature of the stretching bath is preferably 40 ° C to 85 ° C, more preferably 50 ° C to 85 ° C. If it is such temperature, it can extend | stretch at high magnification, suppressing melt | dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, when the stretching temperature is lower than 40 ° C., there is a possibility that the stretching cannot be satisfactorily performed even in consideration of plasticization of the resin base material with water. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical properties cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

  When employing an underwater stretching method, it is preferable to stretch the laminate by immersing it in an aqueous boric acid solution (stretching in boric acid in water). By using an aqueous boric acid solution as the stretching bath, the PVA resin layer can be provided with rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink with a PVA resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, the film can be stretched satisfactorily, and a polarizing film having excellent optical properties can be produced.

  The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight with respect to 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.

  When a dichroic substance (typically iodine) is previously adsorbed to the PVA-based resin layer by dyeing described later, preferably, an iodide is blended in the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. Among these, potassium iodide is preferable. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight with respect to 100 parts by weight of water.

  The draw ratio (maximum draw ratio) of the laminate is preferably 5.0 times or more with respect to the original length of the laminate. Such a high draw ratio can be achieved, for example, by employing an underwater drawing method (boric acid underwater drawing). In the present specification, the “maximum stretch ratio” refers to a stretch ratio immediately before the laminate is ruptured. Separately, a stretch ratio at which the laminate is ruptured is confirmed, and a value that is 0.2 lower than that value. .

  In a preferred embodiment, the laminate is stretched in the air at a high temperature (for example, 95 ° C. or higher), and then the boric acid solution is stretched and dyed as described below. Such air stretching can be positioned as preliminary or auxiliary stretching for boric acid water stretching, and is hereinafter referred to as “air-assisted stretching”.

  In some cases, the laminate can be stretched at a higher magnification by combining air-assisted stretching. As a result, a polarizing film having more excellent optical characteristics (for example, the degree of polarization) can be produced. For example, when a polyethylene terephthalate-based resin is used as the resin base material, the orientation of the resin base material is suppressed by combining the air auxiliary stretching and the boric acid water stretching rather than stretching by boric acid water stretching alone. While stretching. As the orientation of the resin base material is improved, the stretching tension increases, and stable stretching becomes difficult or breaks. Therefore, the laminate can be stretched at a higher magnification by stretching while suppressing the orientation of the resin substrate.

  Moreover, the orientation of the PVA resin can be improved by combining the air-assisted stretching, whereby the orientation of the PVA resin can be improved even after the boric acid solution is stretched. Specifically, by previously improving the orientation of the PVA resin by air-assisted stretching, the PVA resin is easily cross-linked with boric acid during boric acid water stretching, and boric acid is a nodal point. It is presumed that the orientation of the PVA-based resin is increased even after stretching in boric acid solution by being stretched in such a state. As a result, a polarizing film having excellent optical characteristics (for example, the degree of polarization) can be produced.

  The draw ratio in the air auxiliary drawing is preferably 3.5 times or less. The stretching temperature of the air auxiliary stretching is preferably equal to or higher than the glass transition temperature of the PVA resin. The stretching temperature is preferably 95 ° C to 150 ° C. In addition, the maximum draw ratio in the case of combining the air auxiliary stretching and the boric acid solution stretching is preferably 5.0 times or more, more preferably 5.5 times or more, and further preferably, the original length of the laminate. Is 6.0 times or more.

A-3. Dyeing The dyeing | staining of the said laminated body is typically performed by making a PVA-type resin layer adsorb | suck a dichroic substance (preferably iodine). As the adsorption method, for example, a method of immersing a PVA resin layer (laminate) in a staining solution containing iodine, a method of applying the staining solution to the PVA resin layer, and applying the staining solution to the PVA resin layer The method of spraying etc. are mentioned. Preferably, it is a method of immersing the laminate in the staining solution. This is because iodine can be adsorbed well.

  The staining solution is preferably an iodine aqueous solution. The compounding amount of iodine is preferably 0.1 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the aqueous iodine solution. Specific examples of the iodide are as described above. The blending amount of iodide is preferably 0.02 to 20 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of water. The liquid temperature during dyeing of the dyeing liquid is preferably 20 ° C. to 50 ° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the staining solution, the immersion time is preferably 5 seconds to 5 minutes in order to ensure the transmittance of the PVA resin layer. The staining conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the finally obtained polarizing film is within a predetermined range. In one embodiment, immersion time is set so that the polarization degree of the polarizing film obtained may be 99.98% or more. In another embodiment, the immersion time is set so that the single transmittance of the obtained polarizing film is 40% to 44%.

  The staining process can be performed at any appropriate timing. When performing the said underwater extending | stretching, Preferably, it performs before an underwater extending | stretching.

A-4. Other treatments In addition to stretching and dyeing, the laminate may be appropriately subjected to treatment for using the PVA resin layer as a polarizing film. Examples of the treatment for forming the polarizing film include insolubilization treatment and crosslinking treatment. In addition, the frequency | count, order, etc. of these processes are not specifically limited.

  The insolubilization treatment is typically performed by immersing the PVA resin layer in an aqueous boric acid solution. By performing the insolubilization treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilizing bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization treatment is performed before the above-described underwater stretching or the above-described dyeing treatment.

  The crosslinking treatment is typically performed by immersing the PVA resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water. Moreover, when performing a crosslinking process after the said dyeing | staining process, it is preferable to mix | blend an iodide further. By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 60 ° C. Preferably, the crosslinking treatment is performed before the underwater stretching. In a preferred embodiment, the dyeing process, the crosslinking process and the underwater stretching are performed in this order.

A-5. Polarizing Film The polarizing film is substantially a PVA resin film in which a dichroic substance is adsorbed and oriented. The thickness of the polarizing film is typically 25 μm or less, preferably 15 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and particularly preferably 5 μm or less. On the other hand, the thickness of the polarizing film is preferably 0.5 μm or more, more preferably 1.5 μm or more. The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more, further preferably 42.0% or more, and particularly preferably 43.0% or more. The polarization degree of the polarizing film is preferably 99.8% or more, more preferably 99.9% or more, and further preferably 99.95% or more.

B. First Cleaning Step In the first cleaning step, the laminate in which the polarizing film is laminated on the resin base material obtained in the polarizing film manufacturing step is immersed in a cleaning solution containing iodide for cleaning. Specific examples of the iodide are as described above, preferably potassium iodide. In one embodiment, the cleaning liquid is an aqueous potassium iodide solution. The iodide concentration in the cleaning solution is preferably 0.5 wt% to 10 wt%, preferably 0.5 wt% to 5 wt%, more preferably 1 wt% to 4 wt%. The temperature of the cleaning liquid is usually 10 ° C to 50 ° C, preferably 20 ° C to 35 ° C. The immersion time is usually 1 second to 1 minute, preferably 10 seconds to 1 minute. If the cleaning is insufficient, boric acid may be deposited from the obtained polarizing film.

C. Second Washing Step In the second washing step, only the resin substrate side surface of the laminate after the first washing is further washed. When a cleaning liquid (for example, water) contacts the polarizing film side surface, the hue may change and affect the optical characteristics of the polarizing film. Such a hue change tends to be large in a polarizing film obtained through an underwater stretching method.

  The cleaning in the second cleaning step can be performed by any appropriate method. The cleaning is preferably performed by bringing the surface of the laminate on the resin substrate side into contact with the cleaning liquid. For example, in one embodiment, the cleaning is performed by spraying the cleaning liquid on the surface of the resin base material while transporting the laminate in the longitudinal direction. FIG. 2 is a schematic diagram illustrating an example of the embodiment.

The long laminate 10 is transported in the longitudinal direction from the cleaning bath 20 by a transport roll 21. The cleaning liquid is sprayed by the spraying means (shower in the illustrated example) 30 on the surface of the laminate 10 being transported in this way on the resin base material layer 11 side. The cleaning liquid is preferably sprayed over the entire width of the surface of the resin substrate 11 side. The spray amount of the cleaning liquid is, for example, 0.3 L to 0.7 L per unit area (m ² ) of the laminate to be cleaned. Only one spraying means may be provided, or a plurality of spraying means may be provided.

  In another embodiment, the cleaning is performed by providing a liquid dam that holds the cleaning liquid so that the surface of the resin base material sequentially contacts the cleaning liquid while conveying the laminate in the longitudinal direction. The liquid dam method is more preferable than the spraying method in that more uniform cleaning is possible, or in that the cleaning liquid can be prevented from flowing around the polarizing film 12 side. FIG. 3A and FIG. 3B are a schematic diagram illustrating an example of the embodiment and a schematic perspective view of main parts thereof, respectively.

  The long laminate 10 is transported in the longitudinal direction from the cleaning bath 20 by a transport roll 21. The transport direction is preferably 70 ° to 90 °, more preferably 80 ° to 90 ° with respect to the horizontal direction. The liquid dam 40 includes the laminated body 10 being conveyed in this way, a blade 50 as a dam bottom provided so that the tip thereof is in sliding contact with the surface of the laminated body 10 on the resin base material 11 side, and the laminated body from the blade 50. 10, the both ends of the liquid dam 40 in the width direction are open.

The cleaning liquid is supplied to the space defined by the laminate 10, the blade 50, and the water shielding wall 60 by the liquid supply means (nozzle in the illustrated example) 70 to form the liquid dam 40. The cleaning liquid may be supplied directly to the space or may be supplied so as to come into contact with the stacked body 10. According to such a liquid dam 40, since the surface of the laminate 10 conveyed in the longitudinal direction is in contact with the cleaning liquid sequentially held in the liquid dam, the surface is uniformly cleaned. Can do. The supply amount of the cleaning liquid is, for example, 0.1 L to 0.3 L per unit area (m ² ) of the laminate to be cleaned.

  Preferably, the cleaning liquid is continuously supplied from the liquid supply means 70. Thereby, since the excess cleaning liquid continuously overflows from the open end in the width direction of the liquid dam, it is possible to avoid the increase of the iodide concentration in the cleaning liquid by suitably replacing the cleaning liquid. Only one liquid supply means 70 may be provided, or a plurality of liquid supply means 70 may be provided. When only one is provided, it is preferably provided at the approximate center in the width direction. This is because the cleaning liquid can be suitably replaced.

  The length of the long side of the blade 50 (hereinafter, for the sake of convenience, the length of the long side of the blade is referred to as the width of the blade) is equal to or greater than the width of the laminate 10, and preferably wider than the width of the laminate 10. When the width of the blade 50 is wider than the width of the laminated body 10, the cleaning liquid overflowing from the end portion in the width direction of the liquid dam 40 drops to the blade extension portion 52 extending in the width direction of the liquid dam 40 and then drops. Therefore, it is possible to prevent the laminate 10 from entering the surface of the polarizing film 12 side. On the other hand, the length of the long side of the impermeable wall 60 (hereinafter, for convenience, the length of the long side of the impermeable wall is referred to as the width of the impermeable wall) is preferably less than the width of the laminate 10. More preferably, it is narrower by about 5 mm to 15 mm than the width of the laminate 10 (in this case, the water shielding walls are preferably arranged so that both ends thereof are equidistant from the ends of the laminate). When the width of the laminated body 10, the blade 50, and the impermeable wall 60 satisfies such a relationship, the surface of the resin base material 11 of the laminated body can be cleaned uniformly and the cleaning liquid overflowing from the end in the width direction of the liquid dam 40 Can be prevented from entering the surface of the laminate 10 on the polarizing film 12 side.

  An angle α formed between the blade 50 and the laminate 10 (an angle formed between the blade 50 and the traveling direction of the laminate 10) α may be any appropriate angle. The angle is preferably 30 ° to 85 °, more preferably 45 ° to 85 °. If it is such an angle, the liquid dam 40 can be formed suitably. Further, it is possible to suitably prevent the cleaning liquid overflowing from the end portion in the width direction of the liquid dam 40 from flowing around the surface of the laminated body 10 on the polarizing film 12 side.

  It is preferable that the tip of the laminated body 10 of the blade 50 in contact with the surface of the resin base material 11 is subjected to curved chamfering (so-called R chamfering). By performing the R chamfering process, it is possible to prevent the resin base material 11 side surface from being damaged. The R chamfer dimension (curvature radius R) is preferably 0.5 mm or more, and more preferably 0.5 mm to 1.5 mm.

  The height, arrangement position, and the like of the impermeable wall 60 are set to any appropriate value according to the angle formed by the blade 50 and the laminated body 10, the supply amount of the cleaning liquid, and the like.

  The material of the blade 50 and the water shielding wall 60 is not particularly limited. These are, for example, made of metal or resin.

  The cleaning liquid overflowing from the liquid dam is preferably recovered by an optional recovery means 80. By providing the recovery means 80, it is possible to prevent the iodide concentration of the cleaning liquid containing iodide from being lowered.

  As the cleaning liquid used in the second cleaning step, a liquid that does not contain impurities that may precipitate after drying is preferable. Specifically, water such as distilled water, deionized water, pure water, alcohol such as ethanol, or a mixture thereof can be used.

  The blade 50, the liquid supply means 70, and the recovery means 80 are each fixed by any appropriate fixing tool (not shown).

D. Drying step In the drying step, the laminate after the second cleaning is dried. Drying of the laminate is performed by any appropriate drying method such as natural drying, air drying, heat drying, hot air drying and the like. Heat drying using heating means such as an oven is preferred. The drying temperature is, for example, 30 ° C to 100 ° C, preferably 50 ° C to 80 ° C. The drying time can be appropriately set according to the drying temperature, and is, for example, 10 seconds to 10 minutes.

E. Other Steps The production method of the present invention may further include a step of draining the liquid adhering to the laminate surface after the second cleaning step and before the drying step. Even if a small amount of iodide remains on the surface of the laminated substrate after the second washing, the remaining amount can be further reduced by draining. Moreover, the drying efficiency performed after that can be improved.

  In FIG. 2 and FIGS. 3A and 3B, a pair of liquid draining rollers is used as the liquid draining means 90. As the liquid draining roller, a rubber roller having a crown shape is preferably used. The crown amount (difference in outer diameter (mm) between the roll end and the center) is, for example, 2 to 10, preferably 3 to 10, and more preferably 3 to 7. The liquid draining means may also be an air blower, a blade or the like.

F. Optical laminated body The optical laminated body of this invention obtained through the said drying process is equipped with the resin base material and the polarizing film formed in the one side. The optical layered body of the present invention is typically wound into a roll by a winding device and used for storage or a step of laminating an optical functional film (for example, a protective film) on the polarizing film side of the layered body. Is done. Since the optical layered body of the present invention is dried in a state where the adhesion of iodide is reduced on the surface of the resin base material as described above, precipitation of iodide on the surface of the resin base material side can be suppressed. As a result, even when the obtained optical layered body is rolled up, deformation of the polarizing film due to precipitates (resulting in uneven defects) can be suppressed.

  An optical functional film laminate (having a structure of [resin base material / polarizing film / optical functional film]) on which an optical functional film is laminated can be used as it is as a polarizing plate. Alternatively, the resin base material is peeled from the optical functional film laminate, and another optical functional film (for example, a protective film) is laminated on the peeled surface to form an [optical functional film / polarizing film / optical functional film]. The polarizing plate which has can also be obtained.

G. Apparatus According to another aspect of the present invention, a blade disposed such that the tip is in sliding contact with one surface of a long sheet conveyed in the longitudinal direction; There is provided an apparatus comprising: a wall; and a liquid supply means for supplying a liquid to a liquid dam defined by a long sheet, a blade, and a water shielding wall. According to this apparatus, only one side of the sheet can be uniformly brought into contact with a desired liquid while conveying the long sheet. Therefore, for example, it can be preferably used when only one side of the long film (for example, a surface to which foreign matter, dirt, etc. are attached) is washed while conveying the long film. Each component of the apparatus of the present invention and its arrangement are as described in Section C above.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of each characteristic is as follows.
1. Thickness Measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
2. Glass transition temperature (Tg)
It measured according to JIS K7121.
3. Evaluation of unevenness defect A black plate (matte) was placed on a workbench, and an optical laminate was placed thereon. The optical laminate was irradiated with light from a fluorescent lamp, and the number of bright spots visible at that time was counted as irregular defects (brightness on the workbench at the time of inspection was 1300 to 3000 Lx).
4). Evaluation of scratches A black plate (matte) was placed on the workbench, and an optical laminate was placed thereon. The optical laminate was irradiated with light from a fluorescent lamp, and the number of scratches visible at that time was counted (brightness on the workbench at the time of inspection was 1300 to 3000 Lx).
5. Water contact angle Automatic contact angle meter manufactured by Kyowa Interface Science Co., Ltd. Measured using DM500 and analyzed using FAMAS (contact angle measurement add-in software).

[Example 1 and Comparative Example 1]
As a resin base material, an amorphous polyethylene terephthalate (A-PET) film (Mitsubishi Chemical Co., Ltd., trade name “Novaclear”) having a long shape, water absorption of 0.60%, Tg of 80 ° C., and an elastic modulus of 2.5 GPa, thickness : 100 μm, width: 2650 mm).
One side of the resin substrate is subjected to corona treatment (treatment conditions: 55 W · min / m ² ), and 90 parts by weight of polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetate are applied to the corona treatment surface. An aqueous solution containing 10 parts by weight of acetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name “Gosefimer Z200”) It was applied and dried at 60 ° C. to form a PVA resin layer having a thickness of 10 μm, and a laminate was produced. The water contact angle on the resin substrate side surface of the obtained laminate was 70 °.

The obtained laminate was uniaxially stretched at a free end 1.8 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120 ° C. (air-assisted stretching).
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, it is immersed for 60 seconds in a dyeing bath having a liquid temperature of 30 ° C. (an iodine aqueous solution obtained by blending 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide with respect to 100 parts by weight of water). (Staining treatment).
Subsequently, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (Crosslinking treatment).
Thereafter, the laminate was immersed in a boric acid aqueous solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ° C. However, uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds (underwater stretching). Here, it extended | stretched until just before a laminated body fracture | ruptures (a maximum draw ratio is 6.0 times).
Thereafter, the laminate was immersed in a cleaning bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (first cleaning process).

  While transporting the laminate (width: 1610 mm) upward from the cleaning bath, as shown in FIGS. 3A and 3B, a blade (width: 1800 mm) having a corner chamfered at the tip to have a curvature radius (R) of 1 mm. 50) was placed so that the tip thereof was in sliding contact with the laminated body 10 at an angle of 50 °. On the surface of the blade 50, there was provided a water shielding wall 60 (width: 1600 mm) having a height of 20 mm that rises substantially perpendicularly to a portion at a distance of 8 mm to 10 mm from the tip. With this arrangement, drainage of the surface of the laminate 10 on the side of the resin base material 11 up to 10 lots was performed (Comparative Example 1). From the time when the processing for 10 lots is finished, pure water is continuously supplied from the water supply nozzle 70 to the space defined by the laminate 10, the blade 50, and the water shielding wall 60 to form a liquid dam. The surface of the laminate 10 on and after the 11th lot was washed with water by contacting the washing water in the liquid dam with the laminate (Example 1). The washing water overflowing from the liquid dam was collected in the collection tank 80.

  After draining with only the blade or rinsing with a liquid dam, draining was performed using a rubber roller 90 with a crown amount of 5.

  Thereafter, the laminate was transported into an oven maintained at 60 ° C. and heated for 5 minutes to produce an optical laminate having a polarizing film having a thickness of 5 μm. Subsequently, the obtained optical laminated body was wound up in a roll shape with a winding device.

[Example 2]
An optical laminate was produced in the same manner as in Example 1 except that drainage was performed with a rubber roller 90 having a crown amount of 2.3.

[Comparative Example 2]
An optical laminate was produced in the same manner as in Comparative Example 1 except that the corner portion at the tip of the blade 50 was not subjected to R chamfering.

[Reference Example 1]
When the laminated body which performed until the 1st washing process similarly to Example 1 was immersed in the pure water bath with a liquid temperature of 30 degreeC and washed with water, the formation component of the polarizing film eluted and the change of the hue produced.

  The transition of the number of irregularities in the optical laminate obtained by continuous production in Example 1 and Comparative Example 1 is shown in FIG. Table 1 shows the evaluation of unevenness defects and scratches in the optical laminates obtained in each Example and Comparative Example.

  As is clear from Table 1 and FIG. 4, by selectively cleaning the resin substrate side surface of the laminate, it was possible to significantly reduce the occurrence of irregularities without affecting the polarizing film. .

  The optical laminate of the present invention is a liquid crystal television, liquid crystal display, mobile phone, digital camera, video camera, portable game machine, car navigation system, copy machine, printer, fax machine, clock, microwave oven, etc., and an organic EL device. It is suitably used as an antireflection film.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 Resin base material 12 Polyvinyl alcohol-type resin layer (polarizing film)
DESCRIPTION OF SYMBOLS 20 Washing bath 30 Spraying means 40 Liquid dam 50 Blade 60 Impermeable wall 70 Liquid supply means 80 Recovery tank 90 Liquid draining means

Claims (5)

A method for producing an optical laminate in which a polarizing film is laminated on a resin substrate,
Stretching and dyeing a laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and producing a polarizing film on the resin substrate;
A first cleaning step of immersing and cleaning the laminate in a cleaning solution containing iodide;
A second cleaning step of cleaning only the resin substrate side surface of the laminate;
Drying the laminate,
Only including,
The cleaning in the second cleaning step is performed by providing a liquid dam that holds the cleaning liquid so that the surface of the resin base material sequentially contacts the cleaning liquid while conveying the laminate in the longitudinal direction.
The liquid dam is transported in the longitudinal direction, the blade disposed so that the tip thereof is in sliding contact with the surface of the resin base material, and a water-impervious wall rising from the blade so as to face the laminate. The manufacturing method in which both ends in the width direction are open . The width of the blade is wider than the width of the laminate, the manufacturing method according to claim 1. Said stretching comprises a solution stretching process according to claim 1 or 2. The manufacturing method in any one of Claim 1 to 3 which drains the liquid adhering to the said laminated body surface after a said 2nd washing | cleaning process.   A blade arranged so that the tip thereof is in sliding contact with one surface of the long sheet conveyed in the longitudinal direction; a water-impervious wall rising from the blade to face the long sheet; the long sheet, the blade, and the water-impervious A liquid supply means for supplying liquid to a liquid dam defined by the wall.