KR20150075035A - Method of manufacturing optical laminate - Google Patents

Abstract

Provided is a method for manufacturing a polarizing film with an excellent appearance. According to an embodiment of the present invention, a method for manufacturing an optical laminate comprises: a step of stretching and dyeing a laminate including a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and manufacturing a polarizing film on the resin substrate; a step of submerging and cleaning the laminate into a cleaning solution containing iodide; and a step of drying the laminate after removing the cleaning solution in order that an adhesion amount of the cleaning solution is 0.005 g/m^2 or less in the surface of the resin substrate of the laminate.

Description

METHOD OF MANUFACTURING OPTICAL LAMINATE [0002]

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 representative image display device, a polarizing film is disposed on both sides of the liquid crystal cell due to the image forming method. As a method for producing a polarizing film, there has been proposed 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 For example, Japanese Laid-Open Patent Publication No. 2000-338329). According to such a method, a polarizing film having a thin thickness can be obtained, and thus it has been attracting attention as contributing to the recent thinning of an image display apparatus.

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

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and its main object is to provide a method of manufacturing a polarizing film in which apparent problems such as irregularity defects are improved.

The inventors of the present invention have investigated the above-mentioned irregularities and defects, and the mechanism of their occurrence is presumed as follows. That is, the polarizing film is prepared by stretching and dyeing a laminate having a resin substrate and a PVA resin layer, washing with a washing liquid typically containing iodide, and finally drying. Here, when drying is performed in a state in which the cleaning liquid containing iodide remains on the surface of the laminate, the surface of the resin base material having higher hydrophobicity than the surface of the PVA resin layer (polarizing film) . Subsequently, when the laminate in such a state is conveyed by a conveying roller or is recovered by winding it in a roll form, it is presumed that the shape of the precipitate is easily transferred to the polarizing film because the thickness of the polarizing film is thin,

The present inventors have further studied based on the above-mentioned conjecture. After cleaning with a cleaning liquid containing iodide, the inventors adjusted the adhesion amount of the cleaning liquid on the resin-material-side surface of the laminate to a predetermined range and then dried , Irregularity defects, and the like can be solved, and the present invention has been accomplished.

A method for producing an optical laminate in which a polarizing film is laminated on a resin substrate of the present invention is characterized in that a laminate having a resin substrate and a polyvinyl alcohol resin layer formed on one side of the resin substrate is stretched and dyed, A step of immersing the laminate in a cleaning liquid containing iodide to clean the laminate; and a step of removing the cleaning liquid so that the adhesion amount of the cleaning liquid on the resin-material-side surface of the laminate is 0.005 g / And then drying the laminated body.

In one embodiment, the water contact angle of the resin-material-side surface of the laminate is 60 ° to 80 °.

In one embodiment, the thickness of the polarizing film is 0.5 占 퐉 to 15 占 퐉.

In one embodiment, the concentration of iodide in the cleaning liquid is 0.5 wt% to 10 wt%.

In one embodiment, the stretching comprises underwater stretching.

In one embodiment, the removal of the cleaning liquid on the resin-material-side surface of the laminate is carried out by wiping or spraying of gas.

According to another aspect of the present invention, there is provided an optical laminate. The optical laminate of the present invention is obtained by the above-described production method.

According to the present invention, after a laminate in which a polarizing film is laminated on a resin substrate is cleaned with a cleaning liquid containing iodide, an adhesion amount of the cleaning liquid on the resin substrate side surface of the laminate is adjusted to a predetermined range, The precipitation of iodide can be suppressed, and as a result, apparent problems such as irregularities and defects can be solved.

1 is a partial cross-sectional view of a laminate according to a preferred embodiment of the present invention.
2 is a schematic view for explaining an example of a drying step of removing a cleaning liquid on a resin-material-side surface of a laminate by wiping.
3 is a schematic view for explaining an example of a drying step of removing a cleaning liquid on a resin-material-side surface of a laminate by wiping;
4 is a schematic view for explaining an example of a drying step of removing a cleaning liquid on a resin-material-side surface of a laminate by jetting a gas.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A process for producing an optical laminate according to the present invention comprises the steps of stretching and dyeing a laminate having a resin base material and a polyvinyl alcohol based resin layer formed on one side of the resin base material and preparing a polarizing film on the resin base material, A step of dipping the laminate in a cleaning liquid containing iodide to remove the cleaning liquid so that the adhesion amount of the cleaning liquid on the resin base material side surface of the laminate is 0.005 g / . Hereinafter, each step will be described.

A. Production process of polarizing film

A-1. The laminate

1 is a partial cross-sectional view of a laminate according to a preferred embodiment of the present invention. The laminate 10 has a resin base material 11 and a polyvinyl alcohol-based resin layer 12. The laminate 10 is produced by forming a polyvinyl alcohol-based resin layer 12 on a resin substrate 11 of a long-length phase. Any appropriate method may be employed as the method of forming the polyvinyl alcohol-based resin layer 12. [ Preferably, a coating liquid containing a polyvinyl alcohol-based resin (hereinafter referred to as " PVA-based resin ") is applied onto the resin substrate 11 and dried to form the PVA-based resin layer 12.

As the material for forming the resin base material, any suitable thermoplastic resin may be employed. Examples of the thermoplastic resin include, for example, ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate- And copolymer resins. Among them, a norbornene resin and an amorphous polyethylene terephthalate resin are preferable.

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

In the case of adopting an underwater stretching method in the stretching described later, the resin base material can absorb water and plasticize the water by acting as a plasticizer. As a result, the stretching stress can be largely lowered and the stretching can be performed at a high magnification, so that the stretching property can be more excellent than that at the time of the pneumatic 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 of 0.2% or more, and more preferably 0.3% or more. On the other hand, the water absorption of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, it is possible to prevent the dimensional stability at the time of production from remarkably lowering, and the appearance of the obtained polarizing film deteriorates. In addition, it is possible to prevent the base material from breaking or the PVA resin layer from peeling off from the resin base during the underwater stretching. The absorption rate of the resin base material can be adjusted by introducing a transformer into the forming material, for example. The water absorption rate is a value determined in accordance with JIS K 7209.

The glass transition temperature (Tg) of the resin substrate is preferably 170 占 폚 or less. By using such a resin base material, it is possible to sufficiently secure the stretchability of the laminate while suppressing the crystallization of the PVA-based resin layer. Further, considering that plasticization of the resin substrate by water and good drawing in water are carried out well, it is more preferable to be 120 DEG C or less. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 DEG C or higher. By using such a resin base material, it is possible to prevent the resin base material from being deformed (for example, unevenness, sagging, wrinkling, etc.) when the coating liquid containing the PVA resin is applied and dried, A laminate can be manufactured. In addition, the PVA resin layer can be stretched satisfactorily at a preferable temperature (for example, about 60 캜). In another embodiment, when the coating liquid containing PVA resin is applied and dried, the glass transition temperature may be lower than 60 占 폚 unless the resin base material is deformed. Further, the glass transition temperature of the resin base material can be adjusted, for example, by heating using a crystallization material which introduces a transformer into the forming material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

The thickness of the resin substrate before stretching is preferably 20 mu m to 300 mu m, more preferably 50 mu m to 200 mu m. If it is less than 20 占 퐉, formation of the PVA-based resin layer may become difficult. When it exceeds 300 탆, for example, in the underwater stretching, it takes a long time for the resin substrate to absorb water, and there is a fear that an excessive load is required for stretching.

As the PVA-based resin forming the PVA-based resin layer, any suitable resin may be employed. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually from 85 mol% to 100 mol%, preferably from 95.0 mol% to 99.95 mol%, and more preferably from 99.0 mol% to 99.93 mol%. The saponification degree can be obtained according to JIS K 6726-1994. By using such a saponification degree PVA resin, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, there is a fear of gelation.

The average degree of polymerization of the PVA resin may be appropriately selected depending on the purpose. The average polymerization degree is usually 1000 to 10000, preferably 1200 to 5000, and more preferably 1500 to 4500. The average polymerization degree can be obtained according to JIS K 6726-1994.

The coating liquid is typically a solution in which the PVA resin is dissolved in a solvent. Examples of the solvent include water, polyhydric alcohols such as dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols and trimethylolpropane, polyhydric alcohols such as ethylenediamine and diethylenetriamine Amines. These may be used alone or in combination of two or more. Among them, water is preferable. The concentration of the PVA resin in the solution is preferably 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhered to the resin base material can be formed.

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

As the easy-to-adhere component, for example, a 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.

[Chemical Formula 1]

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

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

The modified PVA is preferably added in an amount of 3% by weight or more based on the total weight of the PVA-based resin contained in the coating liquid, more preferably 5% by weight or more. On the other hand, the added amount of the modified PVA is preferably 30% by weight or less.

Any suitable method may be employed as the coating method of the coating liquid. Examples of the coating method 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, and a knife coating method (comma coating method).

The coating and drying temperature of the coating liquid is preferably 50 占 폚 or higher.

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

Before forming the PVA resin layer, the resin substrate may be subjected to a surface treatment (e.g., corona treatment or the like), or an easy adhesion layer may be formed on the resin substrate. Among these, it is preferable to form an easy-to-adhere layer (coating treatment). As the material for forming the adhesion-facilitating layer, for example, an acrylic resin, a polyvinyl alcohol-based resin, or the like is used, and a polyvinyl alcohol-based resin is particularly preferable. Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and a modified product thereof. As the modified product of the polyvinyl alcohol resin, the above-mentioned acetoacetyl-modified PVA can be mentioned. The thickness of the easy-to-adhere layer is preferably about 0.05 to 1 mu m. By performing such a treatment, the adhesion between the resin substrate and the PVA-based resin layer can be improved. As a result, for example, the problem of peeling the PVA resin layer from the substrate can be suppressed, and dyeing and underwater stretching described later can be satisfactorily performed.

The water contact angle of the resin-material-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 the laminate

As the stretching method of the laminate, any appropriate method may be employed. Concretely, it may be a fixed end stretching or a uniaxial stretching by passing a laminate between rolls having different end velocities (for example, a peripheral velocity). It is preferably free-standing stretching.

The stretching direction of the laminate can be appropriately set. In one embodiment, the elongated-layer laminate is elongated in the longitudinal direction. In this case, typically, a method of passing the laminate between rolls having different main speeds and stretching is employed. In another embodiment, the elongated-layer laminate is stretched in the width direction. In this case, typically, a method of stretching using a tenter stretcher is employed.

The drawing method is not particularly limited, and may be a pneumatic drawing method or an underwater drawing method. Preferably an underwater stretching method. According to the in-water 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 캜), and the PVA resin layer is stretched at a high magnification while suppressing the crystallization thereof . As a result, a polarizing film having excellent optical characteristics can be produced.

The laminate may be stretched in one step or in multiple steps. In the case of multi-stage execution, for example, the above-described free-standing drawing and fixed-end drawing may be combined, or the underwater drawing method and the pneumatic drawing method may be combined. In the case of multi-step execution, the draw ratio (maximum draw ratio) of the laminate to be described later is the product of the draw ratio at each step.

The drawing temperature of the laminate can be set to any appropriate value depending on the forming material of the resin base material, the drawing method, and the like. In the case of adopting a pneumatic drawing method, the drawing temperature is preferably not less than the glass transition temperature (Tg) of the resin base, more preferably not less than the glass transition temperature (Tg) of the resin base + 10 DEG C or more, 15 ° C or higher. On the other hand, the stretching temperature of the laminate is preferably 170 占 폚 or less. By stretching at such a temperature, the crystallization of the PVA resin can be inhibited from proceeding rapidly, and the problems caused by the crystallization (for example, the orientation of the PVA resin layer due to stretching can be prevented) can be suppressed.

When the underwater stretching method is employed, the temperature of the stretching bath is preferably 40 ° C to 85 ° C, and more preferably 50 ° C to 85 ° C. With such a temperature, stretching can be performed at a high magnification while suppressing the dissolution of the PVA resin layer. Concretely, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60 ° C or more in relation to the formation of the PVA-based resin layer. In this case, if the drawing temperature is lower than 40 캜, there is a possibility that the drawing can not be performed satisfactorily even considering the plasticization of the resin substrate by the water. On the other hand, as the temperature of the drawing bath becomes higher, the solubility of the PVA resin layer becomes higher, and there is a possibility that excellent optical characteristics may not be obtained. The immersing time of the laminate in the drawing bath is preferably 15 seconds to 5 minutes.

When an underwater stretching method is employed, it is preferable to immerse the laminate in an aqueous boric acid solution to stretch it (stretching in boric acid in water). By using an aqueous boric acid solution as the drawing bath, the PVA-based resin layer can be provided with rigidity to withstand the tensile force at the time of drawing and water resistance not to be dissolved in water. Specifically, the boric acid can be crosslinked by hydrogen bonding with the PVA resin to produce tetrahydroxyboran anion in an aqueous solution. As a result, it is possible to produce a polarizing film having a stiffness and a water resistance to the PVA-based resin layer and being satisfactorily stretched and having excellent optical characteristics.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight based on 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. Further, 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 material (typically iodine) is adsorbed to the PVA resin layer in advance by dyeing described later, iodide is preferably added to the drawing bath (aqueous solution of boric acid). By combining iodide, the elution of iodine adsorbed to the PVA-based 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. Of 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 based on 100 parts by weight of water.

The draw ratio (maximum draw ratio) of the laminate is preferably at least 5.0 times the original length of the laminate. Such a high stretching magnification can be achieved, for example, by employing an in-water stretching method (boric acid in water stretching). In the present specification, the term "maximum draw ratio" refers to the draw ratio immediately before the laminate is broken, and refers to a value that is 0.2 lower than the value obtained by confirming the draw ratio at which the laminate is broken.

In a preferred embodiment, the laminate is subjected to air drawing at a high temperature (for example, 95 ° C or higher), followed by drawing the laminate in water and dyeing described later. Such a pneumatic stretching can be positioned as a preliminary or auxiliary stretching for boric acid in-water stretching, and is hereinafter referred to as " air-assisted stretching ".

By combining air-assisted stretching, the laminate may be stretched at a higher magnification. As a result, a polarizing film having better optical characteristics (for example, polarization degree) can be produced. For example, in the case of using a polyethylene terephthalate resin as the resin base material, it is possible to stretch while suppressing the orientation of the resin base material by combining air-assisted stretching and boric acid in-water stretching rather than stretching only in boric acid water. As the orientation of the resin base material is improved, the stretching tension is increased, which makes it difficult to stably stretch or break the resin base material. Thus, by stretching while suppressing the orientation of the resin substrate, the laminate can be stretched at a higher magnification.

The combination of air assisted stretching improves the orientation of the PVA resin, thereby improving the orientation of the PVA resin even after stretching in boric acid water. Specifically, by improving the orientation of the PVA-based resin by air-assisted stretching in advance, the PVA-based resin is easily crosslinked with the boric acid at the time of stretching in boric acid water and is stretched in a state where the boric acid becomes a nodal point, It is presumed that the orientation of the PVA resin is increased. As a result, a polarizing film having excellent optical characteristics (for example, polarization degree) can be produced.

The stretching ratio in the air-assisted stretching is preferably 3.5 times or less. The stretching temperature of the air-assisted stretching is preferably at least the glass transition temperature of the PVA-based resin. The stretching temperature is preferably 95 ° C to 150 ° C. The maximum stretching ratio in the case of combining air-assisted stretching and boric acid in-water stretching is preferably at least 5.0 times, more preferably at least 5.5 times, and still more preferably at least 6.0 times the original length of the laminate .

A-3. dyeing

The dyeing of the laminate is typically performed by adsorbing a dichroic material (preferably iodine) on the PVA resin layer. Examples of the adsorption method include a method of immersing a PVA resin layer (laminate) in a dyeing solution containing, for example, iodine, a method of applying the dyeing solution to a PVA resin layer, a method of applying the dyeing solution to a PVA resin layer And the like. Preferably, the laminate is immersed in the dyeing solution. This is because iodine can be adsorbed well.

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

The dyeing process can be carried out at any appropriate timing. When the underwater stretching is carried out, the stretching is preferably performed before underwater stretching.

A-4. Other processing

In addition to stretching and dyeing, the laminate may be suitably subjected to a treatment for converting the PVA resin layer into a polarizing film. Examples of the treatment for forming a polarizing film include a treatment for insolubilization and a treatment for crosslinking. In addition, the number, order, and the like of these processes are not particularly limited.

The insolubilization treatment is typically performed by immersing the PVA resin layer in an aqueous solution of boric acid. By carrying out the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer. The concentration of the aqueous boric acid solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. The temperature of the insoluble base (aqueous solution of boric acid) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization treatment is carried out before the underwater drawing or the dyeing treatment.

The crosslinking treatment is typically performed by immersing a PVA-based resin layer in an aqueous solution of boric acid. By carrying out the crosslinking treatment, it is possible to impart water resistance to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight based on 100 parts by weight of water. Further, in the case of carrying out the crosslinking treatment after the dyeing treatment, it is preferable to further add iodide. By combining iodide, the elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The compounding amount of iodide is preferably 1 part by weight to 5 parts by weight based on 100 parts by weight of water. Specific examples of the iodide are as described above. The solution temperature of the crosslinking bath (aqueous solution of boric acid) is preferably 20 ° C to 60 ° C. Preferably, the crosslinking treatment is carried out before the underwater stretching. In a preferred embodiment, dyeing treatment, crosslinking treatment and underwater stretching are carried out in this order.

A-5. Polarizer film

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

B. Cleaning Process

In the cleaning step, the laminated body in which the polarizing film is laminated on the resin base material obtained in the production step of the polarizing film is immersed in a cleaning liquid containing iodide and cleaned. A specific example of the iodide is as described above, and preferably potassium iodide. In one embodiment, the cleaning liquid is an aqueous potassium iodide solution. The concentration of iodide in the cleaning liquid is preferably 0.5% by weight to 10% by weight, preferably 0.5% by weight to 5% by weight, more preferably 1% by weight to 4% by weight. 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 washing is insufficient, boric acid may precipitate from the resulting polarizing film.

C. Drying process

In the drying step, the adhesion amount of the cleaning liquid on the resin-material-side surface of the laminate cleaned in the cleaning step is 0.005 g / m 2 or less, preferably 0.003 g / m 2 or less, more preferably 0.002 g / After removing the cleaning liquid as much as possible, the laminate is dried. If a laminate having a cleaning liquid adhered in an amount exceeding 0.005 g / m < 2 > on the surface of the resin base material is provided for the drying treatment, unevenness defects (for example, irregularities having a diameter of 150 mu m or more) May occur.

It is not necessary to consider the concentration change of the cleaning liquid due to natural drying or the like because the time from the completion of the cleaning process to the provision of the drying treatment is generally 60 seconds or less and the conveyance of the laminate is carried out at room temperature. The removal is preferably carried out immediately after the laminate passes through the cleansing bath (for example, within 30 seconds, preferably within 15 seconds).

The cleaning liquid removal is carried out in any suitable manner. The removal of the cleaning liquid can be carried out, for example, by wiping the cleaning liquid on the resin-material-side surface of the laminate, or by spraying gas onto the surface.

The wiping of the cleaning liquid is carried out using any suitable wiping means such as an absorption roll, a liquid removal roll, a blade and the like. The wiping means may be used alone, or a plurality of wiping means may be used, or two or more wiping means may be used in combination. Fig. 2 and Fig. 3 are schematic views for explaining an example of a drying process for removing the cleaning liquid on the resin-material-side surface of the laminate by wiping, respectively.

When the absorbent roll 20 is used (refer to FIG. 2), the absorbent roll 20 is folded in the resin base material 10 (see FIG. 2) of the laminated body 10 so as to rotate in accordance with the conveyance of the laminated body 10 after immersion in, for example, 11). Typically, the surface of the absorbing roll is formed of a porous material such as sponge, nonwoven fabric, or woven fabric. Examples of the sponge include a urethane sponge, a rubber sponge, and a polyolefin sponge. The roll diameter is, for example, 80 mm to 110 mm. Reference numeral 110 in the drawing denotes a transport roll.

In the case where a liquid removing roll is used (see FIGS. 2 and 3), for example, a pair of liquid removing rolls 30 are disposed so as to be opposed to each other so that the laminate 10 is interposed therebetween. As the liquid removing roll 30 is rotated in accordance with the conveyance of the laminate 10, the laminate 10 is squeezed from the front and back sides, thereby removing the liquid. The liquid removing roll is typically made of rubber. The liquid removing roll may have a crown shape. By having a crown shape, it is possible to uniformly remove the liquid in the width direction of the laminate.

3), the blade 40 is disposed on the surface of the laminate 10 on the side of the resin substrate 11, which is typically transported in the longitudinal direction, such that the tip of the blade 40 is in sliding contact with the blade 40 . By this arrangement, the water is wiped by the blade 40 from the surface of the resin base material 10 side in accordance with the conveyance of the laminate 10. Examples of the material for forming the blade include rubber, resin, metal and the like. The portion of the blade that makes sliding contact with the laminated body may be chamfered in a curved shape from the viewpoint of avoiding the occurrence of scratches.

Gas injection onto the resin-material-side surface of the laminate can be carried out using a commercially available air blowing apparatus. 4 is a schematic view for explaining an example of a drying step of removing the cleaning liquid on the resin-material-side surface of the laminate by jetting a gas. The air blowing apparatus 50 is arranged so that the angle of spraying of the air against the surface of the laminate 10 on the side of the resin base material 11 is preferably 25 ° to 65 °. The conditions of the air blow can be appropriately set according to the type of the resin base material and the like. The pressure of the air is, for example, 20 to 25 KPa. The wind speed of the air is, for example, 20 to 60 m / min. As shown in the drawing, the wiping means (in the illustrated example, the absorbing roll 20 and the liquid removing roll 30) and the air blowing device 50 may be used in combination.

The drying of the laminate after the removal of the cleaning liquid is carried out by any suitable drying method such as natural drying, air blow drying, heat drying, hot air drying and the like. Preferably, it is heat drying using a heating means 60 such as an oven. The drying temperature is, for example, 30 ° C to 100 ° C, preferably 40 ° C to 100 ° C. The drying time may be appropriately set according to the drying temperature, for example, 10 seconds to 10 minutes.

D. Optical laminate

The optical laminate of the present invention obtained through the above drying step has a resin substrate and a polarizing film formed on one side thereof. The optical laminate of the present invention is typically provided in a roll-up manner by a winding device and is provided to a step of stacking an optical functional film (for example, a protective film) on the polarizing film side of the storage or laminate. Since the optical laminate of the present invention is dried in a state in which the adhesion of the cleaning liquid on the side of the resin substrate is reduced as described above, precipitation of iodide on the resin substrate side surface can be suppressed. As a result, even when the optical laminate thus obtained is rolled up in a roll, the deformation of the polarizing film caused by the precipitate (consequently leading to the irregular defect) can be suppressed.

The optical function film laminate (having the constitution of [resin substrate / polarizing film / optical function film]) in which the optical function film is laminated can be used as a polarizing plate as it is. Alternatively, the resin base material may be peeled from the optical functional film laminate, and another optical function film (for example, a protective film) may be laminated on the peeling surface thereof to form the optical function film / polarizing film / optical function film A polarizing plate may be obtained.

Example

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows.

1. Thickness

And measurement was conducted using a digital micrometer (product name: "KC-351C", manufactured by Anritsu).

2. Glass transition temperature (Tg)

And measured according to JIS K7121.

3. Water contact angle

Measured using a DM500 automatic contact angle meter manufactured by Kyowa Interface Science Co., Ltd., and analyzed using FAMAS (contact angle measurement add-in software).

4. Evaluation of irregularities

The polarizing films on the backlight side and the viewer side of a 32-inch TV (model number: LC32-SC1) manufactured by SHARP and a 32-inch TV manufactured by Panasonic (model number: THL32C3) were peeled off, Was bonded to the backlight side and the visual side using a pressure-sensitive adhesive. The liquid crystal display device was turned on in the dark room and the black display state was set to count the number of bright spots having a long diameter of 150 mu m or more in the visible area.

5. Measurement of water content on the resin substrate side surface of the laminate

The absorbing roll was brought into contact with the resin substrate side surface of the laminate for a certain period of time to absorb moisture, and then the weight was measured and the moisture amount per unit area was measured from the change in weight.

[Example 1]

As the resin base material, an amorphous polyethylene terephthalate (A-PET) film (trade name "NOVA CLEAR", thickness: 100 μm) having a water absorption rate of 0.60%, a Tg of 80 ° C and an elastic modulus of 2.5 GPa was used.

90 parts by weight of polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and 90 parts by weight of acetoacetyl-modified PVA (degree of saponification) were added to the corona- 1200, acetoacetyl modification degree: 4.6%, saponification degree: 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: GOSE PYMER Z200) was applied at 60 캜 and dried to obtain a PVA-based A resin layer was formed, and a laminate was produced. The water contact angle of the surface of the obtained laminate on the resin base material side was 60 °.

The resultant laminate was subjected to free-end uniaxial stretching (air assisted stretching) in an oven at 120 캜 at a stretch ratio of 1.8 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential velocities.

Subsequently, the laminate was immersed (insolubilization treatment) for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 占 폚.

Subsequently, the resultant was immersed in a dyeing bath (an iodine aqueous solution obtained by blending 0.2 parts by weight of iodine with 100 parts by weight of water and 1.0 part by weight of potassium iodide) at a liquid temperature of 30 DEG C for 60 seconds (dyeing treatment).

Subsequently, the resultant was immersed in a crosslinking bath (aqueous solution of boric acid obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at 30 占 폚 for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid at a liquid temperature of 70 占 폚 (an aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water and 5 parts by weight of potassium iodide) (Longitudinal direction) in the direction of drawing (underwater drawing). Here, the laminate was stretched until it broke (maximum stretch ratio 6.0 times).

Thereafter, the laminate was immersed in a cleansing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 DEG C (cleaning treatment).

Subsequently, as shown in Fig. 2, the cleaning liquid on the resin-material-side surface of the laminate was removed. More specifically, the laminated body returned from the cleansing bath was subjected to liquid removal using a pair of rubber-made liquid removing rolls. Subsequently, three absorbent rolls (a roll of 80 mm formed of a urethane sponge material) And the cleaning liquid was wiped off by rotating the roll in accordance with the conveyance of the laminate.

Thereafter, the laminate was conveyed in an oven kept at 60 占 폚 and heated for 5 minutes to produce an optical laminate having a polarizing film having a thickness of 5 占 퐉. Then, the obtained optical laminate was wound into a roll with a winding device. The amount of water (adhesion amount of the cleaning liquid) on the resin-material-side surface of the laminate immediately after the removal of the cleaning liquid (immediately after passing through the third absorption roll) was 0.0016 g / m 2.

[Example 2]

An optical laminate was produced in the same manner as in Example 1 except that the cleaning liquid on the resin-material-side surface of the laminate was removed by using an air blow device instead of the absorption roll, and the laminate was wound in a roll by a winding device. The cleaning liquid was removed in the following manner. That is, the laminated body returned from the cleansing bath was subjected to liquid removal using a pair of rubber-made liquid removing rolls, and then an air blow device (product number: VB-060-E2, manufactured by Hitachi, Ltd.) Was arranged so that the jetting angle of the air was about 45 deg. With respect to the resin base material side surface of the laminate and the distance between the jetting port and its surface was about 2 cm, and air was jetted. The pressure of the air was 23 kPa. The wind speed of the air was 30 m / min. The water content (adhesion amount of the cleaning liquid) on the resin-material-side surface of the laminate immediately after the cleaning liquid was removed (immediately after air injection) was 0.0045 g / m 2.

[Comparative Example 1]

An optical laminate was prepared in the same manner as in Example 1 except that the liquid was removed using a liquid removing roll and then the laminate was conveyed into the oven without removing the additional cleaning liquid, . The amount of water (the amount of adhesion of the cleaning liquid) on the resin-material-side surface of the laminate immediately before being conveyed to the oven was 0.0064 g / m 2.

Table 1 shows the evaluation of the unevenness defects in each of the examples and comparative examples. The quality in the panel visible area was evaluated according to the following criteria.

[Evaluation standard]

Good: When the liquid crystal display device is turned on in the dark room and the black display state is set, there is no bright spot having a long diameter of 150 占 퐉 or more in the visible region.

Bad: When the liquid crystal display device is turned on in the dark room and the black display state is set, there is a bright spot having a long diameter of 150 占 퐉 or more in the visible area.

Amount of cleaning liquid
(g / m 2) Number of irregularities Quality in panelist area Long diameter 150 ㎛ or more Long diameter less than 150 ㎛ Example 1 0.0016 0 10 Good Example 2 0.0045 0 60 Good Comparative Example 1 0.0064 20 60 Bad

As shown in Table 1, when the laminated body was dried in a state in which the amount of the cleaning liquid adhered on the resin-material-side surface of the laminate was reduced to a predetermined range, the irregular defect could be reduced.

The optical laminate of the present invention can be applied to liquid crystal panels such as liquid crystal televisions, liquid crystal displays, cellular phones, digital cameras, video cameras, portable game machines, car navigation systems, copying machines, printers, facsimiles, .

10:
11: resin substrate
12: polyvinyl alcohol-based resin layer (polarizing film)
20: Absorption roll
30: Liquid removal roll
40: blade
50: Air blow device
60: drying means

Claims (7)

A method for producing an optical laminate in which a polarizing film is laminated on a resin substrate,
A step of stretching and staining a laminate having the resin base material and a polyvinyl alcohol based resin layer formed on one side of the resin base material to produce a polarizing film on the resin base material,
A step of immersing the laminate in a cleaning liquid containing iodide to clean the laminate,
And removing the cleaning liquid so that the amount of the cleaning liquid deposited on the surface of the resin substrate side of the laminate is 0.005 g / m 2 or less, followed by drying the laminate. The method according to claim 1,
Wherein a water contact angle of the surface of the resin-material-side surface of the laminate is 60 ° to 80 °. The method according to claim 1,
Wherein the thickness of the polarizing film is 0.5 mu m to 15 mu m. The method according to claim 1,
Wherein the concentration of iodide in the cleaning liquid is 0.5 wt% to 10 wt%. The method according to claim 1,
Wherein the stretching comprises underwater stretching. The method according to claim 1,
Wherein the cleaning liquid removal on the resin-material-side surface of the laminate is carried out by wiping or spraying of gas. An optical laminate obtained by the manufacturing method according to claim 1.

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