TWI570462B - Manufacturing method of optical laminated body - Google Patents

Description

Optical laminate manufacturing method

The present invention relates to a method of producing an optical layered body having a polarizing film.

Background technique

In a liquid crystal display device which is a representative image display device, a polarizing film is disposed on both sides of a liquid crystal cell due to an image forming method. As a method of producing a polarizing film, for example, a method of stretching a laminate having a resin base material and a polyvinyl alcohol (PVA) resin layer, followed by performing a dyeing treatment to obtain a polarizing film on a resin substrate is proposed. (For example, Japanese Laid-Open Patent Publication No. 2000-338329). According to such a method, a polarizing film having a small thickness can be obtained. Therefore, it is advantageous in recent years to reduce the thickness of the image display device.

However, the polarizing film produced using the above resin substrate may have an appearance problem such as unevenness.

Summary of invention

The present invention has been made to solve the above problems, and a main object thereof is to provide a method for producing a polarizing film having improved appearance problems such as unevenness defects.

The inventors of the present invention conducted research on the above-mentioned unevenness and the like, and as a result, the mechanism of occurrence is as follows. In other words, the polarizing film is produced by stretching and dyeing a laminate having a resin substrate and a PVA-based resin layer, and then washing it with a cleaning liquid containing an iodide, and finally drying. When drying is performed in a state in which the cleaning liquid containing the iodide remains on the surface of the laminated body, the surface of the resin substrate side having a higher degree of hydrophobicity is iodine than the surface of the PVA-based resin layer (polarizing film) side. The compound precipitates at a large particle size. Then, when the laminate in this state is conveyed by a conveyance roller or wound into a roll, the thickness of the polarizing film is thin, so that the shape of the precipitate is easily transferred to the polarizing film to cause unevenness. .

The inventors of the present invention conducted research based on the above-described estimation, and found that the amount of the cleaning liquid adhering to the resin substrate side surface of the laminate is adjusted to a predetermined range by washing with a cleaning liquid containing an iodide. Then, drying is performed to improve the appearance of defects such as unevenness, and the present invention has been completed.

The method for producing an optical layered body in which a polarizing film is laminated on a resin substrate of the present invention comprises the steps of: stretching a laminate having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate; a step of preparing a polarizing film on the resin substrate, a step of immersing the layered body in a cleaning liquid containing an iodide for cleaning, and removing the cleaning liquid to clean the side surface of the resin substrate of the layered body The amount of the liquid adhered was 0.005 g/m ² or less, and then the layered body was dried.

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

In one embodiment, the polarizing film has a thickness of 0.5 μm to 15 μm .

In one embodiment, the iodide concentration in the cleaning liquid is from 0.5% by weight to 10% by weight.

In one embodiment, the stretching comprises stretching in water.

In one embodiment, the removal of the cleaning liquid on the resin substrate side surface of the laminate is performed by wiping or gas blowing.

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

According to the present invention, the layered body in which the polarizing film is laminated on the resin substrate is washed with a cleaning liquid containing an iodide, and then the amount of the cleaning liquid on the resin substrate side surface of the laminate is adjusted to a predetermined value. The range is then dried to suppress the precipitation of iodide, and as a result, the appearance problem such as unevenness can be improved.

10‧‧‧Layer

11‧‧‧Resin substrate

12‧‧‧Polyvinyl alcohol resin layer (polarizing film)

20‧‧‧Water supply roller; suction roller

30‧‧‧Removal roller

40‧‧‧Scraper

50‧‧‧Blowing device

60‧‧‧Drying agency

100‧‧‧clean bath

110‧‧‧Conveying roller

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial cross-sectional view showing a laminate according to a preferred embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a drying step of removing the cleaning liquid on the side surface of the resin substrate of the laminate by wiping.

3 is a schematic view showing an example of a drying step of removing the cleaning liquid on the side surface of the resin substrate of the laminate by wiping.

4 is a schematic view showing an example of a drying step of removing the cleaning liquid on the side surface of the resin substrate of the laminate by gas blowing.

Form for implementing the invention

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

The method for producing an optical layered body of the present invention comprises the steps of: stretching and dyeing a layered body having a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and producing the layered body on the resin substrate a step of immersing the layered body in a cleaning liquid containing an iodide for cleaning; and removing the cleaning liquid so that the amount of the cleaning liquid adhered to the resin substrate side surface of the layered body is 0.005 g/m ² Hereinafter, the step of drying the above laminated body is then carried out. Hereinafter, each step will be described.

A. Step of making polarizing film

A-1. Laminated body

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial cross-sectional view showing a laminated body in accordance with a preferred embodiment of the present invention. The laminated body 10 has a resin base material 11 and a polyvinyl alcohol-based resin layer 12. The laminated body 10 is produced by forming the polyvinyl alcohol-based resin layer 12 on the elongated resin substrate 11. As a method of forming the polyvinyl alcohol-based resin layer 12, any appropriate method can be employed. 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 a PVA-based resin layer 12.

As a material for forming the above resin substrate, any suitable As a thermoplastic resin. Examples of the thermoplastic resin include an ester resin such as a polyethylene terephthalate resin, a cycloolefin resin such as a norbornene resin, an olefin resin such as polypropylene, a polyamine resin, and a poly A carbonate resin, a copolymer resin thereof or the like. Among them, a norbornene-based resin and an amorphous polyethylene terephthalate-based resin are preferable.

In one embodiment, an amorphous (uncrystallized) polyethylene terephthalate resin is preferably used. Among them, an amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further comprising isophthalic acid as a dicarboxylic acid, and further comprising cyclohexane dimethanol as a diol. Things.

When the underwater stretching method is used for the stretching described later, the resin substrate absorbs water, and the water acts as a plasticizer, and plasticization can be performed. As a result, the tensile stress can be greatly reduced, and the stretching can be performed at a high magnification, and the stretchability can be more excellent than that in the air stretching. As a result, a polarizing film having excellent optical characteristics can be produced. In one embodiment, the water absorption of the resin substrate is preferably 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, and more preferably 1.0% or less. By using such a resin substrate, it is possible to prevent problems such as a significant decrease in dimensional stability during production and deterioration in appearance of the obtained polarizing film. Further, it is possible to prevent the substrate from being broken when the water is stretched or the PVA-based resin layer from being peeled off from the resin substrate. Further, the water absorption rate of the resin substrate is adjusted, for example, by introducing a modifying group into the forming material. The water absorption rate is a value obtained in accordance with JIS K 7209.

The glass transition temperature (Tg) of the resin substrate is preferably 170 ° C or lower. By using such a resin substrate, crystallization of the PVA-based resin layer can be suppressed, and the stretchability of the laminate can be sufficiently ensured. Further, in consideration of plasticization of the resin base material using water and good stretching in water, it is more preferably 120 ° C or lower. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 ° C or higher. When the coating liquid containing the PVA-based resin is applied and dried by using such a resin substrate, it is possible to prevent problems such as deformation of the resin substrate (for example, occurrence of irregularities, slacks, wrinkles, etc.), and it can be favorably produced. Laminated body. Further, the stretching of the PVA-based resin layer can be favorably performed at a suitable temperature (for example, about 60 ° C). In another embodiment, when the coating liquid containing a PVA resin is applied and dried, the glass transition temperature of less than 60 ° C may be used as long as the resin substrate is not deformed. Further, the glass transition temperature of the resin substrate can be adjusted, for example, by heating and heating the crystallized material into which the modifying group is introduced 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 from 20 μm to 300 μm, more preferably from 50 μm to 200 μm. When it is less than 20 μm, formation of a PVA-based resin layer becomes difficult. When it exceeds 300 μm, for example, in water drawing, it takes a long time for the resin substrate to absorb water, and stretching requires an excessive load.

As the PVA-based resin forming the PVA-based resin layer, any appropriate resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer Got it. The degree of saponification of the PVA-based resin is usually from 85 mol% to 100 mol%, preferably from 95.0 mol% to 99.95 mol%, and further preferably from 99.0 mol% to 99.93 mol%. The degree of saponification can be determined in accordance with JIS K 6726-1994. By using such a saponification degree PVA-based resin, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, gelation occurs.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually from 1,000 to 10,000, preferably from 1200 to 5,000, further preferably from 1,500 to 4,500. Further, the average degree of polymerization can be determined in accordance with JIS K 6726-1994.

The coating liquid is typically a solution obtained by dissolving the PVA-based resin in a solvent. Examples of the solvent include polyhydric alcohols such as water, dimethyl hydrazine, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, and trimethylolpropane. And amines such as ethylenediamine and diethylenetriamine. These may be used singly or in combination of two or more. Among them, water is preferred. The PVA-based resin concentration of the solution is preferably from 3 parts by weight to 20 parts by weight per 100 parts by weight of the solvent. If it is such a resin concentration, a uniform coating film which is in close contact with the resin base material can be formed.

An additive may be blended in the coating liquid. Examples of the additive include a plasticizer, a surfactant, and the like. 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 additives may be used to further improve the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer. Moreover, as an additive, the easy-adhesion component is mentioned, for example. By using an easy-adhesive component, the adhesion between the resin substrate and the PVA-based resin layer can be improved. Sex. As a result, for example, it is possible to suppress problems such as peeling of the PVA-based resin layer from the substrate, and it is possible to satisfactorily perform dyeing and stretching in water as described later.

As the above-mentioned easy-adhesive component, for example, a modified PVA such as an ethylene oxide-modified PVA can be used. As the ethyl acetonitrile-modified PVA, a polymer having at least a repeating unit represented by the following formula (I) can be preferably used.

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

The degree of saponification of the ethyl acetate-modified PVA is preferably 97 mol% or more. Further, the pH of the 4% by weight aqueous solution of the acetamidine-modified PVA is preferably from 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, and more preferably 5% by weight or more. On the other hand, the amount of the modified PVA added is preferably 30% by weight or less.

As a coating method of a coating liquid, any appropriate method can be employ|adopted. For example, 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 (such as a comma coating method), and the like can be given.

The application and drying temperature of the coating liquid is preferably 50 ° C or higher.

The thickness of the PVA-based resin layer before stretching is preferably from 3 μm to 40 μm. More preferably, it is 5 μm to 20 μm.

Before the formation of the PVA-based resin layer, the resin substrate may be subjected to a surface treatment (for example, corona treatment or the like), or an easy-adhesion layer may be formed on the resin substrate. Among them, an easy-adhesion layer (coating treatment) is preferably formed. As a material for forming the easy-adhesion layer, for example, an acrylic resin, a polyvinyl alcohol-based resin, or the like can be 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 ethyl acetylated group-modified PVA can be mentioned. Further, the thickness of the easy-adhesion layer is preferably set to about 0.05 to 1 μm. 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, it is possible to suppress problems such as peeling of the PVA-based resin layer from the substrate, and it is possible to satisfactorily perform dyeing and stretching in water as described later.

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

A-2. Stretching of laminated body

As the stretching method of the laminate, any appropriate method can be employed. Specifically, it may be a fixed end drawing or a free end drawing (for example, a method of uniaxially stretching a laminate body between rolls having different circumferential speeds). Preferably, the free end is stretched.

The stretching direction of the laminate can be appropriately set. In one embodiment, the stretching is performed along the longitudinal direction of the elongated laminate. In the above case, a method of stretching the laminated body between rolls having different circumferential speeds is typically employed. In other embodiments, along a long strip of laminate Stretching in the width direction of the body. In the above case, a method of stretching using a tenter stretching machine is typically employed.

The stretching method is not particularly limited, and may be an air stretching method or an underwater stretching method. It is preferably a water stretching method. The stretching method in the water can be carried out at a temperature lower than the glass transition temperature (typically about 80 ° C) of the resin substrate or the PVA-based resin layer, and the PVA-based resin layer can be prevented from crystallizing. And stretch at a high magnification. As a result, a polarizing film having excellent optical characteristics can be produced.

The stretching of the laminate may be carried out in one stage or in multiple stages. In the case of performing in multiple stages, for example, the above-mentioned free end stretching and fixed end stretching may be combined, and the above-described underwater stretching method and aerial stretching method may be combined. In addition, when it progresses in multiple stages, the draw ratio (maximum draw ratio) of the laminated body mentioned later is the product of the draw ratio of each stage.

The stretching temperature of the laminate can be set to any appropriate value depending on the material to be formed of the resin substrate, the stretching method, and the like. When the air stretching method is employed, the stretching temperature is preferably at least the glass transition temperature (Tg) of the resin substrate, and further preferably the glass transition temperature (Tg) of the resin substrate is +10 ° C or more, particularly preferably Tg. +15 ° C or more. 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 it is possible to suppress defects caused by the crystallization (for example, to hinder the alignment of the PVA-based resin layer by stretching).

When using the water stretching method, the liquid temperature of the stretching bath is preferably 40 °C~85°C, more preferably 50°C~85°C. If it is such a temperature, the dissolution of the PVA-based resin layer can be suppressed, and stretching can be performed at a high magnification. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is related to the formation of the PVA-based resin layer, and is preferably 60 ° C or higher. In the above case, when the stretching temperature is lower than 40 ° C, even if plasticization of the resin base material using water is considered, there is a possibility that the stretching cannot be performed satisfactorily. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and the inability to obtain excellent optical characteristics. The immersion time of the laminate in the stretching bath is preferably from 15 seconds to 5 minutes.

When the water stretching method is employed, it is preferred to carry out stretching (boring in water by boiling) by immersing the layered body in an aqueous boric acid solution. By using a boric acid aqueous solution as the stretching bath, the PVA-based resin layer can be imparted with rigidity to withstand the tension applied during stretching and water resistance to water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and stretching can be performed favorably, and a polarizing film having excellent optical characteristics 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 from 1 part by weight to 10 parts by weight per 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. Further, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent in addition to boric acid or borate may be used.

When a dichroic substance (typically iodine) is adsorbed on the PVA-based resin layer in advance by dyeing as described later, it is preferred to incorporate an iodide in the stretching bath (aqueous boric acid solution). By doping the iodide, iodine elution adsorbed on 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, cesium iodide, calcium iodide, tin iodide, and titanium iodide. Wait. Among them, potassium iodide is preferred. The concentration of the iodide is preferably from 0.05 part by weight to 15 parts by weight, more preferably from 0.5 part by weight to 8 parts by weight, per 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 a stretching method in water (stretching in boric acid water). In the present specification, the "maximum stretching ratio" refers to the stretching ratio immediately before the fracture of the laminate, and the stretching ratio at which the laminate is broken, and is 0.2 lower than the value.

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

By combining air-assisted stretching, it is sometimes possible to stretch the laminate at a higher magnification. As a result, a polarizing film having more excellent optical characteristics (for example, a degree of polarization) can be produced. For example, when a polyethylene terephthalate resin is used as the resin substrate, it is possible to suppress the resin when combined with air-assisted stretching and boric acid water stretching in comparison with stretching by boric acid in water alone. The alignment of the substrate is simultaneously stretched. The resin substrate is improved with its alignment When the tensile strength is high, the tensile strength becomes difficult, or the stretching becomes difficult or breaks. Therefore, the laminate can be stretched at a higher magnification by suppressing the alignment of the resin substrate while stretching.

Further, by combining air-assisted stretching, the alignment property of the PVA-based resin can be improved, whereby the orientation of the PVA-based resin can be improved even after stretching in boric acid water. Specifically, it is presumed that the PVA-based resin is easily cross-linked with boric acid when it is stretched in boric acid water by the air-assisted stretching in advance, and is pulled in a state where boric acid becomes a connection point. When stretched, the PVA-based resin is also highly oriented after stretching in boric acid water. As a result, a polarizing film having excellent optical characteristics (for example, a degree of polarization) can be produced.

The draw 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 from 95 ° C to 150 ° C. Moreover, the maximum stretching ratio in the case of the combined air-assisted stretching and the above-mentioned boric acid water stretching is preferably 5.0 times or more, more preferably 5.5 times or more, and still more preferably 6.0 times or more with respect to the original length of the laminated body.

A-3. Dyeing

The dyeing of the above laminated body is typically carried out by adsorbing a dichroic substance (preferably iodine) on the PVA-based resin layer. Examples of the adsorption method include a method of immersing a PVA-based resin layer (layered product) in a dyeing liquid containing iodine, a method of applying the dyeing liquid on a PVA-based resin layer, and spraying the dyeing liquid to a PVA system. A method of a resin layer or the like. Preferably, the laminate is immersed in The method of dyeing liquid. This is because iodine can be adsorbed well.

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

The dyeing treatment can be carried out at any suitable timing. When the above water stretching is carried out, it is preferably carried out before stretching in water.

A-4. Other treatment

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

The insolubilization treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. By implementing insolubilization treatment, Water resistance is imparted to the PVA-based resin layer. The concentration of the aqueous boric acid solution is preferably from 1 part by weight to 4 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilizing bath (aqueous boric acid solution) is preferably from 20 ° C to 50 ° C. The insolubilization treatment is preferably carried out before the above-described stretching in water and the above dyeing treatment.

The crosslinking treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. Water resistance can be imparted to the PVA-based resin layer by performing the crosslinking treatment. The concentration of the aqueous boric acid solution is preferably from 1 part by weight to 5 parts by weight per 100 parts by weight of water. Further, when the crosslinking treatment is carried out after the above dyeing treatment, it is preferred to further incorporate an iodide. By doping the iodide, iodine elution adsorbed on the PVA-based resin layer can be suppressed. The blending amount of the iodide is preferably from 1 part by weight to 5 parts by weight per 100 parts by weight of the water. Specific examples of the iodide are as described above. The liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably from 20 ° C to 60 ° C. The crosslinking treatment is preferably carried out before stretching in the above water. In a preferred embodiment, the dyeing treatment, the crosslinking treatment, and the stretching in water are sequentially performed.

A-5. Polarizing film

The polarizing film is substantially a PVA-based resin film in which a dichroic substance is adsorbed and aligned. 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, and more preferably 1.5 μm or more. The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The monomer transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, and 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, further preferably 99.95% or more.

B. Cleaning steps

In the cleaning step, the layered body in which the polarizing film is laminated on the resin substrate obtained in the production step of the polarizing film is immersed in a cleaning liquid containing iodide and washed. Specifically, for example, as described above, the iodide is potassium iodide. In one embodiment, the cleaning solution is an aqueous potassium iodide solution. The concentration of the iodide in the cleaning liquid is preferably 0.5% by weight to 10% by weight, more preferably 0.5% by weight to 5% by weight, still more preferably 1% by weight to 4% by weight. The temperature of the cleaning liquid is usually from 10 ° C to 50 ° C, preferably from 20 ° C to 35 ° C. The immersion time is usually from 1 second to 1 minute, preferably from 10 seconds to 1 minute. When the cleaning is insufficient, boric acid may be precipitated from the obtained polarizing film.

C. Drying step

In the drying step, the cleaning liquid is removed so that the amount of the cleaning liquid adhering to the resin substrate side surface of the layered product washed in the cleaning step is 0.005 g/m ² or less, preferably 0.003 g/m ² or less, more preferably It is 0.002 g/m ² or less, and then the laminated body is dried. When a laminate having a cleaning liquid adhered to the surface of the resin substrate side in an amount of more than 0.005 g/m ² is subjected to a drying treatment, uneven defects of a visible size (for example, uneven defects having a diameter of 150 μm or more) may be generated. .

Moreover, after the completion of the washing step, the time until the drying treatment is generally within 60 seconds, and the conveyance of the laminated body is performed at room temperature, so that it is not necessary to consider the cleaning liquid caused by natural drying or the like. The concentration changes, but the removal of the above cleaning liquid is preferably carried out immediately after the layered body passes through the cleaning bath (for example, within 30 seconds, preferably within 15 seconds).

The removal of the above cleaning liquid can be carried out by any appropriate method. The removal of the cleaning liquid can be performed, for example, by wiping the cleaning liquid on the resin substrate side surface of the laminate or by blowing a gas onto the surface.

The wiping of the cleaning liquid can be performed by any appropriate wiping mechanism such as a water absorbing roller, a liquid removing roller, or a squeegee. The wiping mechanism may be used alone, or a plurality of wiping mechanisms may be used, or two or more wiping mechanisms may be used in combination. FIG. 2 and FIG. 3 are schematic views each showing an example of a drying step of the cleaning liquid for removing the resin substrate side surface of the laminate by wiping.

When the water absorbing roller is used (see FIG. 2), for example, the water absorbing roller 20 and the surface of the resin substrate 11 of the laminated body 10 are rotated so as to rotate along with the conveyance of the laminated body 10 immersed in the cleaning bath 100. contact. For the water absorbing roller, typically, the surface is formed of a porous material such as a sponge, a nonwoven fabric, or a woven fabric. Examples of the sponge include a urethane sponge, a rubber sponge, and a polyolefin sponge. The roller diameter is, for example, 80 mm to 110 mm. Further, reference numeral 110 in the drawing is a conveying roller.

When the liquid removal roller is used (see FIGS. 2 and 3), for example, the pair of liquid removal rollers 30 are opposed to each other so as to sandwich the laminated body 10. The liquid removal roller 30 rotates while transporting the laminated body 10, and the laminated body 10 is pressed from the front and back surfaces, thereby performing liquid removal. The liquid removal roller is typically made of rubber. In addition, the liquid removal roller may have a crown shape. By having a crown shape, it is possible to uniformly remove the liquid throughout the width direction of the laminate.

When the squeegee 40 is used (refer to FIG. 3), representatively, the squeegee is disposed 40, the front end thereof is brought into sliding contact with the side surface of the resin substrate 11 of the above-mentioned laminated body 10 conveyed along the longitudinal direction. By disposing in this way, the water is wiped from the side surface of the resin substrate 10 by the squeegee 40 as the laminated body 10 is conveyed. Examples of the material for forming the squeegee include rubber, resin, metal, and the like. The portion in which the squeegee is in sliding contact with the above-mentioned laminated body can be chamfered into a curved shape from the viewpoint of avoiding scratches.

The gas blowing to the resin substrate side surface of the laminate can be carried out using a commercially available air blowing device. 4 is a schematic view showing an example of a drying step of removing the cleaning liquid on the side surface of the resin substrate of the laminate by gas blowing. The air blowing device 50 is disposed such that the air spray angle with respect to the resin substrate 11 side surface of the laminated body 10 is preferably 25 to 65 degrees. The conditions of the blowing can be appropriately set depending on the type of the resin substrate or 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. Further, as shown in the drawing, a wiping mechanism (illustrated as the water absorbing roller 20 and the liquid removing roller 30 in the drawing) and the air blowing device 50 may be used in combination.

The drying of the layered body after removing the cleaning liquid can be carried out by any appropriate drying method such as natural drying, air drying, heat drying, and hot air drying. It is preferred to use a heating and drying of the heating mechanism 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 can be appropriately set depending on the drying temperature, for example, 10 seconds to 10 minutes.

D. Optical laminate

The optical layered body of the present invention obtained through the above drying step includes a resin substrate and a polarizing film formed on one side thereof. Optical layered body of the invention The step of winding up into a roll shape by a winding device for storage or laminating an optical functional film (for example, a protective film) on the polarizing film side of the laminated body. As described above, since the optical layered body of the present invention is dried while reducing the adhesion of the cleaning liquid on the side surface of the resin substrate, precipitation of iodide on the surface of the resin substrate side can be suppressed. As a result, even when the obtained optical layered body is wound into a roll shape, deformation of the polarizing film due to the precipitates can be suppressed (as a result of the deformation, unevenness defects are caused).

An optical functional film laminate (having a structure of [resin substrate/polarizing film/optical functional film)) laminated with an optical functional film can be directly used as a polarizing plate. Alternatively, the resin substrate may be peeled off from the optical functional film laminate, and another optical functional film (for example, a protective film) may be laminated on the release surface to obtain a polarized light having a structure of [optical functional film/polarizing film/optical functional film]. board.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the examples. Moreover, the measuring method of each characteristic is as follows.

Thickness

The measurement was performed using a digital micrometer (manufactured by ANRITSU Co., Ltd., product name "KC-351C").

2. Glass transition temperature (Tg)

The measurement was carried out in accordance with JIS K 7121.

3. Water contact angle

The measurement was performed using an automatic contact angle meter DM500 manufactured by Kyowa Interface Science Co., Ltd., and FAMAS (contact angle measurement additional software) was used. analysis.

4. Evaluation of bump defects

The polarizing film on the backlight side and the viewing side of a 32-inch TV (model: LC32-SC1) manufactured by SHARP and a 32-inch TV (model: THL32C3) manufactured by Panasonic is peeled off, instead of the polarizing film, examples or comparisons are made using a binder. The optical laminate obtained in the example was adhered to the backlight side and the viewing side. The liquid crystal display device is turned on in the dark room to be in a black display state, and the number of bright dots having a long diameter of 150 μm or more in the viewing region is counted.

5. Determination of the moisture content of the side surface of the resin substrate of the laminate

The water absorbing roller 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 amount of water per unit area was measured in accordance with the amount of change in weight.

[Example 1]

As a resin substrate, an amorphous polyethylene terephthalate (A-PET) film (manufactured by Mitsubishi Chemical Corporation, Ltd.) having a long strip shape and a water absorption ratio of 0.60%, a Tg of 80 ° C, and an elastic modulus of 2.5 GPa was used. Trade name "NOVA CLEAR", thickness: 100 μm).

One side of the resin substrate was subjected to halo treatment (treatment conditions: 55 W ‧ min/m ² ), and at 60 ° C, 90 parts by weight of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetamidine were contained. Ethyl hydrazide-modified PVA (degree of polymerization: 1200, acetamidine modification degree: 4.6%, saponification degree: 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Co., Ltd., trade name "Gohsefimer Z200"), 10 parts by weight of an aqueous solution The surface was applied to the corona-treated surface and dried to form a PVA-based resin layer having a thickness of 10 μm to prepare a laminate. The water contact angle of the resin substrate side surface of the obtained laminate was 60°.

The obtained laminate was uniaxially stretched (air-assisted stretching) to 1.8 times in the longitudinal direction (longitudinal direction) between the rolls having different circumferential speeds in an oven at 120 °C.

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ° C for 30 seconds (insolubilization treatment).

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

Subsequently, the mixture was immersed 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 in 100 parts by weight of water) for 30 seconds (crosslinking treatment).

Then, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 ° C (an aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water and 5 parts by weight of potassium iodide) while being placed between rolls having different circumferential speeds. Uniaxial stretching (water stretching) is performed in the longitudinal direction (longitudinal direction). Here, the stretching was performed until the laminate was about to be broken (the maximum stretching ratio was 6.0 times).

Then, the laminate was immersed in a cleaning bath having a liquid temperature of 30 ° C (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).

Then, as shown in FIG. 2, the cleaning liquid on the resin substrate side surface of the laminate is removed. Specifically, a pair of rubber-made liquid removal rolls are used to remove the liquid layer from the cleaning bath, and then the tree with the laminated body Three water absorbing rolls (a roll of φ 80 mm formed of a urethane sponge material) were placed in contact with the side surface of the grease base material, and the rolls were rotated as the laminated body was conveyed, thereby wiping the washing liquid.

Thereafter, the laminate was conveyed in an oven maintained at 60 ° C and heated for 5 minutes to prepare an optical layered body having a polarizing film having a thickness of 5 μm. Next, the obtained optical layered body was taken up in a roll shape by a winding device. Further, immediately after the removal of the cleaning liquid (just after passing through the third water supply roller), the moisture content (the amount of the cleaning liquid adhered) on the resin substrate side surface of the laminate was 0.0016 g/m ² .

[Embodiment 2]

An optical layered product was produced in the same manner as in Example 1 except that the cleaning liquid was removed from the surface of the resin substrate by the air blasting device, and the winding device was wound up in a roll shape. The removal of the cleaning liquid is specifically carried out as follows. In other words, the liquid removal of the laminated body by the cleaning bath is performed by using a pair of rubber-removing rolls, and then the air injection angle is about 45° with respect to the resin substrate side surface of the laminated body, and the ejection port is used. An air blowing device (manufactured by Hitachi Industrial Equipment Systems Co., Ltd., product number "VB-060-E2") was placed in such a manner that the distance from the surface was about 2 cm, and air was sprayed. The pressure of the air is 23 kPa. In addition, the wind speed of the air was 30 m/min. Moreover, the moisture content (the amount of the cleaning liquid adhered) on the surface of the resin substrate side of the laminate immediately after the removal of the cleaning liquid (just after the air was sprayed) was 0.0045 g/m ² .

[Comparative Example 1]

An optical laminate was produced in the same manner as in Example 1 except that the liquid removal was carried out by using a liquid removal roller, and then the removal of the cleaning liquid was carried out in the same manner as in Example 1. Take a roll. The moisture content (the amount of the cleaning liquid adhered) on the resin substrate side surface of the laminate before being conveyed to the oven was 0.0064 g/m ² .

The evaluation of the unevenness defects in each of the examples and the comparative examples is shown in Table 1. Moreover, the quality in the panel viewing area was evaluated according to the following criteria.

[evaluation benchmark]

Good: When the liquid crystal display device is turned on in the dark room to make it appear in a black display state, there is no bright spot having a long diameter of 150 μ or more in the viewing area.

Defect: When the liquid crystal display device is turned on in the dark room to make it appear in the black display state, there is a bright spot having a long diameter of 150 μm or more in the viewing area.

As shown in Table 1, the laminate is dried in a state where the amount of the cleaning liquid on the resin substrate side surface of the laminate is lowered to a predetermined range, whereby the unevenness can be reduced.

Industrial availability

The optical laminate of the present invention can be suitably used as a liquid crystal television or a liquid A liquid crystal panel such as a crystal display, a mobile phone, a digital camera, a digital camera, a portable game machine, an automatic navigation system, a photocopying machine, a printer, a facsimile machine, a clock, an induction cooker, and an antireflection film of an organic EL device.

10‧‧‧Layer

11‧‧‧Resin substrate

12‧‧‧Polyvinyl alcohol resin layer (polarizing film)

20‧‧‧Water feed roller

30‧‧‧Removal roller

60‧‧‧Drying agency

100‧‧‧clean bath

110‧‧‧Conveying roller

Claims (6)

A manufacturing method of a method for producing an optical layered body in which a polarizing film is laminated on a resin substrate, comprising the steps of: laminating a resin substrate and a polyvinyl alcohol-based resin layer formed on one side of the resin substrate a step of forming a polarizing film on the resin substrate by stretching and dyeing, a step of immersing the layered body in a cleaning liquid containing an iodide for cleaning, and removing a cleaning liquid to form a resin substrate of the layered body The amount of the cleaning liquid adhering to the side surface is 0.005 g/m ² or less, and then the laminate is dried. The manufacturing method of claim 1, wherein the water contact angle of the resin substrate side surface of the laminate is 60 to 80. The manufacturing method of claim 1, wherein the polarizing film has a thickness of 0.5 μm to 15 μm. The method of claim 1, wherein the concentration of the iodide in the cleaning liquid is from 0.5% by weight to 10% by weight. The manufacturing method of claim 1, wherein the stretching comprises stretching in water. The method of claim 1, wherein the cleaning of the cleaning liquid on the resin substrate side surface of the laminate is performed by wiping or gas blowing.