TWI580574B - Method for manufacturing optical continuum - 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, and thus it is possible to attract attention in recent years in order 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 its main object is to provide a polarizing film having improved appearance problems such as unevenness defects. Method of making.

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 where 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 laminated body in such a state is wound into a roll and collected, since the thickness of the polarizing film is thin, it is estimated that the shape of the precipitate is easily transferred to the polarizing film to cause unevenness.

The present inventors have conducted research based on the above-described estimation, and as a result, it has been found that the surface of the resin substrate side of the layered body washed with the cleaning liquid containing the iodide is further washed to remove the iodide, thereby improving the unevenness defect. The problem of appearance, etc., thereby completing the present invention.

The method for producing an optical layered product 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 first cleaning step of immersing the layered body in a cleaning liquid containing an iodide, and cleaning only a second cleaning of the side surface of the resin substrate of the layered body a step; and a step of drying the above laminated body.

In one embodiment, the cleaning in the second cleaning step is performed by The side surface of the resin substrate of the laminate is brought into contact with the cleaning liquid.

In one embodiment, the cleaning in the second cleaning step is performed to maintain the cleaning liquid while sequentially contacting the resin substrate side surface with the cleaning liquid while transporting the laminated body in the longitudinal direction. The liquid bank is carried out.

In one embodiment, the liquid bank is provided by the laminated body conveyed in the longitudinal direction, a squeegee disposed so that the tip end is in sliding contact with the resin substrate side surface, and the laminated body facing the laminated body The water retaining wall is defined by the manner of standing, and both ends of the liquid bank in the width direction are open.

In one embodiment, the width of the squeegee is wider than the width of the laminate.

In one embodiment, the cleaning in the second cleaning step is performed by dispersing a cleaning liquid on the resin substrate side surface while conveying the laminate in the longitudinal direction.

In one embodiment, the stretching comprises stretching in water.

In one embodiment, after the second cleaning step, the liquid removal of the liquid adhering to the surface of the laminate is performed.

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

According to another aspect of the present invention, there is provided a device comprising: a squeegee disposed in a manner that a front end is slidably coupled to a long strip conveyed in a longitudinal direction; and the self-scraping plate is erected to face the long strip a water retaining wall; and a liquid supply mechanism for supplying a liquid to the liquid bank defined by the long strip, the scraper and the water retaining wall.

According to the present invention, the laminate having the polarizing film laminated on the resin substrate is washed with a cleaning liquid containing an iodide, and then the resin substrate side surface of the laminate is further washed, whereby iodide can be suppressed. Precipitation, as a result, can improve the appearance of defects such as unevenness.

10‧‧‧Layer

11‧‧‧Resin substrate

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

20‧‧‧Clean bath

21‧‧‧Conveying roller

30‧‧‧Distribution agency

40‧‧‧Liquid

50‧‧‧Scraper

52‧‧‧Extension

60‧‧ ‧ water retaining wall

70‧‧‧ liquid supply mechanism

80‧‧‧Recycling tank/recycling agency

90‧‧‧Liquid removal mechanism/rubber 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 second washing step.

Fig. 3A is a schematic view showing another example of the second washing step.

Fig. 3B is a schematic side view of the main part of the embodiment shown in Fig. 3A.

4 is a graph showing the number of uneven defects in Example 1 and Comparative Example 1.

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 polarizing the film; a first cleaning step of immersing the layered body in a cleaning liquid containing an iodide; a second cleaning step of cleaning only the surface of the resin substrate side of the layered body; and drying the layered body step. 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 laminate according to 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 the material for forming the resin substrate, any appropriate thermoplastic resin can be used. 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, it is particularly preferable to use an amorphous (hard to crystallize) polyethylene terephthalate resin. 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. The stretchability can be more excellent than when it is stretched in the air. 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 increased, for example, by using a crystallized material in which a modifying group is introduced into the forming material. The heat is adjusted accordingly. 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. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. 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. 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. In addition, the pH of the 4% by weight aqueous solution of the acetamidine-modified PVA is preferably It is 3.5~5.5.

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 from 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 another embodiment, the stretching is performed along the width direction of the elongated laminate. 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 may be based on the material of the resin substrate, The stretching method or the like is set to any appropriate value. 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 the water stretching method is employed, the liquid temperature of the stretching bath is preferably from 40 ° C to 85 ° C, more preferably from 50 ° C to 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, it is possible to impart rigidity and water resistance to the PVA-based resin layer, and to perform stretching well, and to produce excellent optical characteristics. Polarized film.

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, 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, 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 for stretching in boric acid water The preliminary stretching or the auxiliary stretching is hereinafter referred to as "air-assisted 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. As the resin substrate increases in the alignment property, the tensile strain becomes large, and stable stretching becomes difficult or fracture occurs. 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 body) 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. A method of immersing the layered body in the dyeing liquid is preferred. 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. Water resistance can be imparted to the PVA-based resin layer by performing insolubilization treatment. 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 system in which a dichroic substance is adsorbed and aligned. Resin film. 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, still more preferably 99.95% or more.

B. The first cleaning step

In the first cleaning step, the layered body in which the polarizing film is laminated on the resin substrate obtained in the polarizing film forming step 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. The second cleaning step

In the second cleaning step, only the resin substrate side surface of the laminate after the first cleaning is further washed. When the cleaning liquid (for example, water) is in contact with the side surface of the polarizing film, the hue changes, and sometimes the optical characteristics of the polarizing film are made. Influential. Such a hue change tends to be large in a polarizing film obtained by a stretching treatment in a water stretching manner.

The washing in the second washing step can be carried out by any appropriate method. This cleaning is preferably carried out by bringing the resin substrate side surface of the laminate into contact with the cleaning liquid. For example, in one embodiment, the cleaning is performed by dispersing a cleaning liquid on the resin substrate side surface while conveying the laminate in the longitudinal direction. Fig. 2 is a schematic view showing an example of the embodiment.

The long laminated body 10 is conveyed from the cleaning bath 20 by the conveying roller 21 along its longitudinal direction. The cleaning liquid is scattered on the surface of the resin base material layer 11 side of the laminated body 10 thus conveyed by a scattering mechanism (illustrated as a shower head in the drawing) 30. The cleaning liquid is preferably dispersed throughout the entire width of the side surface of the resin substrate 11. For example, the amount of washing liquid dispersed per unit area of the cleaning object laminate (m ²⁾ of 0.3L ~ 0.7L. The distribution mechanism may be set to one or more.

In the other embodiment, the cleaning is performed by providing the liquid bank for holding the cleaning liquid so that the resin substrate side surface is sequentially brought into contact with the cleaning liquid while the laminate is conveyed in the longitudinal direction. The liquid bank method is more preferable than the above-described scattering method in that it can be more uniformly cleaned or a point where the cleaning liquid can be appropriately prevented from being bypassed toward the polarizing film 12 side. 3A and 3B are respectively a schematic view showing an example of the embodiment and a schematic side view of the main part thereof.

The long laminated body 10 is conveyed from the cleaning bath 20 in the longitudinal direction thereof by the conveying roller 21. The conveying direction is preferably 70° to 90° with respect to the horizontal direction, More preferably in the direction of 80° to 90°. The liquid bank 40 is formed by the laminated body 10 thus conveyed, the squeegee 50 as a bank bottom, which is disposed so as to be in contact with the resin substrate 11 side surface of the laminated body 10, and the self-scraping plate 50 facing the laminated layer. The water retaining wall 60 in the manner of the body 10 defines that both ends of the liquid bank 40 in the width direction are open.

The cleaning liquid is supplied to a space defined by the laminated body 10, the squeegee 50, and the water retaining wall 60 by a liquid supply mechanism (illustrated as a nozzle), and a liquid bank 40 is formed. The cleaning liquid may be directly supplied to the space or may be supplied in contact with the laminated body 10. With such a liquid bank 40, the side surface of the resin substrate 11 of the laminated body 10 conveyed in the longitudinal direction comes into contact with the cleaning liquid held in the liquid bank in order, so that the surface can be uniformly washed. For example, the cleaning liquid supply amount per unit area of the cleaning object laminate (m ²⁾ of 0.1L ~ 0.3L.

Preferably, the self-feeding mechanism 70 continuously supplies the cleaning liquid. Thereby, the remaining cleaning liquid continuously overflows from the open end portion in the width direction of the liquid bank, so that the cleaning liquid can be appropriately replaced, and the concentration of the iodide in the cleaning liquid can be prevented from increasing. The liquid supply mechanism 70 may be provided by only one or a plurality of the liquid supply mechanisms 70. When only one is provided, it is preferably provided at substantially the center in the width direction. This is because the cleaning liquid can be appropriately replaced.

The length of the long side of the squeegee 50 (hereinafter, the length of the long side of the squeegee is referred to as the width of the squeegee) is equal to or greater than the width of the laminated body 10, and is preferably wider than the width of the laminated body 10. When the width of the squeegee 50 is wider than the width of the laminated body 10, the cleaning liquid overflowing from the end portion in the width direction of the liquid bank 40 travels to the squeegee extending portion 52 extending in the width direction of the liquid bank 40, and then falls. It is possible to prevent the surface of the polarizing film 12 side of the laminated body 10 from being bypassed. On the other hand, the length of the long side of the water retaining wall 60 (hereinafter, for convenience, the length of the long side of the water retaining wall is referred to as the width of the water retaining wall) is preferably smaller than the width of the laminated body 10, and more preferably the laminated body 10 The width is narrow from 5 mm to 15 mm (in the above case, the water retaining wall is preferably arranged such that both ends thereof are equidistant from the end of the laminated body). When the width of the laminated body 10, the squeegee 50, and the water retaining wall 60 satisfies such a relationship, the surface of the resin substrate 11 of the laminated body can be uniformly washed, and the cleaning liquid which overflows from the end portion in the width direction of the liquid bank 40 can be prevented. The surface of the polarizing film 12 of the laminated body 10 is wound around the side surface.

The angle formed by the squeegee 50 and the laminated body 10 (the angle formed by the squeegee 50 and the traveling direction of the laminated body 10) α may be any appropriate angle. The angle is preferably from 30 to 85, more preferably from 45 to 85. If it is such an angle, the liquid bank 40 can be suitably formed. In addition, it is possible to suitably prevent the cleaning liquid that has overflowed from the end portion in the width direction of the liquid bank 40 from bypassing the surface of the polarizing film 12 side of the laminated body 10.

The tip end portion of the squeegee 50 that is in contact with the side surface of the resin substrate 11 of the laminated body 10 is preferably subjected to a curved chamfering (so-called R chamfering). By performing the R chamfering process, scratching on the side surface of the resin substrate 11 can be prevented. The size of the R chamfer (curvature radius R) is preferably 0.5 mm or more, more preferably 0.5 mm to 1.5 mm.

The height, the arrangement position, and the like of the water retaining wall 60 are set to any appropriate values depending on the angle formed by the squeegee 50 and the laminated body 10, the amount of liquid to be supplied to the cleaning liquid, and the like.

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

The cleaning liquid overflowing from the liquid bank is preferably recovered by an arbitrarily arranged recovery mechanism 80. By providing the recovery mechanism 80, it is possible to prevent the iodide concentration of the iodide-containing cleaning liquid from being lowered.

The cleaning liquid used in the second cleaning step preferably contains no impurities which may precipitate after drying. Specifically, water such as distilled water, deionized water, or pure water, an alcohol such as ethanol, or the like can be used.

The squeegee 50, the liquid supply mechanism 70, and the recovery mechanism 80 are each fixed by any suitable fixture (not shown).

D. Drying step

In the drying step, the layered body after the second cleaning is dried. The drying of the laminate 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 a heating mechanism such as an oven. The drying temperature is, for example, 30 ° C to 100 ° C, preferably 50 ° C to 80 ° C. The drying time can be appropriately set depending on the drying temperature, for example, 10 seconds to 10 minutes.

E. Other steps

The production method of the present invention may further comprise the step of removing the liquid adhering to the surface of the laminate after the second cleaning step and before the drying step. Even when a small amount of iodide remains on the surface of the resin substrate side of the laminate after the second cleaning, the amount of residue can be further reduced by performing liquid removal. In addition, the drying efficiency performed later can be improved.

In FIG. 2 and FIG. 3A and FIG. 3B, as the liquid removal mechanism 90, one is used. For the liquid removal roller. As the liquid removing roller, a rubber roller having a crown shape can be preferably used. The crown amount (the difference in outer diameter (mm) between the end portion of the roller and the center) is, for example, 2 to 10, preferably 3 to 10, more preferably 3 to 7. The liquid removal mechanism can also be a blower, a scraper, or the like.

F. Optical laminate

The optical layered body of the present invention obtained through the above drying step is provided with a resin substrate and a polarizing film formed on one side thereof. The optical layered body of the present invention is typically wound into a roll shape by winding, and is stored in a step of laminating an optical functional film (for example, a protective film) on the side of the polarizing film of the laminated body. As described above, the optical layered body of the present invention is dried while reducing the adhesion of the iodide to the resin substrate side surface, so that the precipitation of iodide on the resin substrate side surface can be suppressed. As a result, even when the obtained optical layered body is wound into a roll shape, deformation of the polarizing film by the precipitated matter can be suppressed (as a result of the deformation, unevenness defects are caused).

An optical functional film laminate having a structure of an optical functional film (having a structure of [resin substrate/polarizing film/optical functional film)) can be directly used as a polarizing plate. Alternatively, the resin substrate is peeled off from the optical functional film laminate, and a polarizing plate having a structure of [optical functional film/polarizing film/optical functional film] is obtained in the other optical functional film (for example, a protective film) of the peeling layer.

G. device

According to another aspect of the present invention, there is provided a device comprising: a squeegee disposed in a manner that a front end is slidably coupled to a long strip conveyed in a longitudinal direction; and the self-scraping plate is erected to face the long strip Water retaining wall; A liquid supply mechanism for supplying liquid from a liquid bank defined by a long strip, a squeegee and a water retaining wall. According to this device, it is possible to uniformly contact only one surface of the sheet with a desired liquid while conveying the elongated sheet. Therefore, for example, it is possible to suitably use only one side of the long film (for example, a surface to which foreign matter, dirt, or the like adheres) while the long film is being conveyed. The respective constituent members of the apparatus of the present invention and their configurations are as described in the above item C.

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. Evaluation of bump defects

A black plate (extinction) is placed on the console, and an optical laminate is placed thereon. When the optical layered body is irradiated with the light of the fluorescent lamp, the number of bright spots that can be visually recognized is counted as a concave-convex defect (the brightness on the stage at the time of inspection is 1300 to 3000 Lx).

4. Evaluation of scratches

A black plate (extinction) is placed on the console, and an optical laminate is placed thereon. The optical laminate was irradiated with the light of the fluorescent lamp, and at this time, the number of visible scratches was counted (the brightness on the stage at the time of inspection was set to 1300 to 3000 Lx).

5. Water contact angle

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

[Example 1 and Comparative 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. Product name "NOVA CLEAR", thickness: 100 μm, width: 2650 mm).

One side of the resin substrate was subjected to corona treatment (processing 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 70°.

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 blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (first cleaning treatment).

A squeegee (width:: 1800 mm) 50 such that the front end is slidably coupled to the laminated body 10 at an angle of 50°. A water-blocking wall 60 (width: 1600 mm) having a height of 20 mm which stands substantially perpendicularly at a distance of 8 mm to 10 mm from the front end of the squeegee 50 is provided on the surface of the squeegee 50. With such an arrangement, water removal on the surface of the resin substrate 11 side of the laminated body 10 up to 10 batches was carried out (Comparative Example 1). From the time when the processing of the 10 batches is completed, the pure water as the washing water is continuously supplied to the space water supply nozzles 70 defined by the laminated body 10, the squeegee 50, and the water retaining wall 60, thereby forming a liquid bank, and the liquid bank is formed by the liquid bank. The contact between the cleaning water and the laminate was washed with water on the side of the resin substrate 11 of the 11 or more batches of the laminate 10 (Example 1). Further, the washing water overflowing from the liquid bank is recovered in the recovery tank 80.

After the water removal by the above-mentioned squeegee or the water washing using the liquid bank, the rubber roller 90 having a crown amount of 5 is used for water removal.

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 laminate was taken up in a roll shape by a winding device.

[Embodiment 2]

An optical layered body was produced in the same manner as in Example 1 except that the rubber roller 90 having a crown amount of 2.3 was used for water removal.

[Comparative Example 2]

An optical laminate was produced in the same manner as in Comparative Example 1, except that the corner portion of the tip end of the blade 50 was subjected to R chamfering.

[Reference Example 1]

In the same manner as in the first embodiment, the first cleaning treatment was carried out, and the laminate was immersed in a pure water bath having a liquid temperature of 30 ° C and washed with water. As a result, the formation component of the polarizing film was eluted, and a change in hue occurred.

The transition of the number of uneven defects in the optical layered body obtained by the continuous production of Example 1 and Comparative Example 1 is shown in Fig. 4 . In addition, various embodiments and ratios The evaluation of the unevenness and the scratches in the optical layered body obtained in the comparative example is shown in Table 1.

In the case of the unevenness defect, the number of defects per unit length (m) of the laminate was less than three, and it was evaluated as good, and the case where the number of defects was three or more was evaluated as defective.

As shown in Table 1 and FIG. 4, by selectively cleaning the side surface of the resin substrate of the laminate, the occurrence of unevenness defects can be remarkably reduced without affecting the polarizing film.

Industrial availability

The optical laminate of the present invention can be suitably used as a liquid crystal panel for a liquid crystal television, a liquid 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 the like. An antireflection film of an organic EL device.

10‧‧‧Layer

11‧‧‧Resin substrate

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

20‧‧‧Clean bath

21‧‧‧Conveying roller

40‧‧‧Liquid

50‧‧‧Scraper

60‧‧ ‧ water retaining wall

70‧‧‧ liquid supply mechanism

80‧‧‧Recycling tank

90‧‧‧Liquid removal mechanism

Claims (6)

A manufacturing method is 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 first washing step of immersing the layered body in a cleaning liquid containing an iodide, and cleaning only the resin substrate side of the layered body a second cleaning step of the surface; and a step of drying the laminated body; and cleaning the second cleaning step by sequentially transporting the side surface of the resin substrate while cleaning the laminated body in the longitudinal direction The liquid contact is provided in a liquid bank for holding the cleaning liquid, and the liquid bank is provided by the laminated body that is transported in the longitudinal direction, and the scraper that is disposed so that the tip end is in sliding contact with the resin substrate side surface, and The squeegee is defined by a water retaining wall that rises toward the laminated body, and both ends of the liquid levee in the width direction are open. The manufacturing method of claim 1, wherein the width of the squeegee is wider than a width of the laminated body. The manufacturing method of claim 1, wherein the stretching comprises stretching in water. The manufacturing method of claim 1, wherein the liquid removal of the liquid adhering to the surface of the layered body is performed after the second cleaning step. An optical laminate obtained by the production method of claim 1. A device comprising: a squeegee disposed in a manner that a front end is slidably coupled to a long strip conveyed in a longitudinal direction; a water retaining wall that rises from the squeegee in a manner to face the long strip; and The liquid supply mechanism for supplying liquid to the liquid bank defined by the long strip, the scraper and the water retaining wall.