KR102379795B1 - Method of manufacturing polarizing plate - Google Patents

Abstract

(Project) To provide a manufacturing method of a polarizing plate having an excellent external appearance.
(Solution) The method for producing a polarizing plate of the present invention comprises a step of forming a long resin substrate and a polyvinyl alcohol-based resin layer on one side of the resin substrate to obtain a laminate 10, and a polyvinyl alcohol-based resin layer. The process of dyeing, the process of extending|stretching the laminated body 10, the process of slitting the width direction edge part 10a of the laminated body 10 before extending|stretching, After dyeing and extending|stretching, a polyvinyl alcohol-type resin layer is elongate. The process of bonding the protective film of an upper part is included. The width of the laminated body 10 after extending|stretching respond|corresponds to the width|variety of the laminated body at the time of bonding.

Description

The manufacturing method of a polarizing plate {METHOD OF MANUFACTURING POLARIZING PLATE}

The present invention relates to a method for manufacturing a polarizing plate.

In a liquid crystal display device, which is a typical image display device, polarizing films are disposed on both sides of a liquid crystal cell due to the image formation method thereof. As a method for producing a polarizing film, for example, a method of obtaining a polarizing film on a resin substrate by stretching a laminate having a resin substrate and a polyvinyl alcohol (PVA)-based resin layer and performing dyeing treatment has been proposed ( For example, Patent Document 1). According to such a method, since a thin polarizing film is obtained, it attracts attention because it can contribute to thickness reduction of the image display apparatus in recent years.

By the way, normally, a protective film is pasted together, and the said polarizing film is used as a polarizing plate. When bonding a protective film together to the polarizing film (laminated body) formed on the said resin base material, there exists a problem that folds and wrinkles are easy to generate|occur|produce at an edge part. Then, before bonding a protective film, removing the edge part of a laminated body is proposed (patent document 2). However, according to such a method, there exists a problem that the external appearance of the polarizing plate obtained is inferior.

Japanese Laid-Open Patent Publication No. 2000-338329 Specification of Japanese Patent No. 5124704

This invention was made|formed in order to solve the said subject, and making it into the objective is providing the manufacturing method of the polarizing plate which has the outstanding external appearance.

The method for manufacturing a polarizing plate of the present invention includes a step of forming a long resin substrate and a polyvinyl alcohol-based resin layer on one side of the resin substrate to obtain a laminate, a step of dyeing the polyvinyl alcohol-based resin layer, and the A step of stretching the laminate, a step of slitting the end of the laminate in the width direction before the stretching, and a step of bonding a long protective film to the polyvinyl alcohol-based resin layer after the dyeing and stretching. , the width of the laminate after stretching corresponds to the width of the laminate at the time of bonding.

In one Embodiment, it slits so that the width|variety of the laminated body after the said extending|stretching may correspond to the width|variety of the said protective film.

In one embodiment, the said slit is performed before the said dyeing|staining.

In one embodiment, the process of winding up the said laminated body in roll shape is further included, and the said slit is performed after the winding up.

In one embodiment, the said extending|stretching is longitudinal uniaxial stretching.

In one embodiment, the said extending|stretching is underwater extending|stretching.

In one embodiment, the draw ratio of the said extending|stretching is 2.0 times or more.

In one embodiment, the said laminated body is extended|stretched in multiple steps.

In one embodiment, before the said slit, the said laminated body is extended|stretched beforehand.

According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the said manufacturing method.

ADVANTAGE OF THE INVENTION According to this invention, by slitting before extending|stretching, it is a bonding process with a protective film. WHEREIN: It can prevent effectively that a foreign material mixes between a PVA-type resin layer and a protective film. When the slit is carried out in the state in which the orientation of the PVA-type resin layer was increased by extending|stretching specifically, it will be easy to generate|occur|produce a burr at the slit end, and this burr may become a foreign material at the time of bonding. Moreover, the PVA-type resin layer of the state with high orientation may tear easily, and a slit may become difficult. Therefore, by slitting before extending|stretching, mixing of a foreign material and generation|occurrence|production of the bubble accompanying mixing of a foreign material can be effectively prevented, performing slitting favorably. As a result, a polarizing plate excellent in appearance can be obtained. In addition, if the above-mentioned wrinkles, folds, irregularities such as winding body, etc., and knurling are previously formed at the end of the laminate in the width direction, the knurling etc. can be removed before stretching, so stretching is carried out stably. can do.

1 is a partial cross-sectional view of a laminate according to an embodiment of the present invention.
It is an external appearance perspective view which shows an example of the slit process of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, although one Embodiment of this invention is described, this invention is not limited to these embodiment.

The manufacturing method of the polarizing plate of this invention forms a long resin base material and a PVA-type resin layer on one side of this resin base material, The process (lamination process) of obtaining a laminated body, The process of dyeing a PVA-type resin layer (dyeing process) And, the process of extending|stretching a laminated body (stretching process), the process of slitting the width direction edge part of a laminated body (slit process), And the process of bonding a long protective film to a PVA-type resin layer (bonding process). . Hereinafter, each process is demonstrated.

A. Lamination process

1 is a partial cross-sectional view of a laminate according to a preferred embodiment of the present invention. The laminate 10 has a resin substrate 11 and a polyvinyl alcohol-based resin layer 12 . The laminated body 10 is produced by forming the polyvinyl alcohol-type resin layer 12 in the elongate resin base material 11. As shown in FIG. Any suitable method may be employed as a method for forming the polyvinyl alcohol-based resin layer 12 . In one embodiment, on the resin base material 11, the coating liquid containing a polyvinyl alcohol-type resin (henceforth "PVA-type resin") is apply|coated, and by drying, the PVA-type resin layer 12 to form

Any suitable material may be employed as the material for forming the resin substrate. For example, ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, (meth)acrylic resins, polyamide resins, polycarbonate resins, and copolymer resins thereof can be heard Preferably, a polyethylene terephthalate-type resin is used. Among them, an amorphous polyethylene terephthalate-based resin is preferably used. Specific examples of the amorphous polyethylene terephthalate-based resin include a copolymer further containing isophthalic acid as a dicarboxylic acid, and a copolymer further containing cyclohexanedimethanol as glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 120°C or lower, more preferably 100°C or lower. It is because, when extending|stretching a laminated body, stretchability (in particular in underwater extending|stretching) can fully be ensured, suppressing crystallization of a PVA-type resin layer. As a result, a polarizing film having excellent optical properties (eg, polarization degree) can be produced. On the other hand, the glass transition temperature of a resin substrate becomes like this. Preferably it is 60 degreeC or more. In addition, a glass transition temperature (Tg) is a value calculated|required according to JISK7121.

The water absorption of the resin substrate is preferably 0.2% or more, more preferably 0.3% or more. Such a resin substrate can absorb water, and the water functions as a plasticizer and can be plasticized. As a result, the stretching stress can be significantly reduced, and the stretchability can be excellent. On the other hand, the water absorption of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, the problem that the dimensional stability of a resin base material falls remarkably at the time of manufacture, and the external appearance of the polarizing film obtained deteriorates can be prevented. In addition, it is possible to prevent breakage during stretching in water or peeling of the PVA-based resin layer from the resin substrate. In addition, water absorption is a value calculated|required according to JISK7209.

The thickness of the resin substrate is preferably 20 µm to 300 µm, and more preferably 50 µm to 200 µm. A surface modification process (for example, corona treatment etc.) may be given to the resin base material surface, and the easily bonding layer may be formed. According to such a process, the laminated body excellent in the adhesiveness of a resin base material and a PVA-type resin layer can be obtained.

Any suitable resin may be employed as the PVA-based resin forming the PVA-based resin layer. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of PVA-type resin is 85 mol% - 100 mol% normally, Preferably they are 95.0 mol% - 99.95 mol%, More preferably, they are 99.0 mol% - 99.93 mol%. Saponification degree can be calculated|required according to JISK6726-1994. By using the PVA-based resin having such a degree of saponification, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin may be appropriately selected according to the purpose. Average degree of polymerization is 1000-10000 normally, Preferably it is 1200-4500, More preferably, it is 1500-4300. In addition, an average degree of polymerization can be calculated|required according to JISK6726-1994.

As for the said coating liquid, the solution which melt|dissolved the said PVA-type resin in the solvent is used typically. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, ethylenediamine, and diethylenetriamine. and amines. These can be used individually or in combination of 2 or more types. Among these, preferably, it is water. The concentration of the PVA-based resin in the solution can be set to any appropriate value. For example, it is set according to the polymerization degree, saponification degree, etc. of PVA-type resin. The concentration of the PVA-based resin in the solution is, for example, 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent.

An additive may be contained in the said coating liquid. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. As a plasticizer, polyhydric alcohols, such as ethylene glycol and glycerol, are mentioned, for example. As surfactant, a nonionic surfactant is mentioned, for example. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. By using an easily bonding component, the adhesiveness of a resin base material and a PVA-type resin layer can be improved. As a result, for example, problems, such as a PVA-type resin layer peeling from a resin base material, can be suppressed, and dyeing and underwater extending|stretching mentioned later can be performed favorably. As a component for easy adhesion, modified PVA, such as acetoacetyl modified PVA, is used, for example.

Any suitable method can be employ|adopted as a coating method of a coating liquid. For example, the roll coat method, the spin coat method, the wire bar coat method, the dip coat method, the die coat method, the curtain coat method, the spray coat method, the knife coat method (comma coat method, etc.) etc. are mentioned. The application and drying temperature of the coating liquid is, for example, 20°C or higher, preferably 50°C or higher.

The thickness of a PVA-type resin layer becomes like this. Preferably they are 3 micrometers - 40 micrometers, More preferably, they are 3 micrometers - 20 micrometers. The width of the laminate can be set to any appropriate value. It is 1500 mm or more typically, Preferably they are 2000 mm - 5000 mm.

In one embodiment, the PVA-type resin layer (laminated body) is previously extended|stretched. For example, the PVA-type resin layer (laminated body) is extended|stretched in the longitudinal direction (for example, by an aerial stretching system). The draw ratios of the said extending|stretching are 1.5 times - 3.5 times, for example, Preferably they are 2.0 times - 3.0 times. Extending|stretching temperature is 95 degreeC - 150 degreeC, for example.

B. Dyeing process

The said dyeing is typically performed by dyeing|staining a PVA system resin layer with a dichroic substance. Preferably, it carries out by adsorbing a dichroic substance to a PVA-type resin layer. As the said adsorption method, for example, the method of immersing a PVA-type resin layer (laminated body) in the dyeing solution containing a dichroic substance, the method of coating the said dyeing solution to a PVA-type resin layer, The said dyeing solution is PVA The method of spraying on a system resin layer, etc. are mentioned. Preferably, it is a method of immersing a PVA-type resin layer in a dyeing solution. This is because dichroic substances can be adsorbed favorably.

Examples of the dichroic substance include iodine and organic dyes. These can be used individually or in combination of 2 or more types. The dichroic substance is preferably iodine. In the case of using iodine as the dichroic substance, the dyeing solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.1 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is preferable to mix|blend an iodide with iodine aqueous solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among these, preferably, it is potassium iodide. The blending amount of the iodide is preferably 0.02 parts by weight to 20 parts by weight, more preferably 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of water.

In order that the liquid temperature at the time of dyeing|staining of a dyeing liquid suppresses dissolution of PVA-type resin, Preferably they are 20-50 degreeC. In order to ensure the transmittance|permeability of a PVA-type resin layer for immersion time when making a dyeing solution immerse a PVA-type resin layer, Preferably they are 5 second - 5 minutes. In addition, dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the polarizing film finally obtained may become a predetermined range. In one embodiment, immersion time is set so that the polarization degree of the polarizing film obtained may become 99.98 % or more. In another embodiment, immersion time is set so that the single transmittance|permeability of the polarizing film obtained may be set to 40 % - 44 %.

C. Stretching process

Any suitable method can be employ|adopted as a extending|stretching method of a laminated body. Specifically, fixed-end stretching (eg, a method using a tenter stretching machine) may be used, or free-end stretching (eg, a method of uniaxial stretching by passing a laminate between rolls having different peripheral speeds) may be used. Moreover, simultaneous biaxial stretching (for example, the method using a simultaneous biaxial stretching machine) may be sufficient, and sequential biaxial stretching may be sufficient. Extending|stretching of a laminated body may be performed in one step, and may be implemented in multiple steps. When carrying out in multiple steps, the draw ratio (maximum draw ratio) of the laminated body mentioned later is the product of the draw ratios of each step.

The underwater stretching system performed while immersing a laminated body in a stretching bath may be sufficient as extending|stretching, and the air stretching system may be sufficient as it. Preferably, stretching in water is performed at least once, More preferably, stretching in air and stretching in water are combined. According to the underwater stretching, stretching can be performed 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 is stretched at a high magnification while suppressing its crystallization. can do. As a result, a polarizing film having excellent optical properties can be manufactured. In addition, when combining aerial stretching and underwater stretching, it is preferable to perform underwater extending|stretching after aerial stretching.

Any suitable direction can be selected as an extending|stretching direction of a laminated body. In one embodiment, it extends|stretches in the longitudinal direction of a long laminated body. Specifically, a laminate is conveyed in a longitudinal direction, and it is the conveyance direction (MD). In another embodiment, it extends|stretches in the width direction of a long laminated body. Specifically, the laminate is conveyed in the longitudinal direction, and it is the direction (TD) orthogonal to the conveyance direction (MD).

The extending|stretching temperature of a laminated body can be set to arbitrary appropriate values according to the forming material of a resin base material, an extending|stretching method, etc. When the aerial stretching method is employed, the stretching temperature is preferably not less than the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10°C or more, particularly preferably Tg. +15 ℃ or higher. On the other hand, the extending|stretching temperature of a laminated body becomes like this. Preferably it is 170 degrees C or less. By extending|stretching at such a temperature, it can suppress that crystallization of PVA-type resin advances rapidly, and the problem (for example, the orientation of the PVA-type resin layer by extending|stretching is hindered) by the said crystallization can be suppressed.

When an underwater extending|stretching system is employ|adopted as an extending|stretching system, Preferably the liquid temperature of a stretching bath is 40 degreeC - 85 degreeC, More preferably, it is 50 degreeC - 85 degreeC. If it is such a temperature, it can extend|stretch at a high magnification, suppressing melt|dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is, in relation to the formation of the PVA-based resin layer, preferably 60°C or higher. In this case, when extending|stretching temperature is less than 40 degreeC, even if it considers plasticization of the resin base material by water, there exists a possibility that it may not be able to extend|stretch favorably. On the other hand, as the temperature of the stretching bath becomes high, the solubility of the PVA-based resin layer increases, and there is a fear that excellent optical properties may not be obtained.

When the underwater stretching method is employed, the laminate is preferably immersed in an aqueous solution of boric acid for stretching (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, the rigidity which withstands the tension|tensile_strength applied at the time of extending|stretching, and the water resistance which does not melt|dissolve in water can be provided to a PVA-type resin layer. Specifically, boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution, and can be crosslinked with a PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be provided to a PVA-type resin layer, can be extended|stretched favorably, and the polarizing film which has the outstanding optical characteristic can be produced.

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

Preferably, iodide is mix|blended with the said stretching bath (boric acid aqueous solution). By mix|blending an iodide, the elution of the iodine made to adsorb|suck to the PVA-type resin layer can be suppressed. The specific example of an iodide is as above-mentioned. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.

The immersion time for the stretching bath of the laminate is preferably from 15 seconds to 5 minutes.

Preferably the draw ratio (maximum draw ratio) of a laminated body is 5.0 times or more with respect to the original length of a laminated body. Such a high draw ratio can be achieved, for example by employ|adopting the underwater extending|stretching system (boric acid underwater extending|stretching). The draw ratio by extending|stretching in water of a laminated body becomes like this. Preferably it is 2.0 times or more. In addition, in this specification, "maximum draw ratio" means the draw ratio just before the laminated body fractures|ruptures, the draw ratio at which a laminated body fracture|ruptures is confirmed separately, and it means a value 0.2 lower than that value.

Preferably, stretching in water is carried out after said dyeing.

D. Slit process

It is an external appearance perspective view which shows an example of a slit process. As shown in FIG. 2, the width direction edge part 10a, 10a of the laminated body 10 is slit along the longitudinal direction 20 of the laminated body 10 before the said extending|stretching. The slit piece 10a by which the slit was carried out contains the said resin base material and a PVA system resin layer. The slit width (width of the slit piece) is typically 10 mm to 1000 mm. In one embodiment, the slit width is set so that the width (width of the laminated body at the time of bonding mentioned later) of the laminated body after the said extending|stretching may correspond to the width|variety of the protective film mentioned later. Thus, by matching the width|variety of both, the wrinkle of the width direction edge part can be eliminated, and a laminated body and a protective film can be stuck together stably. When the stretching is longitudinal stretching (MD stretching), the slit width may be set in consideration of that the width of the laminate may be reduced by stretching. Specifically, the slit width can be set smaller than that for slitting after stretching.

By slitting before extending|stretching, it can prevent effectively that a foreign material mixes between a PVA-type resin layer and a protective film in the bonding process with the protective film mentioned later. When the slit is carried out in the state in which the orientation of the PVA-type resin layer was increased by extending|stretching specifically, it will be easy to generate|occur|produce a burr at the slit end, and this burr may become a foreign material at the time of bonding. Moreover, the PVA-type resin layer of the state with high orientation may tear easily, and a slit may become difficult. Therefore, by slitting before extending|stretching, mixing of a foreign material and generation|occurrence|production of the bubble accompanying mixing of a foreign material can be effectively prevented, performing slitting favorably. As a result, a polarizing plate excellent in appearance can be obtained. Moreover, since the above-mentioned wrinkles, folds, unevenness|corrugation, such as a winding body, and knurling, etc. can be removed before extending|stretching, when knurling is previously formed in the width direction edge part of a laminated body, extending|stretching can be performed stably.

In addition to the above, by slitting before extending|stretching, the polarizing film excellent in the optical characteristic can be obtained. Specifically, in the case of performing stretching (uniaxial stretching) by the circumferential speed difference between rolls, by slitting the ends in the width direction before stretching, L/W increases, and the orientation and optical properties of the resulting polarizing film can be remarkably improved. . In addition, L represents the distance between stretching (the distance to which tension|tensile_strength is added by the circumferential speed difference between rolls), and W represents the width|variety of a laminated body.

When extending|stretching of the said laminated body in multiple steps, before a slit, the laminated body may be extended|stretched beforehand as mentioned above. What is necessary is just to perform a slit before extending|stretching of the last step at least specifically,. By slitting and extending|stretching in the state which the orientation of a PVA-type resin layer raised by extending|stretching beforehand, the orientation and optical characteristic of the polarizing film obtained can further be improved. In this case, it is preferable to extend|stretch before a slit to such an extent that the said burr does not generate|occur|produce at the time of a slit. Moreover, it is preferable to set the draw ratio of the extending|stretching after a slit high. The draw ratio of the extending|stretching after a slit is 1.5 times or more, for example, Preferably it is 2.0 times or more. It is because the orientation and optical characteristic of the polarizing film obtained can further be improved by extending|stretching large in the state with said L/W high.

Preferably, the said slitting is performed before the said dyeing|staining. By slitting before dyeing, it is the bonding process with the protective film mentioned later WHEREIN: It can prevent more effectively that a foreign material mixes between a PVA-type resin layer and a protective film. Specifically, the PVA-based resin layer may be crosslinked by dyeing (eg, with iodine) to become brittle. When a slit is performed in such a state, slit dregs are easy to generate|occur|produce, and this slit dregs may become a foreign material at the time of bonding. Therefore, by slitting before dyeing, mixing of foreign substances and generation of air bubbles accompanying mixing of foreign substances can be prevented more effectively. As a result, a polarizing plate excellent in appearance can be obtained.

As a method for slitting the laminate, any suitable method may be employed. For example, the elongate laminate may be slit while wound in the longitudinal direction, or may be slit without being wound. As a slit (cutting) means, cutting blades, such as a round blade and a plate blade, and a laser are mentioned, for example. In addition, it is preferable that a slit piece is removed by winding-up or suction.

E. Others

As for the said laminated body, the process for making this PVA system resin layer into a polarizing film other than the above can be performed suitably. As a process for setting it as a polarizing film, an insolubilization process, a crosslinking process, a washing process, a drying process, etc. are mentioned, for example. In addition, the number of times, timing, order, etc. of these processes are not specifically limited.

The said insolubilization process is typically performed by immersing a PVA-type resin layer in boric-acid aqueous solution. By performing an insolubilization process, water resistance can be provided to a PVA-type resin layer. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of an insolubilization bath (boric acid aqueous solution) becomes like this. Preferably it is 20 degreeC - 50 degreeC. Preferably, an insolubilization process is performed before the said underwater extending|stretching or the said dyeing process.

The said crosslinking process is typically performed by immersing a PVA-type resin layer in boric-acid aqueous solution. By performing a crosslinking process, water resistance can be provided to a PVA-type resin layer. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Moreover, when performing a crosslinking process after the said dyeing|staining process, it is preferable to mix|blend iodide further. By mix|blending an iodide, the elution of the iodine made to adsorb|suck to the PVA-type resin layer can be suppressed. To [ the compounding quantity of an iodide / 100 weight part of water ], Preferably they are 1 weight part - 5 weight part. The specific example of an iodide is as above-mentioned. The liquid temperature of a crosslinking bath (boric acid aqueous solution) becomes like this. Preferably it is 20 degreeC - 60 degreeC. Preferably, the crosslinking treatment is performed before the above-mentioned underwater stretching. In a preferable embodiment, a dyeing process, a crosslinking process, and extending|stretching in water are implemented in this order.

The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution. The drying temperature in the said drying process becomes like this. Preferably it is 30 degreeC - 100 degreeC.

In one embodiment, the said laminated body is wound up in roll shape, it is set as a raw roll, and the said slit is performed after winding up. The winding tension is typically 300N to 600N. You may perform winding-up so that a PVA-type resin layer may become inside (the core material side), and you may perform so that a PVA-type resin layer may become an outside. When the said laminated body is wound up in the manufacturing process of a polarizing film, for example, if there exists a partial film thickness nonuniformity in a laminated body, winding|winding and wrinkles will generate|occur|produce. Such a problem is easy to generate|occur|produce in the width direction edge part. Therefore, by performing the said slit after winding-up, extending|stretching can be performed stably. Moreover, since it slits after winding-up, irrespective of the width|variety of the protective film to bond together, the original roll of the same width can be used and it can contribute to the improvement of productivity.

F. Bonding process

After the said dyeing|staining and extending|stretching, a protective film is stuck to the PVA-type resin layer (polarizing film) of a laminated body. Specifically, a long protective film is bonded to the PVA-based resin layer in parallel with each other in the longitudinal direction. In one embodiment, the width|variety of the laminated body after the said extending|stretching respond|corresponds to the width|variety of the laminated body at the time of bonding. Specifically, between the extending process and the bonding process, a new slitting process is not substantially applied to the laminate.

The width of the protective film can be set to any appropriate value. Typically, they are 500 mm or more and 3000 mm or less, Preferably they are 1000 mm or more and 2500 mm or less.

Any suitable resin film may be employed as the protective film. As a forming material of a protective film, For example, Cellulose-type resin, such as triacetyl cellulose (TAC), Cycloolefin-type resin, such as norbornene-type resin, Olefin-type resin, such as polyethylene and polypropylene, polyester-type resin, (meth)acrylic resin etc. are mentioned. In addition, "(meth)acrylic-type resin" means an acrylic resin and/or methacryl-type resin.

The thickness of a protective film is 10 micrometers - 100 micrometers typically. In addition, various surface treatments may be given to a protective film. A protective film can function not only as a protective film of a polarizing film, but also retardation film etc.

Any appropriate adhesive or adhesive is used for bonding of a protective film. In one embodiment, an adhesive agent is apply|coated to the polarizing film surface, and a protective film is pasted together. As an adhesive agent, a water-based adhesive agent may be sufficient and a solvent-type adhesive agent may be sufficient. Preferably, a water-based adhesive is used.

As the water-based adhesive, any suitable water-based adhesive may be employed. Preferably, a water-based adhesive comprising a PVA-based resin is used. The average degree of polymerization of the PVA-type resin contained in the water-based adhesive is preferably about 100 to 5000, more preferably 1000 to 4000 from the viewpoint of adhesiveness. An average degree of saponification becomes like this from an adhesive point, Preferably they are about 85 mol% - 100 mol%, More preferably, they are 90 mol% - 100 mol%.

The PVA-based resin contained in the water-based adhesive preferably contains an acetoacetyl group. It is because it is excellent in the adhesiveness of a PVA-type resin layer and a protective film, and may be excellent in durability. Acetoacetyl group-containing PVA-type resin is obtained by making PVA-type resin and diketene react by arbitrary methods, for example. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol% or more, preferably about 0.1 mol% to 40 mol%, more preferably 1 mol% to 20 mol%, particularly preferably Preferably, it is 2 mol% - 7 mol%. In addition, the degree of acetoacetyl group modification is the value measured by NMR.

The resin concentration of the water-based adhesive is preferably 0.1 wt% to 15 wt%, more preferably 0.5 wt% to 10 wt%.

The thickness at the time of application of the adhesive can be set to any suitable value. For example, after heating (drying), it is set so that an adhesive bond layer with a desired thickness may be obtained. The thickness of the adhesive layer is preferably 10 nm to 300 nm, more preferably 10 nm to 200 nm, and particularly preferably 20 nm to 150 nm.

After bonding a protective film to a PVA-type resin layer, it is preferable to heat. The heating temperature is preferably 50°C or higher, more preferably 60°C or higher, and particularly preferably 80°C or higher. In addition, the heating performed after bonding a protective film may serve as the drying process mentioned above.

G. Peeling Process

In one embodiment, the resin base material is peeled from the PVA-type resin layer (polarizing film). Preferably, before peeling a resin base material, the width direction edge part of the polarizing film laminated body by which the protective film was pasted by the said laminated body is slitted. In the bonding part of the width direction edge part of a laminated body, and a protective film, bonding defect (for example, wrinkles) generate|occur|produces easily, and the outstanding peelability of a resin base material can be achieved by removing this part with a slit. Specifically, it is possible to prevent the poor bonding portion from being a starting point from causing a peeling defect (eg, breakage) of the resin substrate, and to allow the resin substrate to be peeled off satisfactorily. As a result, the polarizing plate which was more excellent in an external appearance can be obtained.

H. Polarizer

The polarizing plate of this invention has the said polarizing film and the said protective film arrange|positioned on one side of this polarizing film. The polarizing film is substantially a PVA-based resin film in which a dichroic substance is adsorbed and oriented. The thickness of the polarizing film is preferably 10 µm or less, more preferably 7 µm or less, and particularly preferably 5 µm or less. On the other hand, the thickness of a polarizing film becomes like this. Preferably it is 0.5 micrometer or more, More preferably, it is 1.0 micrometer or more. The polarizing film preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, particularly preferably 43.0% or more. The degree of polarization of the polarizing film is preferably 99.8% or more, more preferably 99.9% or more, still more preferably 99.95% or more.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of each characteristic is as follows.

1. Thickness

It measured using the digital micrometer (The Anritsu Corporation make, product name "KC-351C").

2. Glass transition temperature (Tg)

It measured according to JISK7121.

[Example 1]

(Production of laminate)

As the resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (width: 4000 mm, thickness: 100 µm) having a water absorption rate of 0.75% and a Tg of 75°C was used as the resin substrate.

One side of a resin substrate is corona-treated, and 90 parts by weight of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, saponification on the corona-treated surface) 99.0 mol% or more, an aqueous solution containing 10 parts by weight of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosepimer Z200") was applied and dried at 60° C. to form a PVA-based resin layer having a thickness of 10 μm to form a laminate produced.

The free-end uniaxial stretching of the obtained laminated body was carried out at 2.0 times in the longitudinal direction between the rolls from which circumferential speed differs within 115 degreeC oven (air extending|stretching). Then, the laminated body was wound up in roll shape.

Unwinding a laminated body from the laminated body roll wound up in roll shape, the width direction both ends of a laminated body were each slit so that the width after a slit might be 2500 mm.

Next, the layered product was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment).

Then, it was immersed in the dyeing bath with a liquid temperature of 30 degreeC, adjusting an iodine concentration and immersion time so that the polarizing plate obtained might become a predetermined|prescribed transmittance|permeability. In this example, 0.2 parts by weight of iodine was blended with respect to 100 parts by weight of water, and 1.0 parts by weight of potassium iodide was blended and immersed in an aqueous iodine solution obtained for 60 seconds (dyeing treatment).

Then, it was made to immerse for 30 second in the crosslinking bath (a boric-acid aqueous solution obtained by mix|blending 3 weight part of potassium iodide and 3 weight part of boric acid with respect to 100 weight part of water) of 30 degreeC liquid temperature (crosslinking process).

Thereafter, while immersing the laminate in an aqueous solution of boric acid at a liquid temperature of 70°C (aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) between rolls having different peripheral speeds in the longitudinal direction Uniaxial stretching was performed at 2.7 times (underwater stretching).

Thereafter, the laminate was immersed in a washing bath having a liquid temperature of 30°C (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) for 10 seconds, and then dried with warm air at 60°C for 60 seconds (washing/drying) fair).

In this way, a polarizing film with a thickness of 5 µm was formed on the resin substrate.

Then, on the surface of the polarizing film of the laminate, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosepimer (registered trademark) Z-200", resin concentration: 3 wt%) is applied, A triacetyl cellulose film (manufactured by Konica Minolta, trade name "KC4UY", thickness 40 µm) having a width corresponding to the width of the polarizing film was bonded and heated in an oven maintained at 60° C. for 5 minutes to obtain a polarizing plate.

[Example 2]

Except having slitted so that the width|variety after a slit might be set to 2100 mm, it carried out similarly to Example 1, and produced the polarizing plate.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 1 except that the timing to perform a slit was after underwater stretching.

(evaluation)

The following evaluation was performed about the obtained polarized light. Table 1 summarizes the evaluation results.

1. Appearance

The obtained polarizing plate was observed visually.

2. Polarization

The single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) of the polarizing plate were measured using an ultraviolet visible spectrophotometer (manufactured by Nippon Kogyo Co., Ltd., product name "V7100"), and the degree of polarization (P) was calculated by the following formula was saved by

Polarization degree (P) (%) = {(Tp - Tc)/(Tp + Tc)} ^1/2 × 100

In addition, said Ts, Tp, and Tc are Y values which measured with the 2 degree field of view (C light source) of JISZ8701, and performed visibility correction|amendment.

3. Orientation (evaluation method of orientation function of PVA)

The measuring apparatus used the Fourier transform infrared spectrophotometer (FT-IR) (The Perkin Elmer company make, brand name: "SPECTRUM2000"). Polarized light was used as measurement light, and the surface of the PVA-based resin layer was evaluated by ATR:attenuated total reflection (ATR) measurement. Calculation of the orientation function was performed in the following procedure. Measurement was performed in the state which made the measurement polarization|polarized-light into 0 degrees and 90 degrees with respect to the extending|stretching direction. Using the intensity of 2941 cm ^-1 of the obtained spectrum, it was calculated according to (Equation 1) described below. In addition, as for the following intensity|strength I, 3330 cm ^-1 was used as a reference peak, and the value of 2941 cm ^-1 /3330 cm ^-1 was used. Also, it is fully oriented when f = 1 and random when f = 0. In addition, the peak at 2941 cm ^-1 is known as absorption of a vibration group of the main chain (-CH ₂ -) of PVA.

(Equation 1) f = (3<cos2θ>-1)/2 = (1 - D)/[c(2D + 1)]

only,

c = (3cos2β - 1)/2

β = 90 deg ⇒ f = -2 × (1 - D)/(2D + 1)

θ: molecular chain/stretch direction

β: molecular chain transition dipole moment

D = (I⊥)/(I//), (The value of D increases as the PVA is oriented.)

I⊥ : Intensity measured when polarized light is incident in a direction perpendicular to the stretching direction

I//: Intensity measured when polarized light is incident in a direction parallel to the stretching direction

The polarizing plate of the present invention is suitable as an antireflection film for liquid crystal panels, organic EL devices, liquid crystal panels, such as liquid crystal televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game consoles, car navigation systems, copiers, printers, fax machines, watches, and microwave ovens. is used sparingly

10 ; laminate
11 ; resin substrate
12 ; Polyvinyl alcohol-based resin layer (polarizing film)

Claims (10)

A step of forming a polyvinyl alcohol-based resin layer on an entire surface of one side of a long resin substrate and the resin substrate to obtain a laminate;
A step of aerial stretching the laminate;
A step of dyeing the polyvinyl alcohol-based resin layer,
A step of stretching the laminate in water;
A step of slitting an edge portion in the width direction of the laminate before the underwater stretching after the aerial stretching;
After the said dyeing and extending|stretching in water, the process of bonding a long protective film to the said polyvinyl alcohol-type resin layer is included,
The width of the laminate after the underwater stretching corresponds to the width of the laminate at the time of bonding,
The manufacturing method of the polarizing plate which performs the said slit before the said dyeing|staining. The method of claim 1,
The manufacturing method of the polarizing plate which slits so that the width|variety of the laminated body after the said underwater extending|stretching may correspond to the width|variety of the said protective film. delete The method of claim 1,
The manufacturing method of the polarizing plate which further includes the process of winding up the said laminated body in roll shape, and performs the said slit after the winding up. 5. The method of claim 1, 2 or 4,
The said underwater extending|stretching is longitudinal uniaxial stretching, the manufacturing method of a polarizing plate. delete 5. The method of claim 1, 2 or 4,
The draw ratio of the said underwater extending|stretching is 2.0 times or more, The manufacturing method of a polarizing plate. delete delete delete

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