KR20200022539A - Polarizing plate - Google Patents

Abstract

The present invention provides a polarizing plate having improved durability as a polarizing plate that can be used while the polarizing film is laminated on a resin substrate. The polarizing plate of this invention has a polyester resin base material and the polarizing film whose thickness laminated | stacked on the one side of this polyester resin base material is 10 micrometers or less. The crystallinity degree computed by the total reflection attenuation spectroscopy measurement of this polyester-type resin base material is 0.55-0.80, and the boric acid concentration in this polarizing film is 10 weight%-20 weight%.

Description

Polarizer {POLARIZING PLATE}

The present invention relates to a polarizing plate.

The method of obtaining a polarizing film by forming a polyvinyl alcohol-type resin layer on a resin base material, and extending | stretching and dyeing this laminated body is proposed (for example, patent document 1). According to such a method, since a thin polarizing film is obtained, it is attracting attention as it can contribute to the thinning of an image display apparatus, for example.

The said polarizing film can be used in the state laminated | stacked on the said resin base material (patent document 2). However, in such embodiment, since the crack may generate | occur | produce in a polarizing plate, the improvement of durability is calculated | required.

Japanese Unexamined Patent Publication No. 2000-338329 Japanese Patent No. 4979833

This invention is made | formed in order to solve the said problem, The main objective is to provide the polarizing plate with which durability was improved as a polarizing plate which can be used with the polarizing film laminated | stacked on the resin base material.

According to this invention, the polarizing plate which has a polyester resin base material and the polarizing film whose thickness laminated | stacked on the one side of this polyester resin base material is 10 micrometers or less is provided. In the polarizing plate of this invention, the crystallinity degree computed by the total reflection attenuation spectroscopy (ATR) measurement of this polyester-type resin base material is 0.55-0.80, and the boric acid concentration in this polarizing film is 10 weight%-20 weight%.

In one embodiment, the said polyester resin is polyethylene terephthalate or its copolymer.

In one embodiment, the said polarizing film is laminated | stacked on the one side of the said polyester resin base material without interposing an adhesive layer.

In one embodiment, the said polarizing plate does not have a protective film on the opposite side to the side in which the said polyester-type resin base material of the said polarizing film is laminated | stacked.

In one embodiment, the said polarizing plate has an easily bonding layer between the said polyester resin base material and the said polarizing film.

According to another situation of this invention, the manufacturing method of the said polarizing plate is provided. The manufacturing method includes forming a polyvinyl alcohol-based resin film on a polyester-based resin substrate to produce a laminate, stretching the laminate, dyeing the polyvinyl alcohol-based resin film, and the polyester It crystallizes a system resin base material.

According to this invention, in the polarizing plate obtained by extending | stretching and dyeing the laminated body in which the polyvinyl alcohol-type resin film was formed on the resin base material, the polarizing film is a resin base material by adjusting the crystallinity of the resin base material and the boric acid concentration in a polarizing film to a specific range. It can be used while being laminated | stacked on and the polarizing plate excellent in durability can be obtained.

(A) and (b) are schematic sectional drawing of the polarizing plate in one Embodiment of this invention, respectively.

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

A. Polarizer

The polarizing plate of this invention has a polyester resin base material and the polarizing film whose thickness laminated | stacked on the one side of this polyester resin base material is 10 micrometers or less. 1 (a) is a schematic cross-sectional view of a polarizing plate in one embodiment of the present invention. The polarizing plate 10a adhere | attaches the polyester resin base material 11 and one surface of this polyester resin base material 11, in other words, laminated | stacked the polarizing film 12 laminated | stacked without interposing an adhesive layer. Have FIG.1 (b) is schematic sectional drawing of the polarizing plate in other embodiment of this invention. The polarizing plate 10b further has the protective film 13. The protective film 13 is arrange | positioned on the opposite side to the side in which the polyester-based resin base material 11 of the polarizing film 12 is arrange | positioned. The protective film 13 may be laminated | stacked on the polarizing film 12 through an adhesive layer, and may be laminated | stacked (not interposing an adhesive layer), and may be laminated | stacked. In the polarizing plates 10a and 10b, the polyester resin base material 11 can function as a protective film. In this invention, it can be used as a protective film, without peeling the resin base material used at the time of extending | stretching and dyeing in the manufacturing process of a polarizing film, The structure which has this resin base material (protective film) only on one side of a polarizing film (FIG. 1) Even if it is the structure of (a), generation | occurrence | production of a crack can be suppressed. In addition, the polarizing plates 10a and 10b may have an easily bonding layer (not shown) between the polyester resin base material 11 and the polarizing film 12.

Generally, in the polarizing plate obtained by extending | stretching and dyeing the laminated body with polyvinyl alcohol (Hereinafter, it may be called "PVA") type resin film on a resin base material, it originates in relaxation of an orientation stress, generation of shrinkage stress, etc. Dimensional changes occur in the resin substrate and the PVA-based resin film. In this case, since the amount of dimensional change is different from each other, it is assumed that deformation occurs at the interface and leads to crack generation. On the other hand, in this invention, the polyester resin base material which has a crystallinity degree of a specific range is used as a resin base material, and the boric acid concentration in a polarizing film is adjusted to a specific range. As a result, the amount of dimensional change of the resin substrate and the amount of dimensional change of the polarizing film are balanced in both the absorption axis direction of the polarizing film and the direction orthogonal to the direction, so that deformation is less likely to occur at the resin substrate / polarizing film interface. In addition, the deformations generated are also distributed in both directions. As a result, the occurrence of cracks can be suppressed. In addition, in this specification, the "orthogonal direction" includes the case of 90 degrees +/- 5.0 degree, Preferably it is 90 degrees +/- 3.0 degree, More preferably, it is 90 degrees +/- 1.0 degree. In addition, the "parallel direction" includes the case where it is 0 degrees +/- 5.0 degree, Preferably it is 0 degrees +/- 3.0 degree, More preferably, it is 0 degrees +/- 1.0 degree.

A-1. Polarizer

The said polarizing film is a PVA system resin film in which iodine was adsorptively oriented. The thickness of a polarizing film is 10 micrometers or less, Preferably it is 7.5 micrometers or less, More preferably, it is 5 micrometers 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 1.5 micrometers or more. When thickness is too thin, there exists a possibility that the optical characteristic of the polarizing film obtained may fall. The polarizing film preferably shows absorption dichroism at any wavelength having a 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, and still more preferably 42.0% or more. The polarization degree of the polarizing film is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

Arbitrary appropriate resin can be employ | adopted as PVA system resin which forms the said PVA system resin film. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of PVA system 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 PVA-type resin of such saponification degree, the polarizing film excellent in durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin may be appropriately selected according to the purpose. The average degree of polymerization is usually 1000 to 10,000, preferably 1200 to 4500, and more preferably 1500 to 4300. In addition, an average degree of polymerization can be calculated | required according to JISK6726-1994.

The polarizing film contains boric acid. The boric acid concentration in a polarizing film is 10 weight%-20 weight%, Preferably it is 12 weight%-19 weight%. When boric acid concentration is in the said range, the dimension change rate of a polarizing film in an absorption axis direction and the direction orthogonal to that direction can be made into the value close to the dimension change rate of a polyester-type resin base material, and also in the absorption axis direction The difference between the dimensional change rate of the polarizing film and the dimensional change rate of the polyester resin substrate can be prevented from becoming too large as compared with the difference between the dimensional change rate of the polarizing film and the dimensional change rate of the polyester resin substrate in the direction orthogonal to the absorption axis. The boric acid concentration in the polarizing film is, for example, by changing the boric acid concentration in the stretching bath, insolubilization bath, crosslinking bath, etc., changing the immersion time for these baths, or the like in the method of manufacturing a polarizing plate described later. I can adjust it. In addition, the boric acid concentration (weight%) in a polarizing film can be determined using the boric acid amount index computed, for example from total reflection attenuation spectroscopy (ATR) measurement.

(Boric acid amount index) = (strength of boric acid peak 665 cm ^-1 ) / (intensity of reference peak 2941 cm ^-1 )

(Boric acid concentration) = (boric acid index) × 5.54 + 4.1

Here, "5.54" and "4.1" are all integers obtained by measuring the fluorescent X-ray intensity of the sample for which boric acid concentration is already known, and creating a calibration curve.

A-2. Polyester resin base material

As a formation material of the said polyester-type resin base material, For example, Alicyclic ring containing polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), isophthalic acid, a cyclohexane ring, etc. Copolymer PET (PET-G), other polyesters, and these copolymers, blends, etc. which contain a dicarboxylic acid or alicyclic diol etc. of a formula can be used. Especially, it is preferable to use PET or copolymerized PET. According to these resins, in the unstretched state, they have excellent stretchability suitable for high magnification stretching in an amorphous state, and can be given heat resistance and dimensional stability by crystallization by stretching and heating. Moreover, the heat resistance of the grade which can apply | coat and dry PVA system resin in an unstretched state can be ensured.

The glass transition temperature (Tg) of a polyester resin base material becomes like this. Preferably it is 170 degrees C or less. By using such a resin base material, stretchability can fully be ensured, suppressing crystallization of a PVA system resin film. It is more preferable that it is 120 degrees C or less, considering the plasticization of the resin base material by water and favorable extending | stretching in water. In one embodiment, the glass transition temperature of a polyester resin base material becomes like this. Preferably it is 60 degreeC or more. By using such a polyester-based resin substrate, the polyester-based resin substrate is deformed (for example, unevenness, sagging, wrinkles, etc.) when the coating liquid containing the PVA-based resin described later is dried. Etc. problems can be prevented. Moreover, extending | stretching of a laminated body can be performed at preferable temperature (for example, about 60 degreeC-about 70 degreeC). In another embodiment, when apply | coating and drying a coating liquid containing PVA system resin, a glass transition temperature lower than 60 degreeC may be sufficient, if a polyester resin base material is not deformed. In addition, glass transition temperature (Tg) is a value calculated | required according to JISK71121.

In one embodiment, it is preferable that a water absorption is 0.2% or more, and, as for a polyester resin base material, More preferably, it is 0.3% or more. Such a polyester resin base material absorbs water and can plasticize by acting as a plasticizer. As a result, extending | stretching stress can be reduced significantly in underwater extending | stretching, and it can be excellent in stretchability. On the other hand, the water absorption of a polyester resin base material becomes like this. Preferably it is 3.0% or less, More preferably, it is 1.0% or less. By using such a polyester resin base material, the dimensional stability of a polyester resin base material falls remarkably at the time of manufacture, and the problem of deterioration of the external appearance of the laminated body obtained can be prevented. Moreover, it can prevent breaking at the time of extending | stretching in water, or peeling a PVA system resin film from a polyester resin base material. In addition, water absorption is a value calculated | required according to JISK7209.

The thickness of a polyester resin base material becomes like this. Preferably it is 10 micrometers-200 micrometers, More preferably, it is 20 micrometers-150 micrometers.

The crystallinity degree calculated by the total reflection attenuation spectroscopy (ATR) measurement of a polyester resin base material is 0.55-0.80, Preferably it is 0.58-0.80, More preferably, it is 0.60-0.75. When the degree of crystallinity of the polyester-based resin substrate is within the above range, the dimensional change rate of the polyester-based resin base material in the absorption axis direction of the polarizing film and the direction orthogonal to the direction can be made a value close to the dimensional change rate of the polarizing film, and The difference between the dimensional change rate of the polarizing film in the absorption axis direction and the dimensional change rate of the polyester resin base material is excessively compared with the difference between the dimensional change rate of the polarizing film in the direction orthogonal to the absorption axis and the dimensional change rate of the polyester resin base material. It can prevent the growth. The crystallinity degree of a polyester resin base material can be adjusted by changing the heating temperature and / or heating time at the time of crystallization, for example. In addition, the crystallinity degree of the said polyester resin base material is computed based on the following formula | equation.

(Degree of crystallization) = (intensity of crystal peak 1340 cm ^-1 ) / (intensity of reference peak 1410 cm ^-1 )

A-3. Protective film

As a forming material of the said protective film, For example, cellulose resins, such as (meth) acrylic-type resin, diacetyl cellulose, and triacetyl cellulose, olefin resins, such as cycloolefin resin, polypropylene, and polyethylene terephthalate resin Ester resin, polyamide resin, polycarbonate resin, these copolymer resin, etc. are mentioned. The thickness of a protective film becomes like this. Preferably it is 10 micrometers-100 micrometers.

A-4. Easy adhesion layer

The easily bonding layer may be a layer substantially formed only of the composition for easily bonding layer formation, or may be a layer or region in which the composition for easily bonding layer formation and the forming material of the polarizing film are mixed (including commercial use). When the easily bonding layer is formed, excellent adhesiveness can be obtained. It is preferable that the thickness of an easily bonding layer shall be about 0.05 micrometer-about 1 micrometer. An easily bonding layer can be confirmed by observing the cross section of a polarizing plate with a scanning electron microscope (SEM), for example. The composition for easily bonding layer formation is explained in detail in section B.

A-5. Adhesive layer

The adhesive layer is formed of any suitable adhesive or pressure-sensitive adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive. The adhesive layer is typically formed of a vinyl alcohol adhesive.

B. Manufacturing Method of Polarizing Plate

The manufacturing method of the polarizing plate of this invention typically forms a PVA system resin film on a polyester resin base material, produces a laminated body, extends this laminated body, dyes the PVA system resin film, It crystallizes the polyester resin base material.

B-1. Fabrication of the laminate

Arbitrary suitable methods can be employ | adopted as a method of forming a PVA system resin film on a polyester resin base material. Preferably, the PVA system resin film is formed by apply | coating and drying the coating liquid containing PVA system resin on a polyester resin base material. In one embodiment, an easily bonding layer is formed by apply | coating and drying a composition for easily bonding layer formation on a polyester resin base material, and a PVA system resin film is formed on this easily bonding layer.

The forming material of the said polyester resin base material is as above-mentioned. The thickness (thickness before extending | stretching mentioned later) of a polyester-type resin base material becomes like this. Preferably it is 20 micrometers-300 micrometers, More preferably, they are 50 micrometers-200 micrometers. If it is less than 20 micrometers, there exists a possibility that formation of a PVA system resin film may become difficult. When it exceeds 300 micrometers, for example, in underwater stretching, while a polyester resin base material requires a long time for absorbing water, there exists a possibility that an excessive load may be required for extending | stretching. In addition, the crystallinity degree computed by the total reflection attenuation spectroscopy (ATR) measurement of a polyester-based resin substrate at the time of being used for preparation of a laminated body may be 0.20 to 0.50, for example.

The said coating liquid is typically the solution which melt | dissolved the said PVA system resin in the solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, ethylenediamine, diethylenetriamine, and the like. Amines may be mentioned. These can be used individually or in combination of 2 or more types. Among these, Preferably, it is water. The PVA system resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. If it is such resin concentration, the uniform coating film in close_contact | adherence to a polyester-type resin base material can be formed.

You may mix | blend an additive with a coating liquid. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. As a plasticizer, polyhydric alcohols, such as ethylene glycol and glycerin, 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, dyeing property, and stretchability of the obtained PVA system resin film. Moreover, as an additive, an easily bonding component is mentioned, for example. By using an easily bonding component, the adhesiveness of a polyester resin base material and a PVA system resin film can be improved. As a result, the problem of peeling a PVA system resin film from a base material, etc. can be suppressed, for example, and dyeing mentioned later and underwater extending | stretching can be performed favorably. As an easily bonding component, modified PVA, such as acetacetyl modified PVA, is used, for example.

Arbitrary appropriate methods can be employ | adopted as a coating method of a coating liquid. For example, roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spray coating method, knife coating method (comma coating method etc.) etc. are mentioned.

Coating and drying temperature of a coating liquid becomes like this. Preferably it is 50 degreeC or more.

The thickness (thickness before extending | stretching mentioned later) of the said PVA system resin film becomes like this. Preferably it is 3 micrometers-20 micrometers.

Before forming a PVA-type resin film, you may surface-treat (for example, corona treatment etc.) to a polyester-based resin base material, and apply | coat (coating process) the composition for easily bonding layer formation on a polyester-based resin base material do. By performing such a process, the adhesiveness of a polyester resin base material and a PVA system resin film can be improved. As a result, for example, the problem of peeling a PVA system resin film from a base material can be suppressed, and the dyeing and extending | stretching mentioned later can be performed favorably.

The composition for easily bonding layer formation preferably contains a polyvinyl alcohol-based component. As the polyvinyl alcohol-based component, any suitable PVA-based resin can be used. Specifically, polyvinyl alcohol and modified polyvinyl alcohol are mentioned. As modified polyvinyl alcohol, the polyvinyl alcohol modified | modified with an acetacetyl group, a carboxylic acid group, an acryl group, and / or a urethane group is mentioned, for example. Among these, acetacetyl-modified PVA is used preferably. As acetacetyl-modified PVA, the polymer which has at least a repeating unit represented by the following general formula (I) is used preferably.

[Formula 1]

In said Formula (I), the ratio of n with respect to l + m + n becomes like this. Preferably it is 1%-10%.

The average polymerization degree of acetacetyl-modified PVA becomes like this. Preferably it is 1000-10000, Preferably it is 1200-5000. The degree of saponification of acetacetyl-modified PVA is preferably 97 mol% or more. The pH of the 4 wt% aqueous solution of acetacetyl-modified PVA is preferably 3.5 to 5.5. In addition, average polymerization degree and saponification degree can be calculated | required according to JISK6726-1994.

The composition for easily bonding layer formation may further contain a polyolefin component, a polyester component, a polyacrylic component, or the like according to the purpose and the like. Preferably, the composition for easily bonding layer formation further contains a polyolefin component.

Arbitrary suitable polyolefin resin can be used as said polyolefin component. As an olefin component which is a main component of polyolefin resin, C2-C6 olefin hydrocarbons, such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, are mentioned, for example. These can be used individually or in combination of 2 or more types. Among these, olefin hydrocarbons having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, and 1-butene are preferable, and ethylene is more preferably used.

The ratio which an olefin component occupies among the monomer components which comprise the said polyolefin resin becomes like this. Preferably it is 50 weight%-95 weight%.

It is preferable that the said polyolefin resin has a carboxyl group and / or its anhydride group. Such a polyolefin resin may be dispersed in water, and an easy adhesion layer may be well formed. As a monomer component which has such a functional group, unsaturated carboxylic acid, its anhydride, the half ester of unsaturated dicarboxylic acid, and half amide are mentioned, for example. As these specific examples, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid are mentioned.

The molecular weight of polyolefin resin is 5000-80000, for example.

In the composition for easily bonding layer formation, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (the former: the latter (solid content)) is preferably 5:95 to 60:40, more preferably 20:80 to 50. : 50. When there are too many polyvinyl alcohol-type components, there exists a possibility that adhesiveness may not fully be acquired. Specifically, there exists a possibility that peeling force required when peeling a polarizing film from a resin base material falls, and sufficient adhesiveness may not be obtained. On the other hand, when there are too few polyvinyl alcohol-type components, there exists a possibility that the external appearance of the polarizing plate obtained may be impaired. Specifically, at the time of formation of the easily bonding layer, problems such as clouding of the coating film may occur, and it may be difficult to obtain a polarizing plate having excellent appearance.

The composition for easily bonding layer formation is preferably water-based. The easily bonding layer forming composition may contain an organic solvent. As an organic solvent, ethanol, isopropanol, etc. are mentioned, for example. Solid content concentration of the composition for easily bonding layers is preferably 1.0 weight%-10 weight%.

Arbitrary appropriate methods can be employ | adopted as a coating method of the composition for easily bonding layers forming. After application of the composition for easy adhesion layer formation, the coating film may be dried. Drying temperature is 50 degreeC or more, for example.

B-2. Stretch

Arbitrary appropriate methods can be employ | adopted as the extending method of a laminated body. Specifically, it may be fixed end stretching (for example, a method using a tenter stretching machine) or free end stretching (for example, a method of uniaxial stretching by passing a laminate between rolls having different circumferential speeds). Moreover, simultaneous biaxial stretching (for example, the method of using a simultaneous biaxial stretching machine) may be sufficient, and sequential biaxial stretching may be sufficient as it. The stretching of the laminate may be performed in one step or may be performed in multiple steps. When performing in multiple steps, the draw ratio (maximum draw ratio) of the laminated body mentioned later is a product of draw ratio of each step.

The extending | stretching process may be the underwater extending | stretching system performed by immersing a laminated body in an extending | stretching bath, or the air-stretching system may be sufficient. In one embodiment, the underwater stretching treatment is performed at least once, and preferably, the underwater stretching treatment and the aerial stretching treatment are combined. According to underwater stretching, it can extend | stretch at temperature lower than the glass transition temperature (typically about 80 degreeC) of the said polyester resin base material or PVA system resin film, and it is high magnification, suppressing the crystallization of a PVA system resin film. You can stretch. As a result, the polarizing film which has the outstanding polarization characteristic can be manufactured.

Arbitrary appropriate directions can be selected as the extending direction of a laminated body. In one embodiment, it extends in the longitudinal direction of a long laminated body. Specifically, the laminate is conveyed in the longitudinal direction and stretched in the conveying direction MD. In another embodiment, it extends in the width direction of an elongate laminated body. Specifically, the laminate is conveyed in the longitudinal direction and stretched in the direction TD orthogonal to the conveying direction MD.

The extending | stretching temperature of a laminated body can be set to arbitrary appropriate values according to the formation material, extending | stretching system, etc. of a polyester-type resin base material. When employ | adopting an air-stretch system, extending | stretching temperature becomes like this. Preferably it is more than glass transition temperature (Tg) of a polyester-type resin base material, More preferably, it is more than glass transition temperature (Tg) +10 degreeC of a polyester-type resin base material. Especially preferably, it is Tg + 15 degreeC or more. On the other hand, extending | stretching temperature of a laminated body becomes like this. Preferably it is 170 degrees C or less. By extending | stretching at such temperature, it can suppress that the crystallization of PVA system resin advances rapidly, and can suppress the problem by the said crystallization (for example, hinders the orientation of the PVA system resin film by extending | stretching).

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

When employ | adopting an underwater extending | stretching system, it is preferable to immerse and extend | stretch a laminated body in boric-acid aqueous solution (stretching in boric acid underwater). By using boric acid aqueous solution as the stretching bath, the PVA-based resin film can be provided with rigidity that withstands the tension applied at the time of stretching and water resistance not dissolved in water. Specifically, boric acid can produce tetrahydroxyboron anion in aqueous solution, and can bridge | crosslink by PVA system resin and a hydrogen bond. As a result, rigidity and water resistance can be provided to a PVA system resin film, it can extend | stretch favorable, and the polarizing film which has the outstanding polarization characteristic can be manufactured.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight with respect to 100 parts by weight of water. By making a boric acid concentration 1 weight part or more, dissolution of a PVA system resin film can be suppressed effectively, and the polarizing film of a higher characteristic can be produced. In addition to boric acid or borates, 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 system resin film can be suppressed. Examples of 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, potassium iodide is preferable. 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.

Immersion time with respect to the extending | stretching bath of a laminated body becomes like this. Preferably it is 15 second-5 minutes. Preferably, the underwater stretching treatment is carried out after the dyeing treatment.

The draw ratio (maximum draw ratio) of the laminate is preferably 4.0 times or more, and more preferably 5.0 times or more with respect to the original length of the laminate. Such a high draw ratio can be achieved by employ | adopting an underwater extending | stretching system (boric acid underwater extending | stretching), for example. In addition, in this specification, a "maximum draw ratio" means the draw ratio immediately before a laminated body breaks, and separately confirms the draw ratio which a laminated body breaks, and means the value lower than the value.

B-3. dyeing

Dyeing of a PVA system resin film is typically performed by making iodine adsorb | suck to a PVA system resin film. As the adsorption method, for example, a method of immersing a PVA-based resin film (laminate) in a dyeing solution containing iodine, a method of coating the dyeing solution on a PVA-based resin film, and the dyeing solution are PVA-based resins. The spraying method to a film | membrane, etc. are mentioned. Preferably, it is a method of immersing a PVA system resin film (laminate) in a dyeing liquid. This is because iodine can be adsorbed well.

The dyeing solution is preferably an iodine aqueous solution. The compounding quantity of iodine is 0.1 weight part-0.5 weight part preferably with respect to 100 weight part of water. In order to increase the solubility of iodine in water, it is preferable to mix iodide with an iodine aqueous solution. Specific examples of the iodide are as described above. The compounding quantity of iodide becomes like this. Preferably it is 0.02 weight part-20 weight part, More preferably, it is 0.1 weight part-10 weight part with respect to 100 weight part of water. In order to suppress dissolution of PVA system resin, the solution temperature at the time of dyeing of a dyeing liquid becomes like this. Preferably it is 20 degreeC-50 degreeC. When the PVA system resin film is immersed in the dyeing solution, the immersion time is preferably 5 seconds to 5 minutes in order to secure the transmittance of the PVA system resin film. 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, the immersion time is set so that the polarization degree of the polarizing film obtained may be 99.98% or more. In another embodiment, the immersion time is set so that the unitary transmittance of the polarizing film obtained may be 40%-44%.

The dyeing process can be performed at any suitable timing. In the case of performing the underwater stretching, the stretching is preferably performed before the underwater stretching.

B-4. crystallization

Crystallization of a polyester resin base material is performed by heating a polyester resin base material (substantially a laminated body), for example. Crystallization is preferably performed after dyeing and stretching the PVA-based resin film.

The heating temperature is typically a temperature exceeding the glass transition temperature (Tg) of the polyester resin base material. Heating temperature becomes like this. Preferably it is 90 degreeC or more, More preferably, it is 100 degreeC or more. Moreover, heating temperature becomes like this. Preferably it is 125 degrees C or less, More preferably, it is 120 degrees C or less. By heating at such a temperature, a polyester resin base material can be made into a desired crystallinity degree. The heating time may be appropriately set according to the heating temperature or the like. The heating time may be, for example, 3 seconds to 2 minutes.

In the said crystallization, it is preferable to crystallize so that the haze value of a polyester-type resin base material may be 2% or less.

B-5. Other treatment

In addition to extending | stretching and dyeing, the said PVA system resin film (laminated body) can be suitably performed the process for making it a polarizing film. As a process for making it a polarizing film, an insolubilization process, a crosslinking process, a washing process, a drying process, etc. are mentioned, for example. In addition, the frequency | count, order, etc. of these processes are not specifically limited.

The insolubilization treatment is typically performed by immersing a PVA-based resin film (laminate) in an aqueous boric acid solution. By performing insolubilization treatment, water resistance can be imparted to the PVA-based resin film. The concentration of the boric acid aqueous 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, the insolubilization treatment is performed before the underwater stretching or the dyeing treatment.

The said crosslinking process is typically performed by immersing a PVA system resin film (laminated body) in boric-acid aqueous solution. By performing a crosslinking process, water resistance can be provided to a PVA system resin film. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Moreover, when crosslinking process is performed after the said dyeing process, it is preferable to mix | blend an iodide further. By mix | blending an iodide, the elution of the iodine made to adsorb | suck to the PVA system resin film can be suppressed. The compounding quantity of iodide is 1 weight part-5 weight part preferably with respect to 100 weight part of water. Specific examples of the iodide are as described above. 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 carried out before the underwater stretching. In a preferred embodiment, aerial stretching, dyeing treatment and crosslinking treatment are performed in this order.

The said washing process is typically performed by immersing a PVA system resin film (laminated body) in the potassium iodide aqueous solution. The drying temperature in the said drying process becomes like this. Preferably it is 30 degreeC-100 degreeC.

As described above, the polarizing plate of the present invention can be obtained by forming a polarizing film on the polyester resin substrate and crystallizing the polyester resin substrate.

C. Use of Polarizer

The polarizing plate of the present invention may be mounted on, for example, a liquid crystal display device. In this case, it is preferable to mount so that a polarizing film may be arrange | positioned rather than a polyester-type resin base material on the liquid crystal cell side. According to such a structure, the influence which the phase difference which a polyester resin base material can have on the image characteristic of the liquid crystal display device obtained can be excluded.

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. In addition, "part" and "%" in a following example and a comparative example represent "weight part" and "weight%", respectively.

≪Thickness≫

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

≪Dimension change rate≫

From the polarizing plates obtained by the Example and the comparative example, after peeling a polarizing film and a resin base material by giving a meter to an edge part, after heating up from 30 degreeC to 100 degreeC at 10 degreeC / min by a thermomechanical measuring apparatus (TMA), it was further The dimensional change rate at the time of holding at 100 degreeC for 60 minutes was measured. Moreover, in Example 6 which pinches an easily bonding layer between, the thing which isolate | separated the polarizing film and the resin base material in the same order from the polarizing plate produced similarly except not providing an easily bonding layer was provided for a polarizing film and It was set as the dimensional change of a resin base material.

Dimensional rate of change (%) = (dimension after heat treatment-dimension before heat treatment) / dimension before heat treatment × 100

<< crystallinity degree >>

The polyester-based resin substrates obtained in Examples and Comparative Examples were determined by total reflection attenuation spectroscopy (ATR) measurement using a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name "SPECTRUM2000"). The intensity of the peak 1340 cm ^-1 and the intensity of the reference peak 1410 cm ^-1 were measured. The crystallinity was calculated from the obtained crystal peak intensity and reference peak intensity by the following formula.

(Degree of crystallization) = (intensity of crystal peak 1340 cm ^-1 ) / (intensity of reference peak 1410 cm ^-1 )

≪Glass transition temperature: Tg≫

It measured in accordance with JIS K 7121.

≪Boric acid concentration≫

Measurement of total reflection attenuation spectroscopy (ATR) using polarized light as measurement light using a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name "SPECTRUM2000") for the polarizing films obtained in Examples and Comparative Examples. The intensity | strength of the boric acid peak (665 cm <^-1> ) and the intensity | strength of the reference peak (2941 cm <^-1> ) were measured by this. From the obtained boric acid peak intensity and reference peak intensity, the boric acid amount index was calculated by the following formula, and the boric acid concentration was further determined by the following formula from the calculated boric acid amount index.

(Boric acid amount index) = (strength of boric acid peak 665 cm ^-1 ) / (intensity of reference peak 2941 cm ^-1 )

(Boric acid concentration) = (boric acid index) × 5.54 + 4.1

≪Crack evaluation≫

The polarizing plate obtained by the Example and the comparative example was heated 240 h in 100 degreeC oven in the state bonded together to glass via an adhesive so that a polyester resin base material might come to the surface side. The presence or absence of the crack of the polarizing plate after heating was confirmed, and it evaluated according to the following criteria.

Good: No crack

Poor: There is a crack

Example 1

As a resin base material, it is elongate, 0.75% of water absorption, and the amorphous isophthalic-acid copolymerization polyethylene terephthalate (IPA copolymerization PET) film (thickness: 100 micrometers) of Tg75 degreeC was used.

Corona treatment was performed on one side of the resin substrate, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (polymerization degree 1200, acetacetyl modification degree 4.6%, saponification degree 99.0). The aqueous solution which contains mol% or more, the Nippon Synthetic Chemical Co., Ltd. make, brand name "Gosepamer Z200") in the ratio of 9: 1 was apply | coated and dried at 25 degreeC, and the PVA system resin layer of thickness 11micrometer was formed. In this way, a laminated body was produced.

The obtained laminated body was uniaxially stretched at the free end uniaxially by 1.8 times in the longitudinal direction (length direction) between the rolls from which a circumferential speed differs in 120 degreeC oven (air auxiliary extension).

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

Subsequently, it was immersed for 60 second in the dye bath of 30 degreeC of liquid temperature (0.2 weight part of iodine, and 1.5 weight part of potassium iodide mix | blended with respect to 100 weight part of water).

Subsequently, it was immersed for 30 second in the crosslinking bath of 30 degreeC of liquid temperature (3 weight part of potassium iodide, and 3 weight part of boric acid solution blended with boric acid) with respect to 100 weight part of water (crosslinking process).

Thereafter, the laminate is immersed in a boric acid aqueous solution (an aqueous solution obtained by blending 3 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70 ° C, between rolls having different circumferential speeds. Uniaxial stretching was performed so that the total draw ratio might be 5.5 times in the longitudinal direction (length direction) (underwater stretching).

Then, the laminated body was immersed in the washing bath of 30 degreeC of liquid temperature (the aqueous solution obtained by mix | blending 4 weight part of potassium iodide with respect to 100 weight part of water) (washing process).

Subsequently, the laminated body was put into 100 degreeC oven for 30 second, and the resin base material was crystallized.

Thus, the polarizing plate which laminated | stacked the polarizing film of thickness 5micrometer on the resin base material was obtained.

Example 2

A polarizing plate was obtained in the same manner as in Example 1 except that the laminate was placed in an oven at 110 ° C. for 30 seconds to crystallize the resin substrate.

Example 3

A polarizing plate was obtained in the same manner as in Example 1 except that the laminate was placed in an oven at 120 ° C. for 30 seconds to crystallize the resin substrate.

Example 4

A polarizing plate was obtained in the same manner as in Example 1 except that the amount of boric acid blended in the stretching bath at the time of underwater stretching was 3.5 parts by weight, and the laminate was put in an oven at 110 ° C. for 30 seconds to crystallize the resin substrate.

Example 5

A polarizing plate was obtained in the same manner as in Example 1 except that the amount of boric acid blended in the stretching bath at the time of stretching in water was 2.5 parts by weight, and the laminate was put in an oven at 110 ° C. for 30 seconds to crystallize the resin substrate.

Example 6

By the following method, the easily bonding layer was formed in the single side | surface of the resin base material.

Corona treatment is performed on one side of the resin base material, and acetacetyl-modified PVA (Nippon Synthetic Chemical Industry Co., Ltd. product, brand name "High Sepamer Z200", polymerization degree 1200, saponification degree 99.0 mol% or more, acetacetyl modification on this corona treatment surface) 4.6%) of the 4.0% aqueous solution, the modified polyolefin resin aqueous dispersion (Unitica company make, brand name "arrow base SE1030N", solid content concentration 22%), and the mixed liquid (solid content concentration 4.0%) which mixed pure water, the thickness after drying It applied so that it might be set to 2000 nm, and it dried at 60 degreeC for 3 minutes, and formed the easily bonding layer. Here, the solid content compounding ratio of acetacetyl-modified PVA and modified polyolefin in the liquid mixture was 30:70.

The polarizing plate was obtained like Example 1 except having performed the corona treatment on the easily bonding layer surface, and forming the PVA system resin layer in this corona treatment surface.

Comparative Example 1

A polarizing plate was obtained in the same manner as in Example 1 except that the laminate was placed in an oven at 85 ° C. for 30 seconds to crystallize the resin substrate.

Comparative Example 2

A polarizing plate was obtained in the same manner as in Example 1 except that the amount of boric acid blended in the stretching bath at the time of underwater stretching was 4.0 parts by weight, and the laminate was put in an oven at 110 ° C. for 30 seconds to crystallize the resin substrate.

Comparative Example 3

A polarizing plate was obtained in the same manner as in Example 1 except that the laminate was placed in an oven at 95 ° C. for 30 seconds to crystallize the resin substrate.

Table 1 shows the production conditions of the polarizing plates in the examples and the comparative examples and the respective characteristics of the obtained polarizing plates. In addition, MD in a table | surface is the absorption axis direction of a polarizer, and TD is a direction orthogonal to an absorption axis.

As shown in Table 1, generation | occurrence | production of a crack is suppressed in the polarizing plate of the Example which has the resin base material which has a specific crystallinity degree, and the polarizing film which satisfy | fills a specific boric acid concentration. On the other hand, a crack has generate | occur | produced in the polarizing plate of a comparative example, and it turns out that durability is inferior to the polarizing plate of an Example. Moreover, compared with the polarizing plate of another Example or a comparative example, the polarizing plate of Example 6 is excellent in the adhesiveness of a resin base material and a polarizing film (PVA system resin layer), and at the time of manufacture of a polarizing film or processing of a polarizing plate (for example, punching) Unwanted peeling or lifting of the polarizing film (PVA system resin layer) or resin base material in the city was preferably prevented.

The reason why a crack was suppressed in the polarizing plate of the Example is estimated as follows. That is, in the polarizing plate of the Example, the difference between the dimensional change rate of the resin base material in the MD direction and the dimensional change rate of the polarizing film (dimension change rate of the resin base material-dimensional change rate of the polarizing film) and the dimensional change rate of the resin base material in the TD direction and polarized light The difference between the dimensional change rate of the film (dimension change rate of the resin substrate-the dimensional change rate of the polarizing film) is all within 5%, and the difference (absolute value) of the dimensional change rate in the TD direction is the difference of the dimensional change rate in the MD direction (absolute value). ) Is close to (within ± 1.5%). Since the polarizing film is oriented in the stretching direction MD, the direction TD orthogonal to the stretching direction tends to be weak as mechanical properties. Therefore, by making the difference (absolute value) of the dimensional change rate in the TD direction close to the difference (absolute value) of the dimensional change rate in the MD direction, deformation is not biased in the TD direction and cracks are suppressed. I think.

Industrial availability

The polarizing plate of this invention is used suitably for an image display apparatus, for example.

Claims (6)

As a polarizing plate which has a polyester resin base material and the polarizing film whose thickness laminated | stacked on the one side of this polyester resin base material is 10 micrometers or less,
The crystallinity calculated by the total reflection attenuation spectroscopy measurement of the polyester resin substrate is 0.55 to 0.80,
The polarizing plate whose boric acid concentration in this polarizing film is 10 weight%-20 weight%. The method of claim 1,
Polarizing plate whose said polyester-type resin is polyethylene terephthalate or its copolymer. The method according to claim 1 or 2,
The said polarizing film is laminated | stacked on one side of the said polyester resin base material without interposing an adhesive layer. The method according to any one of claims 1 to 3,
The polarizing plate which does not have a protective film in the opposite side to the side in which the said polyester resin base material of the said polarizing film is laminated | stacked. The method according to any one of claims 1 to 4,
The polarizing plate which has an easily bonding layer between the said polyester resin base material and the said polarizing film. Forming a polyvinyl alcohol-based resin film on a polyester-based resin substrate to produce a laminate,
Stretching the laminate,
Dyeing the polyvinyl alcohol-based resin film, and
To crystallize the polyester-based resin substrate
The manufacturing method of the polarizing plate of any one of Claims 1-5 containing.

Images