KR20190132995A - Manufacturing method of polarizer - Google Patents

Abstract

An object of this invention is to provide the manufacturing method of the polarizer which can be dyed more efficiently. The manufacturing method of the polarizer of this invention includes the process of dyeing a polyvinyl alcohol-type resin film using the solution containing the oxidizing agent for iodide and iodine ion. This oxidizing agent is an ionic compound consisting of a cation and an anion, and the standard electrode potential of either the anion or the cation is larger than the standard electrode potential of the iodine ion. By dyeing using such a solution, the polyvinyl alcohol-based resin film can be more efficiently dyed.

Description

Manufacturing method of polarizer

The present invention relates to a method for producing a polarizer.

The polarizer is used for image display apparatuses, such as a liquid crystal display device. In recent years, the demand for thinning an image display device is increasing. Therefore, thickness reduction is progressing also about a polarizer. The polarizer is typically produced by dyeing a polyvinyl alcohol (PVA) resin film with a dichroic substance such as iodine (for example, Patent Documents 1 and 2). When manufacturing a thin polarizer, since the thickness of a resin film also becomes thin, it may not be fully dyed. Therefore, the method which can dye | dye a resin film more efficiently is calculated | required.

It is also known that iodine sublimes in the dyeing process so that the iodine concentration in the dyeing solution decreases with time. This is particularly noticeable in staining solutions containing high concentrations of iodine. Further, in the dyeing step, since iodine is transferred to the PVA resin film, the iodine concentration in the dyeing solution decreases. Therefore, in order to perform the dyeing process stably and continuously, it is necessary to appropriately adjust the iodine concentration in the dyeing solution. In order to return the reduced iodine concentration to the iodine concentration at the time of preparation, it is necessary to add a solution containing iodine of a higher concentration than the dyeing solution used in the dyeing step. High concentrations of iodine are concerned about adverse effects on the environment and human body. Therefore, the method of adjusting the iodine content in a dyeing solution more simply is calculated | required.

Japanese Patent Publication No. 5048120 Japanese Unexamined Patent Publication No. 2013-156391

This invention is made | formed in order to solve the said conventional subject, The main objective is to provide the manufacturing method of the polarizer which can dye | stain a PVA system resin film more efficiently.

The polarizer manufacturing method of this invention includes the process of dyeing a polyvinyl alcohol-type resin film using the solution containing the oxidizing agent for iodide and iodine ion. This oxidizing agent is an ionic compound consisting of a cation and an anion, and the standard electrode potential of either the anion or the cation is larger than the standard electrode potential of the iodine ion.

In one embodiment, the standard electrode potential of the anion or cation is at least 0.55V.

In one embodiment, the content of iodide in the solution is 1 part by weight to 40 parts by weight with respect to 100 parts by weight of the solvent.

In one embodiment, the content of the oxidizing agent in the solution is 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of the solvent.

In one embodiment, the molar ratio of the iodide to the oxidant is 2/1 to 50/1.

In one embodiment, the oxidant comprises trivalent iron ions as cations.

In one embodiment, the oxidizing agent is at least one member selected from the group consisting of ferric sulfate, ferric chloride and ferric nitrate.

In one embodiment, the thickness of the polarizer obtained by the manufacturing method of the said polarizer is 10 micrometers or less.

According to this invention, a PVA system resin film can be dyed more efficiently. Specifically, the PVA resin film is dyed using a solution containing an oxidizing agent for iodide and iodine ions. As a result, iodine ions are oxidized by the oxidizing agent in the solution, so that polyiodine ions (for example, I ₃ ⁻ ions) are formed, and the content of polyiodine ions contained in the solution can be efficiently increased. By using this solution as a dyeing solution, a PVA system resin film can be dyed more efficiently. Moreover, according to the manufacturing method of this invention, content of polyiodine ion can be raised, without using iodine which is solid. Therefore, adverse effects on the environment and the human body by iodine at the time of preparing the dyeing solution can also be prevented.

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

The manufacturing method of the polarizer of this invention includes the process of dyeing a PVA system resin film using the solution containing the oxidizing agent for iodide and iodine ion (henceforth a dyeing solution). This oxidizing agent is an ionic compound consisting of a cation and an anion, and the standard electrode potential of either the anion or the cation is larger than the standard electrode potential of the iodine ion. By this oxidant, iodine ions can be oxidized to form polyiodine ions. By dyeing using this dyeing solution, the PVA resin film can be dyed more efficiently. The detail of a dyeing process is mentioned later. A polarizer can be manufactured by providing a PVA system resin film to a swelling process, a dyeing process, a crosslinking process, an extending process, a washing process, and a drying process, for example.

As PVA system resin which forms a PVA system resin film, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned, for example. 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 the PVA-based resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.99 mol%, and more preferably 99.0 mol% to 99.99 mol%. Saponification degree can be calculated | required according to JISK6726-1994. By using PVA-type resin of such saponification degree, the polarizer excellent in durability can be obtained.

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 10000, preferably 1200 to 4500, more preferably 1500 to 4300. In addition, an average degree of polymerization can be calculated | required according to JISK6726-1994.

There is no restriction | limiting in particular in the thickness of a PVA system resin film, It can be set according to the thickness of a desired polarizer. The thickness of a PVA system resin film is 0.5 micrometer-200 micrometers, for example. The dyeing solution used by this invention can dye | stain a PVA system resin film very efficiently. Therefore, even if a PVA resin film is less than 10 micrometers, for example, it can fully dye in a short time, and can provide the characteristic which can fully function as a polarizer.

In one embodiment, the PVA system resin film may be a PVA system resin layer formed on the substrate. The laminated body of a base material and a resin layer can be obtained by the method of apply | coating the coating liquid containing the said PVA system resin to a base material, the method of laminating | stacking a PVA system resin film on a base material, etc., for example. Arbitrary suitable resin base materials can be used as a base material, For example, a thermoplastic resin base material can be used.

As mentioned above, a polarizer can be manufactured by providing a PVA system resin film to a swelling process, a dyeing process, a crosslinking process, an extending process, a washing process, and a drying process, for example. Each process is performed at any suitable timing. Moreover, if necessary, arbitrary processes other than a dyeing process may be abbreviate | omitted, several processes may be performed simultaneously, and each process may be performed in multiple times. Hereinafter, each process is demonstrated.

The swelling process is usually performed before the dyeing process. The swelling process may be performed together with the dyeing process in the same immersion bath. A swelling process is performed by immersing a PVA system resin film in a swelling bath, for example. Arbitrary suitable liquid can be used as a swelling bath, For example, water, such as distilled water and pure water, is used. The swelling bath may contain any suitable other components other than water. As another component, solvent, such as alcohol, additives, such as surfactant, an iodide, etc. are mentioned. 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. Preferably potassium iodide is used. The temperature of the swelling bath is, for example, 20 ° C to 45 ° C. In addition, immersion time is 10 second-300 second, for example.

In the stretching step, the PVA-based resin film is stretched at any suitable draw ratio according to the desired performance and thickness. Typically, a PVA system resin film is uniaxially stretched 3 to 7 times the original length. The stretching direction may be the longitudinal direction (MD direction) of the film, or may be the width direction (TD direction) of the film. The stretching method may be dry stretching, wet stretching, or a combination thereof. In addition, when performing a crosslinking process, a swelling process, a dyeing process, etc., you may extend | stretch a PVA system resin film. In addition, the extending direction may correspond to the absorption axis direction of the polarizer obtained.

In the dyeing step, the PVA resin film is dyed using a solution containing an iodine and an oxidizing agent for iodine ions. This oxidant is an ionic compound consisting of cations and anions. The standard electrode potential of either of these anions or cations is greater than the standard electrode potential of iodine ions. As described above, in this dyeing solution, iodine ions are oxidized to form polyiodine ions. As a result, content of the polyiodine ion contained in a dyeing solution becomes high, and can dye | stain the PVA system resin film efficiently. Furthermore, compared with the case where iodine is added to an aqueous solution containing water or iodide to prepare a dyeing solution, the content of polyiodine ions in the dyeing solution can be increased with a small amount of iodine. Therefore, the amount of iodine used in the step of preparing the dyeing solution can be reduced, and adverse effects due to the high concentration of iodine on the environment and the human body when preparing the dyeing solution can be prevented. Moreover, in this invention, the iodine content in a dyeing solution can be adjusted by adding the oxidizing agent with respect to iodine ion in a dyeing solution. Therefore, content of the polyiodine ion in a dyeing solution can be adjusted more conveniently simply.

The content of the iodide contained in the dyeing solution is preferably 1 part by weight to 40 parts by weight, and more preferably 3 parts by weight to 30 parts by weight with respect to 100 parts by weight of the solvent. When content of an iodide is the said range, sufficient polyiodine ion can be formed in a dyeing solution. As iodide, the thing illustrated above can be used. Preferably potassium iodide.

In this invention, the ionic compound which consists of a cation and an anion is used as an oxidizing agent with respect to iodine ion. As an indicator of the oxidizing or reducing power in the redox reaction, the standard electrode potential is known. In the ionic compound used as the oxidizing agent, the standard electrode potential of either anion or cation is larger than the standard electrode potential of iodine ions. Specifically, the standard electrode potential of the anion or cation is larger than the standard electrode potential (0.536V) of the iodine ion. The standard electrode potential of the anion or cation is preferably 0.55 V or more, and more preferably 0.60 V or more. This is because it can function preferably as an oxidizing agent for iodine ions. In addition, the standard electrode potential of the anion or cation is for example 2.00 V or less.

Examples of the anion or cation include Fe ³⁺ (0.771V), Ag ⁺ (0.7991V), Ag ²⁺ (1.980V), Au ⁺ (1.83V), Au ³⁺ (1.52V), Co ³⁺ (1.92 ^{V), Cu 2+ (0.559V)} , Mn 3+ (1.5V), a cation such as ^{Pt 2+ (1.188V), Br 3-} (1.0503V), ClO 3 - (0.622V), ClO 2 - ( may be an anion such as ^{(0.56V) - 0.681V), ClO} - (0.890V), Cr 2 O 7 2- (1.36V), NO 3 - (0.835V, 0.94V, 0.9557V), MnO 4 . Preferably it is trivalent iron ion (Fe3 ⁺ ). Trivalent iron ions exist in the dyeing solution as divalent iron ions after oxidizing iodine ions. Trivalent iron ions and divalent iron ions can be blown into the PVA-based resin film in the dyeing process. These iron ions have a function of dehydrating PVA. Therefore, the action which polyiodine ion extracts from a PVA system resin film can be suppressed in a subsequent process. As a result, since the dyeability of a PVA system resin film can be improved further, it is preferable. In the present specification, the standard electrode potential refers to a value in an aqueous solution at 25 ° C. at a standard pressure of 1 atm. The standard electrode potential in an aqueous solution at 25 deg. In this specification, the value described in the said electrochemical manual is used.

As said oxidizing agent, what is necessary is just an ionic compound in which the electrode reaction used as a desired standard electrode potential arises in a dyeing solution, and arbitrary appropriate compounds can be used. For example, compounds containing Fe ³⁺ such as ferric sulfate, ferric chloride and ferric nitrate as cations, compounds containing MnO ^4- such as potassium permanganate as anions, Cu ² such as copper chloride and copper sulfate ^The compound containing ⁺ as a cation, etc. are mentioned. It is preferable to use at least 1 sort (s) of compound chosen from the group which consists of ferric sulfate, ferric chloride, and ferric nitrate at the point containing Fe3 ⁺ . Only 1 type may be used for an oxidizing agent and may be used for it in combination of 2 or more type.

The content of the oxidizing agent in the dyeing solution is preferably 0.1 parts by weight to 10 parts by weight, and more preferably 0.5 parts by weight to 4 parts by weight with respect to 100 parts by weight of the solvent. The content of the oxidant in the dyeing solution may be determined according to the content of iodide contained in the dyeing solution.

The molar ratio of iodide to oxidizing agent can be set to any suitable value, for example, 2/1 to 50/1, preferably 10/1 to 50/1. If the molar ratio of iodide to oxidizing agent is in the said range, an oxidizing agent can fully function as an oxidizing agent with respect to iodide ion.

Iodides and oxidants can be used in any suitable combination. For example, the combination which uses potassium iodide as an iodide and ferric sulfate as an oxidizing agent is preferable at the point which can obtain the polarizer which has the outstanding characteristics, such as durability.

Arbitrary suitable solvent can be used as a solvent of a dyeing solution, Water is normally used.

The dyeing solution may contain any suitable other compound in addition to the iodide and the oxidizing agent. For example, the dyeing solution may further contain iodine. When the dyeing solution further contains iodine, the iodine content in the dyeing solution is, for example, 1 part by weight or less based on 100 parts by weight of the solvent.

Iodide ion (I ^-) included in the staining solution and poly iodine ions (I ₃ ^-) and the content ratio of preferably has a large content of the iodide. When the content rate of iodine ion is large, the sublimation amount of iodine in a dyeing solution can be reduced. Therefore, the influence on the environment and human body by sublimation of iodine can also be suppressed. The content rate of the iodine ion and polyiodine ion contained in a dyeing solution can be evaluated by the intensity of the absorbance of a dyeing solution.

The smaller the amount of iodine sublimation of the dyeing solution, the better. For example, the amount of iodine sublimation is less than 1000 µg / L, preferably 430 µg / L or less. In addition, an iodine sublimation amount is 250 micrograms / L or less, for example. As mentioned above, the dyeing solution used by this invention contains an iodide and an oxidizing agent. As a result, the iodine sublimation amount can be realized. In addition, in this specification, the amount of iodine sublimation can be obtained by the method as described in an Example.

As a dyeing method, the method of immersing a PVA system resin film in the said dyeing solution, the method of coating the said dyeing solution on a PVA system resin film, the method of spraying the said dyeing solution to a PVA system resin film, etc. are mentioned, for example. Since it can be dyed satisfactorily, Preferably it is a method of immersing a PVA system resin film in a dyeing solution.

The liquid temperature at the time of dyeing of the dyeing solution can be set to any suitable value, for example, 20 ° C to 50 ° C. When immersing a PVA system resin film in a dyeing solution, immersion time is 1 second-1 minute, for example.

In the crosslinking step, a boron compound is usually used as the crosslinking agent. Examples of the boron compound include boric acid and borax. Preferably boric acid. In the crosslinking process, the boron compound is usually used in the form of an aqueous solution.

When using boric acid aqueous solution, the boric acid concentration of boric acid aqueous solution is 2 weight%-15 weight%, for example, Preferably it is 3 weight%-13 weight%. The boric acid aqueous solution may further contain zinc compounds, such as iodide, such as potassium iodide, zinc sulfate, and zinc chloride.

The crosslinking process can be carried out by any suitable method. For example, a method of dipping a PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to a PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound to a PVA-based resin film Can be mentioned. It is preferable to be immersed in the aqueous solution containing a boron compound.

The temperature of the solution used for crosslinking is 25 degreeC or more, for example, Preferably it is 30 degreeC-85 degreeC, More preferably, it is 40 degreeC-70 degreeC. Immersion time is 5 second-800 second, for example, Preferably it is 8 second-500 second.

The cleaning process is carried out using water or an aqueous solution containing the iodide. Typically, this is carried out by immersing a PVA-based resin film in an aqueous potassium iodide solution. The temperature of the aqueous solution in a washing process is 5 degreeC-50 degreeC, for example. Immersion time is 1 second-300 second, for example.

The drying process can be carried out by any suitable method. For example, natural drying, ventilation drying, reduced pressure drying, heat drying, etc. are mentioned, and heat drying is used preferably. When carrying out heat drying, the heating temperature is, for example, 30 ° C to 100 ° C. In addition, a drying time is 10 second-10 minutes, for example.

The thickness of the polarizer obtained by the manufacturing method of this invention is 0.5 micrometer-80 micrometers, for example, Preferably it is 0.6 micrometer-20 micrometers. In one embodiment, the thickness of a polarizer becomes like this. Preferably it is 0.8 micrometer-10 micrometers. The thickness of the polarizer is more preferably 5 µm or less, still more preferably 3 µm or less, and particularly preferably 2 µm or less. As described above, the dyeing solution used in the present invention can dye the PVA-based resin film efficiently. Therefore, even a thin polarizer can provide a desired single transmittance sufficiently.

The single transmittance of the polarizer obtained by the production method of the present invention is, for example, 30% or more. In addition, the theoretical upper limit of a single transmittance is 50%, and a practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value measured by a 2-degree field of view (C light source) of JIS Z8701 and subjected to correction of visibility, for example, using a spectrophotometer with an integrating sphere (manufactured by Nihon spectrophotometer, product name: V7100). It can be measured. In addition, the polarization degree of a polarizer is 99.0% or more, for example.

Iodine content of the polarizer obtained by the manufacturing method of this invention is 5 weight part-30 weight part, for example, Preferably they are 8 weight part-25 weight part. By manufacturing a polarizer by said method, the iodine content contained in a polarizer can be raised.

EXAMPLE

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

Example 1

As a thermoplastic resin base material, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymer PET) film (thickness: 100 micrometers) of 0.75% water absorption and Tg 75 degreeC was used. Corona treatment was performed on one side of the substrate, and polyvinyl alcohol (polymerization degree 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol%). The aqueous solution containing Nippon Synthetic Chemicals Co., Ltd. and the brand name "Gyofimer Z200") in a ratio of 9: 1 is applied and dried at 25 ° C to form a PVA resin layer having a thickness of 11 µm, to prepare a laminate. It was.

The obtained laminated body was uniaxially stretched free end by 2.0 times in the longitudinal direction (length direction) between the rolls from which a circumferential speed differs in 120 degreeC oven (air auxiliary stretching).

Subsequently, the laminate was immersed in an insolubilization bath (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, the laminate was immersed in a 30 ° C. dyeing solution (aqueous solution in which 3.4 parts by weight of potassium iodide and 0.8 parts by weight of ferric sulfate n-hydrate were added) to 100 parts by weight of water, and dyed (dyed). The molar ratio of iodide to oxidant in the dyeing solution was 13.3 / 1. Moreover, about ferric sulfate n hydrate added to the dyeing solution, it confirmed that it was an average 6.7 hydrate by iodine titration. Therefore, the molar ratio with iodide was computed by making the average molecular weight of ferric sulfate n hydrate into 520.

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

Thereafter, the rolls differ in circumferential speed while the laminate is immersed in a boric acid aqueous solution (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 at a liquid temperature of 70 ° C. Uniaxial stretching was performed so that total draw ratio might be 5.5 times in the longitudinal direction (length direction) between (underwater stretching).

Then, the laminated body was immersed for 10 second in the washing bath (water solution obtained by mix | blending 4 weight part of potassium iodide with respect to 100 weight part of water) with a liquid temperature of 30 degreeC (washing process).

Then, it dried for 120 second in 50 degreeC oven, and obtained the laminated body 1 which has a PVA-type resin layer (polarizer) of 5 micrometers in thickness.

Example 2

Except for making the dyeing solution an aqueous solution (molar ratio of iodide to oxidizing agent in the dyeing solution = 13.3 / 1) to which 1.7 parts by weight of potassium iodide and 0.4 parts by weight of ferric sulfate were added based on 100 parts by weight of water. In the same manner as in Example 1, a laminate 2 having a PVA-based resin layer (polarizer) having a thickness of 5 μm was obtained.

Example 3

In the same manner as in Example 1, a laminate was produced.

The obtained elongate laminated body was 4.5 times air-drawn at 140 degreeC by the tender drawing machine in the direction orthogonal to the longitudinal direction of a laminated body.

Subsequently, the laminate was immersed in a 30 ° C. dyeing solution (an aqueous solution in which 6.0 parts by weight of potassium iodide and 0.8 parts by weight of ferric sulfate n-hydrate was added) based on 100 parts by weight of water, followed by dyeing (dyeing treatment). ). The molar ratio of iodide to oxidant in the dyeing solution was 23.5 / 1.

Subsequently, it was immersed for 35 second in the crosslinking bath (The boric acid aqueous solution obtained by mix | blending 3 weight part of potassium iodide and boric acid 3 weight part with respect to 100 weight part of water) of liquid temperature of 60 degreeC (crosslinking process).

Subsequently, the laminate was immersed for 10 seconds in a washing bath having a liquid temperature of 25 ° C. (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment).

Then, it dried for 120 second in 60 degreeC oven, and obtained the laminated body 3 which has a 2.5-micrometer-thick PVA system resin layer (polarizer).

Example 4

Using a laminate having a PVA-based resin layer having a thickness of 7 µm, and 30 parts by weight of potassium iodide included in the dyeing solution (molar ratio of iodide and oxidant in the dyeing solution = 46.9 / 1) A laminate 4 having a PVA-based resin layer (polarizer) having a thickness of 1.5 μm was obtained in the same manner as in Example 3 except for the above.

Example 5

A PVA system having a thickness of 1.5 µm in the same manner as in Example 4, except that 15.0 parts by weight of potassium iodide contained in the dyeing solution (molar ratio of iodide to oxidant in the dyeing solution = 23.5 / 1) was used. The laminated body 5 which has a strata (polarizer) was obtained.

Example 6

A PVA-based resin layer having a thickness of 1.5 µm in the same manner as in Example 4, except that 10.0 parts by weight of potassium iodide contained in the dyeing solution (molar ratio of iodide to oxidant in the dyeing solution = 15.6 / 1) was used ( A laminate 6 having a polarizer) was obtained.

Example 7

A PVA-based resin layer having a thickness of 1.5 µm in the same manner as in Example 4, except that 7.0 parts by weight of potassium iodide contained in the dyeing solution (molar ratio of iodide to oxidant in the dyeing solution = 11.0 / 1) was used. A laminate 7 having a polarizer) was obtained.

Example 8

A laminate 8 having a PVA resin layer (polarizer) having a thickness of 1.0 μm was obtained in the same manner as in Example 5, except that the laminate formed with a PVA resin layer having a thickness of 5 μm was used.

Example 9

Except having used the laminated body which formed the PVA-type resin layer of 4 micrometers in thickness, it carried out similarly to Example 5, and obtained the laminated body 9 which has a 0.8-micrometer-thick PVA-type resin layer (polarizer).

(Reference example)

The dyeing solution was laminated in the same manner as in Example 4 except that the dyeing solution was used as an aqueous solution in which 7 parts by weight of potassium iodide and 1 part by weight of iodine were added based on 100 parts by weight of water. Sieve 10 was obtained.

Using the laminated body obtained in Examples 1-9 and the reference example, the unitary transmittance | permeability, dyeability, and the iodine sublimation amount of the dye solution of PVA system resin (polarizer) were evaluated by the following method. The results are shown in Table 1.

1. Single transmittance

The single body transmittance of the laminated body was measured using the spectrophotometer with an integrating sphere (manufactured by Nippon Spectrum Co., Ltd., product name: V7100).

2. Dyeing (dyeing index)

The dyeability of the PVA system resin layer (polarizer) of the obtained laminated body was evaluated by the dyeing index calculated from the following formula. The higher the dyeing index, the more fully dyed and indicating that it has a high function as a polarizer. If the dyeing index is 0.4 or more, it shows that it has sufficient function as a polarizer. The dyeing index is preferably 1.5 or more, more preferably 2.0 or more, and still more preferably 2.5 or more.

3. Iodine sublimation amount of dyeing solution

20 mL of the dyeing solution used in each Example and Reference Example was injected into the Tedlar bag (made by JULS Science) which put 2 L of nitrogen. Subsequently, it was heated for 24 hours in a dryer at 30 ° C. Thereafter, 1.5 L of gas in the Tedlar bag was collected in a hydrazine absorbent liquid (hydrazine aqueous solution, hydrazine concentration: 0.05% by weight) using an impinger. Thereafter, the hydrazine absorbent liquid was diluted 1000-fold with pure water, and quantitative analysis was performed using an ion chromatography apparatus (Thermo Scientific, product name: ICS-3000). Measurement conditions were performed as follows.

<Measurement conditions>

Separation column: Dionex Ion Pac AS18-fast (4mm × 150mm)

Guard column: Dionex ion pack AG18-fast (4 mm × 30 mm)

Removal System: Dionex AERS-500 (External Mode)

Detector: electrical conductivity detector

Eluent: KOH aqueous solution (eluent generator EGCII)

Eluent flow rate: 1.2 mL / min

Sample injection volume: 250 μL

TABLE 1

The polarizers obtained in Examples 1 to 9 were all dyed well, and functioned sufficiently as polarizers. In Examples 3 to 5, 8, and 9, the dyeing index was 1.5 or more, the amount of iodine sublimation in the dyeing solution was 250 µg / L or less, and the environmental load and the influence on the human body could also be suppressed.

[Industry availability]

The manufacturing method of this invention can dye a PVA system resin film more efficiently, and can provide the polarizer fully dyed even if it is thin. The polarizer obtained by the manufacturing method of this invention can be applied widely to liquid crystal panels, such as a liquid crystal television, a liquid crystal display, a mobile telephone, a digital camera, a video camera, a portable game machine, car navigation, a copier, a printer, a fax, a clock, and a microwave oven. Can be.

Claims (8)

As a manufacturing method of light polarizer which includes the process of dyeing a polyvinyl alcohol-type resin film using the solution containing the oxidizing agent with respect to iodide and iodide ion,
The said oxidizing agent is an ionic compound containing a cation and an anion, The manufacturing method of the polarizer in which the standard electrode potential of either an anion or a cation is larger than the standard electrode potential of iodine ion. The method of claim 1,
The manufacturing method of the polarizer whose standard electrode potential of the said anion or cation is 0.55V or more. The method according to claim 1 or 2,
The manufacturing method of light polarizer whose content of the iodide in the said solution is 1 weight part-40 weight part with respect to 100 weight part of solvents. The method according to any one of claims 1 to 3,
The manufacturing method of light polarizer whose content of the oxidizing agent in the said solution is 0.1 weight part-10 weight part with respect to 100 weight part of solvents. The method according to any one of claims 1 to 4,
The molar ratio of the said iodide and the said oxidizing agent is a manufacturing method of the polarizer which is 2/1-50/1. The method according to any one of claims 1 to 5,
The manufacturing method of light polarizer in which the said oxidant contains trivalent iron ion as a cation. The method of claim 6,
And said oxidizing agent is at least one member selected from the group consisting of ferric sulfate, ferric chloride and ferric nitrate. The method according to any one of claims 1 to 7,
The manufacturing method of light polarizer whose thickness of light polarizer is 10 micrometers or less.