TW202028785A - Polarizer and method of manufacturing the same - Google Patents

Abstract

An objective of the present invention is to provide a polarizer having excellent heat resistance.

As a solution, provided is a polarizer having a ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds of 0.45 or more and 0.9 or less.

Description

Polarizer and its manufacturing method

The present invention relates to a polarizer that can be used as a constituent member of a polarizing plate and its manufacturing method.

As the polarizer, a polyvinyl alcohol-based resin film in which a dichroic dye such as iodine or a dichroic dye has been adsorbed and aligned is known. Patent Documents 1 to 3 propose zinc-containing resin films as such polyvinyl alcohol-based resin films.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2003-29042 A

[Patent Document 2] JP 2004-61565 A

[Patent Document 3] JP 2014-102353 A

When a polarizer is used as a component of a polarizer at a high temperature for a long time, it may be discolored. Therefore, it is required to improve the heat resistance of the polarizer.

The subject of the present invention is to provide a polarizer with good heat resistance.

The present invention provides the following polarizers, polarizers, and methods for manufacturing polarizers.

[1] A polarizer in which the ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds exceeds 0.47 and does not reach 0.9.

[2] The polarizer according to [1], wherein the ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds in a direction parallel to the absorption axis of the polarizer is more than 0.47 and less than 0.9.

[3] The polarizer as described in [1] or [2], which has a thickness of 1.5 μm or less.

[4] A polarizing plate comprising the polarizer described in any one of [1] to [3], a first thermoplastic resin film provided on one side of the polarizer, and a first thermoplastic resin film provided on the other side of the polarizer The second thermoplastic resin film.

[5] The polarizing plate according to [4], wherein the second thermoplastic resin film is a retardation film.

[6] The polarizing plate as described in [4] or [5], the absolute value △Ty of the luminosity factor corrected for the difference in monomer transmittance Ty before and after the durability test at 105°C and 1000 hours Below 4%.

[7] The polarizing plate as described in any one of [4] to [6], the difference between the maximum value of the TD transmittance at a wavelength of 500nm to 600nm before and after the durability test at 105°C and 1000 hours The absolute value of ΔTD is 0.014 or less.

[8] The polarizing plate according to any one of [4] to [7], wherein the absolute value Δa of the difference in the orthogonal hue a value before and after the durability test at 105° C. and 1000 hours is 2.5 or less.

[9] An in-vehicle display device comprising the polarizing plate described in any one of [4] to [8], a translucent member arranged on the first thermoplastic resin film side of the polarizing plate, and arrangement The display device on the second thermoplastic resin film side of the aforementioned polarizing plate.

[10] A method for manufacturing a polarizer, which is the method for manufacturing a polarizer according to any one of [1] to [3], wherein

The aforementioned polarizer contains polyvinyl alcohol resin,

This production method includes a step of applying a treatment to a polyvinyl alcohol-based resin film using a treatment liquid containing a zinc salt.

With the present invention, a polarizer with good heat resistance can be provided.

100: Polarizing plate

101: Polarizer

102: The first thermoplastic resin film

103: The second thermoplastic resin film

Fig. 1 is a flowchart showing a method of manufacturing a polarizer according to one aspect of the present invention.

Fig. 2 is a schematic cross-sectional view showing a polarizing plate according to an aspect of the present invention.

<Polarizer>

One aspect of the polarizer of the present invention is an absorption-type polarizer that absorbs linearly polarized light having a vibration plane parallel to the absorption axis, and has the absorption axis perpendicular to the The property of linearly polarized light penetrating through the vibrating surface (parallel to the penetrating axis). The polarizer can be, for example, a polarizer formed by adsorbing and aligning a dichroic dye such as iodine on a uniaxially stretched polyvinyl alcohol-based resin film, and such a polarizer can be manufactured in accordance with the manufacturing method described below. It can be used as a polarizing plate by bonding with a protective film or the like on the surface of the polarizer with an adhesive or adhesive. Unless otherwise specified below, the polarizing plate refers to a polarizing plate provided with a thermoplastic resin film on at least one side of the polarizer. The polyvinyl alcohol-based resin may be the same as the one exemplified in the description of the method for manufacturing the polarizer described later.

The polarizer of one aspect of the present invention can exhibit excellent heat resistance. It is preferable that the polarizer of one aspect of the present invention can prevent yellowing, whitening, and redness when a durability test is performed using a polarizer as a component of the polarizing plate. The durability test in the present invention refers to a durability test performed in accordance with the method described in the paragraph of the following examples. The yellowing, whitening, and redness are as explained in the paragraphs mentioned later.

The polarizing plate of the vehicle-mounted display device is attached to the image display unit by, for example, an adhesive or adhesive, and the adhesive or adhesive is applied to the surface opposite to the surface attached to the image display unit. Laminate with translucent members such as glass plates and touch panels. The polarizing plate of the vehicle-mounted display device may be used for a long time at a relatively high temperature, and discoloration tends to occur in this case. The inventors of the present invention conducted research on discoloration and found that the discoloration of polarizers that have been used for a long time at a higher temperature can be roughly classified into three types: yellowing, whitening, and reddening. Hereinafter, yellowing, whitening, and redness are sometimes collectively referred to as discoloration.

Yellowing is the change in color that is visible when observed through an optical microscope before and after the durability test of the polarizing plate. According to the results of the inventor’s research on yellowing, it can be seen that the absolute value △Ty (hereinafter referred to as "△Ty) of the difference between the luminous factor correction monomer transmittance (Ty) before and after the durability test of the polarizing plate using the polarizer ") When it is smaller, the yellowing also tends to be less. Although it is presumed that the yellowing is caused by heating the polarizing plate to over 90°C, part of the polyiodide complexes I ₃ ^- and I ₅ ^- oriented and adsorbed in the polyvinyl alcohol-based resin film are thermally decomposed and become I ₂ , Due to the dehydration reaction generated by I ₂ detaching the hydroxyl group in the polyvinyl alcohol-based resin film to form a double bond. However, the present invention is not limited to this speculator. The luminescence factor corrected monomer transmittance (Ty) is measured in accordance with the measurement method described in the paragraph of the examples described later.

Whitening refers to a situation in which light leakage is observed in the darkest visual field by rotating the polarizing plate when observing other polarizing plates through an optical microscope before and after the durability test of the polarizing plate. According to the results of the inventor’s research on whitening, the absolute value △TD (hereinafter referred to as "△TD") of the difference between the maximum value (TDmax) of the TD transmittance at a wavelength of 500nm to 600nm before and after the durability test is small At times, bleaching also has less tendency. Although it is presumed that whitening occurs because the polyiodide complexes I ₃ ^- and I ₅ ^- in the polyvinyl alcohol-based resin film aligned and adsorbed in the polarizer are thermally decomposed in the durability test, and the polymerization in the polarizer The content of iodine complexes I ₃ ^- and I ₅ ^- decreased. However, the present invention is not limited to this speculator. The maximum value (TDmax) of the TD transmittance at a wavelength of 500 nm or more and 600 nm or less (TDmax) is measured in accordance with the measurement method described in the paragraph of Examples described later.

Redness refers to the change in color that is visible when observed through an optical microscope before and after the durability test of the polarizing plate. From the results of the inventor’s research on redness, it can be seen that when the absolute value Δa (hereinafter referred to as "Δa") of the difference between the orthogonal hue a before and after the durability test of the polarizer using the polarizer is small, the redness is also There is also a tendency to decrease. While the presumed cause redness generating system because the alignment of the adsorbed iodine complexes with polyethylene of maximum absorption of visible light in the longer wavelength side of the polyvinyl alcohol-based resin film in a polarizing sheet I ₅ ^- subjected to heat in the durability test Decomposition, and the content of I ₅ ^- is reduced. However, the present invention is not limited to this speculator. The orthogonal hue a is measured in accordance with the measurement method described in the paragraph of Examples described later.

The ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds (hereinafter also referred to as I-Zn/II bonding ratio) of the polarizer is more than 0.47 and less than 0.9, which is preferably due to the absorption of the polarizer The I-Zn/II bonding ratio in the direction parallel to the axis exceeds 0.47 and does not reach 0.9. The iodine-iodine bond (hereinafter also referred to as II bond) is a bond between iodine atoms in an iodine compound adsorbed and aligned to a film (for example, a polyvinyl alcohol-based resin film). Iodine compounds, for example, may be _{^{I 3 -, I 5 -,}} I 2 and the like. The iodine-zinc bond (hereinafter also referred to as I-Zn bond) is a bond between an iodine atom and a zinc atom in an iodine compound. When the I-Zn/II bonding ratio exceeds 0.47, there is a tendency to easily suppress yellowing and redness. In addition, when the I-Zn/II bonding ratio is less than 0.9, there is a tendency to easily suppress whitening. The I-Zn/II bonding ratio is measured in accordance with the measurement method described in the paragraph of Examples described later.

From the viewpoint of discoloration suppression during long-term use at high temperatures, the I-Zn/I-I bonding ratio is preferably 0.48 or more and 0.85 or less, more preferably 0.5 or more and 0.8 or less, and still more preferably 0.55 or more and 0.75 or less.

Regarding the method of setting the I-Zn/I-I bonding ratio within the above-mentioned range, for example, adjusting the content of the zinc element in the polarizer, adjusting the thickness of the polarizer, and the like. For example, when the content of zinc element is reduced, the I-Zn/I-I bonding ratio tends to be lower, and when the content of zinc element is increased, the I-Zn/I-I bonding ratio tends to be higher. In addition, when the thickness of the raw material of the film used (for example, a polyvinyl alcohol resin film) is reduced, the ratio of the I-Zn/I-I bonding ratio to the zinc element content ratio tends to decrease.

The thickness of the polarizer can be, for example, 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less, and still more preferably 14 μm or less Below, it is particularly preferably 13 μm or less, and more particularly preferably 12 μm or less. When the thickness of the polarizer is 30 μm or less, whitening tends to be easily prevented. In addition, making the thickness of the polarizer thinner is beneficial to thinning the polarizer. The thickness of the polarizer is usually 2 μm or more, for example, 5 μm or more.

The thickness of the polarizer can be set to the thickness of the above-mentioned range by, for example, selection of a polyvinyl alcohol-based resin film, adjustment of a stretching ratio, and the like.

The polarizer can contain any amount of zinc. When the I-Zn/II bonding ratio is 0.48 or more, it tends to easily suppress yellowing and redness. When the I-Zn/II bonding ratio is less than 0.85, it is easy to suppress The tendency of whitening, therefore, it is better to adjust to this range.

For example, when the thickness of the polarizer is 20 μm or less (preferably 15 μm or less), in terms of preventing yellowing and redness, the content of zinc element is preferably 0.305 mass% or more, and more preferably 0.31 mass% or more. On the other hand, in terms of preventing whitening, the content of zinc element is preferably 0.75 mass% or less, more preferably 0.7 mass% or less, more preferably 0.65 mass% or less, and more preferably 0.5 mass% or less good. The content of zinc element can be measured in accordance with the measurement method described in the paragraph of Examples described later.

The content of the zinc element can be adjusted, for example, by adjusting the zinc salt concentration in the treatment solution for treating the polyvinyl alcohol resin film, the time the polyvinyl alcohol resin film is immersed in the treatment solution containing the zinc salt, the temperature of the treatment solution, etc. And set it as the content of zinc element in the said range.

It is inferred that by making the polarizer contain zinc in the above-mentioned range, the thermal decomposition of polyiodide complexes I ₃ ^- and I ₅ ^- and the formation of I ₂ in the polarizer can be suppressed, and the result is It is difficult to cause discoloration such as yellowing or reddish/whitening. However, the present invention is not limited to this speculator.

The luminescence factor correction monomer transmittance (Ty) of the polarizer before the durability test can exceed 40.5%, for example, and the lower limit of the luminescence factor correction monomer transmittance (Ty) is preferably 41.0% or more. The limit is usually below 50%, and preferably below 47%.

The ΔTy of the polarizer may be 4% or less, and more preferably 3.5% or less.

When the luminescence factor correction monomer transmittance (Ty) before the durability test of the polarizer is 41.5%, the luminescence factor correction polarization degree (Py) can exceed 99.980, for example, and the luminescence factor correction monomer transmittance (Ty) is 41.5 %, the lower limit of the luminous factor correction polarization (Py) is preferably 99.985 or more.

The maximum value (TDmax) of the TD transmittance of the polarizer at a wavelength of 500 nm or more and 600 nm or less before the durability test may be 0.01 or less, and preferably 0.008 or less.

The ΔTD of the polarizer can be, for example, 0.014 or less, and preferably 0.01 or less.

The orthogonal hue a of the polarizer before the durability test can be, for example, 2.6 or less, and preferably 1 or less.

The Δa of the polarizer can be, for example, 2.5 or less, and preferably 2.45 or less.

The luminescence factor correction monomer transmittance (Ty), △Ty, △TD, luminescence factor correction polarization degree (Py), orthogonal hue a and △a of the polarizer can be in accordance with the method described in the paragraphs of the embodiments described later The measurement is carried out in the same operation as when measuring the polarizing plate.

<Method of manufacturing polarizer>

The manufacturing method of another aspect of the polarizer of the present invention will be described with reference to the drawings.

The manufacturing method shown in Figure 1 is a manufacturing method of a polarizer containing a polyvinyl alcohol resin film, which may include the following steps:

Dyeing step S20 in which the polyvinyl alcohol-based resin film is immersed in a dyeing tank containing a treatment solution containing a dichroic dye to perform dyeing; and

The film after the dyeing step is immersed in a cross-linking tank containing a treatment liquid containing a cross-linking agent to perform a cross-linking step S30 of cross-linking treatment.

The manufacturing method may further include other steps than the above. The specific example shown in Figure 1 is a swelling step S10 in which a polyvinyl alcohol resin film is immersed in a swelling tank containing a water-containing treatment solution before the dyeing step S20. The washing step S40 in which the film after the crosslinking step S30 is immersed in a washing tank, and the drying step S50 after the washing step S40. In addition, the polyvinyl alcohol-based resin film is uniaxially stretched in any one or more stages of the polarizer manufacturing step, more specifically, in any one or more stages from before the swelling step S10 to the crosslinking step S30 During the uniaxial stretching process (stretching step).

In the manufacturing method, at least one treatment liquid system for treating the polyvinyl alcohol-based resin film contains a zinc salt. Examples of the processing tank that contains the processing liquid include a swelling tank, a dyeing tank, a cross-linking tank, a washing tank, and the color correction tank described later. The treatment tank containing the treatment solution containing zinc is preferably the treatment tank located after the dyeing tank and before the cleaning tank, preferably at least one selected from the cross-linking tank and the complementary color tank, and more than two When the cross-linking tank is selected from at least one of the last cross-linking tank and complementary color tank, it is more preferable. By immersing the polyvinyl alcohol-based resin film in a treatment solution containing zinc salt, the obtained polarizer can contain zinc element. The content of the zinc element in the polarizer can be adjusted to the zinc element in the above range by adjusting the zinc concentration in the treatment liquid, the time for immersing the polyvinyl alcohol resin film in the treatment liquid containing the zinc salt, the temperature of the treatment liquid, etc. The content.

Examples of the zinc salt contained in the treatment liquid include zinc halides such as zinc chloride and zinc iodide, or zinc sulfate, zinc acetate, and zinc nitrate. Among them, in terms of small changes in tension, zinc nitrate is preferred. Zinc salt can be added to the treatment solution as a zinc solution.

The concentration of the zinc salt in the treatment liquid may be different in each treatment tank, but it may be, for example, 2 parts by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the treatment liquid contained in the treatment tank.

The immersion time of the polyvinyl alcohol resin film in the treatment liquid and the temperature of the treatment liquid may be different in each treatment tank. The specific immersion time and the temperature of the treatment liquid are as described in the respective steps in the later paragraphs.

The various processing steps included in the manufacturing method of the present invention can be continuously performed by continuously conveying the polyvinyl alcohol-based resin film as the raw film along the film conveying path of the polarizer manufacturing apparatus. The film transport path is equipped with equipment (processing tank, furnace, etc.) for performing the above-mentioned various processing steps according to the implementation sequence.

In addition to the above-mentioned equipment, it is also possible to construct a film transport path by arranging guide rolls or nip rolls at appropriate positions. For example, guide rollers can be arranged before and after each treatment tank or in the treatment tank, whereby the film can be introduced, immersed in the treatment tank, and drawn out of the treatment tank. More specifically, by arranging two or more guide rollers in each treatment tank and transporting the film along these guide rollers, the film can be immersed in each treatment tank.

As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film as the raw material film, a saponified polyvinyl acetate-based resin can be used. In addition to the homopolymers of vinyl acetate, polyvinyl acetate-based resins can be exemplified by copolymers of vinyl acetate and other monomers copolymerizable with the vinyl acetate. Other monomers that can be copolymerized with vinyl acetate include: for example, unsaturated Carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth)acrylamides with ammonium groups, etc. The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. The "(meth)acrylic acid" in this specification means at least one selected from an acrylic group and a methacrylic group. The same applies to "(meth)acrylic acid base".

The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formaldehyde, polyvinyl acetal, polyvinyl butyral, etc. modified by aldehydes can be used.

The average degree of polymerization of the polyvinyl alcohol resin is preferably 100 or more and 10,000 or less, more preferably 1,500 or more and 8,000 or less, and more preferably 2,000 or more and 5,000 or less. The average degree of polymerization of the polyvinyl alcohol-based resin is determined based on JIS K 6726 (1994). If the average degree of polymerization is less than 100, it is difficult to obtain good polarization performance, and when it exceeds 10,000, the processability of the film will deteriorate.

The thickness of the polyvinyl alcohol-based resin film is, for example, about 10 μm or more and 50 μm or less. When the thickness of the polarizer is 15 μm or less, it is preferably 40 μm or less, and more preferably 30 μm or less.

The polyvinyl alcohol-based resin film as the raw material film can be prepared as a long unstretched or stretched polyvinyl alcohol-based resin film roll (winding product). In this case, the polarizer can also be obtained as a long object. The steps are described in detail below.

(1) Swelling step S10

The swelling treatment in this step is based on the polyvinyl alcohol resin film as the raw material film to remove foreign matter, remove plasticizers, impart easy dyeability, and plasticize the film as needed. Specifically, it can be The polyvinyl alcohol resin film is immersed in a swelling tank containing a treatment liquid containing water for treatment. The film can be immersed in one swelling tank or in more than 2 swelling tanks in sequence in. Before swelling treatment, during swelling treatment, or before swelling treatment and during swelling treatment, the film can be subjected to uniaxial stretching treatment.

In addition to water (for example, pure water), the treatment liquid contained in the swelling tank may also be an aqueous solution to which a water-soluble organic solvent such as alcohol has been added. As mentioned above, the treatment liquid contained in the swelling tank may contain zinc salt.

The temperature of the treatment liquid contained in the swelling tank when the film is immersed is usually about 10 to 70°C, preferably about 15 to 50°C, and the immersion time of the film is usually about 10 to 600 seconds, preferably about 20 to 300 seconds .

(2) Dyeing step S20

The dyeing treatment in this step is based on the purpose of allowing the polyvinyl alcohol resin film to absorb and align iodine. Specifically, the polyvinyl alcohol resin film can be immersed in a dyeing tank containing a treatment solution containing iodine. deal with. The film can be immersed in one dyeing tank or in two or more dyeing tanks in sequence. In order to improve the dyeability of iodine, the film used in the dyeing step may also be subjected to at least some degree of uniaxial stretching treatment. It is also possible to perform the uniaxial stretching treatment during the dyeing treatment to replace the uniaxial stretching treatment before the dyeing treatment, or perform it together with the uniaxial stretching treatment before the dyeing treatment.

Moreover, iodine can also be used together with a dichroic organic dye. When using dichroic organic dyes, the dichroic organic dyes can be used in combination with iodine in one dyeing tank. When two or more dyeing tanks are used, they can be used in a dyeing tank that is different from the dyeing tank that uses iodine. . Specific examples of dichroic organic dyes include Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black. The dichroic dye may be used alone or in combination of two or more.

In the treatment liquid contained in the dyeing tank using iodine, an aqueous solution containing iodine and potassium iodide can be used. Other iodides such as zinc iodide can be used instead of potassium iodide, or potassium iodide and other iodides can be used together. In addition, compounds other than iodides such as boric acid, zinc chloride, and cobalt chloride may coexist. When boric acid is added, it is distinguished from the cross-linking treatment described later according to the content of iodine. The content of iodine in the above-mentioned aqueous solution is usually 0.01 part by mass to 1 part by mass per 100 parts by mass of water. In addition, the content of iodides such as potassium iodide is usually 0.5 to 20 parts by mass per 100 parts by mass of water. As mentioned above, the treatment liquid contained in the dyeing tank may contain zinc salt.

The temperature of the treatment solution contained in the dyeing tank when immersing the film is usually 10°C or more and 45°C or less, preferably 10°C or more and 40°C or less, and more preferably 20°C or more and 35°C or less. The immersion time of the film Generally, it is 30 seconds or more and 600 seconds or less, and preferably 60 seconds or more and 300 seconds or less.

When using dichroic organic dyes, the treatment liquid contained in the dyeing tank can be an aqueous solution containing dichroic organic dyes. The content of the dichroic organic dye in the aqueous solution is usually 1×10 ^-4 parts by mass to 10 parts by mass per 100 parts by mass of water, preferably 1×10 ^-3 parts by mass to 1 part by mass. Dyeing auxiliaries and the like may also coexist in the dyeing tank, for example, containing inorganic salts such as sodium sulfate or surfactants. The dichroic organic dye may be used alone or in combination of two or more. The temperature of the treatment solution contained in the dyeing tank when the film is dipped is, for example, 20°C or more and 80°C or less, preferably 30°C or more and 70°C or less. The immersion time of the film is usually 30 seconds or more and 600 seconds or less, and 60 seconds or more and 300 The second is better.

(3) Cross-linking step S30

The cross-linking treatment of the polyethanol resin film after the dyeing step with a cross-linking agent is based on the purpose of water resistance or color adjustment by cross-linking. Specifically, the film after the dyeing step can be immersed in It contains cross-linking agent and is contained in the treatment liquid in the cross-linking tank. The film can be immersed in one cross-linking tank or in two or more cross-linking tanks in sequence. Uniaxial stretching can be performed during cross-linking treatment.

Examples of the crosslinking agent include boric acid, glyoxal, and glutaraldehyde, and boric acid can be preferably used. Two or more crosslinking agents can also be used at the same time. The content of boric acid in the treatment liquid contained in the cross-linking tank is usually 0.1 to 15 parts by mass per 100 parts by mass, preferably 1 part by mass to 10 parts by mass. When the dichroic dye is iodine, the treatment liquid contained in the crosslinking tank preferably contains iodide in addition to boric acid. The content of iodide in the treatment liquid contained in the cross-linking tank is usually 0.1 to 15 parts by mass per 100 parts by mass of water, preferably 5 parts by mass to 12 parts by mass. Examples of the iodide include potassium iodide and zinc iodide. In addition, compounds other than iodides, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may coexist in the crosslinking tank. As described above, the treatment liquid contained in the crosslinking tank may contain zinc salt. When there are more than two cross-linking tanks, it is better that the treatment solution contained in the last cross-linking tank contains zinc salt.

The temperature of the treatment liquid contained in the cross-linking tank when the film is immersed is usually 50°C or more and 85°C or less, preferably 50°C or more and 70°C or less. The film immersion time is usually 10 seconds or more and 600 seconds or less, and 20 seconds or more. 300 seconds or less is better.

In the crosslinking step S30, the number of crosslinking tanks may be two or more. At this time, the composition and temperature of the treatment liquid contained in each crosslinking tank may be the same or different. The treatment liquid contained in the cross-linking tank may have a concentration or temperature of a cross-linking agent, iodide, etc. according to the purpose of impregnating the polyvinyl alcohol-based resin film. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for adjusting hue (complementary color) can be performed in multiple steps (for example, several tanks) separately.

When performing both the cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for adjusting the hue (complementary color), the tank for the cross-linking treatment for adjusting the hue (complementary color) is usually arranged in After the paragraph. The temperature of the treatment liquid contained in the color correction tank is, for example, 10°C or more and 55°C or less, and preferably 20°C or more and 50°C or less. The content of the crosslinking agent in the treatment liquid contained in the color correction tank is, for example, 1 part by mass to 5 parts by mass per 100 parts by mass of water. The content of iodide in the treatment liquid contained in the color correction tank is, for example, 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of water. As mentioned above, the treatment liquid contained in the complementary color tank may contain zinc salt.

As described above, when manufacturing a polarizer, the polyvinyl alcohol-based resin film is uniaxially stretched in any one or two or more stages from before the swelling step S10 to the crosslinking step S30 (stretching step, Fig. 1). From the viewpoint of improving the dyeability of dichroic pigments, the film used in the dyeing step is preferably a film with at least a certain degree of uniaxial stretching treatment, or uniaxial stretching treatment during dyeing treatment instead of dyeing The uniaxial stretching treatment before the treatment or together with the uniaxial stretching treatment before the dyeing treatment.

The uniaxial stretching treatment may be either dry stretching in the air or wet stretching in the groove, or both types of stretching may be performed. The uniaxial stretching treatment may be inter-roll stretching, hot roll stretching, and tenter stretching in which longitudinal uniaxial stretching is performed between two rolls at a circumferential speed difference, but it is preferable to include inter-roll stretching. Stretching magnification based on raw film made (in 2 When the stretching treatment is performed in the above stages, the cumulative stretching magnification) is about 3 times or more and 8 times or less. In order to impart good polarization characteristics, the extension ratio is preferably 4 times or more, and more preferably 5 times or more.

(4) Cleaning step S40

The cleaning treatment in this step is based on the purpose of removing the excess crosslinking agent or dichroic pigment attached to the polyvinyl alcohol resin film, and is performed as needed. This treatment uses a water-containing cleaning solution to clean the crosslinking The polyvinyl alcohol resin film after the step. Specifically, a process of immersing the polyvinyl alcohol-based resin film after the cross-linking step in a treatment liquid (cleaning liquid) contained in a cleaning tank can be adopted. The film can be immersed in one cleaning tank or in two or more tanks in sequence. Alternatively, the cleaning treatment may be to spray a cleaning solution by showering on the polyethanol-based resin film after the crosslinking step, or a combination of the above-mentioned dipping and spraying.

The cleaning liquid may be water (for example, pure water), or may be an aqueous solution to which a water-soluble organic solvent such as alcohol has been added. The temperature of the cleaning solution can be, for example, 5°C or more and 40°C or less.

The cleaning step S40 is an optional step and may be omitted, and the cleaning process may be performed in the drying step S50 as described later. It is advisable to perform a drying step S50 on the film after the cleaning step S40.

(5) Drying step S50

The drying step S50 is a zone for drying the polyvinyl alcohol resin film after the washing step S40. While continuously conveying the polyvinyl alcohol-based resin film after the cleaning step S40, the film is introduced into the drying step S50 to be dried, thereby obtaining a polarizer.

The drying process can be performed by the drying method (heating method) of the film. A suitable example of the drying means is a drying furnace. The drying furnace should be capable of controlling the temperature in the furnace. The drying oven can be A hot blast stove that increases the temperature in the furnace by supplying hot blast. In addition, the drying treatment performed by the drying means may be a treatment in which the polyvinyl alcohol resin film after the cleaning step S40 is adhered to one or more heating bodies having a convex surface, or the film may be heated by a heater. Heat treatment.

Examples of the heating body include a roller (for example, a guide roller that also serves as a heat roller) that includes a heat source (for example, a heat medium such as warm water or an infrared heater) and can increase the surface temperature. Examples of the above-mentioned heater include infrared heaters, halogen heaters, plate heaters, and the like.

The temperature of the drying treatment (for example, the furnace temperature of the drying furnace, the surface temperature of the hot roll, etc.) is usually 30°C or more and 100°C or less, and preferably 50°C or more and 90°C or less. The drying time is not particularly limited, and is, for example, 30 seconds or more and 600 seconds or less.

After the above steps, a polarizer with dichroic pigments adsorbed and aligned on a uniaxially stretched polyvinyl alcohol resin film can be obtained.

The obtained polarizer can be directly transported, for example, to the next polarizing plate manufacturing step (a step of attaching a thermoplastic resin film to one or both sides of the polarizer).

<Polarizer>

A polarizing plate according to another aspect of the present invention includes the above-mentioned polarizer, a first thermoplastic resin film provided on one side of the polarizer, and a second thermoplastic resin film provided on the other side of the polarizer. The polarizing plate will be described with reference to the drawings. The polarizing plate 100 shown in FIG. 2 includes a first thermoplastic resin film 102 on one side of a polarizer 101 and a second thermoplastic resin film 103 on the other side. Hereinafter, the first thermoplastic resin film and the second thermoplastic resin film are collectively referred to as a thermoplastic resin film.

The thermoplastic resin film may be a transparent resin film containing the following: a thermoplastic resin such as a polyolefin resin such as a chain polyolefin resin (polypropylene resin, etc.), a cyclic polyolefin resin (norbornene resin, etc.) ; Cellulose ester tree such as cellulose triacetate or cellulose diacetate Grease; such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate polyester resin; polycarbonate resin; such as polymethyl methacrylate resin (Meth) acrylic resin; or these mixtures, copolymers, etc.

Either or both of the first thermoplastic resin film and the second thermoplastic resin film may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, by stretching a transparent resin film containing the above-mentioned materials (uniaxial stretching, biaxial stretching, etc.) or forming a liquid crystal layer on the film, a retardation film that gives an arbitrary retardation value can be produced.

A surface treatment layer (coating layer) such as a hard coat layer, an anti-glare layer, an anti-reflection layer, an anti-static layer, and an anti-fouling layer can be formed on the surface of the thermoplastic resin film opposite to the polarizer 101.

Regarding the thinning of the polarizing plate 100, although the thickness of the thermoplastic resin film is preferably thinner, if it is too thin, the strength will be reduced and the workability will tend to deteriorate. Therefore, 5 to 150μm is preferred, and 5 to 100μm is preferred. More preferably, and even more preferably 10 to 50 μm.

The polarizing plate 100 can be obtained by laminating (laminating) a thermoplastic resin film on both sides of the polarizing plate 101 through an adhesive. The adhesive used for bonding between the polarizer 101 and the thermoable resin film includes active energy ray curable adhesives such as ultraviolet curable adhesives, aqueous solutions of polyvinyl alcohol-based resins, or crosslinking agents blended therein Aqueous adhesives such as aqueous solutions and urethane emulsion adhesives. When the thermoplastic resin film is bonded to both sides of the polarizer 101, the adhesives forming the two adhesive layers may be the same type or different types. For example, when laminating a thermoplastic resin film on both sides, one side can be laminated using an aqueous adhesive, and the other side can be laminated using an active energy ray curable adhesive. The ultraviolet curable adhesive may be a mixture of a radically polymerizable (meth)acrylic compound and a photo-radical polymerization initiator, or a mixture of a cationically polymerizable epoxy compound and a photocationic polymerization initiator. In addition, cationic polymerizability can be used in combination The epoxy compound and the radically polymerizable (meth)acrylic compound can also be used in combination with a photocationic polymerization initiator and a photoradical polymerization initiator as the initiator.

When an active energy ray-curable adhesive is used, the adhesive is cured by irradiating the active energy ray after bonding. The light source of the active energy line is not particularly limited, but the active energy line (ultraviolet) with a luminous distribution below the wavelength of 400nm is preferred. Specifically, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, Chemical lamp, black light lamp, microwave excited mercury lamp, metal halide lamp, etc.

In order to improve the adhesion between the polarizer 101 and the thermoplastic resin film, before the polarizer 101 and the thermoplastic resin film are bonded, corona treatment, flame treatment, and electrical treatment can be applied to the bonding surface of the polarizer 101 and/or the thermoplastic resin film. Surface treatment such as slurry treatment, ultraviolet irradiation treatment, primer coating treatment, saponification treatment, etc.

Although it is possible to manufacture the polarizing plate 100 of the present invention by bonding a thermoplastic resin film to the polarizer 101 which is a single-layer film as described above, it is not limited to this method. It can also be produced by a method using a base film as described in JP 2009-98653 A. The latter method is advantageous for obtaining a polarizer having a thin-film polarizer (polarizer layer), and includes, for example, the following steps.

The resin layer forming step is to apply a coating liquid containing a polyvinyl alcohol-based resin to at least one side of the base film and then dry it to form a polyvinyl alcohol-based resin layer to obtain a laminated film,

The stretching step is to stretch the laminated film to obtain a stretched film,

In the dyeing step, a polarizer layer (equivalent to a polarizer) is formed by dyeing the polyvinyl alcohol-based resin layer of the stretched film with a dichroic dye to obtain a polarizing laminated film,

In the first bonding step, the thermoplastic resin film is bonded to the polarizer layer of the polarizing laminated film using an adhesive to obtain a bonded film,

The peeling step is to peel and remove the base film from the laminated film to obtain a polarizing plate with a thermoplastic resin film on one side.

Among them, in the above-mentioned dyeing step, by making the treatment liquid containing the dichroic dye contain zinc salt, the polarizer can be made to contain zinc element.

When the thermoplastic resin film is laminated on both sides of the 101 polarizer (polarizer), a second bonding step is included. The second bonding step uses an adhesive to bond the second thermoplastic resin film on one side with the first thermoplastic The surface of the polarizer of the polarizer of the resin film.

In the above method using the base film, the dyeing step for obtaining the polarizing laminated film (for example, after the crosslinking step in the dyeing step for obtaining the polarizing laminated film or after the washing step) may include a drying step. The polarizers contained in the above-mentioned polarizing laminated film, the polarizer with a thermoplastic resin film on one side, and the polarizer with the thermoplastic resin film on both sides obtained through the second bonding step, or the polarizers separated from them, belong to The polarizer of the present invention.

The I-Zn/I-I bonding ratio, zinc content, thickness, raw material, etc. of the polarizer 101 are the same as those exemplified in the paragraph of the description of the polarizer.

The luminous factor correction monomer transmittance (Ty) of the polarizer before the durability test can exceed 40.5%, for example, the lower limit of the luminous factor correction monomer transmittance (Ty) is preferably 41.0% or more, the upper limit The value is usually below 50%, and preferably below 47%.

The ΔTy of the polarizing plate may be 4% or less, and preferably 3.5% or less.

When the transmittance (Ty) of the luminescence factor correction monomer of the polarizer before the durability test is 41.5%, the luminescence factor correction polarization degree (Py) can exceed 99.980, for example, the luminescence factor correction unit The lower limit of the luminous factor correction polarization (Py) when the volume transmittance (Ty) is 41.5% is preferably above 99.985. The luminous factor correction polarization (Py) can be measured in accordance with the method described in the paragraph of the embodiment described later.

The maximum value (TDmax) of the TD transmittance at a wavelength of 500 nm or more and 600 nm or less of the polarizing plate before the durability test may be, for example, 0.01 or less, preferably 0.008 or less.

The ΔTD of the polarizing plate may be 0.014 or less, and preferably 0.01 or less.

The cross hue a of the polarizing plate before the durability test may be, for example, 2.6 or less, preferably 1 or less.

The Δa of the polarizing plate may be 2.5 or less, preferably 2.45 or less.

The polarizing plate can be used in a display device. The display device may be any of a liquid crystal display device, an organic EL display device, etc., but a liquid crystal display device is preferred. The liquid crystal display device includes a liquid crystal panel and a backlight as a liquid crystal cell as an image display element. When constructing a liquid crystal display device, the polarizing plate can be used as a polarizing plate arranged on the viewing side, as a polarizing plate arranged on the backlight side, or as a polarizing plate on both the viewing side and the backlight side.

The polarizing plate is suitable for an in-vehicle display device including a polarizing plate, a translucent member arranged on the first thermoplastic resin film side of the polarizing plate, and a display device arranged on the second thermoplastic resin film side of the polarizing plate in this order. The light-transmitting member may be a glass plate, a resin film having light-transmitting properties, or the like.

Examples are shown below to explain the present invention more specifically, but the present invention is not limited to these examples.

(Example)

〔Durability test〕

A 40mm×40mm test piece was cut out from the manufactured polarizer, and a 40mm×40mm alkali-free glass was bonded to both sides of the cut out polarizer using an acrylic adhesive with a thickness of 25 μm. The obtained polarizing plate with laminated glass on both sides was used as a sample to carry out the maximum value of TD transmittance (TDmax), luminescence factor correction monomer transmittance (Ty), luminescence factor correction and polarization correction at a wavelength of 500nm or more and 600nm or less Determination of degree (Py) and orthogonal hue a. Next, the measured sample piece was heated in an oven at 105°C for 1000 hours. The samples taken out of the oven were measured for the maximum value of TD transmittance (TDmax), the transmittance of luminous factor correction monomer (Ty), and the optical properties of orthogonal hue a at a wavelength of 500nm above and below 600nm.

[Determination of zinc content]

The measurement of the zinc content in the polarizer was carried out in the following manner.

Nitric acid was added to the accurately weighed polarizer, and the solution obtained by acid decomposition with the microwave sample pretreatment device (ETHOS D) manufactured by Milestone General was used as the measurement liquid. The zinc concentration is determined by the ICP spectrophotometer (5110 ICP-OES) manufactured by Agilent Technologies to quantitatively measure the zinc concentration of the solution, and calculate the mass of zinc relative to the mass of the polarizer.

〔Determination of I-Zn/I-I Bonding Ratio〕

The X-ray absorption spectrum of the iodine-K absorption end was measured by the XAFS (X-ray Absorption Fine Structure) measuring device installed in the Beamline NW-10A, the Radiological Science Facility of the High Energy Accelerator Research Institute.

In the measurement, Si(311) spectroscopic crystal was used. The incident X-ray intensity was a 17cm ionization chamber with argon as the detection gas, and the penetrating X-ray intensity was 31cm ionization with krypton as the detection gas. Room, and measured by penetration method. For the sample system, 100 polarizers are aligned and overlapped with the absorption axis so that the absorption axis of the polarizer becomes parallel The method is placed in the beam for measurement. The obtained absorption spectrum is Fourier transformed by the data analysis program REX2000 (manufactured by Rigaku) to obtain a radial distribution function. In the radial distribution function, the peak near 2.1Å is derived from the I-Zn bond, and the peak near 2.7Å is derived from the II bond. The ratio of the height of each peak is taken as the I-Zn/II bond ratio

〔Maximum value of TD transmittance (TDmax) at wavelength of 500nm above 600nm below

Using a spectrophotometer with integrating sphere ("V7100" manufactured by JASCO Corporation) on a polarizing plate, measure the TD transmittance in the wavelength range of 380 to 780 nm, and obtain the maximum TD in the wavelength range of 500nm to 600nm Penetration rate.

[Luminescence factor correction monomer transmittance (Ty) and luminescence factor correction polarization degree (Py)]

Using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) on a polarizing plate, measure the MD transmittance and TD transmittance in the wavelength range of 380 to 780 nm,

And calculate the monomer transmittance and polarization degree of each wavelength according to the following formula:

Single penetration rate (%)=(MD+TD)/2

Polarization (%)=((MD-TD)/(MD+TD))×100

"MD transmittance" refers to the transmittance when the direction of polarized light emitted from Glan-Thompson prism is parallel to the transmission axis of the polarizer, and is represented by "MD" in the above formula. In addition, "TD transmittance" refers to the transmittance when the direction of polarized light emitted from Glan Thompson's beam is perpendicular to the transmission axis of the polarizer, and is represented by "TD" in the above formula.

According to JIS Z 8701: 1999 "Method of Representing Color-XYZ Color System and X10Y10Z10 Color System", the 2 degree viewing angle (C light source) is used to correct the luminous factor of the obtained monomer transmittance and polarization to obtain the luminescence Factor correction monomer transmittance (Ty) and luminescence factor correction polarization (Py).

[Orthogonal Hue a]

Orthogonal hue a is the value of a in the Lab color system, and the standard light is measured using a spectrophotometer with integrating sphere ("V7100" manufactured by JASCO Corporation). As stated in JIS K 5981: 2006 "Synthetic resin powder coating film", "5.5 Accelerated weather resistance test", the Lab color system is represented by Hunter's lightness index L and hue a and b. Lightness index L and hue The values of a and b are based on the tristimulus values X, Y, and Z specified in JIS Z 8722:2009 "Methods of Color Measurement-Reflected and Penetrated Object Color", and are calculated according to the following formula.

L=10Y ^1/2

a=17.5(10.2XY)/Y ^1/2

b=7.0(Y-0.847Z)/Y ^1/2 .

In the Lab color system, the hue a value and b value can indicate the position corresponding to the saturation. When the hue a value increases, the hue becomes red, and the hue b value increases, and the hue becomes yellow. In addition, the closer to 0, the closer the two are to colorless.

<Example 1>

A long strip of polyvinyl alcohol (PVA) embryo film with a thickness of 30μm (trade name "Kuraray Poval Film VF-PE # 3000, average polymerization degree 2400, saponification degree 99.9 mol% or more) manufactured by Kuraray Co., Ltd.) The roll is continuously transported while being drawn out, and immersed in a swelling tank containing pure water at 20°C for an immersion time of 80 seconds (swelling step). Then, it is pulled out of the swelling tank The film was immersed in a dyeing tank containing a 30°C treatment solution containing potassium iodide/boric acid/water of 1.3/0.3/100 (mass ratio) with an immersion time of 130 seconds (dyeing step). Next, the film drawn from the dyeing tank was immersed in a cross-linking tank containing a 56°C treatment solution with a potassium iodide/boric acid/water ratio of 13.9/3.0/100 (mass ratio) for an immersion time of 50 seconds (cross-linking step) . Continue to immerse the film drawn from the cross-linking tank in a 40°C treatment solution containing potassium iodide/boric acid/zinc nitrate hexahydrate/water (mass ratio) of 9.0/3.0/2.0/100 (mass ratio) for an immersion time of 10 seconds. In the slot (complementary color step).

Next, the film drawn from the cross-linking tank was immersed in a washing tank containing pure water at 70°C for an immersion time of 10 seconds (washing step), and then introduced into a heating furnace at 80°C to immerse The drying process (drying step) was performed for 150 seconds to obtain a polarizer with a thickness of 12 μm. In the swelling step, the dyeing step, the cross-linking step, the color correction step, and the cleaning step, the longitudinal uniaxial extension is performed at the magnification shown in Table 1 by extending between the rollers in the tank. The total extension magnification based on embryonic membrane is 6.0 times. The zinc content of the obtained polarizer was measured. The results are shown in Table 1.

<Example 2>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color complementary tank in the color complementary step was changed to 9.0/3.0/3.0/100, the rest was prepared by the same operation as in Example 1. A polarizer with a thickness of 12μm.

<Example 3>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color correction tank in the color correction step of the polarizer is changed to 9.0/3.0/4.0/100, the rest is the same as in Example 1. A polarizer with a thickness of 12μm is produced by operation.

<Comparative Example 1>

Except that the mass ratio of potassium iodide/boric acid/water in the treatment solution contained in the color correction tank in the color correction step was changed to 9.0/3.0/100, the same operation as in Example 1 was used to prepare a polarizer with a thickness of 12 μm.

<Comparative Example 2>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color compensation tank in the color compensation step was changed to 9.0/3.0/1.0/100, the rest was prepared by the same operation as in Example 1. A polarizer with a thickness of 12μm.

<Comparative Example 3>

A long strip of polyvinyl alcohol (PVA) embryo film with a thickness of 75μm (trade name "Kuraray Poval Film VF-PS # 7500, average degree of polymerization 2400, saponification degree of 99.9 mol% or more) manufactured by Kuraray Co., Ltd.) The roll is drawn out and transported continuously, and immersed in a treatment solution containing pure water at 25°C for an immersion time of 150 seconds (swelling step). Then, the film drawn from the swelling tank is immersed for an immersion time of 170 seconds In a dyeing tank (dyeing step) containing an iodine-containing 30°C treatment solution with a potassium iodide/boric acid/water ratio of 2.0/0.6/100 (mass ratio). Next, the film drawn from the dyeing tank is immersed for 80 Soak in a cross-linking tank (cross-linking step) containing a treatment solution of potassium iodide/boric acid/water at a ratio of 15.4/4.0/100 (mass ratio) at 56°C. Continue the immersion time for the film drawn from the cross-linking tank For 10 seconds, it was immersed in a color correction tank containing a 40°C treatment solution of potassium iodide/boric acid/zinc nitrate hexahydrate/water (mass ratio) of 15.4/4.0/0/100 (color correction step).

Next, the film drawn from the cross-linking tank was immersed in a cleaning tank containing pure water containing 8°C for 10 seconds for an immersion time (cleaning step), and then introduced into a heating furnace at 80°C. Thereby, a drying process (drying step) was performed for an immersion time of 300 seconds to obtain a polarizer having a thickness of 28 μm. In the swelling step, the dyeing step, the cross-linking step, the color correction step, and the cleaning step, the longitudinal uniaxial extension is performed according to the magnification shown in Table 1 by extending between the rollers in the tank. The total extension magnification based on embryonic membrane is 6.0 times.

<Comparative Example 4>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color compensation tank in the color compensation step was changed to 9.0/3.0/5.0/100, the rest was prepared by the same operation as in Comparative Example 3. A polarizer with a thickness of 28μm.

<Comparative Example 5>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color compensation tank in the color compensation step was changed to 9.0/3.0/7.0/100, the rest was prepared by the same operation as in Comparative Example 3. A polarizer with a thickness of 28μm.

<Comparative Example 6>

A long strip of polyvinyl alcohol (PVA) embryonic membrane with a thickness of 60 μm (trade name "Kuraray Poval Film VF-PS # 6000, average polymerization degree 2400, saponification degree 99.9 mol% or more) manufactured by Kuraray (Co., Ltd.) The roll is continuously transported while being drawn out, and immersed in a treatment solution contained in a swelling tank containing pure water at 25°C for an immersion time of 150 seconds (swelling step). Then, the film drawn from the swelling tank is immersed Immerse in a dyeing tank (dyeing step) containing potassium iodide/boric acid/water of 1.3/0.6/100 (mass ratio) containing iodine-containing treatment solution at 30°C for 170 seconds. Next, the film will be pulled out from the dyeing tank Immerse in a cross-linking tank (cross-linking step) containing potassium iodide/boric acid/water of 13.9/4.0/100 (mass ratio) of a 56°C treatment solution for an immersion time of 80 seconds. Continue to pull it out from the cross-linking tank The membrane is immersed in a house containing potassium iodide/boric acid/nitric acid for an immersion time of 10 seconds Zinc hexahydrate/water ratio of 15.4/5.0/0/100 (mass ratio) in the color correction tank of the 40°C treatment solution (color correction step).

Next, the film drawn from the cross-linking tank was immersed in a washing tank containing pure water at 8°C for 10 seconds (washing step), and then introduced into a heating furnace at 80°C to perform a 300 second Drying process (drying step) was performed for the drying time of, to obtain a polarizer with a thickness of 22 μm. In the swelling step, the dyeing step, the cross-linking step, the color correction step, and the cleaning step, the longitudinal uniaxial extension is performed according to the magnification shown in Table 1 by extending between the rollers in the tank. The total stretching ratio based on the raw film is 6.0 times.

<Comparative Example 7>

Except that the mass ratio of potassium iodide/boric acid/zinc nitrate hexahydrate/water in the treatment solution contained in the color compensation tank in the color compensation step was changed to 9.0/3.0/5.0/100, the rest was prepared by the same operation as in Comparative Example 6. A polarizer with a thickness of 22μm.

<Example 4>

An aqueous adhesive containing 3 parts by mass of polyvinyl alcohol in 100 parts by mass of water is prepared.

After applying the saponification treatment on one side of the cellulose triacetate (TAC) film with a thickness of 40μm, apply the aforementioned aqueous adhesive to the saponification treatment surface using a bar coater, and apply the saponification treatment on one side of the low retardation TAC film with a thickness of 40μm After that, the aforementioned aqueous adhesive was applied to the saponified surface using a bar coater. Layer a TAC film on one area of the polarizer with the adhesive layer facing the polarizer side of Example 1, and layer a low retardation TAC film on the other area to obtain a TAC film/adhesive layer/polarizer/adhesive layer/low A laminate composed of layers of retardation TAC film. By using a hot air dryer to heat the resulting laminate at 80°C for 140 seconds, A polarizing plate composed of TAC film/adhesive layer/polarizer/adhesive layer/low retardation TAC film. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Example 5>

Except that the polarizer made in Example 2 was used as the polarizer, the remaining operations were the same as in Example 4 to make a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Example 6>

Except that the polarizer made in Example 3 was used as the polarizer, the other operations were the same as in Example 4 to make a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 8>

Except that the polarizer produced in Comparative Example 1 was used as the polarizer, the same operation as in Example 4 was used to produce a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 9>

Except that the polarizer prepared in Comparative Example 2 was used as the polarizer, the same operation as in Example 4 was used to prepare a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 10>

Except that the polarizer made in Comparative Example 3 was used as the polarizer, and the low retardation TAC film was changed to a TAC film with a thickness of 40μm, the remaining operations were the same as in Example 4 to obtain a TAC film/adhesive layer/polarizer /Adhesive layer/Laminate of TAC film. By The obtained laminate was heated at 80° C. for 300 seconds with a hot air dryer to prepare a polarizing plate having a layer structure of TAC film/adhesive layer/polarizer/adhesive layer/low retardation TAC film. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 11>

Except that the polarizer produced in Comparative Example 4 was used as the polarizer, the same operation as in Comparative Example 10 was performed to obtain a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 12>

Except that the polarizer produced in Comparative Example 5 was used as the polarizer, the same operation as in Comparative Example 10 was performed to obtain a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 13>

Except that the polarizer produced in Comparative Example 6 was used as the polarizer, a polarizing plate was obtained by the same operation as in Comparative Example 10. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

<Comparative Example 14>

Except that the polarizer produced in Comparative Example 7 was used as the polarizer, the same operation as in Comparative Example 10 was performed to obtain a polarizer. The durability test was performed on the obtained polarizing plate. The results are shown in Table 1.

[Table 1]

Claims (10)

A polarizer, the ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds is more than 0.47 and less than 0.9. The polarizer described in the first item of the scope of patent application, wherein the ratio of the number of iodine-zinc bonds to the number of iodine-iodine bonds in a direction parallel to the absorption axis of the polarizer is more than 0.47 and less than 0.9. The polarizer described in item 1 or 2 of the scope of the patent application has a thickness of 1.5 μm or less. A polarizing plate is provided with the polarizer described in any one of items 1 to 3 in the scope of patent application, a first thermoplastic resin film provided on one side of the polarizer, and a second thermoplastic resin film provided on the other side of the polarizer Thermoplastic resin film. The polarizing plate described in claim 4, wherein the second thermoplastic resin film is a retardation film. For the polarizing plate described in item 4 or 5 of the scope of the patent application, the absolute value ΔTy of the difference between the luminescence factor correction monomer transmittance Ty before and after the durability test at 105°C and 1000 hours is 4% or less. The polarizing plate described in any one of items 4 to 6 in the scope of the patent application, the absolute value of the difference between the maximum value of the TD transmittance at a wavelength of 500nm to 600nm before and after the durability test at 105°C and 1000 hours The value ΔTD is 0.014 or less. The polarizing plate described in any one of items 4 to 7 in the scope of the patent application, the absolute value of the difference of the orthogonal hue a value before and after the durability test at 105°C and 1000 hours is 2.5 or less An in-vehicle display device is provided with the polarizing plate described in any one of items 4 to 8 in the scope of patent application, a translucent member arranged on the first thermoplastic resin film side of the polarizing plate, and The display device on the second thermoplastic resin film side of the aforementioned polarizing plate. A method for manufacturing a polarizer is the method for manufacturing a polarizer according to any one of items 1 to 3 in the scope of the patent application, wherein: The aforementioned polarizer contains polyvinyl alcohol resin, At least one treatment liquid system for treating the polyvinyl alcohol resin film contains a zinc salt.

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