Method for manufacturing a polarizing film

Abstract

A production method that is for a polarizing film and that subjects a polyvinyl alcohol film to at least a swelling step, a dyeing step, a first crosslinking / stretching step, a second crosslinking / stretching step, and a third crosslinking / stretching step in this order, wherein: the thickness of the polyvinyl alcohol film is 5-100 μm; the average degree of polymerization of a polyvinyl alcohol contained in the polyvinyl alcohol film is 2000-4000; in the swelling step, the polyvinyl alcohol film is swollen through immersion in water at 10-50°C; in the dyeing step, the polyvinyl alcohol film is immersed in an aqueous solution at 10-50°C containing a total of 0.5-3 mass% of iodine and potassium iodide, so that the polyvinyl alcohol film is impregnated with an iodine-based dichroic dye while the polyvinyl alcohol film is uniaxially stretched by a total stretching factor of 2-3; in the first crosslinking / stretching step, the polyvinyl alcohol film is uniaxially stretched in an aqueous solution at a temperature T1 containing 1-5 mass% of boric acid so that, in this step, the stretching factor is 1.1-1.3 and the total stretching factor is 2.5-3.5; in the second crosslinking / stretching step, the polyvinyl alcohol film is uniaxially stretched in an aqueous solution at a temperature T2 containing 1-5 mass% of boric acid so that, in this step, the stretching factor is 1.3-1.8 and the total stretching factor is 4-6; in the third crosslinking / stretching step, the polyvinyl alcohol film is uniaxially stretched in an aqueous solution of temperature T3 containing 1-5 mass% of boric acid so that, in this step, the stretching factor is 1.1-1.3 and the total stretching factor is 4.5-7; and T1, T2, and T3 satisfy formulae (1) and (2). As a result, even in the case where the average degree of polymerization of the PVA is low, a polarizing film that maintains excellent polarizing performance and still has small shrinkage stress while maintaining production stability can be obtained. (1): 25≤T1≤45 (2): T1<T2<T3≤75

Description

Technical Field

[0001] The present invention relates to a method for producing a polarizing film with low shrinkage stress, which is made of a polyvinyl alcohol film containing an iodine-based dichroic dye.

Background Art

[0002] A polarizing film used in a polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD). Many polarizing plates have a structure in which a protective film such as a triacetyl cellulose (TAC) film is laminated on the surface of the polarizing film. As the polarizing film, a stretched film obtained by uniaxially stretching and orienting a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" may be referred to as "PVA") and adsorbed with a dichroic dye such as iodine-based dyes (I3 - or I5 - etc.) is the mainstream. Such a polarizing film is manufactured by a method of subjecting a PVA film to a swelling step, a dyeing step, a crosslinking step, a stretching step, an immobilization step, and a drying step.

[0003] In recent years, LCDs have been widely used in mobile applications such as notebook computers and mobile phones. Such LCDs for mobile devices are used in various environments. Therefore, there is a demand for a polarizing film having low shrinkage stress at high temperatures and excellent dimensional stability.

[0004] Patent Document 1 describes that in order to reduce the shrinkage stress of a polarizing film, stretching is performed in an aqueous solution at 50 °C containing boric acid in a first crosslinking stretching step, and then stretching is performed in an aqueous solution at 65 °C containing boric acid and potassium iodide in a second crosslinking stretching step.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the method described in Patent Document 1, since the first cross-linking and stretching step is performed at a high temperature of 50°C after the dyeing step, when the average degree of polymerization of PVA contained in the PVA film is low, if the stretching temperature is increased in the second cross-linking and stretching step, the film may break, and it may be difficult to reduce the shrinkage stress while maintaining the polarization performance. In addition, iodine adsorbed on the film in the dyeing step may elute in the first cross-linking and stretching step, making it difficult to adjust to the desired transmittance. Furthermore, as a result of the eluted iodine coloring the boric acid aqueous solution in the first cross-linking and stretching step, the PVA film may be colored in the first cross-linking and stretching step, making it difficult to maintain production stability.

[0007] The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing a polarizing film with a small shrinkage stress while maintaining excellent polarization performance while maintaining production stability even when the average degree of polymerization of PVA is low.

Means for Solving the Problems

[0008] The method for producing a polarizing film of the present invention is [1] A method for producing a polarizing film in which at least a swelling step, a dyeing step, a first cross-linking and stretching step, a second cross-linking and stretching step, and a third cross-linking and stretching step are performed on a polyvinyl alcohol film in this order, the thickness of the polyvinyl alcohol film is 5 to 100 μm, the average degree of polymerization of the polyvinyl alcohol contained in the polyvinyl alcohol film is 2000 to 4000, in the swelling step, the polyvinyl alcohol film is swollen by immersing it in water at 10 to 50°C, In the dyeing step, the polyvinyl alcohol film is immersed in an aqueous solution at 10 to 50 °C containing a total of 0.5 to 3% by mass of iodine and potassium iodide to impregnate the polyvinyl alcohol film with an iodine-based dichroic dye, and is uniaxially stretched so that the total draw ratio becomes 2 to 3 times. In the first crosslinking and stretching step, it contains 1 to 5% by mass of boric acid and is uniaxially stretched in an aqueous solution at temperature T1 so that the draw ratio during the step is 1.1 to 1.3 times and the total draw ratio becomes 2.5 to 3.5 times. In the second crosslinking and stretching step, it contains 1 to 5% by mass of boric acid and is uniaxially stretched in an aqueous solution at temperature T2 so that the draw ratio during the step is 1.3 to 1.8 times and the total draw ratio becomes 4 to 6 times. In the third crosslinking and stretching step, it contains 1 to 5% by mass of boric acid and is uniaxially stretched in an aqueous solution at temperature T3 so that the draw ratio during the step is 1.1 to 1.3 times and the total draw ratio becomes 4.5 to 7 times. A method for manufacturing a polarizing film, wherein T1, T2, and T3 satisfy the following formulas (1) and (2). 25 ≦ T1 ≦ 45 (1) T1 < T2 < T3 ≦ 75 (2) [2] A method for manufacturing a polarizing film according to [1], wherein T2 and T3 satisfy the following formulas (3) and (4). 50 ≦ T2 ≦ 65 (3) 55 ≦ T3 ≦ 75 (4) [3] After the third crosslinking and stretching step, a fourth crosslinking and stretching step is performed. In the fourth crosslinking and stretching step, it contains 1 to 5% by mass of boric acid and is uniaxially stretched in an aqueous solution at temperature T4 so that the draw ratio during the step is 1.1 to 1.3 times and the total draw ratio becomes 5 to 8 times. A method for manufacturing a polarizing film according to [1] or [2], wherein T1, T2, T3, and T4 satisfy the following formula (5). T1 < T2 < T3 ≦ T4 ≦ 75 (5) [4] A method for manufacturing a polarizing film according to [3], wherein T4 satisfies the following formula (6). 60 ≦ T4 ≦ 75 (6) [5] In the fourth crosslinking and stretching step, the maximum draw stress is 10 N / mm 2 The following method for manufacturing a polarizing film according to [3] or [4]. [6] The shrinkage stress is 50 N / mm2 The method for manufacturing a polarizing film according to [1] to [5], which obtains the following polarizing film [7] The method for manufacturing a polarizing film according to [1] to [6], which obtains a polarizing film having a polarization degree of 99.80% or more when the single transmittance is 43.5% is achieved by providing.

Effect of the Invention

[0009] According to the manufacturing method of the present invention, even when the average degree of polymerization of PVA is low, it is possible to obtain a polarizing film with small shrinkage stress while maintaining excellent polarization performance and production stability.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] The present invention is a method for manufacturing a polarizing film in which at least a swelling step, a dyeing step, a first cross-linking stretching step, a second cross-linking stretching step, and a third cross-linking stretching step are performed on a PVA film in this order. Among them, it is particularly important that the temperature T1 in the first cross-linking stretching step, the temperature T2 in the second cross-linking stretching step, and the temperature T3 in the third cross-linking stretching step satisfy the following formulas (1) and (2). 25 ≦ T1 ≦ 45 (1) T1 < T2 < T3 ≦ 75 (2)

[0012] As can be seen from the comparison between the following-described Examples and Comparative Examples, in Comparative Example 3 that does not satisfy Formula (1) where the temperature T1 is 50°C, the iodine adsorbed on the PVA film in the dyeing step eluted in the first cross-linking and stretching step, so the boric acid aqueous solution in the first cross-linking and stretching step was colored, and it was difficult to maintain production stability. Further, in Comparative Examples 1 to 3 that do not satisfy Formula (2) where the temperature T2 and the temperature T3 are the same temperature, the reduction in the shrinkage stress of the obtained polarizing film was insufficient. In contrast, in Examples 1 to 3 that satisfy Formulas (1) and (2) where the temperature T1 is 32°C, the temperature T2 is approximately 61°C, and the temperature T3 is approximately 64°C, it became clear that a polarizing film with a small shrinkage stress can be produced while maintaining excellent polarization performance. Therefore, the significance of the present invention adopting such a method is great.

[0013] For the PVA contained in the base PVA film used in the production of the polarizing film of the present invention, what can be used is obtained by saponifying a polyvinyl ester obtained by polymerizing one or more vinyl esters. Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, isopropenyl acetate, etc. Among these, vinyl acetate is preferable from the viewpoints of ease of PVA production, availability, cost, etc.

[0014] The polyvinyl ester may be obtained using only one or more vinyl esters as monomers, but within a range that does not impair the effects of the present invention, it may also be a copolymer of one or more vinyl esters and other monomers copolymerizable therewith.

[0015] Examples of other monomers copolymerizable with the vinyl ester include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, and isobutene; (meth)acrylic acid or its salts; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate; (meth)acrylamide derivatives such as (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, diacetone(meth)acrylamide, (meth)acrylamidopropanesulfonic acid or its salts, (meth)acrylamidopropyldimethylamine or its salts, and N-methylol(meth)acrylamide or its derivatives; N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanides such as (meth)acrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters, or acid anhydrides; itaconic acid or its salts, esters, or acid anhydrides; vinylsilyl compounds such as vinyltrimethoxysilane; and unsaturated sulfonic acids. The above polyvinyl ester can have structural units derived from one or more of the above-mentioned other monomers. As the other monomer, an α-olefin is preferred, and ethylene is particularly preferred.

[0016] The proportion of structural units derived from other monomers in the polyvinyl ester is preferably 15 mol% or less, more preferably 10 mol% or less, and still more preferably 5 mol% or less, based on the number of moles of all structural units constituting the polyvinyl ester.

[0017] In particular, when the other monomer is a monomer that may promote the water solubility of the resulting PVA, such as (meth)acrylic acid, unsaturated sulfonic acid, etc., in order to prevent the PVA from dissolving during the production process of the polarizing film, the proportion of structural units derived from these monomers in the polyvinyl ester is preferably 5 mol% or less, more preferably 3 mol% or less, based on the number of moles of all structural units constituting the polyvinyl ester.

[0018] The PVA used in the present invention may be modified with one or more graft copolymerizable monomers as long as the effects of the present invention are not impaired. Examples of the graft copolymerizable monomer include unsaturated carboxylic acids or their derivatives; unsaturated sulfonic acids or their derivatives; α-olefins having 2 to 30 carbon atoms, etc. The proportion of structural units derived from the graft copolymerizable monomer in the PVA (structural units in the graft-modified part) is preferably 5 mol% or less, based on the number of moles of all structural units constituting the PVA.

[0019] A part of the hydroxyl groups of the PVA may or may not be crosslinked. Also, a part of the hydroxyl groups of the above PVA may react with an aldehyde compound such as acetaldehyde or butyraldehyde to form an acetal structure.

[0020] The degree of polymerization of the PVA is in the range of 2,000 to 4,000. When the degree of polymerization is 2,000 or more, the PVA film can be stretched without breaking even when stretched at a high temperature in the second cross-linking and stretching step. It is more preferable that the degree of polymerization is 2,200 or more. On the other hand, when the degree of polymerization is 4,000 or less, the shrinkage stress of the obtained polarizing film can be reduced. It is more preferable that the degree of polymerization is 3,500 or less, even more preferably 3,000 or less, and particularly preferably less than 2,500. The degree of polymerization of PVA in this specification means the average degree of polymerization measured according to the description in JIS K6726-1994. Although the PVA in the polarizing film contains a cross-linked structure formed by a boron compound such as boric acid, if it is dissociated by hydrolyzing the borate ester or the like, there is no substantial change in the average degree of polymerization of PVA itself.

[0021] From the viewpoint of the polarization performance of the polarizing film and the like, the saponification degree of PVA is preferably 98 mol% or more, more preferably 98.5 mol% or more, and even more preferably 99 mol% or more. When the saponification degree is less than 98 mol%, PVA is likely to elute during the production process of the polarizing film, and the eluted PVA may adhere to the film and reduce the polarization performance of the polarizing film. The saponification degree of PVA in this specification refers to the ratio (mol%) of the number of moles of vinyl alcohol units to the total number of moles of structural units (typically vinyl ester units) that can be converted into vinyl alcohol units by saponification in PVA. The saponification degree can be measured according to the description in JIS K6726-1994. The saponification degree of PVA in the original film and the PVA in the obtained polarizing film are substantially the same.

[0022] In the PVA film used in the present invention, the content of PVA is preferably in the range of 50 to 99% by mass from the viewpoint of ease of manufacturing the desired polarizing film. The content is more preferably 75% by mass or more, further preferably 80% by mass or more, and particularly preferably 85% by mass or more. Also, it is more preferably 98% by mass or less, further preferably 96% by mass or less, and particularly preferably 95% by mass or less.

[0023] The PVA film preferably contains a plasticizer from the viewpoint of improving the stretchability when stretching it. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and the PVA film can contain one or more of these plasticizers. Among these, glycerin is preferable from the viewpoint of the effect of improving stretchability.

[0024] The content of the plasticizer in the PVA film is preferably in the range of 1 to 20 parts by mass with respect to 100 parts by mass of PVA contained therein. When the content is 1 part by mass or more, the stretchability of the PVA film can be further improved. On the other hand, when the content is 20 parts by mass or less, it is possible to prevent the PVA film from becoming too flexible and the handleability from deteriorating. The content of the plasticizer in the PVA film is more preferably 2 parts by mass or more, further preferably 4 parts by mass or more, and particularly preferably 5 parts by mass or more with respect to 100 parts by mass of PVA. Also, the content of the plasticizer is more preferably 15 parts by mass or less, and further preferably 12 parts by mass or less. Note that depending on the manufacturing conditions of the polarizing film, etc., since the plasticizer contained in the PVA film may elute during the production of the polarizing film, not all of it remains in the polarizing film.

[0025] The PVA film may further contain components such as antioxidants, antifreeze agents, pH adjusters, masking agents, anti-coloring agents, sizing agents, and surfactants, as necessary.

[0026] In the production method of the present invention, the thickness of the PVA film used is 5 to 100 μm. When the thickness is 100 μm or less, a thin polarizing film can be easily obtained. The thickness of the PVA film is preferably 60 μm or less. Also, the thickness of the PVA film is preferably 20 μm or more, more preferably 30 μm or more, in order to ensure handleability. On the other hand, when the thickness is less than 5 μm, it becomes difficult to manufacture the polarizing film and uneven dyeing is likely to occur. The thickness of the PVA film is preferably 7 μm or more. The thickness here refers to the thickness of the PVA layer in the case of a multilayer film.

[0027] The PVA film may be a single-layer film, or a multilayer film having a PVA layer and a base resin layer may be used. In the case of a single-layer film, the thickness of the film is preferably within the above range. On the other hand, in the case of a multilayer film, the thickness of the PVA layer can be 20 μm or less, or 15 μm or less. The thickness of the base resin layer in the multilayer film is usually 20 to 500 μm.

[0028] When using a multilayer film having a PVA layer and a base resin layer as the PVA film, the base resin must be capable of being stretched together with the PVA. Polyester, polyolefin resin, etc. can be used. Among them, an amorphous polyester resin is preferred, and an amorphous polyester resin copolymerized with polyethylene terephthalate and copolymerization components such as isophthalic acid and 1,4-cyclohexanedimethanol is preferably used. It is preferable to produce the multilayer film by applying a PVA solution to the base resin film. At this time, in order to improve the adhesiveness between the PVA layer and the base resin layer, the surface of the base resin film may be modified or an adhesive layer may be formed between the two layers.

[0029] The shape of the PVA film is not particularly limited, but it is preferably a long PVA film because it can be continuously supplied when manufacturing a polarizing film. The length (the length in the longitudinal direction) of the long PVA film is not particularly limited and can be appropriately set according to the use of the polarizing film to be manufactured, etc. For example, it can be in the range of 5 to 20,000 m.

[0030] The width of the PVA film is not particularly limited and can be appropriately set according to the use of the polarizing film to be manufactured, etc. In recent years, as the screens of liquid crystal TVs and liquid crystal monitors have been getting larger, if the width of the PVA film is 0.5 m or more, more preferably 1 m or more, it is optimal for these uses. On the other hand, if the width of the PVA film is too wide, it tends to be difficult to stretch it uniformly when manufacturing a polarizing film with an existing device. Therefore, the width of the PVA film is preferably 7 m or less.

[0031] Using the PVA film described above as a raw material, the polarizing film of the present invention is manufactured. Specifically, at least a swelling step, a dyeing step, a first cross-linking stretching step, a second cross-linking stretching step, and a third cross-linking stretching step are performed in this order to manufacture a polarizing film. It is also preferable to perform a cleaning step or a drying step after the third cross-linking stretching step. Hereinafter, each step will be described in detail.

[0032] In the manufacturing method of the present invention, first, the PVA film is subjected to a swelling step. In the swelling step, the PVA film is immersed in water at 10 to 50°C to swell the PVA film. The temperature of the water is preferably 20°C or higher and also preferably 40°C or lower. By immersing the PVA film in water within such a temperature range, the PVA film can be efficiently and uniformly swollen. The time for immersing the PVA film in water is preferably in the range of 0.1 to 5 minutes, and more preferably in the range of 0.5 to 3 minutes. By setting the immersion time in this way, the PVA film can be efficiently and uniformly swollen. Note that the water in which the PVA film is immersed is not limited to pure water, and may be an aqueous solution in which various components are dissolved, or may be a mixture of water and a water-soluble organic solvent. In the swelling step, it is preferable to perform uniaxial stretching on the PVA film. The draw ratio in that case is not particularly limited, but is preferably 1.2 to 2.8 times. The draw ratio is more preferably 1.5 times or more and also more preferably 2.5 times or less.

[0033] In the manufacturing method of the present invention, after the swelling step, it is subjected to a dyeing step. In the dyeing step, it is immersed in an aqueous solution at 10 to 50°C containing a total of 0.5 to 3% by mass of iodine and potassium iodide to impregnate the PVA film with an iodine-based dichroic dye, and uniaxially stretched so that the total draw ratio becomes 2 to 3 times. Thereby, the PVA film is dyed with the iodine-based dichroic dye, the molecular chains of PVA in the film are oriented, and the iodine-based dichroic dye is also oriented.

[0034] Dyeing is performed by immersing the PVA film in a dyeing bath containing an iodine-based dichroic dye. The dyeing bath is prepared by mixing iodine (I2) and potassium iodide (KI) with water. By mixing iodine and potassium iodide with water, I3 - and I5 -It is possible to generate iodine-based dichroic dyes such as etc. The total content of iodine and potassium iodide in the dyeing bath is 0.5 to 3% by mass in total. The total content of iodine and potassium iodide is preferably 0.8% by mass or more and also preferably 2.5% by mass or less. By dyeing within such a concentration range, it is possible to dye efficiently and uniformly. The mass ratio of potassium iodide to iodine (KI / I2) is preferably 10 to 200, and more preferably 15 to 150. The dyeing bath may contain boron compounds such as borates such as boric acid and borax, but the content thereof is usually less than 5% by mass in terms of boric acid, and preferably 1% by mass or less.

[0035] The temperature of the dyeing bath is 10 to 50°C. The temperature is preferably 15°C or higher and more preferably 20°C or higher. Also, the temperature is preferably 40°C or lower and more preferably 35°C or lower. By dyeing within such a temperature range, the PVA film can be dyed efficiently and uniformly. Also, the time for immersing the PVA film in the dyeing bath is preferably in the range of 0.1 to 10 minutes, and more preferably in the range of 0.2 to 5 minutes. By setting the time within such a range, the PVA film can be dyed without spots.

[0036] In the dyeing step, the PVA film is dyed and uniaxially stretched so that the total stretch ratio becomes 2 to 3 times. By subsequently subjecting the PVA film having such a total stretch ratio to at least three stages of crosslinking and stretching steps, a polarizing film having excellent polarizing performance and low shrinkage stress can be obtained. The total stretch ratio after the steps including the swelling step and the dyeing step may be 2 to 3 times. The stretch ratio in the dyeing step may exceed 1 time, and is more preferably 1.05 times or more.

[0037] In the manufacturing method of the present invention, after the dyeing step, it is subjected to a first crosslinking and stretching step, a second crosslinking and stretching step, and a third crosslinking and stretching step. By performing three-stage crosslinking and stretching steps with different conditions, the crystal state and orientation state of the obtained polarizing film can be controlled, and a polarizing film having excellent polarization performance and low shrinkage stress can be obtained. As will be described later, it is a preferred embodiment to perform a fourth crosslinking and stretching step after the third crosslinking and stretching step. Hereinafter, these four crosslinking and stretching steps will be described.

[0038] In the first crosslinking and stretching step, in an aqueous solution containing 1 to 5% by mass of boric acid and having a temperature T1 of 25 to 45°C, uniaxial stretching is performed so that the stretching magnification during the step is 1.1 to 1.3 times and the total stretching magnification is 2.5 to 3.5 times. The boric acid aqueous solution in which the PVA film is immersed contains 1 to 5% by mass of boric acid. The concentration of boric acid is preferably 1.5% by mass or more and preferably 4% by mass or less. By setting such a concentration, the intermolecular crosslinking reaction by boric acid can proceed at an appropriate rate. Note that boric acid may be any substance that can become boric acid or boric acid ions in an aqueous solution, and either boric acid or borate can be used, but boric acid is preferably used. The concentration in the case of using borate is calculated in terms of the mass of boric acid (H3BO3). The boric acid aqueous solution may contain potassium iodide, and in that case, the concentration is preferably in the range of 0.01 to 10% by mass. By containing potassium iodide, the polarization performance of the obtained polarizing film can be adjusted. Potassium iodide may be contained in the first crosslinking and stretching step, may be contained in the second to fourth crosslinking and stretching steps described later, or may be contained in all steps.

[0039] The temperature T1 of the aqueous solution containing boric acid in the first crosslinking and stretching step is 25 to 45°C. That is, the temperature T1 satisfies the following formula (1). 25 ≤ T1 ≤ 45 (1)

[0040] As can be seen from the comparison between the following-described examples and comparative examples, in Comparative Example 3 where the temperature T1 is 50 °C and does not satisfy formula (1), the iodine adsorbed on the PVA film eluted in the first crosslinking and stretching step, so the boric acid aqueous solution in the first crosslinking and stretching step was colored, and it was difficult to maintain production stability. In contrast, in the present invention where the temperature T1 is within this range, even when the average degree of polymerization of PVA is low, a polarizing film with excellent polarizing performance and low shrinkage stress can be produced while maintaining excellent polarizing performance. When the temperature T1 is less than 25 °C, the progress of the crosslinking reaction by boric acid becomes insufficient, and the polarizing performance of the obtained polarizing film may decrease. On the other hand, when the temperature T1 exceeds 45 °C, the iodine adsorbed on the PVA film elutes due to the dyeing process, so the boric acid aqueous solution in the first crosslinking and stretching step may be colored, and it may become difficult to maintain production stability. The temperature T1 is preferably 28 °C or higher, more preferably 30 °C or higher. Also, the temperature T1 is preferably 40 °C or lower, more preferably 38 °C or lower. And within the above temperature range, uniaxial stretching is performed so that the stretching ratio is 1.1 to 1.3 times and the total stretching ratio is 2.5 to 3.5 times. The total stretching ratio is preferably 2.6 times or more and also preferably 3.4 times or less. Thus, in the first crosslinking and stretching step, while maintaining the temperature T1 within the above range, uniaxial stretching is performed slightly to appropriately orient and advance the boric acid crosslinking reaction. As a result, even when immersed in a high-temperature boric acid aqueous solution in the subsequent second crosslinking and stretching step and subsequent steps, PVA does not elute from the film into the boric acid aqueous solution and the strength of the film does not significantly decrease, and further stretching at a higher magnification can be performed.

[0041] Subsequently, in the second crosslinking and stretching step, uniaxial stretching is performed in an aqueous solution containing 1 to 5% by mass of boric acid, where the temperature T2 exceeds the temperature T1 of the first crosslinking and stretching step and is less than 75 °C, and the stretching ratio during this step is 1.3 to 1.8 times and the total stretching ratio is 4 to 6 times. As the composition of the aqueous solution containing boric acid used, the same composition as that in the range used in the first crosslinking and stretching step can be used.

[0042] In the second crosslinking and stretching process, the temperature T2 of the aqueous solution containing boric acid is higher than the temperature T1 in the first crosslinking and stretching process and less than 75°C. Preferably, the temperature T2 is 50°C or higher. Also preferably, the temperature T2 is 70°C or lower, and more preferably 65°C or lower. If the temperature is too low, the shrinkage stress will increase, while if the temperature is too high, PVA will elute from the film into the boric acid aqueous solution or the polarization degree will decrease. And within the above temperature range, uniaxial stretching is performed so that the stretching ratio is 1.3 to 1.8 times and the total stretching ratio is 4 to 6 times. The stretching ratio during the second crosslinking process is preferably 1.4 times or more and also preferably 1.7 times or less. Also, the total stretching ratio is preferably 4.1 times or more and also preferably 5.9 times or less. That is, the boric acid crosslinking reaction is allowed to proceed while stretching at a relatively high ratio in a high-temperature aqueous solution containing boric acid, and as a result, it is possible to prevent PVA from eluting from the film into the boric acid aqueous solution or breaking in the subsequent third crosslinking and stretching process.

[0043] Subsequently, in the third crosslinking and stretching process, uniaxial stretching is performed in an aqueous solution containing 1 to 5% by mass of boric acid, where the temperature T3 is higher than the temperature T2 in the second crosslinking and stretching process and 75°C or lower, and the stretching ratio during the process is 1.1 to 1.3 times and the total stretching ratio is 4.5 to 7 times. As the composition of the aqueous solution containing boric acid used, the same composition as that in the range used in the first crosslinking and stretching process can be used. As shown in FIG. 1, a partition plate or the like may be provided in one tank to such an extent that the temperatures T2 and T3 can be set, and the second crosslinking and stretching process and the third crosslinking and stretching process may be performed, or as shown in FIG. 3, the second crosslinking and stretching process and the third crosslinking and stretching process may be performed in separate tanks.

[0044] In the third crosslinking and stretching process, the temperature T3 of the aqueous solution containing boric acid is higher than the temperature T2 in the second crosslinking and stretching process and 75°C or lower. That is, the temperatures T1, T2, and T3 satisfy the following formula (2). T1 < T2 < T3 ≤ 75 (2)

[0045] As can be seen from the comparison between the following-described Examples and Comparative Examples, in Comparative Examples 1 to 3 that do not satisfy Formula (2) in which temperature T2 and temperature T3 are the same temperature, the reduction in the shrinkage stress of the obtained polarizing film was insufficient. On the other hand, in Examples 1 to 3 that satisfy Formula (2) in which temperature T1 is 32°C, temperature T2 is approximately 61°C, and temperature T3 is approximately 64°C, it became clear that a polarizing film with a small shrinkage stress can be manufactured while maintaining excellent polarization performance. Therefore, in the manufacturing method of the present invention, it is important to satisfy the above Formula (2).

[0046] The temperature T3 is preferably 55°C or higher, and more preferably 58°C or higher. Also, the temperature T3 is preferably 75°C or lower, and more preferably 72°C or lower. If the temperature is too low, the shrinkage stress will increase, while if the temperature is too high, PVA will elute from the film into the aqueous solution containing boric acid or the degree of polarization will decrease. Then, in the above temperature range, uniaxial stretching is performed so that the stretching ratio is 1.1 to 1.3 times and the total stretching ratio is 4.5 to 7 times. The film stretched in the third crosslinking stretching step can prevent PVA from eluting from the film into the aqueous solution containing boric acid or breaking while allowing the boric acid crosslinking reaction to proceed while stretching at a relatively high magnification in the high-temperature aqueous solution containing boric acid.

[0047] As the above T2 and T3, it is a preferred embodiment to satisfy the following Formulas (3) and (4). 50 ≦ T2 ≦ 65 (3) 55 ≦ T3 ≦ 75 (4)

[0048] In the manufacturing method of the present invention, it is a preferred embodiment to perform a fourth cross-linking and stretching step after the third cross-linking and stretching step. In the fourth cross-linking and stretching step, an aqueous solution containing 1 to 5% by mass of boric acid is used, and in the aqueous solution at temperature T4, uniaxial stretching is performed such that the stretching ratio during the step is 1.1 to 1.3 times and the total stretching ratio is 5 to 8 times, and it is preferable that T1, T2, T3, and T4 satisfy the following formula (5). The composition of the aqueous solution containing boric acid used can be the same as that in the range used in the first cross-linking and stretching step. As shown in FIG. 2, a partition plate or the like may be provided in one tank to the extent that the temperature T2, temperature T3, and temperature T4 can be set, and the second cross-linking and stretching step, the third cross-linking and stretching step, and the fourth cross-linking and stretching step may be performed, or as shown in FIG. 4, the second cross-linking and stretching step, the third cross-linking and stretching step, and the fourth cross-linking and stretching step may be performed in separate tanks. T1 < T2 < T3 ≦ T4 ≦ 75 (5)

[0049] In the fourth cross-linking and stretching step, the temperature T4 of the aqueous solution containing boric acid is preferably not less than the temperature T3 of the third cross-linking and stretching step and not more than 75°C. It may be the same temperature as the temperature T3 of the third cross-linking and stretching step. The temperature T4 is preferably 60°C or higher, more preferably 62°C or higher. Also, the temperature T4 is more preferably 74°C or lower. If the temperature is too low, the shrinkage stress will increase, while if the temperature is too high, PVA will elute from the film into the aqueous solution containing boric acid or the polarization degree will decrease. And within the above temperature range, uniaxial stretching is performed such that the stretching ratio is 1.1 to 1.3 times and the total stretching ratio is 5 to 8 times. The film stretched in the fourth cross-linking and stretching step can prevent PVA from eluting from the film into the aqueous solution containing boric acid or breaking while allowing the boric acid cross-linking reaction to proceed while stretching at a relatively high ratio in the high-temperature aqueous solution containing boric acid.

[0050] As the above T4, it is a preferred embodiment to satisfy the following formula (6). 60 ≦ T4 ≦ 75 (6)

[0051] In the fourth cross-linking and stretching step, the maximum stretching stress is 10 N / mm 2The following are preferred. Here, the maximum stretching stress is the value obtained by dividing the tensile stress applied between adjacent rolls in the fourth crosslinking and stretching step by the cross-sectional area of the raw PVA film. By reducing the maximum stretching stress, a polarizing film with a small shrinkage stress can be obtained. The maximum stretching stress is preferably 8 N / mm 2 or less, more preferably 5 N / mm 2 or less, even more preferably 4 N / mm 2 or less. Also, usually, the maximum stretching stress is 1 N / mm 2 or more.

[0052] In the first to fourth crosslinking and stretching steps, when the PVA film is uniaxially stretched, it can be carried out by using a stretching device provided with a plurality of rolls parallel to each other in the boric acid aqueous solution in the first to fourth crosslinking and stretching steps and changing the peripheral speed between each roll.

[0053] It is preferable to subject it to a washing step after the third crosslinking and stretching step or the fourth crosslinking and stretching step. In the washing step, unnecessary chemicals and foreign substances on the film surface are removed, or the optical performance of the finally obtained polarizing film is adjusted. The washing step can be carried out by immersing the PVA film in a washing bath or spraying a washing liquid on the PVA film. Water can be used as the washing liquid, but potassium iodide may be contained therein. When potassium iodide is contained, the color tone of the polarizing film can be adjusted. The content of potassium iodide is preferably 0.1 to 10% by mass. The temperature of the washing liquid is usually 10 to 40°C, preferably 15 to 30°C. The washing bath may use not only one layer but also a plurality of tanks. Also, the composition of the washing liquid in each tank when using a plurality of tanks can be adjusted according to the purpose.

[0054] Subsequent to the washing step, it is preferably subjected to a drying step. The temperature in the drying step is not particularly limited, but it is preferably 30 to 150°C, more preferably 50 to 130°C. By drying at a temperature within the above range, a polarizing film excellent in dimensional stability is easily obtained.

[0055] The thickness of the polarizing film obtained in the present invention is preferably 1 to 30 μm. When the thickness is less than 1 μm, it may be difficult to produce at high speed, and more preferably, it is 3 μm or more. On the other hand, when the thickness exceeds 30 μm, the stretching tension during stretching may become high and the apparatus may be damaged, and more preferably, it is 25 μm or less. The thickness referred to here means the thickness of the PVA layer in the case of a multilayer film.

[0056] When the obtained polarizing film is a single-layer film of PVA, in order to ensure handleability, the thickness of the polarizing film is preferably 5 μm or more, and more preferably 7 μm or more. On the other hand, in the case of a polarizing film composed of a multilayer film, the thickness of the polarizing film layer can be 5 μm or less, or can be 3 μm or less. The thickness of the base resin layer in the multilayer film is usually 10 to 250 μm.

[0057] The single transmittance of the polarizing film obtained in the present invention is preferably 42 to 45%. When the single transmittance is less than 42%, the brightness of the liquid crystal display decreases. The single transmittance is more preferably 42.5% or more. On the other hand, in a polarizing film with a single transmittance exceeding 45%, it is difficult to obtain a polarizing film with a high degree of polarization, and the single transmittance is more preferably 44.5% or less. Further, the degree of polarization of the polarizing film of the present invention is preferably 99.80% or more. The degree of polarization is more preferably 99.90% or more.

[0058] The shrinkage stress of the polarizing film obtained in the present invention is preferably 50 N / mm 2 or less. Due to the small shrinkage stress, it has excellent dimensional stability even when used at high temperatures. The shrinkage stress is more preferably 42 N / mm 2 or less, still more preferably 38 N / mm 2 or less, and particularly preferably 35 N / mm 2 or less. Here, the shrinkage stress means the value obtained by dividing the tension when the polarizing film as a sample is fixed and maintained at 80°C for 4 hours by the cross-sectional area of the sample.

[0059] In addition, the polarizing film obtained in the present invention preferably has a degree of polarization of 99.80% or more, more preferably 99.90% or more, still more preferably 99.95% or more, and particularly preferably 99.98% or more when the single transmittance is 43.5%. This value is calculated by assuming that the single transmittance (T) of the polarizing film is 43.5% when it is not 43.5%.

[0060] The method for calculating the "degree of polarization when the single transmittance is 43.5%" is as follows. First, the relationship between the transmittance (T') excluding surface reflection and the single transmittance (T) is shown by Equation (7). At this time, the refractive index of PVA is assumed to be 1.5, and the reflectance at the surface is assumed to be 4%. The relationship between the transmittance (T'), the degree of polarization (V), and the dichroic ratio (R) is shown by Equation (8), and Equation (9) is obtained by transforming Equation (8). Here, since the dichroic ratio (R) hardly varies depending on the dye concentration in the range where the single transmittance (T) does not vary greatly, for example, in the range of 42 to 45%, it can be treated as a constant. Therefore, after measuring the single transmittance (T) and the degree of polarization (V), the dichroic ratio (R) of the polarizing film can be calculated as a constant by solving Equations (7) and (8) using these values. From Equation (9) and Equation (7) substituting the calculated R, the degree of polarization (V) when T = 43.5 (%) can be obtained. T’=T / (1 - 0.04) 2 (7) R={-ln[T’(1 - V)]} / {-ln[T’(1 + V)]} (8) T’=[1 - V] 1 / (R-1) / [1 + V] R / (R-1) (9)

[0061] The polarizing film obtained in the present invention is usually used as a polarizing plate by laminating a protective film on both sides or one side thereof. Examples of the protective film include those that are optically transparent and have mechanical strength. Specifically, for example, a triacetyl cellulose (TAC) film, an acetate butyrate cellulose (CAB) film, an acrylic film, a polyester film, etc. can be used. Further, examples of the adhesive for lamination include a PVA-based adhesive, a urethane-based adhesive, or an ultraviolet curable adhesive.

[0062] The polarizing plate thus obtained can be used for high-performance liquid crystal displays (LCDs). It is possible to provide a polarizing plate that is bright, has good polarization characteristics, and has excellent dimensional stability even when used under high-temperature conditions. Therefore, it can be suitably used as a polarizing plate for various high-performance LCDs, particularly for LCDs for mobile applications.

Examples

[0063] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples in any way. The evaluation methods and the like were carried out according to the methods shown below.

[0064] [Optical performance of polarizing film] From the central part in the width direction (TD direction) of the polarizing film obtained in the following examples and comparative examples, a rectangular measurement sample with a length of 4 cm in the machine flow direction (MD direction) of the polarizing film and a width of 1.5 cm in the width direction (TD direction) was collected. For this measurement sample, using a spectrophotometer with an integrating sphere (「V7100」 manufactured by JASCO Corporation), in accordance with JIS Z8722 (Method for measuring object color), after performing visual sensitivity correction in the visible light region with a C light source and a 2° field of view, the single transmittance and the degree of polarization were measured. By the method described above, the degree of polarization when the single transmittance was 43.5% was calculated.

[0065] [Shrinkage stress of polarizing film] The shrinkage stress was measured using an autograph AG-X with a thermostat manufactured by Shimadzu Corporation. For the measurement, a polarizing film (15 cm in the length direction and 1.5 cm in the width direction) conditioned at 20°C / 20% RH for 18 hours was attached to a chuck (chuck interval: 5 cm), and simultaneously with the start of tension, the temperature of the thermostat was raised to 80°C. The polarizing film was stretched at a speed of 1 mm / min, and when the tension reached 2 N, the stretching was stopped, and the tension was measured until 4 hours later in that state. At this time, since the distance between the chucks changes due to the thermal expansion of the shaft, a scale seal was attached to the chuck, and the measurement was performed in such a way that the distance between the chucks could be corrected by the amount that the scale seal attached to the chuck moved using a video extensometer TR ViewX120S. Note that the value obtained by subtracting the initial tension of 2 N from the measured value of the tension after 4 hours was defined as the shrinkage force of the polarizing film, and the value obtained by dividing that value by the sample cross-sectional area was defined as the shrinkage stress (N / mm 2 ).

[0066] [Maximum drawing stress in the fourth crosslinking and stretching step] In the following Examples and Comparative Examples, the film width (mm) and film thickness (mm) of the PVA film (unprocessed raw film) used for manufacturing the polarizing film in advance were determined, and the cross-sectional area (mm 2 ) was calculated by multiplying these values. Next, in the fourth crosslinking and stretching step when manufacturing the polarizing film, the tensile stress (N) applied between adjacent rolls was measured with a tensiometer. By dividing the obtained tensile stress (N) by the cross-sectional area (mm 2 ) obtained above, the maximum drawing stress (N / mm 2 ) in the fourth crosslinking and stretching step was determined.

[0067] [Coloring of the boric acid aqueous solution in the first crosslinking and stretching step] Regarding the coloring of the boric acid aqueous solution in the first crosslinking and stretching step, 20 cc of the boric acid aqueous solution 1 hour after starting continuous stretching was collected in a 30 cc screw tube and visually confirmed. When the color did not change compared to the boric acid aqueous solution before continuous stretching, it was marked as ○, and when the color changed and there was iodine coloring, it was marked as ×.

[0068] [Example 1] 100 parts by mass of PVA (saponified vinyl acetate polymer, degree of polymerization 2400, degree of saponification 99.9 mol%, ethylene modification 2.0 mol%), 10 parts by mass of glycerin as a plasticizer, 0.1 part by mass of sodium polyoxyethylene lauryl sulfate as a surfactant, and water were used to prepare a casting stock solution, and a roll of PVA film with a thickness of 45 μm was obtained by casting. For this PVA film, a swelling step, a dyeing step, a first cross-linking stretching step, a second cross-linking stretching step, a third cross-linking stretching step, a fourth cross-linking stretching step, a washing step, and a drying step were sequentially performed to produce a polarizing film. Schematic diagrams of the polarizing film manufacturing apparatus are shown in FIGS. 1 to 4.

[0069] Specifically, the polarizing film was manufactured as follows. First, in the swelling step, while the above PVA film was immersed in water at a temperature of 30 °C for 1.6 minutes, it was uniaxially stretched in the length direction (MD) to twice the original length (first-stage stretching). Subsequently, in the dyeing step, while immersed in an aqueous solution at a temperature of 32 °C containing 0.06% by mass of iodine and 1.4% by mass of potassium iodide for 2.3 minutes, it was uniaxially stretched in the length direction (MD) to 2.5 times the original length (second-stage stretching). Subsequently, in the first cross-linking stretching step, while immersed in an aqueous solution at a temperature of 32 °C containing boric acid at a concentration of 2.6% by mass for 2 minutes, it was uniaxially stretched in the length direction (MD) to three times the original length (third-stage stretching). Subsequently, in the second cross-linking stretching step, while immersed in an aqueous solution at a temperature of 60.6 °C containing boric acid at a concentration of 2.8% by mass and potassium iodide at a concentration of 5% by mass, it was uniaxially stretched in the length direction (MD) to 4.46 times the original length (fourth-stage stretching). Subsequently, in the third cross-linking stretching step, while immersed in an aqueous solution at a temperature of 63.6 °C containing boric acid at a concentration of 2.8% by mass and potassium iodide at a concentration of 5% by mass, it was uniaxially stretched in the length direction (MD) to 5.27 times the original length (fifth-stage stretching). Subsequently, in the fourth cross-linking stretching step, while immersed in an aqueous solution at a temperature of 64.6 °C containing boric acid at a concentration of 2.8% by mass and potassium iodide at a concentration of 5% by mass, it was uniaxially stretched in the length direction (MD) to six times the original length (sixth-stage stretching). The maximum stretching stress in the fourth cross-linking stretching step was 1.4 N / mm 2It was. Subsequently, in the washing step, the film was washed by immersing it for 10 seconds in an aqueous solution at 22°C containing 1.5% by mass of boric acid and 5% by mass of potassium iodide. Subsequently, in the drying step, a polarizing film with a thickness of 14.0 μm was produced by drying it in a dryer at 80°C for 120 seconds. The conditions of each cross-linking and stretching step and the value of the maximum stretching stress in the fourth cross-linking and stretching step are shown in Table 1, and the evaluation results are shown in Table 2.

[0070] [Examples 2 to 3, Comparative Examples 1 to 3] A polarizing film was produced in the same manner as in Example 1, except that the temperature of the aqueous solution containing boric acid in the first cross-linking and stretching step, the temperature of the aqueous solution containing boric acid and the total stretching ratio in the second cross-linking and stretching step, the temperature of the aqueous solution containing boric acid and the total stretching ratio in the third cross-linking and stretching step, and the temperature of the aqueous solution containing boric acid and the total stretching ratio in the fourth cross-linking and stretching step were changed as shown in Table 1. The conditions of each cross-linking and stretching step and the value of the maximum stretching stress in the fourth cross-linking and stretching step are shown in Table 1, and the evaluation results are shown in Table 2. Also, the evaluation results of Example 3 and Comparative Example 2, where the total stretching ratio is 6.6 times, are shown in Table 3. Note that Examples 1 and 2 and Comparative Examples 1 and 3 in Table 2 are all examples with a total stretching ratio of 6 times.

[0071]

Table 1

[0072]

Table 2

[0073]

Table 3

Explanation of Symbols

[0074] 1 Polarizing film manufacturing apparatus 2 PVA film roll 3 Swelling step 4 Dyeing step 5 First cross-linking and stretching step 6 Second Bridge Extension Project 7 Third Bridge Extension Project 8 Fourth Bridge Extension Project 9 Cleaning Process 10 Drying Process

Claims

1. A method for manufacturing a polarizing film, which comprises subjecting a polyvinyl alcohol film to at least a swelling step, a dyeing step, a first cross-linking stretching step, a second cross-linking stretching step, and a third cross-linking stretching step in this order, wherein the thickness of the polyvinyl alcohol film is 5 to 100 μm, the average degree of polymerization of the polyvinyl alcohol contained in the polyvinyl alcohol film is 2000 to 4000, in the swelling step, the polyvinyl alcohol film is immersed in water at 10 to 50 °C to swell the polyvinyl alcohol film, in the dyeing step, the polyvinyl alcohol film is immersed in an aqueous solution at 10 to 50 °C containing a total of 0.5 to 3% by mass of iodine and potassium iodide to impregnate the polyvinyl alcohol film with an iodine-based dichroic dye, and uniaxially stretched so that the total stretching ratio becomes 2 to 3 times, In the first crosslinking and stretching step, uniaxially stretch in an aqueous solution containing 1 to 5% by mass of boric acid and having a temperature T １ so that the stretching ratio during the step is 1.1 to 1.3 times and the total stretching ratio is 2.5 to 3.5 times, In the second crosslinking and stretching step, a temperature T is maintained in an aqueous solution containing 1 to 5% by mass of boric acid, ２ and the material is uniaxially stretched so that the stretching ratio during the step is 1.3 to 1.8 times and the total stretching ratio is 4 to 6 times. In the third crosslinking and stretching step, it contains 1 to 5% by mass of boric acid and has a temperature T ３ in an aqueous solution, and is uniaxially stretched so that the stretching ratio during the step is 1.1 to 1.3 times and the total stretching ratio is 4.5 to 7 times, The above-mentioned T １ , T ２ and T ３ satisfy the following formulas (1) and (2), a method for manufacturing a polarizing film. 25 ≤ T １ ≤ 45 (1) T １ <T ２ <T ３ ≦75 (2)

2. The above T ２ and T ３ The method for producing a polarizing film according to claim 1, wherein the above satisfy the following formulas (3) and (4). 50 ≤ T ２ ≤ 65 (3) 55 ≤ T ３ ≤ 75 (4)

3. After the third crosslinking and stretching step, a fourth crosslinking and stretching step is carried out. In the fourth crosslinking and stretching step, an aqueous solution containing 1 to 5% by mass of boric acid and having a temperature T ４ is uniaxially stretched so that the stretching ratio during the step is 1.1 to 1.3 times and the total stretching ratio is 5 to 8 times, and T １ , T ２ , T ３ and T ４ satisfy the following formula (5). The method for producing a polarizing film according to claim 1 or 2. T １ <T ２ <T ３ ≦T ４ ≦75 (5)

4. The above T ４ The method for producing a polarizing film according to claim 3, wherein T satisfies the following formula (6). 60 ≤ T ４ ≤ 75 (6)

5. In the fourth crosslinking extension step, the maximum extension stress is 10 N / mm ２ The method for producing a polarizing film according to claim 3 or 4, wherein the maximum extension stress is 10 N / mm or less. ２

6. The shrinkage stress is 50 N / mm ２ The method for producing a polarizing film according to any one of claims 1 to 5, which obtains a polarizing film having the following properties.

7. The method for manufacturing a polarizing film according to any one of Claims 1 to 6, wherein a polarizing film having a polarization degree of 99.80% or more when the single transmittance is 43.5% is obtained.

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