TWI848133B - Polarizing film and method for producing same - Google Patents

Abstract

酸及於水的存在下可轉化為該單

酸之化合物的群組中的至少1種含硼化合物(B)、及選自包含下式(II)所示之二

酸及於水的存在下可轉化為該二

酸之化合物的群組中的至少1種含硼化合物(C)，其中，由含硼化合物(B)而來之硼元素相對於由含硼化合物(C)而來之硼元素的質量比(B/C)為4.0~8.0，而且由含硼化合物(C)而來的硼元素含量，相對於100質量份的聚乙烯醇(A)而言，為0.05~0.3質量份。該偏光薄膜在高溫下的收縮力小，耐濕熱性亦優良。 A polarizing film comprising polyvinyl alcohol (A), a monomer selected from the group consisting of

Acid and in the presence of water can be converted into the monomer

At least one boron-containing compound (B) in the group of compounds of the present invention, and two compounds selected from the group consisting of

Acid and in the presence of water can be converted into the two

At least one boron-containing compound (C) in the group of compounds of polyvinyl alcohol (A), wherein the mass ratio (B/C) of the boron element from the boron-containing compound (B) to the boron element from the boron-containing compound (C) is 4.0-8.0, and the content of the boron element from the boron-containing compound (C) is 0.05-0.3 parts by mass relative to 100 parts by mass of the polyvinyl alcohol (A). The polarizing film has low shrinkage at high temperature and excellent moisture and heat resistance.

酸基係以硼-碳鍵連接]。 [In formula (I), R ¹ is ^a monovalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond].

酸基係以硼-碳鍵連接]。 [In formula (II), R ² is ^a divalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond].

Description

Polarizing film and its manufacturing method

The present invention relates to a polarizing film having low shrinkage force at high temperature, excellent optical performance and moisture and heat resistance, and a method for manufacturing the same.

Polarizing plates, which have the functions of transmitting and shielding light, are the basic components of liquid crystal displays (LCDs), along with liquid crystals that change the polarization state of light. In recent years, circular polarizing plates combined with 45° phase plates have been used to prevent external light reflection in organic electroluminescent displays (OLEDs). Most polarizing plates or circular polarizing plates have a structure in which a protective film such as a triacetate cellulose (TAC) film is attached to the surface of the polarizing film in order to prevent the polarizing film from fading and shrinking. As polarizing films, the mainstream is one in which iodine-based pigments (I ₃ ^- or I ₅ ^- , etc.) or dichroic dyes are adsorbed on a substrate formed by uniaxially stretching a polyvinyl alcohol film (hereinafter, "polyvinyl alcohol" may be referred to as "PVA").

LCD is used in a wide range of applications, including small devices such as computers and watches, smartphones, notebook computers, liquid crystal displays, liquid crystal color projectors, liquid crystal televisions, car navigation systems, and measuring devices for indoor and outdoor use. OLED is used in a wide range of applications, including smartphones, OLED televisions, and smart watches. These devices are required to be thin and flexible, and as a result, the thinning of LCD panels or OLED panels has been developing in recent years. As a result, the occurrence of warping of LCD panels or OLED panels and the fading of polarizing plates or circular polarizing plates under high temperatures and high humidity have become problems. The main cause of warping of LCD panels or OLED panels is believed to be the shrinkage of polarizing films at high temperatures, so polarizing films with low shrinkage at high temperatures are required. In addition, the main reason for the fading of polarizing plates or circular polarizing plates under high temperature and high humidity is the decomposition of iodine complexes caused by moisture in iodine-based polarizing films. In the past, the moisture permeability of the protective film was reduced, but as the protective film becomes thinner, the moisture permeability of the protective film becomes higher. Therefore, polarizing films with high stability of iodine complexes even under high temperature and high humidity are also required, that is, iodine-based polarizing films with excellent moisture and heat resistance.

In addition, as means for reducing the shrinkage force of polarizing films, there are known methods: a method of reducing the amount of inorganic boric acid in the PVA film and providing a step of drying the PVA film between the inorganic boric acid treatment step and the water washing step (Patent Document 1), a method of thinning the polarizing film and controlling the ratio of the film thickness to the stretching ratio (Patent Document 2), and a method of appropriately controlling the drying temperature according to the moisture content of the PVA film (Patent Document 3).

However, if the amount of inorganic boric acid in the polarizing film is reduced as in Patent Document 1, it is difficult to sufficiently reduce the shrinkage force while having high moisture and heat resistance.

When the polarizing film is thinned as in Patent Document 2, there is a problem that the moisture and heat resistance of the polarizing film itself is reduced.

As described in Patent Document 3, if the drying temperature is properly managed according to the moisture content of the PVA film, a polarizing film with low shrinkage can be manufactured. However, the method of Patent Document 3 may reduce the optical performance or cause the polarizing film to dissolve and break during drying due to high-moisture content film drying, making it difficult to implement industrially.

酸系化合物的水溶液中使PVA薄膜延伸以製造偏光薄膜的方法(專利文獻5)、以

酸系化合物來處理PVA薄膜的方法(專利文獻6)、以二

酸來處理PVA薄膜的方法(專利文獻7)、使用對排立構度(syndiotacticity)高的PVA來得到偏光薄膜的方法(專利文獻8)、使用高聚合度的PVA來得到偏光薄膜的方法(專利文獻9)等。 Secondly, as a means of improving the moisture and heat resistance of iodine-based polarizing films, it is known that: a method of crosslinking a PVA film with a polyaldehyde (Patent Document 4);

A method for producing a polarizing film by stretching a PVA film in an aqueous solution of an acid compound (Patent Document 5),

A method for treating PVA film with an acid compound (Patent Document 6),

There are a method for treating a PVA film with an acid (Patent Document 7), a method for obtaining a polarizing film using PVA having a high syndiotacticity (Patent Document 8), a method for obtaining a polarizing film using PVA having a high degree of polymerization (Patent Document 9), etc.

However, the method using polyvalent aldehydes in Patent Document 4 is difficult to implement industrially because the aldehydes are easily volatile and the concentration is difficult to manage.

酸系化合物的水溶液中使PVA薄膜延伸以製造偏光薄膜的方法、以

酸系化合物來處理PVA薄膜的方法，雖可得到耐濕熱性優良的偏光薄膜，但在延伸時頻繁發生斷裂而難以在工業上實施，或收縮力的降低不充分。 Patent Documents 5 and 6 disclose that by dissolving two

A method for producing a polarizing film by stretching a PVA film in an aqueous solution of an acid compound,

Although the method of treating PVA film with acid compounds can obtain a polarizing film with excellent moisture and heat resistance, it is difficult to implement industrially because it frequently breaks during stretching, or the reduction of shrinkage force is insufficient.

酸來處理的方法，雖可得到耐濕熱性優良的偏光薄膜，但二

酸對於水不穩定而會進行分解，因此濃度管理不易，難以在工業上實施。 Patent Literature 7-2

Although the acid treatment method can obtain a polarizing film with excellent moisture and heat resistance,

Acids are unstable in water and will decompose, so concentration management is difficult and difficult to implement industrially.

For example, Patent Document 8 uses PVA with a high degree of isotropic structure. Although a polarizing film with high moisture and heat resistance can be obtained, the PVA has high crystallinity and must be stretched at high temperatures, making it difficult to implement industrially.

For example, Patent Document 9 uses PVA with a high degree of polymerization. Although a polarizing film with high moisture and heat resistance can be obtained, the shrinkage force becomes higher, so it is difficult to have both low shrinkage force and high moisture and heat resistance.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2013-148806

[Patent Document 2] Japanese Patent Application No. 2001-343522

[Patent Document 3] Japanese Patent Application No. 2018-004707

[Patent Document 4] Japanese Patent Publication No. 6-235815

[Patent Document 5] Publication No. KR10-2014-0075154

[Patent Document 6] International Publication Number WO2018/021274

[Patent Document 7] Japanese Patent Publication No. 2018-180022

[Patent Document 8] Japanese Patent Publication No. 6-265727

[Patent Document 9] Japanese Patent Publication No. 01-084203

This invention is made to solve the above-mentioned problems, and its purpose is to provide a polarizing film with small shrinkage force at high temperature and excellent moisture and heat resistance.

酸及於水的存在下可轉化為該單

酸的化合物之群組中的至少1種含硼化合物(B)、及選自包含下式(II)所示之二

酸及於水的存在下可轉化為該二

酸的化合物之群組中的至少1種含硼化合物(C)，其中，由含硼化合物(B)而來之硼元素相對於由含硼化合物(C)而來之硼元素的質量比(B/C)為4.0~8.0，而且由含硼化合物(C)而來的硼元素含量，相對於100質量份的聚乙烯醇(A)而言，為0.05~0.3質量份。 The above-mentioned problem is solved by providing the following polarizing film: a polarizing film comprising PVA (A), a monomer selected from the group consisting of

Acid and in the presence of water can be converted into the monomer

At least one boron-containing compound (B) in the group of compounds containing an acid, and two compounds selected from the group consisting of

Acid and in the presence of water can be converted into the two

At least one boron-containing compound (C) in the group of compounds containing polyvinyl alcohol (A), wherein the mass ratio (B/C) of the boron element from the boron-containing compound (B) to the boron element from the boron-containing compound (C) is 4.0-8.0, and the content of the boron element from the boron-containing compound (C) is 0.05-0.3 parts by mass relative to 100 parts by mass of the polyvinyl alcohol (A).

酸基係以硼-碳鍵連接]。 [In formula (I), R ¹ is ^a monovalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond].

酸基係以硼-碳鍵連接]。 [In formula (II), R ² is ^a divalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond].

In this case, ^R1 and ^R2 are preferably saturated aliphatic groups. ^R1 and ^R2 are also preferably aliphatic alkyl groups. The carbon number of ^R1 is also preferably 2-5, and the carbon number ^{of R2} is also preferably 3-5.

The above-mentioned problem can also be solved by providing the following method for manufacturing a polarizing film: A method for manufacturing the aforementioned polarizing film, which comprises a dyeing process of dyeing a PVA film with a dichroic pigment and a stretching process of uniaxially stretching the film, wherein the process comprises: immersing the film in an aqueous solution containing a boron-containing compound (B) and immersing the film in an aqueous solution containing a boron-containing compound (C).

At this time, it is preferred to immerse the aforementioned PVA film in an aqueous solution containing a boron-containing compound (B) and then immerse it in an aqueous solution containing a boron-containing compound (C). Furthermore, it is more preferred that the boron content of the aforementioned PVA film from the boron-containing compound (B) after immersion in an aqueous solution containing a boron-containing compound (B) is less than 1.3 parts by mass relative to 100 parts by mass of PVA (A).

The polarizing film of the present invention has a small shrinkage force at high temperature and excellent moisture and heat resistance. Therefore, by using the polarizing film of the present invention, an LCD panel or OLED panel that is not easy to warp at high temperature and has excellent moisture and heat resistance can be obtained. In addition, such a polarizing film can be manufactured according to the manufacturing method of the present invention.

1: Hydrogen peak from heavy water as the measurement solvent

2: Hydrogen peak from the methyl group of PVA

3: Hydrogen peak from the methylene group of PVA

4: Hydrogen peaks from the hydrocarbon groups contained in the boron-containing compound (B) and the boron-containing compound (C) overlapping with the hydrogen peaks from PVA

5: Although it does not overlap with the hydrogen peak from PVA, the hydrogen peak from the hydrocarbon groups of the boron-containing compound (B) and the boron-containing compound (C) overlap with each other

6: Hydrogen peak from the methyl group of the boron-containing compound (B) that does not overlap with the hydrogen peak from PVA and the hydrogen peak from the boron-containing compound (C)

FIG. 1 is a ¹ H-NMR chart of the polarizing film obtained in Example 1.

FIG2 is a graph showing the shrinkage force on the horizontal axis and the attenuation coefficient of the PVA-iodine complex on the vertical axis for the polarizing films of Examples 1 and 2 and Comparative Examples 1 to 12.

[Form used to implement the invention]

酸及於水的存在下可轉化為該單

酸之化合物的群組中的至少1種含硼化合物(B)、選自包含下式(II)所示之二

酸及於水的存在下可轉化為該二

酸之化合物的群組中的至少1種含硼化合物(C)，其中，由含硼化合物(B)而來之硼元素相對於由含硼化合物(C)而來之硼元素的質量比(B/C)為4.0~8.0而且由含硼化合物(C)而來的硼元素含量，相對於100質量份之PVA(A)而言，為0.05~0.3質量份。 The polarizing film of the present invention comprises PVA (A), a monomer selected from the group consisting of

Acid and in the presence of water can be converted into the monomer

At least one boron-containing compound (B) in the group of compounds containing an acid is selected from two compounds represented by the following formula (II):

Acid and in the presence of water can be converted into the two

At least one boron-containing compound (C) in the group of compounds of an acid, wherein the mass ratio (B/C) of the boron element from the boron-containing compound (B) to the boron element from the boron-containing compound (C) is 4.0-8.0 and the content of the boron element from the boron-containing compound (C) is 0.05-0.3 parts by mass relative to 100 parts by mass of PVA (A).

The polarizing film of the present invention has not only low shrinkage but also excellent moisture and heat resistance. This effect is believed to be achieved because the boron-containing compound (B) required to reduce shrinkage is adsorbed on the PVA film, and PVA (A) is cross-linked with the boron-containing compound (B) and the boron-containing compound (C) in an appropriate ratio.

酸係上述式(I)所示之化合物，1分子中具有1個

酸基[-B(OH)₂]。式(I)的R¹為碳數1~20的1價脂肪族基。前述

酸基具有鍵結有2個羥基的硼原子鍵於碳原子的結構，於式(I)所示之化合物中，R¹與

酸基係以硼-碳鍵連接。無機硼酸[B(OH)₃]中係硼原子與3個羥基鍵結，對比之下

酸基則係具有硼-碳鍵，在此點上有所不同。然後，

酸基所具有的硼-碳鍵不會水解，因此於存在水的環境中亦為穩定。作為於水的存在下可轉換為

酸基的含硼基，可列舉後述

酸酯基作為代表，但不限於此。 single

Acid is a compound represented by the above formula (I), having one

Acid group [-B(OH) ₂ ]. R ¹ in formula (I) is a monovalent aliphatic group having 1 to 20 carbon atoms.

The acid group has a structure in which a boron atom bonded to two hydroxyl groups is bonded to a carbon atom. In the compound represented by formula (I), R ¹ and

The acid groups are connected by boron-carbon bonds. In inorganic boric acid [B(OH) ₃ ], the boron atom is bonded to three hydroxyl groups.

The acid group is different in that it has a boron-carbon bond.

The boron-carbon bond of the acid group does not hydrolyze, so it is stable even in the presence of water.

The acid-containing boron groups can be listed below.

Acid ester groups are representative, but not limited thereto.

酸係上述式(II)所示之化合物，1分子中具有2個

酸基[-B(OH)₂]。式(II)中的R²為碳數1~20的2價脂肪族基，R²與

酸基係以硼-碳鍵連接。 two

The acid is a compound represented by the above formula (II), which has two

Acid group [-B(OH) ₂ ]. R ² in formula (II) is a divalent aliphatic group having 1 to 20 carbon atoms ^.

The acid groups are linked via boron-carbon bonds.

酸或二

酸所包含的

酸基中的羥基，與無機硼酸中的羥基相同，可形成醇與酯。下式(III)係使1分子的醇(R-OH)對

酸基反應而成的

酸單酯基的例子。此處，當

酸基係與PVA(A)的羥基鍵結的情況，下式(III)中的R為PVA鏈，而且含碳基係透過硼原子而鍵結於PVA鏈。 single

Acid or

Acid contains

The hydroxyl group in the acid group can form alcohols and esters, just like the hydroxyl group in inorganic boric acid. The following formula (III) is a reaction between one molecule of alcohol (R-OH) and

Acid-based reaction

Here, when

When the acid group is bonded to the hydroxyl group of PVA (A), R in the following formula (III) is the PVA chain, and the carbon-containing group is bonded to the PVA chain via a boron atom.

酸基反應而成的

酸二酯基的例子。此處，當

酸基係與PVA的羥基鍵結的情況，結構式(IV)中的2個R皆為PVA鏈。 The following structural formula (IV) is a pair of two alcohol molecules (R-OH)

Acid-based reaction

Here, when

When the acid group is bonded to the hydroxyl group of PVA, the two Rs in the structural formula (IV) are both PVA chains.

酸，其具有2個可與PVA的羥基反應而形成酯的羥基，可使得PVA鏈適度地交聯。此交聯因為對於熱是穩定的，因此偏光薄膜在高溫下的收縮力變小。藉此可抑制使用了偏光薄膜的LCD面板或OLED面板在高溫下的翹曲。又，據認為藉由進行分子內交聯而在PVA鏈中導入環結構藉此降低PVA鏈的運動性，此亦有助於降低偏光薄膜的收縮力。 single

Acid, which has two hydroxyl groups that can react with the hydroxyl groups of PVA to form esters, can moderately crosslink the PVA chains. Since this crosslinking is stable to heat, the shrinkage force of the polarizing film at high temperatures becomes smaller. This can suppress the warping of LCD panels or OLED panels using polarizing films at high temperatures. In addition, it is believed that by introducing a ring structure into the PVA chain through intramolecular crosslinking, the mobility of the PVA chain is reduced, which also helps to reduce the shrinkage force of the polarizing film.

酸，其具有4個可與PVA的羥基反應而形成酯的羥基，可使得PVA鏈堅固地交聯。此交聯因為對於熱是穩定的，因此偏光薄膜在高溫下的收縮力變小。藉此可抑制使用了偏光薄膜的LCD面板或OLED面板在高溫下的翹曲。又，據認為使PVA鏈堅固地交聯，藉此降低PVA鏈在高溫且高濕度下的運動性，因此偏光薄膜的耐濕熱性提升。 two

Acid, which has 4 hydroxyl groups that can react with the hydroxyl groups of PVA to form esters, can crosslink the PVA chains firmly. Since this crosslinking is stable to heat, the shrinkage force of the polarizing film at high temperatures becomes smaller. This can suppress the warping of LCD panels or OLED panels using polarizing films at high temperatures. In addition, it is believed that by crosslinking the PVA chains firmly, the mobility of the PVA chains at high temperatures and high humidity is reduced, so the moisture and heat resistance of the polarizing film is improved.

In the above formula (I), ^R1 is a monovalent aliphatic group having 1 to 20 carbon atoms. By making ^R1 have an appropriate length, the solubility of the boron-containing compound (B) in water and its reactivity with the hydroxyl group of PVA (A) can be controlled. The carbon number of ^R1 is preferably 10 or less, more preferably 6 or less, and even more preferably 5 or less. On the other hand, from the perspective of particularly good balance between optical properties and shrinkage of the polarizing film, the carbon number of ^R1 is preferably 2 or more, and more preferably 3 or more.

酸基係以硼-碳鍵連接即可。R¹可為飽和脂肪族基，亦可為不飽和脂肪族基，但前者較佳。藉由使R¹為飽和脂肪族基，可抑制所得之偏光薄膜的著色，且可提升耐久性。又，藉由使R¹為飽和脂肪族基，雙色性色素的配向性會提升，而光學性能進一步提升。另外，不飽和脂肪族基係指具有包含多鍵的結構的脂肪族基，該多鍵係碳-碳雙鍵或碳-碳三鍵、碳-氧雙鍵、碳-氮雙鍵、氮-氮雙鍵、碳-硫雙鍵等鍵結次數在2以上者，而飽和脂肪族基係指僅具有單鍵之結構的脂肪族基。作為R¹為飽和脂肪族基的單

酸，可例示：甲基

酸、乙基

酸、丙基

酸、丁基

酸、戊基

酸、己基

酸、庚基

酸、辛基

酸、壬基

酸、癸基

酸、十一基

酸、十二基

酸、十三基

酸、十四基

酸、十五基

酸、十六基

酸、十七基

酸、十八基

酸、十九基

酸、二十基

酸及此等的異構物、環丙基

酸、環丁基

酸、環戊基

酸、環己基

酸、環庚基

酸、環辛基

酸、環壬基

酸、環癸基

酸、環十一基

酸、環十二基

酸、環十三基

酸、環十四基

酸、環十五基

酸、環十六基

酸、環十七基

酸、環十八基

酸、環十九基

酸、環二十基

酸及此等的異構物、2-氧雜-丙基

酸、2-氧雜-丁基

酸、2-氧雜-己基

酸、2-氧雜-庚基

酸、2-氧雜-辛基

酸、2-氧雜-壬基

酸、2-氧雜-癸基

酸、2-氧雜-十一基

酸、2-氧雜-十二基

酸、2-氧雜-十三基

酸、2-氧雜-十四基

酸、2-氧雜-十五基

酸、2-氧雜-十六基

酸、2-氧雜-十七基

酸、2-氧雜-十八基

酸、2-氧雜-十九基

酸、2-氧雜-二十基

酸及此等的異構物、2-氮雜-丙基

酸、2-氮雜-丁基

酸、2-氮雜-己基

酸、2-氮雜-庚基

酸、2-氮雜-辛基

酸、2-氮雜-壬基

酸、2-氮雜-癸基

酸、2-氮雜-十一基

酸、2-氮雜-十二基

酸、2-氮雜-十三基

酸、2-氮雜-十四基

酸、2-氮雜-十五基

酸、2-氮雜-十六基

酸、2-氮雜-十七基

酸、2-氮雜-十八基

酸、2-氮雜-十九基

酸、2-氮雜-二十基

酸及此等異構物、2-磷雜-丙基

酸、2-磷雜-丁基

酸、2-磷雜-己基

酸、2-磷雜-庚基

酸、2-磷雜-辛基

酸、2-磷雜-壬基

酸、2-磷雜-癸基

酸、2-磷雜-十一基

酸、2-磷雜-十二基

酸、2-磷雜-十三基

酸、2-磷雜-十四基

酸、2-磷雜-十五基

酸、2-磷雜-十六基

酸、2-磷雜-十七基

酸、2-磷雜-十八基

酸、2-磷雜-十九基

酸、2-磷雜-二十基

酸及此等異構物、2-硫雜-丙基

酸、2-硫雜-丁基

酸、2-硫雜-己基

酸、2-硫雜-庚基

酸、2-硫雜-辛基

酸、2-硫雜-壬基

酸、2-硫雜-癸基

酸、2-硫雜-十一基

酸、2-硫雜-十二基

酸、2-硫雜-十三基

酸、2-硫雜-十四基

酸、2-硫雜-十五基

酸、2-硫雜-十六基

酸、2-硫雜-十七基

酸、2-硫雜-十八基

酸、2-硫雜-十九基

酸、2-硫雜-二十基

酸及此等異構物等。又，作為於水的存在下可轉化為所例示之單

酸的化合物，可列舉該單

酸的鹽等。 In the above formula (I), as long as R ¹ is a monovalent aliphatic group and R ¹ and

The acid group is connected by a boron-carbon bond. ^R1 can be a saturated aliphatic group or an unsaturated aliphatic group, but the former is preferred. By making ^R1 a saturated aliphatic group, the coloring of the obtained polarizing film can be suppressed and the durability can be improved. In addition, by making ^R1 a saturated aliphatic group, the orientation of the dichroic pigment is improved, and the optical performance is further improved. In addition, an unsaturated aliphatic group refers to an aliphatic group having a structure including multiple bonds, such as a carbon-carbon double bond or a carbon-carbon triple bond, a carbon-oxygen double bond, a carbon-nitrogen double bond, a nitrogen-nitrogen double bond, a carbon-sulfur double bond, etc., having a bonding frequency of 2 or more, and ^a saturated aliphatic group refers to an aliphatic group having only a single bond.

Acid, exemplified by: methyl

Acid, Ethyl

Acid, Propyl

Acid, Butyl

Acid, Amyl

Acid, Hexyl

Acid, Heptyl

Acid, Octyl

Acid, Nonyl

Acid, Decyl

Acid, undecyl

Acid, dodecyl

Acid, Tridecyl

Acid, Tetradecyl

Acid, Pentadecyl

Acid, Hexadecyl

Acid, heptadeca

Acid, Octadecyl

Acid, 19-yl

Acid, eicosyl

Acid and its isomers, cyclopropyl

Acid, Cyclobutyl

Acid, Cyclopentyl

Acid, Cyclohexyl

Acid, Cycloheptyl

Acid, Cyclooctyl

Acid, Cyclononyl

Acid, Cyclodecyl

Acid, Cycloundecyl

Acid, Cyclododecyl

Acid, Cyclotridecyl

Acid, Cyclotetradecyl

Acid, Cyclopentadeca

Acid, Cyclohexadecyl

Acid, Cycloheptadecyl

Acid, Cyclooctadecyl

Acid, Cyclohexadecyl

Acid, Cycloic acid

Acid and its isomers, 2-oxo-propyl

Acid, 2-oxo-butyl

Acid, 2-oxa-hexyl

Acid, 2-oxahedral

Acid, 2-oxo-octyl

Acid, 2-oxa-nonyl

Acid, 2-oxo-decyl

Acid, 2-oxa-undecyl

Acid, 2-oxa-dodecyl

Acid, 2-oxa-tride

Acid, 2-oxa-tetradecyl

Acid, 2-oxa-pentadecayl

Acid, 2-oxa-hexadecyl

Acid, 2-oxahedral

Acid, 2-oxa-octadecyl

Acid, 2-oxa-nonadecanyl

Acid, 2-oxa-icosyl

Acid and its isomers, 2-aza-propyl

Acid, 2-aza-butyl

Acid, 2-Aza-hexyl

Acid, 2-Aza-heptyl

Acid, 2-Aza-octyl

Acid, 2-Aza-nonyl

Acid, 2-Aza-Decyl

Acid, 2-Aza-Undecyl

Acid, 2-Aza-dodecyl

Acid, 2-Aza-tride

Acid, 2-Aza-tetradecyl

Acid, 2-Aza-pentadecayl

Acid, 2-Aza-hexadecyl

Acid, 2-Aza-heptadecayl

Acid, 2-Aza-octadecyl

Acid, 2-Aza-19-yl

Acid, 2-Aza-icosyl

Acid and its isomers, 2-phospho-propyl

Acid, 2-phospho-butyl

Acid, 2-phospho-hexyl

Acid, 2-phospha-heptyl

Acid, 2-phospho-octyl

Acid, 2-phospha-nonyl

Acid, 2-phospho-decyl

Acid, 2-phospho-undecyl

Acid, 2-phospho-dodecyl

Acid, 2-phospho-tride

Acid, 2-phospho-tetradecyl

Acid, 2-phospho-pentadecayl

Acid, 2-phospho-hexadecyl

Acid, 2-phospho-heptadecayl

Acid, 2-phospho-octadecyl

Acid, 2-phospho-nonadecanyl

Acid, 2-phospho-icosyl

Acid and its isomers, 2-thio-propyl

Acid, 2-thiobutyl

Acid, 2-thio-hexyl

Acid, 2-thia-heptyl

Acid, 2-thio-octyl

Acid, 2-thia-nonyl

Acid, 2-thia-decyl

Acid, 2-thia-undecyl

Acid, 2-thia-dodecyl

Acid, 2-thia-tride

Acid, 2-thia-tetradecyl

Acid, 2-thia-pentadecayl

Acid, 2-thia-hexadecyl

Acid, 2-thia-heptadecayl

Acid, 2-thia-octadecyl

Acid, 2-thia-nonadecanyl

Acid, 2-thia-icosyl

Acids and isomers thereof. In addition, as monomers which can be converted into the monomers exemplified in the presence of water,

Acid compounds can be listed in this list

Acid salt, etc.

酸，具體而言，可例示：甲基

酸、乙基

酸、丙基

酸、丁基

酸、戊基

酸、己基

酸、庚基

酸、辛基

酸、壬基

酸、癸基

酸、十一基

酸、十二基

酸、十三基

酸、十四基

酸、十五基

酸、十六基

酸、十七基

酸、十八基

酸、十九基

酸、二十基

酸及此等的異構物、環丙基

酸、環丁基

酸、環戊基

酸、環己基

酸、環庚基

酸、環辛基

酸、環壬基

酸、環癸基

酸、環十一基

酸、環十二基

酸、環十三基

酸、環十四基

酸、環十五基

酸、環十六基

酸、環十七基

酸、環十八基

酸、環十九基

酸、環二十基

酸及此等的異構物等。又，作為於水的存在下可轉化為所例示之單

酸的化合物，可列舉該單

酸的鹽等。 ^R1 may be an aliphatic hydrocarbon group, and may also contain impurity atoms such as oxygen, nitrogen, sulfur, and halogen. In consideration of the ease of acquisition, ^R1 is preferably an aliphatic hydrocarbon group that does not contain impurity atoms. As an aliphatic hydrocarbon group, a straight chain aliphatic hydrocarbon group without branches is preferred. It is believed that this will improve the adsorption of the PVA film, and the effect of improving the optical performance and reducing the shrinkage force will be further improved. In addition, as a single aliphatic hydrocarbon group, ^R1 is preferably an aliphatic hydrocarbon group.

Acid, specifically, methyl

Acid, Ethyl

Acid, Propyl

Acid, Butyl

Acid, Amyl

Acid, Hexyl

Acid, Heptyl

Acid, Octyl

Acid, Nonyl

Acid, Decyl

Acid, undecyl

Acid, dodecyl

Acid, Tridecyl

Acid, Tetradecyl

Acid, Pentadecyl

Acid, Hexadecyl

Acid, heptadeca

Acid, Octadecyl

Acid, 19-yl

Acid, eicosyl

Acid and its isomers, cyclopropyl

Acid, Cyclobutyl

Acid, Cyclopentyl

Acid, Cyclohexyl

Acid, Cycloheptyl

Acid, Cyclooctyl

Acid, Cyclononyl

Acid, Cyclodecyl

Acid, Cycloundecyl

Acid, Cyclododecyl

Acid, Cyclotridecyl

Acid, Cyclotetradecyl

Acid, Cyclopentadeca

Acid, Cyclohexadecyl

Acid, Cycloheptadecyl

Acid, Cyclooctadecyl

Acid, Cyclohexadecyl

Acid, Cycloic acid

Acids and their isomers, etc. In addition, as monomers that can be converted into the monomers exemplified in the presence of water,

Acid compounds can be listed in this list

Acid salt, etc.

Specifically, ^R1 is preferably an alkyl group, more preferably an alkyl group represented by the following formula (V).

-C _n H _2n+1 (V)

In the above formula (V), n is 1 to 20. n is preferably 10 or less, more preferably 6 or less, and even more preferably 5 or less. On the other hand, n is preferably 2 or more, and even more preferably 3 or more.

From the viewpoint of obtaining a polarizing film with lower shrinkage force at high temperature and excellent optical performance, ^R1 is particularly preferably a saturated aliphatic hydrocarbon group having 2 to 5 carbon atoms. If the carbon number is less than 2, the bonding stability between PVA (A) and the boron-containing compound (B) will be reduced, and the effect of reducing shrinkage force and improving optical performance may become insufficient. If the carbon number is greater than 5, the boron-containing compound (B) will be located at an offset position on the surface of the polarizing film, and the effect of reducing shrinkage force and improving optical performance may become insufficient.

酸，具體而言，可例示：甲基

酸、乙基

酸、丙基

酸、丁基

酸、戊基

酸、己基

酸、庚基

酸、辛基

酸、壬基

酸、癸基

酸、十一基

酸、十二基

酸、十三基

酸、十四基

酸、十五基

酸、十六基

酸、十七基

酸、十八基

酸、十九基

酸、二十基酸及此等的異構物等。從對於PVA薄膜的吸附性良好且提升光學性能的效果高的觀點而言，特佳為丙基

酸、丁基

酸及戊基

酸。又，作為於水的存在下可轉化為上述式(I)表示之單

酸的化合物，可列舉：該單

酸的鹽、單

酸酯等。 As the monomer represented by the above formula (I)

Acid, specifically, methyl

Acid, Ethyl

Acid, Propyl

Acid, Butyl

Acid, Amyl

Acid, Hexyl

Acid, Heptyl

Acid, Octyl

Acid, Nonyl

Acid, Decyl

Acid, undecyl

Acid, dodecyl

Acid, Tridecyl

Acid, Tetradecyl

Acid, Pentadecyl

Acid, Hexadecyl

Acid, heptadeca

Acid, Octadecyl

Acid, 19-yl

Acid, eicosyl acid and their isomers, etc. From the viewpoint of good adsorption to PVA film and high effect of improving optical performance, propyl

Acid, Butyl

Acid and amyl

In addition, as a monomer which can be converted into the monomer represented by the above formula (I) in the presence of water

Acid compounds can be listed as follows:

Acid salt, mono

Acid esters, etc.

In the above formula (II), ^R2 is a divalent aliphatic group having 1 to 20 carbon atoms. By making ^R2 have an appropriate length, the solubility of the boron-containing compound (C) in water and its reactivity with the hydroxyl group of PVA (A) can be controlled. The carbon number of ^R2 is preferably 10 or less, more preferably 8 or less, further preferably 6 or less, and particularly preferably 5 or less. On the other hand, from the perspective of further improving the moisture and heat resistance of the polarizing film, the carbon number of ^R2 is preferably 3 or more, more preferably 4 or more.

酸基係以硼-碳鍵連接即可。R²可為飽和脂肪族基，亦可為不飽和脂肪族基，但前者較佳。藉由使R²為飽和脂肪族基，可抑制所得之偏光薄膜的著色。又，據認為藉由使R²為飽和脂肪族基，含硼化合物(C)對於偏光薄膜中的擴散性會提升，而提升耐濕熱性的效果、降低收縮力的效果進一步提高。 In the above formula (II), as long as R ² is a divalent aliphatic group and R ² and

The acid group may be connected by a boron-carbon bond. ^R2 may be a saturated aliphatic group or an unsaturated aliphatic group, but the former is preferred. By making ^R2 a saturated aliphatic group, the coloring of the obtained polarizing film can be suppressed. In addition, it is believed that by making ^R2 a saturated aliphatic group, the diffusibility of the boron-containing compound (C) in the polarizing film will be improved, and the effect of improving the moisture and heat resistance and reducing the shrinkage force will be further improved.

^R2 may be an aliphatic hydrocarbon group, and may also contain impurity atoms such as oxygen, nitrogen, sulfur, halogen, etc. If the ease of acquisition is considered, ^R2 is preferably an aliphatic hydrocarbon group containing no impurity atoms. As an aliphatic hydrocarbon group, a straight chain aliphatic hydrocarbon group without branches is preferred. It is believed that by this, the adsorption of the boron-containing compound (C) to the PVA film will become good, and the effect of improving the moisture and heat resistance and reducing the shrinkage force will be further improved.

Specifically, ^R2 is preferably an alkylene group, more preferably an alkylene group represented by the following formula (VI).

-C _n H _2n - (VI)

In the above formula (VI), n is 1 to 20. n is preferably 10 or less, more preferably 8 or less, still more preferably 6 or less, and particularly preferably 5 or less. On the other hand, n is preferably 3 or more, and more preferably 4 or more.

From the viewpoint of obtaining a polarizing film with excellent moisture and heat resistance, R ² is particularly preferably a saturated aliphatic hydrocarbon group having 3 to 5 carbon atoms. When the carbon number is less than 3, the crosslinking efficiency between PVA chains caused by the boron-containing compound (C) is reduced, and the effect of improving moisture and heat resistance may become insufficient. When the carbon number is greater than 5, the boron-containing compound (C) is present at an offset position on the surface of the polarizing film, and the effect of improving moisture and heat resistance may become insufficient. In addition, the water solubility of the boron-containing compound (C) is also reduced, and the boron-containing compound (C) is easily precipitated on the surface of the polarizing film.

酸，具體而言，可例示：甲烷二

酸、乙烷二

酸、丙烷二

酸、丁烷二

酸、戊烷二

酸、己烷二

酸、庚烷二

酸、辛烷二

酸、壬烷二

酸、癸烷二

酸、十一烷二

酸、十二烷二

酸、十三烷二

酸、十四烷二

酸、十五烷二

酸、十六烷二

酸、十七烷二

酸、十八烷二

酸、十九烷二

酸、二十烷二

酸及此等的異構物等。從對於前述偏光薄膜的吸附性良好且提升耐濕熱性的效果高的觀點來看，特佳為丙烷

酸、丁烷二

酸、戊烷二

酸。又，作為於水的存在下可轉化為上述式(II)所示之二

酸 之化合物，可列舉：該二

酸的鹽、二

酸酯等。 As the second of the above formula (II)

Acids, specifically, include methane di

Acid, ethane

Acid, propane

Acid, butane

Acid, pentane

Acid, hexane

Acid, heptane

Acid, Octane

Acid, nonane

Acid, Decane

Acid, undecane

Acid, dodecane

Acid, tridecane

Acid, tetradecane

Acid, Pentadecane

Acid, hexadecane

Acid, heptadecanedioic acid

Acid, octadecane

Acid, nonadecanedioic acid

Acid, eicosanoid

Acids and their isomers, etc. Propane is particularly preferred from the viewpoint of good adsorption to the polarizing film and high effect of improving moisture and heat resistance.

Acid, butane

Acid, pentane

Acid. In addition, in the presence of water, it can be converted into the two compounds shown in the above formula (II)

Acid compounds include:

Acid salt, di

Acid esters, etc.

In the polarizing film of the present invention, the mass ratio (B/C) of the boron element from the boron-containing compound (B) to the boron element from the boron-containing compound (C) must be 4.0 to 8.0. By adjusting the mass ratio (B/C) within this range, a polarizing film with excellent shrinkage and moisture-heat resistance can be obtained. On the other hand, if the mass ratio (B/C) deviates from the above range and either the boron-containing compound (B) or the boron-containing compound (C) is excessively adsorbed on the PVA film, the excessively adsorbed boron-containing compound will hinder the effect of the other boron-containing compound, so that either the shrinkage or moisture-heat resistance will become insufficient. The mass ratio (B/C) is preferably 5 or more. On the other hand, the mass ratio (B/C) is preferably 7 or less, and more preferably 6.5 or less.

The content of boron element from the boron-containing compound (C) in the polarizing film is 0.05 to 0.3 parts by mass or less relative to 100 parts by mass of PVA (A). When the content of the boron-containing compound (C) is less than 0.05 parts by mass, the effect of improving moisture and heat resistance becomes insufficient. The content of the boron element is preferably 0.07 parts by mass or more, and more preferably 0.08 parts by mass or more. On the other hand, when the content of the boron element from the boron-containing compound (C) exceeds 0.3 parts by mass, the reason is not yet clear, but it will lead to insufficient reduction in shrinkage. In addition, there are concerns about reduced productivity such as long processing time and the need to process at high temperature. Therefore, the content of the boron element is preferably 0.2 parts by mass or less. The boron content of the boron-containing compound (B) and the boron-containing compound (C) in the polarizing film can be obtained by ¹ H-NMR measurement.

The boron content of the boron-containing compound (B) in the polarizing film can be appropriately determined by the above-mentioned mass ratio (B/C) and the boron content of the boron-containing compound (C). There is no particular limitation, and it is preferably 0.1 to 2.0 parts by mass relative to 100 parts by mass of PVA (A). When the above-mentioned boron content is less than 0.1 parts by mass, there is a concern that the shrinkage force may be reduced and become insufficient. The above-mentioned boron content is more preferably 0.4 parts by mass or more. On the other hand, when the above-mentioned boron content exceeds 2.0 parts by mass, there is a concern that the effect of the boron-containing compound (C) may be hindered and the moisture and heat resistance may become insufficient. The above-mentioned boron content is preferably 1.6 parts by mass or less, and more preferably 1.4 parts by mass or less.

The polarizing film of the present invention may also contain inorganic boric acid. Thereby, the optical performance is improved. At this time, the total boron content in the polarizing film is preferably 0.2 mass% or more. Here, the total boron content is the total amount of boron from the boron-containing compound (B) and the boron-containing compound (C), the boron from the inorganic boric acid, and the boron from the boron-containing compound (B), the boron-containing compound (C) and the boron-containing compound other than the inorganic boric acid contained in the polarizing film. On the other hand, if the total boron content in the polarizing film is too much, there is a concern that the shrinkage force of the polarizing film will increase. The total boron content in the polarizing film is usually less than 5.5 mass%, preferably less than 5.0 mass%, more preferably less than 4.5 mass%, and even more preferably less than 4.0 mass%. The total boron content in the polarizing film can be obtained by ICP luminescence analysis, etc.

The degree of polymerization of PVA(A) contained in the polarizing film of the present invention is preferably in the range of 1,500 to 6,000, more preferably in the range of 1,800 to 5,000, and even more preferably in the range of 2,000 to 4,000. By making the degree of polymerization above 1,500, the durability of the polarizing film obtained by uniaxially stretching the film can be improved. On the other hand, by making the degree of polymerization below 6,000, the increase in manufacturing cost and the poor passability of the film-making step can be suppressed. In addition, the degree of polymerization of PVA(A) in this specification means the average degree of polymerization measured in accordance with the description of JIS K6726-1994.

The saponification degree of PVA (A) contained in the polarizing film of the present invention is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 98 mol% or more from the viewpoint of water resistance of the polarizing film obtained by uniaxially stretching the film. In addition, the saponification degree of PVA in this specification refers to the ratio (mol%) of the molar number of the vinyl alcohol unit relative to the total molar number of the structural unit (typically vinyl ester unit) and the vinyl alcohol unit that can be converted into the vinyl alcohol unit ( _-CH2 -CH(OH)-) by saponification of the PVA. The saponification degree can be measured in accordance with the description of JIS K6726-1994.

The method for producing PVA (A) used in the present invention is not particularly limited. For example, a method of converting the vinyl ester unit of polyethylene ester obtained by polymerizing vinyl ester monomers into vinyl alcohol units can be cited. The vinyl ester monomers used in the production of PVA (A) are not particularly limited, but for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl trimethylacetate, vinyl neodecanoate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, etc. From an economic point of view, vinyl acetate is preferred.

Furthermore, the PVA (A) used in the present invention may also be: a vinyl ester monomer is copolymerized with other monomers copolymerizable therewith and the vinyl ester units of the obtained vinyl ester copolymer are converted into vinyl alcohol units. As other monomers copolymerizable with the vinyl ester monomer, for example: α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, 1-butene, isobutylene, etc.; (meth)acrylic acid or its salt; (meth)acrylate methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, etc.; (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N, (Meth)acrylamide derivatives such as N-dimethyl (meth)acrylamide, diacetone (meth)acrylamide, (meth)acrylamide propanesulfonic acid or its salts, (meth)acrylamide propyl dimethylamine or its salts, N-hydroxymethyl (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, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tertiary butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; vinyl cyanide such as (meth)acrylonitrile; vinyl chloride, vinylidene chloride (vinylidene chloride), vinyl fluoride, vinylidene fluoride and other halogenated vinyls; allyl compounds such as allyl acetate and allyl chloride; maleic acid or its salts, esters or anhydrides; itaconic acid or its salts, esters or anhydrides; vinyl silane compounds such as ethylene trimethoxysilane; unsaturated sulfonic acid, etc. The above-mentioned vinyl ester copolymer may have structural units derived from one or more of the above-mentioned other monomers. The other monomers may be used by being pre-existing in the reaction vessel when the vinyl ester monomer is supplied to the polymerization reaction, or by being added to the reaction vessel during the polymerization reaction. From the perspective of polarization performance, the content of units derived from other monomers is preferably less than 10 mol%, more preferably less than 5 mol%, and even more preferably less than 2 mol%, relative to the molar number of all structural units constituting PVA (A).

From the perspective of improving the elongation and being able to stretch at a higher temperature, reducing the occurrence of problems such as stretching cracks, and improving the productivity of polarizing films, ethylene is preferably used as a monomer that can be copolymerized with the above-mentioned vinyl ester monomer. When PVA (A) contains ethylene units, from the perspective of the above-mentioned elongation and stretchable temperature, the content of ethylene units is preferably 1 to 10 mol%, and more preferably 2 to 6 mol%, relative to the molar number of all structural units constituting PVA (A).

The PVA film used in the manufacture of the polarizing film of the present invention, in addition to the above-mentioned PVA (A), may contain a plasticizer. As a preferred plasticizer, polyols can be listed, specifically: ethylene glycol, glycerol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, trihydroxymethylpropane, etc. Furthermore, one or more of these plasticizers may be included. Among these, glycerol is preferred from the perspective of improving the effect of elongation.

The plasticizer content in the PVA film used in the manufacture of the polarizing film of the present invention is preferably in the range of 1 to 20 parts by mass, more preferably in the range of 3 to 17 parts by mass, and even more preferably in the range of 5 to 15 parts by mass relative to 100 parts by mass of PVA (A). By making the content greater than 1 part by mass, the elongation of the film is improved. On the other hand, by making the content less than 20 parts by mass, the film can be prevented from becoming too soft and causing reduced operability.

The PVA film used in the manufacture of the polarizing film of the present invention may be further appropriately blended with fillers, processing stabilizers such as copper compounds, weathering stabilizers, colorants, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, flame retardants, other thermoplastic resins, lubricants, fragrances, defoamers, deodorants, extenders, stripping agents, mold release agents, reinforcing agents, crosslinking agents, mold inhibitors, preservatives, crystallization rate retarders and other additives other than PVA (A) and plasticizers according to needs. The content of other additives in the aforementioned PVA film is usually less than 10% by mass, preferably less than 5% by mass.

The expansion of the PVA film used in the manufacture of the polarizing film of the present invention is preferably in the range of 160-240%, more preferably in the range of 170-230%, and particularly preferably in the range of 180-220%. By making the expansion above 160%, the crystallization can be extremely suppressed and the film can be stably stretched to a high ratio. On the other hand, by making the expansion below 240%, the dissolution during stretching can be suppressed, and stretching can be achieved even under higher temperature conditions.

The thickness of the PVA film used in the manufacture of the polarizing film of the present invention is not particularly limited, but is generally 1 to 100 μm, preferably 5 to 60 μm, and particularly preferably 10 to 45 μm. If the aforementioned PVA film is too thin, it is prone to stretching fracture during the uniaxial stretching process used to manufacture the polarizing film. In addition, if the aforementioned PVA film is too thick, it is prone to uneven stretching during the uniaxial stretching process used to manufacture the polarizing film, or the shrinkage force of the manufactured polarizing film tends to increase.

The width of the PVA film used in the manufacture of the polarizing film of the present invention is not particularly limited and can be determined according to the purpose of the polarizing film to be manufactured. In recent years, LCD TVs and LCD displays have developed toward large screens, so if the width of the PVA film used in the manufacture of the polarizing film is made to be more than 3m, it can be applied to such uses. On the other hand, if the width of the PVA film used in the manufacture of the polarizing film becomes too large, it is difficult to uniformly perform uniaxial stretching when manufacturing the polarizing film with a practical device, so the width of the PVA film used in the manufacture of the polarizing film is preferably less than 10m.

The method for manufacturing the PVA film used in the manufacture of the polarizing film of the present invention is not particularly limited, and it is preferably a method that makes the thickness and width of the film uniform after film formation. For example, the following film-forming stock solution can be used for manufacturing: a film-forming stock solution in which PVA (A) is dissolved in a liquid medium and, as required, one or more of the aforementioned plasticizer, the aforementioned other additives, and the later-mentioned surfactant are further dissolved; or a film-forming stock solution containing PVA (A) and, as required, one or more of the aforementioned plasticizer, other additives, surfactants, and liquid medium, and PVA (A) is melted. In the case where the film-forming stock solution contains at least one of the plasticizer, other additives, and surfactants, it is preferred that these components are uniformly mixed.

As the above-mentioned liquid medium used in the preparation of the membrane stock solution, for example, water, dimethyl sulfoxide, dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone, ethylene glycol, glycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trihydroxymethyl propane, ethylenediamine, diethylenetriamine, etc. can be listed. One or more of these can be used. Among them, water is preferred from the perspective of environmental load and recyclability.

The volatile fraction of the film-forming stock solution (the proportion of volatile components such as liquid media that are removed due to volatility or evaporation during film formation in the film-forming stock solution) varies depending on the film-forming method, film-forming conditions, etc., but is generally preferably in the range of 50 to 95 mass%, and more preferably in the range of 55 to 90 mass%. By making the volatile fraction of the film-forming stock solution above 50 mass%, the viscosity of the film-forming stock solution will not become too high, and filtration and defoaming during the preparation of the film-forming stock solution can be smoothly performed, making it easier to produce a film with fewer foreign matter and defects. On the other hand, by making the volatile fraction of the film-forming stock solution below 95 mass%, the concentration of the film-forming stock solution will not become too low, making it easier to form a film industrially.

The film-forming stock solution preferably contains a surfactant. By containing a surfactant, the film-forming property is improved, the uneven thickness of the film is suppressed, and the film can be easily peeled off from the metal roller or belt used in the film-forming. In the case of manufacturing a PVA film from a film-forming stock solution containing a surfactant, the film may contain a surfactant. The type of the above-mentioned surfactant is not particularly limited, but from the perspective of the peeling property of the metal roller or belt, an anionic surfactant or a non-ionic surfactant is preferred.

As anionic surfactants, for example, carboxylic acid type such as potassium laurate is suitable; sulfate ester type such as polyoxyethylene lauryl ether sulfate, sodium alkyl sulfate, potassium alkyl sulfate, ammonium alkyl sulfate, triethanolamine alkyl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxypropylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, octyl sulfate; sodium alkyl sulfonate, potassium alkyl sulfonate, ammonium alkyl sulfonate, triethanolamine alkyl sulfonate , sodium alkylbenzene sulfonate, sodium dodecyl diphenyl ether disulfonate, sodium alkylnaphthalene sulfonate, sodium alkyl sulfosuccinate, sodium polyoxyethylene alkyl sulfosuccinate, sodium dodecylbenzene sulfonate, etc. sulfonic acid type; sodium alkyl phosphate, potassium alkyl phosphate, ammonium alkyl phosphate, triethanolamine alkyl phosphate, sodium polyoxyethylene alkyl ether phosphate, sodium polyoxypropylene alkyl ether phosphate, sodium polyoxyethylene alkylphenyl ether phosphate, etc. phosphate ester type, etc.

As non-ionic surfactants, for example, suitable ones are: alkyl ether type such as polyoxyethylene oleyl ether; alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether; alkyl ester type such as polyoxyethylene laurate; alkyl amine type such as polyoxyethylene laurylamine ether; alkyl amide type such as polyoxyethylene lauric acid amide; polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether; alkanol amide type such as lauric acid diethanolamide and oleic acid diethanolamide; allyl phenyl ether type such as polyoxyalkylene allyl phenyl ether, etc.

These surfactants can be used alone or in combination of two or more.

When the film-forming stock solution contains a surfactant, its content is preferably in the range of 0.01 to 0.5 parts by mass, more preferably in the range of 0.02 to 0.3 parts by mass, and particularly preferably in the range of 0.05 to 0.2 parts by mass relative to 100 parts by mass of PVA (A) contained in the film-forming stock solution. By making the content greater than 0.01 parts by mass, the film-forming property and the peeling property are further improved. On the other hand, by making the content less than 0.5 parts by mass, the surfactant can be prevented from seeping into the surface of the PVA film to cause agglomeration and reduce the operability.

As methods for producing PVA films using the above-mentioned film-forming stock solution, for example, casting film method, extrusion film method, wet film method, gel film method, etc. can be listed. Only one of these film-forming methods can be used or two or more can be combined. From the perspective of obtaining a PVA film with uniform thickness and width and good physical properties, casting film method and extrusion film method are preferred among these film-forming methods. The film-formed PVA film can be dried and heat-treated as needed.

As an example of a specific method for manufacturing a PVA film used in the present invention for manufacturing a polarizing film, for example, the following method can be preferably adopted in industry: using a T-slit die, a hopper plate, an I-type die, a die lip coating die, etc., the above-mentioned film-making stock solution is ejected or poured onto the circumference of the first roller (or belt) that is rotated and heated at the most upstream side, and the volatile components are evaporated from one side of the film ejected or poured onto the circumference of the first roller (or belt) to perform drying, and then the film is further dried on the circumference of one or more rotating and heated rollers arranged on its downstream side, or the film is further dried in a hot air drying device and then wound by a winding device. Drying with a heated roller and drying with a hot air drying device can also be appropriately combined. In addition, a layer containing PVA (A) can be formed on one side of a substrate film composed of a single resin layer to produce a multi-layer PVA film.

There is no particular limitation on the method for manufacturing the polarizing film of the present invention. A suitable manufacturing method is a method for manufacturing a polarizing film, which comprises a dyeing treatment of dyeing a PVA film with a dichroic pigment and a stretching treatment of uniaxially stretching the film, wherein the film is immersed in an aqueous solution containing a boron-containing compound (B) and immersed in an aqueous solution containing a boron-containing compound (C). At this time, the method can be listed as a method of dyeing the PVA film, a uniaxial stretching treatment, and further swelling treatment, inorganic boric acid crosslinking treatment, fixing treatment, washing treatment, drying treatment, heat treatment, etc. according to needs. In this case, the order of each treatment such as swelling treatment, dyeing treatment, inorganic boric acid crosslinking treatment, uniaxial stretching treatment, and fixing treatment is not particularly limited, and one or more treatments may be performed simultaneously. In addition, one or more of each treatment may be performed twice or more.

The swelling treatment can be performed by immersing the PVA film in water. The water temperature for immersing the film is preferably in the range of 20 to 40°C, more preferably in the range of 22 to 38°C, and more preferably in the range of 25 to 35°C. In addition, the immersion time in water is preferably in the range of 0.1 to 5 minutes, and more preferably in the range of 0.2 to 3 minutes. In addition, the water for immersing the film is not limited to pure water, but can be an aqueous solution in which various components are dissolved, or a mixture of water and a hydrophilic medium.

The dyeing treatment can be performed by bringing a dichroic pigment into contact with the PVA film. As the dichroic pigment, an iodine-based pigment or a dichroic dye is generally used. The dyeing treatment can be performed at any stage before the uniaxial stretching treatment, during the uniaxial stretching treatment, or after the uniaxial stretching treatment. The dyeing treatment is generally performed by immersing the PVA film in a solution (especially an aqueous solution) containing iodine-potassium iodide as a dyeing bath, or in a solution (especially an aqueous solution) containing a plurality of dichroic dyes. The iodine concentration in the dyeing bath is preferably in the range of 0.01~0.5 mass %, and the potassium iodide concentration is preferably in the range of 0.01~10 mass %. In addition, the temperature of the dyeing bath is preferably 20~50°C, and particularly preferably 25~40°C. The preferred dyeing time is 0.2 to 5 minutes. When using a dichroic dye, the dichroic dye is preferably an aqueous dye. In addition, the dye concentration in the dye bath is preferably 0.001 to 10% by mass. In addition, dyeing auxiliaries may be used as required, and inorganic salts such as sodium sulfate and surfactants may also be used. When sodium sulfate is used, it is preferably 0.1 to 10% by mass. The dyeing temperature is preferably 30 to 80°C. Specific dichroic dyes include: C.I. Direct Yellow 28, C.I. Direct Orange 39, C.I. Direct Yellow 12, C.I. Direct Yellow 44, C.I. Direct Orange 26, C.I. Direct Orange 71, C.I. Direct Orange 107, C.I. Direct Red 2, C.I. Direct Red 31, C.I. Direct Red 79, C.I. Direct Red 81, C.I. Direct Red 247, C.I. Direct Green 80, C.I. Direct Green 59, etc., but the dichroic dyes developed for the manufacture of polarizing plates are preferred.

The PVA film may also be subjected to an inorganic boric acid crosslinking treatment. In this case, it is more effective to prevent PVA (A) from dissolving into water during wet stretching at high temperature. From this point of view, the inorganic boric acid crosslinking treatment is preferably performed before the uniaxial stretching treatment. The inorganic boric acid crosslinking treatment can be performed by immersing the PVA film in an aqueous solution containing an inorganic boric acid crosslinking agent. As the inorganic boric acid crosslinking agent, one or more boron-containing inorganic compounds such as inorganic boric acid, borax and other inorganic borates can be used. The concentration of the inorganic boric acid crosslinking agent in the aqueous solution containing the inorganic boric acid crosslinking agent is preferably in the range of 0.1 to 6.0 mass %. The concentration of the inorganic boric acid crosslinking agent is more preferably 0.2 mass % or more. Furthermore, it is more preferably 4.0 mass % or less. By making the concentration of the inorganic boric acid crosslinking agent within the above range, the elongation may be improved. If the concentration of the inorganic boric acid crosslinking agent is too high, it will become difficult to contain the boron-containing compound (B) and the boron-containing compound (C) in the subsequent steps, so the concentration should not be too high. The aqueous solution containing the inorganic boric acid crosslinking agent may also contain auxiliary agents such as potassium iodide. The temperature of the aqueous solution containing the inorganic boric acid crosslinking agent is preferably in the range of 20~50°C, and particularly preferably in the range of 25~40°C.

In addition to the uniaxial stretching treatment described later, the PVA film may be stretched (pre-stretched) during or between the above-mentioned treatments. Thus, the total stretching ratio (the ratio obtained by multiplying the stretching ratios in each treatment) of the pre-stretching performed before the uniaxial stretching treatment is preferably 1.5 times or more, more preferably 2.0 times or more, and even more preferably 2.5 times or more, based on the original length of the raw material PVA film before stretching, from the perspective of the optical properties of the obtained polarizing film. On the other hand, the total stretching ratio is preferably 4.0 times or less, more preferably 3.5 times or less. As the stretching ratio in the swelling treatment, it is preferably 1.05 to 2.5 times. As the stretching ratio in the dyeing treatment, it is preferably 1.1 to 2.5 times. The stretching ratio in the inorganic boric acid crosslinking treatment is preferably 1.1~2.5.

The uniaxial stretching treatment can be performed by either a wet stretching method or a dry stretching method. In the case of the wet stretching method, the stretching is performed in an aqueous solution. The stretching can also be performed in the above-mentioned dyeing bath or in an inorganic boric acid aqueous solution. In addition, in the case of the dry stretching method, the uniaxial stretching treatment can be performed directly at room temperature, while being heated, or by using a PVA film after absorbing water to perform the uniaxial stretching treatment in the air. Among these, the wet stretching method is preferred, and the uniaxial stretching treatment in an aqueous solution containing inorganic boric acid is more preferred. The inorganic boric acid concentration in the inorganic boric acid aqueous solution is preferably in the range of 0.5 to 6% by mass, and more preferably in the range of 1 to 5% by mass. Furthermore, the inorganic boric acid aqueous solution may also contain potassium iodide, and the concentration thereof is preferably in the range of 0.01 to 10% by mass. The stretching temperature in the uniaxial stretching treatment is preferably above 30°C, more preferably above 40°C, and even more preferably above 50°C. On the other hand, the stretching temperature is preferably below 90°C, more preferably below 80°C, and even more preferably below 70°C. Furthermore, the stretching ratio in the uniaxial stretching treatment is preferably 2.0 to 4.0 times. From the viewpoint of the optical properties of the resulting polarizing film, the stretching ratio is preferably above 2.2 times. On the other hand, the stretching ratio is preferably below 3.5 times. In addition, the total stretching ratio before the fixing treatment described below is preferably 5 times or more, and more preferably 5.5 times or more, based on the original length of the raw material PVA film before stretching, from the perspective of the optical performance of the obtained polarizing film. There is no particular upper limit on the stretching ratio, but the stretching ratio is preferably 8 times or less.

When a long PVA film is subjected to uniaxial stretching, the direction of the uniaxial stretching is not particularly limited. It can be uniaxial stretching in the long side direction, uniaxial stretching in the transverse direction, or so-called oblique stretching. However, from the perspective of obtaining a polarizing film with excellent optical properties, uniaxial stretching in the long side direction is preferred. For uniaxial stretching in the long side direction, a stretching device having multiple rollers parallel to each other can be used, and the circumferential speed between the rollers can be changed. On the other hand, uniaxial stretching in the transverse direction can be performed using a tenter-type stretching machine.

When manufacturing polarizing film, in order to firmly adsorb dichroic pigments (iodine pigments, etc.) to PVA film, it is preferred to perform fixing treatment after uniaxial stretching treatment. As the fixing treatment bath used in the fixing treatment, an aqueous solution containing a boron-containing compound (B) or a boron-containing compound (C) can be appropriately used. In addition, inorganic boric acid, iodine compounds, metal compounds, etc. can be further added to the fixing treatment bath as required. The temperature of the fixing treatment bath is preferably 10~80℃. The stretching ratio in the fixing treatment is preferably less than 1.3 times, more preferably less than 1.2 times, and more preferably less than 1.1 times.

In the above-mentioned manufacturing method, the PVA film is immersed in an aqueous solution containing a boron-containing compound (B) and an aqueous solution containing a boron-containing compound (C), so that the boron-containing compound (B) and the boron-containing compound (C) can be adsorbed on the film. At this time, by immersing the PVA film in an aqueous solution containing both the boron-containing compound (B) and the boron-containing compound (C), the boron-containing compound (B) and the boron-containing compound (C) can be adsorbed on the film at one stage, but from the perspective of allowing the boron-containing compound (B) and the boron-containing compound (C) to be adsorbed on the film without competition and having both the effect of reducing shrinkage and the effect of improving moisture and heat resistance, it is better to immerse the film in an aqueous solution containing a boron-containing compound (B) and an aqueous solution containing a boron-containing compound (C), respectively.

At this time, it is preferred that the PVA film be immersed in an aqueous solution containing a boron-containing compound (B) before being immersed in an aqueous solution containing a boron-containing compound (C). If the order of these treatments is reversed, the boron-containing compound (C) significantly hinders the adsorption of the boron-containing compound (B), so there is a concern that the effect of reducing the shrinkage force becomes insufficient and the optical performance is reduced. In addition, after being immersed in an aqueous solution containing a boron-containing compound (B), the boron content of the PVA film from the boron-containing compound (B) before being immersed in an aqueous solution containing a boron-containing compound (C) is preferably 1.3 parts by mass or less, and particularly preferably 1.0 parts by mass or less. If the above content exceeds 1.3 parts by mass, the adsorption of the boron-containing compound (C) will be hindered, and there is a concern that the moisture and heat resistance will become insufficient. On the other hand, if the content of the boron-containing compound (B) is too small, the reduction of the shrinkage force will become insufficient. Therefore, after immersion in an aqueous solution containing the boron-containing compound (B), the boron content of the PVA film from the boron-containing compound (B) before immersion in an aqueous solution containing the boron-containing compound (C) is preferably 0.1 parts by mass or more.

In the aqueous solution containing the boron-containing compound (B), the concentration of the boron-containing compound (B) is preferably 15% by mass or less. When the above concentration is higher than 15% by mass, a high-density adsorption layer of the boron-containing compound (B) is formed on the surface of the polarizing film in a short time, and there is a concern that the adsorption of the boron-containing compound (C) to the polarizing film is hindered. In addition, there is a concern that the boron-containing compound (B) is biased near the surface of the polarizing film, resulting in a concern that the optical performance is reduced. The above concentration is preferably 10% by mass or less, more preferably 5.0% by mass or less, particularly preferably 3.5% by mass or less, still more preferably 1.5% by mass or less, and most preferably 0.8% by mass or less. On the other hand, the concentration of the boron-containing compound (B) is preferably 0.1% by mass or more.

As long as it does not hinder the effect of the present invention, the aqueous solution containing the boron-containing compound (B) may also contain the boron-containing compound (C), but in the aqueous solution, the ratio (C/B) of the concentration (mass %) of the boron-containing compound (C) relative to the concentration (mass %) of the boron-containing compound (B) is preferably 0.1 or less, more preferably 0.01 or less, and most preferably substantially no boron-containing compound (C) is contained. If the ratio (C/B) of the concentration (mass %) exceeds 0.1, the adsorption of the boron-containing compound (B) will be hindered by the boron-containing compound (C), and there is a concern that the effect of reducing the contractile force will become insufficient.

In the aqueous solution containing the boron-containing compound (C), the concentration of the boron-containing compound (C) is preferably less than 2.0% by mass, more preferably less than 1.5% by mass, and even more preferably less than 0.8% by mass. If the concentration of the aqueous solution of the boron-containing compound (C) is high, the shrinkage force may not be sufficiently reduced, although the reason is unclear. On the other hand, if the concentration of the boron-containing compound (C) is too low, the moisture and heat resistance may not be sufficiently improved, so the concentration is preferably 0.1% by mass or more, and particularly preferably 0.3% by mass or more.

As long as it does not hinder the effect of the present invention, the aqueous solution containing the boron-containing compound (C) may also contain the boron-containing compound (B), but in the aqueous solution, the ratio (B/C) of the concentration [mass %] of the boron-containing compound (B) to the concentration [mass %] of the boron-containing compound (C) is preferably less than 1, more preferably less than 0.5, and even more preferably less than 0.1, and it is particularly preferred that the boron-containing compound (B) is substantially absent. When the ratio (B/C) of the concentration [mass %] is greater than 1, the adsorption of the boron-containing compound (C) may be hindered by the boron-containing compound (B), and there is a concern that the effect of improving moisture-heat resistance may become insufficient.

From the viewpoint of optical performance, the aqueous solution containing the boron compound (B) or the boron compound (C) preferably contains an iodide additive such as potassium iodide, and the concentration of the iodide is preferably 0.5-15% by mass. In addition, the temperature of such aqueous solution is preferably 10-80°C. If the temperature is too low, the boron compound (B) or the boron compound (C) may precipitate in the treatment bath. The temperature of the aqueous solution is more preferably above 15°C, and more preferably above 20°C. On the other hand, if the temperature is too high, it is difficult to manufacture polarizing films industrially under mild conditions. The temperature of the aqueous solution is more preferably below 70°C, and more preferably below 60°C, and particularly preferably below 50°C. The immersion time in the aqueous solution is preferably 5-400 seconds.

The boron-containing compound (B) and the boron-containing compound (C) can also be adsorbed on the PVA film in any step of the dyeing treatment, inorganic boric acid crosslinking treatment, uniaxial stretching treatment, and fixing treatment. However, from the perspective of suppressing the breakage of the PVA film during the uniaxial stretching treatment and obtaining a polarizing film with particularly excellent optical properties, it is preferably carried out after the uniaxial stretching treatment, and it is particularly preferably carried out during the fixing treatment after the uniaxial stretching treatment.

When the boron-containing compound (B) and the boron-containing compound (C) are adsorbed on the polarizing film during the fixing treatment, a suitable manufacturing method is to implement the following steps in the order of swelling treatment, uniaxial stretching treatment, fixing treatment with the boron-containing compound (B), and fixing treatment with the boron-containing compound (C); to implement the following steps in the order of swelling treatment, inorganic boric acid crosslinking treatment, uniaxial stretching treatment, fixing treatment with the boron-containing compound (B), and fixing treatment with the boron-containing compound (C); or to implement the following steps in the order of swelling treatment, uniaxial stretching treatment, fixing treatment with the boron-containing compound (B), fixing treatment with the boron-containing compound (C), and inorganic boric acid crosslinking treatment. Afterwards, one or more treatments selected from washing, drying and heat treatment may be performed as needed. On the other hand, it is not advisable to perform the fixation treatment with the boron-containing compound (C) before the fixation treatment with the boron-containing compound (B). When the fixation treatment is performed in this order, the boron-containing compound (C) is firmly bonded to the hydroxyl group of the PVA film, thereby hindering the adsorption of the boron-containing compound (B) to the polarizing film, which may result in a decrease in optical performance or insufficient reduction in shrinkage.

The cleaning treatment is generally performed by immersing the film in distilled water, pure water, aqueous solution, etc. At this time, from the perspective of optical performance, it is preferred to use an aqueous solution containing iodide such as potassium iodide as an auxiliary agent, and the concentration of the iodide is preferably 0.5~10 mass%. In addition, the temperature of the aqueous solution in the cleaning treatment is generally 5~50℃, preferably 10~45℃, and more preferably 15~40℃. From an economic perspective, the temperature of the aqueous solution should not be too low. If the temperature of the aqueous solution is too high, it may lead to a decrease in optical performance.

The drying conditions are not particularly limited, but it is preferably dried at a temperature in the range of 30~150°C, especially in the range of 50~130°C. By drying at a temperature in the range of 30~150°C, it is easy to obtain a polarizing film with excellent dimensional stability.

By performing heat treatment after drying, the dimensional stability may be further improved. This heat treatment refers to further heating the polarizing film with a moisture content of less than 5% after drying. There is no particular restriction on the conditions of the heat treatment, but it is preferably performed in the range of 60℃~150℃, especially in the range of 70℃~150℃. If the heat treatment temperature is less than 60℃, the dimensional stabilization effect may become insufficient, and if it exceeds 150℃, the polarizing film may be drastically reddened.

The polarizing film of the present invention thus obtained has a small shrinkage force at high temperature and excellent moisture and heat resistance. The shrinkage force of the polarizing film is preferably less than 5N, and more preferably less than 4N. In addition, in the aforementioned polarizing film, the attenuation coefficient of the PVA-iodine complex is preferably greater than -0.5, and more preferably greater than -0.4. The shrinkage force of the aforementioned polarizing film and the attenuation coefficient of the PVA-iodine complex are measured by the method described in the following embodiments.

The polarizing film of the present invention is usually used as a polarizing plate by laminating an optically transparent and mechanically strong protective film on both sides or one side. As the protective film, triacetate cellulose (TAC) film, cellulose acetate and butyrate (CAB) film, acrylic film, polyester film, etc. can be used. In addition, as the adhesive for laminating, PVA adhesive and UV curing adhesive can be listed.

The polarizing plate obtained in the above manner can also be bonded to a phase difference film, a viewing angle enhancement film, a brightness enhancement film, etc. In addition, after applying an acrylic adhesive or the like on the polarizing plate, it can be bonded to a glass substrate and used as a component of an LCD.

[Implementation example]

The present invention is described in more detail below through examples, but the present invention is not limited by these examples. In addition, the various measurement or evaluation methods used in the following examples and comparative examples are shown below.

[Measurement of boron content from boron-containing compounds (B) and boron-containing compounds (C) in polarizing films containing boron-containing compounds (B) and boron-containing compounds (C)]

After dissolving the polarizing film in heavy water to a content of 0.003 mass %, the solution was concentrated by a rotary evaporator to a content of 0.15 mass %, and used as a sample for ¹ H-NMR measurement. ¹ H-NMR (JNM-AL400: 400 MHz, manufactured by JEOL Ltd.) was measured at 80°C, and the cumulative number of times was set to 256. ALICE2 (manufactured by JEOL Ltd.) was used for analysis in the following manner. For the measured ¹ H-NMR spectrum, the phase was adjusted to smooth the baseline, and the average point was set to 20 to automatically correct the baseline. Then, as a reference, the peak 1 of heavy water as the measurement solvent was automatically set to 4.65 ppm. Then, as shown in Figure 1, the peak area (Area A) of the hydrogen peak 6 of the methyl group from the boron-containing compound (B) appearing in the range of 1.2 to 1.3 ppm was calculated. Next, the peak area (Area B) of the hydrogen peak 5 of the alkyl group from the boron-containing compound (B) and the boron-containing compound (C) overlapping in the range of 1.0 to 1.2 ppm was calculated. Furthermore, the hydrogen peak in the range of 1.6 to 2.3 ppm is regarded as the sum of the hydrogen peak 3 from the methylene group of PVA and the hydrogen peak 4 from the alkyl group of the boron-containing compound (B) and the boron-containing compound (C) overlapping with the hydrogen peak 3 from the methylene group of PVA, and the total area of the hydrogen peak in the range of 1.6 to 2.3 ppm (area C) is calculated. At this time, the area (area A) of the hydrogen peak 6 of the methyl group from the boron-containing compound (B) which does not overlap with the hydrogen peak from PVA or the hydrogen peak from the boron-containing compound (C) is used as the standard of the peak area, and is set to 3, which is the same as the hydrogen number of the methyl group. Thereafter, the area D is calculated by subtracting the area U of the hydrogen peak 4 of the alkyl groups from the boron-containing compound (B) and the boron-containing compound (C) which overlaps with the hydrogen peak of the methylene group from PVA from the area C. The values obtained by these methods are substituted into the following formula (1) to calculate the content (parts by mass) of the boron element from the boron-containing compound (B) relative to 100 parts by mass of PVA (A). In addition, W in the following formula (1) is the number of boron per molecule of the boron-containing compound (B). Furthermore, the following formula (1) is the formula used when unmodified PVA is used. When modified PVA is used as a raw material, the following formula (1) must be appropriately modified.

The content of boron element from the boron-containing compound (B) relative to 100 parts by mass of PVA (A) (parts by mass) = {(area A/3)/(area D/2)}×(10.811×W/44.0526)×100 (1)

Next, substitute the obtained value into the following formula (2) to calculate the boron content from the boron-containing compound (C) per 100 parts by mass of PVA (A). In addition, X in the following formula (2) is the number of hydrogen atoms of the hydrocarbon group from the boron-containing compound (B) overlapping with the hydrogen peak of the hydrocarbon group from the boron-containing compound (C) in the range of 1.0 to 1.2 ppm, and Y is the number of hydrogen atoms per molecule of the hydrocarbon group from the boron-containing compound (C) in the range of 1.0 ppm to 1.2 ppm. In addition, Z is the number of boron atoms per molecule of the boron-containing compound (C). In addition, the following formula (2) is the formula used when using unmodified PVA. When using modified PVA as a raw material, the following formula (2) must be appropriately modified.

The content of boron element from the boron-containing compound (C) relative to 100 parts by mass of PVA (A) (parts by mass) = {(area A/3)/(area D/2)}×{(area B)-X}/Y×(10.811×Z/44.0526)×100 (2)

In formula (2), 10.811 is the atomic weight of boron, and 44.0526 is the molecular weight per mol of the repeating unit of the unmodified PVA. In addition, the ¹ H-NMR spectrum of FIG1 is the result obtained by measuring the polarizing film of Example 1.

[Measurement of the boron content from the boron-containing compound (B) or the boron-containing compound (C) in a polarizing film containing only one of the boron-containing compound (B) and the boron-containing compound (C)]

Referring to the method of Patent Document 6, the measurement is performed in the following order. After dissolving the polarizing film or stretched film in heavy water so that its content is 0.003 mass %, it is concentrated by a rotary evaporator so that its content becomes 0.15 mass %, and this solution is used as a measurement sample for ¹ H-NMR. ¹ H-NMR (JNM-AL400: 400 MHz manufactured by JEOL Ltd.) measurement is performed at 80°C, and the cumulative number of times is set to 256 times. Using ALICE2 (manufactured by JEOL Ltd.), analysis is performed in the following manner. For the measured ¹ H-NMR spectrum, after adjusting the phase to smooth the baseline, the average point is set to 20 to automatically correct the baseline. Then, as a reference, the peak of heavy water as the measurement solvent is automatically set to 4.65 ppm. Then, the peak area (area E) of the hydrogen peak of the hydrocarbon group derived from the boron-containing compound (B) or the boron-containing compound (C) is calculated by integrating the peak area of the hydrogen peak of the hydrocarbon group derived from the boron-containing compound (B) or the boron-containing compound (C) that does not overlap with the hydrogen peak derived from PVA. The peak area is set as a reference so that the hydrogen number of the hydrocarbon group related to the boron-containing compound (B) or the boron-containing compound (C) is the same as the value of the area F. Next, the hydrogen peak in the range of 1.6ppm to 2.3ppm is regarded as the sum of the hydrogen peak derived from the methylene group of PVA and the hydrogen peak of the hydrocarbon group contained in the boron-containing compound (B) or the boron-containing compound (C) overlapping with the hydrogen peak derived from the methylene group of PVA, and the peak area (area G) is calculated. Thereafter, the number of hydrogens of the hydrocarbon group derived from the boron-containing compound (B) or the boron-containing compound (C) overlapping with the hydrogen peak of the methylene group derived from PVA is subtracted from the area G to calculate the area H. The values obtained by these methods are substituted into the following formula (3) to calculate the content (mass parts) of the boron element derived from the boron-containing compound (B) or the boron-containing compound (C) relative to 100 parts by mass of PVA (A). In the following formula (3), S is the number of hydrogen atoms in the alkyl group of the boron-containing compound (B) or the boron-containing compound (C) which does not overlap with the peak of PVA, and T is the number of boron atoms per molecule of the boron-containing compound (B) or the boron-containing compound (C). In addition, formula (3) is used when unmodified PVA is used. When modified PVA is used as a raw material, formula (3) must be appropriately modified.

The content of boron element from the boron-containing compound (B) or the boron-containing compound (C) relative to 100 parts by mass of PVA (A) (parts by mass) = {(area F/S)/(area H/2)}×(10.811×T/44.0526)×100 (3)

In formula (3), 10.811 is the atomic weight of boron, and 44.0526 is the molecular weight per mol of the repeating unit of unmodified PVA.

[Calculate the total boron content (mass %) in the polarizing film]

The mass [I(g)] of the polarizing film was measured. The polarizing film was dissolved in 20 mL of distilled water so that the content was 0.005 mass%. The aqueous solution in which the polarizing film was dissolved was used as a measurement sample, and its mass [J(g)] was measured. Then, the boron concentration [K(ppm)] of the sample was measured using a polymorphic ICP luminescence analyzer (ICP) manufactured by Shimadzu Corporation. Then, the value was substituted into the following formula (4) for calculation, and the calculated value was used as the total boron element content (mass %) in the polarizing film.

Total boron content in polarizing film (mass %) = [(K×10 ^-6 ×J)/I]×100 (4)

[Optical properties of polarizing films] (1) Measurement of visual sensitivity corrected single body transmittance Ts

The sensitivity-corrected single transmittance Ts (hereinafter sometimes referred to as "sensitivity-corrected single transmittance Ts") of the polarizing film obtained in the following examples or comparative examples was measured using a spectrophotometer with an integrating sphere ("V-7100" manufactured by JASCO Corporation) and an automatic polarizing film measuring device VAP-7070S (manufactured by JASCO Corporation) equipped with a Gran-Taylor polarizer. From the central part of the obtained polarizing film, a sample of 4 cm in the extension direction and 2 cm in the width direction of the polarizing film was taken. For the polarizing film taken, the MD transmittance (%) and TD transmittance (%) in the range of 380nm~780nm were measured, and the transmittance Ts (%) was calculated using the "Polarizing Film Evaluation Program" (manufactured by JASCO Corporation). Here, "MD transmittance" indicates the transmittance (%) when the direction of polarized light from the Glan-Taylor polarizer is parallel to the transmission axis of the polarizing film sample. Also, "TD transmittance" indicates the transmittance (%) when the direction of polarized light from the Glan-Taylor polarizer is orthogonal to the transmission axis of the polarizing film sample. The transmittance Ts is calculated from the MD transmittance and the TD transmittance by multiplying the sensitivity correction called the sensitivity correction.

(2) Measurement of visual sensitivity correction polarization V

The polarizing film samples used in the measurement of the transmittance Ts(%) were measured using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and an automatic polarizing film measuring device VAP-7070S (manufactured by JASCO Corporation) equipped with a Gran-Taylor polarizer. The MD transmittance (%) and TD transmittance (%) of the samples in the range of 380nm~780nm were measured, and the visual sensitivity correction polarization degree V(%) was calculated using the "Polarizing Film Evaluation Program" (manufactured by JASCO Corporation) (hereinafter, "visual sensitivity correction polarization degree V" may be referred to as "polarization degree V").

[Contraction force of polarizing film]

The shrinkage force is measured using the Autograph "AG-X" with a thermostat and the image extensometer "TR ViewX120S" manufactured by Shimadzu Corporation. The measurement is performed using a polarizing film that has been humidified at 20°C/20%RH for 18 hours. After the thermostat of the Autograph "AG-X" is set to 20°C, a rectangular polarizing film [15 cm in the length direction (stretching direction), 1.5 cm in the width direction] is mounted on a fixture (5 cm between fixtures), and the thermostat is heated to 80°C at the same time as the stretching begins. The polarizing film is stretched at a speed of 1 mm/min, and the stretching is stopped when the tension reaches 2N. The tension is measured 4 hours later in this state. At this time, the distance between the clamps changes due to thermal expansion, so a marking sticker is attached to the clamp, and the image extensometer "TR ViewX120S" is used to correct the distance between the clamps by the amount of movement of the marking sticker attached to the clamp so that the distance between the clamps becomes constant, while measuring. In addition, if the minimum value of tension occurs at the beginning of the measurement (within 10 minutes of the measurement), the minimum value of tension is subtracted from the measured value of tension 4 hours later, and the difference is used as the shrinkage force of the polarizing film. If the minimum value does not occur, the tension at the time of stopping the stretching, that is, 2N, is subtracted from the measured value of tension 4 hours later, and the resulting value is used as the shrinkage force of the polarizing film.

[Wet and heat resistance]

The moisture and heat resistance of the polarizing film is evaluated using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and an automatic polarizing film measuring device VAP-7070S (manufactured by JASCO Corporation) equipped with a Gran-Taylor polarizer. The sampled polarizing film is fixed to a metal frame as an evaluation sample. Then, the initial (0 hour) orthogonal transmittance (%) at 610 nm of the evaluation sample is measured using a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation) and an automatic polarizing film measuring device VAP-7070S (manufactured by JASCO Corporation) equipped with a Gran-Taylor polarizer. In addition, the orthogonal transmittance (%) is the value calculated by the following formula (5). Then, the calculated cross transmittance at 610 nm was substituted into the following formula (6) to calculate the initial (0 hour) cross absorbance A ₀ at 610 nm. After that, the cross transmittance (%) at 610 nm was measured at each standing time of 1 hour, 2 hours, 4 hours, 6 hours, and 8 hours of the evaluation sample in a 60°C/90%RH environment using a small constant temperature and humidity machine ("IW223" manufactured by Yamato Scientific Co., Ltd.), and the cross transmittance (%) at 610 nm was substituted into the following formula (6) to calculate the cross absorbance A at each standing time. In addition, the cross transmittance was measured using the same evaluation sample until 8 hours. Then, using Microsoft Excel, the relationship between the test time and Ln (A/A ₀ ) was plotted, and approximated as a linear equation passing through the origin, and its slope was calculated. This slope was used as the attenuation coefficient of the PVA-iodine complex, as an indicator of fading (an indicator of moisture and heat resistance) in the present invention. The smaller the attenuation coefficient, the faster the fading of the iodine-based polarizing film proceeds, so a small attenuation coefficient indicates low moisture and heat resistance.

Orthogonal transmittance at 610nm at each static time (%) = (MD transmittance at 610nm at each static time × TD transmittance at 610nm at each static time)/100 (5)

Absorbance at each static time A=2-Log(orthogonal transmittance at 610nm at each static time) (6)

[PVA film swelling]

Cut the PVA film into 5cm×10cm and soak it in 1000mL of distilled water at 30℃ for 30 minutes. Then, take out the PVA film, wipe the water on the surface of the PVA film with filter paper, and measure the mass of the PVA film after soaking (mass L). Then, put the PVA film in a dryer at 105℃ and dry it for 16 hours, then measure the mass of the PVA film after drying (mass M). The swelling degree of the PVA film is calculated by substituting the values of mass L and mass M into the following formula (7).

Swelling degree (%) = (mass L/mass M) × 100 (7)

[Implementation Example 1]

An aqueous solution containing 100 parts by mass of PVA (99.9 mol% saponification degree, 2400 degree of polymerization), 10 parts by mass of glycerol as a plasticizer, and 0.1 parts by mass of sodium polyoxyethylene lauryl ether sulfate as a surfactant, with a PVA content of 9% by mass, was used as a film-making stock solution, which was dried on a metal roll at 80°C, and the resulting film was heat-treated at 120°C for 10 minutes in a hot air dryer to produce a PVA film with a swelling adjusted to 200% and a thickness of 30μm.

酸及3.5質量%的碘化鉀之比例的水溶液(第一固定處理浴)(溫度30℃)30秒。第一固定處理中，PVA薄膜未延伸(延伸倍率1.0倍)。之後，再浸漬於含有0.5質量%的1,4-丁烷二

酸及8.5質量%的碘化鉀之比例的水溶液(第二固定處理浴)(溫度50℃)100秒。第二固定處理中，PVA薄膜未經延伸(延伸倍率1.0倍)。最後於60℃乾燥4分鐘，以製造偏光薄膜。 From the central part of the width direction of the PVA film thus obtained, a sample of 5 cm in width and 9 cm in length was cut out in such a way that it could be uniaxially stretched within a range of 5 cm in width and 5 cm in length. This sample was immersed in pure water at 30°C for 30 seconds and uniaxially stretched 1.1 times in the length direction to perform swelling treatment. Then, it was immersed in an aqueous solution (dyeing treatment bath) containing 0.043 mass % of iodine and 4.3 mass % of potassium iodide (KI) (temperature 30°C) for 60 seconds and uniaxially stretched 2.2 times in the length direction (2.4 times overall) to allow iodine to be adsorbed. Furthermore, while being immersed in an aqueous solution (crosslinking treatment bath) containing 3.0 mass % of inorganic boric acid and 3 mass % of potassium iodide (temperature 30°C) for 45 seconds, the film was uniaxially stretched 1.2 times (2.7 times overall) in the length direction to allow the inorganic boric acid to adsorb. Then, while being immersed in an aqueous solution (stretching treatment bath) containing 4.0 mass % of inorganic boric acid and 6.0 mass % of potassium iodide (temperature 60°C), the film was uniaxially stretched 2.2 times (6.0 times overall) in the length direction to allow alignment. After that, the film was immersed in an aqueous solution (stretching treatment bath) containing 0.7 mass % of n-propyl

The PVA film was immersed in an aqueous solution containing 0.5% by mass of 1,4-butanediol and 3.5% by mass of potassium iodide (first fixing treatment bath) (temperature 30°C) for 30 seconds. During the first fixing treatment, the PVA film was not stretched (stretching ratio 1.0 times).

Aqueous solution of 1.5% potassium iodide and 1.5% potassium iodide (second fixing treatment bath) (temperature 50°C) for 100 seconds. During the second fixing treatment, the PVA film was not stretched (stretching ratio 1.0 times). Finally, it was dried at 60°C for 4 minutes to produce a polarizing film.

酸而來的烴基之氫峰值重疊的由正丙基

酸而來之甲基的氫峰值6，因此將此峰值面積(面積A)設定為3。然後，算出在1.0ppm~1.2ppm的範圍出現的由正丙基

酸與1,4-丁烷二

酸而來的烴基之氫重疊而成的氫峰值5的峰值面積(面積B)。之後，PVA的亞甲基的氫峰值3與由正丙基

酸與1,4-丁烷二

酸而來的烴基之氫峰值4重疊，因此將1.6~2.3ppm之範圍的氫峰值視為由PVA之亞甲基而來的氫峰值3與由正丙基

酸與1,4-丁烷二

酸而來的烴基之氫峰值4的總和，求出1.6~2.3ppm之範圍的氫峰值的總面積(面積C)。以 面積C減去由正丙基

酸與1,4-丁烷二

酸而來的烴基之氫峰值的面積(面積U，實施例1中相當於面積B)，求出面積D。將此等的值代入前述式(1)，結果相對於100質量份之PVA(A)而言，由含硼化合物(B)而來的硼元素含量為0.49質量份。再者，將此等的值代入上述式(2)，結果相對於100質量份之PVA(A)而言，由含硼化合物(C)而來的硼元素含量為0.08質量份。測量偏光薄膜中所有硼元素含量，結果為1.9質量%。 The ¹ H-NMR of the polarizing film was measured and analyzed. The results showed that the peak of hydrogen not related to the hydroxyl group from PVA and the peak of 1,4-butanediol from 1.2-1.3ppm appeared.

The peak of hydrogen from the alkyl group from the acid overlaps with that from the n-propyl group.

The hydrogen peak of methyl from acid is 6, so the area of this peak (area A) is set to 3. Then, calculate the hydrogen peak of n-propyl from 1.0ppm to 1.2ppm.

Acid and 1,4-butanediol

The peak area of the hydrogen peak 5 formed by the overlap of the hydrogen of the alkyl group from the acid (area B).

Acid and 1,4-butanediol

The hydrogen peak 4 from the alkyl group of PVA overlaps, so the hydrogen peak in the range of 1.6~2.3ppm is regarded as the hydrogen peak 3 from the methylene group of PVA and the hydrogen peak 4 from the propyl group of PVA.

Acid and 1,4-butanediol

The sum of the hydrogen peaks 4 of the alkyl groups from the acid is used to calculate the total area of the hydrogen peaks in the range of 1.6 to 2.3 ppm (area C).

Acid and 1,4-butanediol

The area of the hydrogen peak of the hydrocarbon group from the acid (area U, equivalent to area B in Example 1) is used to calculate area D. Substituting these values into the above formula (1), the result is that the boron content from the boron-containing compound (B) is 0.49 mass parts relative to 100 mass parts of PVA (A). Furthermore, substituting these values into the above formula (2), the result is that the boron content from the boron-containing compound (C) is 0.08 mass parts relative to 100 mass parts of PVA (A). The total boron content in the polarizing film was measured and the result was 1.9 mass%.

The optical properties of the polarizing film were measured, and the results showed that the transmittance Ts was 44.09% and the polarization degree V was 99.92%. In addition, the shrinkage force of the polarizing film was measured, and the result was 2.7N. Then, the attenuation coefficient of the PVA-iodine complex was -0.35. These results are shown in Table 1 and Figure 2.

In addition, the boron content from the boron-containing compound (B) in the stretched film obtained by drying the PVA film at 60°C for 4 minutes after the first fixing treatment was measured, and the result was 0.81 parts by mass. This result is also shown in Table 1.

[Example 2]

酸及5.5質量%的碘化鉀之比例的水溶液(溫度30℃)，除此之外，與實施例1相同地製作偏光薄膜，藉由上述方法進行各測量及各評價。結果顯示於表1與圖2。 The second fixed treatment bath was a 1,4-butane dihydrate containing 0.5 mass %

A polarizing film was prepared in the same manner as in Example 1 except that 2-nitrogen iodide and 5.5 mass % potassium iodide aqueous solution (temperature 30° C.) were used, and various measurements and evaluations were performed by the above methods. The results are shown in Table 1 and FIG. 2 .

[Comparison Example 1]

The second fixing treatment was not performed. Other than that, the polarizing film was prepared in the same manner as in Example 1, and each measurement and evaluation was performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 2]

The immersion time in the first fixing treatment bath was set to 100 seconds, and the second fixing treatment was not performed. A polarizing film was prepared in the same manner as in Example 1, and each measurement and evaluation were performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 3]

酸之比例的水溶液(溫度10℃)，並將浸漬於第1固定處理浴的時間設為20秒，且不進行第2固定處理，除此之外，與實施例1相同地製作偏光薄膜，藉由上述方法進行各測量及各評價。此時，關於由含硼化合物(B)而來的硼元素相對於100質量份之PVA(A)而言的含量之測量，由於以累計次數256次並無法檢測含硼化合物(B)，因此將累計次數變更為4096次，而測量由含硼化合物(B)而來的硼元素相對於100質量份之PVA(A)而言的含量。結果顯示於表1與圖2。 The first fixed treatment bath is a 1.0 mass % n-butyl

The polarizing film was prepared in the same manner as in Example 1 except that the immersion time in the first fixing treatment bath was set to 20 seconds and the second fixing treatment was not performed. Each measurement and each evaluation were performed by the above method. At this time, regarding the measurement of the content of the boron element from the boron-containing compound (B) relative to 100 parts by mass of PVA (A), since the boron-containing compound (B) could not be detected with the cumulative number of 256 times, the cumulative number of times was changed to 4096 times, and the content of the boron element from the boron-containing compound (B) relative to 100 parts by mass of PVA (A) was measured. The results are shown in Table 1 and Figure 2.

[Comparison Example 4]

The immersion time in the first fixed treatment bath was changed to 100 seconds. A polarizing film was prepared in the same manner as in Example 2, and each measurement and evaluation were performed by the above method. The results are shown in Table 1. However, the boron-containing compound (C) was not adsorbed on the polarizing film, so the evaluation of shrinkage, optical performance and moisture and heat resistance was not performed.

[Comparison Example 5]

酸及 4.0質量%的碘化鉀之比例的水溶液(溫度30℃)，並將浸漬於第1固定處理浴的時間設定為100秒，且不進行第2固定處理，除此之外，與實施例1相同地製作偏光薄膜，藉由上述方法進行各測量及各評價。結果顯示於表1與圖2。 The first fixing treatment bath was a 1,4-butanediol containing 0.5 mass %

A polarizing film was prepared in the same manner as in Example 1 except that an aqueous solution of 4.0 mass % of potassium iodide (temperature 30°C) was added to the first fixing treatment bath, and the immersion time in the first fixing treatment bath was set to 100 seconds, and the second fixing treatment was not performed. Each measurement and each evaluation were performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 6]

酸及5.5質量%的碘化鉀之比例的水溶液(溫度50℃)，除此之外，與實施例1相同地製作偏光薄膜，藉由上述方法進行各測量及各評價。結果顯示於表1與圖2。 The second fixing treatment bath was a 1,4-butanediol containing 1.0 mass %

A polarizing film was prepared in the same manner as in Example 1 except that 2-nitrogen iodide and 5.5 mass % potassium iodide aqueous solution (temperature 50° C.) were used, and various measurements and evaluations were performed by the above methods. The results are shown in Table 1 and FIG. 2 .

[Comparison Example 7]

酸及0.3質量%的1,4-丁烷二

酸及5.0質量%的碘化鉀之比例的水溶液(固定處理浴)(溫度50℃)，並將浸漬於第1固定處理浴的時間設定為100秒，且不進行第2固定處理，除此之外，與實施例1相同地製作偏光薄膜，藉由上述方法進行各測量及各評價。結果顯示於表1與圖2。 The first fixing treatment bath is a 0.2 mass % n-propyl

acid and 0.3 mass% of 1,4-butanediol

A polarizing film was prepared in the same manner as in Example 1 except that an aqueous solution of 1:10% by weight of 1:1 acid and 5.0% by weight of potassium iodide (fixing treatment bath) (temperature 50°C) was added, and the immersion time in the first fixing treatment bath was set to 100 seconds, and the second fixing treatment was not performed. Each measurement and each evaluation were performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 8]

The first fixing treatment bath uses an aqueous solution (temperature 30°C) containing 2.0 mass % of inorganic boric acid and 2.0 mass % of potassium iodide, and the immersion time in the first fixing treatment bath is set to 100 seconds. The second fixing treatment is not performed. Except for this, the polarizing film is prepared in the same manner as in Example 1, and each measurement and evaluation are performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 9]

The first fixing treatment bath uses an aqueous solution (temperature 30°C) containing 0.5 mass % of inorganic boric acid and 2.0 mass % of potassium iodide, and the immersion time in the first fixing treatment bath is set to 100 seconds. The second fixing treatment is not performed. Except for this, the polarizing film is prepared in the same manner as in Example 1, and each measurement and evaluation are performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 10]

The polarizing film was prepared in the same manner as in Example 1 except that the first fixing treatment and the second fixing treatment were not performed, and each measurement and evaluation were performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 11]

As the first fixing treatment bath, an aqueous solution (temperature 30°C) containing potassium iodide at a ratio of 2.0 mass % was used, and the immersion time in the first fixing treatment bath was set to 5 seconds. The second fixing treatment was not performed. Except for this, the polarizing film was prepared in the same manner as in Example 1, and each measurement and evaluation were performed by the above method. The results are shown in Table 1 and Figure 2.

[Comparison Example 12]

The immersion time in the first fixing treatment bath was set to 20 seconds. A polarizing film was prepared in the same manner as in Comparative Example 11, and each measurement and evaluation was performed by the above method. The results are shown in Table 1 and Figure 2.

In addition, in Example 2 and Comparative Examples 1 to 12, an aqueous solution (temperature 30°C) containing iodine and potassium iodide at a mass ratio of 1:100 was used as the dyeing treatment bath. At this time, the concentrations of iodine and potassium iodide in the dyeing treatment bath were adjusted so that the transmittance of the polarizing film after drying became 43.8% to 44.2%.

Figure 2 is a graph plotting the polarizing films of Examples 1 and 2 and Comparative Examples 1 to 12, with the horizontal axis being the shrinkage force and the vertical axis being the attenuation coefficient of the PVA-iodine complex. As shown in Figure 2, the shrinkage force of the polarizing films of Examples 1 and 2 that meet the requirements of the present invention is less than 5N, and the attenuation coefficient of the PVA-iodine complex is above -0.5. It can be seen that in addition to the low shrinkage force, the moisture and heat resistance is also excellent.

On the other hand, the polarizing films of Comparative Examples 1 to 3, in which only the former is adsorbed, are insufficient in terms of shrinkage reduction and moisture-heat resistance. The polarizing film of Comparative Example 5, in which only the latter is adsorbed, and the polarizing film of Comparative Example 6, in which the concentration of the boron-containing compound (C) is high during the second fixing treatment and the boron-containing compound (C) is excessively adsorbed, have sufficient moisture-heat resistance but insufficient shrinkage reduction. The polarizing film of Comparative Example 7, in which an aqueous solution containing the boron-containing compound (B) and the boron-containing compound (C) is used to simultaneously adsorb the two, has a low mass ratio (B/C) and insufficient shrinkage reduction. Then, the polarizing films of Comparative Examples 10 to 12, which do not contain either the boron-containing compound (B) or the boron-containing compound (C), have insufficient reduction in shrinkage force or insufficient resistance to moisture and heat.

Claims (7)

A polarizing film comprising polyvinyl alcohol (A), a monomer selected from the group consisting of

Acid and in the presence of water can be converted into the monomer

At least one boron-containing compound (B) in the group of compounds of the present invention, and two compounds selected from the group consisting of

Acid and in the presence of water can be converted into the two

At least one boron-containing compound (C) in the group of compounds containing polyvinyl alcohol (A), wherein the mass ratio of the boron element from the boron-containing compound (B) to the boron element from the boron-containing compound (C) (B/C) is 4.0-8.0, and the content of the boron element from the boron-containing compound (C) is 0.05-0.3 parts by mass relative to 100 parts by mass of the polyvinyl alcohol (A);

[In formula (I), R ¹ is ^a monovalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond];

[In formula (II), R ² is ^a divalent aliphatic group having 1 to 20 carbon atoms,

The acid group is connected by a boron-carbon bond]. The polarizing film of claim 1, wherein R ¹ and R ² are saturated aliphatic groups. The polarizing film of claim 1 or 2, wherein R ¹ and R ² are aliphatic hydrocarbon groups. The polarizing film of claim 1 or 2, wherein the carbon number of R ¹ is 2-5, and the carbon number of R ² is 3-5. A method for producing a polarizing film as claimed in any one of claims 1 to 4, comprising a dyeing process of dyeing a polyvinyl alcohol film with a dichroic pigment and a stretching process of uniaxially stretching the film, characterized by: immersing the film in an aqueous solution containing a boron-containing compound (B) and immersing the film in an aqueous solution containing a boron-containing compound (C). A method for manufacturing a polarizing film as claimed in claim 5, wherein the polyvinyl alcohol film is immersed in an aqueous solution containing a boron-containing compound (B) and then immersed in an aqueous solution containing a boron-containing compound (C). The method for manufacturing a polarizing film as claimed in claim 6, wherein the content of the boron element from the boron-containing compound (B) in the aforementioned polyvinyl alcohol film after being immersed in an aqueous solution containing the boron-containing compound (B) is 0.1 to 1.3 parts by mass relative to 100 parts by mass of polyvinyl alcohol (A).