TW202340768A - Polarizer and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a polarizer in which iodine is adsorbed and oriented in a polyvinyl alcohol-based resin film. When the polarizer is provided with a cut processing portion, the length of the crack in the polarizer after a thermal shock test, starting from the cut processing portion, is less than 200 μm, wherein the thermal shock test entails performing alternately and repeatedly 30 cycles of the temperature -40℃. and the temperature 85℃., and the total erosion length of the polarizer after a hot water resistance test where the polarizer is immersed in hot water of 60℃ for 4 hours is 250 μm or less.

Description

Polarizing element and manufacturing method thereof

The present invention relates to a polarizing element and a manufacturing method thereof, and further relates to a circularly polarizing plate provided with a polarizing element.

It is known that polarizers are used in displays such as liquid crystal displays and organic EL displays. As for polarizers, those in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film are widely used. Such polarizers are generally produced by performing a dyeing process in which a polyvinyl alcohol-based resin film is dyed with iodine, a cross-linking process in which a cross-linking agent is used, and a stretching process in which the polyvinyl alcohol-based resin film is stretched. .

In cross-linking treatments, boric acid has been widely used as a cross-linking agent. Moreover, diboric acid is known as a crosslinking agent used for crosslinking treatment (for example, Japanese Patent Application Laid-Open No. 2018-180022, Japanese Patent Application Laid-Open No. 2019-015926, and International Publication No. 2018/021274).

If a polarizer manufactured using boric acid as a cross-linking agent is subjected to a temperature and water resistance test, the shrinkage of the polarizer and the detachment of iodine from the polarizer may occur significantly. In addition, the polarizing element may be provided with a cut-processed portion such as a through hole or a cutout corresponding to the position of a camera lens or the like installed on the display. When a polarizer manufactured using boric acid as a cross-linking agent is provided with a cut-processed portion, cracks may be significantly generated around the through-hole after a thermal shock test.

An object of the present invention is to provide a polarizing plate that has excellent durability in a temperature water resistance test and a thermal shock test and has a neutral hue and a manufacturing method thereof.

The present invention provides the following polarizer and its manufacturing method, as well as a circularly polarizing plate.

[1] A polarizing element in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film,

When a cut-processed part is provided, the length of the crack from the cut-processed part after the thermal shock test of the polarizer is less than 200 μm , wherein the thermal shock test is conducted alternately at a temperature of -40°C and a temperature of 85°C. Repeat for 30 cycles,

The total erosion length of the polarizer after the hot water resistance test after being immersed in warm water at a temperature of 60°C for 4 hours is 250 μm or less.

[2] The polarizing element according to [1], wherein the cut portion is a side surface of the through hole.

[3] The polarizer as described in [1] or [2], which further contains a cross-linked structure (C1) and a cross-linked structure (C2),

The aforementioned cross-linked structure (C1) is obtained by cross-linking the polyvinyl alcohol-based resin contained in the aforementioned polyvinyl alcohol-based resin film with a diboric acid-based compound represented by the following formula (I),

The aforementioned cross-linked structure (C2) is formed by cross-linking the aforementioned polyvinyl alcohol-based resin with boric acid,

[In formula (I),

X is a single bond or an organic group with a carbon number of 1 to 20,

When X is the aforementioned organic group, X is bonded to two boronic acid groups through boron-carbon bonds respectively].

[4] The polarizer according to [3], wherein the ratio of the mass of the cross-linked structure (C2) to the mass of the cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure ( C1)) is above 10/90 but less than 85/15.

[5] A polarizing element in which iodine is adsorbed and aligned on a polyvinyl alcohol-based resin film, wherein:

The polarizer contains a cross-linked structure (C1) and a cross-linked structure (C2),

The aforementioned cross-linked structure (C1) is obtained by cross-linking the polyvinyl alcohol-based resin contained in the aforementioned polyvinyl alcohol-based resin film with a diboric acid-based compound represented by the following formula (I),

The aforementioned cross-linked structure (C2) is formed by cross-linking the aforementioned polyvinyl alcohol-based resin with boric acid,

The ratio of the material amount of the aforementioned cross-linked structure (C2) to the material amount of the aforementioned cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure (C1)) is more than 10/90 and less than 85/15,

[In formula (I),

X is a single bond or an organic group with a carbon number of 1 to 20,

When X is the aforementioned organic group, X is bonded to two boronic acid groups through boron-carbon bonds respectively].

[6] A circularly polarizing plate including the polarizer according to any one of [1] to [5] and a λ/4 phase difference layer.

[7] A method of manufacturing a polarizing element, wherein the polarizing element is adsorbed and aligned with iodine on a polyvinyl alcohol-based resin film,

The manufacturing method includes the step of contacting the polyvinyl alcohol-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound represented by the following formula (I), wherein

The content ratio (boric acid/diboric acid-based compound) of the boric acid and the diboric acid-based compound contained in the aqueous solution is 10/90 or more and 90/10 or less on a mass basis.

[In formula (I),

X is a single bond or an organic group with a carbon number of 1 to 20,

When X is the aforementioned organic group, X is bonded to two boronic acid groups through boron-carbon bonds respectively].

[8] A method of manufacturing a polarizing element, wherein the polarizing element is adsorbed and aligned with iodine on a polyvinyl alcohol-based resin film,

The manufacturing method includes the step of contacting the polyvinyl alcohol-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound represented by the following formula (I), wherein

In the contact step, the polyvinyl alcohol-based resin film is stretched.

[In formula (I),

X is a single bond or an organic group with a carbon number of 1 to 20,

When X is the aforementioned organic group, X is bonded to two boronic acid groups through boron-carbon bonds respectively].

According to the present invention, it is possible to provide a polarizing element that has excellent durability in a hot water resistance test and a thermal shock test and has a neutral hue.

1: Laminated body

1a: The end of the protective film (the end of the protective film)

2: Area where polarizer does not exist

3: The discolored part of the polarizer (the discolored part)

4: Shrunk polarizer (polarizer)

5:Control Department

L: total erosion length

Figure 1 is a schematic diagram showing the test method of the hot water resistance test.

[Embodiment 1]

The polarizer of this embodiment has iodine adsorbed and aligned on a polyvinyl alcohol-based resin film (hereinafter also referred to as a "PVA-based resin film").

When the polarizer is provided with a cut-processed portion, the length of the crack from the cut-processed portion after the thermal shock test of the polarizer is less than 200 μm , may be 180 μm or less, or may be 150 μm or less, The thermal shock test was repeated for 30 cycles at a temperature of -40°C and a temperature of 85°C, alternately. The length of the above-mentioned crack is the length of the crack from the cut-processed portion in a plan view of the polarizer, and preferably is the length of the crack from the side surface of the through hole in the plan view of the polarizer. The thermal shock test can be performed by the method described in the Examples described below, and the length of the crack can be measured by the method described in the Examples described below.

The cut-processed part refers to a part with a cut surface formed by cutting, punching, cutting or laser processing of the raw polarizer. Examples of the cut-processed portion include the end surface of the polarizer, the end surface of a cutout obtained by cutting the end surface of the polarizer into a concave shape, and the side surface of a through hole provided in the polarizer.

The total erosion length L after the polarizer is immersed in warm water at a temperature of 60° C. for 4 hours and subjected to a temperature water resistance test is 250 μm or less, preferably 220 μm or less, and more preferably 200 μm or less. The total erosion length L can be measured by the method described in the Examples mentioned later.

The polarizer having the crack length and the total erosion length L in the above range preferably contains a cross-linked structure (C1) and a cross-linked structure (C2); the cross-linked structure (C1) is polyvinyl alcohol contained in the PVA-based resin film The resin is cross-linked with a diboric acid-based compound represented by the following formula (I) (hereinafter also referred to as "diboric acid-based compound (I)"). The cross-linked structure (C2) is formed by boric acid (B( OH) ₃ ) Cross-linked.

[In formula (I),

X is a single bond or an organic group with a carbon number of 1 to 20,

When X is an organic group, X and two boronic acid groups are bonded through boron-carbon bonds respectively].

The number of carbon atoms in the organic group constituting It may be 10 or less, 8 or less, or 6 or less.

The organic group constituting X in the diboric acid compound (I) may be a hydrocarbon group, or may contain heteroatoms such as oxygen, nitrogen, sulfur, and halogen. The organic group is preferably a hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but is preferably an aliphatic hydrocarbon group. The aliphatic hydrocarbon group may have branches, but is preferably a linear aliphatic hydrocarbon group without branches. The aliphatic hydrocarbon group may be an unsaturated aliphatic hydrocarbon group, but is more preferably a saturated aliphatic hydrocarbon group.

Examples of the organic group include methylene, ethylidene, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane- Aliphatic hydrocarbon groups such as 1,6-diyl; aromatic hydrocarbon groups such as phenyl, naphthylene, and phenylene.

Examples of the diboric acid-based compound (I) in which X in the formula (I) is a single bond include diboric acid.

Examples of the diboronic acid-based compound (I) in which X in the formula (I) is an organic group include:

Methane diboric acid, 1,2-ethane diboric acid, 1,3-propane diboric acid, 1,4-butane diboric acid, 1,5-pentane diboric acid, 1,6-hexane diboric acid, 1, 7-Heptane diboric acid, 1,8-octane diboric acid, 1,9-nonane diboric acid, 1,10-decane diboric acid, 1,11-undecane diboric acid, 1,12-dodecane diboric acid Alkanediboric acid, 1,13-tridecanediboric acid, 1,14-tetradecanediboric acid, 1,15-pentadecanediboric acid, 1,16-hexadecanediboric acid, 1,17-heptadecanediboric acid alkanediborane Acid, 1,18-octadecanediboric acid, 1,19-nonadecanediboric acid, 1,20-eicosanediboric acid, and these isomers, X in equation (I) is a hydrocarbon group Diboric acid compounds;

2-oxa-1,3-propane diboric acid, 3-oxa-1,5-pentane diboric acid, 4-oxa-1,7-heptane diboric acid, and their isomer equations (I) A diboric acid compound in which X contains a heteroatom;

1,4-phenylene diboric acid, 1,3-phenylene diboronic acid, and these isomers, diboric acid-based compounds in which X in the equation (I) represents an aromatic group, and the like.

The diboric acid compound (I) is preferably one selected from the group consisting of diboric acid, 1,2-ethane diboric acid, 1,3-propane diboric acid, and 1,4-butane diboric acid. More than 1 species.

It is considered that the cross-linked structure (C1) cross-linked by the diboric acid-based compound (I) contains the structure (C1a). This structure (C1a) is: the hydroxyl group (hereinafter, also referred to as Referred to as "diboric acid-based hydroxyl group") reacts with the hydroxyl group of the polyvinyl alcohol-based resin of the PVA-based resin film (hereinafter also referred to as "PVA-based hydroxyl group"), and the boron atom (B) of the diboric acid-based compound (I) It is bonded to the polyvinyl alcohol chain of the polyvinyl alcohol resin through oxygen atoms (O). The cross-linked structure (C1) is considered to be formed by allowing one molecule of the diboric acid-based compound (I) to have two or more of the above-mentioned structures (C1a). The cross-linked structure (C1) only needs to contain the above-mentioned structure (C1a) through one or more diboric acid-based compounds among the diboric acid-based compounds (I), and may also be formed through two or more types of diboric acid-based compounds. And contains the above-mentioned structure (C1a). Since the diboric acid-based compound (I) has four diboric acid-based hydroxyl groups in one molecule, it can effectively crosslink the polyvinyl alcohol-based resin in the PVA-based resin film.

The cross-linked structure (C2) cross-linked by boric acid (B(OH) ₃ ) is considered to contain a structure (C2a), which is a hydroxyl group in boric acid (hereinafter also referred to as "boric acid-based hydroxyl group") It reacts with the PVA-based hydroxyl group and bonds the boron atom (B) of the boric acid to the polyvinyl alcohol chain of the polyvinyl alcohol-based resin via the oxygen atom (O). This structure (C2a) is easily hydrolyzed. Therefore, it is considered that in the cross-linked structure (C2), the above-mentioned structure (C2a) and the structure (C2b) in which a boric acid-based hydroxyl group and a PVA-based hydroxyl group are hydrogen-bonded have the ability to reversibly change due to dehydration and moisture absorption. structure. The cross-linked structure (C2) is considered to be formed when one molecule of boric acid has a total of two or more of the above-mentioned structures (C2a) and (C2b).

On the other hand, the above-mentioned structure (C1a) contained in the cross-linked structure (C1) cross-linked by the diboric acid-based compound (I) is not easily hydrolyzed. Therefore, it is considered that compared with the cross-linked structure (C2), the cross-linked structure (C1) is less likely to change in volume due to dehydration and moisture absorption, and can suppress the shrinkage of the polarizer due to dehydration accompanying heating. Therefore, by introducing the cross-linked structure (C1) into the polarizer, it is easy to obtain the length of the crack from the cut processing part after the thermal shock test and the total erosion length L after the hot water resistance test. The length L is adjusted to the above range. Polarizer with excellent durability. Furthermore, it is considered that if a polarizer having cross-linked structures (C1) and (C2) is compared with a polarizer having only a cross-linked structure (C2) without a cross-linked structure (C1), even if the polarizer is introduced into the polarizer The total amount of the cross-linked structure is the same, and the length of the above-mentioned cracks in the polarizer having the cross-linked structures (C1) and (C2) is further suppressed.

In order for a polarizer to exhibit good absorption dichroism in the visible light region, polyiodide ions (I ₃ ^- , I ₅ ^-, etc.) and polyvinyl alcohol-based resin must form a complex. When only the cross-linked structure (C1) is introduced into the polarizer, it is particularly difficult to form a complex of polyiodide ions I ₃ ^- and polyvinyl alcohol-based resin. In addition, when only the cross-linked structure (C2) is introduced into the polarizer, iodide ions (I ^- ) flow out during the cleaning step in the manufacturing process of the polarizer, resulting in an increase in polyiodide ions I ₅ ^- and the polarizer becomes deformed. It is easy to have blue color. However, by having a cross-linked structure (C1), the outflow of iodide ions can be suppressed, and therefore the blue color of the polarizer can be suppressed. Therefore, by providing the polarizer with the cross-linked structures (C1) and (C2), it is easy to obtain a polarizer that has a neutral hue and exhibits good absorption dichroism in the visible light region.

The ratio of the mass of the cross-linked structure (C2) to the mass of the cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure (C1)) is preferably 10/90 or more, and may also be 30/70 Above, it can also be 50/50 or above, it can also It is 70/30 or more, and it may be 80/20 or more, and preferably it is less than 85/15, it may be 83/17 or less, or it may be 82/18 or less. The material amounts of the cross-linked structures (C1) and (C2) are values measured by the method described in the Examples described below. By setting the ratio (crosslinked structure (C2)/crosslinked structure (C1)) within the above range, it is easy to obtain a polarizing element that has excellent durability in a hot water resistance test and a thermal shock test and has a neutral hue.

When two polarizers are arranged to form cross-polarized light, the orthogonal b ^* of the hues is preferably within ±1.5, more preferably within ±1.0, may be within ±0.7, or may be within ±0.5. The orthogonal b ^* can be calculated by the method described in the Examples described later.

The polarizing element of this embodiment can be obtained by a manufacturing method including a step of contacting a PVA-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound (I). When the polarizer has cross-linked structures (C1) and (C2), the material amounts and ratios of each structure (cross-linked structure (C2)/cross-linked structure (C1)) can be adjusted by adjusting the boric acid and dioxin contained in the above aqueous solution. The amount of the boric acid-based compound (I), the contact time between the PVA-based resin film and the aqueous solution, etc. are adjusted.

[Embodiment 2]

The polarizer of this embodiment has iodine adsorbed and aligned on a PVA-based resin film. The polarizer contains a cross-linked structure (C1) and a cross-linked structure (C2). The cross-linked structure (C1) is a polyvinyl alcohol-based resin contained in the PVA-based resin film through diboric acid represented by the above formula (I). It is formed by cross-linking compounds, and the cross-linked structure (C2) is formed by cross-linking with boric acid. In the polarizer, the ratio of the mass of the cross-linked structure (C2) to the mass of the cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure (C1)) is 10/90 or more and less than 85/ 15.

The details of the diboric acid-based compound (I), the cross-linked structure (C1) and the cross-linked structure (C2) are as described in the previous embodiment. In addition, the preferable range of the ratio (crosslinked structure (C2)/crosslinked structure (C1)) can be exemplified by the range described in the previous embodiment.

By making the polarizer contain the cross-linked structure (C1), it is easy to obtain a polarizer excellent in durability in the thermal shock test and the hot water resistance test. In addition, by making the polarizer contain the cross-linked structures (C1) and (C2), it is easy to obtain a polarizer having a neutral hue. In particular, by setting the ratio (crosslinked structure (C2)/crosslinked structure (C1)) within the above range, it is easy to obtain a polarizing element excellent in the above durability and hue.

The polarizing element of this embodiment may be provided with a cutting processing portion. The cutting processing portion is as described in the previous embodiment. The orthogonal b ^* of the polarizer is preferably within the range described in the previous embodiment.

The polarizing element of this embodiment can be obtained by a manufacturing method including a step of contacting a PVA-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound (I). Methods for adjusting the amounts of the cross-linked structures (C1) and (C2) and the ratio (cross-linked structure (C2)/cross-linked structure (C1)) include the methods described in the previous embodiments.

[Embodiment 3]

The method of manufacturing a polarizer of this embodiment is a method of manufacturing a polarizer in which iodine is adsorbed and aligned on a PVA-based resin film. The manufacturing method of a polarizer includes the step of contacting a PVA-based resin film with an aqueous solution (S) containing boric acid and a diboric acid-based compound (I) (hereinafter, also referred to as the "first contact step"). The content ratio of boric acid and diboric acid-based compound (I) contained in the aqueous solution (S) (boric acid/diboric acid-based compound (I)) is 10/90 or more and 90/10 or less on a mass basis.

The above content ratio may be 30/70 or more, 50/50 or more, or 70/30 or more, and may be 85/15 or less, or 80/20 or less. It is considered that by performing the first contact step using an aqueous solution (S) containing a ratio (boric acid/diboric acid compound (I)) within the above range to produce a polarizer, the above-described cross-linked structure (C1) and (C2). This makes it possible to obtain a polarizing element that has excellent durability in thermal shock tests and hot water resistance tests and has a neutral hue.

Details of the diboric acid-based compound (I) contained in the aqueous solution (S) are as described in the previous embodiment. In the aqueous solution (S), the total content of the boric acid and the diboric acid-based compound (I) relative to 100 parts by mass of water can be, for example, 1 to 10 parts by mass. The content of boric acid in the aqueous solution (S) may be, for example, 0.05 to 5 parts by mass relative to 100 parts by mass of water, or may be 0.5 to 3 parts by mass. The content of the diboric acid compound (I) in the aqueous solution (S) may be, for example, 0.01 to 5 parts by mass relative to 100 parts by mass of water, or may be 0.1 to 1 part by mass.

The aqueous solution (S) may contain, in addition to boric acid and diboric acid-based compound (I), iodides such as potassium iodide and zinc iodide, and organic solvents compatible with water. The iodide is preferably potassium iodide. In the aqueous solution (S), the content of the iodide may be, for example, 1 to 30 parts by mass, or 5 to 25 parts by mass relative to 100 parts by mass of water.

The first contact step can be performed by, for example, a method of immersing the PVA-based resin film in the aqueous solution (S) by transporting the PVA-based resin film into a tank containing the aqueous solution (S), or by immersing the PVA-based resin film in a tank containing the aqueous solution (S). A method of spraying an aqueous solution (S) onto a PVA-based resin film from a shower device, etc., a combination thereof, etc. The first contact step is preferably performed on an iodine-dyed PVA-based resin film. The first contact step is preferably performed while stretching the iodine-dyed PVA-based resin film. The stretching ratio of the PVA-based resin film in the first contact step may be, for example, more than 1 time, may be 1.02 times or more, may be 1.04 times or more, usually may be 3.0 times or less, may be 2.0 times or less, or may be 1.1 times or less.

In the first contact step, the temperature of the aqueous solution (S) can be, for example, 50°C or more and 70°C or less. In the first contact step, the time for the aqueous solution (S) to contact the PVA-based resin film can be, for example, 10 seconds or more and 600 seconds or less.

In addition to the first contact step, the manufacturing method of the polarizer of this embodiment may further include a swelling step of swelling the PVA-based resin film, a dyeing step of dyeing the PVA-based resin film with iodine, and other steps other than the first contact step. The steps include a cross-linking step of cross-linking the polyvinyl alcohol-based resin, an extending step of stretching the PVA-based resin film, a washing step of washing the PVA-based resin film, and a drying step of drying the PVA-based resin film.

[Embodiment 4]

The method of manufacturing a polarizer of this embodiment is a method of manufacturing a polarizer in which iodine is adsorbed and aligned on a PVA-based resin film. The manufacturing method of a polarizer includes the step of contacting a PVA-based resin film with an aqueous solution (S) containing boric acid and a diboric acid-based compound (I) (hereinafter, also referred to as the "second contact step"). In the second contact step, the PVA-based resin film is stretched. Thereby, the above-mentioned cross-linked structures (C1) and (C2) can be formed in the polarizer, and a polarizer with excellent durability in the thermal shock test and hot water resistance test and a neutral hue can be obtained.

The stretching ratio of the PVA-based resin film in the second contact step may be, for example, more than 1 time, may be 1.02 times or more, may be 1.04 times or more, usually may be 3.0 times or less, may be 2.0 times or less, or may be 1.1 times or less.

The content ratio of boric acid and diboric acid-based compound (I) contained in the aqueous solution (S) (boric acid/diboric acid-based compound (I)) is preferably 10/90 or more and 90/10 or less on a mass basis. Details about the diboric acid-based compound (I), the preferred range of the above-mentioned content ratio, the contents of boric acid and the diboric acid-based compound (I), and the components and contents that can be contained in the aqueous solution (S) are as described in the previous article. explained in the embodiment.

The second contact step can be performed by, for example, a method of immersing the PVA-based resin film in the aqueous solution (S) by transporting the PVA-based resin film into a tank containing the aqueous solution (S), or by immersing the PVA-based resin film in a tank containing the aqueous solution (S). A method of spraying an aqueous solution (S) onto a PVA-based resin film from a shower device, etc., a combination thereof, etc. The second contact step is preferably performed on an iodine-dyed PVA-based resin film. About the aqueous solution (S) in the second contact step Examples of the temperature and contact time between the aqueous solution (S) and the PVA-based resin film include those described in the first contact step.

In addition to the second contact step, the manufacturing method of the polarizer of this embodiment may also include the swelling step, dyeing step, cross-linking step, stretching step, washing step, drying step, etc. described in the previous embodiment. .

Below, details of the polarizer and its manufacturing method will be described.

(Polarized parts)

The polarizing element is an absorptive polarizing film with the following properties: it absorbs linearly polarized light having a vibration surface parallel to its absorption axis, and polarizes linearly polarized light having a vibration surface orthogonal to the absorption axis (parallel to the transmission axis). Linearly polarized light transmission. The thickness of the polarizer is usually 5 μm or more, and may be 7 μm or more, or 10 μm or more, and is usually 50 μm or less, or 30 μm or less, or 20 μm . or less, and may be 15 μm or less.

A polarizing plate can be obtained by laminating a protective film on one or both sides of the polarizer through an adhesive layer or pressure-sensitive adhesive. Examples of the protective film include films made of thermoplastic resins excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, elongation, etc. (hereinafter also referred to as "thermoplastic resin films"). ”). The thermoplastic resin is not particularly limited, and examples thereof include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; and having a ring system and norbornene structure. Cyclic polyolefin resin, etc. The protective film may be a thermoplastic resin film provided with a surface treatment layer. As for the surface treatment layer, examples include brightness enhancement film, hard coating layer, anti-reflection layer, anti-adhesive agent, anti-glare layer, diffusion layer, etc. The surface treatment layer may be another layer (film) laminated on the thermoplastic resin film, or may be formed by performing surface treatment on the surface of the thermoplastic resin film. The thickness of the protective film is, for example, 3 μm or more, and may be 5 μm or more, and is usually 100 μm or less, or 70 μm or less, 50 μm or less, or 30 μm . the following.

(circular polarizing plate)

The circularly polarizing plate includes the above-mentioned polarizing element or polarizing plate and a λ/4 phase difference layer. The circularly polarizing plate can be obtained by laminating a λ/4 retardation layer on a polarizer or a polarizing plate through an adhesive layer or an adhesive layer. When the polarizing plate only has a protective film on one side of the polarizer, it is preferable to layer a λ/4 phase difference layer on the side of the polarizer opposite to the protective film. The λ/4 phase difference layer may have reverse wavelength dispersion. The circularly polarizing plate may further include a positive C layer on the side of the λ/4 retardation layer opposite to the polarizer side, or between the λ/4 retardation layer and the polarizer. Alternatively, the circularly polarizing plate may include a λ/2 retardation layer between the λ/4 retardation layer and the polarizer. The λ/4 retardation layer, the positive C layer, and the λ/2 retardation layer may each independently be a stretched film, or may be a cured product layer obtained by polymerizing and curing a polymerizable liquid crystal compound, or may be a cured product layer containing the Alignment film. Each layer constituting the circularly polarizing plate can be laminated via an adhesive layer or an adhesive layer.

The circularly polarizing plate can have an adhesive layer for bonding to the optical display elements of the display on the side of the λ/4 retardation layer opposite to the polarizer side, and can also have a release film for covering the adhesive layer. .

The adhesive layer can be formed by hardening the curable component in the adhesive. The adhesives used to form the adhesive layer are adhesives other than pressure-sensitive adhesives (adhesives), and examples include water-based adhesives such as polyvinyl alcohol-based adhesives and active energy adhesives such as ultraviolet curable adhesives. Line hardening adhesive.

The adhesive layer is a layer formed using a so-called pressure-sensitive adhesive that exhibits adhesion by sticking itself to an adherend. As for the adhesive, conventionally known adhesives can be used without particular restrictions. Adhesives with excellent optical transparency include adhesives with base polymers such as acrylic, urethane, silicone, and polyvinyl ether based polymers.

The release film is disposed releasably to the adhesive layer and is used to cover and protect the surface of the adhesive layer. Examples of the release film include those in which a base film formed using a resin has been subjected to a release treatment. The resin constituting the base film is not particularly limited, and examples thereof include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate (Polyarylate). In addition, regarding the release treatment performed on the base film, a conventional release treatment may be performed, and a method of applying a release agent such as a fluorine compound or a silicon oxide compound to the base film is preferred.

Polarizers, polarizing plates, and circular polarizing plates can be suitably used as optical elements constituting displays such as liquid crystal displays and organic EL displays.

(PVA resin film)

Among the PVA-based resin films constituting the polarizer, a film formed using a polyvinyl alcohol-based resin can be used. Polyvinyl alcohol-based resin is usually obtained by saponifying polyvinyl acetate-based resin. The degree of saponification is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. The polyvinyl acetate-based resin may be, for example, polyvinyl acetate, which is a homopolymer of vinyl acetate, or may be a copolymer of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably 1,500 to 5,000. The average degree of polymerization of polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

These polyvinyl alcohol-based resins can be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified with aldehydes can be used.

The method of forming a film of polyvinyl alcohol-based resin is not particularly limited, and a conventional method can be used. The PVA-based resin film used as a raw material film for manufacturing polarizers may be an unstretched film or a stretched film that has been stretched in the gas phase in advance. The thickness of the PVA-based resin film as the raw material film may be, for example, 65 μm or less, 50 μm or less, or 30 μm or less, usually 10 μm or more, or 15 μm or more.

(Manufacturing method of polarizer)

The polarizer can be produced by, for example, carrying out a swelling step, a dyeing step, a cross-linking step, a stretching step, and a washing step in addition to the first contact step or the second contact step while conveying a PVA-based resin film as a raw material film. steps, and drying steps. The polarizing element is preferably manufactured by carrying out the processing in each of the above steps while continuously conveying the PVA-based resin film. The PVA-based resin film is preferably conveyed along a conveyance path constructed by a nip roller and a guide roller.

(swelling step)

The purpose of the swelling step is to remove foreign matter adhered to the surface of the PVA-based resin film as the raw material film, to remove the plasticizer in the PVA-based resin film, to impart easy dyeing, and to plasticize the PVA-based resin film. conduct. The swelling step can be performed by bringing the PVA-based resin film into contact with a swelling liquid. An example of a method of bringing the PVA-based resin film into contact with the swelling liquid is a method of immersing the PVA-based resin film in the swelling liquid by transporting the PVA-based resin film into a swelling tank containing the swelling liquid. , the method of spraying the swelling liquid onto the PVA-based resin film through a shower device, etc., a combination of these, etc.

As the swelling liquid used in the swelling step, in addition to water, boric acid, chloride, inorganic acid, water-soluble organic solvent, alcohol, etc. added in the range of, for example, 0.01 mass % or more and 10 mass % or less can be used. of aqueous solution. The temperature of the swelling liquid can be, for example, 10°C or more and 70°C or less. The time for bringing the swelling liquid into contact with the PVA-based resin film can be, for example, 10 seconds or more and 300 seconds or less.

(staining step)

The dyeing step is performed for the purpose of adsorbing and aligning iodine to the PVA-based resin film or the like that has been subjected to swelling treatment in the swelling step. The dyeing step can be performed by bringing the PVA-based resin film subjected to swelling treatment into contact with a dyeing solution. Examples of the method of bringing the PVA-based resin film into contact with the dyeing liquid include: a method of immersing the PVA-based resin film in the dyeing liquid by transporting the PVA-based resin film into a dyeing tank containing the dyeing liquid; A method of spraying dyeing liquid onto a PVA-based resin film using a shower device, etc., or a combination of these. In the dyeing step, the PVA-based resin film may be stretched if necessary.

As the dyeing liquid used in the dyeing step, for example, an aqueous solution having a mass ratio of iodine/potassium iodide/water=0.003 or more and 0.3 or less/0.1 or more and 10 or less/100 can be used. As the staining solution, iodides such as zinc iodide can be used instead of potassium iodide, or potassium iodide and other iodides can be used in combination. The dyeing solution can coexist with boric acid, zinc chloride, cobalt chloride, etc. as needed. The temperature of the dyeing liquid can be, for example, 20°C or more and 80°C or less. The time for bringing the dyeing liquid into contact with the PVA-based resin film can be, for example, 30 seconds or more and 600 seconds or less.

(cross-linking step)

The cross-linking step is performed for the purpose of making the PVA-based resin film that has been dyed in the dyeing step water-resistant and adjusting the hue. The cross-linking step is a different step from the above-mentioned first contact step and second contact step, and is preferably performed between the dyeing step and the first contact step or the second contact step. The cross-linking step can be performed by bringing the dyed PVA-based resin film into contact with a cross-linking liquid. As a method of bringing the PVA-based resin film into contact with the cross-linking liquid, for example, the PVA-based resin film is immersed in the cross-linking tank by transporting the PVA-based resin film into a cross-linking tank containing the cross-linking liquid. liquid method, a method of spraying the cross-linking liquid onto the PVA-based resin film through a shower device, etc., a combination of these, etc. The cross-linking step can also be performed in two or more stages by using cross-linking solutions with different concentrations of chemicals, etc. In the cross-linking step, the PVA-based resin film may be stretched if necessary.

As the cross-linking liquid, a solution obtained by dissolving a cross-linking agent other than the diboric acid-based compound (I) in a solvent can be used. Examples of the cross-linking agent include boron compounds such as boric acid and borax, and glyoxal and glutaraldehyde. One or more of these may be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may also be included. The concentration of the cross-linking agent contained in the cross-linking liquid is not particularly limited, and may be, for example, 1 mass % or more and 20 mass % or less.

The cross-linking liquid may be, for example, an aqueous solution containing 1 to 10 parts by mass of boric acid based on 100 parts by mass of water. The cross-linking liquid preferably contains, in addition to boric acid, iodides such as potassium iodide and zinc iodide from 1 part by mass to 30 parts by mass. For example, as the cross-linking liquid, an aqueous solution having a mass ratio of boric acid/iodide/water=3 or more and 10 or less/1 or more and 20 or less/100 can be used. In the cross-linking liquid, if necessary, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, sodium sulfite, sodium sulfate, etc. can coexist. The temperature of the cross-linking liquid can be, for example, 50°C or more and 70°C or less. The time for bringing the crosslinking liquid into contact with the PVA-based resin film can be, for example, 10 seconds or more and 600 seconds or less.

(washing step)

The washing step is performed for the purpose of removing excess chemicals such as iodine, boric acid, and diboric acid-based compound (I) adhered to the PVA-based resin film after the first contact step or the second contact step. The cleaning step can be performed by contacting the PVA-based resin film that has been treated in the first contact step or the second contact step with a cleaning solution. An example of a method for bringing the PVA-based resin film into contact with the cleaning liquid is to immerse the PVA-based resin film in the cleaning tank by transporting the PVA-based resin film into a cleaning tank containing the cleaning liquid. liquid method, a method of spraying the cleaning liquid onto the PVA-based resin film through a shower device, etc., a combination of these, etc.

As the cleaning solution, in addition to water (pure water, etc.), an aqueous solution in which a water-soluble organic solvent such as alcohol is added can also be used. The temperature of the cleaning liquid can be, for example, 2°C or more and 40°C or less. The time for which the cleaning liquid is brought into contact with the PVA-based resin film can be, for example, 1 second or more and 300 seconds or less.

(drying step)

The drying step is performed for the purpose of drying the PVA-based resin film that has been washed in the washing step. The drying step can be performed by drying the PVA-based resin film in a drying oven, for example, using a drying oven equipped with a hot air dryer. The drying temperature performed by the hot air dryer can be, for example, 30°C or more and 100°C or less. The drying time with the hot air dryer can be, for example, 30 seconds or more and 600 seconds or less.

(Extended steps)

The stretching step is performed for the purpose of uniaxial stretching or biaxial stretching of the PVA-based resin film. The stretching process performed in the stretching step is preferably uniaxial stretching. The extension step may be performed simultaneously with one or more of the dyeing step, the cross-linking step, the first contact step or the second contact step, or may be performed before or after one or more of these steps. The extension step can be performed in one stage or in multiple stages of two or more stages. The stretching treatment can be dry stretching, wet stretching, or a combination of these. When the stretching process is uniaxial stretching, it can be stretched between rollers with different peripheral speeds, or it can be stretched using heated rollers. The stretching ratio in the stretching step (cumulative stretching ratio when performed in multiple stages) is usually 3 times or more and 8 times or less.

(Manufacturing method of circularly polarizing plate)

The circularly polarizing plate can be obtained by laminating the above-mentioned polarizing element or polarizing plate and a λ/4 retardation layer via an adhesive or adhesive. When the circularly polarizing plate contains a positive C layer or a λ/2 retardation layer in addition to the λ/4 retardation layer, the λ/4 retardation layer and the positive C layer or λ/2 retardation layer will be bonded via an adhesive or adhesive. The retardation laminate formed by bonding agent layers can be bonded to the polarizer or polarizing plate through an adhesive or adhesive layer. Alternatively, the λ/4 retardation layer and the positive C layer or the λ/2 retardation layer can be sequentially laminated on the polarizer or polarizing plate via an adhesive or adhesive layer to form a layer structure of a circularly polarizing plate.

(Example)

Hereinafter, Examples and Comparative Examples are shown to further explain the present invention in detail, but the present invention is not limited to these Examples.

[Example 1]

Using a heating roller stretching device, the heating roller stretching is continuously performed in such a manner that it becomes longitudinal uniaxial stretching. From the long PVA-based resin film (thickness: 20 μm , saponification degree: 99.3 mol% or more) as the raw material film, Make long strips of stretch film. During heating roll stretching, the surface temperature of the heating roll was set to 123°C, and the peripheral speed of the heating roll was set to be larger than the peripheral speed of the first roll. The difference in peripheral speed was used to provide a stretch magnification of 4.5 times. Tension (pulling force). The PVA-based resin film was humidified by passing through a humidification furnace before being introduced into the heating roller stretching device and then supplied to the heating roller for stretching. The moisture content of the PVA-based resin film after being humidified by the humidification furnace was 7.9% by mass.

The produced stretched film is kept in a taut state, immersed in pure water at a temperature of 30°C for 31 seconds (swelling step), and then dyed at an iodine-containing temperature of 28°C with a mass ratio of potassium iodide/water = 5.7/100. Soak in liquid for 65 seconds (dyeing step). The stretched film treated by the dyeing step was immersed in a cross-linking solution at a temperature of 63°C with a mass ratio of potassium iodide/boric acid/water = 15/5/100 for 99 seconds (cross-linking step), and then dried with a mass ratio of potassium iodide/boric acid/1 , 4-butane diboric acid/water = 15/1/0.3/100, immersed in an aqueous solution (S) at a temperature of 63°C for 48 seconds (contact step). In the contact step, the aqueous solution (S) is immersed while performing stretching treatment so that the stretching ratio becomes 1.04 times. After the stretched film treated in the contact step was washed with pure water at a temperature of 5°C for 5 seconds, the stretched film was kept in a taut state and dried at a temperature of 45°C for 68 seconds to obtain a PVA-based resin film with iodine adsorbed and aligned. Polarizer (average film thickness: 7.8 μm ). The total cumulative stretch magnification of the polarizer based on the PVA-based resin film as the raw material film: 4.64 times.

[Comparative example 1]

A polarizer (average film thickness: 7.8 μm ) was obtained in the same procedure as in Example 1, except that an aqueous solution not containing 1,4-butane diboronic acid was used instead of the aqueous solution (S) in the contact step.

<Evaluation>

The following evaluation was performed on the polarizers obtained in Examples and Comparative Examples. The results are shown in Table 1.

[Quantification of cross-linked structures (C1) and (C2)]

The cross-linked structures (C1) and (C2) were quantified by microwave acid hydrolysis/ICP luminescence method. Specifically, 0.1 g of the polarizer was dissolved in the measurement solvent, and the DD-MAS spectrum of the polarizer was obtained by ¹¹ B-solid-state NMR. In the obtained DD-MAS spectrum, the ratio of the area of the peak derived from 1,4-butane diboric acid to the area of the peak derived from boric acid, and the boron (B) in the polarizer determined by the ICP luminescence method concentration, calculate the material amount of 1,4-butane diboric acid and the material amount of boric acid per unit mass (100g) of the polarizer, and use these as polyvinyl alcohol-based resins through 1,4-butane diboric acid. The material quantity of the cross-linked structure (C1) formed by cross-linking and the cross-linked structure (C2) formed by boric acid.

[Measurement of orthogonal b ^* ]

The optional accessory "film holder with polarizer" was attached to a UV-visible spectrophotometer (UV2450, manufactured by Shimadzu Corporation), and the UV-visible light spectrum in the transmission axis direction and absorption axis direction of the polarizer was measured. Calculate the orthogonal b ^* of the hue when two polarizers are arranged to form orthogonal polarization according to JIS Z 8729. The closer the absolute value of orthogonal b ^* is to 0 (zero), the more neutral the hue can be considered.

[Temperature water resistance test]

The polarizer and the protective film (cycloolefin-based film with hard coat layer, thickness: 25 μm ) are bonded together using a water-based adhesive to obtain a polarizing plate. The absorption axis direction of the polarizer (the extension direction of the PVA resin film) is set as the long side, and the obtained polarizing plate is cut into a strip shape of 8 cm × 2 cm, and is bonded to the glass (thickness) using an acrylic adhesive. :700 μm ) to obtain a laminated body. The layer structure of the laminate is protective film/water-based adhesive layer/polarizer/acrylic adhesive layer/glass.

Figure 1 is a schematic diagram showing the test method of the hot water resistance test. In FIG. 1 , (a) shows the laminated body 1 before being immersed in warm water, and (b) shows the laminated body 1 after being immersed in warm water. As shown in FIG. 1 , one short side (coincident with the short side of the polarizing plate) of the laminate 1 obtained above is held by the holding part 5 , and from the short side opposite to the side held by the holding part 5 , The longitudinal direction of the laminate 1 (coincident with the longitudinal direction of the polarizing plate) was immersed in warm water at a temperature of 60° C. for approximately 80% of the length in the longitudinal direction, and maintained for 4 hours. Thereafter, the laminated body 1 was taken out of the warm water and wiped dry.

Since the polarizer included in the laminated body 1 shrinks when immersed in warm water, as shown in FIG. 1(b) , a gap without the polarizer (shrunk polarizer) 4 is formed between the protective film and the glass. Area 2. The distance from the end 1a of the protective film to the end of the shrunk polarizer 4 in the center of the short side of the laminated body 1 is defined as the shrinkage length. By immersing in warm water, iodine is eluted from the peripheral portion of the polarizer in contact with the warm water, and a discolored portion 3 is formed on the peripheral portion of the polarizer 4 included in the laminate 1 . The length of the discolored portion of the polarizer 4 at the center of the short side of the laminated body 1 is defined as the iodine detachment length. The total length of the above-mentioned shrinkage length and iodine detachment length is defined as the total erosion length L. That is, the total erosion length L is the length of the short side of the laminated body 1 opposite to the side held by the holding portion 5 along the laminated body 1 from the end 1 a of the protective film to the area where the characteristic color of the polarizer remains. Lengthwise distance. The smaller the total erosion length L, the better the temperature water resistance.

[Production of circular polarizing plates]

(Preparation of composition for horizontal alignment film formation)

A composition for forming a horizontal alignment film was obtained by mixing 5 parts by mass of a photo-alignment material with the following structure (weight average molecular weight: 30,000) and 95 parts by mass of cyclopentanone, and stirring the resulting mixture at 80° C. for 1 hour.

Photoalignment materials:

(Modulation of the composition for forming a λ /4 phase difference layer)

啉基苯基)丁烷-1-酮(「Irgacure369(Irg369)」，BASF Japan股份有限公司製)6質量份。 To 100 parts by mass of a mixture obtained by mixing the polymerizable liquid crystal compound A and the polymerizable liquid crystal compound B shown below at a mass ratio of 90:10, 1.0 leveling agent (F-556; manufactured by DIC Co., Ltd.) was added Mass parts and 2-dimethylamino-2-phenylmethyl-1-(4- as polymerization initiator

6 parts by mass of lynylphenyl)butan-1-one ("Irgacure369 (Irg369)", manufactured by BASF Japan Co., Ltd.).

Furthermore, N-methyl-2-pyrrolidone (NMP) was added so that the solid content concentration became 13% by mass, and the mixture was stirred at 80° C. for 1 hour, thereby obtaining a λ/4 retardation layer forming composition.

The polymerizable liquid crystal compound A is produced by the method described in Japanese Patent Application Laid-Open No. 2010-31223. In addition, the polymerizable liquid crystal compound B was produced according to the method described in Japanese Patent Application Laid-Open No. 2009-173893.

Polymerizable liquid crystal compound A:

Polymerizable liquid crystal compound B:

(Preparation of λ/4 phase difference layer)

A corona treatment machine (AGF-B10, manufactured by Kasuga Electric Co., Ltd.) was used on a base film composed of a cyclic olefin polymer (COP) film (ZF-14, manufactured by Nippon Zeon Co., Ltd., thickness 23 μm ). Perform one corona treatment at an output of 0.3kW and a processing speed of 3m/min. The composition for forming a horizontal alignment film obtained above is coated on the surface of the corona-treated substrate using a bar coater. The coating film was dried at 80° C. for 1 minute, and polarized UV exposure was performed with a cumulative light amount of 100 mJ/cm ² using a polarized UV irradiation device (SPOT CURE SP-7; manufactured by Ushio, Inc.). Thereby, a base film with a horizontal alignment film is obtained. The thickness of the horizontal alignment film was measured using a laser microscope (LEXT, manufactured by Olympus Corporation), and the result was 100 nm.

Next, the λ/4 retardation layer forming composition obtained above was passed through a PTFE membrane filter (manufactured by ADVANTEC TOYO KAISHA, LTD.) with a pore size of 0.2 μm at a room temperature of 25° C. and a humidity of 30% RH. No.: T300A025A), use a bar coater to coat on a substrate film with a horizontal alignment film that is kept at 25°C. By drying the coating film at 120°C for 1 minute, using a high-pressure mercury lamp (UnicureVB-15201BY-A, manufactured by Ushio Inc.), irradiating it with ultraviolet rays (in a nitrogen atmosphere, wavelength: 365nm, cumulative light amount at 365nm: 1000mJ/cm ² ) to obtain a hardened material layer and prepare a λ /4 retardation layer. The thickness of the hardened material layer was measured with a laser microscope (LEXT, manufactured by Olympus Corporation) and was found to be 2 μm . The λ/4 retardation layer shows reverse wavelength dispersion.

(Preparation of vertical alignment film forming composition)

Mix 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipenterythritol triacrylate and bis(2-vinyloxyethyl) ether in a ratio of 1:1:4:5, and LUCIRIN TPO was added as a polymerization initiator in a proportion of 4% to obtain a mixture, and this mixture was used as a composition for forming a vertical alignment film.

(Preparation of composition for forming positive C layer)

The composition for forming the positive C layer is prepared by preparing a photopolymerizable nematic liquid crystal compound (RMM28B manufactured by Merck & Co., Ltd.) and a solvent so that the solid content becomes 1 to 1.5 g. A mixed solvent in which methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone (CHN) were mixed at a mass ratio (MEK: MIBK: CHN) of 35:30:35 was used as the solvent.

(Preparation of positive C layer)

A polyethylene terephthalate (PET) film with a thickness of 38 μm was prepared as the base film. The vertical alignment film forming composition obtained above was applied to one side of the base film so that the film thickness became 3 μm , and ultraviolet light of 200 mJ/cm ² was irradiated to produce a vertical alignment film.

The composition for forming the positive C layer is coated on the vertical alignment layer formed on the base film by mold coating. The coating amount is 4 to 5g (wet). The drying temperature was set to 75°C, the drying time was set to 120 seconds, and the coating film was dried. Thereafter, the coating film is irradiated with ultraviolet rays (UV) to obtain a cured material layer in which the polymerizable liquid crystal compound has been polymerized, thereby producing a positive C layer. The thickness of the positive C layer (vertical alignment layer and hardened material layer) is 4 μm .

(Production of circular polarizing plates)

The surface of the λ/4 retardation layer and the positive C layer formed on the base film obtained above on the side opposite to the base film side is used as a bonding surface, and the λ/4 retardation layer is bonded via an ultraviolet curable adhesive. After the difference layer and the positive C layer are bonded together, ultraviolet rays are irradiated to harden the ultraviolet curable adhesive. Thereby, a retardation laminated body having a laminated structure of λ /4 retardation layer/adhesive layer/positive C layer was produced. The λ /4 retardation layer contains a horizontal alignment film on the opposite side to the adhesive layer, and the positive C layer contains a vertical alignment film on the opposite side to the adhesive layer.

Use an acrylic adhesive to bond the polarizer side of the polarizing plate to the λ /4 retardation layer side of the retardation laminate. The polarizing plate is produced by the same production process as in the above-mentioned temperature water resistance test. After obtaining the result, an acrylic adhesive layer is further formed on the positive C layer side of the retardation laminate, and a release film is laminated on the surface of the acrylic adhesive layer. Thereby, a protective film/water-based adhesive layer/polarizer/acrylic adhesive layer (thickness: 5 μm )/ λ /4 phase difference layer/adhesive layer/positive C layer/acrylic adhesive layer is obtained. A circular polarizing plate with a layer structure (thickness: 15 μm )/release film.

[Thermal shock test]

The circular polarizing plate obtained above was punched into a rectangular shape of 55 mm × 90 mm, and a through hole (diameter: 0.3 cm) was provided near the center of the circular polarizing plate by laser processing. The acrylic adhesive layer exposed by peeling off the release film from the circular polarizing plate provided with the through hole was bonded to the glass to obtain an evaluation sample. The layer structure of the sample for evaluation is protective film/water-based adhesive layer/polarizer/acrylic adhesive layer/ λ /4 retardation layer/adhesive layer/positive C layer/acrylic adhesive layer/glass.

The sample for evaluation was put into a constant temperature bath, and a thermal cycle was maintained at -40°C for 30 minutes and then at 85°C for 30 minutes as one cycle, and a thermal shock test was performed in which the thermal cycle was repeated. For the evaluation sample before starting the thermal cycle (before the thermal shock test) and after 30 cycles of thermal cycling, use a magnifying glass to observe the surroundings of the through hole provided in the polarizer when looking down to confirm the presence of cracks. When the presence of a crack is confirmed, the length of the crack from the side surface of the through hole is evaluated based on the following criteria in a plan view of the evaluation sample.

A: The length of the crack is less than 200 μm

B: The length of the crack is more than 200 μm

[Table 1]

1: Laminated body

1a: End of protective film

2: Area where polarizer does not exist

3: The discolored part of polarizer

4: Shrunk polarizer

5:Control Department

L: total erosion length

Claims (8)

A polarizer, which has iodine adsorbed and aligned on a polyvinyl alcohol-based resin film, When a cut-processed part is provided, the length of the crack from the cut-processed part after the thermal shock test of the polarizer is less than 200 μm , wherein the thermal shock test is conducted alternately at a temperature of -40°C and a temperature of 85°C. Repeat for 30 cycles, The total erosion length of the polarizer after the hot water resistance test after being immersed in warm water at a temperature of 60°C for 4 hours is 250 μm or less. The polarizing element according to claim 1, wherein the cutting portion is a side surface of the through hole. The polarizing element as described in claim 1, which further contains a cross-linked structure (C1) and a cross-linked structure (C2), The aforementioned cross-linked structure (C1) is obtained by cross-linking the polyvinyl alcohol-based resin contained in the aforementioned polyvinyl alcohol-based resin film with a diboric acid-based compound represented by the following formula (I), The aforementioned cross-linked structure (C2) is formed by cross-linking the aforementioned polyvinyl alcohol-based resin with boric acid,

In formula (I), X is a single bond or an organic group with a carbon number of 1 to 20, When X is the aforementioned organic group, X and two boronic acid groups are bonded via boron-carbon bonds respectively. The polarizing element according to claim 3, wherein the ratio of the material amount of the aforementioned cross-linked structure (C2) to the material amount of the aforementioned cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure (C1)) It is above 10/90 and less than 85/15. A polarizer, which has iodine adsorbed and aligned on a polyvinyl alcohol-based resin film, wherein the polarizer contains a cross-linked structure (C1) and a cross-linked structure (C2), The aforementioned cross-linked structure (C1) is obtained by cross-linking the polyvinyl alcohol-based resin contained in the aforementioned polyvinyl alcohol-based resin film with a diboric acid-based compound represented by the following formula (I), The aforementioned cross-linked structure (C2) is formed by cross-linking the aforementioned polyvinyl alcohol-based resin with boric acid, The ratio of the substance amount of the aforementioned cross-linked structure (C2) to the substance amount of the aforementioned cross-linked structure (C1) (cross-linked structure (C2)/cross-linked structure (C1)) is 10/90 or more and less than 85/15,

In formula (I), X is a single bond or an organic group with a carbon number of 1 to 20, When X is the aforementioned organic group, X and two boronic acid groups are bonded via boron-carbon bonds respectively. A circularly polarizing plate, which includes the polarizer as described in any one of claims 1 to 5 and a λ/4 phase difference layer. A method of manufacturing a polarizing element, the polarizing element is adsorbed and aligned with iodine on a polyvinyl alcohol-based resin film, The manufacturing method includes the step of contacting the polyvinyl alcohol-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound represented by the following formula (I), wherein The content ratio of the boric acid and the diboric acid-based compound contained in the aqueous solution (boric acid/diboric acid-based compound) is 10/90 or more and 90/10 or less on a mass basis,

In formula (I), X is a single bond or an organic group with a carbon number of 1 to 20, When X is the aforementioned organic group, X and two boronic acid groups are bonded via boron-carbon bonds respectively. A method of manufacturing a polarizing element, the polarizing element is adsorbed and aligned with iodine on a polyvinyl alcohol-based resin film, The manufacturing method includes the step of contacting the polyvinyl alcohol-based resin film with an aqueous solution containing boric acid and a diboric acid-based compound represented by the following formula (I), wherein In the aforementioned contacting step, the aforementioned polyvinyl alcohol-based resin film is stretched,

In formula (I), X is a single bond or an organic group with a carbon number of 1 to 20, When X is the aforementioned organic group, X and two boronic acid groups are bonded via boron-carbon bonds respectively.

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