TW202302352A - Polarizing plate and image display device - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate in which cracks are less likely to occur in holes in a thermal shock test. A polarizing plate of the present invention has a polarization element formed by adsorbing and orientating a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein the polyvinyl alcohol-based resin layer has a boron adsorption rate of 5.70% by mass or more; the polarization element has a boron content of 4.0% by mass or more and 8.0% by mass or less; and in a plane in the planar view, there is at least one hole, the shape of which satisfies both conditions (1a) and (1b). (1a) The shape of the hole has two linear portions substantially parallel to the transmission axis of the polarization element, and the linear portions have a length of 10 mm or less. (1b) The shape of the hole has at least two curved portions with a radius of curvature ranging from 0.5 mm to 11 mm.

Description

Polarizing plate and image display device

The present invention relates to a polarizing plate, and relates to an image display device equipped with a polarizing plate.

Liquid crystal display devices (LCD) are not only suitable for LCD TVs, but also widely used in portable devices such as computers and mobile phones, and car applications such as driving navigation. Generally speaking, a liquid crystal display device has a liquid crystal panel with a polarizer laminated on both sides of the liquid crystal cell through an adhesive (pressure-sensitive adhesive, also known as pressure-sensitive adhesive) layer, and the liquid crystal panel controls the light from the backlight member. to display. In addition, organic EL display devices have been widely used in recent years, like liquid crystal display devices, in portable devices such as televisions and mobile phones, and car applications such as car navigation systems. In an organic EL display device, in order to suppress the reflection of external light on the metal electrode (cathode) and be regarded as a mirror, sometimes a circular polarizing plate (with a polarizing element and a λ/4 plate) is arranged on the viewing side surface of the image display panel. layered body).

As mentioned above, there are increasing opportunities for polarizing plates to be mounted in automobiles as components of liquid crystal display devices or organic EL display devices. Compared with other portable devices such as TVs and mobile phones, polarizers used in automotive image display devices are often exposed to high-temperature environments, and require small changes in high-temperature characteristics (high-temperature durability). A polarizer for the purpose of securing this durability has been proposed (Patent Document 1). The polarizing element described in Patent Document 1 ensures high-temperature durability, has a high boron content, and tends to have a high-temperature shrinkage force.

[Prior Art Literature]

[Patent Document]

Patent Document 1: International Publication No. 2019/188779.

In recent years, the number of holes provided in polarizers has been increasing. For example, a polarizing plate used in an image display device for a car is provided with a hole for a pin to pass through an instrument panel, or a hole for a camera hole is provided in a polarizing plate used in a smartphone. However, when the polarizing plate provided with the hole portion uses a polarizing element with high high-temperature durability (large shrinkage force) as described above, if a thermal shock test is performed, there will be a tendency in the hole portion to absorb in the direction of the polarizing element. Tendency to break.

The object of the present invention is to provide a polarizing plate in which holes are less likely to be cracked in a thermal shock test even if a polarizing element with high high-temperature durability is used.

The present invention provides the following polarizing plate and image display device.

[1] A polarizing plate comprising a polarizing element formed by absorbing and aligning a dichroic pigment on a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein,

The boron adsorption rate of the polyvinyl alcohol-based resin layer is 5.70% by mass or more,

The boron content of the aforementioned polarizing element is not less than 4.0% by mass and not more than 8.0% by mass,

There is at least one hole in the planar plane of the polarizer,

The shape of the aforementioned hole satisfies the following conditions (1a) and (1b);

(1a) The shape of the aforementioned hole has two linear portions approximately parallel to the transmission axis of the aforementioned polarizing element, and the length of the linear portion approximately parallel to the penetration axis of the aforementioned polarizing element is 10 mm or less;

(1b) The shape of the aforementioned hole has at least two curved portions, and the radius of curvature of the aforementioned curved portions is not less than 0.5 mm and less than 11 mm.

[2] The polarizing plate according to [1], wherein the shape of the hole further satisfies the following condition (1c);

(1c) It further has two linear portions approximately parallel to the absorption axis of the aforementioned polarizer.

[3] The polarizing plate according to [1] or [2], wherein the shape of the polarizing plate in plan view is rectangular, and the length of the diagonal is 6 inches or more.

[4] An image display device comprising the polarizing plate according to any one of [1] to [3].

According to the present invention, it is possible to provide a polarizing element with high durability even when used at high temperature. In the thermal shock test, the holes are also less likely to produce cracked polarizers.

1: polarizer

2: Hole

2a, 2b, 2c, 2d: straight line

10: polarizer

11: Polarizing element

12: Transparent protective film

f1, f2, f3, f4: straight line

21: Penetration axis direction

22: Absorption axis direction

41: Spacing

Fig. 1 is a schematic plan view showing an example of hole shape.

Fig. 2 is a schematic plan view showing an example of a polarizing plate.

Fig. 3 is a schematic cross-sectional view showing an example of the layer configuration of a polarizing plate.

FIG. 4(A) is a plan view showing an example of a state in which the cutting tool moves helically relative to the laminated film in the first cutting step. Figure (B) is a plan view showing a state in which a cutting tool moves relative to a laminated film as a comparative example. The arrowed lines in the figure show the relative moving path of the cutting tool when viewed from a direction perpendicular to the main surface of the laminated film.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In all the following drawings, the scales are adjusted appropriately for easy understanding of each constituent element. The scale scale of each constituent element shown in the diagram may not be consistent with the actual scale scale of the constituent elements.

<Polarizer>

A polarizing plate according to one aspect of the present invention has a polarizing element formed by adsorbing and aligning a dichroic dye on a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein the boron adsorption rate of the polyvinyl alcohol-based resin layer is 5.70% by mass As mentioned above, the content of boron in the polarizing element is not less than 4.0% by mass and not more than 8.0% by mass, and the polarizer has at least one hole in the plan view, and the shape of the hole satisfies the following conditions (1a) and (1b) ).

(1a) The shape of the hole has two linear portions approximately parallel to the transmission axis of the polarizer, and the length of the linear portions approximately parallel to the transmission axis of the polarizer is 10 mm or less.

(1b) The shape of the hole has at least two curved parts, and the radius of curvature of the curved parts is 0.5 mm or more and less than 11 mm.

In addition, in this specification, planar view means viewing from the thickness direction (lamination direction) of a polarizing plate.

The hole portion of the polarizing plate penetrates in a direction perpendicular to the main surface of the polarizing plate. The shape of the hole may be, for example, a shape in which the corners of a rectangle are curved lines (hereinafter referred to as a rounded rectangle shape). As shown in Figure 1, the rounded rectangular shape is, for example, a shape with 4 curved parts and 4 straight parts [Figure 1 (a), (b), (c)]; it has 2 curved parts and 2 The shape of the straight line [Figure 1(d), (e)]; or the shape with 2 curved lines and 5 straight lines [Figure 1(f)], etc. The main surface of the polarizing plate is a surface in plan view.

[Condition (1a)]

The shape of the hole has two straight lines approximately parallel to the transmission axis of the polarizer. In this specification, one straight line part means the part which consists of only one straight line in the shape of a hole part. For example, in the shape of Figure 1(f), the part formed by two parallel straight lines f1 and f2 separated on the same line, or the part connected by two non-parallel straight lines f3 and f4, the number of both straight lines is 2 . Also, in this specification, being slightly parallel to the transmission axis is not limited to being strictly parallel. For example, the angle between the transmission axis of the polarizing element and the straight line is preferably less than 5°, more preferably less than 3°, and even more preferably Below 1°, the best is 0°. When the shape of the hole is the shape with 4 straight parts as shown in Figure 1 (a), (b) and (c), a pair of facing straight parts are slightly parallel to the transmission axis of the polarizer. For example, in the polarizing plate 1 shown in FIG. 2 , the straight line portions 2 a and 2 c constituting the shape of the hole portion 2 may be approximately parallel to the transmission axis direction 21 . The length of the linear portion approximately parallel to the transmission axis of the polarizer is preferably 9 mm or less, more preferably 0.2 mm or more and 8 mm or less, and more preferably 0.5 mm or more and 7 mm or less. In the polarizing plate, the hole has two straight lines that are approximately parallel to the transmission axis of the polarizing element, so that it is less prone to breakage in the thermal shock test. The shape of the hole may have two or more linear portions approximately parallel to the transmission axis of the polarizer.

[Condition (1b)]

The shape of the hole part has at least two curved parts. The curved portion refers to a portion composed of continuous curved lines in the shape of the hole. For example, in Fig. 1(a), (b) and (c), the number of curved parts is four, and in Fig. 1(d), (e), the number of curved parts is two. Also, as shown in Figure 1(a), (b), (d) and (f), the radius of curvature of the curved portion is all the same, and as shown in Figure 1(c) and (e), the radius of curvature of the curved portion The radii of curvature are not all the same. The radius of curvature of the curved portion is preferably from 1 mm to 10 mm, more preferably from 1.5 mm to 9 mm. In the polarizing plate, the hole portion has at least two of the above-mentioned curved portions, whereby cracking tends to be less likely to occur in a thermal shock test. The shape of the hole is preferably four curves with the same radius of curvature.

In the polarizing plate, the shape of the holes may further satisfy the following condition (1c).

(1c) It further has two linear portions approximately parallel to the absorption axis of the polarizer.

In this specification, being slightly parallel to the absorption axis is not limited to being strictly parallel. For example, the angle between the absorption axis of the polarizing element and the straight line is preferably less than 5°, more preferably less than 3°, and more preferably less than 1°. The best is 0°. When the shape of the hole is 4 straight parts as shown in Fig. 1 (a), (b) and (c), a pair of facing straight parts can be slightly parallel to the transmission axis of the polarizer. For example, in the polarizing plate 1 shown in FIG. 2 , the linear portions 2 b and 2 d constituting the shape of the hole 2 may be approximately parallel to the absorption axis direction 22 . The length of the linear portion approximately parallel to the absorption axis of the polarizer may be, for example, less than 11 mm, preferably not less than 0.5 mm and not more than 10.5 mm, more preferably not less than 1 mm and not more than 10 mm.

The shape of the polarizing plate can be rectangular in plan view, for example, it can be square, rectangular, square with rounded corners, rectangular with rounded corners, and the like.

When the shape of the polarizing plate is rectangular in plan view, for example, the length of the diagonal can be more than 6 inches (152.4 mm), preferably more than 6 inches (more than 152.4 mm) and less than 30 inches (767 mm).

The relationship between the shape of the polarizer and the direction of the absorption axis of the polarizer is not particularly limited. For example, when the polarizer is rectangular in plan view, the direction of the absorption axis of the polarizer can be parallel to the direction of the long side or parallel to the direction of the short side. direction. The direction of the absorption axis of the polarizer can be a direction where the included angle between the absorption axis direction of the polarizer and the long side direction (or short side direction) is 45±5°, preferably 45±2°. The absorption axis of the polarizer may be the extension axis of the polarizer.

The thickness of the polarizing plate is usually not less than 5 μm and not more than 200 μm, not more than 150 μm, or not more than 120 μm.

FIG. 3 shows an example of the layer configuration of a polarizing plate. The polarizing plate 10 shown in FIG. 3 has a polarizing element 11 and a transparent protective film 12 . The polarizer 11 and the transparent protective film 12 can pass through the adhesive lamination layer described later. The polarizing plate may further have an optical function layer, a bonding layer, and a protective film (protect film) which will be described later.

[Polarizer]

A known polarizer can be used for a polarizer in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol (hereinafter referred to as "PVA") resin layer (referred to as a "PVA resin layer" in this specification). Examples of the polarizing element include: using a PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye, and stretching it uniaxially; or coating a coating solution containing a PVA-based resin on a substrate film. The laminated film is formed by using the laminated film, dyeing the PVA-based resin layer of the coating layer of the laminated film with a dichroic dye, and stretching the laminated film uniaxially.

The polarizer is formed of PVA-based resin obtained by saponifying polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include copolymers of vinyl acetate and other monomers that can be copolymerized with the vinyl acetate, in addition to polyvinyl acetate that is a homopolymer of vinyl acetate. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

In the present invention, the PVA-based resin layer is formed of a PVA-based resin having a boron adsorption rate of 5.70% by mass or higher. That is, in the raw material stage before dyeing or stretching, the boron adsorption rate of the PVA-based resin is 5.70% by mass or more. By using this PVA-based resin, the transmittance is not easily lowered even when exposed to a high-temperature environment with a temperature of 105° C., for example. When the polarizing element is produced using PVA resin, the boron adsorption rate of the PVA resin is more preferably at least 5.72 mass %, more preferably at least 5.75 mass %, most preferably at least 5.80 mass %. In addition, the boron adsorption rate of the PVA-based resin is preferably 10% by mass or less. Using this PVA-based resin to make a polarizing element eliminates the need to set the concentration of boric acid in the boric acid treatment bath to a high concentration, and shortens the treatment time of boric acid treatment, making it easy to obtain the desired polarizing element and improving the productivity of the polarizing element. . When the boron adsorption rate of the PVA-based resin is 10% by mass or less, boron is properly introduced into the PVA-based resin layer, and the contraction force of the polarizing element tends to decrease. As a result, when the polarizing element is assembled into an image display device, troubles such as peeling between other members such as a front panel and the polarizing plate are less likely to occur. Also, boron in PVA-based resin If the adsorption rate is less than 5.70%, the penetration rate is likely to decrease when exposed to a high-temperature environment at a temperature of 105°C, for example, and further, productivity will be lowered as described above. The boron adsorption rate of the PVA-based resin can be measured by the method described in the examples described later.

The boron adsorption rate of the PVA-based resin reflects the characteristics of the PVA-based resin, the distance between molecular chains in the PVA-based resin or the crystal structure. Compared with PVA-based resins with a boron adsorption rate of less than 5.70% by mass, PVA-based resins with a boron adsorption rate of more than 5.70% by mass have larger distances between molecular chains and less crystallization of PVA-based resins. Therefore, it is estimated that boron is easily introduced into the PVA-based resin layer, and polyeneization is easily prevented in a high-temperature environment.

For example, pretreatments such as hot water treatment, acid solution treatment, ultrasonic irradiation treatment, and radiation irradiation treatment can be performed on the PVA-based resin in the stage before manufacturing the polarizing element, thereby adjusting the boron adsorption rate of the PVA-based resin. Through these treatments, the distance between molecular chains in the PVA-based resin can be increased, or the crystal structure can be destroyed. The hot water treatment may, for example, be immersed in pure water at 30° C. to 100° C. for 1 second to 90 seconds and then dried. The acidic solution treatment can be, for example, immersed in a 10% to 20% boric acid aqueous solution for 1 second to 90 seconds and then dried. Ultrasonic treatment may, for example, irradiate ultrasonic waves with a frequency of 20 to 29kc at an output of 200W to 500W for 30 seconds to 10 minutes. Ultrasonic treatment can be carried out in solvents such as water.

The degree of saponification of the PVA-based resin is preferably at least 85 mol%, more preferably at least 90 mol%, and more preferably 99 mol% to 100 mol%. The degree of polymerization of the PVA-based resin is 1,000 to 10,000, preferably 1,500 to 5,000. The PVA-based resin can be modified, for example, it can be polyvinyl formal, polyvinyl acetal, polyvinyl butyral, etc. modified by aldehydes.

The thickness of the polarizing element in this embodiment is preferably 5 to 50 μm, more preferably 8 to 28 μm, still more preferably 12 to 22 μm, most preferably 12 to 15 μm. The thickness of the polarizing element is 50μm In the following, it is possible to suppress the effect of polyeneization of PVA-based resins on the reduction of optical properties in a high-temperature environment, and the thickness of the polarizing element is 5 μm or more, so that it is easy to form a structure that achieves the desired optical properties.

In the polarizing element, the content of boron is preferably from 4.0% by mass to 8.0% by mass, more preferably from 4.2% by mass to 7.0% by mass, still more preferably from 4.4% by mass to 6.0% by mass. When the boron content of the polarizing element exceeds 8.0% by mass, the shrinkage force of the polarizing element will increase, and when the polarizing element is assembled into an image display device, peeling will occur between other components such as the front panel attached to the polarizing plate and other bad situations. Moreover, when the content rate of boron is less than 2.4 mass %, desired optical characteristics cannot be achieved. In addition, the content of boron in the polarizer can be calculated, for example, by high-frequency Inductively Coupled Plasma (ICP) emission spectroscopy to calculate the mass fraction (mass %) of boron relative to the mass of the polarizer. Boron is considered to exist in the state of boric acid in the polarizing element or in the state of a cross-linked structure formed by boron and polyvinyl alcohol-based resin constituents, but the boron content referred to here is the value of the boron atom (B) itself.

By setting the boron content of the polarizing element to 4.0% by mass or more and 8.0% by mass or less, the decrease in transmittance can be suppressed even when exposed to a high-temperature environment as a component of an image display device having an interlayer filling structure. The reason for this is presumed to be as follows. When the boron content of the polarizing element is 4.0% by mass or more and 8.0% by mass or less, polyeneization is less likely to occur in a high-temperature environment, and the decrease in transmittance is suppressed.

From the viewpoint of suppressing the decrease in the optical properties of the polarizing element in a high-temperature environment, the content of potassium in the polarizing element is preferably at least 0.28% by mass, more preferably at least 0.32% by mass, and still more preferably at least 0.34% by mass. Moreover, from a viewpoint of suppressing the hue change in a high-temperature environment, Preferably it is 0.60 mass % or less, More preferably, it is 0.55 mass % or less, More preferably, it is 0.50 mass % or less.

From the viewpoint of suppressing the decrease in optical properties and the change in hue of the polarizing element in a high temperature environment, the content of zinc in the polarizing element is preferably at least 0.01% by mass, more preferably at least 0.02% by mass, and still more preferably at least 0.05% by mass. % or more, and preferably less than 2.00% by mass, more preferably 1.00% by mass or less, and more preferably not more than 0.50% by mass. The zinc content in the polarizing element can be determined, for example, as follows. Nitric acid was added to the polarizer of the precision scale, acid-decomposed with a microwave sample pretreatment device (ETHOSD) manufactured by Milestone General, and the resulting solution was used as a measurement solution. The zinc concentration was quantitatively measured with an ICP emission spectrometer (5110 ICP-OES) manufactured by Agilent Technologies, and calculated from the mass of zinc relative to the mass of the polarizer.

Although the detailed mechanism is still unclear, it is speculated as follows. Compared with the conventional polarizing element, since the content of boron is more and the content of potassium is less, the polyvinyl alcohol in the polarizing element is cross-linked by boric acid. The hydroxyl group is protected (stabilized), and the iodide ion as a counter ion in the polarizing element is stabilized by an appropriate amount of potassium content, thereby suppressing polyenylation.

The light sensitivity correction monomer transmittance of the polarizing plate is preferably 38.8% to 44.8%, more preferably 40.4% to 43.2%, and still more preferably 40.7% to 43.0%. If the transmittance of the single element of the light sensitivity correction exceeds 44.8%, there may be cases where the deterioration of optical characteristics such as redness increases under high temperature environments. Polyeneization may increase the deterioration of optical characteristics.

Measure the Y value corrected by visual sensitivity by measuring the 2-degree viewing angle (C light source) stipulated in JIS Z8701-1982, so as to obtain the single transmittance of visual sensitivity correction.

The sensitivity correction polarization degree of the polarizing plate may be, for example, 99.00% or more, preferably 99.90% or more, usually 100% or less, for example, may be less than 100%.

The absolute value of the difference in light sensitivity correction monomer transmittance before and after the high temperature durability test of the polarizing plate may be, for example, 6% or less, preferably 4% or less, more preferably 2% or less.

The absolute value of the difference in sensitivity-corrected polarization degree before and after the high-temperature durability test of the polarizing plate may be, for example, less than 0.5%, preferably less than 0.4%, more preferably less than 0.2%.

The absolute value of the hue change (color difference: NBS unit) of the polarizing plate before and after the high-temperature durability test may be, for example, 15 NBS or less, preferably 10 NMB or less, more preferably 7 NBS or less.

The high-temperature endurance test can be carried out according to the method described in the examples described later.

The transmittance of the light sensitivity correction monomer, the light sensitivity polarization degree, and the hue can be easily measured with a spectrophotometer (model: V7100) manufactured by JASCO Corporation, for example.

The manufacturing method of the polarizing element is not particularly limited, and a typical method is: a method in which a polyvinyl alcohol-based resin film wound in a roll is sent out in advance, and then stretched, dyed, cross-linked, etc. (hereinafter referred to as "Manufacturing method 1"); or a method comprising the steps of applying a coating liquid containing a polyvinyl alcohol-based resin on a base film to form a polyvinyl alcohol-based resin layer of the coating layer, and stretching the obtained laminate (hereinafter referred to as "manufacturing method 2").

Production method 1 can be produced through the following steps: a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing a polyvinyl alcohol-based resin film with a dichroic dye such as iodine, and adsorbing the dichroic dye . A step of treating the polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid, and a step of washing with water after the treatment with an aqueous solution of boric acid.

The concentration of the boron component supply material such as boric acid, borate, borax and other boron compounds contained in any of the treatment baths in the swelling step, dyeing step, crosslinking step, elongation step, and water washing step, and halogenated potassium iodide, etc. The concentration of potassium component supply substances such as potassium, the treatment temperature and treatment time of the above-mentioned treatment baths can control the content of boron and potassium contained in the polarizing element. In particular, in the crosslinking step and the elongation step, the boron content can be easily adjusted to a desired range by processing conditions such as the concentration of the boron component supply material. In addition, in the water washing step, boron, From the viewpoint that components such as potassium are eluted from or adsorbed to the polyvinyl alcohol-based resin film, it is easy to adjust the content of boron and the content of potassium to desired ranges.

The swelling step is a treatment step of immersing the polyvinyl alcohol-based resin film in a swelling bath, which can remove dirt or end-capping agents on the surface of the polyvinyl alcohol-based resin film, and can make the polyvinyl alcohol-based resin film swell and inhibit staining uneven. Swelling baths usually use water, distilled water, pure water and other media with water as the main component. Surfactant, alcohol, etc. can be suitably added to a swelling bath according to a normal method. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can be used in the swelling bath. At this time, the concentration of potassium iodide in the swelling bath is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and more preferably 1.0% by mass or less. 0.5% by mass or less.

The temperature of the swelling bath is preferably above 10°C and below 60°C, more preferably above 15°C and below 45°C, and more preferably above 18°C and below 30°C. The degree of swelling of the polyvinyl alcohol-based resin film will be affected by the temperature of the swelling bath, so the immersion time in the swelling bath cannot be determined uniformly, but it is preferably 5 to 300 seconds, more preferably 10 to 200 seconds, and more preferably 20 to 100 seconds. The swelling step may be performed only once, or may be performed multiple times as necessary.

The dyeing step is a treatment step of immersing the polyvinyl alcohol-based resin film in a dyeing bath (iodine solution). Dichroic pigments such as iodine or dichroic dyes can be adsorbed and aligned on the polyvinyl alcohol-based resin film. The iodine solution is generally preferably an iodine aqueous solution, which may contain iodide as iodine and a dissolution aid. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among them, potassium iodide is preferable from the viewpoint of controlling the content of potassium in the polarizing element.

The concentration of iodine in the dyeing bath is preferably from 0.01 to 1% by weight, more preferably from 0.02 to 0.5% by weight. The concentration of iodide in the dyeing bath is preferably from 0.01 to 10% by weight, more preferably from 0.05 to 5% by weight, still more preferably from 0.1 to 3% by weight.

The temperature of the dyeing bath is preferably from 10 to 50°C, more preferably from 15 to 45°C, and still more preferably from 18 to 30°C. Also, the degree of dyeing of the polyvinyl alcohol-based resin film is affected by the temperature of the dyeing bath, so the immersion time in the dyeing bath cannot be determined uniformly, but it is preferably 10 to 300 seconds, more preferably 20 to 240 seconds. The dyeing step may be carried out only once, or may be carried out a plurality of times if necessary.

The cross-linking step is a treatment step in which the polyvinyl alcohol-based resin film dyed in the dyeing step is immersed in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based resin film is cross-linked by the boron compound, and Iodine molecules or dye molecules can be adsorbed to the crosslinked structure. The boron compound may, for example, be boric acid, borate, borax or the like. The cross-linking bath is generally an aqueous solution, but it can also be a mixed solution of an organic solvent that is miscible with water and water. From the viewpoint of controlling the content of potassium in the polarizer, the crosslinking bath preferably contains potassium iodide.

In the crosslinking bath, the concentration of the boron compound is preferably 1 to 15% by weight, more preferably 1.5 to 10% by weight, and more preferably 2 to 5% by weight. Also, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably 1 to 15% by weight, more preferably 1.5 to 10% by weight, and even more preferably 2 to 5% by weight.

The temperature of the crosslinking bath is preferably from 20 to 70°C, more preferably from 30 to 60°C. Also, the degree of crosslinking of the polyvinyl alcohol-based resin film will be affected by the temperature of the crosslinking bath, so the immersion time in the crosslinking bath cannot be determined uniformly, but it is preferably 5 to 300 seconds, more preferably 10 to 200 seconds . The crosslinking step may be carried out only once, or may be carried out a plurality of times as necessary.

The stretching step is a processing step of stretching the polyvinyl alcohol-based resin film to a predetermined ratio in at least one direction. Generally, a polyvinyl alcohol-type resin film is uniaxially stretched to a conveyance direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be used. The extension step can be only It may be implemented once, or it may be implemented multiple times as needed. The extending step can be performed at any stage in the manufacture of the polarizer.

As the treating bath (stretching bath) in the wet stretching method, a solvent such as water or a mixed solution of an organic solvent having miscibility with water and water can generally be used. From the viewpoint of controlling the content of potassium in the polarizer, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably 1 to 15% by weight, more preferably 2 to 10% by weight, and more preferably 3 to 6% by weight. Also, from the viewpoint of suppressing film rupture during stretching, the treatment bath (stretching bath) may contain a boron compound. At this time, the concentration of the boron compound in the stretching bath is preferably 1 to 15% by weight, more preferably 1.5% by weight. to 10% by weight, and more preferably 2 to 5% by weight.

The temperature of the stretching bath is preferably from 25 to 80°C, more preferably from 40 to 75°C, and still more preferably from 50 to 70°C. The stretching degree of the polyvinyl alcohol-based resin film will be affected by the temperature of the stretching bath, so the immersion time in the stretching bath cannot be determined uniformly, but it is preferably 10 to 800 seconds, more preferably 30 to 500 seconds. The stretching treatment in the wet stretching method may be performed together with any one of the swelling step, the dyeing step, the crosslinking step, and the washing step.

Examples of the dry stretching method include an inter-roll stretching method, a heating roll stretching method, and a compression stretching method. Also, the dry stretching method can be carried out together with the drying step.

The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be appropriately set depending on the purpose, but is preferably 2 to 7 times, more preferably 3 to 6.8 times, and still more preferably 3.5 to 6.5 times.

The washing step is a treatment step of immersing the polyvinyl alcohol-based resin film in a washing bath to remove foreign matter remaining on the surface of the polyvinyl alcohol-based resin film. Cleaning baths usually use water, distilled water, pure water and other media with water as the main component. Also, from the viewpoint of controlling the content of potassium in the polarizing element, cleaning The bath preferably uses potassium iodide. At this time, the concentration of potassium iodide in the cleaning bath is preferably 1 to 10% by weight, more preferably 1.5 to 4% by weight, and even more preferably 1.8 to 3.8% by weight.

The temperature of the cleaning bath is preferably from 5 to 50°C, more preferably from 10 to 40°C, and still more preferably from 15 to 30°C. Also, the degree of cleaning of the polyvinyl alcohol-based resin film is affected by the temperature of the cleaning bath, so the immersion time in the cleaning bath cannot be determined uniformly, but it is preferably 1 to 100 seconds, more preferably 2 to 50 seconds , and more preferably 3 to 20 seconds. The washing step may be performed only once, or may be performed a plurality of times as necessary.

Next, in the above steps or as a different step from the above steps, there may be a metal ion treatment step. The metal ion treatment step is carried out by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a metal salt of metal ions. Metal ions can be contained in the polyvinyl alcohol-based resin film by the metal ion treatment step.

Metal ions are not particularly limited as long as they are metal ions other than potassium ions, but are preferably ions of metals other than alkali metals, especially from the viewpoint of color tone adjustment or durability imparting, preferably containing cobalt, nickel, zinc, and chromium. , at least one metal ion of a transition metal such as aluminum, copper, manganese, and iron. Among these metal ions, zinc ions are preferred from the viewpoints of color tone adjustment, heat resistance imparting, and the like. Examples of the zinc salt include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

A metal salt solution is used in the metal ion treatment step. The immersion treatment in the zinc-containing solution will be described below using a zinc salt aqueous solution as a representative example in the metal ion treatment step.

The concentration of zinc ions in the zinc salt solution is in the range of 0.1 to 10% by mass, preferably in the range of 0.3 to 7% by mass. Also, since an aqueous solution containing potassium ions and iodide ions by potassium iodide or the like is used, zinc ions are easily impregnated, so a zinc salt solution is preferable. The concentration of potassium iodide in the zinc salt solution is 0.1 to 10% by mass, more preferably 0.2 to 5% by mass.

During the immersion treatment of the zinc-containing solution, the temperature of the zinc salt solution is usually 15 to 85°C, preferably 25 to 70°C. The dipping time is usually in the range of 1 to 120 seconds, preferably in the range of 3 to 90 seconds. During the immersion treatment of the zinc-containing solution, the zinc content in the polyvinyl alcohol-based resin film can be made by adjusting the concentration of the zinc salt solution, the immersion temperature of the polyvinyl alcohol-based resin film in the zinc salt solution, and the immersion time. The amount is adjusted to the above range. There is no particular limitation on when to perform the immersion treatment in the zinc-containing solution. The immersion treatment in the zinc-containing solution can be carried out alone, or the zinc salt can coexist in the dyeing bath, the crosslinking bath, and the stretching bath, and it can be carried out simultaneously with at least one of the dyeing step, the crosslinking step, and the stretching step.

The drying step is a step of drying the polyvinyl alcohol-based resin film washed in the washing step to obtain a polarizing element. Drying can be performed by any appropriate method, and examples thereof include natural drying, air drying, and heat drying.

Production method 2 can be produced through the following steps: a step of applying the coating liquid containing the above-mentioned polyvinyl alcohol-based resin on the base film, a step of uniaxially stretching the obtained laminated film, and a step of uniaxially stretching the PVA laminated film. A step of dyeing the resin layer with a dichroic dye to absorb the dichroic dye to form a polarizing element, a step of treating the film adsorbed with the dichroic dye with an aqueous solution of boric acid, and washing with water after the treatment with an aqueous solution of boric acid steps to manufacture. The base film used to form the polarizer can be used as a protective layer of the polarizer. The base film can also be peeled and removed from the polarizing element as needed.

[Transparent protective film]

The transparent protective film (hereinafter referred to as "protective film") used in this embodiment is attached to at least one side of the polarizing element through the adhesive layer. The transparent protective film can be pasted on one side or both sides of the polarizing element, but is preferably pasted on both sides.

The protective film may have other optical functions at the same time, and may also form a laminated structure in which multiple layers are laminated. From the point of view of optical properties, the film thickness of the protective film is preferably thinner, but if it is too thin, the strength will decrease. will be reduced, and the workability will be deteriorated. An appropriate film thickness is 5 to 100 μm, preferably 10 to 80 μm, more preferably 15 to 70 μm.

As the protective film, cellulose acylate film, film made of polycarbonate resin, film made of cycloolefin resin such as norbornene, (meth)acrylic polymer film, Films such as polyester resin films such as polyethylene terephthalate. When a protective film is provided on both sides of the polarizing element, if a water-based adhesive such as PVA adhesive is used for bonding, from the viewpoint of moisture permeability, it is preferable that the protective film on at least one side is a cellulose acyl compound film or Any of the (meth)acrylic polymer films, more preferably a cellulose acylate film.

At least one protective film can have a retardation function for purposes such as viewing angle compensation. In this case, the protective film itself may have a retardation function, may have a retardation layer separately, or may be a combination of both.

In addition, although the structure in which the film having a retardation function is directly bonded to the polarizer through an adhesive is described, it may also be bonded through an adhesive or an adhesive through another protective film bonded to the polarizer.

[adhesive layer]

Any appropriate adhesive agent can be used for the adhesive agent which comprises the adhesive agent layer for bonding a protective film to a polarizing element. As the adhesive, water-based adhesives, solvent-based adhesives, active energy ray-curable adhesives, and the like can be used, but water-based adhesives are preferred. From the viewpoint of improving heat resistance, the adhesive layer preferably contains at least one urea-based compound selected from urea, urea derivatives, thiourea, and thiourea derivatives.

The thickness at the time of applying the adhesive can be set to any appropriate value. For example, it is set so that an adhesive layer having a desired thickness can be obtained after hardening or heating (drying). The thickness of the adhesive layer is preferably from 0.01 μm to 7 μm, more preferably from 0.01 μm to 5 μm, still more preferably from 0.01 μm to 2 μm, most preferably from 0.01 μm to 1 μm.

(water-based adhesive)

Water-based adhesive Any suitable water-based adhesive can be used. Among them, it is preferable to use a water-based adhesive (PVA-based adhesive) containing a PVA-based resin. From the viewpoint of adhesion, the average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably from 100 to 5,500, and more preferably from 1,000 to 4,500. From the viewpoint of adhesion, the average degree of saponification is preferably from 85 mol % to 100 mol %, and more preferably from 90 mol % to 100 mol %.

The PVA-based resin contained in the water-based adhesive is preferably one containing an acetoacetyl group, because the PVA-based resin layer has excellent adhesion to the protective film and excellent durability. The PVA-based resin containing an acetoacetyl group can be obtained by reacting the PVA-based resin with diacetone by any method. The modification degree of the acetyl acetyl group of the PVA-based resin containing acetyl acetyl group is typically 0.1 mol % or more, preferably 0.1 mol % to 20 mol %.

The resin concentration of the above water-based adhesive is preferably from 0.1% by mass to 15% by mass, and more preferably from 0.5% by mass to 10% by mass.

The water-based adhesive may also contain a crosslinking agent. As the crosslinking agent, known crosslinking agents can be used. As a crosslinking agent, a water-soluble epoxy compound, dialdehyde, isocyanate, etc. are mentioned, for example.

When the PVA-based resin is a PVA-based resin containing acetoacetyl group, the crosslinking agent is preferably any one of glyoxal, glyoxylate, and methylol melamine, more preferably glyoxal or acetaldehyde Any of acid salts, particularly preferably glyoxal.

The water-based adhesive may also contain an organic solvent. From the viewpoint of miscibility with water, alcohols are preferable as organic solvents, and methanol or ethanol is preferable among alcohols. Some urea derivatives have low solubility in water, but conversely have sufficient solubility in alcohol. At this time, as one of the better forms, the urea system After dissolving the compound in alcohol to prepare an alcoholic solution of the urea-based compound, the alcoholic solution of the urea-based compound was added to the PVA aqueous solution to prepare an adhesive.

The concentration of methanol in the water-based adhesive is preferably from 10% by mass to 70% by mass, more preferably from 15% by mass to 60% by mass, still more preferably from 20% by mass to 60% by mass. By setting the concentration of methanol to 10% by mass or more, it becomes easier to suppress polyeneization in a high-temperature environment. Moreover, deterioration of hue can be suppressed by making the content rate of methanol 70 mass % or less.

(Active energy ray hardening type adhesive)

Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, and examples include adhesives containing polymerizable compounds and photopolymerizable initiators, adhesives containing photoreactive resins, adhesives containing Adhesives for adhesive resins and photoreactive crosslinking agents, etc. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and compounds derived from these monomers. oligomers, etc. Examples of the photopolymerization initiator include compounds containing substances that generate active species by irradiation with active energy rays such as ultraviolet rays. The active species include neutral radicals, anion radicals, cationic radicals, and the like.

(urea compound)

When the adhesive layer contains a urea-based compound, the urea-based compound is at least one selected from urea, urea derivatives, thiourea, and thiourea derivatives. In the method of containing the urea-based compound in the adhesive layer, it is preferable to contain the urea-based compound in the above-mentioned adhesive. In addition, in the process of forming an adhesive layer through a drying step from the adhesive, a part of the urea-based compound may migrate from the adhesive layer to the polarizing element or the like. That is, the polarizing element may contain a urea-based compound. Urea-based compounds include those that are water-soluble and those that are hardly water-soluble. Both types of urea-based compounds can be used in the adhesive of this embodiment. When the water-based adhesive uses a poorly water-soluble urea-based compound, it is preferable to study the dispersion method after the adhesive layer is formed so as not to increase the haze.

When the adhesive is a water-based adhesive containing PVA resin, the amount of the urea compound added is preferably 0.1 to 400 parts by mass, more preferably 1 to 200 parts by mass, and more preferably 3 parts by mass relative to 100 parts by mass of the PVA resin. to 100 parts by mass.

(urea derivatives)

The urea derivative is a compound in which at least one of the four hydrogen atoms of the urea molecule is substituted as a substituent. In this case, the substituent is not particularly limited, and is preferably a substituent composed of carbon atoms, hydrogen atoms, and oxygen atoms.

Specific examples of urea derivatives include methyl urea, ethyl urea, propyl urea, butyl urea, isobutyl urea, N-octadecyl urea, 2-hydroxyethyl urea, Hydroxyurea, acetyl urea, allyl urea, 2-propynyl urea, cyclohexyl urea, phenyl urea, 3-hydroxyphenyl urea, (4-methoxyphenyl) urea, benzyl urea, Benzoyl urea, o-tolyl urea, p-tolyl urea.

2-substituted urea includes 1,1-dimethyl urea, 1,3-dimethyl urea, 1,1-diethyl urea, 1,3-diethyl urea, 1,3-bis(hydroxymethyl urea base) urea, 1,3-tert-butyl urea, 1,3-dicyclohexyl urea, 1,3-diphenyl urea, 1,3-bis(4-methoxyphenyl) urea, 1- Acetyl-3-methylurea, 2-imidazolidinone (ethylene urea), tetrahydro-2-pyrimidinone (propylene urea).

4-substituted urea includes tetramethyl urea, 1,1,3,3-tetraethyl urea, 1,1,3,3-tetrabutyl urea, 1,3-dimethoxy-1,3- Dimethyl urea, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

(thiourea derivative)

Thiourea derivatives are compounds in which at least one of the four hydrogen atoms of the thiourea molecule is substituted as a substituent. In this case, the substituent is not particularly limited, and is preferably a substituent composed of carbon atoms, hydrogen atoms, and oxygen atoms.

Specific examples of thiourea derivatives include N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, and cyclohexylthiourea. , N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N- (2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, p-tolylthiourea.

Examples of 2-substituted thiourea include 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3 -Dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N'-diphenylthiourea, 1 ,3-bis(o-tolyl)thiourea, 1,3-bis(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N -Allyl-N'-(2-hydroxyethyl)thiourea, ethylenethiourea.

Examples of 3-substituted thiourea include trimethylthiourea, and examples of 4-substituted thiourea include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

When used in an image display device composed of interlayer filling, urea derivatives or thiourea derivatives are preferred, and urea derivatives are more preferred from the viewpoint of suppressing the decrease in transmittance under high temperature environments. . Among the urea derivatives, mono-substituted urea or di-substituted urea is preferred, and mono-substituted urea is more preferred. The 2-substituted urea includes 1,1-substituted urea and 1,3-substituted urea, more preferably 1,3-substituted urea.

[other layers]

The polarizing plate may further have, for example, an optical function layer, an adhesive layer, and a protective film as other layers.

[Optical functional layer]

The optical functional layer may be, for example, a retardation layer. Examples of the retardation layer include a layer imparting a retardation of λ/2, a layer imparting a retardation of λ/4 (positive type A plate), and a positive type C plate. The optical functional layer can contain alignment The layers and substrates may each have two or more liquid crystal layers, alignment layers, and substrates. When the polarizing plate has a polarizing element and a film that imparts a phase difference of λ/4, the polarizing plate may be a circular polarizing plate.

The transparent protective film may also serve as a retardation layer, but a retardation layer may be laminated separately in addition to these films. In the latter case, the retardation layer can be laminated on the polarizing plate through the adhesive layer or the adhesive layer.

Examples of the retardation layer include a birefringent film formed of a stretched film of a light-transmitting thermoplastic resin, the above-mentioned liquid crystal layer formed on a base film, and the like.

The base film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as cellulose triacetate.

Examples of other optical functional layers include light collecting plate, brightness enhancement film, reflective layer (reflective film), semi-transmissive reflective layer (semi-transmissive reflective film), light diffusion layer (light diffuser film), anti-reflection film, etc.

[adhesive layer]

The adhesive layer may have the function of bonding the polarizing plate to image display elements, optical members, and the like. The adhesive layer can be disposed on the outermost surface of any one of the polarizing plates. Hereinafter, a polarizing plate provided with an adhesive layer is referred to as a polarizing plate with an adhesive layer.

The adhesive layer can be provided on the polarizing plate in an appropriate manner. For example, the base polymer or its composition is dissolved or dispersed in a solvent composed of a suitable solvent such as toluene or ethyl acetate alone or in a mixture to prepare an adhesive solution of about 10 to 40% by mass. It is directly placed on the polarizing plate in an appropriate way such as casting or coating; or the method of forming an adhesive layer on the separator and transferring it to the polarizing plate, etc.

The (meth)acrylic resin (base polymer) used in the adhesive composition is suitable to use butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, (meth) A polymer or copolymer of one or more (meth)acrylates such as 2-ethylhexyl acrylate as a monomer. Base A polar monomer is preferably copolymerized in the polymer. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, (meth)acrylic acid N , N-dimethylaminoethyl ester compound, glycidyl (meth)acrylate compound and other monomers having carboxyl group, hydroxyl group, amido group, amino group, epoxy group, etc.

The adhesive composition may contain only the above-mentioned base polymer, but usually further contains a crosslinking agent. Examples of the crosslinking agent include metal ions that are divalent or higher and form a metal carboxylate salt with a carboxyl group, a polyamine compound that forms an amide bond with a carboxyl group, or a polyamine compound that forms an ester bond with a carboxyl group. Epoxy compounds or polyols, polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are preferred.

The active energy ray-curable adhesive composition has the property of being cured by being irradiated with active energy rays such as ultraviolet rays or electron rays, and has adhesiveness even before irradiating active energy rays and can be adhered to an adherend such as a film, And the property of adhesion can be adjusted by hardening by irradiating active energy rays. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray-curable adhesive composition further contains an active energy ray polymerizable compound in addition to the base polymer and the crosslinking agent. A photopolymerization initiator, a photosensitizer, etc. may also be contained as needed.

The adhesive composition may contain microparticles, beads (resin beads, glass beads, etc.), glass fibers, resins other than base polymers, adhesiveness imparting agents, fillers (metal powder or other) for imparting light scattering properties. Inorganic powder, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators and other additives.

An adhesive layer can be formed by coating the above-mentioned organic solvent dilution of the adhesive composition on the substrate film, the image display unit or the surface of the polarizing plate and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof includes a release film subjected to mold release treatment. The separation membrane can be, for example, formed on the membrane If the surface of the adhesive layer is subjected to release treatment such as silicone treatment, the film system is composed of resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and polyarylate.

For example, the adhesive composition can be directly coated on the release-treated surface of the separation film to form an adhesive layer, and then the adhesive layer attached to the separation film can be laminated on the surface of the polarizer. It is also possible to directly coat the adhesive composition on the surface of the polarizing plate to form an adhesive layer, and then layer a separation film on the outer surface of the adhesive layer.

When the adhesive layer is placed on the surface of the polarizing plate, it is preferable to implement surface activation treatment on the bonding surface of the polarizing plate and/or the bonding surface of the adhesive layer, such as plasma treatment, corona treatment, etc., more preferably implementing Corona treatment.

In addition, the adhesive composition can be coated on the second separation membrane to form an adhesive layer, and then a separation membrane can be laminated on the formed adhesive layer to prepare an adhesive sheet. After peeling off the second separation membrane from the adhesive sheet, Laminate the adhesive layer with the separation film on the polarizing plate. The 2nd separation membrane uses the one which is weaker than the separation membrane in the adhesive force with the adhesive layer, and is easy to peel off.

The thickness of the adhesive layer is not particularly limited, for example, it is preferably 1 μm to 100 μm, more preferably 3 μm to 50 μm, and may be 20 μm or more.

[protective film]

The polarizing plate may contain a protective film for protecting its surface (typically, the surface of the protective film of the polarizing plate). For example, after the polarizing plate is bonded to the image display element or other optical components, the protective film is peeled off together with the adhesive layer of the polarizing plate and removed.

The pellicle is composed of, for example, a base film and an adhesive layer laminated on the base film. For the adhesive layer, the above-mentioned description can be cited.

The resin constituting the base film can be, for example, polyethylene-based resins such as polyethylene; polypropylene-based resins such as polypropylene; polyester-based resins such as polyethylene terephthalate or polyethylene naphthalate; polycarbonate Thermoplastic resin of ester resin. Polyester-based resins such as polyethylene terephthalate are preferable.

The thickness of the pellicle is not particularly limited, but is preferably in the range of not less than 20 μm and not more than 200 μm. When the thickness of a base material is 20 micrometers or more, it exists in the tendency which provides intensity|strength to a polarizing plate easily.

[Manufacturing method of polarizing plate]

The manufacturing method of the polarizing plate of this embodiment includes a lamination step of laminating a polarizing element and a transparent protective film to obtain a laminated film, and a cutting process of cutting and processing the laminated film. The cutting process step includes a first cutting step, which is an operation of relatively moving the cutting tool in a spiral shape when viewed from a direction perpendicular to the main surface of the laminated film on which the polarizing element and the transparent protective film are laminated, In this way, the laminated film is cut.

[Stacking steps]

The lamination step may be a step of laminating the polarizing element and the transparent protective film through the above-mentioned adhesive layer.

[Cutting process steps]

The cutting tool used in the cutting process is not particularly limited as long as it can cut and process the laminated film, and examples thereof include a cutting tool having a rotatable handle and an outer peripheral edge in which the outer peripheral edge and the handle are integrally formed. It is also possible to use a cutting tool that has a rotatable handle, an outer peripheral edge, and a bottom edge, and the outer peripheral edge and the bottom edge are respectively integrally formed with the handle. The peripheral cutting edge and the bottom cutting edge may also be integrally formed. Examples of the cutting tool include end mills and the like.

The number of peripheral edges and bottom edges of the cutting tool is not particularly limited, for example, it may be 1 or more and 6 or less, and may be 2, 3 or 4. If the number of flutes is small, chips tend to be easily discharged, but the rigidity of the cutting tool tends to decrease.

The inclination angle of the peripheral edge and the bottom edge of the cutting tool is usually more than 0° and less than 20°, and may be more than 3° and less than 15°. If the inclination angle is too large, the blade tends to be easily damaged.

The clearance angle between the peripheral edge and the bottom edge of the cutting tool is, for example, more than 0° and less than 20°, and may be not less than 3° and not more than 15°. If the clearance angle is 0°, the laminated film will rub against the blade, and if the clearance angle is too large, the blade tends to be easily chipped.

The peripheral edge can be twisted along the shank. The twist angle of the peripheral edge of the cutting tool can be -75° to 75°, or -65° to 65°. If the torsion angle is too large, chips tend to be difficult to discharge.

The outer peripheral edge of the cutting tool is preferably the longest diameter of the rotating part constituting the cutting tool. The diameter of the outer peripheral edge of the cutting tool (the longest diameter in the direction perpendicular to the shank) is, for example, not less than 1.0 mm and not more than 10 mm, preferably not less than 1.5 mm and not more than 8 mm. If the diameter is too small, the end mill tends to be easily bent, and if it is too large, it will be difficult to perform fine cutting.

The feed rate of the cutting tool is usually not less than 50 mm/min and not more than 30000 mm/min, may be not less than 100 mm/min, preferably not less than 200 mm/min and not more than 20000 mm/min.

In addition, the rotational speed of the peripheral cutting edge and the bottom cutting edge of the end mill may be 5,000 rpm to 100,000 rpm, 10,000 rpm to 80,000 rpm, or 30,000 rpm to 60,000 rpm. If the rotation speed is too slow, delamination of the laminated film tends to easily occur, and if the rotation speed is too fast, there is a possibility of heat generation and damage to the laminated film.

[First cutting step]

In the first cutting step, for example, as shown in FIG. 4(A), the laminated film is cut by moving the cutting tool helically relative to one another as viewed from a direction perpendicular to the main surface of the laminated film.

A helix is a curved line that rotates while moving away from the outside. Spirals can be, for example, spirals with equal spacing between spirals (Archimedes spiral, etc.), spirals with wider distances between spirals (logarithmic spirals, etc.) Spirals (parabolic spirals, etc.) in which the distance between lines becomes narrower as they go outward. The spirals with equal intervals between the spirals can be fixed intervals within every other cycle (such as half a cycle, 1/4 cycle, etc.) and the radius is equal to The spiral of enlargement. During a part of one spiral revolution, the pitch between the spirals is zero, ie a new uncut portion can be obtained from a cut portion. The operation of relatively moving the cutting tool in a helical shape refers to the operation of relatively moving the cutting tool and the outer side only by the width of the helical distance in at least a part of the cut portion that has been cut. Thereby, in at least a part of the cut portion that has been cut, only the thickness of the pitch width between the spirals is cut on the outer laminated film.

The helix in the first cutting step may be at least one turn, and it is preferable that at least the outermost periphery be cut by a helical relative movement when cutting the laminated film.

Compared with the case of cutting by relative movement of a combination of linear and circular motions (Fig. 4(B) etc.), if the cutting tools are opposed to each other in a spiral shape when viewed from a direction perpendicular to the main surface of the laminated film By moving and cutting the laminated film, delamination of the laminated film can be suppressed. Moreover, if cutting is performed by relative movement in a spiral shape, the time required to form a cut portion of a target size can be shortened.

The shape of the cut portion formed by the first cutting step has a curved portion and a straight line portion. For example, when cutting the laminated film into the shape shown in FIG. moving, and the cutting tool is relatively moved in a helical shape while increasing the radius from the center. When the linear portions 2a and 2c in FIG. 2 that are approximately parallel to the transmission axis of the polarizer are formed, the relative movement direction of the cutting tool can be approximately parallel to the transmission axis of the polarizer.

In the first cutting step, the laminated film is preferably cut by bringing the outer peripheral edge of the cutting tool into contact with the laminated film. When the cutting tool has a rotatable handle, the rotatable handle may be perpendicular or inclined relative to the main surface of the laminated film, but it is preferable to make the cutting tool in a state perpendicular to the main surface of the laminated film. The operation of moving. Thereby, the cut surface is perpendicular to the main surface of the laminated film.

In the first cutting step, the operation of relatively moving the cutting tool is generally performed in a direction parallel to the main surface of the laminated film. This operation may further be accompanied by vertical movement with respect to the main surface of the laminated film. When the movement perpendicular to the main surface of the laminated film is accompanied, for example, an operation of relatively moving a cutting tool in a helical shape can be exemplified. The cutting performed by relatively moving the cutting tool in a helical shape can collectively form through-holes described later.

In the first cutting step, the distance between the spirals is, for example, 0.01 mm to 0.5 mm, preferably 0.02 mm to 0.3 mm, more preferably 0.03 mm to 0.2 mm. When the pitch between the spirals is within the above range, the laminated film can be cut to a desired size without taking too much time. Also, if the pitch between the spirals is too large, the chipped laminated film tends to be prone to defects.

In the first cutting step, the laminated film may be cut one by one, or a laminate formed by overlapping a plurality of laminated films may be cut. In the first cutting step, when a plurality of laminated films are stacked and cut, the cutting tool can be cut in a direction perpendicular to the main surface of the laminated body by relatively moving the cutting tool in a helical shape. Each laminated film. The number of laminated films constituting the laminated body may be, for example, 10 to 500 sheets. The thickness of the laminate may be, for example, not less than 1 mm and not more than 50 mm in the lamination direction of the laminated film.

[Through-hole forming step]

The manufacturing method of the present invention preferably further includes a through-hole forming step of forming a through-hole penetrating in a direction perpendicular to the main surface of the laminated film. The through-hole forming step and the disposing step described below are usually performed before the first cutting step. The size of the through hole is the same as or larger than the longest diameter perpendicular to the handle of the cutting tool, so that the cutting tool can be arranged in the through hole.

Preferably, the through-hole is formed by relatively moving the cutting tool in a direction perpendicular to the main surface of the laminated film. For example, when a cutting tool has a rotatable handle and a bottom edge integrally formed with it, the main surface of the cutting tool facing the laminated film is relatively moved in a vertical direction so that the bottom edge can cut the laminated film, and the laminated film can be cut. A through hole having the same diameter as the longest diameter perpendicular to the handle of the cutting tool is formed. In the through-hole forming step, the operation of relatively moving the cutting tool in a direction parallel to the main surface of the laminated film may be performed simultaneously with or independently of the relative movement in a direction perpendicular to the main surface of the laminated film. Through this operation, a through hole larger than the longest diameter perpendicular to the shank of the cutting tool can be formed. The operation of relatively moving in a direction parallel to the main surface of the laminated film includes an operation of circularly moving a cutting tool and an operation of linearly moving the cutting tool as viewed from a direction perpendicular to the main surface of the laminated film.

A plurality of laminated films may be stacked to form a laminated body, and then the through-hole forming step may be performed. In the through-hole forming step, the cutting tool is relatively moved in a direction perpendicular to the main surface of the laminate, whereby through-holes can be formed in each of the laminated films constituting the laminate. When the through-hole forming step is performed using the laminated film as a laminate, the subsequent arrangement step and first cutting step may be performed on the laminate in which the through-holes are formed.

The through holes can be formed by known methods such as punching and laser methods. The through hole formed by the above method is preferably larger than the longest diameter perpendicular to the handle of the cutting tool.

[Configuration steps]

The manufacturing method of the present invention preferably further includes an arranging step of arranging the cutting tool so as to pass through the through hole. It may be arranged so that the cutting tool penetrates through the through hole so that the outer peripheral edge of the cutting tool is in contact with the inner side of the through hole. Specifically, after the through-hole is formed, the cutting tool may be arranged so as to pass through the through-hole.

When the through-hole is formed by the cutting tool, the cutting tool can be arranged so as to penetrate the through-hole without pulling up the cutting tool which moves relatively in a direction perpendicular to the main surface of the laminated film. After the cutting tool is moved in a direction perpendicular to the main surface of the laminated film to form a through-hole, the cutting tool can be pulled up from the through-hole in the vertical direction to remove grinding debris, and the cutting tool can be placed in the through-hole again.

A plurality of laminated films can be stacked to form a laminated body, and then the configuration step can be performed. At this time, the cutting tool is arranged so as to pass through the through holes formed in the respective laminated films constituting the laminated body. When the step of arranging the laminate is performed, the first cutting step can be directly performed on the laminate.

[grinding procedure]

The production method of the present invention preferably further includes a grinding step of grinding the cut portion formed by the first cutting step or the second cutting step described below.

A plurality of laminated films can be stacked to form a laminated body, and then the grinding step can be performed. In the grinding step, the cut portion of each laminated film constituting the laminated body may be ground by grinding the laminated body. After performing the first cutting step or the second cutting step on the laminate, the laminate may be ground directly.

The grinding method is not particularly limited as long as it is a method that can make the cut surface smoother, and examples include grinding methods using grinding paper (sandpaper), grinding cloth, fine particle abrasives, grinding stones, etc., electrical grinding methods, and using solvents. Chemical grinding methods, etc. It is also possible to use a cutting tool such as an end mill used in the first cutting step and grind the cut surface at a reduced feed rate, reduced grinding amount, or both. In addition, dirt, dust, etc. attached in the previous steps can also be removed by grinding.

[Second cutting step]

The production method of the present invention may further include a second cutting step, which is further performed by relatively moving a cutting tool in a direction parallel to the main surface of the laminated film in the laminated film obtained in the first cutting step. cutting.

A plurality of laminated films can be stacked to form a laminated body, and then the second cutting step is performed. In the second cutting step, each laminated film constituting the laminate is further cut by relatively moving the cutting tool in a direction parallel to the principal surface of the laminate. It is also possible to perform the first cutting step on the laminate and directly perform the second cutting step on the laminate.

The second cutting step is further continued from the cut portion formed by the first cutting step, whereby a polarizing plate cut into a target shape can be obtained.

<Image display device>

The polarizing plate of this embodiment is used in various image display devices such as liquid crystal display devices and organic EL display devices. The image display device may, for example, include an image display unit, a first adhesive layer laminated on the viewing side surface of the image display unit, and a polarizer laminated on the viewing side surface of the first adhesive layer. The image display device may further include a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the surface of the second adhesive layer. In particular, the polarizing plate of this embodiment is suitable for use in an image display device having an interlayer filling structure. The interlayer filling structure is to arrange a transparent member on the viewing side of the image display device, and attach a polarized light through the first adhesive layer. plate and image display unit, and attach the polarizing plate and the transparent member through the second adhesive layer. In this specification, either or both of the 1st adhesive layer and the 2nd adhesive layer may only be called an "adhesive layer".

In addition, the member used for bonding the polarizing plate and the image display unit, and the member used for bonding the polarizing plate and the transparent member are not limited to the adhesive layer, and may be an adhesive layer.

[Image display unit]

As the image display unit, a liquid crystal unit or an organic EL unit may be mentioned. The liquid crystal unit can be a reflective liquid crystal unit utilizing external light, a transmissive liquid crystal unit utilizing light from a light source such as a backlight, or a transflective liquid crystal unit utilizing both external light and light from a light source. one. When the liquid crystal unit utilizes light from a light source, in an image display device (liquid crystal display device), a polarizer is also arranged on the side opposite to the viewing side of the image display unit (liquid crystal unit), and a light source is further arranged. The polarizer on the light source side and the liquid crystal unit are preferably bonded through an appropriate adhesive layer. As the driving method of the liquid crystal cell, for example, any type such as VA mode, IPS mode, TN mode, STN mode, or bend alignment (π type) can be used.

As the organic EL unit, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitting body (organic electroluminescent light emitting body). The organic light-emitting layer is a laminate of various organic thin films. For example, a laminate of a hole injection layer made of triphenylamine derivatives and a light-emitting layer made of fluorescent organic solids such as anthracene, or the Various layers such as a laminate of a light-emitting layer and an electron injection layer composed of an ammonium derivative, or a laminate of a hole injection layer, a light-emitting layer, and an electron injection layer.

[Adhesion of image display unit and polarizing plate]

An adhesive layer (adhesive sheet) is suitably used for bonding the image display unit and the polarizing plate. Among them, the method of bonding the above-mentioned polarizing plate with the adhesive layer and the image display unit together is preferable from the viewpoint of workability and the like. The organic solvent dilution of the above adhesive composition can also be coated on the image display unit to form an adhesive layer, and then bonded to the polarizing plate.

[transparent member]

Examples of the transparent member arranged on the viewing side of the image display device include a front panel (window layer) or a touch panel. The front panel is a front panel with proper mechanical strength and thickness. The front panel can be, for example, a transparent resin plate made of polyimide resin, acrylic resin, or polycarbonate resin, or a glass plate. Functional layers such as anti-reflection layers can be laminated on the viewing side of the front panel. Also, when the front panel is a transparent resin board, a hard coat layer for improving physical strength or a low moisture permeability layer for reducing moisture permeability may be laminated.

Various types of touch panels such as resistive film method, electrostatic capacitance method, optical method, and ultrasonic method, or glass plates or transparent resin plates with touch sensing functions can be used for the touch panel. When a capacitive touch panel is used as the transparent member, it is preferable to provide a front panel made of glass or a transparent resin plate on the viewing side of the touch panel.

[Adhesion of polarizing plate and transparent member]

Adhesives or active energy ray-curable adhesives are suitable for bonding the polarizing plate and the transparent member. When an adhesive is used, the adhesive may be set in an appropriate manner. The specific setting method can be, for example, the setting method of the adhesive layer used for bonding the image display unit and the polarizing plate mentioned above.

When using an active energy ray-curable adhesive, in order to prevent the diffusion of the adhesive solution before curing, the method of providing a dam so as to surround the peripheral portion of the image display panel, and The transparent member is placed on the embankment, and then the adhesive solution is injected. After injecting the adhesive solution, alignment and defoaming are performed as necessary, and then curing is performed by irradiating active energy rays.

(Example)

Hereinafter, the present invention will be specifically described based on examples. Materials, reagents, amounts of substances and their ratios, operations, etc. shown in the following examples can be appropriately changed within the scope not departing from the gist of the present invention. Therefore, the present invention is not limited to the following examples.

(1) Determination of the thickness of the polarizing element:

It measured using the digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Determination of boron content:

0.2 g of the polarizer was dissolved in 200 g of a 1.9% by mass mannitol aqueous solution. Then titrate the obtained aqueous solution with 1 mol/L sodium hydroxide aqueous solution, and calculate the boron content rate of the polarizing element by comparing the amount of sodium hydroxide aqueous solution required for neutralization with the calibration curve.

(3) Determination of boron adsorption rate of PVA resin film:

The PVA-type resin film cut into 100 mm square was immersed in 30 degreeC pure water for 60 seconds, and then immersed in the 60 degreeC aqueous solution containing 5 parts of boric acid for 120 seconds. The PVA-based resin film taken out from the boric acid aqueous solution was oven-dried at 80° C. for 11 minutes. Humidity was adjusted in an environment of 23° C. and 55% RH for 24 hours to obtain a boron-containing PVA film. Dissolve 0.2 g of the boron-containing PVA-based resin film thus obtained in 1.9% by mass of mannitol Aqueous solution 200g. Then titrate the resulting aqueous solution with 1 mol/L sodium hydroxide aqueous solution, and calculate the boron content of the PVA-based resin film by comparing the amount of sodium hydroxide aqueous solution required for neutralization with the calibration line. The boron content rate of the PVA-type resin film thus obtained was used as the boron adsorption rate of the PVA-type resin film.

(4) Determination of the light sensitivity correction monomer transmittance, light sensitivity correction polarization degree and hue of the polarizing plate:

Measured using a spectrophotometer with an integrating sphere [JASCO Co., Ltd. "V7100", 2-degree viewing angle; C light source].

(Making polarizing element 1)

A polyvinyl alcohol-based resin film with a thickness of 30 μm and a boron adsorption rate of 5.71% by mass was immersed in pure water at 21.5°C for 79 seconds (swelling treatment), and then immersed in a mass ratio of potassium iodide/boric acid/water of 2/2/100 and 23°C aqueous solution containing 1.0 mM iodine for 151 seconds (staining step). Then, immerse in a 62.8° C. aqueous solution with a mass ratio of potassium iodide/boric acid/water of 2.5/4/100 for 76 seconds (the first crosslinking step). Then immerse in a 45° C. aqueous solution with a mass ratio of potassium iodide/boric acid/zinc chloride/water of 3/5.5/0.6/100 for 11 seconds (second crosslinking step, metal ion treatment step). Then, it was immersed in a cleaning bath and washed (cleaning step), and dried at 38° C. (drying step) to obtain a polarizing element having a thickness of 12 μm in which polyvinyl alcohol adsorbed and aligned iodine. The extension is mainly carried out in the steps of the dyeing step and the first cross-linking step, and the total extension ratio is 5.85 times. The zinc ion content rate of the obtained polarizing element was 0.07 mass %, and the boron content rate was 4.48 mass %.

(Making polarizing element 2)

A polyvinyl alcohol-based resin film with a thickness of 30 μm and a boron adsorption rate of 5.71% by mass was immersed in pure water at 21.5°C for 79 seconds (swelling treatment), and then immersed in a mass ratio of potassium iodide/boric acid/water of 2/2/100 and 23°C aqueous solution containing 1.0 mM iodine for 151 seconds (staining step). Then, immerse in a 62.8° C. aqueous solution with a mass ratio of potassium iodide/boric acid/water of 2.5/4/100 for 76 seconds (the first crosslinking step). Next, impregnate in potassium iodide/boric acid/chlorine The mass ratio of zinc chloride/water is 3/3.5/0.6/100 in an aqueous solution at 45° C. for 11 seconds (second cross-linking step, metal ion treatment step). Then, it was dipped in a cleaning bath and washed (cleaning step), and dried at 38° C. (drying step) to obtain a polarizing element having a thickness of 12 μm in which polyvinyl alcohol adsorbed and aligned iodine. The extension is mainly carried out in the steps of the dyeing step and the first cross-linking step, and the total extension ratio is 5.85 times. The zinc ion content rate of the obtained polarizing element was 0.14 mass %, and the boron content rate was 3.91 mass %.

(PVA solution for preparing adhesive)

Dissolve 50 g of a modified PVA-based resin containing acetyl acetyl groups (manufactured by Mitsubishi Chemical Corporation: GOHSENXZ-410) in 950 g of pure water, heat at 90°C for 2 hours, then cool to room temperature to obtain PVA for adhesives solution.

(Adhesive for modulating polarizing plate 1)

The prepared adhesive was prepared with PVA solution, pure water, and methanol in such a way that the PVA concentration was 3.0%, the methanol concentration was 35%, and the urea concentration was 0.5%, to obtain the adhesive agent 1 for polarizing plates.

(saponification of cellulose acyl compound film)

A commercially available cellulose acylate film TJ40UL (manufactured by FUJIFILM Co., Ltd.: film thickness 40 μm) was immersed in a 1.5 mol/L NaOH aqueous solution (saponified solution) maintained at 55° C. for 2 minutes, and then washed with water. Then, after immersing in a 0.05 mol/L sulfuric acid aqueous solution at 25° C. for 30 seconds, the film was further passed through a water bath under running water for 30 seconds to bring the film into a neutral state. Then, the water was drained 3 times repeatedly with an air knife to remove the water, and then it was left in a drying zone at 70° C. for 15 seconds and dried to prepare a saponified film.

(Making laminated film 1)

On both sides of the polarizing element 1, through the adhesive 1 for the polarizing plate, the saponified cellulose acyl compound film prepared above was adjusted so that the thickness of the adhesive layer after drying was 100 nm on both sides, and applied by a roller Machine fit. Then dry at 80°C for 3 minutes to obtain double-sided cellulose acylate film Polarizer 1. A protective surface film (a peelable film in which an adhesive layer was formed on one side of a polyethylene terephthalate film: thickness 57 μm) was bonded to one side of the polarizing plate 1 produced in this way.

Next, an acrylic adhesive (manufacturing company: Lintec Co., Ltd.) was applied on a release film (polyethylene terephthalate film subjected to release treatment: thickness 38 μm) to form an adhesive layer. The adhesive layer is laminated on the opposite side of the polarizing plate 1 produced above, where the surface to which the protective surface film is pasted is produced to produce a laminated film 1 with peelable protective films on both sides.

Except for changing the polarizing element 1 of the laminated film 1 to the polarizing element 2, the laminated film 2 having a peelable protective film on both sides was produced in the same manner.

(Example 1)

The laminated film 1 was cut into a rectangular size of 296.2mm×114mm [diagonal length: about 317.4mm (about 12.5 inches)] so that the long side direction was parallel to the absorption axis of the polarizer.

Thirty sheets of the cut laminated film 1 were laminated to form a laminated body. The cutting system uses an end mill with a diameter of 2mm and 2 blades. First, the end mill is moved in a direction perpendicular to the main surface of the laminate, a through hole is formed with the bottom edge of the end mill, and the end mill is arranged so as to penetrate the through hole. Then, the laminated film was cut to form holes with a straight line portion of 0.5 mm and four corners with a radius of curvature of 1 mm. The shape of the hole is composed of 4 straight parts with a length of 0.5mm and 4 curved parts with a radius of curvature of 1mm. One pair of facing straight parts in the 4 straight parts is parallel to the transmission axis of the polarizer. The other pair of facing linear parts are parallel to the absorption axis of the polarizer. At this time, the rotatable handle of the end mill is made perpendicular to the main surface of the laminated film, and the end mill is relatively moved in a direction parallel to the main surface of the laminated film, and in this case For cutting. The feed speed of the end mill was 15000 mm/min, and the rotation speed was 30000 rpm. The center position of the hole was formed at a position 47.96 mm from the long-side end and 56.92 mm from the short-side end.

(Examples 2 to 4, Comparative Examples 1 to 11)

Except having changed the kind of laminated|multilayer film and the shape of a hole part to what is shown in Table 1, it carried out hole-drilling process (cutting process) in the same manner as Example 1. Also, in Comparative Examples 1 to 3 and 8 to 10, the shape of the hole is a circle without a straight line, and the radius of curvature of the circle is shown in the column of the radius of curvature of the corners of the hole 4 in Table 1. The results are shown in Table 1.

(thermal shock test)

The polarizing plate that has been processed with holes is attached to the non-alkali glass plate through the adhesive layer. Then, 300 cycles of the thermal shock test were performed on the polarizing plate, wherein one cycle was maintained at a low temperature of -40°C for 30 minutes and at a high temperature of 85°C for 30 minutes. After the test, the polarizing plate was taken out, and the size of the crack around the hole was measured with a microscope. In the table, the case where the size of the crack is 0.0 mm means that no crack was observed after the test.

(Making laminated film 3)

Peel off the protective surface film of the laminated film 1. An acrylic adhesive (manufacturing company: Lintec Co., Ltd.) was coated on a release film (release-treated polyethylene terephthalate film: thickness 38 μm) to form an adhesive layer. The adhesive layer was bonded to the surface exposed by peeling off the protective surface film, and the laminated film 3 was produced.

(Making laminated film 4)

The laminated film 4 was produced in the same manner except that the polarizing element 1 of the laminated film 3 was changed to the polarizing element 2 .

(High temperature durability test (105°C))

The laminated films 3 and 4 produced above were cut to a size of 40 mm×40 mm, respectively. The double-sided release film was peeled off, and the surface of each adhesive layer was attached to an alkali-free glass [trade name "EAGLEXG", manufactured by Corning Incorporated] to prepare an evaluation sample. In addition, when preparing these samples, in order to adjust the water content of the polarizing element before bonding the glass plates, the optical layered body 72 was stored at a temperature of 20°C and a relative humidity of 40%. Hour. For all samples, the quality of the storage after 66 hours, 69 hours, and 72 hours has not changed. Therefore, it can be considered that each layer containing the polarizer has reached the equilibrium moisture content at a temperature of 20°C and a relative humidity of 40%.

After the evaluation sample was autoclaved at a temperature of 50°C and a pressure of 5kgf/cm ² (490.3kPa) for 1 hour, it was left to stand in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours. After measuring the initial value of the sensitivity-corrected polarization degree, the sensitivity-corrected monomer transmittance, and the hue of the polarizing plate, it was stored in a high-temperature environment at a temperature of 115°C for 48 hours. Measure the sensitivity-corrected polarization degree, the sensitivity-corrected monomer transmittance, and the hue of the polarizing plate after storage, and calculate the amount of change from the initial value.

The variation of sensitivity-corrected monomer transmittance of laminated film 3 is -1.3%, the variation of sensitivity-corrected polarization is -0.18%, and the variation of hue is 6.4NBS.

The variation of sensitivity-corrected monomer transmittance of laminated film 4 is -6.8%, the variation of sensitivity-corrected polarization is -0.50%, and the variation of hue is 15.4NBS.

[Table 1]

As shown in Table 1, although the polarizing plates obtained in Examples 1 to 4 used the polarizing element 1 with high high-temperature durability, no cracks occurred in the holes in the thermal shock test. On the other hand, the polarizing element 2 used in the polarizing plates obtained in Comparative Examples 1 to 3 had low high-temperature durability, and it was confirmed that cracks occurred in the holes in the thermal shock test. In the polarizing plates obtained in Comparative Examples 4 to 7, no cracks occurred in the holes in the thermal shock test, but the polarizing element 2 used had low high-temperature durability. In addition, in the polarizing plates obtained in Comparative Examples 8 to 11, the polarizing element 1 having high high-temperature durability was used, but it was confirmed that the holes were cracked in the thermal shock test. Therefore, according to the present invention, even if a polarizing element with high high-temperature durability is used, a polarizing plate without cracks in the hole portion in the thermal shock test can be obtained.

Claims (4)

A polarizing plate comprising a polarizing element formed by absorbing and aligning a dichroic pigment on a polyvinyl alcohol-based resin layer, and a transparent protective film, wherein, The boron adsorption rate of the polyvinyl alcohol-based resin layer is 5.70% by mass or more, The boron content of the aforementioned polarizing element is not less than 4.0% by mass and not more than 8.0% by mass, There is at least one hole in the planar plane of the polarizer, The shape of the aforementioned hole satisfies the following conditions (1a) and (1b); (1a) The shape of the aforementioned hole has two linear portions approximately parallel to the transmission axis of the aforementioned polarizer, and the length of the linear portion approximately parallel to the transmission axis of the aforementioned polarizer is 10 mm or less; (1b) The shape of the aforementioned hole has at least two curved portions, and the radius of curvature of the aforementioned curved portions is not less than 0.5 mm and less than 11 mm. A polarizing plate, wherein the shape of the hole further satisfies the following condition (1c); (1c) It further has two linear portions approximately parallel to the absorption axis of the aforementioned polarizer. The polarizing plate according to claim 1 or 2, wherein the shape of the polarizing plate in plan view is rectangular, and the length of the diagonal corners is more than 6 inches. An image display device comprising the polarizing plate according to any one of Claims 1 to 3.

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