CN-114096900-B - Polarizing film, laminated polarizing film, image display panel, and image display device

Abstract

A polarizing film is provided, wherein transparent protective films are bonded to both surfaces of a polarizing film, wherein the polarizing film is formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, wherein the iodine concentration is 6 wt% or more, wherein the moisture permeability of at least one of the transparent protective films is 200 g/(m 2 -24 h) or less, and wherein the polarizing film satisfies the condition that the amount of change in the transmittance of a monomer represented by the general formula (1): ΔTs (%) = Ts 750 －Ts 0 (ΔTs) is 0% or more and 5% or less. The polarizing film has a good initial polarization degree, and also has an excellent effect of suppressing a decrease in the transmittance of the monomer due to the coloring of the polarizing film in a high-temperature environment, and further has an excellent effect of suppressing a decrease in the polarization degree in a high-temperature and high-humidity environment (humidification durability).

Inventors

• Komoda Takuo
• YAMASHITA TOMOHIRO

Assignees

• 日东电工株式会社

Dates

Publication Date

20260508

Application Date

20200825

Priority Date

20190828

Claims (8)

1. 1. A polarizing film is provided, wherein transparent protective films are bonded to both sides of the polarizing film, The polarizing film is formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, and has an iodine concentration of 6 wt% or more, The polarizing film contains a compound having a radical trapping function and/or contains more than 2 wt% of chloride ions, At least one of the transparent protective films has a moisture permeability of 200 g/(m 2 -24 h) or less, The polarizing film satisfies a condition that the amount of change in the transmittance of a monomer (DeltaTs) represented by the general formula (1) DeltaTs (%) = Ts 750 －Ts 0 % is 0% to 5%, In the general formula (1), ts 0 represents the single body transmittance of a laminate in which a glass plate is bonded to one surface of the polarizing film via an adhesive layer, and Ts 750 represents the single body transmittance after the laminate is heat-treated at 95 ℃ for 750 hours.
2. 2. The polarizing film of claim 1, wherein, The thickness of the polarizing film is 15 μm or less.
3. 3. The polarizing film according to claim 1 or 2, wherein, The compound having a radical trapping function is a compound having a nitroxyl radical or a nitroxyl radical.
4. 4. The polarizing film according to claim 1 or 2, which has a degree of polarization of 99.98% or more.
5. 5. A laminated polarizing film, wherein, The polarizing film according to any one of claims 1 to 4, which is bonded to an optical layer.
6. 6. An image display panel having an image display unit to which the polarizing film according to any one of claims 1 to 4 or the laminated polarizing film according to claim 5 is attached.
7. 7. An image display device comprising a front surface transparent member on the polarizing film or laminated polarizing film side of the image display panel according to claim 6.
8. 8. The image display device according to claim 7, which is an in-vehicle image display device.

Description

Polarizing film, laminated polarizing film, image display panel, and image display device Technical Field The invention relates to a polarizing film, a laminated polarizing film, an image display panel, and an image display device. Background Conventionally, as a polarizing film used for various image display devices such as a liquid crystal display device and an organic EL display device, a polyvinyl alcohol film (containing a dichroic substance such as iodine or a dichroic dye) which has been subjected to a dyeing treatment has been used in view of having both a high transmittance and a high polarization degree. The polarizing film is produced by subjecting a polyvinyl alcohol film to various treatments such as swelling, dyeing, crosslinking, stretching, etc., in a bath, then subjecting the film to a washing treatment, and then drying the film. The polarizing film is generally used in the form of a polarizing film (polarizing plate) having a protective film such as cellulose triacetate attached to one or both surfaces thereof by an adhesive. The polarizing film is used in the form of a laminated polarizing film (optical laminate) in which other optical layers are laminated as necessary, and the polarizing film or the laminated polarizing film (optical laminate) is laminated between an image display unit such as a liquid crystal cell or an organic EL element and a front surface transparent plate (window layer) on the visible side or a front surface transparent member such as a touch panel via an adhesive layer or an adhesive layer to manufacture the various image display devices (patent document 1). In recent years, such various image display devices are used as image display devices for vehicles such as car navigation devices and rear view monitors, in addition to mobile devices such as mobile phones and tablet terminals, and their uses are expanding. Accordingly, there has been proposed an image display device which is required to have high durability in a severe environment (for example, a high-temperature environment) as compared with conventional requirements, and which is aimed at securing such durability (patent document 2). Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2014-102353 Patent document 2 Japanese patent application laid-open No. 2018-101117 Disclosure of Invention Problems to be solved by the invention When a polarizing film or a laminated polarizing film using an iodine-based polarizing film is exposed to a high-temperature environment, polyvinyl alcohol constituting the polarizing film becomes multi-functionalized by a dehydration reaction, and thus the polarizing film is colored, which has a problem that the transmittance of a monomer thereof is lowered. As a result of intensive studies, the present inventors have found that iodine contained in an iodine-based polarizing film promotes multiolefination in a high-temperature environment. Thus, in order to suppress the decrease in the transmittance of the monomer due to the coloration of the polarizing film in a high-temperature environment, it is effective to reduce the iodine concentration (content) in the polarizing film. On the other hand, it is difficult to obtain a polarizing film having a good degree of polarization and a high iodine concentration. In addition, in a high-temperature and high-humidity environment, the polarizing film and the laminated polarizing film have a problem in that the degree of polarization is lowered due to the removal of boric acid crosslinking in the polarizing film and the destruction of the iodine complex. In view of the above, an object of the present invention is to provide a polarizing film having a polarizing film with a high iodine concentration, which has a good initial polarization degree, has an excellent effect of suppressing a decrease in the transmittance of a monomer due to coloring of the polarizing film in a high-temperature environment, and has an excellent effect of suppressing a decrease in the polarization degree in a high-temperature and high-humidity environment (humidification durability). Another object of the present invention is to provide a laminated polarizing film, an image display panel, and an image display device using the polarizing film. Means for solving the problems Specifically, the present invention relates to a polarizing film in which transparent protective films are laminated on both surfaces of a polarizing film, wherein the polarizing film is formed by adsorbing iodine to a polyvinyl alcohol film and orienting the film, and the iodine concentration is 6% by weight or more, and the moisture permeability of at least one of the transparent protective films is 200 g/(m 2 -24 h) or less, and wherein the polarizing film satisfies the condition that the amount of change in the monomer transmittance (ΔTs) represented by the formula (1) is equal to or more than 0% and equal to or less than 5% as represented by ΔTs (%)