TWI868338B - Polarizing film, optical film, and image display device - Google Patents

Abstract

A polarizing film, characterized in that it has a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer, the adhesive layer is formed by a cured layer of an adhesive composition, and the adhesive composition contains more than 25 parts by weight of monomer components having more than two polymerizable functional groups when the total amount of monomer components is 100 parts by weight, and after a humidified durability test in an environment of 65°C-95% humidity for 1000 hours, there is no bright spot originating from foreign matter more than 3mm from the end face. The polarizer preferably contains a metal component that can be converted into a divalent metal cation in water, especially zinc.

Description

Polarizing film, optical film, and image display device

Field of Invention The present invention relates to a polarizing film having a polarizing element and an adhesive layer adjacent to the polarizing element or an optical film other than the polarizing element. The polarizing film can be used alone or as an optical film laminated with the polarizing film to form an image display device such as a mobile phone, a car navigation device, a display for a personal computer, a television, etc.

Background technology Liquid crystal display devices are rapidly expanding in the market for mobile phones, car navigation devices, personal computer monitors, and televisions. Liquid crystal display devices use the switching of liquid crystals to visualize the polarization state, and use polarizers based on their display principle. In particular, in applications such as TVs, high brightness, high contrast, and wide viewing angles are increasingly required, and polarizing films are increasingly required to have high transmittance, high polarization degree, and high color reproducibility.

Due to its high transmittance and high polarization degree, the most widely used polarizer is an iodine-based polarizer, which has a structure such as iodine adsorbed on polyvinyl alcohol (hereinafter, also referred to as "PVA") and stretched. The polarizing film generally used is a transparent protective film bonded to both sides of the polarizer using a so-called water-based adhesive in which the polyvinyl alcohol-based material is dissolved in water (see Patent Document 1 below). The transparent protective film can use cellulose triacetate with high moisture permeability. When the aforementioned water-based adhesive is used (so-called wet lamination), a drying step must be performed after bonding the polarizer and the transparent protective film.

On the other hand, an active energy ray-curable adhesive has been proposed to replace the aforementioned water-based adhesive. When an active energy ray-curable adhesive is used to manufacture a polarizing film, since a drying step is not required, the productivity of the polarizing film can be improved. For example, a free radical polymerization type active energy ray-curable adhesive has been proposed, which uses an N-substituted amide monomer as a curing component (Patent Document 2 below). The adhesive layer formed using the active energy ray-curable adhesive described in Patent Document 2 can, for example, completely pass a water resistance test for evaluating the presence of discoloration and peeling after immersion in 60°C warm water for 6 hours. However, in recent years, polarizing films are not only used in mobile phones, but are also often used in image display devices for vehicle use. Compared with mobile use, vehicle use must meet durability tests under higher temperature and humidity conditions.

Prior art documents Patent documents Patent document 1: Japanese Patent Publication No. 2001-296427 Patent document 2: Japanese Patent Publication No. 2012-052000

Summary of the invention Problems that the invention aims to solve As a durability test required for polarizing films used for automotive applications, there is a humidified durability test in which the film is exposed to an environment of 65°C-95% humidity for 1000 hours. Here, the inventor of this case carefully studied the appearance of the polarizing film after the humidified durability test and found that bright spots from whitish foreign matter would appear at the ends of the polarizing film, making the product a defective product in terms of appearance characteristics. This phenomenon can only be observed after the durability test in a high temperature and high humidity environment, and it must be carefully studied again to solve it.

The present invention is developed in view of the above-mentioned facts, and its purpose is to provide a polarizing film which can suppress the generation of bright spots originating from foreign matter even after a humidification durability test and has excellent appearance characteristics.

Means for solving the problem The above problem can be solved by using the following structure. That is, the present invention relates to a polarizing film, which is characterized by: having a polarizing element and an adhesive layer adjacent to the polarizing element or an optical film other than the polarizing element, the adhesive layer is formed by a cured layer of an adhesive composition, and the adhesive composition contains more than 25 parts by weight of a monomer component having more than two polymerizable functional groups when the total amount of the monomer component is 100 parts by weight, and after a humidified durability test in an environment of 65°C-95% humidity for 1000 hours, there is no bright spot originating from foreign matter more than 3mm from the end face.

In the polarizing film, the adhesive composition preferably contains 40 parts by weight or less of a monomer component having a hydroxyl group when the total amount of the monomer component is 100 parts by weight.

In the above-mentioned polarizing film, the aforementioned polarizer preferably contains a metal component that can be converted into divalent metal cations in water.

In the polarizing film, the metal component is preferably zinc.

In the polarizing film, the polarizing film preferably has a polarizing element, and an optical film is laminated on at least one side of the polarizing element via a water-based adhesive layer, and an adhesive layer is provided on the surface of the optical film opposite to the water-based adhesive layer.

In the polarizing film, the adhesive layer is preferably formed of a cured layer of an active energy ray-curable adhesive composition.

In the polarizing film, the aforementioned adhesive layer is preferably formed by a cured layer of an adhesive composition, and when the cured product obtained by curing the adhesive composition is immersed in pure water at 23°C for 24 hours, the overall water absorption rate expressed by the following formula is less than 10% by weight: Formula: {(M2-M1)/M1}×100(%), However, M1: the weight of the cured product before immersion, M2: the weight of the cured product after immersion.

Furthermore, the present invention relates to an optical film and an image display device. The optical film is characterized by being laminated with at least one polarizing film as described above. The image display device is characterized by using a polarizing film as described above and/or an optical film as described above.

Effect of the invention Polarizing films used for automotive applications are required to have excellent appearance characteristics even after a 1000-hour humidification durability test in an environment of 65°C-95% humidity. After the humidification durability test, the polarizing film of the present invention has no bright spots originating from foreign matter more than 3 mm from the end face, and thus has excellent appearance characteristics.

In particular, the polarizing film of the present invention has excellent appearance characteristics even when it has a polarizer containing a metal component that can be converted into divalent metal cations in water, especially zinc. Although the reason for this effect is not clear, the following reasons can be inferred, for example.

In a polarizing film having a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer, metal components contained in the polarizer that can be converted into divalent metal cations in water, especially zinc, will move to the adhesive layer through vapor and condensation at the end of the polarizing film during a humidification durability test. Here, in the adhesive layer, components other than those contained in the adhesive composition constituting the raw material, such as oxalic acid, exist in an ionized state, but as long as they are not bonded with the metal component to become oxalate, oxalic acid will not be detected as a foreign matter in the adhesive layer. However, during the humidification durability test, if the specific metal components contained in the polarizer are mixed into the adhesive layer from the end, the ionized oxalic acid and the metal components will bond, so oxalate will be generated especially at the end of the adhesive layer, and it will become a white bright spot and be detected as a foreign matter. As a result, the appearance characteristics of the polarizing film will deteriorate.

In particular, the adhesive layer of the polarizing film of the present invention is formed by a cured layer of an adhesive composition, and the adhesive composition contains more than 25 parts by weight of monomer components having more than two polymerizable functional groups when the total amount of monomer components is 100 parts by weight, thereby inhibiting the bonding of ionized oxalic acid and metal components in the adhesive layer, especially at the end, and further inhibiting the migration of oxalate from the end of the polarizing film to the inside. As a result, even after the humidification durability test, the appearance characteristics of the polarizing film are still significantly improved.

The polarizing film of the present invention has a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer, and after a humidification durability test in an environment of 65°C-95% humidity for 1000 hours, there is no bright spot originating from foreign matter more than 3mm from the end face. In particular, when the polarizer of the present invention has an adhesive layer whose overall water absorption rate of the cured layer of the adhesive composition designed as the raw material is less than 10% by weight, even if the specific metal component contained in the polarizer has been mixed into the adhesive layer from the end, the bonding between the ionized oxalic acid and the metal component can be suppressed, and further, the migration of oxalate from the end of the polarizing film to the inside can be suppressed. As a result, the appearance characteristics of the polarizing film were particularly improved even after the humidification durability test.

Figure 1 shows an example of a cross-sectional schematic diagram of a polarizing film of an embodiment of the present invention. The polarizing film 10 of the embodiment has a polarizer 1 and an adhesive layer 5 adjacent to a first optical film 4 other than the polarizer 1. More specifically, it has a polarizer 1, and a first optical film (phase difference film) 4 is laminated on at least one side of the polarizer 1 through an aqueous adhesive layer 2, and an adhesive layer 5 is provided on the surface of the first optical film 4 opposite to the aqueous adhesive layer 2. In particular, the polarizing film 10 of this embodiment has a second optical film (transparent protective film) 3 laminated on one side of the polarizing element 1 through a water-based adhesive layer 2, and a first optical film (phase difference film) 4 laminated on the other side of the polarizing element 1 through a water-based adhesive layer 2, an adhesive layer 5 laminated on the first optical film (phase difference film) 4, and a third optical film (phase difference film) 6 laminated on the adhesive layer 5. The polarizing film 10 further has an adhesive layer 7 laminated on the third optical film 6, and is laminated on an image display unit through the adhesive layer 7.

FIG2 shows another example of a cross-sectional schematic diagram of a polarizing film of an embodiment of the present invention. The polarizing film 10 of the embodiment has a polarizer 1 and an adhesive layer 5 adjacent to the polarizer 1. More specifically, the polarizing film 10 of the embodiment has a second optical film (transparent protective film) 3 laminated on one side of the polarizer 1 through an aqueous adhesive layer 2, and a first optical film (phase difference film) 4 laminated on the other side of the polarizer 1 through an adhesive layer 5. The polarizing film 10 further has an adhesive layer 7 laminated on the optical film 4, and is laminated on an image display unit, etc. through the adhesive layer 7.

In the polarizing film shown in FIG. 1 and FIG. 2 , the aqueous adhesive layer 2 preferably uses an aqueous solution of an aqueous adhesive such as an isocyanate adhesive, a polyvinyl alcohol adhesive, a gelatin adhesive, a vinyl latex adhesive, or an aqueous polyester adhesive (for example, a solid component concentration of 0.5 to 60% by weight). The thickness of the aqueous adhesive layer 2 is not particularly limited, and is usually 0.01 μm to 0.5 μm after drying.

In the polarizing film 10 shown in FIG. 1 and FIG. 2 , during the humidification durability test, the metal components contained in the polarizer 1 that can be converted into divalent metal cations in water, especially zinc, will move to the adhesive layer 5 through steam or condensation at the end of the polarizing film 10. Here, in the adhesive layer 5, components other than those contained in the adhesive composition constituting the raw material, such as oxalic acid, exist in an ionized state, but as long as they are not bonded with the metal components to become oxalate, oxalic acid will not be detected as a foreign matter in the adhesive layer. Here, during the humidification durability test, if a specific metal component contained in the polarizer 10 is mixed into the adhesive layer 5, the ionized oxalic acid and the metal component will bond, thereby generating oxalate salts, which will become white bright spots and be detected as foreign matter. However, after the polarizing film 10 shown in Figures 1 and 2 was exposed to a humidification durability test in an environment of 65°C-95% humidity for 1000 hours, there was no bright spot originating from foreign matter more than 3 mm from the end surface, and preferably more than 2 mm from the end surface.

The following describes the various structures of the polarizing film of the present invention. In the present invention, the polarizing film comprises a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer.

<Polarizer> The material of the polyvinyl alcohol film used in the polarizer can be polyvinyl alcohol or its derivatives. In addition to polyvinyl formaldehyde and polyvinyl acetal, the derivatives of polyvinyl alcohol include ethylene, propylene and other alkenes, acrylic acid, methacrylic acid, crotonic acid and other unsaturated carboxylic acids and their alkyl esters, and those modified by acrylamide and the like. Polyvinyl alcohol generally uses polyvinyl alcohol with a degree of polymerization of 1000~10000 and a saponification degree of 80~100 mol%.

The polyvinyl alcohol film may also contain additives such as plasticizers. Examples of plasticizers include polyols and condensates thereof, such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethylene glycol, etc. The amount of plasticizer used is not particularly limited, but is preferably less than 20% by weight in the polyvinyl alcohol film.

When manufacturing polarizers, the polyvinyl alcohol film is dyed with iodine and stretched in at least one direction. Generally, the polyvinyl alcohol film is subjected to a series of steps including swelling, dyeing, crosslinking, stretching, washing and drying.

The swelling step can be performed, for example, by immersing the polyvinyl alcohol film in a swelling bath (water bath). This treatment can clean the dirt or anti-caking agent on the surface of the polyvinyl alcohol film, and at the same time, by swelling the polyvinyl alcohol film, uneven dyeing and other unevenness can be prevented. Glycerin or potassium iodide can also be appropriately added to the swelling bath. The temperature of the swelling bath is usually 20 to 60°C, and the immersion time in the swelling bath is usually 0.1 to 10 minutes.

The dyeing step can be performed, for example, by immersing the polyvinyl alcohol film in an iodine solution. The iodine solution is usually an iodine aqueous solution, and contains iodine and potassium iodide as a dissolution aid. The iodine concentration is usually 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. The potassium iodide concentration is usually 0.01 to 10% by weight, preferably 0.02 to 8% by weight.

In the iodine dyeing step, the temperature of the iodine solution is usually 20-50°C, preferably 25-40°C. The immersion time is usually 10-300 seconds, preferably 20-240 seconds. During the iodine dyeing treatment, in order to make the iodine content and potassium content in the polyvinyl alcohol film within the above range, it is advisable to adjust the concentration of the iodine solution, the immersion temperature and immersion time of the polyvinyl alcohol film in the iodine solution.

The crosslinking step can be carried out, for example, by immersing the iodine-dyed polyvinyl alcohol film in a treatment bath containing a crosslinking agent. Any appropriate crosslinking agent can be used as the crosslinking agent. Specific examples of the crosslinking agent include boric acid, borax and other boron compounds, glyoxal, glutaraldehyde, etc. These can be used alone or in combination. The solvent used in the solution of the crosslinking bath is generally water, and an organic solvent that is miscible with water can also be added in an appropriate amount. The crosslinking agent is usually used in a ratio of 1 to 10 parts by weight relative to 100 parts by weight of the solvent. The solution of the crosslinking bath should further contain an auxiliary agent such as iodide. The concentration of the auxiliary agent should be 0.05 to 15% by weight, and more preferably 0.5 to 8% by weight. The temperature of the crosslinking bath is usually 20-70°C, preferably 40-60°C. The immersion time in the crosslinking bath is usually 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

The stretching step is a step of stretching the polyvinyl alcohol film in at least one direction. Generally speaking, the polyvinyl alcohol film is uniaxially stretched in the conveying direction (longitudinal direction). There is no special limitation on the stretching method, and either a wet stretching method or a dry stretching method can be adopted. When the wet stretching method is adopted, the polyvinyl alcohol film is stretched to a predetermined ratio in a treatment bath. The solution of the stretching bath is preferably a solution in which various compounds required for treatment are added to a solvent such as water or an organic solvent (such as ethanol). Examples of dry stretching methods include an inter-roller stretching method, a heated roller stretching method, and a compression stretching method. When manufacturing polarizers, the stretching step can be performed at any stage. Specifically, it can be performed simultaneously with swelling, dyeing, and cross-linking, and can also be performed before or after each of these steps. Moreover, stretching can also be carried out in multiple stages. The cumulative stretching ratio of the polyvinyl alcohol film is usually more than 5 times, preferably 5 to 7 times.

In the present invention, the polarizer preferably contains a metal component that can be converted into a divalent metal cation in water, more preferably contains magnesium, calcium, copper or zinc, and particularly preferably contains zinc. By making the polarizer contain zinc, there is a tendency to suppress the decrease in transmittance and hue degradation of the polarizing film after the heating test. When the polarizer contains zinc, the zinc content in the polarizer is preferably 0.002 to 2% by weight, and more preferably 0.01 to 1% by weight.

In the present invention, the polarizer preferably contains sulfuric acid ions. By making the polarizer contain sulfuric acid ions, there is a tendency to suppress the decrease in transmittance of the polarizing film after the heating test. When the polarizer contains sulfuric acid ions, the content of sulfuric acid ions in the polarizer is preferably 0.02~0.45% by weight, preferably 0.05~0.35% by weight, and more preferably 0.1~0.25% by weight. In addition, the content of sulfuric acid ions in the polarizer can be calculated from the sulfur atom content.

In order to make the polarizer contain zinc, it is preferable to perform zinc infiltration treatment in the manufacturing step of the polarizer. In addition, in order to make the polarizer contain sulfate ions, it is preferable to perform sulfate ion treatment in the manufacturing step of the polarizer.

Zinc penetration treatment can be carried out, for example, by immersing the polyvinyl alcohol film in a zinc salt solution. The zinc salt is preferably an inorganic salt compound of an aqueous solution of zinc halides such as zinc chloride and zinc iodide, zinc sulfate, zinc acetate, etc. In addition, various zinc complexes can also be used in the zinc penetration treatment. In addition, it is more ideal to use an aqueous solution containing potassium ions and iodine ions such as potassium iodide as the zinc salt solution is easy to penetrate zinc ions. The concentration of potassium iodide in the zinc salt solution is preferably set to 0.5~10% by weight, and further to 1~8% by weight.

The sulfate ion treatment can be performed, for example, by immersing the polyvinyl alcohol film in an aqueous solution containing a metal sulfate salt. The metal sulfate salt is preferably the following: it is easy to separate into sulfate ions and metal ions in the treatment solution, and the metal sulfate salt is easy to be introduced into the polyvinyl alcohol film in an ionic state. For example, the types of metals that form the metal sulfate salt include: alkaline metals such as sodium and potassium; alkali earth metals such as magnesium and calcium; transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron.

When manufacturing polarizers, the zinc penetration treatment and sulfuric acid ion treatment can be performed at any stage. That is, the zinc penetration treatment and sulfuric acid ion treatment can be performed before the dyeing step or after the dyeing step. The zinc penetration treatment and the sulfuric acid ion treatment can also be performed simultaneously. In the present invention, it is more ideal to use zinc sulfate as the aforementioned zinc salt and the aforementioned metal sulfate, and immerse the polyvinyl alcohol-based film in a treatment bath containing zinc sulfate, whereby the zinc penetration treatment and the sulfuric acid ion treatment can be performed simultaneously. In addition, the aforementioned zinc salt or the aforementioned metal sulfate can also coexist in the dyeing solution, and the zinc penetration treatment and/or the sulfuric acid ion treatment can be performed simultaneously with the dyeing step. Zinc infiltration treatment and sulfuric acid ion treatment can also be carried out simultaneously with stretching.

During the zinc penetration treatment and sulfuric acid ion treatment, the zinc content and sulfuric acid ion content in the polarizer can be adjusted by adjusting the concentration of the zinc salt solution and the metal sulfate solution, the immersion temperature and immersion time of the polyvinyl alcohol film in the treatment bath, etc. During the zinc penetration treatment and sulfuric acid ion treatment, the temperature of the zinc salt solution and the metal sulfate solution is usually 15~85℃, preferably 25~70℃. The immersion time is usually 1~120 seconds, preferably 3~90 seconds. The concentrations of the zinc salt solution and the metal sulfate solution vary depending on the type of zinc salt or metal sulfate, but are generally 0.5-20% by weight, preferably 1-10% by weight, and more preferably 2-7% by weight. By setting the zinc salt concentration and the metal sulfate concentration within this range, the zinc content and the sulfate ion content in the polarizer can be set within the aforementioned ideal range.

The polyvinyl alcohol-based film (stretched film) that has been subjected to the above treatments can be subjected to water washing and drying steps according to common methods.

The water washing step can usually be performed by immersing the polyvinyl alcohol film in a water washing bath. The water washing bath can be pure water or an aqueous solution of iodide (such as potassium iodide, sodium iodide, etc.). The concentration of the iodide aqueous solution is preferably 0.1-10% by weight. Auxiliary agents such as zinc sulfate and zinc chloride can also be added to the iodide aqueous solution.

The water washing temperature is usually 5-50°C, preferably 10-45°C, and more preferably 15-40°C. The immersion time is usually 10-300 seconds, preferably 20-240 seconds. The water washing step can be performed only once or multiple times as needed. When multiple water washing steps are performed, the type or concentration of additives contained in the water washing bath used for each treatment can be appropriately adjusted.

The drying step of the polyvinyl alcohol film can be performed by any appropriate method (such as natural drying, air drying, and heat drying). The thickness of the polarizer after the drying step is preferably 3-20 μm.

In the present invention, the surface modification treatment of the produced polarizer can also be performed. Examples of surface modification treatment include corona treatment, plasma treatment, ITRO treatment, etc., and corona treatment is particularly preferred. By performing corona treatment, reactive functional groups such as carbonyl or amine groups are generated on the surface of the polarizer, and the adhesion with the durability enhancement layer is improved. In addition, the ashing effect can be used to remove foreign matter on the surface or reduce surface unevenness, thereby producing a polarizing film with excellent appearance characteristics.

In the present invention, the polarizing film has a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer. The polarizing film 10 shown in FIG1 has an adhesive layer adjacent to an optical film (phase difference film) 4 other than the polarizer 1. In addition, the polarizing film 10 shown in FIG2 has an adhesive layer 5 adjacent to the polarizer 1. The adhesive layer is described below.

<Adhesive layer> The adhesive layer is formed by a cured layer of an adhesive composition, and is preferably formed by a cured layer of an active energy ray curable adhesive composition such as electron ray curable, ultraviolet ray curable, and visible light curable. From the perspective of improving the appearance characteristics of the polarizing film, the thickness of the adhesive layer after drying is preferably 0.01μm~5μm, and more preferably 0.01μm~3μm. Active energy ray curable adhesive compositions can be divided into free radical polymerization curable adhesive compositions and cationic polymerization adhesive compositions. In the present invention, active energy rays in the wavelength range of 10nm to less than 380nm are marked as ultraviolet rays, and active energy rays in the wavelength range of 380nm to 800nm are marked as visible rays.

The monomer components constituting the free radical polymerization curable adhesive composition include free radical polymerizable compounds. Examples of free radical polymerizable compounds include compounds having free radical polymerizable functional groups of carbon-carbon double bonds such as (meth)acryloyl and vinyl. Such monomer components may use any of monofunctional free radical polymerizable compounds or polyfunctional free radical polymerizable compounds having two or more polymerizable functional groups. Furthermore, such free radical polymerizable compounds may be used alone or in combination of two or more. Such free radical polymerizable compounds are preferably compounds having (meth)acryloyl groups, for example. In addition, in the present invention, the so-called (meth)acryloyl group means an acryl group and/or a methacryloyl group, and hereinafter "(meth)" is synonymous.

Monofunctional free radical polymerizable compounds include, for example, (meth)acrylamide derivatives having a (meth)acrylamide group. (Meth)acrylamide derivatives are ideal in terms of ensuring adhesion to polarizers or various transparent protective films, fast polymerization speed, and excellent productivity. Specific examples of (meth)acrylamide derivatives include: N-methyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hexyl (meth)acrylamide and other N-alkyl-containing (meth)acrylamide derivatives; N-hydroxymethyl (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-hydroxymethyl-N-propyl (meth)acrylamide; (meth)acrylamide derivatives containing N-hydroxyalkyl groups such as alkyl(meth)acrylamide; (meth)acrylamide derivatives containing N-aminoalkyl groups such as aminomethyl(meth)acrylamide and aminoethyl(meth)acrylamide; (meth)acrylamide derivatives containing N-alkoxy groups such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide; (meth)acrylamide derivatives containing N-alkyl groups such as ethyl(meth)acrylamide and ethyl(meth)acrylamide. In addition, examples of heterocyclic (meth)acrylamide derivatives in which the nitrogen atom of the (meth)acrylamide group forms a heterocyclic ring include N-acryloylpiperidine, N-methylacrylpiperidine, N-acryloylpyrrolidine, and the like.

Among the aforementioned (meth)acrylamide derivatives, those containing N-hydroxyalkyl groups are preferred from the viewpoint of adhesion to polarizers or various transparent protective films. Examples of monofunctional free radical polymerizable compounds include various (meth)acrylic acid derivatives having a (meth)acryloyloxy group. Specifically, examples include alkyl (meth)acrylates (having a carbon number of 1 to 20) such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, dibutyl (meth)acrylate, tertiary butyl (meth)acrylate, n-pentyl (meth)acrylate, tertiary pentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, and n-octadecyl (meth)acrylate.

The (meth)acrylic acid derivatives include, for example, cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aryl (meth)acrylates such as benzyl (meth)acrylate; 2-isoborneol (meth)acrylate, 2-norbornenyl methyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornenyl methyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and 1,2-diisobornenyl (meth)acrylate. polycyclic (meth)acrylates such as dicyclopentenyloxyethyl (meth)acrylate and dicyclopentyl (meth)acrylate; (meth)acrylates containing alkoxy groups or phenoxy groups such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethylcarbitol (meth)acrylate, phenoxyethyl (meth)acrylate, and alkylphenoxypolyethylene glycol (meth)acrylate.

Examples of the (meth)acrylic acid derivatives include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. Or (meth)acrylates containing hydroxyl groups such as [4-(hydroxymethyl)cyclohexyl]methacrylate, cyclohexanedimethanol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate; (meth)acrylates containing epoxy groups such as glycidyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate glycidyl ether; (meth)acrylate 2,2,2-trifluoroethyl(meth)acrylate, 2,2,2-trifluoroethyl(meth)acrylate; Halogen-containing (meth)acrylates such as (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate; (meth)acrylate alkylaminoalkyl esters such as dimethylaminoethyl ester; (meth)acrylate 3-oxacyclobutane methyl ester, (meth)acrylate 3-methyl-oxacyclobutane methyl ester, (meth)acrylate (meth)acrylates containing oxygen-containing cyclobutyl groups such as 3-ethoxycyclobutyl (meth)acrylate, 3-butyloxycyclobutyl (meth)acrylate, and 3-hexyloxycyclobutyl (meth)acrylate; (meth)acrylates containing heterocyclic groups such as tetrahydrofurfuryl (meth)acrylate and butyrolactone (meth)acrylate; or (meth)acrylate adducts of hydroxytrimethylacetate, neopentyl glycol, and (meth)acrylate, and p-phenylphenol (meth)acrylate.

Examples of the monofunctional free radical polymerizable compound include carboxyl group-containing monomers such as (meth)acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

Examples of monofunctional free radical polymerizable compounds include vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; and vinyl monomers having nitrogen-containing heterocyclic rings such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperidone, vinylpyrrolidone, vinylpyrrole, vinylimidazole, vinyloxazole, and vinyloxaline.

In addition, the monofunctional free radical polymerizable compound may be a free radical polymerizable compound having an active methylene group. The free radical polymerizable compound having an active methylene group is a compound having an active double bond group such as a (meth)acryl group at the end or in the molecule and having an active methylene group. Examples of the active methylene group include acetoacetyl group, alkoxypropanoyl group, or cyanoacetyl group. The aforementioned active methylene group is preferably acetoacetyl group. Specific examples of free radical polymerizable compounds having an active methylene group include acetoacetoxyalkyl (meth)acrylates such as 2-acetoacetoxyethyl (meth)acrylate, 2-acetoacetoxypropyl (meth)acrylate, and 2-acetoacetoxy-1-methylethyl (meth)acrylate; 2-ethoxypropanoyloxyethyl (meth)acrylate, 2-cyanoacetoxyethyl (meth)acrylate, N-(2-cyanoacetoxyethyl)acrylamide, N-(2-propionylacetoxybutyl)acrylamide, N-(4-acetoacetoxymethylbenzyl)acrylamide, and N-(2-acetoacetylaminoethyl)acrylamide. The free radical polymerizable compound having an active methylene group is preferably acetoacetoxyalkyl (meth)acrylate.

In addition, examples of the polyfunctional free radical polymerizable compound having two or more polymerizable functional groups include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol diacrylate, 2-ethyl-2-butylpropylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate, bisphenol A ethylene oxide adduct di(meth)acrylate, bisphenol A propylene oxide adduct di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate. , esters of (meth)acrylic acid and polyols such as neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, cyclotrihydroxymethylpropane acetal (meth)acrylate, dialkylene glycol di(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, neopentylethol tri(meth)acrylate, neopentylethol tetra(meth)acrylate, dipentylethol penta(meth)acrylate, dipentylethol hexa(meth)acrylate, EO-modified diglycerol tetra(meth)acrylate, and 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene. Specific examples include ARONIX M-220 (manufactured by Toagosei Co., Ltd.), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd.), LIGHT ACRYLATE DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.), etc. In addition, various epoxy (meth)acrylates, urethane (meth)acrylates, polyester (meth)acrylates, or various (meth)acrylate monomers may be used as needed.

In the present invention, the polarizing film has a polarizing element and an adhesive layer adjacent to the polarizing element or an optical film other than the polarizing element. The adhesive layer is formed by a cured layer of an adhesive composition. When the cured product obtained by curing the adhesive composition is immersed in pure water at 23°C for 24 hours, the overall water absorption rate expressed by the following formula is preferably less than 10% by weight: Formula: {(M2-M1)/M1}×100(%), However, M1: the weight of the cured product before immersion, M2: the weight of the cured product after immersion. According to the above structure, even when the specific metal component contained in the polarizer has been mixed into the adhesive layer from the end, the bonding between the ionized oxalic acid and the metal component can be suppressed, and the oxalate salt moves from the end of the polarizing film to the inside. As a result, the appearance characteristics of the polarizing film are particularly improved even after the humidification durability test. The overall water absorption rate is preferably less than 8% by weight, and more preferably less than 6% by weight.

In the present invention, the polarizing film has a polarizing element and an adhesive layer adjacent to the polarizing element or an optical film other than the polarizing element, and the (carbon atoms)/(oxygen atoms + nitrogen atoms) determined based on the element ratio of the adhesive layer is preferably above 2.5. It is generally believed that the bonding of ionized oxalic acid and metal components, and further the migration of oxalate, is generated through water. Here, when the (carbon atoms)/(oxygen atoms + nitrogen atoms) determined based on the element ratio of the adhesive layer is above 2.5, water can be inhibited from invading the adhesive layer from the end, and the bonding of ionized oxalic acid and metal components in the adhesive layer, especially at the end, can be inhibited, and further the migration of oxalate from the end of the polarizing film to the inside. As a result, even after the humidification durability test, the appearance of the polarizing film was significantly improved. The method for determining the element ratio of the coating is described below.

In the present invention, the polarizing film has a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer, the adhesive layer is formed by a cured layer of an adhesive composition, and the logPow representing the octanol/water partition coefficient obtained by weighted average of the molar fraction of the monomer components contained in the adhesive composition is preferably above 1.6. It is believed that the bonding of the ionized oxalic acid and the metal component, and further the migration of the oxalate, is generally generated through water. Here, when the logPow, which is the octanol/water partition coefficient obtained by weighted average of the molar fraction of the monomer components contained in the adhesive composition, is above 1.6, water can be inhibited from invading the adhesive layer from the end, and the bonding between the ionized oxalic acid and the metal component in the adhesive layer, especially at the end, can be inhibited, and the oxalate can be further moved from the end of the polarizing film to the inside. As a result, the appearance characteristics of the polarizing film are significantly improved even after the humidification durability test.

The octanol/water partition coefficient (logPow) is an indicator of the lipophilicity of a substance, which means the logarithmic value of the octanol/water partition coefficient. A high logPow means that the substance is lipophilic, that is, it has a low water absorption rate. The logPow value can be measured (flask penetration method described in JIS-Z-7260) or calculated. In this manual, the logPow value calculated by Chem Draw Ultra manufactured by CambridgeSoft is used.

The following shows the logPow of the main free radical polymerizable compounds. Examples include hydroxyethyl acrylamide (trade name "HEAA", manufactured by Kojin Co., Ltd., LogPow: -0.56), diethyl acrylamide (trade name "DEAA", manufactured by KJ Chemical Co., Ltd., LogPow: 1.69), unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone (trade name "PLACCEL FA1DDM", manufactured by DAICEL, LogPow: 1.06), N-vinyl formamide (trade name "BEAMSET770", manufactured by Arakawa Chemicals, LogPow: -0.25), acrylamide phenoxylate (trade name "ACMO", manufactured by Kojin, LogPow: -0.20), gamma-butyrolactone acrylate (trade name "GBLA", manufactured by Osaka Organic Chemical Industry, LogPow: 0.19), acrylic acid dimer (trade name "β-CE A”, manufactured by DAICEL, LogPow; 0.2), N-vinyl pyrrolidone (trade name “NVP”, manufactured by Nippon Catalyst Co., Ltd., LogPow; 0.24), acetyl acetyloxyethyl methacrylate (trade name “AAEM”, manufactured by Nippon Synthetic Chemical Co., Ltd., LogPow; 0.27), 2-hydroxyethyl acrylate (trade name “HEA”, manufactured by Osaka Organic Chemical Industry Co., Ltd., LogPow; 0.28), glycidyl methacrylate (trade name “LIGHT ESTER G", manufactured by Kyoeisha Chemical, LogPow; 0.57), dimethyl acrylamide (trade name "DMAA", manufactured by Kojin Co., Ltd., LogPow; 0.58), tetrahydrofurfuryl alcohol acrylate polymer (trade name "VISCOAT#150D", manufactured by Osaka Organic Chemical Industry Co., Ltd., LogPow; 0.60), 4-hydroxybutyl acrylate (trade name "4-HBA", manufactured by Osaka Organic Chemical Industry Co., Ltd., LogPow; 0.68), acrylic acid (trade name "acrylic acid", manufactured by Mitsubishi Chemical Co., Ltd., LogPow; 0.69), triethylene glycol diacrylate (trade name "LIGHT ACRYLATE 3EG-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 0.72), PEG400# diacrylate (trade name "LIGHT ACRYLATE 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; -0.1), polypropylene glycol diacrylate (trade name "ARONIX M-220", manufactured by Toagosei Co., Ltd., LogPow; 1.68), dicyclopentyl acrylate (trade name "FANCRYL FA-511AS", manufactured by Hitachi Chemical Co., Ltd., LogPow; 2.26), butyl acrylate (trade name "butyl acrylate", manufactured by Mitsubishi Chemical Co., Ltd., LogPow; 2.35), 1,6-hexanediol diacrylate (trade name "LIGHT ACRYLATE 1.6HX-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 2.43), dicyclopentyl acrylate (trade name "FANCRYL FA-513AS", manufactured by Hitachi Chemical Co., Ltd., LogPow; 2.58), trihydroxymethyl-tricyclodecane diacrylate (trade name "LIGHT ACRYLATE DCP-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 3.05), isoborneol acrylate (trade name "LIGHT ACRYLATE IB-XA", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 3.27), hydroxytrimethylacetic acid neopentyl glycol acrylate adduct (trade name "LIGHT ACRYLATE HPP-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 3.35), 1,9-nonanediol diacrylate (trade name "LIGHT ACRYLATE 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 3.68), o-phenylphenol EO modified acrylate (trade name "FANCRYL FA-301A", manufactured by Hitachi Chemical, LogPow; 3.98), 2-ethylhexyloxycyclobutane (trade name "ARON OXETANE OXT-212", manufactured by Toagosei, LogPow; 4.24), bisphenol A-diepoxypropyl ether (trade name "JER828", manufactured by Mitsubishi Chemical, LogPow; 4.76), bisphenol A EO6 mole modified diacrylate (trade name "FA-326A", manufactured by Hitachi Chemical, LogPow; 4.84), bisphenol A EO4 mole modified diacrylate (trade name "FA-324A", manufactured by Hitachi Chemical, LogPow; 5.15), bisphenol A PO2 mole-modified diacrylate (trade name "FA-P320A", manufactured by Hitachi Chemical Co., Ltd., LogPow; 6.10), bisphenol A PO3 mole-modified diacrylate (trade name "FA-P323A", manufactured by Hitachi Chemical Co., Ltd., LogPow; 6.26), bisphenol A PO4 mole-modified diacrylate (trade name "FA-P324A", manufactured by Hitachi Chemical Co., Ltd., LogPow; 6.43), lauryl acrylate (trade name "LIGHT ACRYLATE L-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow; 6), isooctadecyl acrylate (trade name "ISTA", manufactured by Osaka Organic Chemical Industries, Ltd., LogPow; 7.46), etc.

Since the adhesive layer is formed by the cured material layer of the adhesive composition, and the logPow representing the octanol/water partition coefficient obtained by weighted average of the molar fraction of the monomer components contained in the adhesive composition is above 1.6, it is preferable that the monomer components have an alkyl group with a carbon number of 8 or more, and 25 parts by weight or more, when the total amount of the monomer components is 100 parts by weight. Examples of the monomer components having an alkyl group with a carbon number of 8 or more include the aforementioned dicyclopentyl acrylate (trade name "FANCRYL FA-513AS", manufactured by Hitachi Chemical Co., Ltd., LogPow: 2.58), lauryl acrylate (trade name "LIGHT ACRYLATE L-A", manufactured by Kyoeisha Chemical Co., Ltd., LogPow: 6), isooctadecyl acrylate (trade name "ISTA", manufactured by Osaka Organic Chemical Industry Co., Ltd., LogPow: 7.46), etc.

Since the adhesive layer is formed by the cured layer of the adhesive composition, and the logPow representing the octanol/water partition coefficient obtained by weighted average of the molar fractions of the monomer components contained in the adhesive composition is above 1.6, the content of the monomer component having a hydroxyl group is preferably set to 40 parts by weight or less. In addition, the monomer component having a hydroxyl group can be exemplified by the monomer component having a hydroxyl group among the above-mentioned monomer components.

In the present invention, the polarizing film has a polarizer and an adhesive layer adjacent to the polarizer or an optical film other than the polarizer. The adhesive layer is formed by a cured layer of an adhesive composition, and the adhesive composition preferably contains more than 25 parts by weight of monomer components having more than two polymerizable functional groups when the total amount of monomer components is 100 parts by weight, and more preferably contains more than 30 parts by weight. Even if oxalate has been generated in the adhesive layer, the high hardness of the adhesive layer will hinder the crystal growth of oxalate. As a result, the generation of foreign matter caused by oxalate can be suppressed, and the appearance characteristics of the polarizing film are significantly improved.

The monomer component having two or more polymerizable functional groups may be exemplified by the aforementioned multifunctional free radical polymerizable compound having two or more polymerizable functional groups. In particular, when the adhesive composition contains 25 parts by weight or more of the monomer component having two or more polymerizable functional groups based on 100 parts by weight of the total amount of the monomer component, the content of the monomer component having a hydroxyl group is preferably set to 40 parts by weight or less.

In the present invention, in addition to the radical polymerizable compound, the adhesive composition of the raw material constituting the adhesive layer of the polarizing film may also contain an acrylic oligomer polymerized from a (meth)acrylic acid monomer. By including an acrylic oligomer in the adhesive composition, the curing shrinkage when the composition is irradiated with active energy rays and cured can be reduced, and the interface stress between the adhesive layer and the adherend such as the polarizer and the optical film can be reduced. As a result, the decrease in the adhesion between the adhesive layer and the adherend can be suppressed.

In consideration of workability or uniformity during application, the active energy ray-curable adhesive should preferably have a low viscosity, and therefore, the acrylic oligomer obtained by polymerization of (meth) acrylic acid monomers should also have a low viscosity. The acrylic oligomer, which has a low viscosity and can prevent the curing shrinkage of the adhesive layer, should preferably have a weight average molecular weight (Mw) of 15,000 or less, more preferably 10,000 or less, and particularly preferably 5,000 or less. On the other hand, in order to fully suppress the curing shrinkage of the cured material layer (adhesive layer), the weight average molecular weight (Mw) of the acrylic oligomer should preferably be 500 or more, more preferably 1,000 or more, and particularly preferably 1,500 or more. The (meth)acrylic acid monomer constituting the acrylic oligomer may be specifically exemplified by methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, S-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, tripentyl (meth)acrylate, 3-pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, (meth)acrylate (carbon number 1-20) alkyl esters such as n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl-2-propylpentyl (meth)acrylate, N-octadecyl (meth)acrylate; and examples thereof include: cycloalkyl (meth)acrylates (e.g., cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, etc.); aralkyl (meth)acrylates (e.g., benzyl (meth)acrylate, etc.); polycyclic (meth)acrylates (e.g., 2-isoborneol (meth)acrylate, 2 -norbornyl methyl ester, 5-norbornyl-2-yl-methyl (meth)acrylate, 3-methyl-2-norbornyl methyl (meth)acrylate, etc.); hydroxyl-containing (meth)acrylates (e.g., hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2,3-dihydroxypropylmethyl-butyl (meth)methacrylate, etc.); alkoxy- or phenoxy-containing (meth)acrylates (2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate , ethylcarbitol (meth)acrylate, phenoxyethyl (meth)acrylate, etc.); epoxy-containing (meth)acrylates (e.g., glycidyl (meth)acrylate, etc.); halogen-containing (meth)acrylates (e.g., 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethyl ethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, etc.); alkylaminoalkyl (meth)acrylates (e.g., dimethylaminoethyl (meth)acrylate, etc.). These (meth)acrylates may be used alone or in combination of two or more. Specific examples of acrylic oligomers (E) include "ARUFON" manufactured by Toagosei Co., Ltd., "ACTFLOW" manufactured by Soken Chemical Co., Ltd., and "JONCRYL" manufactured by BASF JAPAN.

The amount of acrylic oligomer blended is usually preferably 15 parts by weight or less relative to 100 parts by weight of the total monomer components in the adhesive composition. If the content of acrylic oligomer in the composition is too high, the reaction rate will decrease dramatically when the composition is irradiated with active energy rays, and sometimes the curing may be poor. On the other hand, in order to fully suppress the curing shrinkage of the adhesive layer, the composition preferably contains 3 parts by weight or more of acrylic oligomer.

When using a free radical polymerizable compound, the photopolymerization initiator can be appropriately selected according to the active energy line. When using ultraviolet light or visible light to harden it, a photopolymerization initiator that can be decomposed by ultraviolet light or visible light can be used. Examples of the aforementioned photopolymerization initiator include diphenyl ketone compounds such as diphenyl ketone, diphenyl ketone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxydiphenyl ketone; aromatic ketone compounds such as 4-(2-hydroxyethoxy)phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α-hydroxycyclohexyl phenyl ketone; methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy Acetophenone compounds such as acetophenone, 2-methyl-1-[4-(methylthio)-phenyl]-2-oxo-1-propanone; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisole methyl ether; aromatic ketal compounds such as diphenylethylenedione dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; optically active oxime compounds such as 1-benzophenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; 9-oxysulfur , 2-chloro-9-oxysulfuron , 2-methyl 9-oxosulfuron , 2,4-dimethyl 9-oxosulfuron 、Isopropyl 9-oxysulfide , 2,4-dichloro-9-oxysulfuron , 2,4-diethyl 9-oxysulfide 、2,4-Diisopropyl 9-oxysulfide 、Dodecyl 9-oxysulfide 9-Oxysulfuron Series compounds; camphorquinone; halogenated ketone; acyl phosphine oxide; acyl phosphonate, etc.

When the total amount of the active energy ray-curable adhesive composition is 100 wt %, the amount of the photopolymerization initiator is less than 20 wt %. The amount of the photopolymerization initiator is preferably 0.01-20 wt %, more preferably 0.05-10 wt %, and further preferably 0.1-5 wt %.

When the curable adhesive for polarizing film of the present invention is a visible light curable adhesive containing a free radical polymerizable compound as a curable component, a photopolymerization initiator having high sensitivity to light of 380 nm or more is preferably used. The photopolymerization initiator having high sensitivity to light of 380 nm or more is described below.

The photopolymerization initiator is preferably a compound represented by the following general formula (1) alone:

[Chemical formula 1] (wherein, ^R1 and ^R2 represent -H, _-CH2CH3 , _-iPr or Cl, and ^R1 and ^R2 may be the same or different), or the compound represented by the general formula (1) is used in combination with a photopolymerization initiator having high sensitivity to light above 380 nm as described later. Compared with the case where a photopolymerization initiator having high sensitivity to light above 380 nm is used alone, the adhesion is excellent when the compound represented by the general formula (1 ₎ is used. Among the compounds represented by the general formula (1), diethyl 9-thiothiocyanate wherein ^R1 and ^R2 are _-CH2CH3 The composition ratio of the compound represented by the general formula (1) in the adhesive composition is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 4 parts by weight, and even more preferably 0.9 to 3 parts by weight relative to 100 parts by weight of the total amount of the curable component.

Furthermore, a polymerization initiation aid may be added as needed. Examples of the polymerization initiation aid include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, etc., and ethyl 4-dimethylaminobenzoate is particularly preferred. When a polymerization initiation aid is used, its addition amount is generally 0 to 5 parts by weight, preferably 0 to 4 parts by weight, and most preferably 0 to 3 parts by weight, relative to 100 parts by weight of the total amount of the curable component.

Furthermore, a known photopolymerization initiator may be used in combination as necessary. A transparent protective film having UV absorption capability does not transmit light below 380 nm, and therefore, a photopolymerization initiator having high sensitivity to light above 380 nm is preferably used. Specific examples include 2-methyl-1-(4-methylthiophenyl)-2-oxo-1-propanone, 2-benzyl-2-dimethylamino-1-(4-oxo-1-propanone)-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-oxo-1-propanone)-1-butanone, 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzyl)-phenylphosphine oxide, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, and the like.

In particular, in addition to the photopolymerization initiator of the general formula (1), it is more preferable to use a compound represented by the following general formula (2):

[Chemical formula 2] (In the formula, R ³ , R ⁴ and R ⁵ represent -H, -CH ₃ , -CH ₂ CH ₃ , -iPr or Cl, and R ³ , R ⁴ and R ⁵ may be the same or different.) As the compound represented by the general formula (2), 2-methyl-1-(4-methylthiophenyl)-2-N-isopropyl-1-propanone (trade name: IRGACURE 907, manufacturer: BASF) which is also a commercial product can be suitably used. In addition, 2-benzyl-2-dimethylamino-1-(4-N-thiophenylphenyl)-1-butanone (trade name: IRGACURE369, manufacturer: BASF) and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-thiophenyl)phenyl]-1-butanone (trade name: IRGACURE379, manufacturer: BASF) are more ideal because of their high sensitivity.

In the present invention, among the above-mentioned photopolymerization initiators, it is preferred to use a photopolymerization initiator containing a hydroxyl group. When the active energy ray-curable adhesive composition contains a photopolymerization initiator containing a hydroxyl group as a polymerization initiator, the solubility of the adhesive layer having a high concentration of component A on the polarizer side will be improved, and the curability of the adhesive layer will be improved. Examples of photopolymerization initiators having a hydroxyl group include: 2-methyl-2-hydroxypropiophenone (trade name "DAROCUR1173", (manufactured by BASF), 1-hydroxycyclohexyl phenyl ketone (trade name "IRGACURE184", manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (trade name "IRGACURE184", manufactured by BASF), URE2959, manufactured by BASF), 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one (trade name "IRGACURE127", manufactured by BASF), etc. 1-Hydroxycyclohexylphenyl ketone is particularly preferred because it has excellent solubility in adhesive layers with a high concentration of component A.

Cationic polymerizable compounds used in cationic polymerizable adhesive compositions can be classified into monofunctional cationic polymerizable compounds having one cationic polymerizable functional group in the molecule and polyfunctional cationic polymerizable compounds having two or more cationic polymerizable functional groups in the molecule. Monofunctional cationic polymerizable compounds have a low liquid viscosity, and therefore, by including them in a resin composition, the liquid viscosity of the resin composition can be reduced. In addition, monofunctional cationic polymerizable compounds often have functional groups that exhibit various functions. Therefore, by including them in the cationic polymerizable adhesive composition, the cationic polymerizable adhesive composition and/or the cured product of the cationic polymerizable adhesive composition can exhibit various functions. Multifunctional cationic polymerizable compounds can cause the cured product of the cationic polymerizable adhesive composition to produce three-dimensional crosslinking. Therefore, it is preferable to include them in the cationic polymerizable adhesive composition. The ratio of the monofunctional cationic polymerizable compound to the polyfunctional cationic polymerizable compound is preferably in the range of 10 parts by weight to 1000 parts by weight of the polyfunctional cationic polymerizable compound relative to 100 parts by weight of the monofunctional cationic polymerizable compound. Examples of cationic polymerizable functional groups include epoxy groups, cyclohexane groups, or vinyl ether groups. Examples of compounds having epoxy groups include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. Based on excellent curability or adhesion, the cationic polymerizable adhesive composition of the present invention preferably contains alicyclic epoxy compounds. Examples of the alicyclic epoxy compounds include 3,4-epoxyepoxyhexylmethyl-3,4-epoxyepoxyhexanecarboxylate, caprolactone-modified products of 3,4-epoxyepoxyhexylmethyl-3,4-epoxyepoxyhexanecarboxylate, trimethyl caprolactone-modified products, and valerolactone-modified products. Specifically, examples include CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, and CELLOXIDE 2085 (all manufactured by DAICEL Chemical Industries, Ltd.), CYRACURE UVR-6105, CYRACURE UVR-6107, CYRACURE 30, and R-6110 (all manufactured by Dow Chemical Japan Co., Ltd.). The compound having an oxacyclobutane group has the effect of improving the curability of the cationic polymerizable adhesive composition or reducing the liquid viscosity of the composition, and therefore it is preferable to contain it. Examples of compounds having an oxadiazole group include 3-ethyl-3-hydroxymethyloxadiazole, 1,4-bis[(3-ethyl-3-oxadiazole)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)oxadiazole, di[(3-ethyl-3-oxadiazole)methyl]ether, 3-ethyl-3-(2-ethylhexyloxymethyl)oxadiazole, phenol novolac oxadiazole, etc. Commercially available products include ARON OXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-211, ARON OXETANE OXT-221, and ARON OXETANE OXT-212 (all manufactured by Toa Gosei Co., Ltd.). Compounds having a vinyl ether group have the effect of improving the curability of the cationic polymerizable adhesive composition or reducing the liquid viscosity of the composition, and therefore are preferably contained. Examples of compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol-type tetravinyl ether, and the like.

The cationic polymerizable adhesive composition contains at least one compound selected from the above-described compounds having an epoxy group, compounds having an oxycyclobutane group, and compounds having a vinyl ether group as a curing component, and all of them are cured by cationic polymerization, so a photo-cationic polymerization initiator can be mixed. The photo-cationic polymerization initiator generates cationic species or Lewis acids by irradiation with active energy rays such as visible light, ultraviolet light, X-rays, and electron rays, and initiates the polymerization reaction of the epoxy group or the oxycyclobutane group. The photo-cationic polymerization initiator is preferably a photoacid generator described below. Furthermore, when the cationic polymerizable adhesive composition is used for visible light curing, it is preferable to use a photocationic polymerization initiator that is particularly highly sensitive to light of 380 nm or longer. However, the photocationic polymerization initiator is generally a compound that exhibits maximum absorption in the wavelength region around 300 nm or shorter. Therefore, by mixing with a photosensitizer, the photosensitizer will exhibit maximum absorption in the wavelength region longer than the wavelength, specifically, light with a wavelength longer than 380 nm, and can be sensitive to light of the nearby wavelength, thereby promoting the generation of cationic species or acid from the photocationic polymerization initiator. Examples of photosensitizers include anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreduction pigments, etc., and two or more of these compounds may be mixed for use. Anthracene compounds are particularly preferred due to their excellent photosensitizing effect. Specifically, ANTHRACURE UVS-1331 and ANTHRACURE UVS-1221 (manufactured by Kawasaki Chemical Co., Ltd.) may be used. The content of the photosensitizer is preferably 0.1% to 5% by weight, and more preferably 0.5% to 3% by weight.

<Optical film> In the present invention, the optical film of the polarizing film may be, for example, a transparent protective film or a phase difference film. In addition, not only the polarizing element but also the optical film may be subjected to surface modification treatment. Examples of surface modification treatment include corona treatment, plasma treatment, ITRO treatment, etc., and corona treatment is particularly preferred.

The material constituting the transparent protective film may be, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier, isotropy, etc. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate, polyester resins, polyether resins, polyester resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film may also contain one or more arbitrary appropriate additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, coloring agents, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50-100% by weight, preferably 50-99% by weight, more preferably 60-98% by weight, and particularly preferably 70-97% by weight. When the content of the thermoplastic resin in the transparent protective film is below 50% by weight, there is a risk that the original high transparency of the thermoplastic resin cannot be fully exhibited.

The material forming the transparent protective film should preferably have excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc., and preferably have a moisture permeability of 150 g/m ² /24h or less, more preferably 140 g/m ² /24h or less, and even more preferably 120 g/m ² /24h or less.

On the surface of the transparent protective film not in contact with the polarizer, a hard coating layer, an anti-reflection layer, an anti-adhesion layer, a diffusion layer, or even an anti-glare layer and other functional layers may be disposed. In addition, the above-mentioned hard coating layer, anti-reflection layer, anti-adhesion layer, diffusion layer, or anti-glare layer and other functional layers may be disposed on the transparent protective film itself or may be disposed separately as an entity different from the transparent protective film.

The thickness of the transparent protective film can be appropriately determined. From the perspective of strength, handling, thinness, etc., it is generally 1-500 μm, preferably 1-300 μm, more preferably 5-200 μm. In particular, 10-200 μm is preferred, and 20-80 μm is preferred.

The transparent protective film may be a retardation film having a front retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The front retardation is usually controlled within the range of 40 to 200 nm, and the thickness direction retardation is usually controlled within the range of 80 to 300 nm. When a retardation film is used as a transparent protective film, the retardation film also has the function of a transparent protective film, so that thinning can be sought.

Examples of retardation films include birefringent films made by uniaxial or biaxial stretching of polymer materials, oriented films of liquid crystal polymers, and films that support the oriented layers of liquid crystal polymers. There is no particular limit to the thickness of retardation films, which is generally 20 to 150 μm.

The phase difference film may also be a reverse wavelength dispersion type phase difference film satisfying the following formulas (1) to (3): 0.70＜Re[450]/Re[550]＜0.97…(1) 1.5×10-3＜Δn＜6×10-3…(2) 1.13＜NZ＜1.50…(3) (wherein, Re[450] and Re[550] are the in-plane phase difference values of the phase difference film measured at 23°C using light of wavelengths of 450nm and 550nm, respectively, Δn is the in-plane birefringence of nx-ny when the refractive indexes in the slow axis direction and fast axis direction of the phase difference film are nx and ny, respectively, and NZ is the ratio of the birefringence in the thickness direction of the phase difference film, nx-nz, to the in-plane birefringence, nx-ny, when nz is the refractive index in the thickness direction of the phase difference film).

The polarizing film of the present invention can be manufactured using, for example, the following manufacturing method. A method for manufacturing a polarizing film, the polarizing film having a polarizer and an adhesive layer adjacent to a first optical film other than the polarizer, the method for manufacturing the polarizing film having: a first bonding step, which connects the polarizer and the first optical film through a water-based adhesive layer; and a second bonding step, which connects the first optical film and the second optical film through the adhesive layer. The polarizer preferably contains a metal component that can be converted into a divalent metal cation in water, especially zinc. In addition, the adhesive layer is preferably formed by a hardened layer of an active energy ray-hardening adhesive composition.

Furthermore, the polarizing film of the present invention can also be manufactured using, for example, the following manufacturing method. A method for manufacturing a polarizing film, the polarizing film having a polarizing element and an adhesive layer adjacent to the polarizing element, the method for manufacturing the polarizing film having a first connecting step, the first connecting step connecting the polarizing element and the first optical film through the adhesive layer. The polarizing element preferably contains a metal component that can be converted into a divalent metal cation in water, especially zinc. Furthermore, the adhesive layer is preferably formed by a hardened layer of an active energy ray-hardening adhesive composition.

In the above-mentioned bonding step, various adhesive compositions are applied to the bonded bodies such as polarizers or optical films, and the bonded bodies such as polarizers or optical films are bonded to harden the adhesive compositions. The method of applying the adhesive composition can be appropriately selected according to the viscosity or target thickness of the adhesive composition, and examples thereof include: reverse coater, gravure coater (direct, reverse or indirect), rod reverse coater, roll coater, die coater, rod coater, rod coater, etc. The bonding of the bonded bodies such as polarizers or optical films can be performed using a roll lamination machine, etc.

The aforementioned adhesive layer is formed by a cured layer of an adhesive composition, and is particularly preferably formed by a cured layer of an active energy ray-curable adhesive composition such as electron ray-curable, ultraviolet ray-curable, and visible light-curable. In the next step, the adhesive composition is cured by irradiating active energy rays (electron rays, ultraviolet rays, visible light, etc.) to form an adhesive layer. The irradiation direction of the active energy rays (electron rays, ultraviolet rays, visible light, etc.) can be irradiated from any appropriate direction. When the polarizing film of the present invention is manufactured by a continuous production line, the production line speed varies according to the curing time of the adhesive composition, but is preferably 5~100m/min, preferably 10~50m/min, and more preferably 20~30m/min. When the production line speed is too slow, productivity will be insufficient, or the transparent protective film will be too damaged, and it will not be possible to produce a polarizing film that can withstand durability tests, etc. When the production line speed is too fast, the curing of the curable resin composition will become insufficient, and sometimes the target adhesion cannot be obtained.

When the polarizing film of the present invention is actually used, it can be made into an optical film that has been laminated with other optical layers. There is no special limitation on the optical layer. For example, one or more layers of reflective plates or semi-transmissive plates, phase difference plates (including 1/2 or 1/4 wavelength plates), viewing angle compensation films, etc. can be used to form optical layers of liquid crystal display devices. It is particularly desirable to laminate a reflective polarizing film or a semi-transmissive polarizing film on the polarizing film of the present invention, an elliptical polarizing film or a circular polarizing film on the polarizing film, a viewing angle compensation film on the polarizing film, or a polarizing film on the polarizing film.

The optical film having the above optical layer stacked on the polarizing film can also be formed by sequentially stacking the layers individually during the manufacturing process of the liquid crystal display device, etc. However, the optical film made by pre-stack has the advantages of quality stability or excellent assembly work, which can improve the manufacturing steps of the liquid crystal display device, etc. When stacking, an appropriate bonding mechanism such as an adhesive layer can be used. When the above polarizing film or other optical film is connected, the optical axis of the film can be set to a suitable configuration angle according to the target phase difference characteristics, etc.

An adhesive layer for bonding with other components such as a liquid crystal unit may also be provided on the aforementioned polarizing film or an optical film having at least one layer of polarizing film laminated thereon. There is no particular limitation on the adhesive forming the adhesive layer. For example, an adhesive having an acrylic polymer, a polysilicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer or a rubber-based polymer as a base polymer may be appropriately selected and used. In particular, an adhesive having excellent optical transparency, moderate wettability, cohesion and adhesion, and excellent weather resistance or heat resistance, such as an acrylic adhesive, is preferably used.

The adhesive layer can also be made into a superimposed layer of different compositions or types and disposed on one or both sides of the polarizing film or optical film. Furthermore, when disposed on both sides, adhesive layers of different compositions, types or thicknesses can be made on the front and back of the polarizing film or optical film. The thickness of the adhesive layer can be appropriately determined according to the purpose of use or the bonding force, and is generally 1 to 100 μm, preferably 5 to 30 μm, and particularly preferably 10 to 20 μm.

During the period until the actual use, a separating piece is temporarily attached to or covered on the exposed surface of the adhesive layer for the purpose of preventing contamination. This prevents contact with the adhesive layer under conventional handling conditions. As a separating piece, in addition to the above-mentioned thickness conditions, suitable thin sheets such as plastic films, rubber sheets, paper, cloth, non-woven fabrics, meshes, foam sheets or metal foils, laminates thereof, etc., which are coated with suitable stripping agents such as polysilicone, long-chain alkyl, fluorine or molybdenum sulfide as needed, etc., can be used, and other suitable items in accordance with previous standards.

The polarizing film or optical film of the present invention can be appropriately used in forming various devices such as liquid crystal display devices. When forming a liquid crystal display device, it can be carried out in accordance with the previous standards. That is, a liquid crystal display device is generally formed by properly assembling a liquid crystal unit with a polarizing film or optical film and a lighting system as required, and installing a driving circuit, etc. In the present invention, there is no special restriction except that the polarizing film or optical film of the present invention is used, and the previous standards can be followed. The liquid crystal unit can also use any type of liquid crystal unit such as TN type, STN type or π type.

A liquid crystal display device can be formed in which a polarizing film or an optical film is arranged on one side or both sides of a liquid crystal unit, or a liquid crystal display device using a backlight source or a reflective plate in a lighting system. In this case, the polarizing film or the optical film of the present invention can be arranged on one side or both sides of the liquid crystal unit. When the polarizing film or the optical film is arranged on both sides, they can be the same or different. Furthermore, when forming a liquid crystal display device, one or more layers of appropriate parts such as a diffusion plate, an anti-glare layer, an anti-reflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight source, etc. can be arranged at an appropriate position.

Embodiments The following describes embodiments of the present invention, but the embodiments of the present invention are not limited thereto.

<Manufacturing polarizers> A polyvinyl alcohol film with an average degree of polymerization of 2700 and a thickness of 45μm was stretched and transported while being dyed between rollers with different peripheral speed ratios. First, the polyvinyl alcohol film was immersed in a 30°C water bath for 1 minute to swell and was stretched 1.2 times in the conveying direction (first stretching). Then, it was immersed in an aqueous solution (liquid temperature 30°C) of potassium iodide (0.03% by weight) and iodine (0.3% by weight) for 1 minute to be stretched 3 times in the conveying direction (based on the unstretched film) while being dyed (second stretching). Next, the stretched film was immersed in an aqueous solution (bath) of boric acid (4% by weight), potassium iodide (5% by weight) and zinc sulfate (3.5% by weight) for 30 seconds while being stretched 6 times in the conveying direction (based on the unstretched film) (third stretching). The stretched film was dried to obtain polarizer 1. The thickness of polarizer 1 after drying was 18 μm. Polarizer 2 was obtained by the same method as polarizer 1 except that a polyvinyl alcohol film with a thickness of 30 μm was used. The thickness of polarizer 2 after drying was 12 μm.

<Active Energy Ray> Active energy rays use visible light (gallium-enclosed metal halogen lamp), irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., bulb: V bulb, peak illuminance: 1600mW/cm ² , integrated irradiation dose 1000/mJ/cm ² (wavelength 380~440nm). In addition, the illuminance of visible light is measured using the Sola-Check system manufactured by Solatell.

<Method for measuring the element ratio of the adhesive layer> The element ratio of the adhesive layer of the polarizing film is measured by the following measurement method. First, for either of the following polarizing film structures (1) and (2), an adhesive that does not constitute a polarizing film is applied to the surface of the second optical film and fixed to a metal support. Then, an ultra-thin slicer is used to remove the adhesive and the first optical film or the second optical film to expose the adhesive layer of the measurement object. Then, an Ar-GCIB etching treatment is performed, and the exposed adhesive layer after the Ar-GCIB etching treatment is pressed and fixed to the sample table with a Mo plate. Then, ESCA analysis was performed using a scanning X-ray photoelectron spectrometer (Quantum 2000, manufactured by ULVAC-PHI) and a wide-area scanning measurement was performed for qualitative analysis. Furthermore, a narrow-range detailed scanning measurement was performed for carbon, oxygen, and nitrogen to calculate the element ratio (atomic%). From the obtained carbon ratio (atomic%), oxygen ratio (atomic%), and nitrogen ratio (atomic%), (carbon atoms)/(oxygen atoms + nitrogen atoms) was calculated.

<Panel lighting test> The on-dash monitor (TKH703) manufactured by MAXWIN was disassembled and the liquid crystal panel was taken out. The polarizing film attached to the viewing side of the liquid crystal panel was peeled off and replaced with the polarizing film of each embodiment and comparative example cut into the same size as the polarizing film peeled off from the liquid crystal panel, and pasted through an adhesive layer (thickness 20μm) in a manner that the transmission axis would form the same structure as the peeled polarizing film, thereby producing a liquid crystal panel.

The LCD panel prepared in the above process was placed in an environment of 65℃95% for 1000 hours, and then placed in an environment of normal temperature and humidity for 24 hours. Then, it was reinstalled on the display frame of the disassembled LCD panel, and a black image was displayed and visually confirmed. As a result, the situation where only a black screen was displayed was set as ○, and the situation where a part of the screen caused a white display defect was set as ×.

<Third optical film> The third optical film using the following polarizing film structure (1) is manufactured using the following manufacturing method.

In an autoclave equipped with a stirrer, a cooling tube, a nitrogen inlet tube and a thermometer, 48 parts by weight of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical, trade name METOLOSE 60SH-50), 15601 parts by weight of distilled water, 8161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethoxy-3-oxocyclobutane methyl acrylate and 45 parts by weight of tertiary butyl peroxyisobutyrate as a polymerization initiator were placed, nitrogen bubbled for 1 hour, and then kept at 49°C for 24 hours while stirring to carry out free radical suspension polymerization. Then, the autoclave was cooled to room temperature, and the suspension containing the generated polymer particles was centrifuged and separated. The obtained polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure.

The prepared fumarate resin (a polymer having negative birefringence) was dissolved in a toluene-methyl ethyl ketone mixed solution (toluene/methyl ethyl ketone 50 wt%/50 wt%) to prepare a 20% solution. Furthermore, 5 parts by weight of tributyl trimellitate was added as a plasticizer to 100 parts by weight of the fumarate resin to prepare a dope.

The support film was a biaxially stretched film of polyester (polyethylene terephthalate/isophthalate copolymer) (thickness 75 μm, width 1350 mm). The tensile modulus (MD) of the support at 140°C was 800 MPa.

The support film roll is placed in the feeding part of the film forming device, and the support film is fed out and transported to the downstream side while being heated in a heating furnace. The temperature of the heating treatment is adjusted by changing the ambient gas temperature in the heating furnace. The heating time is adjusted by changing the transport speed of the support. On the support after the heat treatment, the dopant prepared in Synthesis Example A is coated to a film thickness of 6.3μm after drying, and dried at 140°C. The dried coating is rolled up together with the support to form a laminate.

The laminate was placed in the feeding section of the stretching device, and the laminate was fed out and transported to the downstream side while being subjected to free-end uniaxial stretching in a stretching furnace at a temperature of 140°C. The support was peeled off from the stretched laminate to obtain a 6μm thick phase difference film. The stretching ratio was adjusted so that the in-plane delay structure of the phase difference film after peeling off the support was 35nm.

Example 1 The next agent is an aqueous solution containing an acetylacetyl-containing polyvinyl alcohol resin (average degree of polymerization of 1200, saponification degree of 98.5 mol%, acetylacetyl degree of 5 mol%) and hydroxymethyl melamine in a weight ratio of 3:1. Using the adhesive, a second optical film (cellulose triacetate film with a hard coating (manufactured by FUJIFILM, trade name "TG40UL", film thickness 40μm)) is bonded to one side (visual recognition side) of the polarizer 1 by a roll laminator at a temperature of 30°C, and a first optical film (cycloolefin film with phase difference added (manufactured by ZEON, Japan, trade name "ZT12", film thickness 17μm)) is bonded to the other side (image display unit side surface) of the polarizer 1, and then heated and dried in an oven to obtain a laminated film with optical films laminated on both sides of the polarizer.

Next, an MCD coating machine (manufactured by Fuji Machinery Co., Ltd.) (unit shape: honeycomb, number of gravure roller lines: 1000 lines/inch, rotation speed 140%/relative production line speed) was used to apply the adhesive composition adjusted to the amount of admixture listed in Table 1 to a thickness of 1 μm on the side of the cycloolefin film with phase difference added to the laminated film prepared above, and the adhesive composition was bonded to the third optical film described above by a roller machine (film thickness 6 μm). Then, the adhesive composition was irradiated with visible light from the side of the third optical film using an active energy ray irradiation device to cure it, and then hot-dried at 70°C for 3 minutes to obtain a polarizing film (the polarizing film of this structure is referred to as "polarizing film structure (1)"). The thickness of the adhesive layer after drying was 1 μm. The lamination production line speed is 25m/min.

A sample for humidification durability test evaluation was prepared by laminating the polarizing film prepared in Example 1 to one surface of 0.7 mm thick alkali-free glass through an adhesive layer (thickness 20 μm). The sample was exposed to a humidification durability test for 1000 hours in an environment of 65°C-95% humidity. For the samples for evaluating the humidification durability test after the humidification durability test, a polarizing film for orthogonal polarizers is bonded to the other side of the alkali-free glass bonded with the polarizing film of Example 1, through an adhesive layer (thickness 20 μm), in a manner that the transmission axes of the polarizing films are perpendicular to each other. Thereafter, the samples are placed on a backlight source (with the polarizing film of Example 1 on the upper side), and the polarizing film of Example 1 is visually observed to evaluate whether bright spots originating from foreign matter are generated.

After a humidification durability test in an environment of 65°C-95% humidity for 1000 hours, it was found that the polarizing film of Example 1 had no bright spots originating from foreign matter at a distance of more than 3 mm from the end surface.

Example 4 The bonding agent is an aqueous solution containing an acetylacetyl-containing polyvinyl alcohol resin (average degree of polymerization of 1200, saponification degree of 98.5 mol%, acetylacetyl degree of 5 mol%) and hydroxymethyl melamine in a weight ratio of 3:1. Using the bonding agent, a second optical film (cellulose triacetate film with a hard coating layer (manufactured by FUJIFILM, trade name "TG40UL", film thickness 40μm)) is bonded to one side (visual side) of the polarizer 1 by a roller bonding machine at a temperature of 30°C, and then heated and dried in an oven to obtain a laminated film having an optical film laminated on one side of the polarizer.

Next, an MCD coating machine (manufactured by Fuji Machinery Co., Ltd.) (unit shape: honeycomb, number of gravure roller lines: 1000 lines/inch, rotation speed 140%/relative production line speed) was used to apply the adhesive composition adjusted to the doping amount listed in Table 1 to a thickness of 1 μm on the polarizer 1 side of the aforementioned laminated film, and then bonded to the first optical film (cycloolefin film (manufactured by ZEON Corporation of Japan, trade name "ZF14", film thickness 13 μm)) using a roller. Then, using an active energy ray irradiation device, the above-mentioned visible light was irradiated from the cycloolefin film side to cure the adhesive composition, and then hot air dried at 70°C for 3 minutes to obtain a polarizing film (the polarizing film with this structure is referred to as "polarizing film structure (2)"). After drying, the thickness of the coating is 1μm. The lamination line speed is 25m/min.

The polarizing film of Example 4 was subjected to a humidification durability test in an environment of 65° C.-95% humidity for 1000 hours, as in Example 1, and visual observation was used to observe whether bright spots originated from foreign matter were generated.

After a humidification durability test in an environment of 65°C-95% humidity for 1000 hours, it was found that the polarizing film of Example 2 had no bright spots originating from foreign matter at a distance of more than 3 mm from the end surface.

Examples 3-5, Comparative Examples 1-6 Except that the structure of the polarizing film, the admixture of the adhesive composition, and the type of polarizer are changed to those described in Table 1, the same method as in Examples 1 and 4 is used to observe whether bright spots originating from foreign matter are generated.

[Table 1]

Table 1 lists the details of each component as follows. (Monofunctional free radical polymerizable compound) ． Unsaturated fatty acid hydroxyalkyl ester modified ε-caprolactone (monomer component with hydroxyl group) (trade name "PLACCEL FA1DDM", manufactured by DAICEL, molecular weight 230.26, LogPow; 1.06) ． Acryloyl phenoxylate (trade name "ACMO", manufactured by Kojin, molecular weight 141.17, LogPow; -0.20) ． Diethylacrylamide (trade name "DEAA", manufactured by KJ Chemicals, molecular weight 127.18, LogPow; 1.69) ． Lauryl acrylate (trade name "LIGHT ACRYLATE LA", manufactured by Kyoeisha Chemicals, molecular weight 240.39, LogPow; 6) ． Isostearyl acrylate (trade name "ISTA"), manufactured by Osaka Organic Chemical Industry Co., Ltd., molecular weight 324.5, LogPow; 7.46) ． Dicyclopentyl acrylate (trade name "FANCRYL FA-513AS", manufactured by Hitachi Chemical Co., Ltd., molecular weight 206.28, LogPow; 2.58) (multifunctional free radical polymerizable compound) ． PEG400# diacrylate (trade name "LIGHT ACRYLATE 9EG-A", manufactured by Kyoeisha Chemical Co., Ltd., molecular weight 536.61, LogPow; -0.1) ． Polypropylene glycol diacrylate (trade name "ARONIX M-220", manufactured by Toagosei Co., Ltd., molecular weight 300.35, LogPow; 1.68) ． 1,9-nonanediol diacrylate (trade name "LIGHT ACRYLATE 1,9ND-A", manufactured by Kyoeisha Chemical Co., Ltd., molecular weight 268.35, LogPow; 3.68) ． Trihydroxymethyl-tricyclodecane diacrylate (trade name "LIGHT ACRYLATE DCP-A", manufactured by Kyoeisha Chemical Co., Ltd., molecular weight 304.38, LogPow; 3.05) (acrylic oligomer) ． 34/66 molar ratio copolymer of butyl acrylate and methacrylate (trade name "ARUFON UP-1190", manufactured by Toagosei Co., Ltd., molecular weight 1700, LogPow; 1.95) (initiator) ． 2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907, manufactured by IGM Resins BV, molecular weight 279.13, LogPow 2.09) ． Diethyl 9-oxythiophene (Trade name: "KAYACURE DETX-S", manufactured by Nippon Kayaku Co., Ltd., molecular weight: 268.37, LogPow: 5.12)

In Table 1, "(number of carbon atoms)/(number of oxygen atoms+number of nitrogen atoms)" is calculated based on the aforementioned "method for determining the element ratio of the adhesive layer", and respectively, "average logPow" means "logPow representing the octanol/water partition coefficient obtained by weighted average of the molar fractions of the monomer components contained in the adhesive composition", and "distance from the end face to the foreign matter (μm)" means "the distance from the end face of the polarizing film to the bright spot confirmed to originate from the foreign matter".

1: Polarizer 2: Water-based adhesive 3, 4, 6: Optical film 5: Adhesive layer 7: Adhesive layer 10: Polarizer film

FIG1 is an example of a schematic cross-sectional view of a polarizing film in an embodiment of the present invention. FIG2 is another example of a schematic cross-sectional view of a polarizing film in an embodiment of the present invention.

1: Polarizer

2: Water-based adhesive

3, 4, 6: Optical Film

5: Next is the agent layer

7: Adhesive layer

10: Polarizing film

Claims (6)

A polarizing film, characterized in that: it has a polarizer, and a first optical film is laminated on at least one side of the polarizer through a water-based adhesive layer, and an adhesive layer is provided on the surface of the first optical film opposite to the water-based adhesive layer; the polarizer contains zinc; the adhesive layer is formed by a cured layer of an adhesive composition and contains oxalic acid, and the adhesive composition contains more than 25 parts by weight of a monomer component having more than two polymerizable functional groups when the total amount of monomer components is 100 parts by weight; and after a humidified durability test in an environment of 65°C-95% humidity for 1000 hours, there is no bright spot derived from oxalate salt more than 3mm away from the end face. As in claim 1, the polarizing film, wherein the aforementioned adhesive composition contains 40 parts by weight or less of hydroxyl-containing monomer components when the total amount of monomer components is 100 parts by weight. As in claim 1 or 2, the polarizing film, wherein the adhesive layer is formed by a hardened layer of an active energy ray-hardening adhesive composition. For the polarizing film of claim 1 or 2, the aforementioned adhesive layer is formed by a cured layer of an adhesive composition, and when the cured product obtained by curing the adhesive composition is immersed in pure water at 23°C for 24 hours, the overall water absorption rate expressed by the following formula is less than 10% by weight: Formula: {(M2-M1)/M1}×100(%), except that M1: the weight of the cured product before immersion, and M2: the weight of the cured product after immersion. An optical film characterized by being laminated with at least one polarizing film as described in any one of claims 1 to 4. An image display device is characterized by using a polarizing film as described in any one of claims 1 to 4 and/or an optical film as described in claim 5.