KR102565143B1 - Polarizer, polarizing film, multilayer polarizing film, image display panel and image display device - Google Patents

Abstract

A polarizer formed of a polyvinyl alcohol-based film, wherein the polarizer contains boron and potassium, the content of the boron in the polarizer is 4% by weight or more and 6% by weight or less, and the boron content (% by weight) A polarizer in which the value multiplied by the content (% by weight) of potassium is 1.2 or more. The said polarizer is excellent in the inhibitory effect of the fall of an optical characteristic in a high-temperature environment.

Description

Polarizer, polarizing film, laminated polarizing film, image display panel, and image display device

The present invention relates to a polarizer, a polarizing film, a laminated polarizing film, an image display panel, and an image display device.

Conventionally, as polarizers used in various image display devices such as liquid crystal display devices and organic EL display devices, dyed polyvinyl alcohol-based films (containing dichroic substances) are used because they have both high transmittance and high polarization degree. there is. The said polarizer is manufactured by performing washing|cleaning process after performing each process, such as swelling, dyeing, crosslinking, and extending|stretching, for example in a bath to a polyvinyl alcohol-type film, and then drying. In addition, the said polarizer is normally used as a polarizing film (polarizing plate) to which the protective film, such as triacetyl cellulose, was bonded using the adhesive agent on one side or both surfaces.

The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as necessary, and the polarizing film or the laminated polarizing film (optical laminate) is an image display cell such as a liquid crystal cell or an organic EL element. It is bonded through an adhesive layer between transparent plates, such as a front plate and a touch panel in a visual recognition side, and is used as said various image display apparatuses.

In recent years, such various image display devices have been used as in-vehicle image display devices such as car navigation devices and back monitors in addition to mobile devices such as mobile phones and tablet terminals, and their applications are spreading. Accordingly, the polarizing film and the laminated polarizing film are required to have higher durability under a harsher environment (for example, under a high temperature environment) than has been conventionally required, and to ensure such durability. A target polarizing film has been proposed (Patent Document 1).

Japanese Patent Publication No. 2012-516468

When exposed to a high-temperature environment, the conventional polarizing film or laminated polarizing film as described above has a problem in that the polarizer is colored and the optical properties are deteriorated due to polyenization of polyvinyl alcohol. In particular, an image display device configured by bonding the above polarizing film or laminated polarizing film through an adhesive layer between an image display cell and a transparent plate has a problem in that the polarizer is significantly colored and the optical properties are significantly deteriorated.

In view of the above circumstances, an object of the present invention is to provide a polarizer excellent in the effect of suppressing the decrease in optical properties in a high-temperature environment.

Further, an object of the present invention is to provide a polarizing film, a laminated polarizing film, an image display panel, and an image display device using a polarizer excellent in the effect of suppressing the deterioration of the above-mentioned optical properties.

That is, the present invention is a polarizer formed of a polyvinyl alcohol-based film, the polarizer includes boron and potassium, the content of the boron in the polarizer is 4% by weight or more and 6% by weight or less, and the content of the boron ( weight %) and the value obtained by multiplying the potassium content (% by weight) is 1.2 or more.

Moreover, this invention relates to the polarizing film by which the transparent protective film was bonded to at least one surface of the said polarizer.

Further, the present invention relates to a laminated polarizing film in which the polarizing film is bonded to an optical layer.

Further, the present invention relates to an image display panel in which the polarizing film or the laminated polarizing film is bonded to an image display cell.

Further, the present invention relates to an image display device provided with a transparent plate on the polarizing film or laminated polarizing film side of the image display panel.

Although the details of the action mechanism of the effect in the polarizer of the present invention, the polarizing film having the polarizer, the laminated polarizing film, the image display panel, and the image display device are unknown, it is estimated as follows. However, the present invention need not be construed as being limited to this mechanism of action.

The polarizer of the present invention is formed of a polyvinyl alcohol-based film and contains boron and potassium. The content of the boron in the polarizer is 4% by weight or more and 6% by weight or less, and the value obtained by multiplying the content of the boron (% by weight) by the content (% by weight) of the potassium is 1.2 or more. Although it is known that conventional polarizers contain boron and potassium, the polarizer of the present invention can further improve heat resistance compared to conventional polarizers by containing the specific amounts of boron and potassium. In particular, it is not known that a polarizer having a value obtained by multiplying the boron content (wt%) by the potassium content (wt%) of 1.2 or more, like the polarizer of the present invention, exhibits better heat resistance than a polarizer having less than that.

When an image display device constructed by bonding a conventional polarizing film or laminated polarizing film through an adhesive layer between an image display cell and a transparent plate is exposed to a high-temperature environment, moisture contained in the polarizer or the pressure-sensitive adhesive layer is absorbed into the image display device. Since deterioration (polyenization) of polyvinyl alcohol in the polarizer is promoted by being trapped, there is a problem that the optical properties are significantly deteriorated, but when the polarizer of the present invention is used, the content of boron is higher than that of conventional polarizers, and the content of potassium is small. Therefore, polyenization as described above is suppressed in that the hydroxyl terminal of polyvinyl alcohol in the polarizer is protected (stabilized) by boric acid crosslinking, and the iodine ion serving as the counter ion in the polarizer is stabilized by the appropriate amount of potassium content. presumed to be able to

In addition, in the image display device exposed to the above high-temperature environment, there was a problem that the polarizer was cracked in addition to deterioration due to polyenization. Since the end of the polarizing film is usually covered by a bezel, the crack is allowed to have poor appearance, but in recent image display devices, from the viewpoint of design, the bezel is thinned and even bezel-less is commercialized. Therefore, it is very important in commercialization of an image display device to be able to prevent the said crack since even a slight edge part problem of a polarizing film impairs an external appearance. On the other hand, the polarizer of the present invention can exhibit the effect of preventing the occurrence of cracks as described above by adjusting the upper limit of the content of a specific amount of boron in the polarizer to 5.2% by weight or less.

In addition, when a polarizer to which a transparent protective film having a low moisture permeability (for example, a water vapor permeability of 200 g/(m 2 24 h) or less) is bonded in the image display device is used, moisture in the polarizer is difficult to transmit through the transparent protective film. Since it is difficult, it is presumed that the above polyenization is further promoted as a result of the moisture being trapped from inside the polarizer. Therefore, the light polarizer of this invention is useful especially for the embodiment in which the transparent protective film with low water permeability was bonded to the surface of at least one of the said polarizers.

<Polarizer>

The polarizer of the present invention is formed of a polyvinyl alcohol-based film, contains boron and potassium, and the content of the boron in the polarizer is 4% by weight or more and 6% by weight or less, and the content of the boron (% by weight) The value multiplied by the potassium content (% by weight) is 1.2 or more.

The polyvinyl alcohol (PVA)-based film has light transmittance in the visible ray region, and can be used without particular limitation for dispersing and adsorbing a dichroic material such as iodine or a dichroic dye. Further, the PVA-based film usually used as a raw film preferably has a thickness of about 10 to 100 μm, more preferably about 20 to 75 μm, and preferably about 100 to 5000 mm in width.

Examples of the material for the polyvinyl alcohol-based film include polyvinyl alcohol or derivatives thereof. As a derivative of the said polyvinyl alcohol, it is polyvinyl formal and polyvinyl acetal, for example; olefins such as ethylene and propylene; Unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and crotonic acid, and what modified|denatured with the alkyl ester, acrylamide, etc. are mentioned. The polyvinyl alcohol preferably has an average degree of polymerization of about 100 to 10,000, more preferably about 1,000 to 10,000, and still more preferably about 1,500 to 4,500. In addition, the polyvinyl alcohol preferably has a saponification degree of about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol%. In addition, the said average degree of polymerization and the said saponification degree can be calculated|required according to JISK6726.

The polyvinyl alcohol-based film may contain additives such as plasticizers and surfactants. As said plasticizer, polyols, such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, and polyethylene glycol, its condensate, etc. are mentioned, for example. The amount of the additive used is not particularly limited, but, for example, about 20% by weight or less of the polyvinyl alcohol-based film is suitable.

The polarizer contains boron and potassium, the content of the boron in the polarizer is 4% by weight or more and 6% by weight or less, and the value obtained by multiplying the content of the boron (% by weight) by the content (% by weight) of the potassium 1.2 or higher. In addition, when the boron content (wt%) is defined as "B" and the potassium content (wt%) is defined as "K", the boron content (wt%) is the potassium content (wt% ) can also be defined as "B×K≥1.2" when the value multiplied by 1.2 or more.

The content of the boron in the polarizer is preferably 4.0% by weight or more, more preferably 4.2% by weight or more, from the viewpoint of suppressing the deterioration of the optical properties of the polarizer in a high-temperature environment, and cracks in the polarizer in a high-temperature environment It is preferably 5.2% by weight or less, and more preferably 5.0% by weight or less, from the viewpoint of suppressing the generation of.

The content of the potassium in the polarizer is preferably 0.28% by weight or more, more preferably 0.32% by weight or more, more preferably 0.34% by weight or more, from the viewpoint of suppressing the decrease in optical properties of the polarizer in a high temperature environment, And from the viewpoint of suppressing color change in a high temperature environment, it is preferably 0.60% by weight or less, more preferably 0.55% by weight or less, and still more preferably 0.50% by weight or less.

The value obtained by multiplying the content of boron (% by weight) in the polarizer by the content (% by weight) of potassium (content of boron (% by weight) × content of potassium (% by weight)) is the optical properties of the polarizer in a high temperature environment From the viewpoint of suppressing the decrease of , it is preferably 1.2 or more, more preferably 1.3 or more, still more preferably 1.4 or more, and from the viewpoint of suppressing color change in a high-temperature environment, it is preferably 3.5 or less, and more preferably 3.0 or less. It is preferable, and it is more preferable that it is 2.5 or less.

The value obtained by dividing the boron content (wt%) in the polarizer by the potassium content (wt%) (boron content (wt%) ÷ potassium content (wt%)) is the optical properties of the polarizer in a high temperature environment It is preferably 5 or more from the viewpoint of suppressing the fall, more preferably 8 or more, still more preferably 10 or more, and from the viewpoint of improving the initial hue of the polarizer, it is preferably 30 or less, and more preferably 25 or less, , more preferably 20 or less.

<Method for manufacturing polarizer>

The said polarizer is obtained by giving the said polyvinyl alcohol-type film a dyeing process, a crosslinking process, and an extending process, and also performing at least 1 treatment process of a swelling process, a washing process, and a drying process as an arbitrary process. The boron content and the potassium content contained in the polarizer are boron such as boric acid, borate, borax, etc. It can be controlled by the concentration of a boron component-donating substance such as a compound, the concentration of a potassium component-donating substance such as potassium halide such as potassium iodide, and the treatment temperature and treatment time by each treatment bath. In particular, in the crosslinking step and the stretching step, it is easy to adjust the boron content to a desired range depending on processing conditions such as the concentration of the boron component-donating substance. In addition, in the cleaning step, components such as boron and potassium are eluted from the polyvinyl alcohol-based film or polyvinyl It is easy to adjust the content of the said boron and the said potassium content to a desired range from the viewpoint of being able to adsorb|suck to an alcohol-type film.

The swelling step is a treatment step in which the polyvinyl alcohol-based film is immersed in a swelling bath, and stains and blocking agents on the surface of the polyvinyl alcohol-based film can be removed, and dyeing stains can be eliminated by swelling the polyvinyl alcohol-based film. can be suppressed The swelling bath usually uses a medium containing water as a main component, such as water, distilled water, or pure water. Surfactant, alcohol, etc. may be suitably added to the said swelling bath according to a conventional method. Further, from the viewpoint of controlling the content of potassium in the polarizer, potassium iodide may be used in the swelling bath, and in this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by weight or less, and more preferably 1.0% by weight or less It is preferable, and it is more preferable that it is 0.5 weight% or less.

The temperature of the swelling bath is preferably about 10 to 60°C, more preferably about 15 to 45°C, and still more preferably about 18 to 30°C. In addition, the immersion time in the swelling bath cannot be collectively determined because the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, and about 10 to 200 seconds More preferably, it is more preferable that it is about 20 to 100 seconds. The said swelling process may be performed only once, and may be performed multiple times as needed.

The dyeing process is a treatment process in which a polyvinyl alcohol-based film is immersed in a dyeing bath (iodine solution), and a dichroic material such as iodine or a dichroic dye can be adsorbed and oriented on the polyvinyl alcohol-based film. The iodine solution is preferably an aqueous iodine solution, and contains iodine and iodide as a solubilizing agent. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Among these, potassium iodide is suitable from a viewpoint of controlling content of the said potassium in the said polarizer.

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

The temperature of the dyeing bath is preferably about 10 to 50 ° C, more preferably about 15 to 45 ° C, and more preferably about 18 to 30 ° C. In addition, the immersion time in the dyeing bath cannot be determined collectively because the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, but it is preferably about 10 to 300 seconds, and about 20 to 240 seconds is more preferable. The said dyeing process may be performed only once, and may be performed multiple times as needed.

The crosslinking step is a treatment step in which the polyvinyl alcohol-based film dyed by the dyeing step is immersed in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol-based film is crosslinked by the boron compound to form iodine molecules or Dye molecules can adsorb to the cross-linked structure. As said boron compound, boric acid, a borate, borax etc. are mentioned, for example. The crosslinking bath is generally an aqueous solution, but may be, for example, a mixed solution of a water-miscible organic solvent and water. Moreover, it is preferable that the said bridge|crosslinking bath contains potassium iodide from a viewpoint of controlling content of the said potassium in the said polarizer.

The concentration of the boron compound in the cross-linking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and more preferably about 2 to 5% by weight. In addition, when potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1 to 15% by weight, more preferably about 1.5 to 10% by weight, and about 2 to 5% by weight it is more preferable

The temperature of the crosslinking bath is preferably about 20 to 70°C, more preferably about 30 to 60°C. In addition, the immersion time in the cross-linking bath cannot be collectively determined because the degree of cross-linking of the polyvinyl alcohol-based film is affected by the temperature of the cross-linking bath, but it is preferably about 5 to 300 seconds, and about 10 to 200 seconds. is more preferable. The said crosslinking process may be performed only once, and may be performed multiple times as needed.

The stretching step is a treatment step of stretching the polyvinyl alcohol-based film at a predetermined magnification in at least one direction. In general, the polyvinyl alcohol-based film is uniaxially stretched in the transport direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method may be employed. The said stretching process may be performed only once, and may be performed multiple times as needed. The said extending|stretching process may be performed at any stage in manufacture of a polarizer.

As the treatment bath (stretching bath) in the above wet stretching method, a solvent such as water or an organic solvent miscible with water and a mixed solution of water can be used. It is preferable that the said stretching bath contains potassium iodide from a viewpoint of controlling content of the said potassium in the said polarizer. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by weight, more preferably about 2 to 10% by weight, and more preferably about 3 to 6% by weight. desirable. In addition, the treatment bath (stretching bath) may contain the boron compound from the viewpoint of suppressing film breakage during stretching, and in this case, the concentration of the boron compound in the stretching bath is preferably about 1 to 15% by weight , It is more preferably about 1.5 to 10% by weight, and more preferably about 2 to 5% by weight.

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

Examples of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. In addition, you may carry out the said dry stretching method together with the said drying process.

The total draw ratio (cumulative draw ratio) applied to the polyvinyl alcohol-based film can be appropriately set depending on the purpose, but it is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and 3.5 to 6.5 times. It is more desirable that the degree

The cleaning process is a treatment process in which the polyvinyl alcohol-based film is immersed in a cleaning bath, and foreign substances remaining on the surface of the polyvinyl alcohol-based film and the like can be removed. The washing bath usually uses a medium containing water as a main component, such as water, distilled water, or pure water. In addition, from the viewpoint of controlling the potassium content in the polarizer, it is preferable to use potassium iodide in the washing bath, and in this case, the concentration of potassium iodide in the washing bath is preferably about 1 to 10% by weight, and 1.5 It is more preferably about 4% by weight, more preferably about 1.8 to 3.8% by weight.

The temperature of the washing bath is preferably about 5 to 50 ° C, more preferably about 10 to 40 ° C, and even more preferably about 15 to 30 ° C. In addition, the immersion time in the washing bath cannot be collectively determined because the degree of washing of the polyvinyl alcohol-based film is affected by the temperature of the washing bath, but it is preferably about 1 to 100 seconds, and about 2 to 50 seconds. It is more preferable that it is, and it is more preferable that it is about 3 to 20 seconds. The said swelling process may be performed only once, and may be performed multiple times as needed.

The said drying process is a process of drying the polyvinyl alcohol-type film wash|cleaned by the said washing|cleaning process, and obtaining a polarizer, and the polarizer which has a desired moisture content is obtained by drying. The drying is performed by any appropriate method, and examples thereof include natural drying, air drying, and heat drying. It is preferable that the water content of the polarizer is about 8 to 25% by weight, and more preferably about 12 to 20% by weight. In addition, the water content of the polarizer is calculated by the following formula based on the initial weight of the sample cut out to a size of 100 mm x 100 mm and the dry weight after drying at 120 ° C. for 2 hours.

Moisture content (wt%) = {(initial weight - dry weight)/initial weight} × 100

It is preferable that the temperature of the said drying is about 20-150 degreeC, and it is more preferable that it is about 25-100 degreeC. In addition, the drying time is preferably about 30 to 600 seconds, more preferably about 60 to 300 seconds, although it cannot be collectively determined because the degree of drying of the polarizer is affected by the drying temperature. The said drying process may be performed only once, and may be performed multiple times as needed.

The polarizer preferably has a thickness of about 10 to 30 μm, more preferably about 12 to 20 μm.

<Polarizing film>

In the polarizing film of the present invention, a transparent protective film is bonded to at least one surface of the polarizer.

The transparent protective film is not particularly limited, and various transparent protective films conventionally used for polarizing films can be used. As a material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, water barrier properties, isotropy, etc. is used. Examples of the thermoplastic resin include cellulose ester-based resins such as triacetyl cellulose, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone-based resins, polysulfone-based resins, polycarbonate-based resins, nylon, and the like. Polyamide-based resins such as aromatic polyamides, polyimide-based resins, polyolefin-based resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic-based resins, and cyclic polyolefin-based resins having a cyclo- or norbornene structure. (norbornene-based resin), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof. In addition, the transparent protective film may use a cured layer formed of a thermosetting resin or an ultraviolet curable resin such as (meth)acrylic, urethane, acrylurethane, epoxy, or silicone. Among these, cellulose ester-type resin, polycarbonate-type resin, (meth)acrylic-type resin, cyclic polyolefin-type resin, and polyester-type resin are suitable.

The thickness of the transparent protective film can be determined appropriately, but is generally preferably about 1 to 500 μm, more preferably about 1 to 300 μm, from the viewpoint of workability such as strength and handling, and thin layer properties. It is more preferable that it is about 5-100 micrometers. In addition, the thickness of the transparent protective film is preferably about 10 to 100 μm, more preferably about 20 to 100 μm, and still more preferably about 30 to 100 μm, from the viewpoint of reducing the water vapor transmission rate of the transparent protective film. do.

The transparent protective film preferably has a moisture permeability of 800 g/(m 2 24 h) or less, more preferably 400 g/(m 2 24 h) or less, and 200 g/(m 2 24 h) or less, and even more preferably 150 g/(m 2 24 h) or less. It is preferable that the transparent protective film of one side of the said polarizer is 200 g/(m<2>*24h) or less, and it is more preferable that it is 150 g/(m<2>24h) or less. In addition, according to the moisture permeability test (cup method) of JIS Z0208, a sample cut to a diameter of 60 mm was set in a moisture permeable cup containing about 15 g of calcium chloride, and placed in a thermostat at a temperature of 40 ° C and a humidity of 90% R. H. and left for 24 hours. It can be calculated by measuring the weight increase of calcium chloride before and after.

When the transparent protective film is bonded to both surfaces of the polarizer, the transparent protective films on both surfaces may be the same or different.

The transparent protective film may use a retardation plate having a front retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The frontal retardation is usually controlled in the range of 40 to 200 nm, and the thickness direction retardation is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, since the retardation plate also functions as a transparent protective film, thinning can be achieved.

Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymeric material, an orientation film of liquid crystal polymer, and a film in which an orientation layer of liquid crystal polymer is supported. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. Alternatively, the phase plate may be bonded to a transparent protective film having no retardation before use.

The transparent protective film may be subjected to surface modification treatment. Examples of the surface modification treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

The surface of the transparent protective film to which the polarizer is not bonded may be subjected to a hard coat treatment, an antireflection treatment, a treatment for the purpose of preventing sticking, diffusion, or antiglare. In addition, hard coat treatment, anti-reflection layer, anti-sticking layer, diffusion layer, or treatment for the purpose of anti-glare can be formed on the transparent protective film itself, and can be formed as a separate optical layer separate from the transparent protective film. may be

The transparent protective film may contain any appropriate additives such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, antistatic agents, pigments and colorants.

An adhesive is usually used to bond the polarizer and the transparent protective film together. Examples of the adhesive include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex adhesives, and water-based polyesters. The adhesive is usually used as an adhesive composed of an aqueous solution, and usually contains a solid content of 0.5 to 60% by weight. Examples of the adhesive include ultraviolet curing adhesives and electron beam curing adhesives other than those described above. Further, the adhesive may contain a metal compound filler or the like.

Application of the adhesive may be applied to either the transparent protective film or the polarizer, or to both. After bonding, a drying step is performed to form an adhesive layer composed of a coating and drying layer. Bonding of the polarizer and the transparent protective film can be performed by a roll laminator or the like. After the drying process, ultraviolet rays or electron beams may be irradiated as needed. The thickness of the adhesive layer is not particularly limited, but is preferably about 30 to 5000 nm, and more preferably about 100 to 1000 nm.

<Laminate polarizing film>

In the laminated polarizing film (optical laminate) of the present invention, the polarizing film is bonded to the optical layer. Although the optical layer is not particularly limited, for example, a reflection plate, a transflective plate, a retardation plate (including a wave plate such as 1/2 or 1/4), a visual compensation film, etc. One layer or two or more layers can be used for the optical layer that may be used. As the laminated polarizing film, in particular, a reflective polarizing film or transflective polarizing film formed by further laminating a reflector or a transflective reflector on the polarizing film, an elliptically polarizing film formed by further laminating a retardation plate on the polarizing film, or a circular polarizing film, A wide viewing angle polarizing film formed by further laminating a visual compensation film on the polarizing film, or a polarizing film formed by further laminating a luminance enhancing film on the polarizing film.

On one or both surfaces of the polarizing film or the laminated polarizing film, another member such as an image display cell such as a liquid crystal cell or an organic EL element and a transparent plate such as a front transparent plate or a touch panel on the viewing side is attached. An adhesive layer for bonding may be provided. As the adhesive layer, an adhesive layer is suitable. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, those having acrylic polymers, silicone-based polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers as base polymers are appropriately selected and used. can In particular, those having excellent optical transparency, showing appropriate wettability, cohesiveness, and adhesiveness, and having excellent weather resistance and heat resistance, such as adhesives containing acrylic polymers, are preferably used.

The pressure-sensitive adhesive layer preferably has a low content of organic acid monomers such as acrylic acid. By lowering the organic acid monomer content in the pressure-sensitive adhesive layer, even when the image display device is exposed to a high-temperature environment, a decrease in transmittance due to polyenization of polyvinyl alcohol is suppressed.

The application of the pressure-sensitive adhesive layer to one side or both sides of the polarizing film or the laminated polarizing film can be performed in an appropriate manner. As the application of the pressure-sensitive adhesive layer, for example, a pressure-sensitive adhesive solution is prepared and applied directly on the polarizing film or the laminated polarizing film by an appropriate spreading method such as a casting method or a coating method, or on a separator A method of forming a pressure-sensitive adhesive layer and transferring it onto the polarizing film or the laminated polarizing film may be mentioned. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use or adhesive strength, and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm.

The exposed surface of the pressure-sensitive adhesive layer is preferably covered with a separator for the purpose of preventing contamination or the like until practical use. Thereby, contamination of the adhesive layer and the like can be prevented in the usual handling condition. As the separator, for example, a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foam sheet, metal foil, and a suitable thin film such as a laminate thereof may be selected from a silicone type, long chain alkyl type, fluorine type, molybdenum sulfide, etc. as necessary. What was coated with the suitable release agent of the , etc. are used.

<Image display panel and image display device>

In the image display panel of the present invention, the polarizing film or the laminated polarizing film is bonded to an image display cell. Moreover, the image display apparatus of this invention equips the polarizing film or laminated polarizing film side (visible side) of the said image display panel with a transparent plate.

As said image display cell, a liquid crystal cell, an organic electroluminescent cell, etc. are mentioned, for example. As the liquid crystal cell, for example, a reflection type liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, or a transflective liquid crystal cell using both external light and light from a light source. You may use it. In the case where the liquid crystal cell uses light from a light source, a polarizing film is disposed on the side opposite to the viewing side of the image display cell (liquid crystal cell) in the image display device (liquid crystal display device), and a light source is further disposed. It is preferable that the polarizing film and the liquid crystal cell on the side of the light source are bonded through an appropriate adhesive layer. As the driving method of the liquid crystal cell, for example, VA mode, IPS mode, TN mode, STN mode, band alignment (π type), etc., arbitrary types can be used.

As the organic EL cell, for example, a light emitting body (organic electroluminescent light emitting body) formed by sequentially laminating a transparent electrode, an organic light emitting layer, and a metal electrode on a transparent substrate is preferably used. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or a light emitting layer and a perylene derivative thereof. Various layer configurations, such as a laminate of electron injection layers made of or the like, or a laminate of a hole injection layer, a light emitting layer, and an electron injection layer, can be employed.

As a transparent plate arrange|positioned on the viewing side of the said image display cell, a front transparent plate (window layer), a touchscreen, etc. are mentioned, for example. As the front transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as an acrylic resin or a polycarbonate resin or a glass plate is used. As said touch panel, various touch panels, such as a resistive film method, a capacitance method, an optical method, and an ultrasonic method, a glass plate, a transparent resin board, etc. provided with a touch sensor function are used, for example. When a capacitive touch panel is used as the transparent plate, it is preferable that a front transparent plate made of glass or a transparent resin plate is installed on the viewer side more than the touch panel.

(Example)

The present invention will be described in more detail by way of examples below, but the present invention is not limited only to these examples.

<Example 1>

<Production of polarizer>

A polyvinyl alcohol film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 µm was prepared. The polyvinyl alcohol film is immersed for 30 seconds in a swelling bath (water bath) at 20°C between rolls having different circumferential speed ratios, and stretched 2.4 times in the transport direction while swelling (swelling step), followed by a dyeing bath (iodine concentration of 0.03 While dyeing by immersing for 45 seconds in an aqueous solution having a concentration of 0.3% by weight and potassium iodide by weight), the original polyvinyl alcohol film (a polyvinyl alcohol film not stretched at all in the conveying direction) is stretched 3.7 times in the conveying direction as a standard. (dyeing process). Next, the dyed polyvinyl alcohol film is immersed in a 40°C crosslinking bath (aqueous solution having a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) for 20 seconds, and the original polyvinyl alcohol film is used as a standard in the transport direction. It was stretched to 4.2 times (crosslinking process). Further, the obtained polyvinyl alcohol film was immersed in a 65°C stretching bath (aqueous solution having a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) for 50 seconds, and the original polyvinyl alcohol film was 6.0% by weight in the conveying direction as a standard. After stretching to the stomach (stretching step), it was immersed for 5 seconds in a washing bath (aqueous solution having a potassium iodide concentration of 2.5% by weight) at 18°C (washing step). The washed polyvinyl alcohol film was dried at 30°C for 2 minutes to produce a polarizer. The boron content in the polarizer determined by the following measuring method was 4.2% by weight, and the potassium content in the polarizer was 0.32% by weight. In addition, the thickness of the polarizer was 18 μm, and the moisture content of the polarizer was 16% by weight.

[Method for measuring boron content (% by weight) in polarizer]

A polarizer (about 0.2 g) dried at 120 ° C. for 2 hours was dissolved in water, and a 0.1 mol / L NaOH aqueous solution was neutralized and titrated using a burette to an aqueous solution to which a small amount of mannitol and BTB solution was added dropwise. It was calculated based on the formula.

Boron content of polarizer (% by weight) = C × V × Mw / M × 100

C: Concentration of NaOH aqueous solution (mol/L)

V: dropping amount of NaOH aqueous solution (L)

Mw: Molecular weight of boron (g/mol)

M: 120°C, weight of polarizer after drying for 2 hours (g)

[Measurement method of potassium content (wt%) in polarizer]

About the polarizer, the fluorescence X-ray intensity (kcps) of the potassium element was measured using the fluorescence X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX100E", measurement diameter: ?10 mm). On the other hand, the thickness (μm) of the polarizer was measured using a spectral film thickness meter (manufactured by PEACOCK OZAKI MFG. CO., LTD., trade name “DG-205”). Potassium content (wt%) was calculated|required using the following formula from the obtained fluorescent X-ray intensity and thickness. In addition, the following "2.99" is derived by measuring the fluorescence X-ray intensity (kcps) of a sample (for example, a PVA-based resin film to which a certain amount of KI is added) whose thickness (μm) and potassium concentration (% by weight) are known is the coefficient of the calibration curve. Potassium content (wt%) in polarizer = 2.99 × (fluorescence X-ray intensity of elemental potassium) / (thickness of polarizer)

<Production of polarizing film>

As an adhesive, an aqueous solution containing a polyvinyl alcohol resin (average degree of polymerization of 1,200, degree of saponification of 98.5 mol% and degree of acetoacetylation of 5 mol%) containing an acetoacetyl group and methylolmelamine at a weight ratio of 3:1 was used. Using this adhesive, as a second transparent protective film, a transparent protective film having a thickness of 30 µm made of (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) on one surface (image display cell side surface) of the polarizer obtained above. (Saturation absorption 0.2 g/m 2 , moisture permeability 125 g/(m 2 24 h)) (hereinafter, this film is referred to as “transparent film A”), and as a first transparent protective film, hard on the other side (visible side) A triacetyl cellulose film (water vapor transmission rate of 342 g/(m 2 24 h), manufactured by KONICA MINOLTA, INC., trade name “KC4UYW”) having a coating layer and having a thickness of 40 μm (hereinafter, this film is referred to as “transparent film B”) After bonding with a roll bonding machine, it was subsequently heat-dried in an oven (temperature: 88° C., time: 10 minutes) to produce a polarizing film in which a transparent protective film was bonded on both sides of the polarizer.

<Production of pseudo image display device>

The polarizing film obtained above is cut into a size of 150 × 50 cm so that the absorption axis of the polarizer becomes the long side, and an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm is interposed on one side of the polarizing film (the surface on the side of the transparent film A), and a glass plate ( similar image display cell) is bonded, and a separate glass plate is attached to the other side of the polarizing film (transparent film B-side side) with an acrylic acid monomer-free adhesive having a thickness of 200 μm (manufactured by NITTO DENKO CORPORATION, trade name “LUCIACS CS9868”) interposed therebetween. were bonded together to fabricate a similar image display device.

[Evaluation of optical properties in high temperature environment]

The simulated image display device obtained above was left still in a hot air oven at a temperature of 95°C for 500 hours, and the single transmittance (ΔTs) and polarization degree (ΔP) before and after injection (heating) were measured. The single transmittance and polarization degree were measured using a spectrophotometer (manufactured by MURAKAMI COLOR RESEARCH LABORATORY, product name "DOT-3"). The single transmittance is a Y value obtained by performing visibility correction with a 2-degree field of view (C light source) of JIS Z 8701-1982. In addition, the measurement wavelength is 380-700 nm (every 10 nm).

ΔTs(%)=Ts ₅₀₀ -Ts ₀

ΔP(%)=P ₅₀₀ -P ₀

Here, Ts ₀ and P ₀ are single transmittance and polarization degree before heating, and Ts ₅₀₀ and P ₅₀₀ are single transmittance and polarization degree after heating for 500 hours. The results are shown in Table 1.

The degree of polarization is the parallel transmittance (Tp) obtained when a similar image display device and a reference polarizing film (manufactured by NITTO DENKO CORPORATION, trade name "CWQ1463CU") are disposed in a state in which absorption axes are parallel to each other so that absorption axes are 90°. It is defined by the following formula by the orthogonal transmittance (Tc) obtained after making it orthogonal.

P(%)=[(Tp-Tc)/(Tp+Tc)] ^1/2 × 100

The ΔTs (%) is preferably -1.0 to 1.0, and more preferably -0.5 to 0.5. Further, the ΔP (%) is preferably -0.010 to 0.000, and more preferably -0.005 to 0.000.

[Evaluation of Appearance in High-Temperature Environment]

The simulated image display device obtained above was left still in a hot air oven at a temperature of 95°C for 500 hours, and the external appearance after being charged (heated) was visually evaluated according to the following criteria. The results are shown in Table 1.

○: There is no abnormality in appearance, or a crack of less than 100 μm is generated at the end of the polarizing film.

x: Abnormal appearance (polyenidation) exists, or a crack of 100 micrometers or more generate|occur|produces at the edge part of a polarizing film.

<Example 2>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a crosslinking bath (boric acid concentration of 3.5% by weight and potassium iodide concentration of 2.5% by weight of aqueous solution) was used in the crosslinking step, and a stretching bath (boric acid concentration of 4.5% by weight and potassium iodide concentration of 2.5% by weight) was used in the stretching step. A polarizer was produced by operation similar to Example 1 except having used (aqueous solution which is 5.0 weight%) and also having used the washing|cleaning bath (aqueous solution whose potassium iodide concentration is 1.8 weight%) in a washing|cleaning process. Boron content in the obtained polarizer was 5.2 weight%, and potassium content was 0.28 weight%. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Example 3>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a stretching bath (aqueous solution having a concentration of boric acid of 3.5% by weight and a concentration of potassium iodide of 5.0% by weight) was used in the stretching step, and a washing bath (aqueous solution having a concentration of potassium iodide of 3.0% by weight) was used in the washing step. Except having used, the polarizer was produced by operation similar to Example 1. Boron content in the obtained polarizer was 4.0 weight%, and potassium content was 0.34 weight%. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Example 4>

<Production of polarizer, polarizing film, pseudo image display device>

As a polarizer, the polarizer obtained in Example 3 was prepared. In the preparation of the polarizing film, as a second transparent protective film, a triacetyl cellulose film having a thickness of 80 µm (water vapor transmission rate of 560 g / (m 2 24 h), manufactured by KONICA MINOLTA, INC., on one side of the polarizer (surface on the image display cell side), A polarizing film and a simulated image display device were produced by the same operation as in Example 1 except that a trade name "KC8UYW") (hereinafter, this film is referred to as "transparent film C") was used.

<Example 5>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a crosslinking bath (boric acid concentration of 3.5% by weight and potassium iodide concentration of 2.5% by weight aqueous solution) was used in the crosslinking step, and a stretching bath (boric acid concentration of 5.0% by weight and potassium iodide concentration of 2.5% by weight) was used in the stretching step. A polarizer was produced by operation similar to Example 1 except having used (aqueous solution which is 5.0 weight%) and also having used the washing|cleaning bath (aqueous solution whose potassium iodide concentration is 1.8 weight%) in a washing|cleaning process. The boron content in the obtained polarizer was 5.3% by weight, and the potassium content was 0.28% by weight. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Comparative Example 1>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a crosslinking bath (an aqueous solution having a concentration of boric acid of 2.5% by weight and a concentration of potassium iodide of 2.5% by weight) was used in the crosslinking step, and a drawing bath (a concentration of boric acid of 3.0% by weight and a potassium iodide concentration of 2.5% by weight) was used in the stretching step. 5.0% by weight aqueous solution) was used, and a polarizer was produced by operation similar to Example 1 except that a washing bath (aqueous solution having a potassium iodide concentration of 4.0% by weight) was used in the washing step. The boron content in the obtained polarizer was 3.9% by weight, and the potassium content was 0.36% by weight. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Comparative Example 2>

<Production of polarizer, polarizing film, pseudo image display device>

A polarizer was produced by operation similar to Example 1 except having used the washing|cleaning bath (aqueous solution whose potassium iodide concentration is 1.3 weight%) in the washing|cleaning process in preparation of a polarizer. The boron content in the obtained polarizer was 4.1% by weight, and the potassium content was 0.27% by weight. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Comparative Example 3>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a stretching bath (aqueous solution having a concentration of boric acid of 3.5% by weight and a potassium iodide concentration of 5.0% by weight) was used in the stretching step, and a washing bath (aqueous solution having a potassium iodide concentration of 1.5% by weight) was used in the washing step. Except having used, the polarizer was produced by operation similar to Example 1. The boron content in the obtained polarizer was 4.0% by weight, and the potassium content was 0.28% by weight. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

<Comparative Example 4>

<Production of polarizer, polarizing film, pseudo image display device>

In the production of the polarizer, a crosslinking bath (aqueous solution having a concentration of boric acid of 1.5% by weight and a concentration of potassium iodide of 2.5% by weight) was used in the crosslinking step, and a drawing bath (a concentration of boric acid of 1.5% by weight and a potassium iodide concentration of 2.5% by weight) was used in the stretching step. A polarizer was produced by the same operation as in Example 1, except that a 5.0% by weight aqueous solution) was used and a washing bath (aqueous solution having a potassium iodide concentration of 10.0% by weight) was used in the washing step. The boron content in the obtained polarizer was 2.4% by weight, and the potassium content was 0.65% by weight. Furthermore, a polarizing film and a simulated image display device were produced by the same operation as in Example 1 using the obtained polarizer.

Using the similar image display devices of Examples 2 to 5 and Comparative Examples 1 to 4 obtained above, evaluation in the above [Evaluation of optical properties in high temperature environment] and [Evaluation of appearance in high temperature environment] did The results are shown in Table 1.

Claims (7)

As a polarizer formed of a polyvinyl alcohol-based film,
The polarizer includes boron and potassium,
The content of boron in the polarizer is 4% by weight or more and 5.2% by weight or less, the content of potassium is 0.32% by weight or more, and the value obtained by dividing the content of boron (% by weight) by the content (% by weight) of potassium It is 8 or more and 20 or less, and the value obtained by multiplying the content (% by weight) of the boron by the content (% by weight) of the potassium is 1.2 or more, the polarizer characterized by the above-mentioned. A polarizing film characterized in that a transparent protective film is bonded to at least one surface of the polarizer according to claim 1. According to claim 2,
The polarizing film, characterized in that the transparent protective film has a moisture permeability of 200 g / (m 2 24 h) or less. A laminated polarizing film characterized in that the polarizing film according to claim 2 is bonded to an optical layer. An image display panel characterized in that the polarizing film according to claim 2 or 3 or the laminated polarizing film according to claim 4 is bonded to an image display cell. An image display device comprising a transparent plate on the side of the polarizing film or laminated polarizing film of the image display panel according to claim 5. delete