CN111919149A - Polarizer, polarizing film, laminated polarizing film, image display panel and image display device - Google Patents

Abstract

A polarizer, which is formed of a polyvinyl alcohol-based film, the polarizer contains boron and potassium, in the polarizer, the content of the boron is more than 4% by weight and less than 6% by weight, and the content of the boron (% by weight) ) multiplied by the aforementioned potassium content (% by weight) is 1.2 or more. This polarizer is excellent in the effect of suppressing the degradation of optical properties in a high temperature environment.

Description

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

technical field

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

Background technique

Conventionally, as polarizers used in various image display devices such as liquid crystal display devices and organic EL display devices, dyed polyethylene (containing a dichroic substance) has been used because it has both high transmittance and high degree of polarization. Alcohol based film. This polarizer is manufactured by subjecting a polyvinyl alcohol-based film to various processes such as swelling, dyeing, cross-linking, and stretching in a bath, followed by washing and drying. In addition, the polarizer is generally used as a polarizing film (polarizing plate) in which a protective film such as cellulose triacetate is bonded to one side or both sides using an adhesive.

The polarizing film is used by laminating other optical layers as necessary, and the polarizing film (optical laminate) is laminated, and the polarizing film or the laminated polarizing film (optical laminate) is bonded to a liquid crystal cell, an organic Between an image display unit such as an EL element and a transparent plate such as a front panel and a touch panel on the visual recognition side, it is used as the above-mentioned various image display devices.

In recent years, such various image display apparatuses have been widely used as in-vehicle image display apparatuses such as in-vehicle navigation apparatuses and back monitors, in addition to mobile devices such as mobile phones and tablet terminals. Accordingly, the polarizing film and the laminated polarizing film are required to have high durability in a severer environment (for example, in a high-temperature environment) than those required in the past, and polarized light for the purpose of ensuring such durability has been proposed. thin film (Patent Document 1).

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Publication No. 2012-516468

SUMMARY OF THE INVENTION

Invention to solve problem

The above-described conventional polarizing films and laminated polarizing films have the following problems: when exposed to a high-temperature environment, polyvinyl alcohol is polyalkylated, whereby the polarizer is colored and the optical properties thereof are degraded. In particular, an image display device constructed by laminating the above-mentioned polarizing film between an image display unit and a transparent plate via an adhesive layer, or laminating the polarizing film, has problems in that the coloring of the polarizer is remarkable, and the optical properties thereof are significantly degraded.

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

Another 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 having an excellent effect of suppressing the above-mentioned reduction in optical properties.

solution to the problem

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

In addition, the present invention relates to a polarizing film in which a transparent protective film is attached to at least one side of the polarizer.

In addition, the present invention relates to a laminated polarizing film in which the above-mentioned polarizing film is bonded to an optical layer.

In addition, the present invention relates to an image display panel in which the above-mentioned polarizing film or the above-mentioned laminated polarizing film is bonded to an image display unit.

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

effect of invention

The details of the mechanism of action of the polarizer, polarizing film having the polarizer, laminated polarizing film, image display panel, and image display device of the present invention are unclear, but are presumed as follows. However, the present invention is not to be construed limitedly by this mechanism of action.

The polarizer of the present invention is formed of a polyvinyl alcohol-based film, and contains boron and potassium. In the polarizer, the boron content is 4 wt % or more and 6 wt % or less, and a value obtained by multiplying the boron content (wt %) by the potassium content (wt %) is 1.2 or more. It is known that the conventional polarizer contains boron and potassium, but the polarizer of the present invention can further improve heat resistance compared with the conventional polarizer by including the above-mentioned specific amounts of boron and potassium. In particular, as in the polarizer of the present invention, a polarizer having a value obtained by multiplying the content of boron (% by weight) by the content of potassium (% by weight) of 1.2 or more exhibits superior performance compared to a polarizer less than the above-mentioned value. Heat resistance, this is not known.

Conventionally, an image display device constructed by bonding a polarizing film or a laminated polarizing film between an image display unit and a transparent plate via an adhesive layer has the following problems: when exposed to a high-temperature environment, the polarizer, adhesive Moisture and the like contained in the mixture layer and the like are trapped in the image display device, and as a result, the deterioration (polyolefinization) of the polyvinyl alcohol in the polarizer is accelerated, and therefore the optical properties are significantly reduced. In the polarizer of the invention, since the content of boron is high and the content of potassium is small compared with the conventional polarizer, the hydroxyl end of the polyvinyl alcohol in the polarizer is protected (stabilized) by the cross-linking of boric acid. An appropriate potassium content stabilizes the iodide ion as a counter ion in the polarizer, and it is presumed that the above-described polyolefination can be suppressed.

In addition, in the image display device exposed to the high temperature environment as described above, in addition to the deterioration of the polarizer due to polyolefinization, there is a problem that cracks occur in the polarizer. As for this crack, the edge of the polarizing film is usually covered by the frame, so the appearance of the edge is permissible. However, in recent image display devices, from the viewpoint of design, the frame is being thinned and even manufactured. For borderless type. Therefore, even a slight edge defect of the polarizing film impairs the appearance, and it is therefore important to prevent such cracks for the production of image display devices. On the other hand, in the polarizer of the present invention, by adjusting the upper limit of the content of the specific amount of boron in the polarizer to 5.2 wt % or less, it is possible to exhibit the effect of preventing the occurrence of cracks as described above.

Furthermore, when a polarizer to which a transparent protective film having a low moisture permeability (for example, a moisture permeability of 200 g/(m ² ·24h) or less) is attached is used in the above-described image display device, due to the Since it is difficult for moisture to permeate through the transparent protective film, the moisture is trapped in the polarizer, and as a result, it is presumed that the above-described polyolefinization is further promoted. Therefore, the polarizer of the present invention is particularly useful for a method in which a transparent protective film with low moisture permeability is bonded to at least one surface of the polarizer.

Detailed ways

<Polarizer>

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

As the polyvinyl alcohol (PVA)-based film, a film having light transmittance in the visible light region and having a dichroic substance such as iodine and a dichroic dye dispersed and adsorbed can be used without particular limitation. In addition, generally, the thickness of the PVA-based film used as a blank is preferably about 10 to 100 μm, more preferably about 20 to 75 μm, and the width is preferably about 100 to 5000 mm.

As a material of the said polyvinyl alcohol-type film, polyvinyl alcohol or its derivative(s) can be mentioned. Examples of derivatives of the polyvinyl alcohol include polyvinyl formal and polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; and alkanes thereof. base esters, acrylamides, etc. are modified. The average degree of polymerization of the polyvinyl alcohol is preferably about 100 to 10,000, more preferably about 1,000 to 10,000, still more preferably about 1,500 to 4,500. Moreover, it is preferable that the saponification degree of the said polyvinyl alcohol is about 80-100 mol%, and it is more preferable that it is about 95-99.95 mol%. In addition, the said average degree of polymerization and the said saponification degree can be calculated|required based on JISK6726.

Additives, such as a plasticizer and surfactant, may be contained in the said polyvinyl alcohol-type film. As said plasticizer, polyhydric alcohols, such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethylene glycol, and its condensate, etc. are mentioned, for example. The usage-amount of the said additive is not specifically limited, For example, in a polyvinyl alcohol-type film, about 20 weight% or less is suitable.

The polarizer includes boron and potassium. In the polarizer, the content of the boron is 4 wt % or more and 6 wt % or less, and the value obtained by multiplying the boron content (wt %) by the potassium content (wt %) is 1.2 or more. In addition, when the content (wt%) of the aforementioned boron is defined as “B” and the content (wt%) of the aforementioned potassium is defined as “K”, the content (wt%) of the aforementioned boron is multiplied by the aforementioned potassium The obtained value of the content (% by weight) of 1.2 or more can also be defined as “B×K≧1.2”.

In the polarizer, the content of boron is preferably 4.0 wt % or more, more preferably 4.2 wt % or more, from the viewpoint of suppressing degradation of the optical properties of the polarizer in a high temperature environment, and is From the viewpoint of the occurrence of cracks in the polarizer, it is preferably 5.2% by weight or less, and more preferably 5.0% by weight or less.

In the polarizer, the content of the potassium is preferably 0.28 wt % or more, more preferably 0.32 wt % or more, further preferably 0.34 wt % or more, from the viewpoint of suppressing the decrease in the optical properties of the polarizer under a high temperature environment, Furthermore, from the viewpoint of suppressing the hue change in a high temperature environment, it is preferably 0.60% by weight or less, more preferably 0.55% by weight or less, and even more preferably 0.50% by weight or less.

In the polarizer, the value obtained by multiplying the content of boron (% by weight) by the content of potassium (% by weight) (content of boron (% by weight) × content of potassium (% by weight)), from the suppression of high temperature environment From the viewpoint of reducing the optical properties of the polarizer, 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 the hue change in a high temperature environment, it is preferably 3.5 or less, more preferably 3.0 or less, more preferably 2.5 or less.

In the polarizer, the value obtained by dividing the content of boron (% by weight) by the content of potassium (% by weight) (content of boron (% by weight) ÷ content of potassium (% by weight)), from the suppression of high temperature environment From the viewpoint of reducing the optical properties of the polarizer, it is preferably 5 or more, more preferably 8 or more, still more preferably 10 or more, and from the viewpoint of making the initial hue of the polarizer good, it is preferably 30 or less, more preferably 25 or less, more preferably 20 or less.

<Manufacturing method of polarizer>

The polarizer is obtained by subjecting the polyvinyl alcohol-based film to a dyeing process, a crosslinking process, and a stretching process, and further performing at least one treatment process among a swelling process, a washing process, and a drying process as optional processes. The content of the boron and the content of the potassium contained in the polarizer can be determined by the boric acid, borate, boric acid contained in any one of the treatment baths in the swelling process, the dyeing process, the cross-linking process, the stretching process and the washing process. The concentration of a boron component supply material such as a boron compound such as borax, the concentration of a potassium component supply material such as potassium halide such as potassium iodide, and the treatment temperature and treatment time of each of the above-mentioned treatment baths are controlled. In particular, in the crosslinking step and the stretching step, it is easy to adjust the content of boron to a desired range by processing conditions such as the concentration of the boron component supply material. In addition, in the washing step, in consideration of processing conditions such as the amount of the boron component supply material and the potassium component supply material used in the dyeing process, the crosslinking process, or the stretching process, etc., components such as boron and potassium can be removed from the polyethylene From the viewpoint of elution of the alcohol-based film or adsorption to the polyvinyl-alcohol-based film, it is easy to adjust the content of the boron and the content of the potassium to a desired range.

The swelling step is a treatment step in which the polyvinyl alcohol-based film is immersed in a swelling bath, and it is possible to remove stains, blocking agents, etc. on the surface of the polyvinyl alcohol-based film. In addition, by swelling the polyvinyl alcohol-based film, it is possible to suppress dyeing. all. The aforementioned swelling bath usually uses a medium containing water, such as water, distilled water, and pure water, as a main component. Surfactant, alcohol, etc. can be suitably added to the aforementioned swelling bath by a conventional method. In addition, from the viewpoint of controlling the content of potassium in the polarizer, potassium iodide may be used in the swelling bath. In this case, the concentration of potassium iodide in the swelling bath is preferably 1.5% by weight or less, more preferably 1.0% by weight Below, 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, still more preferably about 18 to 30°C. In addition, since the degree of swelling of the polyvinyl alcohol-based film is affected by the temperature of the swelling bath, the immersion time in the swelling bath cannot be determined uniformly, but it is preferably about 5 to 300 seconds, and more preferably 10 to 200 seconds. seconds, more preferably about 20 to 100 seconds. The said swelling process may be implemented only once, and may be implemented multiple times as needed.

The dyeing step is a treatment step in which the polyvinyl alcohol-based film is immersed in a dyeing bath (iodine solution), and a dichroic substance such as iodine or a dichroic dye can be adsorbed and oriented in the polyvinyl alcohol-based film. The aforementioned iodine solution is preferably an aqueous iodine solution containing iodine and an iodide as a dissolution aid. In addition, as said iodide, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, and tin iodide are exemplified. , titanium iodide, etc. Among these, potassium iodide is suitable from the viewpoint of controlling the content of potassium in the polarizer.

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

The temperature of the said dyeing bath becomes like this. Preferably it is about 10-50 degreeC, More preferably, it is about 15-45 degreeC, More preferably, it is about 18-30 degreeC. In addition, since the degree of dyeing of the polyvinyl alcohol-based film is affected by the temperature of the dyeing bath, the immersion time in the dyeing bath cannot be determined uniformly, but it is preferably about 10 to 300 seconds, and more preferably 20 to 240 seconds. seconds or so. The said dyeing process may be implemented only once, and may be implemented multiple times as needed.

The cross-linking step is a treatment step of immersing the polyvinyl alcohol-based film dyed in the dyeing step in a treatment bath (cross-linking bath) containing a boron compound, and the polyvinyl alcohol-based film is cross-linked by the boron compound, Iodine molecules or dye molecules can be adsorbed on the cross-linked structure. As said boron compound, a boric acid, a borate, a borax, etc. are mentioned, for example. The above-mentioned crosslinking bath is usually an aqueous solution, but may be, for example, a mixed solution of an organic solvent miscible with water and water. Moreover, it is preferable that the said crosslinking bath contains potassium iodide from a viewpoint of controlling the content of the said potassium in the said polarizer.

In the crosslinking bath, the concentration of the boron compound 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 more preferably about 2 to 5% by weight .

The temperature of the crosslinking bath is preferably about 20 to 70°C, and more preferably about 30 to 60°C. In addition, the immersion time in the above-mentioned cross-linking bath cannot be determined uniformly 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 more preferably About 10 to 200 seconds. The said crosslinking process may be implemented only once, and may be implemented multiple times as needed.

The stretching step is a treatment step of stretching the polyvinyl alcohol-based film to a predetermined ratio in at least one direction. Usually, the polyvinyl alcohol-based film is uniaxially stretched in the conveyance direction (longitudinal direction). The method of the aforementioned stretching is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. The aforementioned stretching step may be performed only once, or may be performed multiple times as necessary. The aforementioned stretching process can be performed at any stage in the manufacture of the polarizer.

As the treatment bath (stretching bath) in the wet stretching method, a solvent such as water or a mixed solution of an organic solvent miscible with water and water can usually be used. From the viewpoint of controlling the content of the potassium in the polarizer, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15 wt %, more preferably about 2 to 10 wt %, and more preferably about 3 to 6 wt %. In addition, from the viewpoint of suppressing film breakage during stretching, the treatment bath (stretching bath) may contain the boron compound, and in this case, the concentration of the boron compound in the stretching bath is preferably 1 to 15 wt. %, more preferably about 1.5 to 10% by weight, 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, still more preferably about 50 to 70°C. In addition, since the degree of stretching of the polyvinyl alcohol-based film is affected by the temperature of the stretching bath, the immersion time in the stretching bath cannot be determined uniformly, but it is preferably about 10 to 800 seconds, and more preferably About 30 to 500 seconds. It should be noted that the stretching treatment in the wet stretching method may be performed together with any one or more treatment steps among the swelling step, the dyeing step, the crosslinking step, and the washing step.

Examples of the dry stretching method include a roll-to-roll stretching method, a heated roll stretching method, a compression stretching method, and the like. In addition, the said dry stretching method can be implemented together with the said drying process.

The total stretch ratio (accumulated stretch ratio) applied to the polyvinyl alcohol-based film can be appropriately set according to the purpose, but is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and even more preferably 3.5 to 3.5 times. 6.5 times or so.

The said washing|cleaning process is a process process of immersing a polyvinyl-alcohol-type film in a cleaning bath, and can remove the foreign material which remained on the surface etc. of a polyvinyl-alcohol-type film. A medium containing water such as water, distilled water, and pure water as a main component is usually used for the cleaning bath. In addition, from the viewpoint of controlling the content of potassium in the polarizer, potassium iodide is preferably used in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably about 1 to 10% by weight, more preferably 1.5% by weight. About to 4 weight%, More preferably, it is about 1.8 to 3.8 weight%.

The temperature of the said cleaning bath becomes like this. Preferably it is about 5-50 degreeC, More preferably, it is about 10-40 degreeC, More preferably, it is about 15-30 degreeC. In addition, the immersion time in the cleaning bath cannot be determined uniformly because the degree of cleaning of the polyvinyl alcohol-based film is affected by the temperature of the cleaning bath, but it is preferably about 1 to 100 seconds, and more preferably 2 to 50 seconds. seconds, more preferably about 3 to 20 seconds. The said swelling process may be implemented only once, and may be implemented multiple times as needed.

The drying step is a step of drying the polyvinyl alcohol-based film washed in the washing step to obtain a polarizer, and by drying, a polarizer having a desired moisture content can be obtained. The above-mentioned drying can be performed by any appropriate method, and examples thereof include natural drying, air drying, and heat drying. The moisture content of the polarizer is preferably about 8 to 25% by weight, and more preferably about 12 to 20% by weight. In addition, the moisture content of a polarizer was calculated by the following formula based on the initial weight of a sample cut into a size of 100 mm square, and the dry weight after drying at 120° C. for 2 hours.

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

The drying temperature is preferably about 20 to 150°C, and more preferably about 25 to 100°C. In addition, since the degree of drying of the polarizer is affected by the drying temperature, the drying time cannot be determined uniformly, but is preferably about 30 to 600 seconds, more preferably about 60 to 300 seconds. The aforementioned drying step may be performed only once, or may be performed multiple times as necessary.

The thickness of the polarizer is preferably about 10 to 30 μm, and more preferably about 12 to 20 μm.

<Polarizing film>

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

The said transparent protective film is not specifically limited, Various transparent protective films conventionally used for polarizing films can be used. As the material constituting the above-mentioned transparent protective film, for example, thermoplastic resins excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like are used. Examples of the thermoplastic resin include cellulose ester-based resins such as cellulose triacetate, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, and polyethersulfone-based resins. , Polysulfone-based resins, polycarbonate-based resins, polyamide-based resins such as nylon and aramid, polyimide-based resins, polyolefin-based resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (Meth)acrylic resin, cyclic and/or cyclic polyolefin resin having norbornene structure (norbornene resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin , and their mixtures. In addition, the above-mentioned transparent protective film can be cured using a thermosetting resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, silicone, or the like, or an ultraviolet curable resin. Floor. Among these, cellulose ester-based resins, polycarbonate-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins, and polyester-based resins are suitable.

The thickness of the transparent protective film can be appropriately determined, but is usually preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and still more preferably about 5 to 100 μm from the viewpoints of strength, handling properties such as handling properties, and thin layer properties. about. The thickness of the transparent protective film is preferably about 10 to 100 μm, more preferably about 20 to 100 μm, even more preferably about 30 to 100 μm, from the viewpoint of reducing the moisture permeability of the transparent protective film.

The above-mentioned transparent protective film has a moisture permeability of preferably 800 g/(m ² ·24h) or less, more preferably 400 g/(m ² ·24h) or less, and even more preferably 200 g, from the viewpoint of suppressing a decrease in polarization performance in a high-temperature and high-humidity environment. /(m ² ·24h) or less, more preferably 150 g/(m ² ·24h) or less. The moisture permeability of the transparent protective film on one side of the polarizer is preferably 200 g/(m ² ·24h) or less, and more preferably 150 g/(m ² ·24h) or less. It should be noted that the moisture permeability can be calculated as follows: According to the moisture permeability test (cup method) of JIS Z 0208, a sample cut into a diameter of 60 mm is placed in a moisture permeable cup containing about 15 g of calcium chloride and placed. The temperature was 40° C. and the humidity was 90% RH in a thermostat, and the weight gain of calcium chloride before and after being left to stand for 24 hours was measured and calculated.

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

As the above-mentioned transparent protective film, a retardation plate having a retardation of 40 nm or more in front phase difference and/or 80 nm or more in thickness direction retardation can be used. The front 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 above-mentioned transparent protective film, since the retardation plate also functions as a transparent protective film, thickness reduction can be achieved.

Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, an alignment film of a liquid crystal polymer, and an alignment layer in which a liquid crystal polymer is supported by a film. film, etc. The thickness of the retardation plate is not particularly limited, but is usually about 20 to 150 μm. In addition, it can be used by bonding the said phase plate to the transparent protective film which does not have retardation.

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

The surface of the transparent protective film to which the polarizer is not attached may be subjected to hard coating treatment, anti-reflection treatment, or treatment for the purpose of anti-sticking, diffusion, and/or anti-glare. It should be noted that the hard coat treatment, anti-reflection layer, anti-adhesion layer, diffusion layer, and/or treatment for the purpose of anti-glare, etc. may be provided on the transparent protective film itself, and may be provided on the transparent protective film itself as an optical layer. A different object than a clear protective film.

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

In order to bond the said polarizer and the said transparent protective film, an adhesive agent is usually used. As said adhesive agent, an isocyanate type adhesive agent, a polyvinyl alcohol type adhesive agent, a gelatin type adhesive agent, a vinyl type latex type, a water type polyester etc. are mentioned, for example. The aforementioned adhesive is usually used as an adhesive containing an aqueous solution, and usually contains a solid content of 0.5 to 60% by weight. As said adhesive agent, in addition to the above, an ultraviolet curable adhesive agent, an electron beam curable adhesive agent, etc. are mentioned. Moreover, a metal compound filler etc. may be contained in the said adhesive agent.

The application of the adhesive may be performed on either of the transparent protective film and the polarizer, or may be performed on both. After bonding, a drying step is performed to form an adhesive layer including a coating dry layer. The bonding of the polarizer and the transparent protective film can be performed by a roll laminator or the like. After the aforementioned drying step, ultraviolet rays and electron beams may be irradiated as necessary. The thickness of the said adhesive bond layer is not specifically limited, Preferably it is about 30-5000 nm, More preferably, it is about 100-1000 nm.

<Laminated polarizing film>

In the laminated polarizing film (optical laminate) of the present invention, the above-mentioned polarizing film is bonded to the optical layer. The optical layer is not particularly limited, and for example, one or more layers of reflective plates, semi-transmissive plates, retardation plates (including 1/2, 1/4 wavelength plates, etc.), viewing angle compensation films and other liquid crystal display devices can be used. An optical layer sometimes used in the formation of etc. Examples of the above-mentioned laminated polarizing film include, in particular, a reflective polarizing film or a semi-transmissive polarizing film obtained by laminating a reflective plate or a semi-transmissive reflecting plate on the above-mentioned polarizing film, and a retardation plate further laminated on the above-mentioned polarizing film. The resulting elliptical polarizing film or circular polarizing film, the wide viewing angle polarizing film formed by laminating the viewing angle compensation film on the above polarizing film, or the polarizing film formed by laminating the light enhancement film on the above polarizing film.

The polarizing film or the laminated polarizing film may be attached to one or both surfaces of the above-mentioned polarizing film. It is used to attach image display units such as liquid crystal cells and organic EL elements to other components such as a front transparent plate and a transparent plate such as a touch panel on the visual recognition side. combined adhesive layer. As the adhesive layer, an adhesive layer is suitable. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, or the like can be appropriately selected and used. as a binder for the base polymer. In particular, it is preferable to use an adhesive which is excellent in optical transparency, and which exhibits moderate wettability, cohesiveness, adhesiveness, weather resistance, heat resistance, and the like, such as an adhesive containing an acrylic polymer.

The aforementioned pressure-sensitive adhesive layer preferably has a low content of organic acid monomers such as acrylic acid. By reducing the organic acid monomer content in the adhesive layer, even when the image display device is exposed to a high-temperature environment, it is possible to suppress a decrease in transmittance caused by polyolefinization of polyvinyl alcohol.

The attachment of the pressure-sensitive adhesive layer to one side or both sides of the polarizing film and the laminated polarizing film can be carried out in an appropriate manner. As the attachment of the pressure-sensitive adhesive layer, for example, a method of preparing a pressure-sensitive adhesive solution and directly attaching it to the polarizing film and the laminated polarizing film by a suitable development method such as a casting method and a coating method can be mentioned. or form an adhesive layer on the separator and transfer it to the above-mentioned polarizing film, the above-mentioned laminated polarizing film, and the like. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use, adhesive force, etc., but is usually 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm.

It is preferable to temporarily adhere and protect the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination or the like until it is actually used. Thereby, contamination of an adhesive layer etc. can be prevented in a normal processing state. As the separator, for example, a thin layer body suitable for plastic films, rubber sheets, paper, cloth, nonwoven fabrics, nets, foam sheets, metal foils, and laminates thereof can be used as needed. , Long-chain alkyl-based, fluorine-based, molybdenum sulfide and other suitable release agents are coated with separators and the like.

<Image Display Panel and Image Display Device>

In the image display panel of the present invention, the above-mentioned polarizing film or the above-mentioned laminated polarizing film is bonded to the image display unit. In addition, the image display device of the present invention includes a transparent plate on the polarizing film or laminated polarizing film side (visual recognition side) of the image display panel.

As said image display unit, a liquid crystal cell, an organic EL cell, etc. are mentioned, for example. As the liquid crystal cell, for example, a reflective liquid crystal cell using external light, a transmissive liquid crystal cell using light from a light source such as a backlight, and a semi-transmissive liquid crystal cell using both light from the outside and light from the light source can be used. Any of the reflective liquid crystal cells. When the aforementioned liquid crystal cell utilizes light from a light source, the image display device (liquid crystal display device) further disposes a polarizing film on the side opposite to the visual recognition side of the image display cell (liquid crystal cell), and further disposes the light source. The polarizing film on the light source side and the liquid crystal cell are preferably bonded together via a suitable adhesive layer. As the driving method of the liquid crystal cell, for example, any type of mode such as VA mode, IPS mode, TN mode, STN mode, bend alignment (π type) can be used.

As the organic EL unit, for example, an organic EL unit in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light-emitting body (organic electroluminescent light-emitting body) can be suitably used. The organic light-emitting layer is a laminate of various organic thin films, for example, a laminate of a hole-injection layer containing a triphenylamine derivative or the like and a light-emitting layer containing a fluorescent organic solid such as anthracene can be used. A laminate of an electron injection layer including a perylene derivative or the like, or a laminate of a hole injection layer, a light-emitting layer, and an electron injection layer, etc., is constituted by various layers.

As a transparent plate arrange|positioned at the visual recognition side of the said image display unit, a front transparent plate (window layer), a touch panel, etc. are mentioned, for example. As the front transparent plate, a transparent plate having suitable mechanical strength and thickness can be used. As such a transparent plate, for example, a transparent resin plate such as an acrylic resin or a polycarbonate resin, a glass plate, or the like can be used. As the above-mentioned touch panel, for example, various touch panels of a resistive film method, an electrostatic capacitance method, an optical method, and an ultrasonic method, a glass plate having a touch sensor function, a transparent resin plate, and the like can be used. When a capacitive touch panel is used as the transparent plate, it is preferable to provide a front transparent plate formed of glass or a transparent resin plate on the side closer to visibility than the touch panel.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited 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 was swollen by immersing it in a swelling bath (water bath) at 20° C. for 30 seconds between rolls with different peripheral speed ratios, and stretched to 2.4 times in the conveying direction (swelling step), then, at 20° C. Dyeing was carried out by immersing in a dyeing bath (aqueous solution with an iodine concentration of 0.03% by weight and a potassium iodide concentration of 0.3% by weight) for 45 seconds, and the original polyvinyl alcohol film (a polyvinyl alcohol film that was completely unstretched in the conveying direction) was dyed. ) is stretched to 3.7 times in the conveying direction (dyeing process). Next, the dyed polyvinyl alcohol film was immersed for 20 seconds in a cross-linking bath (aqueous solution with a boric acid concentration of 3.0 wt % and a potassium iodide concentration of 3.0 wt %) at 40° C. The conveying direction was stretched to 4.2 times (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed for 50 seconds in a stretching bath (aqueous solution having a boric acid concentration of 4.0 wt % and a potassium iodide concentration of 5.0 wt %) at 65° C. and was conveyed along the original polyvinyl alcohol film as a reference. After stretching to 6.0 times in the direction (stretching step), it was immersed in a cleaning bath (aqueous solution with a potassium iodide concentration of 2.5 wt %) at 18° C. for 5 seconds (cleaning step). The cleaned polyvinyl alcohol film was dried at 30° C. for 2 minutes to produce a polarizer. The boron content in the polarizer was 4.2 wt %, and the potassium content in the polarizer was 0.32 wt %, as determined by the following measurement methods. 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 polarizers]

Dissolve the polarizer (about 0.2g) dried at 120°C for 2 hours in water, add a small amount of mannitol and BTB solution dropwise to the aqueous solution, use a burette to neutralize and titrate with 0.1mol/L NaOH aqueous solution, The boron content of the polarizer was calculated based on the following formula.

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

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

V: Dropwise amount of NaOH aqueous solution (L)

Mw: molecular weight of boron (g/mol)

M: Weight of polarizer after drying at 120°C for 2 hours (g)

[Method for Measuring Potassium Content (% by Weight) in Polarizers]

With respect to the polarizer, the fluorescence X-ray intensity (kcps) of potassium element was measured using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX100E", measurement diameter: φ10 mm). On the other hand, the thickness (μm) of the polarizer was measured using a spectroscopic film thickness meter (manufactured by PEACOCK, trade name "DG-205"). The potassium content (% by weight) was determined by the following formula from the obtained fluorescent X-ray intensity and thickness. In addition, the following "2.99" is the fluorescence X-ray intensity ( kcps) coefficients of the standard curve derived from the measurement.

Potassium content in polarizer (wt%)=2.99×(fluorescence X-ray intensity of potassium element)/(thickness of polarizer)

<Production of polarizing film>

As the binder, a polyvinyl alcohol resin having an acetoacetyl group (average degree of polymerization: 1,200, degree of saponification: 98.5 mol %, degree of acetoacetylation: 5 mol %) and methylol melamine were used in a weight ratio of 3:1. of aqueous solution. Using this adhesive, one side (surface on the side of the image display unit) of the polarizer obtained in the above was bonded by a roll laminator with a (meth)acrylic resin (modified acrylic polymer having a lactone ring structure). A transparent protective film with a thickness of 30 μm (saturated water absorption: 0.2 g/m ² , water vapor transmission rate: 125 g/(m ² ·24h)) (hereinafter referred to as “transparent film A”) was used as the second transparent film A protective film, and a 40 μm-thick triacetate cellulose film (water vapor permeability: 342 g/(m ² ·24 h), manufactured by KONICA MINOLTA, INC., trade name "KC4UYW") (hereinafter referred to as "transparent film B") was used as the first transparent protective film, and then heated and dried in an oven (at a temperature of 88° C. for 10 minutes) to prepare a film on a polarizer. A polarizing film with a transparent protective film laminated on both sides.

<Production of analog image display device>

The polarizing film obtained above was cut into a size of 150 × 50 cm so that the absorption axis of the polarizer became the long side, and an acrylic adhesive with a thickness of 20 μm was used on one surface of the polarizing film (the surface on the transparent film A side). A glass plate (analog image display unit) was laminated to the other side of the polarizing film (the side on the B side of the transparent film) through an acrylic monomer-free adhesive with a thickness of 200 μm (manufactured by Nitto Denko Co., Ltd., trade name “LUCIACS”). CS9868”) is attached to another glass plate to make an analog image display device.

[Evaluation of Optical Properties in High Temperature Environment]

The simulated image display device obtained above was left to stand in a hot air oven at a temperature of 95° C. for 500 hours, and the monomer transmittance (ΔTs) and the degree of polarization (ΔP) before and after input (heating) were measured. The single transmittance and the degree of polarization were measured using a spectrophotometer (manufactured by Murakami Color Institute Co., Ltd., product name "DOT-3"). This single-body transmittance is a Y value corrected for visual sensitivity according to a 2-degree field of view (C light source) according to JlS Z8701-1982. In addition, the measurement wavelength is 380-700 nm (per 10 nm).

ΔTs(%)=Ts ₅₀₀ -Ts ₀

ΔP(%)=P ₅₀₀ -P ₀

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

The above-mentioned degree of polarization is based on the parallel transmittance (Tp) obtained when the analog image display device and the reference polarizing film (manufactured by Nippon Electric Co., Ltd., trade name "CWQ1463CU") are arranged in parallel with the absorption axes, The orthogonal transmittance (Tc) obtained by making the absorption axis 90° orthogonal to each other is defined by the following formula.

P(%)=[(Tp-Tc)/(Tp+Tc)] ^1/2 ×100

The aforementioned ΔTs (%) is preferably -1.0 to 1.0, and more preferably -0.5 to 0.5. In addition, the aforementioned 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 to stand in a hot air oven at a temperature of 95° C. for 500 hours, and the appearance after injection (heating) was visually evaluated according to the following criteria. The results are shown in Table 1.

○: There is no abnormality in appearance, or cracks smaller than 100 μm are generated at the ends of the polarizing film.

×: Abnormal appearance (polyolefinization), or cracks of 100 μm or more occurred at the edge of the polarizing film.

<Example 2>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a cross-linking bath (aqueous solution with a boric acid concentration of 3.5 wt % and a potassium iodide concentration of 2.5 wt %) was used in the cross-linking step, and a stretching bath (boric acid concentration of 4.5 wt %) was used in the stretching step. %, an aqueous solution with a potassium iodide concentration of 5.0 wt %), and a cleaning bath (aqueous solution with a potassium iodide concentration of 1.8 wt %) was used in the cleaning step, and a polarizer was produced in the same manner as in Example 1. The boron content in the obtained polarizer was 5.2 weight%, and the potassium content was 0.28 weight%. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Example 3>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a stretching bath (aqueous solution with a boric acid concentration of 3.5 wt % and a potassium iodide concentration of 5.0 wt %) was used in the stretching step, and a cleaning bath (a solution with a potassium iodide concentration of 3.0 wt %) was used in the cleaning step. Aqueous solution), except that, it carried out similarly to Example 1, and produced the polarizer. The boron content in the obtained polarizer was 4.0 wt %, and the potassium content was 0.34 wt %. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Example 4>

<Production of polarizer, polarizing film, and analog image display device>

As the polarizer, the polarizer obtained in Example 3 was prepared. In the production of the polarizing film, as the second transparent protective film, a triacetate cellulose film with a thickness of 80 μm (water vapor transmission rate: 560 g/(m ² ·24 h), KONICA and KONICA were used on one surface of the polarizer (the surface on the side of the image display unit). A polarizing film and an analog image display device were produced in the same manner as in Example 1, except that the product was manufactured by MINOLTA, INC., trade name "KC8UYW") (hereinafter the film is referred to as "transparent film C").

<Example 5>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a cross-linking bath (aqueous solution with a boric acid concentration of 3.5 wt % and a potassium iodide concentration of 2.5 wt %) was used in the cross-linking step, and a stretching bath (boric acid concentration of 5.0 wt %) was used in the stretching step. %, an aqueous solution with a potassium iodide concentration of 5.0 wt %), and a cleaning bath (aqueous solution with a potassium iodide concentration of 1.8 wt %) was used in the cleaning step, and a polarizer was produced in the same manner as in Example 1. The boron content in the obtained polarizer was 5.3 weight%, and the potassium content was 0.28 weight%. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Comparative Example 1>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a cross-linking bath (aqueous solution with a boric acid concentration of 2.5 wt % and a potassium iodide concentration of 2.5 wt %) was used in the cross-linking step, and a stretching bath (boric acid concentration of 3.0 wt %) was used in the stretching step. %, an aqueous solution with a potassium iodide concentration of 5.0 wt %), and a cleaning bath (aqueous solution with a potassium iodide concentration of 4.0 wt %) was used in the cleaning step, and a polarizer was produced in the same manner as in Example 1. The boron content in the obtained polarizer was 3.9 wt %, and the potassium content was 0.36 wt %. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Comparative Example 2>

<Production of polarizer, polarizing film, and analog image display device>

In production of the polarizer, a polarizer was produced in the same manner as in Example 1, except that a cleaning bath (aqueous solution having a potassium iodide concentration of 1.3 wt %) was used in the cleaning step. The boron content in the obtained polarizer was 4.1 wt %, and the potassium content was 0.27 wt %. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Comparative Example 3>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a stretching bath (aqueous solution with a boric acid concentration of 3.5 wt % and a potassium iodide concentration of 5.0 wt %) was used in the stretching step, and a cleaning bath (a solution with a potassium iodide concentration of 1.5 wt %) was used in the cleaning step. Aqueous solution), except that, it carried out similarly to Example 1, and produced the polarizer. The boron content in the obtained polarizer was 4.0 wt %, and the potassium content was 0.28 wt %. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

<Comparative Example 4>

<Production of polarizer, polarizing film, and analog image display device>

In the production of the polarizer, a cross-linking bath (aqueous solution with a boric acid concentration of 1.5 wt % and a potassium iodide concentration of 2.5 wt %) was used in the cross-linking step, and a stretching bath (boric acid concentration of 1.5 wt %) was used in the stretching step. %, an aqueous solution with a potassium iodide concentration of 5.0 wt %), and a cleaning bath (aqueous solution with a potassium iodide concentration of 10.0 wt %) was used in the cleaning step, and a polarizer was produced in the same manner as in Example 1. The boron content in the obtained polarizer was 2.4 weight%, and the potassium content was 0.65 weight%. Moreover, using the obtained polarizer, by the same operation as Example 1, a polarizing film and a simulated image display device were produced.

Using the simulated image display devices of Examples 2 to 5 and Comparative Examples 1 to 4 obtained above, the evaluations in the above-mentioned [Evaluation of Optical Properties in a High-Temperature Environment] and [Evaluation of the Appearance in a High-Temperature Environment] were performed. The results are shown in Table 1.

[Table 1]

Claims (8)

1. A polarizing plate comprising a polyvinyl alcohol film,

the polarizer includes boron and potassium,

the polarizing plate has a boron content of 4 wt% or more and 6 wt% or less, and a value obtained by multiplying the boron content (% by weight) by the potassium content (% by weight) is 1.2 or more.

2. A light polarizer according to claim 1, wherein the potassium is contained in an amount of 0.28 wt% or more.

3. A polarizer according to claim 1 or 2, wherein the content of boron is 5.2 wt% or less.

4. A polarizing film comprising the polarizing device according to any one of claims 1 to 3 and a transparent protective film bonded to at least one surface of the polarizing device.

5. A polarizing film as claimed in claim 4, wherein the transparent protective film has a moisture permeability of 200 g/(m)²24h) or less.

6. A laminated polarizing film, wherein the polarizing film according to claim 4 or 5 is bonded to an optical layer.

7. An image display panel, wherein the polarizing film according to claim 4 or 5 or the laminated polarizing film according to claim 6 is bonded to an image display unit.

8. An image display device comprising a transparent plate on the polarizing film or laminated polarizing film side of the image display panel according to claim 7.