JP7191578B2 - Polarizer, polarizing plate, and image display device - Google Patents

Description

The present invention relates to polarizers, polarizing plates, and image display devices. More specifically, the present invention relates to a polarizer having excellent humidification durability even when it has a cut portion, a polarizing plate including this polarizer, and an image display device including this polarizing plate.

Polarizing plates are used in various image display devices such as mobile phones and notebook personal computers (PCs). A polarizer is usually used by being cut into a shape according to the application. For example, Patent Literature 1 discloses a method for manufacturing a polarizing member by cutting a roll-shaped polarizing member into chip-shaped polarizing members. When the polarizer has a cut portion, there is a problem that the polarizer loses color due to moisture from the cut end portion in a humid environment. Therefore, there is a demand for a polarizer that is excellent in humidification durability.

Japanese Patent Publication No. 2017-500606

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems described above, and a main object thereof is to provide a polarizer that is excellent in humidification durability even if it has a cut portion.

The polarizer of the present invention has a dyed portion, a cut portion formed in the dyed portion, and a barrier portion formed between the dyed portion and the cut portion. The width of this barrier portion is 1 mm or more.
In one embodiment, the barrier section is a bleaching section.
In one embodiment, the cut portion is formed in at least a part of the periphery of the stained portion.
In one embodiment, the cut portion is formed along the entire periphery of the stained portion.
In one embodiment, the cut section is formed within the dyeing section.
A polarizing plate is provided in another situation of this invention. A polarizing plate of the present invention includes the above polarizer.
In still another aspect of the present invention, an image display device is provided. This image display device includes the polarizing plate.

According to the present invention, it is possible to provide a polarizer that is excellent in humidification durability even when it has a cut portion. The polarizer of the present invention has a dyed portion, a cut portion formed in the dyed portion, and a barrier portion formed between the dyed portion and the cut portion. The width of this barrier portion is 1 mm or more. Since the barrier part is formed between the dyed part and the cut part of the polarizer, even if moisture enters from the cut end, the moisture stays at the barrier part and does not reach the dyed part. can be prevented. As a result, it is possible to prevent the polarizer from decoloring and impairing the polarization properties. In addition, even if a cut portion is formed, it is excellent in humidification durability, so even if it is processed into a more complicated shape, it is possible to maintain the desired polarization characteristics. Furthermore, when the barrier section is the bleaching section, various colors can be applied without being affected by the color of the polarizer. Therefore, it can contribute to the diversification of the design of the image display device using the polarizer.

1 is a schematic plan view of a polarizer in one embodiment of the invention; FIG. FIG. 5 is a schematic plan view of a polarizer in another embodiment of the invention; FIG. 5 is a schematic plan view of a polarizer in still another embodiment of the invention;

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Polarizer The polarizer of the present invention has a dyed portion, a cut portion formed in the dyed portion, and a barrier portion formed between the dyed portion and the cut portion. The width of this barrier portion is 1 mm or more. A polarizer is typically imparted with polarizing properties by dyeing a resin film with a dichroic substance. That is, in the polarizer, the portion that exhibits its function is the dyed portion dyed with the dichroic substance. A polyvinyl alcohol-based resin is typically used as the resin constituting the resin film. When the dyed portion of the polarizer has a cut portion, a problem may arise that the polarizing property is impaired (color loss) due to the intrusion of moisture from the cut end portion. The polarizer of the present invention has a barrier portion formed between a dyed portion and a cut portion formed in the dyed portion. This barrier portion is a portion that is not dyed with a dichroic substance or has a significantly lower content of the dichroic substance than the dyed portion. Therefore, the barrier section does not have a polarizing function like the dyeing section. Moisture entering through the cut end can be absorbed by this barrier. Therefore, it is possible to prevent moisture from reaching the dyed portion, which is the portion where the function of the polarizer is exhibited. In the polarizer of the present invention, the width of this barrier portion is 1 mm or more. By forming a barrier part with a width of 1 mm or more between the dyed part and the cut part, even if water enters from the cut end, the water stays in the barrier part and prevents it from reaching the dyed part. can be prevented. Therefore, it is possible to prevent the polarizer from decoloring and deteriorating the polarization characteristics. This barrier section is preferably a decolorizing section. Since the barrier section is the decolorizing section, various colors can be applied without being affected by the color of the polarizer. Therefore, it is possible to provide image display devices with more diverse designs.

FIG. 1 is a schematic plan view of a polarizer in one embodiment of the invention. The illustrated polarizer 10 is a polarizer in which the entire periphery of the dyed portion 12 is cut. A typical example is a chip-cut sheet polarizer. The illustrated polarizer 10 is rectangular, and the peripheral edge of the dyed portion 12 is the cut portion 11 . In the illustrated example, a barrier section 13 is formed between the dyeing section 12 and the cutting section 11 . The width of this barrier portion 13 is 1 mm or more. By forming such a barrier portion 13, even if moisture enters from the cut end portion (that is, the peripheral portion of the polarizer), the moisture stays at the barrier portion and reaches the dyeing portion 12. can be prevented. Although the barrier portions 13 are formed with the same width in the illustrated example, they may have different widths as long as the width is 1 mm or more. Specifically, the width of the barrier portion 13 in the short side direction and the width of the barrier portion 13 in the long side direction may be different.

FIG. 2 is a schematic cross-sectional view of a polarizer in another embodiment of the invention. The illustrated polarizer 10 has a cut portion 11 formed inside a dyed portion 12 . In the illustrated example, the cut 11 is a circular opening. In the illustrated example, a barrier portion 13 concentric with the opening is formed between the dyeing portion 12 and the circular opening (cutting portion 11).

FIG. 3 is a schematic cross-sectional view of a polarizer in still another embodiment of the invention. The illustrated polarizer 10 is a polarizer having a notch. In the polarizer 10 of the illustrated example, the notch formed in the dyed portion 12 is the cut portion 11 . In this polarizer 10 , a barrier portion 13 is formed between the notch portion (cut portion 11 ) and the dyed portion 12 .

In yet another embodiment, additional openings and/or notches are formed within the dyed portion of a chip-cut polarizer (eg, the polarizer of FIG. 1). In this embodiment, a barrier portion between the periphery of the polarizer and the staining portion and a barrier portion between the opening and/or notch and the staining portion may be formed. Even in the case of having two or more cut portions as in this embodiment, by forming a barrier portion between the dyed portion and the cut portion, the moisture entering from the cut ends remains in the barrier portion, It can be prevented from reaching the dyeing part. Therefore, even when the polarizer has a more complicated shape and design, it is possible to provide a polarizer with excellent humidification durability.

The polarizer 10 can be designed in any suitable shape depending on the application etc. in which it is used. Examples of the shape of the polarizer 10 include rectangular, circular, rhombic, irregular shape, and the like. Since the polarizer of the present invention is formed with a barrier portion, moisture from the cut end is retained at the barrier portion and can be prevented from entering the dyed portion 12 . Therefore, even when the polarizer is cut into a more complicated shape, it is possible to provide a polarizer having excellent humidification durability.

The thickness of the polarizer can be set to any suitable value. The thickness is typically 0.5 μm or more and 80 μm or less, preferably 30 μm or less, more preferably 25 μm or less, still more preferably 18 μm or less, particularly preferably 12 μm or less, and even more preferably. is less than 8 μm. The lower limit of the thickness is preferably 1 μm or more. The thin thickness can contribute to thinning of the image display device. Moreover, when the barrier part is the decolorized part, the thinner the thickness, the better the decolorized part can be formed. For example, when contacting with a basic solution, which will be described later, the decolorized portion can be formed in a shorter time. In addition, the thickness of the portion contacted with the basic solution may become thinner than the other portions. By making the thickness thin, the difference in thickness between the portion contacted with the basic solution and the other portion can be reduced.

As described above, a polarizer is typically obtained by dyeing a resin film with a dichroic substance such as iodine. Any appropriate resin can be used as the resin that forms the resin film. Preferably, a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") is used. Examples of PVA-based resins include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. is. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer with excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, more preferably 1,500 to 4,300. The average degree of polymerization can be determined according to JIS K 6726-1994.

Dichroic substances include, for example, iodine and organic dyes. These may be used alone or in combination of two or more. Iodine is preferably used. This is because, when the barrier portion is a decolorizing portion, the barrier portion can be satisfactorily formed by contact with a basic solution described later.

The polarizer (dyed portion) preferably exhibits absorption dichroism in the wavelength range of 380 nm to 780 nm. The single transmittance (Ts) of the polarizer (dyed portion) is preferably 39% or higher, more preferably 39.5% or higher, even more preferably 40% or higher, and particularly preferably 40.5% or higher. The theoretical upper limit of single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value measured with a JIS Z8701 2-degree field of view (C light source) and corrected for visibility. can be measured. The degree of polarization of the polarizer (dyed portion) is preferably 99.8% or higher, more preferably 99.9% or higher, and still more preferably 99.95% or higher.

As described above, the barrier portion does not contain the dichroic substance, or the content of the dichroic substance is much lower than that of the dyed portion. That is, the barrier portion is a portion that is not dyed (non-stained portion) or a decolorized portion. The barrier section is preferably the bleaching section. Durability of the barrier portion can be improved by being the decolorizing portion.

In the polarizer of the present invention, the width of the barrier portion is 1 mm or more, preferably 3 mm or more, and more preferably 5 mm or more. If the width of the barrier portion is within such a range, even if moisture enters from the cut end portion, the moisture stays in the barrier portion and can be prevented from reaching the dyed portion. The width of the barrier portion is, for example, 10 mm or less from the viewpoint of securing the dyed portion. From the viewpoint of design, the barrier portion may be 10 mm or more.

When the barrier part is the bleaching part, the transmittance of the bleaching part (for example, the transmittance measured with light having a wavelength of 550 nm at 23° C.) is preferably 50% or more, more preferably 60% or more, and still more preferably 75%. 90% or more, particularly preferably 90% or more. When the transmittance is within such a range, various colors can be applied without being affected by the color of the polarizer. Therefore, it is possible to provide image display devices with more diverse designs.

When the barrier part is the decolorizing part, the content of the dichroic substance in the decolorizing part is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, and still more preferably 0.2% by weight or less. be. If the content of the dichroic substance in the decolorized portion is within such a range, it is possible to appropriately prevent moisture from entering through the cut ends. On the other hand, the lower limit of the content of the dichroic substance in the bleached portion is usually below the detection limit. When iodine is used as the dichroic substance, the iodine content can be obtained from, for example, a calibration curve prepared in advance using standard samples from X-ray intensities measured by fluorescent X-ray analysis.

B. Method for Producing Polarizer The polarizer of the present invention can be produced by any appropriate method. The method for producing a polarizer of the present invention includes a step of imparting a polarizing function to a resin film (a step of forming a dyed portion), a step of forming a cut portion, and a step of forming a barrier portion. These steps can be performed in any suitable order.

B-1. Step of imparting polarizing function A polarizing function can be imparted to the resin film by any appropriate method. Typically, a polarizing function can be imparted by subjecting a resin film to various treatments such as swelling treatment, stretching treatment, dyeing treatment with a dichroic substance such as iodine, cross-linking treatment, washing treatment, and drying treatment. In addition, when the resin film is subjected to a treatment for imparting a polarizing function, the resin film may be a resin layer formed on a substrate. A laminate of a substrate and a resin layer can be obtained, for example, by a method of applying a coating liquid containing the resin film-forming material to the substrate, a method of laminating a resin film on the substrate, or the like.

In the stretching treatment, the resin film is typically uniaxially stretched 3 to 7 times. The stretching direction can correspond to the absorption axis direction of the resulting polarizer.

Dyeing treatment is typically performed by adsorbing a dichroic substance. Examples of the adsorption method include a method of immersing the resin film in a dyeing solution containing a dichroic substance, a method of coating the resin film with the dyeing solution, and a method of spraying the resin film with the dyeing solution. . A preferred method is to immerse the resin film in a dyeing solution. This is because the dichroic substance can be well adsorbed. Dichroic substances are described above.

When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the staining solution. The amount of iodine compounded is preferably 0.04 to 5.0 parts by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the iodine aqueous solution. Potassium iodide is preferably used as the iodide. The amount of iodide compounded is preferably 0.3 to 15 parts by weight per 100 parts by weight of water.

In one embodiment, the resin film is subjected to a dyeing treatment while protecting the cut portion and/or the portion corresponding to the barrier portion with any suitable protective material. Specifically, examples of protective materials include protective films and surface protective films. The protective film can be used as it is as a protective film for the polarizer. A surface protective film is used temporarily during the production of a polarizer. Since the surface protection film is removed from the resin film at any appropriate timing, it is typically attached to the resin film via an adhesive layer. Another specific example of the protective material is photoresist.

B-2. Step of forming the cut portion The cut portion can be formed by cutting the resin film by any appropriate cutting method. Cutting methods include lasers, cutters, punching blades such as Thomson blades and Pycnal blades, and the like.

The cut portion may be formed in a resin film imparted with a polarizing function (a resin film having a dyed portion), or may be formed in a resin film not imparted with a polarizing function. When forming on a resin film not imparted with a polarizing function, a cut portion may be formed in the resin film before being subjected to various treatments for imparting a polarizing function, and the cut portion may be protected by the protective material of the resin film. You may form a cut part in the part which was cut.

B-3. Step of Forming Barrier Portion The barrier portion can be formed by any appropriate method. As described above, the barrier area is an unstained area or depigmented area. When the barrier portion is a non-dyed portion, the barrier portion can be formed, for example, by performing a dyeing treatment while protecting the portion corresponding to the barrier portion with the protective material. Also, the barrier portion may be formed by the step of forming the cut portion. Specifically, various treatments for imparting a polarizing function, such as dyeing, are applied to the resin film while the portions corresponding to the cut portion and the barrier portion are protected by a protective material, and the resin film is protected by the protective material. By forming the cut portion so as to leave the portion to be the barrier portion on the other portion, the barrier portion can be formed simultaneously with the formation of the cut portion.

As described above, the barrier section is preferably the decolorization section. The decolorized portion can be formed by subjecting the resin film, which has been subjected to the above various treatments, to any appropriate decolorizing treatment. For example, decolorization treatment with a laser, or decolorization treatment by contact with a basic solution containing a basic compound, or the like can be mentioned. Preferred is contact with a basic solution. By forming the bleached portion by contact with the basic solution, the strength of the bleached portion can be improved. In addition, the transparency of the bleached portion can be maintained over time.

Any appropriate method can be adopted as a method for contacting the basic solution. Examples thereof include a method of dropping, coating, or spraying a basic solution onto a resin film, and a method of immersing a resin film in a basic solution.

The polarizer (resin film) may be protected with any appropriate protective material so that the basic solution does not come into contact with other than the desired site (discoloration) when the basic solution comes into contact. Specifically, the above-described protective material can be used.

Any appropriate basic compound can be used as the basic compound. Examples of basic compounds include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, and inorganic alkali metal salts such as sodium carbonate. , organic alkali metal salts such as sodium acetate, aqueous ammonia, and the like. Among these, alkali metal and/or alkaline earth metal hydroxides are preferably used, and sodium hydroxide, potassium hydroxide and lithium hydroxide are more preferably used. The dichroic substance can be efficiently ionized, and the decolorized portion can be formed more easily. These basic compounds may be used alone or in combination of two or more.

Any suitable solvent can be used as the solvent for the basic solution. Specific examples include water, alcohols such as ethanol and methanol, ethers, benzene, chloroform, and mixed solvents thereof. Among these, water and alcohol are preferably used because the ionized dichroic substance can be transferred well to the solvent.

The concentration of the basic solution is, for example, 0.01N-5N, preferably 0.05N-3N, more preferably 0.1N-2.5N. If the concentration is within such a range, the desired decolorized portion can be formed satisfactorily.

The liquid temperature of the basic solution is, for example, 20°C to 50°C. The contact time between the resin film and the basic solution can be set according to the thickness of the resin film, the type of basic compound, and the concentration of the basic solution, and is, for example, 5 seconds to 30 minutes.

When decolorization is performed by contact with a basic solution, hydroxides of alkali metals and/or alkaline earth metals may remain in the contact area. Also, by bringing a basic solution into contact with the resin film, metal salts of alkali metals and/or alkaline earth metals can be generated at the contact portion. These can generate hydroxide ions, and the generated hydroxide ions can act (decompose/reduce) dichroic substances (e.g., iodine complexes) present around the contact area to widen the decolorization area. . Therefore, after contact with the basic solution, it is preferable to reduce the alkali metal and/or alkaline earth metal contained in the resin film at the contact portion with which the basic solution is contacted. A decolorized portion having excellent dimensional stability can be obtained by reducing the alkali metal and/or alkaline earth metal content.

As the above-mentioned reduction method, a method of contacting the treatment liquid to the contact portion with the basic solution is preferably used. According to such a method, the alkali metal and/or alkaline earth metal can be transferred from the resin film to the treatment liquid to reduce the content thereof.

Any appropriate method can be adopted as the method of contacting the treatment liquid. Examples thereof include a method of dropping, coating, or spraying the treatment liquid onto the portion in contact with the basic solution, and a method of immersing the portion in contact with the basic solution in the treatment liquid.

When the resin film is protected with any appropriate protective material when it comes into contact with the basic solution, it is preferable to contact the treatment liquid in that state (especially when the temperature of the treatment liquid is 50° C. or higher). According to such a configuration, it is possible to prevent deterioration of the polarizing properties due to the treatment liquid at the portion other than the contact portion with the basic solution.

The treatment liquid may contain any suitable solvent. Examples of solvents include water, alcohols such as ethanol and methanol, ethers, benzene, chloroform, and mixed solvents thereof. Among these, water and alcohol are preferably used from the viewpoint of efficiently transferring alkali metals and/or alkaline earth metals. Any appropriate water can be used as the water. Examples include tap water, pure water, and deionized water.

The temperature of the treatment liquid during contact is, for example, 20° C. or higher, preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher. At such a temperature, the alkali metal and/or alkaline earth metal can be efficiently transferred to the processing liquid. Specifically, it is possible to significantly improve the swelling rate of the resin film and physically remove alkali metals and/or alkaline earth metals in the resin film. On the other hand, the temperature of water is substantially below 95°C.

The contact time can be appropriately adjusted according to the contact method, the temperature of the treatment liquid (water), the thickness of the resin film, and the like. For example, when immersed in warm water, the contact time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 15 minutes, even more preferably 60 seconds to 10 minutes.

In one embodiment, an acidic solution is used as the treatment liquid. The alkali metal and/or alkaline earth metal hydroxide remaining in the resin film is neutralized by using an acidic solution to chemically remove the alkali metal and/or alkaline earth metal in the resin film. be able to.

Any appropriate acidic compound can be used as the acidic compound contained in the acidic solution. Examples of acidic compounds include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, hydrogen fluoride and boric acid, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid and benzoic acid. The acidic compound contained in the acidic solution is preferably an inorganic acid, more preferably hydrochloric acid, sulfuric acid or nitric acid. These acidic compounds may be used alone or in combination of two or more.

Preferably, an acidic compound having stronger acidity than boric acid is suitably used as the acidic compound. This is because it can also act on metal salts (borates) of alkali metals and/or alkaline earth metals. Specifically, boric acid can be liberated from the borate to chemically remove alkali metals and/or alkaline earth metals in the resin film.

An example of the index of acidity is the acid dissociation constant (pKa), and an acidic compound having a pKa smaller than the pKa of boric acid (9.2) is preferably used. Specifically, the pKa is preferably less than 9.2, more preferably 5 or less. The pKa may be measured using any appropriate measuring device, and the values described in literature such as Kagaku Binran, Basic Edition, Revised 5th Edition (Edited by The Chemical Society of Japan, Maruzen Publishing) may be referred to. Also, in an acidic compound that dissociates in multiple steps, the pKa value may change at each step. When such an acidic compound is used, one whose pKa value at each stage is within the above range is used. In addition, in this specification, pKa means the value in 25 degreeC aqueous solution.

The difference between the pKa of the acidic compound and the pKa of boric acid is, for example, 2.0 or more, preferably 2.5-15, more preferably 2.5-13. Within such a range, the alkali metal and/or alkaline earth metal can be efficiently transferred to the treatment liquid, and as a result, the desired alkali metal and/or alkaline earth metal content in the decolorizing portion can be achieved. can be realized.

Examples of acidic compounds that can satisfy the above pKa include hydrochloric acid (pKa: −3.7), sulfuric acid (pK ₂ : 1.96), nitric acid (pKa: −1.8), hydrogen fluoride (pKa: 3 .17), inorganic acids such as boric acid (pKa: 9.2), formic acid (pKa: 3.54), oxalic acid (pK ₁ : 1.04, pK ₂ : 3.82), citric acid (pK ₁ : 3.09, pK ₂ : 4.75, pK ₃ : 6.41), acetic acid (pKa: 4.8), benzoic acid (pKa: 4.0), and the like.

The solvent of the acidic solution (treatment liquid) is as described above, and physical removal of the alkali metal and/or alkaline earth metal in the resin film does not occur even in the present embodiment in which the acid solution is used as the treatment liquid. obtain.

The concentration of the acid solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, more preferably 0.1N to 2.5N.

The liquid temperature of the acidic solution is, for example, 20°C to 50°C. The contact time with the acid solution can be set according to the thickness of the resin film, the type of acid compound, and the concentration of the acid solution, and is, for example, 5 seconds to 30 minutes.

B-4. Other Steps The method for producing a polarizer of the present invention further includes any appropriate other treatment steps in addition to the step of imparting a polarizing function, the step of forming a cut portion, and the step of forming a barrier portion. You can stay. Other processing steps include removal of basic and/or acidic solutions, washing, and the like.

Specific examples of the method for removing the basic solution and/or the acidic solution include wiping removal with a waste cloth or the like, suction removal, natural drying, heat drying, air drying, and reduced pressure drying. The drying temperature is, for example, 20°C to 100°C.

Washing treatment is performed by any suitable method. Examples of solutions used for the cleaning process include pure water, alcohols such as methanol and ethanol, acidic aqueous solutions, and mixed solvents thereof. The washing process can be performed at any suitable stage. The washing treatment may be performed multiple times.

C. Polarizing Plate The polarizing plate of the present invention has the above polarizer. The polarizing plate of the present invention is typically used with a protective film laminated on at least one side thereof. Materials for forming the protective film include, for example, cellulose-based resins such as diacetyl cellulose and triacetyl cellulose, (meth)acrylic-based resins, cycloolefin-based resins, olefin-based resins such as polypropylene, and ester-based resins such as polyethylene terephthalate-based resins. , polyamide-based resins, polycarbonate-based resins, copolymer resins thereof, and the like.

The surface of the protective film on which the polarizer is not laminated may be provided with a surface treatment layer such as a hard coat layer, an antireflection treatment layer, or a treatment layer for the purpose of diffusion or antiglare.

The thickness of the protective film is preferably 10 μm to 100 μm. A protective film is typically laminated on a polarizer via an adhesive layer (specifically, an adhesive layer, an adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activated energy ray-curable adhesive. The adhesive layer is typically formed with an acrylic adhesive.

D. Image Display Device The image display device of the present invention includes the polarizing plate described above. Examples of image display devices include liquid crystal display devices and organic EL devices. Specifically, the liquid crystal display device includes a liquid crystal panel including a liquid crystal cell and the polarizers arranged on one side or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel on which the polarizer is arranged on the viewing side. As described above, even when water enters the polarizer of the present invention through the cut ends, the water stays in the barrier portion and can be prevented from reaching the dyed portion. As a result, it is possible to prevent the polarizer from decoloring and impairing the polarization properties. In addition, even when a cut portion is formed, the durability to humidification is excellent, so even when processed into a more complicated shape, the desired polarization characteristics can be maintained. Moreover, when the barrier section is the decolorizing section, various colors can be applied without being affected by the color of the polarizer. Therefore, image display devices with various designs can be provided.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

[Example 1]
A long amorphous isophthalic acid-copolymerized polyethylene terephthalate (IPA-copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and a Tg of 75° C. was used as a substrate. One side of the substrate was subjected to corona treatment, and the corona-treated side was coated with polyvinyl alcohol (degree of polymerization: 4,200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1,200, degree of acetoacetyl modification: 4.6). %, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOSEFIMER Z200") at a ratio of 9:1. A PVA-based resin layer was formed to produce a laminate.
The resulting laminate was uniaxially stretched 2.0 times at the free end in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 120° C. (in-air auxiliary stretching).
Next, the laminate was immersed in an insolubilizing bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Then, it was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was added to 100 parts by weight of water, and 1.5 parts by weight of potassium iodide was added to the resulting iodine aqueous solution for 60 seconds (dyeing treatment). .
Next, it was immersed for 30 seconds in a cross-linking bath at a liquid temperature of 30°C (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (crosslinking treatment).
After that, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). Meanwhile, the film was uniaxially stretched in the machine direction (longitudinal direction) between rolls with different circumferential speeds so that the total draw ratio was 5.5 (underwater stretching).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 30° C. (aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOSEFIMER (registered trademark) Z-200”, resin concentration: 3% by weight) was applied to the surface of the PVA-based resin layer of the laminate. A protective film (thickness: 25 μm) was attached to the substrate by hand, and heated in an oven maintained at 60° C. for 5 minutes. After that, the substrate was peeled off from the PVA-based resin layer to obtain a polarizing plate (polarizer (transmittance: 42.3%, thickness: 5 μm)/protective film).

A test piece having a length of 20 cm and a width of 30 cm was cut out from the polarizing plate having a total thickness of 30 μm obtained above. A basic solution (sodium hydroxide aqueous solution, 1.0 mol/L (1N) at normal temperature is applied to the peripheral edge of the polarizer so that the width of the decolorized portion (barrier portion) is 10 mm on the polarizer surface of the cut polarizing plate. ) was applied and left for 60 seconds. Then, the applied aqueous sodium hydroxide solution was removed with a waste cloth. After removing the sodium hydroxide aqueous solution, 1.0 mol/L (1N) hydrochloric acid was applied and left for 30 seconds. Next, the hydrochloric acid was removed with a waste cloth to obtain a polarizer in which decolorized portions were formed along the cut portions.

[Example 2]
A polarizer having a bleached portion with a width of 10 mm was obtained in the same manner as in Example 1. The bleached portion formed on the four sides of the polarizing plate is cut with a cutting machine so that the width of the bleached portion (barrier portion) of the polarizer is 1 mm, and the width between the dyed portion and the cut portion (polarizer peripheral portion) is A polarizer having a 1 mm decolorized portion (barrier portion) was obtained.

(Comparative example 1)
A polarizer was obtained in the same manner as in Example 2, except that the barrier part was cut so that the width of the barrier part was 0 mm (that is, all the bleached parts were cut).

(Comparative example 2)
A polarizer having a bleached portion with a width of 10 mm was obtained in the same manner as in Example 1. A polarizer was obtained by cutting a decolorized portion (barrier portion) of the obtained polarizer with a width of −1 mm (that is, a portion on the dyed portion side of 1 mm from the boundary portion between the decolorized portion and the dyed portion).

The following evaluations were performed using the polarizers obtained in Examples 1 and 2 and Comparative Examples 1 and 2. Table 1 shows the results.

(Humidification durability test)
The polarizing plates obtained in Examples and Comparative Examples were placed under conditions of 85° C. and 85% RH, and after 24 hours and 48 hours, the short and long sides of the polarizer were checked for color loss with an optical microscope. , the length of the color loss portion was measured. In addition, the length of the longest part of the length of the color missing part was taken as the length of the color missing part of the polarizer.

(glycerin test)
Glycerin was applied to the entire periphery of the polarizing plates obtained in Examples and Comparative Examples. Then, the polarizing plate was placed under conditions of 65° C. and 90% RH for 72 hours. Next, the presence or absence of color loss on the short side and long side of the polarizer was checked with an optical microscope, and the length of the color loss portion was measured. In addition, the length of the longest part of the length of the color missing part was taken as the length of the color missing part of the polarizer.

In the polarizers of Examples 1 and 2, in which a barrier portion (decolorized portion) having a width of 1 mm or more is formed between the dyed portion and the cut portion, the color loss of the polarizer is well prevented even after the humidification test. was done. Even in the more severe glycerin test, the effect of improving the humidification durability became more remarkable. On the other hand, in Comparative Example 1 having no barrier portion and Comparative Example 2 in which the inside of the dyed portion was cut, there was a problem in durability to humidification due to significant color loss of the polarizer. In particular, there was a tendency for color loss to become noticeable on the long sides.

The polarizer of the present invention is suitably used for image display devices such as liquid crystal display devices and organic EL devices.

10 Polarizer 11 Cutting Section 12 Dyeing Section 13 Barrier Section

Claims (3)

Consists of a single polyvinyl alcohol-based resin film dyed with a dichroic material,
A dyed portion, which is a portion of the resin film dyed with a dichroic substance, and a barrier portion formed around the entire periphery of the resin film and the entire periphery of an opening formed in the dyed portion. have
The barrier portion is a decolorizing portion that does not have a polarizing function,
The width of the barrier portion is 1 mm or more,
Polarizer. A polarizing plate comprising the polarizer according to claim 1 . An image display device comprising the polarizing plate according to claim 2 .

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