KR102193246B1 - Polarizer, polarizing plate, and image display apparatus - Google Patents

Abstract

(Task) To provide a polarizer excellent in humidification durability even when it has a cut part.
(Solution means) 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, and the width of the barrier portion is 1 mm or more. The polarizer of the present invention can prevent moisture from remaining in the barrier portion and reaching the dyed portion even when moisture enters from the cut end. As a result, it is possible to prevent the polarizer from losing color and impairing the polarization characteristics.

Description

A polarizer, a polarizing plate, and an image display device TECHNICAL FIELD [POLARIZER, POLARIZING PLATE, AND IMAGE DISPLAY APPARATUS}

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

Polarizing plates are used in various image display devices such as mobile phones and notebook personal computers (PCs). The polarizer is usually cut into a shape according to a purpose and used. For example, Patent Document 1 discloses a method for manufacturing a polarizing member in which a polarizing member is cut from a roll-shaped polarizing member into a chip shape. When the polarizer has a cut portion, there is a problem that color loss occurs in the polarizer due to moisture from the cut end under a humidified environment. Therefore, a polarizer excellent in humidification durability is required.

Japanese Patent Publication No. 2017-500606

The present invention has been made to solve the above conventional problems, and its main purpose is to provide a polarizer having excellent humidification durability even when having 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 portion is a discoloration portion.

In one embodiment, the cut portion is formed in at least a part of the peripheral edge portion of the dyeing portion.

In one embodiment, the cutout portion is formed over the entire peripheral edge portion of the dyeing portion.

In one embodiment, the cut part is formed in the dyeing part.

In another aspect of the present invention, a polarizing plate is provided. The polarizing plate of the present invention includes the polarizer.

In yet 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, a polarizer excellent in humidification durability can be provided 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 portion is formed between the dyed portion and the cut portion of the polarizer, even when moisture enters from the cut end, it is possible to prevent moisture from staying at the barrier portion and reaching the dyed portion. As a result, it is possible to prevent the polarizer from losing color and impairing the polarization characteristics. In addition, even when the cut portion is formed, the humidification durability is excellent, and therefore, even when processed into a more complex shape, desired polarization characteristics can be maintained. In addition, when the barrier portion is a decolorization portion, various colors can be applied without affecting the color of the polarizer. Therefore, it can also contribute to diversification of the design of an image display device in which a polarizer is used.

1 is a schematic plan view of a polarizer in an embodiment of the present invention.
2 is a schematic plan view of a polarizer in another embodiment of the present invention.
3 is a schematic plan view of a polarizer in another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described, 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. The polarizer is typically imparted with polarization characteristics by dyeing a resin film with a dichroic substance. That is, in the polarizer, a portion that exhibits its function is a dyed portion dyed with a dichroic material. Further, as a resin constituting this resin film, a polyvinyl alcohol-based resin is typically used. In the case where the cut portion is formed in the dyed portion of the polarizer, it may be a problem that the polarization characteristic is impaired (color dropout) due to intrusion of moisture from the cut end. The polarizer of the present invention has a barrier portion formed between a dyed portion and a cut portion formed on the dyed portion. This barrier portion is not dyed with a dichroic material, or the content of the dichroic material is significantly lower than that of the dyed portion. Therefore, the barrier portion does not have the same polarization function as the dyed portion. Moisture entering from the cut end can be absorbed into this barrier portion. Therefore, it is possible to prevent moisture from reaching the dyed portion, which is a portion that exhibits the function of a polarizer. In the polarizer of the present invention, the width of this barrier portion is 1 mm or more. Since the barrier portion having a width of 1 mm or more is formed between the dyed portion and the cut portion, even when moisture enters from the cut end, it is possible to prevent moisture from staying at the barrier portion and reaching the dyed portion. Therefore, it is possible to prevent the polarizer from losing color and impairing the polarization characteristics. It is preferable that this barrier portion is a discoloration portion. When the barrier portion is a decolorization portion, it becomes possible to apply various colors without affecting the color of the polarizer. For this reason, it becomes possible to provide an image display device of more various designs.

1 is a schematic plan view of a polarizer in an embodiment of the present invention. The polarizer 10 in the illustrated example is a polarizer in which the entire peripheral edge portion of the dyed portion 12 is cut off. Representatively, a chip-cut single-leaf polarizer is mentioned. The polarizer 10 in the illustrated example has a square shape, and the peripheral edge of the dyeing portion 12 is a cut portion 11. In the illustrated example, the barrier portion 13 is formed between the dyed portion 12 and the cut portion 11. The width of this barrier part 13 is 1 mm or more. By providing such a barrier portion 13, even when moisture enters from the cut end (that is, the peripheral edge portion of the polarizer), moisture stays in the barrier portion and is prevented from reaching the dyed portion 12. I can. Further, in the illustrated example, the barrier portions 13 are formed with the same width, but 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.

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

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

In still another embodiment, an opening and/or a cutout are further formed in the dyed portion of the chip-cut polarizer (eg, the polarizer of FIG. 1 ). In this embodiment, a barrier portion between the peripheral edge portion and the dyeing portion of the polarizer, and a barrier portion between the opening portion and/or the cutout portion and the dyeing 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, it is possible to prevent moisture that has penetrated from the cut end stay in the barrier portion and reach the dyed portion. Therefore, even when it is made into a polarizer of a more complicated shape and design, a polarizer excellent in humidification durability can be provided.

The polarizer 10 may be designed in any suitable shape depending on the intended use or the like. As the shape of the polarizer 10, for example, a square, a circle, a rhombus, a deformed shape, etc. are mentioned. In the polarizer of the present invention, since the barrier portion is formed, moisture from the cut end remains at the barrier portion and can be prevented from entering the dye portion 12. Therefore, even when the polarizer is cut into a more complex shape, a polarizer excellent in humidification durability can be provided.

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, particularly More preferably, it is less than 8 μm. The lower limit of the thickness is preferably 1 µm or more. By being thin, it can contribute to thinning of the image display device. In addition, when the barrier portion is a decolorization portion, the thinner the thickness, the better the decolorization portion can be formed. For example, when the basic solution described later is brought into contact, a decolorization part can be formed in a shorter time. In addition, the thickness of the portion contacted with the basic solution may become thinner than that of other portions. By being thin, it is possible to reduce the difference in thickness between the portion contacted with the basic solution and the other portion.

As described above, the polarizer is typically obtained by dyeing a resin film with a dichroic material such as iodine. As the resin for forming the resin film, any suitable resin can be used. Preferably, polyvinyl alcohol-based resin (hereinafter, referred to as "PVA-based resin") is used. Examples of the PVA-based resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol% or more and less than 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be obtained according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizer having excellent durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

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 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. In addition, the average polymerization degree can be calculated|required according to JIS K 6726-1994.

As a dichroic substance, iodine, an organic dye, etc. are mentioned, for example. These may be used alone or in combination of two or more. Preferably iodine is used. This is because when the barrier portion is a decolorization portion, the barrier portion can be formed satisfactorily by contact with a basic solution to be described later.

The polarizer (dyed portion) preferably exhibits absorption dichroism in a wavelength range of 380 nm to 780 nm. The single transmittance (Ts) of the polarizer (dyed portion) is preferably 39% or more, more preferably 39.5% or more, still more preferably 40% or more, and particularly preferably 40.5% or more. In addition, the theoretical upper limit of the single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value obtained by measuring with a 2-degree field of view (C light source) of JIS Z8701 and performing luminous sensitivity correction, and can be measured using, for example, a microscopic spectroscopy system (manufactured by Lambda Vision, LVmicro). I can. The degree of polarization of the polarizer (dyed portion) is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

As described above, the barrier portion does not contain a dichroic substance, or the content of the dichroic substance is a portion that is significantly lower than that of the dyed portion. That is, the barrier portion is a portion that has not been subjected to a dyeing treatment (undyed portion) or a decolored portion. The barrier portion is preferably a discolored portion. By being a decolorization part, durability of a barrier part can be improved.

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. When the width of the barrier portion is within such a range, even when moisture enters from the cut end, 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 portion is a decolorization portion, the transmittance of the decolorization portion (e.g., transmittance measured with light having a wavelength of 550 nm at 23°C) is preferably 50% or more, more preferably 60% or more, further preferably It is 75% or more, particularly preferably 90% or more. When the transmittance is in such a range, it becomes possible to apply various colors without affecting the color of the polarizer. For this reason, it becomes possible to provide an image display device of more various designs.

When the barrier portion is a decolorization portion, the content of the dichroic substance in the decolorization portion 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. If the content of the dichroic substance in the decolorization portion is in such a range, intrusion of moisture from the cut end can be appropriately prevented. On the other hand, the lower limit of the content of the dichroic substance in the decolorization portion is usually less than or equal to the detection limit. In addition, when iodine is used as the dichroic substance, the iodine content is obtained by a calibration curve previously prepared using a standard sample from the X-ray intensity measured by fluorescence X-ray analysis, for example.

B. Manufacturing method of polarizer

The polarizer of the present invention can be manufactured by any suitable method. The manufacturing method of the 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. Process of imparting polarization function

A polarizing function can be imparted to the resin film by any suitable method. Typically, a polarizing function can be imparted to a resin film by performing various treatments such as swelling treatment, stretching treatment, dyeing treatment with a dichroic substance such as iodine, crosslinking treatment, washing treatment, and drying treatment. In addition, when performing a treatment to impart a polarization function to the resin film, the resin film may be a resin layer formed on the substrate. The laminate of the substrate and the resin layer can be obtained, for example, by a method of applying a coating liquid containing the material for forming the resin film to the substrate, a method of laminating a resin film on the substrate, or the like.

In the said extending|stretching process, a resin film is uniaxially stretched typically 3 times-7 times. In addition, the stretching direction can correspond to the absorption axis direction of the obtained polarizer.

The dyeing treatment is typically performed by adsorbing a dichroic substance. Examples of the adsorption method include a method of immersing a resin film in a dyeing solution containing a dichroic substance, a method of applying the dyeing solution to a resin film, and a method of spraying the dyeing solution onto a resin film. I can. Preferably, it is a method of immersing the resin film in the dyeing solution. This is because the dichroic material can be adsorbed well. As for the dichroic material, it is the same as above.

When iodine is used as the dichroic substance, an aqueous iodine solution is preferably used as the dyeing solution. The blending amount of iodine is preferably 0.04 parts by weight to 5.0 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to mix iodide with an aqueous iodine solution. As the iodide, potassium iodide is preferably used. The blending amount of iodide is preferably 0.3 parts by weight to 15 parts by weight based on 100 parts by weight of water.

In one embodiment, the resin film is provided for dyeing treatment in a state in which the portion corresponding to the cut portion and/or the barrier portion is protected with an arbitrary suitable protective material. Specifically, as a protective material, a protective film and a surface protective film are mentioned, for example. The protective film can be used as it is as a protective film of a polarizer. The surface protection film is temporarily used at the time of manufacture of a polarizer. Since the surface protection film is removed from the resin film at any appropriate timing, typically, it is bonded to the resin film via an adhesive layer. As another specific example of a protective material, a photoresist etc. are mentioned.

B-2. The process of forming the cut

The cutting part can be formed by cutting the resin film by any suitable cutting method. As a cutting method, punching blades, such as a laser, a cutter, a Thompson blade, and a pick blade blade, etc. are mentioned.

The cut portion may be formed on a resin film to which a polarizing function is provided (a resin film in which a dyed portion is formed), or may be formed on a resin film to which a polarizing function is not provided. In the case of forming on a resin film to which a polarization function is not provided, a cut portion may be formed in the resin film before various treatments for imparting a polarization function are performed, or a cut portion may be formed in the portion of the resin film protected by the protective material. do.

B-3. Barrier formation process

The barrier portion can be formed by any suitable method. As described above, the barrier portion is an undyed portion or a decolored portion. When the barrier portion is a non-dyed portion, for example, the barrier portion can be formed by performing dyeing treatment while protecting a portion corresponding to the barrier portion with the protective material. Further, a barrier portion may be formed by the step of forming the cut portion. Specifically, various treatments for imparting a polarizing function such as dyeing treatment to the resin film in a state where portions corresponding to the cut portion and the barrier portion are protected with a protective material, and the barrier portion is applied to the portion protected by the protective material of the resin film. By forming the cut portion so as to leave the portion to be cut, the barrier portion can be formed simultaneously with the formation of the cut portion.

As described above, it is preferable that the barrier portion is a decolorization portion. The decolorization part can be formed by subjecting the resin film to which the above various treatments have been applied to any suitable decolorization treatment. For example, a decolorization treatment by laser or a decolorization treatment by contact with a basic solution containing a basic compound, etc. are mentioned. Preferably, it 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. Moreover, the transparency of the decolorization part can be maintained over time.

As the contact method of the basic solution, any suitable method can be employed. For example, a method of dripping, coating, and spraying a basic solution with respect to a resin film, and a method of immersing a resin film in a basic solution are mentioned.

When the basic solution is in contact, the polarizer (resin film) may be protected with any suitable protective material so that the basic solution does not contact (not discolor) other than the desired site. Specifically, as a protective material, the above can be used.

As the basic compound, any suitable basic compound can be used. Examples of the basic compound include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, hydroxides of alkaline earth metals such as calcium hydroxide, inorganic alkali metal salts such as sodium carbonate, organic alkali metal salts such as sodium acetate, and aqueous ammonia. Can be lifted. Among these, a hydroxide of an alkali metal and/or an alkaline earth metal is preferably used, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferably used. The dichroic material can be ionized efficiently, and a decolorization part can be formed more easily. These basic compounds may be used alone or in combination of two or more.

As the solvent of the basic solution, any suitable solvent can be used. Specifically, alcohols such as water, ethanol and methanol, ether, benzene, chloroform, and mixed solvents thereof are mentioned. Among these, water and alcohol are preferably used because the ionized dichroic substance can transfer favorably to the solvent.

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

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

When performing decolorization by contacting a basic solution, an alkali metal and/or alkaline earth metal hydroxide may remain in the contact portion. Further, by contacting the resin film with the basic solution, a metal salt of an alkali metal and/or an alkaline earth metal can be generated in the contact portion. These can generate hydroxide ions, and the generated hydroxide ions act on (decompose/reduce) a dichroic substance (eg, iodine complex) existing around the contact portion, thereby widening the decolorization region. Therefore, it is preferable to reduce the alkali metal and/or alkaline earth metal contained in the resin film in the contact portion to which the basic solution is brought into contact after the contact with the basic solution. By reducing the alkali metal and/or alkaline earth metal, it is possible to obtain a bleached portion excellent in dimensional stability.

As the reduction method, a method of bringing a treatment liquid into contact with a contact portion with a 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, and the content thereof can be reduced.

As a method of contacting the treatment liquid, any suitable method may be employed. For example, a method of dropping, coating, and spraying a treatment liquid on a contact portion with a basic solution, and a method of immersing the contact portion with a basic solution in the treatment liquid.

When the resin film is protected by any suitable protective material at the time of contact with the basic solution, it is preferable to contact the treatment liquid as it is (in particular, when the temperature of the treatment liquid is 50°C or higher). According to such an aspect, it is possible to prevent a decrease in polarization characteristics due to the treatment liquid in a portion other than the contact portion with the basic solution.

The treatment liquid may contain any suitable solvent. Examples of the solvent include alcohols such as water, ethanol, and methanol, ether, benzene, chloroform, and mixed solvents thereof. Among these, water and alcohol are preferably used from the viewpoint of efficiently transferring an alkali metal and/or an alkaline earth metal. As water, any suitable water can be used. For example, tap water, pure water, deionized water, etc. are mentioned.

The temperature of the treatment liquid upon contact is, for example, 20°C or higher, preferably 50°C or higher, more preferably 60°C or higher, and still more preferably 70°C or higher. At such a temperature, the alkali metal and/or alkaline earth metal can be efficiently transferred to the treatment liquid. Specifically, the swelling ratio of the resin film can be remarkably improved, and the alkali metal and/or alkaline earth metal in the resin film can be physically removed. On the other hand, the temperature of water is substantially 95°C or less.

The contact time can be appropriately adjusted depending on the contact method, the temperature of the treatment liquid (water), the thickness of the resin film, and the like. For example, in the case of immersion in hot water, the contact time is preferably 10 seconds to 30 minutes, more preferably 30 seconds to 15 minutes, and still more preferably 60 seconds to 10 minutes.

In one embodiment, an acidic solution is used as the treatment liquid. By using an acidic solution, the alkali metal and/or alkaline earth metal hydroxide remaining in the resin film can be neutralized, and the alkali metal and/or alkaline earth metal in the resin film can be chemically removed.

As the acidic compound contained in the acidic solution, any suitable acidic compound can be used. Examples of the acidic compound 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, as the acidic compound, an acidic compound having a stronger acidity than boric acid is preferably used. This is because it can act on a metal salt (borate) of an alkali metal and/or an alkaline earth metal. Specifically, boric acid can be released from a boric acid salt, and alkali metal and/or alkaline earth metal in the resin film can be chemically removed.

As an index of the acidity, an acid dissociation constant (pKa) is mentioned, for example, and an acidic compound having a smaller pKa than the pKa (9.2) of boric acid is preferably used. Specifically, pKa is preferably less than 9.2, more preferably 5 or less. The pKa may be measured using any suitable measuring device, or a value described in literature such as the 5th edition of the Basic Edition of the Chemical Handbook (Japanese Chemical Society, Maruzen Publication) may be referred to. In addition, in an acidic compound that dissociates in multiple stages, the value of pKa may change in each step. In the case of using such an acidic compound, any of the values of pKa in each step is used within the above range. 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 to 15, and more preferably 2.5 to 13. In 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 content of the alkali metal and/or alkaline earth metal in the decolorization portion can be realized.

As an acidic compound capable of satisfying the pKa, for example, hydrochloric acid (pKa: -3.7), sulfuric acid (pK ₂ : 1.96), nitric acid (pKa: -1.8), hydrogen fluoride (pKa: 3.17), boric acid ( Inorganic acids such as 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) and organic acids such as benzoic acid (pKa: 4.0), and the like.

In addition, the solvent of the acidic solution (treatment liquid) is as described above, and also in this embodiment in which an acidic solution is used as the treatment liquid, physical removal of the alkali metal and/or alkaline earth metal in the resin film may occur.

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

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

B-4. Other processes

The manufacturing method of the polarizer of the present invention may further include any suitable other processing steps other than the step of imparting the polarizing function, the step of forming a cut portion, and the step of forming a barrier portion. As another treatment process, removal of a basic solution and/or an acidic solution, and washing|cleaning etc. are mentioned.

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

The cleaning treatment is carried out by any suitable method. Examples of the solution used for the washing treatment include pure water, alcohol such as methanol and ethanol, an acidic aqueous solution, and a mixed solvent thereof. The cleaning treatment can be carried out in any suitable step. The washing treatment may be performed a plurality of times.

C. Polarizer

The polarizing plate of this invention has the said polarizer. The polarizing plate of the present invention is typically used by laminating a protective film on at least one side thereof. Examples of the material for forming the protective film include cellulose resins such as diacetyl cellulose and triacetyl cellulose, (meth)acrylic resins, cycloolefin resins, olefin resins such as polypropylene, polyethylene terephthalate resins, etc. Ester resins, polyamide resins, polycarbonate resins, and copolymer resins thereof.

On the surface of the protective film on which the polarizer is not laminated, as a surface treatment layer, a hard coat layer, an antireflection treatment layer, and a treatment layer for the purpose of diffusion or anti-glare may be formed.

The thickness of the protective film is preferably 10 µm to 100 µm. The 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 pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive.

D. Image display device

The image display device of the present invention includes the polarizing plate. As an image display device, a liquid crystal display device and an organic EL device are mentioned, for example. Specifically, a liquid crystal display device includes a liquid crystal cell and a liquid crystal panel including the polarizer disposed on one or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel in which the polarizer is disposed on the viewing side. As described above, the polarizer of the present invention can prevent moisture from remaining in the barrier portion and reaching the dyed portion even when moisture enters from the cut end. As a result, it is possible to prevent the polarizer from losing color and impairing the polarization characteristics. In addition, even when the cut portion is formed, the humidification durability is excellent, so even when processed into a more complex shape, desired polarization characteristics can be maintained. In addition, when the barrier portion is a decolorization portion, various colors can be applied without affecting the color of the polarizer. Therefore, it is possible to provide an image display device of various designs.

Example

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[Example 1]

As the substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 µm) having a water absorption rate of 0.75% and a Tg of 75°C was used. Corona treatment was performed on one side of the substrate, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol) % Or more, Nippon Synthetic Chemical Co., Ltd. make, brand name "Go Sephimer Z200") in a ratio of 9:1 was applied and dried at 25°C to form a PVA-based resin layer having a thickness of 11 μm, thereby forming a laminate. Was prepared.

The obtained laminate was uniaxially stretched at a free end by 2.0 times in the longitudinal direction (lengthwise direction) between rolls having different circumferential speeds in an oven at 120°C (air auxiliary stretching).

Next, the laminate was immersed for 30 seconds in an insolubilization bath at a liquid temperature of 30°C (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).

Subsequently, it was immersed in a dyeing bath at a liquid temperature of 30° C. while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was blended with respect to 100 parts by weight of water, and 1.5 parts by weight of potassium iodide was blended and immersed in an aqueous iodine solution for 60 seconds (dyeing treatment).

Then, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid) at a liquid temperature of 30°C (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid at a liquid temperature of 70°C (an aqueous solution obtained by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide based on 100 parts by weight of water), while between rolls having different circumferential speeds. Uniaxial stretching was performed so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction) (underwater stretching).

Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 30°C (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment).

Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., brand name "Go Sephimer (registered trademark) Z-200", resin concentration: 3% by weight) was applied to the surface of the PVA-based resin layer of the layered product, and a protective film (Thickness 25 µm) was bonded and heated in an oven maintained at 60°C for 5 minutes. Then, the base material was peeled off from the PVA system resin layer, and the polarizing plate (polarizer (transmittance 42.3%, thickness 5 micrometers)/protective film) was obtained.

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 (1 N)) at room temperature was applied to the peripheral edge of the polarizer so that the width of the decolorization portion (barrier portion) was 10 mm on the polarizer surface of the cut out polarizing plate, and 60 It was left for a second. Subsequently, the applied aqueous sodium hydroxide solution was removed with waste. After removing the aqueous sodium hydroxide solution, 1.0 mol/L (1 N) of hydrochloric acid was applied and allowed to stand for 30 seconds. Subsequently, hydrochloric acid was removed with a waste, and a polarizer with a decolorization part formed along the cut part was obtained.

[Example 2]

It carried out similarly to Example 1, and obtained the polarizer which has a width 10 mm decolorization part. The bleaching portion formed on the four sides of the polarizing plate is cut with a cutter so that the width of the bleaching portion (barrier portion) of the polarizer is 1 mm, and the bleaching portion (barrier portion) having a width of 1 mm between the dyed portion and the cut portion (the peripheral edge portion of the polarizer) ) Was formed.

(Comparative Example 1)

A polarizer was obtained in the same manner as in Example 2, except that the barrier portion was cut so that the width of the barrier portion was 0 mm (that is, all the discolored portions were cut).

(Comparative Example 2)

In the same manner as in Example 1, a polarizer having a decolorization portion having a width of 10 mm was obtained as a decolorization portion. The width of the decolorization part (barrier part) of the obtained polarizer was -1 mm (that is, the part on the side of the dyed part 1 mm from the boundary part of the discolored part and the dyed part) was cut to obtain a polarizer.

The following evaluation was performed using the polarizer obtained in Examples 1-2 and Comparative Examples 1-2. 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 presence or absence of color loss in the short and long sides of the polarizer was confirmed with an optical microscope, and the length of the color missing portion Was measured. In addition, the length of the portion where the length of the portion where the color is missing was the longest was the length of the portion where the color was missing from 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 for 72 hours under the conditions of 65°C and 90% RH. Subsequently, the presence or absence of color loss on the short side and the long side of the polarizer was confirmed with an optical microscope, and the length of the color missing portion was measured. In addition, the length of the portion where the length of the portion where the color is missing was the longest was the length of the portion where the color was missing from the polarizer.

In the polarizers of Examples 1 and 2 in which a barrier portion (decolorization portion) having a width of 1 mm or more was formed between the dyed portion and the cut portion, the color loss of the polarizer was well prevented even after the humidification test. Even in the harsher glycerin test, the effect of improving the humidification durability became more remarkable. On the other hand, in Comparative Example 1 without a barrier portion and Comparative Example 2 in which the inside of the dyed portion was cut, color loss of the polarizer was large, and there was a problem in humidification durability. In particular, in the long side, there was a tendency for color loss to become remarkable.

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

10 polarizer
11 cut
12 Dyeing area
13 Barrier part

Claims (7)

A polarizer having a dyed portion, a cut portion formed in the dyed portion, and a barrier portion formed between the dyed portion and the cut portion, and the width of the barrier portion is 1 mm or more. The method of claim 1,
A polarizer, wherein the barrier portion is a decolorization portion. The method of claim 2,
A polarizer, wherein the cut portion is formed on at least a part of a peripheral edge portion of the dyeing portion. The method of claim 2,
A polarizer, wherein the cut portion is formed on the entire circumferential edge portion of the dyeing portion. The method of claim 2,
A polarizer in which the cut portion is formed in the dyed portion. A polarizing plate provided with the polarizer according to any one of claims 1 to 5. An image display device comprising the polarizing plate according to claim 6.

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