KR102205072B1 - Polarizer, polarizing plate, and image display apparatus - Google Patents

Abstract

(Task) To provide a polarizer that can realize an image display device with excellent design.
(Solution means) The polarizer of the present invention has a dyed portion and a non-dyed portion. This undyed portion is formed around the entire circumference along the outer edge of the polarizer.

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 capable of realizing an image display device having excellent design, 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). Recently, an image display device including a camera and various sensors has been developed. As a polarizer used in such an image display device, a polarizer in which a portion corresponding to a camera is partially decolored has been proposed (Patent Document 1). In recent years, there is a demand for an image display device having not only a function but also excellent design. For example, an image display device having a narrower bezel portion and an image display device having a smaller step difference between the display portions (full flat design) have been proposed. There is a demand for a polarizer capable of responding to these high design demands.

Japanese Unexamined Patent Publication No. 2014-112238

The present invention has been made in order to solve the above conventional problems, the main object of which is to provide a polarizer capable of realizing an image display device having excellent design, a polarizing plate including the polarizer, and an image display device including the polarizing plate. There is one.

The polarizer of the present invention has a dyed portion and a non-dyed portion. This undyed portion is formed around the entire circumference along the outer edge of the polarizer.

In one embodiment, the said non-dyed part is a discolored part.

In one embodiment, the width of the undyed portion is 1 mm or more.

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 capable of realizing an image display device having excellent design can be provided. The polarizer of the present invention has a dyed portion and a non-dyed portion, and the non-dyed portion is formed around the entire circumference along the outer edge of the polarizer. In the non-dyed portion, since various colors can be applied without affecting the color of the polarizer, the design of the outer edge portion can be diversified. Further, it is possible to prevent a polarizer from interfering with the functions of a camera and various sensors included in the image display device. Therefore, various functions provided by the image display device can be exhibited more highly. Further, by using the polarizer of the present invention, it is possible to provide a (flat) image display device having a smaller step difference.

1 is a schematic plan view of a polarizer in an 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 and a non-dyed portion. This non-dyed portion is formed around the entire periphery along the outer edge of the polarizer. Therefore, it is possible to provide a polarizer capable of realizing an image display device having more excellent design. In addition, even in an image display device equipped with functions such as various sensors and cameras, these functions are prevented from being disturbed, and various functions can be exhibited more highly.

1 is a plan view of a polarizer in an embodiment of the present invention. The polarizer 10 in the illustrated example has a dyed portion 12 and a non-dyed portion 11. In the illustrated example, the polarizer 10 is a square. In the illustrated example, the non-dyed portion 12 is formed around the outer edge of the polarizer 10, that is, the entire circumference along the four sides. Since the non-dyed portion 12 is formed around the entire circumference along the outer edge of the polarizer, it is possible to provide an image display device having more excellent design. In addition, in high-performance image display devices such as smartphones and PCs, cameras and sensors may be provided at the periphery. Since the non-dyed portion is formed around the entire circumference along the outer edge of the polarizer, these functions are prevented from being disturbed, and various functions can be exhibited more highly.

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.

The polarizer is typically manufactured 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 undyed portion is a decolored portion, the undyed portion can be formed satisfactorily by contact with a basic solution described later.

The dyed part 12 refers to a part dyed with a dichroic substance of a resin film. The non-dyed portion 11 may be a portion not dyed with a dichroic substance, or may be a portion decolored by any suitable method after dyeing with a dichroic substance. The non-dyed part is preferably a part (discolored part) which is bleached after dyeing with a dichroic material. By decolorizing after dyeing, the strength of the undyed portion can be improved.

The width of the undyed portion is set to any appropriate value. The width of the undyed portion is preferably 1 mm or more, and more preferably 10 mm or more. If the width of the non-dyed portion is within such a range, color loss of the polarizer can be preferably prevented. As described above, by forming the undyed portion, the width of the design of the image display device can be expanded. From the viewpoint of design, there is no upper limit of the undyed portion, and it can be set to any appropriate width.

The transmittance of the undyed portion (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, still more preferably 75% or more, particularly Preferably it is 90% or more. With such transmittance, an image display device having excellent design can be provided. In addition, by preventing obstruction of functions such as cameras and sensors, various functions can be exhibited more highly.

The polarizer (excluding the undyed portion) preferably exhibits absorption dichroism in a wavelength range of 380 nm to 780 nm. The single transmittance (Ts) of the polarizer (excluding the undyed 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 (excluding the undyed portion) is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

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. The thinner the thickness, the better the undyed portion can be formed by decolorization. For example, when the basic solution described later is brought into contact, a non-dyed portion 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.

When the non-dyed portion is a decolorized portion, the content of the dichroic substance in the decolored 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. When the content of the dichroic substance in the decolorization portion is such a range, desired transparency can be sufficiently imparted to the undyed portion (decolorization portion). On the other hand, the lower limit of the content of the dichroic substance in the undyed 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. For example, it can be manufactured by subjecting a resin film to various treatments such as swelling treatment, stretching treatment, dyeing treatment with a dichroic substance such as iodine, crosslinking treatment, washing treatment, and drying treatment. When the non-dyed part is formed by not performing the dyeing treatment, the non-dyed part can be formed by performing various treatments such as dyeing treatment while protecting the part to be the non-dyed part using any suitable protective material. In addition, when the undyed portion is a decolored portion, the undyed portion can be formed by performing decolorization treatment around the entire periphery along the outer edge of the dyed polarizer. Typically, a non-dyed portion can be formed by subjecting the polarizer cut into a single leaf to be subjected to a decolorization treatment. In addition, when performing various treatments, 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.

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 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 a non-dyed portion can be formed satisfactorily by contact with a basic solution described later.

In the case of forming the undyed portion by not performing the dyeing treatment, it is preferable to protect the entire periphery (the portion corresponding to the undyed portion) along the outer edge of the resin film with an arbitrary suitable protective material, and to perform the dyeing treatment . Specifically, as a protective material of a resin film, 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 through an adhesive layer. As another specific example of a protective material, a photoresist etc. are mentioned.

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 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.

When the non-dyed portion is a decolored portion, decolorization of the polarizer can be performed by any suitable method. For example, decolorization by laser, or contact with a basic solution containing a basic compound, etc. are mentioned. It is preferably contact with a basic solution. By forming the undyed portion by contact with the basic solution, the transparency of the undyed portion can be maintained over time. In addition, the strength of the undyed portion may be improved. Further, the barrier property of the non-dyed portion can be improved, and color loss of the polarizer can be prevented.

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 contacted, the polarizer may be protected with any suitable protective material so that the basic solution does not contact (not decolorized) other than the desired site. As the protective material, a protective material used to protect the non-dyed portion can be mentioned.

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 efficiently ionized, and a non-dyed portion 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 undyed 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.

By bringing the basic solution into contact with the resin film, 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 and reduce) a dichroic substance (eg, an iodine complex) existing around the contact portion, thereby widening the non-dyed 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, a non-dyed portion excellent in dimensional stability can be obtained.

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 undyed 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.

The polarizer of the present invention can be obtained by subjecting a resin film containing a dichroic substance to these treatments. In addition, the resin film can be further subjected to any appropriate other treatment in addition to the above treatment. Other treatments include removal of a basic solution and/or an acidic solution, and washing.

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 has a non-dyed portion formed around the entire circumference along the outer edge of the polarizer. Therefore, the color of the peripheral edge portion of the image display device is not limited. Therefore, an image display device having more excellent design can be provided. In addition, it is possible to provide an image display device capable of exhibiting various functions more highly by preventing the functions of cameras and sensors from being obstructed.

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 Undyed area
12 Dyeing area

Claims (6)

As a polarizer having a dyed portion and a non-dyed portion,
The non-dyed portion is formed around the entire circumference along the outer edge of the polarizer,
A polarizer having a width of 1 mm or more of the undyed portion. The method of claim 1,
The non-dyed portion is a decolored portion, a polarizer. delete delete A polarizing plate comprising the polarizer according to claim 1 or 2. An image display device comprising the polarizing plate according to claim 5.

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