KR101887735B1 - Method of manufacturing polarizer - Google Patents

Abstract

[PROBLEMS] To provide a method for producing a polarizer having a non-light-emitting portion with high productivity.
[MEANS FOR SOLVING PROBLEMS] A method for producing a polarizer of the present invention comprises the steps of: forming a polyvinyl alcohol-based resin layer on a resin substrate to obtain a laminate; staining the polyvinyl alcohol-based resin layer with iodine; And a step of forming a non-light-emitting portion by contacting the polyvinyl alcohol-based resin layer with a basic solution after dyeing and stretching.

Description

[0001] METHOD OF MANUFACTURING POLARIZER [0002]

The present invention relates to a method for producing a polarizer. More particularly, the present invention relates to a method for producing a polarizer having a non-light-emitting portion.

BACKGROUND ART [0002] An image display device such as a cellular phone or a notebook type personal computer (PC) has an internal electronic component such as a camera mounted thereon. In order to improve the camera performance and the like of such an image display apparatus, various studies have been made. However, further improvement of camera performance and the like has been demanded by the rapid spread of smart phones and touch panel type information processing apparatuses. In order to cope with the diversification and high functionality of the image display apparatus, a polarizer having a partially non-light-emitting portion is required.

Usually, the non-light-emitting portion is formed by performing a perforation process on a polarizer, and there is a problem that a crack occurs in the polarizer at the time of processing. Thus, after a laminated film obtained by forming a polyvinyl alcohol-based resin layer on the surface of a resin substrate film is stretched, a flame-retardant layer is formed on the surface of the polyvinyl alcohol-based resin layer and dyed with a dichroic dye to obtain a polarizer (See Patent Document 1).

However, depending on the forming material, the flame-retardant layer formed on the surface of the polyvinyl alcohol-based resin layer needs to be cleaned and removed after dyeing. Even if the flame retardant layer is not removed, there is a problem that bubbles are likely to be generated when the protective film is stuck, for example, since the flame retardant layer is partially present on the surface of the polarizer. In addition, there is a problem that a non-polarized portion having a predetermined shape is not obtained or a precision is bad due to a problem that a part of the flame-retarding layer is peeled from the surface of the polyvinyl alcohol-based resin layer during dyeing. Thus, a new manufacturing method of a polarizer having a non-light-emitting portion is desired.

Japanese Laid-Open Patent Publication No. 2014-211548

The present invention has been made to solve the above problems, and its main object is to provide a method for producing a polarizer having a non-light-emitting portion with high productivity.

A method for producing a polarizer according to the present invention includes the steps of forming a polyvinyl alcohol resin layer on a resin substrate to obtain a laminate, dyeing the polyvinyl alcohol resin layer with iodine, And a step of forming a non-light-emitting portion by contacting the polyvinyl alcohol-based resin layer with a basic solution after the dyeing and stretching.

In one embodiment, the content of iodine in the non-light-emitting portion is 1.0 wt% or less.

In one embodiment, the basic solution is brought into contact with the surface of the polyvinyl alcohol-based resin layer covered with the surface protective film so that at least a part thereof is exposed.

In one embodiment, a through hole is formed in the surface protective film.

In one embodiment, the basic solution is brought into contact with a polyvinyl alcohol-based resin layer having a thickness of 13 mu m or less.

In one embodiment, the laminate is obtained by applying a coating liquid containing a polyvinyl alcohol-based resin to the resin substrate.

In one embodiment, the laminate is stretched after the dyeing.

In one embodiment, the stretching is in-water stretching.

In one embodiment, a protective film is laminated on the side of the polyvinyl alcohol-based resin layer of the laminate, the resin substrate is peeled off, and a surface protective film is peelably bonded to the peelable surface. The basic solution is contacted.

In one embodiment, the polarizing film laminate is elongated, and the surface protective film is provided with a through hole at a predetermined interval in the longitudinal direction and / or the width direction.

In one embodiment, the acidic solution is brought into contact with the portion of the polyvinyl alcohol-based resin layer in contact with the basic solution.

According to the present invention, a polarizer having a non-light-emitting portion can be obtained by a simple operation of bringing a basic solution into contact with a polyvinyl alcohol-based resin layer subjected to dyeing and stretching. Further, according to the present invention, a laminate can be stretched even after dyeing, and a polarizer having an excellent optical property can be obtained.

1 is a plan view of a polarizer according to an embodiment of the present invention.

Hereinafter, one embodiment of the present invention will be described, but the present invention is not limited to these embodiments.

A. Polarizer

1 is a plan view of a polarizer according to an embodiment of the present invention. The polarizer 1 has the non-light-deflecting portion 2 formed thereon. The non-light-emitting portion (2) is formed by making the content of the dichroic substance contained in the polarizer smaller than that of the other portion (3). According to such a configuration, cracks, delamination (delamination) can be prevented as compared with the case where the through holes are formed mechanically (for example, by a method of mechanically piercing using a flake cutter, a plotter, a water jet, , Problems of quality such as release of the pressure-sensitive adhesive are avoided. Further, since the content of the dichroic material itself is reduced, the transparency of the non-light-shielding portion is kept better than when the non-polarized portion is formed by decomposing the dichroic substance by laser light or the like.

In the illustrated example, the small circular circular polarization light portion 2 is formed at the central portion of the upper end of the polarizer 1, but the number, arrangement, shape, size, etc. of the polarization light portion can be appropriately designed. For example, it is designed according to the position, shape, size, etc. of the camera hole portion of the image display device to be mounted. In this case, it is preferable that the non-light-emitting portion has a substantially circular shape with a diameter of 10 mm or less.

The transmittance of the non-light-emitting portion (for example, the transmittance measured with light at a wavelength of 550 nm at 23 캜) is preferably 50% or more, more preferably 60% or more, further preferably 75% Preferably 90% or more. With such a transmittance, desired transparency can be secured. For example, when the non-light-emitting portion is made to correspond to the camera hole portion of the image display apparatus, adverse effects on the photographing performance of the camera can be prevented.

The polarizer (excluding the non-light-emitting portion) preferably exhibits absorption dichroism at a wavelength of 380 nm to 780 nm. The transmittance of the polarizer (excluding the non-light-emitting portion) is preferably not less than 40.0%, more preferably not less than 42.0%, still more preferably not less than 42.5%, particularly preferably not less than 43.0%. The degree of polarization of the polarizer (excluding the non-light-emitting portion) is preferably not less than 99.8%, more preferably not less than 99.9%, still more preferably not less than 99.95%.

The thickness of the polarizer is preferably 13 占 퐉 or less, more preferably 8 占 퐉 or less, and further preferably 5 占 퐉 or less. With such a thickness, a non-polarized portion having high transparency and excellent surface smoothness (for example, suppressing the generation of wrinkles) can be formed. As a result, for example, when the non-light-emitting portion is made to correspond to the camera hole portion of the image display apparatus, adverse effects on the performance of the camera can be prevented more effectively. By setting the thickness to the above value, the non-polarized light portion can be formed satisfactorily. For example, in the contact with the basic solution described later, the non-light-emitting portion can be formed in a short time. On the other hand, the thickness of the polarizer is preferably 1.0 占 퐉 or more, and more preferably 2.0 占 퐉 or more.

As the dichroic substance, iodine is preferably used. By using iodine, for example, the non-light-emitting portion can be preferably formed by contact with a basic solution to be described later.

The non-light-blocking portion is a portion having a smaller content of the dichroic substance than the other portion. The content of the dichroic substance in the non-light-emitting portion is preferably 1.0 wt% or less, more preferably 0.5 wt% or less, and further preferably 0.2 wt% or less. When the content of the dichroic substance in the non-light-emitting portion is in this range, desired transparency can be imparted to the non-light-emitting portion. For example, when the non-light-emitting portion is made to correspond to the camera hole portion of the image display device, excellent photographing performance can be realized in terms of both lightness and color taste (color taste). On the other hand, the lower limit of the content of the dichroic substance in the non-light-emitting portion is usually not more than the detection limit value. When iodine is used as the dichroic substance, the iodine content of the non-light-emitting portion is determined from a calibration curve prepared using a standard sample in advance from, for example, X-ray intensity measured by fluorescent X-ray analysis.

The difference between the content of the dichroic substance in the other region and the content of the dichroic substance in the non-light-emitting region is preferably 0.5% by weight or more, more preferably 1% by weight or more.

As the material for forming the polarizer, any suitable resin may be used. Preferably, a polyvinyl alcohol-based resin (hereinafter referred to as " PVA-based resin ") is used. As the PVA resin, for example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. 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 resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% or more, more preferably 99.0 mol% or more, and particularly preferably 99.93 mol% or more. The saponification degree can be obtained according to JIS K 6726-1994. By using such a saponification degree PVA resin, a polarizer excellent in durability can be obtained.

The average degree of polymerization of the PVA resin can be suitably selected according to the purpose. The average degree of polymerization is usually from 1000 to 10000, preferably from 1200 to 6000, and more preferably from 2000 to 5000. [ The average polymerization degree can be obtained according to JIS K 6726-1994.

B. Manufacturing method of polarizer

The polarizer includes, for example, a step of forming a PVA resin layer on a resin substrate to obtain a laminate, a step of dyeing the PVA resin layer with iodine, a step of stretching the laminate, And a step of contacting the PVA resin layer with a basic solution to form a non-light-emitting portion. According to such a method, a polarizer that satisfies the above-described thickness and optical characteristics (single transmittance, polarization degree) can be obtained.

B-1. Fabrication of laminate

As the material for forming the resin base material, any suitable resin may be used. (Meth) acrylic resin, a polyamide resin, a polycarbonate resin, a copolymer resin thereof, and the like, for example, an ester resin such as polyethylene terephthalate resin, a cycloolefin resin, an olefin resin such as polypropylene, . Preferably, a polyethylene terephthalate resin is used. Of these, an amorphous polyethylene terephthalate resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as the dicarboxylic acid and a copolymer containing the cyclohexanedimethanol as the glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 120 DEG C or lower, more preferably 100 DEG C or lower. This is because, when the laminate is stretched, the stretchability (particularly in water stretching) can be sufficiently secured while suppressing the crystallization of the PVA resin layer. As a result, a polarizer having excellent optical properties (for example, polarization degree) can be produced. On the other hand, the glass transition temperature of the resin substrate is preferably 60 占 폚 or higher. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

The water absorption of the resin base material is preferably 0.2% or more, and more preferably 0.3% or more. Such a resin substrate absorbs water, and water can function as a plasticizer to plasticize. As a result, the stretching stress can be largely lowered, and the stretchability can be excellent. On the other hand, the water absorption rate of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, the dimensional stability of the resin base material at the time of production is remarkably reduced, and problems such as deterioration of the appearance of the obtained polarizer can be prevented. In addition, it is possible to prevent the PVA resin layer from being peeled off from the resin base or broken at the time of underwater stretching. The water absorption rate is a value obtained in accordance with JIS K 7209.

The thickness of the resin base material is preferably 20 mu m to 300 mu m, more preferably 50 mu m to 200 mu m. The surface of the resin substrate may be subjected to a surface modification treatment (for example, corona treatment or the like), or an adhesion-facilitating layer may be formed. According to such a treatment, a laminate having excellent adhesion between the resin substrate and the PVA-based resin layer can be obtained. Further, the resin base material can be used as a protective film as it is.

The laminate may be manufactured by any suitable method. For example, it is produced by applying a coating liquid containing the PVA resin to a resin substrate, and drying it if necessary. It is also produced by laminating a film containing the PVA resin on a resin substrate by any suitable method.

Typically, a solution obtained by dissolving the PVA resin in a solvent is used as the coating liquid. Examples of the solvent include water, polyhydric alcohols such as dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols and trimethylolpropane, ethylene diamine, diethylene triamine And the like. These may be used alone or in combination of two or more. Among them, water is preferable. The PVA resin concentration of the solution can be set to any suitable value. For example, the degree of polymerization and saponification degree of the PVA resin are set. The PVA resin concentration of the solution is, for example, 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent.

The coating liquid may contain an additive. Examples of the additive include plasticizers, surfactants, and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. The surfactant includes, for example, nonionic surfactants. These can be used for further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer. As the additive, for example, an easy-to-adhere component can be mentioned. By using the easy-to-adhere component, the adhesion between the resin base material and the PVA-based resin layer can be improved. As a result, for example, problems such as peeling of the PVA resin layer from the resin base can be suppressed, and dyeing and in-water stretching described later can be satisfactorily performed. As the easy-to-adhere component, for example, a modified PVA such as acetoacetyl-modified PVA is used.

As a method of applying the coating liquid, any appropriate method may be employed. Examples of the coating method include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method). The coating and drying temperature of the coating liquid is, for example, 20 DEG C or more.

The thickness of the PVA resin layer (before stretching) is preferably 3 to 40 占 퐉, more preferably 3 to 20 占 퐉, and still more preferably 3 to 15 占 퐉.

B-2. dyeing

Examples of the dyeing method include a method in which a PVA resin layer (laminate) is dipped in a dyeing solution containing iodine, a method in which the dyeing solution is applied to a PVA resin layer, a method in which the dyeing solution is PVA And spraying the resin layer. Preferably, a method of immersing the PVA resin layer in the dyeing solution is used.

The dyeing solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.1 part by weight to 0.5 part by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to an aqueous solution of iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Of these, potassium iodide is preferable. The blending amount of iodide is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of water.

The liquid temperature of the dyeing solution is preferably 20 ° C to 50 ° C. The immersion time is preferably 5 seconds to 5 minutes. In addition, the dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or the simple transmittance of the finally obtained polarizer is in a predetermined range.

B-3. Stretching

As the stretching method of the laminate, any suitable method may be employed. Concretely, it may be a fixed-end stretching (for example, a method using a tenter stretcher) or a free-end stretching (for example, a method of uniaxially stretching by passing a laminate between rolls different in circumferential speed). In addition, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or continuous biaxial stretching may be used. Stretching of the laminate may be performed in one step or in multiple steps. In the case of multi-stage execution, the drawing magnification of the laminate to be described later is the product of the drawing magnifications of the respective steps.

In the stretching direction of the laminate, any appropriate direction can be selected. In one embodiment, the elongated laminate is stretched in the longitudinal direction of the laminate. Specifically, the stacked body is transported in the longitudinal direction, and its transport direction (MD) is. In another embodiment, the elongated-layer laminate is stretched in the width direction. Specifically, it is a direction (TD) in which the stack is transported in the longitudinal direction and is perpendicular to the transport direction (MD).

The laminate is preferably stretched 4.0 times or more from the original length, and more preferably 5.0 times or more.

The stretching method is not particularly limited and may be, for example, a pneumatic stretching method or an underwater stretching method in which the laminate is immersed in a stretching bath. Preferably, the underwater stretching is performed at least once, and more preferably, the publicly stretching and underwater stretching are combined. According to the underwater stretching, the resin substrate and the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 deg. C), and the PVA resin layer is stretched at a high magnification while suppressing the crystallization thereof . As a result, a polarizer having excellent optical characteristics can be produced. Further, in the case of combining the pneumatic stretching and the water stretching, it is preferable to undergo water stretching after the pneumatic stretching.

The drawing temperature of the laminate can be set to any appropriate value according to the forming material of the resin base material, the drawing method, and the like. In the case of adopting the pneumatic drawing method, the drawing temperature is preferably at least the glass transition temperature (Tg) of the resin base, more preferably at least the glass transition temperature (Tg) of the resin base + 10 DEG C or more, particularly preferably Tg + 15 ° C or higher. On the other hand, the stretching temperature of the laminate is preferably 170 占 폚 or less. By stretching at such a temperature, the crystallization of the PVA resin can be inhibited from proceeding rapidly, and the problems caused by the crystallization (for example, the orientation of the PVA resin layer due to stretching can be prevented) can be suppressed.

When an underwater stretching method is employed as the stretching method, the temperature of the stretching bath is preferably 40 占 폚 to 85 占 폚, and more preferably 50 占 폚 to 85 占 폚. With such a temperature, stretching can be performed at a high magnification while suppressing the dissolution of the PVA resin layer. Concretely, as described above, the glass transition temperature (Tg) of the resin base material is preferably 60 占 폚 or higher in relation to the formation of the PVA base resin layer. In this case, if the drawing temperature is lower than 40 캜, there is a possibility that the drawing can not be performed satisfactorily even considering the plasticization of the resin substrate by water. On the other hand, the higher the temperature of the drawing bath is, the higher the solubility of the PVA-based resin layer becomes, and there is a possibility that excellent optical characteristics may not be obtained. The immersing time of the laminate in the drawing bath is preferably 15 seconds to 5 minutes.

When an underwater stretching method is employed, it is preferable to immerse the laminate in an aqueous boric acid solution to stretch it (stretching in boric acid in water). By using an aqueous solution of boric acid as the drawing bath, the PVA resin layer can be provided with rigidity to withstand tensile force at the time of stretching and water resistance that does not dissolve in water. The aqueous boric acid solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight based on 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed.

Preferably, iodide is added to the aqueous boric acid solution. This is because if the PVA resin layer is dyed in advance, the elution of iodine can be suppressed. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight based on 100 parts by weight of water.

The underwater stretching is preferably carried out after dyeing. This is because the extensibility can be better. As described above, it is one of the characteristics of the present invention that the laminate can be stretched after dyeing, and according to the present invention, underwater stretching can be satisfactorily performed.

As described above, it is preferable to combine the in-water drawing and the pneumatic drawing. In one embodiment, the laminate is subjected to air-drawing at, for example, 95 ° C to 150 ° C, followed by dyeing, and then stretched by in-water stretching. In this case, the draw ratio of the laminate by air drawing is, for example, 1.5 to 3.5 times, preferably 2.0 to 3.0 times. The stretching magnification of the laminate by in-water stretching is preferably 2.0 times or more.

B-4. Contact with basic solution

The non-light-shielding portion is preferably formed by contacting the PVA-based resin layer with a basic solution. When iodine is used as the dichroic substance, the iodine content of the contact portion can be easily reduced by bringing a basic solution into contact with a desired portion of the PVA-based resin layer. Specifically, the basic solution can penetrate into the PVA-based resin layer by contact. The iodine complex contained in the PVA resin layer is reduced by the base contained in the basic solution to become an iodide ion. By reducing the iodine complex to iodine ion, the transmittance of the contact portion can be improved. Then, the iodine which has become iodine ion moves from the PVA resin layer into the solvent of the basic solution. The non-light-emitting portion thus obtained can be kept in good transparency. Specifically, when the iodine complex is broken to improve the transmittance, the iodine remaining in the PVA resin layer may form an iodine complex again with the use of the polarizer, thereby lowering the transmittance. When the iodine content is reduced Such a problem is prevented.

As a method of contacting the basic solution, any suitable method may be employed. For example, a method of dropping, coating and spraying a basic solution with respect to the PVA resin layer, and a method of immersing the PVA resin layer in a basic solution. Upon contact with the basic solution, the PVA resin layer is coated with any suitable means (e.g., protective film, surface protective film) so that the basic solution other than the desired site is not contacted (the dichroic substance concentration is not lowered) It may be protected. The protective film can be used as it is as a protective film of a polarizer. The surface protective film is used temporarily during the production of the polarizer. Since the surface protective film is removed from the polarizer at any appropriate timing, it is typically bonded to the PVA-based resin layer via a pressure-sensitive adhesive layer.

As the basic compound contained in the basic solution, 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; . Among them, a hydroxide of an alkali metal is preferable, and sodium hydroxide, potassium hydroxide and lithium hydroxide are more preferable. By using a basic solution containing a hydroxide of an alkali metal, the iodine complex can be efficiently ionized and the non-light-emitting portion can be formed more easily. These basic compounds may be used alone or in combination of two or more.

As a solvent for the basic solution, any suitable solvent may be used. Specific examples include water, alcohols such as ethanol and methanol, ether, benzene, chloroform, and mixed solvents thereof. Of these, water and alcohol are preferably used because iodine ions can be favorably converted into a solvent.

The concentration of the basic solution is, for example, 0.01 N to 5 N, preferably 0.05 N to 3 N, more preferably 0.1 N to 2.5 N. When the concentration of the basic solution is in this range, the non-light-emitting portion can be efficiently formed.

The liquid temperature of the basic solution is, for example, 20 ° C to 50 ° C, preferably 25 ° C to 50 ° C. By contacting the basic solution at such a temperature, the non-light-emitting portion can be efficiently formed.

The contact time of the basic solution is set according to, for example, the thickness of the PVA resin layer and the kind and concentration of the basic compound contained in the basic solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

The thickness of the polarizer may correspond to the thickness of the PVA-based resin layer upon contact with the basic solution.

In one embodiment, upon contact of the basic solution, the surface of the PVA resin layer is covered with a surface protective film such that at least a part of the surface is exposed. The polarizer of the illustrated example is produced by, for example, sticking a surface protective film having a small circular through-hole in the PVA resin layer and bringing the basic solution into contact with the surface protective film. At this time, it is preferable that the other side of the PVA resin layer (the side on which the surface protective film is not disposed) is also protected.

The thickness of the surface protective film is typically 20 to 250 占 퐉, preferably 30 to 150 占 퐉. The surface protective film is preferably a film having high hardness (e.g., elastic modulus). And deformation of the through hole can be prevented. Examples of the material for forming the surface protective film include ester based resins such as polyethylene terephthalate based resins, cycloolefin based resins such as norbornene based resins, olefin based resins such as polypropylene, polyamide based resins, polycarbonate based resins , And the like. Preferably, it is an ester-based resin (particularly, a polyethylene terephthalate-based resin). Details of the protective film will be described later.

In a preferred embodiment, a protective film is laminated on the PVA resin layer side of the laminate, the resin substrate is peeled off, and a surface protective film is peelably bonded to the peeled surface, and then a basic solution is contacted . By previously bonding a protective film different from the resin substrate to one side of the PVA resin layer in advance, the surface protective film can be satisfactorily bonded even when the thickness of the PVA resin layer is as thin as described above. In addition, the obtained polarizing film laminate can have excellent transportability. When the polarizing film laminate is a long film, the surface protective film is provided with through holes at predetermined intervals in the longitudinal direction and / or the width direction, for example.

In the above embodiment, the protective film is bonded only to one side of the PVA-based resin layer. In such a structure, curling tends to occur (in particular, when the thickness of the PVA resin layer is 15 탆 or more), problems such as poor adhesion of the surface protective film and lowering of transportability tend to occur. However, When thin, the generation of curl can be suppressed well.

B-5. Other

Prior to the contact with the basic solution, the PVA resin layer may be subjected to any appropriate treatment other than the dyeing / stretching described above. Examples thereof include an insolubilization treatment, a crosslinking treatment, a washing treatment and a drying treatment.

(Insolubilization treatment)

The insolubilization treatment is typically performed by immersing the PVA resin layer in an aqueous solution of boric acid. In particular, in the case of adopting an underwater stretching method, water resistance can be imparted to the PVA resin layer by performing the insolubilization treatment. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. The liquid temperature of the insoluble body (aqueous solution of boric acid) is preferably 20 ° C to 40 ° C. Preferably, the insolubilization treatment is carried out after the production of the laminate, before the dyeing treatment or underwater stretching treatment.

(Crosslinking treatment)

The cross-linking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By carrying out the crosslinking treatment, it is possible to impart water resistance to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. Further, in the case of carrying out the crosslinking treatment after the dyeing treatment, it is preferable to further add iodide. By combining iodide, the elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight based on 100 parts by weight of water. Specific examples of the iodide are as described above. The temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the crosslinking treatment is carried out before the underwater stretching treatment. In a preferred embodiment, dyeing treatment, crosslinking treatment and underwater stretching treatment are carried out in this order.

(Cleaning treatment)

The cleaning treatment is typically performed by immersing a PVA resin layer in an aqueous solution of potassium iodide.

(Dry treatment)

The drying temperature of the drying treatment is preferably 30 ° C to 100 ° C.

In one embodiment, the basic solution is removed from the PVA-based resin layer by contact with the PVA-based resin layer and by any suitable means. According to this embodiment, for example, it is possible to more reliably prevent a reduction in the transmittance of the non-light-emitting portion accompanying the use of the polarizer. Specific examples of the basic solution removing method include cleaning with a wiping agent, removing wiping with a wastepaper, removal of a suction, natural drying, heat drying, air blow drying, and vacuum drying. Preferably, the basic solution is cleaned. Examples of the solution used for washing include water (pure water), alcohol such as methanol and ethanol, acidic aqueous solution, and mixed solvent thereof. Preferably, water is used. The number of times of cleaning is not particularly limited and may be carried out plural times. When the basic solution is removed by drying, the drying temperature is, for example, 20 ° C to 100 ° C.

Preferably, the acidic solution is brought into contact with the portion where the basic solution of the PVA resin layer is contacted. By contacting with the acidic solution, the basic solution remaining in the non-light-emitting portion can be removed to a better level. In addition, the dimensional stability (durability) of the non-light-emitting portion can be improved. The contact with the acidic solution may be performed after the removal of the basic solution or without removing the basic solution.

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 and hydrogen fluoride, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid and benzoic acid. Among them, 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.

As the solvent of the acidic solution, those exemplified as the solvent of the basic solution can be used. 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 of the acidic solution is, for example, 5 seconds to 5 minutes. The contact method of the acidic solution may be the same as the contact method of the basic solution. Further, the acidic solution can be removed from the PVA-based resin layer. As the method for removing the acidic solution, the same method as the method for removing the basic solution may be employed.

C. polarizer

The polarizing plate of the present invention has the polarizer. The polarizing plate typically has a polarizer and a protective film disposed on at least one side of the polarizer. As the protective film, the resin base material may be used as it is, or a film different from the resin base material may be used. Examples of the material for forming the protective film include cellulose resins such as diacetylcellulose and triacetylcellulose, olefin resins such as (meth) acrylic resins, cycloolefin resins and polypropylene, polyethylene terephthalate resins and the like Ester-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof.

The surface of the protective film on which the polarizer is not laminated may be subjected to a treatment for the purpose of hard coat layer, anti-reflection treatment, diffusion or anti-glare as the surface treatment layer. The surface treatment layer is preferably a layer having a low moisture permeability for the purpose of improving durability of humidification of the polarizer, for example. The hard coat treatment is carried out for the purpose of preventing scratches on the surface of the polarizing plate. The hard coat layer can be formed by, for example, a method of adding a cured coating film having excellent hardness and sliding property by a suitable ultraviolet curable resin such as acrylic or silicone to the surface. The hard coat layer preferably has a pencil hardness of 2H or higher. The antireflection treatment is carried out for the purpose of preventing the reflection of external light on the surface of the polarizing plate. The antireflection treatment utilizes the effect of removing the reflected light due to the interference action of light disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2005-248173 Or by forming a low reflection layer such as a structure type in which low reflectance is exhibited by giving a fine structure to the surface as disclosed in Japanese Patent Laid-Open Publication No. 2011-2759. The anti-glare treatment is carried out for the purpose of preventing external light from being reflected on the surface of the polarizing plate to inhibit the visibility of the light transmitted through the polarizing plate. For example, the anti-glare treatment may be carried out by a sandblasting method, an embossing method, Or by adding a micro concavo-convex structure to the surface of the protective film in an appropriate manner such as a blending method. The anti-glare layer may also serve as a diffusion layer (time magnification function or the like) for diffusing the polarized-plate transmitted light to enlarge the viewing angle or the like.

The thickness of the protective film is preferably 10 mu m to 100 mu m. Typically, the protective film is laminated on the polarizer via an adhesive layer (specifically, an adhesive layer and a pressure-sensitive adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activation 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 apparatus of the present invention has the above polarizing plate. Examples of the image display device include a liquid crystal display device and an organic EL device. Specifically, the liquid crystal display device includes a liquid crystal cell and a liquid crystal panel having the polarizing plate disposed on one side or both sides of the liquid crystal cell. The organic EL device has an organic EL panel in which the polarizing plate is disposed on the viewer side. Typically, the polarizer is disposed so as to correspond to a camera hole portion of an image display device on which the non-polarized light portion is mounted.

Example

Hereinafter, the present invention will be described concretely with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows.

1. Thickness

And measurement was conducted using a digital micrometer (product name: "KC-351C", manufactured by Anritsu).

2. Absorption Rate

And measured according to JIS K7209.

3. Glass transition temperature (Tg)

And measured according to JIS K7121.

[Example 1]

(Preparation of laminate)

As the resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 mu m) having an absorption rate of 0.75% and a Tg of 75 DEG C was used.

(Polymerization degree: 4200, degree of saponification: 99.2 mol%) and acetoacetyl modified PVA (degree of polymerization: 1200, degree of acetoacetyl modification: 4.6%, degree of saponification: 99.0 mol%) were added to the corona- Manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name " Gosei Pimer Z200 ") at a ratio of 9: 1 was applied at 25 캜 and dried to form a PVA resin layer having a thickness of 11 탆 to prepare a laminate .

(Production of polarizing plate)

The obtained laminate was immersed (insolubilized) for 30 seconds in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 占 폚.

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

Subsequently, the resultant was immersed in a crosslinking bath (aqueous solution of boric acid obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at 30 占 폚 for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 캜 (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) Uniaxial stretching was performed 5.0 times in the longitudinal direction (longitudinal direction) (underwater stretching).

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

After cleaning, a PVA-based resin aqueous solution (trade name: GOSE PYMER (registered trademark) Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., resin concentration: 3% by weight) was applied to the surface of the PVA resin layer of the laminate, A cellulose film (trade name: KC4UY, manufactured by Konica Minolta Co., Ltd., thickness: 40 占 퐉) was laminated and heated in an oven maintained at 60 占 폚 for 5 minutes to prepare a polarizing plate having a polarizer with a thickness of 5 占 퐉.

(Formation of the non-light-emitting portion)

The resin base material was peeled off from the obtained polarizing plate, and a surface protective film having a circular through hole having a diameter of 4 mm formed thereon was stuck on the peeling surface (polarizing surface), and this was applied to a 1 mol / l (1 N) aqueous solution of sodium hydroxide for 10 seconds (Alkali treatment), and then immersed in 0.1 N hydrochloric acid for 30 seconds (acid treatment). Thereafter, the film was dried at 60 占 폚 and the surface protective film was peeled off to obtain a polarizing plate having a non-light-blocking portion. As the surface protective film, a PET film (38 占 퐉 thick, manufactured by Mitsubishi Plastics, Inc., trade name: Diafoil) having a pressure-sensitive adhesive layer having a thickness of 5 占 퐉 was used.

[Example 2]

The resultant laminate was subjected to the above-mentioned insolubilization treatment after free-end uniaxial stretching (air-assisted stretching) in the longitudinal direction (longitudinal direction) at different angles in the longitudinal direction The polarizing plate having a non-light-emitting portion was obtained in the same manner as in Example 1 except that the stretching magnification was 5.5 times.

[Example 3]

A polarizing plate having a non-light-emitting portion was obtained in the same manner as in Example 1 except that a polarizer having a thickness of 12 占 퐉 was formed on a resin substrate and that the immersion time in an aqueous solution of sodium hydroxide was changed to 30 seconds in the alkali treatment.

[Example 4]

(Preparation of laminate)

(Trade name: " GOSE PIMER (registered trademark) Z-200 ", manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) as an adhesive and a polyvinyl alcohol film having a thickness of 20 탆 (degree of polymerization: 4300, degree of saponification: 99.3 mol% Resin concentration: 3% by weight) was laminated to obtain a laminate. As the resin substrate, a surface of amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (Tg 75 DEG C, absorption rate 0.75%) having a thickness of 100 mu m was subjected to corona treatment.

(Production of polarizing plate)

The resultant laminate was free-end uniaxially stretched 2.0 times in the longitudinal direction (longitudinal direction) between rolls different in the main speed in an oven at 120 캜 (air drawing).

Subsequently, the obtained laminate was immersed in a swelling bath (pure water) at a liquid temperature of 30 캜 (swelling treatment).

Subsequently, the laminate was immersed in a dyeing bath at a liquid temperature of 30 캜 while adjusting the iodine concentration and immersion time so that the polarizing plate thus obtained had a predetermined transmittance. In this embodiment, 0.15 parts by weight of iodine was blended with 100 parts by weight of water, and 1.0 part by weight of potassium iodide was blended, followed by immersion for 60 seconds in an aqueous iodine solution (dyeing treatment).

Subsequently, the resultant was immersed in a crosslinking bath (aqueous solution of boric acid obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at 30 占 폚 for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a boric acid aqueous solution having a liquid temperature of 70 캜 (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) And uniaxial stretching was performed so that the stretching ratio in the longitudinal direction was 5.5 times (in-water stretching).

Subsequently, a PVA-based resin aqueous solution (trade name: GOSE PIMER (registered trademark) Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., resin concentration: 3 wt%) was applied to the surface of the polyvinyl alcohol film of the laminate, (Manufactured by Konica Minolta Co., Ltd., trade name " KC4UY ", thickness 40 占 퐉) was laminated and heated in an oven kept at 60 占 폚 for 5 minutes to prepare a polarizing plate having a polarizer with a thickness of 8 占 퐉.

Thereafter, a retardation portion was formed in the same manner as in Example 1 to obtain a polarizer having a retardation portion.

[Example 5]

Except that a PVA film (PE3000, manufactured by Kuraray Co., Ltd.) having a thickness of 30 占 퐉, an iodine concentration of a dyeing bath of 0.1 weight%, and an immersion time of 30 seconds in an aqueous solution of sodium hydroxide in an alkali treatment 4, a polarizing plate having a non-light-emitting portion was obtained.

[Example 6]

(Preparation of laminate)

(Trade name: " GOSE PIMER (registered trademark) Z-200 ", manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) as an adhesive and a polyvinyl alcohol film having a thickness of 20 탆 (degree of polymerization: 4300, degree of saponification: 99.3 mol% Resin concentration: 3% by weight) was laminated to obtain a laminate. As the resin substrate, a surface of amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (Tg 75 DEG C, absorption rate 0.75%) having a thickness of 100 mu m was subjected to corona treatment.

A polarizing plate having a non-light-emitting portion was obtained in the same manner as in Example 1 except that the above-mentioned laminate was used and that the iodine concentration in the dyeing bath was 0.15 wt% and the potassium iodide concentration was 1.0 wt%.

[Example 7]

(Preparation of laminate)

As the resin substrate, a cycloolefin-based resin film (ARTON manufactured by JSR Corporation) having a Tg of about 120 캜 was used.

An aqueous solution of a polyvinyl alcohol resin having a degree of polymerization of 4300 and a degree of saponification of 99.2% was applied to one side of the resin substrate at 80 DEG C and dried to form a PVA resin layer having a thickness of 12 mu m to prepare a laminate.

(Production of polarizing plate)

The laminate thus obtained was stretched to 4.5 times the draw ratio by free uniaxial stretching under heating at 140 占 폚. The thickness of the PVA resin layer after the stretching treatment was 5 占 퐉 (air drawing).

Subsequently, the resultant was immersed in a dyeing bath (an iodine aqueous solution obtained by blending 0.5 parts by weight of iodine and 3.5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 占 폚 for 60 seconds (dyeing treatment).

Subsequently, the resultant was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 5 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a temperature of 60 占 폚 for 60 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in a cleansing bath (an aqueous solution obtained by mixing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment).

After cleaning, a PVA-based resin aqueous solution (trade name: GOSE PYMER (registered trademark) Z-200, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., resin concentration: 3% by weight) was applied to the surface of the PVA resin layer of the laminate, A cellulose film (trade name: KC4UY, manufactured by Konica Minolta Co., Ltd., thickness: 40 占 퐉) was laminated and heated in an oven maintained at 60 占 폚 for 5 minutes to prepare a polarizing plate having a polarizer with a thickness of 5 占 퐉.

Thereafter, a retardation portion was formed in the same manner as in Example 1 to obtain a polarizer having a retardation portion.

The following evaluations were carried out for each example. The evaluation results are shown in Table 1. The polarization degree of the polarizer shows a value at a single transmittance of 42.0%.

1. Optical properties

In each of the examples, samples were prepared by changing the diameter of the small holes of the surface protective film to 20 mm, and these were provided for measurement.

(Ts), a parallel transmittance (Tp) and a quadrature transmittance (Tc) of a polarizer were measured using an ultraviolet visible spectrophotometer (product name: "V7100" . Further, Ts, Tp, and Tc are Y values measured by the second view field (C light source) of JIS Z 8701 and subjected to visibility correction.

(%) = {(Tp - Tc) / (Tp + Tc)} ^1/2 100

2. Appearance of non-miners

The appearance of the non-light-emitting portion (the portion corresponding to the small hole of the surface protective film) was observed by an optical microscope (MX61, manufactured by OLYMPUS CO., LTD., Magnification: 5 times).

In each of the examples, a non-polarizing portion was preferably formed. Further, in Example 7, the polarization degree was lower than the other. In Examples 3 and 5, wrinkles were found in the non-light-emitting portion to such an extent that they could not be visually confirmed. It is predicted that wrinkles are generated by partially absorbing the contact portion of the basic solution after the alkali treatment (before the acid treatment) and expanding by the subsequent treatment.

The polarizer of the present invention is preferably used for a camera-equipped image display device (liquid crystal display device, organic EL device) such as a mobile phone such as a smart phone, a notebook PC, and a tablet PC.

1: Polarizer
2:

Claims (11)

A step of forming a polyvinyl alcohol-based resin layer on a resin substrate to obtain a laminate,
A step of dyeing the polyvinyl alcohol-based resin layer with iodine,
A step of stretching the laminate,
The step of forming a non-light-emitting portion by contacting a basic solution to the polyvinyl alcohol-based resin layer after the dyeing and stretching includes contacting the basic solution with a polyvinyl alcohol-based resin layer having a thickness of 8 탆 or less to form a non- A method for producing a polarizer,
A protective film is laminated on the side of the polyvinyl alcohol-based resin layer of the laminate, the resin base material is peeled off, and a surface protective film is peelably bonded to the peeled surface, the basic solution is contacted with the polarizing film laminate And,
Wherein the polarizing film laminate is elongated, and the surface protective film is provided with through holes at a predetermined interval in the longitudinal direction, the width direction, or the longitudinal direction and the width direction. The method according to claim 1,
And the content of iodine in the non-light-emitting portion is 1.0 wt% or less. The method according to claim 1,
And the basic solution is contacted with the surface protective film so that the surface of the polyvinyl alcohol-based resin layer is at least partially exposed. delete delete 4. The method according to any one of claims 1 to 3,
Wherein the laminate is obtained by applying a coating liquid containing a polyvinyl alcohol resin to the resin substrate. 4. The method according to any one of claims 1 to 3,
And the laminate is stretched after the dyeing. 8. The method of claim 7,
Wherein the stretching is in-water stretching. delete delete 4. The method according to any one of claims 1 to 3,
Wherein an acidic solution is brought into contact with a portion of the polyvinyl alcohol-based resin layer in contact with the basic solution.

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