KR101752069B1 - Polarizing film, polarizing plate and method of manufacturing the polarizing film - Google Patents

Abstract

Provided is a polarizing plate having a thin polarizing film (thickness? 10 占 퐉) capable of suppressing light leakage when mounted on a display device. Also provided is a method for producing a polarizing film having a thickness of 10 mu m or less and a deviation of absorption axis in a plane of 0.2 DEG or less, which comprises the following step (1). (1) A longitudinally stretched base film comprising a thermoplastic resin, wherein the standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD direction is not more than 0.80 m and the waveform is Fourier transformed, A step of preparing a base film having a standard deviation? 2 calculated from a waveform having a thickness obtained by inverse Fourier transforming a spectrum of 1/3 (1 / m) or more in a range of 0.65 mu m or less

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing film, a polarizing plate, and a polarizing film.

The present invention relates to a polarizing film, a polarizing plate and a process for producing the polarizing film.

The polarizing plate is widely used as a polarizing light supplying element in a liquid crystal display device and also as a polarizing light detecting element. As a polarizing plate, a polarizing film made mainly of a polyvinyl alcohol-based resin is bonded to a protective film made of triacetyl cellulose or the like through an adhesive. Recently, a liquid crystal display device has been developed in mobile devices such as notebook PCs and mobile phones, Has been required to be thinner and thinner due to the development of a large-size television.

A conventional polarizing film is produced by stretching and dyeing a master of a film of a polyvinyl alcohol-based resin (usually about 75 to 30 탆 in thickness), and the film thickness after stretching is usually about 30 to 12 탆. When a film having a thickness of 30 占 퐉 or less is used as a film original of a polyvinyl alcohol-based resin for thinning, there is a problem of productivity such as a film being easily broken at the time of stretching.

To cope with thinning of the polarizing plate, therefore, a method of coating a coating liquid containing a polyvinyl alcohol-based resin on a base film has been proposed. In this method, a coating solution containing a polyvinyl alcohol-based resin is coated on a base film to form a polyvinyl alcohol-based resin layer to obtain a laminated film, and then the laminated film is subjected to stretching and dyeing treatment, And a polarizing function is imparted to the alcoholic resin layer to obtain a polarizing film (Patent Documents 1 and 2).

Patent Document 1: JP-A-2011-150313 Patent Document 2: JP-A-2012-159778

As described above, in the method of obtaining a polarizing film by coating a coating liquid containing a polyvinyl alcohol-based resin and producing a polarizing plate, it is possible to achieve a relatively simple thinning of the polarizing plate. However, when a polarizing plate manufactured by the above-described method is mounted on a liquid crystal display device, light leakage occurs, and a high contrast ratio can not be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a polarizing plate capable of suppressing light leakage when a polarizing plate having such a thin polarizing film (thickness? 10 m) And a method for producing such a polarizing film and a polarizing plate.

The present invention includes the following.

[1] A polarizing film having a thickness of 10 μm or less and a deviation of an absorption axis in a plane of 0.2 ° or less.

[2] A polarizer formed by bonding a protective film to a polarizing film described in [1].

[3] A display device having the polarizing film according to [1] or the polarizing plate according to [2].

[4] A method of producing a polarizing film having a thickness of 10 μm or less and a deviation of an absorption axis in a plane of 0.2 ° or less, which comprises the following steps (1) to (5).

(1) A long base film comprising a thermoplastic resin, wherein a ratio (? 1 / d) of a standard deviation? 1 calculated from a waveform obtained by measuring the thickness of the base film in the MD direction to a thickness d of the base film is 9.0 x 10 ^-3 ,

The ratio (? 2 / d (d / 2)) of the standard deviation? 2 calculated from the waveform of the thickness obtained by inverse Fourier transforming the spectra of the region having a wavenumber of 1/3 ) Of 8.0 x 10 < ^-3 >

(2) a step of coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film

(3) a step of uniaxially stretching the laminated film to obtain a stretched film

(4) a step of staining the stretched film to obtain a polarizing laminated film

(5) a step of obtaining a polarizing film by peeling the base film from the polarizing laminated film

[5] A method of producing a polarizing film having a thickness of 10 μm or less and a deviation of an absorption axis in a plane of 0.2 ° or less, which comprises the following steps (1) to (5).

(1) A long base film comprising a thermoplastic resin, wherein a standard deviation? 1 calculated from a waveform obtained by measuring the thickness of the base film in the MD direction is 0.80 占 퐉 or less,

Further, a step of preparing a base film having a standard deviation? 2 calculated from a waveform having a thickness obtained by performing inverse Fourier transform on a spectrum having a wavenumber of 1/3 (1 / m) or more after Fourier transformation of the above waveform is 0.65 占 퐉 or less

(2) a step of coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film

(3) a step of uniaxially stretching the laminated film to obtain a stretched film

(4) a step of staining the stretched film to obtain a polarizing laminated film

(5) a step of obtaining a polarizing film by peeling the base film from the polarizing laminated film

[6] A process for producing a polarizing film as described in [4] or [5], which comprises laminating a protective film on a polarizing film in the polarizing laminated film through an adhesive or a pressure-sensitive adhesive.

[7] The method for producing a polarizing film according to [4] or [5], wherein the base film prepared in the step (1) is a base film formed by melt extrusion.

[8] The method for producing a polarizing film according to [4], wherein the base film prepared in the step (1) has a thickness of 5 to 300 μm.

[9] The method for producing a polarizing film according to [5], wherein the base film prepared in the step (1) has a thickness of 20 to 150 μm.

[10] The method for producing a polarizing film according to [4] or [5], wherein the base film prepared in the step (1) is a base film comprising a polyolefin resin.

According to the method of the present invention, it is possible to provide a polarizing plate capable of suppressing light leakage when mounted on a display device, and a display device including such a polarizing plate can achieve a high contrast ratio.

1 is a view for explaining a method of measuring a deviation of an absorption axis.
2 is a schematic view showing an example of the layer structure of the polarizing plate of the present invention.
3 is a schematic view showing an example of the layer structure of the display device of the present invention.

The polarizing film of the present invention can be produced by a process including the following steps (1) to (5). Each step will be described in sequence.

(1) A long base film comprising a thermoplastic resin, wherein the standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD direction is not more than 0.80 占 퐉,

Further, a step of preparing a base film having a standard deviation? 2 calculated from a waveform having a thickness obtained by performing inverse Fourier transform on a spectrum having a wavenumber of 1/3 (1 / m) or more after Fourier transformation of the above waveform is 0.65 占 퐉 or less

(2) a step of coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film

(3) a step of uniaxially stretching the laminated film to obtain a stretched film

(4) a step of staining the stretched film to obtain a polarizing laminated film

(5) a step of obtaining a polarizing film by peeling the base film from the polarizing laminated film

The polarizing film of the present invention can also be produced by a process including the following steps (1) to (5).

(1) A longitudinally stretched base film comprising a thermoplastic resin, wherein the ratio (? 1 / d) of the standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD direction to the thickness d of the base film is 9.0 x 10 ^-3 ,

The ratio (? 2 / d (d / 2)) of the standard deviation? 2 calculated from the waveform of the thickness obtained by inverse Fourier transforming the spectra of the region having a wavenumber of 1/3 ) Of 8.0 x 10 < ^-3 >

(2) a step of coating a coating liquid containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film

(3) a step of uniaxially stretching the laminated film to obtain a stretched film

(4) a step of staining the stretched film to obtain a polarizing laminated film

(5) a step of obtaining a polarizing film by peeling the base film from the polarizing laminated film

[Step (1)]

In the step (1), a long base film including a thermoplastic resin is used. The standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD direction is 0.80 mu m or less and the waveform is Fourier transformed And a standard deviation 2 calculated from a waveform of thickness obtained by inverse Fourier transforming the spectrum of a region having a wavenumber of 1/3 (1 / m) or more is 0.65 mu m or less.

The base film prepared in the step (1) is an elongated base film comprising a thermoplastic resin. The ratio of the standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD direction to the thickness d of the base film 1 / d) is 9.0 x 10 < ^-3 > or less,

The ratio (? 2 / d (d / 2)) of the standard deviation? 2 calculated from the waveform of the thickness obtained by inverse Fourier transforming the spectra of the region having a wavenumber of 1/3 ) Is not more than 8.0 x 10 < ^-3 >

(Substrate film)

The resin forming the base film preferably includes a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability and the like. Examples of the thermoplastic resin include a cellulose ester-based resin such as cellulose triacetate; Polyester-based resin; Polyether sulfone type resin; Polysulfone resins; Polycarbonate resin; Polyamide based resin; Polyimide resin; Polyolefin resins such as a chain polyolefin resin and a cyclic polyolefin resin (norbornene resin and the like); (Meth) acrylic resins; Polyarylate resins; Polystyrene type resin; Polyvinyl alcohol-based resins, and the like. On the other hand, in the present specification, the (meth) acrylic resin means the methacrylic resin and the acrylic resin collectively.

The cellulose ester resin is an ester of cellulose and a fatty acid. Examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Of these, cellulose triacetate is preferred. Cellulose triacetate is commercially available since many kinds of products are available, and it is advantageous in terms of cost and availability. Examples of commercially available products of cellulose triacetate include Fujisac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujixac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.) (Registered trademark) TD80UZ (manufactured by FUJIFILM Corporation), Fuji ™ (registered trademark) TD40UZ (manufactured by Fuji Film), KC8UX2M (manufactured by Konica Minolta Opt), and KC4UY Manufactured by Konica Minolta Opt Co., Ltd.).

Examples of the chain polyolefin-based resin include homopolymers such as polyethylene resins and polypropylene resins, and copolymers comprising two or more kinds of chain olefins.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized with cyclic olefin as a polymerization unit, and examples thereof include those described in JP-A-1-240517, JP-A-3-14882, And resins described in publications and the like. Examples of the cyclic polyolefin-based resin include a ring-opening polymer of cyclic olefins, ring-opening copolymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically, random copolymers) of cyclic olefins and chain olefins such as ethylene and propylene, Graft polymers modified with carboxylic acids and derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin obtained by polymerizing a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is preferable.

As the cyclic polyolefin-based resin, various products are commercially available. (Commercially available from TOPAS ADVANCED POLYMERS GmbH, available from Polyplastics Co.), " ATON (registered trademark) " (JSR ZEONOR (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), APEL (registered trademark) (Manufactured by Mitsui Chemicals, Inc.).

As the (meth) acrylic resin, any (meth) acrylic resin may be employed. Examples thereof include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymers, methyl methacrylate- (meth) acrylate copolymers, methyl methacrylate- Styrene copolymer (MS resin), a polymer having an alicyclic hydrocarbon group (e.g., a methyl methacrylate-cyclohexyl copolymer, a methacrylic acid methyl- (meth) acrylate copolymer, ) Acrylate norbornyl copolymer). Preferably, poly (meth) acrylate having 1 to 6 carbon atoms in the alkyl moiety, such as poly (meth) acrylate, and the like can be used. More preferably, methyl methacrylate is used as the main component %, Preferably 70 to 100% by weight) of a methyl methacrylate resin.

It is preferable that the base film is at least one resin selected from the group consisting of a cellulose ester resin, a polyolefin resin and a (meth) acrylic resin from the standpoint of excellent stretchability of a laminated film obtained by laminating a polyvinyl alcohol- . Among them, the base film preferably contains a chain polyolefin resin in view of easy adjustment of the phase transition temperature, and more preferably a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene Or the like), or a polyethylene-based resin (such as a homopolymer of ethylene or a copolymer mainly composed of ethylene resin or ethylene).

The chain polyolefin resin often has crystallinity and the polypropylene resin which is a homopolymer of propylene has a melting point (Tm) in a range of approximately 150 to 180 ° C. In the case of a polyethylene resin which is a homopolymer of ethylene, the melting point (Tm) may vary depending on the density and the like. The melting point (Tm) thereof is in the range of 100 to 140 캜. A polypropylene resin obtained by copolymerizing propylene with another kind of monomer such as ethylene can obtain a copolymer having a melting point lower than the melting point of the propylene homopolymer. Thus, the phase transition temperature of the polypropylene type resin can be controlled by adjusting the presence or absence of the copolymerization component or the kind and content of the copolymerization component.

Examples of other types of monomers copolymerizable with propylene include ethylene,? -Olefin, and the like. As the? -olefin, an? -olefin having 4 or more carbon atoms is preferable, and an? -olefin having 4 to 10 carbon atoms is more preferable. Examples of the? -Olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; Vinylcyclohexane and the like. The copolymer of propylene and other monomers copolymerizable with polypropylene may be a random copolymer or a block copolymer. On the other hand, the content of the constituent unit derived from the other monomer in the copolymer can be measured by an infrared (IR) spectroscopy measurement according to the method described on page 616 of "Polymer Analysis Handbook" (published by Kinokuniya Shoten in 1995) . ≪ / RTI >

As the polypropylene-based resin, propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, or propylene-ethylene-1-butene random copolymer are preferable.

The stereoregularity of the polypropylene resin is preferably isotactic or syndiotactic. A base film comprising a resin layer made of a polypropylene resin having isotactic or syndiotactic stereoregularity is preferable from the viewpoints of a relatively good handling property and a high mechanical strength under a high temperature environment.

In addition to the thermoplastic resin, an additive may be added to the base film. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments and colorants.

The content of the thermoplastic resin in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, and still more preferably 60 to 98% by weight.

When the content of the thermoplastic resin in the base film is less than 50% by weight, the light transmittance of the thermoplastic resin may not be sufficiently expressed.

The thickness of the base film is preferably 1 to 500 占 퐉, more preferably 5 to 300 占 퐉, further preferably 10 to 200 占 퐉, and still more preferably 20 to 150 占 퐉, from the viewpoint of workability such as strength and handling properties .

The base film used in the production of the polarizing film of the present invention may be a single layer film composed of a single layer or a multilayer film composed of a plurality of layers. It is preferable to use a multilayer film in the sense of imparting fracture resistance in the drawing process in the subsequent process (refer to Japanese Patent Application Laid-Open No. 2013-101241)

The elongated base film prepared in the step (1) has a standard deviation? 1 calculated from the waveform obtained by measuring the thickness of the base film in the MD (Machine Direction) direction of 0.80 mu m or less and the waveform is Fourier transformed The standard deviation 2 calculated from the waveform of the thickness obtained by performing the inverse Fourier transform on the spectrum of the region whose wave number is 1/3 (1 / m) or more is 0.65 mu m or less.

In the measurement of the thickness of the base film, the measurement position in the TD (Transverse Direction) direction of the base film is arbitrary, but usually measured at the midpoint of the base film.

From the viewpoint of the reliability of the values of the standard deviation sigma 1 and the standard deviation sigma 2, the length of the elongate base film in the MD direction is preferably 10 m or more, and more preferably 100 m or more. Further, in consideration of the length of the actual elongated base film, the length in the MD direction is usually 10000 m or less.

In the present invention, it is necessary to measure a thickness change of a wave number of 1/3 m < ^-1 > or more, that is, a thickness change whose period is 3 m or less. Therefore, from the viewpoint of the reliability of the values of the standard deviation sigma 1 and the standard deviation sigma 2, the interval of the thickness data acquisition positions is usually 50 cm or less, and preferably 5 cm or less. The interval of the thickness data acquisition positions is usually 1 cm or more.

In the case of continuously measuring the thickness while conveying the elongate base film while the measuring apparatus is fixed, the conveying speed of the base film is adjusted to satisfy the thickness data obtaining interval in accordance with the period in which the measuring apparatus acquires the thickness data You can choose to. For example, when the measuring device measures the thickness data in a cycle of 1 second, the conveying speed of the base film is 3 m / min. Or less.

The method for measuring the thickness of the film may be a method capable of measuring a thickness displacement of 0.1 占 퐉 or less, but a method using light such as a laser or infrared ray is preferable, and a method using a laser is more preferable.

The base film satisfying the standard deviation sigma 1 and the standard deviation sigma 2 can be produced, for example, as follows.

When a multilayer film is used as the base film, a base film can be produced by a co-extrusion molding method (also referred to as a co-extrusion casting method) or an extrusion lamination method. A method of molding by a co-extrusion molding method (co-extrusion casting method) is preferable from the viewpoints of productivity and cost. The co-extrusion molding method comprises extruding a desired number of extruders in the form of a film in the state that the extruders are connected to one T-die by a resin from the T-die, cooling and solidifying them with a cooling roll, Is a method for producing a film.

Specifically, as an example of a method for producing a multilayer base film by a co-extrusion molding method, a method for producing a base film made of a three-layer polypropylene type resin will be described below.

The three extruders are each heated to about 200 to 300 DEG C, and a polypropylene resin is fed to each extruder. A polypropylene resin is melted and kneaded by screws of the respective extruders, and melt-co-extruded from a T die into a sheet form is contacted with a cooling roll by various means and cooled to produce a multilayer base film.

The temperature of the multilayer film of a polypropylene resin in the form of a coextruded molten sheet (hereinafter may be referred to as a melt multilayer film) is preferably about 250 to 300 占 폚, more preferably 260 to 290 占 폚. If the temperature of the molten multi-layer film is lower than 250 캜, the melt-kneading state of the polypropylene resin in the extruder becomes insufficient, the appearance of the obtained film becomes extremely deteriorated, and the thickness precision of the film in the TD direction also deteriorates have. Further, when the temperature of the molten multi-layer film is lower than 250 占 폚, the resulting multilayer film may be inferior in transparency. When the temperature exceeds 300 캜, the polypropylene resin tends to be deteriorated or decomposed easily, and bubbles or carbides are contained in the sheet. Further, since the resin viscosity at the time of melting is extremely lowered, the molten multi-layer film can not be stably cooled and solidified, and the thickness precision of the resulting film may be deteriorated.

The three extruders may be a single-screw extruder or a twin-screw extruder, and the respective extruders may not be unified. Further, by selecting the sizes of the three extruders based on the composition ratio of each layer in the base film, it is possible to make the extruded amount to be stable by the facility. Each resin melted and kneaded by each extruder is supplied to a feed block or a converting adapter through a temperature-regulated single pipe called an adapter. These are appropriately selected depending on the type of T die. If there is only one channel in the T die, the resin is arranged in advance in the feed block according to the resin composition of the multilayer film, and then supplied to the T die. On the other hand, in the case of a facility having a plurality of channels in a T die called a multi-manifold, since the resin layers are stacked in front of the T die lip, the flow path from each extruder is converted into T Connect to each channel in the die.

It is preferable that the pressure in each extruder at this time be such that the variation value is within 0.5 MPa. When the fluctuation value of the pressure exceeds 0.5 MPa, the flow rate of the resin from the T die changes, and thus the thickness precision of the obtained film in the MD direction may be deteriorated.

On the other hand, from the viewpoint of suppressing the extrusion fluctuation of each resin constituting the multilayer film, a gear pump is attached between each extruder and the T die through an adapter to stabilize the pressure in each extruder and supply resin to the T die It is also good.

Further, it is preferable to remove foreign matter contained in the propylene resin by a leaf disk filter. The number of leaves and the filtration area per sheet of the leaf disk filter can be arbitrarily selected depending on the viscosity of the molten resin, the amount of extrusion (flow rate), and the heat resistance of the resin. It is preferable to use a filter having a foreign particle size of not more than 10 mu m so that the amount of water entrained in the film can be reduced and the quality of the film can be improved. It is more preferable to use a filter having a particle size of not more than 5 占 퐉 and a filter having a particle size of not more than 3 占 퐉 where the trapping rate of the foreign matter is not less than 98% . The installation position of the leaf disk filter is preferably in the order of an extruder, a gear pump, a leaf disk filter, and a T die in order to stably remove foreign matter.

The molten multi-layer film is then contacted with a metal cooling roll (also referred to as a chill-roll or casting roll) and cooled by being brought into close contact with a cooling roll to form a multilayer film containing a polypropylene type resin ) Can be obtained. At this time, the method of close contact with the cooling roll may influence the transparency. The adhesion to the cooling roll can be carried out, for example, by a method in which a molten multilayered film is electrostatically charged and the surface state of the molten multilayered film is brought into close contact with a quenching roll, A method in which a metal foil is pressed between a metal roll capable of being elastically deformable (also referred to as a touch roll) or a metal belt and cooled by being brought into close contact with a cooling roll, a method in which a molten multilayer film is brought into contact with a cooling roll, A method in which the molten multi-layer film is brought into close contact with the cooling roll by air blown from the air chamber from the viewpoint of productivity and quality, and the like.

In the method in which the molten multi-layer film is brought into close contact with the cooling roll by the air ejected from the air chamber to cool the molten multi-layer film, the molten multi-layer film extruded from the T die is contacted with the cooling roll, By spraying air by the chamber, the molten multilayer film is brought into close contact with the cooling roll. The air chamber may be any suitable commercially available one. The air to be sprayed is sucked through a high-performance air filter (HEPA filter: High Efficiency Particulate Air Filter), for example, by blowing air in a manufacturing environment space, so that the inside of the air chamber is pressurized to 50 to 300 Pa More preferably 100 to 200 Pa in a pressurized state. When the pressure in the air chamber is higher than 300 Pa, the pressure applied to the molten multilayer film becomes excessively large, and the film thickness precision in the plane of the multilayer film obtained by causing flaking of the molten multilayer film is significantly deteriorated. Especially, The fluctuation in thickness of the period tends to increase. When the pressure in the air chamber is smaller than 50 Pa, the wind pressure applied to the molten multilayered film becomes too small to bring the multilayered film into close contact with the cooling roll, so that the haze of the multilayered film is increased. The adhesion is uneven, the multilayer film is cooled in a dark state, and the appearance is deteriorated, so that the thickness precision may be significantly deteriorated.

The cooling roll used in the above-mentioned three types of systems is preferably adjusted, for example, to a surface temperature of 10 to 60 캜. If the surface temperature of the cooling roll exceeds 60 캜, it takes time to cool and solidify the molten multi-layer film, so that the crystalline component in the propylene resin constituting the molten multi-layer film grows. If the obtained multilayer film is poor in transparency . On the other hand, if the surface temperature of the cooling roll is lower than 10 占 폚, the surface of the cooling roll becomes dewy and water droplets adhere to it, which may deteriorate the appearance of the resulting multilayered film.

The processing speed at the time of producing the multilayered film including the polypropylene type resin layer is determined according to the time required for cooling and solidifying the polypropylene type resin in the molten multilayered film. With regard to the processing speed, when the diameter of the cooling roll to be used is increased, the distance at which the molten multi-layer film is in contact with the cooling roll becomes longer, so that the multilayer film can be manufactured at higher speed. Specifically, when a multilayered film comprising a transparent propylene resin layer having a haze value of 20% or less is produced using a 600 mm? Metal cooling roll, the processing speed is 20 to 40 m / min. Respectively. When the processing speed is lower than 20 m / min, the film thickness tends to come out unevenly in the MD direction, and the thickness fluctuation of the period of 3 m or less tends to be large. When the processing speed is higher than 40 m / min., The crystallization progresses uniformly, but since the crystallization rate is slow, the haze increases and the transparency of the multilayered film may be poor.

By selecting the optimal conditions for the temperature of the molten multi-layer film, the pressure in the air chamber, the temperature of the cooling roll, and the processing speed appropriately, it is possible to obtain a multilayer base film having excellent film thickness accuracy.

On the other hand, the base film obtained may be subjected to a corona treatment, a plasma treatment, a flame treatment, or the like on the surface on which the polyvinyl alcohol-based resin layer is formed in order to improve the adhesion with the polyvinyl alcohol-based resin layer.

The ratio (? 1 / d) of the standard deviation? 1 to the thickness d of the base film is 9.0 占^10-3 or less and the ratio? 2 / d of the standard deviation ^{? A} base film having a thickness of ³占 퐉 or less can be produced in the same manner as a base film satisfying the standard deviation? 1 and the standard deviation? 2. When? 1 / d and? 2 / d satisfy the above ranges, the polarizing film of the present invention can be produced regardless of the thickness of the base film, which is preferable.

[Step (2)]

In the step (2), a coating liquid containing a polyvinyl alcohol-based resin is applied to at least one surface of the base film to obtain a coating film. Then, the coating film is dried to form a polyvinyl alcohol-based resin layer.

(Coating liquid containing a polyvinyl alcohol-based resin)

The coating liquid is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a powder of a polyvinyl alcohol-based resin in a good solvent (for example, water). Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and derivatives thereof. Examples of derivatives of polyvinyl alcohol resins include polyvinyl formal, polyvinyl acetal and the like, modified polyvinyl alcohol resins with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid; Acrylamide, and the like. The modification ratio is preferably less than 30 mol%, more preferably less than 10 mol%. When the modification is performed in an amount exceeding 30 mol%, it becomes difficult to adsorb the dichroic dye, which may cause a problem that the polarization performance is lowered. Of the polyvinyl alcohol-based resins described above, polyvinyl alcohol resins are preferably used.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably in the range of 100 to 10000, more preferably in the range of 1000 to 10000, more preferably in the range of 1500 to 8000, . The average degree of polymerization can be determined by the method described in JIS K 6726-1994 " Polyvinyl alcohol test method ". When the average degree of polymerization is less than 100, it is difficult to obtain a desired polarizing performance. When the average degree of polymerization is more than 10,000, the solubility in a solvent deteriorates and it becomes difficult to form a polyvinyl alcohol-based resin layer.

The polyvinyl alcohol-based resin is preferably a saponified polyvinyl acetate-based resin. The degree of saponification is preferably 80 mol% or more, more preferably 90 mol% or more, particularly preferably 94 mol% or more. If the degree of saponification is too low, there is a possibility that the water resistance and humidity resistance of the polarizing laminated film or polarizing plate may become insufficient. If the degree of saponification is excessively high, the dyeing speed is slowed. In order to give sufficient polarizing performance, the production time may be prolonged, and in some cases, sufficient polarization performance (e.g., Or can not obtain a polarizing film having a polarizing film. Therefore, the degree of saponification is preferably 99.5 mol% or less, and more preferably 99.0 mol% or less.

The degree of saponification indicates the unit ratio (mol%) of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin as the raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification treatment, The following formula:

Saponification degree (mol%) = [(number of hydroxyl groups) / (number of hydroxyl groups + number of acetic acid groups)] x 100

.

The higher the degree of saponification, the higher the ratio of hydroxyl groups, which means that the proportion of acetic acid groups that inhibit crystallization is smaller. The saponification degree can be determined by the method described in JIS K 6726-1994 " Polyvinyl alcohol test method ".

As the polyvinyl acetate resin, a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, and other monomers copolymerizable with vinyl acetate, and the like can be given. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

PVA124 "(saponification degree: 98.0 to 99.0 mol%) and" PVA117 "(saponification degree: 98.0 to 99.0 mol%) commercially available from Kuraray Co., (Saponification degree: 99.5 mol% or more), "PVA624" (saponification degree: 95.0 to 96.0 mol%), "PVA617" (saponification degree: 94.5 to 95.5 mol%), "PVA117H" AH-26 "(saponification degree: 97.0 to 98.8 mol%)," AH-22 "(saponification degree: 97.5 to 98.5 mol%)," NH-18 " : 98.0 to 99.0 mol%), "N-300" (saponification degree: 98.0 to 99.0 mol%); (Saponification degree: 99.0 mol% or more), JM-33 (saponification degree: 93.5 to 95.5 mol%) and JM-26 (saponification degree: JF-17L "(saponification degree: 98.0 to 99.0 mol%) and" JF-17L "(saponification degree: 98.0 to 95.5 mol% 99.0 mol%) and "JF-20" (saponification degree: 98.0 to 99.0 mol%).

The coating liquid may contain an additive such as a plasticizer and a surfactant if necessary. Examples of the plasticizer include polyols and condensates thereof, and specific examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

(Coating of Coating Solution and Drying of Coating Film)

The method of applying the coating solution onto the base film may be a wire bar coating method; Roll coating methods such as reverse coating and gravure coating; Die coating method; Comma coat method; Lip coating method; Spin coating method; Screen coating method; Fountain coating method; Dipping method; Spray method, and the like.

When a coating liquid is applied to both surfaces of the base film, it may be coated one by one in order by the above-described method, or may be coated on both sides of the base film simultaneously by a dipping method or a spray coating method.

The drying temperature and the drying time of the coating film (polyvinyl alcohol-based resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 2 to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed on only one side of the base film or on both sides of the base film. When the polyvinyl alcohol-based resin layer is formed on both sides, curling of the film that may occur in the production of a polarizing laminated film or a polarizing plate can be suppressed, and two polarizing films can be obtained from a single polarizing laminated film , And is also advantageous in terms of production efficiency of the polarizing film.

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably from 3 to 30 탆, more preferably from 5 to 20 탆. If the polyvinyl alcohol-based resin layer having a thickness within this range is used, a polarizing film having good dyability of the dichroic dye and excellent polarizing performance and having a thickness of 10 m or less is obtained through the steps (3) and (4) Can be obtained. When the thickness of the polyvinyl alcohol-based resin layer exceeds 30 占 퐉, the thickness of the polarizing film may exceed 10 占 퐉. If the thickness of the polyvinyl alcohol-based resin layer is less than 3 占 퐉, the layer tends to become too thin after stretching to deteriorate the dyeability.

In order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer prior to coating of the coating liquid, a surface of the base film on which the polyvinyl alcohol-based resin layer is formed is subjected to corona treatment, plasma treatment, flame (flame) Treatment or the like may be carried out.

(Primer layer)

In addition, in order to improve adhesion between the base film and the polyvinyl alcohol-based resin layer prior to coating of the coating liquid, a polyvinyl alcohol-based resin layer may be formed on the base film through a primer layer or an adhesive layer.

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of a base film and then drying it. The coating solution for forming a primer layer includes a component exhibiting a strong adhesion to some extent to both the base film and the polyvinyl alcohol-based resin layer. The coating solution for forming a primer layer usually contains a resin component and a solvent which give such adhesion. The resin component is preferably a thermoplastic resin excellent in transparency, thermal stability and stretchability, and examples thereof include a (meth) acrylic resin and a polyvinyl alcohol resin. Among them, a polyvinyl alcohol-based resin which gives good adhesion is preferable.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and derivatives thereof. Examples of derivatives of polyvinyl alcohol resins include polyvinyl formal, polyvinyl acetal and the like, modified polyvinyl alcohol resins with olefins such as ethylene and propylene; Modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid; Acrylamide, and the like. Of the polyvinyl alcohol-based resins described above, polyvinyl alcohol resins are preferably used.

As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component can be employed. As the solvent, aromatic hydrocarbons such as benzene, toluene and xylene; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Esters such as ethyl acetate and isobutyl acetate; Chlorinated hydrocarbons such as methylene chloride, trichlorethylene, and chloroform; Ethanol, 1-propanol, 2-propanol, and 1-butanol. However, when the primer layer is formed of a coating solution for forming a primer layer containing an organic solvent, the base film may be dissolved, so it is preferable to select a solvent in consideration of the solubility of the base film. Considering the environmental impact, it is preferable to form the primer layer with a coating solution containing water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating solution for forming a primer layer. As the crosslinking agent, an appropriate one among known ones such as an organic type and an inorganic type is appropriately selected depending on the kind of the thermoplastic resin to be used. Examples of the cross-linking agent include an epoxy cross-linking agent, an isocyanate cross-linking agent, a dialdehyde cross-linking agent, and a metal cross-linking agent.

The ratio of the resin component and the crosslinking agent in the coating solution for forming a primer layer may be suitably determined in accordance with the kind of the resin component and the type of the crosslinking agent, etc., in the range of 0.1 to 100 parts by weight, relative to 100 parts by weight of the resin component, To 50 parts by weight. The solid content of the coating solution for forming a primer layer is preferably 1 to 25 parts by weight based on 100 parts by weight of the solvent in the coating solution for forming a primer layer.

The thickness of the primer layer is preferably 0.05 to 1 mu m, more preferably 0.1 to 0.4 mu m. If the thickness is smaller than 0.05 탆, the effect of improving the adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and if it is thicker than 1 탆, it is disadvantageous for thinning of the polarizing laminated film or polarizing plate.

As a method of coating the primer layer-forming coating solution onto the base film, a method such as a method of coating a coating solution containing a polyvinyl alcohol-based resin can be mentioned. The coating solution for forming the primer layer is coated on the surface (one side or both sides of the base film) on which the coating solution for forming the polyvinyl alcohol-based resin layer is coated. The drying temperature and drying time of the coating layer obtained from the coating solution for forming a primer layer are set according to the type of the solvent contained in the coating solution. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 30 seconds to 20 minutes.

When a primer layer is provided, the order of coating the base film is not particularly limited. For example, in the case of forming a polyvinyl alcohol-based resin layer on both surfaces of a base film, a primer layer is formed on both surfaces of the base film, A polyvinyl alcohol resin layer may be formed on both sides of the base film, and a primer layer and a polyvinyl alcohol resin layer are sequentially formed on one side of the base film, and then a primer layer, a polyvinyl alcohol And a resin layer may be sequentially formed.

[Step (3)]

In the step (3), the laminated film is uniaxially stretched to obtain a stretched film. The stretching magnification of the laminated film can be appropriately selected in accordance with the desired polarization characteristics, but is preferably 5 times or more and 17 times or less, more preferably 5 times or more and 8 times or less the original length of the laminated film . When the stretching magnification is 5 times or less, the polymer chains of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin layer are not sufficiently oriented, so that the degree of polarization of the polarizing film may not be sufficiently increased. On the other hand, when the stretching magnification exceeds 17 times, the film tends to break at the time of stretching, and the thickness of the stretched film becomes thin more than necessary, which may lower the workability and handling property in the subsequent step.

The laminated film may be stretched in the MD direction or transverse stretching or oblique stretching in the TD direction. Examples of the longitudinal stretching method include roll-to-roll stretching in which rolls are used to stretch (a method in which longitudinal uniaxial stretching is performed by a difference in circumferential speed between the two nip rolls while conveying between two nip rolls arranged at a distance) Roll stretching (passing between a heat roll whose surface has been heated to a desired temperature for stretching and a guide roll (or a heat roll) having a circumferential speed higher than that of the heat roll, A method of longitudinal uniaxial stretching at the time of contact (on a heat roll) or in the vicinity thereof], compression stretching, and stretching by a chuck. Examples of the transverse stretching method include a tenter method and the like. As the stretching treatment, any of a wet stretching method and a dry stretching method (stretching in air) can be employed, but a dry stretching method is preferable in that the stretching temperature can be selected within a wide range.

The stretching temperature is set to a temperature higher than the temperature at which the laminated film (the polyvinyl alcohol-based resin layer and the base film) shows fluidity to such an extent that stretching is possible. Preferably, the stretching temperature is in the range of -30 to + 30 占 폚, more preferably -30 占 폚 to + 5 占 폚, and still more preferably -25 占 폚 to + 0 占 폚. When the base film is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures of the plurality of resin layers.

When the stretching temperature is lower than -30 캜 of the phase transition temperature, high-magnification stretching exceeding 5 times is difficult to achieve, or the fluidity of the base film is too low to make the stretching process difficult. If the stretching temperature exceeds + 30 ° C of the phase transition temperature, the fluidity of the base film becomes too high, and the stretching tends to be difficult. The stretching temperature is within the above range, and more preferably 120 DEG C or more, because it is easier to achieve a high stretching magnification of more than 5 times. When the stretching temperature is 120 占 폚 or higher, even if the stretching magnification exceeds 5 times, there are many cases in which the stretching process is not accompanied with difficulty.

Examples of the heating method of the laminated film in the stretching treatment include a zone heating method (for example, heating in a stretching zone such as a heating furnace adjusted to a predetermined temperature by blowing hot air); A method of heating the roll itself in the case of stretching by thermal roll stretching; A heater heating method (a method of heating an infrared heater, a halogen heater, a panel heater, and the like on the laminated film and heating it by radiant heat). In the roll-to-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature. In this case, the two nip rolls may be provided in a temperature-controlled stretching zone or outside the stretching zone, but it is preferable that they are provided outside the stretching zone to prevent adhesion between the laminated film and the nip roll.

On the other hand, the stretching temperature means the atmosphere temperature in the zone (for example, in the heating furnace) in the case of the zone heating method, and the atmosphere temperature inside the furnace in the case of heating in the furnace in the heater heating method. In the case of thermal roll drawing, it means the surface temperature of the heat roll.

The stretching of the laminated film is not limited to the stretching in one stage but can also be carried out in multiple stages. In this case, it is preferable that the stretching process is carried out such that the total stages of the stretching process are combined to have a stretching magnification of more than 5 times.

Prior to the step (3), a preheating treatment step for preheating the laminated film may be provided. As the preheating method, the same method as the heating method in the stretching treatment can be applied. When the stretching method is inter-roll stretching, the preheating may be performed at any timing before passing through the nip roll on the upstream side, during passing, and after passing. When the stretching method is thermal roll stretching, preheating is preferably performed at a timing before passing through the thermal roll. When the stretching method is stretching by chucking, preheating is preferably performed at a timing before widening the chucking distance. The preheating temperature is preferably in the range of (stretching temperature -50) DEG C to (stretching temperature +0) DEG C, more preferably in the range of (stretching temperature -40) DEG C to (stretching temperature -10)

After the stretching of the laminated film in the step (3), a heat fixing treatment step may be carried out. The heat fixation treatment is a heat treatment at a crystallization temperature or more of the polyvinyl alcohol-based resin layer while keeping the end portion of the stretched film tightly held by a clip, while maintaining the stretched state. By the heat-setting treatment, the crystallization of the polyvinyl alcohol-based resin layer is promoted. The temperature of the heat setting treatment is preferably in the range of (stretching temperature -80) DEG C to (stretching temperature +0) DEG C, more preferably in the range of (stretching temperature -50) Do.

[Step (4)]

In the step (4), the polyvinyl alcohol-based resin layer of the drawn film is dyed with a dichroic dye, and the dichroic dye is adsorbed and oriented to obtain a polarizing laminated film. A polarizing laminated film in which a polarizing film is laminated on one side or both sides of a base film through this step can be obtained.

Examples of the dichroic dye include iodine and dichroic organic dyes. Examples of the dichroic organic dyes include red BR, red LR, red R, pink LB, rubin BL, bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, violet B, H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct First Orange S, and First Black. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

The dyeing can be carried out by immersing the stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution in which the dichroic dye is dissolved in a solvent can be used. As a solvent for the dyeing solution, water is generally used, but an organic solvent having compatibility with water may be added. The concentration of the dichroic dye in the dyeing solution is preferably 0.010 to 10% by weight, more preferably 0.020 to 7% by weight, and still more preferably 0.025 to 5% by weight.

When iodine is used as the dichroic dye, it is preferable to further add iodide to the dyeing solution containing iodine because the dyeing efficiency can be further improved. 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 and titanium iodide. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. Among iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably 1: 6 to 1:80, 7 to 1: 70.

The time for immersing the stretched film in the dyeing solution is usually 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably 10 to 60 캜, more preferably 20 to 40 캜.

On the other hand, in the step (4), the stretched film may be subjected to further stretching treatment. As an embodiment of this case,

1) An aspect in which, in the step (3), the stretching process is performed so that the total stretch ratio becomes the target stretch ratio during the dyeing process in the step (4)

As described later, when the crosslinking treatment is carried out after the dyeing treatment,

2) In the step (3), after the stretching is performed at a lower magnification than the target, stretching is performed to such an extent that the total stretching magnification does not reach the target magnification during the staining processing in the step (4) And an aspect in which the stretching process is performed during the crosslinking process so that the stretching ratio becomes the target multiplication factor.

Step (4) preferably includes a crosslinking treatment step which is carried out subsequent to the dyeing treatment.

The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known materials can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde.

The crosslinking agent may be used alone or in combination of two or more.

The crosslinking solution is specifically a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, water may be used, but an organic solvent having compatibility with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably from 1 to 20% by weight, more preferably from 6 to 15% by weight.

The crosslinking solution may contain iodide. By adding iodide, the polarization performance in the plane of the polarizing film can be more uniform. 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 and titanium iodide. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

The time for immersing the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes. The temperature of the crosslinking solution is preferably 10 to 90 ° C.

On the other hand, the crosslinking treatment may be carried out before the dyeing treatment, or may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing solution. The stretching treatment may be performed during the crosslinking treatment. The specific embodiment in which the stretching treatment is carried out during the crosslinking treatment is as described above.

It is preferable to carry out the washing step (step (4 ')) and the drying step (step (4' ')) after the step (4) , Ion-exchanged water, distilled water, etc. The water-cleaning temperature is usually 3 to 50 ° C, preferably 4 to 20 ° C.

The immersing time in water is usually from 2 to 300 seconds, preferably from 3 to 240 seconds.

The step (4 ') may be a combination of a water washing step and a cleaning step with an iodide solution. In addition to water, a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, and propanol may suitably be contained in the washing liquid used in the water washing step and / or the washing treatment with the iodide solution.

For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C, and the drying time is usually 1 to 15 Minute. The polarizing laminated film obtained in the above-described manner can be used as a polarizing element as it is, and is also useful as an intermediate for producing a polarizing plate including a polarizing film and a protective film.

The thickness of the polarizing film of the polarizing laminated film is 10 占 퐉 or less, preferably 7 占 퐉 or less. By making the thickness of the polarizing film 10 mu m or less, a thin polarizing laminated film can be formed.

[Step (5)]

Step (5) peels the base film from the polarizing laminated film. Through this step (5), a polarizing film having no base film on the polarizing film can be obtained. When the polarizing laminated film has polarizing films on both surfaces of the base film, two polarizing films can be obtained from one polarizing laminated film by the step (5). The method of peeling off the base film is not particularly limited, and can be peeled off in the same manner as the peeling process of a separator (peeling film) which is performed in a polarizing plate having an ordinary pressure-sensitive adhesive.

Prior to peeling of the base film, a protective film may be laminated on the polarizing film of the polarizing laminated film through an adhesive or a pressure-sensitive adhesive. A polarizing plate having a polarizing film and a protective film can be obtained by peeling off a base film from a laminate obtained by laminating a protective film on a polarizing film in a polarizing laminated film.

(Protective film)

Examples of the protective film include polyolefin resins such as a chain polyolefin resin (polypropylene resin and the like) and a cyclic polyolefin resin (norbornene resin and the like); Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins; Or mixtures and copolymers thereof, and the like.

The protective film may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a phase difference film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching or biaxially stretching) a resin film made of the above material, or forming a liquid crystal layer or the like on the film.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface of the protective film opposite to the bonding surface with the polarizing film. The method of forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be applied. The optical layer may be formed on the protective film in advance, or may be formed after bonding the protective film to the polarizing laminated film.

In joining the protective film on the polarizing film, a plasma treatment, a corona treatment, an ultraviolet ray irradiation treatment, a flame (flame) treatment, and the like are carried out in advance on the bonding surface of the protective film with the polarizing film, (A bonding treatment) such as a treatment, a saponification treatment or the like may be performed. Among them, plasma treatment, corona treatment or saponification treatment is preferably carried out. For example, when the protective film is made of a cyclic polyolefin-based resin, a plasma treatment or a corona treatment is usually carried out. In the case of a cellulose ester resin, the saponification treatment is usually carried out. As the saponification treatment, there may be mentioned a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

Though the thickness of the protective film is preferably thin, if it is too thin, the strength is lowered and the workability is poor. On the other hand, if the thickness is excessively large, there arises a problem that the transparency is lowered and the curing time required after bonding is prolonged. Therefore, the thickness of the protective film is preferably 90 占 퐉 or less, more preferably 5 to 60 占 퐉, and still more preferably 5 to 50 占 퐉. From the viewpoint of thinning of the polarizing plate, the total thickness of the polarizing film and the protective film is preferably 100 占 퐉 or less, more preferably 90 占 퐉 or less, further preferably 80 占 퐉 or less.

(glue)

As the adhesive, an aqueous adhesive or a photo-curing adhesive can be used. Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component emulsion type urethane emulsion adhesive, and the like. Particularly, when a cellulose ester resin film surface-treated (hydrophilized) by saponification treatment or the like is used as a protective film, it is preferable to use an aqueous adhesive composed of a polyvinyl alcohol-based resin aqueous solution.

Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol-based copolymers obtained by saponifying a copolymer of vinyl acetate and other monomers copolymerizable therewith, as well as a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, Or a modified polyvinyl alcohol polymer obtained by partially modifying the hydroxyl group of these polymers. The water-based adhesive may contain additives such as polyvalent aldehyde, water-soluble epoxy compound, melamine compound, zirconia compound, and zinc compound. The thickness of the adhesive layer obtained from the aqueous adhesive is usually 1 m or less.

The two films can be laminated by applying an aqueous adhesive on the polarizing film and / or the protective film of the polarizing laminated film, bonding the two films through the adhesive layer, and pressing them with a bonding roll or the like. The coating method of the water-based adhesive (the same applies to the photo-curing adhesive) is not particularly limited, and a coating method such as a casting method, a Meyer bar coating method, a gravure coating method, a comma coater method, a doctor blade method, a die coating method, A conventional method such as a spraying method and a spraying method can be applied.

When an aqueous adhesive is used, it is preferable to carry out a drying step of drying the film in order to remove water contained in the water-based adhesive after the above-described bonding. The drying can be carried out by introducing a polarizing film obtained by bonding a protective film into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 占 폚. If it is less than 30 DEG C, the protective film tends to be easily peeled from the polarizing film. If the drying temperature exceeds 90 DEG C, there is a fear that the polarization performance of the polarizing film is deteriorated by heat. The drying time is usually 10 to 1000 seconds, preferably 60 to 750 seconds, and more preferably 150 to 600 seconds from the viewpoint of productivity.

After drying, it may be cured at a room temperature or a slightly higher temperature, for example, at a temperature of 20 to 45 DEG C for 12 to 600 hours. The curing temperature is generally set to be lower than the drying temperature.

The photo-curing adhesive refers to an adhesive which is cured by irradiating active energy rays such as ultraviolet rays. Examples of the photo-curing adhesive include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, an adhesive containing a binder resin and a photoreactive crosslinking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as epoxy-based monomers, acrylic monomers and urethane-based monomers, and oligomers derived from photopolymerizable monomers. Examples of the photopolymerization initiator include compounds that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays. As the photo-curable adhesive containing a polymerizable compound and a photo-polymerization initiator, an adhesive comprising a photo-curable epoxy-based monomer and a photo cationic polymerization initiator can be preferably used.

In the case of using a photo-curable adhesive, the polarizing film and the protective film are bonded to each other, and if necessary, a drying step is performed (when the photo-curable adhesive contains a solvent, etc.) . A light source of an active energy ray is preferably a light source having a light emission distribution at a wavelength of 400 nm or less and is preferably a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, Do.

The light irradiation intensity to the photo-curing adhesive is suitably determined according to the composition of the photo-curing adhesive and is preferably set so that the irradiation intensity in the wavelength range effective for activation of the polymerization initiator is 0.1 to 6000 mW / cm 2. When the irradiation intensity is 0.1 mW / cm < 2 > or more, the reaction time does not become excessively long, and when the irradiation intensity is 6000 mW / cm < 2 >, the heat radiated from the light source and the yellowing of the photocurable adhesive due to heat generation during curing of the photo- There is little fear of causing deterioration.

The light irradiation time to the photo-curable adhesive is suitably determined according to the composition of the photo-curable adhesive, and it is preferable that the accumulated light quantity, which is expressed as a product of the irradiation intensity and the irradiation time, is set to 10 to 10,000 mJ / . When the accumulated light quantity is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be generated sufficiently to allow the curing reaction to proceed more surely. When the total amount is 10,000 mJ / cm 2 or less, the irradiation time is not excessively long, .

On the other hand, the thickness of the adhesive layer after irradiation with active energy rays is usually 0.001 to 5 mu m, preferably 0.01 to 2 mu m, more preferably 0.01 to 1 mu m.

(adhesive)

The pressure-sensitive adhesive that can be used for bonding the protective film is usually composed of a pressure-sensitive adhesive composition in which an acrylic resin, a styrene resin, a silicone resin, or the like is used as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound or an aziridine compound is added thereto . It may also be a pressure sensitive adhesive containing fine particles and exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is usually from 1 to 40 占 퐉, but preferably from 3 to 25 占 퐉, preferably within a range of from 3 to 25 占 퐉, so long as the properties of workability and durability are not impaired. A thickness of 3 to 25 mu m is suitable for suppressing the dimensional change of the polarizing film while having good processability. If the pressure-sensitive adhesive layer is less than 1 m, the pressure-sensitive adhesive property tends to deteriorate. If the pressure-sensitive adhesive layer is more than 40 m, the pressure-sensitive adhesive tends to be discharged from the end of the polarizing plate. In the method of bonding the protective film to the polarizing film in the polarizing laminated film by the pressure-sensitive adhesive, the pressure-sensitive adhesive layer may be formed on the surface of the protective film and then bonded to the polarizing film, After that, a protective film may be bonded thereto.

The method of forming the pressure-sensitive adhesive layer is not particularly limited, and a pressure-sensitive adhesive composition containing the above-mentioned base polymer and each component is coated on the surface of the protective film or polarizing film, and dried to form a pressure- The protective film and the polarizing film may be bonded to each other. After the pressure-sensitive adhesive layer is formed on the separator (release film), the pressure-sensitive adhesive layer is transferred onto the surface of the protective film or the surface of the polarizing film, . When the pressure-sensitive adhesive layer is formed on the surface of the protective film or on the surface of the polarizing film, surface treatment, corona treatment or the like may be performed on the surface of the protective film or the surface of the polarizing film or on one or both surfaces of the pressure- .

(Polarizing film or polarizing plate)

In the polarizing film or the polarizing plate obtained in the process including the above steps (1) to (5), the deviation of the absorption axis in the plane is 0.2 DEG or less. The standard deviation of the absorption axis in such a plane is preferably 0.04 or less. However, in the case of a polarizing laminated film having a polarizing film on both surfaces of a base film, the absorption axes of the respective polarizing films are generally the same, but the deviation of the absorption axis on at least one surface is 0.2 DEG or less, It is preferable that the deviation of the axis is 0.2 DEG or less.

The deviation of the absorption axis in the plane will be described with reference to Fig. First, the angle is set at 0 DEG with respect to the MD direction 2 in Fig. And an angle formed between the MD direction 2 and the absorption axis 6 is obtained. Refers to a smaller angle (an angle indicated by? In Fig. 1) among the angles formed by the MD direction 2 and the absorption axis 6, and also refers to an absorption angle in the direction of the dashed arrow 7 When the shaft 6 is viewed, the angle in the counterclockwise direction with respect to the MD direction is defined as a positive angle, and the angle in the clockwise direction is defined as a negative angle. However, positive and negative angles are arbitrary, and any direction may be positive. In Fig. 1, a polarizing film is further laminated on the surface of the base film 4 on which the polarizing film 3 is not laminated (In the case where polarizing films are laminated on both surfaces of the base film). The deviation of the absorption axis in the plane means the absolute value of the difference between the maximum value and the minimum value of the in-plane absorption axis angle measured by the above method. The deviation of the in-plane absorption axis can be obtained, for example, by measuring the in-plane absorption axis angles at two or more different positions within the polarizing film surface of the present invention obtained in step (5) or in the polarizing laminated film obtained in step (4).

From the viewpoint of the reliability of the value, the number of measurement sites of the absorption axis angle is more preferably 40 or more, and usually 100 or less measurements are sufficient. It is also preferable that the measurement site of the absorption axis angle is evenly distributed in the film plane in that the reliability of the value is higher. In the case of a polarizing laminated film having a polarizing film on both sides of a base film, since the absorption axes of the respective polarizing films are generally the same as described above, the absorption axis angle of the polarizing laminated film can be regarded as the absorption axis of each polarizing film have.

The structure of a polarizing plate in which a protective film is bonded to the polarizing film of the present invention will be described. Fig. 2 shows a polarizing plate having a protective film 8 on both sides of the polarizing film 3. Fig.

The polarizing film of the present invention or the polarizing plate of the present invention can be suitably inserted into a display device. Examples of the display device include a liquid crystal display device and an organic EL display device. 3 (a) shows a liquid crystal display 12 having a polarizing plate 9, a liquid crystal cell 10, a polarizing plate 91 and a backlight unit 11 of the present invention in this order. 3 (b) shows a liquid crystal display 12 having a polarizing plate 91, a liquid crystal cell 10, a polarizing plate 9, and a backlight unit 11 in this order. The polarizing plate 91 may be a polarizing plate of the present invention or a known polarizing plate. That is, at least one of the pair of polarizers of the liquid crystal display device is the polarizer of the present invention. On the other hand, the polarizing film (3) may be applied instead of the polarizing plate (9).

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

≪ Example 1 >

(1) Production of base film A

A homopolymer of propylene (hereinafter referred to as " propylene homopolymer ") was laminated on both sides of a resin layer composed of a random copolymer of propylene / ethylene containing about 5% by weight of an ethylene unit (" Sumitomonobrene W151 ", manufactured by Sumitomo Chemical Co., (Sumitomonoblene FLX80E4, manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 DEG C) was placed on a long base film A having a three-layer structure by co-extrusion molding using a multilayer extrusion molding machine .

At this time, the resin temperature of each layer was melt-kneaded with a 50 mm? Extruder heated to 280 占 폚, and then extruded from a 600 mm wide T die in a molten state to obtain a melt multilayered film. This molten multi-layer film was cooled by a cooling roll controlled at 25 캜 to obtain a multilayer base film.

The total thickness of the base film A was about 90 占 퐉, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

[Measurement of Thickness Change of Base Material Film A in MD Direction]

The thickness of the base film A having a length in the TD direction of 300 mm and a length in the MD direction of 200 m in the TD direction was measured continuously over the length of 200 m in the MD direction by a laser measuring device LT9010 manufactured by KEYENCE CO., LTD. (4096-1) 占 2.5m / minute 占 60sec / minute for the measurement of the thickness change in the MD direction, the data acquisition was sampled at 4096 points at intervals of 1 second (since the measurement was carried out at 2.5m / Min = 170.625 m, thickness variation data of 170.625 m was obtained).

The standard deviation? 1 was calculated from the waveform of the obtained thickness change, and was found to be 0.63.

[Fourier Transform]

Fast Fourier transform (FFT) processing was performed on the data thus acquired. At this time, if the length (m) of the film is taken as the variable in the MD direction, the intensity distribution with respect to the wave number (1 / m) can be obtained by the FFT processing.

[Wave Separation and Inverse Fourier Transformation and Calculation of Thickness Change]

The intensity distribution data obtained by Fourier transform was subjected to inverse Fourier transform with respect to 4096 intensity data obtained by multiplying only the spectrum intensity of 112 points corresponding to less than 1/3 (1 / m) of wave number by zero. The standard deviation sigma 2 was calculated from the waveform of the obtained thickness change to be 0.59.

[Calculation of the ratio of standard deviation to thickness]

By dividing the value of the standard deviations σ1 and σ2 standard deviation by an average thickness d of the base film A, the standard deviation and calculated a ratio (σ1 / σ2, and d / d) of the thickness of the bar, respectively, 7.07 × 10 ^-3 and 6.62 × 10 ^-3 . On the other hand, the average thickness d of the base film A was an average value of the total measured values of the base film thickness at the time of measuring the thickness change in the MD direction.

(2) Formation of primer layer

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Gohsei Kagaku Kogyo Co., Ltd., average polymerization degree: 1100, average saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% It was prepared. 5 parts by weight of a crosslinking agent (Sumirez Resin (registered trademark) 650 manufactured by Sumitomo Chemical Co., Ltd.) was added to the obtained aqueous solution in an amount of 6 parts by weight based on the polyvinyl alcohol powder. The obtained mixed aqueous solution was coated on the corona-treated surface of the substrate film A subjected to the corona treatment by a micro gravure coater and dried at 80 DEG C for 10 minutes to form a primer layer. Subsequently, the same treatment was applied to the surface opposite to the primer layer in the base film A to obtain a base film A having a primer layer on both surfaces. The thickness of the primer layer was all 0.5 m.

(3) Formation of a polyvinyl alcohol-based resin layer

A polyvinyl alcohol aqueous solution having a concentration of 8% by weight was prepared by dissolving a polyvinyl alcohol powder ("PVA 124" manufactured by Kuraray Co., Ltd., average degree of polymerization: 2400, average degree of saponification: 98.0 to 99.0 mol%) in hot water at 95 ° C. The obtained aqueous solution was coated on the primer layer by a lip coater and dried under the conditions of 80 占 폚 for 2 minutes, 70 占 폚 for 2 minutes and then at 60 占 폚 for 4 minutes to obtain a substrate film A / primer layer / polyvinyl alcohol Layer laminate film having a three-layer structure composed of a resin layer. Subsequently, the same treatment was applied to the surface of the substrate film A opposite to the polyvinyl alcohol-based resin layer to obtain a laminated film having a polyvinyl alcohol-based resin layer on both surfaces. The thicknesses of the polyvinyl alcohol-based resin layers were 9.2 탆 and 9.5 탆, respectively.

(4) Production of stretched film

The laminated film was uniaxially stretched at a stretching temperature of 160 캜 at a ratio of 5.3 times to obtain a stretched film.

(Dyeing process)

Thereafter, the stretched film was dyed in dyeing solution 1, which is a mixed aqueous solution of iodine and potassium iodide at 30 캜 for about 180 seconds, and then dyed. Then, the extra iodine solution was washed with pure water at 10 캜. Subsequently, the substrate 1 was immersed in a crosslinking solution 1 of an aqueous boric acid solution at 78 占 폚 for 120 seconds. Subsequently, the substrate was immersed in a crosslinking solution 2 at 70 DEG C containing boric acid and potassium iodide for 60 seconds. Thereafter, it was washed with pure water at 10 캜 for 10 seconds, and finally dried at 80 캜 for 300 seconds. By the above steps, a polarizing film was formed of a polyvinyl alcohol-based resin layer to obtain a polarizing laminated film. The mixing ratio of each solution is as follows. The thickness of the polarizing film was all 6.8 탆.

≪ Dyeing solution 1 >

Water: 100 parts by weight

Iodine: 0.6 parts by weight

Potassium iodide: 10 parts by weight

≪ Crosslinking solution 1 &

Water: 100 parts by weight

Boric acid: 10.4 parts by weight

≪ Crosslinking solution 2 &

Water: 100 parts by weight

Boric acid: 5.7 parts by weight

Potassium iodide: 12 parts by weight

(5) Evaluation test of a polarizing laminated film

The polarizing laminated film thus obtained was measured for absorption axis by a retardation film / optical material inspection apparatus (trade name "RETS") manufactured by Otsuka Denshi Co., The absorption axis of the polarizing laminated film was measured for a total of 49 points by taking a range of 480 mm around the center of the TD direction of the prepared polarizing laminated film and dividing the range of the 480 mm width by 10 mm. Standard deviations were calculated from the absorption axes of these 49 points. The absolute value of the difference between the maximum value and the minimum value of the in-plane absorption axis angles was defined as the deviation of the absorption axis. On the other hand, the polarizing laminated film used in the measurement has polarizing films on both sides of the base film, but since the absorption axis angles at the respective measurement points are almost the same in the respective polarizing films, the absorption axis angles of the polarizing laminated films are It can be regarded as the absorption axis angle of the polarizing film.

From the obtained data, the standard deviation of the absorption axis of the polarizing laminated film was calculated to be 0.021 °. That is, the standard deviation of the absorption axis of each polarizing film is 0.021 °. The deviation of the absorption axis of each polarizing film was 0.12 占. If the standard deviation of the absorption axis of the polarizing film is less than 0.04 占 and the deviation of the absorption axis of the polarizing film is less than 0.2 占 the in-plane uniformity of the absorption axis can be judged to be good.

≪ Example 2 >

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.77 and a standard deviation sigma 2 of 0.61 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.027 ° and the deviation of the absorption axis was 0.11 °.

≪ Example 3 >

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.78 and a standard deviation sigma 2 of 0.63 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.033 deg. And the deviation of the absorption axis was 0.13 deg.

<Example 4>

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.67 and a standard deviation sigma 2 of 0.66 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.041 deg. And the deviation of the absorption axis was 0.14 deg.

&Lt; Example 5 >

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.73 and a standard deviation sigma 2 of 0.69 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.046 deg. And the deviation of the absorption axis was 0.16 deg.

&Lt; Example 6 >

(1) Preparation of Base Film B

As the base film B, an unoriented polyethylene terephthalate film ("Orpan" manufactured by OJ Cay) was used.

[Measurement of Thickness Change of Base Film B in MD Direction]

The thickness of the base film B having a length of 640 mm in the TD direction and a length of 131 m in the MD direction was continuously measured over 131 m in the MD direction by a laser measuring instrument LT9010 manufactured by KEYENCE CO., LTD. At the time of measurement of the thickness change in the MD direction, the data acquisition was performed at 512 points at an interval of 1 second (1 second × (512-1) × 2 · 5 m / minute ÷ 60 seconds / Min = 21.292 m, thickness change data of 21.292 m was obtained).

The standard deviation? 1 was calculated from the waveform of the obtained thickness change, which was 1.79.

[Fourier transformation, wavenumber separation and inverse Fourier transform and calculation of thickness variation]

Fast Fourier transform (FFT) processing was performed on the obtained thickness variation data. Next, with respect to the intensity distribution data obtained by Fourier transformation, 512 intensity data obtained by multiplying only the spectral intensity of seven points corresponding to less than 1/3 (1 / m) of wave number by 0 was subjected to inverse Fourier transform. The standard deviation [sigma] 2 was calculated from the waveform of the obtained thickness change, and was found to be 1.68.

[Calculation of the ratio of standard deviation to thickness]

Standard deviation σ1 and standard deviation is calculated by dividing the value of σ2 to an average thickness d of the substrate film B and a non-standard deviation (σ1 / σ2, and d / d) of the thickness of the bar, respectively, 7.97 × 10 ^-3 and 7.48 × 10 ^-3 .

(2) Formation of primer layer

As in Example 1, one side of the base film B was corona-treated to form a primer layer on the corona-treated side. The thickness of the primer layer was 0.5 mu m.

(3) Formation of a polyvinyl alcohol-based resin layer

A polyvinyl alcohol resin layer was formed on the primer layer in the same manner as in Example 1 to produce a laminated film having a three-layer structure composed of the base film B / primer layer / polyvinyl alcohol resin layer. The thickness of the polyvinyl alcohol-based resin layer was 5.1 mu m.

(4) Production of stretched film

The laminated film was uniaxially stretched at a draw ratio of 1.8 times at a stretching temperature of 90 캜 to obtain a stretched film.

(Dyeing process)

The stretched film was immersed in the crosslinking solution 3 which is an aqueous solution of boric acid at 30 占 폚 for 30 seconds. Subsequently, the dyed solution 2 was dyed in dyeing solution 2, which is an aqueous solution of iodine and potassium iodide at 30 ° C for about 120 seconds, and then dyed. Then, the excess iodine solution was washed away with pure water at 7 ° C. And then immersed in a crosslinking solution 4 at 40 DEG C containing boric acid and potassium iodide for 120 seconds. Subsequently, the resultant was immersed in a crosslinking solution 5 at 75 DEG C containing boric acid and potassium iodide for 60 seconds, and subjected to free uniaxial uniaxial stretching (total draw ratio: 5.4 times) such that the draw ratio was 3.0 times. Thereafter, the resultant was washed with an aqueous solution of potassium iodide at 7 DEG C (an aqueous solution obtained by mixing 4.9 parts by weight of potassium iodide with 100 parts by weight of water) for 5 seconds, and finally dried at 60 DEG C for 180 seconds. By the above steps, a polarizing film was formed of a polyvinyl alcohol-based resin layer to obtain a polarizing laminated film. The mixing ratio of each solution is as follows. The thickness of the polarizing film was 3.7 탆.

&Lt; Dyeing solution 2 >

Water: 100 parts by weight

Iodine: 0.59 parts by weight

Potassium iodide: 1.6 parts by weight

&Lt; Crosslinking solution 3 >

Water: 100 parts by weight

Boric acid: 3.0 parts by weight

&Lt; Crosslinking Solution 4 >

Water: 100 parts by weight

Boric acid: 3.0 parts by weight

Potassium iodide: 3.1 parts by weight

&Lt; Crosslinking solution 5 &

Water: 100 parts by weight

Boric acid: 4.0 parts by weight

Potassium iodide: 5.0 parts by weight

(5) Evaluation test of a polarizing laminated film

The polarizing laminated film thus obtained was measured for absorption axis by a retardation film / optical material inspection apparatus (trade name "RETS") manufactured by Otsuka Denshi Co., The absorption axis of the polarizing laminated film was measured for a total of 11 points by taking a range of 110 mm around the center of the TD direction of the prepared polarizing laminated film and dividing the range of 110 mm width into 10 mm intervals. Standard deviations were calculated from the absorption axes of these 11 points. The absolute value of the difference between the maximum value and the minimum value of the in-plane absorption axis angles was defined as the deviation of the absorption axis.

From the obtained data, the standard deviation of the absorption axis of the polarizing laminated film was calculated to be 0.063 °. The standard deviation of the absorption axis of the polarizing film is 0.063 °. The deviation of the absorption axis of the polarizing film was 0.18 占.

&Lt; Comparative Example 1 &

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.77 and a standard deviation sigma 2 of 0.72 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.064 ° and the deviation of the absorption axis was 0.26 °.

&Lt; Comparative Example 2 &

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 0.97 and a standard deviation sigma 2 of 0.84 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.072 deg. And the deviation of the absorption axis was 0.24 deg.

&Lt; Comparative Example 3 &

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 1.17 and a standard deviation sigma 2 of 0.95 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.080 deg. And the deviation of the absorption axis was 0.27 deg.

&Lt; Comparative Example 4 &

A polarizing laminated film was obtained in the same manner as in Example 1 except that the base film A having a standard deviation sigma 1 of 1.26 and a standard deviation sigma 2 of 1.13 was used. As a result of the evaluation, the standard deviation of the absorption axis was 0.142 deg. And the deviation of the absorption axis was 0.57 deg.

The above results are shown in Table 1.

In Table 1, it was judged that the deviation of the absorption axis was 0.13 or less, and when the deviation of the absorption axis was more than 0.13 and less than 0.2, it was determined as &amp; cir &amp; From Table 1, it can be seen that the polarizing films obtained in Examples 1 to 6 have an absorption axis deviation of 0.2 DEG or less, and the contrast ratio of the liquid crystal display device in which such polarizing plates are inserted is improved.

According to the present invention, it is possible to provide a polarizing plate having an excellent absorption axis accuracy, and a display device having such a polarizing plate inserted therein can achieve a high contrast ratio.

1: TD direction, 2: MD direction, 3: polarizing film, 4: base film, 5: polarizing laminated film, 6: absorption axis, 7: dashed arrow, 8: protective film, : Liquid crystal cell, 11: backlight unit, 12: liquid crystal display

Claims (10)

The deviation of an absorption axis within a plane expressed by an absolute value of a difference between a maximum value and a minimum value of an in-plane absorption axis angle when the thickness is 10 占 퐉 or less and 0 占 with respect to the MD direction is 0.2 占 or less, A process for producing a polarizing film comprising the following steps (1) to (5):
(1) A long base film comprising a thermoplastic resin, wherein a ratio (? 1 / d) of a standard deviation? 1 calculated from a waveform obtained by measuring the thickness of the base film in the MD direction to a thickness d of the base film is 9.0 x 10 ^-3 ,
The ratio (? 2 / d (d / 2)) of the standard deviation? 2 calculated from the waveform of the thickness obtained by inverse Fourier transforming the spectra of the region having a wavenumber of 1/3 ) Of 8.0 x 10 &lt; ^-3 &gt;
(2) a step of coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film
(3) a step of uniaxially stretching the laminated film to obtain a stretched film
(4) a step of staining the stretched film to obtain a polarizing laminated film
(5) A step of obtaining a polarizing film by peeling the base film from the polarizing laminated film. The deviation of an absorption axis within a plane expressed by an absolute value of a difference between a maximum value and a minimum value of an in-plane absorption axis angle when the thickness is 10 占 퐉 or less and 0 占 with respect to the MD direction is 0.2 占 or less, A process for producing a polarizing film comprising the following steps (1) to (5):
(1) A long base film comprising a thermoplastic resin, wherein a standard deviation? 1 calculated from a waveform obtained by measuring the thickness of the base film in the MD direction is 0.80 占 퐉 or less,
Further, a step of preparing a base film having a standard deviation? 2 calculated from a waveform having a thickness obtained by performing inverse Fourier transform on a spectrum having a wavenumber of 1/3 (1 / m) or more after Fourier transformation of the above waveform is 0.65 占 퐉 or less
(2) a step of coating a coating solution containing a polyvinyl alcohol-based resin on at least one surface of the base film to obtain a coating film, and then drying the coating film to form a polyvinyl alcohol-based resin layer to obtain a laminated film
(3) a step of uniaxially stretching the laminated film to obtain a stretched film
(4) a step of staining the stretched film to obtain a polarizing laminated film
(5) A step of obtaining a polarizing film by peeling the base film from the polarizing laminated film. The polarizing film producing method according to claim 1 or 2, comprising a step of laminating a protective film on the polarizing film in the polarizing laminated film through an adhesive or a pressure-sensitive adhesive. The method for producing a polarizing film according to claim 1 or 2, wherein the base film prepared in the step (1) is a base film formed by melt extrusion. The method for producing a polarizing film according to claim 1, wherein the base film prepared in the step (1) has a thickness of 5 to 300 탆. The method of producing a polarizing film according to claim 2, wherein the base film prepared in the step (1) has a thickness of 20 to 150 탆. The method for producing a polarizing film according to claim 1 or 2, wherein the base film prepared in the step (1) is a base film comprising a polyolefin-based resin. delete delete delete

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