KR20160108097A - Polyvinylalcohol-based resin film, polarizing film and polarizing plate - Google Patents

Abstract

The present invention relates to a polyvinyl alcohol-based resin film, obtained by coating with a solution containing a polyvinyl alcohol-based resin. More specifically, provided is a polyvinyl alcohol-based resin film of which the relation between viscosity P (mPas) for 4 wt% of the aqueous polyvinyl alcohol-based resin and a long period of crystallization L (nm) of the polyvinyl-based resin film satisfies equation 1, L < 6.7909 ln(P) - 17.337.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyvinyl alcohol-based resin film, a polarizing film and a polarizing plate. [0002] POLYVINYLALCOHOL-BASED RESIN FILM, POLARIZING FILM AND POLARIZING PLATE [0003]

The present invention relates to a polyvinyl alcohol-based resin film, a polarizing film and a polarizing plate.

BACKGROUND ART A polarizing plate is widely used in an image display apparatus typified by a liquid crystal display apparatus. As the polarizing plate, a polarizing film formed by adsorbing and orienting a dichroic dye such as iodine on a polyvinyl alcohol-based resin film is generally formed by bonding a protective film to one side or both sides of the polarizing film (JP-A-2014-59564 Japanese Patent No. 5390053 (Patent Document 2), Japanese Patent Laid-Open No. 2006-188655 (Patent Document 3), etc.). 2. Description of the Related Art In recent years, with the development of image display apparatuses such as mobile apparatuses and thin type televisions, polarizers, and polarizing films, are increasingly required to be thinned.

However, if the polarizing film is made thinner, there is a problem that the film strength is lowered. In Patent Documents 1 to 3, it is described that the polarizing characteristic of the polarizing film is improved by adjusting the long period of the polyvinyl alcohol film, but means for improving the film strength is not disclosed.

It is an object of the present invention to provide a polyvinyl alcohol based resin film capable of producing a polarizing film having a high film strength even if it is thin. It is another object of the present invention to provide a polarizing film having a high film strength even though it is thin, and a polarizing plate having high durability using such a polarizing film.

The present invention provides a polyvinyl alcohol-based resin film, a polarizing film and a polarizing plate described below.

[1] A polyvinyl alcohol-based resin film obtained by forming a film using a solution containing a polyvinyl alcohol-based resin,

Wherein a viscosity P (mPa 占 퐏) of an aqueous 4 wt% solution of the polyvinyl alcohol-based resin and a crystalline long period L (nm) of the polyvinyl-based resin film satisfy a relationship of the following formula (1) film.

L < 6.7909 x ln (P) - 17.337 (1)

[2] A polarizing film obtained by stretching and dyeing the polyvinyl alcohol-based resin film according to [1].

[3] A polarizing film in which the viscosity P '(mPa · s) of a 4 wt% aqueous solution and the long period L' (nm) in the absorption axis direction satisfy the relationship of the following formula (2).

L '<14.3 × ln (P') - 43.9 (2)

The 4 wt% aqueous solution was prepared after the polarizing film was stored for 7 days under an environment of 80 캜 and 90% RH.

[4] The polarizing film according to [2] or [3], wherein the puncture strength per unit thickness is 5.0 g / 탆 or more.

[5] A polarizing plate comprising a polarizing film and a protective film laminated on at least one side of the polarizing film,

Wherein a viscosity P '(mPa · s) of an aqueous 4 wt% solution of the polarizing film isolated from the polarizing plate and a long period L' (nm) of an absorption axis direction of the polarizing film isolated from the polarizing plate satisfy the following formula Polarizer satisfying the relationship.

L '<14.3 × ln (P') - 43.9 (2)

The 4% by weight aqueous solution of the polarizing film was prepared after the polarizing film isolated from the polarizing plate was stored for 7 days under an environment of 80 캜 and 90% RH.

According to the present invention, it is possible to provide a polyvinyl alcohol-based resin film capable of producing a polarizing film having a high film strength even if it is thin. Further, according to the present invention, it is possible to provide a polarizing film having a high film strength even though it is thin, and a polarizing plate having high durability using such a polarizing film.

1 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate according to the present invention.
2 is a schematic cross-sectional view showing another example of the layer structure of the polarizing plate according to the present invention.
3 is a flow chart showing a preferred example of the method for producing a polarizing plate according to the present invention.
4 is a schematic cross-sectional view showing an example of the layer structure of the laminated film obtained in the resin layer forming step.
5 is a schematic cross-sectional view showing an example of the layer structure of a stretched laminated film obtained in a stretching step.
6 is a schematic sectional view showing an example of the layer structure of the polarizing laminated film obtained in the dyeing step.
7 is a schematic cross-sectional view showing an example of the layer structure of the bonding film obtained in the first bonding step.
8 is a graph showing the relationship between the viscosity P of the polyvinyl alcohol-based resin and the crystal long period L in Examples and Comparative Examples.
9 is a diagram showing the relationship between the viscosity P 'of the polarizing film in the examples and the comparative example and the long period L' in the absorption axis direction.

&Lt; Polyvinyl alcohol based resin film >

The polyvinyl alcohol-based resin film according to the present invention is obtained by forming a film using a solution containing a polyvinyl alcohol-based resin (hereinafter also referred to as a &quot; raw material solution &quot;), which is used for producing a polarizing film.

As a method of forming a polyvinyl alcohol-based resin film using a raw material liquid, for example, the following method can be mentioned.

[a] A method of producing a polyvinyl alcohol-based resin film as a single-layer film by a known method such as a melt extrusion method or a solvent cast method using a raw material liquid.

[b] A method for producing a polyvinyl alcohol-based resin film by coating a raw material liquid on a base film and drying the same.

It is preferable that the film is formed by the film forming method of the above-mentioned [b] because a polarizing film having a small thickness can be easily obtained and handling of the polarizing film of the thin film during the process is also excellent. The polyvinyl alcohol-based resin film formed by the above-mentioned film-forming method of [b] is obtained as a laminate with a base film. The thickness of the polyvinyl alcohol-based resin film before stretching is, for example, about 3 to 150 m.

The viscosity P (mPa 占 퐏) of the 4 wt% aqueous solution of the polyvinyl alcohol-based resin used in the raw material liquid and the crystalline long period L (nm) of the polyvinyl-based resin film according to the present invention satisfy the relationship represented by the following formula .

L < 6.7909 x ln (P) - 17.337 (1)

The viscosity P of the 4 wt% aqueous solution can be measured using a cone-plate type rotational viscometer. First, the polyvinyl alcohol resin is sufficiently vacuum dried for about 24 hours to remove moisture, and then weighed with a precision balance so that the weight percentage after dissolution becomes 4% by weight. Thereafter, a predetermined amount of pure water is added, and the solution is heated to 90 ° C or higher and sufficiently dissolved for 1 hour or more. At this time, moisture should evaporate so that the solid content does not deviate from the target. The obtained solution is returned to room temperature to be stabilized, and the solution is allowed to stand for 24 hours to remove bubbles. Since the viscosity can not be accurately measured when there is bubbles, the viscosity P is measured with a cone-type flat plate rotational viscometer (cone plate type) after confirming that the bubbles are missing. It is also necessary to confirm whether or not the solid content of the aqueous solution to be measured is not deviated from 4% by weight. However, the weight of the aqueous solution is measured by measuring about 5 ml of the aqueous solution in a previously dried container, After drying and cooling, the weight of the remaining resin is measured. The weight of the remaining resin is calculated as the solid content contained in the collected aqueous solution, and it is confirmed that this is 4.0 wt%. In the case where the solid content is out of the target, a plurality of aqueous solutions having different solid contents are prepared, and plotting the solid content on the horizontal axis and the logarithm of the viscosity on the vertical axis and reading the viscosity P at 4.0 wt% from the approximate line .

The crystal long period L can be obtained by performing measurement by the X-ray small angle scattering method. In the measurement, a polyvinyl alcohol-based resin film obtained by peeling the base film from the laminate in the case of the film forming method of the polyvinyl alcohol-based resin film film (the above-mentioned [b]) was measured by a transmission (through) method, Dimensional scattering is obtained by detecting the two-dimensional scattering on the two-dimensional plane. The scattering obtained in the two-dimensional direction is integrated in the overall circumferential direction (360 degrees) to generate a one-dimensional profile. Hereinafter, the one-dimensional profile thus obtained is used. In order to perform background correction, first, a one-dimensional profile of background scattering is obtained by measuring without sample. Next, the sample is set and measured again to obtain a one-dimensional profile of the sample. From the ratio of these two transmitted light intensities, the transmittance is calculated. After considering the transmittance, the one-dimensional profile of the sample is taken as the one-dimensional profile of the sample, minus the one-dimensional profile of the background. In the one-dimensional profile in which the vertical axis thus obtained is the scattering intensity and the horizontal axis is the scattering angle, the scattering angle of the horizontal axis is converted into the cycle length by using the Bragg's equation and the peak position of the scattering intensity is converted into the period of the scattering L). Since measurement can not achieve accuracy when the thickness of the film is thin, the film thickness is set so that sufficient thickness can be obtained by superimposing the film when necessary.

A polarizing film having a high film strength can be obtained by producing a polarizing film using a polyvinyl alcohol-based resin film satisfying the relationship of the above-mentioned formula (1). The above equation (1) is an equation derived based on experimental values. The reason why a polarizing film having a high film strength can be produced by using a polyvinyl alcohol-based resin film satisfying the relationship of the above-mentioned formula (1) can be investigated as follows. But is not limited to.

First, the viscosity P of the 4 wt% aqueous solution of the polyvinyl alcohol-based resin used for the raw material liquid is considered to indicate the diffusion state of the polyvinyl alcohol-based resin used in the raw material liquid in water. The more the chain of the polyvinyl alcohol-based resin is diffused, the more the interaction between the chain and the chain of the polyvinyl alcohol-based resin acts and the higher the viscosity is measured. Examples of the resin having a high viscosity include a resin having a high molecular weight and a high affinity with water. The larger molecular weight tends to be diffused originally because the molecule itself is large, but it is not merely that the molecular weight is larger than the larger molecular weight, but also depends on the number of branches and the molecular weight dispersion. The affinity with water also depends on the degree of saponification, the copolymer composition, the copolymerization ratio and the like, as long as it is a copolymer. Although there are a plurality of factors for spreading the chain in this manner, it is considered that this is an index of diffusion of the chain in water anyway.

Next, the crystal long period L of the polyvinyl alcohol-based resin film is a distance between crystals and crystals obtainable by X-ray small angle scattering analysis. Although the distance between crystal-crystals depends on the physical properties of the polyvinyl alcohol-based resin, the inventors of the present invention have found that the distance can also be controlled according to the drying conditions at the time of film formation. In the present invention, control is performed so that the crystal periodic period L satisfies the relational expression (1) in accordance with the polyvinyl alcohol-based resin to be used.

The meaning of the formula (1) is that the left side is a crystal long period while the right side is a factor indicating the diffusion of molecular chains of the polyvinyl alcohol resin in water. It is considered that controlling the long period (i.e., the distance between crystals and crystals) of the molecular chain to be less than a predetermined value, that is, controlling the amount of molecular chains existing between crystals and crystals, It is believed that they control the molecular chains to a predetermined amount or more so that they form a mesh structure in a network shape and that the film strength of the polyvinyl alcohol resin film becomes high and the film strength of the polarizing film produced using the film becomes high. On the other hand, when the crystal long period is longer than the predetermined value with respect to the diffusion of the molecular chains, it is difficult to form such a mesh structure, and the crystals become independent, and thus the film strength is considered to be low.

Particularly, in a polarizing film having a thin film thickness, since the strength as a whole film becomes small, it is necessary to strengthen the intensity per unit thickness rather than the case where the film thickness is thick. Use of the technique of the present invention is very useful for a thin film polarizing film, particularly a polarizing film of 10 m or less, since the strength of the film can be increased per unit thickness as compared with the conventional polarizing film.

A description will now be given of a method of controlling the distance between crystals and crystals (a long period of crystallization) by the drying conditions at the time of film formation, and the reason why control can be performed. The method of controlling the distance between crystals and crystals (crystal long period) of the polyvinyl alcohol resin film can be carried out, for example, by controlling the drying rate in a range of water content of 30% by weight or less in the end stage of drying, but is not limited thereto . The reason why the moisture content can be controlled at a drying rate at the time point of 30% by weight is that crystal nuclei start to be generated in the vicinity of this moisture content, and the drying in the vicinity thereof is carried out slowly, , Thereby making it possible to shorten the distance between crystals and crystals (the crystal long period).

In a region where the water content exceeds 30% by weight, the polyvinyl alcohol resin exists as a homogeneous solution, and since the solution state in which the molecular chains are uniformly existed is stable, generation of crystal nuclei with a stable critical size or hardly occurs. When the water content is close to 30% by weight, crystal nuclei are formed and crystallization is stabilized, so that crystal nuclei of a stable critical size or larger are produced. This is because a homogeneous solution is formed in a region where the water content exceeds 30% by weight, and unintentional crystallization or the like can be prevented from occurring. An aqueous solution having a moisture content lower than 30% by weight is highly likely to undergo crystallization unintentionally during storage or transportation.

On the other hand, in a region significantly below 30% by weight, the drying progresses further, and as a result, the amount of water as the two solvents becomes smaller, and the mobility of the chain of the polyvinyl alcohol-based resin is lowered, . Taking these points into consideration, a drying rate of about 30 wt% is important. Therefore, as the raw material liquid, it is preferable to prepare a raw material liquid having a water content of 30 wt% or more containing a polyvinyl alcohol-based resin, and after the film formation using the raw material liquid, a drying rate at a moisture content of about 30 wt% A polyvinyl alcohol based resin film having a distance (a long period of crystallization)

(Polyvinyl alcohol-based resin)

As the polyvinyl alcohol-based resin used for producing the polyvinyl alcohol-based resin film, a saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be mentioned in addition to polyvinyl acetate as a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. If the degree of saponification is less than 80.0 mol%, the water resistance of the resulting polarizing film tends to deteriorate. When a polyvinyl alcohol-based resin having a saponification degree of more than 99.5 mol% is used, the dyeing speed is slowed, the productivity is lowered, and a polarizing film having sufficient polarization performance can not be obtained.

The degree of saponification is a 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 process, Is defined by the following equation. The saponification degree can be obtained according to JIS K 6726 (1994). The higher the degree of saponification, the higher the proportion of hydroxyl groups, and thus the lower the proportion of acetic acid groups that inhibit crystallization.

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

The polyvinyl alcohol resin may be a modified polyvinyl alcohol partially modified. The ratio of denaturation is preferably less than 30 mol%, more preferably less than 10%. When the modification is carried out in an amount exceeding 30 mol%, it is difficult to adsorb the dichroic dye and a polarizing film having sufficient polarization performance can not easily be obtained.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined in accordance with JIS K 6726 (1994).

<Polarizing Film>

The polarizing film of the present invention is preferably produced using the above-mentioned polyvinyl alcohol-based resin film. By using the above-mentioned polyvinyl alcohol-based resin film, a polarizing film having a high film strength can be obtained.

In the polarizing film of the present invention, it is preferable that the viscosity P '(mPa · s) of the 4 wt% aqueous solution and the long period L' (nm) of the absorption axis direction satisfy the following relationship (2).

L '<14.3 × ln (P') - 43.9 (2)

The polarizing film of the present invention can be produced by stretching and dyeing the above-mentioned polyvinyl alcohol-based resin film to obtain a polarizing film satisfying the relationship of the formula (2). By satisfying the relationship of the expression (2), a polarizing film having a high film strength can be obtained.

The 4 wt% aqueous solution used for measuring the viscosity P 'was adjusted after the polarizing film was stored for 7 days under an environment of 80 캜 and 90% RH. Since the iodine and boric acid added by dyeing and crosslinking are removed by keeping them under such an environment for 7 days, the viscosity P '(mPa · s) of the 4 wt% aqueous solution which is not affected by iodine and boric acid added is measured . The viscosity P 'is measured according to the above-described method of measuring the viscosity P. [ The long axis L 'of the polarizing film in the absorption axis direction is measured according to the aforementioned measuring method for the crystal long period L described above.

The above equation (2) is an equation derived based on experimental values. The reason why the polarizing film having a high film strength can be obtained by satisfying the relation of the formula (2) is that by using a polyvinyl alcohol-based resin film satisfying the above-mentioned relation (1) The reason why a polarizing film having a high film strength can be produced can be similarly examined, but such consideration does not limit the present invention.

To describe the polarization performance of the polarizing film in more detail, the polarization performance is generally evaluated by two parameters called "visual sensitivity correction single transmittance Ty" and "visual sensitivity correction polarization degree Py". These parameters are the transmittance and the degree of polarization in the visible region (wavelength 380 to 780 nm) corrected so that the weight of the nearest 550 nm, which is the highest sensitivity of human eyes, is the largest. Since light having a wavelength of less than 380 nm is not visible to the human eye, Ty and Py are not considered.

Visual Sensitivity Correction of Polarizing Film The simple transmittance Ty may be a value usually found in an image display apparatus such as a liquid crystal display apparatus to which the above-mentioned polarizing film or a polarizing plate including the polarizing film is applied. Specifically, it is preferably within a range of 40 to 47% Do. Ty is more preferably in the range of 41 to 45%, and in this case, the balance between Ty and Py is better. If Ty is too high, Py is lowered and the display quality of the image display device is lowered. If Ty is excessively low, the luminance of the image display device is lowered and the display quality is lowered, or the input power must be increased in order to sufficiently increase the luminance. The visual sensitivity correction polarization degree Py of the polarizing film is preferably 99.9% or more, and more preferably 99.95% or more.

The thickness of the polarizing film may be, for example, 30 占 퐉 or less, more preferably 20 占 퐉 or less, but is preferably 10 占 퐉 or less and more preferably 8 占 퐉 or less from the viewpoint of thinning of the polarizing plate. The thickness of the polarizing film is usually 2 m or more.

The polarizing film preferably has a piercing strength per unit thickness of 5.0 g / m or more, more preferably 6.0 g / m or more. When the piercing strength is 5.0 g / 탆 or more, the incidence of cracking of the polarizing film in the durability test such as the heat shock test can be remarkably suppressed.

<Polarizer>

(1) Layer structure of polarizer

1 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate according to the present invention. Like the polarizing plate 1 shown in Fig. 1, the polarizing plate of the present invention can be a polarizing plate with a single-sided protective film including a polarizing film 5 and a first protective film 10 laminated on one side thereof. The first protective film 10 can be laminated on the polarizing film 5 through the first adhesive layer 15. [

The polarizing plate according to the present invention may be obtained by further bonding a protective film to the other surface of the polarizing film 5. Specifically, like the polarizing plate 2 shown in Fig. 2, the polarizing film 5, , A first protective film (10) laminated on one side thereof, and a second protective film (20) laminated on the other side. The second protective film 20 can be laminated on the polarizing film 5 through the second adhesive layer 25. [

The polarizing plate according to the present invention may be a polarizing plate disposed on the visual (front) side of an image display device such as a liquid crystal cell when inserted into an image display device such as a liquid crystal display device, (Backlight side of the device).

(2) polarizing film

The polarizing plate according to the present invention includes, as the polarizing film 5, the polarizing film according to the present invention described above. Therefore, with respect to the details of the polarizing film 5, the above-mentioned description is cited. Further, as described above, it is preferable that a polarizing film satisfying the relationship of the above-mentioned formula (2) is used as the polarizing film 5 constituting the polarizing plate. It is also preferable that the polarizing film 5 isolated from the polarizing plate satisfies the relation of the above-mentioned formula (2). In this case, the 4 wt% aqueous solution used for measuring the viscosity P 'was adjusted after the polarizing film peeled off from the polarizing plate was stored for 7 days under an environment of 80 캜 and 90% RH. The viscosity P 'of the polarizing film before the polarizing plate is formed and the long period L' of the absorption axis direction and the viscosity P 'of the polarizing plate separated from the polarizing plate and the longitudinal period L' Are almost equal to each other.

The polarizing plate as described above has a high film strength of the polarizing film and can significantly suppress the occurrence rate of the polarizing film crack in the durability test such as the heat shock test.

(3) The first protective film

The first protective film 10 is preferably a thermoplastic resin having translucency (preferably optically transparent) such as a thermoplastic resin such as a chain polyolefin resin (polypropylene resin), a cyclic polyolefin resin (norbornene resin, etc.) Polyolefin resin; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester-based resin; Polycarbonate resin; (Meth) acrylic resins; Polystyrene type resin; Or mixtures thereof, copolymers thereof, and the like.

The first protective film 10 may be a protective film having optical functions such as a retardation film and a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching a film made of the thermoplastic resin (such as uniaxial stretching or biaxial stretching) or forming a liquid crystal layer or the like on the film.

Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more kinds of chain olefins.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers 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 unsaturated carboxylic acids or their derivatives, and hydrides thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. These copolymers and those obtained by modifying a part of hydroxyl groups with other substituents may also be used. Of these, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable.

The polyester-based resin is a resin other than the cellulose ester-based resin having an ester bond, and is generally composed of a polycondensation product of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, cyclohexanedimethanol and the like.

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexane Dimethyl naphthalate.

The polycarbonate resin is composed of a polymer having a monomer unit bonded through a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate modified with a polymer skeleton, a copolymerized polycarbonate, or the like.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Specific examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.) . Preferably, a polymer mainly composed of a poly (meth) acrylate C _1-6 alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100% by weight, By weight, preferably 70 to 100% by weight) is used.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer may be formed on the surface of the first protective film 10 opposite to the polarizing film 5 . The first protective film 10 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent and an antioxidant.

The thickness of the first protective film 10 is preferably 90 占 퐉 or less, more preferably 50 占 퐉 or less, still more preferably 30 占 퐉 or less, from the viewpoint of thinning of the polarizing plate. The thickness of the first protective film 10 is usually 5 占 퐉 or more from the viewpoints of strength and handleability.

(4) First adhesive layer

The first adhesive layer 15 is a layer for adhering and fixing the first protective film 10 to one surface of the polarizing film 5. The adhesive forming the first adhesive layer 15 may be an active energy ray curable adhesive containing a curable compound which is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam or X-ray or an adhesive such as a polyvinyl alcohol- Based adhesive in which the component is dissolved or dispersed in water.

As the active energy ray curable adhesive for forming the first adhesive layer 15, the active energy ray curable adhesive composition comprising a cationically polymerizable curable compound and / or a radically polymerizable curable compound is preferably used . The active energy ray curable adhesive may further comprise a cation polymerization initiator and / or a radical polymerization initiator for initiating the curing reaction of the curable compound.

Examples of the cationically polymerizable curable compound include epoxy-based compounds (compounds having one or two or more epoxy groups in the molecule), oxetane-based compounds (compounds having one or two or more oxetane rings in the molecule) . &Lt; / RTI &gt; Examples of the radically polymerizable curable compound include (meth) acrylic compounds (compounds having one or more (meth) acryloyloxy groups in the molecule), other vinyl compounds having a radically polymerizable double bond, or And combinations thereof. A cationically polymerizable curable compound and a radical polymerizable curable compound may be used in combination.

The active energy ray-curable adhesive can be used in the form of a coating solution containing a cationic polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, a defoaming agent, May contain additives.

The thickness of the first adhesive layer 15 is usually about 0.001 to 5 mu m, preferably 0.01 to 3 mu m.

(5) Second protective film

The second protective film 20 of the polarizing plate 2 with a double-sided protective film shown in Fig. 2 may be a film made of the thermoplastic resin exemplified above as in the case of the first protective film 10, It may be a protective film having an optical function such as an enhancement film. As for the surface treatment layer and the thickness of the film that the second protective film 20 can have, the above description about the first protective film 10 is cited. The first protective film 10 and the second protective film 20 may be a protective film made of the same kind of resin or a protective film made of different kinds of resin.

(6) Second adhesive layer

The second adhesive layer 25 is a layer for adhering and fixing the second protective film 20 to the other surface of the polarizing film 5. With respect to the details of the second adhesive layer 25, reference to the above-mentioned first adhesive layer 15 is cited. The adhesive forming the second adhesive layer (25) may have the same composition as the adhesive forming the first adhesive layer (15) or may have a different composition.

(7) Pressure-sensitive adhesive layer

The first protective film 10 or the second protective film 10 on the polarizing film 5 in the polarizing plate 1 with a one-sided protective film shown in Fig. 1 or on the polarizing plate 2 with a two- 2 A pressure-sensitive adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell in the case of application to a liquid crystal display) may be laminated on the protective film 20. The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is usually composed of a pressure-sensitive adhesive composition comprising a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound and an aziridine compound added thereto, usually a (meth) acrylic resin, a styrene resin or a silicone resin. Further, a pressure-sensitive adhesive layer containing fine particles and exhibiting light scattering properties may be used. The thickness of the pressure-sensitive adhesive layer is usually 1 to 40 占 퐉, preferably 3 to 25 占 퐉.

(8) Other optical layers

The polarizing plate according to the present invention may further include another optical layer laminated on the first and / or second protective films 10 and 20 or the polarizing film 5. As another optical layer, a reflective polarizing film that transmits polarized light of a certain kind and reflects polarized light exhibiting properties opposite to that of the polarized light; An antireflection film having a concavo-convex shape on its surface; A film having a surface antireflection function; A reflecting film having a reflecting function on the surface; A transflective film having both a reflective function and a transmissive function; And a viewing angle compensation film.

&Lt; Polyvinyl alcohol based resin film, polarizing film and method for producing polarizing plate >

The polyvinyl alcohol-based resin film, polarizing film and polarizing plate of the present invention can be suitably produced by the method shown in Fig. The manufacturing method shown in Fig. 3 comprises the following steps:

(1) a resin layer forming step S10 for forming a polyvinyl alcohol-based resin film by coating a coating solution (raw material solution) containing a polyvinyl alcohol-based resin on at least one surface of a base film and then drying,

(2) a stretching step S20 in which a laminated film is stretched to obtain a stretched film having a polyvinyl alcohol-based resin film stretched on a base film,

(3) a dyeing step S30 for obtaining a polarizing laminated film by dyeing a polyvinyl alcohol-based resin film of a stretched film with iodine to form a polarizing film (polarizer layer)

(4) a first bonding step S40 of bonding a protective film to the polarizing film of the polarizing laminated film to obtain a bonded film,

(5) a peeling step S50 for peeling off the base film from the bonding film to obtain a polarizing plate with one side protective film

In this order.

In the case of producing the polarizing plate 2 with a double-sided protective film shown in Fig. 2, after the peeling step S50,

(6) A second bonding step S60 for bonding a protective film to the polarizing film side of the polarizing plate with one side protective film

.

Hereinafter, each step will be described with reference to Figs. 4 to 7. Fig. In the resin layer forming step S10, a polyvinyl alcohol-based resin film may be formed on both surfaces of the base film. Hereinafter, a case where the polyvinyl alcohol-based resin film is mainly formed on one surface will be described.

(1) Resin layer formation step S10

4, the present step is a step of forming a laminated film 100 by forming a polyvinyl alcohol-based resin film 6 on at least one side of the base film 30. This polyvinyl alcohol based resin film 6 is a layer that becomes a polyvinyl alcohol based resin film 6 'through a stretching step S20 and becomes a polarizing film 5 through a dyeing step S30. The polyvinyl alcohol-based resin film (6) can be formed by coating a coating liquid containing a polyvinyl alcohol-based resin on one side or both sides of the base film (30) and drying the coated layer. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that it is easy to obtain a polarizing film 5 of a thin film.

The base film 30 may be composed of a thermoplastic resin, and it is preferable that the base film 30 is made of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability, and the like. Specific examples of such a thermoplastic resin include polyolefin resins such as a chain polyolefin resin and a cyclic polyolefin resin (norbornene resin and the like); Polyester-based resin; (Meth) acrylic resins; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polycarbonate resin; Polyvinyl alcohol-based resin; Polyvinyl acetate resin; Polyarylate resins; Polystyrene type resin; Polyether sulfone type resin; Polysulfone resins; Polyamide based resin; Polyimide resin; And mixtures and copolymers thereof.

The substrate film 30 may have a single-layer structure composed of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a multilayer structure in which a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated. The base film 30 is preferably composed of a resin that can be stretched at a drawing temperature suitable for drawing the polyvinyl alcohol-based resin layer 6 when the laminated film 100 is stretched in a stretching step S20 described later Do.

The base film (30) may contain an additive. Specific examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a colorant.

The thickness of the base film 30 is usually 1 to 500 占 퐉, preferably 1 to 300 占 퐉, more preferably 5 to 200 占 퐉, and still more preferably 5 to 150 占 퐉, from the viewpoints of strength and handling properties .

The coating liquid applied to the base film 30 is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a polyvinyl alcohol-based resin powder in a good solvent (for example, water). Details of the polyvinyl alcohol-based resin are as described above. The coating liquid may contain an additive such as a plasticizer and a surfactant if necessary.

The method of applying the coating solution to the base film (30) 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.

The drying temperature and the drying time of the coating layer (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 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher.

The polyvinyl alcohol-based resin film (6) may be formed on only one side of the base film (30) or on both sides. It is possible to suppress the curling of the film which may occur in the production of the polarizing laminated film 300 (see Fig. 6) and to obtain two polarizing plates from one polarizing laminated film 300 , And is also advantageous in terms of production efficiency of the polarizing plate.

The thickness of the polyvinyl alcohol-based resin film 6 in the laminated film 100 is preferably 3 to 30 占 퐉, and more preferably 5 to 20 占 퐉. If the polyvinyl alcohol-based resin layer 6 having a thickness within this range is used, it is preferable that the polyvinyl alcohol-based resin layer 6 having a thickness of 10 탆 or less ) Polarizing film 5 can be obtained

The substrate film 30 on which the polyvinyl alcohol based resin film 6 is to be formed is preferably formed so as to improve the adhesion between the base film 30 and the polyvinyl alcohol based resin film 6 prior to coating of the coating liquid. A corona treatment, a plasma treatment, a frame (flame) treatment, or the like may be performed on the surface of the substrate. For the same reason, the polyvinyl alcohol-based resin film 6 may be formed on the base film 30 through a primer layer or the like.

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of the base film 30 and then drying it. This coating liquid contains a component exhibiting a strong adhesion to some extent to both the base film (30) and the polyvinyl alcohol-based resin film (6), and usually includes a resin component and a solvent for imparting such adhesion. As the resin component, a thermoplastic resin excellent in transparency, thermal stability and stretchability is preferably used, 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 preferably used. More preferably, it is a polyvinyl alcohol resin. As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used, but 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. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, organometallic compounds) and high molecular weight crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component forming the primer layer, a polyamide epoxy resin, a methylol melamine resin, a dialdehyde-based cross-linking agent, a metal chelate-based cross-linking agent and the like are suitably used.

The thickness of the primer layer is preferably about 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 30 and the polyvinyl alcohol-based resin layer 6 is small, and if it is thicker than 1 탆, the polarizing plate becomes thinner.

The method of coating the primer layer-forming coating solution on the base film 30 may be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The drying temperature of the coating layer composed of the coating solution for forming a primer layer is, for example, 50 to 200 캜, preferably 60 to 150 캜. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher.

(2) Drawing process S20

5, the present step is a step of stretching a laminated film 100 made of a base film 30 and a polyvinyl alcohol based resin film 6, To obtain a stretched film 200 having a polyvinyl alcohol-based resin film 6 '. The stretching treatment is usually uniaxial stretching.

The stretching magnification of the laminated film 100 can be appropriately selected in accordance with a desired polarization characteristic. It is preferably 1.1 to 17 times, more preferably 1.5 to 8 times, the original length of the laminated film 100. If the stretching magnification exceeds 17 times, the film tends to break at the time of stretching, and the thickness of the stretched film 200 becomes thinner than necessary, which may lower the workability and handling property in the subsequent step.

The stretching treatment is not limited to stretching to one end but may be performed in multiple steps. In this case, all of the multi-stage drawing process may be performed continuously before the dyeing process S30, and the drawing process after the second step may be performed together with the dyeing process and / or the crosslinking process in the dyeing process S30. When the stretching process is performed in such a multi-stage, it is preferable that the stretching process is performed so that the overall stretching process steps are combined so as to have a stretching ratio of more than four times.

The stretching treatment may be vertical stretching in which stretching is performed in the longitudinal direction of the film (film transport direction), transverse stretching in the film width direction, or warp stretching. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck. The transverse stretching method includes a tenter method and the like. Any of the wet drawing method and the dry drawing method can be employed for the drawing treatment, but a dry drawing method is preferable because the drawing temperature can be selected within a wide range.

The stretching temperature is set to be equal to or higher than a temperature at which the entirety of the polyvinyl alcohol resin layer 6 and the substrate film 30 can be stretched to exhibit fluidity and is preferably set to a temperature at which the base film 30 has a phase transition temperature (melting point or glass transition temperature ) To -30 캜, more preferably -30 캜 to + 5 캜, and still more preferably -25 캜 to + 0 캜. When the base film 30 is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

If the stretching temperature is lower than -30 캜 of the phase transition temperature, high-magnification stretching exceeding 4 times is difficult to achieve, or the flowability of the base film 30 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 30 tends to be excessively large and the stretching tends to become difficult. The stretching temperature is within the above range, and more preferably 120 deg. C or more, since it is easier to attain a high stretching magnification of more than 4 times.

Examples of the heating method of the laminated film 100 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 using a roll; A heater heating method (a method in which an infrared heater, a halogen heater, a panel heater, and the like are disposed above and below the laminated film 100 and heated 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.

The stretching temperature means an atmosphere temperature in a zone (for example, in a heating furnace) in the case of the zone heating method, and also means an atmosphere temperature in the furnace in the case of heating in the furnace. In the case of the method of heating the roll itself, it means the surface temperature of the roll.

Prior to the stretching step S20, a preheating treatment step for preheating the laminated film 100 may be provided. As the preheating method, the same method as the heating method in the stretching treatment can be used. The preheating temperature is preferably in the range of -50 ° C to ± 0 ° C of the drawing temperature, and more preferably in the range of -40 ° C to -10 ° C of the drawing temperature.

After the stretching treatment in the stretching step S20, a heat fixing treatment step may be provided. The heat setting process is a process in which heat treatment is performed at a crystallization temperature or higher while keeping the end portion of the stretched film 200 in a state of being held in a state of being clipped by a clip. The crystallization of the polyvinyl alcohol-based resin film 6 'stretched by the heat setting treatment is promoted. The heat-setting treatment temperature is preferably in the range of -0 to -80 占 폚 of the stretching temperature, and more preferably in the range of -0 to -50 占 폚 of the stretching temperature.

(3) Dyeing process S30

6, the present step is a step of staining the polyvinyl alcohol-based resin film 6 'of the stretched film 200 with iodine and adsorbing the same to obtain a polarizing film 5. The polarizing laminated film 300 in which the polarizing film 5 is laminated on one side or both sides of the base film 30 'through this step can be obtained.

The dyeing step can be carried out by immersing the entire stretched film 200 in a solution (dyeing solution) containing iodine. As the dyeing aqueous solution, a solution in which iodine is dissolved in a solvent can be used. As the solvent, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of iodine in the dyeing aqueous solution is preferably 0.01 to 10% by weight, and more preferably 0.02 to 7% by weight.

It is preferable to further add iodide to the dyeing aqueous solution because the dyeing efficiency can be 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 aqueous solution is preferably 0.01 to 20% by weight. It is preferable to add potassium iodide even in iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably from 1: 5 to 1: 100, more preferably from 1: 6 to 1:80, by weight. The temperature of the dyeing aqueous solution is preferably from 10 to 60 캜, more preferably from 20 to 40 캜.

The dyeing step S30 may include 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) in which the crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent 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. As the solvent of the crosslinking solution, water may be used, but an organic solvent having compatibility with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is preferably 0.2 to 20 wt%, more preferably 0.5 to 10 wt%.

The crosslinking solution may further contain iodide. By adding iodide, the polarization performance in the plane of the polarizing film 5 can be made more uniform. Specific examples of the iodide are the same as described above. 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 temperature of the crosslinking solution is preferably 1 to 90 占 폚.

The crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing aqueous solution. The treatment of immersing in a crosslinking solution may be performed twice or more using two or more kinds of crosslinking solutions having different compositions.

After the dyeing step S30, it is preferable to carry out a cleaning step and a drying step before the first bonding step S40 described later. The cleaning process usually includes a water cleaning process. The water washing treatment can be carried out by immersing the film after the dyeing treatment or after the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 to 50 占 폚, preferably 4 to 20 占 폚. The cleaning step may be a combination of a water washing step and a cleaning step with an iodide solution. As the drying step performed after the cleaning step, any suitable method such as natural drying, air blow drying, and heat drying can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C.

(4) First bonding step S40

7, the present step is carried out in such a manner that an adhesive layer (not shown) is formed on the polarizing film 5 of the polarizing laminated film 300, that is, on the opposite side of the polarizing film 5 from the base film 30 ' To obtain a bonded film (400). 7 shows an example of bonding the first protective film 10 through the first adhesive layer 15. In the case of producing the polarizing plate 2 with a double-sided protective film, the second adhesive layer 25 The second protective film 20 may be bonded. The adhesive forming the first adhesive layer 15 or the second adhesive layer 25 is as described above.

When the polarizing laminated film 300 has the polarizing film 5 on both sides of the base film 30 ', the protective film is usually bonded onto the polarizing film 5 on both sides. In this case, these protective films may be the same kind of protective film or different kinds of protective films.

As an example of bonding the first protective film 10 using the active energy ray-curable adhesive, a method of bonding and adhering the protective film will be described. The active energy ray-curable adhesive to be the first adhesive layer 15 After the first protective film 10 is laminated on the polarizing film 5, active energy rays such as ultraviolet rays, visible light, electron beams and X-rays are irradiated to cure the adhesive layer. Among them, ultraviolet rays are suitable. As the light source in this case, 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, a metal halide lamp and the like can be used.

In bonding the protective film to the polarizing film 5, the bonding surface of the protective film and / or the polarizing film 5 may be subjected to plasma treatment, corona treatment, ultraviolet ray It is preferable to perform surface treatment (easy adhesion treatment) such as irradiation treatment, frame (flame) treatment and saponification treatment, and among these, plasma treatment, corona treatment or saponification treatment is preferably performed.

(5) Peeling step S50

This step is a step of peeling off the base film 30 'from the bonding film 400. Through this process, the same one-side protective film polarizing plate as in Fig. 1 can be obtained. When the polarizing laminated film 300 has the polarizing film 5 on both sides of the base film 30 'and the protective film is bonded to both of the polarizing films 5, Two polarizing plates with a single-sided protective film can be obtained from the polarizing laminated film 300 of the sheet.

The method of peeling off the base film 30 '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 usual polarizing plate with a pressure-sensitive adhesive. The base film 30 'may be peeled immediately after the first bonding step S40, or may be peeled off in a subsequent step after being peeled off in the subsequent step after the first bonding step S40.

(6) Second bonding step S60

In this step, a protective film is further bonded on the polarizing film 5 of the polarizing plate with one-side protective film, that is, on the side opposite to the protective film bonded in the first joining step S40, This is a step of obtaining a polarizing plate 2 with a double-side protective film. In the case where the first protective film 10 is bonded in the first bonding step S40, when the second protective film 20 is bonded in this step and the second protective film 20 is bonded in the first bonding step S40 , The first protective film 10 is bonded in this step. The bonding of the second protective film 20 through the second adhesive layer 25 can be performed in the same manner as the bonding of the first protective film 10.

The method of forming the polarizing film by the polyvinyl alcohol-based resin layer coated on the base film and subsequently producing the polarizing plate has been described in detail above, but the present invention is not limited to this, and the film forming method of (b) The polarizing plate may be manufactured by bonding the first protective film 10 or the first and second protective films 10 and 20 to the polarizing film 5 made of a single (single) film.

The polyvinyl alcohol based resin film 6 'and the polarizing film 5 made of a single (single) film can be obtained by a process comprising the steps of: preparing a polyvinyl alcohol based resin film by a known method such as melt extrusion or solvent casting; A step of uniaxially stretching a polyvinyl alcohol-based resin film to obtain a polyvinyl alcohol-based resin film (6 '); Dyeing a polyvinyl alcohol-based resin film with iodine and adsorbing it; Treating the stretched polyvinyl alcohol-based resin film adsorbed with iodine with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous solution of boric acid to obtain a polarizing film (5). Uniaxial stretching can be carried out before dyeing iodine, after dyeing, or after dyeing. When uniaxial stretching is carried out after dyeing, this uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed in these plural stages.

In the case of producing a polarizing plate with a double-sided protective film by bonding both of the first and second protective films 10 and 20, these protective films may be sequentially bonded through an adhesive layer or may be bonded at the same time.

Example

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

&Lt; Example 1 >

(1) Primer layer formation process

Polyvinyl alcohol powder ("Z-200", average degree of polymerization 1100, saponification degree 99.5 mol%) manufactured by Nihon Seika Kagaku Kogyo Co., Ltd. was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3% Respectively. The obtained aqueous solution was mixed with 5 parts by weight of a crosslinking agent ("Sumirez Resin 650" manufactured by Taoka Chemical Co., Ltd.) per 6 parts by weight of the polyvinyl alcohol powder to obtain a coating solution for forming a primer layer.

Next, an unoriented polypropylene (PP) film (melting point: 163 占 폚) having a thickness of 90 占 퐉 was prepared as a base film, corona treatment was performed on one side thereof, and a gravure coater having a small diameter was used on the corona- The coating solution for forming a primer layer was coated and dried at 80 캜 for 10 minutes to form a primer layer having a thickness of 0.2 탆.

(2) Production of laminated film (resin layer forming step)

A polyvinyl alcohol resin powder having a viscosity of 80 mPa · sec in an aqueous 4 wt% solution was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 7.5 wt%, which was then coated with a polyvinyl alcohol- Respectively.

On the surface of the primer layer of the base film having the primer layer prepared in (1) above, a coating liquid for forming a polyvinyl alcohol-based resin layer was coated to a thickness of 130 탆 by using a die coater, hot air at 70 캜 was blown And drying was carried out. At the time of drying, the water content was controlled with an infrared multi-component system ("IRMA-5162S" manufactured by CHINO Corporation) while changing the wind speed so that the drying rate at a water content of 30 wt% was controlled to 1.30 wt% / sec. Thereafter, drying was continued while controlling the average drying rate from 30% by weight to 10% by weight to be 1.35% by weight / sec, and drying was continued until the water content became 4.86% by weight. The film thickness of the dried polyvinyl alcohol-based resin film was 9.2 占 퐉. Thus, a laminated film composed of a base film / primer layer / polyvinyl alcohol based resin film was obtained.

(3) Production of stretched film (stretching process)

The laminated film prepared in (2) above was subjected to free-end uniaxial stretching at a maximum temperature of 150 DEG C at a maximum temperature of 500 DEG C during air drawing using a vertical longitudinal uniaxial stretching apparatus (air drawing) To obtain a stretched film provided with a polyvinyl alcohol-based resin film stretched on the stretched film. The thickness of the polyvinyl alcohol-based resin film after stretching was 5.1 占 퐉.

(4) Production of a polarizing laminated film (dyeing process)

The stretched laminated film prepared in the above (3) was immersed in a dyeing aqueous solution (containing 0.6 parts by weight of iodine and 10.0 parts by weight of potassium iodide per 100 parts by weight of water) containing iodine and potassium iodide for about 180 seconds After dyeing, the extra dyeing solution was washed with pure water at 10 ° C.

Subsequently, the first crosslinked aqueous solution containing boric acid (containing 10.4 parts by weight of boric acid per 100 parts by weight of water) was immersed for 120 seconds at 78 ° C, and then a second crosslinked aqueous solution containing boric acid and potassium iodide at 70 ° C (Containing 5.0 parts by weight of boric acid and 12.0 parts by weight of potassium iodide per 100 parts by weight of water) for 60 seconds and immersed in pure water at 10 DEG C for about 10 seconds to carry out crosslinking treatment. Immediately thereafter, the liquid attached to both surfaces was removed using an air blower to obtain a polarizing laminated film including a polarizing film.

(5) Fabrication of Polarizer with One Side Protective Film (First Bonding Step, Peeling Step)

A polarizing film of the polarizing laminated film prepared in (4) above was subjected to corona treatment through a bonding layer made of an ultraviolet ray-curable adhesive ("KR-75T" manufactured by ADEKA Corporation) ("ZF14", manufactured by Nippon Zeon Co., Ltd.), which is made of cycloolefin, was bonded. Subsequently, the adhesive layer was cured by irradiating ultraviolet rays using a high-pressure mercury lamp to obtain a bonded film composed of a protective film / adhesive layer / polarizing film / base film layer (first bonding step). Thereafter, the base film was peeled off from the obtained bonded film to obtain a polarizing plate with a one side protective film (peeling step).

(6) Fabrication of polarizer with double-sided protective film (second bonding step)

A protective film (a protective film made of cyclic cycloolefin (&quot; ZF14 &quot; manufactured by Nippon Zeon Co., Ltd.), which had been subjected to corona treatment on the bonding surface of the polarizing film on which the base film of the polarizing plate with single- )) Were bonded to obtain a polarizing plate with a double-side protective film (second bonding step).

&Lt; Examples 2 to 7 and Comparative Examples 1 to 5 >

In Examples 2 to 7 and Comparative Examples 1 to 5, the viscosity of the 4 wt% aqueous solution of the polyvinyl alcohol resin powder used in the step (2) was the values shown in Table 1, and in the step (2) A polarizing film, a polarizing film, a polarizing film with a double-side protective film, a polarizing film, and a protective film with a double-side protective film were prepared in the same manner as in Example 1 except that the crystallization period of the polyvinyl alcohol- &Lt; / RTI &gt;

[Measurement of crystal long period of polyvinyl alcohol based resin film]

The crystal long period L of the polyvinyl alcohol-based resin film obtained in the above (2) was determined by X-ray small angle scattering measurement of the transmission method. Cu-K? (Wavelength: 0.154 nm) was used as the source of the light by using a small angle scattering X-ray analyzer ("NANO-STAR" manufactured by Bruker AXS). The length of the camera was adjusted to 1060 ㎚, and a 2 - dimensional PSPC (position sensitive proportional counter) was used for the detector. The measurement was carried out at room temperature under a vacuum atmosphere, and the exposure time was 30 minutes. First, a background measurement was performed without installing a sample at first, and the obtained two-dimensional scattering data was integrated in the entire circumferential direction to obtain a one-dimensional profile. Next, 64 polyvinyl alcohol-based resin films obtained by peeling the base film from the laminated film were stacked in the longitudinal direction to prepare samples for evaluation. After the measurement of the sample for evaluation, the same one-dimensional profile was obtained by integrating in the entire circumferential direction. The transmittance of the sample for evaluation is calculated from the intensity of the transmitted light at the background measurement and the intensity of the transmitted light at the time of measuring the sample for evaluation, and after considering this, the one-dimensional profile of the background is subtracted from the one- Dimensional scattering profile of the sample. A peak attributable to the periodic structure was observed at about 1.1 degrees in terms of the diffraction angle (2?), And this peak was converted into the period length by the Bragg equation. This period length was defined as the crystalline long period L of the polyvinyl alcohol-based resin. The results are shown in Table 1.

[Measurement of piercing strength of polarizing film]

The base film was peeled from the polarizing laminated film obtained in the above (4), and the polarizing film was extracted to obtain an evaluation sample. First, the thickness of the polarizing film of the evaluation sample was measured with a contact type film thickness meter (trade name "DIGIMICRO MH-15M", manufactured by Nikon Corporation). Thereafter, using a handy compression tester "KES-G5 Needle Penetration Measurement Specification " manufactured by KATO TECH CO., LTD. Equipped with a needle having a tip diameter of 1 mmφ and 0.5 R, Under a measurement condition of 0.33 cm / sec, the polarizing film was pierced, and the force applied to the needle when the polarizing film was passed through was measured. This measurement was carried out on 12 evaluation samples, and the average value was used as a measurement value of the sample. The piercing strength per unit thickness was calculated by dividing the measured value by the thickness of the polarizing film. The results are shown in Table 1.

[Heat Shock Test of Polarizer]

The surface of the protective film bonded in the second bonding step of the polarizing plate with a double-sided protective film obtained in the above (6) was subjected to corona treatment, and then an acrylic pressure-sensitive adhesive ("P-3132" manufactured by Lintec Corporation) was bonded. The obtained polarizer with a pressure-sensitive adhesive layer was cut into a polarizing plate chip having a size of 5-inch diagonal and the polarizing plate chip was bonded to glass using the pressure-sensitive adhesive layer to obtain a sample for evaluation. Thereafter, the sample was kept at -40 ° C for 30 minutes on the low temperature side and then held for 30 minutes on the high temperature side at 85 ° C by a cold / impact tester (TSA-301 LW) manufactured by Espec Co., A heat shock test was performed. During the heat shock test, it was not exposed to room temperature.

Each of the 50 evaluation samples was subjected to a heat shock test of 150 cycles each, and the number of appearance of a crack-like appearance defect in the polarizing film among the 50 samples for evaluation was visually confirmed as the "heat shock test" Respectively. For example, "0/50" in Example 1 means that, out of 50 evaluation samples, the number of appearance of a crack-like appearance defect was visually confirmed to be zero.

[Measurement of long period of polarizing film constituting polarizing plate]

From the polarizing plate with a double-side protective film obtained in the above (6), the two protective films were dissolved and removed by using cyclohexane, and the polarizing film was isolated. Sixty-four polarizing films thus obtained were superimposed on each other in the direction of the absorption axis (longitudinal direction) to prepare samples for evaluation. With respect to the sample for evaluation, measurement was performed by X-ray small angle scattering measurement in the same manner as the measurement of the crystal long period of the polyvinyl alcohol based resin film described above. The exposure time was 60 minutes. In the two-dimensional scattering pattern obtained, a period length peak was detected at a position inclined 20 degrees from the absorption axis direction. In order to obtain a one-dimensional scattering profile in the absorption axis direction, scattering in the range of ± 5 degrees in the absorption axis direction was integrated to obtain a profile. Further, in order to perform the background correction, measurement was also performed in a state in which no evaluation sample was provided, and the same angular range was integrated to obtain a profile in the absorption axis direction. These were subtracted in consideration of the transmittance to obtain a one-dimensional profile in the absorption axis direction of the evaluation sample. Based on this profile, the cycle length was converted by Bragg equation. This period length was defined as a long period L 'in the absorption axis direction of the polarizing film. The results are shown in Table 1.

Likewise, in order to obtain a one-dimensional profile in the cycle length direction (direction inclined 20 degrees from the absorption axis direction), a range of ± 5 degrees from the center direction of the cycle length was integrated to obtain a profile in the cycle length direction. Based on this profile, the cycle length was converted by Bragg equation. This period length was defined as a long period in the periodic direction of the polarizing film. The results are shown in Table 1.

[Measurement of viscosity of 4 wt% aqueous solution of polarizing film constituting polarizing plate]

From the polarizing plate with a double-side protective film obtained in the above (6), the two protective films were dissolved and removed by using cyclohexane, and the polarizing film was isolated. The isolated polarizing film was suspended in an oven controlled at 80 캜 and 90% RH, and subjected to wet heat treatment for about 7 days. As a result, iodine and boric acid were removed and a transparent film was obtained. The obtained transparent film was dissolved to prepare a 4 wt% aqueous solution, and its viscosity P 'was measured. The method of measuring the viscosity P 'is as described above. The results are shown in Table 1.

[Review]

Fig. 8 is a graph showing the results of a comparison between Examples 1 to 7 (Test Examples in which the piercing strength is 5.0 g / 탆 or more and the appearance defect of the polarizing film is not observed by the heat shock test) and Comparative Examples 1 to 5 (the piercing strength is 5.0 g / And the appearance defect was observed by the heat shock test, the graph plotted with the viscosity P as the abscissa axis and the crystal long period L as the ordinate axis is plotted for the polyvinyl alcohol type resin film of the test example). In Fig. 8, Examples 1 to 7 were plotted as &quot; o &quot;, and Comparative Examples 1 to 5 were plotted as &quot; x &quot;. From Fig. 8, it is confirmed that the curve of L = 6.7909 x ln (P) - 17.337 is suitable as the boundary line of the examples and the comparative example.

9 is a graph plotting the viscosity P 'of the polarizing film isolated from the polarizing plates of Examples 1 to 7 and Comparative Examples 1 to 5 as the abscissa axis and plotting the long axis L' of the absorption axis direction as the ordinate axis. In Fig. 9, Examples 1 to 7 were plotted as &quot;? &Quot;, and Comparative Examples 1 to 5 were plotted as &quot; x &quot;. From Fig. 9, it is confirmed that the curve of L '= 14.3 x ln (P') - 43.9 is suitable as a boundary line of the embodiment and the comparative example.

Claims (5)

A polyvinyl alcohol-based resin film obtained by film formation using a solution containing a polyvinyl alcohol-based resin,
Wherein a viscosity P (mPa 占 퐏) of an aqueous 4 wt% solution of the polyvinyl alcohol-based resin and a crystalline long period L (nm) of the polyvinyl-based resin film satisfy a relationship of the following formula (1) film.
L < 6.7909 x ln (P) - 17.337 (1) A polarizing film obtained by stretching and dyeing the polyvinyl alcohol-based resin film according to claim 1. Wherein the viscosity P '(mPa 占 퐏) of the 4 wt% aqueous solution and the long-term L' (nm) in the absorption axis direction satisfy the relation of the following formula (2).
L '<14.3 × ln (P') - 43.9 (2) The polarizing film according to claim 2 or 3, wherein the piercing strength per unit thickness is 5.0 g / m or more. A polarizing plate comprising a polarizing film and a protective film laminated on at least one side of the polarizing film,
Wherein a viscosity P '(mPa · s) of a 4 wt% aqueous solution of the polarizing film isolated from the polarizing plate and a long period L' (nm) of an absorption axis direction of the polarizing film isolated from the polarizing plate satisfy the following formula Polarizer satisfying the relationship.
L '<14.3 × ln (P') - 43.9 (2)

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