TW201632350A - Elongated film, polarizing film and polarizing plate comprising the polarizing film - Google Patents

Abstract

The present invention provides an elongated film for manufacturing polarizing film and containing a polyvinyl alcohol resin including a lamellae crystalline, wherein, a thickness L(nm) of the lamellae crystalline calculated by the following formula (1) by using a crystal melting peak temperature T(K) of the elongated film detected by the differential scanning calorimeter is 13.0 nm or more and 45.0 nm or less. L=0.66x{516/(516-T)}...(1).

Description

Stretch film, polarizing film and polarizing plate containing the same

The present invention relates to a stretched film, a polarizing film, and a polarizing plate containing the polarizing film.

The polarizing plate is widely used for an image display device typified by a liquid crystal display device or the like. As a polarizing plate, generally, a protective film is bonded to one surface or both surfaces of a polarizing film formed by adsorbing a dichroic dye such as iodine to a polyvinyl alcohol-based resin film. In recent years, with the expansion of image display devices toward mobile devices, thin televisions, and the like, a polarizing plate has been demanded, and a polarizing film has been thinned.

In the method for producing a polarizing film which is formed by a single layer of a polyvinyl alcohol resin film, a method for producing a polarizing film of a polyvinyl alcohol resin film is formed on the substrate film by a method of producing a polyvinyl alcohol resin layer. This is stretched and dyed together with the base film to obtain a polarizing film, and the thin polarizing film can be more uniformly produced.

Since the polyvinyl alcohol-based resin constituting the polarizing film is hydrophilic, Therefore, when the stretched film is immersed in a production step of a dyeing liquid or the like, there is a problem that it is easily dissolved in an aqueous solution (hereinafter also referred to as "solubility"). When the polyvinyl alcohol-based resin is dissolved, the appearance is poor, the film strength is lowered, and the polarizing performance is lowered. In the method of forming a polyvinyl alcohol-based resin layer on a base film and extending and dyeing the same with a substrate to obtain a polarizing film, the base material can be used to prevent complete collapse of the polyvinyl alcohol-based resin layer. However, it does not solve the problem that the polyvinyl alcohol-based resin will dissolve.

Patent Document 1 discloses an insolubilization step of immersing a stretched laminate in a boric acid aqueous solution in advance before immersing in a dyeing liquid in order to prevent dissolution of the polyvinyl alcohol-based resin layer.

However, in the case where the insolubilization step is provided, the production process becomes complicated, and the stretched film composed of the polyvinyl alcohol-based resin which has undergone the insolubilization step has a permeability of the dyeing liquid in the dyeing step (hereinafter also referred to as "dyeability"). reduce. When the dyeing liquid is sufficiently permeated to increase the dyeing time, the productivity is lowered and the film strength is lowered.

The present invention has an object of providing a stretched film having suppressed solubility and good dyeability, a polarizing film produced using the stretched film, and a polarizing plate.

In the present invention, a stretched film, a polarizing film, and a polarizing plate shown below are provided.

[1] A stretched film for use in the production of a polarizing film, which is a stretched film composed of a polyvinyl alcohol-based resin containing a lamella type crystal; wherein the stretched film is measured by differential scanning calorimetry using the above-mentioned stretched film Measured The thickness L (nm) of the layered crystal calculated by the following formula (1) is 13.0 nm or more and 45.0 nm or less in the predetermined crystal melting peak temperature T (K); L = 0.66 × {516 / (516 - T)}...(1).

[2] The stretched film according to the above [1], wherein the polyvinyl alcohol-based resin contains a monomer which adjusts the thickness L (nm) of the layered crystal as a constituent monomer.

[3] The stretched film according to [1] or [2], which is obtained by extending a polyvinyl alcohol-based resin layer provided on a base film.

[4] A polarizing film obtained by dyeing a stretched film according to any one of [1] to [3] using a dichroic dye.

[5] The polarizing film according to [4], wherein the puncture strength per unit thickness is 6.0 g/μm or more.

[6] A polarizing plate comprising: the polarizing film according to [4] or [5]; and a protective film laminated on at least one surface of the polarizing film.

According to the present invention, it is possible to provide a stretched film having suppressed solubility and good dyeability, a polarizing film produced using the stretched film, and a polarizing plate.

1‧‧‧ polarizing plate with protective film on one side

2‧‧‧ polarizing plates with protective film on both sides

5‧‧‧ polarizing film

6‧‧‧Polyvinyl alcohol resin layer

6'‧‧‧Stretch film

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

30‧‧‧Base film

30'‧‧‧Extended base film

50‧‧‧Layered crystal

51‧‧‧ polymer chain

100‧‧‧ laminated film

200‧‧‧Extended laminating film

300‧‧‧Polarized laminated film

400‧‧‧Finished film

L‧‧‧ thickness

X‧‧‧Width

Y‧‧‧depth

Fig. 1 is a schematic view showing a part of a polymer chain constituting a layered crystal.

Fig. 2 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention.

Fig. 3 is a schematic cross-sectional view showing another example of the layer configuration of the polarizing plate of the present invention.

Fig. 4 is a flow chart showing a preferred example of the method for producing a polarizing plate of the present invention.

Fig. 5 is a schematic cross-sectional view showing an example of a layer configuration of a laminated film obtained by the resin layer forming step.

Fig. 6 is a schematic cross-sectional view showing an example of a layer configuration of an extended laminated film obtained by the stretching step.

Fig. 7 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing laminate film obtained by the dyeing step.

Fig. 8 is a schematic cross-sectional view showing an example of a layer configuration of a bonded film obtained by the first bonding step.

<stretch film>

The stretched film of the present invention is used for the production of a polarizing film. The stretched film is composed of a polyvinyl alcohol-based resin containing a layered crystal. A layered crystal contained in a polyvinyl alcohol-based resin, which is characterized by using a crystal melting peak temperature T (K) measured by differential scanning calorimetry (DSC), and is represented by the following formula (1) The calculated thickness L (nm) is 13.0 nm or more and 45.0 nm or less. Further, the thickness L (nm) of the layered crystal can be calculated by the following formula (1).

L (nm) = 0.66 × {516 / (516 - T)} (1).

The stretched film is formed by stretching and stretching a polyvinyl alcohol-based resin. The method for forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a conventional method. Since a polarizing film having a small thickness and a polarizing film of a film in the step are easily handled, it is preferable to coat the polyethylene. A method of forming a film by coating a solution of an alcohol resin on a substrate film. The method of stretching the polyvinyl alcohol-based resin after forming a film is not limited, and is preferably one-axis extension.

The thickness of the stretched film is appropriately selected depending on whether or not the film is stretched in the step of producing the polarizing film, and may be, for example, 30 μm or less, or 20 μm or less. From the viewpoint of reducing the thickness of the polarizing plate, it is preferably 10 μm or less. It is more desirable to be 8 μm or less. The thickness of the stretched film is usually 2 μm or more. Further, in the case where the polarizing film is produced by re-expansion, it is suitable to use a thicker than the above.

(polyvinyl alcohol resin)

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

(layered crystal)

A polyvinyl alcohol-based resin is known to form a crystal of a folded structure formed by multi-folding of a polymer chain generally called a layered crystal. Fig. 1 is a schematic view showing a part of a polymer chain constituting a layered crystal. In the layered crystal 50, the polymer chain 51 is folded back in the width direction to form a folded structure, and such a folded structure is formed by multiplexing in the depth direction. The thickness L of the layered crystal 50 is a distance in the longitudinal direction of the polymer chain 51 having a folded structure. The width X of the layered crystal 50, which is the distance in the folding direction of the polymer chain 51, becomes larger as the number of times of folding. The depth Y of the layered crystal 2 is the distance in the depth direction of the folded structure of the polymer chain 51.

In the layered crystal 50, the thickness L affects the stability. The larger the thickness L, the more stable the layered crystal 51 is. In the present invention, it is found that the thickness L of the layered crystal contained in the polyvinyl alcohol-based resin constituting the stretched film is 13.0 nm or more and 45.0 nm or less, whereby solubility is suppressed and dyeability is good. When the stretched film of the present invention is used, since the dissolution of the polyvinyl alcohol-based resin with respect to the dyeing aqueous solution or the like can be suppressed, a polarizing film having a good appearance, good film strength, and good polarizing performance can be obtained. Further, since the dyeability is good, high productivity can be maintained in the production process of the polarizing film.

When the thickness L of the layered crystal is less than 13.0 nm, the polyvinyl alcohol-based resin is easily dissolved in the dyeing aqueous solution, and the polyvinyl alcohol-iodine (I ₃ ) complex having high water resistance selectively falls off and fades to blue. The skin is roughened, and the alignment of the polyvinyl alcohol-based resin which has been aligned is moderated, and the polarizing performance of the polarizing film is lowered. The thickness L of the layered crystal is preferably 14.0 nm or more, more preferably 15.5 nm or more.

When the thickness L of the layered crystal exceeds 45.0 nm, In the production process of the segment polarizing film, the dyeability is lowered and the productivity is impaired. The thickness L of the layered crystal is more preferably 35.0 nm or less.

The thickness L of the layered crystal can be introduced as a constituent monomer (hereinafter also referred to as "layered growth control monomer unit") by introducing a monomer having a thickness L of the layered crystal, and such a layer The growth is controlled by adjusting the position and frequency of the monomer unit. The layered growth control monomer unit is preferably a monomer unit having one or more substituents having a volume of a certain volume or more and having a tendency to be crystallized by steric hindrance, which is likely to be present in the crystal lattice of the layered crystal. . The layered growth control monomer unit having such a substituent has a high probability of being present in the folded portion of the polymer chain constituting the folded structure. Therefore, the layered growth controls the position and frequency of the monomer unit in the polymer chain, affecting the thickness L of the layered crystal. The higher the frequency of such a layered growth control monomer unit, the shorter the thickness L of the layered crystal of the polymer chain becomes.

The length of the substituent having a certain volume or more in the layered growth controlling monomer unit is preferably 3.0 Å or more. Usually, the bond between atoms is 1.2 to 1.6 Å. Therefore, in the case of a substituent having a length of 3.0 Å or more, the folding structure is an obstacle, and the possibility of extrusion from the folded structure becomes high. For example, in the case where the substituent is a n-propyl group, since the C-C bond is three bonds, the length becomes 4.5 Å from the standard length of 1.5 Å of the C-C bond. Therefore, it has been found that it is suitable as a substituent having a certain volume or more.

The layered growth controlling monomer unit has one large volume of a substituent, and is represented, for example, by the following chemical formula (1).

In the chemical formula (1), the substituent X has a certain volume or more, and the above length is preferably 3.0 Å or more. Such a substituent X is preferably an atom having two or more hydrogen atoms (H). When the number of atoms other than the hydrogen atom (H) is less than two, the volume of the substituent X is insufficient, and the possibility of being extruded from the folded structure of the layered crystal is low. For example, when the substituent X is CH ₃ or H, such a unit in the polyvinyl alcohol does not become an obstacle to the folded structure of the layered crystal even if it is present alone or continuously, and the folded portion of the layered crystal cannot be controlled. . In addition, when the substituent X is too large, the number of atoms other than the hydrogen atom (H) of the substituent X is preferably 10 or less, and the hydrogen atom (H) is preferable because the crystallization is inhibited. Other atoms, such as carbon (C), oxygen (O), chlorine (Cl), etc., are not limited thereto.

As the substituent X, for example, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, butyl, phenyl, benzyl, ethoxy, propoxy, butoxy Base. The substituent X may contain, in addition to the saturated bond, an unsaturated bond such as C=C or C=O, and may be an allyl group, a propynyl group, a butenyl group, a butynyl group, a butoxy group or the like. The substituent X may further contain a bond such as an ether bond, an ester bond or a urethane bond in the chain, or may contain a hydroxyl group or the like.

The layered growth control monomer unit is not limited to the one shown in the above chemical formula (1), and may have two substituents, for example, the following chemical formula (2) Shown.

In the chemical formula (2), the substituent X has a certain volume or more as described for the substituent X in the chemical formula (1). The substituent Y may be a certain volume or more, or may not be. In the case where the substituent Y is a volume having a certain volume or more, it is as described for the substituent X in the chemical formula (1). In this case, it may be the same as or different from the substituent X.

Further, the layered growth control monomer unit in the polymer chain controls the folded portion of the polymer chain while controlling the vinyl alcohol monomer unit from the folded portion of the polymer chain to the next folded portion (may also include The number of monomer units that do not become a steric hindrance of the crystal lattice. The same applies hereinafter. That is, since the position and frequency of the layered growth control monomer unit are adjusted, the number of continuous vinyl alcohol monomer units in the polymer chain is reflected, so that it is a continuous vinyl alcohol monomer unit with the polymer chain. The average of the number of numbers (hereinafter also referred to as "average number of consecutive units") is related. The larger the average value of the number of continuous vinyl alcohol monomer units, the more the thickness L of the layered crystal tends to become larger.

As a method of adjusting the thickness L of the layered crystal of the polyvinyl alcohol-based resin in the stretched film, the method of adjusting the position and frequency of the layered growth control monomer unit contained in the polyvinyl alcohol-based resin does not The polarization property and the contraction force of the polarizing film are important and can be adjusted. The point of the thickness L of the layered crystal is more suitable.

In addition, as a method of adjusting the thickness L of the layered crystal of the polyvinyl alcohol-based resin in the stretched film, a method of adjusting the stretch ratio and the heat history can be used. The higher the stretching ratio, the more the thickness L of the layered crystal tends to increase. The stretching ratio is preferably adjusted within a range in which the polarizing performance and the contraction force are not a problem. The adjustment of the heat history, for example, the heat applied during film drying of the polyvinyl alcohol-based resin, that is, the temperature, the time, or the extension temperature is adjusted. Further, the range of the thickness L of the layered crystal which can be adjusted by the heat history is smaller than the above method of adjusting the position and frequency of the layered growth control unit cell. Therefore, as a method of adjusting the thickness L of the layered crystal, it is preferable to separately adjust the position and frequency of the layered growth control unit cell, or to combine it with other methods.

The thickness L of the layered crystal in the present specification is the thickness L obtained by the above formula (1) using the crystal melting peak temperature T (K) measured by differential scanning calorimetry (DSC) of the stretched film. The differential calorimeter was measured by using a differential calorimeter while measuring the temperature at a temperature of 10 ° C/min from 50 ° C to 250 ° C. The crystal melting of the polyvinyl alcohol-based resin starts from more than 200 ° C, and then a crystal melting peak appears. The temperature at the peak position of the crystal melting peak from 200 ° C to 250 ° C from the crystal was taken as the crystal melting peak temperature T (K). As the differential calorimeter, for example, "DSC 6220" manufactured by Seiko Instruments Co., Ltd., or the like can be mentioned.

The width X and the depth Y of the layered crystal 50 are not affected. The thermodynamic stability of the layered crystal 50 affects the crystal size and the degree of crystallization, thus affecting the time required for the polyvinyl alcohol resin to dissolve. This is because the crystal size and degree of crystallization are related to the dissolution rate.

The width X and the depth Y of the layered crystal 50 can be adjusted, for example, by the heat history of the polyvinyl alcohol resin. The adjustment of the heat history is, for example, adjusting the amount of heat applied during film drying of the polyvinyl alcohol-based resin, that is, adjusting the temperature, time, or adjusting the extension temperature. The degree of crystallization of the polyvinyl alcohol-based resin is preferably 15% or more, more preferably 20% or more, and still more preferably 25% or more from the viewpoint of suppressing the dissolution rate. Therefore, it is preferable to appropriately adjust the width X and the depth Y of the layered crystal 50 so as to select the heat history of the polyvinyl alcohol resin so as to have such a degree of crystallization.

<polarized film>

The polarizing film of the present invention is produced by using the above-mentioned stretched film, and the above-mentioned stretched film is dyed with a dichroic dye. By using the above-mentioned stretched film, the dissolution of the aqueous dye solution by the polyvinyl alcohol-based resin is suppressed, so that a polarizing film having a good appearance, good film strength, and good polarizing performance can be obtained. Further, since the above-mentioned stretched film has excellent dyeability, high productivity can be maintained in the production process of the polarizing film.

When the polarizing performance of the polarizing film is described in more detail, the polarizing performance is generally evaluated using two parameters called "visibility correction monomer transmittance Ty" and "visuality correction polarization Py". These parameters are the transmittance and the degree of polarization of the corrected visible light region (wavelength 380 to 780 nm) in such a manner that the weight of the human eye having the highest sensitivity at around 550 nm is maximized. Light with a wavelength of less than 380 nm is unrecognizable by the human eye and is not considered in Ty and Py.

The illuminance correction unit transmittance Ty of the polarizing film may be a value generally obtained in an image display device such as a liquid crystal display device to which the polarizing film or the polarizing plate including the polarizing film is applied, specifically 40 to 47%. The scope is ideal. Ty is more preferably in the range of 41 to 45%, in which case the balance of Ty and Py becomes better. When Ty is too high, Py is lowered, and the display quality of the image display device is lowered. In the case where Ty is too low, the brightness of the image display device is lowered, the display quality is lowered, or the input power must be increased in order to sufficiently increase the brightness. The luminosity correction polarization degree Py of the polarizing film is preferably 99.9% or more, more preferably 99.95% or more.

The thickness of the polarizing film is, for example, 30 μm or less, and may be 20 μm or less. From the viewpoint of reducing the thickness of the polarizing plate, it is preferably 10 μm or less, more preferably 8 μm or less. The thickness of the polarizing film is usually 2 μm or more.

The polarizing film preferably has a puncture strength per unit thickness of 6.0 g/μm or more. As long as the puncture strength is 6.0 g/μm or more, the durability of the polarizing film can be remarkably suppressed in the durability test such as the thermal shock test.

<Polarizer> (1) Layer composition of polarizing plate

Fig. 2 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention. The polarizing plate of the present invention of the polarizing plate 1 shown in Fig. 2 may be a first protective film 10 including a polarizing film 5 and a surface laminated on one side thereof. A polarizing plate with a protective film on one side. The first protective film 10 can be laminated on the polarizing film 5 via the first adhesive layer 15.

Further, in the polarizing plate of the present invention, a protective film may be attached to the other surface of the polarizing film 5, and specifically, the polarizing plate 2 shown in Fig. 3 may be provided with a polarizing film 5 and laminated thereon. A polarizing plate having a protective film on both sides of the first protective film 10 on one surface and the second protective film 20 laminated on the other surface. The second protective film 20 can be laminated on the polarizing film 5 via the second adhesive layer 25.

When the polarizing plate of the present invention is incorporated in an image display device such as a liquid crystal display device, it may be a polarizing plate disposed on the front side of the image display element such as a liquid crystal cell, or may be disposed on an image display. A polarizing plate on the back side of the device (for example, the backlight side of the liquid crystal display device).

(2) polarizing film

The polarizing plate of the present invention comprises the above-described polarizing film of the present invention as the polarizing film 5. Therefore, the details of the polarizing film 5 are referred to the above description.

(3) First protective film

The first protective film 10 may be a thermoplastic resin having light transmissivity (preferably optically transparent), for example, a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin. a polyolefin-based resin such as a terpene-based resin; a cellulose ester-based resin such as cellulose triacetate or cellulose diacetate; a polyester resin; a polycarbonate resin; and a (meth)acrylic resin Resin; polystyrene resin; or a mixture of such copolymers, copolymers, etc. The film.

The first protective film 10 may be a protective film having an optical function such as a retardation film or a brightness enhancement film. For example, a film made of the above thermoplastic resin, such as stretching (one-axis stretching or biaxial stretching), or a liquid crystal layer formed on the film may be used as a retardation film which has been given an arbitrary retardation value.

In addition to the homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin, a copolymer composed of two or more kinds of chain olefins may be mentioned as the chain polyolefin resin.

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene. (representatively, a random copolymer) and a graft copolymer modified with an unsaturated carboxylic acid or a derivative thereof, and the like, and the like. Among them, as the cyclic olefin, a norbornene-based resin having a norbornene-based monomer such as a polydecene-based monomer or a polycyclic norbornene-based monomer is preferably used.

A 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. Further, these copolymers may be used, and a part of the hydroxyl group may be modified by other substituents. Among these, cellulose triacetate (triethylenesulfonyl cellulose: TAC) is particularly preferable.

The polyester resin is a resin other than the above cellulose ester resin having an ester bond, and is generally a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. The polycondensate is formed. As the polyvalent carboxylic acid or a derivative thereof, a dicarboxylic acid or a derivative thereof such as terephthalic acid, isophthalic acid, dimethyl terephthalate or dimethyl naphthalate may be used. As the polyol, a diol such as ethylene glycol, propane diol, butane diol, neopentyl glycol, cyclohexane dimethanol or the like can be used.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polybutylene terephthalate. Ester, propylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

The polycarbonate resin is composed of a polymer in which a monomer unit is bonded via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate or a copolymerized polycarbonate which modifies a polymer skeleton.

The (meth)acrylic resin is a resin mainly composed of a compound having a (meth)acryl fluorenyl group. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-( Methyl) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of an alicyclic hydrocarbon group-containing compound (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl (meth) acrylate), and the like. More desirably used such as poly (meth) acrylate of poly (meth) acrylic acid C _1-6 alkyl ester as a main component polymer, more preferably used as a main component methyl methacrylate (50 to 100% by weight, preferably 70 to 100% by weight, based on the methyl methacrylate resin.

A surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, or an antifouling layer can be formed on the surface of the first protective film 10 on the side opposite to the polarizing film 5. Further, 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 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less from the viewpoint of reducing the thickness of the polarizing plate. The thickness of the first protective film 10 is usually 5 μm or more from the viewpoint of strength and workability.

(4) The first adhesive layer

The first adhesive layer 15 is a layer for subsequently fixing the surface of the first protective film 10 on one side 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 rays, visible light, electron beams, or X-rays, and may be, for example, polyethylene. A water-based adhesive in which an adhesive component of an alcohol resin is dissolved or dispersed in water.

As the active energy ray-curable adhesive forming the first adhesive layer 15, since it exhibits good adhesion, it is preferable to use a cationically polymerizable curable compound and/or a radical polymerizable curable compound. Active energy ray-curable adhesive composition. Active energy The strand curable adhesive may further contain a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having one or two or more epoxy groups in the molecule) and an oxetane compound (having 1 in the molecule). One or two or more compounds of the oxetane ring) or a combination of these. Examples of the radically polymerizable curable compound include a (meth)acrylic compound (a compound having one or two or more (meth)acryloxy groups in the molecule) and a radical polymerizable double. Other vinyl compounds of the bond or combinations of these. A cationically polymerizable curable compound and a radically polymerizable curable compound may also be used in combination.

The active energy ray-curable adhesive may contain a cationic polymerization accelerator, an ion scavenger, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, and an anti-static agent as needed. Additives such as electrostatic agents, leveling agents, and solvents.

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

(5) 2nd protective film

The second protective film 20 of the polarizing plate 2 having the protective film on both sides of the protective film shown in Fig. 3 may be a film composed of the above-exemplified thermoplastic resin, or may be phased, similarly to the first protective film 10. A protective film with an optical function that is a poor film or a brightness enhancement film. The thickness of the surface treatment layer and the film which the second protective film 20 can have, and the like described above for the first protective film 10 Loaded. The first protective film 10 and the second protective film 20 may be a protective film made of the same type of resin, or may be a protective film made of a different type of resin.

(6) 2nd adhesive layer

The second adhesive layer 25 is a layer for subsequently fixing the surface of the second protective film 20 on the other side of the polarizing film 5. The details of the second adhesive layer 25 are described with reference to the first adhesive layer 15 described above. The adhesive forming the second adhesive layer 25 may have the same composition as the adhesive forming the first adhesive layer 15, and may have a different composition.

(7) Adhesive layer

The first protective film 10 or the second protective film of the polarizing plate 2 having the protective film on both sides of the protective film shown in Fig. 2 on the polarizing film 5 of the protective film-attached polarizing plate 1 shown in Fig. 2 In the case of 20, an adhesive layer for bonding a polarizing plate to another member such as a liquid crystal cell applied to a liquid crystal display device can be laminated. The adhesive for forming the adhesive layer is usually a matrix polymer of a (meth)acrylic resin, a styrene resin, a phthalocyanine resin, or the like, and an isocyanate compound, an epoxy compound, an aziridine is added thereto. (aziridine) The composition of the adhesive of the crosslinking agent of the compound. Further, it may be an adhesive layer which exhibits light scattering properties by containing fine particles. The thickness of the adhesive layer is usually from 1 to 40 μm, preferably from 3 to 25 μm.

(8) Other optical layers

The polarizing plate of the present invention may further include other optical layers laminated on the first and/or second protective films 10 and 20 and the polarizing film 5. As another optical layer, for example, a polarized polarizing film that transmits light of a certain polarized light, reflects light having a polarized light of opposite nature, a film with an anti-glare function having a concave-convex shape on the surface, and a surface anti-reflection function a film; a reflective film having a reflective function on the surface; a semi-transmissive reflective film having both a reflective function and a penetrating function; a viewing angle compensation film.

<Method for Producing Stretch Film, Polarizing Film, and Polarizing Plate>

The stretched film, the polarizing film, and the polarizing plate of the present invention can be suitably produced by the method shown in Fig. 4. The manufacturing method shown in FIG. 4 includes the following steps: (1) applying a coating liquid containing a polyvinyl alcohol-based resin to at least one surface of the base film, followed by drying to form a poly a vinyl alcohol-based resin layer to obtain a resin layer forming step S10 of the laminated film; (2) extending the laminated film to obtain an extending step of the extended laminated film having the stretched film of the stretched polyvinyl alcohol-based resin layer on the base film S20; (3) forming a polarizing film (polarized sub-layer) by iodine dyeing the stretched film of the extended laminated film to obtain a dyeing step S30 of the polarizing laminated film; (4) on the polarizing film of the polarizing laminated film, The protective film is bonded to obtain a first bonding step S40 of the bonding film, and (5) the substrate film is peeled off from the bonding film to obtain a peeling step S50 of the polarizing plate having the protective film on one side.

Applying a protective film on both sides as shown in Figure 3 In the case of the light plate 2, after the peeling step S50, the second bonding step S60 of bonding the protective film to the surface of the polarizing film of the polarizing plate having the protective film on one side is further included.

Hereinafter, each step will be described with reference to FIGS. 5 to 8. In the resin layer forming step S10, the polyvinyl alcohol-based resin layer may be formed on both surfaces of the base film, but the case where it is formed on one surface will be mainly described below.

(1) Resin layer forming step S10

Referring to Fig. 5, this step is a step of forming a polyvinyl alcohol-based resin layer 6 on at least one surface of the base film 30 to obtain a laminated film 100. The polyvinyl alcohol-based resin layer 6 is a layer which becomes the stretched film 6' in the extending step S20 and becomes the polarizing film 5 through the dyeing step S30. The polyvinyl alcohol-based resin layer 6 can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one side or both surfaces of the base film 30 to dry the coating layer. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that the polarizing film 5 of the film is easily obtained.

The base film 30 may be composed of a thermoplastic resin, and is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation. Specific examples of the thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (such as a decene-based resin); a polyester resin; and a (meth)acrylic resin. a resin; a cellulose ester resin such as cellulose triacetate or cellulose diacetate; a polycarbonate resin; a polyvinyl alcohol resin; a polyvinyl acetate resin; Polyarylate resin; polystyrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures and copolymers thereof.

The base film 30 may have a single layer structure composed of one resin layer composed of one or two or more thermoplastic resins, or may be a resin composed of one or two or more thermoplastic resins. The multilayer construction of the layer. When the laminated film 100 is stretched in the extending step S20 to be described later, the base film 30 is preferably made of a resin which can be extended at an extending temperature suitable for extending the polyvinyl alcohol-based resin layer 6.

The base film 30 may contain an additive. Specific examples of the additive include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and color formers.

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

The coating liquid applied to the base film 30 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). The details of the polyvinyl alcohol-based resin are as described above. The coating liquid may contain an additive such as a plasticizer or a surfactant as needed.

The method of applying the above coating liquid to the base film 30 can be carried out by a wire bar coating method; for example, a roll coating method such as a reverse coating method or a gravure coating method; a die coating method; a notch wheel coating method (comma coating); lip coating method; spin coating method; screen coating method; fountain coating method; Dip coating method; spraying method and the like are appropriately selected.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set depending on the kind 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 contains water, the drying temperature is preferably 80 ° C or more.

The polyvinyl alcohol-based resin layer 6 may be formed only on one surface of the base film 30 or on both surfaces. When formed on both sides, curling of the film which may occur during the production of the polarizing laminated film 300 (refer to FIG. 7) can be suppressed, and two polarizing plates can be obtained from one polarizing laminated film 300, so that the production efficiency of the polarizing plate is obtained. The level is also beneficial.

The thickness of the polyvinyl alcohol-based resin layer 6 of the laminated film 100 is preferably 3 to 30 μm, more preferably 5 to 20 μm. As long as the polyvinyl alcohol-based resin layer 6 having the thickness within the range is subjected to the stretching step S20 and the dyeing step S30 described later, the dyeing property of iodine is good, the polarizing property is good, and the film thickness is sufficiently thin (for example, the thickness is 10 μm or less). Polarizing film 5.

Before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin layer 6, at least the surface of the base film 30 on the side of the polyvinyl alcohol-based resin layer 6 to be formed can be applied. Corona treatment, plasma treatment, flame treatment, and the like. Further, for the same reason, the polyvinyl alcohol-based resin layer 6 may be formed on the base film 30 via an undercoat layer or the like.

The undercoat layer can be formed by applying a coating liquid for forming an undercoat layer onto the surface of the base film 30 and then drying it. The coating liquid contains a component that exerts a certain degree of adhesion to both the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually includes a tree that imparts such adhesion. Fat composition and solvent. As the resin component, a thermoplastic resin such as a (meth)acrylic resin or a polyvinyl alcohol-based resin, which is excellent in transparency, heat stability, and elongation, is preferably used. Among them, a polyvinyl alcohol-based resin which imparts a good adhesion is preferably used. More preferably, it is a polyvinyl alcohol resin. As a solvent, a general organic solvent or an aqueous solvent which can dissolve the above resin component is usually used, and an undercoat layer is preferably formed from a coating liquid containing water as a solvent.

In order to increase the strength of the undercoat layer, a crosslinking agent may also be added to the coating liquid for forming an undercoat layer. Specific examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, metal salts, metal oxides, metal hydroxides, and organometallic compounds), and polymer-based crosslinking agents. When a polyvinyl alcohol-based resin is used as the resin component for forming the undercoat layer, a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelating agent crosslinking agent, or the like is preferably used. .

The thickness of the undercoat layer is preferably from about 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, 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 μm, it is disadvantageous for thinning of the polarizing plate.

The method of applying the coating liquid for forming an undercoat layer to the base film 30 can be the same as the coating liquid for forming a polyvinyl alcohol-based resin layer. The drying temperature of the coating layer composed of the coating liquid for forming an undercoat layer is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. In the case where the solvent contains water, the drying temperature is preferably 80 ° C or more.

(2) Extension step S20

Referring to Fig. 6, in this step, the laminated film 100 composed of the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched to obtain an extended polyvinyl alcohol-based resin on the stretched base film 30'. The step of extending the laminated film 200 of the stretched film 6' of the layer. The extension process is typically a one-axis extension.

The stretching ratio of the laminated film 100 can be appropriately selected depending on the desired polarization characteristics and the thickness L of the layered crystal. It is preferably 1.1 to 17 times, more preferably 1.5 to 8 times, with respect to the original length of the laminated film 100. When the stretching ratio exceeds 17 times, the film is likely to be broken at the time of stretching, and the thickness of the extended laminated film 200 becomes thinner than necessary, and the workability and workability in the subsequent step may be lowered.

The extension process is not limited to one-stage extension and can be performed in multiple stages. In this case, all of the multi-stage stretching treatment may be continuously performed before the dyeing step S30, or the stretching treatment after the second stage may be performed simultaneously with the dyeing treatment and/or the crosslinking treatment of the dyeing step S30. In the case where the stretching treatment is performed in multiple stages in this manner, it is preferable to carry out the stretching treatment so that all the stages of the stretching treatment are combined to have a stretching ratio of more than four times.

The stretching treatment may be a longitudinal extension extending in the longitudinal direction of the film (the conveying direction of the film), or a lateral extension or an oblique extension extending in the width direction of the film. As a longitudinal extension method, for example, a roller extending extension between rollers, a compression extension, and a chuck (or a clip) extension may be used. As a lateral extension method, for example, a tenter may be mentioned. Law and so on. The extension process can adopt the wetting extension method and the dry extension method. Any of the methods of stretching, but using the dry stretching method, is preferable in that the extension temperature can be selected from a wide range.

The elongation temperature is set to a temperature at which the polyvinyl alcohol-based resin layer 6 and the base film 30 all exhibit a degree of fluidity which is extensible, and is preferably a phase transition temperature (melting point or glass transition temperature) of the base film 30. The range of 30 ° C to +30 ° C is more preferably in the range of -30 ° C to +5 ° C, more preferably in the range of -25 ° C to +0 ° C. The base film 30 is composed of a plurality of resin layers, and the phase transition temperature means the highest phase transition temperature among the phase transition temperatures indicated by the plurality of resin layers.

When the stretching temperature is lower than -30 ° C of the phase transition temperature, it is difficult to achieve a high-magnification extension of more than 4 times, or the fluidity of the base film 30 is too low, and the elongation treatment tends to be difficult. When the stretching temperature exceeds +30 ° C of the phase transition temperature, the fluidity of the base film 30 is too high, and the elongation tends to be difficult. In the case where it is easier to achieve a high stretching ratio of more than 4 times, the stretching temperature is in the above range, and more preferably 120 ° C or more.

The heating method of the laminated film 100 for stretching treatment includes a zone heating method (for example, a method of heating in an extended region of a heating furnace in which hot air is adjusted to a predetermined temperature); a method of heating the roller itself in the case of using a roller to extend; heater heating A method (a method in which an infrared heater, a halogen lamp heater, a plate heater, or the like is provided on the upper and lower sides of the laminated film 100 by radiant heat) or the like. In the method of extending between the rolls, from the viewpoint of the uniformity of the stretching temperature, the area heating method is preferred.

In addition, the extension temperature refers to the ambient temperature in the region (for example, in the heating furnace) in the case of the zone heating method, and is heated by the heater. In the method, the heating in the furnace refers to the ambient temperature in the furnace. Moreover, in the case of the method of heating the roller itself, it means the surface temperature of the roller.

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

Moreover, after the extending process of the step S20 is extended, a heat fixing process step can be set. In the heat-fixing treatment, the edge portion of the extended laminated film 200 is held in a state of being held by a jig, and the heat treatment is performed at a crystallization temperature or higher. The crystallization of the stretched film 6' is promoted by the heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0 ° C to -80 ° C of the elongation temperature, and more preferably in the range of -0 ° C to -50 ° C of the elongation temperature.

(3) Dyeing step S30

Referring to Fig. 7, this step is a step of dyeing the stretched film 6' of the laminated film 200 with iodine so as to adsorb and align to form the polarizing film 5. Through this step, the polarizing film 5 is laminated on the single-sided or double-sided polarizing laminated film 300 of the base film 30'.

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

In order to improve the dyeing efficiency, it is preferable to add an iodide to the dyeing aqueous solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide in the aqueous dye solution is preferably from 0.01 to 20% by weight. Among the iodides, it is preferred to add potassium iodide. In the case of adding potassium iodide, the ratio of iodine to potassium iodide, in terms of a weight ratio, is preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80. The temperature of the aqueous dyeing solution is preferably in the range of 10 to 60 ° C, more preferably in the range of 20 to 40 ° C.

The dyeing step S30 may include a crosslinking treatment step performed after the dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) in which a crosslinking agent has been dissolved in a solvent. Examples of the crosslinking agent include a boron compound such as boric acid or 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, and an organic solvent compatible with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is desirably from 0.2 to 20% by weight, more desirably from 0.5 to 10% by weight.

The cross-linking solution may further comprise an iodide. By the addition of iodide, the in-plane polarization characteristics of the polarizing film 5 can be more uniform. Specific examples of the iodide are the same as described above. The concentration of the iodide in the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight. The temperature of the cross-linking solution is preferably from 1 to 90 °C.

Further, the crosslinking treatment can be carried out simultaneously with the dyeing treatment by blending a crosslinking agent in the aqueous dyeing solution. Further, two or more kinds of cross-linking solutions having different compositions may be used, and two or more immersed in the cross-linking solution may be used.

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

(4) First bonding step S40

With reference to Fig. 8, this step is applied to the polarizing film 5 of the polarizing laminate film 300, that is, the surface of the polarizing film 5 opposite to the side of the base film 30', and the protective film is bonded through the adhesive layer. The step of bonding the film 400. In the eighth embodiment, the first protective film 10 is bonded to each other via the first adhesive layer 15. However, when the polarizing plate 2 having the protective film on both sides is formed, it may be bonded via the second adhesive layer 25. The second protective film 20. The adhesive for forming the first adhesive layer 15 and the second adhesive layer 25 is as described above.

Further, the polarizing laminated film 300 has the polarizing film 5 on both surfaces of the base film 30', and is usually formed on the polarizing film 5 on both sides. Fit the protective film. In this case, the protective films may be the same type of protective film or different types of protective films.

In the case where the first protective film 10 is bonded by using an active energy ray-curable adhesive, an active energy ray-curable adhesive which is the first adhesive layer 15 is interposed between the protective film and the method of bonding the protective film. After the first protective film 10 is laminated on the polarizing film 5, an active energy ray such as ultraviolet rays, visible light, electron beams, and X-rays is irradiated to cure the adhesive. Among them, ultraviolet light is suitable, and as a light source in this case, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, or the like can be used.

When the protective film is bonded to the polarizing film 5, the bonding surface of the protective film and/or the polarizing film 5 is subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, and flame in order to improve the adhesion to the polarizing film 5. Surface treatment (easily followed by treatment) such as flame treatment, saponification treatment, etc., wherein plasma treatment, corona treatment or saponification treatment is preferred.

(5) Stripping step S50

This step is a step of peeling off the base film 30' from the bonded film 400. Through this step, a polarizing plate having a protective film on one side as in the second drawing was obtained. The polarizing laminated film 300 has a polarizing film 5 on both surfaces of the base film 30', and when the two polarizing films 5 are bonded to the protective film, the polarizing laminated film 300 is removed from the polarizing film 300 by the peeling step S50. Two polarizing plates with a protective film on one side are obtained.

The method of peeling off the base film 30' is not particularly limited. The peeling can be carried out in the same manner as the peeling step of a separator (release film) which is usually performed by a polarizing plate with an adhesive. The base film 30' may be directly peeled off immediately after the first bonding step S40, or may be wound into a roll once after the first bonding step S40, and peeled off while being rolled out in the subsequent steps. .

(6) Second bonding step S60

This step is performed on the polarizing film 5 of the polarizing plate having the protective film on one side, that is, the surface opposite to the protective film adhered in the first bonding step S40, and then the protective film is bonded thereto to obtain The step of attaching the polarizing plate 2 of the protective film to both sides of the configuration shown in Fig. 3 is shown. When the first protective film 10 is bonded to the first bonding step S40, the second protective film 20 is bonded in the first bonding step 20, and the second protective film 20 is bonded to the first bonding step S40. Then, the first protective film 10 is bonded in this step. The second protective film 20 is bonded to each other via the second adhesive layer 25, and can be carried out in the same manner as the bonding of the first protective film 10.

In the above, a method of forming a polarizing film from a polyvinyl alcohol-based resin layer coated on a substrate film and then producing a polarizing plate will be described in detail, but it is not limited to the above, and a polarizing film composed of a single (separate) film may be used. 5, the first protective film 10 or the first and second protective films 10 and 20 are bonded together to manufacture a polarizing plate.

The stretched film 6' composed of a single (separate) film and the polarizing film 5 can be produced, for example, by the following steps: a polyvinyl alcohol-based resin is produced by a conventional method such as a melt extrusion method or a solvent casting film method. a step of filming; a step of stretching a polyvinyl alcohol-based resin film to obtain a stretched film 6'; a step of dyeing the stretched film with iodine to adsorb it; and adsorbing iodine The step of treating the stretching film with an aqueous solution of boric acid; and washing with water after treatment with an aqueous solution of boric acid to obtain a polarizing film 5. One-axis extension can be performed before, during or after dyeing of iodine. In the case where the one-axis extension is carried out after dyeing, the one-axis extension can be carried out before boric acid treatment or boric acid treatment. Moreover, one-axis extension can be performed at these multiple stages.

In the case where the polarizing plates having the protective film on both sides are bonded to each of the first and second protective films 10 and 20, the protective films may be bonded to each other via the adhesive layer, or may be bonded at the same time.

(7) Adjustment of the thickness L of the layered crystal of the polyvinyl alcohol-based resin in the stretched film

The method of setting the thickness L of the layered crystal of the polyvinyl alcohol-based resin in the stretched film to the above-specified range is not particularly limited, and it is preferred to use a position where the layered growth control monomer unit has been adjusted as described above and A method of forming a film from a polyvinyl alcohol-based resin having a frequency. The degree of adjustment of the position and frequency of the layered growth control monomer unit of the polyvinyl alcohol-based resin can be confirmed by the average value of the number of continuous vinyl alcohol monomer units in the polyvinyl alcohol-based resin.

In addition, the thickness L of the layered crystal of the polyvinyl alcohol-based resin in the stretched film can be set as described above by the above-mentioned method, or by adjusting the stretching ratio and the heat history of the polyvinyl alcohol-based resin layer. In the range.

[Examples]

Hereinafter, examples and comparative examples will be shown, more specifically The invention is exemplified, but the invention is not limited to the examples.

<Example 1> (1) Undercoat layer forming step

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 3% by weight. Aqueous solution. In the obtained aqueous solution, a crosslinking agent ("SUMIREZ RESIN 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed at a ratio of 5 parts by weight based on 6 parts by weight of the polyvinyl alcohol powder to obtain a coating for forming an undercoat layer. Cloth liquid.

Then, an unstretched polypropylene (PP) film (melting point: 163 ° C) having a thickness of 90 μm was prepared as a substrate film, and after one side of the corona treatment, a small-diameter gravure coater was used on the corona-treated surface. The coating liquid for forming an undercoat layer was applied and dried at 80 ° C for 10 minutes to form an undercoat layer having a thickness of 0.2 μm.

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

The polyvinyl alcohol-based resin powder having an average number of consecutive units of 30 was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 7.5% by weight, and this was used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The surface of the undercoat layer of the base film having an undercoat layer produced in the above (1) was coated with the coating liquid for forming a polyvinyl alcohol-based resin layer using a die coater, and then hot air was blown at 70 ° C. Simultaneous drying is carried out to form a polyvinyl alcohol-based resin layer on the undercoat layer to obtain a substrate film/primer coating/ A laminated film composed of a polyvinyl alcohol-based resin layer. The thickness of the dried polyvinyl alcohol-based resin layer was 9.2 μm.

(3) Production of extended laminated film (extension step)

The laminated film produced in the above (2) was subjected to a floating longitudinal one-axis stretching device (air extension), and a free end-axis extension of 5.3 times was carried out at a maximum temperature of 150 ° C in the air extension to obtain a substrate film. An extended laminated film of a stretched film made of a polyvinyl alcohol-based resin is provided. The stretched film made of the polyvinyl alcohol-based resin after stretching had a thickness of 5.1 μm.

(4) Production of polarizing laminated film (dyeing step)

The extended laminated film produced in the above (3) was immersed in a dyeing aqueous solution containing 30% by weight of iodine and potassium iodide (containing 0.35 parts by weight (iodine concentration: 13.8 mM) and 10.0 parts by weight of potassium iodide per 100 parts by weight of water) The immersion time was appropriately adjusted so that the luminosity-corrected monomer transmittance Ty measured by the evaluation described later was 41.5%. After the dyeing treatment of the stretched film, the excess dyeing aqueous solution was washed with pure water at 10 °C. The dyeing time for the aqueous dye solution is shown in Table 1.

Then, it was immersed in a first crosslinking solution containing boric acid at 78 ° C (containing 10 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, and then immersed in a second crosslinking solution containing boric acid and potassium iodide at 70 ° C. (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 then immersed in pure water at 10 ° C for about 10 seconds to carry out crosslinking treatment. Then, immediately use a blower to remove the liquid attached to both sides. A polarizing laminated film including a polarizing film was obtained.

(5) Production of a polarizing plate with a protective film on one side (first bonding step, peeling step)

A protective film is bonded to the polarizing film of the polarizing laminated film produced in the above (4) via an adhesive layer made of an ultraviolet curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.). A transparent protective film made of triacetyl cellulose (TAC) ("KC-2UAW" manufactured by Konica Minolta Opto Co., Ltd.)]. Then, the adhesive layer is cured by irradiating ultraviolet rays with a high-pressure mercury lamp to obtain a bonded film composed of a layer structure of a protective film/adhesive layer/polarizing film/base film (first bonding step). Then, the base film was peeled off from the obtained bonded film, and a polarizing plate with a protective film on one side was obtained (peeling step).

<Examples 2 to 13, Comparative Examples 1 to 5>

In the examples 2 to 13, in the example 1, except that the polyvinyl alcohol-based resin powder having the average number of continuous units shown in Table 1 was used as the point of the polyvinyl alcohol-based resin powder used in the above (2), 3) The temperature at the time of extension is set to the temperature shown in Table 1, the magnification in the above (3) is set to the magnification shown in Table 1, Examples 10 to 13 and Comparative Examples 3 to 5 The same procedure as in Example 1 was carried out except that the first cross-linked aqueous solution of the above (4) was subjected to 3.0-fold or 1.1-fold extension of the free-end one-axis. When the stretching ratio in the first crosslinked aqueous solution shown in Table 1 is "1.0 times", it means that the stretching is not carried out in the first crosslinked aqueous solution.

[Calculation of Thickness L of Layered Crystal]

From the extended laminated film obtained in the above (3), the base film was peeled off, and the stretched film was taken out, and the film was conditioned for one day at 23 ° C and 55% RH, and then 5 mg was filled in an aluminum pan for measurement and sealed to prepare a sample for evaluation. . Use a sealed aluminum pan as a reference. For the sample for evaluation and the reference standard, a differential scanning calorimeter (product name: DSC6220, manufactured by Seiko Instruments Inc.) was used to measure the absorbed heat at a temperature of 10 ° C/min from 50 ° C to 250 ° C. . The temperature at the peak position of the crystal melting peak from 200 ° C to 250 ° C in the crystal is taken as the crystal melting peak temperature T (K), and the thickness L of the layered crystal is calculated from the formula (1). The results are shown in Table 1.

[Evaluation of staining]

According to the immersion time (dyeing time) of the dyeing aqueous solution (iodine concentration: 13.8 mM) required for the above (4), the case where the dyeing time is within 300 seconds is evaluated as "good", and the case where the dyeing time exceeds 300 seconds is evaluated as " bad". The results are shown in Table 1.

The reason why the criterion for the evaluation of the dyeability is 300 seconds is that the production line speed at which a certain level of productivity can be obtained is 10 m/min or more. In this case, in order to secure the dyeing residence time exceeding 300 seconds, the production line retention length is set. Must be set more than 50m, the productivity will deteriorate. When the cross-linking groove, the complementary color groove, and the like are provided after the dyeing, the strand retention length is further lengthened. When the dyeing time is, for example, 100 seconds, since the strand retention length can be made 20 m or less, it can be sufficiently carried out by a general dyeing apparatus.

Further, by increasing the iodine concentration of the dyeing aqueous solution, the residence time can be shortened. However, since high concentration of iodine causes corrosion of the equipment, it is difficult to continuously produce a dyeing aqueous solution having an iodine concentration of 20.0 mM or more for a long period of time. Further, when the iodine concentration of the dyeing aqueous solution becomes high, not only the corrosion due to the dyeing aqueous solution but also the iodine sublimated from the dyeing aqueous solution causes corrosion outside the dyeing tank, and therefore the iodine concentration of the dyeing aqueous solution is preferably 15.0 mM or less.

[Appearance evaluation]

In the dyeing step of the above (4), elution and fading due to dissolution of the polyvinyl alcohol-based resin in the dyeing tank were visually confirmed. None of the dissolution and fading were confirmed, and the appearance was good, and it was "good", and any of the cases in which dissolution or fading was observed was "poor". The results are shown in Table 1.

[Evaluation of puncture strength]

From the polarizing laminated film obtained in the above (4), the base film was peeled off, and the polarizing film was taken out to obtain a sample for evaluation. First, the thickness of the polarizing film of the sample for evaluation was measured using a contact type film thickness meter (trade name "DIGIMICRO MH-15M" manufactured by Nikon Co., Ltd.). Then, the load is loaded with a tip diameter of 1 mm The 0.5K needle KATO TECH (many) compression tester "KES-G5 needle penetration force measurement specification", at a temperature of 23 ± 3 ° C, at a puncture speed of 0.33 cm / sec The polarizing film was pierced under the measurement conditions, and the force applied to the needle when passing through the polarizing film was measured. The measurement was performed on 12 sheets of the evaluation sample, and the average value thereof was taken as the measured value of the sample. The piercing strength per unit thickness was calculated by dividing such a measured value by the thickness of the polarizing film. The results are shown in Table 1.

[Measurement of Ty and Py]

The surface of the polarizing plate having the protective film on one side of the protective film obtained in the above (5) is subjected to a corona treatment, and a (meth)acrylic resin-based adhesive (P-3132, manufactured by Lintec Co., Ltd.) is bonded. "). The obtained polarizing plate with an adhesive layer was bonded to the glass using the adhesive layer to obtain a sample for evaluation. For the polarizing plate for the sample for evaluation, an absorbance photometer ("V7100" manufactured by JASCO Corporation) equipped with an integrating sphere was used, and the obtained transmittance and polarization degree were obtained by a 2 degree field of view of JIS X 8701 (C The light source is subjected to visual sensitivity correction, and the visual sensitivity correction unit transmittance Ty and the visual sensitivity correction polarization Py are measured. At the time of measurement, a sample for evaluation was set so that the incident light was irradiated to the glass side. The results are shown in Table 1.

6'‧‧‧Stretch film

30'‧‧‧Extended base film

200‧‧‧Extended laminating film

Claims (11)

A stretched film for use in the production of a polarizing film, which is a stretched film composed of a polyvinyl alcohol-based resin containing a layered crystal; wherein a crystal melting peak measured by differential scanning calorimetry using the stretched film is used The thickness L (nm) of the layered crystal calculated by the following formula (1) at a temperature T (K) is 13.0 nm or more and 45.0 nm or less; L = 0.66 × {516 / (516 - T)} ( 1). The stretched film according to the first aspect of the invention, wherein the polyvinyl alcohol-based resin contains a monomer for controlling the thickness L (nm) of the layered crystal as a constituent monomer. The stretched film according to claim 1 or 2, which is obtained by extending a polyvinyl alcohol-based resin layer provided on a base film. A polarizing film obtained by dyeing a stretched film according to claim 1 or 2 using a dichroic dye. A polarizing film obtained by dyeing a stretch film described in claim 3 of the patent application using a dichroic dye. The polarizing film according to claim 4, wherein the puncture strength per unit thickness is 6.0 g/μm or more. The polarizing film according to claim 5, wherein the puncture strength per unit thickness is 6.0 g/μm or more. A polarizing plate comprising: the polarizing film according to item 4 of the patent application; and a protective film laminated on a surface of at least one side of the polarizing film. A polarizing plate comprising: the polarizing film according to claim 5; and a protective film laminated on at least one side of the polarizing film. A polarizing plate comprising: the polarizing film according to claim 6; and a protective film laminated on at least one side of the polarizing film. A polarizing plate comprising: the polarizing film according to claim 7; and a protective film laminated on a surface of at least one side of the polarizing film.