TWI604232B - Polarizing plate - Google Patents

Description

Polarizer

The present invention relates to a polarizing film and a polarizing plate comprising the polarizing film.

The polarizing plate is widely used in an image display device such as a liquid crystal display device. In the case of a polarizing plate, a protective film is bonded to one surface or both surfaces of a polarizing film, and the polarizing film is formed by adsorbing a dichroic dye such as iodine to a polyvinyl alcohol resin film. In recent years, with the application of image display devices in portable devices, thin televisions, and the like, there has been an increasing demand for thinning of polarizing plates and polarizing films.

Japanese Laid-Open Patent Publication No. 2013-182162 discloses a method of producing a polarizing plate having a thickness of a polarizing film (polarized sub-layer) of 10 μm or less.

Prior technical literature

Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2013-182162

In the case of a polarizing film, the smaller the thickness, the greater the influence of moisture intruding from the surface, and when exposed to a hot and humid environment, when exposed or immersed in warm water, the polarizing property is likely to be lowered, and the color is likely to be generated. The tendency of partial characteristics to deteriorate. Further, in the present specification, the resistance to deterioration of characteristics caused by being placed in a hot and humid environment is referred to as "moisture resistance", and the resistance to deterioration due to exposure or immersion in warm water is referred to as resistance. "Temperature resistant to water", and these are collectively referred to as "water resistance."

In the invention described in Japanese Laid-Open Patent Publication No. 2013-182162, the moisture permeability of the polarizing plate is improved by using a lower moisture permeability of the protective film bonded to the polarizing film. However, when this method is used, the material and thickness of the protective film to be used are limited.

The object of the present invention is to improve the water resistance of the polarizing film itself. Further, another object of the present invention is to provide a polarizing plate which is excellent in water resistance.

The present invention provides a polarizing film and a polarizing plate shown below.

[1] A polarizing film which has a ratio W _I /Ty of the iodine element content rate W _I [% by weight] to the photometric correction monomer transmittance Ty [%] of 0.145 or more.

[2] The polarizing film according to [1], wherein the W _I /Ty is 0.5 or less.

[3] The polarizing film according to [1] or [2] wherein the thickness is 10 μm or less.

[4] The polarizing film according to any one of [1] to [3] wherein a polyvinyl alcohol-based resin is contained.

[5] The polarizing film according to any one of [1] to [4] wherein the aforementioned Ty is 40 to 47%.

[6] A polarizing film according to any one of [1] to [5], wherein the polarizing film is laminated on at least one surface of the polarizing film.

According to the present invention, a polarizing film and a polarizing plate having excellent water resistance can be provided.

1, 2‧‧‧ polarizing plate

5‧‧‧ polarizing film

6, 6'‧‧‧ polyvinyl alcohol resin layer

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

30, 30'‧‧‧ base film

100‧‧‧ laminated film

200‧‧‧Extension film

300‧‧‧Polarized laminated film

400‧‧‧Finished film

Fig. 1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate of the present invention.

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

Fig. 3 is a flow chart showing a preferred embodiment of the method for producing a polarizing plate of the present invention.

Fig. 4 is a schematic cross-sectional view showing an example of a layer structure of a laminated film obtained in the resin layer forming step.

Fig. 5 is a schematic cross-sectional view showing an example of a layer structure of a stretched film obtained in the stretching step.

Figure 6 shows the layer of the polarizing laminate film obtained in the dyeing step. A schematic cross-sectional view of an example of a structure.

Fig. 7 is a schematic cross-sectional view showing an example of a layer structure of a bonded film obtained in the first bonding step.

<polarized film>

The polarizing film of the present invention is characterized in that the ratio W _I /Ty of the iodine element content rate W _I to the photometric correction monomer transmittance Ty is 0.145 or more. The polarizing film of the present invention having a W _I /Ty of 0.145 or more is excellent in water resistance (moisture resistance and temperature resistance), and is not easily polarized even when exposed to a hot and humid environment, exposed or immersed in warm water. Characteristics such as reduced characteristics and color shift are degraded. When the polarizing film of the present invention is used, since it has excellent water resistance, it is not limited by the material and thickness of the protective film which is bonded to the film which is low in moisture permeability, and can provide excellent water resistance. Polarized plate.

The following is a description of the technical significance of setting W _I /Ty to 0.145 or more. A polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a polyvinyl alcohol-based resin and a iodine-based complex (hereinafter referred to as "PVA-iodine complex") are conventionally known by The complex exhibits absorption of dichroism and exhibits polarizing properties. Although iodine does not form PVA-iodine complex in the polarizing film, the iodine does not have too much absorption in the visible region, so it is not helpful for the polarizing performance. In particular, iodine, which is present in the state of iodide ion (I ^- ), does not absorb in the visible region, so it does not contribute to the polarizing performance of the polarizing film itself, and does not contribute to the appearance (hue) of the polarizing film. .

When the polarizing performance of the polarizing film is described in more detail, the polarizing performance is generally referred to as "luminosity correction unit transmittance Ty" and "luminosity correction degree of polarization Py". Parameters to evaluate. These parameters are the transmittance and the degree of polarization of the visible region (wavelength 380 to 780 nm) which are corrected so that the weighting value around 550 nm, which has the highest sensitivity to human macroscopicity, is maximized. Because the human eye can't visually recognize light with a wavelength of less than 380 nm, it is not considered in the Ty and Py systems. Thus, for example, iodide ions (I ^- ) having an absorption band in a wavelength region of about 200 to 230 nm do not themselves affect the Ty and Py of the polarizing film, that is, the polarization performance.

For the reasons described above, the iodine, especially the iodide ion (I ^- ), in which the PVA-iodine complex is not formed is not discussed when the polarizing performance of the polarizing film and the polarizing plate using the same is previously performed. . However, in spite of such prior art knowledge, the inventors of the present invention have intensively studied and found that in order to improve the water resistance of the polarizing film and the polarizing plate using the polarizing film, not only the PVA-iodine complex, but also in Ty and The iodide ion (I ^- ) which is not present in Py is important, and more specifically, the following matters have been found.

a) The iodide ion in the polarizing film greatly affects the formation of the PVA-iodine complex. As a rule of thumb, in the polarizing film, the equilibrium of the following formula (1) is established: I ^- + PVA- I ₅ complex n PVA-I ₃ complex + (2-n) I ₃ ^- (1).

b) When the polarizing film and the polarizing plate are placed in a hot and humid environment, exposed or immersed in warm water, when the iodide ion (I ^- ) is easily detached from the polarizing film, due to the detachment of the iodide ion (I ^- ), The equilibrium of the above formula (1) tends to the left side and the PVA-I ₃ complex is easily reduced. Therefore, since the PVA-I ₃ complex formed in the absorption band on the short-wavelength (blue) side becomes small, the polarizing film and the polarizing plate become less likely to absorb blue light and cause color shift (blue color shift). Further, when the blue color shift occurs due to the decrease in the PVA-I ₃ complex, the degree of polarization also decreases with this. Further, when the equilibrium of the above formula (1) is on the left side, the PVA-I ₅ complex formed in the absorption band on the long wavelength (red) side tends to increase.

c) In the polarizing film, the balance of the above formula (1) tends to be on the right side, because the "content of iodide ion" with respect to the "content of PVA-iodine complex" is excessive. Therefore, even if the iodine ion (I ^- ) is slightly desorbed, the equilibrium of the above formula (1) does not easily and simply tend to the left side, and the content of the PVA-I ₃ complex can be stabilized by a sufficient amount. Thereby, the blue color shift and the degree of polarization can be suppressed from being lowered.

The derivation of the iodine element content rate W _I with respect to the illuminance-corrected monomer transmittance Ty, that is, the parameter of W _I /Ty, is based on the results of the above studies. In other words, first, the "content of PVA-iodine complex" described in the above c) can correspond to "Ty". This is because the content of the PVA-iodine complex of the absorption band forming the visible region is proportional to Ty. In addition, in order to make the "content of iodide ion" as described in the above c) excessive with respect to the "content of PVA-iodine complex", the "amount of total iodine atom" contained in the polarizing film is relatively "The content of the PVA-iodine complex" can be increased, so that the "content of the iodide ion" can correspond to the "amount of total iodine atom". Here, the "total iodine atomic amount" is synonymous with the above-mentioned "iodine element content rate W _I ". Therefore, the "content of iodide ion" can be replaced with "the content of iodine element W _I " with respect to "the content of PVA-iodine complex", that is, W _I /Ty.

As described above, in order to improve the water resistance of the polarizing film and the polarizing plate, it is not necessary to increase the "iodine element content rate W _I " itself, but to increase W _I /Ty. As a result of the study, it was found that in order to improve the water resistance of the polarizing film and the polarizing plate, it is necessary to increase W _I /Ty to 0.145 or more. When it is less than 0.145, the improvement of water resistance cannot be confirmed. From the viewpoint of improving water resistance, W _I /Ty is preferably 0.150 or more.

On the other hand, the upper limit of W _I /Ty is not particularly limited. When the value is too large, the iodide ion (I ^- ) content becomes too large as a result, and the PVA-I ₃ complex is The balance of the amount of the PVA-I ₅ complex is biased off (i.e., the equilibrium of the above formula (1) is too much toward the right side, resulting in the formation of the PVA-I ₅ complex of the absorption band on the long wavelength (red) side. Insufficient), and the initial hue of the polarizing film and the polarizing plate cannot be maintained in a neutral color. Therefore, W _I /Ty is preferably 0.5 or less, and more preferably 0.4 or less.

The iodine element content rate W _I of the polarizing film is defined as the total weight of the iodine element contained in the polarizing film per weight unit, and specifically, can be obtained according to the following formula (2): W _I [% by weight] = {total weight of iodine element [mg] / weight of polarizing film [mg]} × 100. The total weight of the iodine element contained in the polarizing film can be determined by the combustion-ion chromatography method of JIS K 0127:2013. This method is a method in which a polarizing film sample is burned in a combustion gas containing oxygen, and the generated gas is collected in an absorption liquid, and then quantified by ion chromatography. The fuel pretreatment of the polarizing film (measurement sample) is in accordance with JIS specification 6.3.5. In addition, in the "weight of the polarizing film" of the above formula, when the iodine content W _I is 1% or more, it is 10 to 20 mg, and when it is less than 1%, it is 100 mg or more.

In order to make W _I /Ty in the range of 0.145 to 0.5, the iodine element content rate W _I of the polarizing film is preferably from 5 to 15, more preferably from 6 to 10.

Further, the absorbance at a wavelength of 217 nm of the polarizing film to be described later is preferably 2.5 or more, more preferably 3.0 or more, and the upper limit is preferably 4.2 or less, more preferably 4.0 or less.

The photometric correction monomer transmittance Ty of the polarizing film may be a value generally required in an image display device such as a liquid crystal display device to which the polarizing film and the polarizing plate including the polarizing film are applied, specifically, 40 It is better in the range of 47%. More preferably, Ty is in the range of 41 to 45%, and at this time, 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. When Ty is too low, the brightness of the image display device is lowered to lower the display quality, or the input power needs to be increased in order to sufficiently increase the brightness.

Moreover, as another means for improving the water resistance of the polarizing film, for example, it is conceivable to increase the amount of adsorption of iodine to reduce Ty. But the method As described above, the brightness is lowered. On the other hand, according to the present invention, a sufficiently high Ty can be maintained while the water resistance of the polarizing film is improved.

The luminosity correction polarization Py of the polarizing film is preferably 99.9% or more, more preferably 99.95% or more. From the viewpoint of maintaining the display quality of the image display device even after the water resistance test (humidity resistance test or temperature resistance water resistance test), the Py after the test is preferably 98.0% or more.

Ty and Py of the polarizing film can be measured as a measurement sample when the polarizing film is present as a monomer. On the other hand, when the polarizing plate having the protective film is bonded to the polarizing film, the protective film and the adhesive layer are removed from the polarizing plate, and the polarizing film contained in the polarizing plate is separated and used as The sample was measured, or the polarizing plate itself was used as a measurement sample, and Ty and Py were measured, and the measured Ty and Py were set as Ty and Py of the polarizing film. The Ty and Py measured by using the polarizing plate as a measurement sample are substantially the same as Ty and Py measured by using the polarized film after separation as a measurement sample.

The polarizing film of the present invention is obtained by adsorbing iodine as a dichroic dye, preferably containing a polyvinyl alcohol-based resin, and more specifically, iodine-adsorbing the polyethylene in a uniaxially oriented direction. A film made of an alcohol resin (polyvinyl alcohol resin film).

The thickness of the polarizing film is, for example, 30 μm or less, and may be 20 μm or less. However, 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 smaller the thickness, the easier the water resistance is, but according to the invention, it is possible to provide a water resistance even if the thickness is 10 μm or less. Good polarizing film.

As the polyvinyl alcohol-based resin constituting the polarizing film, a polyvinyl acetate-based resin can be used. As the polyvinyl acetate-based resin, a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate can be exemplified in addition to the polyvinyl acetate of the homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

A film made of the above polyvinyl alcohol-based resin is used as a polarizing film. The method of forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. However, it is easy to obtain a polarizing film having a small thickness, and in the step of being a polarizing film of a film, it is excellent in rationality. A method of forming a film by coating a solution of a polyvinyl alcohol-based resin on a substrate film is preferred.

The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, and more preferably in the range of 94.0 to 99.0 mol%. When the degree of saponification is less than 80.0 mol%, the water resistance of the obtained polarizing film is liable to lower. When a polyvinyl alcohol-based resin having a degree of saponification of more than 99.5 mol% is used, the dyeing speed is slow, the productivity is lowered, and a polarizing film having sufficient polarizing performance cannot be obtained.

The degree of saponification is a ratio of the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification step. The expression of the ear %) can be defined by the following formula: degree of saponification (% by mole) = 100 × (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups). The degree of saponification can be determined in accordance with JIS K 6726 (1994). The higher the degree of saponification, the higher the ratio of the hydroxyl group, and thus the lower the ratio of the acetate group which inhibits crystallization.

The polyvinyl alcohol-based resin may also be a part of the modified modified polyvinyl alcohol. For example, the polyvinyl alcohol-based resin may be an olefin such as ethylene or propylene; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid; an alkyl ester of an unsaturated carboxylic acid or a (meth) acrylamide. Founder. The modified ratio is preferably less than 30 mol%, more preferably less than 10%. When the modification is more than 30 mol%, the dichroic dye is less likely to be adsorbed, and the polarizing film 5 having sufficient polarizing performance is not easily obtained. In the present specification, the term "(meth)acryloyl) means at least one selected from the group consisting of an acryloyl group and a methacryl group. The same applies to "(meth)acrylonitrile".

The average degree of polymerization of the polyvinyl alcohol-based resin 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).

<Polarizing plate>

(1) Layer structure of polarizing plate

Fig. 1 is a schematic cross-sectional view showing an example of a layer structure of a polarizing plate of the present invention. The polarizing plate 1 as shown in Fig. 1 is a partial of the present invention The light plate may be a polarizing plate including a polarizing film 5 and a protective film on one side of the first protective film 10 laminated on one surface of the polarizing film 5. 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 further bonded to the other surface of the polarizing film 5. Specifically, the polarizing plate 2 shown in Fig. 2 is provided with a polarizing film 5 and laminated on the polarizing film 5. The first protective film 10 on one side and the polarizing plate on the both surfaces of the second protective film 20 laminated on the other surface of the polarizing film 5 with a protective film. 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 into an image display device such as a liquid crystal display device, it may be a polarizing plate disposed on the visual (front) side of the image display element such as a liquid crystal cell, or may be disposed on the image display device. A polarizing plate on the back side (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. The iodine element content rate W _I of the polarizing film 5 included in the polarizing plate can be measured for the polarized film 5 after separation by removing the protective film and the adhesive layer from the polarizing plate.

(3) First protective film

The first protective film 10 may be a film containing a translucent (preferably optically transparent) thermoplastic resin such as a chain. a polyolefin resin such as a polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin); a cellulose such as cellulose triacetate or cellulose diacetate; An ester resin; a polyester resin; a polycarbonate resin; a (meth)acrylic resin; a polystyrene resin; or a mixture or a copolymer thereof. In order to further improve the water resistance of the polarizing plate, it is preferable to use a protective film such as a polyolefin resin, a polyester resin, a (meth)acrylic resin, or a polystyrene resin as the first protective film 10. A protective film with a low moisture permeability.

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 retardation film which imparts an arbitrary retardation value by stretching a film containing the thermoplastic resin (uniaxial stretching or biaxial stretching or the like) or forming a liquid crystal layer on the film may be used.

In addition to the homopolymer of a chain olefin of a polyethylene resin or a polypropylene resin, a copolymer containing two or more kinds of chain olefins is mentioned as a chain polyolefin resin.

The cyclic polyolefin resin is a general term for a resin polymerized by using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and copolymerization of a cyclic olefin with a chain olefin such as ethylene or propylene. (representatively, a random copolymer); and a graft polymer obtained by modifying the unsaturated carboxylic acid and a derivative thereof; and the hydride or the like. Among them, a norbornene-based resin which uses a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is particularly 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, it is also possible to use such a copolymer and a part of a hydroxyl group which is modified by another substituent. Among these, cellulose triacetate (cellulose triacetate: TAC) is particularly preferred.

The polyester resin is a resin other than the cellulose ester resin having an ester bond, and usually contains a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a dicarboxylic acid or a derivative thereof can be used, and examples thereof include p-citric acid, isononanoic acid, dimethyl p-nonanoic acid ester, and dimethyl naphthalene dicarboxylate. As the polyhydric alcohol, a diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polypropylene terephthalate. Polypropylene naphthalate, poly(p-hexane cyclohexane), poly(naphthalene dicarboxylate) dimethyl dimethyl ester.

The polycarbonate resin is a polymer obtained by bonding a monomer unit via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate, a copolymerized polycarbonate or the like modified with a polymer skeleton.

The (meth)acrylic resin is a resin having a compound having a (meth)acryl fluorenyl group as a main constituent monomer. 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- (meth) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-(meth)acrylic acid-lowering-based copolymer, etc.). It is preferred to use a polymer having a poly(meth)acrylic acid C _1-6 alkyl ester as a main component such as poly(methyl methacrylate), and it is preferred to use methyl methacrylate as a main component (50 to 100% by weight, more preferably 70 to 100% by weight, of a methyl methacrylate-based 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 opposite to the polarizing film 5 of the first protective film 10. Further, the first protective film 10 may contain one or more additives such as a smoothing agent, a plasticizer, a dispersing agent, 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 the reduction in 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 handleability.

(4) The first adhesive layer

The first adhesive layer 15 is a layer for subsequently fixing the first protective film 10 to one surface of the polarizing film 5. The adhesive forming the first adhesive layer 15 may be contained by irradiation such as ultraviolet rays, visible light, electron rays, and X-rays. An active energy ray-curable adhesive for a curable compound which is cured by active energy rays; and a water-based adhesive obtained by dissolving or dispersing an adhesive component such as a polyvinyl alcohol-based resin in water. Among them, in particular, from the viewpoint of improving the water resistance of the polarizing plate, it is preferred to use an active energy ray-curable adhesive. A preferred example of the active energy ray-curable adhesive is an ultraviolet curable adhesive.

Since the active energy ray-curable adhesive forming the first adhesive layer 15 exhibits good adhesion, the active energy of the cationically polymerizable curable compound and/or the radically polymerizable curable compound can be suitably used. A radiation curable adhesive composition. The active energy ray-curable adhesive may further contain a cationic polymerization initiator and/or a radical polymerization initiator for causing the curable compound to start a curing reaction.

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 (one in the molecule). Or a compound of two or more oxetane rings), or a combination thereof. Examples of the radically polymerizable curable compound include a (meth)acrylic compound (having one or two or more (meth) acryloyl groups or (meth) acryloyloxy groups in the molecule. The compound), another vinyl compound having a radical polymerizable double bond, or a combination thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may also be used in combination.

Active energy ray hardening adhesive, depending on the desired system There are cationic polymerization accelerators, ion trapping agents, antioxidants, chain transfer agents, adhesion agents, thermoplastic resins, fillers, flow regulators, plasticizers, defoamers, antistatic agents, leveling agents, solvents And other additives.

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

(5) 2nd protective film

The second protective film 20 included in the polarizing plate 2 having the protective film on both sides shown in FIG. 2 is the same as the first protective film 10, and may be a film containing the thermoplastic resin exemplified above. A protective film having an optical function such as a retardation film or a brightness enhancement film. The thickness of the surface treatment layer and the film which the second protective film 20 can have can be referred to as described in the first protective film 10. The first protective film 10 and the second protective film 20 may be protective films containing resins of the same kind, or may be protective films containing different kinds of resins. In order to further improve the water resistance of the polarizing plate, a protective film having a low moisture permeability including a protective film such as a polyolefin resin, a polyester resin, a (meth)acrylic resin, or a polystyrene resin is selected. It is also preferable as the second protective film 20.

(6) 2nd adhesive layer

The second adhesive layer 25 is a layer for subsequently fixing the second protective film 20 to the other surface of the polarizing film 5. For the details of the second adhesive layer 25, the description of the first adhesive layer 15 described above can be cited. The second adhesive layer 25 is made of active energy from the viewpoint of improving the water resistance of the polarizing plate. A ray-curable adhesive is preferably formed. 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) Adhesive layer

The adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell used in a liquid crystal display device) can be laminated on the polarizing film 5 of the polarizing plate 1 of the single-sided protective film shown in FIG. The first protective film 10 or the second protective film 20 of the polarizing plate 2 having the protective film on both sides shown in FIG. 2 is used. The adhesive which forms the adhesive layer usually contains an adhesive composition which is a (meth)acrylic resin, a styrene resin, an anthrone-based resin or the like as a matrix polymer, and is added thereto. A crosslinking agent of an isocyanate compound, an epoxy compound, or an aziridine compound. It is also possible to further contain fine particles and become an adhesive layer which exhibits light scattering properties. 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 contain other optical layers laminated on the first and/or second protective films 10, 20 and the polarizing film 5. Examples of the other optical layer include a polarized polarizing film that transmits a certain polarized light and reflects a property opposite to the polarized light display; a film with an anti-glare function having a concave-convex shape on the surface; and an anti-reflection function with a surface a film; a reflective film having a reflective function on the surface; a transflective function having both a reflective function and a transmissive function Film; viewing angle compensation film, etc.

<Method for Producing Polarizing Film and Polarizing Plate>

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

When the polarizing plate 2 having the protective film on both sides as shown in Fig. 2 is produced, after the peeling step S50, the film further includes: (6) a second bonding step S60, which is applied to a polarizing plate having a protective film on one side thereof. The polarizing film is bonded to the protective film.

Hereinafter, the steps will be described with reference to FIGS. 4 to 7. Further, in the resin layer forming step S10, it may be attached to the two base film layers. The polyvinyl alcohol-based resin layer is formed on the surface, but the following mainly describes the case where it is formed on one side.

(1) Resin layer forming step S10

Referring to Fig. 4, 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 of the polarizing film 5 through the stretching step S20 and 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 or both surfaces of the base film 30 and drying the coating layer. In the case where the polarizing film 5 of the film is easily obtained, a method of forming a polyvinyl alcohol-based resin layer by such coating is advantageous.

The base film 30 may be composed of a thermoplastic resin, and particularly preferably a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, and elongation. Specific examples of such a thermoplastic resin include, for example, a polyolefin resin such as a chain polyolefin resin or a cyclic polyolefin resin (northene based resin); a polyester resin; (methyl) Acrylic resin; cellulose ester resin such as cellulose triacetate or cellulose diacetate; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; polyaryl ester resin; Polystyrene resin; polyether oxime resin; polyfluorene resin; polyamine resin; polyimine resin; and mixtures and copolymers thereof.

The base film 30 may be a single layer structure comprising one or more resin layers of one or more thermoplastic resins, or may be one or more thermoplastic resins containing a plurality of layers. Resin layer The resulting multi-layer structure. 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 substrate film 30 may contain an additive. Specific examples of the additive include: an ultraviolet absorber, an antioxidant, a smoothing agent, a plasticizer, a mold release agent, a color preventive agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a color former.

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

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 also 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 suitably selected by the following methods: wire bar coating method; roll coating method such as reverse coating, gravure coating; die coating method; Coating method; lip coating method; spin coating method; screen coating method; fountain coating method; dipping method;

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) can be 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 higher.

The polyvinyl alcohol-based resin layer 6 may be only one of the substrate films 30 The surface is formed and can be formed on both sides. When the both surfaces are formed, it is possible to suppress the film curl which may occur when the polarizing laminated film 300 (see FIG. 6) is manufactured, and to obtain two polarizing plates from one polarizing laminated film 300, so that the polarizing plate is produced. It is also advantageous in terms of efficiency.

The thickness of the polyvinyl alcohol-based resin layer 6 of the laminated film 100 is preferably 3 to 30 μm, preferably 5 to 20 μm. When the polyvinyl alcohol-based resin layer 6 having the thickness in the range is formed, the dyeing property of iodine is excellent, the polarizing performance is excellent, and the film is sufficiently thin (for example, thickness) through the stretching step S20 and the dyeing step S30 which will be described later. The polarizing film 5 of 10 μm or less.

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 on the side of the base film 30 where the polyvinyl alcohol-based resin layer 6 is to be formed. The surface is subjected to corona treatment, plasma treatment, flame treatment, and the like. Further, for the same reason, the polyvinyl alcohol-based resin layer 6 can be formed on the base film 30 via a primer layer or the like.

The primer layer can be formed by applying a coating liquid for forming a primer layer on the surface of the base film 30 and then drying it. The coating liquid contains a component which exerts a certain degree of strong adhesion to both of the base film 30 and the polyvinyl alcohol-based resin layer 6, and usually contains a resin component and a solvent which impart such adhesion. As the resin component, a thermoplastic resin which is excellent in transparency, heat stability, and elongation is preferably used, and examples thereof include a (meth)acrylic resin and a polyvinyl alcohol resin. Among them, a polyvinyl alcohol-based resin which imparts a good adhesion is particularly preferably used. A polyvinyl alcohol resin is preferred. Make As the solvent, a general organic solvent and an aqueous solvent which can dissolve the above resin component can be usually used, but it is preferred to form a primer layer with a coating liquid containing water as a solvent.

In order to increase the strength of the primer layer, a crosslinking agent may be added to the coating liquid for forming a primer layer. Specific examples of the crosslinking agent include an epoxy-based, isocyanate-based, dialdehyde-based, metal-based (for example, a metal salt, a metal oxide, a metal hydroxide, or an organometallic compound), and a polymer-based crosslinking agent. When a polyvinyl alcohol-based resin is used as the resin component for forming the primer layer, a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, a metal chelate compound crosslinking agent, or the like can be suitably used. .

The thickness of the primer 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 when it is thicker than 1 μm, it is disadvantageous for thinning of the polarizing plate.

The method of applying the coating liquid for forming a primer 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 formed from the coating liquid for forming a primer layer 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 higher.

(2) Extension step S20

Referring to Fig. 5, in this step, the laminated film 100 including the base film 30 and the polyvinyl alcohol-based resin layer 6 is stretched to obtain an extended base film 30' and a polyvinyl alcohol-based resin layer 6'. The step of stretching the film 200. The extension process is typically a uniaxial extension.

The stretching ratio of the laminated film 100 is appropriately selected depending on the desired polarizing characteristics, and is preferably more than 5 times and 17 times or less with respect to the original length of the laminated film 100, and more preferably more than 5 times and 8 times or less. When the stretching ratio is 5 or less, the polyvinyl alcohol-based resin layer 6' is not sufficiently oriented, so that the degree of polarization of the polarizing film 5 may not be sufficiently increased. On the other hand, when the stretching ratio exceeds 17 times, the film is likely to be broken at the time of stretching, and the stretched film 200 is thinned to a thickness larger than necessary, and the workability and handleability in the subsequent step are lowered.

The extension processing is not limited to one-stage extension, and may be performed in multiple stages. At this time, all of the multi-stage stretching treatment may be continuously performed before the dyeing step S30, or the stretching treatment after the second stage or the dyeing treatment and/or the crosslinking treatment of the dyeing step S30 may be simultaneously performed. When the stretching treatment is carried out in such a plurality of stages, it is preferable to carry out the stretching treatment so that the total length of all the stages of the elongation processing is greater than 5 times.

The stretching treatment may be a lateral extension extending in the film length direction (film conveyance direction), or a lateral extension or oblique extension extending in the film width direction. Examples of the longitudinal stretching method include stretching between rolls by a roll, compression and extension, extension using a fixture (clamp), and the like, and a tenter method or the like is exemplified as a lateral stretching method. The stretching treatment may be any of a wet stretching method and a dry stretching method, but it is preferable to use a dry stretching method insofar as the stretching temperature can be selected from a wide range.

Extension temperature, which can be set to the polyvinyl alcohol resin layer 6 and the temperature at which the base film 30 as a whole exhibits a degree of fluidity which is extensible, preferably in the range of -30 ° C to +30 ° C from the phase transition temperature (melting point or glass transition temperature) of the base film 30, Preferably, it is in the range of from -30 ° C to +5 ° C, and more preferably in the range of from -25 ° C to +0 ° C. When the base film 30 includes a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the resin layers of the plurality of 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 5 times, or the fluidity of the base film 30 is too low, which tends to make the stretching process difficult. When the elongation temperature exceeds +30 ° C of the phase transition temperature, the fluidity of the base film 30 tends to be too large and the elongation tends to be difficult. Since it is easier to achieve a high stretching ratio of more than 5 times, the stretching temperature is within the above range, and more preferably 120 ° C or more.

As a heating method of the laminated film 100 in the extension processing, there is a zone heating method (for example, a method of heating in an extension zone of a heating furnace adjusted to a predetermined temperature by blowing hot air); when the roller is used for stretching, the roller is used A method of heating by itself; a heater heating method (a method of providing an infrared heater, a halogen heater, a plate heater, or the like on the upper and lower sides of the laminated film 100, and heating by radiant heat). From the viewpoint of the uniformity of the elongation temperature, the inter-roll stretching method is preferably a zone heating method.

Further, the extension temperature means the gas ambient temperature in the region (for example, in the heating furnace) in the district heating method, and the gas in the furnace when the heater heating method is used. Ambient temperature. Moreover, in the method of heating the roller itself, it means the surface temperature of the roller.

A preheating step of preheating the laminated film 100 may also 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 from the extending temperature, and more preferably in the range of -40 ° C to -10 ° C from the extending temperature.

Moreover, after the extending process of the extending step S20, a heat fixing process step may also be provided. The heat-fixing treatment maintains the tension state while holding the end portion of the stretched film 200 using the jig, and performs heat treatment at a temperature higher than the crystallization temperature. By the heat setting treatment, crystallization of the polyvinyl alcohol-based resin layer 6' can be promoted. 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. 6, this step is a step of forming the polarizing film 5 by dyeing the polyvinyl alcohol-based resin layer 6' of the stretched film 200 with iodine and adsorbing it. Through this step, the polarizing laminated film 300 in which the polarizing film 5 is laminated on one surface or both surfaces of the base film 30' can be obtained.

The dyeing step can be carried out by immersing the stretched film 200 as a whole in an iodine-containing solution (dyeing solution). As the dyeing solution, a solution in which iodine is dissolved in a solvent can be used. As the solvent, water is usually used, and an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing solution is preferably from 0.01 to 10% by weight, preferably from 0.02 to 7% by weight.

Since the dyeing efficiency can be improved, it is preferred to further add iodide to the dyeing 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. Wait. The concentration of the iodide in the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. 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 solution is preferably from 10 to 60 ° C, more preferably from 20 to 40 ° C.

Further, although the dyeing step S30 may be performed before the extending step S20, the steps may be simultaneously performed, but it is preferable to apply the laminated film 100 in such a manner that the iodine adsorbed on the polyvinyl alcohol-based resin layer can be well oriented. After at least some extent of the stretching process, a dyeing step S30 is performed.

The dyeing step S30 may include a crosslinking treatment step carried out by successive dyeing treatment. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) in which a crosslinking agent is dissolved in a solvent. Examples of the crosslinking agent include a boron compound such as boric acid and borax; glyoxal, glutaraldehyde, and the like. 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 compatible with water may be further contained. The concentration of the crosslinking agent in the crosslinking solution is preferably from 0.2 to 20% by weight, preferably from 0.5 to 10% by weight.

The crosslinking solution may further contain an iodide. By adding an iodide, the polarization in the plane of the polarizing film 5 can be further uniformized. 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 crosslinking solution is preferably from 1 to 90 °C.

Further, the crosslinking treatment can also be carried out simultaneously with the dyeing treatment by formulating a crosslinking agent in the dyeing solution. Further, two or more kinds of crosslinking solutions having different compositions may be used, and two or more times of immersion in the crosslinking solution may be performed.

After the dyeing step S30, it is preferable to perform the washing step and the drying step before the first bonding step S40 to be described later. The washing step typically 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 using an iodide solution. As the drying step performed after the washing step, any appropriate method such as natural drying, air drying, and heat drying can be employed. For example, when heat-dried, the drying temperature is usually 20 to 95 °C.

(4) First bonding step S40

Referring to Fig. 7, in this step, the protective film is bonded to the polarizing film 5 of the polarizing laminated film 300 via the adhesive layer, that is, bonded to the opposite side of the polarizing film 5 from the side of the base film 30'. In this way, the step of bonding the film 400 is obtained. FIG. 7 shows an example in which the first protective film 10 is bonded via the first adhesive layer 15. When the polarizing plate 2 having the protective film on both sides is produced, the second protective layer 25 can be bonded to the second protective layer 25 Membrane 20. The adhesive agent for forming the first adhesive layer 15 and the second adhesive layer 25 is as described above.

Further, the polarizing laminated film 300 is attached to the base film 30' When the polarizing film 5 is provided on the surface, the protective film is usually bonded to the polarizing film 5 on both surfaces. In this case, the protective films may be the same kind of protective film or different kinds of protective films.

By attaching the first protective film 10 with an active energy ray-curable adhesive as an example, a method of bonding the protective film will be described, and the active energy ray-curable adhesive as the first adhesive layer 15 will be used. After the first protective film 10 is laminated on the polarizing film 5, the active energy ray such as ultraviolet rays, visible light, electron rays, and X rays is irradiated to cure the adhesive layer. Among them, ultraviolet light is preferred. As the light source at this time, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a fluorescent 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 may be subjected to plasma treatment, corona treatment, or ultraviolet irradiation treatment in order to improve the adhesion to the polarizing film 5. The surface treatment of the flame treatment and the saponification treatment (easily followed by treatment), in particular, 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 first drawing can be obtained. When the polarizing film 5 is provided on both surfaces of the base film 30 ′ and the protective film is bonded to both of the polarizing films 5 , the polarizing film 300 can be separated from the polarizing film 300 by one peeling step S50 . Two sheets of a polarizing plate with a protective film on one side were obtained.

The method of peeling off the base film 30' is not particularly limited, and it can be peeled off by the same method as the peeling step of the separator (release film) which is usually performed on the polarizing plate with an adhesive. The base film 30' may be peeled off immediately after the first bonding step S40, or may be temporarily wound into a reel shape after the first bonding step S40, and may be peeled off at the same time as the subsequent step.

(6) Second bonding step S60

In this step, the polarizing film 5 of the polarizing plate having the protective film on one side thereof, that is, the surface opposite to the protective film adhered to the first bonding step S40, is further bonded to the protective film. The step of attaching the polarizing plate 2 of the protective film on both sides of the configuration shown in Fig. 2 . When the first protective film 10 is bonded in the first bonding step S40, the second protective film 20 is bonded in this step; when the second protective film 20 is bonded in the first bonding step S40, this step is performed. The first protective film 10 is bonded. The bonding of the second protective film 20 via the second adhesive layer 25 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 manufacturing a polarizing plate is described in detail, but not limited thereto, and a monomer (separate) film may be contained. The polarizing film 5 is bonded to the first protective film 10 or the first and second protective films 10 and 20 to produce a polarizing plate.

The polarizing film 5 comprising a monomer (separate) film can be produced by a method comprising the steps of: producing a polyvinyl alcohol-based resin film by a known method such as melt extrusion or solvent casting; Poly a step of uniaxially stretching the enol-based resin film; a step of dyeing and adsorbing the polyvinyl alcohol-based resin film using iodine; a step of treating the polyvinyl alcohol-based resin film adsorbed with iodine using an aqueous solution of boric acid; and The step of washing with water after the aqueous solution is carried out. Uniaxial stretching can be carried out prior to dyeing of iodine, simultaneously with dyeing or after dyeing. When uniaxially extending after dyeing, the uniaxial stretching can be carried out before boric acid treatment or in boric acid treatment. Moreover, uniaxial stretching can also be performed at a plurality of stages.

When both the first and second protective films 10 and 20 are bonded together to produce a polarizing plate having a double-sided protective film, the protective films may be sequentially bonded via the adhesive layer or may be bonded at the same time.

(7) Regulation of W _I /Ty

The method of increasing the iodine element content rate W _I with respect to the luminosity-corrected monomer transmittance Ty and setting W _I /Ty within the above predetermined range is not particularly limited, and examples thereof include the following methods.

a) In the dyeing step, the film is immersed in a method containing a dyeing solution having a relatively large amount of iodide (including iodine and iodide ions) in comparison with the usual amount. At this time, W _I /Ty can be regulated by adjusting the concentration of iodide in the dye solution, the temperature of the dye solution, the residence time of the film, and the like.

b) In the cross-linking treatment step, the film is immersed in a method comprising a cross-linking solution of iodide ions in a relatively large amount compared to the amount generally employed. At this time, W _I /Ty can also be regulated by adjusting the concentration of iodide ions in the crosslinking solution, the temperature of the crosslinking solution, the residence time of the film, and the like.

c) A method of making the iodide ions contained in the film not detached. Iodide ions that were once contained are more easily washed away by washing with water. Therefore, as a method of not dissociating the iodide ion, a method of increasing the concentration of the crosslinking agent in the crosslinking solution can be mentioned. When the concentration of the crosslinking agent is increased, the crosslinking amount of the crosslinking agent increases, so that the iodide ion can be prevented from being washed away when the water is washed. In order to more effectively suppress the iodine ion detachment, the temperature of the crosslinking solution is preferably set to a low temperature as much as possible. Further, as another method for preventing the iodide ions from being detached, it is also effective to use a pneumatic blade or a blower to blow off the liquid adhering to the surface of the film and remove it by a water absorbing roll or the like instead of washing. Iodide ion detachment can be avoided by not washing with water.

d) A combination of two or more of the above a) to c).

Among the above, the methods of b) and c) are particularly effective, and the method of c) is most effective.

In order to obtain a polarizing film having a W _I /Ty of 0.145 or more, one of the preferred embodiments is a method comprising a crosslinking treatment step of immersing the film in a temperature as low as possible and containing a crosslinking agent and an iodide. Ion cross-linking solution. One of the preferred embodiments is a method comprising a crosslinking treatment step of immersing the film at a liquid temperature of 3 to 30 ° C, preferably 5 to 15 ° C, and containing a crosslinking agent 0.5 to 10% by weight, preferably 1 to 5% by weight, and in a cross-linking solution containing iodide ions excessively. When the cross-linking treatment step is carried out using a cross-linking solution of 2 or more tanks, the cross-linking solution may be at least one cross-linking solution.

More preferably, after performing the crosslinking treatment step of the above preferred embodiment, the water is not washed, but a pneumatic blade, a blower, and a suction are used. A liquid roller or the like removes the liquid adhering to the surface of the film. Further, the conditions of the subsequent drying step are not particularly limited, and even at a higher temperature, the iodide ions are less likely to be detached.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples and comparative examples, but the present invention is not limited by the examples.

<Example 1>

(1) Primer layer forming step

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, saponification degree: 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polycondensate having a concentration of 3% by weight. Aqueous vinyl alcohol 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 primer layer. Use a coating solution.

Next, an unstretched polypropylene (PP) film (melting point: 163 ° C) having a thickness of 90 μm was prepared as a base film, and after the corona treatment was performed on one surface thereof, the primer layer was coated with a small-diameter gravure coater. The cloth liquid was coated on its corona-treated surface, and dried at 80 ° C for 10 minutes, thereby forming a primer layer having a thickness of 0.2 μm.

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

Polyvinyl alcohol powder ("PVA124" manufactured by KURARAY Co., Ltd., average polymerization degree 2400, saponification degree 98.0 to 99.0 mol %) A hot water solution at 95 ° C was dissolved to prepare a polyvinyl alcohol aqueous solution having a concentration of 8 wt%, and this was used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The coating liquid for forming a polyvinyl alcohol-based resin layer was applied onto the surface of the primer layer of the base film having the primer layer produced in the above (1), and then dried at 70 ° C for 4 minutes. Thus, a polyvinyl alcohol-based resin layer was formed on the primer layer to obtain a laminated film including a base film/primer layer/polyvinyl alcohol-based resin layer.

(3) Production of stretch film (extension step)

The laminated film produced in the above (2) was subjected to a 5.3-fold free end uniaxial stretching at 160 ° C using a non-fixed longitudinal uniaxial stretching device to obtain a stretched film. The thickness of the stretched polyvinyl alcohol-based resin layer was 5.1 μm.

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

The stretched film prepared in the above (3) was immersed in a dyeing aqueous solution containing 30% by weight of iodine and potassium iodide (containing 0.6 parts by weight of iodine and 10.0 parts by weight of potassium iodide per 100 parts by weight of water) for about 180 seconds to carry out a polyvinyl alcohol-based resin. After the dyeing treatment of the layer, the excess aqueous dye solution was rinsed with pure water at 10 °C.

Next, it was immersed in a first crosslinked aqueous solution containing boric acid at 78 ° C (containing 10.4 parts by weight of boric acid per 100 parts by weight of water) for 120 seconds, and then immersed in a second crosslinked aqueous solution containing 70% of boric acid and potassium iodide (per 100 parts by weight of water containing 5.7 parts by weight of boric acid and 12.0 parts by weight of potassium iodide for 60 seconds, and then immersed in a third crosslinked aqueous solution containing boric acid and potassium iodide at 10 ° C (3.0 parts by weight of boric acid per 100 parts by weight of water, and 15.0 parts by weight of potassium iodide). ) The crosslinking treatment was carried out for about 10 seconds. Immediately thereafter, the air adhering to both surfaces was removed using a blower to obtain a polarizing laminated film including a polarizing film.

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

The protective film is bonded to the polarizing film of the polarizing laminated film produced in the above (4) via an adhesive layer containing an ultraviolet curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.). Transparent protective film of cellulose acetate (TAC) ("KC-2UAW" manufactured by Konica Minolta Opto Co., Ltd.)]. Next, the adhesive layer is cured by irradiation with ultraviolet rays using a high-pressure mercury lamp to obtain a laminated film including a protective film/adhesive layer/polarizing film/base film layer structure (first bonding step). Thereafter, the base film was peeled off from the obtained bonded film to obtain a polarizing plate having a single-sided protective film (peeling step).

(6) Manufacture of sample for evaluation

The surface of the obtained polarizing plate of the polarizing plate having a single-sided protective film was subjected to a corona treatment, and a (meth)acrylic resin-based adhesive ("P-3132" manufactured by LINTEC Co., Ltd.) was bonded thereto. ). The obtained polarizing plate with the adhesive layer was attached to the glass with an adhesive layer to obtain a sample for evaluation.

<Example 2>

In addition to the content of potassium iodide in the third cross-linked aqueous solution is set to every 100 The polarizing plate having a single-sided protective film was prepared in the same manner as in Example 1 except that the water-repellent roller was used in place of the air blower to remove the liquid on both sides, and the evaluation sample was prepared. .

<Comparative Example 1>

A polarizing plate having a single-sided protective film was prepared in the same manner as in Example 1 except that the content of potassium iodide in the third cross-linked aqueous solution was 4 parts by weight per 100 parts by weight of water, and the evaluation was carried out for evaluation. Sample.

<Comparative Example 2>

A polarizing plate having a single-sided protective film was produced in the same manner as in Example 1 except that water was immersed in water at 10 ° C instead of being impregnated in the third cross-linked aqueous solution, and a sample for evaluation was prepared.

[Measurement of Ty, Py and single hue b]

For the polarizing plate of the obtained evaluation sample, an absorption spectrophotometer ("V7100" manufactured by JASCO Corporation) was used, and a 2 degree field of view (C light source) of JIS Z 8701 was used. The obtained transmittance and the degree of polarization were subjected to photometric correction to measure the photometric correction unit transmittance Ty and the photometric correction polarization Py. Moreover, the monomer hue b was measured using the same absorptiometer. At the time of measurement, the sample for evaluation was attached to the glass side so that it can irradiate incident light. The obtained photometric correction unit transmittance Ty, the photometric correction polarization Py, and the single color h are set as the photometric correction unit transmittance Ty, the photometric correction polarization Py, and the single color h of the polarizing film, respectively. will The results are shown in Table 1.

[Iodine element content rate W _I and W _I /Ty determination]

The protective film and the adhesive layer were removed from the obtained polarizing plate with a single-sided protective film, and the polarizing film was separated, and this was set as a measurement sample, and by combustion-ion chromatography according to JIS K 0127:2013 The iodine element content rate W _I [% by weight] was determined by the method. In the combustion-ion chromatography apparatus, a chlorine/sulfur analyzer "TOX-100" manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used as a combustion apparatus, and "DX-500" manufactured by Thermo Fisher Scientific Co., Ltd. was used as an ion chromatography apparatus. A 12.2 mg polarizing film was used as a measurement sample, and the fuel pretreatment of the measurement sample was carried out in accordance with JIS Standard 6.3.5. Further, W _I /Ty was calculated using the Ty obtained as described above. The results are shown in Table 1.

[Measurement of Absorbance at Wavelength 217 nm]

The protective film and the adhesive layer were removed from the obtained polarizing plate having a single-sided protective film, and the polarizing film was separated, and this was used as a measurement sample, and an absorbance photometer (manufactured by Shimadzu Corporation) was used: UV2450) measures the absorbance in the wavelength region of 190 to 800 nm. In order to avoid the influence of the polarizing caused by the device, the average value of the absorption spectrum measured by measuring the absorption spectrum of the measurement sample with respect to the device and the rotation spectrum measured by 90 degrees is used as the absorption spectrum of the polarizing film. . From the light absorption spectrum, the absorbance at a wavelength of 217 nm derived from the iodide ion (I ^- ) was obtained. The results are shown in Table 1.

In the polarizing films of the first to second examples and the comparative examples 1 to 2, the obtained absorbance was proportional to the iodine element content W _I obtained by the combustion-ion chromatography. This is because the amount of polyiodide which forms a complex with PVA is substantially equal between the four kinds of polarizing films, and the iodine element content ratio measured by combustion-ion chromatography is W. The size of _I will reflect the amount of iodide ion (I ^- ). From this result, it was found that the iodine element content rate W _I obtained from the combustion-ion chromatography method reflects the amount of iodide ion (I ^- ).

[Evaluation of water resistance of polarizing plate]

(1) Evaluation of heat and humidity resistance

4 cm × 4 cm of the evaluation sample was placed in an oven adjusted to a temperature of 80 ° C and 90% RH for 48 hours, and then the sample was taken out and allowed to stand in an environment of 23 ° C and 55% RH for about 12 hours. Thereafter, the photometric correction polarization Py is measured in the same manner as described above. The results are shown in Table 1.

(2) Evaluation of temperature and water resistance

After immersing the sample for evaluation of 4 cm × 4 cm in water at 60 ° C for 30 minutes, the sample was pulled up and allowed to stand in an environment of 23 ° C and 55% RH for about 12 hours, and then the measurement method was measured in the same manner as above. Body hue b. Further, the hue of the sample after the test was visually confirmed, and it was judged as A when the neutral gray color was maintained after the test, and as B when the blue color shift occurred. The results are shown in Table 1.

1‧‧‧Polar plate

5‧‧‧ polarizing film

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

Claims (6)

A polarizing plate comprising: a polarizing film having an iodine element content W _I [% by weight] of 8.09 or less, a photometric corrected monomer transmittance Ty [%] of 40 to 47%, and the aforementioned iodine element content ratio W _I relative The ratio W _I /Ty of the photometric correction monomer transmittance Ty[%] is 0.145 or more, the photometric correction polarization Py is 99.986% or more, the absorbance at a wavelength of 217 nm is 2.57 or more, and the protective film is via active energy. The radiation curable adhesive is then fixed to at least one side of the aforementioned polarizing film. A polarizing plate comprising: a polarizing film having an iodine element content W _I [% by weight] of 8.09 or less, a photometric corrected monomer transmittance Ty [%] of 40 to 47%, and the aforementioned iodine element content ratio W _I relative The ratio W _I /Ty of the photometric correction monomer transmittance Ty[%] is 0.145 or more, the photometric correction polarization degree Py is 99.986% or more, and the absorbance at a wavelength of 217 nm is 2.57 or more; and the adhesive layer (excluding the inclusion selection) One or more kinds of the phosphoric acid compound and the (meth)acrylic polymer which are a group of the compound represented by the following formula (1) and the compound represented by the following formula (1) Adhesive layer formed by the acrylic adhesive composition) In the formula, R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon residue having 1 to 18 carbon atoms which may contain an oxygen atom. The polarizing plate according to claim 1 or 2, wherein the polarizing film has a W _I /Ty of 0.5 or less. The polarizing plate according to claim 1 or 2, wherein the polarizing film has a thickness of 10 μm or less. The polarizing plate according to claim 1 or 2, wherein the polarizing film contains a polyvinyl alcohol resin. The polarizing plate according to claim 2, further comprising a protective film laminated on at least one surface of the polarizing film.