TW201632560A - Polyvinylalcohol resin film, polarizing film and polarizing plate - Google Patents

Abstract

The present invention provides a polyvinylalcohol resin film obtained by forming a film with a solution including a polyvinylalcohol resin, wherein the viscosity P(mPa,s) of a 4 weight % aqueous solution of the polyvinylalcohol resin and the crystalline length period L(nm) of the polyvinylalcohol resin satisfy the relationship represented by the following formula (1) L < 6.7909*ln(P)-17.337...(1).

Description

Polyvinyl alcohol resin film, polarizing film and polarizing plate

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

The polarizing plate is widely used in an image display device such as a liquid crystal display device. In general, a protective film is bonded to one or both sides of a polarizing film in which a dichroic dye such as iodine is adsorbed to a polyvinyl alcohol-based resin film (Japanese Patent Laid-Open Publication No. 2014-59564 (Patent Document) 1) Japanese Patent No. 5390053 (Patent Document 2), JP-A-2006-188655 (Patent Document 3), and the like.

In recent years, with the development of image display devices toward portable machines and thin televisions, there has been an increasing demand for thinning of polarizing plates and even polarizing films.

However, when the polarizing film is made thinner, there is a problem that the film strength is lowered. In Patent Documents 1 to 3, the content of the polarizing film is improved by adjusting the long period of the polyvinyl alcohol resin film. However, the means for improving the film strength has not been disclosed.

It is an object of the present invention to provide a A polyvinyl alcohol-based resin film which is a thin film and has a high film strength polarizing film. Further, an object of the present invention is to provide a polarizing film which has a high film strength even in a thin form, and a polarizing plate having high durability using such a polarizing film.

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

[1] A polyvinyl alcohol-based resin film obtained by forming a film of a solution containing a polyvinyl alcohol-based resin, and a viscosity P (mPa) of a 4% by weight aqueous solution of the polyvinyl alcohol-based resin ‧ s) The crystal long period L (nm) of the polyvinyl alcohol-based resin film satisfies the relationship of the following formula (1).

L<6.7909×ln(P)-17.337...(1)

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

[3] A polarizing film having a viscosity P' (mPa‧s) in a 4% by weight aqueous solution and a long period L' (nm) in the absorption axis direction satisfying the relationship of the following formula (2).

L'<14.3×ln(P')-43.9...(2)

In the 4% by weight aqueous solution, the polarizing film was stored in an environment of 80° C. and 90% RH for 7 days, and then prepared.

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

[5] A polarizing plate comprising: a polarizing film; and a protective film laminated on at least one surface of the polarizing film, and a viscosity P' of the 4% by weight aqueous solution of the polarizing film separated from the polarizing plate (mPa) ‧)) The long period L' (nm) in the absorption axis direction of the polarizing film which is separated from the polarizing plate satisfies the relationship of the following formula (2).

L'<14.3×ln(P')-43.9...(2)

In addition, the 4 wt% aqueous solution of the polarizing film was prepared by accommodating the polarizing film which was separated from the polarizing plate in an environment of 80 ° C and 90% RH for 7 days.

According to the present invention, it is possible to provide a polyvinyl alcohol-based resin film which can produce a polarizing film having a high film strength even in a thin form. Further, according to the present invention, it is possible to provide a polarizing film having a high film strength even in a thin form, and a polarizing plate having high durability using such a polarizing film.

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

2‧‧‧2-sided polarizing plate with protective film

5‧‧‧ polarizing film

6‧‧‧Polyvinyl alcohol resin layer

6'‧‧‧ Stretched polyvinyl alcohol resin layer

10‧‧‧1st protective film

15‧‧‧1st adhesive layer

20‧‧‧2nd protective film

25‧‧‧2nd adhesive layer

30‧‧‧Base film

30'‧‧‧Stretched base film

100‧‧‧ laminated film

200‧‧‧ stretch film

300‧‧‧Polarized laminated film

400‧‧‧Finished film

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

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

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

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

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

Fig. 6 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing laminate film obtained in the dyeing step.

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

Fig. 8 is a graph showing the relationship between the viscosity P of the polyvinyl alcohol-based resin and the crystal long period L in the examples and the comparative examples.

Fig. 9 is a graph showing the relationship between the viscosity P' of the polarizing film in the examples and the comparative examples and the long period L' in the absorption axis direction.

<Polyvinyl alcohol resin film>

The polyvinyl alcohol-based resin film of the present invention can be obtained by using a film of a polyvinyl alcohol-based resin (hereinafter also referred to as "raw material liquid") as a manufacturer of a polarizing film.

The method of forming a polyvinyl alcohol-type resin film using a raw material liquid, for example, the following methods are mentioned.

[a] A method of producing a polyvinyl alcohol resin film into a single layer film by using a raw material liquid, for example, by a generally known method such as a melt extrusion method or a solvent casting method.

[b] A method of producing a polyvinyl alcohol-based resin film by applying a raw material liquid onto a base film and drying it.

From the easy to obtain a thin polarizing film, and in the step In view of the excellent handleability of the polarizing film of the film, it is preferred to form the film by the film forming method of the above [b]. The polyvinyl alcohol-based resin film formed by the film forming method of the above [b] can be obtained as a laminate with the base film. The thickness of the polyvinyl alcohol-based resin film before stretching is, for example, about 3 to 150 μm.

The viscosity P (mPa ‧ s) of the 4 wt% aqueous solution of the polyvinyl alcohol-based resin used in the raw material liquid, and the crystal long period L (nm) of the polyvinyl alcohol-based resin film of the present invention satisfy the following formula (1) )Relationship.

L<6.7909×ln(P)-17.337...(1)

The measurement of the viscosity P of a 4% by weight aqueous solution can be measured using a cone-and-plate type rotational viscometer. First, the polyvinyl alcohol-based resin was sufficiently vacuum-dried for 24 hours to remove water, and then weighed by a precision balance so that the weight % after dissolution was 4% by weight. Then, a predetermined amount of pure water was added and heated to 90 ° C or higher, and sufficiently dissolved for 1 hour or more. At this point the water will evaporate and care must be taken to avoid deviations from the target. After the obtained solution was returned to room temperature and stabilized, it was allowed to stand for about 24 hours to carry out defoaming. If there is a bubble, the viscosity cannot be accurately measured. Therefore, after confirming the elimination of the bubble, the viscosity P is measured by a conical flat-plate rotational viscometer (cone-plate type). Further, the measured aqueous solution was measured for a solid content, and it was confirmed whether or not it was deviated from 4% by weight. However, about 5 ml of an aqueous solution was weighed in a container which had been dried beforehand, and the weight of the aqueous solution was measured, and then dried at 105 ° C for 2 hours and cooled. The weight of the residual resin was measured. The solid content contained in the aqueous solution as the weight of the residual resin was counted, and it was confirmed whether this was 4% by weight. When the amount of solid component deviates from the target, it is taken as follows: A method of preparing a plurality of aqueous solutions having different amounts of solid components, wherein the horizontal axis is a solid content, and the viscosity is plotted on a logarithmic point on the vertical axis, and the viscosity P at 4% by weight is read from the approximate line (straight line).

The crystal long period L system can be determined by small angle X-ray scattering (SAXS: Small Angle X-ray Scattering). In the measurement, when the single film of the polyvinyl alcohol resin film is used in the measurement (in the above [b]), the polyvinyl alcohol resin obtained by peeling the base film from the laminate is measured. Membrane), and the scattered light is detected on a two-dimensional plane to obtain a two-dimensional scattergram. The two-dimensionally obtained scattering is integrated around the entire circumferential direction (360 degrees) to produce a one-dimensional contour. The following uses the one-dimensional contour thus obtained. In order to perform the background correction, the one-dimensional contour of the background scattering is first obtained by performing the measurement in the sample-free state. The sample is then set and the measurement is performed again to obtain a one-dimensional profile of the sample. The transmittance was calculated from the ratio of the transmitted light intensities of the two. After considering this penetration rate, the one-dimensional contour of the background is subtracted from the one-dimensional contour of the sample and used as a one-dimensional contour of the sample. In the contour thus obtained, where the vertical axis is the scattering intensity and the horizontal axis is one of the scattering angles, the scattering angle of the horizontal axis is converted into the period length using the Bragg equation, and the peak position of the scattering intensity is obtained as the length of the scattering. Cycle (crystallization long period L). In the measurement, since the film thickness cannot be obtained when the thickness of the film is small, it is possible to form a film thickness having sufficient strength by superposing as necessary, and then measuring.

By using a polyvinyl alcohol-based resin film that satisfies the relationship of the above formula (1), a polarizing film is produced, whereby a polarizing film having a high film strength can be obtained. The above formula (1) is an expression derived from experimental values. By using the above formula (1) The reason why the polyvinyl alcohol-based resin film of the relationship can produce a polarizing film having a high film strength can be considered as follows, but the contents of the examination are not intended to limit the present invention.

First, the viscosity P of the 4% by weight aqueous solution of the polyvinyl alcohol-based resin film used for the raw material liquid can be considered as the degree of expansion of the polyvinyl alcohol-based resin used in the raw material liquid in water. The more the chain of the polyvinyl alcohol-based resin is present, the more the chain-chain interaction of the polyvinyl alcohol-based resin is exhibited, and the higher viscosity is measured. The resin having a high viscosity may, for example, be one having a large molecular weight or a high affinity with water. In the case of a large molecular weight, the molecule itself is large, and the original has a tendency to easily expand. However, the larger the molecular weight, the easier it is to expand, and the number of branching chains or the molecular weight dispersion. Further, the affinity with water is also affected by the degree of saponification or the copolymer, and also by the copolymerization composition or the copolymerization ratio. As such, there are many factors for chain expansion, and regardless of the reason, it is possible to consider the degree of expansion of the chain in the water.

Next, the crystal long period L of the polyvinyl alcohol-based resin film is a distance between crystal-crystals obtained by a small-angle X-ray scattering analysis method. The distance between the crystal and the crystal is also affected by the physical properties of the polyvinyl alcohol-based resin. However, the inventors of the present invention have found that they can be controlled by drying conditions at the time of film formation as will be described later. In the present invention, the polyvinyl alcohol-based resin to be used is controlled so that the crystal long period L satisfies the relationship of the formula (1).

The meaning of the formula (1) is that the right side shows a factor of the degree of expansion of the molecular chain of the polyvinyl alcohol-based resin in water with respect to the long period of the crystal on the left side. Relative to the expansion of the molecular chain, the long period is controlled to not reach The fixed value (that is, the distance between the crystal and the crystal) can also be considered to control the amount of the molecular chain existing between the crystal and the crystal, by controlling the molecular chain connecting the crystal and the crystal to a predetermined level or more. This can form a network-like mesh structure, improve the film strength of the polyvinyl alcohol-based resin film, and improve the film strength of the polarizing film produced by using the film. On the other hand, when the crystal long period is equal to or greater than a predetermined value with respect to the expansion of the molecular chain, it is difficult to form the mesh structure, and the crystal is in an isolated state, and the film strength is deteriorated.

In particular, in a polarizing film having a small film thickness, since the strength of the entire film is small, it is necessary to increase the strength per unit thickness as compared with a case where the film thickness is thick. When the method of the present invention is used, the strength per unit thickness can be improved as compared with the polarizing film up to the present, and it is extremely useful in a film polarizing film, particularly a polarizing film of 10 μm or less.

Next, a method of controlling the distance between crystal-crystals (crystal long period) by drying conditions at the time of film formation, and the reason why control can be performed will be described. The distance between crystals and crystals (crystal long period) of the polyvinyl alcohol-based resin film can be controlled, for example, by controlling the drying rate in a region where the water content is 30% by weight or less in the final stage of drying, but is not limited thereto. herein. The reason why the control can be carried out at a drying rate at a time when the water content is 30% by weight is that since the crystal nucleus is formed from the vicinity of the water content, the crystal can be sufficiently dried by slowly performing the drying in the vicinity. The formation of nuclei shortens the distance between crystals and crystals (long period of crystal growth).

In the region where the water content exceeds 30% by weight, since the polyvinyl alcohol-based resin exists as a homogeneous solution, and the solution state in which the molecular chain is uniformly present is stabilized, it hardly causes a stable critical size or more. The formation of a crystal nucleus. When the water content is close to 30% by weight, since the state of crystallization is stabilized by the formation of the crystal nucleus, the formation of a crystal nucleus having a stable critical size or more is started. This is because a uniform solution is formed in a region where the water content exceeds 30% by weight, and it is possible to prevent unintended crystallization and the like. An aqueous solution in a region having a water content of less than 30% by weight may have a high possibility of causing unanticipated crystallization between storage or transportation.

On the other hand, in the region of substantially less than 30% by weight, since drying proceeds to a desired level or more, water as a good solvent is reduced, and the mobility of the chain of the polyvinyl alcohol-based resin is lowered, and it is difficult to cause a critical size or more. The formation of a stable crystal nucleus. In view of these points, the drying speed in the vicinity of the water content of 30% by weight is important. Therefore, as the raw material liquid, it is preferred to prepare a raw material liquid containing a polyvinyl alcohol-based resin having a water content of 30% by weight or more, and after using the film to form a film, the drying rate in the vicinity of the water content of 30% by weight can be adjusted. A polyvinyl alcohol-based resin film having a desired crystal-crystal distance (crystal long period) is obtained.

(polyvinyl alcohol resin)

A polyvinyl alcohol-based resin used for the production of the polyvinyl alcohol-based resin film can be used by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate resin, in addition to the polyvinyl acetate of the homopolymer of vinyl acetate, a copolymer of vinyl acetate and other monomers copolymerizable with the vinyl acetate can be exemplified. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol resin can be 80.0 to The range of 100.0 mol%, preferably in the range of 90.0 to 99.5 mol%, particularly 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 the degree of saponification exceeds 99.5 mol%, the dyeing speed is slowed down when a polyvinyl alcohol-based resin is used, productivity is lowered, and a polarizing film having sufficient polarizing performance may not be obtained.

The saponification degree means that the acetoxy group contained in the polyvinyl acetate-based resin which is a raw material of the polyvinyl alcohol-based resin by the saponification step is represented by a unit ratio (% by mole) (acetoxy group: -OCOCH) ₃ ) The ratio of conversion to a hydroxyl group, and is 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 hinders crystallization.

The polyvinyl alcohol-based resin may be a partially modified modified polyvinyl alcohol. The ratio of the modification is preferably less than 30% by mole, and particularly preferably less than 10% by mole. When the modification is more than 30 mol%, it is difficult to adsorb the dichroic dye, and it is difficult to obtain a polarizing film having sufficient polarizing performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, particularly preferably from 1,500 to 8,000, 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).

<polarized film>

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

In the polarizing film of the present invention, the viscosity P' (mPa‧s) of the 4% by weight aqueous solution and the long period L' (nm) in the absorption axis direction preferably satisfy the relationship of the following formula (2).

L'<14.3×ln(P')-43.9...(2)

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

The 4% by weight aqueous solution used for the measurement of the viscosity P' was prepared by storing the polarizing film in an environment of 80 ° C and 90% RH for 7 days. By storing in this environment for 7 days, the iodine and boric acid added by dyeing and crosslinking can be removed, and the viscosity P' of the 4% by weight aqueous solution which is not affected by the added iodine and boric acid can be measured (mPa‧s ). The viscosity P' is measured in accordance with the above-described measurement method of the viscosity P. The long period L' (nm) in the absorption axis direction of the polarizing film is measured in accordance with the measurement method of the above-described crystal long period L.

The above formula (2) is an expression derived from experimental values. The reason why the polarizing film having a high film strength can be obtained by satisfying the relationship of the above formula (2) can be similarly obtained by using a polyvinyl alcohol-based resin film which satisfies the relationship of the above formula (1) as described above. The reason for the high film strength polarizing film is the same, but the content of the examination is not intended to limit the present invention.

When the polarizing performance of the polarizing film is described in detail, the polarizing performance Usually, it is evaluated by two parameters called "visual sensitivity correction unit transmittance Ty" and "visual sensitivity correction polarization Py". These parameters are the transmittance and the degree of polarization in the visible light region (wavelength 380 to 780 nm) corrected so that the weight near the 550 nm where the sensitivity of the human eye is the highest is maximized. Since the human eye cannot recognize the light that does not reach the wavelength of 380 nm, Ty and Py do not consider this.

The illuminance correction monomer transmittance Ty of the polarizing film may be a value generally obtained in an image display device to which the polarizing film or the liquid crystal display device including the polarizing plate is applied, and specifically, preferably located 40 to 47% range. Ty is preferably in the range of 41 to 45%, and the balance between Ty and Py can be made better. When Ty is too high, Py is lowered to lower the display quality of the image display device. When Ty is too low, the brightness of the image display device is lowered to lower the display image quality, or the input power must be greatly increased in order to sufficiently increase the brightness. The viscous degree of the polarizing film is preferably adjusted to have a degree of polarization Py of 99.9% or more, and particularly 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, the thickness of the polarizing film is preferably 10 μm or less, and particularly preferably 8 μm or less. The thickness of the polarizing film is usually 2 μm or more.

The puncture film has a puncture strength per unit thickness of preferably 5.0 g/μm or more, and more preferably 6.0 g/μm or more. When the puncture strength is 5.0 g/μm or more, the rate of occurrence of cracking of the polarizing film can be remarkably suppressed in the durability test such as a thermal shock test.

<Polarizer>

(1) Basic composition of polarizing plate

Fig. 1 is a schematic cross-sectional view showing an example of a layer configuration of a polarizing plate of the present invention. As in the case of the polarizing plate 1 shown in Fig. 1, the polarizing plate of the present invention may include a polarizing film 5 and a polarizing plate having a protective film on one surface of the first protective film 10 laminated on one surface thereof. 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, the protective film may be bonded to the other surface of the polarizing film 5, and specifically, as in the polarizing plate 2 shown in Fig. 2, the polarizing plate 5 may be provided and laminated. A polarizing plate having a protective film on both sides of the first protective film 10 on one side 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 viewing (front) side of the liquid crystal display-like image display element or disposed on the back side of the image display element. A polarizing plate (for example, a backlight side of a 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. As described above, the polarizing film 5 constituting the polarizing plate is preferably a polarizing film that satisfies the relationship of the above formula (2). Further, it is preferable that the polarizing film 5 which is separated from the polarizing plate satisfies the relationship of the above formula (2). In this case, the 4% by weight aqueous solution used for the measurement of the viscosity P' was adjusted after being stored in an environment of 80 ° C and 90% RH for 7 days in a polarizing film peeled off from the polarizing plate. By. The viscosity P' of the previous polarizing film constituting the polarizing plate and the long period L' of the absorption axis direction are longer than the viscosity P' of the polarizing film which is separated from the polarizing plate by using the polarizing plate, and the absorption axis direction. The period L' is almost the same value.

The polarizing plate-based polarizing film has high film strength, and in the durability test such as a thermal shock test, the occurrence rate of cracking of the polarizing film can be remarkably suppressed.

(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 (northene). Polyolefin resin such as resin; cellulose triacetate, cellulose acetate resin such as cellulose diacetate; polyester resin; polycarbonate resin; (meth) acrylic resin a polystyrene-based resin; or a film composed of a mixture, a copolymer, or the like.

The first protective film 10 may be a protective film having an optical function like a retardation film or a brightness enhancement film. For example, a film made of the above thermoplastic resin may be stretched (uniaxially stretched or biaxially stretched), or a liquid crystal layer or the like may be formed on the film to form an arbitrary phase difference value. Phase difference film.

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

The cyclic polyolefin-based 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 and an addition polymerization of a cyclic olefin. a copolymer of a cyclic olefin, a cyclic olefin and an ethylene-like olefinic chain olefin (typically any copolymer), and a graft polymer modified with an unsaturated carboxylic acid or the derivative, and Such hydrides and the like. Among them, it is preferable to use a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a norbornene-based resin of a cyclic olefin.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, a copolymer such as these may be used, or a part of the hydroxyl group may be modified by another substituent or the like. Among them, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred.

The polyester resin is a resin other than the above cellulose ester resin having an ester bond, and is generally composed of 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 terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. A diol may be used for the polyhydric alcohol, 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 polytrimethylene terephthalate. Ester, trimethyl methylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

Polycarbonate-based resin The base-bonded polymer is composed of a polymer. The polycarbonate resin may be a resin called a modified polycarbonate which is modified by a polymer skeleton, or a copolymerized polycarbonate or the like.

The (meth)acrylic resin is a resin having a compound having a (meth)acrylonitrile group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, poly(methyl) acrylate-like poly(meth) acrylate; methyl methacrylate-(meth)acrylic acid copolymer; methacrylic acid Ester-(meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl methacrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl methacrylate methacrylate copolymer, etc.). It is preferred to use a polymer having a poly(methyl) acrylate-like poly(meth)acrylic acid C _1-6 alkyl ester as a main component, and it is particularly preferred to use methyl methacrylate as a main component (50 to 100% by weight, 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 may be formed on the surface of the first protective film 10 opposite to the polarizing film 5. Further, the first protective film 10 may contain one or more kinds of lubricants, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidant-like additives.

The thickness of the first protective film 10 is preferably 90 μm or less, and particularly preferably 50 μm or less, from the viewpoint of reducing the thickness of the polarizing plate. Good is 30μm or less. 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 for forming the first adhesive layer 15 may be an active energy ray-curable adhesive containing a curable compound which is cured by irradiation of an ultraviolet ray, a visible light, an electron beam, or an X-ray active energy ray, or A water-based adhesive in which a binder component such as a polyvinyl alcohol-based resin is dissolved or dispersed in water.

Since the active energy ray-curable adhesive forming the first adhesive layer 15 exhibits good adhesion, activation of a cationically polymerizable curable compound and/or a radically polymerizable curable compound can be preferably used. A radiation curable adhesive. The active energy ray-curable adhesive may further include a cationic polymerization initiator and/or a radical polymerization initiator for starting the hardening 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) or an oxonium compound (one or two in the molecule). The above oxoquinone compound), or a combination thereof. 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), or a radical polymerizable property. Other vinyl compounds of the double bond, or combinations thereof. A cationically polymerizable curable compound and a radically polymerizable curable compound may also be used in combination.

An active energy ray-curable adhesive, if necessary, a cationic polymerization accelerator, an ion trapping agent, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow regulator, a plasticizer, an antifoaming agent, Anti-charge agent, flattening agent, solvent and other additives.

The thickness of the first adhesive layer 15 is usually 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 composed of the above-exemplified thermoplastic resin. It is a protective film that has an optical function like a retardation film and 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 the above description of the first protective film 10. The first protective film 10 and the second protective film 20 may be a protective film made of the same type of resin or a protective film made of a different type of resin.

(6) 2nd adhesive layer

The second adhesive layer 25 is a layer for fixing the second protective film 20 to the other surface of the polarizing film 5 next. The details of the second adhesive layer 25 can be referred to as described in the first adhesive layer 15. The adhesive forming the second adhesive layer 25 may have the same composition as the adhesive forming the first adhesive layer 15, or a different composition.

(7) Adhesive layer

The polarizing film 5 of the polarizing plate 1 with a protective film on one side shown in Fig. 1 or the first polarizing plate 2 with a protective film on both sides shown in Fig. 2 On the protective film 10 or the second protective film 20, an adhesive layer for bonding the polarizing plate to another member (for example, a liquid crystal cell when applied to a liquid crystal display device) can be laminated. The adhesive for forming the adhesive layer is usually a (meth)acrylic resin, a styrene resin, a polyoxymethylene resin or the like as a matrix polymer, and is an isocyanate compound, an epoxy compound or an aziridine compound. The cross-linking agent is added to the adhesive composition. Further, it may be configured as an adhesive layer further containing fine particles to exhibit 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 include other optical layers laminated on the first and/or second protective films 10 and 20 or the polarizing film 5. Other optical layers include a reflective polarizing film that allows a certain polarized light to pass through and reflects light having a polarized light of opposite nature, and a film having an anti-glare function having a concave-convex shape on the surface; A film having a surface anti-reflection function; a reflective film having a reflective function on the surface; a transflective semi-reflective film having both a reflective function and a penetrating function; a viewing angle compensation film.

<Method for Producing Polyvinyl Alcohol Resin Film, Polarizing Film, and Polarizing Plate>

The polyvinyl alcohol-based resin film, the polarizing film, and the polarizing plate of the present invention can be preferably produced by the method shown in Fig. 3. The manufacturing method shown in Fig. 3 includes the following steps: (1) applying a coating liquid (raw material liquid) containing a polyvinyl alcohol-based resin to at least one surface of a base film, and drying to form polyvinyl alcohol. a resin layer forming step S10 in which a resin film is obtained to obtain a laminated film, (2) Stretching the laminated film to obtain a stretched step S20 of a stretched film having a stretched polyvinyl alcohol-based resin film on a base film, and (3) a polyvinyl alcohol-based stretched film with iodine The resin film is dyed to form a polarizing film (polarizing sheet layer), thereby obtaining a dyeing step S30 of the polarizing laminated film, and (4) bonding the protective film to the polarizing film of the polarizing laminated film to obtain the first bonded film. In the bonding step S40, (5) the peeling step S50 of peeling off the base film from the bonding 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 method further includes: (6) bonding the protective film to the polarizing film of the polarizing plate having the protective film on one side thereof. The second bonding step S60 is performed.

Each step will be described below with reference to Figs. 4 to 7. In the resin layer forming step S10, the polyvinyl alcohol-based resin film 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. 4, this step is a step of forming a polyvinyl chloride resin film 6 on at least one surface of the base film 30 to obtain a laminated film 100. The polyvinyl alcohol-based resin film 6 is a layer which becomes a polyvinyl alcohol-based resin film 6' after the stretching step S20, and then becomes a polarizing film 5 through the dyeing step S30. The polyvinyl alcohol-based resin film 6 is formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one surface or both surfaces of the base film 30 and drying the coating layer. The method of forming a polyvinyl alcohol-based resin film 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 properties such as transparency, mechanical strength, thermal stability, and stretchability. Specific examples of such a 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. Resin; cellulose triacetate, cellulose diacetate cellulose ester resin; polycarbonate resin; polyvinyl alcohol resin; polyvinyl acetate resin; polyarylate resin; polyphenylene Ethylene 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 formed of one or more resin layers composed of one or two or more kinds of thermoplastic resins, or a resin composed of one or more thermoplastic resins in a plurality of layers. Multilayer construction of layers. When the laminated film 100 is stretched in the stretching step S20 described later, the base film 30 is preferably made of a resin which can be stretched at a stretching temperature suitable for stretching the polyvinyl alcohol-based resin film 6.

The substrate film 30 may also contain an additive. Specific examples of the additive include a UV absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a color former.

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

The coating liquid applied to the substrate film 30 is preferably made of polyethylene The powder of the enol-based resin is dissolved in a polyvinyl alcohol-based resin solution obtained by 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 necessary.

The method of applying the coating liquid to the base film 30 can be suitably selected from a wire bar coating method; a roll coating method such as reverse coating or gravure coating; a die coating method; a corner wheel coating method; and a lip coating method. Rotary coating method; screen coating method; fountain coating method; dipping method; spray method, and the like.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) can be set depending on the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent contains water, the drying temperature is preferably 80 ° C or higher.

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

The thickness of the polyvinyl alcohol-based resin film 6 in the laminated film 100 is preferably from 3 to 30 μm, particularly preferably from 5 to 20 μm. When the polyvinyl alcohol-based resin film 6 having the thickness in the range is obtained, the dyeing property of iodine is good and the polarizing performance is excellent, and the thickness is extremely thin (for example, the thickness is 10 μm or less) after the stretching step S20 and the dyeing step S30 described later. The polarizing film 5 is.

Before the application of the coating liquid, in order to improve the adhesion between the base film 30 and the polyvinyl alcohol-based resin film 6, at least polyethylene may be formed. The surface of the base film 30 on the side of the alcohol resin film 6 is subjected to a corona treatment, a plasma treatment, a flame (flame) treatment, or the like. Further, for the same reason, the polyvinyl alcohol-based resin film 6 can be formed on the base film 30 by 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 exhibits a certain degree of strong adhesion to both the base film 30 and the polyvinyl alcohol resin film 6, and usually contains a resin component and a solvent which can impart the adhesion. The resin component is preferably a thermoplastic resin excellent in transparency, heat stability, and stretchability, 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 preferably used. It is especially preferred to use a polyvinyl alcohol resin. The solvent is usually a general organic solvent or an aqueous solvent which can dissolve the above resin component, but it is preferred to form a primer layer from 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, it is preferred to use a polyamide solvent, a methylolated melamine resin, a dialdehyde crosslinking agent, and a metal chelate compound to crosslink. Agents, etc.

The thickness of the primer layer is preferably from 0.05 to 1 μm, particularly 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 film 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 resin film. The drying temperature of the coating layer composed of 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) Stretching step S20

Referring to Fig. 5, in this step, the laminated film 100 composed of the base film 30 and the polyvinyl alcohol resin film 6 is stretched to obtain a stretched substrate film 30'. The step of stretching the film 200 of the polyvinyl alcohol-based resin film 6'. The stretching process is usually uniaxial stretching.

The stretching ratio of the laminated film 100 can be appropriately selected in accordance with desired polarizing characteristics. It is preferably 1.1 to 17 times, and particularly preferably 1.5 to 8 times, relative to the original length of the laminated film 100. When the draw ratio exceeds 17 times, breakage of the film is likely to occur at the time of stretching, and the thickness of the stretched film 200 is thinned to a desired level or more, and there is a fear that workability and handleability in the subsequent step are lowered.

The stretching treatment is not limited to stretching in a single stage, and may be carried out 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 may be performed simultaneously with the dyeing treatment and/or the crosslinking treatment in the dyeing step S30. When the stretching treatment is carried out in such a plurality of stages, it is preferred to carry out the stretching treatment so that the total length of the stretching treatment is more than four times the stretching ratio.

The stretching treatment may be a longitudinal stretching in the film length direction (film transport direction), or a stretching in the film width direction. Stretching or oblique stretching, etc. Examples of the longitudinal stretching method include stretching between rolls using a roll, compression stretching, stretching using a suction pad (clamp), and a transverse stretching method, and a tenter method. The stretching treatment may be either a wet stretching method or a dry stretching method, but a dry stretching method is preferred from the viewpoint of wide selection of the stretching temperature.

The stretching temperature is set to a temperature higher than the fluidity at which the entire polyvinyl alcohol resin film 6 and the base film 30 exhibit a stretchable degree, and preferably the phase transition temperature (melting point or glass transition temperature of the base film 30). The range of -30 ° C to +30 ° C is particularly preferably in the range of -30 ° C to +5 ° C, more preferably in the range of -25 ° C to +0 ° C. When the base film 30 is composed of a plurality of resin layers, the above phase transition temperature means the highest phase transition temperature among the phase transition temperatures exhibited by the plurality of resin layers.

When the stretching temperature is set to -30 ° C lower than the phase transition temperature, it is difficult to achieve a high-magnification stretching of more than 4 times, or the fluidity of the base film 30 is too low, and there is a tendency that stretching treatment is difficult. . When the stretching temperature exceeds +30 ° C of the phase transition temperature, the fluidity of the base film 30 is excessively large and tends to be difficult to stretch. In order to more easily achieve a high-magnification stretching of more than 4 times, the stretching temperature is preferably in the above range, more preferably 120 ° C or more.

The heating method of the laminated film 100 in the stretching treatment is a hot zone heating method (for example, a method of heating in a stretching hot zone such as a furnace by blowing hot air and adjusting to a predetermined temperature); A method of heating the roller itself when stretching is performed; a heater heating method (a method in which an infrared heater, a halogen heater, a plate heater, or the like is provided above and below the laminated film 100 and heated by radiant heat) or the like. In the way of stretching between rolls, from From the viewpoint of the uniformity of the stretching temperature, a hot zone heating method is preferred.

When the stretching temperature is in the hot zone heating method, it means the ambient temperature in the hot zone (for example, in the heating furnace). In the heater heating method, when heating in the furnace, it means the ambient temperature in the furnace. Further, 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 be provided before the stretching step S20. The preheating method can use the same method as the heating method in the stretching treatment. The preheating temperature is preferably in the range of -50 ° C to ± 0 ° C of the stretching temperature, and more preferably in the range of -40 ° C to the stretching temperature to - 10 ° C in the stretching temperature.

Further, after the stretching treatment of the stretching step S20, a thermosetting treatment step may be provided. The heat treatment is a treatment in which the heat treatment is performed at a temperature higher than the crystallization while maintaining the tension state in a state where the end portion of the stretched film 200 is held by the clamp. By this thermosetting treatment, crystallization of the stretched polyvinyl alcohol-based resin film 6' can be promoted. The temperature of the thermosetting treatment is preferably in the range of -0 ° C to -80 ° C of the stretching temperature, and particularly preferably in the range of -0 ° C to -50 ° C in the stretching temperature.

(3) Dyeing step S30

Referring to Fig. 6, this step is a step of forming the polarizing film 5 by dyeing and aligning the polyvinyl alcohol-based resin film 6' of the stretched film 200 with iodine. Through this step, a polarizing laminate film 300 having a polarizing film 5 on one side or a double-layer layer of the base film 30' can be obtained.

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

Since the dyeing efficiency can be improved, it is preferred to add iodide to the aqueous 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. The concentration of the iodide in the aqueous dye 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 by weight ratio, particularly preferably from 1:6 to 1:80. The temperature of the aqueous dyeing solution is preferably from 10 to 60 ° C, particularly preferably from 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 is dissolved in a solvent. Examples of the crosslinking agent include boric acid, borax-like boride, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more. The solvent of the crosslinking solution may be water or may further contain an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is preferably from 0.2 to 20% by weight, particularly preferably from 0.5 to 10% by weight.

The crosslinking solution may further comprise an iodide. By the addition of the iodide, the polarizing performance in the plane of the polarizing film 5 can be made 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, particularly preferably from 0.5 to 8% by weight. The temperature of the crosslinking solution is preferably from 1 to 90 °C.

The crosslinking treatment can also be carried out simultaneously with the dyeing treatment by blending the crosslinking agent in the aqueous 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 used.

After the dyeing step S30, it is preferred to perform a washing step and a drying step before the first bonding step S40 described later. The washing step typically includes a water washing step. The water washing step 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 according to the iodide solution. The drying step performed after the washing step may be any appropriate method such as natural drying, air drying, and heat drying. For example, when heated and dried, the drying temperature is usually from 20 to 95 °C.

(4) First bonding step S40

Referring to FIG. 7, this step is a step of bonding a protective film to the polarizing film 5 of the polarizing laminate film 300, that is, a surface of the polarizing film 5 opposite to the side of the substrate film 30'. The step of bonding the film 400 is obtained. In the seventh embodiment, the first protective film 10 is bonded to the first adhesive layer 15, but when the polarizing plate 2 having the protective film on both sides is formed, the second adhesive layer 25 can be interposed. The second protective film 20 is bonded to it. The adhesive for forming the first adhesive layer 15 or the second adhesive layer 25 is as described above.

When the polarizing laminated film 300 has the polarizing film 5 on both surfaces of the base film 30', the protective film is usually bonded to the polarizing film 5 on both surfaces. At this time, the protective films may be the same type of protective film, or different types. Protective film.

When the first protective film 10 is bonded by using an active energy ray-curable adhesive, a method of bonding and adhering the protective film will be described, and the barrier is an active energy ray-curable adhesive of the first adhesive layer 15 . After the first protective film 10 is laminated on the polarizing film 5, the adhesive layer is cured by irradiation of ultraviolet rays, visible light, electron beams, and X-rays to activate the energy ray. Among them, ultraviolet light is preferred, and a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used as the light source.

When the protective film is bonded to the polarizing film 5, in order to improve the adhesion to the polarizing film 5, the bonding surface of the protective film and/or the polarizing film 5 can be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, or flame. Surface treatment (ease of subsequent treatment) of (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 bonding 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 laminated film 300 has the polarizing film 5 on both surfaces of the base film 30', and when the protective film is bonded to the polarizing film 5 of both of them, by the peeling step S50, one piece of polarized light can be obtained. The laminated film 300 obtained two polarizing plates with a protective film on one side.

The method of peeling off the base film 30' is not particularly limited, and it can usually be peeled off by the same method as the peeling step of the separator (release film) by the polarizing plate with the adhesive. The substrate film 30' can be used in the first 1 After the step S40 is applied, the film is directly peeled off, or after the first bonding step S40, it is once wound into a roll shape, and is peeled off while being rolled out in the subsequent step.

(6) Second bonding step S60

In this step, the protective film is further bonded to the polarizing film 5 of the polarizing plate having the protective film on one side thereof, that is, on the surface opposite to the protective film adhered in the first bonding step S40. The step of attaching the polarizing plate 2 of the protective film to both sides of the configuration shown in Fig. 2 is shown. When the first protective film 10 is bonded in the first bonding step S40, the second protective film 20 is bonded in this step, and when the second protective film 20 is bonded in the first bonding step S40, in this step, The first protective film 10 is bonded. The bonding of the second protective film 20 of the second adhesive layer 25 can be performed 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 base film and subsequently manufacturing a polarizing plate has been described in detail. However, the present invention is not limited thereto, and the first protective film 10 may be used as the first. The second protective films 10 and 20 are bonded to the polarizing film 5 composed of the monomer (separate) film formed by the film forming method of the above (b) to produce a polarizing plate.

The polyvinyl alcohol-based resin layer 6' composed of a monomer (separate) film and the polarizing film 5 can be produced by the following steps: for example, by a generally known method such as a melt extrusion method or a solvent casting method. a step of forming a polyvinyl alcohol resin film; a step of uniaxially stretching the polyvinyl alcohol resin film to obtain a polyvinyl alcohol resin layer 6'; and a step of dyeing the polyvinyl alcohol resin film with iodine to adsorb it And a step of treating the stretched polyvinyl alcohol-based resin film having iodine adsorbed thereon with a boric acid aqueous solution; and performing a water-washing treatment with a boric acid aqueous solution to obtain a polarizing film 5. Uniaxial stretching system It is carried out before, during or after dyeing of iodine. When uniaxially stretching after dyeing, the uniaxial stretching can be carried out before boric acid treatment or boric acid treatment. In addition, uniaxial stretching can also be performed in these multiple stages.

When both the first and second protective films 10 and 20 are bonded to each other to form a polarizing plate having a protective film on both sides, these protective films may be bonded to each other or laminated at the same time via the adhesive layer.

[Examples]

Hereinafter, the present invention will be more specifically described by showing examples and comparative examples, but the present invention is not limited to these 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 polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. A crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed with the obtained aqueous solution 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 a primer layer. liquid.

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 applied to the one surface, the primer layer was formed using a micro gravure coater. The coating liquid was applied to the corona-treated surface, and dried at 80 ° C for 10 minutes to form a primer layer having a thickness of 0.2 μm.

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

A polyvinyl alcohol system having a viscosity of 4 m% aqueous solution of 80 mPa ‧ sec The resin powder 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 film.

The coating liquid for forming a polyvinyl alcohol resin film is applied to the surface of the primer layer of the base film having the primer layer produced in the above (1) at a thickness of 130 μm using a die coater. Hot air of 70 ° C was blown to carry out drying. In the case of drying, the air velocity was changed while monitoring the water content by an infrared multicomponent meter ("IRMA-5162S" manufactured by CHINO Corporation), and the drying speed at a water content of 30% by weight was 1.30% by weight/sec. Way to control. Then, while controlling the average value of the drying rate of the water content from 30% by weight to 10% by weight to 1.35 wt%/sec, the drying was continued, and the drying was carried out until the water content became 4.86 wt%. The film thickness of the polyvinyl alcohol-based resin film after drying was 9.2 μm. In this way, a laminated film composed of a base film/primer layer/polyvinyl alcohol resin film was obtained.

(3) Production of stretched film (stretching step)

Using a floating longitudinal uniaxial stretching device (air stretching), the maximum temperature at 150 ° C during stretching in the air, 5.3 times the free end uniaxial stretching of the laminated film produced in the above (2), and obtained A stretched film of a stretched polyvinyl alcohol-based resin film is provided on the base film. The thickness of the polyvinyl alcohol-based resin film after stretching was 5.1 μm.

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

The stretched laminated film produced in the above (3) was immersed in a dyeing aqueous solution containing 30% by weight of iodine and potassium iodide (water containing 0.6 parts by weight of iodine and 10.0 parts by weight of potassium iodide) for about 180 seconds for dyeing. After 10 Wash the excess aqueous dye solution with pure water at °C.

Next, it was immersed in a first crosslinked aqueous solution containing 78% by weight of boric acid (water containing 10.4 parts by weight of boric acid per 100 parts by weight) for 120 seconds, and then immersed in a second crosslinked aqueous solution containing 70% of boric acid and potassium iodide (water per 100 parts by weight of 5.0 parts by weight of boric acid and 12.0 parts by weight of potassium iodide were added for 60 seconds, followed by immersion in pure water at 10 ° C for about 10 seconds for crosslinking treatment. Immediately thereafter, the liquid adhering to both surfaces was removed using a hair dryer 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)

A protective film made of a corona treatment on the bonding surface by an adhesive layer made of an ultraviolet curable adhesive ("KR-75T" manufactured by ADEKA Co., Ltd.) [consisting of a cyclic cycloolefin resin The protective film ("ZF14" manufactured by Zeon Japan Co., Ltd.) was bonded to the polarizing film of the polarizing laminated film produced in the above (4). Next, the high-pressure mercury lamp is irradiated with ultraviolet rays to cure the adhesive layer, and a laminated film composed of a layer of a protective film/adhesive layer/polarizing film/base film is obtained (first bonding step). Then, the base film is peeled off from the obtained bonding film, and a polarizing plate with a protective film on one side is obtained (peeling step).

(6) Production of a polarizing plate with a protective film on both sides (second bonding step)

A protective film (a transparent protective film made of a cyclic cycloolefin resin ("ZF14" manufactured by Zeon Japan Co., Ltd.)) which is subjected to a corona treatment, and is also bonded to the above (5). One side with a protective film The polarizing plate was peeled off from the surface of the polarizing film after the base film, and a polarizing plate having a protective film on both sides was obtained (second bonding step).

<Examples 2 to 7, Comparative Examples 1 to 5>

In the examples 2 to 7 and the comparative examples 1 to 5, the viscosity of the 4 wt% aqueous solution of the polyvinyl alcohol-based resin powder used in the step (2) is the value shown in the first table, and the above is appropriately adjusted ( The drying rate in the step of 2) was obtained by the same method as in Example 1 except that the crystal long period of the polyvinyl alcohol-based resin film was changed to the value shown in the first table. A resin film, a polarizing film, and a polarizing plate with a protective film on both sides.

[Measurement of Crystal Long Period of Polyvinyl Alcohol Resin Film]

The crystal long period L of the polyvinyl alcohol-based resin film obtained in the above (2) can be determined by small-angle X-ray scattering measurement by a penetrating method. A small-angle X-ray scattering analysis apparatus ("NANO-STAR" manufactured by Bruker AS Co., Ltd.) was used, and Cu-Kα (wavelength: 0.154 nm) was used as the radiation source. The camera length was adjusted to 1060 nm, and the detector used a two-dimensional PSPC (Position Sensitive Proportional Counter). The measurement was carried out at room temperature under a vacuum atmosphere, and the exposure time was set to 30 minutes. First, the background measurement is initially performed under the unset sample, and the obtained two-dimensional scattering data is integrated around the entire circumference to obtain a one-dimensional contour. Next, 64 pieces of the polyvinyl alcohol-based resin film obtained by peeling the base film from the laminated film were aligned in the longitudinal direction and superposed to serve as a sample for evaluation. After the measurement of the sample for evaluation, the same is also performed around the entire circumference to obtain a one-dimensional profile. The penetration light intensity at the time of background measurement and the transmitted light intensity at the time of measurement of the sample were used to calculate the transmittance of the sample for evaluation, and after considering the penetration rate, Estimate the one-dimensional profile of the sample, subtracting the one-dimensional contour of the background, and use it as the one-dimensional scattering profile of the sample for evaluation. A peak due to the periodic structure was observed around the diffraction angle (2θ) of about 1.1 degrees, and this was converted into a period long by the Bragg equation. The cycle length is set to the crystal long period L of the polyvinyl alcohol-based resin. The results are shown in Table 1.

[Determination of puncture strength of polarizing film]

The base film was peeled off from the polarizing laminate film obtained in the above (4), 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 by a contact type film thickness meter (trade name "DIGIMICRO MH-15M" manufactured by Nikon Co., Ltd.). Then, the installation has a front end diameter of 1 mm. Hand-held compression tester "KES-G5 needle penetration force measurement specification" manufactured by Kato Tech Co., Ltd., a 0.5R needle, under the conditions of a temperature of 23 ± 3 ° C, at a puncture speed of 0.33 cm / sec. The polarizing film was punctured, and the force applied to the needle when passing through the polarizing film was measured. This measurement was performed on 12 sheets of the evaluation sample, and the average value thereof was used as the measured value of the sample. The measured value is divided by the thickness of the polarizing film, thereby calculating the puncture strength per unit thickness. The results are shown in Table 1.

[Thermal shock test of polarizing plate]

The surface of the protective film adhered to the second bonding step of the polarizing plate having the protective film obtained by the above (6) is subjected to corona treatment, and then bonded with an acrylic adhesive (manufactured by Lintec Co., Ltd.) "P-3132"). The obtained polarizing plate with an adhesive layer was cut into a polarizing plate having a diagonal of 5 inches, and the polarizing plate was laminated to the glass using the adhesive layer to obtain a sample for evaluation. Then, with the cold made by Espec Co., Ltd. The thermal shock tester (TSA-301L-W) was held at a low temperature side of -40 ° C for 30 minutes, and then kept at a high temperature side of 85 ° C for 30 minutes, and this was used as a cycle, and this was subjected to a thermal shock test of 150 cycles. . In the thermal shock test, it is not exposed to normal temperature.

For the 50 samples for evaluation, a thermal shock test of 150 cycles was performed, and in the 50 samples for evaluation, the number of pieces having a crack-like appearance was visually confirmed on the polarizing film, and this was indicated as the first. The column of the "thermal shock test" of the table. For example, "0/50" in the first embodiment means that the number of sheets in which 50 sheets of the sample for evaluation are visually confirmed to have a crack-like appearance is zero.

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

The polarizing plate having the protective film obtained on the both sides obtained in the above (6) was dissolved in cyclohexane to remove two protective films to separate the polarizing film. The obtained polarizing film 64 was aligned and overlapped in the absorption axis direction (longitudinal direction) to serve as a sample for evaluation. The sample for evaluation was measured by a small angle X-ray scattering measurement in the same manner as the measurement of the crystal long period of the polyvinyl alcohol resin film. However, the exposure time is set to 60 minutes. The obtained two-dimensional scattering pattern was detected as a period long peak at a position inclined by 20 degrees from the absorption axis direction. In order to obtain a one-dimensional scattering profile in the absorption axis direction, the scattering in the range of ±5 degrees in the absorption axis direction is integrated to obtain a profile. Further, in order to carry out the correction of the background, the measurement in the state in which the sample for evaluation is not set is performed, and the same angular range is integrated to obtain the contour in the absorption axis direction. After considering the penetration rate, the contours are subtracted to obtain a one-dimensional profile of the absorption axis direction of the sample for evaluation. According to such a contour, with the expression of Prague Converted to a long period. This period is set to a long period L' in the absorption axis direction of the polarizing film. The results are shown in Table 1.

Similarly, in the cycle length direction (direction inclined by 20 degrees from the absorption axis direction), in order to obtain a one-dimensional profile, a range of ±5 degrees in the center direction of the cycle is integrated, and the profile in the cycle length direction is obtained in the same manner. According to this contour, the period of the cycle is converted by the expression of Bragg. This period is set to a long period in the longitudinal direction of the polarizing film. The results are shown in Table 1.

[Measurement of Viscosity of 4% by Weight Aqueous Solution of Polarizing Film constituting Polarizing Plate]

The polarizing plate having the protective film obtained on the both sides obtained in the above (6) was dissolved in cyclohexane to remove two protective films to separate the polarizing film. The polarized film after separation was suspended in an oven adjusted to 80 ° C and 90% RH, and subjected to a wet heat treatment for about 7 days. Thereby, iodine and boric acid are removed to obtain a transparent film. The obtained transparent film was dissolved and adjusted to a 4% by weight aqueous solution, and then the viscosity P' was measured. The method of measuring the viscosity P' is as described above. The results are shown in Table 1.

[investigation]

Fig. 8 is a test example of Examples 1 to 7 (puncture strength of 5.0 g/μm or more, no loss of appearance of the polarizing film was observed in the thermal shock test) and Comparative Examples 1 to 5 (puncture strength was less than 5.0 g/ Μm, a polyvinyl alcohol-based resin of a test example in which a loss of appearance was observed in a thermal shock test, a graph in which the viscosity P is plotted on the horizontal axis and the crystal long period L is plotted on the vertical axis. In Fig. 8, the points 1 to 7 of the examples are plotted as "○", and the points 1 to 5 of the comparative examples are plotted as "x". From Fig. 8, it can be confirmed that the curve of L &lt; 6.7909 × ln(P) - 17.337 is suitable as the boundary between the embodiment and the comparative example.

Fig. 9 is a view showing the polarizing film which is separated from the polarizing plates of Examples 1 to 7 and Comparative Examples 1 to 5, with the viscosity P' as the horizontal axis and the long period L' in the absorption axis direction as the vertical axis. Out of the chart. In Fig. 9, the points 1 to 7 of the examples are plotted as "○", and the points 1 to 5 of the comparative examples are plotted as "x". From Fig. 9, a curve of L' < 14.3 × ln(P') - 43.9 can be confirmed, which is suitable as a boundary line between the examples and the comparative examples.

Claims (5)

A polyvinyl alcohol-based resin film obtained by forming a film of a solution containing a polyvinyl alcohol-based resin, and a viscosity P (mPa ‧ s) of a 4% by weight aqueous solution of the polyvinyl alcohol-based resin The crystal long period L (nm) of the polyvinyl alcohol-based resin film satisfies the relationship of the following formula (1); L < 6.7909 × ln(P) - 17.337 (1). A polarizing film obtained by stretching and dyeing a polyvinyl alcohol-based resin film according to claim 1 of the patent application. A polarizing film having a viscosity P' (mPa‧s) in a 4% by weight aqueous solution and a long period L' (nm) in the absorption axis direction satisfying the relationship of the following formula (2); L'<14.3 × ln (P' )-43.9...(2). The polarizing film according to claim 2, wherein the puncture strength per unit thickness is 5.0 g/μm or more. A polarizing plate comprising: a polarizing film; and a protective film laminated on at least one side of the polarizing film; and a viscosity P′ (mPa·s) of a 4% by weight aqueous solution of the polarizing film separated from the polarizing plate The long period L' (nm) in the absorption axis direction of the polarizing film which is separated from the polarizing plate satisfies the relationship of the following formula (2); L'<14.3 × ln(P') - 43.9... ).