KR20180063205A - Polarizing film manufacturing method, polarizing film, and polarizing plate - Google Patents

Abstract

An object of the present invention is to solve the problems of folding and wrinkling in the pre-manufacturing process of a polarizing film, thereby producing a polarizing film having good productivity and less polarization unevenness. 1) a method for producing a polarizing film having a polyvinyl alcohol film unwound from a roll and transported in a horizontal direction, 2) water swelling process, 3) dyeing process, 4) stretching process, and 5) boric acid crosslinking process, 2. The method of manufacturing a polarizing film according to claim 1, wherein liquid is sprayed to both ends of the film in the width direction before and / or after any one of the steps (2) to (4) to prevent curling of the film.

Description

Polarizing film manufacturing method, polarizing film, and polarizing plate

The present invention relates to a polarizing film production method, a polarizing film and a polarizing plate for use in a liquid crystal display (hereinafter abbreviated as LCD) or the like, and more particularly to a polarizing film and a polarizing plate which are produced by using a polyvinyl alcohol- A method for producing a dyed polarizing film, a polarizing film produced by the method, and a polarizing plate using the polarizing film.

LCDs are used in portable information terminals, liquid crystal TVs, tabletop computers, electronic clocks, personal computers, word processors, automobile and machine instruments, and polarizers are used in these LCDs. As the polarizing plate, a protective film such as triacetyl cellulose is laminated on one side or both sides of a polarizing film made of a polyvinyl alcohol-based film in which an iodine or a dichroic dye is adsorbed and oriented, is generally used, A polarizing plate having a high transmittance and a high degree of polarization in order to provide an LCD having a contrast has been required.

The polarizing film described above is obtained by, for example, swelling a polyvinyl alcohol-based film with water (including hot water), dyeing with iodine, stretching to arrange iodine molecules, Followed by drying and crosslinking. Such a manufacturing process is carried out by continuously feeding a polyvinyl alcohol-based film from a roll and carrying it in a horizontal direction using a winding machine or a nip roll.

However, there has been a problem that the polarizing film can not be produced with high productivity since the film is absorbed or dehydrated by the water swelling, dyeing, stretching, boric acid crosslinking, and drying processes and curled and folded or wrinkled at the end portions in the width direction of the film. Particularly, when the film is thin, the film is broken due to such folding or wrinkling, and the production is interrupted. Such a problem of the end portion also affects the inside of the polarizing film to lower the polarization performance of the entire polarizing film or to make it difficult to uniformly attach the polarizing plate to the liquid crystal cell or to cause the unevenness or discoloration of the liquid crystal display image .

In recent years, with the enlargement of the screen of a liquid crystal TV or the like, a thinner and wider polarizing film is required than in the conventional product, and folding and wrinkling of the end portions must be eradicated.

In order to reduce such folding and creasing, a method of applying a predetermined tension in the width direction of the film by a drying process has been proposed (see, for example, Patent Document 1). In addition, there has been proposed a method in which water is jetted from both ends of the film in the width direction of the film during running underwater (see, for example, Patent Document 2).

Patent Document 1 JP 2006-189560 A Patent Document 2 JP H07-247378 A

However, in the technique disclosed in Patent Document 1, folding or wrinkling in the drying treatment step can be avoided. However, when folding or wrinkling occurs in any of the steps of water swelling, dyeing, stretching and boric acid crosslinking before the drying step, There is a problem that it can not be conveyed to a drying process.

In addition, in the technique disclosed in Patent Document 2, folding and wrinkling in the water can be avoided, but folding and wrinkling occurring in the air can not be prevented.

Therefore, the object of the present invention is to produce a polarizing film having good productivity and less polarization unevenness by solving the problems of folding and wrinkling in the manufacturing process of the polarizing film.

Therefore, the present invention provides the following aspects of the invention.

[Polarizing film production method]

1) a method for producing a polarizing film having a polyvinyl alcohol film unwound from a roll and transported in a horizontal direction, 2) water swelling process, 3) dyeing process, 4) stretching process, and 5) boric acid crosslinking process,

Wherein the film is prevented from curling by spraying a liquid to both end portions in the width direction of the film before and / or after any one of the steps (2) to (4).

[Polarizing film]

A polarizing film produced by the method for producing a polarizing film of the present invention.

[Polarizing plate]

A polarizing plate characterized in that a protective film is provided on at least one surface of the polarizing film of the present invention.

In the present invention, the " film width direction " is generally a direction orthogonal to the longitudinal direction of the strip-shaped film. In particular, in the case of a polyvinyl alcohol film which is fed in the horizontal direction by being withdrawn from the roll, it is a direction substantially perpendicular to the transport direction of the film, and typically refers to a direction when the distance between the edges of the film becomes shortest.

In the present invention, the width direction of the film is referred to as " TD direction ", and the transport direction of the film is referred to as " MD direction ".

In the following, the polyvinyl alcohol film is also simply referred to as " film ".

According to the polarizing film producing method of the present invention, it is possible to produce a polarizing film having a polarizing film at both ends in the width direction of the polyvinyl alcohol film before and / or after any one of 2) water swelling step, 3) dyeing step, and 4) The film is prevented from being curled by spraying, so that the entire surface of the film can be kept flat, so that folding or wrinkling can be avoided.

By the production method of the present invention, a polarizing film having a wide and long thin shape can be produced with good productivity, and a polarizing film having a uniform polarization degree from the central portion to the end portion of the polarizing film can be obtained. In addition, it is possible to easily manufacture a wide, wide thin polarizer, and it is possible to reduce unevenness and discoloration of a liquid crystal display image.

Fig. 1 is a diagram schematically showing the positions of injection of liquid in 1) a disk-cutting step, 2) water swelling step, and 3) dyeing step.
2 schematically shows the distance A between the surface of the water swelling tank and the roll a between the water swelling process and the dyeing process and the distance B between the roll a and the roll b Fig.
3A is a diagram showing a spray shape when a liquid is sprayed onto the surface of a polyvinyl alcohol-based film (PVA film).
FIG. 3B is a view showing a spray shape when a liquid is sprayed on the back surface of a polyvinyl alcohol-based film (PVA film).
Fig. 4 is a view showing an angle? 1 formed by the spraying direction and the film surface in the case of spraying liquid on the surface or the back surface of the polyvinyl alcohol-based film.
Fig. 5 is a graph showing an angle &thetas; 2 between the direction when the spraying direction is perpendicularly projected onto the surface of the polyvinyl alcohol-based film and the direction of transporting the polyvinyl alcohol-based film when the liquid is sprayed on the surface or back surface of the polyvinyl alcohol- Fig.
6 is a graph showing the relationship between the angle &thetas; 1 between the jetting direction and the film surface when the liquid is jetted onto the surface or the back surface of the polyvinyl alcohol-based film, and the direction when the jetting direction is perpendicularly projected onto the surface of the polyvinyl alcohol- 2 is an angle? 2 formed by the transport direction of the polyvinyl alcohol film.
Fig. 7 is a view showing an example of a spray shape when a liquid is sprayed onto a polyvinyl alcohol-based film. Fig.

Hereinafter, the configuration of the present invention will be described in detail, but these are only examples of preferred embodiments, and the present invention is not limited thereto.

The method for producing a polarizing membrane of the present invention comprises the steps of 1) feeding a polyvinyl alcohol film from a roll and transporting it in a horizontal direction, 2) water swelling process, 3) dyeing process, 4) stretching process, and 5) boric acid crosslinking process To produce a polarizing film. Further, 1) the step of feeding the polyvinyl alcohol film from the roll and transporting it in the horizontal direction is also referred to as 1) a step of winding the disc.

The polyvinyl alcohol-based film used in the above-mentioned 1) disc-winding step is formed by forming a polyvinyl alcohol-based resin on a film and winding it on a roll.

As the polyvinyl alcohol-based resin used in the polyvinyl alcohol-based film, a resin prepared by saponifying polyvinyl alcohol-based resin which is unmodified, that is, polyvinyl acetate obtained by polymerizing vinyl acetate is used. The polyvinyl alcohol film used in the present invention is not necessarily limited to this film but may be a copolymer of vinyl acetate and a component copolymerizable with a small amount (for example, 10 mol% or less, preferably 5 mol% or less) A polyvinyl alcohol-based resin obtained by saponifying a copolymer may be used. Examples of the component copolymerizable with vinyl acetate include unsaturated carboxylic acids (including salts, esters, amides, nitriles, etc.), olefins having 2 to 30 carbon atoms (e.g., ethylene, propylene, n -Butene, isobutene, etc.), vinyl ethers, and unsaturated sulfonate salts. It is also possible to use a modified polyvinyl alcohol-based resin obtained by chemically modifying a hydroxyl group after saponification.

As the polyvinyl alcohol-based resin, a polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain may also be used. Such a polyvinyl alcohol-based resin having a 1,2-diol structure in the side chain can be obtained by, for example, (i) saponifying a copolymer of vinyl acetate and 3,4-diacetoxy-1-butene, ) A method of saponifying and decarboxylating a copolymer of vinyl acetate and vinyl ethyl carbonate, (iii) saponifying a copolymer of vinyl acetate with 2,2-dialkyl-4-vinyl-1,3-dioxolane, (Iv) a method of saponifying a copolymer of vinyl acetate and glycerin monoaryl ether, and the like.

The weight average molecular weight of the polyvinyl alcohol-based resin is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, and more preferably 120,000 to 260,000 from the viewpoint of optical performance and stretchability.

The average saponification degree of the polyvinyl alcohol-based resin is preferably 98 mol% or more, particularly preferably 99 mol% or more, more preferably 99.5 mol% or more, particularly preferably 99.8 mol% or more to be.

As the polyvinyl alcohol-based resin to be used in the present invention, two or more other kinds such as modified species, modified amount, weight average molecular weight and average saponification degree may be used in combination.

The polyvinyl alcohol film used in the present invention is prepared by preparing an aqueous polyvinyl alcohol resin solution using the polyvinyl alcohol resin and discharging the aqueous solution to a casting mold such as a cast drum, And casting, film-forming, drying, and winding on a roll.

The polyvinyl alcohol resin aqueous solution may contain, in addition to the polyvinyl alcohol-based resin, a commonly used plasticizer such as glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, trimethyolpropane, It is preferable from the viewpoint of film formability that a surfactant of anionic, anionic, and / or cationic is contained.

The resin concentration of the polyvinyl alcohol-based resin aqueous solution is preferably 10 to 60% by weight, particularly preferably 15 to 55% by weight, and more preferably 20 to 50% by weight.

The temperature of the polyvinyl alcohol-based resin aqueous solution when discharged onto the cast mold is preferably 80 to 100 占 폚, particularly preferably 85 to 98 占 폚. The discharging rate of the polyvinyl alcohol resin aqueous solution discharged to the cast mold is preferably 0.1 to 5 m / min, particularly preferably 0.2 to 4 m / min, and more preferably 0.3 to 3 m / min.

The surface temperature of the cast mold such as a cast drum is preferably 40 to 99 占 폚, particularly preferably 60 to 95 占 폚.

Drying of the cast film is carried out by alternately bringing the surface and the back of the film into contact with the outer circumferential portion of a plurality of lines of the thermal roll. After drying with a hot roll, the film may be subjected to heat treatment. The heat treatment is preferably performed at 60 to 150 占 폚, particularly preferably 80 to 130 占 폚.

Both ends of the film may be slit-cut before the film is wound on a roll.

The thickness of such a polyvinyl alcohol-based film is preferably 5 to 60 占 퐉 in view of thinning of the polarizing film, and particularly preferably 5 to 30 占 퐉 in view of thinning, and more preferably, 10 to 30 mu m.

The width of the polyvinyl alcohol-based film is preferably 3 m or more, more preferably 4 m or more from the standpoint of size reduction, and more preferably 4 to 6 m from the standpoint of avoiding breakage.

The length of the polyvinyl alcohol-based film is preferably 4 km or more, particularly preferably 4.5 km or more, more preferably 5 km or more from the view point of large-area.

The upper limit of the length of the film is preferably 50 km or less, particularly preferably 40 km or less, more preferably 30 km or less, from the viewpoint of avoiding breakage.

In the production method of the present invention, a liquid is sprayed to both ends of the film to be transported in the transverse direction before and / or after any of the water swelling process, the dyeing process, and the stretching process, Prevent curl.

4) After the stretching step 5) After the boric acid crosslinking step 6) Thereafter, after the drying step, the liquid can be injected. However, in this step, since the film becomes hard due to crosslinking or drying, It is difficult to generate, and the effect of spraying is not remarkable.

The time of spraying the liquid is preferably from 2) water swelling process, 3) dyeing process, and 4) stretching process from the viewpoint of avoiding folding, 2) after water swelling process, and / or 3) And particularly preferably 2) from the viewpoint of avoiding the wrinkles, 2) after the water swelling process, and more preferably within 10 seconds after the water swelling process, from the viewpoint of planarization of the polarizing film.

The surface of the film to be sprayed is not particularly limited, and it is possible to spray the surface, back surface, and both surfaces. Generally, a polyvinyl alcohol film as a disc can be obtained by forming an aqueous solution of a polyvinyl alcohol resin by casting and casting in a casting mold such as a cast belt, and continuously drying the film. In such a drying process, there are many cases in which the two-sided state is not completely equal, and there are many cases where the water content on one side is small or the degree of crystallization is high. It is natural that the film having a low water content tends to be absorbed and stretched, so that the film tends to curl on the opposite surface side in the 2) water swelling process in the polarizing film production and 3) the dyeing process. In such a case, in the present invention, it is effective to inject liquid at both ends of the opposite surface side in the curl direction.

Examples of the liquid to be sprayed include liquids such as water (including hot water), methanol, ethanol, isopropyl alcohol, acid / alkaline water, dyeing solution, aqueous glycerin solution and aqueous solutions of various chemicals. Of these, liquids such as water and a staining solution are preferable from the viewpoint of not adversely affecting the performance of the polarizing film, and water is particularly preferable from the viewpoint of facility simplicity. When water is used, the water temperature is preferably 10 to 50 占 폚, particularly preferably 20 to 40 占 폚.

Misted liquid may be used as the liquid to be sprayed, and water in the mist state is preferable from the viewpoints of not adversely affecting the performance of the polarizing film and simplicity of facilities. Hereinafter, the liquid in the mist state is simply referred to as " mist ".

Here, the term mist generally refers to a state in which a liquid is artificially fogged and refers to a minute droplet. The particle size of the mist is usually submicron to several hundred microns. The particle size of the mist used in the present invention is preferably 1 to 500 mu m, particularly preferably 2 to 100 mu m, and more preferably 3 to 50 mu m. If the particle size of the mist is too large, jetting unevenness tends to occur. If the particle size of the mist is too small, control of the jetting pressure becomes difficult, and there is a tendency to float and adversely affect the environment.

The spraying of the mist can be carried out using a commercially available mist spraying apparatus. Examples of such a mist spraying apparatus include a one-fluid system in which a liquid compressed by a pump is sprayed from a nozzle, and a fluid system in which a mist formed by colliding a compressed liquid with compressed air is sprayed. It is desirable to use a first-hand system for the convenience of facilities. The mist flow rate at the time of spraying is preferably 0.01 to 1 L / min, particularly preferably 0.1 to 0.5 L / min, from the viewpoint of the jetting effect.

The ejection shape of the mist from the nozzle may be a point shape, a line shape, a circle shape, an ellipse shape, or the like, but in the present invention, a circle shape is preferable from the viewpoint of a jetting effect. The jetting angle is not particularly limited, but is preferably 1 to 90 degrees from the viewpoint of jetting effect. When a liquid other than water is used, a plastic nozzle having excellent corrosion resistance is preferable.

Hereinafter, the present invention will be described by way of example, as a preferred embodiment of the present invention, 2) the case of spraying liquid after the water swelling process.

Generally, 2) the water swelling process is preferably 10 to 45 캜, particularly preferably 20 to 35 캜, preferably 0.1 to 10 min, particularly preferably 0.1 to 10 min, from the viewpoint of controlling the degree of swelling of the polyvinyl alcohol- Followed by immersion in water for 0.5 to 5 minutes. Water may contain a small amount of an additive such as an iodide compound, a surfactant, or an alcohol.

For example, as shown in Fig. 1, a polyvinyl alcohol film wound on a roll is taken out from the roll and is transported in the horizontal direction 1) The polyvinyl alcohol film put in the water swelling tank is subjected to a disc-winding step. 2) The water swelling of the polyvinyl alcohol-based film is carried out by the water swelling process. Thereafter, the polyvinyl alcohol film pulled up from the water swell bath is transferred to the dye bath through the roll, and 3) the polyvinyl alcohol film is stained in the dyeing step.

In the present invention, the injection of the liquid to both ends of the film is preferably performed on the film as described above, 2) after the water swelling process, and 3) until the dyeing process. Such folding or wrinkling is most likely to occur between such processes and is not easily peeled off once the films adhere to each other due to folding or creasing. In the case where folding or wrinkling occurs in such a process, the processes of 2) and 3) are the first process of the polarizing film production, so that the influence on the subsequent process is very large. The specific position of the injection is, for example, 2) immediately after the water swelling bath of the water swelling process and immediately after the first roll (a). The position and direction of injection are schematically shown by the arrows in Fig.

In the present invention, as shown in Fig. 2, it is preferable that the distance (A) until the film exits the water swell tank in the water swelling step and comes into contact with the first roll (a) is 1 m or less, Is a case where the distance B from the first roll (a) to the roll (b) just before dyeing is also 1 m or less. If the distance A is too long, folds or wrinkles tend to increase. The distance A from the water swelling tank to the roll a indicates the shortest distance from the surface of the water swelling tank to the roll a and is the distance from the first roll a to the roll b immediately before the dyeing And the distance B represents the shortest distance between the roll (a) and the roll (b).

The tensile force between rolls in a series of steps is preferably 1 to 100 N / m. If the tensile force between the rolls is too large, it tends to break. On the other hand, if it is too small, folding and wrinkling tend to be increased.

 In addition, the feed rate of the film from 2) the water swelling process to the 3) dyeing process is preferably 1 m / min or more, particularly preferably 1.5 m / min or more, more preferably 2 m / min or more .

In the case of jetting by liquid, it is preferable to use a nozzle to eject liquid onto one side or both sides of both ends in the width direction of the film. At this time, as shown in Fig. 3A, the liquid may be ejected onto the surface of the film, or the liquid may be ejected to both sides of the film, as shown in Fig. 3B. Such nozzles are not particularly limited, and known nozzles such as point ejection nozzles, line ejection nozzles, and surface ejection nozzles can be used, but point ejection is preferable from the viewpoint of control of the ejection position. A plurality of nozzles of the same kind may be provided, or a plurality of nozzles may be combined.

As shown in Fig. 2, the position of the nozzle is preferably from the point of avoiding folding of the film until the film comes into contact with the transport roll (a) after the water swelling tank in the water swelling process comes out, The distance from the outlet of the water swelling tank to the nozzle is preferably within 1 m from the viewpoint of avoiding wrinkles of the film, and more preferably within 0.5 m from the transporting roll (a) to the nozzle from the viewpoint of flatness of the film. The distance from the outlet of the water swell tank to the nozzle and the distance from the transport roll (a) to the nozzle indicate the shortest distance, respectively.

The distance between the nozzle and the film surface is preferably a distance of 1 to 100 mm from the viewpoint of avoiding the folding of the film, particularly preferably 2 to 50 mm from the viewpoint of avoiding wrinkles of the film. The distance between the nozzle and the film surface indicates the shortest distance, and more specifically, the distance between the nozzle surface and the film surface in a direction perpendicular to the film surface.

In the present invention, the flow velocity of the jet and the jetting angle are important from the viewpoint of the effect of preventing the curl.

The flow rate of the jet is preferably 0.01 to 5 m / sec, particularly preferably 0.02 to 3 m / sec, and more preferably 0.03 to 2 m / sec. If the flow velocity is too low, the effect of curl prevention tends to be lowered, and if the flow velocity is too high, the film tends to have a ripple.

When the direction of ejection of the liquid is perpendicular to the plane of the film, in other words, when the film surface is viewed in the direction perpendicular to the film plane, the direction of ejection of the liquid changes in the width direction of the film (TD direction) ) Is not parallel. Therefore, preferably, the angle of ejection of the liquid is not limited to the angle &thetas; 1 between the ejection direction of the liquid and the surface of the film but also the direction when the ejection direction of the liquid is perpendicularly projected to the surface of the film, 2 " (refer to Figs. 4 to 6).

In Fig. 6, the film transport direction is the x-axis, the film width direction is the y-axis, and the direction perpendicular to the film plane is the z-axis. The film plane is the xy plane, Is a plane perpendicular to the film plane, and a plane parallel to the transport direction of the film is defined as an xz plane.

The angle &thetas; 1 between the direction of ejection of the liquid and the plane of the film is preferably 5 to 80 DEG, particularly preferably 10 to 70 DEG, and more preferably 20 to 60 DEG. If the spraying angle? 1 is too low, the effect of preventing curling tends to deteriorate, and if it is too high, the film tends to have a ripple.

The angle &thetas; 2 between the direction in which the liquid ejection direction is perpendicularly projected to the surface of the film and the conveying direction (MD direction) of the film is preferably 5 to 175 DEG, more preferably 20 to 90 DEG, More preferably 30 to 60 degrees. If the spraying angle? 2 is too low, the effect of curl prevention tends to be deteriorated. If it is too high, wrinkles tend to occur in the film.

7, when a plurality of nozzles are used, the flow velocity and the spray angle of such a jet may be the same for all the nozzles or may be different for each nozzle. As a different method for each nozzle, for example, there may be mentioned a method in which the injection flow velocity is gradually decreased from the upstream side to the downstream side in the transport direction (MD direction) of the film, or the injection angle? 1 is gradually lowered .

In this way, the polyvinyl alcohol film is transported to the following 3) dyeing process and 4) stretching process in the state without folding or wrinkling.

The polarizing film of the present invention can be produced by a process such as 1) a step of unwinding a disc, 2) a water swelling process, 3) a dyeing process, 4) a stretching process, 5) a boric acid crosslinking process, do. Such a manufacturing process is not necessarily performed in the order of 2) to 5), but a plurality of processes may be appropriately combined. For example, 2) water swelling process 4) stretching process 2) water swelling process 3) dyeing process 4) stretching process, 2) water swelling process, 3) After the dyeing step, 5) the boric acid crosslinking step 4), the stretching step may be performed, 2) the water swelling step, 3) the dyeing step, and 5) the boric acid crosslinking step. You may.

Hereinafter, the process after 2) water swelling will be described.

3) The dyeing process is carried out by bringing the film into contact with a liquid containing iodine or a dichroic dye. Usually, an aqueous solution of iodine-potassium iodide is used, the concentration of iodine is 0.1 to 2 g / L, and the concentration of potassium iodide is preferably 1 to 100 g / L. Dyeing time is practically 30 to 500 seconds. The temperature of the treatment bath is preferably 5 to 50 占 폚. The aqueous solution may contain a small amount of an organic solvent compatible with water in addition to the water solvent. As the contact means, any means such as immersion, application, and spraying can be applied.

4) The stretching step is a step of stretching in the uniaxial direction, preferably 3 to 10 times, and particularly preferably 3.5 to 6 times. At this time, a slight stretching (a degree of preventing the shrinkage in the width direction or further stretching) may be performed even in the direction perpendicular to the stretching direction. The temperature at the time of stretching is preferably selected from a temperature range of 30 to 170 캜. The stretching magnification may be set to the above range, and the stretching operation may be carried out not only at the first stage but also at any stage of the manufacturing process.

5) The boric acid crosslinking process is carried out using a boron compound such as boric acid or borax. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture in a concentration of about 10 to 100 g / L, and a small amount of potassium iodide in the solution is preferable from the viewpoint of stabilization of the polarization performance. The temperature for the treatment is preferably about 30 to 70 DEG C, and the treatment time is preferably about 0.1 to 20 minutes.

Thereafter, the film may be subjected to a cleaning treatment. By the cleaning treatment, the precipitate generated on the surface of the film can be removed. The cleaning treatment is carried out, for example, by immersing a polyvinyl alcohol film in an aqueous iodide solution such as water or potassium iodide. When potassium iodide aqueous solution is used, the concentration of potassium iodide is preferably 1 to 80 g / L. The temperature for the cleaning treatment is usually 5 to 50 占 폚, preferably 10 to 45 占 폚. The treatment time is usually from 1 to 300 seconds, preferably from 10 to 240 seconds. The washing with water and the washing with an aqueous solution of potassium iodide may be suitably combined. The film may then be subjected to a drying step.

The drying process may be carried out at 40 to 80 ° C for 1 to 10 minutes in the atmosphere.

The degree of polarization of the polarizing film thus obtained is preferably 99.8% or more, and more preferably 99.9% or more. When the degree of polarization is too low, the contrast in the liquid crystal display tends to be insufficient.

In addition, the degree of polarization is defined as a ratio of the light transmittance (H ₁₁ ) measured with respect to the wavelength? In a state in which two polarizing films are overlapped so that their alignment directions are the same, (H ₁ ) measured with respect to the wavelength? In accordance with the following formula.

_{[(H 11 -H 1) / (} H 11 + H 1) ] ^{/ 2}

The single transmittance of the polarizing film of the present invention is preferably 42% or more. If such a simple mass transmittance is too low, the brightness of the liquid crystal display tends to be unable to be achieved.

The mass transmittance is a value obtained by measuring the light transmittance of a single polarizing film using a spectrophotometer.

The width of the polarizing film of the present invention is preferably not less than 1 m, more preferably not less than 1.3 m from the viewpoint of large surface area, and more preferably not less than 1.5 m from the viewpoint of large- 2.5 m.

The thickness of the polarizing film of the present invention is preferably 15 占 퐉 or less, particularly preferably 10 占 퐉 or less from the viewpoint of further thinning, more preferably 2 to 9 占 퐉, 8 mu m.

The polarizing film of the present invention thus obtained is suitable for producing a high-performance polarizing plate since the polarization unevenness is small.

Hereinafter, a method for producing a polarizing plate using the polarizing film of the present invention will be described.

The polarizing film of the present invention is a polarizing plate obtained by adhering an optically isotropic resin film as a protective film to one side or both sides thereof with an adhesive. Examples of the protective film include cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cycloolefin polymer, cycloolefin copolymer, polystyrene, polyether sulfone, polyarylene ester, And films or sheets such as polyethylene, polypropylene, polyethylene, polypropylene, polyethylene, polypropylene, polyethylene, polypropylene,

The bonding method is carried out by a known method. For example, a liquid adhesive composition is uniformly applied to a polarizing film, a protective film, or both, .

For the purpose of thinning the polarizing film, it is also possible to apply a curable resin such as a urethane resin, an acrylic resin or a urea resin to one side or both sides of the protective film and cure it to form a polarizing plate.

The polarizing film and the polarizing plate obtained by the present invention are excellent in polarizing performance and can be used in a portable information terminal, a PC, a television, a projector, a signage, an electronic tabletop calculator, an electronic clock, a word processor, an electronic paper, a game machine, , Anti-reflection layer for optical devices, medical devices, construction (eg, LCDs, LCDs, organic EL, electronic paper, etc.), liquid crystal display devices such as audio, automobile and machinery instruments, sunglasses, anti- Materials, toys and the like.

(Example)

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

<Measurement Conditions>

The polarizabilities of the polarizing films obtained in Examples and Comparative Examples were measured as follows. The degree of polarization at the central portion in the width direction of the obtained polarizing film and both ends (positions 10 cm from each end) was measured using RETS-1100 A manufactured by Otsuka Denshi Co.,

&Lt; Example 1 &gt;

(Production of polyvinyl alcohol film)

1000 kg of a polyvinyl alcohol resin having a weight average molecular weight of 142,000, a degree of saponification of 99.8 mol%, 2500 kg of water and 100 kg of glycerin as a plasticizer were charged and the temperature was raised to 140 캜 with stirring to adjust the concentration to a resin concentration of 25% To obtain a dissolved polyvinyl alcohol-based resin aqueous solution.

Subsequently, the polyvinyl alcohol resin aqueous solution was fed to a twin-screw extruder having a vent and defoamed. Thereafter, the temperature of the aqueous solution was set at 95 占 폚, and a casting drum having a surface temperature of 90 占 폚 was ejected from a T- Min.

Subsequently, the obtained film was dried with a plurality of heat rolls, and subjected to a heat treatment at 120 DEG C for 3 minutes using a floating drier. The film was slit with a width of 4 m and cut off. Finally, a polyvinyl alcohol film (4 m wide, 5 km long, 15 탆 thick) in the form of a belt having a moisture content of 2% by weight was wound on an aluminum pipe having an outer diameter of 17 cm, an inner diameter of 16 cm and a length of 4.4 m, A roll was obtained.

(Production of polarizing film)

The obtained polyvinyl alcohol film was taken out from the roll and conveyed in the horizontal direction (1) disc pulling step), and stretched in the conveying direction while being dipped in warm water in a swelling bath of water and stretched in the conveying direction ) [2) Water swelling process].

The film was pulled up from the water swelling tank and was fed from both sides of the film horizontally (roll distance: 1 m, inter roll tension: 20 N / m) horizontally at both ends of the film conveyed at a conveying speed of 2 m / Water (23 ° C) was sprayed to prevent curling. The spraying condition of such water is as follows.

Nozzle: Miss Misa manufactured just hose

Nozzle Location: 1m from the water swelling tank

Nozzle position (height): 5 mm from the top of the film

Injection flow rate: 0.1 m / sec

Injection angle θ1: 30 °

Injection angle θ2: 45 °

The obtained film was stretched in the conveying direction while dying in an aqueous solution containing 0.9 g / L of iodine and 30 g / L of potassium iodide (0.5 min at 28 DEG C, 1.6 times in stretching). [3] Dyeing Step]

Subsequently, it was immersed in an aqueous solution having a composition of boric acid of 25 g / L and potassium iodide of 30 g / L, and uniaxially stretched in the conveying direction while the boric acid was crosslinked (55 ° C for 1 minute, draw ratio 2.0 times).

Thereafter, the film was washed with an aqueous solution of potassium iodide and dried to obtain a polarizing film having a total draw ratio of 5.4 times (width: 1.8 m, thickness: 7 탆). No break or wrinkle was observed in the obtained polarizing film, and no break occurred over a length of 12 km. Table 1 shows the polarization characteristics of the obtained polarizing film.

(Production of polarizing plate)

A triacetyl cellulose film (TAC film) having a thickness of 40 占 퐉 was applied to both surfaces of the obtained polarizing film using a polyvinyl alcohol aqueous solution as an adhesive, and dried at 50 占 폚 to obtain a polarizing plate. Polarization unevenness was not observed in the obtained polarizing plate.

&Lt; Examples 2 to 4 &

A polarizing film was obtained in the same manner as in Example 1 except that the conditions for spraying in Example 1 were changed to those shown in Table 1. [ The obtained polarizing film had no folding or wrinkles, and no breakage occurred over a length of 12 km. The obtained polarizing film was evaluated in the same manner as in Example 1. [ The evaluation results are shown in Table 1. Further, a polarizing plate was obtained in the same manner as in Example 1. Polarization unevenness was not observed in the obtained polarizing plate.

&Lt; Example 5 &gt;

A polarizing film was obtained in the same manner as in Example 1 except that water was changed to a mist state in Example 1. Such mist spraying conditions are as follows.

Nozzle: Heat jet nozzle manufactured by Spraying Systems Co.

Nozzle Location: 1m from the water swelling tank

Nozzle position (height): 5 mm from the top of the film

Injection flow rate: 0.1m / sec injection

Angle &amp;thetas; 1: 30 DEG

Injection angle θ2: 45 °

Mist particle size: 20 탆

Mist flow rate: 0.2 L / min

The obtained polarizing film was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. Further, a polarizing plate was obtained in the same manner as in Example 1. Polarization unevenness was not observed in the obtained polarizing plate.

&Lt; Examples 6 to 8 &

A polarizing film was obtained in the same manner as in Example 5 except that the conditions for spraying in Example 5 were changed to those shown in Table 1. [ The obtained polarizing film had no folding or wrinkles, and no breakage occurred over a length of 12 km. The obtained polarizing film was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. Further, a polarizing plate was obtained in the same manner as in Example 1. Polarization unevenness was not observed in the obtained polarizing plate.

&Lt; Comparative Example 1 &

Production of a polarizing film was started in the same manner as in Example 1 except that injection was not performed in Example 1. However, 2) folding or wrinkling was observed at both ends of the film after the water swelling process, and a polarizing film having a length of 1 km was produced, and a breaking occurred in the dyeing bath. Table 1 shows the polarization characteristics of the obtained portion. In addition, the polarizing plate could not be produced because of breakage.

As shown in Table 1, when the polarizing film of the present invention is produced, a polarizing film having a long length can be obtained without folding or wrinkling. In addition, since the degree of polarization is high not only at the center portion of the polarizing film but also at both end portions in the width direction, a polarizing film having a uniform degree of polarization from the central portion to the end portion of the polarizing film can be obtained. In addition, it is possible to easily manufacture a wide, wide thin polarizer, and it is possible to reduce unevenness and discoloration of a liquid crystal display image.

The polarizing film of the present invention can be used in portable information terminals, PCs, televisions, projectors, signage, electronic tabletop calculators, electronic clocks, word processors, electronic papers, game machines, video cameras, photo albums, Reflective coatings for display devices (CRT, LCD, organic EL, electronic paper and the like), optical communication devices, medical equipment, building materials, toys, etc. for use in liquid crystal display devices, sunglasses, antiglare glasses, stereoscopic glasses, wearable displays,

PVA film: polyvinyl alcohol film
θ1 (°): the angle between the direction of injection and the plane of the film
? 2 (°): An angle formed between the direction in which the injection direction is perpendicularly projected to the surface of the polyvinyl alcohol film and the transport direction of the polyvinyl alcohol film
Distance A: Distance between the surface of the water swelling tank and the roll (a)
Distance B: Distance between roll (a) and roll (b)

Claims (15)

1) a method for producing a polarizing film having a polyvinyl alcohol film from a roll and feeding it in a horizontal direction, 2) water swelling process, 3) dyeing process, 4) stretching process, and 5) boric acid crosslinking process,
The method of manufacturing a polarizing film according to any one of the above 2) to 4), wherein liquid is sprayed to both end portions in the width direction of the film to prevent curling of the film. The method according to claim 1,
Wherein the spraying of the liquid is carried out after 2) the water swelling step. The method according to claim 1 or 2,
Wherein an angle between an ejecting direction of the liquid and a surface of the film is 5 to 80 degrees. 4. The method according to any one of claims 1 to 3,
Wherein an angle between the direction when the liquid ejection direction is perpendicularly projected to the surface of the film and the conveying direction of the film is 5 to 175 degrees. 5. The method according to any one of claims 1 to 4,
Wherein the liquid is injected at a flow rate of 0.01 to 5 m / sec. 6. The method according to any one of claims 1 to 5,
Wherein the liquid is water or a dyeing solution. 7. The method according to any one of claims 1 to 6,
Wherein the liquid is a liquid in a mist state. The method of claim 7,
Wherein the liquid in the mist state is formed by spraying the compressed liquid from the nozzle. The method according to claim 7 or 8,
Wherein the mist has a particle diameter of 1 to 500 mu m in the liquid in the mist state. The method according to any one of claims 7 to 9,
Wherein a flow rate of the liquid in the mist state is 0.01 to 1 L / min. The method according to any one of claims 1 to 10,
Wherein the film conveying speed from the 2) water swelling step to the 3) dyeing step is 1 m / min or more. The method according to any one of claims 1 to 11,
Wherein the thickness of the polarizing film is 15 占 퐉 or less. The method according to any one of claims 1 to 12,
Wherein the width of the polarizing film is 1 m or more. A polarizing film produced by the method for producing a polarizing film according to any one of claims 1 to 13. The polarizing plate according to claim 14, wherein a protective film is provided on at least one surface of the polarizing film.

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