KR20210102853A - Method for manufacturing polarizing plate - Google Patents

Abstract

The purpose of the present invention is to provide a method for manufacturing a polarizing film capable of providing a polarizing film which is highly effective in preventing yellowing even when exposed to a high temperature environment exceeding 95℃. More specifically, the present invention provides a method for manufacturing a polarizing film from a polyvinyl alcohol-based resin film, comprising: a first treatment step of contacting the polyvinyl alcohol-based resin film with a first treatment liquid, wherein the first treatment liquid comprises boric acid and an iodide compound, and has a pH of 5.0 or more at 25℃.

Description

The manufacturing method of a polarizing film {METHOD FOR MANUFACTURING POLARIZING PLATE}

This invention relates to the manufacturing method of a polarizing film, Furthermore, it also relates to the manufacturing method of a polarizing plate, a polarizing film, a polarizing plate, and an image display apparatus.

In recent years, the image display device containing a polarizing plate is used not only for mobile devices, such as a cellular phone and a tablet terminal, but also as an image display device for vehicle installations, such as a car navigation device and a back monitor, The use is expanding. . Accordingly, the image display device is required to have high durability under a harsher environment (eg, under a high temperature environment) than conventionally required.

It is disclosed by patent document 1 that pH of a polarizer is reduced and providing the polarizing plate excellent in an optical characteristic and wet-heat durability. Patent Document 1 describes a method of lowering the pH of the polarizer by setting the pH of the dura mater to 1.5 to 3.2.

[Patent Document 1] Japanese Patent Laid-Open No. 2005-62458

Since polyenization of polyvinyl alcohol advances when the polarizing film contained in a polarizing plate is exposed to high temperature environment, the problem of yellowing arises. In particular, under severe temperature conditions exceeding 95°C (eg, 105°C, etc.), the progress of yellowing tends to become more remarkable.

An object of this invention is to provide the manufacturing method of the polarizing film which can provide the polarizing film excellent in the yellowing inhibitory effect even when exposed to the high temperature environment exceeding 95 degreeC.

Another object of the present invention is to provide a method for manufacturing a polarizing plate having a polarizing film excellent in yellowing suppression effect even under a high temperature environment exceeding 95° C., the polarizing film, the polarizing plate, and an image display device including the polarizing plate The purpose.

MEANS TO SOLVE THE PROBLEM This invention provides the manufacturing method of a polarizing film shown below, the manufacturing method of a polarizing plate, a polarizing film, a polarizing plate, and an image display apparatus.

[1] A method for producing a polarizing film from a polyvinyl alcohol-based resin film, comprising:

A first treatment step of bringing the polyvinyl alcohol-based resin film into contact with a first treatment solution,

The said 1st process liquid contains a boric acid and an iodide compound, Furthermore, the manufacturing method of the polarizing film whose pH in 25 degreeC is 5.0 or more.

[2] a second treatment step of bringing the polyvinyl alcohol-based resin film into contact with a second treatment solution;

The said 2nd process liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is less than 5.0,

The said 2nd processing process is the manufacturing method of the polarizing film as described in [1] performed before the said 1st processing process.

[3] The manufacturing method of the polarizing film as described in [1] or [2] whose pH in 25 degreeC is 6.5 or less in the said 1st process liquid.

[4] A test piece having an area of 1500 cm2 obtained by cutting the polarizing film was immersed in 10 ml of 25°C pure water and left for 10 minutes, and the pH of the immersion solution at 25°C after taking out the test piece was 5.3 or more [ The manufacturing method of the polarizing film in any one of 1]-[3].

[5] The process of manufacturing a polarizing film by the manufacturing method of the polarizing film in any one of [1]-[4];

A method of manufacturing a polarizing plate having a bonding process of bonding a protective film to one side or both sides of the polarizing film through a bonding layer.

[6] A polarizing film having a pH of 5.3 or more at 25°C of the immersion liquid after immersing the polarizing film having an area of 1500 cm2 in 10 ml of 25°C pure water and leaving it to stand for 10 minutes, and taking out the polarizing film.

[7] The polarizing film according to [6], wherein the polyvinyl alcohol-based resin film is dyed with a dichroic dye.

[8] A polarizing plate comprising the polarizing film according to [6] or [7], and a protective film laminated on one side or both sides of the polarizing film through a bonding layer.

[9] An image display device in which the polarizing plate according to [8] and an image display element are laminated.

[10] A polarizing film having a bonding layer in which bonding layers are laminated on both surfaces of the polarizing film,

A polarizing film having a bonding layer having an area of 1500 cm2 is immersed in 10 ml of 25°C pure water and left for 10 minutes, and the pH at 25°C of the immersion liquid after taking out the polarizing film having the bonding layer is more than 3.4 A polarizing film having a bonding layer.

[11] A polarizing plate in which a protective film is laminated on the bonding layer of the polarizing film having the bonding layer according to [10].

[12] An image display device in which the polarizing plate according to [11] and an image display element are laminated.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method by which the polarizing film excellent in yellowing suppression effect is obtained even under the high temperature environment exceeding 95 degreeC, the manufacturing method of the polarizing plate provided with the said polarizing film, the said polarizing film, the said polarizing plate, and the image provided with the said polarizing plate A display device may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically the manufacturing method of the polarizing film which concerns on this invention, and an example of the polarizing film manufacturing apparatus used for it.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention was described referring drawings, this invention is not limited to the following embodiment. In the drawings, the scale is appropriately adjusted for easy understanding of each component, and the scale of each component shown in the drawing and the scale of the actual component do not necessarily coincide.

<Method for producing polarizing film>

In this embodiment, a dichroic dye (iodine and a dichroic dye) is adsorbing-oriented to the polyvinyl alcohol-type resin film uniaxially stretched as for a polarizing film. The polyvinyl alcohol-type resin which comprises a polyvinyl alcohol-type resin film is obtained by saponifying polyvinyl acetate-type resin normally. The saponification degree is usually about 85 mol% or more, preferably about 90 mol% or more, and more preferably about 99 mol% or more. The polyvinyl acetate-based resin may be, for example, a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polymerization degree of polyvinyl alcohol-type resin is about 1000-10000 normally, Preferably it is about 1500-5000.

These polyvinyl alcohol-type resins may be modified|denatured, for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, etc. can be used.

In the present embodiment, as a starting material for polarizing film production, unstretched poly having a thickness of 65 µm or less (eg 60 µm or less), preferably 50 µm or less, more preferably 35 µm or less, still more preferably 30 µm or less. A vinyl alcohol-based resin film (original film) is used. Accordingly, it is possible to obtain a thin-film polarizing film, which is increasingly in demand in the market. The width of the raw film is not particularly limited, and may be, for example, 400 to 6000 mm. A raw film is prepared, for example as a roll (original roll) of a long unstretched polyvinyl alcohol-type resin film.

The polarizing film is continuously conveyed along the film conveyance path of the polarizing film manufacturing apparatus while unwinding the above-described elongate raw film from the raw roll, and immersed in the treatment liquid (hereinafter referred to as "treatment bath") accommodated in the treatment tank. It can manufacture continuously as a long polarizing film by performing a drying process after implementing the predetermined|prescribed processing process drawn out later. In addition, the treatment step is not limited to a method of immersing the film in a treatment bath as long as it is a method of treating the film by contacting the treatment liquid, and a method of treating the film by attaching the treatment liquid to the film surface by spraying, dripping, dripping, etc. it's good too When the treatment step is performed by a method of immersing the film in a treatment bath, the treatment bath for performing one treatment step is not limited to one, and one treatment step is completed by sequentially immersing the film in two or more treatment baths. you can do it

Examples of the treatment liquid include swelling liquid, dyeing liquid, crosslinking liquid, complementary color liquid, and washing liquid. And, as the treatment step, a swelling step of performing a swelling treatment by contacting the raw film with a swelling solution, a dyeing step of performing a dyeing treatment by contacting the dyeing solution with the film after the swelling treatment, and a crosslinking solution to the film after the dyeing treatment Examples include a crosslinking step of performing crosslinking treatment by contacting a crosslinking step, a complementary color step of performing a complementary color treatment by contacting a complementary color solution to the film after crosslinking treatment, and a cleaning step of performing a cleaning treatment by contacting the complementary color treatment film with a cleaning solution. In addition, between these series of treatment steps (that is, before and after any one or more treatment steps and/or during any one or more treatment steps), the uniaxial stretching treatment is performed in a wet or dry manner. You may add another treatment process as needed.

In the present specification, a treatment liquid containing boric acid and an iodide compound and having a pH of 5.0 or higher at 25°C is referred to as a first treatment liquid, containing a boric acid and an iodide compound, and a pH of 5.0 at 25°C The lesser processing liquid is called a 2nd processing liquid. Since both the 1st treatment liquid and the 2nd treatment liquid contain boric acid and an iodide compound, it can also be used for the crosslinking treatment of crosslinking a film after a dyeing process, and can also be used for the complementary color treatment which adjusts the hue of a film. Moreover, since the numerical range of pH of both a 1st process liquid and a 2nd process liquid is limited, it can also be used for the pH adjustment process which adjusts the pH of a film.

In this embodiment, the 1st processing process of making a film contact a 1st processing liquid may be included, and the 2nd processing process of making a film contact a 2nd processing liquid may be included. When a 2nd processing process is included, it is preferable to perform before a 1st processing process, It is preferable to process in order of a 2nd processing process, a 1st processing process, When a washing process is included, it is a 2nd The treatment is preferably performed in the order of the treatment step, the first treatment step, and the cleaning step. The second treatment step and the first treatment step are, for example, a crosslinking step and a complementary color step, a first complementary color step and a second complementary color step, a first crosslinking step and a second crosslinking step, and the like. In this embodiment, by including a 1st processing process, the polarizing film excellent in the yellowing suppression effect also on the high temperature environment exceeding 95 degreeC can be manufactured.

Hereinafter, an example of the manufacturing method of the polarizing film which concerns on this invention is demonstrated in detail, referring FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which showed typically the manufacturing method of the polarizing film which concerns on this invention, and an example of the polarizing film manufacturing apparatus used for it. The polarizing film manufacturing apparatus shown in FIG. 1 conveys the raw (unstretched) film 10 which consists of polyvinyl alcohol-type resin along the film conveyance path while unwinding continuously from the raw roll 11, a film conveyance path A swelling bath (swelling solution accommodated in a swelling tank) (13), a dyeing bath (dyeing solution accommodated in a dyeing tank) (15), a crosslinking bath (crosslinking solution accommodated in a crosslinking tank) (17), a complementary color bath (retained in the crosslinking tank) installed on the bed Complementary color liquid contained in the color tone) 18 and the washing bath (cleaning liquid contained in the washing tank) 19 are sequentially passed through, and finally passed through the drying furnace 21 . The arrow in FIG. 1 has shown the conveyance direction of a film.

In the description of FIG. 1, "treatment tank" is a generic term including a swelling tank, a dyeing tank, a crosslinking tank, a complementary color tank, and a washing tank, and "treatment liquid" is a swelling liquid, a dyeing liquid, a complementary color liquid, and a washing liquid. It is a generic term included, and "treatment bath" is a generic term including a swelling bath, a dyeing bath, a crosslinking bath, a complementary color bath, and a washing bath. The swelling bath, the dyeing bath, the crosslinking bath, the complementary color bath, and the washing bath respectively constitute the swelling part, the dyeing part, the crosslinking part, and the washing|cleaning part in the manufacturing apparatus of this embodiment.

The film conveyance path|route of a polarizing film manufacturing apparatus supports the film conveyed other than the said process bath, or the guide roll 30-48, 60, 61 which can further change a film conveyance direction, and press and pinch the film conveyed. And it can construct by arrange|positioning the nip rolls 50-55 which can provide the driving force by the rotation to a film, or can further change a film conveyance direction at an appropriate position. A guide roll and a nip roll can be arrange|positioned before and after each process bath, or in a process bath, and can perform introduction/immersion of the film into a process bath, and immersion in a process bath by this, and withdraw|derive from a process bath (refer FIG. 1). For example, by providing one or more guide rolls in each treatment bath, and conveying a film along these guide rolls, a film can be immersed in each treatment bath.

As for the polarizing film manufacturing apparatus shown in FIG. 1, the nip roll is arrange|positioned before and after each process bath (nip rolls 50-54), and thereby, in any one or more process baths, between the nip rolls arrange|positioned before and behind that. It is possible to perform extending|stretching between rolls which provides a circumferential speed difference and performs longitudinal uniaxial stretching. Hereinafter, each process is demonstrated.

(swelling process)

A swelling process is performed for the objective of foreign material removal on the surface of the raw film 10, the plasticizer removal in the raw film 10, provision of dyeing easiness, plasticization of the raw film 10, etc. The processing conditions are determined within the range that can achieve the above object and within a range that does not cause problems such as extreme melting of the raw film 10 or loss of clarity.

With reference to FIG. 1, a swelling process is conveyed along a film conveyance path, unwinding the raw film 10 from the raw roll 11 continuously, and the raw film 10 is immersed in the swelling bath 13 for a predetermined time. and it can be carried out by continuously withdrawing. In the example of FIG. 1 , from unwinding the raw film 10 until it is immersed in the swelling bath 13, the raw film 10 is constructed by the guide rolls 60 and 61 and the nip roll 50 It is conveyed along the film conveyance path. In a swelling process, it is conveyed along the film conveyance path built by the guide rolls 30-32 and the nip roll 51. As shown in FIG.

As the swelling liquid of the swelling bath 13, in addition to pure water, boric acid (Japanese Patent Laid-Open No. 10-153709), chloride (Japanese Patent Laid-Open No. 6-281816), inorganic acids, inorganic salts, and water-soluble organic solvents It is also possible to use an aqueous solution in which alcohols, etc. are added in an amount of about 0.01 to 10 mass%.

The temperature of the swelling bath 13 is, for example, 10 to 50°C, preferably 10 to 40°C, more preferably 15 to 30°C. The immersion time of the raw film 10 becomes like this. Preferably it is about 10-300 second, More preferably, it is 20-200 second. In addition, when the raw film 10 is a polyvinyl alcohol-type resin film stretched|stretched in base|substrate beforehand, the temperature of the swelling bath 13 is 20-70 degreeC, for example, Preferably it is 30-60 degreeC. The immersion time of the raw film 10 becomes like this. Preferably it is 30 to 300 second, More preferably, it is about 60 to 240 second.

In a swelling process, the problem that the raw film 10 swells in the width direction, and a wrinkle arises in a film tends to generate|occur|produce. As one means for conveying the film while removing the wrinkles, a roll having a widening function, such as an expander roll, a spiral roll, or a crown roll, is used for the guide rolls 30, 31 and/or 32, or a cloth guider, bend Examples include the use of other widening devices such as bars and tenter clips. Another means for suppressing the occurrence of wrinkles is to perform stretching treatment. For example, the uniaxial stretching process can be performed in the swelling bath 13 using the circumferential speed difference of the nip roll 50 and the nip roll 51. As shown in FIG.

In the swelling treatment, since the film swells and expands also in the conveying direction of the film, when not actively stretching the film, in order to eliminate the slack of the film in the conveying direction, for example, before and after the swelling bath 13. It is preferable to take measures, such as controlling the speed of the nip rolls 50 and 51. In addition, for the purpose of stabilizing the film transport in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, or an EPC device (Edge Position Control device: detects the end of the film, the meander of the film) It is also useful to use a device for preventing

In the example shown in FIG. 1 , the film drawn out from the swelling bath 13 passes through the guide roll 32 , the nip roll 51 , and the guide roll 33 in order, and is introduced into the dyeing bath 15 .

(dyeing process)

A dyeing process is performed for the objective of adsorb|sucking and orientating a dichroic dye to the polyvinyl alcohol-type resin film after a swelling process. Treatment conditions are determined within a range that can achieve the above object and within a range in which problems such as extreme dissolution and devitrification of the film do not occur. Referring to FIG. 1, the dyeing process is carried out along the film transport path constructed by the nip roll 51, guide rolls 33 to 36 and nip roll 52, and the film after swelling treatment is transferred to the dye bath 15 ( It can carry out by immersing in the processing liquid accommodated in the dyeing tank for a predetermined time, and withdrawing continuously. In order to increase the dyeability of the dichroic dye, the film provided in the dyeing process is preferably a film subjected to at least some degree of uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, or in the uniaxial stretching treatment before the dyeing treatment In addition, it is preferable to perform a uniaxial stretching process at the time of a dyeing process.

When using iodine as a dichroic dye, the aqueous solution whose density|concentration is iodine/potassium iodide/water=about 0.003-0.3/about 0.1-10/100 by mass ratio can be used for the dyeing solution of the dyeing bath 15, for example. Instead of potassium iodide, other iodides, such as zinc iodide, may be used, and potassium iodide and another iodide may be used together. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride, etc. may coexist. When boric acid is added, it is distinguished from the crosslinking treatment and complementary color treatment described later in that it contains iodine. can be considered as The temperature of the dye bath 15 at the time of immersing a film is 10-45 degreeC normally, Preferably it is 10-40 degreeC, More preferably, it is 20-35 degreeC, The immersion time of a film is 30-600 normally. second, preferably 60 to 300 seconds.

When using a water-soluble dichroic dye as a dichroic dye, the aqueous solution whose density|concentration is a dichroic dye/water = about 0.001-0.1/100 by mass ratio can be used for the dyeing liquid of the dyeing bath 15, for example. The dyeing bath 15 may be made to coexist with a dyeing aid etc. For example, inorganic salts, such as sodium sulfate, surfactant, etc. may be contained. A dichroic dye may be used individually by 1 type, and may use 2 or more types of dichroic dye together. The temperature of the dyeing bath 15 at the time of immersing a film is, for example, 20-80 degreeC, Preferably it is 30-70 degreeC, The immersion time of a film is 30-600 second normally, Preferably it is 60-300 second. .

As described above, in the dyeing step, the film can be uniaxially stretched by the dyeing bath 15 . Uniaxial stretching of a film can be performed by methods, such as providing a circumferential speed difference between the nip roll 51 and the nip roll 52 arrange|positioned before and behind the dyeing bath 15.

Also in the dyeing treatment, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, the guide rolls 33, 34, 35 and/or 36, such as expander rolls, spiral rolls, crown rolls, etc. A roll having a widening function may be used, or another widening device such as a cloth guider, bend bar, or tenter clip may be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment similarly to the swelling treatment.

In the example shown in FIG. 1 , the film drawn out from the dyeing bath 15 passes through the guide roll 36 , the nip roll 52 , and the guide roll 37 in sequence and is introduced into the crosslinking bath 17 .

(crosslinking process)

A crosslinking process is a process which bridge|crosslinks a film for the improvement of water resistance, etc. Referring to Fig. 1, in the crosslinking step, the crosslinking bath 17 (first accommodated in the crosslinking bath) is conveyed along the film conveying path constructed by the nip rolls 52, guide rolls 37 to 40, and the nip rolls 53a. It can carry out by immersing the film after a dyeing process in a crosslinking liquid) for a predetermined time, and taking it out continuously.

As a crosslinking liquid, the solution which melt|dissolved the crosslinking agent in the solvent can be used. As a crosslinking agent, boron compounds, such as boric acid and borax, glyoxal, glutaraldehyde, etc. are mentioned, for example. One type may be sufficient as these, and they may use 2 or more types together. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density|concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1-20 mass %, It is more preferable that it is 6-15 mass %.

The crosslinking solution may be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid with respect to 100 parts by mass of water. When the dichroic dye used by the dyeing process is iodine, it is preferable that the crosslinking liquid contains iodide in addition to boric acid, and the quantity can be made into 1-30 mass parts with respect to 100 mass parts of water, for example. Potassium iodide, zinc iodide, etc. are mentioned as an iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist.

In the crosslinking treatment, the concentrations of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed according to the purpose. The crosslinking solution may be, for example, an aqueous solution having a concentration of boric acid/iodide/water = 3 to 10/1 to 20/100 in a mass ratio. If necessary, other crosslinking agents may be used instead of boric acid, or boric acid and other crosslinking agents may be used in combination. The temperature of the crosslinking bath 17 at the time of immersing a film is 50-70 degreeC normally, Preferably it is 53-65 degreeC, The immersion time of a film is 10-600 second normally, Preferably it is 20-300 second, More preferably, it is 20 to 200 second. In addition, when the dyeing treatment and the crosslinking treatment are performed in this order on the polyvinyl alcohol-based resin film stretched in advance before the swelling treatment, the temperature of the crosslinking bath 17 is usually 50 to 85°C, preferably 55 to 80°C. am.

The crosslinking treatment may be performed multiple times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath to be used may be the same as long as they are within the above-mentioned range, and may differ. The uniaxial stretching process can also be performed in the crosslinking bath 17 using the circumferential speed difference of the nip roll 52 and the nip roll 53a.

Also in the crosslinking treatment, in order to convey the polyvinyl alcohol-based resin film while removing wrinkles on the film as in the swelling treatment, the guide rolls 37, 38, 39, and/or 40 are provided with an expander roll, a spiral roll, and a crown roll. A roll having the same widening function may be used, or another widening device such as a cloth guider, bend bar, or tenter clip may be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment similarly to the swelling treatment.

(Complementary color process)

A complementary color process is a process which adjusts the hue of a film. Referring to Fig. 1, in the complementary color process, the complementary color bath 18 (complementary color accommodated in the complementary color tone) is conveyed along the film conveying path constructed by the nip rolls 53a, guide rolls 41 to 44, and the nip rolls 53b. It can be implemented by immersing the film after a bridge|crosslinking process in liquid) for a predetermined time, and taking it out continuously.

The complementary color solution may be an aqueous solution containing, for example, about 1 to 10 parts by mass of boric acid with respect to 100 parts by mass of water. When the dichroic dye used by the dyeing process is iodine, it is preferable that a complementary color liquid contains iodide in addition to boric acid, and the quantity can be made into 1-30 mass parts with respect to 100 mass parts of water, for example. Potassium iodide, zinc iodide, etc. are mentioned as an iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate, etc. may coexist.

In the complementary liquid, for example, when iodine is used as the dichroic dye, the concentration can use boric acid/iodide/water = 1 to 5/3 to 30/100 by mass ratio. The temperature of the complementary color bath 18 at the time of immersing a film is 10-45 degreeC normally, and the immersion time of a film is 1-300 second normally, Preferably it is 2-100 second.

The complementary color treatment may be performed plural times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each complementary color bath to be used may be the same as long as they are within the above-mentioned range, and may differ. Moreover, the uniaxial stretching process can also be performed within the complementary color bath 18 using the circumferential speed difference of the nip roll 53a and the nip roll 53b.

Also in the complementary color treatment, in order to convey the polyvinyl alcohol-based resin film while removing the wrinkles of the film as in the swelling treatment, the guide rolls 41, 42, 43 and/or 44 are placed on guide rolls such as expander rolls, spiral rolls, and crown rolls. A roll having a widening function may be used, or another widening device such as a cloth guider, bend bar, or tenter clip may be used. Another means for suppressing the occurrence of wrinkles is to perform a stretching treatment similarly to the swelling treatment.

In the example shown in FIG. 1 , the film drawn out from the complementary color bath 18 passes through the guide roll 44 and the nip roll 53b sequentially and is introduced into the washing bath 19 .

(cleaning process)

In the example shown in FIG. 1, the washing|cleaning process after a complementary color process is included. A washing process is performed for the purpose of removing chemical|medical agents, such as excess boric acid and iodine, adhering to the polyvinyl alcohol-type resin film. The washing step is performed, for example, by immersing the polyvinyl alcohol-based resin film subjected to the complementary color treatment in the washing bath 19 . In addition, instead of the process of immersing a film in the washing|cleaning bath 19, the washing|cleaning process can also be performed by spraying a washing|cleaning liquid with a shower with respect to the film, or by combining immersion in the washing|cleaning bath 19 and spraying of a washing|cleaning liquid.

In FIG. 1, the example in the case of performing a washing|cleaning process by immersing a polyvinyl alcohol-type resin film in the washing|cleaning bath 19 is shown. The temperature of the washing|cleaning bath 19 in a washing|cleaning process is 2-40 degreeC normally, and the immersion time of a film is 2-120 second normally.

In addition, in the washing process, for the purpose of conveying the polyvinyl alcohol-based resin film while removing wrinkles, the guide rolls 45, 46, 47 and/or 48 are provided with a widening function such as an expander roll, a spiral roll, and a crown roll. You can use a roll with a blade or other widening device such as a cloth guider, bend bar, or tenter clip. Moreover, in a film washing process, in order to suppress generation|occurrence|production of wrinkles, you may perform an extending|stretching process.

(Stretching process)

As described above, the raw film 10 is subjected to a wet or dry uniaxial stretching treatment between the series of treatment steps (that is, before and after any one or more treatment steps and/or during any one or more treatment steps). A specific method of the uniaxial stretching treatment is, for example, inter-roll stretching in which longitudinal uniaxial stretching is performed by imparting a circumferential speed difference between two nip rolls constituting the film transport path (eg, two nip rolls disposed before and after a treatment bath), Japanese Patent It may be hot roll stretching, tenter stretching, etc. as described in Publication No. 2731813, preferably between rolls. A uniaxial stretching process can be implemented over multiple times until the polarizing film 23 is obtained from the raw film 10. As mentioned above, the extending|stretching process is advantageous also for suppression of the generation|occurrence|production of wrinkles of a film.

The final cumulative draw ratio of the polarizing film 23 on the basis of the raw film 10 is 4.5-7 times normally, Preferably it is 5-6.5 times. An extending process may be performed by any treatment process, and also when performing an extending process by two or more treatment processes, an extending process may be performed by any treatment process.

(1st treatment process)

A 1st processing process is a process of making a film contact a 1st processing liquid, A 1st processing liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is 5.0 or more. It is preferable that it is 5.2 or more, and, as for the pH in 25 degreeC of a 1st process liquid, it is preferable that it is 5.3 or more, It is more preferable that it is 5.5 or more. Moreover, it is preferable that pH in 25 degreeC of 1st process liquid is 6.8 or less, It is more preferable that it is 6.5 or less, It is more preferable that it is 6.3 or less. The first treatment step is, for example, the aforementioned complementary color step. When the first treatment step is a complementary color step, the description of the above-described complementary color step can be directly applied to the description of the first treatment step. A 1st process liquid contains a boric acid and an iodide compound, and pH is 5.0 or more. As the first treatment liquid, an aqueous solution having a concentration of boric acid/iodide/water = 1 to 5/3 to 30/100 in a mass ratio can be used. The 1st processing liquid further contains a pH adjuster. Potassium hydroxide, sodium hydroxide, etc. are illustrated as a pH adjuster. The 1st processing liquid is adjusted so that the pH in 25 degreeC may become 5.0 or more by adjusting the addition amount of a pH adjuster. In this embodiment, by having a 1st processing process, the polarizing film excellent in the yellowing suppression effect also on the high temperature environment exceeding 95 degreeC can be provided.

(Second treatment process)

A 2nd processing process is a process of making a film contact a 2nd processing liquid, The 2nd processing liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is less than 5.0. The second treatment step is, for example, the crosslinking step described above. When a 2nd processing process is a bridge|crosslinking process, the description of the above-mentioned bridge|crosslinking process can be applied to description of a 2nd processing process as it is. A 2nd process liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is less than 5.0. As the second treatment liquid, an aqueous solution having a concentration of boric acid/iodide/water = 3 to 10/1 to 20/100 in a mass ratio can be used. The 2nd processing liquid may adjust the addition amount of a boric acid or an iodine compound to make pH less than 5.0, for example, and may add an acid pH adjuster and may make pH in 25 degreeC less than 5.0. It is preferable that a 2nd process liquid adjusts the addition amount of boric acid so that pH in 25 degreeC may be adjusted so that it may become less than 5.0.

(drying process)

It is preferable to perform the process which dries a polyvinyl alcohol-type resin film after a washing|cleaning process after a 2nd processing process or when a washing|cleaning process is included. The drying of the film is not particularly limited, but may be performed using a drying furnace 21 as in the example shown in FIG. 1 . The drying furnace 21 can be provided with a hot air dryer, for example. The drying temperature is, for example, 30 to 100°C, and the drying time is, for example, 30 to 600 seconds. The process of drying a polyvinyl alcohol-type resin film can also be performed using a far-infrared heater.

(Polyvinyl alcohol-based resin film and other processing steps)

Processing other than the above-described processing may be added. Examples of the treatment that can be added include an immersion treatment in an aqueous iodide solution not containing boric acid and an immersion treatment in an aqueous solution containing zinc chloride or the like without boric acid (zinc treatment).

The polarizing film obtained by making it above may be wound up one by one to a winding roll, and it may be made into roll form, and it can also use it for the manufacturing method of a polarizing plate as it is, without winding up. The polarizing film made into roll form can also be used for the manufacturing method of a polarizing plate after that. One aspect of the manufacturing method of a polarizing plate has the bonding process of bonding a protective film to the single side|surface or both surfaces of a polarizing film through a bonding layer.

<Polarizing film>

It is preferable that the polarizing film which concerns on this embodiment dye|stains a polyvinyl alcohol-type resin film with a dichroic dye. It is preferable that they are 5 micrometers or more and 60 micrometers or less, and, as for the thickness of a polarizing film, it is more preferable that they are 7 micrometers or more and 30 micrometers or less. The test piece having an area of 1500 cm2 obtained by cutting the polarizing film is immersed in 10 ml of 25°C pure water, left to stand at a temperature of 25°C for 10 minutes, and the pH at 25°C of the immersion liquid after taking out the test piece is preferably 5.3 or more and more preferably 5.4 or more, and still more preferably 5.6 or more. It is preferable that it is 6.8 or less, and, as for an upper limit, it is more preferable that it is 6.5 or less, It is still more preferable that it is 6.2 or less. In addition, the details of pH measurement of the immersion liquid of a polarizing film follow the method described in the Example mentioned later. It is preferable that it is 40-47 %, and, as for the visibility correction|amendment single transmittance|permeability (Ty) of a polarizing film, it is preferable that it is 40-47 %, and it is more preferable that it is 41-45 % in consideration of the balance with visibility correction|amendment polarization degree Py. It is preferable that it is 99.9 % or more, and, as for the visibility correction|amendment polarization degree Py, it is more preferable that it is 99.95 % or more. Such a polarizing film can be obtained with the manufacturing method mentioned above.

<Polarizer>

The polarizing plate which concerns on this embodiment can obtain a polarizing plate by laminating|stacking a protective film on the single side|surface or both surfaces of the above-mentioned polarizing film through a bonding layer. Examples of the protective film include a film made of an acetyl cellulose-based resin such as triacetyl cellulose or diacetyl cellulose; a film made of a polyester-based resin such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; polycarbonate-based resin film, cycloolefin-based resin film; acrylic resin film; The film which consists of a chain|strand-shaped olefin resin of polypropylene resin is mentioned.

In order to improve the adhesion between the polarizing film and the protective film, the bonding surface of the polarizing film and/or protective film is subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. also good The bonding layer interposed between the polarizing film and the protective film can be formed using an adhesive or an adhesive. Examples of the adhesive include an active energy ray-curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of a polyvinyl alcohol-based resin or an aqueous solution in which a crosslinking agent is blended, and an aqueous adhesive such as a urethane-based emulsion adhesive. A zinc compound such as zinc nitrate may be added to the water-based adhesive. The ultraviolet curing adhesive may be a mixture of an acrylic compound and a photoradical polymerization initiator, a mixture of an epoxy compound and a photocationic polymerization initiator, or the like. Moreover, a cationically polymerizable epoxy compound and a radically polymerizable acrylic compound can be used together, and a photocationic polymerization initiator and a photoradical polymerization initiator can also be used together as an initiator.

The bonding layer is preferably a layer formed from a water-based adhesive, more preferably a layer formed from a water-based adhesive containing a zinc compound, and still more preferably a layer formed from a water-based adhesive containing a zinc compound and a polyvinyl alcohol-based resin. do.

A polarizing film having a bonding layer in which a bonding layer is laminated on both surfaces of the polarizing film is immersed in 10 ml of 25°C pure water in 10 ml of a polarizing film having an area of 1500 cm 2 , and left at a temperature of 25°C for 10 minutes. and the pH at 25°C of the immersion liquid after taking out the test piece is preferably more than 3.4, more preferably 3.5 or more, still more preferably 4.0 or more, and still more preferably 4.4 or more. It is preferable that it is 6.8 or less, and, as for an upper limit, it is more preferable that it is 6.5 or less, It is still more preferable that it is 6.2 or less, It is especially preferable that it is less than 5.4. In addition, the details of pH measurement of the immersion liquid of the polarizing film which has a bonding layer follow the method described in the Example mentioned later.

It is preferable that it is 50-200 nm, and, as for the thickness of the bonding layer in the polarizing film which has a bonding layer, it is more preferable that it is 70-150 nm.

<Image display device>

A polarizing plate can be used for an image display apparatus. As an image display element used for an image display apparatus, a liquid crystal display element, an organic electroluminescent display element, etc. are mentioned, for example. In constructing a liquid crystal display device, the polarizing plate according to the present invention may be disposed on the viewing side, may be used while disposed on the backlight side, or may be used on both the viewing side and the backlight side. The image display device of the present invention can be used for mobile devices such as televisions, personal computers, mobile phones and tablet terminals, and has a high inhibitory effect on yellowing in a high-temperature environment, and provides a long-term stable image display function. Since it can express, it can utilize especially suitably for the in-vehicle use which is easy to be exposed under more severe temperature conditions. As an in-vehicle application, the image display apparatus etc. used for a car navigation device, a speedometer, the touch panel for air conditioners, a back monitor, a rear monitor, etc. are mentioned, for example.

Example

Hereinafter, the present invention has been more specifically described with reference to examples, but the present invention is not limited by these examples.

<Example 1>

A polarizing film of Example 1 was manufactured from a polyvinyl alcohol-based resin film using the manufacturing apparatus shown in FIG. 1 . Specifically, while unwinding from the roll a long 60 µm thick polyvinyl alcohol (PVA) raw film (trade name "Poval Film OPL Film M-6000" manufactured by Mitsubishi Chemical Co., Ltd., saponification degree of 99.9 mol% or more) It conveyed continuously and was made to be immersed in the swelling bath which consists of 28 degreeC pure water with immersion time 140 second (swelling process). Thereafter, the film taken out from the swelling bath is immersed in a dyeing bath at 30° C. comprising a dyeing solution containing iodine in which iodine/potassium iodide/boric acid/water is 0.03/1.3/0.3/100 (mass ratio) for an immersion time of 130 seconds. (staining process). Subsequently, the film taken out from the dyeing bath was immersed in a crosslinking bath at 56° C. comprising a crosslinking solution having a potassium iodide/boric acid/water ratio of 13.9/3.0/100 (mass ratio) for an immersion time of 50 seconds (crosslinking step, second treatment). process). In addition, the pH in 25 degreeC of a crosslinking bath was 3.8.

Then, the film taken out from the crosslinking bath is immersed in a complementary color bath at 40° C. comprising a complementary color solution obtained by adding an aqueous potassium hydroxide solution to a solution in which potassium iodide/boric acid/water is 9.0/3.0/100 (mass ratio) for an immersion time of 10 seconds. (complementary color process, 1st treatment process). Then, the film taken out from the complementary color bath was immersed in the 7 degreeC washing|cleaning bath which consists of pure water for 10 second of immersion time (washing process). Then, the film taken out from the washing|cleaning bath was made to stay in the drying furnace with a temperature of 80 degreeC for 150 second, and it dried (drying process). In addition, the pH in 25 degreeC of the complementary color liquid (1st process liquid) was 6.1.

The thickness of the obtained polarizing film was 23 micrometers. Moreover, it was 6.14 as a result of measuring the pH of an immersion liquid by the method mentioned later about the obtained polarizing film.

<Example 2>

About the complementary color liquid used at a complementary color process, except the point which added potassium hydroxide and adjusted the pH in 25 degreeC to 5.7, it carried out similarly to Example 1, and produced the polarizing film.

The thickness of the obtained polarizing film was 23 micrometers. Moreover, it was 5.92 as a result of measuring the pH of an immersion liquid by the method mentioned later about the obtained polarizing film.

<Comparative Example 1>

About the complementary liquid used by the complementary color process, it carried out similarly to Example 1, and produced the polarizing film except having added sulfuric acid without adding potassium hydroxide. In addition, the pH in 25 degreeC of the complementary color solution was 3.8.

The thickness of the obtained polarizing film was 23 micrometers. Moreover, it was 5.16 as a result of measuring the pH of an immersion liquid by the method mentioned later about the obtained polarizing film.

<Example 3>

(Preparation of water-based adhesive composition)

Dissolve acetoacetyl group-modified polyvinyl alcohol [trade name "Gosepimer Z-200", manufactured by Nippon Kosei Chemical Co., Ltd., viscosity of 4% aqueous solution = 12.4 mPa sec, degree of saponification = 99.1 mol%] in pure water Thus, an aqueous solution having a concentration of 10% was prepared. This acetoacetyl group-modified polyvinyl alcohol aqueous solution and sodium glyoxylate serving as a crosslinking agent are mixed so that the mass ratio of the former to the latter is 1:0.1, and 1.5 parts by mass of zinc nitrate, acetoacetyl with respect to 100 parts by mass of water It diluted with pure water so that group-modified polyvinyl alcohol might become 2.5 mass parts, and the aqueous adhesive composition was prepared.

A saponification treatment was performed on a 40 µm-thick triacetyl cellulose (TAC) film. Furthermore, the saponification process was performed to the 40-micrometer-thick low retardation TAC film. Each of the two surfaces of the polarizing film of Example 1 was laminated through the water-based adhesive, and a laminate having a layer structure of TAC/adhesive layer/polarizing film/adhesive layer/low retardation TAC film was obtained. About the obtained laminated body, by performing heat processing for 80 degreeC and 140 second with a hot air dryer, the polarizing plate which has the laminated constitution of TAC film / adhesive layer / polarizing film / adhesive layer / low retardation TAC film was produced. About the obtained polarizing plate, the yellowing evaluation test mentioned later was done. A result is shown in Table 1.

<Example 4>

Except having made the polarizing film into the polarizing film produced in Example 2, it carried out similarly to Example 3, and produced the polarizing plate. About the obtained polarizing plate, the yellowing evaluation test mentioned later was done. A result is shown in Table 1.

<Comparative Example 2>

Except having made the polarizing film into the polarizing film produced by the comparative example 1, it carried out similarly to Example 3, and produced the polarizing plate. About the obtained polarizing plate, the yellowing evaluation test mentioned later was done. A result is shown in Table 1.

[Measurement of pH of immersion liquid of polarizing film]

The polarizing films of Examples 1 and 2 and Comparative Example 1 were cut into test pieces each having an area of 1500 cm 2 (30 cm × 50 cm). The said test piece was further cut into the size of 5 cm x 5 cm, and 60 polarizing films of 5 cm x 5 cm size were obtained at a time. All of the obtained 60 polarizing films of the size of 5 cm x 5 cm were put into a 500 ml beaker, and 10 ml of pure water with a temperature of 25 degreeC was added to this using a pipette. After stirring by repeating the operation of sucking up the added pure water with a pipette and discharging from the pipette several times, it was left still at the temperature of 25 degreeC for 10 minutes. Then, the pH in 25 degreeC of the immersion liquid after taking out a test piece was measured using the pH meter (HORIBA D-54). A result is shown in Table 1.

[Measurement of pH of immersion liquid of polarizing film having bonding layer]

It carried out similarly to Example 3 except not performing a saponification process to a 40-micrometer-thick TAC film and a 40-micrometer-thick low retardation TAC film, and a 40-micrometer-thick TAC film/water-based adhesive layer/polarizing film of Example 1/water-based A polarizing plate having a laminate structure of an adhesive layer/thickness of 40 µm low retardation TAC film was obtained. The 40-micrometer-thick TAC film and the 40-micrometer-thick low retardation TAC film were peeled from the obtained polarizing plate, and the polarizing film (polarizing film which has a bonding layer) which has a water-system adhesive bond layer was obtained. The polarizing film which has the obtained water-system adhesive bond layer was cut into the 1500 cm<2> (30 cm x 50 cm) test piece. The said test piece was further cut to the size of 5 cm x 5 cm, and 60 polarizing plates of 5 cm x 5 cm size were obtained at a time. All the obtained test pieces were put into a 500 ml beaker, and 10 ml of pure water at a temperature of 25°C was added thereto using a pipette. After stirring by repeating the operation of sucking up the added pure water with a pipette and discharging from the pipette several times, it was left still at the temperature of 25 degreeC for 10 minutes. Then, the pH in 25 degreeC of the immersion liquid after taking out the polarizing film which has a bonding layer was measured using the pH meter (HORIBA D-54).

Moreover, except having used the polarizing film of Example 2 or the polarizing film of Comparative Example 1, it carried out similarly to the above, and performed the pH measurement of the polarizing film immersion liquid which has each water-system adhesive bond layer. A result is shown in Table 1.

[Yellowing evaluation (105 ° C)]

The polarizing plates of Examples 3, 4 and Comparative Example 2 were cut to a size of 40 mm×40 mm, respectively, and an acrylic adhesive having a thickness of 25 μm was used on both sides of the 40 mm×40 mm alkali-free glass [Corning Co., Ltd. " EAGLE XG"] to prepare an evaluation sample.

The evaluation sample was left at a temperature of 50°C and a pressure of 0.5 MPa (about 5 kg/cm 2 ) for 20 minutes, and then left at a temperature of 23°C and a relative humidity of 55% for 24 hours. Further, after that, heat treatment was performed at 95°C for 3 hours. This sample was subjected to a heating test in which it was stored for 50 hours in a heating environment at a temperature of 105°C, and color change before and after heating was visually confirmed. A indicates that there is almost no change, B indicates that the color change is slightly visible, C indicates that the color change is visible in about half of the surface of the polarizing plate, and D indicates that the color changes substantially on the entire surface of the polarizing plate. . When the evaluation result was A, the heating test of storing for 50 hours in a heating environment at a temperature of 105°C was performed again, and color change before and after heating was visually confirmed. The heating test was terminated when the evaluation result became any one of B to D. The total storage time in the heating test until completion is shown in Table 1 as a result of the yellowing evaluation test.

As shown in Table 1, in the polarizing plate of Examples 3 and 4, until it reached 1000 hours, the color change before and behind a heating could not be confirmed. On the other hand, in the polarizing plate of Comparative Example 2, until 300 hours was reached, the color change before and after heating could not be confirmed, but after the total storage time in the heating test reached 300 hours, it was stored for another 50 hours. After that, the color change before and after heating could be visually confirmed.

10: raw film made of polyvinyl alcohol-based resin
11: Disc roll
13: swelling bath
15: dye bath
17: crosslinking bath
18: Complementary color desire
19: washing bath
21: drying furnace
23: polarizing film
30~48, 60, 61: guide roll
50-52, 53a, 53b, 54, 55: nip roll

Claims (12)

A method for producing a polarizing film from a polyvinyl alcohol-based resin film, comprising:
A first treatment step of bringing the polyvinyl alcohol-based resin film into contact with a first treatment solution,
The manufacturing method of a polarizing film whose said 1st process liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is 5.0 or more. According to claim 1,
a second treatment step of bringing the polyvinyl alcohol-based resin film into contact with a second treatment solution;
The said 2nd process liquid contains a boric acid and an iodide compound, and pH in 25 degreeC is less than 5.0,
A said 2nd processing process is the manufacturing method of a polarizing film performed before a said 1st processing process. The said 1st process liquid is the manufacturing method of the polarizing film of Claim 1 or 2 whose pH in 25 degreeC is 6.5 or less. The immersion liquid according to any one of claims 1 to 3, wherein a test piece having an area of 1500 cm 2 obtained by cutting the polarizing film is immersed in 10 ml of 25°C pure water and left for 10 minutes, and the test piece is taken out. The manufacturing method of the polarizing film whose pH in 25 degreeC is 5.3 or more. The process of manufacturing a polarizing film by the manufacturing method of the polarizing film in any one of Claims 1-4;
A method of manufacturing a polarizing plate having a bonding process of bonding a protective film to one side or both sides of the polarizing film through a bonding layer. The polarizing film whose pH in 25 degreeC of the immersion liquid after immersing the polarizing film whose area is 1500 cm2 in 10 ml of 25 degreeC pure water, leaving it to stand for 10 minutes, and taking out the said polarizing film is 5.3 or more. The polarizing film according to claim 6, wherein the polyvinyl alcohol-based resin film is dyed with a dichroic dye. The polarizing plate which has the polarizing film of Claim 6 or 7, and the protective film laminated|stacked on the single side|surface or both surfaces of the said polarizing film via a bonding layer. The image display apparatus by which the polarizing plate of Claim 8 and the image display element were laminated|stacked. A polarizing film having a bonding layer in which a bonding layer is laminated on both surfaces of the polarizing film,
A polarizing film having a bonding layer having an area of 1500 cm 2 is immersed in 10 ml of 25°C pure water and left for 10 minutes, and the pH at 25°C of the immersion liquid after taking out the polarizing film having the bonding layer is more than 3.4 A polarizing film having a bonding layer. The polarizing plate by which the protective film was laminated|stacked on the bonding layer of the polarizing film which has a bonding layer of Claim 10. The image display apparatus by which the polarizing plate of Claim 11 and the image display element were laminated|stacked.

Images