KR20160120356A - Polyvinyl alcohol film - Google Patents

Abstract

(PROBLEM TO BE SOLVED) To provide a film made of polyvinyl alcohol of high polymerization degree, which is useful as a raw material for producing a polarizing film having high polarization performance.
A polyvinyl alcohol film characterized by comprising a polyvinyl alcohol having a polymerization degree of 5100 to 10000 and having a degree of swelling of 200 to 240% and a retardation of 10 to 40 nm at the central portion in the width direction. In the polyvinyl alcohol film, the saponification degree of the polyvinyl alcohol is preferably 98 mol% or more, and the thickness of the polyvinyl alcohol film is preferably 10 to 120 탆.

Description

[0001] POLYVINYL ALCOHOL FILM [0002]

The present invention relates to a polyvinyl alcohol film which can be used as a raw material of a polarizing film having a good polarizing performance.

Liquid crystal displays (LCDs) have been used in small-sized devices such as electronic desk calculators and wrist watches in the early days of development. Recently, they are used in notebooks, liquid crystal monitors, liquid crystal color projectors, liquid crystal televisions, vehicle navigation systems, Measurement instruments and so on. On the other hand, particularly in applications such as liquid crystal televisions, improvement in display quality, for example, improvement in contrast, is increasingly required, and polarization performance, which is one of the LCD members, is strongly desired to be improved.

A conventionally used polarizing plate is a film obtained by applying a monoaxial stretching, a dyeing treatment with iodine or a dichroic dye, a fixing with a boron compound (hereinafter referred to as " And the like, and a protective film such as a cellulose acetate triacetate film or an acetic acid-butyric acid cellulose film is stuck to one side or both sides of the obtained polarizing film. As a method for improving the polarizing performance of such a polarizing plate, various techniques such as a method of improving the structure of the raw material PVA, a method of controlling the physical properties of the PVA film, and a method of studying the manufacturing conditions of the polarizing plate have been proposed, And has contributed to improvement of contrast.

For example, Patent Document 1 discloses that a polarizing film made of PVA having a polymerization degree of 2500 or more, preferably 6000 to 10000, has excellent optical properties. The use of PVA having a high degree of polymerization is an advantageous method for improving the polarization performance, but it is difficult to carry out the PVA in an industrial manner.

As another method for improving the polarization performance, for example, Patent Document 2 discloses a method in which the relationship between the complete dissolution temperature (X) in the hot water and the equilibrium swelling degree (Y) A method of producing a polarizing film using a PVA-based film is disclosed.

Y> -0.0667X + 6.73 ... (I)

X ≥ 65 ... (II)

However, the degree of polymerization of the PVA used in the invention is preferably in the range of 3500 to 5000, and even if the production method thereof is applied to the high polymerization degree PVA as it is, as described in the comparative example described later, It was proven not to do. That is, in order to industrially produce a polarizing film made of PVA having a high degree of polymerization, it is necessary to find out the optimum raw material condition with all the knowledge about the structure of the PVA and the physical properties of the PVA film.

Japanese Unexamined Patent Publication No. 1-105204 Japanese Patent Application Laid-Open No. 7-120616

Therefore, an object of the present invention is to provide a film made of PVA of high polymerization degree, which is useful as a raw material for producing a polarizing film having a high polarization performance.

The inventors made extensive use of the knowledge on the structure of the PVA and the physical properties of the PVA film. As a result, it has been found out that the PVA film, which is made of PVA having a polymerization degree of 5100 to 10000 and has a swelling degree of 200 to 240% and a retardation in the central part of the width direction of 10 to 40 nm, The present invention has been completed.

In this case, the saponification degree of the PVA is preferably 98 mol% or more.

The thickness of the PVA film is preferably 10 to 120 탆.

The present invention also includes a method for producing the PVA film in which a PVA film having a degree of polymerization of 5100 to 10000 and a film-forming stock solution containing water are used as a raw material.

The present invention also includes a polarizing film obtained by dyeing and stretching the PVA film.

The PVA film of the present invention can be used as a raw material of a polarizing film having a good polarizing performance. The obtained polarizing film is used for the production of a polarizing plate which is a component of a liquid crystal display device such as an electronic desk calculator, a wrist watch, a notebook, a liquid crystal monitor, a liquid crystal color projector, a liquid crystal television, a vehicle navigation system, a mobile phone, Can be used effectively.

Hereinafter, the present invention will be described in detail.

The degree of polymerization of PVA used in the present invention is required to be in the range of 5100 to 10000, preferably in the range of 5200 to 9500, and more preferably in the range of 5400 to 9200 in order to cope with good polarization performance of the polarizing film of the present invention . When the degree of polymerization of PVA is less than 5100, it becomes difficult to exhibit a high polarization performance when a polarizing film is produced. On the other hand, when the degree of polymerization of PVA exceeds 10,000, the productivity of PVA is lowered. The degree of polymerization of the PVA in the present invention means the degree of polymerization (viscosity average degree of polymerization) measured according to the method described in the following Examples.

The saponification degree of PVA is preferably 98 mol% or more, more preferably 99 mol% or more, still more preferably 99.5 mol% or more, and most preferably 99.8 mol% or more. If the degree of saponification of PVA is less than 98 mol%, PVA tends to elute in the production process of the polarizing film, and the eluted PVA adheres to the film, thereby deteriorating the performance of the polarizing film.

The PVA used in the present invention can be produced by saponifying a polyvinyl ester polymer obtained by polymerizing a vinyl ester. Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate and vinyl benzoate. Of these, one or two Select more than species. Among them, vinyl acetate is preferably used in terms of availability, ease of production of PVA, cost, and the like. There is no particular limitation on the polymerization temperature, but when methanol is used as the polymerization solvent, the polymerization temperature is preferably around 60 占 폚 near the boiling point of methanol.

PVA is not limited to a saponified product of a homopolymer of a vinyl ester unless the effect of the present invention is impaired. Modified PVA obtained by graft copolymerizing PVA with an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, or an? -Olefin having 2 to 30 carbon atoms in a proportion of less than 5 mol%; A saponified product of a modified polyvinyl ester obtained by copolymerizing a vinyl ester with an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, an? -Olefin having 2 to 30 carbon atoms in a proportion of less than 15 mol%; A polyvinyl acetal polymer in which a part of the hydroxyl groups of PVA are crosslinked with aldehydes such as formaldehyde, butylaldehyde and benzaldehyde.

The PVA film of the present invention is obtained by producing the PVA film. Examples of the membrane production method include a method of producing a flexible membrane and a method of producing a wet film by discharging the membrane into a poor solvent and a method of producing a gel film by first cooling gelation of a PVA aqueous solution, Solvent extraction and removal), a cast film production method (pouring a PVA aqueous solution onto the base and drying), and a combination of these methods. Of these, the melt extrusion film production method and the flexible film production method are preferable in that a good PVA film can be obtained. Water is preferably used as the solvent used in the film production.

The volatile matter content of the film-forming stock solution mainly composed of PVA and a solvent varies depending on the film production method and the molecular weight of PVA, but is preferably from 50 to 95 mass%, more preferably from 60 to 95 mass%, more preferably from 70 to 95 mass% % Is more preferable. If the volatile fraction is less than 50 mass%, the viscosity of the film-forming stock solution becomes excessively high, which makes filtration and de-foaming difficult at the time of preparation, and it may be difficult to obtain a PVA film free from foreign matters or defects. On the other hand, if the volatile fraction exceeds 95% by mass, the viscosity of the film-forming stock solution becomes excessively low, which may make it difficult to produce a PVA film having a desired thickness and high thickness accuracy.

In producing the PVA film of the present invention, a plasticizer may be used. Examples of the plasticizer include glycerin, diglycerin, ethylene glycol and the like, but are not limited thereto. The amount of the plasticizer to be used is not particularly limited, but is usually in the range of 10 to 15 parts by mass based on 100 parts by mass of the PVA.

The drying method of the PVA film after the film production includes, for example, drying with hot air, contact drying using a heat roll, and drying with an infrared heater. One of these methods may be used alone, or two or more types may be used in combination. The drying temperature is not particularly limited, but is preferably in the range of 50 to 70 占 폚. The drying time at this time is approximately 45 to 75 minutes although it may vary depending on the concentration of the film-forming raw solution and the film-forming conditions.

After adjusting the moisture content (moisture content) of the dried PVA film to adjust the water content (water content), only two parallel sides of the film, preferably only the two sides in the width direction, are fixed and heat treatment is performed in the range of 100 to 140 캜, Gentle stretching can be applied to the film by the generation of stress accompanied by the decrease. This makes it possible to stably impart a low level retardation, which will be described later, to the film. The moisture content of the film at this time is preferably from 1 to 15 mass%, more preferably from 1 to 10 mass%, and even more preferably from 2 to 6 mass%. The heat treatment time is not particularly limited and varies depending on the heat treatment temperature, but is within about 5 minutes.

The thickness of the PVA film of the present invention thus obtained is preferably 10 to 120 탆, more preferably 12 to 80 탆, still more preferably 15 to 75 탆, most preferably 20 to 60 탆. When the thickness is less than 10 占 퐉, there is a fear that the film tends to be broken in a stretching step to be described later. If the thickness exceeds 120 占 퐉, the stress applied to the film at the time of stretching becomes large, and sufficient stretching may become difficult.

The swelling degree of the PVA film of the present invention needs to be 200 to 240%, preferably 205 to 235%, and more preferably 210 to 230%. If the degree of swelling is less than 200%, the tensile strength at the time of stretching becomes too large, and it becomes difficult to perform sufficient stretching. When the degree of swelling exceeds 240%, wrinkles and edge curl tend to occur in the film in the production process of a polarizing film to be described later because of high water absorbency, which may cause breakage at the time of stretching. In order to control the degree of swelling to a predetermined range, for example, the temperature and time at the time of heat-treating the PVA film after the film production may be adjusted within the above range. The degree of swelling of the PVA film can be measured by the method described later in the Examples.

In the PVA film of the present invention, the retardation at the central portion in the width direction needs to be 10 to 40 nm, more preferably 13 to 37 nm, still more preferably 17 to 33 nm, and most preferably 20 to 30 nm desirable. If the retardation is less than 10 nm, the dyeing speed at the time of producing the polarizing film is slowed, and thus uneven dyeing is likely to occur. Further, when the retardation exceeds 40 nm, the film is broken even at a low stretching magnification. The retardation of the PVA film can be measured by the method described later in the items of the examples.

In order to control the retardation of the PVA film to a predetermined range, a method of annealing the above-mentioned PVA film after adjusting the humidity, and a method of stretching the PVA film by a known method are exemplified, but are not limited thereto. Among these, from the viewpoint of fixing the generated retardation, a method of heat treatment after adjusting the humidity is preferable. At this time, it is important to fix only two parallel sides of the PVA film, preferably two sides in the width direction, and perform the heat treatment. When the film is not fixed or heat treated by fixing the four sides, the stress applied to the film becomes isotropic, so that retardation does not occur and the object can not be achieved.

Next, a method for producing a polarizing film using the original PVA film of the present invention will be described. The production process of the polarizing film may include processes such as moisture control, dyeing, stretching, and color adjustment. At this time, it is preferable to perform wet stretching of the film. Further, if necessary, the stretched film obtained may be stretched again in an aqueous boric acid solution after the wet stretching step. Further, if necessary, it may be color-adjusted in an aqueous solution containing, for example, boric acid and potassium iodide, and dried to prepare a polarizing film.

The water content of the PVA film is preferably adjusted by immersing it in pure water or distilled water. The temperature at this time is preferably 20 to 40 占 폚, more preferably 25 to 35 占 폚, and still more preferably 27 to 33 占 폚. If the temperature is lower than 20 占 폚, the water content of the original disc is lowered, and the tension applied to the film at the subsequent stretching is increased, and the polarization performance of the obtained polarizing film may be lowered. On the other hand, if the temperature exceeds 40 캜, the water absorbability of the original film becomes high, and wrinkles and end curls are easily generated in the subsequent steps, which may cause breakage at the time of stretching. On the other hand, the time for immersing the original film is about 30 to 120 seconds.

The dyeing of the PVA film is carried out, for example, in an aqueous solution of iodine-potassium iodide. The concentration of iodine is preferably from 0.01 to 0.1 mass%, the concentration of potassium iodide is preferably from 1 to 10 mass%, more preferably from 0.02 to 0.08 mass% and the concentration of potassium iodide is from 2 to 8 mass% More preferably 0.03 to 0.06 mass% of iodine concentration and 3 to 6 mass% of potassium iodide concentration. The temperature of the aqueous solution is not particularly limited, but is preferably 25 to 40 占 폚.

The wet stretching of the original PVA film may be carried out as a process different from the above-mentioned moisture adjustment or dyeing. It is preferable that the wet stretching is performed in the water regulating water or in an aqueous solution for dyeing, and is preferably an aqueous solution for dyeing, that is, potassium iodide Aqueous solution. In the wet stretching of the master of the PVA film, the stretching magnification expressed by the ratio of the film length before and after stretching is preferably 2.0 to 2.9 times, more preferably 2.2 to 2.8 times, still more preferably 2.4 to 2.8 times.

The temperature at which the PVA film is subjected to wet drawing is preferably 20 to 40 占 폚, more preferably 25 to 40 占 폚, more preferably 25 to 35 占 폚 in terms of obtaining a polarizing film having better polarizing performance And particularly preferably 27 to 33 ° C.

As described above, after the step of wet-drawing the PVA film, the obtained stretched film may be stretched again in an aqueous solution of boric acid. The draw ratio at this time is preferably 3 times or less, more preferably 1.2 to 3 times, further preferably 1.3 to 2.9 times, most preferably 1.4 to 2.8 times.

The boric acid concentration in the aqueous solution at this time is preferably 2 to 6 mass%, more preferably 2 to 5 mass%, and even more preferably 2 to 4 mass%. When the concentration of boric acid is less than 2% by mass, color irregularity may be increased in the resulting polarizing film. When the concentration of boric acid exceeds 6 mass%, the crosslinking of PVA by boric acid becomes excessive, which may make it difficult to stretch the film at a high magnification.

It is also preferable to add potassium iodide to the aqueous solution of boric acid in order to make the color of the polarizing film close to neutral gray. The concentration of potassium iodide is preferably from 3 to 10% by mass, more preferably from 4 to 8% by mass. If the concentration of potassium iodide is less than 3% by mass, the degree of blue of the resulting polarizing film may become strong. On the other hand, when the concentration of potassium iodide exceeds 10 mass%, the degree of redness of the obtained polarizing film may become strong. The boric acid aqueous solution may contain, for example, a metal compound such as iron or zirconium as another component.

In the stretching, the temperature of the aqueous solution is not particularly limited, but is preferably from 50 to 60 캜, more preferably from 55 to 60 캜, still more preferably from 57 to 60 캜. If the stretching temperature is less than 50 캜, sufficient stretching can not be performed, and the degree of polarization of the obtained polarizing film may be lowered. When the stretching temperature exceeds 60 캜, the transmittance of the resulting polarizing film may be lowered.

The stretching magnification through the whole process is preferably 4.5 to 7.0 times, more preferably 4.7 to 6.5 times, still more preferably 5.0 to 6.0 times. If the stretching ratio is less than 4.5 times, the polarizing performance of the obtained polarizing film may be lowered. In addition, when the stretching magnification exceeds 7.0 times, breakage of the film during stretching often occurs, and it may be difficult to stably produce a polarizing film.

The color adjustment after stretching is preferably carried out in an aqueous solution containing boric acid and potassium iodide. At this time, a metal compound such as zinc chloride or zinc iodide may be added to the aqueous solution. The temperature of the aqueous solution is preferably lower than the stretching temperature in order to prevent deterioration of the polarization performance. Specifically, the temperature is preferably 20 to 50 캜, more preferably 30 to 40 캜. The time for color adjustment is not particularly limited.

The polarizing film thus obtained can be dried by various drying methods, such as a batch method, a continuous float method or a continuous roll phase contact method. The drying temperature is preferably 40 to 80 占 폚, preferably 45 to 70 占 폚, in order to prevent sublimation of iodine from the polarizing film and to suppress the desorption reaction of the boric acid crosslinked with PVA , And more preferably 50 to 60 ° C. The drying time is not particularly limited and varies depending on the apparatus and the drying temperature, but is in the range of, for example, 3 to 6 minutes.

Example

Hereinafter, the present invention will be described concretely with examples and the like, but the present invention is not limited at all by the following examples. In Examples and the like, the viscosity average degree of polymerization (P) of the PVA, the swelling degree of the PVA film, the retardation (Re) of the PVA film, the transmittance (Y) of the polarizing film and the degree of polarization (V) were evaluated by the following methods.

(1) Measurement of viscosity average degree of polymerization (P) of PVA

0.28 g of PVA, 70 g of distilled water, and a stirrer were charged into a 100 ml common flask glass-sealed Erlenmeyer flask. The Erlenmeyer flask with a stopper was immersed in a thermostatic chamber at 95 캜, and PVA was dissolved while stirring with a stirrer to prepare a 0.4% PVA aqueous solution. This PVA aqueous solution was filtered with a Buchner funnel-shaped glass filter 3G and cooled in a constant temperature water bath at 30 ° C to obtain a sample for measuring the degree of polymerization. As a reference sample, 70 g of distilled water was placed in a separate 100-ml stoppered glass flask, and the stopper was put thereinto and immersed in a constant-temperature water bath at 30 ° C.

The evaporation dish heated at 105 DEG C for 1 hour was cooled with a desiccator for 30 minutes, and the mass a (g) of the evaporation dish was measured. 10 ml of the sample for measuring the degree of polymerization was transferred to the evaporation dish by a hall pipette, and the resultant was dried in a desiccator for 30 minutes and then the mass b (g) was measured. The concentration c (g / l) of the sample for measuring the polymerization degree was calculated by the following equation.

c = 1000 x (b - a) / 10

A sample for measurement of degree of polymerization or distilled water was introduced into an Ostworld viscometer using a 10 ml hole pipette and stabilized in a constant temperature water bath at 30 占 폚 for 15 minutes. The falling number of seconds t ₁ (s) and the number of falling seconds t ₀ (s) of the charged polymerization degree measuring sample were measured, and the viscosity average degree of polymerization P was calculated by the following formula.

η _r = t ₁ / t ₀

[?] = 2.303 占 Log (? _r / c)

Log (P) = 1.613 x Log ([?] X 10 ⁴ /8.29)

(2) Measurement of degree of swelling of PVA film

The PVA film was cut into 5 cm x 5 cm and immersed in 1 l distilled water at 30 ° C for 4 hours. The PVA film was taken out from the distilled water, sandwiched between two pieces of filter paper to absorb water droplets on the surface, and the mass D was measured. The PVA film was dried in a dryer at 105 DEG C for 16 hours, cooled in a desiccator for 30 minutes, and then the mass E was measured. The degree of swelling of the PVA film was calculated by the following formula.

A = 100 x D / E (%)

(3) Measurement of retardation Re of PVA film

A rectangular sample having a width of 5 cm and a flow direction of 10 cm was taken from the center of the PVA film and the retardation (Re) at a measurement wavelength of 550 nm was measured using an optical material inspection apparatus RETS-1100 manufactured by Otsuka Electronics Co., Were measured.

(4) Measurement of transmittance Y of polarizing film

Two square samples each having a size of 4 cm in the stretching direction and 4 cm in the width direction were collected from the central portion in the width direction of the polarizing film and measured using a spectrophotometer U-4100 (with an integral sphere) manufactured by Hitachi, (The method of measuring the object color), the C light source and the visibility of the visible light region in the 2 ° field of view were corrected, and the transmittance of light in the case of inclining the polarizing film sample by 45 ° with respect to the stretching axis direction was -45 The transmittance of light when tilted was measured, and the average value Y1 (%) thereof was determined. In the same manner for the other polarizing film sample, the transmittance of light at an angle of 45 DEG and the transmittance of light at an angle of -45 DEG were measured, and their average value Y2 (%) was determined. Y1 and Y2 were averaged by the following formula to determine the transmittance Y (%) of the polarizing film.

Y = (Y1 + Y2) / 2

(5) Measurement of polarization degree V of polarizing film

The transmittance Y∥ (%) of light when the two polarizing films collected in (4) above are superimposed so that the stretching directions thereof are parallel to each other and the transmittance Y⊥ (%) of light when the stretching directions are orthogonally crossed, Was measured in the same manner as in the case of the transmittance described in (4), and the degree of polarization V (%) was determined by the following formula.

V = {(Y∥ -Y⊥) / (Y∥ + Y⊥)} ^1/2 × 100

[Example 1]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 120 ° C for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 230%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 29 nm.

Next, the PVA film was cut in a flow direction of 11 cm x 10 cm in the width direction, and the flow direction was set in the stretching direction in a stretching jig having a length of 4 cm between the chucks. The PVA film was immersed in pure water at 30 캜 for one minute, (Temperature: 30 DEG C) containing 0.03 mass% of iodine and 3 mass% of potassium iodide, and stretched 2.6 times at a rate of 0.13 m / min to adsorb iodine.

Subsequently, this stretched film was immersed in a stretching liquid (temperature 57.5 DEG C) containing boric acid at 4 mass% and potassium iodide at a ratio of 6 mass%, stretching 2.3 times at a rate of 0.13 m / min, Was fixed and dried at 50 DEG C for 4 minutes to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above. As a result, polarizing films each having excellent polarizing performance were obtained at 44.0% and 99.99%, respectively.

[Example 2]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat treatment was performed at 115 캜 for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 240%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 26 nm.

Next, in the same manner as in Example 1, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, polarizing films having excellent polarizing performance were obtained at 44.0% and 99.96%, respectively.

[Example 3]

100 mass parts of PVA having a polymerization degree of 9100 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat treatment was performed at 110 캜 for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 230%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 39 nm.

Next, in the same manner as in Example 1 except that the stretching magnification was changed to 2.5 times, the PVA film was stretched while iodine was adsorbed and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, polarizing films with excellent polarizing performance were obtained at 44.0% and 99.95%, respectively.

[Example 4]

100 mass parts of PVA having a degree of polymerization of 5200 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 135 ° C for 3 minutes. The degree of swelling of the PVA film after heat treatment was measured by the method described in (2) above and found to be 205%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 29 nm.

Next, in the same manner as in Example 3, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, polarizing films with excellent polarizing performance were obtained at 44.0% and 99.95%, respectively.

[Example 5]

100 mass parts of PVA having a degree of polymerization of 5500 and a degree of saponification of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 130 ° C for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 215%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 29 nm.

Next, in the same manner as in Example 1, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above. As a result, polarizing films each having excellent polarizing performance were obtained at 44.0% and 99.99%, respectively.

[Comparative Example 1]

100 mass parts of PVA having a degree of polymerization of 4800 and a degree of saponification of 99.8 mol% and a 6.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 120 ° C for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 220%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 28 nm.

Next, in the same manner as in Example 1, except that the stretching magnification was changed to 2.7 times, the PVA film was stretched while iodine was adsorbed and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, the polarizability of the polarizing film was slightly insufficient at 44.0% and 99.92%.

[Comparative Example 2]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 140 ° C for 3 minutes. The degree of swelling of the PVA film after heat treatment was measured by the method described in (2) above and found to be 195%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 29 nm.

Next, in the same manner as in Example 1, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, the polarizability of the polarizing film was slightly insufficient at 44.0% and 99.92%.

[Comparative Example 3]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted at a moisture content of 3 mass% by adjusting its humidity at 26 DEG C and 20% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat treatment was performed at 110 캜 for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 250%. The retardation of the PVA film was measured by the method described in (3) above and found to be 28 nm.

Next, in the same manner as in Example 1, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, the degree of polarization of the polarizing film was slightly insufficient at 44.0% and 99.87%.

[Comparative Example 4]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted to moisture content of 3 mass% by adjusting humidity at 26 DEG C and 20% RH for 16 hours, fixed to all four sides of the metal frame, and heat-treated at 120 DEG C for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 230%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 5 nm.

Next, in the same manner as in Example 1, iodine was adsorbed while stretching the PVA film, and further stretched to obtain a polarizing film. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above to be 44.0% and 99.97%, respectively. The polarizing films were good in polarizing performance, Stain was observed.

[Comparative Example 5]

100 mass parts of PVA having a degree of polymerization of 5800 and a saponification degree of 99.8 mol% and a 5.5 mass% PVA aqueous solution containing 12 mass parts of glycerin as a plasticizer were poured on a metal roll at 60 deg. C and dried for 60 minutes to obtain a PVA A film was obtained. The film was adjusted to a moisture content of 8% by mass by adjusting the humidity at 26 DEG C and 65% RH for 16 hours. Then, both ends in the width direction of the film were fixed to two parallel sides of the metal frame so that the film did not shrink in the width direction And heat-treated at 120 ° C for 3 minutes. The degree of swelling of the PVA film after the heat treatment was measured by the method described in (2) above and found to be 230%. Further, the retardation of the PVA film was measured by the method described in (3) above and found to be 70 nm.

Next, in the same manner as in Example 1, a polarizing film was obtained in the same manner as in Example 1, except that the PVA film was stretched while iodine was adsorbed and the stretching magnification was increased to 1.8 times. The transmittance and the degree of polarization of the polarizing film were measured by the methods described in (4) and (5) above, respectively. As a result, the polarizability of the polarizing film was slightly insufficient at 44.0% and 99.20%. Therefore, in order to improve the polarization degree, the target value of the stretching magnification was changed from 1.8 times to 2.3 times, and as a result, the stretching cut occurred and a polarizing film could not be obtained.

The results are summarized in Table 1.

Industrial availability

The polarizing film obtained from the PVA film of the present invention can be applied to a liquid crystal display device such as an electronic tablet calculator, a wrist watch, a notebook, a liquid crystal monitor, a liquid crystal color projector, a liquid crystal television, a vehicle navigation system, a mobile phone, It can be effectively used for manufacturing a polarizing plate as a component.

Claims (1)

All inventions described in the Detailed Description of the Invention