POLY(VINYL ALCOHOL) FILM AND PRODUCTION METHOD FOR POLARIZING FILM

Abstract

A polyvinyl alcohol film comprises a vinyl alcohol-based polymer, wherein, when the polyvinyl alcohol film being measured by a solid echo method using pulse NMR at 60 C. for waveform separation of a free induction decay curve of 1H spin-spin relaxation into three curves derived from three components a component A, a component B, and a component C in order of short relaxation time, the component A has a resulting relaxation time of 0.0070 milliseconds or more and 0.0092 milliseconds or less, and a resulting component ratio of 20% or more and 50% or less.

Claims

1. A polyvinyl alcohol film comprising a vinyl alcohol-based polymer, wherein, when the polyvinyl alcohol film is measured by a solid echo method using pulse NMR at 60 C. for waveform separation of a free induction decay curve of 1H spin-spin relaxation into three curves derived from three components a component A, a component B, and a component C in order of short relaxation time, the component A has a resulting relaxation time of 0.0070 milliseconds or more and 0.0092 milliseconds or less, and a resulting component ratio of 20% or more and 50% or less.

2. The polyvinyl alcohol film according to claim 1, wherein the vinyl alcohol-based polymer has a degree of saponification of 99 mol % or more.

3. The polyvinyl alcohol film according to claim 1, wherein the vinyl alcohol-based polymer has a degree of polymerization of 2000 or more and 4000 or less.

4. The polyvinyl alcohol film according to claim 1, comprising a plasticizer.

5. The polyvinyl alcohol film according to claim 1, for use in a polarizing film.

6. A method for manufacturing a polarizing film comprising using the polyvinyl alcohol film according to claim 1.

7. The method for manufacturing a polarizing film according to claim 6, comprising steps of dyeing the polyvinyl alcohol film, stretching the polyvinyl alcohol film, and performing a fixation treatment to the dyed polyvinyl alcohol film.

8. The method for manufacturing a polarizing film according to claim 7, wherein the fixation treatment is performed after stretching of the polyvinyl alcohol film.

Description

EXAMPLES

[0080] The present invention is further specifically described with reference to Examples, though the present invention is not limited thereto.

[0081] The measurement method and the evaluation method in the present Examples are as follows.

(1) Measurement of Relaxation Time and Component Ratio of Component A

[0082] A film sample of the PVA films obtained in Examples and Comparative Examples were laminated to a UV release tape (trade name SELFA-SE manufactured by Sekisui Chemical Co., Ltd.) to be fixed using a laminator (l.sub.aminator HOTDOG Leon 13DX manufactured by Lami Corporation Inc.) set at a temperature of 60 C. and a speed of 5. Subsequently, the fixed PVA film was aged in a thermostat at 23 C. and 50% RH for 48 hours. In order to achieve fixation of the PVA film to the UV release tape by the laminator, both are sandwiched with SUS plate having a thickness of 1 mm or less and a release-treated PET film having a thickness of 50 m.

[0083] On the occasion of fixation, the lamination was performed such that the roll width direction of the UV release tape is perpendicularly crossed with the longitudinal direction of the PVA film. The longitudinal direction of the PVA film is the same as the cutting direction of the PVA film when rolled into a cylindrical form for introduction into an NMR tube (longitudinal direction of the film in a cylindrical form).

[0084] The fixed film sample was exposed to UV rays having a wavelength of 365 nm to receive an energy of 1000 mJ/cm.sup.2 at the irradiated surface using a UV irradiation apparatus manufactured by ORC Manufacturing Co., Ltd., apparatus model: JL-4300-3, lamp model: IML-4000, so that the UV release tape was detached from the film sample.

[0085] A film sample having a low water content may wrinkle when aged after fixation with an UV release tape. When wrinkles occur after aging, the UV release tape is detached through the irradiation step, the wrinkles of the PVA film are then smoothed once by a laminator. Fixation is performed through lamination using a new SELFA-SE, and the aging step is performed. The operation may be repeated until the wrinkles disappear.

[0086] A film sample detached from the UV release tape having a weight of about 700 mg was rolled into a cylindrical form and introduced into a sample tube made of glass having a diameter of 10 mm (manufactured by BRUKER, item No. 1824511, diameter: 10 mm, length: 180 mm, flat bottom), such that the height was controlled to 15 mm. The sample was installed in a pulse NMR apparatus (the Minispec MQ20 manufactured by BRUKER), and the temperature was raised stepwise from 25 C. (retained for 40 minutes), to 40 C. (retained for 40 minutes), and to 60 C. (retained for 10 minutes). The measurement was performed by a solid echo method at 60 C., and the resulting free induction decay curve of 1H spin-spin relaxation was subjected to waveform separation into three curves derived from three components a component A, a component B, and a component C. The waveform separation was performed by fitting to both a Gaussian model and an exponential model. From the curves derived from the three components obtained in each measurement, the ratio of each component was obtained. The same type of measurement was performed twice to obtain the ratio of each component as an average.

[0087] Using analytical software TD-NMRA (Version 4.3, Rev. 0.8) manufactured by Bruker Corporation, the component A was fitted to a Gaussian model and the component B and the component C were fitted to an exponential model according to the product manual. Also, in the analysis, fitting was performed using points up to 0.6 milliseconds in the relaxation curve.

[0088] Also, the following equation was used in the fitting.

Y=A1*exp(1/w1*(t/T2A)w1)+B1*exp(1/w2*(t/T2B)w2)+C1*exp(1/w3*(t/T2C)w3),

[0089] where w1 to w3 are Weibull coefficients; w1 is 2; w2 and w3 are 1; A1, B1 and C1 are the component ratios of the component A, the component B and the component C, respectively; T2A, T2B and T2C represent the relaxation times of the component A, the component B and the component C, respectively; and t represents time.

[0090] The component A, the component B and the component C are components defined in order of short relaxation time when the PVA film is measured using pulse NMR. Although each value of the relaxation time is not particularly limited, the normal relaxation time is less than 0.02 milliseconds for the component A, 0.02 milliseconds or more and less than 0.1 milliseconds for the component B, and 0.1 milliseconds or more for the component C.

<Solid echo method>

[0091] Scans: 128 times

[0092] Recycle delay: 1 sec

[0093] Acquisition scale: 1 ms

(2) Elongation at Break

[0094] A PVA film having a width of 10 cm obtained in each of Examples and Comparative Examples was immersed in an aqueous solution dissolving iodine (I.sub.2) .sub.and potassium iodide (KI). In the aqueous solution, the PVA film with a span length of 2 cm was stretched at a stretching rate of 1 cm/second using a stretcher to be broken. The ratio of the film length at the breakage to the film length before stretching was defined as the elongation at break. The aqueous solution comprised 0.4 parts by mass of iodine, 40 parts by mass of potassium iodide, and 1000 parts by mass of water.

(3) Measurement of Degree of Polarization

[0095] The degree of polarization P of a polarizing film obtained in each of Examples and Comparative Examples was evaluated by the following equation using a spectrophotometer UV-3101PC manufactured by Shimadzu Corporation. YP (parallel transmittance) is the transmittance of films superimposed to each other in parallel with the stretching direction of the film, and YC (cross transmittance) is the transmittance of films superimposed to each other in orthogonal to the stretching direction of the film.

Degree of polarization P(%)={(YPYC)/(YP+YC)}.sup.1/2100

[Criteria of Degree of Polarization]

[0096] A: degree of polarization of 99 or more

[0097] B: degree of polarization of 90 or more and less than 99

[0098] C: degree of polarization of less than 90

SYNTHESIS EXAMPLE 1

[PVA1 (Degree of Saponification: 99.5 mol %, Degree of Polymerization: 2700)]

[0099] Into a reaction vessel equipped with a thermometer, a stirrer and a cooling tube, 2000 parts by mass of vinyl acetate monomer and 200 parts by mass of methanol were added, and after nitrogen purge with nitrogen gas blown in for 30 minutes, the reaction vessel was heated at 60 C. for 30 minutes. Subsequently, 0.4 parts by mass of 2,2-azobisisobutyronitrile as polymerization initiator was added thereto and then let the reaction proceed at 60 C. for 4 hours. After completion of the reaction time, the reaction liquid was cooled. The polymerization ratio was 29% based on the measurement of the polymerization ratio after cooling. Subsequently, an operation for removing the residual vinyl acetate monomer together with methanol under reduced pressure was performed along with addition of methanol, so that a methanol solution containing 50 mass % of polyvinyl acetate was obtained. To the methanol solution, a methanol solution of sodium hydroxide was added so that a sodium hydroxide content was 0.08 mol % based on vinyl acetate, and saponification was performed at 40 C. The resulting solid content was pulverized, washed with methanol, and then dried to obtain PVA1. The resulting PVA1 was subjected to measurement of the degree of saponification and the degree of polymerization in accordance with JIS K 6726. The degree of saponification was 99.5 mol % and the degree of polymerization was 2700.

Synthesis Example 2

[PVA2 (Degree of Saponification: 99.5 mol %, Degree of Polymerization: 1500)]

[0100] Into a reaction vessel equipped with a thermometer, a stirrer and a cooling tube, 2000 parts by mass of vinyl acetate monomer and 200 parts by mass of methanol were added, and after nitrogen purge with nitrogen gas blown in for 30 minutes, the reaction vessel was heated at 60 C. for 30 minutes. Subsequently, 0.6 parts by mass of 2,2-azobisisobutyronitrile as polymerization initiator was added thereto and then let the reaction proceed at 60 C. for 4 hours. After completion of the reaction time, the reaction liquid was cooled. The polymerization ratio was 35% based on the measurement of the polymerization ratio after cooling. Subsequently, an operation for removing the residual vinyl acetate monomer together with methanol under reduced pressure was performed along with addition of methanol, so that a methanol solution containing 50 mass % of polyvinyl acetate was obtained. To the methanol solution, a methanol solution of sodium hydroxide was added so that a sodium hydroxide content was 0.08 mol % relative to vinyl acetate, and saponification was performed at 40 C. The resulting solid content was pulverized, washed with methanol, and then dried to obtain PVA2. The resulting PVA2 was subjected to measurement of the degree of saponification and the degree of polymerization in accordance with JIS K 6726. The degree of saponification was 99.5 mol % and the degree of polymerization was 1500.

EXAMPLE 1

(Manufacturing of PVA Film)

[0101] Into a reaction vessel equipped with a thermometer, a stirrer and a cooling tube, 1000 parts by mass of water was fed at 25 C., and 100 parts by mass of PVA1 and 10 parts by mass of glycerol were fed therein while stirring. The mixture liquid was heated to 95 C. and retained at 95 C. for 120 minutes, so that PVA1 and glycerol were dissolved in water. The mixture liquid (PVA solution) was then cooled down to 35 C. at a temperature lowering rate of 1 C./minute. The PVA solution cooled to 35 C. was applied to a glass plate having a thickness of 7 mm, dried at 80 C. for 1 hour, and then detached from the glass plate to obtain a PVA film having a thickness of 30 m. From the resulting film, 10 g of the film was cut out to be subjected to 100 cycles of Soxhlet extraction with methanol. The resulting resin was then subjected to measurement of the degree of saponification and the degree of polymerization in accordance with JIS K 6726. The degree of saponification was 99.5 mol % and the degree of polymerization was 2700.

(Manufacturing of Polarizing Film)

[0102] Next, while immersing the resulting PVA film in an aqueous solution dissolving iodine (I2) and potassium iodide (KI) at 25 C. for 60 seconds, stretching was performed at a stretching ratio of 5 times. The aqueous solution comprised 0.4 parts by mass of iodine, 40 parts by mass of potassium iodide and 1000 parts by mass of water. The PVA film was then immersed in a boric acid aqueous solution with a concentration of 4.0 mass % at 25 C. for 5 minutes, washed with water after pulling out from the aqueous solution, and then dried in a drying oven set at 70 C. to obtain a polarizing film.

EXAMPLE 2

(Manufacturing of PVA Film)

[0103] Into a reaction vessel equipped with a thermometer, a stirrer and a cooling tube, 1000 parts by mass of water was fed at 25 C., and 100 parts by mass of PVA1 and 8 parts by mass of polyethylene glycol having an average molecular weight of 400 were fed therein while stirring. The mixture liquid was heated to 95 C. and retained at 95 C. for 120 minutes, so that PVA1 and polyethylene glycol were dissolved in water. The mixture liquid (PVA solution) was then cooled down to 35 C. at a temperature lowering rate of 1 C./minute. The PVA solution cooled at 35 C. was applied to a glass plate having a thickness of 7 mm, dried at 80 C. for 1 hour, and then detached from the glass plate to obtain a PVA film having a thickness of 30 m. From the resulting film, 10 g of the film was cut out to be subjected to 100 cycles of Soxhlet extraction with methanol. The resulting resin was then subjected to measurement of the degree of saponification and the degree of polymerization in accordance with JIS K 6726. The degree of saponification was 99.5 mol % and the degree of polymerization was 2700.

(Manufacturing of Polarizing Film)

[0104] Next, a polarizing film was manufactured from the resulting film in the same manner as in Example 1.

EXAMPLES 3 AND 4

[0105] The procedure was performed in the same manner as in Example 1, except that the amount of glycerol fed was changed as described in Table 1.

EXAMPLE 5

[0106] The procedure was performed in the same manner as in Example 1, except that the drying time of the PVA solution applied to the glass plate was changed to 2 hours.

EXAMPLE 6

[0107] The procedure was performed in the same manner as in Example 1, except that the temperature lowering rate in cooling of the PVA solution down to 35 C. was changed to 2 C./minute and the PVA solution applied to the glass plate was dried at 90 C. for 30 minutes.

COMPARATIVE EXAMPLE 1

[0108] A PVA film and a polarizing film were obtained in the same manner as in Example 1, except that the type of PVA was changed to PVA2, the amount of glycerol fed was changed to 0 parts by mass, and the stretching ratio in manufacturing the polarizing film was changed to 3 times. From the resulting PVA film, 10 g of the film was cut out to be subjected to 100 cycles of Soxhlet extraction with methanol. The resulting resin was then subjected to measurement of the degree of saponification and the degree of polymerization in accordance with JIS K 6726. The degree of saponification was 99.5 mol % and the degree of polymerization was 1500.

COMPARATIVE EXAMPLE 2

[0109] A PVA film and a polarizing film were obtained in the same manner as in Example 1, except that the type of PVA was changed to PVA2, the amount of glycerol fed was changed to 20 parts by mass, and the stretching ratio in manufacturing the polarizing film was changed to 3 times.

COMPARATIVE EXAMPLE 3

(Manufacturing of PVA Film)

[0110] Into a reaction vessel equipped with a thermometer, a stirrer and a cooling tube, 1000 parts by mass of water was fed at 25 C., and 100 parts by mass of PVA1 and 20 parts by mass of glycerol were fed therein while stirring. The mixture liquid was heated to 95 C. and retained at 95 C. for 120 minutes, so that PVA1 and glycerol were dissolved in water. The PVA solution retained at 95 C. was then applied to a PET film having a thickness of 50 um, dried at 90 C. for 30 minutes, and then detached from the glass plate to obtain a PVA film having a thickness of 30 um.

[0111] (Manufacturing of Polarizing Film)

[0112] Next, a polarizing film was manufactured from the resulting film as in the same manner as in Example 1.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 PVA solution PVA 100 100 100 100 100 composition Plasticizer 10 8 20 1 10 (parts by mass) Water 1000 1000 1000 1000 1000 PVA properties Degree of 99.5 99.5 99.5 99.5 99.5 saponification (mol %) Degree of 2700 2700 2700 2700 2700 polymerization Plasticizer Type Glycerol PEG400 Glycerol Glycerol Glycerol Manufacturing Temperature RT.fwdarw.95 C. RT.fwdarw.95 C. RT.fwdarw.95 C. RT.fwdarw.95 C. RT.fwdarw.95 C. conditions raising condition Retention time Retained for Retained for Retained for Retained for Retained for 2 hours 2 hours 2 hours 2 hours 2 hours Temperature Lowered Lowered Lowered Lowered Lowered lowering down to 35 C. down to 35 C. down to 35 C. down to 35 C. down to 35 C. condition at 1 C./min at 1 C./min at 1 C./min at 1 C./min at 1 C./min Application Glass plate Glass plate Glass plate Glass plate Glass plate (support) Drying 80 C. for 80 C. for 80 C. for 80 C. for 80 C. for condition 1 hour 1 hour 1 hour 1 hour 2 hours Component A Relaxation time 0.0085 0.00086 0.0088 0.0089 0.0075 (milliseconds) Component 33 35 20.1 48 33 ratio (%) Evaluation Elongation at 780 780 850 550 730 results break (%) Degree of A A A A A polarization Comparative Comparative Comparative Example 6 Example 1 Example 2 Example 3 PVA solution PVA 100 100 100 100 composition Plasticizer 10 0 20 20 (parts by mass) Water 1000 1000 1000 1000 PVA properties Degree of 99.5 99.5 99.5 99.5 saponification (mol %) Degree of 2700 1500 1500 2700 polymerization Plasticizer Type Glycerol Glycerol Glycerol Manufacturing Temperature RT.fwdarw.95 C. RT.fwdarw.95 C. RT.fwdarw.95 C. RT.fwdarw.95 C. conditions raising condition Retention time Retained for Retained for Retained for Retained for 2 hours 2 hours 2 hours 2 hours Temperature Lowered Lowered Lowered No lowering lowering down to 35 C. down to 35 C. down to 35 C. of condition at 2 C./min at 1 C./min at 1 C./min temperature Application Glass plate Glass plate Glass plate PET film (support) Drying 90 C. for 80 C. for 80 C. for 90 C. for condition 0.5 hours 1 hour 1 hour 0.5 hours Component A Relaxation time 0.0092 0.009 0.0095 0.0096 (milliseconds) Component 33 65 25 35 ratio (%) Evaluation Elongation at 800 350 700 900 results break (%) Degree of A B B B polarization

[0113] As shown in Examples described above, control of the relaxation time of the component A and the component ratio of the component A to specified ranges resulted in excellent elongation at break, so that the PVA film was unlikely to be broken in manufacturing of a polarizing film. Also, the resulting polarizing film had excellent polarization performance.