JP3251073B2 - Film and polarizing film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol (hereinafter referred to as P) which is suitable as a raw material for producing a high-performance polarizing film.
VA) and a polarizing film.

[0002]

2. Description of the Related Art A polarizing film having a light transmitting function and a light shielding function is used together with a liquid crystal having a light switching function.
It is a basic component of a liquid crystal display (LCD). The field of application of this LCD is from small devices such as calculators and clocks in the early days to high quality and high reliability such as laptop personal computers, word processors, liquid crystal color projectors, car navigation systems, and liquid crystal televisions. Equipment. Under such circumstances, the polarizing film is required to have much better polarization performance and durability than before. In particular, a personal computer and a word processor require the brightness of the screen, so that a polarizing film having a high degree of polarization at a single transmittance of 43% or more is demanded. In general, a polarizing film easily obtains high polarization at a place where the single transmittance is low, but decreases as the single transmittance increases. In addition, since a car navigation system or the like is used under severe conditions, a highly reliable polarizing film having durability even under high temperature and high humidity is demanded.

[0003]

SUMMARY OF THE INVENTION The present invention relates to a film made of a PVA-based resin suitable as a raw material for producing a high-performance polarizing film, and a film having high polarization and high durability, particularly high light transmission. It is intended to provide a polarizing film having a high polarizing property at a high rate.

[0004]

Means for Solving the Problems The present inventors have prepared a stock solution containing a PVA-based resin suitable as a raw material for producing a polarizing film.
As a result of intensive studies on a film formed by continuously discharging a film from a (hereinafter sometimes abbreviated as a PVA film), a molecular dichroic ratio (D) of 1.2 or less was obtained. , And PV having an average crystallinity (Xc) of 50 to 75% by weight
A film was found. When this PVA film is used as a raw material, surprisingly, the molecular dichroic ratio of PVA after uniaxial stretching is improved, and a polarizing film having high polarizing properties and high durability can be produced. It is found that it becomes.

The molecular dichroic ratio (D) of the PVA resin in the PVA film of the present invention is 1.2 or less, preferably 1.15 or less, more preferably 1.10 or less, particularly preferably 1.05 or less. is there. The average crystallinity (Xc) of the PVA-based resin is 50 to 75% by weight, preferably 55 to 7%.
0%. The molecular dichroism ratio (D) of the PVA-based resin is 1.
If it exceeds 2, even if the film is uniaxially stretched, sufficient molecular orientation of PVA cannot be obtained, and the obtained polarizing film does not exhibit desired performance. On the other hand, when the average crystallinity (Xc) of the PVA-based resin exceeds 75% by weight, the dyeability and stretchability become insufficient, and a polarizing film having high polarization performance cannot be obtained. If the average crystallinity (Xc) is less than 50% by weight, a highly durable polarizing film cannot be obtained. Further, the polarizing film of the present invention,
A molecular dichroic ratio D of 3.5 or more, preferably 4.0 or more,
More preferably, it is 4.3 or more. When D is less than 3.5, the polarizing property of the polarizing film decreases.

[0006] The molecular dichroic ratio (D) of the PVA-based resin is a value obtained by the following equation and represents the degree of orientation of the PVA-based resin molecules. D = A1 / A2 Here, A1 and A2 are caused by bending vibration in the molecular chain direction of the methylene group of the PVA-based resin having a peak in a region of 1200 to 1300 cm ⁻¹ measured using an infrared spectrophotometer. A1 is the absorbance when the electric vector of the irradiation polarized light is parallel to the film forming direction of the PVA film (hereinafter abbreviated as MD direction), and A2 is the electric vector of the irradiation polarized light which is the PVA film. Is parallel to the width direction (hereinafter abbreviated as the TD direction). A1 and A2 are measured by ATR method (total reflection absorption measurement method) under measurement conditions (cell: KRS-5, manufactured by Pure Optex, incident angle: 45 degrees). As an internal standard of the absorption intensity when calculating the molecular dichroism ratio (D), the absorbance of water at 1640 cm ^-1 was used. The infrared spectrophotometer used for the measurement is not limited, but the present inventors used JIR-5500 manufactured by JEOL.

The average crystallinity of the PVA resin (X
c) (Average crystallinity of the entire region in the depth direction of the film)
Is a value obtained by the following equation. Xc = Sc / (Sc + Sa) Here, Sc and Sa are the crystal part (Sc) and the amorphous part by using a computer to obtain a curve obtained by removing a blank curve measured without a sample from a diffraction X-ray intensity curve of the relevant sample. (Sa) is the area of the chart corresponding to each. The diffraction X-ray intensity curve is 40 KV, 100 mA
0.154 wavelength by graphite monochromator
While irradiating a non-aligned sample with a CuKα1 ray of 05 nm at a rate of 76 rotations per minute in a plane perpendicular to the incident X-ray, a scattered X-ray in a diffraction angle range of 2θ = 5 to 35 deg is provided by a scintillation counter and Measure and record with a wave height analyzer. There is no limitation on the X-ray diffraction device used for the measurement,
The present inventors have developed a rotary anti-cathode X-ray diffractometer R manufactured by Rigaku Denki.
AD-γC (using a copper negative electrode) was used.

The PVA film of the present invention can be obtained by reducing the MD draw (hereinafter abbreviated as film forming draw) of the film in the film forming step to 1 or less, preferably by reducing the film forming tension as much as possible. it can. In order to form a film under such conditions, it is necessary to strictly perform operation management such as detection of film tension in a film forming apparatus and speed control in conjunction with a dancer roll position. PVA of the present invention
In contrast to the method for producing a film, the conventional method for producing a PVA film has a film forming running stability (prevention of wrinkling due to loosening of the film in the MD direction, prevention of poor appearance of the film, and prevention of film formation). Since the film forming tension was increased so that the film forming draw exceeded 1, only a PVA film having low optical performance was obtained.

Here, the film-forming draw is used in a film-forming process of a PVA film for forming a PVA stock solution into a film.
It is a speed ratio between the casting speed and the winding speed in the process of winding the film formed, and is expressed by the following equation. (Film draw) = (winding speed) / (cast speed) The film forming tension (kg / m) is the maximum tension applied in the MD direction of the film in the film forming process excluding the winding process. It is.

Examples of the film forming apparatus include a belt type film forming machine and a drum type film forming machine. FIG. 1 shows a belt type film forming machine 11 used for manufacturing a PVA film of the present invention.
The belt type film forming machine 11 has a die 10. A stock solution L composed of a PVA-based polymer aqueous solution is supplied to the die 10. The die 10 has a slit-shaped opening that is long in the width direction (the direction perpendicular to the plane of the paper of FIG. 1). 13.

The belt type film forming machine 11 has the endless belt 13 running across a pair of rollers 12, 12, and casts the undiluted solution flowing out of the die 10 onto the belt 13. And dried. The belt 13 is made of, for example, stainless steel,
Its outer peripheral surface is mirror-finished. On the outer circumference and the inner circumference of the belt 13, partition walls 14 are provided to partition spaces in the traveling direction of the belt 13, respectively. Hot air H at 50 to 170 ° C. is blown from a hot air blower (not shown in the drawing) to the outer circumferential surface and the inner circumferential surface of the belt 13 to promote drying of the stock solution.
In the most downstream zone 14A, the film F may be cooled by the normal temperature air C.

A peeling roller 15 is provided in the vicinity of the right roller 12 in the drawing of the pair of rollers 12, 12, and the film F dried to a predetermined moisture content is provided.
Is peeled off from the belt 13 by the peeling roller 15. The film F is wound around a winder 19 through a heat treatment device 16 and a humidity control device 17. The heat treatment machine 16
Is to blow a hot air of about 100 to 200 ° C. onto the film F to change the crystallinity of the film F and the like. The humidity controller 17 adjusts the water content of the film F to, for example, about 5% by weight.

FIG. 2 shows a drum type film forming machine 21. In the figure, a stock solution L is supplied to a die 10 in a fixed amount, a film is formed on a drum-type roll 22, and dried by a drying roll 23 to produce a PVA film F. Film F
Passes through a heat treatment machine 16, a humidity control machine 17, and an inspection machine 18,
It is wound up by the winder 19.

[0014] The drying temperature is appropriately selected from about 50 to 170 ° C. In order to reduce the film-forming draw, it is important to keep the moisture at the time of peeling the film from the belt or the drum low, and in that sense, it is preferable to use a belt-type film-forming machine capable of taking a long drying time. . 25% by weight or less as moisture at the time of film peeling,
It is preferably at most 15% by weight, particularly preferably from 3 to 10% by weight.

Examples of the raw material PVA resin used in the present invention include not only ordinary PVA produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but also unsaturated carboxylic acid or a derivative thereof, About 15 mol% of a saturated sulfonic acid or a derivative thereof, an α-olefin having 2 to 30 carbon atoms, etc.
Less than copolymerized modified PVA, polyvinyl formal, polyvinyl acetoacetate, polyvinyl butyral, and other polyvinyl acetals can also be used. PVA
As the stereoregularity of the system resin, those having an atactic structure are generally used, but those having a rich syndiotactic structure or an isotactic structure can also be used.

The degree of saponification of the PVA resin in the present invention is as follows:
From the viewpoint of durability, it is preferably at least 90 mol%, more preferably at least 95 mol%, particularly preferably at least 98 mol%. The polymerization degree of the PVA-based resin is preferably 1,000 or more, more preferably 1,000 to 20,000, and more preferably 1500 to 2,000 from the viewpoint of the polarization characteristics and durability of the polarizing film obtained by processing.
10,000 is more preferable, and especially 3000 to 1000
0 is preferred.

In the PVA film of the present invention, various polyol plasticizers such as glycerin, and nonionic, anionic and cationic surfactants are appropriately added and used.
When adding these additives, PVA-based resin 10
About 2 to 20 parts by weight is added to 0 parts by weight. The thickness of the PVA film of the present invention is not particularly limited.
150 μm is preferable, and 20 to 100 μm is more preferable. The length and width of the PVA-based film of the present invention are not particularly limited. The lower limit of the width of the PVA-based film is 50
cm or more, more preferably 80 cm or more, and 1
It is particularly preferably at least 00 cm. The upper limit of the width of the PVA-based film is preferably 3 m or less, more preferably 2.5 m or less. The length of the PVA-based film is preferably 1 m or more, more preferably 10 m or more.

Next, the polarizing film of the present invention will be described. The polarizing film of the present invention is characterized by comprising a PVA-based resin having a molecular dichroic ratio (D) of 3.5 or more. The polarizing film of the present invention can be obtained by using the above PVA film as a raw material. That is, the PVA film of the raw material is
If desired, it can be obtained by subjecting to swelling, dyeing, uniaxial stretching, boric acid compound treatment, and drying.

Dyeing can be performed before, during or after stretching. As the dye, iodine-potassium iodide or a dichroic dye can be used. The uniaxial stretching may be performed in warm water, or the film after absorbing water may be performed in air. The raw PVA film of the present invention can have a larger stretching ratio than conventional films, and the uniaxial stretching ratio is preferably 3 times or more, more preferably 4 times or more, and particularly preferably 5 times or more. . The stretching temperature is preferably from 20 to 200 ° C., and the stretching speed varies depending on the temperature conditions, but is usually selected from 10 to 1000% / min based on the original length of the raw PVA film. .

The boric acid compound used in the boric acid compound treatment includes boric acid and borax. The concentration of the boric acid compound aqueous solution is preferably 1 to 8% by weight, and the temperature of the aqueous solution is 20 to 60%. The temperature is appropriately selected from the range of ° C. It is practically preferable to mix an iodine compound in the bath at the time of the boric acid compound treatment. The uniaxially stretched film treated with the boric acid compound is subjected to a heat treatment for drying at a temperature of 50 to 200 ° C. for 1 to 5 minutes. The thickness of the polarizing film of the present invention is not particularly limited, but is preferably 5 to 50 μm, more preferably 10 to 40 μm. The width and length of the polarizing film of the present invention are not particularly limited. The lower limit of the width of the polarizing film is preferably 25 cm or more, more preferably 50 cm or more. The length of the polarizing film is preferably 1 m or more,
10 m or more is more preferable. The polarizing plate of the present invention can be obtained by laminating a support having excellent optical transparency and mechanical strength on both outer surfaces thereof. Examples of the support plate include a conventionally used cellulose acetate-based cellulose triacetate film, an acrylic film, and a polyester-based film.

[0021]

The present invention will be described more specifically with reference to the following examples. In the following examples and comparative examples, common manufacturing conditions in the manufacturing process of the polarizing plate are as follows. The weight ratio of potassium iodide / iodine in the dyeing solution was fixed at 100, and the iodine concentration was appropriately adjusted between 0.1 and 10 g / liter so that the single transmittance of the polarizing film was 43%.
4% by weight of boric acid was added to the stretching bath, and 4% by weight of boric acid and 4% by weight of potassium iodide were added to the boric acid fixing bath.
Drying was performed with hot air at 50 ° C. PVA on both sides of polarizing film
Using a system adhesive, cellulose triacetate having a thickness of 80 μ was bonded to obtain a polarizing plate. For the obtained polarizing plate, the single transmittance and the degree of polarization were measured, and the dichroic ratio was calculated. The durability of the polarizing plate was evaluated by measuring the single transmittance and the degree of polarization after being left at 60 ° C. and 90% RH for 200 hours.

The optical characteristics of the polarizing plate were determined as follows.
JIS in accordance with Japanese Electronic Machinery Industry Standard ED-2521
Applying the standard Z-8701 “color display method using a 2 degree visual field XYZ system”, the stimulus value Y in “the tristimulus value of the transmitted object”
Is the transmittance. The standard light source is a C light source, and the wavelength range is 380 to 380.
780 nm, UV-2200 manufactured by Shimadzu was used as a spectrophotometer. Single transmittance (Y): The transmittance of one polarizing plate was measured. The degree of polarization (V) was determined by the following equation. V = {(Ypara−Ycross) / (Ypara + Ycross)} ^1/2 Ypara is the transmittance when two polarizing plates are stacked so that their orientation directions are parallel, and Ycross is the two polarizing plates. This is the transmittance when they are overlapped so that their orientation directions are orthogonal.

The dichroic ratio (Rd) of the polarizing plate was determined by the following equation from the single transmittance (Y) and the degree of polarization (V). Rd = LogY (1-V) / LogY (1 + V)

Example 1 PVA (degree of polymerization 1750, degree of saponification 99.9 mol%) 40
A solution consisting of 5 parts by weight, 5 parts by weight of glycerin, and 55 parts by weight of water as a solvent is formed into a film by a belt film forming machine, and is further heat-treated by a hot-air treatment device to have a thickness of 75 μm
Was produced. The main film forming conditions are shown below. Film forming machine Stainless steel belt (See Fig. 1) Belt speed 10.0m / min Drying temperature First half 140 ° C Second half 130 ° C Moisture at the time of film peeling 10% by weight Film moisture after humidity control 5% by weight Film forming tension 1.2 kg / m Winding machine Winding speed 9.6 m / min Film forming draw 0.96 A polarizing plate was prepared using the PVA film thus obtained. The uniaxial stretching was performed at a temperature of 35 ° C. at an upper limit magnification of 5.4 times. Table 1 shows the measurement results of the physical properties of the PVA film and the polarizing plate. The dichroic ratio (D) of the molecules of the PVA film was 1.08, and the dichroic ratio (D) of the molecules of the polarizing film was 4.1. The polarizing plate showed excellent polarization properties and durability.

EXAMPLE 2 The same undiluted PVA solution as used in Example 1 was formed into a film by a drum film forming machine, and further treated with hot air to form a 75 μm thick PVA film. The main film forming conditions are shown below. Film forming machine Drum roll (see Fig. 2) Drum rotation speed 6.0 m / min Drum temperature 90 ° C Water at 25 ° C when film is peeled Heat treatment machine Same as in Example 1 Hot air temperature 160 ° C Film moisture at outlet 3% by weight Film moisture after wetting 6% by weight Film forming tension 1.6 kg / m Winding machine Winding speed 5.9 m / min Film forming draw 0.98 Up to 5.2 times the PVA film thus obtained at a stretching temperature of 35 ° C. The film was uniaxially stretched to produce a polarizing plate. Table 1 shows the measurement results of the physical properties of the PVA film and the polarizing plate. The dichroic ratio (D) of the molecules of the PVA film was 1.12, and the dichroic ratio (D) of the molecules of the polarizing film was 3.9. The polarizing plate showed excellent polarization properties and durability.

Example 3 PVA (degree of polymerization: 4400, degree of saponification: 99.9 mol%) 27
1 part by weight, 3 parts by weight of glycerin, and 70 parts by weight of water as a solvent were formed into a film by the belt film forming machine shown in FIG. 1 and further treated with hot air to obtain a 75 μm-thick PVA.
A film was formed. The main film forming conditions are shown below. Film forming machine Same as in Example 1 Belt speed 8.0 m / min Drying temperature First half 140 ° C. Second half 130 ° C. Moisture at the time of film peeling 13% by weight Heat treatment machine Same as in Example 1 Hot air temperature 130 ° C. Film moisture after humidity control 5% by weight Film forming tension 1.3 kg / m Winding machine Winding speed 7.5 m / min Film forming draw 0.94 A polarizing plate was produced using the PVA film thus obtained. The uniaxial stretching was performed at a temperature of 50 ° C. at an upper limit magnification of 5.3 times. Table 1 shows the measurement results of the physical properties of the PVA film and the polarizing plate. The dichroic ratio (D) of the molecules of the PVA film is 1.05, and the dichroic ratio D of the molecules of the polarizing film is 4.3.
Met. The polarizing plate showed excellent polarization properties and durability.

Comparative Example 1 The same PVA stock solution as in Example 1 was used to form a film using the same film forming apparatus as in Example 2, and then heat-treated with a heat treatment apparatus to form a 75 μm thick PVA film. did.
The main film forming conditions are shown below. Film forming machine Same as in Example 2 Drum rotation speed 6.0 m / min Drum temperature 90 ° C. Moisture at the time of film peeling 25% by weight Heat treatment machine Same as in Example 1 Hot air temperature 160 ° C. Film moisture at outlet 3% by weight After humidity control Film moisture 6% by weight Film forming tension 4.8 kg / m Winding machine Winding speed 6.3 m / min Film forming draw 1.05 The dichroic ratio (D) of the molecules of the PVA film thus obtained is 1. 26. This PVA film was uniaxially stretched at a stretching temperature of 35 ° C. and at an upper limit of 4.6 times the stretchable temperature to prepare a polarizing plate. Dichroic ratio of molecules of polarizing film (D)
Was 3.4. Table 1 shows the measurement results of the physical properties of the PVA film and the polarizing plate.

Comparative Example 2 The same PVA stock solution as in Example 1 was used to form a film with the same film forming apparatus as in Example 1, and then heat-treated with a heat treatment apparatus comprising a plurality of heat rolls to form a film. 75 μm
Was formed into a film. (Here, in order to prevent the film from floating between the heat rolls, the film-forming draw was increased. As a result, tension was applied to the film, and the film-forming tension was increased.) The film conditions are shown. Film forming machine Same as in Example 1 Belt speed 10.0 m / min Moisture at film peeling 10% by weight Heat treatment machine Heat roll type Heat roll temperature First half 70 ° C Second half 107 ° C Film moisture at outlet 2% by weight Film after humidity control Moisture 6% by weight Film forming tension 4.1 kg / m Winding machine Winding speed 11.0 m / min Film forming draw 1.10 The dichroic ratio (D) of the molecules of the PVA film thus obtained is 1.40. there were. This PVA film was uniaxially stretched at a stretching temperature of 35 ° C. at an upper limit of 4.4 times the stretchable temperature to prepare a polarizing plate. Dichroic ratio of molecules of polarizing film (D)
Was 2.9. Table 1 shows the measurement results of the physical properties of the PVA film and the polarizing plate.

[0029]

[Table 1]

[0030]

As described above, according to the present invention, a PVA film suitable for producing a polarizing film is provided. Further, according to the present invention, there is provided a polarizing film having high polarization properties and high durability. The polarizing film of the present invention can be used for LC used in laptop personal computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, etc.
This can greatly contribute to higher quality and improved reliability of D.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of a film manufacturing apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing another example of the film manufacturing apparatus according to the present invention.

[Explanation of symbols]

 11: belt type film forming machine, 21: drum type film forming machine.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08L 29:04 C08L 29:04 (72) Inventor Hiroaki Hayase 892, Sakuhi-shi, Saijo, Ehime Prefecture Yoshiaki Mukai 892 Sakuhi-shi, Saijo-shi, Ehime Pref. Kuraray Co., Ltd. A) JP-A-64-84203 (JP, A) JP-A-4-173844 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 5/18 B29C 47/00-47 / 96 G02B 5/30

Claims (3)

(57) [Claims] 1. A stock solution containing a polyvinyl alcohol-based resin.
Is continuously discharged from the die to form a film.
A film comprising a polyvinyl alcohol-based resin having a molecular dichroic ratio (D) of 1.2 or less and an average crystallinity (Xc) of 50 to 75% by weight by an X-ray diffraction method. 2. The film in the MD direction during film formation.
The film according to claim 1, wherein the number of rows is 1 or less. 3. The film according to claim 1 as a raw material
Polystyrene having a molecular dichroic ratio (D) of 3.5 or more obtained by using
Polarizing film made of vinyl alcohol resin.