KR20130129473A - Polyvinyl alcohol polymer film and process for producing same - Google Patents

Abstract

PVA film which satisfies the following formulas (I) and (II), in which the productivity of the stretchable film and the polarizing film is good: Δn (MD) Ave − 0.1 × 10 ⁻³ Δn (TD) Ave Δn (MD) Ave + 0.25 × 10 ⁻³ (I) Δn (TD) Ave ≦ 2.5 × 10 ⁻³ (II) [wherein, Δn (MD) Ave is a value obtained by averaging the birefringence in the longitudinal direction of the PVA film in the film thickness direction, Δn ( TD) Ave represents a value obtained by averaging the birefringence in the width direction of the PVA film in the film thickness direction], and (a) the PVA-containing film-forming stock solution on the first dry roll of the film forming apparatus including a plurality of dry rolls. Of the drying roll when the volatilization fraction of the PVA film with respect to the circumferential speed S ₁ of the first drying roll was 13 mass% the peripheral speed (S _T) ratio (S _T / S ₁₎ the ratio (S _L / S _T) of a 0.990 ~ 1.050 and, (c) a peripheral speed (S _L) of the final drying roll for the main speed (S _T) of 0.960 to 0.980 , (D) ratio (S _L / S ₁₎ a method of producing a film of 0.970 ~ 1.010.

Description

Polyvinyl alcohol polymer film and its manufacturing method {POLYVINYL ALCOHOL POLYMER FILM AND PROCESS FOR PRODUCING SAME}

The present invention relates to a polyvinyl alcohol polymer film, a method for producing the same, and a polarizing film produced from the film. More specifically, the present invention has a high limit draw ratio, and even when stretching at a high magnification, the film does not break well and does not cause interruption of the stretching operation due to breakage of the film, and is excellent in optical performance such as polarization performance. The present invention relates to a polyvinyl alcohol polymer film, a method for producing the same, and a polarizing film produced from the film, which can produce a film with high yield and with good productivity.

A polarizing plate having a function of transmitting and shielding light is an important component of a liquid crystal display device (LCD) together with a liquid crystal having a switching function of light. The field of application of this liquid crystal display device is a measurement device used in a notebook PC, a liquid crystal monitor, a liquid crystal color projector, a liquid crystal television, an in-vehicle navigation system, a mobile phone, indoors and outdoors from small apparatuses such as an electronic desk calculator and a wristwatch of the early stage of development It is expanded to a wide range of devices and the like, and in particular, large screens have been advanced in liquid crystal monitors and liquid crystal televisions.

Generally, a polarizing plate is uniaxially stretched a polyvinyl alcohol-based polymer film and then dyed with iodine or dichroic dye, and a monoaxially stretched polyvinyl alcohol-based polymer film is then fixed with a boron compound. The polarizing film is manufactured by the method of performing, the method of performing a fixing process simultaneously with dyeing, etc. in one of the said methods, and protective films, such as a cellulose triacetate film and a cellulose acetate butyric-acid butyrate cellulose film, on one or both surfaces of the polarizing film obtained by it. It is produced by bonding together.

In recent years, with the expansion of the use of a liquid crystal display device, the cost reduction and the further improvement of handleability are calculated | required further in addition to the improvement of display quality. In terms of cost reduction, it is possible to improve the production speed at the time of manufacturing the polarizing film, to prevent breakage (break) when stretching the polyvinyl alcohol-based polymer film, to reduce the breakage loss, and to improve the yield. It is necessary to prevent the interruption of stretching or dyeing work due to breakage.

As one of the improvement of the productivity at the time of manufacturing a polarizing film, shortening of the drying time at the time of manufacturing a polarizing film is calculated | required, In this point, as a raw film for polarizing films, conventionally the thickness of about 75 micrometers Polyvinyl alcohol-based polymer films have been generally used, but in recent years, thinner polyvinyl alcohol-based polymer films, which are thinner than 70 m, have been required.

However, as the polyvinyl alcohol polymer film becomes thinner, there is a problem that breakage occurs more easily when stretching at a higher magnification. In this respect, the limit draw ratio is high, and even when thin, the stretching can be performed at high magnification without causing breakage. Therefore, the polyvinyl alcohol-type polymer film which can manufacture the polarizing film which has the polarization performance equivalent to or more than a conventional product with good workability, high yield, low cost, and favorable productivity is calculated | required.

Conventionally, for the purpose of improving the stretchability of a polyvinyl alcohol polymer film, the improvement of the uniformity at the time of extending | stretching, the polarization performance, durability improvement, etc. in the polarizing film obtained by extending | stretching a polyvinyl alcohol-type polymer film, etc. In preparing a film while drying using a stock solution containing a polymer, the adjustment of the film production draw (ratio of the conveyance rate of the polyvinyl alcohol polymer film between the rolls used in the film production) and the time of film production Adjustment of the moisture content of a polyvinyl alcohol polymer film, etc. have been performed.

As such a conventional technique, in order to obtain the stretched film fully molecularly oriented when (1) uniaxial stretching is carried out, the film-making operation for producing a polyvinyl alcohol-based polymer film is employed by employing a film-making draw of 1 or less. (2) Method to obtain a polyvinyl alcohol-based polymer film capable of stretching of high magnification; Patent Document 1, in particular its paragraphs [0008], Examples, etc .; When manufacturing a polyvinyl alcohol polymer film using a drum film making machine, the [winding speed of the obtained polyvinyl alcohol polymer film] / [speed of the drum located at the most upstream to which the film-forming raw material is supplied] is 0.8. Method to make-1.3 (patent document 2); (3) Polyvinyl alcohol using a drum film manufacturing machine for the purpose of obtaining the polyvinyl alcohol polymer film which can be extended | stretched with high magnification. In the drying process at the time of manufacturing an all-type polymer film, the speed ratio (Rf / Rc) of the process speed (Rc) and the final winding speed (Rf) at the time when the volatilization fraction of a film becomes 10 weight% or less is 0.9-1.1 The method of making (patent document 3), etc. are known.

Moreover, in order to obtain the polyvinyl alcohol-type film which can manufacture the wide polarizing film which has uniform optical performance also in (4) large area, drying located at the process where the volatile matter of a polyvinyl alcohol film is 10% or less is carried out. Tensile elongation (S _M ) and TD direction of MD direction are controlled by controlling the speed ratio Rf / Rc of the speed Rc of a roll and winding speed Rf to 0.9-1.1, reducing the temperature deviation of a drying process, and Method for producing a polyvinyl alcohol-based film having a ratio (S _M / S _T ) of the tensile elongation (S _T ) of 0.7 to 1.3 (Patent Document 4); (5) a wide width having uniform optical performance even in a large area In order to obtain a polyvinyl alcohol-based film capable of producing a polarizing film of, at the time when the volatile content of the polyvinyl alcohol film reaches 10 to 50% by weight, the polyvinyl alcohol film is peeled off from the drum located at the most upstream side. De located on the most upstream side Way to the speed V1 and, poly velocity ratio V2 / V1 of the polyvinyl alcohol film-volatile content is the speed of the drum which is located on the first step is less than 10% by weight V2 to 1.0 to 1.3 (Patent Document 5) are known.

(6) In order to obtain a polyvinyl alcohol-based polymer film composed of a specific skin layer / core layer / skin layer capable of uniform uniaxial stretching and giving a stretched film free of fine cracks or voids when stretched, While heating a stock solution having a volatilization fraction of 50 to 90 mass% containing an alcohol-based polymer with a first drying roll, hot air is blown to a polyvinyl alcohol-based polymer film surface which is not in contact with the first drying roll under predetermined conditions, and volatilized. At the time when the fraction became 15-30 mass%, the polyvinyl alcohol polymer film was peeled from the first drying roll and brought into contact with the second drying roll to be dried. At that time, the circumferential speed S ₁ of the first drying roll and the second and a method for the non-(S ₂ / S ₁₎ of the peripheral speed (S ₂₎ of the drying roll with 1.000 ~ 1.100 (Patent Document 6) are known.

However, in Patent Documents 1 to 6, the polyvinyl alcohol-based polymer film, especially a polyvinyl alcohol-based polymer film having a thin film thickness when uniaxially stretched at a high magnification, prevents breakage from occurring in the film. It is not disclosed about the method for further improving the limit draw ratio of a film.

Japanese Unexamined Patent Publication No. Hei 6-136151 Japanese Unexamined Patent Publication No. 2001-315141 JP 2001-315146 A Japanese Laid-Open Patent Publication 2002-30164 Japanese Unexamined Patent Publication No. 2002-79531 Japanese Laid-Open Patent Publication 2005-324355

 `` Mineral Properties of Polymer Science One Point 10 Polymers '', First Edition, Kyoritsu Publishing Co., December 15, 2007, p.19-21

An object of the present invention is that the limit draw ratio is high, so that the film can be stretched at high magnification without causing breakage, and thus, stretched films such as polarizing films having an optical performance equivalent to or higher than that of conventional products, have good workability, high yield, and low cost. It is to provide a polyvinyl alcohol polymer film that can be produced with good productivity.

In particular, the object of the present invention has a higher limit draw ratio even if thinner than a polyvinyl alcohol polymer film conventionally used for the production of a polarizing film, and can be smoothly uniaxially stretched without breaking when stretched at a high magnification. It is possible to provide a polyvinyl alcohol-based polymer film which can be made a thinner stretched film than conventionally and further shortens the drying time when producing a polarizing film, and can produce a polarizing film with better productivity.

Moreover, the objective of this invention is providing the method which can manufacture the polyvinyl alcohol polymer film which has the said outstanding characteristic smoothly and continuously with high productivity.

Moreover, the objective of this invention is providing the polarizing film which consists of said polyvinyl alcohol-type polymer film.

In order to achieve the above object, the present inventors earnestly examined, and as a result, a value obtained by averaging the birefringence in the machine flow direction (length direction) of the polyvinyl alcohol-based polymer film in the thickness direction of the film and the birefringence in the width direction is shown in the film. When the value averaged in the thickness direction satisfies a specific relationship, and the value obtained by averaging the birefringence in the width direction of the polyvinyl alcohol-based polymer film in the thickness direction of the film is a specific numerical range, the limit draw ratio of the film This becomes high, and breakage of a film does not occur easily even when extending | stretching by high magnification, and it can manufacture stretched films, such as a polarizing film which is excellent in optical performances, such as polarization performance, with high yield, low cost, and favorable productivity, without interrupting an extending | stretching operation. I found out that I could. Moreover, when the value which averaged the birefringence | index of the machine flow direction of a polyvinyl alcohol-type polymer film in the thickness direction of a film was made into the specific numerical range, it discovered that the limit draw ratio of a film improves further.

In particular, the value obtained by averaging the birefringence in the mechanical flow direction of the polyvinyl alcohol-based polymer film in the thickness direction of the film and the value in which the birefringence in the width direction is averaged in the thickness direction of the film satisfies a specific relationship, and in the width direction In the polyvinyl alcohol polymer film described above, in which the value obtained by averaging the birefringence in the thickness direction of the film is in a specific range, the thickness of the film is that of the polyvinyl alcohol polymer film that has been generally used in the production of polarizing films. Even if the thickness is about 30 to 65 µm, which is thinner than the thickness, it has a high limiting draw ratio, and thus it is possible to smoothly uniaxially stretch at a high magnification without causing breakage, thereby further thinning at the time of manufacturing the polarizing film. It was possible to find out that the drying time at the time of manufacturing a polarizing film can be shortened further.

And the inventors of the present invention, the above-mentioned polyvinyl alcohol-based polymer film having a high limit draw ratio, the film-forming stock solution containing the polyvinyl alcohol-based polymer is provided on the first drying roll of the film-forming apparatus having a plurality of drying rolls After discharging into a film, the plurality of drying rolls were sequentially dried to form a film. At that time, the ratio of the circumferential speed of the drying roll when the volatilization fraction of the polyvinyl alcohol polymer film to the circumferential speed of the first drying roll became 13% by mass. To a specific numerical range, the ratio of the peripheral speed of the final dry roll to the peripheral speed of the dry roll when the volatilization fraction of the polyvinyl alcohol polymer film is 13% by mass is defined as the specific numerical range, and the peripheral speed of the first dry roll By making ratio of the circumferential speed of the final dry roll with respect to a specific numerical range, it turned out that it can manufacture continuously and smoothly with high productivity.

Moreover, the present inventors make the volatilization fraction of a polyvinyl alcohol polymer film at the time of peeling from a 1st dry roll into the specific numerical range in manufacturing the polyvinyl alcohol polymer film with a high limit draw ratio by the said method. It is preferable that the roll surface temperature of each drying roll is 65 degreeC or more, and the volatilization fraction of the film-forming stock solution containing a polyvinyl alcohol-type polymer is 60-75 mass%, and also the roll of a 1st dry roll When surface temperature is 80-120 degreeC, the value and width which averaged the birefringence of the machine flow direction of a polyvinyl alcohol-type polymer film in the thickness direction of a film even if the circumferential speed of a 1st dry roll is a high speed of 8 m / min or more. The value which averaged the birefringence of the direction to the thickness direction of a film satisfy | fills a specific relationship, and the value which averaged the birefringence of the width direction to the thickness direction of a film The polyvinyl alcohol polymer film with a high limit draw ratio in this predetermined numerical range was found to be able to be produced smoothly and with good productivity. Based on these findings, the present inventors further studied to complete the present invention.

That is,

(1) A polyvinyl alcohol polymer film characterized by satisfying the following formulas (I) and (II).

Δn (MD) _Ave -0.1 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.25 × 10 ^-3 (I)

Δn (TD) _Ave ≤ 2.5 × 10 ^-3 (II)

[Wherein, Δn (MD) _Ave represents a value obtained by averaging the birefringence in the machine flow direction of the polyvinyl alcohol polymer film in the thickness direction of the film, and Δn (TD) _Ave is a polyvinyl alcohol polymer Represents a value obtained by averaging the birefringence in the width direction of the film in the thickness direction of the film.]

And, the present invention

(2) The polyvinyl alcohol polymer film of said (1) which satisfy | fills following formula (III),

1.3 × 10 ⁻³ ≦ Δn (MD) _Ave ≦ 2.0 × 10 ⁻³ (III); and

(3) It is a polyvinyl alcohol polymer film of said (1) or (2) which exists in the range of 30-65 micrometers in thickness.

In addition,

(4) As a method for producing a polyvinyl alcohol polymer film,

(a) Using a film production apparatus including a plurality of drying rolls in which the rotation axes are parallel to each other, and discharging the film production stock solution containing the polyvinyl alcohol polymer on the first dry roll of the film production apparatus in a film form. After drying, it is dried again with a drying roll followed by film production;

(b) The ratio (S _T / S ₁ ) of the circumferential speed S _T of the dry roll when the volatilization fraction of the polyvinyl alcohol polymer film became 13 mass% with respect to the circumferential speed S ₁ of the first drying roll was 0.990. To 1.050;

(c) The ratio (S _L / S _T ) of the peripheral speed (S _L ) of the final drying roll to the peripheral speed (S _T ) of the drying roll when the volatilization fraction of the polyvinyl alcohol polymer film is 13% by mass is 0.960 to 0.980;

(d) The ratio (S _L / S ₁ ) of the peripheral speed S _L of the final drying roll to the peripheral speed S ₁ of the first drying roll is 0.970 to 1.010, wherein the polyvinyl alcohol polymer film It is a manufacturing method.

The present invention,

(5) The manufacturing method of said (4) whose volatile fraction of the polyvinyl alcohol-type polymer film at the time of peeling from a 1st dry roll is 17-30 mass%;

(6) The manufacturing method of said (4) or (5) whose roll surface temperature of each dry roll is 65 degreeC or more; And,

(7) poly and vinyl alcohol-based polymer is a film volatile fraction of the prepared stock solution 60 to 75% by weight containing a first and a roll surface temperature of a drying roll 80 ~ 120 ℃, the first peripheral speed (S ₁₎ of the drying roll It is any manufacturing method of said (4)-(6) which is this 8-25 m / min.

The present invention,

(8) It is a polarizing film manufactured from the polyvinyl alcohol polymer film of any of said (1)-(3).

Since the polyvinyl alcohol-based polymer film of the present invention has a high limit draw ratio, even when uniaxially stretched at a high magnification when producing a stretched film, breakage of the film does not occur well, and accordingly, such as polarization performance Stretched films, such as a polarizing film excellent in optical performance, can be manufactured with high yield, low cost, and favorable productivity, without interrupting an extending | stretching operation.

In particular, the polyvinyl alcohol-based polymer film of the present invention may have a thickness of about 30 to 65 μm, which is thinner than the thickness of the polyvinyl alcohol-based polymer film that has been generally used in order to manufacture a polarizing film or the like. Since it has a high limit draw ratio, it can smoothly uniaxially stretch at high magnifications without causing breakage, and accordingly, thinning at the time of manufacturing a stretched film becomes possible, and when manufacturing a polarizing film etc. It is possible to further shorten the drying time and thereby to improve productivity.

Moreover, although the polyvinyl alcohol polymer film whose length exceeds 1000 m is also used recently as a raw film for polarizing films, since the polyvinyl alcohol polymer film of this invention has a high limit draw ratio, it is conventional It can extend | stretch at a higher magnification than that, and, accordingly, the acquisition amount of the polarizing film from a polyvinyl alcohol-type polymer film can be made larger than before.

By employ | adopting the manufacturing method of this invention, the polyvinyl alcohol-type polymer film of this invention which has the said outstanding characteristic can be manufactured continuously and smoothly with high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the sample collection method at the time of measuring (DELTA) n (MD) _Ave of a polyvinyl alcohol-type polymer film.
It is a schematic diagram which shows the sample collection method at the time of measuring (DELTA) n (TD) _Ave of a polyvinyl alcohol-type polymer film.

Hereinafter, the present invention will be described in detail.

In general, in a transparent film produced using a transparent polymer such as a polyvinyl alcohol-based polymer, the polymer chain is oriented in a flow direction (mechanical flow direction: length direction) according to plastic deformation or deformation caused by shear stress to constitute the polymer. The polarization direction of the atomic group to be made becomes macroscopically constant, and birefringence peculiar to a polymer arises by this (nonpatent literature 1).

The birefringence index [Δn (MD)] in the machine flow direction in the polyvinyl alcohol polymer film is obtained from the following formula [i], and the birefringence index [Δn (TD)] in the width direction is obtained from the following formula [ii]: Is saved.

Δn (MD) = nMD -nz [i]

Δn (TD) = nTD -nz [ii]

[Wherein nMD denotes a refractive index in the machine flow direction (length direction) of the film, nTD denotes a refractive index in the width direction of the film, and nz denotes a refractive index in the thickness direction of the film]

As described in Non-Patent Document 1, in a film produced using a transparent polymer such as a polyvinyl alcohol-based polymer, the polymer chains forming the film are easily oriented in the machine flow direction (length direction). In the polyvinyl alcohol-based polymer film including the polyvinyl alcohol-based polymer film described in Patent Literatures 1 to 6, in general, "birefringence [Δn (MD)] in the machine flow direction"> "birefringence in the width direction [DELTA n (TD)] ", that is, the birefringence [Δn (MD)] in the machine flow direction tends to be larger than the birefringence [Δn (TD)] in the width direction.

In contrast, the polyvinyl alcohol polymer film of the present invention is different from the conventional polyvinyl alcohol polymer film in that the following formulas (I) and (II) are satisfied.

Δn (MD) _Ave -0.1 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.25 × 10 ^-3 (I)

Δn (TD) _Ave ≤ 2.5 × 10 ^-3 (II)

[Wherein, Δn (MD) _Ave represents a value obtained by averaging the birefringence in the mechanical flow direction of the polyvinyl alcohol polymer film in the thickness direction of the film, and Δn (TD) _Ave is a polyvinyl alcohol polymer film Represents a value obtained by averaging the birefringence in the width direction of the film in the thickness direction of the film.]

That is, as shown in said Formula (I), in the polyvinyl alcohol-type polymer film (Hereinafter, "polyvinyl alcohol" may be called "PVA."), The machine flow direction (PVA) of a PVA-type polymer film Line direction at the time of continuous film-forming a system polymer film) "(DELTA) n (MD) _Ave " which is the value which averaged the birefringence of the following (it may be called "length direction (MD)" hereafter) in the thickness direction of the said film, "Δn (TD) _Ave " which is a value obtained by averaging the birefringence in the width direction (direction perpendicular to the length direction) (hereinafter may be referred to as "width direction (TD)") of the PVA-based polymer film. Even if it is equal to or somewhat smaller than or exceeds "Δn (TD) _Ave ", the amount is insignificant.

Moreover, the PVA-type polymer film of this invention has a characteristic also in satisfy | filling said Formula (II) with the said Formula (I).

By satisfying said formula (I) and (II), the PVA-type polymer film of this invention has a high limit draw ratio even when the film thickness is thinner than before, Therefore, manufacture of stretched films, such as a polarizing film, Even when uniaxially stretching at high magnification, the breakage of the film hardly occurs, and the thinned stretched film having excellent optical performance such as polarization performance without causing interruption of the stretching operation due to breakage of the film is a high yield. It can manufacture with good productivity.

When it deviates from said Formula (I), the limit draw ratio of a PVA-type polymer film will become low, and break | rupture of a film will generate | occur | produce well when it uniaxially stretches at high magnification, and breakage will generate | occur | produce especially especially when the film thickness is thin.

It is preferable that the PVA system polymer film of this invention satisfy | fills following formula (I '), It is more preferable to satisfy following formula (I' '), It is further more satisfying following formula (I' ''). desirable.

Δn (MD) _Ave -0.05 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.23 × 10 ^-3 (I ＇)

Δn (MD) _Ave ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.2 x 10 ^-3 (I '')

Δn (MD) _Ave + 0.05 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.18 × 10 ^-3 (I ''')

When the Δn (TD) _Ave of the PVA-based polymer film exceeds 2.5 × 10 ⁻³ , the limiting draw ratio of the PVA-based polymer film is lowered, and the PVA-based polymer film is long. It is hard to extend | stretch to high magnification in the direction MD, and the stretched film excellent in optical performance is hard to be obtained.

In order to make Δn (TD) _Ave excessively small, it is necessary to allow dry shrinkage in the width direction at the time of production of the PVA-based polymer film, so that the effective width yield of the PVA-based polymer film tends to be lowered. polymer film, Δn (TD) _Ave is ^{1.5 × 10 -3 ~ 2.2 × 10} - preferably in the range of ^3, and ^{1.6 × 10 -3 ~ 2.0 × 10} - it is more preferable in the range of ^3.

It is preferable that the PVA-type polymer film of this invention further satisfy | fills following formula (III) in addition to said Formula (I) and (II).

1.3 × 10 ⁻³ ≤ Δn (MD) _Ave ≤ 2.0 × 10 ^-3 (III)

When Δn (MD) _Ave of the PVA-based polymer film is 2.0 × 10 ⁻³ or less, the limit draw ratio of the PVA-based polymer film is further increased, and the PVA-based polymer film is easily stretched at a high magnification in the longitudinal direction (MD), The stretched film excellent in optical performance is obtained more easily. On the other hand, in order to make Δn (MD) _Ave of the PVA-based polymer film less than 1.3 × 10 ⁻³ , the peripheral speed ratio of the dry roll needs to be greatly reduced, so that the PVA-based polymer film sags between the dry rolls during film production. This tends to happen well.

PVA-based polymer film of the present invention, Δn (MD) _Ave is ^{1.4 × 10 -3 ~ 1.95 × 10} - more preferably in the range of ^{3 and, 1.5 × 10 -3 ~ 1.9 ×} 10 - in the range of ³ More preferred.

Moreover, in PVA-type polymer films, there are many variations in the values of Δn (MD) _Ave and / or Δn (TD) _Ave in the width direction TD of the film, and in particular, at both ends in the width direction Δn (MD) _{Although Ave} tends to become high, at least the formula (I) and (II) should just satisfy | fill Formula (I)-(III) in the center part of the width direction (TD) of a PVA-type polymer film, and PVA-type polymer film It is preferable that the formulas (I) and (II) are satisfied in the whole region of 80% or more of the width direction TD centered on the center of the width direction TD of the formula (I) to (III). desirable. Both ends of the width direction (TD) of the PVA-based polymer film not satisfying the formulas (I) and (II) can be cut and removed (removal of ear) before the PVA-based polymer film is stretched in the longitudinal direction (MD). have.

"Δn (MD) _Ave " of the PVA-based polymer film [value obtained by averaging the birefringence in the longitudinal direction (MD) of the PVA-based polymer film in the thickness direction of the film] and "Δn (TD) _Ave " [PVA-based polymer film Value obtained by averaging the birefringence in the width direction (TD) in the thickness direction of the film] can be measured by the following method.

<<>> Measurement method of Δn (MD) _Ave :

(Here, the measuring method of (DELTA) n (MD) _Ave in the center part of the width direction (TD) of a PVA-type polymer film is illustrated.

(i) MD * TD = 2mm * 10mm from the center part in the width direction (TD) of a film, as shown to FIG. 1 (a) at arbitrary positions of the longitudinal direction (MD) of a PVA-type polymer film. Three pieces of size are cut out, the pieces are placed between both sides of a PET film having a thickness of 100 µm, and the pieces are put back into a wooden frame and mounted on a microtome apparatus.

(ii) Next, the three pieces collected above are sliced at intervals of 10 μm in parallel with the longitudinal direction (MD) of the three pieces, as shown in FIG. 1 (b) (PET film and wooden frame are not shown). Ten slice pieces (MD * TD = 2mm * 10micrometer) for observation shown in FIG.1 (c) are manufactured. Among the slice pieces, five slice pieces having smooth slice surfaces and no slice thickness variation are selected, and each slice piece is placed on a slide glass and the slice thickness is measured by a microscope (manufactured by Keyence Co., Ltd.). In addition, observation is performed by the eyepiece 10 times and the objective 20 times (total 200 times).

(iii) Then, slice slices are turned up as shown in Fig. 1 (d) so that the slice faces upward, and the slice pieces are faced up and placed on a slide glass and sealed with cover glass and silicone oil (refractive index 1.04), and two-dimensional. The retardation of five slice pieces is measured using photoelastic evaluation system "PA-micro" (Photonic Latissian Corporation).

(iv) In the state where the retardation distribution of each slice piece is displayed on the measurement screen of "PA-micro", a line α perpendicular to the original film surface is drawn to cross the slice piece, and a line analysis is performed on the line segment α. Retardation distribution data of the thickness direction of a film is acquired. In addition, observation is performed by the eyepiece 10 times and the objective 20 times (total 200 times). Moreover, in order to suppress the error by the position which the line segment (alpha) passes on a slice piece, the average value of retardation is employ | adopted to make line width 300 pixels.

(v) The birefringence Δn (MD) distribution in the thickness direction of the film is obtained by dividing the value of the retardation distribution in the thickness direction of the film obtained above by a microscope, and obtaining the birefringence Δn in the thickness direction of the film. MD) The mean value of the distribution is adopted. The average value of birefringence (DELTA) n (MD) distribution of the thickness direction of each film calculated | required about five slice pieces is averaged again, and it is set as "(DELTA) n (MD) _Ave. "

<< 2 >> Measurement method of Δn (TD) _Ave :

(Here, the measuring method of (DELTA) n (TD) _Ave in the center part of the width direction (TD) of a PVA-type polymer film is illustrated.

(i) MD * TD = 10mm * 2mm from the center part in the width direction (TD) of a film, as shown to FIG.2 (a) at the arbitrary position of the longitudinal direction (MD) of a PVA-type polymer film. The three pieces of the size are cut out, and the pieces are placed between both sides of a PET film having a thickness of 100 µm, and the pieces are put back into the wooden frame and mounted on the microtome apparatus.

(ii) Next, the three pieces collected above are sliced at intervals of 10 μm in parallel with the width direction TD of the three pieces, as shown in FIG. 2 (b) (PET film and wooden frame are not shown), Ten slice pieces (MD * TD = 10micrometer * 2mm) for observation shown in FIG.2 (c) are manufactured. Among the slice pieces, five slice pieces having smooth slice surfaces and no slice thickness variation are selected, and each slice piece is placed on a slide glass and the slice thickness is measured by a microscope (manufactured by Keyence Co., Ltd.). In addition, observation is performed by the eyepiece 10 times and the objective 20 times (total 200 times).

(iii) Subsequently, slice slices are turned up as shown in Fig. 2 (d) so that the slice faces upward, and the slice pieces are faced up and placed on a slide glass and sealed with cover glass and silicone oil (refractive index 1.04), and two-dimensional. The retardation of five slice pieces is measured using photoelastic evaluation system "PA-micro" (Photonic Latissian Corporation).

(iv) In the state where the retardation distribution of each slice piece is displayed on the measurement screen of "PA-micro", a line β perpendicular to the original film surface is drawn to cross the slice piece, and a line analysis is performed on the line segment β. Retardation distribution data of the thickness direction of a film is acquired. In addition, observation is performed by the eyepiece 10 times and the objective 20 times (total 200 times). Moreover, in order to suppress the error by the position where the line segment (beta) passes on a slice piece, the average value of retardation is employ | adopted as 300 pixel line width.

(v) The birefringence Δn (TD) distribution in the thickness direction of the film is obtained by dividing the value of the retardation distribution in the thickness direction of the film obtained above by the microscope, and obtaining the birefringence Δn in the thickness direction of the film. TD) mean value of the distribution is employed. The average value of birefringence (DELTA) n (TD) distribution of the thickness direction of each film calculated | required about five slice pieces is averaged again, and it is set as "(DELTA) n (TD) _Ave. "

Although the thickness of the PVA system polymer film of this invention can be made into the range of 5-150 micrometers, When using as a raw material for polarizing films, etc., it is preferable to set it as 30-65 micrometers. Since the PVA-type polymer film of this invention has a high limit draw ratio, 30-65 micrometers whose film thickness is thinner than the PVA-type polymer film of about 75 micrometers in thickness which often used as a disk for polarizing films conventionally In this case, the film can be stretched at high magnification without causing breakage of the film, whereby a stretched film having optical properties such as polarization performance or the like of a conventional product or the like can be produced smoothly and with good productivity at high yield. In addition, by stretching the PVA-based polymer film having a thickness of 30 to 65 µm at a high magnification, the thickness of the film after stretching can be made even thinner than before, and the drying time when the polarizing film is produced can be shortened. The manufacturing speed of a film can be improved.

If the thickness of the PVA-based polymer film is too thick, drying is difficult to be performed quickly when producing the polarizing film, while if the thickness of the PVA-based polymer film is too thin, at the time of uniaxial stretching for producing the polarizing film The breakage of the film is likely to occur.

Although the width | variety of the PVA-type polymer film of this invention is not specifically limited, Recently, since a liquid crystal television and a monitor are large screened, it is preferable that it is 2 m or more in width, and it is more preferable that it is 3 m or more in order that it can utilize effectively for them. It is preferable and it is more preferable that it is 4 m or more. Moreover, when manufacturing a polarizing plate with a realistic producer, since uniform uniaxial stretching may become difficult when the width | variety of a film is too large, it is preferable that the width | variety of a PVA system polymer film is 8 m or less.

It is preferable that the mass swelling degree of the PVA system polymer film of this invention is 180 to 250%, It is more preferable that it is 185 to 240%, It is further more preferable that it is 190 to 230%. When the mass swelling degree of the PVA-based polymer film is too low, it is difficult to draw well, and it is difficult to produce a stretched film having excellent optical performance. On the other hand, when the mass swelling degree is too high, the process passability at the time of stretching is deteriorated. In some cases, a highly durable polarizing film may not be obtained.

The mass swelling degree herein means the percentage of the value obtained by dividing the mass when the PVA-based polymer film is immersed in 30 ° C distilled water for 30 minutes by the mass after drying at 105 ° C for 16 hours after the immersion, specifically, It can measure by the method described in the following Examples.

As the PVA-based polymer forming the PVA-based polymer film of the present invention, for example, a modified PVA-based polymer obtained by graft copolymerization of a comonomer to a main chain of PVA and PVA obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester. Of a hydroxyl group of a modified PVA polymer, an unmodified PVA, or a modified PVA polymer prepared by saponifying a modified polyvinyl ester obtained by copolymerizing a vinyl ester and a comonomer with so-called aldehydes such as formalin, butylaldehyde, and benzaldehyde. Polyvinyl acetal resin etc. are mentioned.

When the PVA system polymer which forms the PVA system polymer film of this invention is a modified PVA system polymer, it is preferable that the modification amount in a PVA system polymer is 15 mol% or less, and it is more preferable that it is 5 mol% or less.

As said vinyl ester used for manufacture of a PVA-type polymer, For example, vinyl acetate, a vinyl formate, a vinyl laurate, a vinyl propionate, a vinyl butyrate, a vinyl pivalate, a vinyl basatic acid, a vinyl stearate, a vinyl benzoate, etc. Can be mentioned. These vinyl esters can be used singly or in combination. Among these vinyl esters, vinyl acetate is preferable from the viewpoint of productivity.

Moreover, as said comonomer, For example, C2-C30 olefins ((alpha) -olefin etc.), such as ethylene, propylene, 1-butene, isobutene; Acrylic acid or its salts; Methyl acrylate, ethyl acrylate, Acrylic esters, such as n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate (for example, acrylic acid C1-C18 alkyl ester); methacrylic acid or its salt; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-methacrylate Methacrylic acid esters, such as -butyl, t-butyl methacrylic acid, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate (for example, C1-C18 alkyl ester of methacrylic acid) ); Acrylamide, N-methyl acrylamide, N-ethyla Acrylamide derivatives such as krillamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid or salts thereof, acrylamidepropyldimethylamine or salts thereof, N-methylolacrylamide or derivatives thereof; Methacrylamides such as amide, N-methyl methacrylamide, N-ethyl methacrylamide, methacrylamide propanesulfonic acid or salts thereof, methacrylamidepropyldimethylamine or salts thereof, N-methylol methacrylamide or derivatives thereof Derivatives; N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n- Vinyl ethers such as butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; acrylonitrile, methacrylonitrile, etc. Triyl; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid and itaconic acid, salts thereof or esters thereof Derivatives thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate; unsaturated sulfonic acids or derivatives thereof, and the like. Of these,? -Olefins are preferable, and ethylene is particularly preferable.

As for the average degree of polymerization of the PVA-type polymer which forms the PVA-type polymer film of this invention, 1000 or more are preferable, 1500 or more are more preferable, and 2000 or more are more preferable in terms of polarization performance, durability, etc. of the polarizing film obtained. On the other hand, the upper limit of the average degree of polymerization of the PVA-based polymer is preferably 8000 or less, particularly preferably 6,000 or less, in view of ease of production of a homogeneous PVA-based polymer film, stretchability and the like.

Here, the "average degree of polymerization" of the PVA polymer in the present specification means the average degree of polymerization measured in accordance with JIS K 6726-1994, and the PVA polymer is subjected to re-saponification and purification, Is obtained from the viscosity.

As for the saponification degree of the PVA-type polymer which forms the PVA-type polymer film of this invention, 95.0 mol% or more is preferable, 98.0 mol% or more is more preferable, 99.0 mol% from a polarizing performance, durability, etc. of the polarizing film obtained. The above is more preferable, and 99.3 mol% or more is the most preferable.

Here, the "saponification degree" of the PVA polymer in this specification means the said vinyl alcohol with respect to the total mole number of the structural unit (typically a vinyl ester unit) and vinyl alcohol unit which can be converted into a vinyl alcohol unit by saponification. The ratio (mol%) which the mole number of a unit occupies says. The saponification degree of the PVA polymer can be measured in accordance with the description of JIS K 6726-1994.

Although the manufacturing method of the PVA-type polymer film of this invention is not specifically limited, As long as it is a method which can manufacture the PVA-type polymer film which satisfy | fills said Formula (I) and (II), you may manufacture by what method, PVA of this invention System polymer film,

 (a) A membrane-forming apparatus including a plurality of drying rolls having parallel rotation axes to each other is used, and the membrane-forming stock solution containing the PVA-based polymer is discharged onto the membrane and partially dried on the first drying roll of the membrane-forming apparatus. After that, the film is dried again with a drying roll followed by film formation;

(b) The ratio (S _T / S ₁ ) of the circumferential speed (S _T ) of the dry roll when the volatile fraction of the PVA polymer film became 13 mass% with respect to the circumferential speed (S ₁ ) of the _1st dry roll was 0.990- 1.050;

(c) PVA-based a ratio (S _L / S _T) of the peripheral speed (S _L), the final dry roll to the main speed (S _T) of the drying roll at the time the polymer film the volatile fraction was 13% by mass of 0.960 ~ 0.980 To;

(d) first made as to the ratio (S _L / S ₁₎ of the first peripheral speed (S _L), the final dry roll on the peripheral velocity (S ₁₎ of the drying roll with 0.970 ~ 1.010, according to the production method of the present invention In addition, it can manufacture continuously and smoothly with high productivity.

The manufacturing method of the above-mentioned PVA-type polymer film of this invention is demonstrated concretely below.

The film-forming stock solution containing a PVA-based polymer can be prepared by mixing the PVA-based polymer with a liquid medium to form a solution, or by melting a PVA-based polymer pellet or the like containing a liquid medium or the like into a melt.

Melting of the PVA-based polymer pellets containing the PVA-based polymer into a liquid medium, a liquid medium, and the like can be performed using a stirring mixing device, a melt extruder, or the like.

As a liquid medium used at that time, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylenediamine, diethylenetriamine, etc. are mentioned, for example, These liquid media Can be used individually by 1 type or in combination of 2 or more type. Of these, water, dimethylsulfoxide, or a mixture of both is preferably used, and water is more preferably used.

It is preferable to add a plasticizer to the film-forming stock solution from the viewpoint of dissolution and melting of the PVA-based polymer into the liquid medium, improvement of process passability during film production, and improvement of the stretchability of the resulting PVA-based polymer film.

As a plasticizer, polyhydric alcohol is used preferably, For example, ethylene glycol, glycerin, diglycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylol propane, etc. are mentioned, These plasticizers, It can be used individually by 1 type or in combination of 2 or more type. Among these, 1 type, or 2 or more types of glycerin, diglycerol, and ethylene glycol are used preferably from the point which is excellent in the effect of extending | stretching property.

As for the addition amount of a plasticizer, 0-30 mass parts is preferable with respect to 100 mass parts of PVA-type polymers, 3-25 mass parts is more preferable, 5-20 mass parts is especially preferable. When the addition amount of a plasticizer exceeds 30 mass parts with respect to 100 mass parts of PVA system polymers, the PVA system polymer film obtained may become soft too much and handleability may fall.

It is preferable to add surfactant to a film-forming stock solution from the viewpoint of the peelability improvement from the dry roll at the time of manufacturing a PVA system polymer film, the handleability of the obtained PVA system polymer film, etc. Although there is no limitation in particular as a kind of surfactant, Anionic surfactant or a nonionic surfactant is used preferably.

As the anionic surfactant, for example, carboxylic acid type such as potassium laurate, sulfate ester type such as octyl sulfate, and sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are preferable.

Moreover, as a nonionic surfactant, For example, Alkyl ether types, such as polyoxyethylene oleyl ether, Alkylphenyl ether types, such as polyoxyethylene octylphenyl ether, Alkyl ester types, such as polyoxyethylene laurate, Alkylamine types, such as polyoxyethylene lauryl amino ether, Alkylamide types, such as polyoxyethylene lauric acid amide, Polypropylene glycol ether types, such as polyoxyethylene polyoxypropylene ether, Alkanolamide, such as oleic acid diethanamide Nonionic surfactants of allylphenyl ether type, such as a type and a polyoxyalkylene allyl phenyl ether, are preferable. These surfactant can be used individually by 1 type or in combination of 2 or more type.

0.01-1 mass part is preferable with respect to 100 mass parts of PVA-type polymers, as for the addition amount of surfactant, 0.02-0.5 mass part is more preferable, 0.05-0.3 mass part is especially preferable. If the amount is less than 0.01 part by mass, the effect of improving film formation and peelability may not be easily exhibited. On the other hand, if the amount is more than 1 part by mass, the surfactant may be eluted to the film surface, causing blocking, and the handling may be deteriorated. have.

The film-forming stock solution contains various additives, for example, stabilizers (e.g., antioxidants, ultraviolet absorbers, heat stabilizers, etc.), compatibilizers, and blocking, within the range of not impairing the properties of the PVA polymer film of the present invention. It may contain an inhibitor, a flame retardant, an antistatic agent, a lubricant, a dispersant, a fluidizing agent, an antibacterial agent and the like. These additives can be used individually by 1 type or in combination of 2 or more type.

60-75 mass% is preferable, and, as for the volatile matter fraction of the film-forming stock solution used for manufacture of a PVA-type polymer film, 65-70 mass% is more preferable. If the volatilization fraction of the membrane-forming stock solution is less than 60% by mass, the viscosity of the membrane-forming stock solution may be high, and the membrane production itself may be difficult in addition to difficulty in filtration and defoaming. On the other hand, when the volatile fraction of a film-forming stock solution is larger than 75 mass%, a viscosity may become low too much and the uniformity of the thickness of a PVA system polymer film may be impaired.

Here, "the volatilization fraction of a film-forming undiluted | stock solution" as used herein means the volatilization fraction calculated | required by following formula [iii].

Volatilization fraction (mass%) of film-forming stock solution = 액 (Wa-Wb) / Wa｝ × 100 [iii]

[Wherein, Wa represents the mass (g) of the membrane-forming stock solution, and Wb represents the mass (g) after drying the membrane-forming stock solution of Wa (g) for 16 hours in a 105 ° C heat transfer dryer.]

In the film production apparatus provided with the some drying roll in which the rotating shafts mutually parallel are used for manufacture of a PVA-type polymer film, it is preferable that the number of dry rolls is three or more, It is more preferable that it is four or more, 5-30 Personal is more desirable.

It is preferable that the some dry roll is formed with metals, such as nickel, chromium, copper, iron, stainless steel, for example, and especially the surface of a roll does not corrode well and is formed with the metal material which has a mirror glossiness, It is more preferable that there is. Moreover, in order to improve the durability of a drying roll, it is more preferable to use the drying roll which plated the nickel layer, the chromium layer, the nickel / chromium alloy layer, etc. combining single layer or two or more layers.

It is preferable that it is 65 degreeC or more, and, as for the roll surface temperature of each dry roll in several drying rolls, it is more preferable that it is 75 degreeC or more. Moreover, although the roll surface temperature of each dry roll is 100 degreeC or more, More preferably, it is 100-120 degreeC about the roll surface temperature of the dry roll which can be used as a heat processing roll in a final process or a process near it, It is preferable that the roll surface temperature of the other dry roll is 100 degrees C or less.

The film production apparatus used by this invention may have a hot-air-type hot air drying apparatus, a heat processing apparatus, a humidity control apparatus, etc. after a some drying roll as needed.

In discharging the film-forming stock solution containing the PVA-based polymer onto the first dry roll of the film-forming apparatus in the form of a film, for example, T-type slit die, hopper plate, I-die, lip coater die or the like Using a known film discharge device (film cast device), the film production stock solution containing the PVA polymer is discharged (flexed) onto the first drying roll in a film form.

The liquid containing the PVA-based polymer discharged in a film form on the first drying roll is dried on the first drying roll, and the volatilization fraction of the PVA-based polymer film is preferably 17 to 30% by mass, more preferably 17 to 29 It peels from a 1st dry roll at the time of becoming mass%, More preferably, 18-28 mass%.

When the volatilization fraction of the PVA polymer film at the time of peeling from a 1st dry roll is less than 17 mass%, the value of (DELTA) n (MD) _Ave with respect to (DELTA) n (TD) _Ave will become large and it will become a thing which does not satisfy Formula (I). On the other hand, when the volatilization fraction of the PVA polymer film at the time of peeling from a 1st dry roll exceeds 30 mass%, peeling from a 1st dry roll becomes difficult and it may be broken in some cases, or a nonuniformity may arise easily. There is a tendency.

Here, "the volatilization fraction of a PVA polymer film or a PVA polymer film" in this specification means the volatilization fraction calculated | required by the following formula [iv].

A (mass%) = ｛(Wc-Wd) / Wc｝ × 100 [iv]

[Wherein, A is the volatile fraction (mass%) of the PVA-based polymer film or PVA-based polymer film, Wc is the mass (g) of the sample taken from the PVA-based polymer film or PVA-based polymer film, and Wd is the sample Wc. (g) is placed in a vacuum drier having a temperature of 50 ° C. and a pressure of 0.1 Pa or less, and shows the mass (g) when dried for 4 hours.]

In the PVA-based polymer film or PVA-based polymer film formed from a film-forming stock solution prepared using a polyhydric alcohol (plasticizer) such as a PVA-based polymer or glycerin, a surfactant, and water, the above-mentioned temperature is 50 ° C and a pressure of 0.1 Pa or less. 4 hours ”, only water is volatilized, and most of the other components other than water are not volatilized and remain in the PVA-based polymer film or PVA-based polymer film. Thus, volatilization of the PVA-based polymer film or PVA-based polymer film A fraction can be calculated | required by measuring the moisture content (water content) contained in a PVA-type polymer film or a PVA-type polymer film.

In drying with a 1st drying roll, it is preferable that the roll surface temperature of a 1st drying roll is 80-120 degreeC from a viewpoint of uniform drying property, a drying rate, etc., and it is more preferable that it is 85-105 degreeC, 93 It is more preferable that it is -99 degreeC. If the surface temperature of a 1st dry roll exceeds 120 degreeC, a film will foam well, On the other hand, below 80 degreeC, drying on a 1st dry roll becomes inadequate and it becomes a cause of a peeling defect.

A first peripheral speed (S ₁₎ of the drying roll, at the surface, such as uniform drying characteristics, drying speed, and productivity of the PVA-based polymer film, and 8 ~ 25 m / min is preferred, and more preferably 11 ~ 23 m / min, It is more preferable that it is 14-22 m / min. If the circumferential speed S ₁ of a 1st dry roll is less than 8 m / min, productivity will fall, and birefringence will become large easily, and it is unpreferable. On the other hand, when the circumferential speed S _{1 of} a 1st dry roll exceeds 25 m / min, drying on a 1st dry roll will become inadequate easily, and it is unpreferable.

Although partial drying on the 1st drying roll of the film-forming stock solution containing the PVA-type polymer discharged | emitted in the film form may be performed only by the heat from a 1st drying roll, it contacts with a 1st drying roll simultaneously with heating with a 1st drying roll. Hot air is sprayed on a film surface (hereinafter referred to as a "first dry roll non-contact surface" below) and heated from both sides of the PVA-based polymer film to perform drying in terms of uniform dryness, drying speed, and the like. desirable.

In spraying hot air to the 1st dry roll non-contacting surface of the PVA-type polymer film on a 1st dry roll, it is preferable to spray the hot air of 1-10 m / sec wind speed with respect to the whole area | region of a 1st dry roll non-contacting surface. It is more preferable to spray hot air with a wind speed of 2 to 8 m / sec, and even more preferable to spray hot wind with a wind speed of 3 to 8 m / sec.

If the wind speed of the hot air sprayed on the non-contacting surface of the first drying roll is too small, the PVA-based polymer film having a high limit draw ratio, which is the object of the present invention, is hardly obtained, and at the time of drying on the first drying roll. Condensation, such as water vapor, arises, and the water droplets are dripped on a PVA-type polymer film, and the defect in the PVA-type polymer film finally obtained arises easily. On the other hand, when the wind speed of the hot air sprayed on a non-contact surface of a 1st dry roll is too big | large, the PVA system polymer film with a high limit draw ratio aimed at in this invention will be hard to be obtained, and to the PVA system polymer film finally obtained The thickness deviation occurs, and troubles such as the occurrence of the dyeing deviation occur well.

It is preferable that it is 50-150 degreeC, and, as for the temperature of the hot air sprayed on the 1st dry roll non-contact surface of a PVA-type polymer film, it is 70-120 degreeC from a viewpoint of drying efficiency, uniformity of drying, etc., 80- It is more preferable that it is 95 degreeC. Moreover, it is preferable that the dew point temperature of the hot air sprayed on the 1st dry roll non-contact surface of a PVA-type polymer film is 10-15 degreeC. When the temperature of the hot air sprayed on the non-contacting surface of the 1st dry roll of a PVA system membrane is too low, drying efficiency, uniform drying property, etc. will fall easily, and when too high, foaming will generate | occur | produce well.

The method for injecting hot air into the first dry roll non-contacting surface of the PVA-based polymer film is not particularly limited, and the hot air having a uniform wind speed and uniform temperature can be applied to the first dry roll non-contacting surface of the PVA-based polymer film, preferably the whole thereof. All the methods which can spray uniformly can be employ | adopted, and a nozzle method, a rectifying plate system, or a combination thereof is especially employ | adopted among these. The direction in which hot air is blown to the first non-contact surface of the PVA-based polymer film may be a direction facing the first non-contact surface of the dry roll, and the direction substantially along the circumference of the first non-contact surface of the PVA-based polymer film (first Direction along the circumference of the roll surface of the 1 dry roll) may be sufficient, or a direction other than that may be sufficient.

Moreover, at the time of drying of a PVA system polymer film on a 1st drying roll, it is preferable to exhaust the volatile matter which generate | occur | produced from the PVA system polymer film by drying, and the hot air after spraying. Although the method of exhaustion is not specifically limited, It is preferable to employ | adopt the exhaust method which does not generate | occur | produce the wind speed deviation and temperature deviation of the hot air sprayed on the 1st dry roll non-contact surface of a PVA system polymer film.

On the first drying roll, the PVA-based polymer film preferably dried to a volatile fraction of 17 to 30% by mass is peeled from the first drying roll, and then the first dry roll non-contact surface of the PVA-based polymer film is opposed to the second drying roll. It is preferable to make it dry with a 2nd drying roll.

The first non-(S ₂ / S ₁₎ of the peripheral speed (S ₂₎ of the second drying rolls to a peripheral speed (S ₁₎ of the drying roll is more preferably, 1.005 ~ 1.090 is preferable, and 1.010 ~ 1.080. When the ratio (S ₂ / S ₁ ) is less than 1.005, the peeling point of the PVA-based polymer film from the first drying roll tends to be uneven, and the birefringence variation in the width direction becomes large, and may not be used as an optical film master. have. Further, if the non-(S ₂ / S ₁₎ is more than 1.090 can not be obtained well-PVA-based polymer film of the present invention has a high stretch rate limit.

In drying with a 2nd dry roll, it is preferable that the roll surface temperature of a 2nd dry roll is 65-100 degreeC from a viewpoint of uniform drying property, a drying rate, etc., It is more preferable that it is 65-98 degreeC, 75- It is more preferable that it is 96 degreeC.

The 3rd dry roll, the 4th dry roll, the 5th dry roll,. It is made to dry sequentially by several drying rolls, such as these.

At that time, in the present invention, the ratio (S _T / S ₁ of the first peripheral speed of the drying roll at the time the, PVA-based polymer film the volatile fraction of the peripheral speed (S ₁₎ of the drying roll was 13 mass% (S _T) ) Is 0.990 to 1.050, and drying is performed while adjusting the tension applied to the PVA-based polymer film. Here, "a dry roll when the volatile fraction of a PVA-type polymer film became 13 mass%" means the said dry roll when the volatile fraction of a PVA-based polymer film became 13 mass% on a dry roll, and it is two dry rolls When the volatilization fraction turns into 13 mass% between, the drying roll located behind in the said two drying rolls is meant. Ratio (S _T / S ₁₎ for by the above-mentioned range, the PVA based polymer film the volatile fraction without the risk of problems such as in the drying process until a 13% by mass, seizure sag or drop of the film , The value [Δn (MD) _Ave ] obtained by averaging the birefringence in the longitudinal direction MD in the thickness direction of the film and the value obtained by averaging the birefringence in the thickness direction of the film [Δn (TD) _Ave ]. The PVA-based polymer film of the present invention that satisfies the above formulas (I) and (II), and furthermore, the formula (III) can be produced smoothly.

The PVA-based non-(S _T / S ₁₎ for producing the polymer film is preferably, 1.000 ~ 1.045.

In the present invention, the PVA-based polymer film having a volatile fraction of 13% by mass is dried again with a subsequent drying roll to produce a PVA-based polymer film. In that case, in this invention, the ratio (S _L / S _T ) of the circumferential speed S _L of a final dry roll with respect to the circumferential speed S _T of a dry roll when the volatilization fraction of a PVA-type polymer film became 13 mass%. ), Drying is carried out while being in the range of 0.960 to 0.980. By making ratio (S _L / S _T ) into the above-mentioned range, in the drying process until the final PVA-based polymer film is obtained, no trouble such as sagging or sticking of the film is generated, and the longitudinal direction ( The value [Δn (MD) _Ave ] obtained by averaging the birefringence of MD) in the thickness direction of the film and the value [Δn (TD) _Ave ] obtained by averaging the birefringence of the film in the thickness direction of the film (I) and (II), Furthermore, the PVA-type polymer film of this invention which satisfy | fills said Formula (III) can be manufactured smoothly.

The PVA-based non-(S _L / S _T) for producing the polymer film is preferably, 0.963 ~ 0.976.

Moreover, in manufacturing a PVA system polymer film by the above-mentioned method, the value [(DELTA) n (MD) _Ave ] which averaged the birefringence index of the longitudinal direction (MD) of a PVA system polymer film to the thickness direction of a film, and the width direction ( The value [Δn (TD) _Ave ] obtained by averaging the birefringence of TD in the thickness direction of the film is the ratio (S _L / S) between the peripheral speed S ₁ of the first drying roll and the peripheral speed S _L of the final drying roll. ₁ ) Fluctuates accordingly. In order to manufacture the PVA-type polymer film of this invention which satisfy | fills said Formula (I) and (II) and also said Formula (III) smoothly, the last dry roll with respect to the circumferential speed S1 of a _1st dry roll. of that required for the ratio (S _L / S ₁₎ of the peripheral speed (S _L) in the range of 0.970 ~ 1.010, and preferably in the range of 0.972 ~ 1.008, it is more preferably in the range of 0.975 ~ 1.006. Thereby, the PVA-type polymer film which satisfy | fills said Formula (I) and (II), and also said Formula (III) can be manufactured smoothly, suppressing generation | occurrence | production of a wrinkle and sagging.

In the above-described manufacturing method of the present invention, the final drying roll or the final drying roll and the final drying roll may be used as a heat treatment roll by increasing the surface temperature thereof. When using a dry roll as a heat processing roll, 90-140 degreeC is preferable and, as for roll surface temperature, 100-130 degreeC is more preferable.

Moreover, you may install a heat processing apparatus separately from a dry roll.

Although there is no restriction | limiting in particular in the heating direction at the time of drying a PVA-type polymer film in the process from a 1st dry roll to a final dry roll, In the point which can dry a PVA-type polymer film more uniformly, it can apply to arbitrary parts of a PVA-type polymer film. It is preferable to dry so that the surface and back surface in contacting each dry roll from a 1st dry roll to a final dry roll alternately.

The PVA-based polymer film of the present invention can be obtained by subjecting the PVA-based polymer film subjected to the drying treatment to a heat treatment, a humidity control treatment, or the like as necessary, and finally winding the roll in a predetermined length.

It is preferable to exist in the range of 1-5 mass%, and, as for the volatile fraction of the PVA system polymer film finally obtained by said series of processes, it is more preferable to exist in the range of 2-4 mass%.

In order to manufacture a polarizing film from the PVA-type polymer film of this invention, for example, a PVA-type polymer film may be dyed, uniaxially stretched, fixed, dried, and further heat-treated as needed. The order of dyeing and uniaxial stretching is not particularly limited and may be a dyeing process before the uniaxial stretching process, a dyeing process simultaneously with the uniaxial stretching process, or a dyeing process after the uniaxial stretching process . Moreover, you may repeat processes, such as uniaxial stretching and dyeing, multiple times.

Examples of the dye used for dyeing the PVA polymer film include iodine or a dichroic organic dye (for example, Direct Black 17, 19, 154; Direct Brown 44, 106, 195, 210, 223; Direct Red 2, 23, 28, 31, 37, 39, 79, 81, 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; dichroic dyes such as Direct Orange 26, 39, 106, 107), and the like. These dyes may be used singly or in combination of two or more. Although dyeing can be normally performed by immersing a PVA-type polymer film in the solution containing the said dye, the processing conditions and a processing method are not specifically limited.

You may perform uniaxial stretching which extends a PVA system polymer film in the longitudinal direction (MD) by either a wet stretching method or a dry heat stretching method. In the case of uniaxial stretching by the wet stretching method, uniaxial stretching may be performed in warm water containing boric acid, uniaxial stretching in a solution containing the above dye or in a latex fixed treatment bath, and the PVA-based polymer film after absorption It may be used to uniaxially stretch in air, or uniaxially stretch by other methods. Although the extending | stretching temperature at the time of a uniaxial stretching process is not specifically limited, When extending | stretching (wet extending | stretching) a PVA system polymer film in hot water, Preferably it is 30-90 degreeC, More preferably, it is 40-70 degreeC, More preferably, it is The temperature of 45-65 degreeC is employ | adopted and when dry-heat-stretching, the temperature of 50-180 degreeC is employ | adopted preferably. Moreover, it is preferable to extend | stretch as much as possible before the film is cut | disconnected from the surface of the polarization performance from the draw ratio of a uniaxial stretching process (when the uniaxial stretching is carried out in multiple stages, total sum ratio). It is preferable that it is the above, It is more preferable that it is 5 times or more, It is further more preferable that it is 5.5 times or more. The upper limit of the draw ratio is not particularly limited as long as the film is not broken, but is preferably 8.0 times or less in order to perform uniform drawing.

The thickness of the film (polarizing film) after extending | stretching is 5-35 micrometers, It is preferable that it is 20-30 micrometers especially.

In manufacture of a polarizing film, in order to strengthen adsorption | suction of the dye with respect to the uniaxially stretched film, in many cases, a fixed process is performed. As a fixing treatment, a method of immersing a film in a treatment bath to which boric acid and / or a boron compound is added is generally widely used. At that time, if necessary, an iodine compound may be added to the treatment bath.

It is preferable that the film subjected to the uniaxial stretching treatment or the uniaxial stretching treatment and the fixing treatment is subsequently subjected to a drying treatment (heat treatment). It is preferable that the temperature of a drying process (heat processing) is 30-150 degreeC, especially 50-140 degreeC. If the temperature of the drying treatment (heat treatment) is too low, the dimensional stability of the resulting polarizing film tends to be lowered, while if too high, a decrease in polarization performance due to decomposition of the dye is likely to occur.

The protective film which is optically transparent and has mechanical strength is bonded together on both surfaces or single side | surface of the polarizing film obtained as mentioned above, and it can be set as a polarizing plate. As a protective film in that case, a cellulose triacetate (TAC) film, an acetic acid butyric acid cellulose (CAB) film, an acrylic film, a polyester film, etc. are used. As the adhesive for bonding the protective film, a PVA adhesive, a urethane adhesive, or the like is generally used, and among them, a PVA adhesive is preferably used.

The polarizing plate obtained as described above can be used as a component of a liquid crystal display device after being coated with a pressure-sensitive adhesive such as acrylic or the like and then adhered to a glass substrate. When bonding a polarizing plate to a glass substrate, you may bond together a retardation film, a viewing angle improvement film, a brightness improving film, etc. simultaneously.

Example

Hereinafter, the present invention will be described concretely with reference to Examples, but the present invention is not limited at all by the following Examples.

In the following Examples and Comparative Examples, the volatile fraction of the membrane-forming stock solution, the volatile fraction (water content) of the PVA film or PVA film, the physical properties of the PVA film, and the optical performance of the polarizing film were measured by the following method.

(1) Volatilization fraction of film production stock:

According to the method mentioned above, it calculated | required by the said Formula [iii].

(2) Volatilization fraction (water content) of PVA film or PVA film:

According to the above method, it calculated | required by said Formula [iv].

In addition, the measurement of the volatile fraction (water content) of a PVA film or PVA film was performed using the sample extract | collected from the width direction (TD) center part of the PVA film or PVA film taken out from the drying roll.

(3) Δn (MD) _Ave of PVA film:

(DELTA) n (MD) _Ave in the center part of the width direction (TD) of a PVA film is calculated | required by the above-mentioned method in the item of "Measurement method of << 1 >> (DELTA) n (MD) _Ave ", and this is the (DELTA) n (MD) of PVA film. _Ave was set.

(4) Δn (TD) _Ave of PVA film:

Δn (TD) _Ave in the center part of the width direction TD of a PVA film is calculated | required by the above-mentioned method in the item of "Measurement method of << 2 >> (DELTA) n (TD) _Ave ", and this is Δn (TD) of PVA film. _Ave was set.

(5) Mass swelling degree of PVA film:

The PVA film was cut to 1.5 g, immersed in 1000 g of 30 ° C. distilled water for 30 minutes, and after immersion for 30 minutes, the PVA film was taken out and the surface water was soaked with filter paper, and the mass (W _e ) was measured. . Then, after drying the PVA film for 16 hours with the 105 degreeC dryer, the mass ( _Wf ) was measured. Obtained by the mass W _e and W from _f, the following expression [v], the degree of swelling was determined by mass of the PVA film.

Mass Swelling (%) = (W _e / W _f ) × 100 [v]

(6) Limit draw ratio of PVA film:

From the center part of the width direction (TD) of the PVA film before extending | stretching obtained by the following example or the comparative example, the test piece of longitudinal direction (MD) x width direction (TD) = 10 cm x 5 cm is extract | collected, and the longitudinal direction of the said test piece Both ends of the fixed portion were fixed to the stretching jig such that the size of the stretched portion became the longitudinal direction (MD) × width direction (TD) = 5 cm × 5 cm, and was immersed in 30 ° C. water for 38 seconds for 12 cm / min. After uniaxial stretching (first stage stretching) in the longitudinal direction (MD) at 2.2 times the original length at the stretching rate, iodine / iodization at a temperature of 30 ° C. containing 0.03 mass% of iodine and 3 mass% of potassium iodide While immersing in aqueous potassium solution for 90 seconds, uniaxially stretching (second stage stretching) in the longitudinal direction (MD) to 3.3 times the original length at a stretching rate of 12 cm / min, and then adding 3% by mass of boric acid and potassium iodide To contain at a concentration of 3% by mass While immersing in an aqueous solution of boric acid / potassium iodide at a temperature of 30 ° C. for about 20 seconds, uniaxial stretching (third stage stretching) in the longitudinal direction (MD) is continued to 3.6 times the original length at a stretching speed of 12 cm / min, and then Longitudinal direction (MD) until the test piece broke at a drawing speed of 12 cm / min while immersing in an aqueous solution of boric acid / potassium iodide at a temperature of about 60 ° C. containing 4% by mass of boric acid and about 5% by mass of potassium iodide. The film was uniaxially stretched, and the draw ratio (ratio of the length at the break to the original length) when the test piece was broken was read.

About the same PVA film, said extending | stretching test was performed 5 times, the average value was taken, and it was set as the limit draw ratio (times) of a PVA film.

(7) Optical performance of polarizing film:

(i) transmittance:

From the central part of the width direction of the polarizing film obtained by the following example or the comparative example, two square samples of 1.5 cm x 1.5 cm were taken in parallel in the orientation direction of a polarizing film, and about each, the spectrophotometer by Hitachi Ltd. In accordance with JIS Z 8722 (Measurement Method of Object Color) using V-7100 (integrated sphere included), the visibility of the C light source and the visible light region in the 2-degree field of view was corrected, and the polarized film samples of one sheet were opened. The transmittance of the light when tilted at 45 degrees with respect to the stretch direction and the light transmittance when tilted at −45 degrees were measured, and their average value (Y ₁ ) was obtained.

For the other one sheet of the polarizing film sample, by measuring the transmittance of light in the case in the same manner as the light transmittance of Fig 45 when tilted and inclined -45 degrees, it was determined their mean value (Y _2).

By averaging the Y ₁ and Y ₂ obtained in the above it was set to the transmittance of the polarizing film (Y) (%).

(ii) Polarization degree:

The transmittance of light (Y⊥) in the case where the two pieces of the polarizing film samples taken from the (i), the alignment direction is parallel to it such that the light transmittance of the overlapped case that (Y ∥), and alignment directions are superposed so as to be orthogonal, It measured by the same method as the measuring method of the said transmittance | permeability, and calculated polarization degree (V) (%) from following formula [vi].

Polarization degree (V) (%) = ｛(Y ∥ Y-) / (Y ∥ Y Y) ⊥ ^1/2 × 100 [vi]

(iii) Polarization degree in 44.25% transmittance:

As described in the following Examples and Comparative Examples, in each Example or Comparative Example, to each of the five polarizing films produced by changing the immersion time in the aqueous solution of iodide / potassium iodide at the time of the second stage stretching The transmittance (Y) and the polarization degree (V) were obtained by the above-described method. For each Example or Comparative Example, five points were plotted on the graph with the transmissivity (Y) as the horizontal axis and the polarization degree (V) as the vertical axis. The approximation curve was calculated | required and the value of the polarization degree (V) when the transmittance | permeability (Y) is 44.25% was calculated | required from this approximation curve.

&Quot; Example 1 &

(1) Production of PVA film:

(i) 100 mass parts of PVA obtained by saponifying polyvinyl acetate (99.9 mol% of degree of polymerization, 2400 degree of polymerization), 12 mass parts of glycerin, 0.1 mass part of ethanolamide laurate, and 66 mass% of volatile fractions consisting of water First drying roll from T-die (surface temperature 93 ° C, circumferential speed (S ₁ ) 16.7 m / min), and dried on a first drying roll until the moisture content reaches 18% by mass while injecting hot air at 90 ° C. at a wind speed of 5 m / sec on the entire first dry roll non-contact surface, Subsequently, it peels from a 1st dry roll, and drying after a 2nd dry roll is performed at roll surface temperature of about 85 degreeC so that the surface and the back surface in arbitrary parts of a PVA film may alternately contact each dry roll, and finally the surface After heat-processing with the final drying roll (heat processing roll) of temperature 108 degreeC, it wound up and obtained the PVA film (60 micrometers in thickness, width 3m, volatile fraction 3 mass%). In this Example 1, the dry roll when the volatile fraction became 13 mass% was a 7th dry roll.

In this Example 1, (S) ratio (S _T ) of the circumferential speed S _T of the drying roll (seventh dry roll) when the volatile fraction became 13 mass% with respect to the circumferential speed S ₁ of the first drying roll. _T / S ₁ ) is 1.000; (β) of the circumferential speed (S _L ) of the final drying roll with respect to the circumferential speed (S _T ) of the drying roll (seventh dry roll) when the volatilization fraction became 13% by mass. Let ratio (S _L / S _T ) be 0.974; (γ) Ratio (S ₂ / S ₁ ) of the peripheral speed S ₂ of the second drying roll to the peripheral speed S _{1 of} the first drying roll is 1.030. and; (δ) peripheral speed (S _{T + 1)} of the peripheral speed, and then drying rolls (eighth drying roll) for (S _T) of the volatile drying roll (seventh drying roll) when the fraction is 13% by mass Let ratio (S _T / S _{T +1} ) be 0.998; (ε) Ratio (S _L / S ₁ ) of the peripheral speed S _L of the final drying roll to the peripheral speed S ₁ of the first drying roll. A PVA film was prepared at 0.975.

(ii) As a result of having measured (DELTA) n (MD) _Ave , (DELTA) n (TD) _Ave , mass swelling degree, and limit draw ratio of the PVA film obtained by said (i) by the above-mentioned method, it was as showing in following Table 1.

(2) Production of Polarizing Film:

(i) The test piece of longitudinal direction (MD) x width direction (TD) = 10 cm x 5 cm is extract | collected from the center part of the width direction (TD) of the PVA film obtained by said (1), and the both ends of the longitudinal direction of the said test piece 12 cm / min of extending | stretching while fixing to the extending | stretching jig so that the size of a extending | stretching part may be length direction (MD) x width direction (TD) = 5 cm x 5 cm, and immersing in water of temperature 30 degreeC for 38 second. After uniaxial stretching (first stage stretching) in the longitudinal direction (MD) at 2.2 times the original length at a speed, the iodine / potassium iodide at a temperature of 30 ° C. containing 0.03% by mass of iodine and 3% by mass of potassium iodide While immersing in an aqueous solution for 60 seconds, uniaxially stretching (second stage stretching) in the longitudinal direction (MD) to 3.3 times the original length at a stretching speed of 12 cm / min, and then adding 3% by mass of boric acid and potassium iodide Boric acid / urine with a temperature of 30 ° C containing at a concentration of mass% While immersing in aqueous potassium hydride solution for about 20 seconds, uniaxially stretching (third stage stretching) in the longitudinal direction (MD) to 3.6 times the original length at a stretching speed of 12 cm / min, and then adding 4% by mass of boric acid and Lengthwise to the draw ratio immediately before the limit draw ratio of the PVA film measured above at a draw rate of 12 cm / min while immersing in an aqueous solution of boric acid / potassium iodide at a temperature of about 60 ° C. containing potassium iodide at a concentration of about 5% by mass. After uniaxial stretching (4th stage stretching) by (MD), it was immersed in the potassium iodide aqueous solution containing potassium iodide at the density | concentration of 3 mass% for 10 second, and an iodide ion impregnation process was performed, It dried for minutes, and produced the polarizing film (thickness about 21 micrometers).

The transmittance | permeability (Y) and polarization degree (V) of the polarizing film obtained by this were calculated | required by the above-mentioned method, and the point was plotted on the graph which makes transverse axis | shaft transmittance (Y) and vertical axis | shaft the polarization degree (V).

(ii) In the above (i), the same operation as in (i) is carried out except that the immersion time in the iodine / potassium iodide aqueous solution at a temperature of 30 ° C at the time of the second stage stretching is changed from 60 seconds to 75 seconds. The stretching speed in the stretching step was 12 cm / min, which was the same as in the above (i)], and a polarizing film (thickness of about 21 μm) was produced.

The transmittance | permeability (Y) and polarization degree (V) of the polarizing film obtained by this were calculated | required by said method, and the point was plotted on the graph of said (i).

(iii) In the above (i), the same operation as in (i) is performed except that the immersion time in the iodine / potassium iodide aqueous solution at a temperature of 30 ° C at the time of the second stage stretching is changed from 60 seconds to 90 seconds. The stretching speed in the stretching step was 12 cm / min, which was the same as in the above (i)], and a polarizing film (thickness of about 21 μm) was produced.

The transmittance | permeability (Y) and polarization degree (V) of the polarizing film obtained by this were calculated | required by said method, and the point was plotted on the graph of said (i).

(iv) In the above (i), the same operation as in (i) is performed except that the immersion time in the iodine / potassium iodide aqueous solution at a temperature of 30 ° C at the time of the second stage stretching is changed from 60 seconds to 105 seconds. The stretching speed in the stretching step was 12 cm / min, which was the same as in the above (i)], and a polarizing film (thickness of about 21 μm) was produced.

The transmittance | permeability (Y) and polarization degree (V) of the polarizing film obtained by this were calculated | required by said method, and the point was plotted on the graph of said (i).

(v) In the above (i), the same operation as in (i) is performed except that the immersion time in the iodine / potassium iodide aqueous solution at a temperature of 30 ° C at the time of the second stage stretching is changed from 60 seconds to 120 seconds. The stretching speed in the stretching step was 12 cm / min, which was the same as in the above (i)], and a polarizing film (thickness of about 21 μm) was produced.

The transmittance | permeability (Y) and polarization degree (V) of the polarizing film obtained by this were calculated | required by said method, and the point was plotted on the graph of said (i).

(vi) An approximate curve of five points plotted on the graph in (i) to (v) is plotted on the graph, and from this approximation curve, the value of polarization degree (V) when transmittance (Y) is 44.25% is determined. As a result, it was 99.98 as shown in Table 1 below.

<< Examples 2-5 >>

(1) In Example 1, the film-forming conditions at the time of manufacturing a PVA film were changed so that it may be described in following Table 1, and PVA film was manufactured like Example 1 (1). However, in Example 2, 100 mass parts of PVA (saponification degree 99.9 mol%, polymerization degree 2400) obtained by saponifying polyvinyl acetate as a film-forming stock solution, 12 mass parts of glycerin, 0.1 mass part of diethanolamide laurate, and water A film production stock solution having a volatilization fraction of 73% by mass was used.

As a result of having measured (DELTA) n (MD) _Ave , (DELTA) n (TD) _Ave , mass swelling degree, and limit draw ratio of each obtained PVA film by the said method, it was as showing in following Table 1.

(2) Example 1 using the test piece of the longitudinal direction (MD) x width direction (TD) = 10 cm x 5 cm taken from the center part of the width direction (TD) of each PVA film obtained by said (1). The same operation as (2) was performed, five types of polarizing films were produced for each Example, the transmittance | permeability (Y) and the polarization degree (V) of each polarizing film were calculated | required, and the horizontal axis | shaft was used as the transmittance | permeability (Y) and a vertical axis | shaft. Plot the point on a graph of the degree of polarization (V), and draw an approximation curve of five points plotted on the graph on the graph, and the polarization degree (V) when the transmittance (Y) is 44.25% from the approximation curve. It was as having shown in following Table 1 when the value of was calculated | required.

`` Comparative Examples 1 to 5 ''

(1) In Example 1, the film-forming conditions at the time of manufacturing a PVA film were changed so that it may be described in following Table 2, and it carried out similarly to (1) of Example 1, and manufactured the PVA film.

(DELTA) n (MD) _Ave , (DELTA) n (TD) _Ave , mass swelling degree, and limit draw ratio of each PVA film obtained by this were measured by the above-mentioned method, and it was as showing in following Table 2.

(2) Example 1 using the test piece of the longitudinal direction (MD) x width direction (TD) = 10 cm x 5 cm taken from the center part of the width direction (TD) of each PVA film obtained by said (1). The same operation as (2) was performed, five types of polarizing films were produced for each comparative example, the transmittance (Y) and the polarization degree (V) of each polarizing film were obtained, and the horizontal axis was used as the transmittance (Y) and the vertical axis. Plot the point on a graph of the degree of polarization (V), and draw an approximation curve of five points plotted on the graph on the graph, and the polarization degree (V) when the transmittance (Y) is 44.25% from the approximation curve. It was as having shown in following Table 2 when the value of was calculated | required.

As shown in the said Table 1 and Table 2, the PVA films of Examples 1-5 are (DELTA) n (MD) _Ave [the value which averaged the birefringence of the longitudinal direction (MD) of a PVA film in the thickness direction of a film], and (DELTA) n (TD) _Ave [Value obtained by averaging the birefringence in the width direction (TD) of the PVA film in the thickness direction of the film] The high limit draw ratio of 6.72 to 6.94 because the expressions (I) and (II) are satisfied. In addition, the polarizing film obtained from the PVA films of Examples 1-5 has the outstanding polarization performance equivalent to or more than the conventional polarizing film.

In contrast, the PVA films of Comparative Examples 1 to 4 did not satisfy the formula (I), and

Since the PVA films of Comparative Examples 4 and 5 do not satisfy the formula (II), the limit draw ratios are all lower than those of the PVA films of Examples 1 to 5.

When manufacturing a polarizing film with a PVA-type polymer film, although uniaxial stretching is normally performed by extending | stretching ratio slightly lower than a limit draw ratio in order to avoid the rupture of the film at the time of extending | stretching, the limit of the PVA film of Examples 1-5 When the draw ratios are all high at 6.72 or more, the PVA films of Examples 1 to 5 can uniaxially stretch at a draw ratio of 6 times or higher when the polarizing film is produced under the conditions of the Examples, and 6.5. Even if it carries out uniaxial stretching at twice or more high draw ratio, it can extend | stretch smoothly, without breaking a film.

In contrast, among the PVA films of Comparative Examples 1 to 5, since the PVA film of Comparative Example 4 has a limit draw ratio of less than 6, when a polarizing film is produced under the conditions of the comparative example, uniaxial stretching is performed at a draw ratio of 6 times or more. If the film is not stretched, the film breaks well, and if the PVA films of Comparative Examples 1 to 3 and 5 also uniaxially stretch at a draw ratio of 6 times or more, there is a concern in terms of breaking of the film.

Moreover, in the raw film for polarizing films, although the length of one volume may be 1000 m or more, for example, in the PVA system polymer film of 1000 m in total length, the limit draw ratio raises by 0.1 point (0.1 times). The length of the stretched film obtained by uniaxial stretching increases 100 m (1000 m x 0.1 times = 100 m), and more polarizing films are obtained from the master film of the same length.

When looking at this about Examples 1-5, since the PVA film of Examples 1-5 is 0.10-0.98 points (times) higher than the PVA film of Comparative Examples 1-5, For example, when the length of a PVA film is 1000 m, when the polarizing film is manufactured on the conditions of the said Example using it, compared with the case where the length of a polarizing film uses the PVA film of Comparative Examples 1-5, it is 100-. It becomes 980m long, and more polarizing film can be obtained.

Industrial availability

The PVA-based polymer film of the present invention has a high limit draw ratio even when the film thickness is as thin as about 30 to 65 µm, and even when uniaxially stretched at a high magnification when producing a polarizing film or the like, breakage of the film occurs well. Since it does not, the stretched film, such as a polarizing film which is excellent in optical performances, such as a polarizing performance, can be manufactured with high yield and favorable productivity with a shorter drying time than before, without interrupting an extending | stretching operation, and a polarizing film It is very useful as a raw film for manufacturing stretched films, etc., and the manufacturing method of this invention is useful as a method for producing the PVA-based polymer film of the present invention smoothly and continuously with high productivity.

Claims (3)

The polyvinyl alcohol polymer film which satisfies the following formulas (I) and (II) is dyed, uniaxially stretched, fixed, and dried.
Δn (MD) _Ave -0.1 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.25 × 10 ^-3 (I)
Δn (TD) _Ave ≤ 2.5 × 10 ^-3 (II)
[Wherein, Δn (MD) _Ave represents a value obtained by averaging the birefringence in the mechanical flow direction of the polyvinyl alcohol polymer film in the thickness direction of the film, and Δn (TD) _Ave is a polyvinyl alcohol polymer film Represents a value obtained by averaging the birefringence in the width direction of the film in the thickness direction of the film.] The polyvinyl alcohol polymer film which satisfies the following formulas (I) and (II) and further satisfies the following formula (III) is dyed, uniaxially stretched, fixed and dried to produce a polarizing film. Way.
Δn (MD) _Ave -0.1 × 10 ^-3 ≤ Δn (TD) _Ave ≤ Δn (MD) _Ave + 0.25 × 10 ^-3 (I)
Δn (TD) _Ave ≤ 2.5 × 10 ^-3 (II)
1.3 × 10 ^-3 ≤ Δn (MD) _Ave ≤ 2.0 × 10 ^-3 (III)
[Wherein, Δn (MD) _Ave represents a value obtained by averaging the birefringence in the mechanical flow direction of the polyvinyl alcohol polymer film in the thickness direction of the film, and Δn (TD) _Ave is a polyvinyl alcohol polymer film Represents a value obtained by averaging the birefringence in the width direction of the film in the thickness direction of the film.] 3. The method according to claim 1 or 2,
The manufacturing method of the polarizing film whose thickness of the said polyvinyl alcohol-type polymer film used for manufacture of a polarizing film exists in the range of 30-65 micrometers.

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