CN103897208A

CN103897208A - Polyvinyl alcohol polymer film and process for producing same

Info

Publication number: CN103897208A
Application number: CN201410068383.6A
Authority: CN
Inventors: 森保二郎; 风藤修; 日笠慎太郎; 胜野良治
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2011-03-29
Filing date: 2012-03-19
Publication date: 2014-07-02
Also published as: TW201244914A; CN103442871B; CN104311853B; CN104311853A; TWI526292B; KR101380528B1; WO2012132984A1; TWI465331B; KR101784042B1; CN103442871A; JP5961475B2; KR20130124585A; JP2012215908A; JP5117639B2; TW201446470A; KR20130129473A; JPWO2012132984A1

Abstract

A PVA film that satisfies expressions (I) and (II), which has satisfactory stretchability and from which a polarizing film can be efficiently produced; and a process for film production which comprises (a) ejecting a PVA-containing film formation dope in a film form onto the first drying roll of a film formation device equipped with a plurality of drying rolls, partly drying the web, and then successively drying the web with the subsequent drying rolls to produce a film, wherein (b) the ratio of the peripheral speed (ST) of the drying roll on which the volatile content of the PVA film has fallen to 13 mass% to the peripheral speed (S1) of the first drying roll, ST/S1, is regulated to 0.990-1.050, (c) the ratio of the peripheral speed (SL) of the last drying roll to the peripheral speed ST, SL/ST, is regulated to 0.960-0.980, and (d) the SL/S1 ratio is regulated to 0.970-1.010. n(MD)Ave-0.110-3= n(TD)Ave= n(MD)Ave+0.2510-3 (I) n(TD)Ave=2.510-3 (II) [In the expressions, n(MD)Ave indicates the value obtained by averaging the machine-direction birefringence values of the PVA film with respect to the film thickness direction, and n(TD)Ave indicates the value obtained by averaging the transverse-direction birefringence values of the PVA film with respect to the film thickness direction.

Description

The manufacture method of polarizing coating

The application is that the national applications number submitted on September 27th, 2013 is the divisional application of 201280015847.6 the denomination of invention application for a patent for invention that is " polymer film of polyvinyl alcohol and manufacture method thereof ".

Technical field

The polarizing coating that the present invention relates to polymer film of polyvinyl alcohol (Off ィ Le system) and manufacture method thereof and made by this film.In more detail, though the present invention relates to have high limit stretching ratio with high magnification stretched film also not easy fracture, can not follow the fracture of film and the interruption of the operation that stretches etc., the polarizing coating that can manufacture the polymer film of polyvinyl alcohol of stretched film of the excellent in optical properties such as polarization property and manufacture method thereof and be made by this film with high rate of finished products, good productivity.

Background technology

The liquid crystal etc. that has the polaroid of optical transmission and function of shielding and have a switching function of light is all the important integrant of liquid crystal indicator (LCD).The vast scopes such as the measuring instrument that the miniature instrument such as counter and wrist-watch of the Application Areas of this liquid crystal indicator during also from initial stage of development expand notebook computer, liquid crystal display, color liquid crystal projector, LCD TV, onboard navigation system, mobile phone to, use in doors, particularly in liquid crystal display, LCD TV etc., the positive development of large screen.

The general manufacture as described below of polaroid: the method etc. that is simultaneously fixed processing in dyeing by the method processing dyeing with iodine, dichroic dye after polymer film of polyvinyl alcohol uniaxial extension, by being fixed the method for processing with boron compound after polymer film of polyvinyl alcohol dyeing uniaxial extension, in above-mentioned any method is manufactured polarizing coating, at the protective membrane such as one or both sides laminating tri cellulose acetate membrane, cellulose acetate butyrate (CAB) film of the polarizing coating obtaining thus.

In recent years, along with expansion of the purposes of liquid crystal indicator etc., except display quality advanced, also require the further reduction of cost and the further raising of treatability.From the aspect reducing costs, need to improve the production rate while manufacturing polarizing coating, and the tension fracture (fracture) need to prevent polymer film of polyvinyl alcohol to stretch time, reduce fracture loss, improve yield rate, and prevent from following the fracture of film and the stretching operation, the interruption of stretching-dyeing operation etc. that produce.

A kind of method of the raising of the productivity during as manufacture polarizing coating, the shortening of time of drying while requiring to manufacture polarizing coating, from this viewpoint, the former film (former anti-Off ィ Le system) of using as polarizing coating, general used thickness was the polymer film of polyvinyl alcohol of 75 μ m left and right in the past, but the polymer film of polyvinyl alcohol of required thickness, further filming thinner than 70 μ m in recent years.

But, exist polymer film of polyvinyl alcohol that the problem of fracture more easily occurs when more Bao Ze stretches with high magnification, from this viewpoint, even if require to have, ultimate elongation multiplying power is high very thinly also can the polymer film of polyvinyl alcohol that fracture in the situation that can stretch with high magnification thereby can have with good operability, high rate of finished products, low cost, good productivity manufacture the polarizing coating of the polarization property more than equal with existing product not occur.

In the past, for improve polymer film of polyvinyl alcohol stretchiness, improve homogeneity while stretching, improve polymer film of polyvinyl alcohol is stretched and the object such as polarization property and weather resistance of polarizing coating, the stoste that contains vinol series polymer in use is dried while when masking, adjustment of the moisture ratio of the vinol series polymer film while being filmed adjustment, the masking of stretch ratio (ratio of the transporting velocity of the vinol series polymer film between the roller used of masking) etc.

As such prior art, known (1) is in order to obtain having carried out fully when the uniaxial extension stretched film of molecular orientation, adopt the masking stretch ratio below 1, ad infinitum reduce masking tension force and carry out the method (patent documentation 1, particularly its paragraph [0008]～[0009], embodiment etc.) for the manufacture of the masking operation of polymer film of polyvinyl alcohol; (2) in order to obtain carrying out the polymer film of polyvinyl alcohol of powerful stretching, in the time manufacturing polymer film of polyvinyl alcohol with drum-type film-making machine, make [coiling speed of the polymer film of polyvinyl alcohol of gained]/[being positioned at the speed of the drum of the upstream of the supply system pleurodiaphragmatic in terspace material] be 0.8～1.3 method (patent documentation 2); (3) in order to obtain carrying out the polymer film of polyvinyl alcohol of powerful stretching, in drying process in the time manufacturing polymer film of polyvinyl alcohol with drum-type film-making machine, the method (patent documentation 3) that the velocity ratio (Rf/Rc) that makes the volatile component ratio of film reach the operation speed Rc of 10 % by weight when following and final coiling speed Rf is 0.9～1.1 etc.

In addition, known (4) are even also have the polyvinyl alcohol mesentery of the polarizing coating of the wide cut of the optical property of homogeneous in order to obtain manufacturing big area, the volatile component that is positioned at polyvinyl alcohol film is reached to the speed (Rc) of the dryer roll of the operation below 10% and the velocity ratio (Rf/Rc) of coiling speed (Rf) is controlled at 0.9～1.1, the temperature that reduces drying process is unequal, thereby manufactures the tensile elongation (S of MD direction _m) and the tensile elongation (S of TD direction _t) ratio (S _m/ S _t) be the method (patent documentation 4) of 0.7～1.3 polyvinyl alcohol mesentery; (5) even also there is the polyvinyl alcohol mesentery of the polarizing coating of the wide cut of the optical property of homogeneous in order to obtain manufacturing big area, reach the moment of 10～50 % by weight at the volatile component of polyvinyl alcohol film, from the drum that is positioned at upstream side, polyvinyl alcohol film is peeled off, and made to be positioned at the method (patent documentation 5) that speed that the speed V1 of drum of upstream side and the volatile component that is positioned at polyvinyl alcohol film just started the speed V2 of the drum of the operation that is less than 10 % by weight is 1.0～1.3 than V2/V1.

Also known (6) are in order to obtain providing the uniaxial extension that can carry out homogeneous, when stretching, there is no fine crackle and the stretched film in space, the polymer film of polyvinyl alcohol that comprises specific skin/core/cortex, be the stoste heating of 50～90 quality % to the volatile component ratio that contains vinol series polymer with the first dryer roll, and under defined terms, the vinol series polymer face not contacting with the first dryer roll is sprayed to hot blast simultaneously, the moment that reaches 15～30 quality % in volatile component ratio peels off vinol series polymer film from the first dryer roll, make it contact to be dried with the second dryer roll, now, make the circumferential speed (S of the first dryer roll ₁) and the circumferential speed (S of the second dryer roll ₂) ratio (S ₂/ S ₁) be method (patent documentation 6) of 1.000～1.100 etc.

But, in above-mentioned patent documentation 1～6, and make while being not disclosed in the polymer film of polyvinyl alcohol of the thin thickness of polymer film of polyvinyl alcohol, particularly film with high magnification uniaxial extension film that the scheme of fracture does not occur, particularly further improve the scheme of the ultimate elongation multiplying power of film.

Prior art document

Patent documentation

Patent documentation 1: Japanese patent laid-open 6-136151 communique

Patent documentation 2: Japanese Patent Laid-Open 2001-315141 communique

Patent documentation 3: Japanese Patent Laid-Open 2001-315146 communique

Patent documentation 4: Japanese Patent Laid-Open 2002-30164 communique

Patent documentation 5: Japanese Patent Laid-Open 2002-79531 communique

Patent documentation 6: Japanese Patent Laid-Open 2005-324355 communique

Non-patent literature

Non-patent literature 1: " the high molecular smooth physical property of polymer science One Point 10 ", the 3rd printing of first edition, vertical Co., Ltd. that publishes altogether, on December 15th, 2007, p.19-21.

Summary of the invention

Invent problem to be solved

The object of this invention is to provide a kind of ultimate elongation multiplying power high, can not there is not the polymer film of polyvinyl alcohol that fracture in the situation that stretches with high magnification thereby can have with good operability, high rate of finished products, low cost, good productivity manufacture the stretched film such as polarizing coating of the optical property more than equal with existing product.

Even if object of the present invention particularly provides the polymer film of polyvinyl alcohol that thinlyyer also has high limit stretching ratio, can carry out swimmingly uniaxial extension in the situation that not there is not fracture in the time stretching with high magnification, can make than in the past thinner stretched film and further shorten time of drying while manufacturing polarizing coating, can manufacture with better productivity polarizing coating in the manufacture of polarizing coating more in the past than the polymer film of polyvinyl alcohol using.

Object of the present invention is also to provide the method that can manufacture continuously swimmingly with high productivity the polymer film of polyvinyl alcohol of the characteristic with above-mentioned excellence.

In addition, the object of this invention is to provide the polarizing coating of being made by above-mentioned polymer film of polyvinyl alcohol.

For solving the means of problem

The inventor has carried out conscientiously research in order to achieve the above object and repeatedly, found that, if the degree of birefringence of the mechanical flow direction (length direction) of polymer film of polyvinyl alcohol on the thickness direction of film equalization and value and the degree of birefringence of width on the thickness direction of film equalization and value meet specific relation, and the degree of birefringence of the width of polymer film of polyvinyl alcohol on the thickness direction of film equalization and value in specific numerical range, the ultimate elongation multiplying power of film raises, even stretch and be also difficult for occurring the fracture of film with high magnification, can be with high rate of finished products in the situation that not interrupting stretching operation, with low cost, manufacture the stretched film such as polarizing coating of the excellent in optical properties such as polarization property with good productivity.In addition also find, if the degree of birefringence of the mechanical flow direction of polymer film of polyvinyl alcohol on the thickness direction of film equalization and value in specific numerical range, the ultimate elongation multiplying power of film further improves.

Particularly find, the degree of birefringence of the mechanical flow direction of polymer film of polyvinyl alcohol on the thickness direction of film equalization and value and the degree of birefringence of width on the thickness direction of film equalization and value meet specific relation, and the degree of birefringence of width on the thickness direction of film equalization and the above-mentioned polymer film of polyvinyl alcohol of value in specific scope in, even the Thickness Ratio of this film in the past in the manufacture of polarizing coating the thickness of conventional polymer film of polyvinyl alcohol thinner, be the thickness of 30～65 μ m left and right, also there is high limit stretching ratio, therefore can in the situation that not there is not fracture, carry out swimmingly uniaxial extension with high magnification, thereby can realize the further filming while manufacturing polarizing coating, can further shorten the time of drying while manufacturing polarizing coating.

In addition, the discoveries such as the inventor, the above-mentioned polymer film of polyvinyl alcohol with high limit stretching ratio can be by the following method manufactured swimmingly continuously with high productivity: the masking stoste that contains vinol series polymer is spued to after possessing on first dryer roll of film forming apparatus of many dryer rolls, be dried to be successively filmed with these many dryer rolls, now, the circumferential speed of the dryer roll while making the volatile component ratio of vinol series polymer film reach 13 quality % with respect to the ratio of the circumferential speed of the first dryer roll in specific numerical range, the ratio of the circumferential speed of the dryer roll while making the circumferential speed of final dryer roll reach 13 quality % with respect to the volatile component ratio of vinol series polymer film is in specific numerical range, the circumferential speed that makes final dryer roll with respect to the ratio of the circumferential speed of the first dryer roll in specific numerical range.

In addition, the discoveries such as the inventor, when by the high polymer film of polyvinyl alcohol of aforesaid method manufacturing limit stretching ratio, the volatile component ratio of the vinol series polymer film while preferably making to peel off from the first dryer roll is in specific numerical range, the roll surface temperature of preferred each dryer roll is more than 65 DEG C, also have, if the volatile component ratio of the masking stoste that contains vinol series polymer is 60～75 quality %, and the roll surface temperature of the first dryer roll is 80～120 DEG C, even if the circumferential speed of the first dryer roll reaches 8m/ minute above high speed, also the degree of birefringence of mechanical flow direction of can be swimmingly manufacturing polymer film of polyvinyl alcohol with good productivity on the thickness direction of film equalization and value and the degree of birefringence of width on the thickness direction of film equalization and value meet specific relation, and the degree of birefringence of width on the thickness direction of film equalization and value regulation numerical range in, the polymer film of polyvinyl alcohol that ultimate elongation multiplying power is high, further repeatedly study based on these discoveries, thereby complete the present invention.

, the present invention is:

(1) polymer film of polyvinyl alcohol, is characterized in that, meets following formula (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)

[in above formula, Δ n (MD) _avethe degree of birefringence of mechanical flow direction that represents polymer film of polyvinyl alcohol on the thickness direction of this film equalization and value, Δ n (TD) _avethe degree of birefringence of width that represents polymer film of polyvinyl alcohol on the thickness direction of this film equalization and value].

In addition, the present invention is:

(2) polymer film of polyvinyl alcohol of above-mentioned (1), it meets following formula (III);

1.3 × 10 ^-3≤ Δ n (MD) _ave≤ 2.0 × 10 ^-3(III); And

(3) polymer film of polyvinyl alcohol of above-mentioned (1) or (2), its thickness is in the scope of 30～65 μ m.

The present invention is still:

(4) manufacture method of polymer film of polyvinyl alcohol, is characterized in that,

(a) use the film forming apparatus that possesses the many dryer rolls that rotating shaft is parallel to each other, by the masking stoste that contains vinol series polymer with membranaceous spue to the first dryer roll of this film forming apparatus and carry out part dry after, be further dried masking with follow-up dryer roll; Now,

(b) circumferential speed (S of the dryer roll when volatile component ratio of vinol series polymer film reaches 13 quality % _t) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _t/ S ₁) be 0.990～1.050;

(c) circumferential speed (S of final dryer roll _l) circumferential speed (S of dryer roll while reaching 13 quality % with respect to the volatile component ratio of vinol series polymer film _t) ratio (S _l/ S _t) be 0.960～0.980;

(d) circumferential speed (S of final dryer roll _l) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _l/ S ₁) be 0.970～1.010.

In addition, the present invention is:

(5) manufacture method of above-mentioned (4), wherein, the volatile component ratio of the vinol series polymer film while peeling off from the first dryer roll is 17～30 quality %;

(6) manufacture method of above-mentioned (4) or (5), wherein, the roll surface temperature of each dryer roll is more than 65 DEG C; And

(7) manufacture method of any one in above-mentioned (4)～(6), wherein, the volatile component ratio of the masking stoste that contains vinol series polymer is 60～75 quality %, the roll surface temperature of the first dryer roll is 80～120 DEG C, the circumferential speed (S of the first dryer roll ₁) be 8～25m/ minute.

In addition, the present invention is:

(8) polarizing coating, its polymer film of polyvinyl alcohol by any one in above-mentioned (1)～(3) is made.

The effect of invention

Polymer film of polyvinyl alcohol of the present invention has high limit stretching ratio, therefore in the time manufacturing stretched film, even be also difficult for occurring the fracture of film with high magnification uniaxial extension, thus can be in the situation that not interrupting stretching operation with high rate of finished products, with low cost, manufacture the stretched film such as polarizing coating of the excellent in optical properties such as polarization property with good productivity.

Even particularly the Thickness Ratio of polymer film of polyvinyl alcohol film of the present invention in the past in order to manufacture polarizing coating etc. the thickness of conventional polymer film of polyvinyl alcohol thinner, be the thickness of 30～65 μ m left and right, also there is high limit stretching ratio, therefore can in the situation that not there is not fracture, carry out swimmingly uniaxial extension with high magnification, thereby can realize the further filming while manufacturing stretched film, can further shorten the time of drying while manufacturing polarizing coating etc., and can boost productivity by this.

In addition, in recent years, the former film of using as polarizing coating, also use length to exceed the polymer film of polyvinyl alcohol of 1000m, and polymer film of polyvinyl alcohol of the present invention has high limit stretching ratio, therefore can stretch with the multiplying power than in the past higher, thereby the amount of obtaining of the polarizing coating of being made up of polymer film of polyvinyl alcohol is more than ever before.

By adopting manufacture method of the present invention, can manufacture continuously swimmingly with high productivity the polymer film of polyvinyl alcohol of the present invention of the characteristic with above-mentioned excellence.

Brief description of the drawings

Fig. 1 is the Δ n (MD) that represents to measure polymer film of polyvinyl alcohol _avetime the schematic diagram of acquisition method of sample.

Fig. 2 is the Δ n (TD) that represents to measure polymer film of polyvinyl alcohol _avetime the schematic diagram of acquisition method of sample.

Embodiment

Below, the present invention is described in detail.

In general, in the transparent film made from transparent polymkeric substance such as vinol series polymers, polymer chain is orientated along flow direction (mechanical flow direction: length direction) under the effect of the viscous deformation and the strain etc. that are caused by shear-stress, the direction of polarization of the atomic group of formation polymkeric substance is consistent on microcosmic, thereby produces the distinctive double refraction of polymkeric substance (non-patent literature 1).

The degree of birefringence [Δ n (MD)] of the mechanical flow direction of polymer film of polyvinyl alcohol is tried to achieve by following formula [i], and in addition, the degree of birefringence of width [Δ n (TD)] is tried to achieve by following formula [ii].

Δn(MD)=nMD-nz [i]

Δn(TD)=nTD-nz [ii]

[in formula, nMD represents the specific refractory power of the mechanical flow direction (length direction) of film, and nTD represents the specific refractory power of the width of film, and nz represents the specific refractory power of the thickness direction of film].

As recorded in non-patent literature 1, in the film made from transparent polymkeric substance such as vinol series polymers, the polymer chain that forms film is easily orientated along mechanical flow direction (length direction), comprise in the polymer film of polyvinyl alcohol of the polymer film of polyvinyl alcohol of recording in above-mentioned patent documentation 1～6, generally be the relation of " degree of birefringence [Δ n (MD)] of mechanical flow direction " > " degree of birefringence [Δ n (TD)] of width ", , the degree of birefringence [Δ n (MD)] of mechanical flow direction is easily larger than the degree of birefringence of width [Δ n (TD)].

In contrast, polymer film of polyvinyl alcohol of the present invention meets following formula (I) and (II), different from existing polymer film of polyvinyl alcohol in this.

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)

; from above formula (I); in polymer film of polyvinyl alcohol of the present invention (sometimes " polyvinyl alcohol " being called to " PVA " below), the degree of birefringence of the mechanical flow direction of PVA series polymer film (the streamline direction while manufacturing continuously PVA series polymer film) [being sometimes referred to as below " length direction (MD) "] on the thickness direction of this film equalization and value " Δ n (MD) _ave" with the degree of birefringence of the width (with the rectangular direction of length direction) [being sometimes referred to as below " width (TD) "] of PVA series polymer film on the thickness direction of this film equalization and value " Δ n (TD) _ave" equal or smaller, even if or exceed " Δ n (TD) _ave", its amount is also little.

PVA series polymer film of the present invention, except this formula (I), also has the feature that meets above formula (II).

PVA series polymer film of the present invention meets above formula (I) and (II), even thereby in the case of the Thickness Ratio of film is in the past thin, also there is high limit stretching ratio, even if thereby be also difficult for occurring the fracture of film with high magnification uniaxial extension in the time manufacturing the stretched film such as polarizing coating, can not cause because of the fracture of film the interruption of stretching operation, can be with high rate of finished products, manufacture the stretched film of the filming of the excellent in optical properties such as polarization property with good productivity.

If do not meet above formula (I), the ultimate elongation multiplying power of PVA series polymer film reduces, and the fracture of film easily occurs during with high magnification uniaxial extension, particularly in the time of the thin thickness of film, easily ruptures.

PVA series polymer film of the present invention preferably meets following formula (I '), more preferably meets following formula (I ' '), further preferably meets following formula (I ' ' ').

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+0.2×10 ^-3 (I’’)

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

In addition, if the Δ n (TD) of PVA series polymer film _avebe greater than 2.5 × 10 ^-3, outside the scope of above-mentioned formula (II), the ultimate elongation multiplying power of PVA series polymer film reduces, and is difficult to make PVA series polymer film to stretch with high magnification at length direction (MD), is difficult to obtain the stretched film of excellent in optical properties.

In order exceedingly to reduce Δ n (TD) _ave, need in the time manufacturing PVA series polymer film, allow the dry shrinkage of width, the tendency that has the effective width yield of PVA series polymer film to reduce, the therefore Δ n (TD) of PVA series polymer film of the present invention _avepreferably 1.5 × 10 ^-3～2.2 × 10 ^-3scope in, more preferably 1.6 × 10 ^-3～2.0 × 10 ^-3scope in.

PVA series polymer film of the present invention, except above formula (I) with (II), preferably also meets following formula (III).

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

By the Δ n (MD) of PVA series polymer film _ave2.0 × 10 ^-3below, the ultimate elongation multiplying power of PVA series polymer film further improves, and easily PVA series polymer film is stretched with high magnification at length direction (MD), more easily obtains the stretched film of excellent in optical properties.On the other hand, in order to make the Δ n (MD) of PVA series polymer film _avebe less than 1.3 × 10 ^-3, need to greatly reduce the circumferential speed ratio of dryer roll, therefore there is PVA based polymer film in the time of masking that lax tendency easily occurs between dryer roll.

The Δ n (MD) of PVA series polymer film of the present invention _avemore preferably 1.4 × 10 ^-3～1.95 × 10 ^-3scope in, further preferably 1.5 × 10 ^-3～1.9 × 10 ^-3scope in.

In addition, in PVA series polymer film, at the upper Δ n (MD) of width (TD) of film _aveand/or Δ n (TD) _avevalue often can change, particularly at the both ends of width, Δ n (MD) _aveeasily raise, but as long as at least meet formula (I) and (II), preferably meet formula (I)～(III) at the central part of the width (TD) of PVA series polymer film, preferably in the whole region of the more than 8 one-tenth part of the width (TD) centered by the central part of the width (TD) of PVA series polymer film, meet formula (I) and (II), preferably meet formula (I)～(III).(deburring) can removed by alongst (MD) stretching cutting before of PVA series polymer film in the both ends that do not meet the width (TD) of formula (I) and PVA series polymer film (II).

" the Δ n (MD) of PVA series polymer film _ave" [degree of birefringence of the length direction (MD) of PVA series polymer film on the thickness direction of this film equalization and value] and " Δ n (TD) _ave" [degree of birefringence of the width (TD) of PVA series polymer film on the thickness direction of this film equalization and value] can measure by the following method.

" 1 " Δ n (MD) _aveassay method:

(that exemplify here is the Δ n (MD) of the central part of the width (TD) of PVA series polymer film _aveassay method.)

(i) on the optional position of the length direction (MD) of PVA series polymer film, as shown in Fig. 1 (a), cut out the big or small shred of MD × TD=2mm × 10mm from the central part of the width (TD) of film, this shred is clamped from both sides with the PET film of thick 100 μ m, be clipped in again in wooden frame, be installed on slicing machine device.

(ii) then, by the length direction (MD) of the shred gathering as mentioned above (PET film and wooden frame are not shown) and shred as shown in Fig. 1 (b), abreast with the cut-space of 10 μ m, (MD × TD=2mm × 10 μ m) to manufacture the section of the observation use shown in 10 Fig. 1 (c).From this section, select 5 tangent planes level and smooth and there is no the section of slice thickness inequality, they are put respectively on slide glass, measure slice thickness with microscope (Keyemce company system).In addition, in the visual field of 10 times, eyepiece, object lens 20 times (amounting to 200 times), observe.

(iii) then, in order to observe tangent plane, to cut into slices and fall as described in Fig. 1 (d), cut side up is put on slide glass, with cover glass and silicone oil (specific refractory power 1.04) sealing, measure the delay of 5 sections by two-dimentional photoelastic evaluation system " PA-micro " (the hotonic Lattice of P Co., Ltd. system).

(iv) under the state on the mensuration picture that the delay distribution of each section is presented to " PA-micro ", to mark the vertical line α in surface coming with pleurodiaphragmatic in terspace across the mode of section, in the enterprising line linearity analysis of this line segment α, obtain the delay distributed data of the thickness direction of film.In addition, in the visual field of 10 times, eyepiece, object lens 20 times (amounting to 200 times), observe.In addition, the error causing in order to suppress the variation of the position of passing through because of the line segment α in section, is made as 300 pixels by live width, gets the mean value of delay.

(v) value delay of the thickness direction of the film obtaining as mentioned above being distributed is divided by the thickness recording with microscope, the degree of birefringence Δ n (MD) that obtains the thickness direction of film distributes, and gets the mean value of degree of birefringence Δ n (MD) distribution of the thickness direction of this film.The mean value that the degree of birefringence Δ n (MD) of the thickness direction of the film of trying to achieve respectively for 5 sections is distributed is further average, as " Δ n (MD) _ave".

" 2 " Δ n (TD) _aveassay method:

(that exemplify here is the Δ n (TD) of the central part of the width (TD) of PVA series polymer film _aveassay method.)

(i) on the optional position of the length direction (MD) of PVA series polymer film, as shown in Fig. 2 (a), cut out the big or small shred of MD × TD=10mm × 2mm from the central part of the width (TD) of film, this shred is clamped from both sides with the PET film of thick 100 μ m, be clipped in again in wooden frame, be installed on slicing machine device.

(ii) then, the width (TD) of the shred gathering as mentioned above (PET film and wooden frame are not shown) and shred as shown in Fig. 2 (b), abreast with the cut-space of 10 μ m, is manufactured to the section (MD × TD=10 μ m × 2mm) of the observation use shown in 10 Fig. 2 (c).From this section, select 5 tangent planes level and smooth and there is no the section of slice thickness inequality, they are put respectively on slide glass, measure slice thickness with microscope (Keyemce company system).In addition, in the visual field of 10 times, eyepiece, object lens 20 times (amounting to 200 times), observe.

(iii) then, in order to observe tangent plane, to cut into slices and fall as described in Fig. 2 (d), cut side up is put on slide glass, with cover glass and silicone oil (specific refractory power 1.04) sealing, measure the delay of 5 sections by two-dimentional photoelastic evaluation system " PA-micro " (the hotonic Lattice of P Co., Ltd. system).

(iv) under the state on the mensuration picture that the delay distribution of each section is presented to " PA-micro ", to mark the vertical line β in surface coming with pleurodiaphragmatic in terspace across the mode of section, in the enterprising line linearity analysis of this line segment β, obtain the delay distributed data of the thickness direction of film.In addition, in the visual field of 10 times, eyepiece, object lens 20 times (amounting to 200 times), observe.In addition, the error causing in order to suppress the variation of the position of passing through because of the line segment β in section, is made as 300 pixels by live width, gets the mean value of delay.

(v) value delay of the thickness direction of the film obtaining as mentioned above being distributed is divided by the thickness recording with microscope, the degree of birefringence Δ n (TD) that obtains the thickness direction of film distributes, and gets the mean value of degree of birefringence Δ n (TD) distribution of the thickness direction of this film.The mean value that the degree of birefringence Δ n (TD) of the thickness direction of the film of trying to achieve respectively for 5 sections is distributed is further average, as " Δ n (TD) _ave".

The thickness of PVA series polymer film of the present invention can, in the scope of 5～150 μ m, in the former film situation of using etc., be preferably 30～65 μ m as polarizing coating.PVA series polymer film of the present invention has high limit stretching ratio, even therefore Film Thickness Ratio in the past the multiplex thickness of making the former film of polarizing coating be that the PVA series polymer film of 75 about μ m is thinner, be in the situation of 30～65 μ m as mentioned above, also can in the case of not there is not the fracture of film, stretch with high magnification, thereby can there is swimmingly with high rate of finished products the stretched film of the optical characteristics such as the polarization property equal above with existing product with good productivity manufacture, and by being that the PVA series polymer film of 30～65 μ m stretches with high magnification by thickness, can make the Thickness Ratio of the film after stretching in the past thinner, and can shorten the time of drying while manufacturing polarizing coating, can improve the manufacturing speed of polarizing coating.

If the thickness of PVA series polymer film is blocked up, in the time manufacturing polarizing coating, be difficult to promptly be dried, on the other hand, if the thickness of PVA series polymer film is excessively thin, in the time of the uniaxial extension for the manufacture of polarizing coating, easily there is the fracture of film.

The width of PVA series polymer film of the present invention is not particularly limited, but in recent years, because the large screen of LCD TV, display screen, so in order effectively to use therein, more than width is preferably 2m, more preferably more than 3m, more preferably more than 4m.In addition, in fact manufacture in the situation of polaroid with production machine, if the width of film is excessive, be difficult to carry out the uniaxial extension of homogeneous, therefore the width of PVA series polymer film is preferably below 8m.

Its quality swelling capacity of PVA series polymer film of the present invention is preferably 180～250%, and more preferably 185～240%, more preferably 190～230%.If the quality swelling capacity of PVA series polymer film is too low, be difficult to stretch, there is the tendency that is difficult to the stretched film of manufacturing excellent in optical properties, on the other hand, if quality swelling capacity is too high, the operation trafficability characteristic variation while stretching, cannot obtain the polarizing coating of high-durability sometimes.

Here said quality swelling capacity refer to after quality when PVA series polymer film is flooded to 30 minutes in the distilled water of 30 DEG C is divided by above-mentioned dipping dry quality after 16 hours at 105 DEG C and the percentage of value, particularly can measure by the method for recording in following examples.

As form the PVA based polymer of PVA series polymer film of the present invention, can exemplify for example will make vinyl ester polymerization and polyvinylesters saponification and PVA, make comonomer graft copolymerization on the main chain of PVA and modified PVA based polymer, will make vinyl ester and comonomer copolymerization and the saponification of modified polyvinyl ester and the modified PVA based polymer made, by a part for the hydroxyl of unmodified PVA or modified PVA based polymer by the crosslinked so-called polyvinyl acetal resin obtaining of the aldehydes such as formaldehyde, butyraldehyde, phenyl aldehyde etc.

The PVA based polymer that forms PVA series polymer film of the present invention is in the situation of modified PVA based polymer, and the modification amount of PVA based polymer is preferably below 15 % by mole, more preferably below 5 % by mole.

The above-mentioned vinyl ester using in manufacture as PVA based polymer, can exemplify such as vinyl-acetic ester, vinyl formate, vinyl laurate, propionate, vinyl butyrate, new vinyl acetate acid, tertiary ethylene carbonate, stearic acid vinyl ester, vinyl benzoate etc.These vinyl ester can be used alone or in combination.In these vinyl ester, from the preferred vinyl-acetic ester of viewpoint of productivity.

In addition,, as above-mentioned multipolymer, can exemplify the olefines (alpha-olefin etc.) of the carbon numbers 2～30 such as such as ethene, propylene, 1-butylene, iso-butylene; Vinylformic acid or its salt; The esters of acrylic acids (for example acrylic acid carbon number 1～18 alkyl ester) such as methyl acrylate, ethyl propenoate, vinylformic acid n-propyl, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, ethyl acrylate, dodecylacrylate, vinylformic acid stearyl; Methacrylic acid or its salt; The methyl acrylic esters (carbon number 1～18 alkyl ester of for example methacrylic acid) such as methyl methacrylate, β-dimethyl-aminoethylmethacrylate, n propyl methacrylate, isopropyl methacrylate, n-BMA, Propenoic acid, 2-methyl, isobutyl ester, Tert-butyl Methacrylate, methacrylic acid-2-ethylhexyl, lauryl methacrylate, methacrylic acid stearyl; The acrylamide derivatives such as acrylamide, N methacrylamide, N-ethyl acrylamide, N,N-DMAA, diacetone-acryloamide(DAA), acrylamido propanesulfonic acid or its salt, acrylamido diemethylamine or its salt, N hydroxymethyl acrylamide or derivatives thereof; The methacrylamide derivatives such as Methacrylamide, N-methyl acrylamide, N-ethyl-methyl acrylamide, methacryloyl amido propanesulfonic acid or its salt, methacryloyl amido diemethylamine or its salt, N-methylol methacrylamide or derivatives thereof; The N-vinylamide classes such as N-vinyl formamide, N-vinyl acetamide, NVP; The vinyl ethers such as methylvinylether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl-ethylene base ether, n-butyl vinyl ether, IVE, tert-Butyl vinyl ether, dodecyl vinyl, stearyl vinyl ether; The nitrile such as vinyl cyanide, methacrylonitrile; The vinyl halides base class such as vinylchlorid, vinylidene chloride, vinyl fluoride, vinylidene; The allylic cpd such as allyl acetate, propenyl chloride; The derivatives such as the unsaturated dicarboxylic acid such as toxilic acid, methylene-succinic acid, its salt or its ester; The vinyl silanes based compounds such as vinyltrimethoxy silane; Methylvinyl acetate; Unsaturated sulfonic acid or derivatives thereof etc.Wherein preferred alpha-olefin, particularly preferably ethene.

From the viewpoint of polarization property and the weather resistance etc. of the polarizing coating of gained, the mean polymerisation degree that forms the PVA based polymer of PVA series polymer film of the present invention is preferably more than 1000, more preferably more than 1500, more preferably more than 2000.On the other hand, from the viewpoint of easiness, the stretchiness etc. of the manufacture of the PVA series polymer film of homogeneous, the upper limit of the mean polymerisation degree of PVA based polymer is preferably below 8000, is particularly preferably below 6000.

Here, " mean polymerisation degree " of the PVA based polymer in this specification sheets refers to the mean polymerisation degree recording taking JIS K6726-1994 as benchmark, according to the limiting viscosity recording in the water of 30 DEG C after the saponification again of PVA based polymer, purifying is tried to achieve.

From the viewpoint of polarization property and the weather resistance etc. of the polarizing coating of gained, the saponification deg that forms the PVA based polymer of PVA series polymer film of the present invention is preferably more than 95.0 % by mole, more preferably more than 98.0 % by mole, more preferably more than 99.0 % by mole, most preferably be more than 99.3 % by mole.

Here, " saponification deg " of the PVA based polymer in this specification sheets refer to respect to can by saponification change into the shared ratio of the mole number of the structural unit (being typically vinyl ester units) of vinyl alcohol units and the total mole number of vinyl alcohol units, this vinyl alcohol units (% by mole).The saponification deg of PVA based polymer is measured with the benchmark that is recited as of JIS K6726-1994.

The method for making of PVA series polymer film of the present invention is not particularly limited, as long as manufacturing the method that meets above formula (I) and PVA series polymer film (II), can manufacture by any method, and PVA series polymer film of the present invention can be manufactured with high productivity swimmingly continuously by manufacture method of the present invention, this manufacture method comprises the steps:

(a) use the film forming apparatus that possesses the many dryer rolls that rotating shaft is parallel to each other, by the masking stoste that contains PVA based polymer with membranaceous spue to the first dryer roll of this film forming apparatus and carry out part dry after, be further dried masking with follow-up dryer roll; Now,

(b) circumferential speed (S of the dryer roll when volatile component ratio of PVA based polymer film reaches 13 quality % _t) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _t/ S ₁) be 0.990～1.050;

(c) circumferential speed (S of final dryer roll _l) circumferential speed (S of dryer roll while reaching 13 quality % with respect to the volatile component ratio of PVA based polymer film _t) ratio (S _l/ S _t) be 0.960～0.980;

The manufacture method of the PVA series polymer film to the invention described above is carried out more specific description below.

The masking stoste that contains PVA based polymer can be made solution or prepare by the meltings such as the PVA based polymer particle that contains liquid medium etc. are made to fused solution by PVA based polymer is mixed with liquid medium.

The dissolving of PVA based polymer in liquid medium, the melting of PVA based polymer particle that contains liquid medium etc. can be carried out with stirring-type mixing device, melt extruder etc.

As liquid medium now used, can exemplify such as water, methyl-sulphoxide, dimethyl formamide, N,N-DIMETHYLACETAMIDE, N-Methyl pyrrolidone, quadrol, diethylenetriamine etc., these liquid mediums can one use separately or be used in combination.Wherein preferably make water, methyl-sulphoxide or both mixtures, particularly preferably make water.

The viewpoint of the stretchiness of operation trafficability characteristic when dissolving, melting, the raising film from promotion PVA based polymer liquid medium manufactured, the PVA series polymer film of raising gained etc. is preferably added softening agent in masking stoste.

As softening agent, preferably use polyvalent alcohol, can exemplify such as ethylene glycol, glycerine, Glycerol dimer, propylene glycol, Diethylene Glycol, triethylene glycol, TEG, TriMethylolPropane(TMP) etc., these softening agent can one use separately or be used in combination.From the viewpoint of the raising effect excellence of stretchiness, wherein preferably use one or more in glycerine, Glycerol dimer and ethylene glycol.

The addition of softening agent is preferably 0～30 mass parts with respect to PVA based polymer 100 mass parts, and more preferably 3～25 mass parts, are particularly preferably 5～20 mass parts.If the addition of softening agent is with respect to PVA based polymer 100 mass parts more than 30 mass parts, the PVA series polymer film of gained is too soft sometimes, and treatability reduces.

The viewpoint of the treatability of the separability the dryer roll during from raising from manufacture PVA series polymer film, the PVA series polymer film of gained etc. is preferably added tensio-active agent in masking stoste.As the kind of tensio-active agent, be not particularly limited, preferably use anionic surfactant or nonionic surfactant.

As anionic surfactant, preference is as the anionic surfactant of the sulfonic acid types such as sulfuric acid ester type, dodecylbenzene sulfonate such as the carboxylic acid types such as potassium laurate, sulfuric acid monooctyl ester.

In addition, as nonionic surfactant, preference is as the nonionic surfactant of the allyl phenyl ether types such as alkylolamide type, polyoxyalkylene allyl phenyl ether such as polypropylene glycol ether type, oleic acid diethyl amide such as alkylamine type, the polyoxyethylene laurylamide etc. such as the alkyl ester types such as the alkyl phenyl ether such as alkyl ether type, polyoxyethylene octyl phenyl ether type, polyoxyethylene lauric acid ester, polyoxyethylene lauryl amino ethers alkylamide type, polyoxyethylene poly-oxygen propylene aether such as polyoxyethylene oleyl ether.These tensio-active agents can one use separately or be used in combination.

The addition of tensio-active agent is preferably 0.01～1 mass parts with respect to PVA based polymer 100 mass parts, and more preferably 0.02～0.5 mass parts, is particularly preferably 0.05～0.3 mass parts.If be less than 0.01 mass parts, be sometimes difficult to embody the raising effect of masking, separability, on the other hand, if more than 1 mass parts, tensio-active agent, in film surface stripping, becomes the reason of adhesion sometimes, and treatability reduces.

Masking stoste can contain various additives in the scope of the characteristic that does not hinder PVA series polymer film of the present invention, such as stablizer (such as antioxidant, UV light absorber, thermo-stabilizer etc.), expanding material (dissolving mutually drug), anti blocking agent, fire retardant, antistatic agent, lubricant, dispersion agent, liquid agent, antiseptic-germicide etc.These additives can one use separately or be used in combination.

The volatile component ratio of the masking stoste using in the manufacture of PVA series polymer film is preferably 60～75 quality %, more preferably 65～70 quality %.If the volatile component ratio of masking stoste is less than 60 quality %, the viscosity of masking stoste raises, and is difficult to filter and deaeration, and in addition masking itself is all very difficult sometimes.On the other hand, if the volatile component ratio of masking stoste is greater than 75 quality %, viscosity is too low sometimes, and the homogeneity of the thickness of PVA series polymer film is impaired.

Here, said in this specification sheets " the volatile component ratio of masking stoste " refers to the volatile component ratio of trying to achieve by following formula [iii].

Volatile component ratio (quality %)={ (Wa-Wb)/Wa} × 100 [iii] of masking stoste

[in formula, Wa represents the quality (g) of masking stoste, and Wb represents the masking stoste of Wa (g) quality (g) after dry 16 hours in the electric air drier of 105 DEG C.]

In the film forming apparatus that possesses the many dryer rolls that rotating shaft is parallel to each other using in the manufacture of PVA series polymer film, the quantity of dryer roll is preferably more than 3, more preferably more than 4, and more preferably 5～30.

Many dryer rolls are for example preferably formed by metals such as nickel, chromium, copper, iron, stainless steels, and the metallic substance that is particularly preferably difficult for burn into by roller surface and has a specular gloss forms.In addition,, in order to improve the weather resistance of dryer roll, more preferably use plating to have the dryer roll of the nickel dam, chromium layer, nickel/chromium alloy layer etc. of individual layer or two-layer above combination.

The roll surface temperature of the each dryer roll in many dryer rolls is preferably more than 65 DEG C, more preferably more than 75 DEG C.In addition, as the roll surface temperature of each dryer roll, in final operation or the roll surface temperature of the dryer roll that can use as Heat treating roll in close operation with it be preferably more than 100 DEG C, more preferably 100～120 DEG C, the roll surface temperature of dryer roll is in addition preferably below 100 DEG C.

The film forming apparatus using in the present invention can have hot-air drying device, thermal treatment unit, humidity control device of hotblast stove formula etc. as required after many dryer rolls.

The masking stoste that contains PVA based polymer is spued on the first dryer roll of film forming apparatus time with membranaceous, for example use the known membranaceous device for discharging fixed (membranaceous casting device) such as T-shaped slit die, hopper plate (hopper plate), I-mould, lip coating machine mould, by the masking stoste that contains PVA based polymer with membranaceous spuing (curtain coating) to the first dryer roll.

Dry on the first dryer roll with the membranaceous liquid that contains PVA based polymer spuing on the first dryer roll, the volatile component ratio of PVA based polymer film reach be preferably 17～30 quality %, more preferably 17～29 quality %, more preferably the moment of 18～28 quality % peels off from the first dryer roll.

If the volatile component ratio of the PVA based polymer film while peeling off from the first dryer roll is less than 17 quality %, there is Δ n (MD) _avevalue with respect to Δ n (TD) _aveincrease and do not meet the tendency of formula (I), on the other hand, if, more than 30 quality %, having, the volatile component ratio of the PVA based polymer film while peeling off from the first dryer roll is difficult to peel off, fracture occurs sometimes or easily produce uneven tendency from the first dryer roll.

Here, " the volatile component ratio of PVA based polymer film or PVA series polymer film " in this specification sheets refers to the volatile component ratio of trying to achieve by following formula [iv].

A (quality %)={ (Wc-Wd)/Wc} × 100 [iv]

[in formula, A represents the volatile component ratio (quality %) of PVA based polymer film or PVA series polymer film, Wc represents the quality (g) of the sample gathering from PVA based polymer film or PVA series polymer film, the quality (g) when Wd represents above-mentioned sample Wc (g) to put into dry 4 hours of temperature 50 C, Vacuumdrier below pressure 0.1kPa].

By using PVA based polymer, the polyvalent alcohols such as glycerine (softening agent), in PVA based polymer film or PVA series polymer film that masking stoste prepared by tensio-active agent and water forms, at above-mentioned " temperature 50 C, below pressure 0.1kPa, 4 hours " condition under when dry, mainly only has water volatilization, other composition beyond water volatilizees hardly, remain in PVA based polymer film or PVA series polymer film, therefore the volatile component ratio of PVA based polymer film or PVA series polymer film can be tried to achieve by measuring contained amount of moisture (moisture ratio) in PVA based polymer film or PVA series polymer film.

When dry with the first dryer roll, from the viewpoint of homogeneous drying property, rate of drying etc., the roll surface temperature of the first dryer roll is preferably 80～120 DEG C, and more preferably 85～105 DEG C, more preferably 93～99 DEG C.If the surface temperature of the first dryer roll is higher than 120 DEG C, film easily foams, and on the other hand, during lower than 80 DEG C, dry insufficient on the first dryer roll, becomes and peel off bad reason.

From the viewpoint of productivity of homogeneous drying property, rate of drying and PVA series polymer film etc., the circumferential speed (S of the first dryer roll ₁) be preferably 8～25m/ minute, more preferably 11～23m/ minute, more preferably 14～22m/ minute.If the circumferential speed (S of the first dryer roll ₁) be less than 8m/ minute, productivity reduces, and double refraction easily increases, not preferred.On the other hand, if the circumferential speed (S of the first dryer roll ₁) be greater than 25m/ minute, dry easily insufficient, not preferred on the first dryer roll.

Dry can only the utilization from the heat of the first dryer roll of part with the membranaceous masking stoste that contains PVA based polymer spuing on the first dryer roll carried out, but from the viewpoint of homogeneous drying property, rate of drying etc., preferably in heating with the first dryer roll, the face not contacting with the first dryer roll (being sometimes referred to as below " the first dryer roll noncontact face ") is sprayed to hot blast, apply heat from the two sides of PVA based polymer film and be dried.

While spraying hot blast to being positioned at the first dryer roll noncontact face of the PVA based polymer film on the first dryer roll, the preferably hot blast of the whole area spray wind speed 1～10m/ second to the first dryer roll noncontact face, more preferably spray wind speed 2～8m/ hot blast of second, further preferably spray wind speed 3～8m/ hot blast of second.

If the wind speed of the hot blast that the first dryer roll noncontact face is sprayed is too small, be difficult to obtain the PVA series polymer film high as the ultimate elongation multiplying power of target of the present invention, and there is the dewfall of water vapour etc. when dry on the first dryer roll, this water droplet drops onto on PVA based polymer film, easily produces defect in the PVA series polymer film finally obtaining.On the other hand, if the wind speed of the hot blast that the first dryer roll noncontact face is sprayed is excessive, be difficult to obtain the PVA series polymer film high as the ultimate elongation multiplying power of target of the present invention, and the PVA series polymer film finally obtaining produces uneven thickness, easily there is the problems such as the uneven generation of dyeing thereupon.

From the viewpoint of drying efficiency, dry homogeneity etc., the temperature of the hot blast that the first dryer roll noncontact face of PVA based polymer film is sprayed is preferably 50～150 DEG C, and more preferably 70～120 DEG C, more preferably 80～95 DEG C.The dew-point temperature of the hot blast in addition, the first dryer roll noncontact face of PVA based polymer film being sprayed is preferably 10～15 DEG C.If the temperature of the hot blast that the first dryer roll noncontact face of PVA based polymer film is sprayed is too low, drying efficiency, homogeneous drying property etc. easily reduce, and on the other hand, if too high, easily foam.

Be not particularly limited for the mode of the first dryer roll noncontact face of PVA based polymer film being sprayed to hot blast, can adopt can be to the first dryer roll noncontact face of PVA based polymer film, preferably its entirety is sprayed any mode of the hot blast of wind speed homogeneous and temperature homogeneous equably, wherein preferably adopts nozzle mode, cowling panel mode or their combination etc.The injection direction of the hot blast on the first dryer roll noncontact face of PVA based polymer film can be both the direction relative with the first dryer roll noncontact face, also can be the direction along the circumferential shapes of the first dryer roll noncontact face of the PVA based polymer film direction of the circumference on the roller surface of the first dryer roll (roughly along) roughly, or can be also direction in addition.

In addition,, when the PVA based polymer film on the first dryer roll dry, preferably the hot blast by the dry volatile component being produced by PVA based polymer film and after spraying will be carried out to exhaust.The method of exhaust is not particularly limited, and preferably employing can not produce the wind speed inequality of the hot blast that the first dryer roll noncontact face of PVA based polymer film is sprayed and the method for exhausting of temperature inequality.

The PVA based polymer film that is preferably dried to volatile component ratio and reaches 17～30 quality % on the first dryer roll is peeled off from the first dryer roll, this time, preferably make the first dryer roll noncontact face of PVA based polymer film relative with the second dryer roll, be dried with the second dryer roll

Circumferential speed (the S of the second dryer roll ₂) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S ₂/ S ₁) be preferably 1.005～1.090, more preferably 1.010～1.080.If ratio (S ₂/ S ₁) be less than 1.005, the pick-up point of PVA based polymer film from the first dryer roll easily becomes heterogeneity, and uneven increase of degree of birefringence of width, cannot be used as the former film of optical film sometimes.In addition, if ratio (S ₂/ S ₁) be greater than 1.090, be difficult to obtain having the PVA series polymer film of the present invention of high limit stretching ratio.

When dry with the second dryer roll, from the viewpoint of homogeneous drying property, rate of drying etc., the roll surface temperature of the second dryer roll is preferably 65～100 DEG C, and more preferably 65～98 DEG C, more preferably 75～96 DEG C.

To peel off from the second dryer roll with the dried PVA based polymer of the second dryer roll film, according to quantity of the dryer roll arranging in film forming apparatus etc., with the 3rd dryer roll, the 4th dryer roll, the 5th dryer roll ... be dried successively etc. many dryer rolls.

Now, in the present invention, regulate to put on the tension force of PVA based polymer film while be dried, so that the circumferential speed (S of the dryer roll of the volatile component ratio of PVA based polymer film while reaching 13 quality % _t) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _t/ S ₁) be 0.990～1.050.Here, as " dryer roll when volatile component ratio of PVA based polymer film reaches 13 quality % ", the in the situation that the volatile component ratio of PVA based polymer film reaching 13 quality % on dryer roll, refer to this dryer roll, volatile component ratio, in the situation that reaching 13 quality % between two dryer rolls, refers to the dryer roll after position in these two dryer rolls is leaned on.By making ratio (S _t/ S ₁) in above-mentioned scope, in drying process till the volatile component ratio of PVA based polymer film reaches 13 quality %, can there is not the problem such as lax, circumvolution of film, swimmingly the degree of birefringence of factory length direction (MD) on the thickness direction of film equalization and value [Δ n (MD) _ave] and the degree of birefringence of width (TD) on the thickness direction of film equalization and value [Δ n (TD) _ave] meet above formula (I) and (II) and then also meet the PVA series polymer film of the present invention of above formula (III).

Above-mentioned ratio (S while manufacturing PVA series polymer film _t/ S ₁) be preferably 1.000～1.045.

In the present invention, the follow-up dryer roll of PVA based polymer film that volatile component ratio is reached to 13 quality % is further dry, makes PVA based polymer film.Now, in the present invention, make the circumferential speed (S of final dryer roll on one side _l) circumferential speed (S of dryer roll while reaching 13 quality % with respect to the volatile component ratio of PVA series polymer film _t) ratio (S _l/ S _t) in 0.960～0.980 scope, be dried on one side.By making ratio (S _l/ S _t) in above-mentioned scope, in drying process till obtaining final PVA series polymer film, can there is not the problem such as lax, circumvolution of film, swimmingly the degree of birefringence of factory length direction (MD) on the thickness direction of film equalization and value [Δ n (MD) _ave] and the degree of birefringence of width (TD) on the thickness direction of film equalization and value [Δ n (TD) _ave] meet above formula (I) and (II) and then also meet the PVA series polymer film of the present invention of above formula (III).

Above-mentioned ratio (S while manufacturing PVA series polymer film _l/ S _t) be preferably 0.963～0.976.

In addition, while manufacturing PVA series polymer film by aforesaid method, the degree of birefringence of the length direction of PVA series polymer film (MD) on the thickness direction of film equalization and value [Δ n (MD) _ave] and the degree of birefringence of width (TD) on the thickness direction of film equalization and value [Δ n (TD) _ave] according to the circumferential speed (S of the first dryer roll ₁) and the circumferential speed (S of final dryer roll _l) ratio (S _l/ S ₁) and change.In order to manufacture swimmingly the PVA series polymer film of the present invention that meets above formula (I) and (II) and then also meet above formula (III), need to make the circumferential speed (S of final dryer roll _l) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _l/ S ₁) in 0.970～1.010 scope, preferably in 0.972～1.008 scope, more preferably in 0.975～1.006 scope.By this, can suppress fold and lax generation while manufacture swimmingly and meet above formula (I) and (II) and then also meet the PVA series polymer film of above formula (III).

In the manufacture method of the invention described above, final dryer roll or close to final dryer roll with final dryer roll can improve its surface temperature and as Heat treating roll.By dryer roll, as in the situation of Heat treating roll, roll surface temperature is preferably 90～140 DEG C, more preferably 100～130 DEG C.

In addition, also can divide the thermal treatment unit that is arranged with dryer roll.

Heating direction when PVA based polymer film is dry process from the first dryer roll to final dryer roll is not particularly limited, because can be equably that PVA based polymer film is drier, so the front and back of the preferred arbitrary portion with PVA based polymer film be dried with the mode that the each dryer roll from the first dryer roll to final dryer roll alternately contacts.

The PVA series polymer film that has carried out above-mentioned drying treatment can be heat-treated as required, conditioning etc., finally coils into roller shape with the length of regulation, thereby obtains PVA series polymer film of the present invention.

The volatile component ratio of the PVA series polymer film finally obtaining by above-mentioned a succession of processing is preferably in the scope of 1～5 quality %, more preferably in the scope of 2～4 quality %.

While manufacturing polarizing coating by PVA series polymer film of the present invention, for example, can dye to PVA series polymer film, uniaxial extension, fixing processing, drying treatment and thermal treatment as required.The order of dyeing and uniaxial extension is not particularly limited, and the processing of both can having dyeed before uniaxial extension is processed, also can process the processing of simultaneously dyeing with uniaxial extension, or the processing of also can dyeing after uniaxial extension is processed.In addition, the operation such as uniaxial extension, dyeing can be repeatedly.

The dyestuff using in dyeing as PVA series polymer film, can use iodine or dichroism organic dye (for example direct black (DirectBlack) 17,19,154; Direct brown (DirectBrown) 44,106,195,210,223; Directly red (DirectRed) 2,23,28,31,37,39,79,81,240,242,247; Directly blue (DirectBlue) 1,15,22,78,90,98,151,168,202,236,249,270; Directly purple (DirectViolet) 9,12,51,98; Sun green (DirectGreen) 1,85; Directly yellow (DirectYellow) 8,12,44,86,87; The dichroic dyes such as direct orange (DirectOrange) 26,39,106,107) etc.These dyestuffs can one use separately or be used in combination.Dyeing conventionally can be by carrying out in the solution that PVA series polymer film is immersed in contain above-mentioned dyestuff, and its treatment condition and treatment process are not particularly limited.

The PVA series polymer film uniaxial extension that alongst (MD) stretches can be undertaken by any method in wet type stretching method or xeothermic stretching method.Undertaken by wet type stretching method in the situation of uniaxial extension, both can in borated warm water, carry out uniaxial extension, also can in the solution that contains above-mentioned dyestuff or in following fixing processing bath, carry out uniaxial extension, also can in air, carry out uniaxial extension with the PVA series polymer film after water suction, can also carry out uniaxial extension by other method.Draft temperature when uniaxial extension is processed is not particularly limited, the in the situation that of PVA series polymer film being stretched in warm water to (wet type stretching), employing is preferably 30～90 DEG C, more preferably 40～70 DEG C, the temperature of 45～65 DEG C more preferably, in the situation of xeothermic stretching, adopt the temperature that is preferably 50～180 DEG C.In addition, as the stretching ratio of uniaxial extension processing (carry out in the situation of uniaxial extension is total stretching ratio with multistep), from the viewpoint of polarization property preferably until film facing fracture, stretch as much as possible, particularly be preferably more than 4 times, more preferably more than 5 times, more preferably more than 5.5 times.The upper limit of stretching ratio, as long as film does not rupture and is just not particularly limited, in order to carry out the stretching of homogeneous, is preferably below 8.0 times.

The thickness of the film (polarizing coating) after stretching is preferably 5～35 μ m, is particularly preferably 20～30 μ m.

While manufacturing polarizing coating, in order to make the absorption on the film of dyestuff after uniaxial extension firm, be mostly fixed processing.The general extensive employing of fixing processing is the method in the processing that is added with boric acid and/or boron compound is bathed by film immersion.Now, can in bathing, processing add iodine compound as required.

Then, preferably to having carried out, uniaxial extension is processed or uniaxial extension is processed and the fixing film of processing carries out drying treatment (thermal treatment).The temperature of drying treatment (thermal treatment) is preferably 30～150 DEG C, is particularly preferably 50～140 DEG C.Drying treatment (thermal treatment) if temperature too low, the dimensional stability of the polarizing coating of gained easily reduces, and on the other hand, if too high, easily follow the decomposition etc. of dyestuff and the reduction of polarization property occurs.

Can be on the two sides of the polarizing coating obtaining as mentioned above or one side laminating optically transparent and there is the protective membrane of physical strength, thereby make polaroid.As protective membrane now, use cellulose triacetate (TAC) film, cellulose acetate butyrate (CAB) (CAB) film, vinylformic acid mesentery, polyester mesentery etc.In addition, as the caking agent for the protective membrane of fitting, generally using PVA is caking agent and urethane adhesive etc., and wherein preferably using PVA is caking agent.

The polaroid obtaining as mentioned above can fit in glass substrate after the caking agents such as coating acrylic acid series, uses as the parts of LCD device.When polaroid is fitted in to glass substrate, the phase retardation film of can simultaneously fitting, viewing-angle increasing film, brightness improve film etc.

Embodiment

By the following examples the present invention is specifically described, but the present invention is not limited in any way the following examples.

In following examples and comparative example, the volatile component ratio of the volatile component ratio of masking stoste, PVA film or PVA film (moisture ratio), each physical property of PVA film and the optical property of polarizing coating are measured by the following method.

(1) the volatile component ratio of masking stoste:

Try to achieve by above formula [iii] according to the method described above.

(2) the volatile component ratio of PVA film or PVA film (moisture ratio):

Try to achieve by above formula [iv] according to the method described above.

In addition, the mensuration of the volatile component ratio of PVA film or PVA film (moisture ratio) is used from the sample of width (TD) the central part collection of the PVA film that taken out by dryer roll or PVA film and carries out.

(3) the Δ n (MD) of PVA film _ave:

By " " 1 " Δ n (MD) _aveassay method " described method is obtained the Δ n (MD) of the central part of the width (TD) of PVA film hereinbefore in project _ave, set it as the Δ n (MD) of PVA film _ave.

(4) the Δ n (TD) of PVA film _ave:

By " " 2 " Δ n (TD) _aveassay method " described method is obtained the Δ n (TD) of the central part of the width (TD) of PVA film hereinbefore in project _ave, set it as the Δ n (TD) of PVA film _ave.

(5) the quality swelling capacity of PVA film:

PVA film is cut into 1.5g, in the distilled water 1000g of 30 DEG C, floods 30 minutes, flood after 30 minutes PVA film is taken out, suck after surperficial water with filter paper, measure its quality (W _e).Then, this PVA film after dry 16 hours, is measured to its quality (W with the drying machine of 105 DEG C _f).By the quality W of gained _eand W _fobtain the quality swelling capacity of PVA film by following formula [v].

Quality swelling capacity (%)=(W _e/ W _f) × 100 [v].

(6) the ultimate elongation multiplying power of PVA film:

The test film of central part acquisition length direction (MD) × width (TD)=10cm × 5cm of the width (TD) of the PVA film before the stretching obtaining from following examples or comparative example, stretching clamp is fixed on in the two ends of the length direction of this test film, so that stretched portion is of a size of length direction (MD) × width (TD)=5cm × 5cm, in the water of 30 DEG C, flooded for 38 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (the first step stretching) to 2.2 times of raw footage, containing iodine with the concentration of 0.03 quality %, in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature that contain potassiumiodide with the concentration of 3 quality %, flooded for 90 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (second step stretching) to 3.3 times of raw footage, then, containing boric acid with the concentration of 3 quality %, in the boric acid/potassium iodide aqueous solution of 30 DEG C of temperature that contain potassiumiodide with the concentration of 3 quality %, flooded for approximately 20 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (the 3rd step stretches) to 3.6 times of raw footage, then, containing boric acid with the concentration of 4 quality % on one side, in boric acid/potassium iodide aqueous solution that the temperature that contains potassiumiodide with the concentration of approximately 5 quality % is approximately 60 DEG C, flood, on one side with the draw speed of 12cm/ minute alongst (MD) uniaxial extension to test film rupture, stretching ratio (length when fracture is with respect to the ratio of raw footage) while reading test film fracture.

For same PVA film, carry out 5 above-mentioned tension tests, get the ultimate elongation multiplying power (doubly) of its mean value as PVA film.

(7) optical property of polarizing coating:

(i) transmissivity:

The central part of the width of the polarizing coating obtaining from following examples or comparative example and the differently-oriented directivity of polarizing coating gather the foursquare sample of 2 1.5cm × 1.5cm abreast, carry out illuminant-C with the spectrophotometer V-7100 (subsidiary integrating sphere) of Hitachi's system taking JIS Z8722 (measuring method of object color) as benchmark respectively for each sample, the apparent brightness correction of the visible region in the 2 degree visuals field, for 1 polarizing coating sample, optical transmission rate when optical transmission rate when mensuration is spent with respect to tensile axis direction inclination 45 and inclination-45 are spent, obtain their mean value (Y ₁).

For another piece polarizing coating sample, also with above-mentioned optical transmission rate when similarly measuring 45 optical transmission rates while spending and inclination-45 and spending, obtain their mean value (Y ₂).

By the Y trying to achieve as mentioned above ₁and Y ₂on average, as the transmissivity (Y) of polarizing coating (%).

(ii) degree of polarization:

For 2 polarizing coating samples that gather in above-mentioned (i), measure optical transmission rate (Y ∥) when overlapping in the parallel mode of its differently-oriented directivity and the optical transmission rate (Y ⊥) when overlapping in the orthogonal mode of differently-oriented directivity by the method same with the measuring method of above-mentioned transmissivity, obtain degree of polarization (V) (%) by following formula [vi].

Degree of polarization (V) (%)={ (Y ∥-Y ⊥)/(Y ∥+Y ⊥) } ^1/2× 100 [vi].

(iii) degree of polarization when transmissivity 44.25%:

As recorded in following embodiment and comparative example, in each embodiment or comparative example, dipping time in iodine/potassium iodide aqueous solution while changing second step stretching, make 5 polarizing coatings, for each polarizing coating, obtain transmissivity (Y) and degree of polarization (V) with aforesaid method respectively, for each embodiment or comparative example, respectively taking transmissivity (Y) as transverse axis, 5 point-renderings are become to figure taking degree of polarization (V) as the longitudinal axis, obtain curve of approximation, the value of the degree of polarization (V) when obtaining transmissivity (Y) and be 44.25% by this curve of approximation.

" embodiment 1 "

(1) manufacture of PVA film:

(i) the volatile component ratio PVA by by polyvinyl acetate saponification is obtained (99.9 % by mole of saponification degs, the polymerization degree 2400) 100 mass parts, glycerine 12 mass parts, lauric acid diethyl amide 0.1 mass parts and water being formed is that the masking stoste of 66 quality % spues to the first dryer roll (93 DEG C of surface temperatures, circumferential speed (S with membranaceous from T-shaped mould ₁) 16.7m/ minute) on, on one side on the first dryer roll, whole the first dryer roll noncontact face is sprayed to the hot blast of 90 DEG C with the wind speed of 5m/ second, being dried to moisture ratio reaches 18 quality % on one side, then, peel off from the first dryer roll, being dried carry out the second dryer roll under the condition of approximately 85 DEG C of roll surface temperatures after, so that the surface of the arbitrary portion of PVA film alternately contacts with each dryer roll with the back side, finally, after heat-treating with the final dryer roll (Heat treating roll) of 108 DEG C of surface temperatures, batch, obtain PVA film (thick 60 μ m, wide 3m, volatile component ratio 3 quality %).In this embodiment 1, dryer roll when volatile component ratio reaches 13 quality % is the 7th dryer roll.

In this embodiment 1, the circumferential speed (S of the dryer roll (the 7th dryer roll) when (α) volatile component ratio reaches 13 quality % _t) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _t/ S ₁) be 1.000; (β) circumferential speed (S of final dryer roll _l) circumferential speed (S of dryer roll (the 7th dryer roll) while reaching 13 quality % with respect to volatile component ratio _t) ratio (S _l/ S _t) be 0.974; (γ) circumferential speed (S of the second dryer roll ₂) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S ₂/ S ₁) be 1.030; (δ) circumferential speed (S of next dryer roll (the 8th dryer roll) _t+1) circumferential speed (S of dryer roll (the 7th dryer roll) while reaching 13 quality % with respect to volatile component ratio _t) ratio (S _t/ S _t+1) be 0.998; (ε) circumferential speed (S of final dryer roll _l) with respect to the circumferential speed (S of the first dryer roll ₁) ratio (S _l/ S ₁) be 0.975, make PVA film.

(ii) measure the Δ n (MD) of the PVA film obtaining in above-mentioned (i) with aforesaid method _ave, Δ n (TD) _ave, quality swelling capacity and ultimate elongation multiplying power, result is as shown in table 1 below.

(2) manufacture of polarizing coating:

(i) test film of central part acquisition length direction (MD) × width (TD)=10cm × 5cm of the width (TD) of the PVA film obtaining from above-mentioned (1), stretching clamp is fixed on in the two ends of the length direction of this test film, so that stretched portion is of a size of length direction (MD) × width (TD)=5cm × 5cm, in the water of 30 DEG C, flooded for 38 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (the first step stretching) to 2.2 times of raw footage, containing iodine with the concentration of 0.03 quality %, in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature that contain potassiumiodide with the concentration of 3 quality %, flooded for 60 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (second step stretching) to 3.3 times of raw footage, then, containing boric acid with the concentration of 3 quality %, in the boric acid/potassium iodide aqueous solution of 30 DEG C of temperature that contain potassiumiodide with the concentration of 3 quality %, flooded for approximately 20 seconds, in this process with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (the 3rd step stretches) to 3.6 times of raw footage, then, containing boric acid with the concentration of 4 quality % on one side, in boric acid/potassium iodide aqueous solution that the temperature that contains potassiumiodide with the concentration of approximately 5 quality % is approximately 60 DEG C, flood, on one side with the draw speed of 12cm/ minute alongst (MD) uniaxial extension (the 4th step stretches) to the stretching ratio facing before the ultimate elongation multiplying power of the PVA film that reaches mensuration described above, in the potassium iodide aqueous solution that contains potassiumiodide with the concentration of 3 quality %, flooded for 10 seconds, carry out iodide ion impregnation processing, then be dried 4 minutes with the drying machine of 60 DEG C, (thick approximately 21 μ m) to make polarizing coating.

Obtain transmissivity (Y) and the degree of polarization (V) of the polarizing coating obtaining thus with aforesaid method, by this point-rendering taking transmissivity (Y) as transverse axis, taking degree of polarization (V) in the figure of the longitudinal axis.

(ii) in above-mentioned (i), dipping time when second step is stretched in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature changed into 75 seconds from 60 seconds, carry out the operation same with above-mentioned (i), (thick approximately 21 μ m) to make the polarizing coating of [draw speed of each draw stage is all similarly 12cm/ minute with above-mentioned (i)].

Obtain transmissivity (Y) and the degree of polarization (V) of the polarizing coating obtaining thus with aforesaid method, by this point-rendering in the figure of above-mentioned (i).

(iii) in above-mentioned (i), dipping time when second step is stretched in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature changed into 90 seconds from 60 seconds, carry out the operation same with above-mentioned (i), (thick approximately 21 μ m) to make the polarizing coating of [draw speed of each draw stage is all similarly 12cm/ minute with above-mentioned (i)].

(iv) in above-mentioned (i), dipping time when second step is stretched in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature changed into 105 seconds from 60 seconds, carry out the operation same with above-mentioned (i), (thick approximately 21 μ m) to make the polarizing coating of [draw speed of each draw stage is all similarly 12cm/ minute with above-mentioned (i)].

(v) in above-mentioned (i), dipping time when second step is stretched in the iodine/potassium iodide aqueous solution of 30 DEG C of temperature changed into 120 seconds from 60 seconds, carry out the operation same with above-mentioned (i), (thick approximately 21 μ m) to make the polarizing coating of [draw speed of each draw stage is all similarly 12cm/ minute with above-mentioned (i)].

(vi) on figure, draw the curve of approximation of drawing 5 points in the drawings in above-mentioned (i)～(v), the value of the degree of polarization (V) when being obtained transmissivity (Y) and be 44.25% by this curve of approximation, result is as shown in table 1 below is 99.98.

" embodiment 2～5 "

(1) in embodiment 1, change the film forming condition while manufacturing PVA film as recorded in following table 1, similarly manufacture PVA film with embodiment 1 (1).But, in embodiment 2, as masking stoste, using the volatile component ratio being made up of the PVA by polyvinyl acetate saponification is obtained (99.9 % by mole of saponification degs, the polymerization degree 2400) 100 mass parts, glycerine 12 mass parts, lauric acid diethyl amide 0.1 mass parts and water is the masking stoste of 73 quality %.

Measure the Δ n (MD) of the each PVA film obtaining thus with aforesaid method _ave, Δ n (TD) _ave, quality swelling capacity and ultimate elongation multiplying power, result is as shown in table 1 below.

(2) test film of length direction (MD) × width (TD)=10cm × 5cm that the central part of the width (TD) of each PVA film that use obtains from above-mentioned (1) gathers, carry out the operation same with embodiment 1 (2), manufacture respectively 5 kinds of polarizing coatings for each embodiment, obtain transmissivity (Y) and the degree of polarization (V) of each polarizing coating, by this point-rendering taking transmissivity (Y) as transverse axis, taking degree of polarization (V) in the figure of the longitudinal axis, on figure, draw the curve of approximation of drafting 5 points in the drawings, the value of the degree of polarization (V) when obtaining transmissivity (Y) and be 44.25% by this curve of approximation, result is as shown in table 1 below.

" comparative example 1～5 "

(1) in embodiment 1, change the film forming condition while manufacturing PVA film as recorded in following table 2, similarly manufacture PVA film with embodiment 1 (1).

Measure the Δ n (MD) of the each PVA film obtaining thus with aforesaid method _ave, Δ n (TD) _ave, quality swelling capacity and ultimate elongation multiplying power, result is as shown in table 2 below.

(2) test film of length direction (MD) × width (TD)=10cm × 5cm that the central part of the width (TD) of each PVA film that use obtains from above-mentioned (1) gathers, carry out the operation same with embodiment 1 (2), manufacture respectively 5 kinds of polarizing coatings for each comparative example, obtain transmissivity (Y) and the degree of polarization (V) of each polarizing coating, by this point-rendering taking transmissivity (Y) as transverse axis, taking degree of polarization (V) in the figure of the longitudinal axis, on figure, draw the curve of approximation of drafting 5 points in the drawings, the value of the degree of polarization (V) when obtaining transmissivity (Y) and be 44.25% by this curve of approximation, result is as shown in table 2 below.

[table 1]

[table 2]

From above-mentioned table 1 and table 2, the Δ n (MD) of the PVA film of embodiment 1～5 _ave[degree of birefringence of the length direction (MD) of PVA film on the thickness direction of film equalization and value] and Δ n (TD) _ave[degree of birefringence of the width (TD) of PVA film on the thickness direction of film equalization and value] meet formula (I) and (II), thereby have 6.72～6.94 such high limit stretching ratios, and the polarizing coating being obtained by the PVA film of embodiment 1～5 has and the equal above excellent polarization property of existing polarizing coating.

In contrast, the PVA film of comparative example 1～4 does not meet formula (I), and the PVA film of comparative example 4 and 5 do not meet formula (II), and therefore, compared with the PVA film of embodiment 1～5, ultimate elongation multiplying power is all low.

While manufacturing polarizing coating by PVA series polymer film, conventionally for fear of stretch time film fracture and carry out uniaxial extension with the stretching ratio more lower slightly than ultimate elongation multiplying power, but because the ultimate elongation multiplying power of the PVA film of embodiment 1～5 is all up to more than 6.72, so manufacture polarizing coating under the condition of this embodiment time, the PVA film of embodiment 1～5 can carry out uniaxial extension with 6 times of above high stretching ratios, even if carry out uniaxial extension and also can not occur the fracture of film with 6.5 times of above high stretching ratios, can stretch swimmingly.

In contrast, in the PVA film of comparative example 1～5, because the ultimate elongation multiplying power of the PVA film of comparative example 4 is less than 6, so manufacture polarizing coating under the condition of this comparative example time, can not carry out uniaxial extension with 6 times of above stretching ratios, in the time stretching, film easily ruptures, in addition, the PVA film of comparative example 1～3 and 5 is in the time of the stretching ratio uniaxial extension with more than 6 times, troubling in the fracture this point of film.

In addition, also the length that has 1 volume in the former film that polarizing coating is used is former film more than 1000m, for example, in the PVA series polymer film of total length 1000m, its ultimate elongation multiplying power 0.1 point of rising (0.1 times), uniaxial extension and the length of stretched film increase 100m (1000m × 0.1 times=100m), can obtain more polarizing coating by the former film of equal length.

About this point, from embodiment 1～5, the PVA film of embodiment 1～5 is compared with the PVA film of comparative example 1～5, ultimate elongation multiplying power is up to 0.10～0.98 point (doubly), for example, if the length of PVA film is 1000m, with PVA film, it manufactures polarizing coating under the condition of above-described embodiment, the length of polarizing coating will be grown 100～980m compared with using the situation of PVA film of comparative example 1～5, can obtain more polarizing coating.

Industrial usability

Even if PVA series polymer film of the present invention is at the thinner thickness of film, be in the situation of 30～65 μ m left and right, also there is high limit stretching ratio, even in the time manufacturing polarizing coating etc. with high magnification uniaxial extension, also be difficult for occurring the fracture of film, therefore can be with high rate of finished products in the situation that not interrupting stretching operation, and with the time of drying than in the past shorter, manufacture the stretched film such as polarizing coating of the excellent in optical properties such as polarization property with good productivity, so extremely useful as the former film for the manufacture of stretched film such as polarizing coatings, and, manufacture method of the present invention is useful as the method for manufacturing continuously swimmingly this PVA series polymer film of the present invention with high productivity.

Claims

1. the manufacture method of polarizing coating, is characterized in that, to meeting, following formula (I) and polymer film of polyvinyl alcohol (II) dye, uniaxial extension, fixing processing and drying treatment;

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)

In above formula, Δ n (MD) _avethe degree of birefringence of mechanical flow direction that represents polymer film of polyvinyl alcohol on the thickness direction of this film equalization and value, Δ n (TD) _avethe degree of birefringence of width that represents polymer film of polyvinyl alcohol on the thickness direction of this film equalization and value.

2. the manufacture method of polarizing coating, is characterized in that, to the polymer film of polyvinyl alcohol that meets following formula (I) and (II) and further meet following formula (III) dye, uniaxial extension, fixing processing and drying treatment;

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)

3. the manufacture method of polarizing coating according to claim 1 and 2, for the thickness of the described vinol series polymer of the manufacture of polarizing coating in the scope of 30 ~ 65 μ m.