TW202118612A

TW202118612A - Polyvinyl alcohol-based film, production method therefor, and polarization film using polyvinyl alcohol-based film

Info

Publication number: TW202118612A
Application number: TW110102629A
Authority: TW
Inventors: 花島學; 御手洗宏志; 早川誠一郎
Original assignee: 日商三菱化學股份有限公司
Priority date: 2016-05-27
Filing date: 2017-05-25
Publication date: 2021-05-16
Also published as: KR102400929B1; JP6834956B2; TWI757067B; TW201815544A; CN109312085B; WO2017204271A1; TWI721171B; JPWO2017204271A1; CN114437385A; CN109312085A; KR20190013765A

Abstract

Provided are: a polyvinyl alcohol-based film that, when immersed in water, is able to reduce the elution amount of a polyvinyl alcohol-based resin, and is unlikely to become curled; a method for producing said polyvinyl alcohol-based film; and a polarization film using said polyvinyl alcohol-based film. The polyvinyl alcohol-based film according to the present invention is characterized in that, when immersed in 50 DEG C water for one minute, the elution amount of a polyvinyl alcohol-based resin is not more than 900 ppm/m2, and the curl angle measured under condition (A) in the short side direction is not more than 135 DEG. (A) A condition in which a test object, comprising a 10 cm (long side) * 5 cm (short side) rectangular test piece cut out in a given direction from the polyvinyl alcohol-based film and a weight having a mass of 5 g and being attached to the center of a first longitudinal end section of the test piece, is suspended while being supported at the center of a second longitudinal end section of the test piece, and is entirely immersed in 30 DEG C water for 10 seconds.

Description

聚乙烯醇系薄膜Polyvinyl alcohol film

本發明係關於溶出至水的雜質少，且即使浸漬於水中也不容易捲曲的聚乙烯醇系薄膜，尤其是能以良好之生產性獲得具有高偏光性能之偏光膜的聚乙烯醇系薄膜，及該聚乙烯醇系薄膜之製造方法，以及使用了該聚乙烯醇系薄膜的偏光膜。The present invention relates to a polyvinyl alcohol-based film that has few impurities eluted into water and is not easy to curl even when immersed in water, especially a polyvinyl alcohol-based film that can obtain a polarizing film with high polarization performance with good productivity. And a manufacturing method of the polyvinyl alcohol-based film, and a polarizing film using the polyvinyl alcohol-based film.

近年來，液晶顯示裝置的發展卓越，廣泛地使用於智慧手機、平板電腦、個人電腦、液晶電視、投影機、車用面板等。於該液晶顯示裝置有使用偏光膜，就偏光膜而言，主要使用使碘吸附配向於聚乙烯醇系薄膜而得者。近年來伴隨著畫面之高精細化、高亮度化、大型化，有跟以往商品相比偏光性能更優良、無色彩不均勻且寬長型之偏光膜的需求。In recent years, the development of liquid crystal display devices has been remarkable, and they are widely used in smart phones, tablet computers, personal computers, LCD TVs, projectors, car panels, etc. A polarizing film is used in this liquid crystal display device. As for the polarizing film, a polyvinyl alcohol-based film is mainly used which has iodine adsorbed and aligned. In recent years, with the high-definition, high-brightness, and large-scale screens, there is a demand for a polarizing film that has better polarization performance, no color unevenness, and a wide and long type than conventional products.

一般而言，偏光膜係將為原料卷之聚乙烯醇系薄膜從輥拉出，邊沿著流動方向(MD方向)運送，邊以水(包含溫水)膨潤後，經過利用碘所為的染色、為了使碘配向之延伸、為了將配向狀態固定之硼酸交聯等步驟所製造而得。在此等步驟中產生之問題會大幅地減低偏光膜的生產性。例如，在膨潤步驟中，若雜質從聚乙烯醇系薄膜溶出而汙染膨潤槽的話，污染會擴散至後續全部的步驟。若雜質也在染色步驟或硼酸交聯步驟從聚乙烯醇系薄膜溶出的話，不僅會使獲得之偏光膜的偏光性能降低，且會需要大量的勞力來過濾或交換於各步驟中所使用的藥液。就該雜質而言，可列舉存在於聚乙烯醇系薄膜中的低分子量聚乙烯醇系樹脂(包含寡聚物)，尤其是分子量5萬以下之低分子量物，有容易溶出至水中且容易形成使偏光度降低之低分子量之碘錯合物之傾向。此外，在膨潤步驟中，若在聚乙烯醇系薄膜之寬度方向(TD方向)的兩端部產生彎折或皺褶的話，不僅有運送變得困難的傾向，且有在延伸時薄膜會破裂之傾向。Generally speaking, the polarizing film is the polyvinyl alcohol-based film of the raw material roll, which is pulled out from the roll, transported along the flow direction (MD direction), swelled with water (including warm water), and then dyed with iodine. It is manufactured by the steps of extending the alignment of iodine and crosslinking with boric acid for fixing the alignment state. The problems generated in these steps will greatly reduce the productivity of the polarizing film. For example, in the swelling step, if impurities are eluted from the polyvinyl alcohol-based film to contaminate the swelling tank, the contamination will spread to all subsequent steps. If impurities are also eluted from the polyvinyl alcohol film in the dyeing step or the boric acid crosslinking step, not only will the polarization performance of the obtained polarizing film be reduced, but also a lot of labor will be required to filter or exchange the drugs used in each step. liquid. The impurities include low-molecular-weight polyvinyl alcohol resins (including oligomers) present in polyvinyl alcohol-based films, especially low-molecular-weight substances with a molecular weight of less than 50,000, which are easily eluted into water and are easily formed The tendency of low-molecular-weight iodine complexes to reduce the degree of polarization. In addition, in the swelling step, if bending or wrinkles occur at both ends of the PVA film in the width direction (TD direction), it not only tends to be difficult to transport, but also the film may break during stretching. The tendency.

另一方面，為原料卷之聚乙烯醇系薄膜，一般而言係將為原料之聚乙烯醇系樹脂溶解於水中，從該水溶液(製膜原液)藉由連續澆鑄法所製造而得。具體而言，係藉由將聚乙烯醇系樹脂之水溶液排出及流延至澆鑄鼓或無端環帶等之澆鑄模所製膜而得之薄膜從澆鑄模剝離後，邊沿著流動方向(MD方向)運送，邊使用數個金屬製加熱輥進行乾燥來製造聚乙烯醇系薄膜。在此等步驟之中，乾燥步驟對於來自聚乙烯醇系薄膜之樹脂的溶出量的控制及上述聚乙烯醇系薄膜之膨潤特性而言係重要的步驟。亦即，若在該乾燥步驟中乾燥不充分的話，在製造偏光膜時溶出的樹脂會增加，且同時在膨潤步驟中聚乙烯醇系薄膜容易產生彎折或皺褶，相反地若過度乾燥，則會有在上述膨潤槽中之膨潤速度降低的傾向。此外，若在乾燥步驟中上述製膜而得之薄膜之正面與背面的特性產生差異的話，會有在膨潤步驟中容易捲曲之傾向。On the other hand, the polyvinyl alcohol-based film that is a raw material roll is generally produced by dissolving the raw material of the polyvinyl alcohol-based resin in water and using the continuous casting method from the aqueous solution (film forming stock solution). Specifically, the film obtained by discharging the aqueous solution of the polyvinyl alcohol resin and casting it to a casting mold such as a casting drum or endless belt, the film obtained is peeled from the casting mold and moved along the flow direction (MD direction) It is transported and dried using several metal heating rollers to produce a polyvinyl alcohol-based film. Among these steps, the drying step is an important step for the control of the elution amount of the resin from the polyvinyl alcohol-based film and the swelling characteristics of the above-mentioned polyvinyl alcohol-based film. That is, if the drying step is insufficient, the eluted resin during the production of the polarizing film will increase, and at the same time, the polyvinyl alcohol-based film is likely to bend or wrinkle during the swelling step. On the contrary, if the drying is excessive, There is a tendency for the swelling rate in the above-mentioned swelling tank to decrease. In addition, if there is a difference in the characteristics of the front and back sides of the film obtained by the above-mentioned film formation in the drying step, there will be a tendency to curl easily in the swelling step.

就上述課題之改良方法而言，例如有人提出減低了聚乙烯醇系樹脂對於水之溶出量的聚乙烯醇系薄膜(例如，參照專利文獻1)。此外，有人提出於30℃之水中浸漬5分鐘時之捲曲角度為180°以下之聚乙烯醇系薄膜(例如，參照專利文獻2)、或厚度為50μm以下，且浸漬於30℃之水中30秒鐘後的捲曲角度為200°以下之聚乙烯醇系薄膜(例如，參照專利文獻3)。此外，有人提出利用特定之乾燥條件所為之聚乙烯醇系薄膜的製造方法(例如，參照專利文獻4)。此處，上述捲曲角度係指上述聚乙烯醇系薄膜之平面部分與該聚乙烯醇系薄膜之寬度方向(TD方向)捲曲部分的端緣部之切線方向之間的夾角[參照圖2(b)之符號α]。 [先前技術文獻] [專利文獻]Regarding the improvement method of the above-mentioned subject, for example, a polyvinyl alcohol-based film having reduced the elution amount of polyvinyl alcohol-based resin into water has been proposed (for example, refer to Patent Document 1). In addition, it has been proposed that a polyvinyl alcohol film with a curl angle of 180° or less when immersed in water at 30°C for 5 minutes (for example, refer to Patent Document 2), or a thickness of 50μm or less, and immersed in water at 30°C for 30 seconds A polyvinyl alcohol-based film whose curl angle after the clock is 200° or less (for example, refer to Patent Document 3). In addition, a method for producing a polyvinyl alcohol-based film using specific drying conditions has been proposed (for example, refer to Patent Document 4). Here, the curl angle refers to the angle between the plane portion of the polyvinyl alcohol-based film and the tangential direction of the edge portion of the curled portion in the width direction (TD direction) of the polyvinyl alcohol-based film [see Figure 2(b) ) The symbol α]. [Prior Technical Literature] [Patent Literature]

[專利文獻1]日本特開2009-221462號公報 [專利文獻2]日本特開2001-315140號公報 [專利文獻3]國際公開第2014/208537號 [專利文獻4]日本特開2011-156874號公報[Patent Document 1] JP 2009-221462 A [Patent Document 2] Japanese Patent Application Publication No. 2001-315140 [Patent Document 3] International Publication No. 2014/208537 [Patent Document 4] JP 2011-156874 A

[發明所欲解決之課題][The problem to be solved by the invention]

然而，即使有上述專利文獻之方法，對於在偏光膜製造時之聚乙烯醇系樹脂之溶出量的抑制及膨潤特性之改良仍無法令人滿意。However, even with the method of the above-mentioned patent document, the suppression of the elution amount of the polyvinyl alcohol-based resin and the improvement of the swelling characteristics during the production of the polarizing film are still unsatisfactory.

上述專利文獻1之揭示技術，將10cm×10cm之正方形的聚乙烯醇系薄膜浸漬於50℃、1公升之水中4小時後的聚乙烯醇系樹脂之溶出液濃度係10~50ppm，若換算為平均每1m² 之薄膜，則有1,000~5,000ppm/m² 之聚乙烯醇系樹脂溶出，就為了因應近年之偏光膜的需求以高生產效率來製造偏光膜而言，有必要再進一步減低聚乙烯醇系樹脂之溶出量。The technique disclosed in Patent Document 1 mentioned above, the concentration of the eluted solution of the polyvinyl alcohol resin after immersing a 10 cm×10 cm square polyvinyl alcohol film in 1 liter of water at 50°C for 4 hours is 10 to 50 ppm. On average, 1,000 to 5,000 ppm/m ² ^{of polyvinyl alcohol resin is eluted per 1m 2} of film. In order to meet the demand for polarizing films in recent years to produce polarizing films with high production efficiency, it is necessary to further reduce poly The eluted amount of vinyl alcohol resin.

就上述專利文獻2之揭示技術而言，捲曲角度180°係彎折之狀態，捲曲角度90°係成為皺褶之狀態，捲曲角度45°係有大的翹曲之狀態，故必須進一步地減低捲曲角度。尤其為了應對近年之對於偏光膜之增寬增長化之需求，必須進一步減低寬長型之聚乙烯醇系薄膜中的捲曲角度。Regarding the technique disclosed in Patent Document 2, the crimp angle of 180° is the state of bending, the crimp angle of 90° is the state of wrinkles, and the crimp angle of 45° is the state of large warpage, so it must be further reduced. Curl angle. In particular, in order to cope with the increasing demand for the broadening of polarizing films in recent years, it is necessary to further reduce the curl angle in the wide and long polyvinyl alcohol film.

就上述專利文獻3之揭示技術而言，雖然藉由使在30℃於水中浸漬30秒鐘時之捲曲角度為200°以下，可一定程度地抑制有關延伸時的破裂，但尤其為了對應近年之產線速度的提高所致之偏光膜生產性的提升，必須更進一步地減低捲曲角度。Regarding the technique disclosed in Patent Document 3, although the curl angle when immersed in water at 30°C for 30 seconds is 200° or less, it is possible to suppress breakage during stretching to a certain extent, but it is particularly in order to respond to recent years. The increase in the productivity of the polarizing film caused by the increase in the production line speed requires a further reduction in the curl angle.

上述專利文獻4之揭示技術藉由使薄膜與各個熱輥之間的接觸時間為1~6秒鐘，雖然確實可減低聚乙烯醇系薄膜之相位延遲(retardation)，但對於減低偏光膜製造時之聚乙烯醇系樹脂的溶出量，就進一步控制乾燥條件之觀點仍有改善之餘地。The technique disclosed in Patent Document 4 mentioned above, by setting the contact time between the film and each heat roller to 1 to 6 seconds, although the retardation of the polyvinyl alcohol-based film can be indeed reduced, it is useful for reducing the time when the polarizing film is manufactured. There is still room for improvement from the viewpoint of further controlling the drying conditions for the elution amount of the polyvinyl alcohol-based resin.

因此，本發明係在如此之背景下，提供偏光膜製造時之聚乙烯醇系樹脂之溶出量的控制性及膨潤特性優良，可獲得偏光性能優良之偏光膜的聚乙烯醇系薄膜，其為能減低浸漬在水中時之聚乙烯醇系樹脂的溶出量，不會污染偏光膜製造設備，且即使浸漬於水中也不容易捲曲，並在偏光膜製造時之膨潤步驟中也不容易產生彎折或皺褶的聚乙烯醇系薄膜，及該聚乙烯醇系薄膜之製造方法，以及使用了該聚乙烯醇系薄膜的偏光膜。 [解決課題之手段]Therefore, under such a background, the present invention provides a polyvinyl alcohol-based film that has excellent controllability and swelling characteristics of the elution amount of the polyvinyl alcohol-based resin during the manufacture of a polarizing film, and can obtain a polarizing film with excellent polarization performance. It can reduce the leaching amount of polyvinyl alcohol resin when immersed in water, will not pollute the polarizing film manufacturing equipment, and it is not easy to curl even when immersed in water, and it is not easy to bend during the swelling step of the polarized film manufacturing. Or a corrugated polyvinyl alcohol-based film, a method for producing the polyvinyl alcohol-based film, and a polarizing film using the polyvinyl alcohol-based film. [Means to solve the problem]

本案發明者們以上述情事為鑑重複深入研究之結果，發現使用對於特定溫度的水之聚乙烯醇系樹脂的溶出量少，且於特定之水浸漬條件下測得之捲曲角度小的聚乙烯醇系薄膜來製造偏光膜的話，可解決上述課題，並以高生產性來製造高性能之偏光膜。The inventors of the present case have repeated in-depth studies using the above-mentioned circumstances as a guide, and found that the use of polyvinyl alcohol-based resins with a specific temperature of water has a small amount of elution, and the polyethylene with a small curl angle measured under specific water immersion conditions If an alcohol-based thin film is used to manufacture a polarizing film, the above-mentioned problems can be solved, and a high-performance polarizing film can be manufactured with high productivity.

也就是說，本發明之第1要旨係一種聚乙烯醇系薄膜，其特徵在於：該聚乙烯醇系薄膜浸漬在50℃之水中1分鐘時之聚乙烯醇系樹脂的溶出量為900ppm/m² 以下，且以下述A之條件測得之短邊方向的捲曲角度為135°以下。 (A)條件，係將具備從該聚乙烯醇系薄膜以任意方向切出之長邊10cm×短邊5cm之長方形的試驗片以及設置於該試驗片之長邊方向之第1端緣部的中央之質量5g之重物的試驗體，於以該試驗片之長邊方向之第2端緣部的中央部分懸掛支撐的狀態下，將該試驗體全體浸漬於30℃的水中10秒鐘。That is, the first gist of the present invention is a polyvinyl alcohol-based film characterized in that the elution amount of the polyvinyl alcohol-based resin when the polyvinyl alcohol-based film is immersed in water at 50°C for 1 minute is 900 ppm/m ² or less, and the curl angle in the short-side direction measured under the following conditions A is 135° or less. (A) Condition: A test piece with a rectangular shape of 10 cm long side x 5 cm short side cut out from the polyvinyl alcohol-based film in any direction, and a first end edge in the long side direction of the test piece A test body with a weight of 5 g in the center was immersed in water at 30° C. for 10 seconds in a state where the test body was suspended and supported by the center of the second end edge in the longitudinal direction of the test piece.

此外，本發明之第2要旨係一種聚乙烯醇系薄膜之製造方法，係上述第1要旨之聚乙烯醇系薄膜之製造方法，具備以下步驟：製膜步驟，將聚乙烯醇系樹脂之水溶液連續地排出並流延至澆鑄模來進行製膜；及，乾燥步驟，將該製膜而得之薄膜從該澆鑄模剝離後，使該製膜而得之薄膜乾燥；該乾燥步驟中該製膜而得之薄膜的乾燥，係使該製膜而得之薄膜的正面與背面交替地與多個金屬製加熱輥接觸來進行。In addition, the second aspect of the present invention is a method of manufacturing a polyvinyl alcohol-based film, which is the method of manufacturing a polyvinyl alcohol-based film of the above-mentioned first aspect, and includes the following steps: In the film forming step, the aqueous solution of the polyvinyl alcohol-based resin is continuously discharged and cast to a casting mold to form a film; and, In a drying step, after peeling the film obtained by forming the film from the casting mold, drying the film obtained by forming the film; The drying of the film obtained by forming the film in the drying step is performed by alternately contacting the front and back surfaces of the film obtained by forming the film with a plurality of metal heating rollers.

然後，本發明之第3要旨係使用了上述第1要旨之聚乙烯醇系薄膜的偏光膜。 [發明之效果]Then, the third aspect of the present invention is a polarizing film using the polyvinyl alcohol-based film of the above-mentioned first aspect. [Effects of Invention]

本發明之第1要旨之聚乙烯醇系薄膜對於特定溫度之水的聚乙烯醇系樹脂之溶出量少，且在特定之水浸漬條件測得之捲曲角度小，故在偏光膜製造時，亦可減少聚乙烯醇系樹脂之溶出量，且可使捲曲角度變小。因此，可發揮能以高生產性來製造偏光性能優良之偏光膜的效果。The polyvinyl alcohol-based film of the first aspect of the present invention has a small amount of elution of the polyvinyl alcohol-based resin in water at a specific temperature, and the curl angle measured under specific water immersion conditions is small. Therefore, it is also used in the production of polarized films. It can reduce the elution amount of polyvinyl alcohol resin, and can make the curl angle smaller. Therefore, the effect of being able to produce a polarizing film with excellent polarization performance with high productivity can be exerted.

尤其在上述A之條件，在令上述試驗體之浸漬時間為2分鐘時，測得之短邊方向的捲曲角度為40°以下之情況，能使在製造偏光膜時之膨潤步驟中不容易產生進一步的彎折，可更進一步防止在製造偏光膜時的破裂。因此，可發揮以更高生產性來製造偏光性能更優良之偏光膜的效果。Especially under the condition of A, when the immersion time of the test body is 2 minutes, the measured curl angle in the short-side direction is 40° or less, which can make it difficult to produce swelling during the polarizing film manufacturing step. Further bending can further prevent cracking during the production of the polarizing film. Therefore, the effect of manufacturing a polarizing film with better polarization performance with higher productivity can be exerted.

此外，上述聚乙烯醇系薄膜係長條之薄膜，在上述試驗片之長邊為該薄膜之長度方向，短邊為該薄膜之寬度方向的情況，可使上述捲曲角度更小，能更抑制在製造偏光膜時之寬度方向之兩端部之上述彎折的產生。因此，可發揮能以更高之生產性來製造偏光性能優良之偏光膜的效果。In addition, the above-mentioned polyvinyl alcohol-based film is a long film, when the long side of the test piece is the length direction of the film, and the short side is the width direction of the film, the curl angle can be made smaller, and it can be more restrained. The occurrence of the above-mentioned bending at both ends in the width direction during the production of the polarizing film. Therefore, the effect of being able to produce a polarizing film with excellent polarization performance with higher productivity can be exerted.

進一步地，在於30℃之水中浸漬2分鐘時之聚乙烯醇系樹脂的溶出量為50ppm/m² 以下之情況，考慮其溶出量少而可更減少在偏光膜製造時之膨潤槽的汙染，故可發揮能提高所製造之偏光膜之偏光性能的效果。Furthermore, when the elution amount of the polyvinyl alcohol-based resin when immersed in water at 30°C for 2 minutes is 50 ppm/m ² or less, considering that the elution amount is small, the pollution of the swelling tank during the production of the polarizing film can be further reduced. Therefore, the effect of improving the polarization performance of the manufactured polarizing film can be exerted.

然後，在厚度20~60μm、長度5km以上、寬度4m以上之情況，可發揮能達成偏光膜之大面積化的效果。Then, in the case of a thickness of 20-60μm, a length of 5km or more, and a width of 4m or more, the effect of increasing the area of the polarizing film can be achieved.

本發明之第2要旨之聚乙烯醇系薄膜的製造方法，藉由使製膜而得之薄膜的正面與背面交替地與多個金屬製加熱輥接觸來使該製膜而得之薄膜乾燥，故可適當地控制該製膜而得之薄膜之正面與背面的乾燥狀態。其結果，可發揮能製造在製造偏光膜時之聚乙烯醇系樹脂的溶出量之抑制及捲曲角度之抑制優良之上述第1要旨的聚乙烯醇系薄膜之效果。The method for producing a polyvinyl alcohol-based film according to the second aspect of the present invention is to dry the formed film by alternately contacting the front and back surfaces of the formed film with a plurality of metal heating rollers. Therefore, the drying state of the front and back sides of the film obtained by forming the film can be appropriately controlled. As a result, the effect of being able to produce the polyvinyl alcohol-based film of the first aspect which is excellent in the suppression of the elution amount of the polyvinyl alcohol-based resin and the suppression of the curl angle during the production of the polarizing film can be exerted.

尤其在下述情況時，會發揮能更抑制在製造偏光膜時之聚乙烯醇系樹脂之溶出量的效果：該乾燥步驟中使用之該金屬製加熱輥的總數為P根，設從該澆鑄模剝離而得之薄膜第n個接觸之該金屬製加熱輥的表面溫度為Tn(℃)，該第n個金屬製加熱輥與該薄膜之接觸時間為Sn(秒鐘)，製造而得之聚乙烯醇系薄膜之厚度為D(μm)，該n為1以上該P以下之整數時，表示Tn×Sn之總和的Σ(Tn×Sn)滿足下列式(1)： 75≦Σ(Tn×Sn)/D≦110　･･･(1)。Especially in the following cases, it will exert the effect of suppressing the elution of the polyvinyl alcohol-based resin during the production of the polarizing film: The total number of the metal heating roller used in the drying step is P, and the surface temperature of the metal heating roller contacted by the nth film peeled from the casting mold is Tn(°C), and the nth When the contact time between the metal heating roller and the film is Sn (seconds), and the thickness of the produced polyvinyl alcohol film is D (μm), when the n is an integer of 1 or more and P or less, Σ(Tn×Sn), which represents the sum of Tn×Sn, satisfies the following formula (1): 75≦Σ(Tn×Sn)/D≦110　･･･(1).

此外，在下述情況時，可發揮能更抑制在製造偏光膜時之捲曲角度的效果：該乾燥步驟中使用之該金屬製加熱輥的總數為P根，且設從該澆鑄模剝離而得之薄膜第x個接觸之該金屬製加熱輥的表面溫度為Tx(℃)，該薄膜第y個接觸之該金屬製加熱輥的表面溫度為Ty(℃)，該第x個金屬製加熱輥與該薄膜之接觸時間為Sx(秒鐘)，該第y個金屬製加熱輥與該薄膜之接觸時間為Sy(秒鐘)，該x為1以上該P以下之奇數，且該y為2以上該P以下之偶數時，表示Tx×Sx之總和的Σ(Tx×Sx)及表示Ty×Sy之總和的Σ(Ty×Sy)滿足下列式(2)： Σ(Ty×Sy)＜Σ(Tx×Sx) ･･･(2)In addition, in the following cases, the effect of suppressing the curl angle during the production of the polarizing film can be exerted: The total number of the metal heating rollers used in the drying step is P, and the surface temperature of the metal heating roller contacted by the xth film peeled from the casting mold is Tx(°C), and the film is The surface temperature of the y-th metal heating roller in contact is Ty (℃), the contact time between the x-th metal heating roller and the film is Sx (seconds), the y-th metal heating roller and the film The contact time is Sy (seconds), when x is an odd number above 1 and below P, and when y is an even number above 2 and below P, Σ(Tx×Sx) representing the sum of Tx×Sx and Σ(Ty×Sy) representing the sum of Ty×Sy satisfy the following formula (2): Σ(Ty×Sy)＜Σ(Tx×Sx) ･･･(2)

此外，在下述情況時，可發揮能更進一步減小在製造偏光膜時之捲曲角度的效果：該乾燥步驟中使用之該金屬製加熱輥的總數為P根，且設從該澆鑄模剝離而得之薄膜第x個接觸之該金屬製加熱輥的表面溫度為Tx(℃)，該薄膜第y個接觸之該金屬製加熱輥的表面溫度為Ty(℃)，該第x個金屬製加熱輥與該薄膜之接觸時間為Sx(秒鐘)，該第y個金屬製加熱輥與該薄膜之接觸時間為Sy(秒鐘)，澆鑄模之表面溫度為T₀ (℃)，該x為1以上該P以下之奇數，且該y為2以上該P以下之偶數時，表示Tx×Sx之總和的Σ(Tx×Sx)及表示Ty×Sy之總和的Σ(Ty×Sy)滿足下列式(3)： Σ(Ty×Sy)+T₀ ≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T₀ ×10 ･･･(3)In addition, in the following cases, the effect of further reducing the curl angle during the production of the polarizing film can be exerted: The total number of the metal heating rollers used in the drying step is P, and it is set to peel off from the casting mold. The surface temperature of the metal heating roller contacted by the xth film obtained is Tx(℃), the surface temperature of the metal heating roller contacted by the film y is Ty(℃), and the xth metal heating roller The contact time between the roller and the film is Sx (seconds), the contact time between the y-th metal heating roller and the film is Sy (seconds), the surface temperature of the casting mold is T ₀ (℃), where x is When the odd number above 1 and below P, and the y is an even number above 2 and below P, Σ(Tx×Sx) representing the sum of Tx×Sx and Σ(Ty×Sy) representing the sum of Ty×Sy satisfy the following Formula (3): Σ(Ty×Sy)+T ₀ ≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T ₀ ×10 ･･･(3)

然後，在下述情況，可發揮能更減少製造偏光膜時之捲曲的發生的效果：藉由將以該乾燥步驟乾燥而得之薄膜捲繞於芯管成為輥狀來製作薄膜捲繞體，且將該薄膜捲繞體在經以水蒸氣阻隔薄膜包裝之狀態下，於環境溫度為25~30℃保存5天以上。Then, in the following cases, the effect of reducing curling during the production of polarizing film can be exerted: A film wound body is produced by winding the film dried in this drying step on a core tube into a roll shape, and the film wound body is packaged with a water vapor barrier film at an ambient temperature of Store at 25~30℃ for more than 5 days.

本發明之第3要旨之偏光膜使用了上述第1要旨之聚乙烯醇系薄膜，故可發揮偏光性能優良之效果。The polarizing film of the third aspect of the present invention uses the polyvinyl alcohol-based film of the above-mentioned first aspect, so that it can exhibit excellent polarizing properties.

以下將詳細地說明本發明。本發明之聚乙烯醇系薄膜之特徵為在浸漬於50℃之水中1分鐘的條件下進行溶出試驗時，聚乙烯醇系樹脂之溶出量為900ppm/m² 以下，且以下述A之條件測定之短邊方向的捲曲角度係135°以下。 (A)條件，係將具備從該聚乙烯醇系薄膜以任意方向切出之長邊10cm×短邊5cm之長方形的試驗片(第1試驗片)以及設置於該試驗片之長邊方向之第1端緣部的中央之質量5g之重物的試驗體，於以該試驗片之長邊方向之第2端緣部的中央部分懸掛支撐的狀態下，將該試驗體全體浸漬於30℃的水中10秒鐘。The present invention will be explained in detail below. The characteristic of the polyvinyl alcohol-based film of the present invention is that when the dissolution test is performed under the condition of immersing in water at 50°C for 1 minute, the dissolution amount of the polyvinyl alcohol-based resin is 900 ppm/m ² or less, and it is measured under the following conditions A The curl angle in the short-side direction is 135° or less. (A) The condition is to have a test piece (the first test piece) of a rectangle with a long side of 10 cm × a short side of 5 cm cut out in any direction from the polyvinyl alcohol-based film, and a test piece placed in the long side direction of the test piece A test body with a weight of 5 g in the center of the first end edge portion was suspended and supported by the center of the second end edge portion in the longitudinal direction of the test piece, and the entire test body was immersed at 30°C In the water for 10 seconds.

如上述減低了聚乙烯醇系樹脂之溶出量及捲曲角度的聚乙烯醇系薄膜，係在利用連續澆鑄法來製造該聚乙烯醇系薄膜的過程中，藉由在乾燥步驟中採用特定的方法來獲得。亦即，如同後述，在上述乾燥步驟中，藉由使以澆鑄模製膜而得之薄膜的正面與背面交替地接觸多個金屬製加熱輥，使該製膜而得之薄膜乾燥。藉此適當地控制上述製膜而得之薄膜的正面與背面的乾燥狀態，經該乾燥步驟所製造而得之聚乙烯醇系薄膜係如上述減低了聚乙烯醇系樹脂之溶出量及捲曲角度。As described above, the polyvinyl alcohol-based film with reduced elution amount and curl angle of the polyvinyl alcohol-based resin is used in the process of manufacturing the polyvinyl alcohol-based film by the continuous casting method by adopting a specific method in the drying step To get. That is, as described later, in the drying step, the front and back surfaces of the film obtained by casting the film are alternately contacted with a plurality of metal heating rollers to dry the film obtained by forming the film. In this way, the drying state of the front and back sides of the film obtained by the above-mentioned film formation is appropriately controlled, and the polyvinyl alcohol-based film produced by the drying step is as described above, and the elution amount and the curl angle of the polyvinyl alcohol-based resin are reduced. .

然後，上述聚乙烯醇系薄膜係經由膨潤步驟、染色步驟、硼酸交聯步驟及延伸步驟等而形成為偏光膜。此處，該聚乙烯醇系薄膜係如上述，對於特定溫度之水之聚乙烯醇系樹脂的溶出量少，為900ppm/m² 以下，且以特定之水浸漬條件所測得之捲曲角度小，為135°以下。因此，在偏光膜製造時，不會污染偏光膜製造設備，且在膨潤步驟中不容易產生彎折或皺褶。其結果，偏光膜之生產性也會提高，獲得之偏光膜係偏光性能優良者。Then, the above-mentioned polyvinyl alcohol-based film is formed into a polarizing film through a swelling step, a dyeing step, a boric acid cross-linking step, a stretching step, and the like. Here, the polyvinyl alcohol-based film is as described above, the elution amount of the polyvinyl alcohol-based resin in water at a specific temperature is small, less than 900 ppm/m ² , and the curl angle measured under specific water immersion conditions is small , Below 135°. Therefore, during the production of the polarizing film, the polarizing film manufacturing equipment will not be contaminated, and bending or wrinkles are not easily generated in the swelling step. As a result, the productivity of the polarizing film is also improved, and the obtained polarizing film is one with excellent polarization performance.

就避免污染偏光膜製造設備的觀點而言，該聚乙烯醇系樹脂之溶出量宜為800ppm/m² 以下，尤其宜為700ppm/m² 以下，若該聚乙烯醇系樹脂之溶出量過多的話，會污染偏光膜製造設備而無法達成本發明之目的。此外，聚乙烯醇系樹脂之溶出量的下限值通常為1ppm/m² 。另外，因為一般而言在製造偏光膜時，聚乙烯醇系薄膜係浸漬於約50℃的溫水中1分鐘左右，故在本發明中，以50℃、1分鐘之浸漬條件作為指標。此外，本發明中之溶出量(ppm/m² )係將溶出濃度(ppm)除以實際上供至溶出試驗之試驗片的面積(m² )，換算為1m² 者。From the viewpoint of avoiding contamination of the polarizing film manufacturing equipment, the elution amount of the polyvinyl alcohol resin is preferably 800 ppm/m ² or less, especially 700 ppm/m ² or less, if the elution amount of the polyvinyl alcohol resin is too much , It will contaminate the polarizing film manufacturing equipment and fail to achieve the purpose of the invention. In addition, the lower limit of the elution amount of the polyvinyl alcohol-based resin is usually 1 ppm/m ² . In addition, in general, when producing a polarizing film, the polyvinyl alcohol-based film is immersed in warm water at about 50°C for about 1 minute. Therefore, in the present invention, the immersion condition at 50°C for 1 minute is used as an index. In addition, the elution amount (ppm/m ² ) in the present invention is calculated by dividing the elution concentration (ppm) by the area (m ² ) of the test piece actually used for the elution test and converted to 1 m ² .

在本發明中，供至上述溶出試驗的試驗片(第2試驗片：聚乙烯醇系薄膜)係於23℃、50%RH經24小時以上調濕而得者。另外，該調濕條件係適用於塑膠薄膜之各種試驗中之一般的環境條件，且係為了將聚乙烯醇系薄膜中之水分率調整至該環境下之平衡水分率之條件。通常，藉由該調濕將上述試驗片中的水分率調整至10%左右。調濕後之上述試驗片迅速地供至上述溶出試驗。另外，該試驗前之調濕也適用於後述之於30℃的溶出試驗中。In the present invention, the test piece (the second test piece: a polyvinyl alcohol-based film) used for the above-mentioned dissolution test is obtained by conditioning the humidity at 23° C. and 50% RH for 24 hours or more. In addition, the humidity control conditions are suitable for general environmental conditions in various tests of plastic films, and are used to adjust the moisture content in the polyvinyl alcohol-based film to the equilibrium moisture content in the environment. Usually, the moisture content in the test piece is adjusted to about 10% by this humidity control. The above-mentioned test piece after the humidity control was quickly supplied to the above-mentioned dissolution test. In addition, the humidity adjustment before the test is also applicable to the dissolution test at 30°C described later.

進一步地，本發明之聚乙烯醇系薄膜於30℃之水中浸漬2分鐘時之聚乙烯醇系樹脂的溶出量宜為50ppm/m² 以下。就該聚乙烯醇系樹脂之溶出量而言，以偏光膜製造時避免污染膨潤槽的觀點，尤其宜為40ppm/m² 以下，進一步宜為30ppm/m² 以下。該溶出量之下限值通常為1ppm/m² 。另外，一般而言，在製造偏光膜時的膨潤步驟中，考慮到聚乙烯醇系薄膜係於約30℃之溫水中膨潤數分鐘，故在本發明中，也如上述以30℃、2分鐘的浸漬條件作為指標。該減低在30℃、2分鐘之浸漬中之溶出量的方法可列舉與上述50℃、1分鐘之浸漬的情況中所說明之方法相同者。Furthermore, the elution amount of the polyvinyl alcohol-based resin when the polyvinyl alcohol-based film of the present invention is immersed in water at 30°C for 2 minutes is preferably 50 ppm/m ² or less. Regarding the elution amount of the polyvinyl alcohol-based resin, from the viewpoint of avoiding contamination of the swelling tank during the production of the polarizing film, it is particularly preferably 40 ppm/m ² or less, and more preferably 30 ppm/m ² or less. The lower limit of the dissolution amount is usually 1 ppm/m ² . In addition, generally speaking, in the swelling step during the production of the polarizing film, considering that the polyvinyl alcohol-based film is swelled in warm water at about 30°C for several minutes, in the present invention, it is also set at 30°C for 2 minutes as described above. The impregnation conditions are used as indicators. The method for reducing the amount of elution in the immersion at 30°C for 2 minutes may be the same as the method described in the case of the immersion at 50°C for 1 minute.

此外，本發明之聚乙烯醇系薄膜以上述A之條件測定之捲曲角度需要為135°以下，尤其宜為90°以下，進一步宜為45°以下。若捲曲角度比135°更大，則在製造偏光膜時容易產生彎折或皺褶，無法達成本發明之目的。In addition, the curl angle of the polyvinyl alcohol-based film of the present invention measured under the conditions of the above A needs to be 135° or less, particularly preferably 90° or less, and more preferably 45° or less. If the curl angle is larger than 135°, it is easy to produce folds or wrinkles during the manufacture of the polarizing film, and the purpose of the invention cannot be achieved.

一般而言，將聚乙烯醇系薄膜浸漬於水中的話，在剛浸漬時捲曲大，且隨著浸漬時間捲曲會緩和，故在本發明中係以剛浸漬於30℃之溫水中，即於浸漬10秒鐘之時間點的捲曲角度作為指標。Generally speaking, when a polyvinyl alcohol-based film is immersed in water, the curl is large at the time of immersion, and the curl will be relaxed with the immersion time. Therefore, in the present invention, it is immersed in warm water at 30°C immediately after immersion. The curl angle at the time of 10 seconds was used as an index.

進一步地，本發明之聚乙烯醇系薄膜在上述A之條件中，將上述試驗體之浸漬時間設為2分鐘時，短邊方向的捲曲角度宜為40°以下，尤其宜為30°以下，進一步宜為20°以下。若該捲曲角度過大的話，會有在製造偏光膜時之膨潤步驟中產生彎折，在聚乙烯醇系薄膜之運送中容易產生破裂之傾向。Further, in the polyvinyl alcohol film of the present invention under the conditions of A, when the immersion time of the test body is set to 2 minutes, the curl angle in the short-side direction is preferably 40° or less, particularly preferably 30° or less, It is further preferably 20° or less. If the curl angle is too large, buckling may occur in the swelling step when manufacturing the polarizing film, and the polyvinyl alcohol-based film may be easily broken during transportation.

一般而言，考慮在製造偏光膜時，聚乙烯醇系薄膜係在約30℃之溫水膨潤數分鐘，故本發明也著眼於在30℃、2分鐘時的捲曲角度並進行測定。In general, it is considered that the polyvinyl alcohol-based film is swelled in warm water at about 30°C for several minutes in the production of a polarizing film. Therefore, the present invention also focuses on the curl angle at 30°C for 2 minutes and measures it.

此處，上述捲曲角度之測定中使用之試驗片(第1試驗片：於上述A之條件的試驗片)係從長條之上述聚乙烯醇系薄膜切出。該切出方向可為任意之方向，沒有特別之限定，考慮到使上述捲曲角度更小，更抑制製造偏光膜時之上述彎折之產生的觀點，以上述試驗片之長邊與薄膜之長度方向(MD方向)一致之方向，且短邊與薄膜之寬度方向(TD方向)一致之方向切出較為理想。Here, the test piece used in the measurement of the curl angle (the first test piece: the test piece under the condition of A) is cut out from the long polyvinyl alcohol-based film. The cutting direction can be any direction and is not particularly limited. Considering that the curl angle is made smaller and the bending of the polarizing film is suppressed, the long side of the test piece and the length of the film are considered. It is ideal to cut out in the same direction (MD direction) and the direction in which the short side is the same as the width direction (TD direction) of the film.

此處，針對本發明之聚乙烯醇系薄膜的製造方法進行說明。亦即，本發明之聚乙烯醇系薄膜的製造方法係具備以下步驟：製膜步驟，將聚乙烯醇系樹脂之水溶液連續地排出並流延至澆鑄模來進行製膜；及，乾燥步驟，將該製膜而得之薄膜從該澆鑄模剝離後，使該製膜而得之薄膜乾燥；該乾燥步驟中該製膜而得之薄膜的乾燥，係使該製膜而得之薄膜的正面與背面交替地與多個金屬製加熱輥接觸來進行。而本發明之製造方法最大的特徵係上述乾燥步驟的設定條件。Here, the manufacturing method of the polyvinyl alcohol film of this invention is demonstrated. That is, the manufacturing method of the polyvinyl alcohol-based film of the present invention includes the following steps: In the film forming step, the aqueous solution of the polyvinyl alcohol-based resin is continuously discharged and cast to a casting mold to form a film; and, In a drying step, after peeling the film obtained by forming the film from the casting mold, drying the film obtained by forming the film; The drying of the film obtained by forming the film in the drying step is performed by alternately contacting the front and back surfaces of the film obtained by forming the film with a plurality of metal heating rollers. The most important feature of the manufacturing method of the present invention is the setting conditions of the above-mentioned drying step.

[製膜工程] 首先，針對上述製膜步驟進行詳細地說明。[Film Making Project] First, the above-mentioned film forming step will be described in detail.

就本發明中使用之聚乙烯醇系樹脂而言，通常使用未改性之聚乙烯醇系樹脂，亦即使用將乙酸乙烯酯聚合而得之聚乙酸乙烯酯再進行皂化所製造之樹脂。因應需求，也可使用將乙酸乙烯酯與少量(通常為10莫耳%以下，宜為5莫耳%以下)之可和乙酸乙烯酯共聚合之成分的共聚物進行皂化所獲得之樹脂。就可和乙酸乙烯酯共聚合之成分而言，可舉例如不飽和羧酸(例如，包含鹽、酯、醯胺、腈等)、碳數2~30之烯烴類(例如乙烯、丙烯、正丁烯、異丁烯等)、乙烯醚類、不飽和磺酸鹽等。此外，也可使用將皂化後之羥基進行化學修飾所獲得之改性聚乙烯醇系樹脂。Regarding the polyvinyl alcohol resin used in the present invention, an unmodified polyvinyl alcohol resin is generally used, that is, a resin produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate. According to demand, a resin obtained by saponifying a copolymer of vinyl acetate and a small amount (usually less than 10 mol%, preferably less than 5 mol%) of components copolymerizable with vinyl acetate can also be used. As for the components that can be copolymerized with vinyl acetate, for example, unsaturated carboxylic acids (for example, containing salts, esters, amides, nitriles, etc.), olefins with 2 to 30 carbon atoms (for example, ethylene, propylene, normal Butene, isobutylene, etc.), vinyl ethers, unsaturated sulfonates, etc. In addition, modified polyvinyl alcohol resins obtained by chemically modifying saponified hydroxyl groups can also be used.

此外，就聚乙烯醇系樹脂而言，也可使用於側鏈具有1,2-二醇結構之聚乙烯醇系樹脂。該於側鏈具有1,2-二醇結構之聚乙烯醇系樹脂，可藉由例如(i)將乙酸乙烯酯與3,4-二乙醯氧基-1-丁烯之共聚物進行皂化之方法、(ii)將乙酸乙烯酯與碳酸乙烯亞乙酯之共聚物進行皂化及脫羧之方法、(iii)將乙酸乙烯酯與2,2-二烷基-4-乙烯基-1,3-二氧雜環戊烷之共聚物進行皂化及脫縮酮化之方法、(iv)將乙酸乙烯酯與甘油單烯丙基醚之共聚物進行皂化之方法等來獲得。In addition, polyvinyl alcohol-based resins can also be used for polyvinyl alcohol-based resins having a 1,2-diol structure in the side chain. The polyvinyl alcohol resin having a 1,2-diol structure in the side chain can be saponified by, for example, (i) saponifying a copolymer of vinyl acetate and 3,4-diethoxy-1-butene The method, (ii) the method of saponifying and decarboxylating the copolymer of vinyl acetate and vinyl ethylene carbonate, (iii) the method of combining vinyl acetate with 2,2-dialkyl-4-vinyl-1,3 -A method of saponifying and deketalizing a copolymer of dioxolane, (iv) a method of saponifying a copolymer of vinyl acetate and glycerol monoallyl ether, etc.

聚乙烯醇系樹脂之重量平均分子量係宜為10萬~30萬，尤其宜為11萬~28萬，進一步宜為12萬~26萬。該重量平均分子量若過小，則會有偏光膜之偏光度降低之傾向，若過大的話，則會有偏光膜製造時之延伸變得困難之傾向。其中，上述聚乙烯醇系樹脂之重量平均分子量係藉由GPC-MALS法所測定之重量平均分子量。The weight average molecular weight of the polyvinyl alcohol resin is preferably 100,000 to 300,000, particularly preferably 110,000 to 280,000, and further preferably 120,000 to 260,000. If the weight average molecular weight is too small, the degree of polarization of the polarizing film tends to decrease, and if it is too large, stretching during the production of the polarizing film tends to become difficult. Wherein, the weight average molecular weight of the above-mentioned polyvinyl alcohol-based resin is the weight average molecular weight measured by the GPC-MALS method.

本發明中使用之聚乙烯醇系樹脂的平均皂化度通常宜為98莫耳%以上，更宜為99莫耳%以上，進一步宜為99.5莫耳%以上，尤其宜為99.8莫耳%以上。該平均皂化度若過小，則會有偏光膜之偏光度降低的傾向。此處，本發明中的平均皂化度係依循JIS K 6726所測定而得者。The average saponification degree of the polyvinyl alcohol resin used in the present invention is generally preferably 98 mol% or more, more preferably 99 mol% or more, further preferably 99.5 mol% or more, and particularly preferably 99.8 mol% or more. If the average saponification degree is too small, the polarization degree of the polarizing film tends to decrease. Here, the average degree of saponification in the present invention is measured in accordance with JIS K 6726.

就本發明中使用之聚乙烯醇系樹脂而言，也可併用2種以上不同改性物質、改性量、重量平均分子量、平均皂化度等之聚乙烯醇系樹脂。Regarding the polyvinyl alcohol-based resin used in the present invention, two or more types of polyvinyl alcohol-based resins with different modification substances, modification amounts, weight average molecular weight, average saponification degree, etc. may be used in combination.

然後，使用上述聚乙烯醇系樹脂來製備為製膜原液之水溶液。亦即，將上述聚乙烯醇系樹脂使用水清洗，並使用離心分離機等進行脫水，使其成為含水率50重量%以下之聚乙烯醇系樹脂濕餅(wet cake)較為理想。若含水率過大，則會有難以成為期望之水溶液濃度的傾向。將該聚乙烯醇系樹脂濕餅溶解於溫水或熱水，製備聚乙烯醇系樹脂水溶液。Then, the above-mentioned polyvinyl alcohol-based resin is used to prepare an aqueous solution of a film-forming stock solution. That is, it is preferable to wash the above-mentioned polyvinyl alcohol-based resin with water, and to perform dehydration using a centrifugal separator or the like to make it into a polyvinyl alcohol-based resin wet cake with a moisture content of 50% by weight or less. If the water content is too high, it tends to be difficult to achieve the desired concentration of the aqueous solution. This polyvinyl alcohol-based resin wet cake is dissolved in warm water or hot water to prepare a polyvinyl alcohol-based resin aqueous solution.

聚乙烯醇系樹脂水溶液之製備方法沒有特別之限定，例如可使用已加熱之多軸擠製機進行製備，也可在具備上下循環流產生型攪拌葉之溶解罐中投入上述聚乙烯醇系樹脂濕餅，並將水蒸氣吹入至罐中，溶解並製備期望濃度之水溶液。The preparation method of the polyvinyl alcohol-based resin aqueous solution is not particularly limited. For example, it can be prepared using a heated multi-axis extruder, or the polyvinyl alcohol-based resin can be put into a dissolution tank equipped with a vertical circulation flow generating type stirring blade. Wet the cake and blow steam into the tank to dissolve and prepare an aqueous solution of the desired concentration.

聚乙烯醇系樹脂水溶液中，含有如上述之聚乙烯醇系樹脂，除此之外，還使其含有甘油、二甘油、三甘油、乙二醇、三乙二醇、聚乙二醇、三羥甲基丙烷等一般使用之塑化劑、或非離子性、陰離子性及陽離子性中之至少一種之界面活性劑的話，就聚乙烯醇系薄膜之製膜性的觀點較為理想。The aqueous solution of polyvinyl alcohol resin contains the polyvinyl alcohol resin as mentioned above. In addition, it also contains glycerin, diglycerin, triglycerin, ethylene glycol, triethylene glycol, polyethylene glycol, and triglycerin. Generally used plasticizers such as methylolpropane, or surfactants of at least one of nonionic, anionic, and cationic properties are preferable from the viewpoint of film forming properties of polyvinyl alcohol-based films.

如此獲得之聚乙烯醇系樹脂水溶液之樹脂濃度宜為15~60重量%，尤其宜為17~55重量%，進一步宜為20~50重量%。該水溶液之樹脂濃度若過低，則會有因為乾燥負荷變大而生產能力降低之傾向，若過高，則會有黏度變過高而變得難以均勻溶解之傾向。The resin concentration of the polyvinyl alcohol-based resin aqueous solution thus obtained is preferably 15 to 60% by weight, particularly preferably 17 to 55% by weight, and further preferably 20 to 50% by weight. If the resin concentration of the aqueous solution is too low, the drying load will tend to decrease and the productivity will tend to decrease. If it is too high, the viscosity will become too high and it will tend to become difficult to dissolve uniformly.

首先，將獲得之聚乙烯醇系樹脂水溶液進行消泡處理。就消泡方法而言，可列舉靜置消泡或利用具有通氣孔之多軸擠製機之消泡等之方法。就具有通氣孔之多軸擠製機而言，通常使用具有通氣孔之雙軸擠製機。First, the obtained polyvinyl alcohol-based resin aqueous solution is subjected to defoaming treatment. As far as the defoaming method is concerned, a method such as static defoaming or defoaming using a multi-axis extruder with vents can be cited. For a multi-axis extruder with vents, a biaxial extruder with vents is usually used.

消泡處理後，聚乙烯醇系樹脂水溶液係以一定量逐次地導入至T型縫模，排出及流延於旋轉之澆鑄鼓上，藉由連續澆鑄法製膜。After the defoaming treatment, the polyvinyl alcohol resin aqueous solution is successively introduced into the T-slot mold in a certain amount, discharged and cast on the rotating casting drum, and the film is formed by the continuous casting method.

T型縫模出口之聚乙烯醇系樹脂水溶液的溫度宜為80~100℃，尤其宜為85~98℃。若該聚乙烯醇系樹脂水溶液之溫度過低，則會有流動不良之傾向，若過高則會有發泡之傾向。The temperature of the polyvinyl alcohol resin aqueous solution at the exit of the T-slot die is preferably 80~100℃, especially 85~98℃. If the temperature of the polyvinyl alcohol-based resin aqueous solution is too low, there will be a tendency for poor flow, and if it is too high, there will be a tendency for foaming.

該聚乙烯醇系樹脂水溶液之黏度在排出時宜為50~200Pa･s，尤其宜為70~150Pa･s。該水溶液之黏度若過低，則會有流動不良之傾向，若過高則會有流延困難之傾向。The viscosity of the polyvinyl alcohol resin aqueous solution is preferably 50~200Pa･s, especially 70~150Pa･s when discharged. If the viscosity of the aqueous solution is too low, it will tend to flow poorly, and if it is too high, it will tend to be difficult to cast.

從T型縫模排出至澆鑄鼓之聚乙烯醇系樹脂水溶液的排出速度宜為0.1~5m/分，尤其宜為0.2~4m/分，進一步宜為0.3~3m/分。若該排出速度過慢則會有生產性降低之傾向，若過快則會有流延困難之傾向。The discharge speed of the polyvinyl alcohol-based resin aqueous solution discharged from the T-slot die to the casting drum is preferably 0.1 to 5 m/min, particularly preferably 0.2 to 4 m/min, and further preferably 0.3 to 3 m/min. If the discharge rate is too slow, there is a tendency for productivity to decrease, and if it is too fast, there is a tendency for difficulty in casting.

就澆鑄鼓而言，通常使用在以鐵作為主成分之不鏽鋼(SUS)之表面施加有為了防止刮傷之金屬鍍敷者。就金屬鍍敷而言，可舉例如鉻鍍敷、鎳鍍敷、鋅鍍敷等，此等可單獨使用或疊層化2層以上來使用。就此等之中，考慮鼓表面之耐久性的點，最外層表面為鉻鍍敷較為理想。As for the casting drum, the surface of stainless steel (SUS) with iron as the main component is usually coated with metal to prevent scratches. The metal plating includes, for example, chromium plating, nickel plating, zinc plating, etc., and these can be used alone or in two or more layers. Among these, considering the durability of the drum surface, the outermost surface is preferably chrome-plated.

該澆鑄鼓之直徑宜為2~5m，尤其宜為2.4~4.5m，進一步宜為2.8~4m。該直徑若過小，則會有乾燥長度不足不易提升速度之傾向，若過大則會有運輸性降低之傾向。The diameter of the casting drum is preferably 2~5m, particularly preferably 2.4~4.5m, and further preferably 2.8~4m. If the diameter is too small, the drying length tends to be insufficient and it is difficult to increase the speed, and if the diameter is too large, the transportability tends to decrease.

該澆鑄鼓之寬度宜為4~7m，尤其宜為5~6m。澆鑄鼓之寬度若過窄則會有生產性降低之傾向，若過寬則會有設備負荷增大之傾向。The width of the casting drum should be 4~7m, especially 5~6m. If the width of the casting drum is too narrow, the productivity will tend to decrease, and if it is too wide, the equipment load will tend to increase.

該澆鑄鼓之旋轉速度宜為3~50m/分，尤其宜為4~40m/分，進一步宜為5~35m/分。若該旋轉速度過慢則會有生產性降低之傾向，若過快則會有製膜而得之薄膜從澆鑄模剝離時之剝離性降低之傾向。The rotation speed of the casting drum is preferably 3-50m/min, particularly preferably 4-40m/min, and further preferably 5~35m/min. If the rotation speed is too slow, there is a tendency for productivity to decrease, and if it is too fast, there is a tendency for the releasability of the film obtained by film formation to decrease when it is peeled from the casting mold.

該澆鑄鼓之表面溫度宜為40~99℃，更宜為50~98℃，進一步宜為60~97℃，尤其宜為70~96℃，最好宜為80~95℃。若該表面溫度過低，則會有將製膜獲得之薄膜從澆鑄模剝離時的剝離性降低的傾向，若過高則會有發泡之傾向。The surface temperature of the casting drum is preferably 40~99°C, more preferably 50~98°C, further preferably 60~97°C, especially 70~96°C, most preferably 80~95°C. If the surface temperature is too low, the releasability of the film obtained when the film is peeled from the casting mold will tend to decrease, and if it is too high, there will be a tendency to foam.

如此來進行上述製膜步驟，並將製膜而得之薄膜從澆鑄鼓剝離。In this way, the above-mentioned film forming step is performed, and the film obtained by forming the film is peeled from the casting drum.

[乾燥工程] 然後，針對將上述剝離而得之薄膜(製膜而得之薄膜)進行加熱來乾燥之上述乾燥步驟進行詳細說明。[Drying Engineering] Next, the above-mentioned drying step of heating and drying the film obtained by the above-mentioned peeling (film-forming film) will be described in detail.

該乾燥步驟如圖1所示，將從澆鑄鼓D剝離而得之薄膜F邊沿著流動方向(MD方向)運送邊使該薄膜F之正面與背面交替地與多個金屬製加熱輥(以下、簡稱為「熱輥」。)R1~R7接觸來進行乾燥。其中，於圖1係展示使用了7根熱輥R1~R7的情況。此外，在圖1中，符號C係表示T型縫模，符號E表示自由輥。該熱輥R1~R7只要是具有加熱功能之金屬製者便沒有特別之限定，宜為表面經鍍硬鉻處理或鏡面處理之直徑0.2~2m的輥，該熱輥之根數，通常為2~30根，宜為10~25根。另外，在本發明中係將表面溫度加熱至40℃以上，及經溫度調整而得者視為熱輥。This drying step is shown in FIG. 1, while the film F peeled from the casting drum D is conveyed in the flow direction (MD direction), the front and back sides of the film F are alternately connected with a plurality of metal heating rollers (hereinafter, Abbreviated as "hot roll".) R1~R7 contact to dry. Among them, Fig. 1 shows the case where 7 heat rollers R1 to R7 are used. In addition, in FIG. 1, the symbol C represents a T-shaped slot die, and the symbol E represents a free roll. The heat rollers R1~R7 are not particularly limited as long as they are made of metal with heating function. They are preferably rollers with a diameter of 0.2~2m with hard chrome plating or mirror treatment on the surface. The number of heat rollers is usually 2 ~30 roots, preferably 10-25 roots. In addition, in the present invention, the surface temperature is heated to 40°C or higher, and the temperature-adjusted product is regarded as a hot roller.

本發明之一大特徵係如上述，在該乾燥步驟中，藉由使從澆鑄鼓剝離而得之薄膜的正面及背面交替地與多個熱輥接觸來使其乾燥。藉此，如上所述，適當地控制上述剝離而得之薄膜的正面及背面的乾燥狀態，並經由該乾燥步驟而製得之聚乙烯醇系薄膜，能減低聚乙烯醇系樹脂之溶出量及捲曲角度。One of the major features of the present invention is as described above. In this drying step, the front and back surfaces of the film peeled from the casting drum are alternately contacted with a plurality of heat rollers to dry it. As a result, as described above, the dry state of the front and back sides of the film obtained by peeling is appropriately controlled, and the polyvinyl alcohol-based film obtained through the drying step can reduce the elution amount of the polyvinyl alcohol-based resin and Curl angle.

此處，針對更適當地控制上述剝離而得之薄膜的正面及背面的乾燥狀態，且更減低上述聚乙烯醇系樹脂之溶出量及捲曲角度之方法進行說明。Here, a method of more appropriately controlling the dry state of the front and back surfaces of the film obtained by the peeling, and further reducing the elution amount and the curl angle of the polyvinyl alcohol-based resin will be described.

本發明中，於乾燥步驟中使用之上述熱輥的總數為P根，設從該澆鑄鼓剝離而得之薄膜第n個接觸之上述熱輥的表面溫度為Tn(℃)，該第n個熱輥與該薄膜之接觸時間為Sn(秒鐘)，製造而得之聚乙烯醇系薄膜之厚度為D(μm)，該n為1以上該P以下之整數時，表示Tn×Sn之總和的Σ(Tn×Sn)宜滿足下列式(1)： 75≦Σ(Tn×Sn)/D≦110　･･･(1)。In the present invention, the total number of the heat rollers used in the drying step is P, and the surface temperature of the heat roller contacted by the nth film peeled from the casting drum is Tn(°C), and the nth The contact time between the heat roller and the film is Sn (seconds), and the thickness of the produced polyvinyl alcohol film is D (μm). When n is an integer of 1 or more and P or less, it means the sum of Tn×Sn Σ(Tn×Sn) should satisfy the following formula (1): 75≦Σ(Tn×Sn)/D≦110　･･･(1).

更宜滿足下列式(1’)，進一步宜滿足下列式(1’’)，尤其宜滿足下列式(1’’’)。 76≦Σ(Tn×Sn)/D≦100 ･･･(1’) 78≦Σ(Tn×Sn)/D≦92 ･･･(1’’) 80≦Σ(Tn×Sn)/D≦90 ･･･(1’’’)It is more preferable to satisfy the following formula (1'), further preferably to satisfy the following formula (1''), and particularly preferably to satisfy the following formula (1'''). 76≦Σ(Tn×Sn)/D≦100 ･･･(1’) 78≦Σ(Tn×Sn)/D≦92 ･･･(1’’) 80≦Σ(Tn×Sn)/D≦90 ･･･(1’’’)

此處，Σ(Tn×Sn)係對於第1~P個之全部熱輥求得各別之Tn×Sn的值，並將它們全部加總所得之值。Σ(Tn×Sn)/D之值，例如在熱輥之總根數為3根，製造之聚乙烯醇系薄膜之厚度D為20μm，乾燥條件為下述情況時，係(70×6+80×7+90×8)÷20=85。・第1個熱輥之表面溫度T₁ =70℃，第1個熱輥與薄膜之接觸時間S₁ =6秒鐘。・第2個熱輥之表面溫度T₂ =80℃，第2個熱輥與薄膜之接觸時間S₂ =7秒鐘。・第3個熱輥之表面溫度T₃ =90℃，第3個熱輥與薄膜之接觸時間S₃ =8秒鐘。Here, Σ(Tn×Sn) is the value obtained by calculating the individual Tn×Sn values for all the heat rollers from the 1st to the P, and adding them up. The value of Σ(Tn×Sn)/D, for example, when the total number of heat rollers is 3, the thickness D of the produced polyvinyl alcohol film is 20μm, and the drying conditions are as follows, it is (70×6+ 80×7+90×8)÷20=85.・The surface temperature of the first heat roller is T ₁ =70°C, and the contact time between the first heat roller and the film S ₁ =6 seconds.・The surface temperature of the second heat roller is T ₂ =80℃, and the contact time between the second heat roller and the film S ₂ =7 seconds.・The surface temperature of the third heat roller is T ₃ =90℃, and the contact time between the third heat roller and the film is S ₃ =8 seconds.

上述Σ(Tn×Sn)/D之值若過小，則在偏光膜製造時之膨潤步驟中，聚乙烯醇系樹脂對於水的溶出會有增加的傾向，相反地，若過大則會有膨潤性降低之傾向。如同上述式(1)~(1’’’)所示，製造之聚乙烯醇系薄膜的厚度越厚，乾燥需要之熱能越大。If the value of Σ(Tn×Sn)/D is too small, the polyvinyl alcohol-based resin will dissolve into water during the swelling step during the production of the polarizing film. On the contrary, if it is too large, it will have swelling properties. The tendency to decrease. As shown in the above formulas (1) to (1’’’), the thicker the thickness of the PVA film produced, the greater the heat energy required for drying.

其中，熱輥與薄膜之接觸時間意指薄膜面内之任意1點與各熱輥之接觸時間。即使薄膜之運送速度為一定，也可藉由改變各熱輥之外徑或配置來控制該接觸時間。Among them, the contact time between the hot roller and the film means the contact time between any one point on the film surface and each hot roller. Even if the transport speed of the film is constant, the contact time can be controlled by changing the outer diameter or configuration of each heat roller.

在本發明中，使用之全部熱輥的表面溫度Tn宜為40~150℃，更宜為50~140℃，進一步宜為60~130℃，尤其宜為70~120℃。若該熱輥之表面溫度過低，則會有乾燥不足之傾向，若熱輥之表面溫度Tn過高，則會有聚乙烯醇系樹脂發生結晶化，而使製造偏光膜時之膨潤性變得不均勻之傾向。In the present invention, the surface temperature Tn of all heat rolls used is preferably 40 to 150°C, more preferably 50 to 140°C, further preferably 60 to 130°C, and particularly preferably 70 to 120°C. If the surface temperature of the heat roller is too low, there will be a tendency for insufficient drying. If the surface temperature Tn of the heat roller is too high, the polyvinyl alcohol resin will crystallize, which will cause the swelling of the polarizing film to be changed. The tendency to get uneven.

在本發明中，各熱輥與薄膜之接觸時間Sn宜為1~60秒鐘，更宜為2~30秒鐘，進一步宜為3~20秒鐘，尤其宜為4~10秒鐘。該接觸時間Sn若過短，則會有乾燥不足之傾向，接觸時間Sn若過長，則會有設備負荷增大之傾向。In the present invention, the contact time Sn between each heated roller and the film is preferably 1 to 60 seconds, more preferably 2 to 30 seconds, further preferably 3 to 20 seconds, and particularly preferably 4 to 10 seconds. If the contact time Sn is too short, the drying will tend to be insufficient, and if the contact time Sn is too long, the equipment load will tend to increase.

進一步地，在本發明中，該乾燥步驟中使用之上述熱輥的總數為P根，且設從該澆鑄模剝離而得之薄膜第x個(奇數個)接觸之上述熱輥的表面溫度為Tx(℃)，該薄膜第y個(偶數個)接觸之上述熱輥的表面溫度為Ty(℃)，該第x個(奇數個)熱輥與該薄膜之接觸時間為Sx(秒鐘)，該第y個(偶數個)熱輥與該薄膜之接觸時間為Sy(秒鐘)時，表示Tx×Sx之總和的Σ(Tx×Sx)及表示Ty×Sy之總和的Σ(Ty×Sy)宜滿足下列式(2)： Σ(Ty×Sy)＜Σ(Tx×Sx) ･･･(2)Further, in the present invention, the total number of the hot rollers used in the drying step is P, and the surface temperature of the x-th (odd number) of the hot rollers in contact with the film peeled from the casting mold is Tx (°C), the surface temperature of the yth (even number) hot roller contacted by the film is Ty (°C), and the contact time between the xth (odd number) hot roller and the film is Sx (seconds) , When the contact time between the yth (even number) heat roller and the film is Sy (seconds), Σ(Tx×Sx) representing the sum of Tx×Sx and Σ(Ty×) representing the sum of Ty×Sy Sy) should satisfy the following formula (2): Σ(Ty×Sy)＜Σ(Tx×Sx) ･･･(2)

更宜滿足下列式(2’)，進一步宜滿足下列式(2’’)。 Σ(Ty×Sy)＜0.9×Σ(Tx×Sx) ･･･(2’) 0.8×Σ(Tx×Sx)＜Σ(Ty×Sy)＜0.9×Σ(Tx×Sx) ･･･(2’’)It is more preferable to satisfy the following formula (2'), and it is further preferable to satisfy the following formula (2''). Σ(Ty×Sy)＜0.9×Σ(Tx×Sx) ･･･(2’) 0.8×Σ(Tx×Sx)＜Σ(Ty×Sy)＜0.9×Σ(Tx×Sx) ･･･(2’’)

例如，在熱輥之總根數為3根，乾燥條件為下列情況時，上述Σ(Tx×Sx)的值為70×6+90×8=1140，上述Σ(Ty×Sy)之值為80×7=560。・第1個熱輥的表面溫度T₁ =70℃，第1個熱輥與薄膜之接觸時間S₁ =6秒鐘。・第2個熱輥的表面溫度T₂ =80℃，第2個熱輥與薄膜之接觸時間S₂ =7秒鐘。・第3個熱輥的表面溫度T₃ =90℃，第3個熱輥與薄膜之接觸時間S₃ =8秒鐘。For example, when the total number of heat rollers is 3 and the drying conditions are as follows, the value of the above Σ(Tx×Sx) is 70×6+90×8=1140, and the value of the above Σ(Ty×Sy) 80×7=560.・The surface temperature of the first heat roller is T ₁ =70°C, and the contact time between the first heat roller and the film S ₁ =6 seconds.・The surface temperature of the second heat roller is T ₂ =80°C, and the contact time between the second heat roller and the film S ₂ =7 seconds.・The surface temperature of the third heat roller is T ₃ =90°C, and the contact time between the third heat roller and the film is S ₃ =8 seconds.

若Σ(Ty×Sy)超過Σ(Tx×Sx)的話，會有在偏光膜製造時之膨潤步驟中，聚乙烯醇系薄膜容易捲曲之傾向。相反地，若Σ(Ty×Sy)過小的話，會有聚乙烯醇系薄膜容易朝相反方向捲曲之傾向。亦即，上述式(2)之目的係考慮製膜而得之薄膜之與澆鑄模接觸的面，通常會接觸第偶數個的熱輥，而將受到來自該第偶數個之熱輥之熱量設定為少於受到來自第奇數個之熱輥的熱量，來使供給至薄膜兩面之熱量為同等。If Σ(Ty×Sy) exceeds Σ(Tx×Sx), the polyvinyl alcohol-based film tends to curl easily during the swelling step during the production of the polarizing film. Conversely, if Σ(Ty×Sy) is too small, the polyvinyl alcohol-based film tends to curl in the opposite direction. That is, the purpose of the above formula (2) is to consider that the surface of the film obtained by forming the film that is in contact with the casting mold will usually contact the even-numbered hot roller, and will receive the heat from the even-numbered hot roller. In order to be less than the heat received from the odd-numbered heat roller, the heat supplied to both sides of the film is equal.

進一步地，在本發明中，設澆鑄模之表面溫度為T₀ (℃)時，表示Tx×Sx之總和的Σ(Tx×Sx)與表示Ty×Sy之總和的Σ(Ty×Sy)宜滿足下列式(3)。 Σ(Ty×Sy)+T₀ ≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T₀ ×10 ･･･(3)Further, in the present invention, when the surface temperature of the casting mold is T ₀ (℃), Σ(Tx×Sx) representing the sum of Tx×Sx and Σ(Ty×Sy) representing the sum of Ty×Sy are suitable The following formula (3) is satisfied. Σ(Ty×Sy)+T ₀ ≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T ₀ ×10 ･･･(3)

更宜滿足下列式(3’)，進一步宜滿足下列式(3’’)。 Σ(Ty×Sy)+T₀ ×2≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T₀ ×6･･･(3’) Σ(Ty×Sy)+T₀ ×3≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T₀ ×4･･･(3’’)It is more preferable to satisfy the following formula (3'), and it is further preferable to satisfy the following formula (3''). Σ(Ty×Sy)+T ₀ ×2≦Σ(Tx×Sx)≦Σ(Ty×Sy)+T ₀ ×6･･･(3') Σ(Ty×Sy)+T ₀ ×3≦Σ (Tx×Sx)≦Σ(Ty×Sy)+T ₀ ×4･･･(3'')

Σ(Tx×Sx)之值不管過小還是過大，都會有在製造偏光膜時之膨潤步驟中，在剛水浸漬後，聚乙烯醇系薄膜容易捲曲之傾向。亦即，上述式(3)之目的係考慮通常薄膜之與澆鑄模接觸的面會接觸第偶數個的熱輥，而將受到來自澆鑄模及該第偶數個之熱輥之熱量設定為與受到來自第奇數個之熱輥的熱量同等，來使供給至薄膜兩面之熱量大約一致。Regardless of whether the value of Σ(Tx×Sx) is too small or too large, there will be a tendency for the PVA film to curl easily immediately after water immersion in the swelling step when manufacturing the polarizing film. That is, the purpose of the above formula (3) is to consider that the surface of the film that is in contact with the casting mold usually contacts the even-numbered hot roller, and the heat received from the casting mold and the even-numbered hot roller is set to be The heat from the odd-numbered heat roller is the same, so that the heat supplied to both sides of the film is approximately the same.

經乾燥之薄膜的水分率宜為10重量%以下，更宜為1~9重量%，進一步宜為2~8重量%。若該水分率過高，則會有最後獲得之聚乙烯醇系薄膜變得乾燥不良之傾向。The moisture content of the dried film is preferably 10% by weight or less, more preferably 1-9% by weight, and further preferably 2-8% by weight. If the moisture content is too high, the finally obtained polyvinyl alcohol-based film tends to become poorly dried.

在本發明中，宜將經乾燥之薄膜進行熱處理，就能使該薄膜兩面之乾燥狀態均勻的觀點，尤其宜從該薄膜之兩面進行熱處理。就該熱處理方法而言，可舉例如使用浮動式乾燥器對於薄膜的兩面吹送熱風之方法，使用紅外線燈對於薄膜的兩面照射近紅外線之方法。該熱處理溫度宜為50~150℃，尤其宜為70~130℃。另外，該熱處理溫度，在該熱處理方法為上述以浮動式乾燥器吹送熱風之方法時，係指該熱風之溫度，在該熱處理方法係上述以紅外線燈照射近紅外線之方法時，係指該近紅外線之溫度。該熱處理時間沒有特別之限定，使用浮動式乾燥器時，宜為10~100秒鐘，尤其宜為20~80秒鐘。另外，上述熱處理方法係不使用熱輥之方法。In the present invention, it is preferable to heat-treat the dried film so that the dry state on both sides of the film can be made uniform, and it is particularly preferable to heat-treat from both sides of the film. The heat treatment method includes, for example, a method of blowing hot air on both sides of the film using a floating dryer, and a method of irradiating near-infrared rays on both sides of the film using an infrared lamp. The heat treatment temperature is preferably 50 to 150°C, especially 70 to 130°C. In addition, the heat treatment temperature refers to the temperature of the hot air when the heat treatment method is the above-mentioned method of blowing hot air with a floating dryer, and when the heat treatment method is the above-mentioned method of irradiating near-infrared rays with an infrared lamp, it refers to the near-infrared light. Infrared temperature. The heat treatment time is not particularly limited. When a floating dryer is used, it is preferably 10-100 seconds, especially 20-80 seconds. In addition, the above heat treatment method is a method that does not use a hot roller.

[聚乙烯醇系薄膜] 上述乾燥步驟後，因應需求進行上述熱處理，獲得於流動方向(MD方向)長的本發明之聚乙烯醇系薄膜。該聚乙烯醇系薄膜係藉由將寬度方向(TD方向)的兩端部切開，並捲繞於芯管成為輥狀來製作薄膜捲繞體。[Polyvinyl alcohol film] After the above-mentioned drying step, the above-mentioned heat treatment is performed as required to obtain the polyvinyl alcohol-based film of the present invention that is long in the flow direction (MD direction). This polyvinyl alcohol-based film cuts the both ends in the width direction (TD direction) and winds it around a core tube into a roll to produce a film roll.

在本發明中，將上述薄膜捲繞體以水蒸氣阻隔薄膜進行包裝來獲得包裝體，將該包裝體於25~30℃之環境溫度保存5天以上較為理想。就保存期間而言，更宜為10天以上，尤其宜為15天以上，進一步宜為15~60天。若該保存期間過短，則會有容易產生水浸漬時之捲曲的傾向。相反地若保存期間過長，則會有偏光膜之製造停滯的傾向。該保存之方法沒有特別之限定，可列舉使用恆溫恆濕室或輥貯藏庫之方法。In the present invention, the above-mentioned film roll is packaged with a water vapor barrier film to obtain a package, and the package is preferably stored at an ambient temperature of 25 to 30°C for more than 5 days. As for the storage period, it is more preferably more than 10 days, particularly preferably more than 15 days, and further preferably 15-60 days. If the storage period is too short, curling tends to occur during water immersion. On the contrary, if the storage period is too long, the production of the polarizing film will tend to stagnate. The storage method is not particularly limited, and a method using a constant temperature and humidity chamber or a roll storage can be mentioned.

另外，上述利用保存來減低水浸漬時之捲曲的理由雖然尚未明瞭，據推測是因為利用上述保存使聚乙烯醇系薄膜之面內及厚度方向之水分率成為一定，以及於高於室溫之溫度會緩和聚乙烯醇系薄膜之面內及厚度方向的應力的緣故。因此，據推測保存溫度為上述範圍外則會產生水分率不均勻或應力不均勻，較不理想。In addition, although the reason for reducing curling during water immersion by the above-mentioned storage is not yet clear, it is presumed to be because the above-mentioned storage makes the moisture content in the plane and the thickness direction of the polyvinyl alcohol film constant, and it is higher than room temperature. The temperature relaxes the stress in the plane and the thickness direction of the polyvinyl alcohol-based film. Therefore, it is estimated that the storage temperature outside the above range will cause uneven moisture content or uneven stress, which is less desirable.

考慮偏光膜之大面積化的觀點，如此獲得之本發明之聚乙烯醇系薄膜的長度宜為5km以上，考慮運輸重量之觀點，尤其宜為5~50km。Considering the viewpoint of increasing the area of the polarizing film, the length of the polyvinyl alcohol-based film of the present invention thus obtained is preferably 5 km or more, and considering the transportation weight, it is particularly preferably 5 to 50 km.

就偏光膜之增寬化之觀點，本發明之聚乙烯醇系薄膜之寬度宜為4m以上，尤其宜為5m以上，考慮製造偏光膜時避免破裂之觀點，進一步宜為5~6m。From the viewpoint of broadening of the polarizing film, the width of the polyvinyl alcohol film of the present invention is preferably 4m or more, especially 5m or more. Considering the viewpoint of avoiding cracking when manufacturing the polarizing film, it is more preferably 5-6m.

此外，本發明之聚乙烯醇系薄膜的厚度宜為10~75μm，考慮薄型化之觀點，宜為厚度10~60μm，考慮減低相位延遲(retardation)之觀點，尤其宜為20~60μm，考慮避免破裂之觀點，進一步宜為30~60μm。In addition, the thickness of the polyvinyl alcohol film of the present invention is preferably 10~75μm, considering the viewpoint of thinning, the thickness is preferably 10~60μm, considering the viewpoint of reducing retardation, especially 20~60μm, considering avoiding From the viewpoint of rupture, it is further preferable to be 30 to 60 μm.

此外，本發明之聚乙烯醇系薄膜，其薄膜之配向軸(遲相軸)與寬度方向(TD方向)之交叉角θ宜為45°以下。該交叉角θ若超過45°，則會有在膨潤時於寬度方向(TD方向)捲曲之傾向。該現象推測是因為吸水並非進入高分子之配向方向，而是以進入高分子間之間隙的形態所引起的。亦即，高分子之配向方向為長度方向(MD方向)之情況，膨潤比起目的之長度方向(MD方向)更容易發生於寬度方向(TD方向)。In addition, in the polyvinyl alcohol film of the present invention, the intersection angle θ between the alignment axis (late axis) of the film and the width direction (TD direction) is preferably 45° or less. If the crossing angle θ exceeds 45°, it tends to curl in the width direction (TD direction) during swelling. This phenomenon is presumed to be caused by the absorption of water not in the alignment direction of the polymer, but in the form of entering the gap between the polymers. That is, when the alignment direction of the polymer is the longitudinal direction (MD direction), swelling is more likely to occur in the width direction (TD direction) than the intended longitudinal direction (MD direction).

進一步地，本發明之聚乙烯醇系薄膜在令長度方向(MD方向)之折射率為nx，寬度方向(TD方向)之折射率為ny，厚度方向之折射率為nz、厚度為D(μm)時，以下列式(4)算出之薄膜的厚度方向的相位差Rth(nm)宜為100nm以上，尤其宜為110nm以上，進一步宜為110~200nm。若該相位差Rth過小，則會有在膨潤時捲曲之傾向。該現象據推測是因為若相位差Rth小的話，高分子鏈朝厚度方向的配向會變強，並阻礙了朝厚度方向之平穩之膨潤。相反地，若相位差過大，也會因為高分子鏈之面配向強，而有容易阻礙朝面方向之平穩之膨潤的傾向。 Rth=[(nx+ny)/2-nz]×1000×D ･･･(4)Furthermore, in the polyvinyl alcohol film of the present invention, the refractive index in the longitudinal direction (MD direction) is nx, the refractive index in the width direction (TD direction) is ny, the refractive index in the thickness direction is nz, and the thickness is D (μm ), the retardation Rth (nm) in the thickness direction of the film calculated by the following formula (4) is preferably 100 nm or more, particularly preferably 110 nm or more, and further preferably 110 to 200 nm. If the retardation Rth is too small, there is a tendency to curl when swelling. This phenomenon is presumably because if the phase difference Rth is small, the alignment of the polymer chains in the thickness direction becomes stronger, and smooth swelling in the thickness direction is prevented. On the contrary, if the phase difference is too large, the surface alignment of the polymer chain will be strong, which tends to hinder the smooth swelling in the surface direction. Rth=[(nx+ny)/2-nz]×1000×D ･･･(4)

另外，在上述實施形態，係以使用了澆鑄鼓(鼓型輥)作為澆鑄模的情況作為例子來說明製造聚乙烯醇系薄膜之方法，但亦可使用澆鑄帶或樹脂薄膜作為澆鑄模來進行製造。In addition, in the above embodiment, a case where a casting drum (drum roll) is used as a casting mold is used as an example to illustrate the method of manufacturing a polyvinyl alcohol-based film, but a casting belt or a resin film can also be used as a casting mold. manufacture.

此外，在上述實施形態，就減低上述聚乙烯醇系樹脂之溶出量之方法而言，在藉由連續澆鑄法來製造聚乙烯醇系薄膜之過程的乾燥步驟中，採用藉由使以澆鑄模製膜而得之薄膜的正面與背面交替地接觸多個金屬製加熱輥來適當地控制上述製膜而得之薄膜的正面及背面的乾燥狀態之方法，但亦可採用其他方法。可舉例如：調整係原料之聚乙烯醇系樹脂之分子量或皂化度之方法、清洗聚乙烯醇系樹脂使純度提高之方法、於聚乙烯醇系樹脂之水溶液中添加界面活性劑之方法、於使用聚乙烯醇系樹脂水溶液進行製膜之步驟，控制高分子之結晶化度或配向狀態之方法、控制製膜而得之薄膜之乾燥狀態之方法等。In addition, in the above-mentioned embodiment, in terms of the method of reducing the elution amount of the polyvinyl alcohol-based resin, in the drying step of the process of producing the polyvinyl alcohol-based film by the continuous casting method, the method of using a casting mold A method in which the front and back surfaces of the film obtained by forming the film are alternately contacted with a plurality of metal heating rollers to appropriately control the dry state of the front and back surfaces of the film obtained by forming the film. However, other methods may also be adopted. Examples include: a method of adjusting the molecular weight or saponification degree of the polyvinyl alcohol-based resin of the raw material, a method of cleaning the polyvinyl alcohol-based resin to increase the purity, a method of adding a surfactant to the aqueous solution of the polyvinyl alcohol-based resin, and Using polyvinyl alcohol-based resin aqueous solution for the steps of film formation, the method of controlling the crystallinity or alignment state of the polymer, the method of controlling the dry state of the film obtained by film formation, etc.

進一步地，在上述實施之形態，就減少上述捲曲角度之方法而言，也在藉由連續澆鑄法來製造聚乙烯醇系薄膜之過程的乾燥步驟中，採用了藉由使以澆鑄模製膜而得之薄膜的正面與背面交替地接觸多個金屬製加熱輥，來適當地控制上述製膜而得之薄膜之正面與背面的乾燥狀態之方法，但亦可採用其他方法。可舉例如：在使用聚乙烯醇系樹脂水溶液進行製膜之步驟中控制高分子之配向狀態之方法、提高製膜時之厚度精度之方法、控制製膜而得之薄膜的乾燥狀態之方法等。Furthermore, in the above-mentioned embodiment, in terms of the method of reducing the above-mentioned curl angle, the drying step of the process of producing the polyvinyl alcohol-based film by the continuous casting method is also adopted by the method of casting the film The front and back sides of the obtained film are alternately contacted with a plurality of metal heating rollers to appropriately control the dry state of the front and back sides of the film obtained by forming the film. However, other methods may also be adopted. Examples include: a method of controlling the alignment state of a polymer in the step of forming a film using a polyvinyl alcohol-based resin aqueous solution, a method of improving the thickness accuracy during film forming, a method of controlling the dry state of the film obtained by forming the film, etc. .

本發明之聚乙烯醇系薄膜在水浸漬時聚乙烯醇系樹脂的溶出少，且減低了捲曲角度，故特別適宜使用作為偏光膜用之原料卷。The polyvinyl alcohol-based film of the present invention has less elution of the polyvinyl alcohol-based resin when immersed in water and reduces the curl angle, so it is particularly suitable for use as a raw material roll for a polarizing film.

此處，針對使用本發明之聚乙烯醇系薄膜獲得之偏光膜的製造方法進行說明。Here, the manufacturing method of the polarizing film obtained using the polyvinyl alcohol film of this invention is demonstrated.

[偏光膜之製造方法] 本發明之偏光膜係將上述聚乙烯醇系薄膜從上述薄膜捲繞體拉出並沿水平方向運送，經膨潤、染色、硼酸交聯、延伸、清洗、乾燥等步驟製造而得。[Method of manufacturing polarizing film] The polarizing film of the present invention is produced by pulling the above-mentioned polyvinyl alcohol-based film from the above-mentioned film winding body and transporting it in a horizontal direction, and undergoing steps such as swelling, dyeing, boric acid cross-linking, stretching, washing, and drying.

膨潤步驟係在染色步驟之前實施。藉由膨潤步驟，不僅可清洗聚乙烯醇系薄膜表面之污垢，也有藉由使聚乙烯醇系薄膜膨潤來防止染色不均勻等之效果。在膨潤步驟中，通常使用水作為處理液。上述處理液只要主成分是水即可，也可少量加入碘化合物、界面活性劑等添加物、醇等。膨潤浴之溫度通常為10~45℃左右，浸漬到膨潤浴之時間，通常為0.1~10分鐘左右。The swelling step is implemented before the dyeing step. The swelling step can not only clean the dirt on the surface of the polyvinyl alcohol-based film, but also has the effect of preventing uneven dyeing by swelling the polyvinyl alcohol-based film. In the swelling step, water is usually used as the treatment liquid. As long as the main component of the above-mentioned treatment liquid is water, additives such as iodine compounds and surfactants, alcohol, etc. may be added in small amounts. The temperature of the swelling bath is usually about 10~45℃, and the time for immersion in the swelling bath is usually about 0.1~10 minutes.

染色步驟係藉由使聚乙烯醇系薄膜接觸含有碘或二色性染料之液體來進行。通常使用碘-碘化鉀之水溶液，碘的濃度適宜為0.1~2g/L，碘化鉀之濃度適宜為1~100g/L。染色時間在實用上為30~500秒鐘左右。處理浴之溫度宜為5~50℃。水溶液中含有水溶劑，除此之外，可少量含有和水具有相溶性的有機溶劑。The dyeing step is performed by contacting a polyvinyl alcohol-based film with a liquid containing iodine or a dichroic dye. Usually, an aqueous solution of iodine-potassium iodide is used, the concentration of iodine is preferably 0.1~2g/L, and the concentration of potassium iodide is preferably 1-100g/L. The dyeing time is practically about 30 to 500 seconds. The temperature of the treatment bath should be 5~50℃. The aqueous solution contains a water solvent, and in addition, it may contain a small amount of an organic solvent compatible with water.

硼酸交聯步驟係使用硼酸或硼砂等硼化合物來進行。硼化合物係以水溶液或水-有機溶劑混合液之形態，並以濃度10~100g/L左右來使用，就偏光性能之安定化的觀點，在液中使碘化鉀共存較為理想。處理時之溫度係30~70℃左右，處理時間宜為0.1~20分鐘左右，此外因應需求也可在處理中進行延伸操作。The boric acid cross-linking step is performed using a boron compound such as boric acid or borax. The boron compound is used in the form of an aqueous solution or a water-organic solvent mixture with a concentration of about 10 to 100 g/L. From the viewpoint of stabilizing the polarization performance, it is ideal to coexist potassium iodide in the liquid. The processing temperature is about 30~70℃, and the processing time should be about 0.1~20 minutes. In addition, it can also be extended during the processing according to the needs.

延伸步驟宜沿著單一軸方向[流動方向(MD方向)]延伸3~10倍，更宜為延伸3.5~6倍。此時，沿著垂直於延伸方向之方向也進行些微之延伸[防止寬度方向(TD方向)之收縮的程度，或其以上之延伸]也無妨。延伸時之溫度宜為30~170℃。進一步地，延伸倍率係最後設定為上述範圍內即可，延伸操作不僅限為一次，在偏光膜製造步驟中亦可實施數次的延伸操作。The extension step should extend 3~10 times along a single axis direction [flow direction (MD direction)], more preferably 3.5~6 times. At this time, a slight extension is also performed in the direction perpendicular to the extension direction [the degree to prevent contraction in the width direction (TD direction), or the extension beyond that]. The temperature during extension should be 30~170℃. Furthermore, the stretching magnification can be finally set within the above-mentioned range, and the stretching operation is not limited to one time, and several stretching operations may also be implemented in the polarizing film manufacturing step.

清洗步驟，例如藉由將聚乙烯醇系薄膜浸漬於水、或碘化鉀等碘化物之水溶液中來進行，可除去產生於該聚乙烯醇系薄膜之表面的析出物。使用碘化鉀水溶液時，碘化鉀之濃度為1~80g/L左右。清洗處理時之溫度通常為5~50℃，宜為10~45℃。處理時間通常為1~300秒鐘，宜為10~240秒鐘。另外，可適當地組合水清洗及藉由碘化鉀水溶液之清洗來進行。The washing step is performed, for example, by immersing the polyvinyl alcohol-based film in water or an aqueous solution of iodide such as potassium iodide, and the precipitates generated on the surface of the polyvinyl alcohol-based film can be removed. When using potassium iodide aqueous solution, the concentration of potassium iodide is about 1~80g/L. The temperature during cleaning is usually 5~50℃, preferably 10~45℃. The processing time is usually 1 to 300 seconds, preferably 10 to 240 seconds. In addition, water washing and washing with potassium iodide aqueous solution can be combined appropriately.

乾燥步驟，例如將上述聚乙烯醇系薄膜於空氣中以40~80℃乾燥1~10分鐘來進行。The drying step is performed, for example, by drying the polyvinyl alcohol-based film in the air at 40 to 80° C. for 1 to 10 minutes.

如此可獲得本發明之偏光膜。本發明之偏光膜的偏光度宜為99.8%以上，更宜為99.9%以上。若偏光度過低，則會有無法確保液晶顯示器之對比的傾向。另外，一般係由在2片偏光膜重疊成使其配向方向為同一方向之狀態下，以波長λ測得之光線透射率(H₁₁ )，及在2片偏光膜重疊成使其配向方向為相互垂直之方向之狀態下，以波長λ測得之光線透射率(H₁ )，根據下式算出偏光度。偏光度＝[(H₁₁ -H₁ )/(H₁₁ +H₁ )]^1/2 In this way, the polarizing film of the present invention can be obtained. The degree of polarization of the polarizing film of the present invention is preferably 99.8% or more, more preferably 99.9% or more. If the polarization is too low, there is a tendency that the contrast of the liquid crystal display cannot be ensured. _{In addition, it is generally based on the light transmittance (H 11} ) measured at the wavelength λ when the two polarizing films are overlapped so that the alignment direction is the same direction, and the two polarizing films are overlapped so that the alignment direction is In the state of mutually perpendicular directions, the light transmittance (H ₁ ) measured at the wavelength λ is used to calculate the degree of polarization according to the following formula. Polarization = [(H ₁₁ -H ₁ )/(H ₁₁ +H ₁ )] ^1/2

此外，本發明之偏光膜的單體透射率宜為42%以上，更宜為43%以上。若該單體透射率過低，則會有無法達成液晶顯示器之高亮度化之傾向。單體透射率係使用分光光度計測定偏光膜單體之光線透射率而得之值。In addition, the monomer transmittance of the polarizing film of the present invention is preferably 42% or more, more preferably 43% or more. If the transmittance of the monomer is too low, there is a tendency that the high brightness of the liquid crystal display cannot be achieved. The monomer transmittance is a value obtained by measuring the light transmittance of the polarizing film monomer using a spectrophotometer.

本發明之偏光膜適宜用於製造偏光度優良，無色彩不均勻之偏光板。此處，針對使用了本發明之偏光膜之偏光板的製造方法進行說明。The polarizing film of the present invention is suitable for manufacturing polarizing plates with excellent polarization and no color unevenness. Here, the manufacturing method of the polarizing plate using the polarizing film of this invention is demonstrated.

[偏光板之製造方法] 上述偏光板係藉由在本發明之偏光膜的單面或兩面，介隔黏著劑貼合光學上為等向性之樹脂薄膜作為保護薄膜來製作。就保護薄膜而言，可舉例如三乙酸纖維素、二乙酸纖維素、聚碳酸酯、聚甲基丙烯酸甲酯、環烯烴聚合物、環烯烴共聚物、聚苯乙烯、聚醚碸、聚亞芳基酯、聚-4-甲基戊烯、聚伸苯醚等之薄膜或片材。[Manufacturing method of polarizing plate] The above-mentioned polarizing plate is produced by bonding an optically isotropic resin film as a protective film on one or both sides of the polarizing film of the present invention via an adhesive. As for the protective film, for example, cellulose triacetate, cellulose diacetate, polycarbonate, polymethyl methacrylate, cyclic olefin polymer, cyclic olefin copolymer, polystyrene, polyether agglomerate, polyacrylic acid Film or sheet of aryl ester, poly-4-methylpentene, polyphenylene ether, etc.

貼合方法可藉由公知方法進行，例如將液狀之黏著劑組成物均勻地塗布於偏光膜、保護薄膜、或其兩者後，將兩者黏貼在一起並壓接，藉由加熱或照射活性能量射線來進行。The bonding method can be performed by a known method, such as uniformly coating a liquid adhesive composition on a polarizing film, a protective film, or both, and then sticking the two together and crimping, by heating or irradiating Active energy rays.

此外，也可於偏光膜之單面或兩面塗布胺甲酸酯(urethane)系樹脂、丙烯酸系樹脂、尿素樹脂等硬化性樹脂，並使其硬化形成硬化層而製成偏光板。藉由如此方式進行製作，則上述硬化層可替代上述保護薄膜，可達成薄膜化。In addition, it is also possible to apply a curable resin such as urethane resin, acrylic resin, or urea resin on one side or both sides of the polarizing film, and then harden it to form a hardened layer to form a polarizing plate. By manufacturing in this way, the hardened layer can replace the protective film, and the film can be made thinner.

使用了本發明之聚乙烯醇系薄膜之偏光膜或偏光板係偏光性能優良，可理想地使用於攜帶資訊終端設備、電腦、電視、投影機、看板、桌上型電子計算機、電子鐘、文書處理器、電子紙、遊戲機、錄放影機、相機、相框、溫度計、音響、汽車或機械類之儀表等液晶顯示裝置、太陽眼鏡、防眩光眼鏡、立體眼鏡、穿戴式顯示器、顯示元件(CRT、LCD、有機EL、電子紙等)用抗反射層、光纖通訊設備、醫療設備、建築材料、玩具等。 [實施例]The polarizing film or polarizing plate using the polyvinyl alcohol film of the present invention has excellent polarization performance, and can be ideally used to carry information terminal equipment, computers, TVs, projectors, signage, desktop computers, electronic clocks, and documents Processors, electronic paper, game consoles, video recorders, cameras, photo frames, thermometers, audio, automotive or mechanical instruments and other liquid crystal display devices, sunglasses, anti-glare glasses, stereo glasses, wearable displays, display components (CRT , LCD, organic EL, electronic paper, etc.) anti-reflection layer, optical fiber communication equipment, medical equipment, building materials, toys, etc. [Example]

以下列舉實施例來更具體地說明本發明，但本發明在不超過其要旨之情況下並不限定於以下之實施例。The following examples are given to explain the present invention more specifically, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

然後，以下之實施例及比較例中聚乙烯醇系薄膜之特性(聚乙烯醇系樹脂之溶出量、捲曲角度)及偏光膜之特性(偏光度、單體透射率、色彩不均勻)之測定及評價係如以下之方式來進行。Then, in the following examples and comparative examples, the characteristics of the polyvinyl alcohol-based film (the elution amount of the polyvinyl alcohol-based resin, the curl angle) and the characteristics of the polarized film (polarization, monomer transmittance, color unevenness) are measured And the evaluation is carried out in the following way.

＜測定條件＞ [聚乙烯醇系樹脂之溶出量(ppm/m² )] 將獲得之聚乙烯醇系薄膜以23℃、50%RH調濕24小時後，切出100mm×100mm(0.01m² )的試驗片(上述第2試驗片)，浸漬於1L之50℃離子交換水中1分鐘來獲得溶出液。在室溫(25℃)於該溶出液10mL中混合發色試藥(離子交換水500g、碘化鉀7.4g、碘0.65g、硼酸10.6g)10mL後，使用分光光度計(島津製作所公司製：UV-3100PC)測定波長690nm之吸光度，從預先作成之檢量線算出聚乙烯醇系樹脂之濃度(ppm)，並藉由面積換算獲得溶出量(ppm/m² )。以如上述同樣的方式來求得浸漬於30℃、2分鐘之情況的溶出量(ppm/m² )。<Measurement conditions> [Dissolution of polyvinyl alcohol resin (ppm/m ² )] The obtained polyvinyl alcohol film is humidified at 23°C and 50% RH for 24 hours, and then cut out 100mm×100mm (0.01m ² ) The test piece (the above-mentioned second test piece) was immersed in 1 L of ion-exchanged water at 50°C for 1 minute to obtain an eluate. At room temperature (25°C), 10 mL of the color reagent (500 g of ion-exchanged water, 7.4 g of potassium iodide, 0.65 g of iodine, and 10.6 g of boric acid) was mixed with 10 mL of the eluate, and then a spectrophotometer (manufactured by Shimadzu Corporation: UV -3100PC) Measure the absorbance at a wavelength of 690nm, calculate the concentration (ppm) of the polyvinyl alcohol resin from the calibration curve created in advance, and obtain the elution amount (ppm/m ² ) by area conversion. ^{The elution amount (ppm/m 2} ) when immersed at 30°C for 2 minutes was determined in the same manner as described above.

[捲曲角度(°)] 從獲得之聚乙烯醇系薄膜切出長邊10cm×短邊5cm之試驗片(上述第1試驗片)。此時，令該試驗片之長邊為上述薄膜之長度方向(MD方向)，短邊為上述薄膜之寬度方向(TD方向)。然後，如圖2(a)所示，以(第1)夾具(KOKUYO製「極小圓孔鋼夾」；夾寬20mm；質量2.1g)2a夾住上述試驗片1之長邊方向下端緣部之中央，並將金屬線2b捲繞於該夾具2a。以此等夾具2a及金屬線2b作為總質量5g之重物2，製作由上述試驗片1及重物2構成之試驗體。之後，以(第2)夾具(同上)3a夾住上述試驗片1之長邊方向的上端緣部的中央，並於該夾具3a綁上線3b(將由夾具3a及線3b構成之懸吊治具3設置於上述試驗片1之長邊方向上端緣部之中央部)。然後，在將附有上述夾具3a之試驗體以上述線3b懸吊之狀態下，將該試驗體全體浸漬於水槽4内之30℃的水4a中。然後，如圖2(b)所示，從水槽4(於圖中未表示)之上部以目視觀察從該浸漬算起經過10秒鐘之時間點及經過2分鐘之時間點之短邊方向(寬度方向)的捲曲角度α(°)。其中，在圖2(b)中，為了容易了解其構成而未以圖示表示上述重物2、懸吊治具3及水槽4。此外，上述捲曲角度α係上述試驗片1之平面部分與上述短邊方向之已捲曲之部分的端緣部之切線方向所形成的夾角。[Curl angle (°)] From the obtained polyvinyl alcohol-based film, a test piece (the above-mentioned first test piece) of 10 cm long side×5 cm short side was cut out. At this time, let the long side of the test piece be the length direction (MD direction) of the above-mentioned film, and let the short side be the width direction (TD direction) of the above-mentioned film. Then, as shown in Fig. 2(a), clamp the lower end edge of the test piece 1 in the longitudinal direction with (1) clamp (KOKUYO "extremely small round hole steel clamp"; clamp width 20mm; mass 2.1g) 2a In the center, the wire 2b is wound around the clamp 2a. Using the jig 2a and the metal wire 2b as the weight 2 with a total mass of 5 g, a test body composed of the above-mentioned test piece 1 and the weight 2 was produced. After that, clamp the center of the upper end edge of the test piece 1 in the longitudinal direction with the (second) clamp (same as above) 3a, and tie a wire 3b to the clamp 3a (a suspension fixture composed of the clamp 3a and the wire 3b) 3 Set at the center of the upper edge of the test piece 1 in the longitudinal direction). Then, in a state where the test body with the jig 3a is suspended by the wire 3b, the entire test body is immersed in the water 4a at 30°C in the water tank 4. Then, as shown in Figure 2(b), visually observe the short side direction ( Width direction) curl angle α (°). However, in FIG. 2(b), in order to make it easy to understand the structure, the said weight 2, the suspension jig 3, and the water tank 4 are not shown in the figure. In addition, the curl angle α is the angle formed by the tangential direction between the flat portion of the test piece 1 and the end edge of the curled portion in the short-side direction.

[偏光度(%)、單體透射率(%)] 從獲得之偏光膜的寬度方向(TD方向)的中央部及兩側端部(係從偏光膜之兩側端之各端算起內側10cm)切出長度4cm×寬度4cm之試驗片，使用自動偏光薄膜測定裝置(日本分光公司製：VAP7070)測定偏光度(%)及單體透射率(%)。對於偏光膜之長度方向(MD方向)之中央部及前端部/末端部(偏光膜之前端及末端之從各端算起內側10m)進行該測定。[Polarization (%), monomer transmittance (%)] Cut out a test piece of length 4cm×width 4cm from the center part in the width direction (TD direction) of the obtained polarizing film and both side ends (10cm inside from each end of the polarizing film). Use automatic A polarizing film measuring device (manufactured by JASCO Corporation: VAP7070) measures the degree of polarization (%) and monomer transmittance (%). This measurement was performed about the center part and the front end/end part of the longitudinal direction (MD direction) of the polarizing film (the inner side 10m from each end of the front end and the end of the polarizing film) of a polarizing film.

[色彩不均勻] 從獲得之偏光膜的寬度方向(TD方向)之中央部及兩側端部(係從偏光膜之兩側端之各端算起內側10cm)切出長度30cm×寬度30cm之試驗片，以45°之角度夾在正交偏光狀態之2片偏光板(單體透射率43.5%、偏光度99.9%)之間，使用表面照度14,000勒克司(lx)之燈箱，以透射模式觀察光學性的色彩不均勻，並藉由以下之基準進行評價。該測定係對於偏光膜之長度方向(MD方向)之中央部及前端部/末端部(係從偏光膜之兩側端的各端算起內側10m)進行。 (評價基準) ○･･･沒有色彩不均勻。 ×･･･有色彩不均勻。對於偏光膜之長度方向(MD方向)之中央部及前端部/末端部(係從偏光膜之前端及末端之各端算起內側10m)進行該評價。[Uneven color] Cut out a test piece of length 30cm×width 30cm from the center part and both side ends of the obtained polarizing film in the width direction (TD direction) (10cm inside from each end of the polarizing film). The angle of ° is sandwiched between two polarizing plates (transmittance of single unit 43.5%, degree of polarization 99.9%) in orthogonal polarization state, using a light box with surface illuminance of 14,000 lux (lx) to observe optical colors in transmission mode Non-uniformity is evaluated based on the following criteria. This measurement was performed with respect to the center part and the front end/end part of the longitudinal direction (MD direction) of the polarizing film (10 m inside from each end of the both ends of the polarizing film). (Evaluation criteria) ○･･･There is no color unevenness. ×･･･There is uneven color. This evaluation was performed on the center part and the front end/end (10m inside from each of the front end and the end of the polarizing film) in the longitudinal direction (MD direction) of the polarizing film.

＜實施例1＞(聚乙烯醇系薄膜之製作) 加入重量平均分子量142,000，皂化度99.8莫耳%之聚乙烯醇系樹脂2,000kg、水5,000kg、作為塑化劑之甘油220kg，邊攪拌邊昇溫至140℃進行加壓溶解後，進行濃度調整將樹脂濃度調整至25重量%，獲得均勻溶解之聚乙烯醇系樹脂水溶液。然後，將上述聚乙烯醇系樹脂水溶液供給至具有通氣孔之雙軸擠製機進行消泡後，將水溶液溫度設為95℃，從T型縫模排出口排出(排出速度2.5m/分)且流延至旋轉之澆鑄鼓(表面溫度92℃)來進行製膜。將該製膜而得之薄膜從澆鑄鼓剝離，邊使該薄膜之正面及背面(與澆鑄鼓之接觸面)交替地與合計15根熱輥接觸邊進行乾燥。乾燥條件[參照上述式(1)~(3)]如同下述表1所示。然後，使用浮動式乾燥器，從上述剝離而得之薄膜的兩面吹送120℃之熱風進行熱處理，獲得厚度60μm的聚乙烯醇系薄膜。最後，藉由將該聚乙烯醇系薄膜之寬度方向(TD方向)之兩端部切開並捲繞於芯管成為輥狀，獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：寬度5m、長度5km)。<Example 1> (Production of polyvinyl alcohol film) Add 2,000 kg of polyvinyl alcohol resin with a weight average molecular weight of 142,000 and a degree of saponification of 99.8 mol%, 5,000 kg of water, and 220 kg of glycerin as a plasticizer. The mixture is heated to 140°C while stirring and dissolved under pressure, and then the concentration is adjusted. The resin concentration was adjusted to 25% by weight to obtain a uniformly dissolved aqueous polyvinyl alcohol resin solution. Then, the above-mentioned polyvinyl alcohol-based resin aqueous solution was supplied to a biaxial extruder with vent holes for defoaming, and the temperature of the aqueous solution was set to 95°C and discharged from the T-slot die outlet (discharge speed 2.5m/min) And cast to a rotating casting drum (surface temperature 92°C) to form a film. The film obtained by forming the film was peeled from the casting drum, and the front and back surfaces (contact surfaces with the casting drum) of the film were alternately contacted with a total of 15 hot rolls, and dried. The drying conditions [refer to the above formulas (1) to (3)] are as shown in Table 1 below. Then, using a floating dryer, hot air at 120° C. was blown from both sides of the film obtained by the above peeling, and heat treatment was performed to obtain a polyvinyl alcohol-based film with a thickness of 60 μm. Finally, the both ends of the polyvinyl alcohol-based film in the width direction (TD direction) were cut and wound on the core tube into a roll shape to obtain a film winding body (the size of the polyvinyl alcohol-based film: width 5m, Length 5km).

(聚乙烯醇系薄膜之保存) 然後，將上述薄膜捲繞體以水蒸氣阻隔薄膜捲繞2層進行包裝，獲得包裝體。使用了鋁蒸鍍聚酯薄膜(蒸鍍鋁50nm而得之聚對苯二甲酸乙二酯薄膜、12μm厚)及聚乙烯薄膜(25μm厚)之疊層薄膜作為上述水蒸氣阻隔薄膜。然後，將上述包裝體保存於環境溫度26℃之輥貯藏庫15天。保存後之聚乙烯醇系薄膜的特性如下述表1所示。(Preservation of polyvinyl alcohol film) Then, the above-mentioned film wound body was wrapped in two layers with a water vapor barrier film to obtain a packaged body. A laminated film of an aluminum vapor-deposited polyester film (a polyethylene terephthalate film obtained by vapor deposition of aluminum 50 nm, 12 μm thickness) and a polyethylene film (25 μm thickness) was used as the water vapor barrier film. Then, the package was stored in a roll storage room at an ambient temperature of 26°C for 15 days. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below.

(偏光膜之製造) 將獲得之上述聚乙烯醇系薄膜從上述薄膜捲繞體拉出，使用運送輥沿水平方向進行運送，首先，邊浸漬於水溫30℃之水槽使其膨潤邊以2分鐘沿流動方向(MD方向)延伸為1.7倍。然後，邊浸漬於由碘0.5g/L、碘化鉀30g/L構成之28℃之水溶液中進行染色邊以0.5分鐘沿流動方向(MD方向)延伸為1.6倍，然後邊浸漬於由硼酸40g/L、碘化鉀30g/L構成之50℃之水溶液中進行硼酸交聯邊以1分鐘沿流動方向(MD方向)進行單軸延伸，延伸為2.1倍。最後以碘化鉀水溶液進行清洗，以50℃乾燥2分鐘進行乾燥而獲得總延伸倍率5.8倍之偏光膜。獲得之偏光膜的特性如下述表2所示。(Manufacturing of Polarizing Film) The obtained polyvinyl alcohol-based film was pulled out from the film winding body and transported in the horizontal direction using a transport roller. First, it was immersed in a water tank with a water temperature of 30°C and swelled in the flow direction for 2 minutes (MD Direction) extension is 1.7 times. Then, while immersing in a 28°C aqueous solution composed of 0.5 g/L of iodine and 30 g/L of potassium iodide, dyeing was carried out while extending 1.6 times in the flow direction (MD direction) for 0.5 minutes, and then immersed in 40 g/L of boric acid. , Boric acid cross-linking in a 50°C aqueous solution composed of 30g/L of potassium iodide is carried out uniaxially in the flow direction (MD direction) for 1 minute, and the extension is 2.1 times. Finally, it was washed with a potassium iodide aqueous solution, and dried at 50° C. for 2 minutes to obtain a polarizing film with a total stretching ratio of 5.8 times. The characteristics of the obtained polarizing film are shown in Table 2 below.

＜實施例2＞以下述表1所示之條件進行製造，除此以外，以與實施例1同樣之方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度60μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性如下述表1所示。再與實施例1同樣地獲得偏光膜。獲得之偏光膜的特性如下述表2所示。<Example 2> The production was carried out under the conditions shown in Table 1 below, except that the film roll was obtained in the same manner as in Example 1 (dimensions of the polyvinyl alcohol-based film: thickness 60 μm, width 5 m, and length 5 km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. In the same manner as in Example 1, a polarizing film was obtained. The characteristics of the obtained polarizing film are shown in Table 2 below.

＜實施例3＞在實施例1中，將排出速度2.5m/分改為1.9m/分，且以下述表1所示之條件進行製造，除此以外，以與實施例1同樣方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度45μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性表示於下述表1。再以與實施例1同樣的方式來獲得偏光膜。獲得之偏光膜的特性表示於下述表2。<Example 3> In Example 1, the discharge speed was changed from 2.5 m/min to 1.9 m/min, and the production was performed under the conditions shown in Table 1 below. Except for this, the film wound body was obtained in the same manner as in Example 1 ( The size of the polyvinyl alcohol film: thickness 45μm, width 5m, length 5km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. In the same manner as in Example 1, a polarizing film was obtained. The characteristics of the obtained polarizing film are shown in Table 2 below.

＜實施例4＞在實施例1中，將排出速度2.5m/分改為1.3m/分，且以下述表1所示之條件進行製造，除此以外，以與實施例1同樣方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度30μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性表示於下述表1。再以與實施例1同樣的方式來獲得偏光膜。獲得之偏光膜的特性表示於下述表2。<Example 4> In Example 1, the discharge speed was changed from 2.5 m/min to 1.3 m/min, and the production was carried out under the conditions shown in Table 1 below, except that the film wound body was obtained in the same manner as in Example 1 ( The size of the polyvinyl alcohol film: thickness 30μm, width 5m, length 5km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. In the same manner as in Example 1, a polarizing film was obtained. The characteristics of the obtained polarizing film are shown in Table 2 below.

＜比較例1＞以下述表1所示之條件進行製造，除此以外，以與實施例1同樣方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度60μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性表示於下述表1。再以與實施例1同樣的方式來獲得偏光膜。獲得之偏光膜的特性表示於下述表2。其中，在製造偏光膜後，以目視確認硼酸交聯槽的藥液時發現有白色混濁，並於藥液之循環過濾器產生堵塞。<Comparative example 1> It was manufactured under the conditions shown in Table 1 below, except that a film roll (size of a polyvinyl alcohol-based film: thickness 60 μm, width 5 m, and length 5 km) was obtained in the same manner as in Example 1 except for this. The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. In the same manner as in Example 1, a polarizing film was obtained. The characteristics of the obtained polarizing film are shown in Table 2 below. Among them, after the production of the polarizing film, when the chemical solution in the boric acid cross-linking tank was visually confirmed, white turbidity was found, and clogging occurred in the circulation filter of the chemical solution.

＜比較例2＞(相當於上述專利文獻3之實施例1) 在實施例1中，將排出速度2.5m/分改為1.9m/分，並以下述表1所示之條件進行製造，除此以外，以與實施例1同樣之方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度45μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性如下述表1所示。再以與實施例1同樣的方式開始製造偏光膜，但在膨潤步驟中於薄膜端部產生彎折而停止製造。獲得之偏光膜部分(前端部)的特性如下述表2所示。<Comparative Example 2> (equivalent to Example 1 of Patent Document 3 above) In Example 1, the discharge speed was changed from 2.5 m/min to 1.9 m/min, and the production was carried out under the conditions shown in Table 1 below. Except for this, the film wound body was obtained in the same manner as in Example 1. (Size of polyvinyl alcohol film: thickness 45μm, width 5m, length 5km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. Further, the production of the polarizing film was started in the same manner as in Example 1, but the end of the film was bent in the swelling step, and the production was stopped. The characteristics of the obtained polarizing film portion (tip portion) are shown in Table 2 below.

＜比較例3＞在實施例1中，將排出速度2.5m/分改為1.3m/分，並以下述表1所示之條件進行製造，除此以外，以與實施例1同樣的方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度30μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性如下述表1所示。欲再以與實施例1同樣的方式來製造偏光膜，但在膨潤步驟中於薄膜端部產生彎折，接著在延伸步驟產生破裂，故無法獲得偏光膜。＜Comparative example 3＞ In Example 1, the discharge speed was changed from 2.5 m/min to 1.3 m/min, and the production was carried out under the conditions shown in Table 1 below. Except for this, the film wound body was obtained in the same manner as in Example 1. (Size of polyvinyl alcohol film: thickness 30μm, width 5m, length 5km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. I tried to manufacture a polarizing film again in the same manner as in Example 1, but the film edge was bent in the swelling step, and then cracked in the stretching step, so the polarizing film could not be obtained.

＜比較例4＞在實施例1中，將排出速度2.5m/分改為2.1m/分，並使用合計18根之熱輥以下述表1所示之條件進行製造，除此以外，以與實施例1同樣的方式來獲得薄膜捲繞體(聚乙烯醇系薄膜之尺寸：厚度50μm、寬度5m、長度5km)。再以與實施例1同樣的方式來保存該薄膜捲繞體。保存後之聚乙烯醇系薄膜的特性如下述表1所示。欲再以與實施例1同樣的方式來製造偏光膜，但在膨潤步驟中於薄膜端部產生彎折，接著於延伸步驟產生破裂，故無法獲得偏光膜。<Comparative Example 4> In Example 1, the discharge speed was changed from 2.5 m/min to 2.1 m/min, and a total of 18 hot rolls were used to manufacture under the conditions shown in Table 1 below. Except for this, the same as in Example 1 Method to obtain a film roll (size of a polyvinyl alcohol-based film: thickness 50μm, width 5m, length 5km). The film wound body was stored in the same manner as in Example 1. The characteristics of the polyvinyl alcohol-based film after storage are shown in Table 1 below. I tried to manufacture a polarizing film in the same manner as in Example 1, but the film edge was bent in the swelling step, and then cracked in the stretching step, so the polarizing film could not be obtained.

【表1】

【Table 1】

【表2】

【Table 2】

實施例1~4的聚乙烯醇系薄膜，其溶於水之樹脂溶出量及水浸漬時之捲曲角度在本發明之特定的範圍內，故可獲得生產性良好、偏光性能優良且無色彩不均勻之偏光膜。相對於此，可知比較例1之聚乙烯醇系薄膜，其溶於水之樹脂溶出量在本發明之特定的範圍外，故獲得之偏光膜係偏光性能低劣，且有色彩不均勻。此外，比較例2~4之聚乙烯醇系薄膜，其水浸漬時之捲曲角度在本發明之特定的範圍外，故無法獲得寬長型之偏光膜。For the polyvinyl alcohol films of Examples 1 to 4, the amount of resin eluted in water and the curl angle during water immersion are within the specified range of the present invention. Therefore, it is possible to obtain good productivity, excellent polarization performance, and no color or discoloration. Uniform polarizing film. In contrast, it can be seen that the polyvinyl alcohol film of Comparative Example 1 has a water-soluble resin elution amount outside the specified range of the present invention, so the obtained polarizing film has poor polarization performance and uneven color. In addition, the polyvinyl alcohol-based films of Comparative Examples 2 to 4 had a curl angle during water immersion outside the specific range of the present invention, so a wide and long polarizing film could not be obtained.

在上述實施例中，係針對本發明之具體的形態予以展示，但上述實施例僅為單純之示例，並沒有限定的含意。對該技術領域中具有通常知識者而言顯而易見之各種變化，均意欲包括於本發明之範圍內。 [產業上利用性]In the above-mentioned embodiment, the specific form of the present invention is shown, but the above-mentioned embodiment is only a mere example and does not have a limiting meaning. Various changes that are obvious to those having ordinary knowledge in the technical field are all intended to be included in the scope of the present invention. [Industrial availability]

使用了本發明之聚乙烯醇系薄膜而得之偏光膜或偏光板係偏光性能優良，可理想地使用於攜帶資訊終端設備、電腦、電視、投影機、看板、桌上型電子計算機、電子鐘、文書處理器、電子紙、遊戲機、錄放影機、相機、相框、溫度計、音響、汽車或機械類之儀表等液晶顯示裝置、太陽眼鏡、防眩光眼鏡、立體眼鏡、穿戴式顯示器、顯示元件(CRT、LCD、有機EL、電子紙等)用抗反射層、光纖通訊設備、醫療設備、建築材料、玩具等。The polarizing film or polarizing plate obtained by using the polyvinyl alcohol-based film of the present invention has excellent polarization performance, and can be ideally used to carry information terminal equipment, computers, televisions, projectors, billboards, desktop computers, and electronic clocks. , Word processors, electronic paper, game consoles, video recorders, cameras, photo frames, thermometers, audio, automotive or mechanical instruments and other liquid crystal display devices, sunglasses, anti-glare glasses, stereo glasses, wearable displays, display components (CRT, LCD, organic EL, electronic paper, etc.) anti-reflection coatings, optical fiber communication equipment, medical equipment, building materials, toys, etc.

C:T型縫模 D:澆鑄鼓 E:自由輥 F:薄膜 R1~R7:熱輥 1:試驗片 2:重物 2a:夾具 2b:金屬線 3:懸吊治具 3a:夾具 3b:線 4:水槽 4a:水 α:捲曲角度C: T-shaped seam die D: Casting drum E: Free roll F: Film R1~R7: hot roller 1: Test piece 2: heavy objects 2a: Fixture 2b: Metal wire 3: Suspension fixture 3a: Fixture 3b: line 4: sink 4a: water α: curl angle

[圖1]為示意性地展示使製膜而得之薄膜與金屬製加熱輥接觸來使其乾燥之方法的說明圖。 [圖2](a)係示意性地展示捲曲角度之測定條件的說明圖，(b)係展示捲曲角度的說明圖。Fig. 1 is an explanatory diagram schematically showing a method of bringing a thin film obtained by forming a film into contact with a metal heating roller to dry it. [Fig. 2] (a) is an explanatory diagram schematically showing the measurement conditions of the curl angle, and (b) is an explanatory diagram showing the curl angle.

Claims

一種聚乙烯醇系薄膜，係厚度20~60μm，長度5km以上，寬度4m以上之聚乙烯醇系薄膜，其特徵在於：該聚乙烯醇系薄膜浸漬在50℃之水中1分鐘時之聚乙烯醇系樹脂的溶出量為900ppm/m² 以下，且以下述A之條件測得之短邊方向的捲曲角度為135°以下； (A)條件，係將具備從該聚乙烯醇系薄膜以任意方向切出之長邊10cm×短邊5cm之長方形的試驗片以及設置於該試驗片之長邊方向之第1端緣部的中央之質量5g之重物的試驗體，於以該試驗片之長邊方向之第2端緣部的中央部分懸掛支撐的狀態下，將該試驗體全體浸漬於30℃的水中10秒鐘。A polyvinyl alcohol-based film, a polyvinyl alcohol-based film with a thickness of 20-60μm, a length of 5km or more, and a width of 4m or more, characterized in that the polyvinyl alcohol-based film is immersed in water at 50°C for 1 minute. The elution amount of the resin is 900ppm/m ² or less, and the curl angle in the short-side direction measured under the following conditions A is 135° or less; (A) The condition is that the polyvinyl alcohol-based film will be able to move in any direction from the polyvinyl alcohol-based film. Cut out a rectangular test piece with a long side of 10 cm × a short side of 5 cm and a test body with a weight of 5 g placed in the center of the first end edge of the test piece in the longitudinal direction. With the central portion of the second end edge portion in the side direction suspended and supported, the entire test body was immersed in water at 30°C for 10 seconds.

如請求項1之聚乙烯醇系薄膜，其中，在該A之條件中，將該試驗體之浸漬時間設為2分鐘時，測得之短邊方向的捲曲角度為40°以下。The polyvinyl alcohol-based film of claim 1, wherein, in the condition of the A, when the immersion time of the test body is set to 2 minutes, the measured curl angle in the short-side direction is 40° or less.

如請求項1或2之聚乙烯醇系薄膜，其中，該聚乙烯醇系薄膜係長條之薄膜，該試驗片之長邊係該薄膜之長度方向，短邊係該薄膜之寬度方向。The polyvinyl alcohol-based film of claim 1 or 2, wherein the polyvinyl alcohol-based film is a long film, the long side of the test piece is the length direction of the film, and the short side is the width direction of the film.

如請求項1或2之聚乙烯醇系薄膜，其中，該聚乙烯醇系薄膜浸漬於30℃之水中2分鐘時之聚乙烯醇系樹脂的溶出量係50ppm/m² 以下。The polyvinyl alcohol-based film of claim 1 or 2, wherein the polyvinyl alcohol-based film has an elution amount of 50 ppm/m ² or less when the polyvinyl alcohol-based film is immersed in water at 30°C for 2 minutes.