JP5125176B2 - Biaxially oriented polyester film for polarizing plate release film and method for producing the same - Google Patents
Biaxially oriented polyester film for polarizing plate release film and method for producing the same Download PDFInfo
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本発明は、液晶表示用途等の部材において、光学特性に優れた偏光板に好適に用いられる偏光板離型フィルム用二軸配向ポリエステルフィルム、およびその製造方法に関するものである。詳しくは、１５０℃３０分間の条件で熱処理したのちのフィルム長手方向およびフィルム幅方向の熱収縮率がそれぞれ５〜７％、７〜９％であり、フィルム幅方向に対する配向主軸の傾き（配向角）が少なくとも５ｍ幅にわたって５度以下である偏光板離型フィルム用二軸配向ポリエステルフィルムおよびその製造方法に関するものである。 The present invention relates to a biaxially oriented polyester film for a polarizing plate release film that is suitably used for a polarizing plate having excellent optical properties in a member for liquid crystal display applications and the like, and a method for producing the same. Specifically, the thermal contraction rates in the film longitudinal direction and the film width direction after heat treatment at 150 ° C. for 30 minutes are 5 to 7% and 7 to 9%, respectively, and the inclination of the orientation main axis with respect to the film width direction (alignment angle) ) Is a biaxially oriented polyester film for polarizing plate release film having a width of at least 5 m or less and a method for producing the same.
近年、従来のディスプレイであるＣＲＴに比べ薄型軽量化、低消費電力、高画質化の利点を有する液晶ディスプレイ（ＬＣＤ）の需要が急速に伸びつつあり、特に１９インチ以上の大画面モニターや３２インチといった大画面ＴＶ用途のＬＣＤが急速に伸びている。ＬＣＤの大画面化に伴って、バックライトの輝度を上げることや、輝度を向上させる機能性フィルムを組み込むことなどにより、大画面でも輝度を十分確保したＬＣＤとする場合が多い。このような高輝度タイプのＬＣＤでは、輝度が高いゆえにディスプレイ中に存在する小さな欠点が問題となる場合が多く、偏光板、位相差板といった構成部材においては、これまでのＬＣＤでは問題にならなかったようなサイズの異物が問題となってきている。そのため、各部材の製造工程における異物の混入を防ぐ一方で、異物が混入したとしても欠点として確実に認知できるような検査性の向上も重要となってきている。
偏光板の欠点検査はクロスニコル法による目視検査が一般的であるが、３２インチといった大画面ＴＶ用に使用する偏光板では、クロスニコル法を利用した自動異物検査器による検査も実施されつつある。
In recent years, the demand for liquid crystal displays (LCDs), which have the advantages of being thinner and lighter, lower power consumption, and higher image quality than the conventional display CRT, is growing rapidly, especially for large screen monitors of 19 inches or more and 32 inches. LCDs for large-screen TV applications are growing rapidly. In many cases, the LCD has a sufficiently large brightness even on a large screen by increasing the brightness of the backlight or incorporating a functional film for improving the brightness as the LCD becomes larger. In such a high-brightness type LCD, since the brightness is high, small defects present in the display are often problematic, and components such as polarizing plates and retardation plates are not a problem with conventional LCDs. The size of foreign objects is becoming a problem. Therefore, while preventing foreign matters from being mixed in the manufacturing process of each member, it is also important to improve inspection properties so that even if foreign matter is mixed, it can be recognized as a defect.
The defect inspection of the polarizing plate is generally a visual inspection by the crossed Nicol method, but the polarizing plate used for a large screen TV of 32 inches is also being inspected by an automatic foreign object inspection device using the crossed Nicol method. .
このクロスニコル法は２枚の偏光板をその配向主軸を直交させて暗視野をつくり、その間に測定対象品を挟んで透過光で観察する方法である。偏光板中に異物や欠点があれば輝点として現れるので、欠点検査ができるというものである。ここで、偏光板には粘着剤層を介して二軸配向ポリエステルフィルムを離型フィルムとして貼り合わせているので、この離型フィルムの光学的異方性が加わることで偏光板から光漏れが生じ、クロスニコル法の検査の障害となり、異物の混入や欠点を見逃しやすくなるという不具合が生じている。そこで、偏光板離型フィルムの光学特性を検討し、光漏れを防ぐために配向角を特定値以下とすることが好ましいという提案が特許文献１にて例示されており、製造されるフィルム幅の中央部２０％程度のみを用いるのが好ましいとされている。通常の二軸延伸法、すなわち縦延伸につづいてテンターによる横延伸を行う方法においては、製品フィルムの幅方向の物性を均一にすることは極めて困難であり、テンター内で横延伸した後に行う熱処理工程において生じるボーイング現象が原因となっている。このボーイング現象はフィルム長手方向におけるポアソン比に基づく収縮率および熱収縮力などに起因して発生するものと考えられており、このボーイング現象がフィルムの幅方向の物性、特に配向角分布などの光学特性、機械的特性、温度膨張率、熱膨張率あるいは熱収縮率を不均一にする原因となっている。ここで配向角とは、フィルム幅方向に対する配向主軸の傾きである。 The crossed Nicols method is a method in which two polarizing plates are made to have a dark field with their orientation principal axes orthogonal, and a product to be measured is sandwiched between them to observe with transmitted light. If there are foreign matters or defects in the polarizing plate, they will appear as bright spots, so that the defect inspection can be performed. Here, since a biaxially oriented polyester film is bonded as a release film to the polarizing plate through an adhesive layer, light leakage occurs from the polarizing plate due to the optical anisotropy of the release film. Therefore, there is an inconvenience that it becomes an obstacle to the inspection of the crossed Nicols method, and it becomes easy to overlook foreign matters and defects. Then, the optical characteristic of a polarizing plate release film is examined and the proposal that it is preferable to make an orientation angle below a specific value in order to prevent light leakage is illustrated by patent document 1, and the center of the film width manufactured is shown. It is considered preferable to use only about 20%. In the normal biaxial stretching method, that is, the method of performing transverse stretching by a tenter following longitudinal stretching, it is extremely difficult to make the physical properties in the width direction of the product film uniform, and heat treatment performed after transverse stretching in the tenter This is due to the bowing phenomenon that occurs in the process. This bowing phenomenon is thought to occur due to shrinkage based on the Poisson's ratio in the longitudinal direction of the film and the heat shrinkage force. This bowing phenomenon is an optical property such as physical properties in the width direction of the film, especially orientation angle distribution. This causes non-uniformity in characteristics, mechanical characteristics, temperature expansion coefficient, thermal expansion coefficient, or thermal contraction ratio. Here, the orientation angle is the inclination of the orientation main axis with respect to the film width direction.
このボーイング現象を抑制するためのいくつかの提案がなされている。たとえば、特許文献２には、長手方向の延伸が完了する前に幅方向の延伸の７０％の完了させる方法、特許文献３には熱固定領域中に冷却領域と加熱領域とを隣接させる方法、特許文献４にはテンターにて横延伸すると同時に長手方向の弛緩処理させる方法が提案されている。
特許文献１では製造されるフィルム幅の中央部２０％程度のみを用いており、生産収率を低下させて製造していた。特許文献２の製造方法では、テンター内部を０．１秒程度で通過してしまう冷却工程であるため、フィルム温度が目的とするガラス転移温度以下に到達せず、ボーイング現象を十分に抑制する効果が得られない。また、得られたフィルム幅も９５０ｍｍと狭いため、偏光板に好適に用いられる偏光板離型フィルム用二軸配向ポリエステルフィルムを少なくとも５ｍ幅にわたって配向角を５度以下にして、製造するには適していない。特許文献３および特許文献４の製造方法でも、テンター内で冷却工程を設けており、フィルム温度を目的とするガラス転移温度以下に十分に冷却しているか示されていない。そのためボーイング現象を十分に抑制する効果が得られず、やはり目的とする配向角を得るには不十分である。 In Patent Document 1, only about 20% of the central part of the produced film width is used, and the production yield is lowered. In the manufacturing method of Patent Document 2, since the cooling process passes through the inside of the tenter in about 0.1 seconds, the film temperature does not reach below the target glass transition temperature, and the effect of sufficiently suppressing the bowing phenomenon. Cannot be obtained. Moreover, since the obtained film width is also as narrow as 950 mm, it is suitable for manufacturing a biaxially oriented polyester film for polarizing plate release film suitably used for polarizing plates with an orientation angle of 5 degrees or less over at least 5 m width. Not. Also in the manufacturing methods of Patent Document 3 and Patent Document 4, a cooling step is provided in the tenter, and it is not shown whether the film temperature is sufficiently cooled below the target glass transition temperature. Therefore, the effect of sufficiently suppressing the bowing phenomenon cannot be obtained, and it is still insufficient for obtaining the target orientation angle.
そこで、本発明は上記した背景技術の課題を解消し、生産収率性を向上できる偏光板離型フィルム用二軸配向ポリエステルフィルムとその製造方法を提供することにある。 Then, this invention is providing the biaxially-oriented polyester film for polarizing plate release films which can eliminate the subject of the above-mentioned background art, and can improve production yield, and its manufacturing method.
上記課題を解決するために鋭意検討した結果、生産収率性を向上するため主として次の特性を有することで上記課題が解決できることを見いだし、本発明に至った。すなわち、本発明は１５０℃３０分間の条件で熱処理したのちのフィルム長手方向およびフィルム幅方向の熱収縮率がそれぞれ５〜７％、７〜９％であり、フィルム幅方向に対する配向主軸の傾き（配向角）が少なくとも５ｍ幅にわたって５度以下である偏光板離型フィルム用二軸配向ポリエステルフィルムであることを特徴とする。 As a result of intensive studies to solve the above problems, it has been found that the above problems can be solved mainly by having the following characteristics in order to improve production yield, and the present invention has been achieved. That is, in the present invention, the thermal shrinkage rates in the film longitudinal direction and the film width direction after heat treatment at 150 ° C. for 30 minutes are 5 to 7% and 7 to 9%, respectively, and the inclination of the orientation main axis with respect to the film width direction ( It is a biaxially oriented polyester film for polarizing plate release film having an orientation angle) of 5 degrees or less over a width of at least 5 m.
また、本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムを製造するには、ボーイング現象を抑制するため熱処理する前にフィルム温度を十分に冷却する構成によって実現できることを見いだし、本発明に至った。すなわち、本発明は未延伸フィルムを縦方向に延伸し、次いで横方向に延伸し、冷却工程を経て熱処理して偏光板離型フィルム用二軸配向ポリエステルフィルムを製造する方法であって、冷却工程にてフィルム温度を２５〜４５℃に冷却したのち、熱処理する偏光板離型フィルム用二軸配向ポリエステルフィルムの製造方法であることを特徴とする。 Further, it has been found that the biaxially oriented polyester film for polarizing plate release film of the present invention can be realized by a configuration in which the film temperature is sufficiently cooled before heat treatment in order to suppress the bowing phenomenon, leading to the present invention. It was. That is, the present invention is a method for producing a biaxially oriented polyester film for polarizing plate release film by stretching an unstretched film in the longitudinal direction, then stretching in the transverse direction, and heat-treating through a cooling step, the cooling step After the film temperature is cooled to 25 to 45 ° C., it is a method for producing a biaxially oriented polyester film for polarizing plate release film that is heat-treated.
本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムは、二軸配向ポリエステルフィルムが有するフィルム幅方向に対する配向主軸の傾き（配向角）が少なくとも５ｍ幅にわたって５度以下という特性を有していることにより、偏光板の欠点検査に好適に用いることができ、生産収率性を向上することができるという効果を有する。 The biaxially oriented polyester film for polarizing plate release film of the present invention has a characteristic that the inclination (orientation angle) of the orientation main axis with respect to the film width direction of the biaxially oriented polyester film is 5 degrees or less over at least 5 m width. Therefore, it can be suitably used for defect inspection of the polarizing plate, and the production yield can be improved.
以下、本発明についてさらに詳細に説明する。本発明において好適に用いることのできるポリエステルは、分子配向により高強度フィルムとなるポリエステルであれば特に限定しないが、主としてポリエチレンテレフタレート、ポリエチレン−２，６−ナフタレートを含むことが好ましい。特に好ましくは価格的にも優位なポリエチレンテレフタレートである。ポリエチレンテレフタレートを用いる場合、エチレンテレフタレート以外のポリエステル共重合体成分としては、例えばジエチレングリコール、プロピレングリコール、ネオペンチルグリコール、ポリエチレングリコール、ｐ−キシリレングリコール、１，４−シクロヘキサンジメタノールなどのジオール成分、アジピン酸、セバシン酸、フタル酸、イソフタル酸、５−ナトリウムスルホイソフタル酸などのジカルボン成分、トリメリット酸、ピロメリット酸などの多官能ジカルボン酸成分、ｐ−オキシエトキシ安息香酸などが目的とするフィルム物性を阻害しない範囲で使用できる。かかるポリエステルは、例えば以下に示す方法で製造することができる。たとえば、酸成分をジオール成分と直接エステル化反応させた後、この反応の生成物を減圧下で加熱して余剰のジオール成分を除去しつつ重縮合させることによって製造する方法や、酸成分としてジアルキルエステルを用い、これとジオール成分とでエステル交換反応させた後、上記と同様にして重縮合させることによって製造する方法等がある。この際、必要に応じて、反応触媒として例えばアルカリ金属、アルカリ土類金属、マンガン、コバルト、亜鉛、アンチモン、ゲルマニウム、チタン化合物を用いることもできる。上記ポリエステルは、固有粘度が０．４〜０．９、好ましくは０．５〜０．７，さらに好ましくは０．５５〜０．６５である。 Hereinafter, the present invention will be described in more detail. The polyester that can be suitably used in the present invention is not particularly limited as long as it is a polyester that becomes a high-strength film by molecular orientation, but preferably mainly includes polyethylene terephthalate and polyethylene-2,6-naphthalate. Particularly preferred is polyethylene terephthalate which is superior in price. When polyethylene terephthalate is used, examples of polyester copolymer components other than ethylene terephthalate include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, and 1,4-cyclohexanedimethanol, adipine Film properties intended for dicarboxylic components such as acid, sebacic acid, phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, and p-oxyethoxybenzoic acid Can be used as long as they are not hindered. Such polyester can be produced, for example, by the method shown below. For example, a method in which an acid component is directly esterified with a diol component and then the product of this reaction is heated under reduced pressure to perform polycondensation while removing excess diol component, or a dialkyl as an acid component There is a method of producing an ester by transesterifying it with a diol component, followed by polycondensation in the same manner as described above. In this case, for example, an alkali metal, an alkaline earth metal, manganese, cobalt, zinc, antimony, germanium, or a titanium compound can be used as a reaction catalyst as necessary. The polyester has an intrinsic viscosity of 0.4 to 0.9, preferably 0.5 to 0.7, and more preferably 0.55 to 0.65.
本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムは、フィルム幅方向に対する配向主軸の傾き（配向角）が少なくとも５ｍ幅にわたって５度以下であるため、生産収率性を向上して製造することができる。ここでいう配向角は、全方位にわたってフィルムに超音波パルスを透過させ、その伝播速度を測定することによって配向性を評価し、配向主軸の傾き（配向角）を測定する。配向角が５度を超える場合には、偏光板を検査するクロスニコル法において偏光板から光漏れが生じ、検査の障害となる場合がある。
さらに、１５０℃３０分間の条件で熱処理したのちのフィルム長手方向およびフィルム幅方向の熱収縮率がそれぞれ５〜７％、７〜９％であることが好ましい。好ましくはそれぞれ５．５〜６．５％、７．５〜８．５％であり、熱収縮率がそれぞれ上記下限範囲を超える場合には、配向角が５度を超える場合がある。
The biaxially oriented polyester film for polarizing plate release film of the present invention is produced by improving the production yield because the inclination (orientation angle) of the orientation principal axis with respect to the film width direction is 5 degrees or less over at least 5 m width. be able to. The orientation angle here refers to the orientation (elongation angle) measured by transmitting the ultrasonic pulse through the film in all directions and measuring the propagation speed to evaluate the orientation. When the orientation angle exceeds 5 degrees, light leakage may occur from the polarizing plate in the crossed Nicol method for inspecting the polarizing plate, which may hinder the inspection.
Furthermore, it is preferable that the thermal contraction rates in the film longitudinal direction and the film width direction after heat treatment at 150 ° C. for 30 minutes are 5 to 7% and 7 to 9%, respectively. Preferably, they are 5.5 to 6.5% and 7.5 to 8.5%, respectively, and when the thermal shrinkage rate exceeds the lower limit range, the orientation angle may exceed 5 degrees.
本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムは、フィルム長手方向の厚みむらが０．５〜１．５μｍであることが肝要である。好ましくは０．５〜１．２μｍであり、厚みむらが１．５μｍを超える場合には、偏光板を検査するクロスニコル法において偏光板から漏れる光の強度のむらが強くなり、検査の障害となる場合がある。一方で、厚みむらが０．５μｍ以下のフィルムを製造することは難しい。 In the biaxially oriented polyester film for polarizing plate release film of the present invention, it is important that the thickness unevenness in the film longitudinal direction is 0.5 to 1.5 μm. Preferably, it is 0.5 to 1.2 μm, and when the thickness unevenness exceeds 1.5 μm, the unevenness of the intensity of light leaking from the polarizing plate in the crossed Nicol method for inspecting the polarizing plate becomes strong, which becomes an obstacle to inspection. There is a case. On the other hand, it is difficult to produce a film having a thickness unevenness of 0.5 μm or less.
本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムは、フィルムのヘイズ値が７〜１３％であることが好ましい。好ましくは８〜１２％、さらに好ましくは９〜１１％である。ヘイズ値が７％未満の場合には偏光板を検査する際に反射光が強すぎ、１３％を超える場合には反射光が弱く、検査の障害となる場合がある。 The biaxially oriented polyester film for polarizing plate release film of the present invention preferably has a haze value of 7 to 13%. Preferably it is 8-12%, More preferably, it is 9-11%. When the haze value is less than 7%, the reflected light is too strong when inspecting the polarizing plate, and when it exceeds 13%, the reflected light is weak, which may hinder the inspection.
また、本発明のフィルムの厚みは２５〜７０μｍ、好ましくは３０〜５０μｍ、さらに好ましくは３５〜４５μｍである。フィルムの厚みがこの範囲内にあると、フィルムのヘイズ値を上記範囲内で調整しやすく、好ましい。 Moreover, the thickness of the film of this invention is 25-70 micrometers, Preferably it is 30-50 micrometers, More preferably, it is 35-45 micrometers. When the thickness of the film is within this range, it is easy to adjust the haze value of the film within the above range, which is preferable.
さらに、本発明のフィルムの表面粗さＳＲａは２０〜３０ｎｍが好ましく、２２〜２８ｎｍがさらに好ましい。 Furthermore, the surface roughness SRa of the film of the present invention is preferably 20 to 30 nm, and more preferably 22 to 28 nm.
本発明のフィルムは単層であっても、２層以上からなる複合フィルムであってもよいが、フィルムのヘイズ値およびフィルムの表面粗さＳＲａを上記範囲にするには、３層複合フィルムからなる場合とくに好適である。この場合、両側の積層部の粒子種あるいは粒子含有量が異なる、Ａ／Ｂ／Ｃの構成でもよいが、同一の組成とするＡ／Ｂ／Ａの構成が設備的に簡易であり、生産性の面からも好ましい。さらに、両層の積層厚さを実質的に同一にした場合、品質の設計が容易である。 The film of the present invention may be a single layer or a composite film composed of two or more layers. However, in order to make the haze value of the film and the surface roughness SRa of the film within the above ranges, from the three-layer composite film This is particularly suitable. In this case, the A / B / C configuration in which the particle types or the particle contents of the laminated portions on both sides are different may be used, but the A / B / A configuration having the same composition is simple in terms of equipment and productivity. This is also preferable. Further, when the thickness of both layers is substantially the same, quality design is easy.
片面における積層厚さは、０．５〜２．５μｍが好ましく、とくに１．０〜２．０μｍが好ましい。 The lamination thickness on one side is preferably 0.5 to 2.5 μm, particularly preferably 1.0 to 2.0 μm.
さらに、積層面に不活性粒子を含有することで、表面粗さＳＲａを適正化でき、併せて、基層部に含有する粒子を適正化することでヘイズ値を所望の範囲とすることができる。 Furthermore, the surface roughness SRa can be optimized by including inert particles on the laminated surface, and the haze value can be adjusted to a desired range by optimizing the particles contained in the base layer portion.
粒子の種類としては、球状シリカ、ケイ酸アルミニウム、二酸化チタン、炭酸カルシウムなどの無機粒子、またその他有機系高分子粒子としては、架橋ポリスチレン樹脂粒子、架橋シリコーン樹脂粒子、架橋アクリル樹脂粒子、架橋スチレン−アクリル樹脂粒子、架橋ポリエステル粒子、ポリイミド粒子、メラミン樹脂粒子等が好ましい。これらの１種もしくは２種以上を選択して用いることもできる。 The types of particles are inorganic particles such as spherical silica, aluminum silicate, titanium dioxide, calcium carbonate, and other organic polymer particles include crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, and crosslinked styrene. -Acrylic resin particles, crosslinked polyester particles, polyimide particles, melamine resin particles and the like are preferable. These 1 type (s) or 2 or more types can also be selected and used.
これらの不活性粒子は、ポリエステル重合工程の段階で添加することにより、不活性粒子含有ポリマーを準備することができる。例えば、ポリエステルのグリコール成分であるエチレングリコールのスラリーとし、重縮合前のエステル交換後、あるいはエステル化後のオリゴマーの段階で不活性粒子含有スラリーを添加し、引き続き、重縮合反応を行うことで、不活性粒子含有ポリマーを得ることができる。 These inert particles can be added at the stage of the polyester polymerization process to prepare an inert particle-containing polymer. For example, by making a slurry of ethylene glycol, which is a glycol component of polyester, adding an inert particle-containing slurry after transesterification before polycondensation or at the oligomer stage after esterification, and subsequently performing a polycondensation reaction, An inert particle-containing polymer can be obtained.
また、添加前の不活性粒子のスラリーは必要に応じ、サンドグラインダー等による分散処理、遠心沈降処理による粗大粒子の分離あるいは、高精度濾過を行うことが、粒径分布を均一化でき、粗大粒子を除去することができ、フィルムの粗大突起の減少に効果的に採用できる。 In addition, if necessary, the slurry of inert particles before addition can be dispersed by a sand grinder or the like, separated by coarse particles by centrifugal sedimentation, or subjected to high-precision filtration to make the particle size distribution uniform and coarse particles. Can be effectively removed to reduce the coarse protrusions of the film.
本発明のフィルムの表面粗さＳＲａおよびヘイズ値とするためには、平均粒子径０．５〜１．５μｍ、好ましく０．８〜１．３μｍの不活性粒子を０．２〜１．０重量％、さらに好ましくは、０．３〜０．８重量％含有させることが好適である。併せて、基層部に同種の不活性粒子を０．０１〜０．１％含有させる、基層部の粒子含有量を調整することにより、表面粗さＳＲａを上記範囲に保ったまま、ヘイズ値を所望の値に適正化することができる。 In order to obtain the surface roughness SRa and haze value of the film of the present invention, 0.2 to 1.0 weight of inert particles having an average particle diameter of 0.5 to 1.5 μm, preferably 0.8 to 1.3 μm is used. %, More preferably 0.3 to 0.8% by weight. In addition, the haze value is maintained while maintaining the surface roughness SRa in the above range by adjusting the particle content of the base layer part to contain 0.01 to 0.1% of the same kind of inert particles in the base layer part. It can be optimized to a desired value.
また、本発明のフィルム表面に存在する高さ０．８μｍ以上の粗大突起は、０．１〜５個／１００ｃｍ２であることが好ましい。さらに好ましくは０．１〜３個／１００ｃｍ２以下である。粗大突起数が上記密度を超えると、離型剤を塗布乾燥する工程や離型フィルム上に粘着剤を塗布乾燥する工程において、ピンホール状の塗布抜けや塗布層の平面性を損なう場合がある。 The height 0.8μm large protrusions equal to or higher than that present in the film surface of the present invention is preferably from 0.1 to 5 pieces / 100 cm 2. More preferably, it is 0.1-3 pieces / 100 cm < 2 > or less. When the number of coarse protrusions exceeds the above density, pinhole-like coating omission and flatness of the coating layer may be impaired in the step of applying and drying the release agent and the step of applying and drying the pressure-sensitive adhesive on the release film. .
本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムは、例えば未延伸フィルムを縦方向に延伸し、次いで横方向に延伸し、冷却工程を経て熱処理して偏光板離型フィルム用二軸配向ポリエステルフィルムを製造する方法であって、ボーイング現象を抑制するため冷却工程にてフィルム温度を２５〜４５℃に冷却したのち、熱処理することを特徴とする偏光板離型フィルム用二軸配向ポリエステルフィルムを製造することができる。 The biaxially oriented polyester film for polarizing plate release film of the present invention is a biaxially oriented polyester film for polarizing plate release film, for example, an unstretched film is stretched in the longitudinal direction, then stretched in the transverse direction, and heat-treated through a cooling step. A method for producing a polyester film, wherein the film temperature is cooled to 25 to 45 ° C. in a cooling step in order to suppress the bowing phenomenon, followed by heat treatment, and a biaxially oriented polyester film for polarizing plate release film Can be manufactured.
次に本発明の偏光板離型フィルム用二軸配向ポリエステルフィルムにおける製造方法に関してさらに詳しく説明する。上述したポリエステルを必要に応じて乾燥し、押出機に供給して、ポリマーをフィルターにより濾過する。ごく小さな異物もフィルム欠陥となるため、このフィルターには例えば５μｍ以上の異物を９５％以上捕集する高精度のものを用いることが有効である。続いてＴ型口金等を用いてシート状に溶融押出し、キャスティングロール上で冷却固化せしめて未延伸フィルムとする。 Next, the manufacturing method in the biaxially oriented polyester film for polarizing plate release films of the present invention will be described in more detail. The above-described polyester is dried as necessary, and supplied to an extruder, and the polymer is filtered through a filter. Since even a very small foreign matter becomes a film defect, it is effective to use a high-precision filter that collects 95% or more of a foreign matter of 5 μm or more, for example. Subsequently, it is melt-extruded into a sheet shape using a T-type die or the like, and cooled and solidified on a casting roll to obtain an unstretched film.
この未延伸フィルムを９０〜１３０℃の延伸温度で長手方向に１段階的に、もしくは多段階的に分けて２．５〜５倍に延伸し、テンターへ導く。ボーイング現象およびフィルム長手方向の厚みムラを抑える観点から、延伸温度は１００〜１２０℃、延伸倍率は３〜４倍が好ましく、延伸むらおよびキズを防止する観点から延伸は２段階以上に分けて行うことが好ましい。次いで、９０〜１３０℃の延伸温度で幅方向に３〜６倍に延伸し、得られた二軸配向フィルムを冷却工程および熱処理工程へ導く。延伸温度が９０℃よりも低く延伸倍率が６倍よりも大きくなるとフィルムが破断しやすくなるため、延伸温度は１００〜１２０℃、延伸倍率は４〜５倍が好ましい。 This unstretched film is stretched 2.5 to 5 times in one step in the longitudinal direction at a stretching temperature of 90 to 130 ° C. or divided into multiple steps and led to a tenter. The stretching temperature is preferably 100 to 120 ° C. and the stretching ratio is preferably 3 to 4 times from the viewpoint of suppressing the thickness irregularity in the longitudinal direction of the film and the bowing. The stretching is performed in two or more stages from the viewpoint of preventing uneven stretching and scratches. It is preferable. Next, the film is stretched 3 to 6 times in the width direction at a stretching temperature of 90 to 130 ° C., and the resulting biaxially oriented film is guided to a cooling step and a heat treatment step. When the stretching temperature is lower than 90 ° C. and the stretching ratio is larger than 6 times, the film is easily broken. Therefore, the stretching temperature is preferably 100 to 120 ° C. and the stretching ratio is preferably 4 to 5 times.
ここで、本発明においては冷却工程を設けてこの二軸配向フィルムのフィルム温度を２５〜４５℃に冷却し、熱処理工程へ導く。この際の冷却の方法は、熱処理を行うテンターで各ゾーンを独立に温度制御する空冷方法、熱処理領域の上下にアルミ板などの遮蔽板で熱風を遮断する空冷方法、ロール冷却方法等が挙げられる。熱処理を行うテンターによる空冷方法では各ゾーンが長手方向に全てつながっているため、随伴気流など高温空気の自由な流れによりフィルム上下や幅方向に温度差が発生し、フィルム温度を十分冷却できない場合がある。その場合は、圧縮空気などを送り込んで積極的に冷却することで対応することもできる。また、ロール冷却方法では、使用するロール本数や設定温度は限られるものではないが、複数本通すことで冷却することが好ましい。冷却温度はフィルム温度を確実に２５〜４５℃にするため２０〜４５℃が好ましく、さらに好ましくは３０〜４０℃である。次いで熱処理することで、１５０℃３０分間の条件で熱処理したのちのフィルム長手方向およびフィルム幅方向の熱収縮率がそれぞれ５〜７％、７〜９％の二軸配向ポリエステルフィルムを得る。熱処理の雰囲気温度はフィルム物性を安定させるため、フィルム上下の温度差が１〜２０℃、好ましくは１〜１０℃、さらに好ましくは１〜５℃である。フィルム上下での温度差が２０℃よりも大きいと、フィルムの幅方向の物性、特に機械的特性あるいは熱収縮率を不均一にする場合がある。上記熱処理においては、必要に応じて弛緩処理を行ってもよい。この際、横方向・長手方向いずれの方向でも良いが、横方向・長手方向を同時に行ったり、これらを組み合わせておこなっても良い。弛緩率はフィルムの全幅に対して好ましくは１〜２０％、さらに好ましくは１〜１０％が熱寸法安定性の優れたフィルムを得るのに有効である。 Here, in this invention, a cooling process is provided, the film temperature of this biaxially oriented film is cooled to 25-45 degreeC, and it guide | induced to the heat treatment process. The cooling method at this time includes an air cooling method in which the temperature of each zone is independently controlled by a tenter that performs heat treatment, an air cooling method in which hot air is blocked by a shielding plate such as an aluminum plate above and below the heat treatment region, and a roll cooling method. . In the air-cooling method with a heat-treating tenter, all zones are connected in the longitudinal direction, so there is a case where the film temperature cannot be sufficiently cooled due to temperature differences in the vertical and width directions of the film due to the free flow of high-temperature air such as an accompanying air flow. is there. In that case, it is possible to cope with this by sending compressed air or the like and actively cooling it. In the roll cooling method, the number of rolls to be used and the set temperature are not limited, but it is preferable to cool by passing a plurality of rolls. The cooling temperature is preferably 20 to 45 ° C., more preferably 30 to 40 ° C., in order to ensure that the film temperature is 25 to 45 ° C. Next, a heat treatment is performed at 150 ° C. for 30 minutes to obtain a biaxially oriented polyester film having a heat shrinkage of 5 to 7% and 7 to 9% in the film longitudinal direction and the film width direction, respectively. In order to stabilize the film physical properties, the temperature difference of the heat treatment is 1-20 ° C, preferably 1-10 ° C, more preferably 1-5 ° C. When the temperature difference between the upper and lower sides of the film is larger than 20 ° C., the physical properties in the width direction of the film, particularly the mechanical properties or the heat shrinkage rate, may be made uneven. In the heat treatment, a relaxation treatment may be performed as necessary. At this time, either the horizontal direction or the longitudinal direction may be used, but the horizontal direction and the longitudinal direction may be performed simultaneously, or a combination thereof may be performed. The relaxation rate is preferably 1 to 20%, more preferably 1 to 10%, based on the entire width of the film, and is effective for obtaining a film having excellent thermal dimensional stability.
実施例および比較例における特性値の測定方法は次の通りである。 The measuring method of the characteristic value in an Example and a comparative example is as follows.
（１）熱収縮率
フィルム表面に、幅１０ｍｍ、測定長約１００ｍｍとなるように２本のラインを引き、この２本のライン間の距離を２３℃で測定しこれをＬ０とする。このフィルムサンプルを１５０℃のオーブン中に３０分間、１．５ｇの荷重下で放置した後、再び２本のライン間の距離を２３℃で測定しこれをＬ１とし、下式により熱収縮率を求めた。
熱収縮率（％）＝｛（Ｌ０−Ｌ１）／Ｌ０｝×１００
フィルムの長手方法および幅方向についてそれぞれ３カ所の測定を行い、平均値を求めた。
(1) Heat shrinkage rate Two lines are drawn on the surface of the film so that the width is 10 mm and the measurement length is about 100 mm, and the distance between the two lines is measured at 23 ° C. and is defined as L0. After this film sample was left in an oven at 150 ° C. for 30 minutes under a load of 1.5 g, the distance between the two lines was measured again at 23 ° C., and this was taken as L1. Asked.
Thermal contraction rate (%) = {(L0−L1) / L0} × 100
Measurement was carried out at three points for the longitudinal direction and the width direction of the film, and the average value was obtained.
（２）配向主軸の傾き（配向角）、収率
野村商事製ＳＯＮＩＣ ＳＨＥＥＴ ＴＥＳＴＥＲ（ＳＳＴ−２５０）を用いて測定をする。試料となるフィルムの幅に対して最も配向主軸が傾く両端部からＡ４サイズに切り出したサンプルの中点（１０５ｍｍ）を測定し、その最大値を配向角とした。なお、配向主軸がフィルム幅方向と平行である時を配向角０度であり、フィルム幅方向に対して時計回りの傾きを＋、反時計回りを−とし、その絶対値を測定結果とした。
両端部で配向主軸の傾き（配向角）が５度を超える場合には、フィルム幅の中央部に向かって幅方向の位置を変えて測定し、下式により収率を求めた。
(2) Measure the tilt (orientation angle) of the orientation main axis and the yield using a Noic Shoji Sonic Sheet Tester (SST-250). The midpoint (105 mm) of the sample cut into A4 size from both ends where the orientation main axis is most inclined with respect to the width of the film as the sample was measured, and the maximum value was taken as the orientation angle. In addition, when the orientation main axis is parallel to the film width direction, the orientation angle is 0 degree, the clockwise inclination with respect to the film width direction is +, and the counterclockwise direction is −, and the absolute value is the measurement result.
When the inclination (orientation angle) of the orientation main axis exceeded 5 degrees at both ends, the measurement was performed by changing the position in the width direction toward the center of the film width, and the yield was determined by the following equation.
収率（％）＝
配向主軸の傾き（配向角）が５度以下を満足する幅長さ／全幅長さ×１００。
Yield (%) =
Width length / full width length × 100 in which the inclination (orientation angle) of the orientation main axis satisfies 5 degrees or less.
（３）フィルム長手方向の厚みむら
安立電気製フィルム厚み連続測定器を用いて、長手方向に１５ｍ測定し、記録されたフィルム厚さチャートから、最大厚みと最小厚みの差を厚みむら（μｍ）として測定した。測定条件は下記の通り。
構成：Ｋ−３０６Ｃ広範囲電子マイクロメータ、Ｋ−３１０Ｃレコーダー、フィルム送り装置
検出器：３Ｒルビー端子、測定力：１５ｇ±５ｇ
フィルム幅：４５ｍｍ、測定長：１５ｍ、フィルム送り速度：３ｍ／分。
(3) Uneven thickness in the longitudinal direction of the film Using a continuous film thickness measuring device manufactured by Anritsu Electric Co., Ltd., measured for 15 m in the longitudinal direction, and from the recorded film thickness chart, the difference between the maximum thickness and the minimum thickness is uneven thickness (μm) As measured. The measurement conditions are as follows.
Configuration: K-306C Wide Range Electronic Micrometer, K-310C Recorder, Film Feeder Detector: 3R Ruby Terminal, Measuring Force: 15g ± 5g
Film width: 45 mm, measurement length: 15 m, film feed speed: 3 m / min.
（４）フィルムのヘイズ値
ＪＩＳ Ｋ７１０５（１９８１）に準じ、フィルム長手方向４ｃｍ×フィルム幅方向３．５ｃｍの寸法に切り出したものをサンプルとし、ヘイズメータ（スガ試験機製ＨＧＭ−２ＤＰ（Ｃ光用））を用いて測定する。フィルム幅方向に対して均等に３点測定し、その平均値を測定結果とした。
(4) Haze value of film According to JIS K7105 (1981), a sample cut into a dimension of 4 cm in the longitudinal direction of the film and 3.5 cm in the width direction of the film is used as a sample, and a haze meter (HGM-2DP (for S light tester) manufactured by Suga Test Instruments) Use to measure. Three points were measured uniformly in the film width direction, and the average value was taken as the measurement result.
（５）フィルム厚み
ＪＩＳ Ｃ２１５１（１９９０）に準じ、マイクロメーター（ミツトヨＯＭＭ−２５）を用いてフィルム幅方向に対して均等に３０点測定し、その平均値を測定結果とした。
(5) Film thickness According to JIS C2151 (1990), 30 points were measured uniformly in the film width direction using a micrometer (Mitutoyo OMM-25), and the average value was taken as the measurement result.
（６）粗大突起数
粗大突起数は１０ｃｍ四方の大きさのフィルムを測定する面同士を２枚重ね合わせて、印加電圧をかけて静電気力で密着し、フィルム表面の粗大突起により発生する干渉縞から高さを決定する。干渉縞が１重環で０．２７μmであり、３重環０．８１μm以上の粗大突起個数を測定した。光源としては、ハロゲンランプに５６４ｎｍのバンドパスフィルターをかけたものを用いた。任意にサンプリングした、１０サンプルについて測定し、その平均値を測定結果とした。
(6) Number of coarse protrusions The number of coarse protrusions is an interference fringe generated by coarse protrusions on the surface of a film, with two surfaces for measuring a 10 cm square film superimposed on each other, applied with an applied voltage and brought into close contact with electrostatic force. Determine the height from The interference fringes were 0.27 μm for a single ring, and the number of coarse protrusions of a triple ring of 0.81 μm or more was measured. As the light source, a halogen lamp provided with a 564 nm band pass filter was used. Ten samples sampled arbitrarily were measured, and the average value was taken as the measurement result.
（７）フィルム温度
ハンディ形放射温度計（株式会社チノー製ＩＲ−ＴＡ）を用いて、フィルム温度を測定した。フィルム幅方向に対して均等に３点測定し、その平均値を測定結果とした。
(7) Film temperature The film temperature was measured using a handy radiation thermometer (IR-TA manufactured by Chino Corporation). Three points were measured uniformly in the film width direction, and the average value was taken as the measurement result.
（８）粒子の平均粒径
フィルムからポリマーをプラズマ低温灰化処理法で除去し、粒子を露出させる。処理条件は、ポリマーは灰化されるが粒子は極力ダメージを受けない条件を選択する。その粒子を走査型電子顕微鏡（ＳＥＭ）で観察し、粒子画像をイメージアナライザで処理する。ＳＥＭの倍率は粒径により、およそ５０００〜２００００倍から適宜選択する。観察箇所をかえて粒子数５０００個以上で粒径とその体積分率から、次式で体積平均径ｄを得る。粒径の異なる２種類以上の粒子を含有している場合には、それぞれの粒子について同様の測定を行い、粒径を求めた。
ｄ＝Σ（ｄｉ・Ｎｖｉ）
ここで、ｄｉは粒径、Ｎｖｉはその体積分率である。
粒子がプラズマ低温灰化処理法で大幅にダメージを受ける場合には、フィルム断面を透過型電子顕微鏡（ＴＥＭ）を用いて、粒径により、３０００〜２００００倍で観察する。ＴＥＭの切片厚さは約１００ｎｍとし、場所をかえて５００視野以上測定し、上記式から体積平均径ｄを求める。
(8) Average particle diameter of particles The polymer is removed from the film by a plasma low-temperature ashing treatment method to expose the particles. The processing conditions are selected such that the polymer is ashed but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. The magnification of SEM is appropriately selected from about 5000 to 20000 times depending on the particle size. The volume average diameter d is obtained by the following formula from the particle diameter and the volume fraction thereof when the number of particles is changed to 5000 or more by changing the observation location. When two or more kinds of particles having different particle diameters were contained, the same measurement was performed for each particle to obtain the particle diameter.
d = Σ (di · Nvi)
Here, di is the particle size, and Nvi is the volume fraction.
When the particles are significantly damaged by the plasma low-temperature ashing treatment method, the film cross section is observed at 3000 to 20000 times depending on the particle size using a transmission electron microscope (TEM). The section thickness of the TEM is about 100 nm, the location is changed, and 500 fields or more are measured, and the volume average diameter d is obtained from the above formula.
（９）固有粘度
オルトクロロフェノール中、２５℃で測定した溶液粘度から、下式で計算した値を用いた。すなわち、
ηｓｐ／Ｃ＝［η］＋Ｋ［η］２・Ｃ
ここで、ηｓｐ＝（溶液粘度／溶媒粘度）−１であり、Ｃは、溶媒１００ｍｌあたりの溶
解ポリマー重量（ｇ／１００ｍｌ、通常１．２）、Ｋはハギンス定数（０．３４３とする）である。また、溶液粘度、溶媒粘度はオストワルド粘度計を用いて測定した。単位は［ｄｌ／ｇ］で示す。
(9) Intrinsic viscosity The value calculated by the following formula from the solution viscosity measured at 25 ° C in orthochlorophenol was used. That is,
ηsp / C = [η] + K [η] 2 · C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assuming 0.343). is there. The solution viscosity and solvent viscosity were measured using an Ostwald viscometer. The unit is indicated by [dl / g].
（１０）フィルム積層厚み
表面からエッチングしながらＸＰＳ（Ｘ線光電子光法）、ＩＲ（赤外分光法）あるいはコンフォーカル顕微鏡などで、その粒子濃度のデプスプロファイルを測定する。片面に積層したフィルムにおける表層では、表面という空気−樹脂の界面のために粒子濃度は低く、表面から遠ざかるにつれて粒子濃度は高くなる。本発明の片面に積層したフィルムの場合は、深さ［Ｉ］で一旦極大値となった粒子濃度がまた減少し始める。この濃度分布曲線をもとに極大値の粒子濃度の１／２になる深さ［ＩＩ］（ここで、ＩＩ＞Ｉ）を積層厚さとした。さらに、無機粒子などが含有されている場合には、二次イオン質量分析装置（ＳＩＭＳ）を用いて、フィルム中の粒子のうち最も高濃度の粒子の起因する元素とポリエステルの炭素元素の濃度比（Ｍ＋／Ｃ＋）を粒子濃度とし、層（Ａ）の表面からの深さ（厚さ）方向の分析を行う。そして上記同様の手法から積層厚さを得る。
(10) Film Laminating Thickness The depth profile of the particle concentration is measured by XPS (X-ray photoelectron optical method), IR (infrared spectroscopy) or confocal microscope while etching from the surface. In the surface layer of the film laminated on one side, the particle concentration is low due to the air-resin interface called the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film laminated on one side of the present invention, the particle concentration once reached the maximum value at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [II] (here, II> I), which is ½ of the maximum particle concentration, was defined as the lamination thickness. Furthermore, when inorganic particles etc. are contained, using a secondary ion mass spectrometer (SIMS), the concentration ratio of the element resulting from the highest concentration of the particles in the film and the carbon element of the polyester Using (M + / C +) as the particle concentration, analysis in the depth (thickness) direction from the surface of the layer (A) is performed. Then, the laminated thickness is obtained from the same method as described above.
（１１）フィルム表面粗さＳＲａ
三次元微細表面形状測定器（小坂製作所製ＥＴ−３５０Ｋ）を用いて測定し、得られたる表面のプロファイル曲線より、ＪＩＳ・Ｂ０６０１に準じ、算術平均粗さＳＲａ値を求めた。測定条件は下記のとおり。
Ｘ方向測定長さ：０．５ｍｍ、Ｘ方向送り速度：０．１ｍｍ／秒。
Ｙ方向送りピッ：５μm、Ｙ方向ライン数：４０本。
カットオフ：０．２５ｍｍ。
触針圧：０．０２ｍＮ。
高さ（Ｚ方向）拡大倍率：５万倍。
(11) Film surface roughness SRa
Measured using a three-dimensional fine surface shape measuring instrument (ET-350K, manufactured by Kosaka Manufacturing Co., Ltd.), an arithmetic average roughness SRa value was determined from the obtained surface profile curve according to JIS B0601. The measurement conditions are as follows.
X direction measurement length: 0.5 mm, X direction feed rate: 0.1 mm / second.
Y-direction feed pitch: 5 μm, number of Y-direction lines: 40.
Cut-off: 0.25 mm.
Stylus pressure: 0.02 mN.
Height (Z direction) magnification: 50,000 times.
以下、実施例で本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail with reference to examples.
実施例１
ジメチルテレフタレートに１．９モルのエチレングリコールおよび酢酸マグネシウム・４水塩を０．０５％、リン酸を０．０１５％加え加熱エステル交換を行い、引き続き三酸化アンチモン０．０２５％を加え、加熱昇温し真空化で重縮合反応を行い、粒子を実質的に含有しない、固有粘度０．６３のホモポリエステルペレットを得た。
Example 1
Dimethyl terephthalate was added with 1.9 moles of ethylene glycol and magnesium acetate tetrahydrate, 0.05% phosphoric acid and 0.015% phosphoric acid for transesterification, followed by addition of 0.025% antimony trioxide and heating to A polycondensation reaction was performed by heating and evacuation to obtain homopolyester pellets having an intrinsic viscosity of 0.63 substantially free of particles.
さらに、平均粒子径１．０μmの炭酸カルシウムを準備し、１０％のエチレングリコールスラリーとした。このスラリーをジェットアジターで一時間分散処理を行い、５μm以上の捕集効率９５％のフィルターで高精度濾過した。このスラリーをエステル交換後に添加し、引き続き、上記と同じように重縮合反応を行い、平均粒子径１．０μmの炭酸カルシウムを１％含む、固有粘度０．６３の炭酸カルシウム含有マスターペレットを得た。 Furthermore, calcium carbonate having an average particle diameter of 1.0 μm was prepared to prepare a 10% ethylene glycol slurry. This slurry was subjected to a dispersion treatment with a jet agitator for one hour, and was subjected to high-precision filtration with a filter having a collection efficiency of 95% of 5 μm or more. This slurry was added after transesterification, and subsequently a polycondensation reaction was performed in the same manner as described above to obtain a calcium carbonate-containing master pellet having an intrinsic viscosity of 0.63 and containing 1% of calcium carbonate having an average particle diameter of 1.0 μm. .
次に、炭酸カルシウム含有マスターペレットおよび、粒子を含有しないホモポリエステルペレットを混合し、炭酸カルシウムを０．５％含有するポリエステルＡ、炭酸カルシウムを０．０５％含有するポリエステルＢを得た。 Next, calcium carbonate-containing master pellets and homopolyester pellets containing no particles were mixed to obtain polyester A containing 0.5% calcium carbonate and polyester B containing 0.05% calcium carbonate.
これらのポリエステルＡ、Ｂをそれぞれ１６０℃で８時間減圧乾燥した後、別々の押出機に供給し、２７５℃で溶融押出して、５μｍ以上の捕集効率９５％の高精度フィルターで濾過した後、矩形の３層用合流ブロックで合流積層し、ポリエステルＡ／ポリエステルＢ／ポリエステルＡからなる３層積層とした。その後、２８５℃に保ったスリットダイを介し静電印可キャスト法を用いて表面温度２５℃のキャスティングロール上に冷却固化し、未延伸フィルムを得た。この未延伸フィルムを、まず１０３℃に加熱したロールとラジエーションヒーターによって長手方向に３．４倍延伸した。続いてテンターにて幅方向に１０５℃で４．４倍に延伸し、冷却温度を４０℃に設定してフィルム温度を４２℃に冷却した。この冷却工程ではロール方式を採用し、次いで１９０℃で熱処理を行って、全フィルム厚み３８μｍ、両層の積層厚さ１．５μｍ、フィルム幅５．１ｍの３層からなる二軸配向ポリエステルフィルムを得た。なお、両層の積層厚さは同一とした。得られた結果を表１に示した。 These polyesters A and B were each dried under reduced pressure at 160 ° C. for 8 hours, then supplied to separate extruders, melt-extruded at 275 ° C., filtered through a high-precision filter with a collection efficiency of 95% of 5 μm or more, The layers were merged and laminated in a rectangular three-layer merge block to form a three-layer laminate comprising polyester A / polyester B / polyester A. Thereafter, the film was cooled and solidified on a casting roll having a surface temperature of 25 ° C. by using an electrostatic application casting method through a slit die maintained at 285 ° C. to obtain an unstretched film. This unstretched film was first stretched 3.4 times in the longitudinal direction with a roll heated to 103 ° C. and a radiation heater. Subsequently, the film was stretched 4.4 times at 105 ° C. in the width direction with a tenter, the cooling temperature was set to 40 ° C., and the film temperature was cooled to 42 ° C. In this cooling step, a roll method is adopted, followed by heat treatment at 190 ° C., to form a biaxially oriented polyester film consisting of three layers with a total film thickness of 38 μm, a laminated thickness of both layers of 1.5 μm, and a film width of 5.1 m. Obtained. Note that the thickness of both layers was the same. The obtained results are shown in Table 1.
実施例２〜４、比較例１〜３
添加する不活性粒子の平均粒子径、含有量、延伸条件、冷却条件、熱処理温度などの製膜条件を変えるほかは実施例１と同様に実施し、３層からなる二軸配向ポリエステルフィルムを得た。得られた結果を表１に示した。
Examples 2-4, Comparative Examples 1-3
A biaxially oriented polyester film consisting of three layers is obtained in the same manner as in Example 1 except that the film forming conditions such as the average particle diameter, content, stretching conditions, cooling conditions, and heat treatment temperature of the inert particles to be added are changed. It was. The obtained results are shown in Table 1.
Claims (4)
フィルム幅方向に対する配向主軸の傾き（配向角）が少なくとも５ｍ幅にわたって５度以下で、
フィルム長手方向の厚みむらが０．５〜１．５μｍである
偏光板離型フィルム用二軸配向ポリエステルフィルム。 A polyester film of a three-layer composite using polyethylene terephthalate, wherein all the resins constituting the three layers of the polyester film are polyethylene terephthalate, and the film longitudinal direction and film width after heat treatment at 150 ° C. for 30 minutes The direction of thermal shrinkage is 5-7%, 7-9%,
The inclination (orientation angle) of the orientation principal axis with respect to the film width direction is 5 degrees or less over a width of at least 5 m,
A biaxially oriented polyester film for polarizing plate release film having a thickness unevenness in the longitudinal direction of the film of 0.5 to 1.5 μm.
未延伸フィルムを縦方向に延伸し、次いで横方向に延伸し、冷却工程を経て熱処理して偏光板離型フィルム用二軸配向ポリエステルフィルムを製造する方法であって、冷却工程にてロールを用いてフィルムの温度を２５〜４５℃に冷却したのち、熱処理する偏光板離型フィルム用二軸配向ポリエステルフィルムの製造方法。 A method for producing a three-layer composite polyester film using polyethylene terephthalate, wherein all the resins constituting the three layers of the polyester film are polyethylene terephthalate,
A method of producing a biaxially oriented polyester film for a polarizing plate release film by stretching an unstretched film in the longitudinal direction and then stretching in the transverse direction, followed by a heat treatment through a cooling step, using a roll in the cooling step A method for producing a biaxially oriented polyester film for polarizing plate release film that is heat-treated after cooling the film temperature to 25 to 45 ° C.
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