JP2004306549A - Manufacturing method of optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film suitable for a stock roll for various optical films used for a liquid crystal display, particularly for a phase difference film, which are excellent in smoothness, small in unevenness in thickness, and uniform in optical property. <P>SOLUTION: A thermoplastic resin is melted and extruded in a film shape from an extruding die 1, and the film with a support layer 9 is sandwiched and pressed in the clearance between a cooling roll 2 made of a metal or a ceramic and a rubber roll 3. After the thermoplastic resin layer 8 with the support layer 9 is transferred until the the thermoplastic layer 8 is cooled, the support layer 9 is peeled and separated to give the thermoplastic resin film 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５５】
表１から明かなように、支持体層とともに溶融樹脂層を挟圧して成形したフィルムは、支持体層の表面粗さ特性に近いフィルムが得られ、ダイラインも殆ど視認できないことがわかる。更に、リターデーションは、支持体層を用いず挟圧しない押出しフィルムに比べて極度に低下していることがわかる。このリターデーションの低下は、実施例３の如く、両面支持体層挟圧がより効果的であるが、実施例１、２、４の如く、片面でも十分に効果がある。そして、リターデーションは支持体層の膜厚にはあまり影響を受けず、また、運転速度にもあまり影響を受けない。
【００５６】
実施例５
実施例１の環状ポリオレフィン樹脂に代えてポリカーボネート（パンライトＬ１２２５ＺＥ、帝人株式会社製）を実施例１と同一の装置によりフィルム状の溶融樹脂層８を押出した。押出し樹脂温度は２８０℃であった。
該溶融樹脂層８に挟圧される支持体層９としては、溶液キャストによって製造されたポリカーボネートの１００μｍのフィルム（鐘淵化学工業株式会社製エルメック）を用い、それ以外は実施例１と同様にして成形フィルム（フィルム製品）を得た。支持体層の溶液キャストフィルムと溶融押出したフィルムとは疑似接着するので、二軸延伸ポリエチレンテレフタレートを運転の当初の部分に剥離ガイドとして挿入して挟圧すると、これより剥離点となり実施例１と同一の個所で剥離が可能となる。得られた成形フィルム１１（フィルム製品１２）の特性値は表２に示した。
【００５７】
比較例２
実施例５で使用した、溶液キャストしたポリカーボネートフィルムの特性値を表２に併記した。
【００５８】
【表２】

【００５９】
表２より明かなように、溶液キャストによって得られたフィルムを支持体層として溶融樹脂層を挟圧してフィルム成形することにより、表面粗さの特性はほぼ溶液キャストフィルムの表面性に近くなり、ダイラインの発生も防ぐことができる。更に、リターデーションは、挟圧によって溶液キャストフィルムに近いリターデーションを有するフィルムが得られる。
【００６０】
【発明の効果】
叙上のとおり、フィルム状に溶融押出した樹脂を熱不良導体の支持体層とともに硬軟ロール間、即ち、金属又はセラミック製ロールとゴムロール間に挟圧して成形する本発明の方法は、ダイラインを解消し、リターデーションが小さく、そのバラツキも少ない光学用に適したフィルムを製造することができる。
【図面の簡単な説明】
【図１】本発明の光学用フィルムを、片面支持体層を配備し挟圧して製造する場合の模式図である。
【図２】本発明の光学用フィルムを、両面支持体層を配備し挟圧して製造する場合の模式図である。
【符号の説明】
１ 押出ダイ
２ 金属又はセラミックからなる冷却ロール
３ ゴムロール
４ バックアップロール
５ 第２冷却ロール
６ 第３冷却ロール
７ ロール
８ 熱可塑性樹脂層、フィルム状溶融樹脂（層）
９ ゴムロール側支持体層
１０ 冷却ロール側支持体層
１１ 成形フィルム
１２ フィルム製品[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an optical film, and more particularly, to a method for producing an optical film having less thickness unevenness, excellent smoothness, and uniform optical characteristics over the entire surface.
[0002]
[Prior art]
2. Description of the Related Art In recent years, optical films or sheets (hereinafter, collectively referred to as films) are frequently used in liquid crystal display devices. The liquid crystal display device has a polarizing film for generating polarized light, a touch panel with a transparent electrode on the surface, a plastic substrate instead of a glass substrate with a transparent electrode, and the optical phase difference from retardation generated from liquid crystal molecules. A phase difference plate or the like for compensating is provided.
[0003]
In the case of a polarizing film, in the case of a stretched polyvinyl alcohol iodine adsorption film or the like, a moisture-resistant protective film is bonded to protect the film from moisture. Usually, a cast film of triacetyl cellulose is used as such a protective film. The touch panel is used by providing a transparent conductive layer on a film substrate, and usually uses a biaxially stretched polyethylene terephthalate film. These films are required to have improved transparency, moisture resistance and birefringence. Further, a plastic substrate has been demanded instead of a glass substrate provided with a transparent electrode. For these, various polymer films have been proposed together with a retardation plate described below.
[0004]
A stretched optical film is used for the retardation plate. Such optical films include polymer films such as polycarbonate, polysulfone, polyarylate, and polyphenylene sulfide. And a phase difference plate is obtained by extending and orienting these polymer films uniaxially or biaxially.
[0005]
In recent years, there has been a demand for rationalization and quality improvement of various optical films for the liquid crystal display device. In order to obtain an accurate liquid crystal display, these optical films must firstly have a low residual stress over the entire surface and a low retardation and a small variation, and secondly, the retardation is proportional to the thickness. Therefore, it is necessary that there be no uneven thickness or die line, and that the thickness be equal to the desired thickness. Third, of course, film flaws, inclusion of foreign matter, wrinkles, and the like must be avoided.
[0006]
Conventionally, the following method has been proposed as a method for producing an optical film.
[0007]
(1) A resin is dissolved in a solvent to form a solution. The solution is cast on an endless metal belt or a base film, and then the solvent is removed by drying to form a resin layer. A method of separating and separating from a metal belt or a base film (see Patent Document 1).
(2) A method in which a resin is melt-extruded from a die using an extruder into a film and cooled by a cooling roll to obtain the resin (see Patent Documents 2 to 4).
[0008]
However, in the method (1), it is difficult to completely dry and remove the solvent, and if the residual solvent becomes uneven, stress becomes uneven during stretching, and a uniform phase difference cannot be realized. Therefore, in order to avoid this, the drying equipment is enriched and a large amount of energy is required. As a result, the manufacturing equipment is increased and the running cost is increased. In addition, the working environment may be degraded by the solvent, and its maintenance is costly.
In the above method (2), a plurality of cooling rolls are often used, so that a contraction stress is generated between the rolls and a tensile stress remains. To avoid this, there are methods such as precise control of the temperature and the rotation speed of the roll, but it is difficult to keep the residual stress constant. In addition, the resulting film tends to have uneven thickness, die lines, and gear marks, and it is difficult to obtain a raw material for optical use.
[0009]
In order to improve the drawbacks of the melt extrusion method, a method has been proposed in which a molten resin discharged from a die of an extruder is pressed by a pair of rolls (see Patent Document 5). However, with this method, it is difficult to provide a film that can be used for optical applications and that has solved die lines, gear marks, and uneven thickness. Further, it is considered that the pinching of the pair of rolls is not sufficient, and a method has been proposed in which an endless metal belt is placed vertically and the molten resin is pinched between the belts (see Patent Document 6). However, even in this method, the place of the squeezing force is only the squeezing force between the rolls for squeezing the metal belt, and it is difficult to obtain a uniform film due to insufficient adhesion between the metal belt and the resin.
[0010]
Many proposals have been made to improve the pinching by the endless metal belt. For example, in the case of polypropylene, there is a method in which one cast roll and one endless metal belt are combined and the metal belt is pressed along the arc of the cast roll (see Patent Documents 7 and 8). Further, based on this method, a method of setting the cooling temperature around the glass transition temperature of the extruded resin (see Patent Document 9) or a method of setting the cooling temperature higher than the glass transition temperature (see Patent Document 10). A method of adjusting the take-up speed after peeling (see Patent Document 11) and a method of providing a peeling roll immediately adjacent to a cast roll (see Patent Document 12) have been proposed. However, these methods make it difficult to obtain a certain quality, such as minimizing the generation of a residual phase difference, and increase the equipment and operation costs.
[0011]
On the other hand, there is an attempt to increase the pressing effect of the molten resin by pressing the metal and the rubber substance from between the metals. As one example, a proposal has been made in which a pressing means such as a spring or a hydraulic piston is combined in order to maintain a constant gap between the rolls (see Patent Document 13), but dissatisfaction remains with the characteristics of the film surface.
[0012]
Further, in order to improve the surface properties of the extruded polyolefin on a substrate, a method of laminating and transferring a film having a specular gloss and performing metal deposition on this surface (see Patent Document 14) is known. This is an improvement in the gloss of the laminated paper as a material, and does not suggest the production of an optical film.
[0013]
[Patent Document 1]
JP-A-4-301415
[Patent Document 2]
JP-A-4-118213
[Patent Document 3]
JP-A-4-166319
[Patent Document 4]
JP-A-4-275129
[Patent Document 5]
JP-A-2-61899
[Patent Document 6]
JP-A-3-75110
[Patent Document 7]
JP-A-6-170919
[Patent Document 8]
JP-A-6-166089
[Patent Document 9]
JP-A-9-239812
[Patent Document 10]
JP 2000-280268 A
[Patent Document 11]
JP-A-9-290427
[Patent Document 12]
JP-A-10-16034
[Patent Document 13]
JP 2000-280315 A
[Patent Document 14]
JP-A-59-5056
[0014]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems of the prior art, and is useful as a raw material for various optical films used in a liquid crystal display device, for example, an optical film for a retardation plate, etc., and has uneven thickness such as die lines and gear marks. An optical film having no residual phase difference having a uniform thickness, and a retardation film or the like manufactured at low cost and with high productivity using the optical film.
[0015]
[Means for Solving the Problems]
In view of such circumstances, the present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a thermoplastic roll melt-extruded into a film from an extrusion die together with a support layer together with a cooling roll and a rubber roll made of metal or ceramic. After being conveyed in a quasi-adhered state by pinching, it was found that a target optical film could be obtained by peeling and removing the support layer, and arrived at the present invention.
[0016]
That is, the invention according to claim 1 of the present invention melts and extrudes a thermoplastic resin into a film shape from a die of an extruder, and a cooling roll made of metal or ceramic and a rubber roll that rotates while being pressed against the circumferential direction of the roll. After pressing the thermoplastic resin layer together with the support layer under cooling tension until the thermoplastic resin layer cools, the support layer is peeled off and separated to form a thermoplastic resin film. The present invention relates to a method for producing an optical film, characterized by being obtained.
[0017]
The invention according to claim 2 of the present invention is directed to the method for producing an optical film according to claim 1, wherein the support layer is a coated paper based on a synthetic resin film or paper.
[0018]
The invention according to claim 3 of the present invention is directed to the method for producing an optical film according to claim 1 or 2, wherein the support layer is disposed on the side in contact with the rubber roll to sandwich the thermoplastic resin layer.
[0019]
The invention according to claim 4 of the present invention is the production of the optical film according to claim 1 or 2, wherein the support layer is provided on both the side in contact with the rubber roll and the side in contact with the cooling roll to sandwich the thermoplastic resin layer. The law shall be the content.
[0020]
The invention according to claim 5 of the present invention includes the method for producing an optical film according to any one of claims 1 to 4, wherein the thermoplastic resin is a cyclic polyolefin.
[0021]
The invention according to claim 6 of the present invention includes the method for producing an optical film according to any one of claims 1 to 5, wherein the support layer is made of biaxially stretched polyethylene terephthalate.
[0022]
The invention according to claim 7 of the present invention is the method according to any one of claims 1 to 6, wherein the smoothness is 0.01 μm or less in average roughness Ra, and the birefringence is 30 nm or less in retardation. Includes a method for manufacturing an optical film.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
When manufacturing optical films by the melt extrusion method, even if various ideas and improvements are repeated, the die line generated from the extrusion die and the resin flow due to the shearing of the molten extruded resin, the resin shrinkage due to cooling and the film due to the take-off Such a stress causes a residual phase difference. In order to improve this, usually, a smooth surface is photographed by sandwiching between a metal roll and a metal roll or a smooth metal belt, and furthermore, the flow of the resin in the extrusion direction and the thickness unevenness of the resin in the extrusion direction such as a die line. Has been tried to eliminate the resin flow by causing the resin flow in the other direction due to the pressure.
[0024]
The present inventors have applied a cooling roll made of a hard material, that is, a metal or ceramics, and a roll made of a soft material, that is, a rubber roll, and a coating based on a synthetic resin film or paper of a poor conductor of heat. By sandwiching the melt-extruded resin layer through a support layer made of paper etc., the flow of resin in the other direction due to pressure is more likely to occur than in the case of sandwiching metal and metal, and a smooth surface is copied. The removal was good, and it was found that the disappearance of the die line and the residual stress due to the flow in the die were greatly reduced.
[0025]
Furthermore, since the melt-extruded resin layer is transported to an appropriate temperature together with the support layer, shrinkage due to cooling and stress of take-off are not given to the target optical film. It has been found that the residual phase difference generated by the process can be eliminated at the same time.
[0026]
As the thermoplastic resin used in the present invention, a resin suitable for producing an optical film is selected. For this purpose, it must be a transparent resin and, for example, in order to enhance the reliability during use of the built-in liquid crystal display device, the heat resistance and the humidity resistance must be practically acceptable. Is required. As such a thermoplastic resin, polycarbonate, polysulfone, polyarylate, cyclic polyolefin and the like are preferable. Among them, the cyclic polyolefin is suitable for producing a raw material of an optical film because birefringence due to the molecular orientation is less likely to occur when the molecule is oriented than other thermoplastic resins.
[0027]
The cyclic polyolefin has an alicyclic structure in a main chain and / or a side chain. Examples of the alicyclic structure include a cycloalkane and a cycloalkene structure, and the cycloalkane structure is suitable for optical use. The unit of these alicyclic structures preferably has 5 to 15 carbon atoms. A polymer containing 50% by weight or more of a unit having these alicyclic structures is preferable. Examples of such a polymer include a norbornene-based polymer, a monocyclic cyclic olefin-based polymer, a cyclic conjugated diene-based polymer, a hydrocarbon polymer having a side chain alicyclic structure, and a hydrogenated product thereof. Can be Among these, a norbornene-based polymer and its hydrogenated product, a cyclic conjugated diene-based polymer and its hydrogenated product are preferable.
[0028]
FIG. 1 is a schematic diagram for explaining the melt extrusion molding method of the present invention. In FIG. 1, the film-like molten resin 8 extruded from the extrusion die 1 is shown. The extruder may be a single-screw, twin-screw or melt-kneader. The shape of each screw is appropriately selected and is not particularly limited. Usually, the diameter of the screw is 40 to 150 mm, the L / D is 20 to 35, preferably 25 to 30, and the compression ratio is 2.5 to 4.
[0029]
It is preferable to reduce the oxygen concentration by purging the inside of the hopper inside the resin and the melting zone of the cylinder with nitrogen so as to obtain a colorless and transparent film with little deterioration.
[0030]
After the molten resin passes through a mesh or a porous filter material to remove foreign substances, it is preferable to secure a constant discharge amount per time through a gear pump. Then, it is extruded from the extrusion die 1 as a film-like molten resin 8. The extrusion die 1 may have a usual shape used for forming a sheet or a film. For example, a coat hanger type, a straight manifold type, and a fish tail type die can be used. The gap between the openings of the extrusion die 1 is selected according to the thickness of the target sheet or film, but is usually about 0.1 to 3 mm.
[0031]
In FIG. 1, a film-like molten resin 8 extruded from an extrusion die 1 is sandwiched between a support layer 9 sandwiched between a cooling roll 2 made of metal or ceramic and a rubber roll 3. The rubber roll 3 is pressed against the cooling roll 2 by a metal backup roll 4 in order to apply a uniform extrusion pressure to the entire width of the molten resin 8. The pressing pressure is appropriately selected, but 5 kg / cm per contact area of the rubber roll. ² ~ 50kg / cm ² It is about. The rubber roll has a structure in which various rubber-like substances are concentrically wound around the outer periphery of a metal core, and the thickness of the rubber-like substance is appropriately selected. The hardness of the rubber-like substance is arbitrary, but is preferably slightly higher. The rubber-like substance is selected from SBR, NBR, chloroprene, chlorinated polyethylene, chlorosulfonated polyethylene, polyester elastomer, urethane rubber, silicone rubber and the like, and blends thereof.
[0032]
The temperature of the cooling roll 2 is precisely controlled, and usually a range of + 50 ° C to -50 ° C around the glass transition temperature of the molten resin 8 is appropriate. The molten resin 8 is conveyed to the second cooling roll 5 while being sandwiched between the cooling roll 2 and the support layer 9 and is quasi-adhered to the support layer 9 and pressed against the cooling roll 5 under a certain tension. And cooled to form a molded film.
[0033]
The molded film 11 and the support layer 9 are taken off from the second cooling roll 5 with a take-off force adjusted by the third cooling roll 6 in a pseudo-adhered state. The film product 12 is sent to a take-up reel (not shown) via the roll 7 and wound up. Each of the rolls is operated so that the support layer 9 and the molten resin 8 or the molded film 11 are conveyed together in conjunction with each other or independently by a driving force.
[0034]
FIG. 2 is a schematic diagram showing a case where the support layers 9 and 10 are arranged on both sides of the film-like molten resin 8, that is, on both the side in contact with the rubber roll 3 and the side in contact with the cooling roll 2. The operation is performed in substantially the same manner as the case of the support layer on one side of FIG. 1 including the temperature condition of the cooling roll. The support film 9 and the support layer 10 of the formed film 11 are separated and separated by the cooling rolls 6 and 7, and are wound as a film product 12.
[0035]
It is important that the support layer to be pinched is a poor conductor of heat as compared with metal. For example, a coated paper based on synthetic resin films or paper is preferable. Since the smoothness of the surface of the support layer may be transferred to the surface of the target film product, a support layer having a surface as flat as possible with less unevenness is preferable, and the center line average roughness specified in JIS B0601 is preferred. A support layer having a surface roughness of 0.01 μm or less is preferred. Further, in the case of synthetic resin films, it must be able to withstand the molten resin extruded into a film. Accordingly, films having relatively high heat resistance, such as polycarbonate, polysulfone, polyethersulfone, polyphenylsulfide, and polyimide, biaxially stretched polyethylene terephthalate, and biaxially stretched films such as biaxially stretched polyethylene naphthalate, and the like. Can be. In particular, from the viewpoint of good smoothness, a film made of the above resin obtained by casting with a solvent, a casting film of triacetyl acetate, and a biaxially stretched polyester film are preferable. Then, the molten resin and the support layer extruded into a film are sandwiched and conveyed together. The extruded resin and the support layer may be of the same type or different types as long as they can be quasi-adhered or separated after cooling.
[0036]
In the case of a paper-based coated paper, a coated paper in which the unevenness of the paper is eliminated is selected. Examples of such coated paper include synthetic leather process paper and art paper. The thickness of the support layer is not limited, but if the thickness is too small, the effect is small, and if the thickness is too large, the operation tends to be hindered. Therefore, usually, 50 μm to 200 μm is suitable.
The support layer can be supplied by being preheated before being pressed with the molten resin. The temperature is a temperature above the cooling temperature of the operation and at which the support layer does not undergo thermal contraction.
[0037]
As described above, the support layer and the molten resin layer are transported together until they are cooled and separated by separation. If the two are of different types, it may be difficult to transport them together due to insufficient adhesion.In such a case, the surface on the lamination side is subjected to corona discharge treatment and ozone treatment to increase the adhesive strength on the support layer side. It is preferable to perform a surface treatment such as a flame treatment and a plasma discharge treatment.
[0038]
As an extruded film used as a raw material of various optical films, a film having no die line and having a uniform film thickness is required. The difference between the maximum and minimum film thickness is preferably 5% or less of the average film thickness, more preferably 2% or less. The surface roughness of the film is preferably 0.01 μm or less in terms of center line average roughness Ra based on JIS B0601. Eliminating the die line is to reduce the foreign matter by passing the molten resin through an appropriate filter material, and to reduce the die line from the die by setting the extrusion conditions with less generation of burnt resin, and the inner surface smoothness of the die extruded into a film shape Of course, this can be achieved by strictly adjusting the die gap and optimizing the operating conditions that are pressed against the support layer.
[0039]
Further, as an extruded film used as a raw material of various optical films, a low birefringence film having almost no variation is required. This variation is preferably 5 nm or less when the retardation is expressed in nm, and it is advantageous that the retardation of the film is small in order to realize this. Therefore, when the film thickness is 100 μm, it is 30 nm or less, preferably 10 nm or less. good. To this end, it is necessary to select an appropriate resin, further select an appropriate support layer, adjust the conditions for pinching, and appropriately set other operating conditions. Such a film having a small variation can be sufficiently achieved by pinch molding with a support layer using a cyclic polyolefin having a small photoelastic coefficient, which is unlikely to cause birefringence during molecular orientation.
[0040]
The optical film obtained as described above can be used as a moisture-resistant protective film for an iodine-adsorbed stretched polyvinyl alcohol polarizing film by bonding it to various pressure-sensitive adhesives or adhesives. Furthermore, in the case of a touch panel having a transparent conductive layer on the surface or a plastic substrate instead of a glass substrate for a liquid crystal display, a metal oxide film, for example, an ITO (indium-tin oxide) film or an AZO (aluminum-doped zinc oxide) film is sputtered. It can be formed by metal deposition.
Further, the retardation plate is preheated from the above optical film as a raw material, and then stretched in the same direction as the film winding direction between two rolls having different peripheral speeds at a constant temperature under a constant temperature. And a retardation film stretched in the machine direction can be obtained. On the other hand, a lateral retardation film can be obtained by grasping the optical film raw material with clamps or pins on both sides of the film and extending the film while traveling in a direction perpendicular to the traveling direction. Similarly, when the clamp or the pin is stretched in both the traveling direction and the direction perpendicular to the traveling direction while traveling, a biaxially stretched film is obtained at the same time, and a retardation film in the thickness direction is obtained. Further, after stretching in the vertical or horizontal direction, the film can be further stretched in two directions in either direction. The stretching ratio is usually 1.5 to 4 times. Instead of stretching, the stretching effect can be obtained by rolling between rolls that does not shrink in the film width direction.
[0041]
The obtained stretched optical film is useful as various optical films. For example, it is usually cut as a retardation plate in a bias direction with respect to the stretching direction and incorporated for optical compensation of a liquid crystal display device.
[0042]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
[0043]
Example 1
According to the schematic diagram of FIG. 1, a cyclic polyolefin resin (ARTON D4531, Tg132 ° C., manufactured by JSR Corporation) is passed through a porous filter with an L / D32 single-screw having an inner diameter of 65 mm, and is then discharged at a constant rate by a gear pump. It was extruded into a film from the extrusion die 1 having a width of 884 mm. A chalkless coat hanger die was used as the extrusion die 1. The temperature of the molten resin 11 discharged from the extrusion die 1 was 278 ° C.
[0044]
A biaxially stretched polyethylene terephthalate film having a thickness of 75 μm and a surface roughness characteristic of 0.005 μm in center line average roughness, 0.07 μm in maximum roughness and 0.07 μm in 10 point average roughness as the support layer 9. (O3LF8, manufactured by Teijin Dupont Films Co., Ltd.) was placed on the rubber roll 3 side, and the film-like molten resin was pressed at a surface pressure of 12 kg / cm. ² And a cooling roll (made of metal) 2. The cooling roll 2 was kept at 90 ° C. The support layer 9 and the molten resin layer 8 are both transported to the second cooling roll 5 maintained at 47 ° C., and then transported to the third cooling roll 6 maintained at 35 ° C. The polyethylene terephthalate film No. 9 was peeled off and wound up, while the molded film 11 was wound up as a film product 12 through the next roll 7. The operation speed of the operation line was 6 m / min.
[0045]
The characteristics of the obtained molded film (film product) were observed and measured by the following methods. The results are shown in Table 1.
[0046]
Die line:
A parallel light beam is made incident on the sample film surface placed obliquely, and the transmitted light beam is projected onto a screen to check the linear density of the light.
[0047]
Film thickness:
The film thickness was measured at 35 locations at intervals of 20 mm in the width direction of the sample film using a film thickness meter to obtain an average value, and the highest and lowest tolerances were obtained.
[0048]
Surface roughness characteristics:
Using an ultra-depth shape measuring microscope VK-8500 manufactured by KEYENCE CORPORATION, three points were sampled in the film width direction from a sample film having an area of 200 μm × 200 μm, and the center line average roughness Ra and the maximum roughness were measured in accordance with JIS B0601. Rmax, 10-point average roughness Rz are calculated to obtain an average value. The measurement was performed with the support layer contact surface (rubber roll side) as the front and the cooling roll side as the back.
[0049]
Retardation:
An automatic birefringence meter KOBRA-21ADH places a Nicol polarizer and a Nicol analyzer in parallel with each other, irradiates a sample film with a single-wavelength light beam and makes one rotation around the light axis. Calculate the phase difference.
Measurement wavelength 590nm, sample size 35mm x 35mm
Five samples were taken in the width direction, and the average value and the maximum and minimum tolerances at five locations were determined.
[0050]
Example 2
A molded film (film product 12) was produced in the same manner as in Example 1 except that the thickness of the biaxially stretched polyethylene terephthalate as the support layer was changed from 75 μm in Example 1 to 125 μm, and various properties were measured. . The results are shown in Table 1.
[0051]
Example 3
Except that one support layer 9 is provided on the rubber roll 3 side and the other support layer 10 is also provided on the cooling roll 2 side, and the molten resin layer 8 is pressed from both sides, the same method as in Example 1 is used. A molded film 11 (film product 12) was obtained and various properties were measured. The results are shown in Table 1.
[0052]
Example 4
The same method as in Example 1 was adopted except that the speed of the operation line of Example 1 was changed to 12 m / min, and the discharge amount corresponding to this was extruded so that the film thickness became substantially the same as that of Example 1. A molded film 11 (film product 12) was obtained. The properties of this film are shown in Table 1.
[0053]
Comparative Example 1
By completely releasing the space between the rubber roll 3 and the cooling roll 2 of the first embodiment, the film-like molten resin layer 8 is extruded so as to be in contact with the top of the cooling roll 2 without using the support layer 9 and without using the rubber roll. The molded film 11 (film product 12) was obtained through the same pass line as in Example 1 without being pinched with 3. Table 1 shows the properties of the obtained film.
[0054]
[Table 1]

[0055]
As is clear from Table 1, in the film formed by pressing the molten resin layer together with the support layer, a film close to the surface roughness characteristics of the support layer was obtained, and the die line was hardly visible. Further, it can be seen that the retardation is extremely reduced as compared with an extruded film which does not use a support layer and does not pinch. This reduction in retardation is more effective by clamping the double-sided support layer as in Example 3, but is sufficiently effective even on one side as in Examples 1, 2, and 4. The retardation is not so affected by the thickness of the support layer, and is not so affected by the operation speed.
[0056]
Example 5
Instead of the cyclic polyolefin resin of Example 1, polycarbonate (Panlite L1225ZE, manufactured by Teijin Limited) was used to extrude a film-like molten resin layer 8 using the same apparatus as in Example 1. The extruded resin temperature was 280 ° C.
As the support layer 9 sandwiched between the molten resin layers 8, a 100 μm polycarbonate film (ELMEC, manufactured by Kanegafuchi Chemical Industry Co., Ltd.) manufactured by solution casting was used. Thus, a molded film (film product) was obtained. Since the solution cast film of the support layer and the melt-extruded film are quasi-adhered to each other, the biaxially stretched polyethylene terephthalate is inserted into the initial part of the operation as a peeling guide and pressed, and the peeling point is obtained from this point, as in Example 1. Peeling is possible at the same location. The characteristic values of the obtained molded film 11 (film product 12) are shown in Table 2.
[0057]
Comparative Example 2
The characteristic values of the solution-cast polycarbonate film used in Example 5 are also shown in Table 2.
[0058]
[Table 2]

[0059]
As is clear from Table 2, the film obtained by solution casting is used as a support layer to form a film by sandwiching the molten resin layer, whereby the surface roughness characteristics are almost close to the surface properties of the solution cast film, The occurrence of die lines can also be prevented. Further, a film having a retardation close to that of a solution cast film can be obtained by squeezing pressure.
[0060]
【The invention's effect】
As described above, the method of the present invention in which the resin melt-extruded into a film is pressed together with the support layer of the heat-defective conductor between the hard and soft rolls, that is, between the metal or ceramic roll and the rubber roll, to eliminate the die line. In addition, it is possible to produce a film suitable for optical use having a small retardation and a small variation.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a case where an optical film of the present invention is manufactured by disposing a single-sided support layer and pressing it.
FIG. 2 is a schematic diagram showing a case where the optical film of the present invention is manufactured by disposing and pressing a double-sided support layer.
[Explanation of symbols]
1 Extrusion die
2 Cooling roll made of metal or ceramic
3 rubber roll
4 Backup roll
5 Second cooling roll
6 Third cooling roll
7 rolls
8. Thermoplastic resin layer, film-like molten resin (layer)
9 Rubber roll side support layer
10 Cooling roll side support layer
11 Molded film
12 Film products

Claims (7)

A thermoplastic resin is melt-extruded into a film form from a die of an extruder, and is pressed together with a support layer in a gap between a cooling roll made of metal or ceramic and a rubber roll that rotates while being pressed against a circumferential direction of the roll, thereby forming a thermoplastic resin layer. A method for producing an optical film, comprising: transporting a thermoplastic resin film together with a support layer under take-up tension until the thermoplastic resin layer cools, and then separating and separating the support layer to obtain a thermoplastic resin film. 2. The method for producing an optical film according to claim 1, wherein the support layer is a synthetic resin film or a coated paper based on paper. 3. The method for producing an optical film according to claim 1, wherein the support layer is disposed on a side in contact with the rubber roll to sandwich the thermoplastic resin layer. 3. The method for producing an optical film according to claim 1, wherein the support layer is provided on both the side in contact with the rubber roll and the side in contact with the cooling roll to sandwich the thermoplastic resin layer. The method for producing an optical film according to any one of claims 1 to 4, wherein the thermoplastic resin is a cyclic polyolefin. The method for producing an optical film according to any one of claims 1 to 5, wherein the support layer is made of biaxially stretched polyethylene terephthalate. The method for producing an optical film according to claim 1, wherein the smoothness is 0.01 μm or less in average roughness Ra and the birefringence is 30 nm or less in retardation.

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