JP2006317734A - Device and method for manufacturing retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film capable of suppressing or preventing color irregularities by improving the flatness as much as possible. <P>SOLUTION: In the device for manufacturing retardation film, a retardation film is manufactured by subjecting a film stock 5 made of thermoplastic resin to longitudinally-uniaxial stretching while causing the film stock to run in a direction between a pair of primary side nip rolls 1A, 1B and a pair of secondary side nip rolls 2A, 2B which are separately arranged and have circumferential speeds different from each other, wherein a preheating area 6, a stretching area 7 and a cooling area 8 are provided in the order from the upstream side of the film running direction between the primary side nip rolls 1A, 1B and the secondary side nip rolls 2A, 2B, and one or more pass rolls 3A, 3B which support the stretched film are arranged on the downstream from the position 5a where the film comes to a final width upon the completion of stretching in the stretching area 7. Surface temperatures of the pass rolls 3A, 3B are set lower than the glass transition temperature Tg of the film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a retardation film manufacturing apparatus and a manufacturing method used for, for example, a liquid crystal display device. More specifically, the present invention relates to an apparatus and method employing a longitudinal uniaxial stretching method in which a raw film made of a thermoplastic resin is stretched in the longitudinal direction.

  In recent years, liquid crystal display devices are being used in large quantities in word processors, notebook computers, mobile phones, automobile and machine instruments, and the like. In these liquid crystal display devices, a retardation film is used for the purpose of compensating for optical distortion resulting from the birefringence of the liquid crystal.

  As a method for producing this retardation film, there are a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse sequential biaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and the like, which are used depending on the intended performance.

Among these, as a method for producing a retardation film by a longitudinal uniaxial stretching method, for example, Patent Document 1 is known. In this method, in order to prevent the in-plane smoothness of the film from being impaired in the cooling step after the end of stretching, a thermal relaxation region (glass transition region) downstream of the stretching region between two pairs of rolls having different peripheral speeds. The pass roll is disposed at a temperature Tg to Tg-10 ° C., and the angle between the film surface in contact with the pass roll and the central axis of the pass roll is set to 90 degrees or more.
JP-A-3-235902

  In the above conventional example, the pass roll is disposed in the heat relaxation zone, which is a cooling zone. In this case, since the film starts to shrink by the time it enters the heat relaxation zone and reaches the pass roll, Is likely to occur.

  Thus, if wrinkles are generated in the manufactured retardation film, the retardation difference is increased, resulting in color unevenness and a loss of appearance.

  Also, as in the conventional example, if the film holding angle of the pass roll is increased, the film pressure for the pass roll will increase, so if the pass roll smoothness and rotational accuracy are set relatively low, The film is easily damaged and the appearance is impaired.

  An object of the present invention is to increase the smoothness as much as possible in a retardation film manufacturing apparatus and a manufacturing method so as to suppress or prevent the occurrence of color unevenness.

  In the present invention, a raw film made of a thermoplastic resin is stretched uniaxially while traveling in one direction between a pair of primary nip rolls and a pair of secondary nip rolls that are spaced apart and have different peripheral speeds. A retardation film, wherein a preheating region, a stretching region, and a cooling region are provided in order from the upstream side in the film running direction between the primary nip roll and the secondary nip roll, In which one or more pass rolls supporting the stretched film are disposed downstream from the position at which the final width of the film ends in stretching, and the surface temperature of the pass roll is set lower than the glass transition temperature Tg of the film. It is characterized by being.

  Further, the present invention provides a longitudinally uniaxial stretching of a raw film made of a thermoplastic resin while traveling in one direction between a pair of primary nip rolls and a pair of secondary nip rolls that are spaced apart and have different peripheral speeds. In the method for producing a retardation film, the surface temperature is lower than the glass transition temperature Tg of the film downstream from the position where the final width of the film ends in the stretching region where the film is stretched uniaxially. The stretched film is cooled using one or more set pass rolls.

  In order to make the peripheral speeds of the primary nip roll and the pair of secondary nip rolls different, it is possible to adjust the outer diameters and rotational speeds of both nip rolls. The stretching region is a temperature not lower than the glass transition temperature Tg, and the cooling region is not higher than the glass transition temperature Tg.

  According to this configuration, since the pass roll is disposed downstream of the position where the final width of the film ends in the stretching area, not the cooling area, that is, the neck-in end position, the stretched film is the outer peripheral surface of the pass roll. The heat shrinkage will be started only after contact with the ink, and further, the heat shrinkage will be performed while being cooled on the pass roll. As a result, the film cooled by the pass roll is made into a smooth surface state following the outer peripheral surface of the pass roll, so that wavy wrinkles as in the conventional example are less likely to occur.

  Accordingly, it is not always necessary to increase the holding angle of the film with respect to the pass roll as in the conventional example. Therefore, even if the smoothness and rotational accuracy of the pass roll are set to be relatively low, the film is hardly damaged.

  The thermoplastic resin is not particularly limited, and examples of the thermoplastic resin include cyclic olefin resins and polycarbonate resins.

  The cyclic olefin-based resin is preferably a norbornene-based resin, for example, a hydrogenated product of a ring-opening (co) polymer of a norbornene-based monomer, an addition copolymer of a norbornene-based monomer and an olefin-based monomer, or a norbornene-based monomer. Examples thereof include addition copolymers or derivatives thereof. These may be used alone or in combination.

  The norbornene-based monomer is not particularly limited as long as it has a norbornene ring. For example, a bicyclic body such as norbornene and norbornadiene; a tricyclic body such as dicyclopentadiene; A pentacycle such as cyclopentadiene trimer; and a heptacycle such as cyclopentadiene tetramer.

  This norbornene-based monomer may have a substituent. Examples of substituents include alkyl groups such as methyl, ethyl, propyl and butyl, alkenyl such as vinyl, alkylidene such as ethylidene, hydrocarbon groups such as aryl such as phenyl, tolyl and naphthyl; ester groups, ether groups, cyano groups, Examples include polar groups such as halogen atoms, alkoxycarbonyl groups, pyridyl groups, hydroxyl groups, carboxylic acid groups, amino groups, hydroxyl groups-free, silyl groups, epoxy groups, acrylic groups, and methacrylic groups.

  In addition, since it is easily available, has excellent reactivity, and the resulting retardation film has excellent heat resistance, a polycyclic norbornene-based monomer having three or more rings is preferable, and tricyclic, tetracyclic, and pentacyclic. Cyclic norbornene monomers are more preferred.

  Norbornene monomers may be used alone or in combination of two or more.

  As the hydrogenated product of the ring-opening (co) polymer of the norbornene monomer, those obtained by subjecting the norbornene monomer to ring-opening polymerization by a known method and then hydrogenating the remaining double bond are widely used. This may be a hydrogenated product of a norbornene-based monomer homopolymer or a hydrogenated product of a copolymer of different norbornene-based monomers.

  Examples of the addition copolymer of the norbornene monomer and the olefin monomer include a copolymer of a norbornene monomer and an α-olefin, a copolymer of a norbornene monomer and a cyclic olefin monomer, and the like.

  The α-olefin is preferably an α-olefin having 2 to 20 carbon atoms, more preferably an α-olefin having 2 to 10 carbon atoms, such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene and the like are copolymerized. Since ethylene is preferable, even when other α-olefin is copolymerized with a norbornene-based monomer, copolymerization is enhanced by coexisting ethylene.

  Examples of the cyclic olefin monomer include cyclooctadiene, cyclooctene, cyclohexene, cyclododecene, cyclododecatriene, and the like.

  In order to obtain a ring-opening (co) polymer of the norbornene-based monomer, for example, the norbornene-based monomer is converted into a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetonate, and a reducing agent. Or in the presence of a catalyst system comprising a metal halide such as titanium, tungsten, molybdenum or the like, or a catalyst system comprising acetylacetonate and an organoaluminum compound, usually in a solvent or without a solvent, generally from −50 to Ring-opening (co) polymerization is performed at a polymerization temperature of 100 ° C. and a polymerization pressure of 0 to 5 MPa.

  In order to obtain the addition copolymer of the norbornene-based monomer and the olefin-based monomer, for example, these monomer components are mixed with a vanadium compound and an organoaluminum compound (preferably a halogen-containing organoaluminum compound) in a solvent or without a solvent. In the presence of a catalyst system consisting of the above, it is usually copolymerized at a polymerization temperature of -50 to 100 ° C and a polymerization pressure of 0 to 5 MPa.

  Specific examples of commercially available norbornene resins include, for example, the product name “Arton” series manufactured by JSR, the product name “ZEONOR” series manufactured by Nippon Zeon, and the product name “Mitsui Chemicals” "Apel" series.

  In addition, if the number average molecular weight of the cyclic olefin-based resin is too small, the mechanical strength of the resulting retardation film may decrease, and if too large, the workability during film formation may decrease. 5000 to 50000 is preferable, and 8000 to 30000 is more preferable. In addition, the number average molecular weight of cyclic olefin resin says what was measured by the gel permeation chromatography method.

  The above cyclic olefin-based resin has the heat resistance, ultraviolet resistance, smoothness, etc. of the retardation film in order to prevent deterioration of the cyclic olefin-based resin during molding within the range that does not hinder the function of the retardation film. In order to improve, antioxidants such as phenols and phosphoruss; thermal degradation inhibitors such as lactones; UV absorbers such as benzophenones, benzotriazoles, and acrylonitriles; esters of aliphatic alcohols, polyhydric alcohols Various additives such as a partial ester type or partial ether type lubricant; an amine type antistatic agent or the like may be added. An additive may be used independently or 2 or more types may be used together.

  In order to form a film from a cyclic olefin resin (which may contain an additive), a conventionally used method is used. Specifically, a method of obtaining a resin film by supplying a cyclic olefin resin to an extruder, melting and kneading, and extruding the molten resin into a film form from a T die attached to the tip of the extruder (a so-called melt extrusion method) In addition, a method in which a solution obtained by dissolving a cyclic olefin resin in an organic solvent is cast on a drum or a band, and then the organic solvent is evaporated to obtain a resin film (so-called solution casting method). Etc.

  If the thickness of the cyclic olefin resin film is too thin, it is difficult to obtain a desired retardation Re (hereinafter abbreviated as Re), and if it is too thick, the liquid crystal display device is thin when incorporated in a liquid crystal display device. Therefore, it is preferable to set in the range of 50 to 200 μm.

  When the thickness of the cyclic olefin resin film is 80 μm or more, it may be difficult to sufficiently evaporate and remove the organic solvent by the solution casting method. It is preferable to produce a cyclic olefin resin film.

  According to the present invention, it is possible to produce a retardation film that can improve smoothness as much as possible and suppress or prevent the occurrence of color unevenness.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a side view of a retardation film manufacturing apparatus, and FIG. 2 is a plan view in which all of the partition walls in FIG. 1 are omitted. In these drawings, 1A and 1B are a pair of primary (upstream) nip rolls, 2A and 2B are a pair of secondary (downstream) nip rolls, and 3A and 3B are a pair of pass rolls.

  This manufacturing apparatus, for example, extrudes a molten thermoplastic resin from a die into a film and cools it by running between a pair of cooling rolls to obtain an original film 5. As shown in FIG. 1 and FIG. 2, the primary nip rolls 1A and 1B and the secondary nip rolls 2A and 2B having different peripheral speeds are stretched uniaxially.

  Between the primary side nip rolls 1A, 1B and the secondary side nip rolls 2A, 2B, from the primary side nip rolls 1A, 1B side to the secondary side nip rolls 2A, 2B side, a preheating zone 6, a stretching zone 7, A cooling zone 8 is secured.

  As shown in FIG. 1, the preheating area 6, the stretching area 7, and the cooling area 8 are separated from each other by a partition wall (not shown), and independent temperature control is possible. However, the partition for partitioning each region 6 to 8 is provided with a slight gap for film passage.

  The stretch zone 7 is set to a temperature equal to or higher than the glass transition temperature Tg of the film. In general, the neck-in in the longitudinal uniaxial stretching starts all at once from the time when the film temperature reaches a temperature near the glass transition temperature Tg in the stretching region 7, particularly a temperature equal to or higher than the glass transition temperature Tg. Therefore, the preheating region 6 is provided in order to quickly reach the glass transition temperature Tg in the stretching region 7. The cooling zone 8 is provided to cool the film temperature more quickly.

  A pair of pass rolls 3A and 3B for supporting the film is disposed in the stretching region 7 between the primary nip rolls 1A and 1B and the secondary nip rolls 2A and 2B.

  In this embodiment, the pair of pass rolls 3A and 3B are arranged in a state where they are arranged in the vertical direction on the upper side and the lower side of the film traveling in a substantially horizontal direction.

  The pair of pass rolls 3 </ b> A and 3 </ b> B is disposed downstream of the position 5 a that is the final width of the film in the stretching region 7.

  The final width at the end of stretching refers to the width at the time when the neck-in is completed 100% (position 5a). Neck-in 100% means that neck-in no longer proceeds, in other words, no further deformation.

  By the way, the pass rolls 3A and 3B are preferably made by using an appropriate metal material as a base material and coating the surface thereof with hard chrome plating or tungsten carbide.

  The surface temperature of the pass rolls 3A and 3B is set to be lower than the glass transition temperature Tg of the film in order to cool the stretched film.

  Next, a retardation film is manufactured using the manufacturing apparatus described above, but Examples 1, 2, and 3 to which the specific matters of the present invention are applied, and Comparative Example 1 that is excluded from the specific matters of the present invention. 2 are manufactured and evaluated, and are shown in Table 1 and described.

まず、実施例１〜３および比較例１，２の位相差フィルムの原材料とする熱可塑性樹脂には、環状オレフィン系樹脂として熱可塑性飽和ノルボルネン系樹脂（日本ゼオン社製、商品名「ゼオノア＃１６００」、数平均分子量：２００００）を用いる。

First, a thermoplastic saturated norbornene resin (manufactured by ZEON Corporation, trade name “ZEONOR # 1600” as a cyclic olefin resin is used as a thermoplastic resin as a raw material for the retardation films of Examples 1 to 3 and Comparative Examples 1 and 2. ”, Number average molecular weight: 20000).

  This resin is supplied to a known single screw extruder (not shown), melted and kneaded, and the molten resin is extruded from a T die attached to the tip of the single screw extruder at a resin temperature of 230 ° C. A raw film 5 having a thickness of 100 μm is prepared and continuously wound into a roll.

The glass transition temperature Tg of the hydrogenated resin of this norbornene polymer was 161.0 ° C. as measured by a differential scanning calorimeter (trade name “DSC220C” manufactured by Seiko Denshi Kogyo Co., Ltd.).
(Example 1)

  The manufacturing conditions of Example 1 will be described.

  (A) Preheating zone 6 is set to 140 ° C, stretching zone 7 is set to 162 ° C, and cooling zone 8 is set to 120 ° C. This temperature is the ambient temperature.

  (B) The length of the preheating zone 6 is 3 m, and the total length of the stretching zone 7 and the cooling zone 8 is 8 m. However, the lengths of the stretching zone 7 and the cooling zone 8 can be changed.

  (C) The separation distance between the pass rolls 3A and 3B and the position 5a that is the final width of the film is set to 500 mm. This separation distance is set to, for example, 300 mm or more, preferably 500 mm or more.

  (D) The surface temperature of the pass rolls 3A and 3B is 120 ° C. The surface temperature is set lower than the glass transition temperature Tg of the film, and is set, for example, in the range of Tg-5 ° C to Tg-40 ° C, preferably Tg-10 ° C to Tg-30 ° C. The surface temperature of the pass rolls 3A and 3B is preferably controlled to vary by about 0.2 ° C. in the width direction and the circumferential direction of the pass rolls 3A and 3B.

(E) The draw ratio is 1.5 times. For example, in the case of the above-described film width of 1000 mm, the final film width is set to 815 mm by performing 1.5-fold longitudinal uniaxial stretching.
(Example 2)

The manufacturing conditions of Example 2 are the same as Example 1 (d), that is, the surface temperature of the pass rolls 3A and 3B is 140 ° C., and the other conditions are the same as those of Example 1.
Example 3

The manufacturing conditions of Example 3 are the same as those of Example 1 (e), that is, the stretching ratio is 1.8 times, and the other conditions are the same as those of Example 1. For example, in the case of the above-described film width of 1000 mm, the final film width is set to 745 mm by performing 1.8-fold longitudinal uniaxial stretching.
(Comparative Example 1)

The manufacturing conditions of Comparative Example 1 are the same as in Example 1 (d), that is, the surface temperature of the pass rolls 3A and 3B is 162 ° C., and the other conditions are the same as in Example 1. Note that the pass rolls 3A and 3B are not controlled in temperature, and are at the atmospheric temperature in the stretching region 7.
(Comparative Example 2)

  The manufacturing conditions of Comparative Example 2 are that in Example 1 (d), that is, the surface temperature of the pass rolls 3A and 3B is 162 ° C., and in Example 1 (e), that is, the draw ratio is 1.8 times. The other conditions are the same as in the first embodiment. Note that the pass rolls 3A and 3B are not controlled in temperature, and are at the atmospheric temperature in the stretching region 7.

  Here, for each retardation film manufactured under the manufacturing conditions of Examples 1 to 3 and Comparative Examples 1 and 2, the color unevenness and the surface state are examined and evaluated.

  First, for the measurement method of color unevenness, sandwiched between two polarizing plates whose absorption axes are orthogonal to each other so that the slow axis of the produced retardation film intersects the absorption axis of the polarizing plate at 45 degrees, The color density was visually identified and evaluated in three stages. Those with no shading are designated as “3 points”, those with obvious shading are designated as “1 point”, and those in the middle are designated as “2 points”.

  Moreover, about the surface state of the manufactured retardation film, the manufactured retardation film is cut into a length of 50 cm in the film running direction at the time of manufacture, and placed on a smooth stainless steel plate, and the surface wave shape is visually observed. It was set as the form to observe.

  Here, the results will be described with reference to Table 1. First, the color unevenness was “3 points” in Examples 1 and 2, “2 points” in Example 3 and Comparative Example 1, and “1 point” in Comparative Example 2. In addition, the surface states of Examples 1 to 3 were “smooth”, Comparative Example 1 was “slightly wave-shaped”, and Comparative Example 2 was “wave-shaped”.

  Based on such evaluation, Examples 1 to 3 satisfy the product standards, but Comparative Examples 1 and 2 are considered not to meet the product standards.

  In short, after the film is stretched and the neck-in is completed in the stretching region 7 instead of the cooling region 8, it is cooled by the pass rolls 3 </ b> A and 3 </ b> B whose surface temperature is set to an appropriate range.

  As a result, the stretched film begins to thermally contract only after contacting the outer peripheral surfaces of the pass rolls 3A and 3B, and is cooled in a state where the stretched film is supported on the outer peripheral surfaces of the pass rolls 3A and 3B. It will heat shrink.

  For this reason, the film cooled by the pass rolls 3A and 3B is made into a smooth surface state following the outer peripheral surfaces of the pass rolls 3A and 3B, so that wavy wrinkles as in the conventional example are less likely to occur.

  Therefore, since it is possible to substantially prevent the occurrence of wrinkles and the like in the stretched film and make it a smooth surface, it becomes possible to suppress or prevent the occurrence of color unevenness and to stably produce a retardation film with high reliability and quality. Will be able to provide.

  Accordingly, since it is not necessary to increase the film holding angle with respect to the pass rolls 3A and 3B as in the conventional example, even if the smoothness and rotational accuracy of the pass rolls 3A and 3B are set to be relatively low, Damage can be suppressed or prevented, and the appearance can be improved.

  Hereinafter, other embodiments of the present invention will be described.

  In the said embodiment, it does not restrain in particular with respect to the installation form and number of pass rolls 3A and 3B.

  However, the number of pass rolls is preferably 2 or more, and a larger holding angle than a small holding angle is preferable for enhancing the cooling effect. This holding angle is preferably in the range of 30 to 90 degrees, except when pinching with a pair of pass rolls.

  First, for example, as shown in FIG. 3, the two pass rolls 3A and 3B are arranged with a predetermined distance in the film running direction and slightly shifted up and down, and the downstream pass roll 3A is also provided on the upper surface of the stretched film. The upstream pass roll 3B can be brought into contact with the lower surface of the sheet.

  In addition, for example, as shown in FIG. 4, the two pass rolls 3A and 3C are arranged in a substantially parallel manner separated by a predetermined distance in the film running direction, and the position is separated downward between the two pass rolls 3A and 3C. As a configuration in which one pass roll 3B is disposed on the upper side of the stretched film, the intermediate pass roll 3B can be brought into contact with the lower surface of the stretched film, and the upstream and downstream pass rolls 3A and 3C can be brought into contact with each other. .

  Furthermore, you may combine suitably the pass roll of the form shown in FIG.1, FIG.3, FIG.4.

It is a side view which shows typically one Embodiment of the manufacturing apparatus of the retardation film which concerns on this invention. It is the top view which omitted all the partition walls of FIG. It is other embodiment of the manufacturing apparatus of the retardation film which concerns on this invention, and is a side view corresponding to FIG. FIG. 6 is a side view corresponding to FIG. 1 in still another embodiment of the retardation film manufacturing apparatus according to the present invention.

Explanation of symbols

1A, 1B Primary side nip roll 2A, 2B Secondary side nip roll 3A, 3B, 3C Pass roll
5 Original film
6 Preheating area
7 Stretch zone
8 Cooling zone

Claims (2)

Retardation film by longitudinally uniaxially stretching a raw film made of thermoplastic resin while traveling in one direction between a pair of primary nip rolls and a pair of secondary nip rolls that are spaced apart and have different peripheral speeds An apparatus for manufacturing
Between the primary nip roll and the secondary nip roll, a preheating area, a stretching area, and a cooling area are provided in order from the upstream side in the film running direction,
One or more pass rolls supporting the stretched film are disposed downstream from the position where the final width of the film ends in the stretching region,
An apparatus for producing a retardation film, wherein the surface temperature of the pass roll is set lower than the glass transition temperature Tg of the film. Retardation film by longitudinally uniaxially stretching a raw film made of thermoplastic resin while traveling in one direction between a pair of primary nip rolls and a pair of secondary nip rolls that are spaced apart and have different peripheral speeds A method of manufacturing
The stretched film is formed using one or more pass rolls whose surface temperature is set lower than the glass transition temperature Tg of the film downstream from the position where the final width of the film ends in the stretching region where the film is stretched uniaxially. A method for producing a retardation film, comprising cooling.

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