JP4956973B2 - Method for producing stretched film - Google Patents

Description

  The present invention relates to a stretched film, its use and production method, and more particularly to a stretched film useful as a component of a large display device and the like, and a retardation film obtained by cutting it. Furthermore, it is related with the manufacturing method of the laminated film containing the said stretched film, a polarizing plate, a liquid crystal display device, and the said stretched film.

  A stretched film formed by stretching a resin is used as an optical material such as a component of a display device by utilizing its optical anisotropy. For example, in a liquid crystal display device, the stretched film is used as a retardation film for optical compensation such as anti-coloring and viewing angle expansion, or the stretched film and a polarizer are bonded together to be used as a polarizing plate. It has been known. In general, a polarizing plate and a retardation film used in a liquid crystal display device have a rectangular shape, and a stretched film constituting the polarizing plate has an in-plane slow axis in a direction inclined with respect to the side. May be required. In the liquid crystal display device, such a retardation film or polarizing plate is provided, and the retardation film and the polarizer are arranged so that the in-plane slow axis and the transmission axis of the polarizer are at a desired angle.

  By the way, as a method for producing a stretched film having an in-plane slow axis in a direction inclined with respect to the side as described above, a transparent resin film is oriented by longitudinal stretching or lateral stretching to form a long shape. After obtaining the stretched film, a method of cutting into a rectangular shape at a predetermined angle with respect to the side of the stretched film is widely known. However, in this method, even if cutting is performed so that the maximum area can be obtained, cutting loss always occurs, and the product yield is poor, and as a result, the desired polarizing plate, retardation film, etc. have a large area, cost reduction, and There was a problem that high accuracy could not be achieved at the same time.

  Therefore, various techniques for reducing the cutting loss have been disclosed so far. For example, in Patent Document 1, both ends of a film are gripped and moved between two rows of chucks that run on tenter rails that are arranged so that the running distances of the chucks in a predetermined running section are different. Is described. However, when such oblique stretching is performed, it is difficult to make the slow axis, refractive index and thickness uniform over a wide width of 1300 mm or more, and as a result, most of the film must be trimmed. That is, the utilization efficiency of the stretched film was low.

  Patent Document 2 describes that the content of volatile components is controlled in oblique stretching so as not to cause wrinkles or the like in the film. However, even with such a method, it is still difficult to make the angle, refractive index and thickness of the slow axis uniform over a wide width of 1300 mm or more.

Japanese Patent Laid-Open No. 2-113920 JP 2002-86554 A

  An object of the present invention is to provide a high-quality retardation film, polarizing plate, and liquid crystal that has a large area and is excellent in production efficiency even when the slow axis in the in-plane direction is oblique to the width direction, and has high accuracy over a wide width. It is providing the elongate stretched film which can give a display apparatus, and its manufacturing method.

  In view of the above problems, the present inventors have conducted various studies, and as a result, in the conventional production of continuous stretched films by oblique stretching, the angle at which the film is oriented and the relative angle at which the film is drawn / wound up are determined. The present inventors have found that a novel stretched film with high accuracy over a wide film width can be obtained by using a specific relationship, and the present invention has been completed.

That is, according to the present invention, the following is provided:
[1] A long stretched film made of a transparent resin, having an in-plane slow axis in a direction inclined by 1 to 30 ° from the width direction of the stretched film, and in-plane with respect to light having a wavelength of 550 nm the slow axis direction of the refractive index n _x, when the refractive index in a direction perpendicular to the slow axis in the plane and n _y, the refractive index in the thickness direction and n _z, at least 1300mm width of stretched film over _{and, (n x -n z) /} (n x -n y) in is the average of the coefficient Nz value of 1.0 to 1.3 represented, the angle precision of slow-phase axis, ± A stretched film having a coefficient Nz value accuracy within ± 0.1 and a thickness accuracy within ± 1 μm within 0.5 °.
[2] The stretched film according to [1], wherein the transparent resin is made of a resin having a positive intrinsic birefringence value.
[3] A retardation film obtained by cutting the stretched film according to [1] or [2] into a predetermined size along a direction substantially perpendicular or substantially parallel to the longitudinal direction.
[4] A long laminated film obtained by laminating the stretched film according to [1] or [2] and a long polarizer with their longitudinal directions aligned.
[5] A polarizing plate obtained by cutting the long laminated film according to [4] into a predetermined size.
[6] A liquid crystal display device comprising the retardation film according to [3].
[7] A liquid crystal display device comprising the polarizing plate according to [5].
[8] The liquid crystal display device according to [6] or [7], which is a reflective liquid crystal display device.
[9] Pull out the long transparent resin film from the feeding roll, hold both ends of the transparent resin film in the width direction with the gripping means, and pass the preheating zone, the stretching zone and the fixing zone to stretch the transparent resin film. A stretched film having a slow axis in a direction inclined by an angle θs from the width direction, releasing both ends of the stretched film from the gripping means, and then winding the stretched film on a take-up roll. In which the drawing-out direction θ1 and the angle θs of the feeding roll with respect to the winding-up direction of the winding roll are performed under conditions that satisfy the following formulas (1) and (2): Production method of stretched film:
1 ° ≦ θs <θ1 ≦ 30 ° (1)
θs <θ1-3 ° (2)

The stretched film of the present invention has a large area and is excellent in production efficiency even if the in-plane slow axis is oblique to the width direction, and can be a long stretched film with high accuracy over a wide width. A high-quality retardation film, polarizing plate and the like can be easily obtained with a small cutting loss and trimming loss, and a high-quality liquid crystal display device can be easily provided.
Moreover, this invention can manufacture the stretched film of the said this invention easily. In particular, if desired, stretching with a coefficient Nz close to 1 and close to free-width stretching can be easily achieved.

  The stretched film of the present invention is made of a transparent resin. A transparent resin is a resin that is transparent to light of a desired wavelength. In particular, a thermoplastic resin is preferable. The transparent resin used in the present invention is preferably made of a resin having a positive intrinsic birefringence value. Transparent resins include polycarbonate resin, polyether sulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polyvinyl chloride resin, diacetyl cellulose, triacetyl cellulose, alicyclic ring And olefin polymers. Of these, alicyclic olefin polymers are preferred.

  Examples of the alicyclic olefin polymer include a cyclic olefin random multiple copolymer described in JP-A No. 05-310845, a hydrogenated polymer described in JP-A No. 05-97978, and JP-A No. 11-124429. And thermoplastic dicyclopentadiene-based ring-opening polymers and hydrogenated products thereof.

  The alicyclic olefin polymer will be described more specifically. An alicyclic olefin polymer is a polymer having an alicyclic structure such as a saturated alicyclic hydrocarbon (cycloalkane) structure or an unsaturated alicyclic hydrocarbon (cycloalkene) structure. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15 in the mechanical strength, The properties of heat resistance and film formability are highly balanced and suitable.

  The proportion of the repeating unit containing the alicyclic structure in the alicyclic olefin polymer may be appropriately selected, but is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight. That's it. When the ratio of the repeating unit having an alicyclic structure in the alicyclic polyolefin resin is within this range, it is preferable because the transparency and heat resistance of the optical material such as a retardation film obtained from the stretched film of the present invention are improved. .

  Examples of the alicyclic olefin polymer include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

  Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. An addition polymer of a monomer having a monomer, an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used.

  Monomers having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.12,5] deca-3,7-diene ( Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.12,5] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0.12, 5.17,10] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different and a plurality may be bonded to the ring. Monomers having a norbornene structure can be used singly or in combination of two or more.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group.

  Other monomers capable of ring-opening copolymerization with monomers having a norbornene structure include monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene; Derivatives thereof; and the like.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer of a monomer having a norbornene structure and another monomer copolymerizable with the monomer have a known ring-opening polymerization catalyst. It can be obtained by (co) polymerization in the presence.

  Examples of other monomers that can be addition copolymerized with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene, cyclopentene, And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and the like. These monomers can be used alone or in combination of two or more. Among these, α-olefin is preferable and ethylene is more preferable.

  An addition polymer of a monomer having a norbornene structure and an addition copolymer of a monomer having a norbornene structure with another monomer copolymerizable with a monomer having a norbornene structure are prepared in the presence of a known addition polymerization catalyst. It can be obtained by polymerization.

  A hydrogenated product of a ring-opening polymer of a monomer having a norbornene structure, a hydrogenated product of a ring-opening copolymer of a monomer having a norbornene structure and another monomer capable of ring-opening copolymerization thereof, Hydrogenated products of addition polymers of monomers having a norbornene structure, and hydrogenated products of addition copolymers of monomers having a norbornene structure and other monomers copolymerizable therewith It can be obtained by adding a known hydrogenation catalyst containing a transition metal such as nickel or palladium to the polymer solution and hydrogenating carbon-carbon unsaturated bonds, preferably 90% or more.

  Among norbornene-based resins, as a repeating unit, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.12,5] decane-7, 9-diyl-ethylene structure, the content of these repeating units is 90% by weight or more with respect to the entire repeating unit of the norbornene-based resin, and the content ratio of X and the content ratio of Y It is preferable that the ratio is 100: 0 to 40:60 by weight ratio of X: Y. By using such a resin, the optical material obtained from the stretched film of the present invention can be made long-term without dimensional change and excellent in optical property stability.

  The molecular weight of the transparent resin used in the present invention is appropriately selected according to the purpose of use, but converted to polyisoprene (solvent) measured by gel permeation chromatography using cyclohexane (toluene when the transparent resin is not dissolved) as a solvent. When is toluene, it is a weight average molecular weight (Mw) in terms of polystyrene, and is usually 10,000 to 100,000, preferably 15,000 to 80,000, more preferably 20,000 to 50,000. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the optical material obtained by the stretched film of the present invention are highly balanced and suitable.

  The glass transition temperature of the transparent resin may be appropriately selected according to the purpose of use, but is preferably 80 ° C. or higher, more preferably 100 to 250 ° C. When the glass transition temperature is in such a range, the optical material obtained by the stretched film of the present invention can be made excellent in durability without causing deformation or stress in use at high temperatures.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the transparent resin is not particularly limited, but is usually 1.0 to 10.0, preferably 1.1 to 4.0, more preferably 1. It is in the range of 2 to 3.5.

The absolute value of the photoelastic coefficient of the transparent resin is preferably 10 × 10 ^-12 Pa ^-1 or less, more preferably 7 × 10 ^-12 Pa ^-1 or less, 4 × 10 ^-12 Pa ^-1 It is particularly preferred that The photoelastic coefficient C is a value represented by C = Δn / σ where birefringence is Δn and stress is σ. When the photoelastic coefficient of the transparent resin is within such a range, variations in retardation (Re) in the in-plane direction, which will be described later, can be reduced.

  The transparent resin used in the present invention contains a coloring agent such as a pigment or dye, a fluorescent brightening agent, a dispersant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like. An agent may be appropriately blended.

  The stretched film of the present invention is a long film. “Long” means a film having a length of at least about 5 times or more with respect to the width direction of the film, preferably having a length of 10 times or more, specifically wound in a roll shape. It has a length that can be stored or transported. The stretched film of the present invention has a width of 1300 mm or more, preferably 1450 mm or more. The film applicable to the present invention may be a single layer film or a multilayer film.

  In the production process, the stretched film of the present invention is optionally prepared by cutting off both ends in the width direction after stretching. In this case, the width of the film referred to above is the dimension after cutting off both ends. be able to.

  The stretched film of the present invention has an in-plane slow axis in a direction inclined by 1 to 30 ° from the width direction. Further, the accuracy of the angle of the slow axis is within ± 0.5 °, preferably within ± 0.4 ° over at least 1300 mm width of the stretched film. When the accuracy of the angle of the slow axis is in such a range, when an optical material such as a retardation film obtained from a stretched film is used for a liquid crystal display device, the brightness and front contrast of the liquid crystal display device are improved. Can do.

Stretched film of the present invention, for light with a wavelength of 550 nm, a slow axis direction of the refractive indices n _x in the plane of the film, the refractive index in a direction perpendicular in the slow axis and the plane of the plane n _y, film the refractive index in the thickness direction when the n _z, an average of (n _x -n _z) / coefficient Nz value represented by (n _x -n _y) is, for at least 1300mm width of the stretched film, 1.0 or more and 1.3 or less. The average of the coefficient Nz values can be larger than 1.0, and is preferably 1.05 or more and 1.25 or less. Furthermore, the accuracy of the coefficient Nz value is within ± 0.1, preferably within ± 0.05, over at least 1300 mm width of the stretched film. When the Nz value is in such a range, when an optical material such as a retardation film obtained from a stretched film is used for a liquid crystal display device, the variation in viewing angle of the liquid crystal display device can be reduced.

The average value of retardation (Re) in the in-plane direction and the average value of retardation (Rth) in the thickness direction of the stretched film of the present invention varies depending on the design of the liquid crystal display device. The average value of 300 nm and Rth is appropriately selected from the range of about 100 to 300 nm. Incidentally, Re in the present invention, the average thickness of the film is taken as Tw, a value defined by _{(n x -n y) × Tw} , Rth in the present _{invention, (((n x + n} y) / 2) -n _z ) × Tw.

  In the stretched film of the present invention, the variation in Re is usually within 10 nm, preferably within 5 nm, and more preferably within 2 nm over at least 1300 mm width of the stretched film. By setting the Re variation within the above range, when an optical material such as a retardation film obtained from a stretched film is used in a liquid crystal display device, the display quality of the liquid crystal display device can be improved. Become. Here, the variation in Re is the maximum value of Re when the Re is measured in the width direction of the stretched film when the light incident angle is 0 ° (when the incident light beam and the retardation film surface of the present invention are orthogonal). And the minimum value.

  The average thickness of the stretched film of the present invention is preferably 30 to 80 μm, more preferably 30 to 60 μm, and particularly preferably 30 to 50 μm from the viewpoint of mechanical strength and the like. Moreover, the thickness accuracy in the width direction of the stretched film of the present invention is within ± 1 μm over at least 1300 mm width of the stretched film. When the thickness accuracy is in such a range, the stretched film of the present invention can be wound up at a high speed at a long length, and an optical material such as a retardation film obtained from the stretched film is applied to a liquid crystal display device. When used, the display quality can be improved.

  The content of the residual volatile component in the stretched film of the present invention is not particularly limited, but is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.02% by weight or less. . By making the content of the volatile component in such a range, the dimensional stability can be improved, the change with time of the Re and Rth can be reduced, and further the retardation obtained from the stretched film of the present invention. Deterioration of the film, the polarizing plate or the liquid crystal display device can be suppressed, and the display on the liquid crystal display device can be stably and satisfactorily maintained for a long time. The residual volatile component is a substance having a molecular weight of 200 or less contained in a trace amount in the film, and examples thereof include a residual monomer and a solvent. The content of residual volatile components can be quantified by analyzing the film by gas chromatography as the sum of the substances having a molecular weight of 200 or less contained in the film.

  The saturated water absorption of the stretched film of the present invention is preferably 0.03% by weight or less, more preferably 0.02% by weight or less, and particularly preferably 0.01% by weight or less. When the saturated water absorption is in the above range, the change with time of Re and Rth can be reduced, and further, deterioration of the retardation film, polarizing plate or liquid crystal display device obtained from the stretched film of the present invention can be suppressed. In particular, the display on the liquid crystal display device can be kept stable and good.

  Saturated water absorption is a value expressed as a percentage of the mass of the test piece before immersion, after the test piece of the film is immersed in water at a constant temperature for a fixed time. Usually, it is measured by immersing in 23 ° C. water for 24 hours. The saturated water absorption rate in the stretched film of the present invention can be adjusted to the above value by, for example, reducing the amount of polar groups in the transparent resin, but it is preferable that the resin does not have polar groups. It is.

  In the method for producing a stretched film of the present invention, a long transparent resin film is pulled out from a feed roll, both ends in the width direction of the transparent resin film are gripped by gripping means, and passed through a preheating zone, a stretching zone, and a fixed zone. The transparent resin film is stretched to obtain a stretched film having a slow axis in a direction inclined by an angle θs from the width direction, both ends of the stretched film are released from the gripping means, and then the stretched film is wound on a take-up roll. A step of taking.

  Hereinafter, the manufacturing method of the stretched film of this invention is demonstrated, referring drawings. FIG. 1 is a top view schematically showing an example of a tenter stretching machine that can be suitably used in the production method of the present invention. FIG. 2 is a view showing a means for gripping the rail portion in the stretching machine of FIG.

The tenter stretching machine shown in FIG. 1 includes a draw roll 21, a take-up roll 22, a temperature-controlled room 10 composed of a preheating zone A, a stretching zone B, and a fixed zone C, and a rail on which gripping means for transporting the film travels. 11 and gripping means 12 (the gripping means is not shown in FIG. 1).
The gripping means 12 grips both ends of the film fed out from the drawing roll 21, guides the film into a temperature-controlled room composed of the preheating zone A, the stretching zone B, and the fixing zone C, and opens the film before the winding roll 22. . The film released from the gripping means is taken up by the take-up roll 22. The rail 11 has a continuous track without a terminal, and returns the gripping means that has traveled as described above from the exit side of the temperature-controlled room to the entrance side.

The film 1 is stretched at a desired stretching ratio by tension from the gripping means while passing through the temperature-controlled room composed of a preheating zone, a stretching zone, and a fixed zone. Although a draw ratio is not specifically limited, Preferably it is 3.0-5.0, More preferably, it can be 3.5-4.5.
In the production method of the present invention, stretching starts near the stretching start point and ends near the stretching end point. The stretching start point refers to the point at which the load on the gripping means increases, and the stretching end point refers to the point at which the load decreases and becomes constant after the load on the gripping means increases. The point where the load on the gripping means increases is near the boundary 13 between the preheating zone and the stretching zone, and the point where the load on the gripping means decreases and becomes constant again is near the boundary 14 between the stretching zone and the fixed zone.
The preheating zone, the stretching zone, and the fixed zone can be set independently of each other, and the temperature is normally kept constant in each zone.
In the method of the present invention, a temperature difference may be provided in the width direction of the film in the stretching zone in order to control the accuracy of the thickness in the width direction. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used.
The length of the preheating zone, the stretching zone and the fixed zone can be appropriately selected. Usually, the length of the preheating zone is usually 100 to 150% and the length of the fixing zone is usually 50 to 100% with respect to the length of the stretching zone. It is.

The gripping means 12 travels on the rail 11 whose arrangement can be changed, for example. The rail 11 is arranged so as to be stretched on the film at a desired stretch ratio. In the present invention, the drawing roll drawing direction θ1 with respect to the winding direction of the winding roll and the angle of the slow axis with respect to the film width direction (hereinafter sometimes referred to as “orientation angle”) θs satisfy the relationship described later. So set up this rail placement.
At the boundary 13 between the preheating zone and the stretching zone and at the boundary 14 between the stretching zone and the fixed zone, a partition plate having a slit through which the film can pass is installed. It is preferable that the boundary between the preheating zone and the stretching zone and the boundary between the stretching zone and the fixed zone, that is, the partition plate is perpendicular to the winding direction D2 of the winding roll.

  The preheating zone A is a zone in which the film is conveyed while warming the film without substantially changing the film width in the direction perpendicular to the film running direction D1. The film running direction D1 in the preheating zone is a direction parallel to the drawing direction of the film from the feeding roll.

  The stretching zone B is a zone for transporting the film while increasing the film length in the direction perpendicular to the film running direction. In FIG. 2, a broken line 20 is a line indicating the correspondence relationship of the corresponding gripping means 12 in the left and right rails 11. In the example shown in the drawing, the left and right gripping means proceed along the film running direction at substantially constant speed, and the film width is expanded in the stretching zone B. Further, the film is caused by the difference in the left and right rail lengths in the stretching zone B (in the example shown in FIG. 2, the travel distance of the upper gripping means in the drawing is longer than the travel distance of the lower gripping means). The stretching direction is an oblique direction with respect to the film width direction and is guided to the fixing zone C. A more specific mode of stretching in the stretching zone will be described later.

  The fixed zone C is a zone in which the film is conveyed while cooling the film without substantially changing the film width in the direction perpendicular to the film running direction D2. The film running direction D2 in the fixed zone is a direction parallel to the direction in which the film is wound on the roll, and is orthogonal to the rotation axis of the winding roll.

The method for producing a stretched film of the present invention is performed under the condition that the drawing-out direction θ1 and the orientation angle θs of the feeding roll with respect to the winding direction of the winding roll satisfy the following expressions (1) and (2). :
1 ° ≦ θs <θ1 ≦ 30 ° (1)
θs <θ1-3 ° (2)
The manufacturing method performed under such conditions will be described more specifically with reference to FIGS.

  FIG. 3 is a schematic top view illustrating a more detailed example of the rail arrangement of the stretching zone in the example of the tenter stretching machine illustrated in FIGS. 1 and 2. The film drawn in the drawing direction D1 from the feeding roll is guided along the rails 33A to 33C and 34A to 34C. In the preheating zone A, the left and right rails 33A and 34A are parallel and guide the film without stretching. The film width in preheat zone A is indicated by line 32. In the stretching zone B, the width between the left and right rails 33B and 34B expands as the film progresses, whereby stretching is performed. Further, due to the difference in length between the rails 33B and 34B, the extending direction becomes an oblique direction. Then, the stretched film further proceeds to the fixing zone C and is guided to the parallel rails 33C and 34C. As a result, the gripping means corresponding to both ends of the line 32 in the preheating zone A corresponds to both ends of the line 35 in the fixed zone C, and an orientation angle θ3S of 1 ° or more (the above formula (1) and The diagonal stretching at (corresponding to θs in (2)) is achieved. The stretched film is wound on a winding roll in the winding direction D2.

  Here, the drawing direction D1 and the winding direction D2 form an angle indicated by θ31 (corresponding to θ1 in the above formulas (1) and (2)). The stretched film of the present invention has a uniform orientation angle, refractive index, and thickness over a wide width direction of 1300 mm or more by setting the angle θ31 to 30 ° or less and further to an angle larger than a predetermined angle than the orientation angle θ3S. Can be obtained. Further, if desired, stretching with a coefficient Nz close to 1 and close to free width stretching can be easily achieved. On the other hand, for example, as shown in FIG. 5, rails 53 </ b> A to 53 </ b> C and 54 </ b> A to 54 </ b> C are laid and a film having a width of the length of the line 52 is stretched in the axial direction shown by the line 55. When the angle θ51 formed by the winding direction is smaller than the orientation angle θ5S, a uniform orientation angle, refractive index, and thickness cannot be obtained over the wide width direction of the film.

  In the production method of the present invention, the drawing-out direction θ1 of the feeding roll and the orientation angle θs with respect to the winding direction of the winding roll have the relationship of the above formula (2), preferably θs <θ1-5 °. . As described above, when θs and θ1 are different from each other by a predetermined value or more, the stretched film of the present invention having a uniform orientation angle, refractive index, and thickness over a wide width direction of 1300 mm or more can be obtained.

In the manufacturing method of the present invention, the rail of the extending zone B is not limited to a straight rail, and may be a curved or bent rail. By changing the shape of the rail, the length of the rail can be changed, and as a result, the orientation angle θs can be adjusted.
Specifically, for example, in the rail pattern shown in FIG. 4, as in the case shown in FIG. 3, the rails 43 </ b> A to 43 </ b> C and 44 </ b> A to 44 </ b> C are laid and The one rail in the extending zone B has a bent line shape as indicated by 44B-1 and 44-B2. Even in such a rail pattern, when the angle θ41 formed by the drawing direction and the winding direction is larger than the orientation angle θ4S, a uniform orientation angle, refractive index, and thickness can be obtained over a wide width direction of the film. it can.

  In the production method of the present invention, the angle θ1 may be tilted in any direction with respect to the traveling direction of the film. For example, in the example of the top view shown in FIGS. 3 to 4, when the winding side is turned to the left (corresponding to the right side of the drawing) when viewed from the take-up side, the positive angle is used. Even when the case is viewed as a positive angle, the requirement of the present invention is satisfied if the above condition is satisfied. Further, for example, when the case of turning to the left when looking at the winding side from the feeding side as shown in FIGS. 3 to 4 is a positive angle of θ1, the orientation angle θS is the right end of the film (the film in the drawing The angle at which the left end of the head is shifted toward the front (that is, the feeding side; the upward direction in the drawing) can be a positive angle. On the other hand, when the right side when looking at the winding side from the feeding side is defined as a positive angle of θ1, the orientation angle θS may be a positive angle at which the left edge of the film is tilted forward. it can. Further, in the obtained stretched film of the present invention, the slow axis in the in-plane direction is tilted in any direction with respect to the film width direction (that is, the left or right end when viewed from the take-out side to the take-up side). (The side may be shifted toward you and tilted.)

  In the production method of the present invention, the film surfaces in the preheating zone, the stretching zone, and the fixing zone are preferably substantially parallel to each other. That is, it is preferable that the film drawn from the drawing roll is flat without being twisted, passes through the preheating zone, the stretching zone, and the fixing zone, and is wound on the winding roll.

  In the manufacturing method of this invention, it is preferable that the running speed of the said holding means is substantially equal at both ends of the film. Although the traveling speed of the gripping means can be selected as appropriate, the traveling speed of the film can be normally set to 5 to 50 m / min. If the left and right gripping means advance at “substantially constant speed”, the right and left speed errors are zero. .1 m / min or less.

  As a method for preparing a long transparent resin film before stretching for use in the production method of the present invention, a known molding method can be employed. For example, either a hot melt molding method or a solution casting method can be employed, but from the viewpoint of reducing volatile components in the sheet, it is preferable to use the hot melt molding method.

  The hot melt molding method can be further classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, it is preferable to use a melt extrusion molding method from the viewpoint of obtaining a stretched film having excellent mechanical strength and surface accuracy.

  The retardation film of the present invention is obtained by cutting the stretched film of the present invention into a predetermined size along a direction substantially perpendicular or substantially parallel to the longitudinal direction. Here, the substantially perpendicular direction means a direction within ± 0.5 ° with respect to the direction perpendicular to the longitudinal direction of the film in the plane of the film, and the substantially parallel direction means the direction of the film in the plane of the film. A direction within ± 0.5 ° with respect to the longitudinal direction.

The laminated film of the present invention is a long laminated film obtained by laminating the stretched film of the present invention and a long polarizer with their longitudinal directions aligned.
The polarizer used in the present invention transmits one of two linearly polarized light intersecting at right angles and absorbs the other. For example, a hydrophilic polymer film such as a polyvinyl alcohol film or an ethylene vinyl acetate partially saponified film is used. Those obtained by adsorbing dichroic substances such as iodine and dichroic dyes and uniaxially stretching, those obtained by uniaxially stretching the hydrophilic polymer film and adsorbing dichroic substances, dehydrated polyvinyl alcohol, Examples include polyene oriented films such as polyvinyl chloride dehydrochlorinated products. The thickness of the polarizer is usually 5 to 80 μm.

  The laminated film of the present invention may be obtained by laminating stretched films on both sides of a polarizer, or may be obtained by laminating stretched films only on one side. Moreover, there is no limitation in particular also in the number of the stretched films laminated | stacked on each surface of a polarizer, You may laminate | stack two or more sheets. When the stretched film is laminated only on one side of the polarizer, a protective film may be laminated on the remaining one side with an appropriate adhesive layer for the purpose of protecting the polarizer.

  An appropriate transparent film can be used as the protective film. Among them, a film having a resin excellent in transparency, mechanical strength, thermal stability, moisture shielding property, etc. is preferably used. Examples of the resin include an acetate polymer such as triacetyl cellulose, an olefin polymer having an alicyclic structure, a polyolefin polymer, a polycarbonate polymer, a polyester polymer such as polyethylene terephthalate, a polyvinyl chloride polymer, a polystyrene polymer, Examples thereof include polyacrylonitrile polymers, polysulfone polymers, polyether sulfone polymers, polyamide polymers, polyimide polymers, acrylic polymers, and the like.

  A preferred production method for obtaining the long laminated film of the present invention is to simultaneously pull out the long stretched film of the present invention wound in a roll shape and the long polarizer wound in a roll shape from the roll. However, it is a method including bringing the stretched film and the polarizer into close contact with each other. An adhesive can be interposed on the adhesion surface between the stretched film and the polarizer. As a method for bringing the stretched film and the polarizer into close contact with each other, there is a method in which the stretched film and the polarizer are passed and pressed together through the nip between two parallel rolls.

  The long stretched film or the long laminated film of the present invention is cut into a desired size according to the usage pattern and used as a retardation film or a polarizing plate. In this case, it is preferable to cut out along a direction substantially perpendicular or substantially parallel to the longitudinal direction of the long film.

  The liquid crystal display device of the present invention comprises a retardation film and / or a polarizing plate cut out from the stretched film of the present invention or the laminated film of the present invention. An example of the liquid crystal display device of the present invention includes a liquid crystal panel that can change the alignment of liquid crystal by adjusting the voltage and the polarizing plate of the present invention that is disposed so as to sandwich the liquid crystal panel. . The retardation film is used in a liquid crystal display device for optical compensation, polarization conversion, and the like. In order to send light to the liquid crystal panel, the liquid crystal display device is usually provided with a backlight device in the transmissive liquid crystal display device and a reflector in the reflective liquid crystal display device on the back side of the display surface. Examples of the backlight device include a cold cathode tube, a mercury flat lamp, a light emitting diode, and an EL. As the liquid crystal display device of the present invention, a reflective liquid crystal display device including a reflective display type liquid crystal panel is preferable. The liquid crystal panel is not particularly limited by the display mode. Examples thereof include a twisted nematic (TN) mode, a super twisted nematic (STN) mode, and a hybrid alignment nematic (HAN) mode. In the liquid crystal display device of the present invention, other appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a brightness enhancement film can be arranged in one or more layers at appropriate positions.

  The stretched film of the present invention can be applied to organic EL display devices, plasma display devices, FED (field emission) display devices, and SED (surface electric field) display devices in addition to liquid crystal display devices.

  The stretched film, retardation film, laminated film, polarizing plate, liquid crystal display device, and stretched film manufacturing method of the present invention may be modified within the same range with respect to the above-mentioned constituent requirements, and are optional. Can be added. For example, in the method for producing a stretched film of the present invention, a long transparent resin film may be continuously supplied while being prepared by a melt extrusion molding method or the like instead of a feeding roll. In this case, the longitudinal direction of the supplied film corresponds to the drawing direction. Moreover, it may replace with winding up a stretched film on a winding roll, and you may use for the process of sticking with other layers, such as a polarizer, continuously.

The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.
Evaluation in this example is performed by the following method.
(1) Thickness Using a film thickness meter (manufactured by Meisho Co., Ltd., RC-1 ROTARY CALIPER), the thickness is measured at intervals of 5 mm over the center part of the film in the width direction of the stretched film 1340 mm, and the average value is calculated. The accuracy was determined as the difference between the maximum value and the minimum value and the average value.
(2) Orientation angle Using a polarizing microscope (manufactured by NICON, ECLIPSE E600 POL), in the width direction of the stretched film, the width direction of the stretched film has a slow axis in the in-plane direction at an interval of 5 cm over the center 1340 mm of the film. The angle to was measured. The average value of the angles was obtained, and the greater difference between the maximum value and the minimum value and the average value was defined as the accuracy.
(3) Nz value Using a phase difference meter (manufactured by Oji Scientific Co., Ltd., KOBRA21-ADH), measure the width of the stretched film in the width direction of the stretched film at a wavelength of 590 nm at intervals of 5 cm, and obtain an average value. The greater difference between the maximum value and the minimum value and the average value was defined as the accuracy.
(4) In-plane retardation (Re)
Using a phase difference meter (manufactured by Oji Scientific Co., Ltd., KOBRA21-ADH), the film was measured at a wavelength of 590 nm at intervals of 5 cm in the width direction of the stretched film over the center part of 1340 mm, and the average value was taken as the measurement value.

Example 1
A norbornene-based resin pellet (ZEONOR1420, manufactured by Nippon Zeon Co., Ltd.) is dried at 100 ° C. for 5 hours, supplied to an extruder, extruded through a polymer pipe and a polymer filter from a T die onto a casting drum, cooled, A long unstretched film (0) having a thickness of 160 μm was obtained. The unstretched film (0) was wound up on a roll.
Next, the unstretched film (0) was pulled out from the roll and continuously supplied to a tenter stretching machine (1) set in a rail pattern as shown in FIG. 3 to perform stretching to obtain a stretched film having a width of 1600 mm. . At this time, θ1, θs (design orientation angle: a value obtained based on the displacement of the gripping means at both ends after stretching), stretching temperature (same temperature in zones A to C), and stretching ratio are shown in Table 1. It was street. After stretching, the stretched film obtained was trimmed at both ends, leaving a central portion of 1340 mm in the width direction, and wound on a roll to obtain a stretched film (2) having a width of 1340 mm. The stretched film (2) was measured for thickness, orientation angle, Nz value, and retardation in the in-plane direction. The results are shown in Table 1.

  As shown in Table 1, the stretched film (2) obtained in Examples 1 and 2 has a coefficient Nz of 1.0 or more and 1.3 or less over the width of 1340 mm, and the angle of the slow axis in the in-plane direction. The accuracy was within ± 0.5 °, the accuracy of the coefficient Nz was within ± 0.1, and the thickness accuracy was within ± 1 μm.

Example 2
A 1340 mm wide stretched film was obtained and measured in the same manner as in Example 1 except that θ1, stretch temperature, and stretch ratio were changed as shown in Table 1. The results are shown in Table 1. As shown in Table 1, the stretched film obtained in Example 2 has a coefficient Nz of 1.0 or more and 1.3 or less over a width of 1340 mm, and the accuracy of the angle of the slow axis in the in-plane direction is ± 0. Within 5 °, the accuracy of the coefficient Nz was within ± 0.1, and the thickness accuracy was within ± 1 μm.

Further, a long polarizing plate (manufactured by Sanlitz, HLC2-5618S, thickness 180 μm) having a polarization transmission axis parallel to the width direction and the stretched film (2) obtained in Example 1 are rolled to roll By sticking together, a wound body of a long optical element was obtained.
The optical element cut out from the wound body is further subjected to a normal retardation film (3) obtained by normal longitudinal uniaxial stretching with Re of 135 nm, and its slow axis is 75 ° with respect to the transmission axis of the polarizing plate. A laminated polarizing plate was obtained by attaching the batch on the stretched film (2) side so as to form an angle.
Subsequently, the polarizing plate provided in the commercially available reflective liquid crystal device was replaced with the polarizing plate. At this time, the retardation film (3) was assembled so that the side on which the retardation film (3) was bonded was disposed on the liquid crystal cell side. When the display characteristics of the obtained liquid crystal display device were confirmed from the front by visual observation, the display was good and uniform.

Comparative Examples 1-2
A 1340 mm wide stretched film was obtained and measured in the same manner as in Example 1 except that θ1, stretch temperature, and stretch ratio were changed as shown in Table 1. The results are shown in Table 1. As shown in Table 1, the stretched films obtained in Comparative Examples 1 and 2 have the accuracy of the angle of the slow axis in the in-plane direction over the width of 1340 mm, the accuracy of the coefficient Nz, and the thickness accuracy of Examples 1-2. The accuracy of the angle of the slow axis in the in-plane direction is within ± 0.5 ° and the accuracy of the coefficient Nz is within ± 0.1 only in the central area of 800 mm in the width direction of the film. And the thickness accuracy was within ± 1 μm.

It is a top view which shows roughly an example of the tenter stretching machine which can be used suitably for the manufacturing method of the stretched film of this invention. It is a top view which shows roughly the holding means of the rail part in the extending | stretching machine of FIG. It is a schematic top view explaining the more detailed example of rail arrangement | positioning in the drawing machine of FIG. It is a schematic top view explaining another example of rail arrangement | positioning in the extending | stretching machine of FIG. It is a schematic top view explaining the example of the rail arrangement | positioning of a comparative example.

Explanation of symbols

1: Film 10: Temperature-controlled room 11, 33A-33C, 34A-34C, 43A-43C, 44A-44C, 53A-53C, 54A-54C: Rail 12: Grasping means 13: Boundary between preheating zone and stretching zone 14: Boundary 21 between the stretching zone and the fixing zone 21: drawer roll 22: take-up roll

Claims (3)

  Pull out the long transparent resin film from the feed roll,
  Grasping both ends in the width direction of the transparent resin film by gripping means,
  Stretching the transparent resin film through a preheating zone, a stretching zone, and a fixed zone to obtain a stretched film having a slow axis in a direction inclined by an angle θs from the width direction,
  Release both ends of the stretched film from the gripping means;
  A method for producing a stretched film, comprising the step of winding the stretched film on a take-up roll,
  A method for producing a stretched film, characterized in that the drawing direction θ1 and the angle θs of the feeding roll with respect to the winding direction of the winding roll are performed under conditions that satisfy the following formulas (1) and (2):
  1 ° ≦ θs <θ1 ≦ 30 ° (1)
  θs <θ1-3 ° (2) The manufacturing method according to claim 1, wherein the transparent resin is made of a resin having a positive intrinsic birefringence value.   The manufacturing method according to claim 1, wherein the traveling speed of the gripping means is substantially equal at both ends of the film.

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