JP2007094007A - Oriented film and method for manufacturing oriented film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide and long oriented film effectively useful for optical compensation in a liquid crystal display apparatus with high use efficiency, to provide a method for manufacturing a wide and long oriented film having uniform thickness in the width direction and having an in-plane lagging axis in a direction greatly inclined from the width direction, and to provide a liquid crystal display device which has the oriented film and is excellent in visibility. <P>SOLUTION: The long oriented film has the film width of 1,300 nm or more and an in-plane lagging axis in a direction inclined by 51 to 85° angle from the width direction of the film, with deviation of the lagging axis being within 1° over the entire width of the film. The film is made of a transparent resin characterized in that a coefficient Nz represented by Nz=(n<SB>x</SB>-n<SB>z</SB>)/(n<SB>x</SB>-n<SB>y</SB>) is 1.3 or less, wherein n<SB>x</SB>represents the refractive index in the direction of the in-plane lagging axis, n<SB>y</SB>represents the refractive index in a direction orthogonal to the in-plane lagging axis in the plane, and n<SB>z</SB>represents the refractive index in the thickness direction, for light at 550 nm wavelength. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a long stretched film and a method for producing a long stretched film.

In a liquid crystal display device having a polarizing plate, various retardation films are used for optical compensation such as coloring prevention and viewing angle expansion. In general, a retardation film used in a liquid crystal display device has a rectangular shape and has an in-plane slow axis in a direction inclined with respect to the side. In a liquid crystal display device, such a retardation film is laminated with a polarizing plate so that the in-plane slow axis of the retardation film and the transmission axis of the polarizing plate are arranged at a desired angle.
By the way, as a method for producing a retardation 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 be long. After obtaining a stretched film in a shape, a method of cutting into a square at a predetermined angle with respect to the sides of the stretched film is widely known. However, this method has a problem that even if the cutting is performed so as to obtain the maximum area, a cutting loss always occurs and the product yield is poor.

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. Further, in Patent Document 2, a plastic film is stretched uniaxially in the transverse or longitudinal direction, and the right and left sides of the stretching direction are stretched in the longitudinal or transverse direction different from the stretching direction at different speeds, and the in-plane It is described that the slow axis is inclined with respect to the uniaxial stretching direction. If a long stretched film obtained by these methods is used, a rectangular retardation film having an in-plane slow axis in a direction inclined with respect to the side is obtained by cutting it parallel to the side. It can be obtained and the utilization efficiency of the long stretched film is increased.
However, in these methods, effective thickness control means in the width direction of the long stretched film has not been found, and as a result, most of the film has to be trimmed, and the utilization efficiency of the stretched film is low. . It was impossible to industrially mass-produce a long stretched film having a uniform thickness in the width direction and a wide width. In particular, it was practically impossible to obtain a wide elongated stretched film having an in-plane slow axis in a direction exceeding 50 ° with respect to the width direction.
Furthermore, in Patent Document 3, the absorption axis of the long polarizing film, the slow axis in the plane of the long half-wave plate, and the slow axis in the plane of the long quarter-wave plate Among them, a method is described in which at least two are not parallel or perpendicular to the longitudinal direction, and a long circular polarizing plate formed by bonding is obtained by oblique stretching. However, here too, a wide stretched film having an in-plane slow axis in a direction exceeding 50 ° with respect to the width direction, which is useful for optical compensation of a liquid crystal display device, has not been obtained. Met. In addition, as a long stretched film having an in-plane slow axis in a direction exceeding 50 ° with respect to the width direction, for example, it has an in-plane slow axis in a direction inclined by 75 ° from the width direction of the film. Such a long stretched film is required. This is also suggested in paragraph 0004 of Patent Document 3.

Japanese Patent Laid-Open No. 2-113920 Japanese Patent Laid-Open No. 2000-9912 Japanese Patent Laid-Open No. 2004-20827

  An object of the present invention is to provide a wide elongated stretched film that is effective for optical compensation of a liquid crystal display device and has high utilization efficiency, in-plane in a direction that is uniform in the width direction and greatly inclined from the width direction. An object of the present invention is to provide a method for producing a wide elongated stretched film having a slow axis and a liquid crystal display device having excellent visibility, comprising a retardation film cut out from the stretched film.

  As a result of intensive studies to solve the above-mentioned object, the present inventor can obtain a stretched film having a specific optical performance and a wide and uniform thickness only by adopting specific stretching conditions. Furthermore, the inventors have found that this retardation film is effective for optical compensation of a liquid crystal display device, and have reached the present invention.

Thus, according to the present invention,
(1) A long film made of a thermoplastic resin,
The width of the film is 1300 mm or more,
An in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction of the film,
The variation of the slow axis is within 1 ° over the entire width of the film, and
Wavelength 550nm to light, the refractive index in a slow axis direction n _x in the _plane, the refractive index in a direction perpendicular in the slow axis and the plane of the plane n _y, the refractive index in the thickness direction and n _z when _a phase difference film, wherein the coefficient Nz value represented by _{(n x -n z) / (} n x -n y) is 1.3 or less,
(2) The thermoplastic film is made of a resin having a positive intrinsic birefringence value. The retardation film according to (1) (3) (1) or (2), A retardation film that is cut into a predetermined size along a direction perpendicular or parallel to the longitudinal direction,
(4) A long laminated film in which the stretched film according to (1) or (2) and a long polarizer are laminated 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) (a) Pull out the long thermoplastic resin film from the first roll,
Grasping both ends of the film with gripping means, passing the first preheating zone, the first stretching zone, and the first fixing zone, stretching the film at a stretching ratio of R ₁ (times),
Release both ends of the film from the gripping means, wind the stretched film on a second roll,
Obtaining a long film intermediate having an in-plane slow axis in a direction inclined from 5 to 50 ° from the width direction of the film;
(B) pulling out the long film intermediate from the second roll;
Grasping both ends of the film by gripping means, passing the second preheating zone, the second stretching zone, and the second fixing zone, stretching the film at a stretching ratio of R ₂ (times),
Release both ends of the film from the gripping means, wind the stretched film on a third roll,
A step of obtaining a long film retardation film having an in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction of the film,
(C) When the average temperature of the first stretching zone is T ₁ (° C.) and the average temperature T ₂ (° C.) of the second stretching zone,
T ₁ <T ₂ and R ₁ <R ₂ are satisfied,
(D) The film traveling direction of the first fixed zone is different from the film traveling direction of the first preheating zone, and the film traveling direction of the second fixed zone is Different from the film running direction in the preheating zone,
A method for producing a long retardation film, characterized in that
Is to provide.

When the stretched film of the present invention is used in a liquid crystal display device, particularly a reflective liquid crystal display device, the viewing angle of the display screen is widened, and a reduction in contrast and coloring can be prevented. In addition, since the thickness in the width direction is uniform, it can be obtained in a long length, so that it can be superposed on another long optical element used in a liquid crystal display device such as a polarizing plate by a roll-to-roll. In a film having an in-plane slow axis parallel to the width direction or the longitudinal direction of the long film, there was a lot of discarded portions because it was necessary to cut obliquely. The stretched film obtained by the production method of the present invention and having an in-plane slow axis obliquely to the width direction can be cut parallel to the width direction or the longitudinal direction, so that there are few discarded portions of the film and excellent productivity. ing.
Furthermore, according to the method for producing a stretched film of the present invention, it is useful for optical compensation of a liquid crystal display device, has a uniform thickness in the width direction, can be wound at a high speed, and is greatly inclined with respect to the width direction. A wide stretched film having an in-plane slow axis in the direction can be easily obtained.

  The stretched film of the present invention is made of a transparent resin. A transparent resin is a resin that is transparent to 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.

  The alicyclic olefin polymer includes a cyclic olefin random multi-component 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 retardation film obtained by the method 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.

Examples of monomers having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7-diene. (Common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4.0. 1 ^2,5 . 1 ^7,10 ] 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 repeating units, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure, the content of these repeating units is 90% by weight or more based on the entire repeating units of the norbornene-based resin, and the content ratio of X and the content ratio of Y Is preferably 100: 0 to 40:60 by weight ratio of X: Y. By using such a resin, it is possible to make the retardation film of the present invention excellent in stability of optical characteristics without long-term dimensional change.

  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 measured by gel permeation chromatography using cyclohexane (toluene when the polymer resin is not dissolved) as a solvent ( When the solvent is toluene, the weight average molecular weight (Mw) in terms of polystyrene 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 retardation 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 retardation 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 expressed as follows: birefringence is Δn and stress is σ.
C = Δn / σ
It is a value represented by 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.

  The stretched film of the present invention has an in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction. Further, the variation of the slow axis is within 1 °, preferably within 0.7 ° over the entire width of the film. When the retardation of the slow axis is in such a range, the luminance and front contrast of the liquid crystal display device can be improved when the retardation film obtained from the stretched film is used in the liquid crystal display device.

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 when the refractive index in the thickness direction of the _{n z,} and _the coefficient Nz value represented by _{(n x -n z) / (} n x -n y) is 1.3 or less, preferably 1 or 1. 3 or less, preferably 1 or more and 1.2 or less. When the Nz value is in such a range, when the retardation film obtained from the 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 in-plane retardation (Re) and thickness direction retardation (Rth) of the stretched film of the present invention vary depending on the design of the liquid crystal display device, but usually Re is in the range of about 100 to 300 nm and Rth is about 100 to 300 nm. Is appropriately selected. Incidentally, Re in the present invention, when the average thickness _{T w} of the film _is a value defined by _{(n x -n y) × T} w, Rth in the present _{invention, (((n x + n} y ) / 2) -n _z ) × T _w .

  In the stretched film of the present invention, Re variation is usually within 10 nm, preferably within 5 nm, more preferably within 2 nm. By setting the variation in Re in the above range, when 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. Here, the variation in Re is the maximum of Re when the light incident angle is 0 ° (when the incident light beam and the retardation film surface of the present invention are orthogonal to each other) when Re is measured in the width direction of the retardation film. It is the difference between the value 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.
Further, the thickness unevenness in the width direction of the stretched film of the present invention is the difference between the maximum value and the minimum value, and is usually 3 μm or less, preferably 2 μm or less. When the thickness unevenness 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 when a retardation film obtained from the stretched film is used in a liquid crystal display device, 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 setting the content of the volatile component in such a range, the dimensional stability can be improved, the change with time of Re and Rth in the thickness direction can be reduced, and further, the content obtained from the stretched film of the present invention. Deterioration of the polarizing plate having the phase difference film and 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. If the content of the residual volatile component exceeds 0.1% by weight, the optical properties of the retardation film obtained from the stretched film may change over 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 a polarizing plate or a liquid crystal display device having a retardation film obtained from the stretched film of the present invention can be suppressed, The display on the liquid crystal display device can be stably and satisfactorily maintained for a long time.
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.

The method for producing a long stretched film of the present invention is as follows.
Pull out the long thermoplastic resin film from the drawer roll,
The film is stretched by gripping both ends of the film with a gripping means, passing through a preheating zone, a stretching zone, and a fixing zone, and having a slow axis in the plane in a direction inclined from the width direction of the film. ,
Release both ends of the stretched film from the gripping means;
Winding the stretched film on a winding roll.
Hereinafter, the manufacturing method of the stretched film of this invention is demonstrated, referring drawings. FIG. 1 is a conceptual diagram showing an example of a tenter stretching machine that can be suitably used for the production of a long film intermediate used in the present invention and the production of a long stretched film of the present invention. FIG. 2 is a view showing a means for gripping the rail portion in the stretching machine of FIG. FIG. 3 is a view for explaining rail arrangement in the stretching machine of FIG.

The tenter stretching machine shown in FIG. 1 includes a drawing roll <21>, a winding roll <22>, a temperature-controlled room <10> composed of a preheating zone <A>, a stretching zone <B>, and a fixed zone <C>, At least a rail <11> on which a gripping means for transporting the film travels and a gripping means <12> (illustration of the gripping means is omitted in FIGS. 1 and 3) are provided.
The gripping means <12> grips both ends of the film fed 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 fixed zone <C>, and winds the film. The film is opened before the take-up roll <22>. The film released from the gripping means is taken up by a 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 outlet side of the temperature-controlled room to the inlet side.

The film <1> is stretched R times by the tension from the gripping means while passing through the temperature-controlled room composed of the preheating zone, the stretching zone, and the fixing zone. In addition, the draw ratio of a film is the value calculated | required from the film cross-sectional area of the surface orthogonal to the direction of the slow axis in the surface of a film, and the film cross-sectional area before extending | stretching.
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, in order to control the thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. 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.

For example, the gripping means <12> travels on a rail <11> whose arrangement can be changed. Rail <11> is arrange | positioned so that it may be extended | stretched by a desired draw ratio to a film. In the present invention, the arrangement of the rails is set so that the film traveling direction is the direction described below. In the present invention, the film running direction is the direction of a line connecting the midpoints of the film width direction from the film drawing roll to the film winding roll.
At the boundary <13> between the preheating zone and the stretching zone and the boundary <14> between the stretching zone and the fixing 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 fixing zone, that is, the partition plate is perpendicular to the film running direction <49> of the fixing zone.

  The preheating zone A is a zone in which the film is conveyed while warming the film without substantially changing the film length in the direction perpendicular to the film running direction <47>. The film running direction <47> in the preheating zone is a direction parallel to the direction in which the film is drawn out from the roll, and is usually orthogonal to the rotation axis of the drawing 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 <48>. The film running direction <48> in the stretching zone indicates that the stretching zone extends from the midpoint of the film at the boundary between the preheating zone and the stretching zone in a rail arrangement in which the stretching zone extends at a constant angle without changing the inclination as shown in FIG. And the direction of a straight line connected to the midpoint of the film at the boundary of the fixed zone.

  The fixed zone <C> is a zone for transporting the film while cooling the film without substantially changing the film length in the direction perpendicular to the film running direction <49>. The film running direction <49> in the fixed zone is a direction parallel to the direction in which the film is wound on the roll, and is usually orthogonal to the rotation axis of the winding roll.

In the method for producing a stretched film of the present invention, stretching is performed in two steps. First, a long transparent resin film is stretched using a tenter stretching machine having a temperature-controlled room composed of the preheating zone, the stretching zone, and the fixed zone, and is tilted by 5 to 50 ° from the width direction of the film. A long film intermediate having an in-plane slow axis is obtained. Next, the long film intermediate is further stretched again using a tenter stretching machine having a temperature-controlled room composed of the preheating zone, the stretching zone, and the fixed zone, and is tilted by 51 to 85 ° from the width direction of the film. A long stretched film having an in-plane slow axis in the selected direction is obtained.
That is, in the method for producing a stretched film of the present invention,
(A) Pull out a long transparent resin film from a first roll (here, having a function of a drawer roll),
Grasping both ends of the film with gripping means, passing the first preheating zone, the first stretching zone, and the first fixing zone, stretching the film at a stretching ratio of R ₁ (times),
Both ends of the film are released from the gripping means, and the stretched film is wound on a second roll (here, having a winding roll function),
Obtaining a long film intermediate having an in-plane slow axis in a direction inclined from 5 to 50 ° from the width direction of the film;
(B) Pulling out the long film intermediate from the second roll (here, having a function of a pulling roll),
Grasping both ends of the film by gripping means, passing the second preheating zone, the second stretching zone, and the second fixing zone, stretching the film at a stretching ratio of R ₂ (times),
Both ends of the film are released from the gripping means, and the stretched film is wound on a third roll (here, having a function of a winding roll)
Obtaining a long stretched film having an in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction of the film.
Here, the angle formed by the width direction of the film and the direction of the slow axis in the plane of the film indicates the smaller angle.
In addition, the tenter stretching machine used for manufacturing the film intermediate and the tenter stretching machine used for manufacturing the stretched film may be the same stretching machine or different stretching machines.

In the method for producing a stretched film of the present invention, the average temperature T ₁ (° C.) of the _first stretch zone, the average temperature T ₂ (° C.) of the second stretch zone, the stretch ratio R ₁ and the stretch ratio R ₂
(C) The relationship of T ₁ <T ₂ and R ₁ <R ₂ is satisfied at the same time.
Preferably, the relationship of T ₁ + 2 ° C. <T ₂ and R ₁ +0.8 times <R ₂ is satisfied at the same time.
By satisfying such a relationship, the thickness unevenness in the width direction of the obtained stretched film is reduced.

Further, when the glass transition temperature of the transparent resin is Tg, it is preferable that Tg + 5 (° C.) <T ₁ is satisfied. When Tg + 5 (° C.) <T ₁ is satisfied, the formability of the stretched film of the present invention is improved and the thickness unevenness is further reduced.
Furthermore, the total sum of the draw ratios, that is, R ₁ + R ₂ is preferably set to 3.5 to 5.0, more preferably 3.7 to 4.7. When the sum of the draw ratios is in such a range, the thickness unevenness of the stretched film becomes smaller. If the sum of the draw ratios is less than 3.5, the coefficient Nz value may be larger than 1.3. If the total stretching ratio exceeds 5.0, an excessive load is applied to the stretching equipment, which may cause damage to the gripping means or the like, or the film may be broken.

  In the method of the present invention, it is preferable that the film surfaces in the preheating zone, the stretching zone, and the fixing zone are 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 method of the present invention, it is preferable that the traveling speed of the gripping means is substantially equal at both ends of the film, and the travel distance of the gripping means from the stretching start point to the stretching end point is different at both film ends. 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 traveling speed of the gripping means can be selected as appropriate, but is usually 10 to 100 m / min.
The point where the load on the gripping means increases is near the boundary between the preheating zone and the stretching zone <13), and the point where the load on the gripping means decreases and becomes constant again is the boundary between the stretching zone and the fixed zone <14>. In the vicinity. Therefore, in FIG. 2, the travel distance of the upper gripping means is longer than the travel distance of the lower gripping means.

In the method of the present invention, as shown in FIG. 3, the film traveling direction of the fixed zone is inclined by an angle θ1 from the film traveling direction of the preheating zone. Furthermore, it is preferable that the angle θ2 is inclined from the direction of a straight line connecting from the midpoint of the film at the boundary between the preheating zone and the stretching zone to the midpoint of the film at the boundary between the stretching zone and the fixed zone. Both θ1 and θ2 are inferior angles, and θ1 and θ2 are mutually equal. In FIG. 3, the rail is bent downward, but it may be bent upward by making the line in the film running direction of the preheating zone of FIG. Both θ1 and θ2 are inferior angles, and θ1 and θ2 are mutually equal.
The angle θ1 is preferably (θs−5 °) or more and θs or less, and more preferably (θs−4 °) or more and θs or less. The angle θ2 is preferably larger than (θs + 5 °) and smaller than (θs + 10 °), more preferably larger than (θs + 6 °) and smaller than (θs + 10 °). As shown in FIG. 3, θs is an inclination angle (hereinafter sometimes referred to as an orientation angle) of the slow axis 50 in the plane of the film intermediate used in the present invention or the stretched film of the present invention. is there. When these angles θ1 and θ2 satisfy the above range, a stretched film having a more uniform thickness in the width direction can be obtained. In addition, in manufacture of this film intermediate body, it adjusts so that (theta) s1 may be in the range of 5-50 (degree). Moreover, in the stretched film of this invention using the film intermediate body, it adjusts so that (theta) s2 may become the range of 51-85 (degree).

The stretching zone may be linear without changing the film running direction, or the film running direction may be changed stepwise or continuously.
When the film running direction in the stretching zone changes stepwise or continuously, the angle formed by the film running direction in the stretching zone and the film running direction in the fixed zone is greater than (θs + 5 °). The range is preferably 50% or more of the entire running range of the stretching zone, and particularly preferably 60% or more. FIG. 4 is a diagram showing an example of rail arrangement in which the film running direction in the stretching zone changes stepwise. In FIG. 4, in the first half <52> of the stretching zone, the film travels in a direction <48-1> forming an angle θ2-1, and in the second half <51>, the film moves in a direction <48-2> forming an angle θ2-2. Running.

  The film running direction in the stretching zone is preferably directed in a direction different from the film running direction in the preheating zone. That is, since θ1 is smaller than θ2, the opening angle of the rail is different on the left and right sides (in FIG. 2, the opening angle of the upper rail is larger than the opening angle of the lower rail). Since the rails in the preheating zone are arranged in parallel, the gripping means <12> at both ends are substantially parallel to the width direction of the film <1> when the pair is connected by a broken line <20>. However, when the gripping means enters the stretching zone, the broken line <20> connecting the gripping means gradually inclines in the right direction in FIG. 2, and the lower gripping means advances to a position ahead of the upper gripping means. Become. The opening angle of the rail can be appropriately selected according to the draw ratio.

Here, when θ1 and θ2 are the same, the opening angle of the rail is the same on the left and right, the running direction from the preheating zone to the stretching zone is straight, and even if the gripping means enters the stretching zone, The line connecting the gripping means remains parallel to the line connecting the gripping means in the preheating zone.
When θ1 becomes larger than θ2, the opening angle of the lower rail becomes larger than the opening angle of the upper rail, the line connecting the gripping means is inclined to the left side, and the upper gripping means is more than the lower gripping means. It will be in the advanced position. When it becomes like these, sagging etc. arise in a film and there exists a possibility that the thickness of the width direction may become non-uniform | heterogenous.

The traveling direction of the fixed zone is inclined from the traveling direction of the preheating zone by an angle θ1 as shown in FIG.
That is, in the method of the present invention,
(D) The film traveling direction of the first fixed zone is different from the film traveling direction of the first preheating zone, and the film traveling direction of the second fixed zone is It is different from the film running direction in the preheating zone. By setting it as such a structure, the stretched film which has an in-plane slow axis in the direction inclined from the width direction of the film can be obtained efficiently.
More specifically, the film traveling direction of the fixed zone is inclined from the film traveling direction of the preheating zone toward the shorter travel distance of the gripping means. In addition, the preferred configuration is that the film traveling direction of the fixed zone is determined from the direction of a straight line connected from the middle point of the film at the boundary between the preheating zone and the stretching zone to the middle point of the film at the boundary between the stretching zone and the stationary zone. The mileage is leaning to the short side. For this reason, the upper gripping means in the figure goes farther than the lower gripping means. When the gripping means reaches the fixed zone, the gripping means at both ends of the film is advanced in a position ahead of the upper gripping means in FIG.
In the production of the film intermediate, the traveling direction of the film in the first fixed zone is preferably inclined within a range of 5 to 50 ° from the traveling direction of the film in the first preheating zone.
In the production of the stretched film of the present invention, the traveling direction of the film in the second fixed zone is preferably inclined within a range of 5 to 50 ° from the traveling direction of the film in the second preheating zone.

  The film that has passed through the temperature-controlled room as described above is released from the gripping means before the take-up roll and is taken up by the take-up roll. The film thus obtained has an in-plane slow axis in a direction inclined with respect to the width direction. Moreover, the thickness is uniform in the width direction.

  As a method for forming the transparent resin for forming the stretched film of the present invention into a film, a known forming 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.

A long laminated film can be obtained by laminating the long stretched film of the present invention and the 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 stretched film of the present invention may be laminated on both sides of the polarizer or on one side, and the number of laminated layers is not particularly limited, and two or more may be laminated.
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 acetate polymers such as triacetyl cellulose, alicyclic olefin polymers, polyolefin polymers, polycarbonate polymers, polyester polymers such as polyethylene terephthalate, polyvinyl chloride polymers, polystyrene polymers, polyacrylonitrile. Examples thereof include a polymer, a polysulfone polymer, a polyether sulfone polymer, a polyamide polymer, a polyimide polymer, and an acrylic polymer.

  A suitable manufacturing method for obtaining the long laminated film of the present invention is the above-mentioned long stretched film wound in a roll shape and a long polarizer wound in a roll shape, while simultaneously pulling out from the roll, The stretched film and the polarizer are adhered to 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 perpendicular or parallel to the longitudinal direction of the long film.

  The liquid crystal display device of this invention is equipped with the retardation film or polarizing plate cut out from the said elongate stretched film or the elongate laminated film. 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 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 snap gauge (manufactured by Mitutoyo Corporation, ID-C112BS), the thickness is measured at intervals of 5 cm in the width direction of the film, and the average value is obtained. Next, the maximum value-minimum value was set to uneven thickness. (2) Orientation angle Using a polarizing microscope (manufactured by NICON, BX51), the slow axis in the in-plane direction was measured at intervals of 5 cm in the width direction of the film. The average value was calculated to determine the orientation angle. Further, the difference between the maximum value and the minimum value of the orientation angle obtained from the slow axis was taken as the variation of the orientation angle. The average value was calculated by measuring at intervals of 5 cm, and the coefficient Nz value was obtained.

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) is pulled out from the roll and continuously supplied to a tenter stretching machine (1) set in a rail pattern as shown in FIG. 3 so that the orientation angle is 45 (°). Film intermediate (2) was obtained. The tenter stretching machine (1) was set to the angle, temperature, and stretch ratio shown in Table 1. The surface of the film intermediate (1) facing upward in the tenter stretching machine is defined as (i) surface. The film intermediate (1) was wound up on a roll.
Further, the film intermediate (1) is pulled out from the roll, and continuously supplied to a tenter stretching machine (2) set in a rail pattern as shown in FIG. A stretched film (A) having a long width was obtained. The tenter stretching machine (2) was set to the angle, temperature, and stretch ratio shown in Table 1. The stretched film (A) was wound up on a roll.

A long polarizing plate (manufactured by Sanlitz, HLC2-5618S, thickness 180 μm) having a transmission axis parallel to the width direction, and an in-plane slow axis in a direction inclined by 15 ° from the width direction of the film, Re A long stretched film (R) having a length of 270 nm and the long stretched film (A) were bonded together in this order with a roll-to-roll to obtain a long optical element. At this time, the films were bonded so that the angle formed by the in-plane slow axis of the stretched film (R) and the in-plane slow axis of the stretched film (A) was 60 °. Further, this optical element was cut to a predetermined size to obtain a polarizing plate (P1).
Subsequently, the polarizing plate provided in the commercially available reflective liquid crystal device was replaced with the polarizing plate (P1). At this time, the stretched film (A) was assembled so that the side to which the stretched film (A) 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.

Example 2
A long stretched film (B) having a width of 1300 mm and a polarizing plate (P2) were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. Table 1 shows the measurement results of the characteristic values of the obtained stretched film (B). The polarizing plate (P2) was replaced with a polarizing plate of a liquid crystal display device of a commercially available reflection type liquid crystal device, and incorporated so that the side on which the stretched film (B) 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 Example 1
According to the method described in JP-A-2-113920, the unstretched film (0) obtained in Example 1 was continuously supplied to a tenter stretching machine set to the angle, temperature, and stretch ratio shown in Table 1. Thus, a stretched film (C) having an orientation angle of 75 ° was obtained, but the thickness unevenness in the width direction of the film was large and could not be wound on a roll. Table 1 shows the measurement results of the characteristic values of the stretched film (C).

Comparative Example 2
A stretched film (D) having a width of 1300 mm was obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. Table 1 shows the measurement results of the characteristic values of the obtained stretched film (D).

Comparative Example 3
A stretched film (E) having a width of 1300 mm was obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. Table 1 shows the measurement results of the characteristic values of the obtained stretched film (E).

From the results shown in Table 1, the following can be understood.
The long stretched film of Example 1 or Example 2 produced by the method of the present invention has a small thickness unevenness, a small in-plane slow axis variation over a width of 1300 mm, and a coefficient Nz value. small.
On the other hand, as shown in Comparative Example 1, when a film having an in-plane slow axis in a direction exceeding 50 ° from the width direction of the film is obtained by a single stretching, the stretching obtained there is obtained. Although the coefficient Nz value of the film is small, the thickness unevenness becomes extremely large so that the film cannot be wound on the roll, and the in-plane slow axis variation becomes large.
In the production of stretched long film of Comparative Example 2, than the average temperature T ₁ of the drawing zone of the first stretch (stage of producing a stretched film intermediate), the second stretch (stretch film intermediate, since further becomes smaller towards the average temperature T ₂ of the drawing zone of step) of stretching, the stretched film, although the coefficient Nz value decreases, larger uneven thickness, large variations in the in-plane slow axis Become. Moreover, the stretched film obtained is insufficient in the optical compensation effect of the liquid crystal display device.
Furthermore, in the production of the long stretched film of Comparative Example 3, since the stretch ratio R2 of the _second stretch is smaller than the stretch ratio R1 of the _first stretch, the stretched film obtained there is Although the coefficient Nz value is small, the thickness unevenness is large and the in-plane slow axis variation is large. Further, the stretched film is insufficient in the optical compensation effect of the liquid crystal display device.

The conceptual diagram which shows an example of the tenter stretching machine which can be used suitably for manufacture of the stretched film of this invention. The figure which showed the holding means of the rail part in the extending | stretching machine of FIG. The figure for demonstrating the rail arrangement | positioning in the extending machine of FIG. The figure which shows another example of the rail arrangement | positioning of a drawing machine.

1: Film 10: Temperature-controlled room 11: Rail 12: Grasping means 13: Boundary between preheating zone and stretching zone 14: Boundary between stretching zone and fixing zone 21: Draw roll 22: Winding roll 47: Film running in preheating zone Direction 48: Film traveling direction 48-1 of stretching zone: Film traveling direction 48-2 of first half of stretching zone 48-2: Film traveling direction of second half of stretching zone 49: Film traveling direction of fixed zone

Claims (9)

It is a long film made of transparent resin,
The width of the film is 1300 mm or more,
An in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction of the film,
The variation of the slow axis is within 1 ° over the entire width of the film, and
Wavelength 550nm to light, the refractive index in a slow axis direction n _x in the _plane, the refractive index in a direction perpendicular in the slow axis and the plane of the plane n _y, the refractive index in the thickness direction and n _{z when,} stretched film, wherein the coefficient Nz value represented by _{(n x -n z) / (} n x -n y) is 1.3 or less. The stretched film according to claim 1, wherein the transparent resin is made of a resin having a positive intrinsic birefringence value. A retardation film obtained by cutting the stretched film according to claim 1 or 2 into a predetermined size along a direction perpendicular or parallel to a longitudinal direction thereof. A long laminated film obtained by laminating the stretched film according to claim 1 or 2 and a long polarizer with their longitudinal directions aligned. A polarizing plate obtained by cutting the long laminated film according to claim 4 into a predetermined size. A liquid crystal display device comprising the retardation film according to claim 3. A liquid crystal display device comprising the polarizing plate according to claim 5. 8. The liquid crystal display device according to claim 6, wherein the liquid crystal display device is a reflective liquid crystal display device. (A) Pull out the long transparent resin film from the first roll,
Grasping both ends of the film with gripping means, passing the first preheating zone, the first stretching zone, and the first fixing zone, stretching the film at a stretching ratio of R ₁ (times),
Release both ends of the film from the gripping means, wind the stretched film on a second roll,
Obtaining a long film intermediate having an in-plane slow axis in a direction inclined from 5 to 50 ° from the width direction of the film;
(B) pulling out the long film intermediate from the second roll;
Grasping both ends of the film by gripping means, passing the second preheating zone, the second stretching zone, and the second fixing zone, stretching the film at a stretching ratio of R ₂ (times),
Release both ends of the film from the gripping means, wind the stretched film on a third roll,
A step of obtaining a long stretched film having an in-plane slow axis in a direction inclined by 51 to 85 ° from the width direction of the film,
(C) When the average temperature of the first stretching zone is T ₁ (° C.) and the average temperature T ₂ (° C.) of the second stretching zone,
T ₁ <T ₂ and R ₁ <R ₂ are satisfied,
(D) The film traveling direction of the first fixed zone is different from the film traveling direction of the first preheating zone, and the film traveling direction of the second fixed zone is Different from the film running direction in the preheating zone,
A method for producing a long stretched film characterized by the above.

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