JP2007090532A - Method for producing oriented film, method for producing phase difference film, and liquid crystal display having the phase difference film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a long extended film or a phase difference film in which a thickness in the width direction is uniform and wide, and a molecular axis is oriented diagonally, the phase difference film obtained by the method, and to provide a liquid crystal display having the phase difference film. <P>SOLUTION: The traveling speed of the gripping means of a tenter drawing machine is made approximately equal at both ends of a film, and the traveling distance from the orientation starting point to the orientation ending point of the gripping means is made different at both ends of the film. By slanting the film traveling direction in a fixed zone to be at least (θ<SB>s</SB>-5°) and θ<SB>s</SB>or smaller from the film traveling direction in a preheating zone, and to be larger than (θ<SB>s</SB>+5°) from the direction of a straight line connected from the middle point of the film in the boundary between the preheating zone and an orientation zone to the midpoint of the film in the boundary between the orientation zone and the fixed zone, the long extended film in which the molecular axis is extended in the direction slanted by an angle θ<SB>s</SB>from the width direction of the oriented film, with the thickness in the width direction being uniform and wide is obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stretched film manufacturing method, a retardation film manufacturing method, and a liquid crystal display device including the retardation film.

  In a liquid crystal display device, various retardation films are used for optical compensation such as coloring prevention and viewing angle expansion. This retardation film is laminated so that its orientation axis is at various angles with respect to the polarization transmission axis of the polarizing plate. In a stretched film obtained by longitudinal or transverse stretching, it must be cut so that the molecular orientation axis is at a predetermined angle with respect to the side, the waste film increases, and the utilization efficiency of the stretched film is low. A stretched film oriented obliquely at a predetermined angle can be cut parallel to the side, and the utilization efficiency of the stretched film is increased.

  A method for obtaining a film having molecular axes oriented obliquely by stretching has been conventionally known. For example, in Patent Document 1, one rail is straight, the other rail is wavy from side to side in a two-dimensional plane, and a difference is provided in the distance traveled by left and right gripping means that travel at the same speed. A method of stretching the film diagonally by bending the traveling direction of the film in a two-dimensional plane and providing a difference in the travel distance of the right and left gripping means that travel at the same speed; A method is described in which the film is formed in a straight line, the other rail is spirally twisted, and the film is stretched obliquely by providing a difference in travel distance between the left and right gripping means that travel at the same speed. Further, in Patent Document 2, one rail is straight and the other rail is waved up and down in the stretching zone, and there is a difference in travel distance between the right and left gripping means that travel at the same speed. A method is described in which the film is stretched obliquely so that the boundary with the zone is parallel to the orientation direction.

Further, Patent Document 3 discloses that the film is slanted by making the traveling speed of the gripping means traveling on one linear rail cos α times the traveling speed of the gripping means traveling on the other straight line α. Describes a method of stretching.
However, no effective width direction thickness control means has been found in these oblique stretching methods, and it is substantially possible to obtain a wide film having a uniform thickness in the width direction and molecular axes oriented obliquely. It was impossible. Therefore, it was impossible to industrially mass-produce a long and wide optical film having molecular axes oriented obliquely.

JP 2002-86554 A Japanese Patent Laid-Open No. 2003-311823 Japanese Patent Laid-Open No. 3-182701

  An object of the present invention is to provide a method for producing a wide stretched stretched film or retardation film having a uniform thickness in the width direction and molecular axes oriented obliquely, a retardation film obtained by the production method, and the position It is providing a liquid crystal display device provided with a phase difference film.

As a result of studying an oblique stretching method using a tenter stretching machine having a preheating zone, a stretching zone, and a fixed zone, the present inventors have obtained a stretched film in which molecular axes are oriented in a direction inclined by an angle θ _s from the width direction of the stretched film. Further, the traveling distance of the gripping means from the point at which the traveling speed of the gripping means of the tenter stretching machine is made substantially equal at both ends of the film and the load on the gripping means becomes large until the load becomes small and becomes constant again. The center of the film is made different at both ends so that the film traveling direction of the fixed zone is not less than (θ _s −5 °) and not more than θ _s from the film traveling direction of the preheating zone, and at the boundary between the preheating zone and the stretching zone. the tilting to be greater than from the direction of the straight line (θ _{s +} 5 °) that connects the middle point of the film in the boundary between the fixing zone and the stretching zone from the Te, long stretched film molecular axis width direction thickness is uniform and wide oblique is oriented found that is obtained, in which the present invention has been completed based on this finding.

Thus, according to the present invention,
(1) a) Pull out the long transparent resin film from the roll,
A stretched film having both ends in the width direction of the film gripped by gripping means, stretched through the preheating zone, the stretching zone, and the fixing zone, and having a molecular orientation axis in a direction inclined by an angle θ _s from the width direction age,
Release both ends of the stretched film from the gripping means;
Winding the stretched film on a roll,
b) 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,
c) The film running direction of the fixed zone is inclined at an angle θ ₁ from the film running direction of the preheating zone, and the angle θ ₁ is (θ _s −5 °) or more and θ _s or less,
d) The film traveling direction of the fixed zone is inclined at an angle θ ₂ from the direction of the straight line connecting 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 fixed zone. And the angle θ ₂ is larger than (θ _s + 5 °),
A method for producing a long stretched film is provided.

As a preferred embodiment of the present invention,
(2) The traveling range in which the angle formed by the film traveling direction of the stretching zone and the film traveling direction of the fixed zone is larger than (θ _s + 5 °) is 50% or more of the entire traveling range of the stretching zone. A method for producing the long stretched film,
(3) The film running direction of the fixed zone is from the film running direction of the preheating zone and 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 method for producing the stretched film, wherein the travel distance of the gripping means is inclined to the short side,
(4) The method for producing the above-described elongated stretched film, wherein the boundary between the preheating zone and the stretching zone and the boundary between the stretching zone and the fixing zone are perpendicular to the film running direction of the fixing zone, and / or ( 5) A method for producing the above-described elongated stretched film in which the film surfaces in the preheating zone, the stretch zone, and the fixed zone are substantially parallel to each other is provided.

  Furthermore, according to the present invention, (6) a long stretched film obtained by the production method, (7) a long laminate film obtained by laminating the stretched film and a long polarizer, (8 ) A method for producing a retardation film comprising cutting the long stretched film into a predetermined size, and (9) a method for producing a polarizing plate comprising cutting the long laminated film into a predetermined size. (10) A liquid crystal display device comprising a retardation film obtained by the production method, (11) a liquid crystal display device comprising a polarizing plate obtained by the production method, and (12) a liquid crystal of a reflective display system. The liquid crystal display device including the panel is provided.

  According to the production method of the present invention, it is possible to easily obtain a wide stretched film having a uniform thickness in the width direction and obliquely oriented molecular axes. A long stretched film having molecular axes oriented obliquely is suitable as a retardation film for liquid crystal display devices and the like. Specifically, when the molecular orientation axis is tilted and overlapped with another long optical element used in a liquid crystal display device such as a polarizing plate at a specific angle, the molecular orientation axis is inclined with respect to the longitudinal direction. If the stretched film is used, it can be overlapped with other long optical elements by roll-to-roll. In a film having a molecular orientation axis parallel to the width direction (TD direction) or the longitudinal direction (MD direction) of a long film, there was a lot of discarded portions because it was necessary to trim the film diagonally. The stretched film having a molecular orientation axis obliquely with respect to the MD direction obtained by the production method of the present invention can be trimmed in parallel with the MD direction or the TD direction.

  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 suitably carry out 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. FIG. 3 is a view for explaining rail arrangement in the stretching machine of FIG.

The method for producing a long stretched film of the present invention is as follows.
Pull out the long transparent resin film from the roll,
Grasping both ends of the film by gripping means, passing the preheating zone, the stretching zone, and the fixing zone to stretch the film to obtain a stretched film having a molecular orientation axis in a direction inclined by an angle θ _s from the width direction,
Release both ends of the stretched film from the gripping means;
Winding the stretched film on a roll.
Here, the angle θ _s is the smaller of the angles formed by the film width direction and the molecular orientation axis. θ _s is equal to an angle obtained by subtracting 90 ° from an angle at an isotope position with respect to the angles θ ₁ and θ ₂ among the angles formed by the film traveling direction of the fixed zone and the molecular orientation axis. θ _s is appropriately selected according to the design of the liquid crystal panel, but is usually 10 to 30 °.

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 FIGS. 1 and 3).
The gripping means 12 grips both ends of the film drawn from the pulling 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 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.
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. Although the temperature of each zone can be selected as appropriate, the preheating zone is usually 140 to 150 ° C, the stretching zone is usually 145 to 155 ° C, and the fixing zone is usually 140 to 155 ° C.
In the present invention, in order to control thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. In order to give 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, and controlling the heating by arranging heaters in the width direction are 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 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 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 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 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 a direction perpendicular to the film running direction 48. The film running direction 48 in the stretching zone is fixed to the stretching zone 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 spreads at a constant angle without changing the inclination as shown in FIG. The direction of the straight line connected to the midpoint of the film at the boundary of the zone.

  The fixing 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 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 coming out of the drawing roll is not twisted and remains flat, passes through the preheating zone, the stretching zone, and the fixing zone, and is wound on the winding roll.

In the stretched film manufacturing method of the present invention, b) 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 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. Therefore, in FIG. 2, the travel distance of the upper gripping means is longer than the travel distance of the lower gripping means.

As shown in FIG. 3, the stretched film manufacturing method of the present invention includes: c) the film traveling direction of the fixed zone is inclined at an angle θ ₁ from the film traveling direction of the preheating zone, and d) the preheating zone and the stretching zone The angle θ _{2 is} inclined from the direction of the straight line connected from the midpoint of the film at the boundary to the midpoint of the film at the boundary between the stretching zone and the fixed zone. 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.
The angle θ ₁ is (θ _s −5 °) or more and θ _s or less, preferably (θ _s −4 °) or more and θ _s or less. Further, the angle θ ₂ is larger than (θ _s + 5 °), preferably larger than (θ _s + 6 °). As shown in FIG. 3, θ _s is an inclination angle of the molecular orientation axis 50 of the stretched film from the width direction. The upper limit of θ ₂ is not particularly limited, but is preferably (θ _s + 10 °). When these angles θ ₁ and θ ₂ satisfy the above range, a stretched film having a uniform thickness in the width direction can be obtained. Both θ ₁ and θ ₂ are inferior angles, and θ ₁ and θ ₂ are mutually isotopes.

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 becomes larger than (θ _s + 5 °). The running range is preferably 50% or more of the entire running range of the stretching zone, 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 Figure 4, the film in the first half 52 of the stretching zone is traveling in the direction 48-1 forming an angle theta _2-1, the film in the second half 51 is traveling in the direction 48-2 forming an angle theta _2-2.

The film running direction in the stretching zone is in a direction different from the film running direction in the preheating zone. That is, theta ₁ is smaller than the theta _2, the opening angle of the rails is different on the left and right (the opening angle of the 2 upper rails, is greater 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 is positioned ahead of the upper gripping means. The opening angle of the rail can be appropriately selected according to the draw ratio. The draw ratio is a value determined from the film cross-sectional area of the surface orthogonal to the direction of the molecular orientation axis and the film cross-sectional area before stretching, and is usually 2.0 to 5.0 times, preferably 2.3 to 4.7. Is double.

Here, when θ ₁ and θ ₂ 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 stretching is performed. The line connecting the gripping means in the zone remains parallel to the line connecting the gripping means in the preheating zone.
If theta ₁ is greater than theta _2, the opening angle of the lower rail becomes larger than the opening angle of the upper rail, the line connecting the gripping means becomes inclined to the left, the upper gripping means lower gripping It becomes the position which advanced ahead of the means. When it becomes like these, sagging etc. arise in a film and 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 θ ₁ as shown in FIG. More specifically, the film traveling direction of the fixed zone is a straight line connecting the film traveling direction of the preheating zone and 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 fixing zone. From this direction, the travel distance of the gripping means is inclined 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.

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 a molecular orientation axis inclined at an angle θ _{s with} respect to the width direction. Moreover, the thickness is uniform in the width direction.
Further, since the tension from the gripping means is applied to the film uniformly in the width direction, birefringence caused by molecular orientation is uniform in the width direction. According to the production method of the present invention, an in-plane retardation Re (= (nx−ny) × d; nx and ny are in-plane main refractive indexes and d is a thickness) of 100 to 300 nm can be easily obtained.

  The film applicable to the present invention is a film made of a long transparent resin. A transparent resin is a resin that is transparent to a desired wavelength. The transparent resin is preferably a thermoplastic resin. 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 Examples thereof include 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 . ^{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 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.

  Although the glass transition temperature of the transparent resin used for this invention should just be selected suitably according to a use purpose, Preferably it is 80 degreeC or more, More preferably, it is the range of 100-250 degreeC. 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, variation in retardation (Re) in the in-plane direction of the retardation film obtained by the method of the present invention 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 film applicable to the present invention may be a single layer film or a multilayer film.

A long laminated film can be obtained by laminating a long stretched film obtained by the production method of the present invention and a long polarizer.
The polarizer used in the present invention transmits one of two linearly polarized light intersecting at right angles. For example, a hydrophilic polymer film such as a polyvinyl alcohol film or an ethylene vinyl acetate partially saponified film adsorbed a dichroic substance such as iodine or a dichroic dye and uniaxially stretched, the hydrophilic polymer film Examples include uniaxially stretched and dichroic substances adsorbed, and polyene oriented films such as polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Other examples include reflective polarizers such as grid polarizers and anisotropic multilayer films. 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 polyethersulfone 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.

  In the retardation film of the present invention, Re variation is usually within 10 nm, preferably within 5 nm, and more preferably within 2 nm. By setting the Re variation within the above range, it is possible to improve the display quality when used for a liquid crystal display device. Here, the variation in Re is the maximum value of Re when the Re is measured in the width direction of the retardation film at a light incident angle of 0 ° (in which the incident light beam and the retardation film surface of the present invention are orthogonal). It is the difference between the value and the minimum value.

The average thickness of the retardation 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.
The thickness unevenness in the width direction of the retardation 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 retardation film of the present invention can be wound up in a long length.

  The content of the residual volatile component in the retardation 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. is there. If the content of the residual volatile component exceeds 0.1% by weight, the optical properties of the laminate may change over time. By making the content of the volatile component in the above range, the dimensional stability can be improved, the change with time of Re and thickness direction retardation (Rth) can be reduced, and the retardation film of the present invention can be reduced. The deterioration of the polarizing plate and the liquid crystal display device can be suppressed, and the display on the display can be kept stable and favorable over the long term. 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 retardation 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 retardation in the thickness direction (Rth) can be reduced, and further the deterioration of the polarizing plate and the liquid crystal display device having the retardation film of the present invention can be reduced. It can be suppressed and the display on the display can be kept stable and good in the long term.
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 retardation film of the present invention can be adjusted to the above value by, for example, reducing the amount of polar groups in the thermoplastic resin, but is preferably a resin having no polar groups. Is desired.

  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 polarization transmission axis by adjusting the voltage and the polarizing plate of the present invention 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 obtained by the production method 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.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not restrict | limited to the following Example. Parts and% are based on weight unless otherwise specified.
(1) Thickness Using a snap gauge (ID-C112BS, manufactured by Mitutoyo Corporation), the thickness is measured at intervals of 5 cm in the width direction to obtain an average value. Next, the maximum value-minimum value was regarded as thickness unevenness. (2) In-plane retardation Re
The in-plane retardation of the stretched film coming out of the stretching machine is measured with a retardation measuring device (manufactured by Oji Scientific Instruments, KOBRA-21SDH) across the film width direction.
(3) Orientation angle θ _s
The slow axis of the stretched film coming out from the stretching machine is measured with a polarizing microscope (BX51, manufactured by Olympus) across the film width direction, and this is taken as the molecular orientation axis. Then, the orientation angle θ _s is obtained from this molecular orientation axis.

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, An unstretched film having a thickness of 160 μm was obtained.
The unstretched film was supplied to a tenter stretching machine to obtain a stretched film having an orientation angle θ _s and a width of 1300 mm. The tenter stretching machine was set to the angle, temperature, and stretch ratio shown in Table 1. Table 1 shows the measurement results of the thickness and orientation angle of the obtained stretched film.

A long polarizing plate (manufactured by Sanritz Corporation, HLC2-5618S, thickness 180 μm) having a polarization transmission axis parallel to the width direction and the stretched film obtained above are bonded together by a roll-to-roll. A wound body of an optical element with a scale 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 (1) was obtained by batch bonding 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 (1). 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.

Example 2
As shown in Table 1, the film running direction in the stretching zone was changed at an intermediate point, except that the first 50% θ _2a was 21 ° and the second 50% θ _2b was 15 °. In the same manner as in Example 1, a stretched film and an optical element were obtained. The evaluation results of the stretched film are shown in Table 1. The optical element was replaced with a polarizing plate of a liquid crystal display device of a commercially available reflective liquid crystal device, and the optical element was incorporated so that the side on which (3) was bonded was placed 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 A diagonally stretched film was obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. The obtained long stretched film had large thickness unevenness in the width direction, and wrinkled when wound on a roll.

The conceptual diagram which shows an example of the tenter drawing machine which can implement suitably the manufacturing method 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.

Explanation of symbols

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 (12)

a) Pull out the long transparent resin film from the roll,
A stretched film having both ends in the width direction of the film gripped by gripping means, stretched through the preheating zone, the stretching zone, and the fixing zone, and having a molecular orientation axis in a direction inclined by an angle θ _s from the width direction And releasing both ends of the stretched film from the gripping means, and then winding the stretched film onto a roll,
b) 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,
c) The film running direction of the fixed zone is inclined at an angle θ ₁ from the film running direction of the preheating zone, and the angle θ ₁ is (θ _s −5 °) or more and θ _s or less,
d) the film traveling direction of the fixed zone is inclined at an angle θ ₂ from the direction of the straight line connecting 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 fixing zone; The angle θ ₂ is greater than (θ _s + 5 °),
A method for producing a long stretched film. The traveling range in which the angle formed by the film traveling direction of the stretching zone and the film traveling direction of the fixed zone is larger than (θ _s + 5 °) is 50% or more of the entire traveling range of the stretching zone. Of producing a long stretched film.   The gripping direction of the film in the fixed zone is from the direction of the straight line connecting the film traveling direction in the preheating zone and 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 fixing zone. The manufacturing method of the stretched film in any one of Claims 1-2 in which the said travel distance of a means inclines to the short side.   Production of a long stretched film according to any one of claims 1 to 3, wherein the boundary between the preheating zone and the stretching zone and the boundary between the stretching zone and the fixed zone are perpendicular to the film running direction of the fixed zone. Method.   The manufacturing method of the elongate stretched film in any one of Claims 1-4 whose film surfaces in a preheating zone, an extending | stretching zone, and a fixed zone are substantially parallel to each other.   The elongate stretched film obtained by the method in any one of Claims 1-5.   A long laminated film obtained by laminating the stretched film according to claim 6 and a long polarizer with their longitudinal directions aligned.   A method for producing a retardation film, comprising: cutting the long stretched film according to claim 6 into a predetermined size along a direction perpendicular or parallel to a longitudinal direction thereof.   A method for producing a polarizing plate, comprising cutting the long laminated film according to claim 7 into a predetermined size.   A liquid crystal display device comprising a retardation film obtained by the method according to claim 8.   A liquid crystal display device comprising a polarizing plate obtained by the method according to claim 9.   12. The liquid crystal display device according to claim 10, further comprising a reflective display type liquid crystal panel.

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