JP2008238514A - Manufacturing method of stretched film, stretched film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a wide and long stretched film where there is no generation of surface waviness or wrinkle, no variation of the orientation direction in the width direction, accuracy of the optical characteristics is excellent, and an orientation axis is inclined within the range of 40-50° with respect to a winding direction. <P>SOLUTION: In the manufacturing method of the stretched film, both end parts in the width direction of the thermoplastic resin film is held with a holding tool, conveyed in a tenter 2, and the stretching where the orientation angle theta is within 45±5° with respect to the film winding direction is performed. The angle θo (°) where the straight line connecting the opened position of the right and left holding tool is formed with respect to the perpendicular direction in the winding direction of the film, the orientation angle θ (°) of the film 13 after being stretched with respect to the winding direction of the film, a taking-over tension T (N/m) of the film 13, and a delivery angle θs (°) of the film with respect to the winding direction of the film satisfy the condition of θ-30<θo<θ+5, 100<T <250, and θ-5<θs<θ+5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a method for producing a stretched film in which a thermoplastic resin film is stretched in an oblique direction with respect to the winding direction, a stretched film produced by the method, a polarizing plate using the stretched film, and the polarizing plate. The present invention relates to a liquid crystal display device.

  Various retardation films are used in liquid crystal display devices in order to improve performance. This retardation film is a liquid crystal display device in which the slow axis is inclined at various specific angles with respect to the polarization transmission axis of the polarizer, the polarization transmission axis of the liquid crystal cell, etc. Installed. The tilt angle of the slow axis may be an angle that is neither parallel to nor perpendicular to the side of the display device.

  Various oblique stretching methods have been proposed as a method for obtaining a retardation film oriented at an angle that is neither parallel nor perpendicular to the side.

For example, Patent Document 1 discloses that an optical polymer film is stretched by holding both ends of a continuously supplied polymer film by holding means, and stretching the holding means while moving the holding means in the longitudinal direction of the film. In the method, the locus L1 of the holding means from the substantial holding start point to the substantial holding release point at one end of the polymer film and the substantial holding release point from the substantial holding start point at the other end of the polymer film. Up to the holding means locus L2 and the distance W between the two substantial holding release points,
Optical that satisfies the relationship of | L2-L1 |> 0.4W, maintains the support of the polymer film, stretches in a state where the volatile content rate is 5% or more, and then reduces the volatile content rate while shrinking. A method for stretching a polymer film for use is disclosed.

  Further, in Patent Document 2, it is obtained by stretching a long film made of a thermoplastic resin, and the optical axis (orientation axis) is a direction that is neither parallel nor perpendicular to the winding direction of the long film. A method for producing a long optical film, wherein in the region where the film is substantially stretched, the moving speed at both ends in the width direction of the facing film is equal and the moving distance is different. A method for producing a long optical film is disclosed in which stretching is performed so that at least one of the pair of jigs holding both ends in the width direction moves on a rail having a wave shape with respect to the film surface. .

However, these left-right asymmetric stretching methods tend to cause phenomena such as a film roll and wrinkles, resulting in a significant defect in the appearance of the product roll, and retardation and a deterioration in the width profile of the orientation axis. On the other hand, Patent Document 3 tries to solve the problem by making the film opening position of the right and left gripper perpendicular to the film transport direction in the oblique stretching process using a tenter. When obtaining a film, the effect is insufficient. Therefore, it was practically impossible to obtain a wide film having a width of 1300 mm or more that is uniformly oriented with no variation at an orientation angle of 40 ° or more in the winding direction.
JP 2002-86554 A JP 2003-232929 A JP 2004-106423 A

  The object of the present invention is that there is no occurrence of talmi and wrinkles and variation in the alignment direction in the width direction, the optical characteristics are excellent, and the alignment axis is inclined in the range of 40 to 50 ° with respect to the winding direction. It is providing the manufacturing method of a elongate stretched film, the stretched film manufactured by this method, the polarizing plate using this stretched film, and the liquid crystal display device using this polarizing plate.

  As a result of studies to achieve the above-mentioned object, the present inventor has properly determined the feeding angle of a specific film, the film take-up tension, and the opening position of the left and right gripping tools in a method for producing an obliquely stretched film using a tenter. It has been found that the above problems can be solved by setting the value to be a wide value and a wide and uniform obliquely stretched film can be obtained. As a result, the productivity of polarizing plates and liquid crystal display devices can be improved.

That is, in the method for producing a stretched film of the present invention, both ends in the width direction of the thermoplastic resin film are gripped by a gripping tool and conveyed in the tenter, and the orientation angle θ is 45 ± 5 ° with respect to the film winding direction. A method for producing a stretched film for stretching in a range, wherein an angle θo (°) formed by a straight line connecting open positions of the right and left gripping tools with respect to a direction perpendicular to the film winding direction is The orientation angle θ (°) of the film after stretching with respect to the take-up direction, the take-up tension T (N / m) of the film after stretching, and the feeding angle θ s (°) of the film with respect to the winding direction of the film,
θ-30 <θo <θ + 5
100 <T <250
θ-5 <θs <θ + 5
It satisfies the following conditions.

  The stretched film of the present invention is produced by the production method of the present invention. The polarizing plate of the present invention is formed by laminating the stretched film of the present invention on at least one surface of a polarizer. Moreover, the liquid crystal display device of this invention is equipped with the polarizing plate of this invention.

  According to the production method of the present invention, there is no occurrence of tarmi or wrinkles, the orientation angle in the width direction is uniform, and the orientation axis is uniformly oriented in a direction of 40 to 50 ° with respect to the film winding direction. A long slanted stretched film can be easily obtained. A long stretched film whose orientation axis is obliquely oriented is suitable as a retardation plate for a liquid crystal display device or the like. Specifically, when the orientation axis is tilted and overlapped with a certain long angle with another long optical element used in a liquid crystal display device such as a polarizing plate, the orientation axis is inclined with respect to the longitudinal direction. If a film is used, it can be overlapped with other long optical elements by roll-to-roll.

  Since the stretched film of the present invention can be trimmed parallel to the longitudinal direction or the width direction, there are few discarded portions of the film, and the productivity is excellent. In addition, the polarizing plate obtained by the production method of the present invention has a wide viewing angle when used in a liquid crystal display device, particularly a reflective liquid crystal display device, and reduces the contrast and coloring of the display screen. Can be prevented.

  The method for producing a stretched film according to an embodiment of the present invention includes a method of stretching a long film made of a thermoplastic resin (hereinafter sometimes referred to as “raw fabric”) and a film winding direction and a film feeding direction after stretching. The original fabric is fed so that the angle θs formed by the following becomes θ-5 <θs <θ + 5, preferably θ-4 <θs <θ + 4. Here, θ represents the orientation angle of the stretched film. And by extending | stretching diagonally within a tenter, it extends | stretches so that orientation angle (theta) may be in the range of 40-50 degrees with respect to the winding direction. When the feeding angle θs is out of the above range, the orientation angle profile in the film width direction is not uniform, and a wide and uniform optical characteristic cannot be obtained.

  Examples of the thermoplastic resin constituting the thermoplastic resin film include polycarbonate, polyester, polyethersulfone, polyarylate, polyimide, and alicyclic polyolefin resin. Of these, alicyclic polyolefin resins are preferred, and alicyclic polyolefin resins having an alicyclic structure in the main chain are particularly preferred from the viewpoints of mechanical strength and heat resistance.

  The alicyclic polyolefin resin is an amorphous resin having an alicyclic structure in the main chain and / or side chain.

  Examples of the alicyclic structure in the alicyclic polyolefin resin include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene) structure. From the viewpoint of mechanical strength, heat resistance, and the like. A cycloalkane structure is preferred. 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, when the mechanical strength, heat resistance, In addition, the moldability characteristics of the film are highly balanced and suitable.

  The ratio of the repeating unit having an alicyclic structure constituting the alicyclic polyolefin resin is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. It is preferable from a viewpoint of transparency and heat resistance that the ratio of the repeating unit which has an alicyclic structure in alicyclic polyolefin resin exists in this range.

  Examples of the alicyclic polyolefin resin include norbornene resin, monocyclic cyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, and hydrides thereof. Among these, norbornene resin can be suitably used because of its good transparency and moldability.

  Examples of the norbornene 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, or a hydride thereof; Examples thereof include addition polymers of monomers having a monomer, addition copolymers of monomers having a norbornene structure and other monomers, and hydrides 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 the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene) and 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. To obtain a film with a small saturated water absorption rate. It is preferable that the amount of polar groups is small, and it is more preferable not to have polar groups.

  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.

  Hydrogenated product of ring-opening polymer of monomer having norbornene structure, hydrogenated product of ring-opening copolymer of monomer having norbornene structure and other monomer capable of ring-opening copolymerization, norbornene structure The hydride of an addition polymer of a monomer having a monomer, and the hydride of an addition copolymer of a monomer having a norbornene structure and another monomer capable of addition copolymerization with these ring-opening (copolymerization) ) A known hydrogenation catalyst containing a transition metal such as nickel or palladium is added to a polymer or addition (co) polymer solution, and brought into contact with hydrogen, so that the carbon-carbon unsaturated bond is preferably 90% or more. It can be obtained by hydrogenation.

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 obtain an optical film that has no dimensional change in the long term and is excellent in stability of optical characteristics.

  The molecular weight of the alicyclic polyolefin resin suitably used in the present embodiment is appropriately selected according to the purpose of use, but gel permeation chromatography using cyclohexane (toluene when the polymer resin does not dissolve) as a solvent. The weight average molecular weight (Mw) of polyisoprene measured in step (in terms of polystyrene when the solvent is toluene) is usually 10,000 to 100,000, preferably 15,000 to 80,000, more preferably 20,000. ~ 50,000. When the weight average molecular weight is in such a range, the mechanical strength and formability of the film are highly balanced, which is preferable.

  Although the glass transition temperature of the thermoplastic resin used for this embodiment should just be suitably selected according to a use purpose, Preferably it is 80 degreeC or more, More preferably, it is the range of 100-250 degreeC. A film made of an alicyclic polyolefin resin having a glass transition temperature in such a range is excellent in durability without being deformed or stressed at a high temperature.

The thermoplastic resin used in the present embodiment preferably has an absolute value of the photoelastic coefficient of 10 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 7 × 10 ⁻¹² Pa ⁻¹ or less. It is particularly preferable that it is 10 ⁻¹² Pa ⁻¹ or less. The photoelastic coefficient C is obtained by dividing the birefringence Δn by the stress σ. That is, it is a value represented by C = Δn / σ. If the photoelastic coefficient of the alicyclic polyolefin resin exceeds 10 × 10 ⁻¹² Pa ⁻¹ , the variation in the in-plane retardation of the stretched film may increase.

  A long original fabric composed of a thermoplastic resin can be obtained by a known method, for example, a cast molding method, an extrusion molding method, an inflation molding method, or the like. Of these, the extrusion method is preferable because it has a small amount of residual volatile components and is excellent in dimensional stability. This original fabric may be a single layer or a laminated film of two or more layers. The laminated film can be obtained by a known method such as a coextrusion molding method, a film lamination method, or a coating method. Of these, the coextrusion method is preferred. In order to make the optical properties after stretching uniform, it is necessary to reduce the thickness unevenness of the original fabric as much as possible, and the maximum value-minimum value is 3 μm or less, preferably 2 μm or less. The thickness of the original fabric is usually 40 to 500 μm, preferably 50 to 300 μm, more preferably 50 to 200 μm.

  The width of the long original fabric used in the present embodiment may be appropriately determined depending on the width of the obtained stretched film and the stretch ratio, but is preferably at least 1000 mm.

  Stretching of a long original fabric is performed using a tenter stretching machine 2 for oblique stretching shown in FIG. The tenter stretching machine 2 for oblique stretching shown in FIG. 1 is a film on which a drawing roll (winding body) 10, a winding roll 12, and a grip clip (gripping tool) (not shown) for transporting the film travel. The rails 14R and 14L are arranged on the left and right sides, and the temperature-controlled room (not shown) in which the rails 14R and 14L are arranged is provided.

  The left and right grip clips that run on the rails 14R and 14L grip both ends of the original fabric 11 fed from the drawer roll 10, guide the original fabric 11 into the temperature-controlled room, and extend it obliquely. Then, the obliquely stretched film 13 is opened at the exit of the temperature-controlled room of the stretching tenter stretching machine 2, that is, before the winding roll 12.

  Here, the position where the right and left grip clips open the obliquely stretched film 13 is the position indicated by x in FIG. 1, and the straight line connecting the positions x indicated on the left and right rails 14R and 14L is the film winding direction. The angle θo formed with respect to the direction perpendicular to the angle satisfies the condition of θ−30 <θo <θ + 5, preferably θ−25 <θo <θ + 5. Thereby, it is possible to suppress the occurrence of film sagging and wrinkles near the exit of the temperature-controlled room of the tenter stretching machine 2 for oblique stretching, and to suppress the deterioration of the profile in the width direction of the film with retardation and orientation angle.

  The obliquely stretched film 13 released from the grip clip is taken up by the take-up roll 12. The take-up tension T (N / m) of the film after oblique stretching can be selected between 100 <T <250, preferably 100 <T <220. When the take-up tension is out of the above range, the film is likely to be damaged or wrinkled, and the retardation and orientation angle profile in the film width direction are deteriorated. The pair of left and right rails 14R and 14L have a continuous endless track without a terminal, and are configured to sequentially return the grip clips with the obliquely stretched film 13 open from the exit side of the temperature-controlled room to the entrance side. Yes.

  In the tenter stretching machine 2 for oblique stretching according to the present embodiment, the rails 14R and 14L are bent on the right side with respect to the running direction of the film, but the left side made symmetrical with respect to the feeding direction of the film in FIG. The rail may be bent.

In addition, although the opening angle of rail 14R, 14L can be suitably selected according to a draw ratio, a draw ratio is 1.3 to 2.0 times normally, Preferably it is 1.5 to 1.8 times. When the draw ratio R is within this range, thickness unevenness in the width direction is preferably reduced. In stretching in the tenter stretching machine 2 for oblique stretching, if the stretching temperature is differentiated in the width direction, the thickness unevenness in the width direction can be further improved. The said draw ratio can be calculated | required from the length change amount of the width direction of a stretched film. Specifically, when the width of the unstretched original fabric is W ₀ and the width of the stretched film is W ₁ , the stretch ratio R can be obtained by W ₁ / W ₀ .

  The stretching temperature in the tenter stretching machine 2 for oblique stretching according to the present embodiment is appropriately selected from the range of Tg to Tg + 30 (° C.) with respect to the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the raw fabric 11. Is done. If the stretching temperature is less than Tg, moldability may be insufficient and defects such as craze may occur, and if the stretching temperature exceeds Tg + 30 ° C., flow stretching occurs and sufficient molecular orientation cannot be obtained to develop retardation.

  In the manufacturing method according to the present embodiment, the traveling speeds of the grip clips are substantially equal at both ends of the film. The traveling speed of the grip clip can be selected as appropriate, but is usually 10 to 100 m / min. The traveling speed of the gripping clip is kept constant from when the film is gripped by the gripping clip until the film is released. The difference in travel speed between the pair of left and right grip clips is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. By causing the gripping clip to travel on the rails 14R and 14L at such a traveling speed, it is possible to prevent the variation in the optical characteristics of the stretched film.

  As described above, an obliquely stretched film having an average orientation angle θ in the range of 40 to 50 ° with respect to the direction perpendicular to the width direction at the stretching end position is produced.

  Next, the stretched film according to this embodiment will be described. The stretched film which concerns on embodiment of this invention is obtained by the manufacturing method of the stretched film of this invention.

The in-plane retardation Re of the stretched film according to this embodiment is about 100 to 300 nm, and an optimum value is selected within this range depending on the design of the display device used. Incidentally, the in-plane direction retardation Re is multiplied by the mean thickness d of the film to the difference between the refractive index n _y in the direction perpendicular to the slow axis in the refractive indices n _x and plane-plane slow axis direction it is a value _{(Re = (n x -n y} ) × d).

  The stretched film according to this embodiment is in the range of 40 to 50 ° when the orientation angle θ is 0 ° in the direction perpendicular to the winding direction of the film, and like the in-plane direction retardation Re, The optimum value within this range is selected depending on the design of the display device used.

  In the stretched film according to this embodiment, the variation in the orientation angle is 1.0 ° or less when measured at 50 mm intervals in at least 1300 mm in the width direction. When a circularly polarizing plate is obtained by laminating a polarizer having a variation in orientation angle exceeding 1.0 ° with a polarizer and this is installed in a liquid crystal display device, light leakage may occur and the contrast may be lowered.

  In the stretched film according to this embodiment, the variation of the in-plane retardation Re is preferably within 5 nm, more preferably within 4 nm, and particularly preferably within 3 nm, at least in the width direction of 1300 mm. By setting the variation of the in-plane retardation Re within the above range, the display quality can be improved when used as a retardation film for a liquid crystal display device. Here, the variation in the in-plane direction retardation Re is obtained by measuring the in-plane direction retardation Re at an interval of 50 mm in the width direction when the light incident angle is 0 ° (a state where the incident light beam and the laminate surface are orthogonal). This is the difference between the maximum value and the minimum value of the in-plane direction retardation Re.

Stretched film according to the present embodiment, the refractive slow axis direction of the refractive indices n _x in the plane of the _film, the refractive index in a direction perpendicular to the slow axis in the film plane n _y, in the thickness direction of the film when the rate was _{n z,} Nz coefficient expressed by _{(n x -n z) / (} n x -n y) is in the range of 1.3 to 2.0. An optimum value within this range is selected depending on the design of the liquid crystal display device used.

  The stretched film according to this embodiment has a variation in Nz coefficient of 0.1 or less when measured at 50 mm intervals in at least 1300 mm in the width direction. If the variation in the Nz coefficient exceeds 0.1, it may cause display quality deterioration such as color unevenness when incorporated in a display device.

  The average thickness of the stretched film according to this embodiment is preferably 20 to 80 μm, more preferably 30 to 60 μm, and particularly preferably 40 to 50 μm from the viewpoint of mechanical strength and the like. Moreover, since the thickness unevenness in the width direction affects the availability of winding, it is preferably 3 μm or less, and particularly preferably 2 μm or less.

In the stretched film according to this embodiment, the content of residual volatile components 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. If the content of residual volatile components is large, the optical characteristics may change over time. When the content of the volatile component in the above range, dimensional stability is improved, the in-plane direction retardation Re and thickness direction retardation _{Rth (= ((n x +} n y) / 2-n z) × d; n _x is the in-plane slow axis direction of the refractive index; n _y is a refractive index in a direction perpendicular to the slow axis in the plane; n _z is the thickness direction of the refractive index; d is the average thickness of the film) of The change with time can be reduced, and the deterioration of the circularly polarizing plate and the liquid crystal display device of the present invention can be suppressed, and the display image can be kept in a good state for a long time.

  The 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 residual monomers and solvents. The content of the volatile component can be quantified by dissolving the film in chloroform and analyzing it by gas chromatography as the total of substances having a molecular weight of 200 or less contained in the film.

  The stretched film according to this embodiment has a saturated water absorption rate of preferably 0.03% by weight or less, more preferably 0.02% by weight or less, and particularly preferably 0.01% by weight or less. When the saturated water absorption is in the above range, the change with time of Re and Rth can be reduced, and further, deterioration of the circularly polarizing plate and the liquid crystal display device of the present invention can be suppressed, and the display image can be kept in a good state for a long time. Can keep. The saturated water absorption is a value expressed as a percentage of the increased mass of the film specimen immersed in water at 23 ° C. for 24 hours with respect to the mass of the film specimen before immersion.

  The stretched film according to this embodiment is long. The long shape means one having a length of at least about 5 times or more with respect to the width direction of the film or laminate, preferably 10 times or more, and specifically in a roll shape. It has a length that is wound and stored or transported.

  The width of the stretched film according to this embodiment is at least 1300 mm, preferably at least 1500 mm. The upper limit is not particularly limited, but 2000 mm is a manufacturing limit.

  The stretched film according to the embodiment of the present invention can be easily obtained by the above manufacturing method and can highly compensate the refractive index. Therefore, the stretched film alone or in combination with other members can be used as a retardation plate or a viewing angle. The compensation film can be widely applied to liquid crystal display devices, organic EL display devices, plasma display devices, FED (field emission) display devices, SED (surface electric field) display devices, and the like.

  The polarizing plate according to the embodiment of the present invention is formed by laminating the stretched film according to the above-described embodiment on at least one surface of a polarizer. For polarizers, films made of appropriate vinyl alcohol polymers such as polypinyl alcohol and partially formalized polyvinyl alcohol, dyeing treatment with dichroic substances such as iodine and dichroic dyes, stretching Appropriate treatments such as treatment and cross-linking treatment can be performed in an appropriate order and manner, and appropriate materials that transmit linearly polarized light when natural light is incident can be used. In particular, those excellent in light transmittance and degree of polarization are preferable. The thickness of the polarizer is generally 5 to 80 μm, but is not limited thereto.

  As a lamination | stacking form, the stretched film which concerns on embodiment of this invention may be laminated | stacked on both surfaces of a polarizer, may be laminated | stacked on one side, and there is no limitation in the number of lamination | stacking, You may laminate | stack two or more sheets. Moreover, as a lamination | stacking method, although it is not an essential method, it can laminate | stack using an adhesive agent. Conventionally, a protective film has been laminated on one or both sides of a polarizer, but by stretching a stretched film according to the present embodiment, the stretched film according to the present embodiment also serves as a protective film for the polarizer. I will also serve. When the stretched film is directly laminated on the polarizer in this manner, one conventionally used protective film can be omitted, which contributes to thinning of the liquid crystal display device.

  In the polarizing plate according to the embodiment of the present invention, another member can be interposed between the stretched film and the polarizer as long as the characteristics of the present invention are not impaired. As another member to interpose, a protective film for protecting a polarizer is mentioned, for example. An appropriate transparent film can be used as the protective film. Among these, a film made of a resin excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like is preferable. Examples of the resin for forming the protective film include acetate polymers such as triacetyl cellulose; polymers having an alicyclic structure; polyester polymers such as polyolefin polymers, polycarbonate polymers and polyethylene terephthalates; polyvinyl chloride polymers and polystyrene. Examples thereof include a polymer, a polyacrylonitrile polymer, a polysulfone polymer, a polyether sulfone polymer, a polyamide polymer, a polyimide polymer, and an acrylic polymer.

  The liquid crystal display device according to the embodiment of the present invention includes the polarizing plate according to the embodiment of the present invention. The display mode of the liquid crystal cell included in the liquid crystal display device is not particularly limited. For example, in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment ( CPA) mode, hybrid alignment nematic (HAN) mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, and optically compensated bend (OCB) mode.

  The liquid crystal display device according to the embodiment of the present invention may include other members. For example, 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. Examples of the light source used in the liquid crystal display device include a cold cathode tube, a mercury flat lamp, a light emitting diode, and an EL.

  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) Orientation angle Measurement was performed at an interval of 50 mm with respect to the width direction of the film using an Olympus polarizing microscope BX51, and the average value was defined as an orientation angle θ. (2) In-plane direction retardation Re, where the maximum value-minimum value was evaluated as variation, and the variation was 1.0 or less.
The average value measured at intervals of 50 mm in the width direction using Oji Scientific Co., Ltd. KOBRA-21SDH was evaluated as the in-plane direction retardation Re, and the maximum value-minimum value was evaluated as variation. .

(3) Appearance of roll The appearance of the rolled stretched film was judged according to the following criteria. ○ ・ ・ ・ No abnormality was observed in the wound form of the wound roll. Wound rolls with poor winding shape (4) Take-up tension T
Load cells were installed at both ends of the first free roll at the exit of the tenter, the load applied to the roll was detected, and the result obtained by dividing the load by the film width was taken as the take-up tension.

Example 1
A pellet of a norbornene resin (ZEONOR1420: glass transition point = 137 ° C., manufactured by Nippon Zeon Co., Ltd.) was dried at 100 ° C. for 5 hours.

  The pellets are supplied to an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter, extruded from a T-die onto a casting drum, cooled, and unstretched with a thickness of 90 μm, a width of 900 mm, and a length of 1000 m. A film was obtained.

  The unstretched film was supplied to a tenter stretching machine at a feeding angle θs = 47 °, and stretched so that the orientation angle θ was 45 degrees at a stretching temperature of 142 ° C. and a stretching ratio of 2.0 times, and both ends of the film were 180 mm. Trimming was performed to obtain a long stretched film having a width of 1340 mm. The obtained long stretched film was uniform in the width direction. Table 1 shows the evaluation of the retardation Re in the in-plane direction of the stretched film, the variation in retardation in the in-plane direction, the orientation angle θ, the variation in the orientation angle θ, and the roll appearance.

  Winding of a polarizing plate having a width of 1340 mm by laminating a long polarizer (manufactured by Sanlitz, HLC2-5618S, thickness 180 μm) having a transmission axis in the width direction and the long stretched film by roll-to-roll. Got the body. The polarizing plate cut out from the wound body is replaced with the upper and lower polarizing plates of a commercially available VA (vertical alignment) mode transflective liquid crystal display device, and the side on which the stretched film is bonded is arranged on the liquid crystal cell side. And the slow axes of the stretched films arranged above and below were incorporated so as to be orthogonal to each other. When the display characteristics of the obtained liquid crystal display device were confirmed from the front by visual observation, color unevenness was not observed over the entire width, and the display was good.

(Examples 2 to 4)
Except having changed into the extending | stretching conditions shown in Table 1, it carried out similarly to Example 1, and obtained the stretched film, the polarizing plate, and the anti-transmissive liquid crystal display device. The obtained long stretched film was uniform in the width direction. Table 1 shows the evaluation of the in-plane direction retardation Re, the in-plane direction retardation Re, the orientation angle, the orientation angle variation, and the roll appearance of the stretched film obtained. The transflective liquid crystal display device using these stretched films was a good display with no color unevenness observed over the entire width.

(Comparative Examples 1 and 2)
The unstretched film is continuously supplied to the tenter stretching machine as it is, and is obliquely stretched in the same manner as in the example at a feeding angle θs = 47 °, a stretching temperature of 140 ° C., and a stretching ratio of 2.0 times, and the position θo of the gripping tool is set. By changing (θo = 0 ° in Comparative Example 1 and θo = 55 ° in Comparative Example 2), an obliquely oriented stretched film having an orientation angle θ = 45 ° was obtained and wound around a winding core. The evaluation results of this stretched film are shown in Table 1. This film had non-uniform optical characteristics, and the film was severely wrinkled and tarmi, and the winding shape was very bad. In the transflective liquid crystal display device using this stretched film, color unevenness was observed in the screen.

(Comparative Examples 3 and 4)
As shown in Table 1, when the drawing angle was changed and the film was stretched, as shown in Table 1, the film after stretching had non-uniform optical properties, and the wrinkles and tarmi of the film were severe and the wound shape was severe. It was very bad. In the transflective liquid crystal display device using this stretched film, color unevenness was observed in the screen.

(Comparative Examples 5 and 6)
When the drawing tension was changed under the conditions shown in Table 1 and the film was stretched, as shown in Table 1, the film after stretching had non-uniform optical properties, and the wrinkles and talmi of the film were severely wound. The figure was very bad. In the transflective liquid crystal display device using this stretched film, color unevenness was observed in the screen.

It is a figure which shows the structure of the tenter drawing machine for diagonal drawing concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Tenter stretching machine for diagonal stretching, 10 ... Draw roll, 11 ... Unstretched film (raw material), 12 ... Winding roll, 13 ... Diagonal stretched film, 14R, 14L ... Rail

Claims (4)

A method for producing a stretched film in which both ends in the width direction of a thermoplastic resin film are gripped by a gripping tool, conveyed in a tenter, and stretched so that the orientation angle θ is in the range of 45 ± 5 ° with respect to the film winding direction. There,
An angle θo (°) formed by a straight line connecting open positions of the right and left grippers with respect to a direction perpendicular to the film winding direction, an orientation angle θ (°) of the film after stretching with respect to the film winding direction, Stretching characterized in that the film take-up tension T (N / m) after stretching and the film feeding angle θs (°) with respect to the film winding direction satisfy the following conditions (1) to (3): A method for producing a film.
θ-30 <θo <θ + 5 (1)
100 <T <250 (2)
θ-5 <θs <θ + 5 (3)   The stretched film manufactured by the manufacturing method of Claim 1.   A polarizing plate obtained by laminating the stretched film according to claim 2 on at least one surface of a polarizer.   A liquid crystal display device comprising the polarizing plate according to claim 3.

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