KR20140143370A - Polyester film roll for an optical phase difference plate and fabrication method for same - Google Patents

Abstract

The present invention is characterized in that the tilt angle (orientation angle) variation of the main axis of alignment with respect to the film width direction is within 6 degrees, the width is 1,200 mm or more and less than 2,000 mm, the retardation value in plane is 50 to 200 nm, A retardation of in-plane retardation value of not more than 20 nm, a local retardation non-uniformity of less than 10 nm, and a thickness of not less than 2 탆 and not more than 10 탆. Also provided is a polyester film roll which can be suitably applied as an optical retarder.

Description

TECHNICAL FIELD [0001] The present invention relates to a polyester film roll for an optical phase difference plate and a method for producing the same. BACKGROUND ART [0002]

The present invention relates to a polyester film roll for an optical retarder suitably used in combination with a polarizing plate in a member such as a liquid crystal display.

In recent years, the spread of display devices using polarizing plates is progressing. In these devices, the problem is pointed out that the screen darkens depending on the viewing angle when polarizing glasses are used.

This is caused by the difference in transmittance between the polarization axis of the polarizing film in the polarizing glasses and the polarizing axis of the polarizing plate disposed on the viewer side of the display device.

This problem can occur in car navigation, PND, aircraft cockpit, PDA, mobile phone, fish finder, etc., which have many opportunities to observe polarized glasses. In recent years, devices such as smart phones and tablets This is especially a problem that can occur. Further, in this device, there is a problem that, when a conventional thick film is applied, it can not meet the demand for lightening.

To solve this problem, an optical retardation plate (? / 4 phase plate,? / 2 retardation plate) having birefringence is provided on the outside (viewer side) of the viewer side polarizer of the display device to convert light from the display device into linearly polarized light (For example, refer to Patent Document 1)

Patent documents 2 and 3 show examples of films used in a? / 4 phase difference plate. However, resins used are polyolefins such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, And cyclic polyolefins based on cyclic olefins such as polyarylate, polyamide, norbornene, and the like.

On the other hand, a film comprising a polyester resin such as polyethylene terephthalate, particularly a biaxially oriented polyester film, has excellent dimensional stability and rigidity. Since the contribution to birefringence due to orientation is larger than that of other resins, 4 retardation plate and a? / 2 retardation plate, it is possible to reduce the thickness of the liquid crystal device compared with the retardation plates described in Patent Documents 2 and 3, and thus the weight of the liquid crystal device can be reduced. However, .

In the biaxially oriented polyester film, the central portion of the film to be produced is stretched in the gravitational direction or in the advancing direction of the manufacturing process due to its own weight or heat shrinkage stress by heating and stretching in a state where the end portion is grasped, This causes a phenomenon called bowing that is caused by the fact that the film in the process forms a sweep line (catenary curve), and the fluctuation of the birefringence in the film width direction and the slope of the alignment main axis in the film width direction Quot;) is generated.

Therefore, when used as an optical phase difference plate, there is a problem that the in-plane retardation differs from position to position, thereby causing unevenness in color tone. In addition, There is a problem in that it can not be used as a? / 4 phase difference plate.

Since the variation of the orientation angle by Boeing increases in a quadratic function corresponding to the distance from the center of the film being formed, it is important to suppress the variation of the orientation angle at a wide width and a position apart from the center of the film It has been a challenge.

In response to such a problem, the biaxially oriented polyester film has conventionally taken countermeasures by the following technique. Patent Document 4 discloses a film in which bowing is suppressed by loosening the stretched film in the longitudinal direction. However, the film described in Patent Document 4 is a film having a thickness of 30 占 퐉, and when the film is made thin, the thickness is uneven and the in-plane retardation varies from position to position.

As a thin film formed in a biaxially oriented polyester film, a polyester film for use in magnetic materials such as the one exemplified in Patent Document 5 can be mentioned. In this technique, the in-plane retardation is set to a condition suitable for the? / 4 retarder Lt; / RTI >

In order to cope with this problem, a method using only a central portion of a film formed is used for a conventional polarizing plate release film or the like. However, as the productivity is deteriorated and the size of a liquid crystal device becomes larger, It was difficult to collect the sample.

It is strongly demanded that the display device is unlikely to have irregularities of color or unevenness of color caused by the above-mentioned unevenness of the orientation and in-plane retardation. In recent devices such as smart phones and tablets, Since the distance is very close, local color irregularities can be easily discriminated, which is a problem. In order to suppress this local color unevenness, there has been known a technique of improving the stretching method of a thermoplastic resin film as in Patent Document 6 to suppress phase difference nonuniformity between two points spaced by 1 cm in the film plane, but in practical use, Local phase difference non-uniformity becomes a problem, so that a phase difference plate that can be satisfactorily practically still can not be obtained.

Japanese Patent Application Laid-Open No. 10-10523 Japanese Patent Application Laid-Open No. 2010-262155 Japanese Patent Laid-Open No. 2007-171978 Japanese Patent Application Laid-Open No. 2004-358742 Japanese Patent Application Laid-Open No. 2005-163020 Japanese Patent Application Laid-Open No. 09-138307

A problem to be solved by the present invention is to provide a polyester film roll which can solve the above-mentioned problems of the background art and which can be suitably applied as an optical retarder.

As a result of intensive studies to solve the above problems, it has been found that the above problems can be solved by having the following characteristics, and the present invention has been accomplished.

(1) the tilt angle (orientation angle) variation of the main axis of alignment with respect to the film width direction is within 6 占, the width is 1,200 mm or more and less than 2,000 mm, the retardation in plane retardation is 50 to 200 nm, Wherein the retardation of the in-plane retardation value is 20 nm or less and the thickness is 2 占 퐉 or more and 10 占 퐉 or less.

(2) the tilt angle (orientation angle) variation of the main axis of alignment with respect to the film width direction is within 10 deg., The width is 2,000 mm or more, the in-plane retardation value is from 50 to 200 nm, Wherein the retardation film has a retardation of 20 nm or less and a thickness of 2 to 10 mu m.

(3) The polyester film roll for an optical retardation plate according to (1) or (2), wherein the local phase difference unevenness is less than 10 nm for the entire width of the film roll and the range of 1,200 mm or more in the longitudinal direction.

(4) The method for producing a polyester film roll for an optical phase difference plate as described in any one of (1) to (3), wherein the film transfer speed in the step of winding the film roll is less than or equal to 50 m / min and less than or equal to 200 m / min.

According to the present invention, the inclination angle (orientation angle) of the alignment main axis and the retardation of the in-plane retardation value are suppressed and the range of the retardation value including the local in-plane retardation unevenness is defined, It becomes possible to provide a polyester film roll for a retarder.

Hereinafter, a polyester film roll for an optical phase difference plate according to an embodiment of the present invention will be described in more detail. The polyester which can be suitably used in the present embodiment is not particularly limited as long as it is a polyester that becomes a high-strength film by molecular orientation, but it preferably contains polyethylene terephthalate and polyethylene-2,6-naphthalate. Particularly preferably, it is polyethylene terephthalate which is superior in price. When polyethylene terephthalate is used, examples of polyester copolymer components other than ethylene terephthalate include diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, 1,4-cyclohexane Dimethanol and the like, dicarboxylic acid components such as adipic acid, sebacic acid, phthalic acid, isophthalic acid and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid , p-oxyethoxybenzoic acid, and the like can be used within a range that does not inhibit the intended physical properties of the film.

Such a polyester can be produced, for example, by the following method. For example, a method may be employed in which an acid component is directly esterified with a diol component, and then the product of the reaction is heated under reduced pressure to remove excess diol components, and polycondensation is carried out, or a method in which a dialkyl ester is used as an acid component Followed by transesterification with the diol component, followed by polycondensation in the same manner as described above. At this time, if necessary, for example, alkali metals, alkaline earth metals, manganese, cobalt, zinc, antimony, germanium and titanium compounds may be used as a reaction catalyst. The polyester has an intrinsic viscosity of 0.4 to 0.9, preferably 0.5 to 0.7, more preferably 0.55 to 0.65.

The polyester film (polymer 1) and the polyimide (polymer 2) may be used as the polyester film to be applied to the polyester film roll for an optical phase difference plate of the present embodiment (hereinafter sometimes referred to as a polyester film roll or simply a film roll) Or a polymer alloy film containing at least one polymer. The polymer alloy referred to herein is a polymer multi-component system, and may be a block copolymer by copolymerization, or may be a polymer blend by mixing or the like. From the viewpoint of stretchability and productivity, a polymer blend having no molecular bond such as copolymerization is more preferable.

Polymer 2 used in this embodiment is a polyimide having an imide group in the molecular chain. The polyimide has an interaction with the polyester which is thought to originate from the interaction of the imide ring and the benzene ring, and generally has a higher glass transition temperature than that of the polyester. As a result, when the film is stretched at a temperature close to the glass transition temperature of the main component of the polymer 1 in the production process, the polyimide having a low molecular mobility near the stretching temperature is capable of suppressing the stretchability due to the orientation crystallization of the polymer 1 It is presumed that it is possible to perform high-magnification stretching if possible.

As the above-mentioned polyimide, for example, it is preferable to contain a structural unit represented by the following formula.

R ¹ in the formula represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group represented by the following formula:

R ² in the formula represents one or two or more groups selected from an aliphatic hydrocarbon group, an alicyclic hydrocarbon group and an aromatic hydrocarbon group as represented by the following formula:

Such a polyimide is obtained by reacting a tetracarboxylic acid and / or an acid anhydride thereof with one or two or more compounds selected from the group consisting of aliphatic primary monoamine, aromatic primary monoamine, aliphatic primary diamine and aromatic primary diamine By dehydration condensation.

From the viewpoint of melt moldability and affinity with polyester, a polyetherimide containing an ether linkage in the polyimide component, such as represented by the following formula, is particularly preferred.

Wherein R ³ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ⁴ is a divalent aromatic moiety having 6 to 30 carbon atoms, an alkyl having 2 to 20 carbon atoms A cycloalkylene group having 2 to 20 carbon atoms, and a polydiorganosiloxane group terminated in an alkylene group having 2 to 8 carbon atoms)

Examples of R ³ and R ⁴ include aromatic residues represented by the following chemical formulas.

In the present embodiment, from the viewpoints of affinity with polyester, cost, melt moldability, etc., 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and m- A polymer having a repeating unit represented by any one of the following two formulas, which is a condensate of a diamine or p-phenylenediamine, is preferred.

(n is an integer of 2 or more, preferably 20 to 50)

This polyetherimide is available under the trade name "Ultem "

It is preferable that Polymer 2 used in this embodiment has good affinity with Polymer 1 among the above. The term "having good affinity (compatibility)" as used herein means, for example, melt mixing using a polymer alloy containing polymer 1 and polymer 2 at a predetermined mixing ratio to form an unoriented or biaxially oriented film (Hereinafter simply referred to as a circle equivalent diameter) which is not caused by additives such as organic particles and inorganic particles when the cross section of the film is observed with a transmission electron microscope at a magnification of 30,000 to 500,000 times, (For example, a polymer domain with poor dispersion) is not observed. However, the method for determining affinity is not particularly limited to this, and a single glass transition point may be observed by temperature-modulated DSC (MDSC), if necessary, so that it can be judged that there is good affinity.

The polyester film to be applied to the polyester film roll for an optical phase difference plate of the present embodiment preferably has a haze value of 3% or less. Preferably 2% or less, more preferably 1% or less. When the haze value is larger than 3%, scattering light from the film is large when used as a retardation film in the circularly polarizing plate, and causes light leakage in the cross-Nicol state.

The film to be used in this embodiment may be a single layer or a composite film including two or more layers. In order to keep the haze value of the film within the above range, the film is particularly suitable when it includes a three-layer composite film. In this case, the configuration of A | B | A having the same composition as that of the other types of particles or the content of particles in the laminated portions on both surface layers may be different, desirable. In addition, when the thicknesses of the two layers are substantially the same, quality design is easy. The thickness of the laminate on one side is preferably 0.5 to 2.5 占 퐉, more preferably 0.8 to 1.5 占 퐉.

In addition, it is possible to make the transportability of the film, the smoothness of the surface, and the haze value to be within a desired range by appropriately containing particles contained in the base layer portion (center layer) by containing inert particles on the laminated surface. Examples of the particles to be contained include inorganic particles such as spherical silica, aluminum silicate, titanium dioxide and calcium carbonate, and other organic polymer particles include crosslinked polystyrene resin particles, crosslinked silicone resin particles, crosslinked acrylic resin particles, crosslinked styrene- Resin particles, crosslinked polyester particles, polyimide particles, melamine resin particles and the like are preferable. One or more of these may be selected and used.

These inert particles can be added at the stage of the polyester polymerization step to prepare an inert particle-containing polymer. For example, an inert particle-containing slurry is added to a slurry of ethylene glycol, which is a glycol component of polyester, after ester exchange before polycondensation or at the stage of oligomer after esterification, and then a polycondensation reaction is carried out, A particle-containing polymer can be obtained.

The slurry of the inert particles before addition may be subjected to dispersion treatment by a sand grinder or the like, separation of coarse particles by centrifugal sedimentation treatment, or high-precision filtration if necessary, thereby making it possible to uniformize the particle diameter distribution, The particles can be removed, and the film can be effectively used for reducing the coarse projections.

The film to be used in the present embodiment preferably contains 0.2 to 1.0 mass%, more preferably 0.3 to 0.8 mass% of inert particles having an average particle diameter of 0.3 to 1.5 占 퐉, preferably 0.8 to 1.3 占 퐉. In addition, the transportability, surface smoothness and haze value of the film can be optimized by adjusting the content of particles in the base layer portion in which 0.01 to 0.1 mass% of the same kind of inert particles are contained in the base layer portion.

The film applied to the polyester film roll for an optical phase difference plate of this embodiment has an in-plane retardation value (in-plane retardation value Re) of 50 to 200 nm, preferably 70 to 180 nm. When the in-plane retardation value is less than 50 nm or more than 200 nm, it does not correspond to 1/4 of the wavelength range of visible light (360 to 750 nm), and thus the function as? / 4 retardation film can not be performed.

The in-plane retardation Re (nm) can be defined by the following equation (1) from the refractive index nx in the longitudinal direction of the film, the refractive index ny in the transverse direction, and the film thickness d (占 퐉).

≪ Equation (1) >

As is clear from the formula (1), in order to make the in-plane retardation within the predetermined range in the polyester film applied to the present embodiment, it is only necessary to control the refractive index difference and thickness in the longitudinal direction and the width direction.

From the viewpoint of the difference in refractive index between the above-mentioned film and a film comprising a polyester resin such as polyethylene terephthalate, particularly biaxially oriented polyester film, it is important that the thickness of the film applied to this embodiment is 2 탆 or more and 10 탆 or less. Preferably not less than 3 mu m and not more than 8 mu m. If the film thickness is larger than 10 mu m, it becomes difficult to achieve the in-plane retardation value retardation required in the polyester film applied in the present embodiment. If the thickness is less than 2 mu m, the workability of the film is deteriorated and it is difficult to apply the film to an optical retarder.

In the case of a film having a variation in refractive index difference and thickness, the color seen in each part when used as a retarder causes different phenomena. Therefore, in the polyester film applied to this embodiment, the in- In-plane retardation (in-plane retardation difference between the maximum and minimum in-plane retardation values of the entire film) of 20 nm or less, preferably 10 nm or less, and local phase difference nonuniformity Is less than 10 nm. When the local phase difference unevenness is 10 nm or more, the viewer of the display device recognizes local color heterogeneity, and a phase difference plate that can be satisfied in practice can not be obtained.

As an example of a device for measuring the in-plane retardation with respect to the width direction of the polyester film applied to the present embodiment, there can be mentioned Cobra (KOBRA) -WPR (manufactured by Oji Keio Co., Ltd.) used in Examples described later. In this specification, the in-plane retardation value retardation in the width direction is measured using such a measuring apparatus, and the fluctuation of the in-plane retardation value retardation in the width direction in the present embodiment is measured with respect to the entire width of the film Is defined as the difference between the maximum value and the minimum value at the time of the operation.

As a device for measuring the in-phase non-uniformity of phase difference of the polyester film applied to the present embodiment, there may be mentioned Cobra-CD (manufactured by Oji Keio Co., Ltd.) described later. The local phase difference non-uniformity referred to in the present specification is measured using such a measuring apparatus. The local phase difference non-uniformity in this embodiment is the maximum in-plane retardation value between two adjacent points within 1 cm of the measurement site Is defined as the difference between the value and the minimum value.

The polyester film to be used in the present embodiment has any one of the following properties a to b.

a. The variation of the tilt angle (orientation angle) of the alignment main axis with respect to the width direction is within 6 degrees, and the width is 1,200 mm or more and less than 2,000 mm.

b. The dynamic variation is within 10 degrees and the width is 2,000 mm or more.

Here, the inclination of the orientation principal axis can be defined as the direction of the slow axis, but the orientation can be evaluated by measuring the propagation velocity of the ultrasonic pulse transmitted through the film over the entire region, and the inclination (orientation angle) of the orientation principal axis can be measured . The inclination of the alignment main axis is parallel to the film width direction, and the alignment angle is 0 degree, and the inclination in the clockwise direction with respect to the film surface is indicated by +, and the counterclockwise direction is indicated with -. The variation of the orientation angle may be within the above-mentioned range of the width, but the orientation angle preferably has the same sign as the slope. The term " the sign of the slope is the same " refers to a state in which the slope of the measurement is the same at both ends of the width of the film.

The orientation angle fluctuation column is defined as the absolute value of the difference between the maximum value and the minimum value of the orientation angle of an arbitrary position in the film measured as described above. When the variation of the orientation angle exceeds 6 degrees (width is 1, 200 mm or more and 2,000 mm (Width of 2,000 mm or more), the angle relationship between the absorption axis of the polarizing plate and the slow axis of the optical phase difference film is not maintained when the polarizing plate is joined to the polarizing plate, There is a case where a spot is generated.

In addition, the bowing phenomenon that generates the orientation angle is a phenomenon caused by the fact that the film in the process constitutes a sweep line (catenary curve), so that the orientation angle increases as the distance from the center of the film formed is increased . This behavior is usually approximated by a quadratic function. In order to obtain a film with the smallest orientation angle variation, it is best to use a film roll of the present embodiment in which the center of the formed intermediate product roll is the widthwise center . However, such a widening can not allow the product to be collected outside the central portion. In addition, in recent years, as the liquid crystal device has become larger in size, the width of the optical phase difference film becomes larger. When the polarizing plate is bonded to the polarizing plate as described above, the angle relationship between the absorption axis of the polarizing plate and the slow axis of the optical phase difference film is not maintained, You will be constrained. Specifically, when combined with the polarizing plate on the optical phase-shifting film roll, the longitudinal direction when the sheet becomes the sheet (sheet) is determined in accordance with the angle of the slow axis (orientation angle) It is necessary to change the width of the film according to the position of the width when the film is formed. As a result, when the angle of cut-off is large, the margin becomes large when cut out from the roll, and the ratio of the area that can not be used as an optical retardation film becomes large, resulting in a problem of poor productivity. From this, it is important that the variation of the orientation angle over a certain width falls within a certain range. As described above, the width of the film in the present embodiment and the variation in the orientation angle thereof are not less than 1,200 mm and less than 2,000 mm, the orientation angle variation is within 6 degrees, preferably within 5 degrees, If the dynamic variation is within 10 deg., Preferably within 8 deg., This problem can be solved. The upper limit of the width is affected by the width as described above. However, considering the film processability and productivity after processing, the upper limit is preferably 3,000 mm or less.

Next, the method for producing a polyester film applied to the present embodiment will be described in more detail. The polyester described above is dried, if necessary, and fed to an extruder, and the polymer is filtered by a filter. Since a very small foreign object also becomes a film defect, it is effective to use, for example, a high-precision filter which collects at least 95% of foreign matter of 5 m or more. Subsequently, the sheet is melt-extruded using a T-shaped cantilever or the like and cooled and solidified on a casting roll to obtain an unstretched film.

Although the molten extruded polymer sheet is cooled by being grounded on the casting roll, the amount of heat of the polymer that can be cooled is limited by the thermal conductivity of the member of the cast roll, and if not completely cooled to the inside of the polymer sheet, Orientation non-uniformity (non-crystal non-uniformity) occurs. Since this orientation non-uniformity (non-crystal non-uniformity) causes local phase difference non-uniformity, it is effective to make the casting roll speed low, for example, and to lengthen the cooling time of the polymer sheet. The cast roll speed is preferably such that the film conveying speed in the step of winding the stretched film after the next step is in the range from 50 m / min to 200 m / min, more preferably from 50 m / min to 150 m / min Range.

The unoriented film is stretched at a stretching temperature of 90 to 130 캜 to obtain a biaxially oriented polyester film for an optical phase difference plate of this embodiment. In the stretching step, it may be a sequential stretching or a simultaneous biaxial stretching. In the production of the polyester film to be applied to this embodiment, it is required to suppress the thickness unevenness which is a factor of fluctuation of the in-plane retardation value. Therefore, it is possible to suppress the thickness unevenness in the longitudinal direction at a low longitudinal stretching magnification A simultaneous biaxial stretching process is preferable.

In the production of the polyester film to be used in the present embodiment, the stretching in the longitudinal direction is performed in a stepwise manner or in a multi-stepwise manner at 2.5 to 5 times, and in the simultaneous biaxial stretching step, Stretch to 6 times. Here, it is preferable that the step of stretching ratio in the longitudinal direction / transverse direction is less than 1.0 with respect to the magnification ratio of the stretching step performed for each step. For this reason, it is possible to suppress bowing in the stretching process by increasing the orientation in the width direction.

When the polyester film to be used in the present embodiment is produced, it is preferable that it does not include a relaxation step in the longitudinal direction during stretching in the transverse direction. The relaxation process in the longitudinal direction is an effective method for suppressing bowing as described in Patent Document 4. Since the polyester film applied to the present embodiment is a film having a thickness of 10 m or less, The in-plane retardation becomes non-uniform for each position.

When the stretching temperature in the stretching process is lower than 90 deg. C and the stretching ratio is higher than 6 times in the production of the polyester film to be applied to the present embodiment, the film tends to break. Therefore, the stretching temperature is 90 deg. Preferably less than 6 times.

The stretching temperature in the first stretching in the width direction is preferably 90 占 폚 or more and less than 100 占 폚, and the rate of temperature rise in the stretching step after initiation of stretching is preferably less than 10 占 폚 / sec. For this reason, if excessive heat is applied in the initial stage of starting the transverse orientation, the orientation by the heat advances and the transverse orientation can not proceed sufficiently. Therefore, by increasing the orientation in the transverse direction, It is impossible to take a manufacturing process for suppressing the above-mentioned problems.

In the production of the polyester film to be used in the present embodiment, it is preferable not to provide a cooling step from the first stretching to the heat treatment step. In the polyester film for magnetic materials such as those exemplified in Patent Document 5, as a method for suppressing fluctuation in quality due to bowing, a cooling step is provided before entering the heat treatment step. In this method, however, Is too strong and it is necessary to make the film thin in order to set the in-plane retardation to a range suitable for the optical retarder, and it is difficult to satisfy the workability.

Subsequently, the polyester film to be applied to the present embodiment is produced through a heat treatment process. The atmospheric temperature of the heat treatment is such that the difference in temperature between the upper and lower portions of the film is 1 to 20 占 폚, preferably 1 to 10 占 폚, and more preferably 1 to 5 占 폚 in order to stabilize the physical properties of the film. If the difference in temperature between the upper and lower portions of the film is larger than 20 占 폚, the physical properties in the width direction of the film, particularly the mechanical properties or the heat shrinkage ratio, may become uneven. In the heat treatment, relaxation treatment may be performed as necessary. At this time, it may be any one of the horizontal direction and the longitudinal direction, but the horizontal direction and the longitudinal direction may be performed at the same time, or these may be combined. The relaxation rate is preferably 1 to 20%, more preferably 1 to 10%, relative to the entire width of the film, and is also effective for obtaining a film having excellent thermal dimensional stability.

Thereafter, an intermediate product (intermediate product roll) obtained by winding the above-mentioned film through the heat treatment process is obtained, and slit is performed to the required picking width finally to obtain the polyester film roll of the present embodiment.

In the polyester film applied to the present embodiment, the orientation angle variation is a point as described above. Since the orientation angle fluctuation occurs due to the bowing, it is preferable that the center of the middle product roll is symmetrically arranged so as to coincide with the center of the film roll in the widthwise direction. On the other hand, if the film roll is picked up asymmetrically so as to include either end of the intermediate product roll without including the center position, the variation of the orientation angle is maximized (in this case, the sign of the orientation angle is the same ). Since the polyester film used in the present embodiment has a small variation in orientation angle, the ratio of the width that can be used in the film width of the formed intermediate product roll is large, and productivity is improved when the film roll is used.

The polyester film obtained from the polyester film roll of the present embodiment is a retardation film with a much thinner thickness than conventional ones due to thinning and strengthening by biaxial stretching and realization of space saving in various liquid crystal display devices . Furthermore, by making the polarized light emitted from the liquid crystal display be elliptically polarized light or circularly polarized light, even when the liquid crystal display device is used in a state in which the polarized glasses are used, the change in the rotational direction (use in vertical or horizontal use) It is possible to suppress variations in color and unevenness, thereby ensuring the visibility at the time of operation of the apparatus.

<Examples>

The methods of measuring the characteristic values in the examples and comparative examples are as follows.

(1) Picking width

The film of the object to be measured was extended to a stand, and the width thereof was measured by a gull (JIS grade 1).

(2) the tilt (orientation angle) and the orientation angle variation of the orientation main axis

The measurement was carried out using a SONIC SHEET TESTER (SST-250) manufactured by Nomura Shoji. The center (105 mm) of the sample cut into A4 size was measured from both ends by overlapping 30 sheets so as to be the same position with respect to the width of the film to be a sample. In order to correct the angular error at the time of cutting the sample, the measurement was performed on the front and back sides, and the value obtained by averaging the absolute values of the measurement results on the front and back sides was taken as a measurement value. When the alignment main axis was parallel to the film width direction, 0, and the slope of the film in the clockwise direction was evaluated as + and the counterclockwise direction was evaluated as -.

The absolute value of the difference between the maximum value and the minimum value was taken as the measurement result in the taking-in width of the object to be subjected to the orientation angle variation.

(3) Film Thickness

Measurement was conducted using a micrometer (Mitsuto OMM-25) according to JIS C2151 (1990). Three points were uniformly measured with respect to the width direction of the film to be a sample, and the average value thereof was determined as a measurement result.

(4) In-plane retardation value in the film width direction retardation (nm)

The measurement was carried out using Cobra-WPR manufactured by Oji Chemical Industry Co., Ltd. In taking the target sampling width, the sample film was cut out and set on the apparatus. The phase difference measurement software Cobra-RE was activated, and the measurement was performed with light having a wavelength of 586.9 nm with the "measurement method" set to "standard ", and the input film thickness was calculated by inputting the value measured in the above- Re (nm) was used as a measurement value. The measurement was carried out on samples taken at both ends and at the center in the taking-over width of the object, and the range of variation of the measured values was confirmed.

In the in-plane retardation value retardation, the difference between the maximum value and the minimum value was taken as a measurement result in the taking-over width of the object.

(5) Local in-plane retardation value retardation (nm)

The measurement was carried out using Cobra-CCD manufactured by Oji Chemical Industry Co., Ltd. In the sample taking-over taking as a target, the sample taken from the entire width of the film roll was placed between two polarizing plates which were placed in the cross-nicol state and the para-nicol state, light was shot at right angles to the film from one side, And the presence or absence of color unevenness was confirmed. The film of the region where the color unevenness was confirmed was cut out and the in-plane retardation value retardation value of the color heterogeneity portion and the normal portion was measured using a Cobra-CD.

The local phase difference non-uniformity was defined as the difference between the maximum value and the minimum value of the in-plane retardation value between two adjacent points within 1 cm of the measurement site.

(6) Thickness unevenness in the longitudinal direction of the film

Manufactured by Anritsu Densen Co., Ltd. Using the continuous thickness meter, the difference between the maximum thickness and the minimum thickness was measured as the thickness unevenness (占 퐉) from the recorded film thickness chart. The measurement conditions are as follows.

Composition: K-306C Wide range of electronic micrometer, K-310C recorder, film transfer device

Detector: 3R ruby terminal, measuring force: 15g ± 5g

Film width: 45 mm, measuring length: 15 m, film feeding speed: 3 m / min

(7) Haze value of film

Was measured using a haze meter (HGM-2DP (manufactured by Suga Shikoku) (manufactured by Suga Shikoku)) in accordance with JIS K7105 (1981) with a size of 4 cm in the film length direction and 3.5 cm in the film width direction. Three points were uniformly measured with respect to the film width direction, and the average value thereof was determined as a measurement result.

(8) Heat shrinkage

Two lines are drawn on the surface of the film so as to have a width of 10 mm and a measurement length of about 100 mm. The distance between the two lines is measured at 23 캜 to obtain L 0. The film sample was left in an oven at 100 캜 for 30 minutes under a load of 1.5 g, and then the distance between the two lines was measured at 23 캜 to obtain L1, and the heat shrinkage rate was calculated by the following equation.

Heat shrinkage percentage (%) = {(L0-L1) / L0} 100

Three measurements were made for each of the film length method and the width direction, and an average value was obtained.

Example 1:

41.1 parts by mass of terephthalic acid and 46.4 parts by mass of bis- beta -hydroxyethyl terephthalate (hereinafter referred to as BHT), which is a reaction product of ethylene glycol, were previously stored in a molten state at 255 DEG C, and further 45.3 parts by mass of terephthalic acid and ethylene glycol 19.5 The slurry containing the mass portion was supplied with a constant amount while maintaining the temperature of the reactor, and water was allowed to flow out to carry out the esterification reaction. After 4 hours and 40 minutes from the initiation of the reaction, the esterification was completed. BHT as a reaction product was transferred to a polycondensation reaction tank, and 0.02 part by mass of trimethyl phosphate was added. Subsequently, 0.06 part by mass of magnesium acetate, 0.001 part by mass of lithium acetate and 0.02 part by mass of antimony trioxide were added, and the pressure was reduced to 25 Pa in 40 minutes, and the mixture was heated to 290 캜 and heated to obtain a polycondensation reaction. . After completion of the reaction, the resultant mixture was discharged from the separating member in the bottom of the polycondensation reaction tank into the strand in the cold water, and homopolyester pellets 1 were obtained which were pelletized into a cylindrical shape by an extruding cutter.

50 parts by mass of pellet (Tg 80 ° C) of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.85 (dl / g) obtained by solid state polymerization of the homopolyester pellet 1 and an intrinsic viscosity 50 parts by mass of "Ultem" 1010 (Tg 216 ° C) (PEI) of 0.68 (dl / g) was fed to a vented twin-screw kneading extruder of the same direction rotating type heated to 290 ° C, PET / PEI blend chip.

Further, magnesium acetate tetrahydrate as an ester exchange reaction catalyst was added to 100 parts by mass of dimethyl terephthalate and 70 parts by mass of ethylene glycol so as to be 40 ppm in terms of magnesium atom number, and the reaction was carried out while slowly raising the temperature from 150 캜 to 225 캜, Thereafter, 10 ppm of ethyl diethylphosphonoacetate in terms of phosphorus atom was added. After 5 minutes, the spherical silica particle EG slurry filtered through a filter having an average particle diameter of 0.06 占 퐉, an EG solution of the particles as a pre-filter beforehand with an absolute filtration accuracy of 3.0 占 퐉 and an absolute filtration accuracy of 1.0 占 퐉 as a main filter was added to the reaction composition Was added over a period of 15 minutes so as to be 1.0% by mass. After 5 minutes, 0.03 part by mass of antimony trioxide was added to the reaction vessel, and the reaction mixture was transferred to a polycondensation reaction vessel. The temperature was raised to 290 占 폚 and polycondensation reaction was finally carried out under a reduced pressure of 25 Pa to obtain polyester pellets 2 of IV 0.61.

Further, 98 parts by mass of the above homopolyester pellets 1 and 20 parts by mass of a 10 mass% water slurry in spherical cross-linked polystyrene particles having an average diameter of 0.3 占 퐉 were charged in a ventilated twin-screw kneading extruder of the same direction rotated at 280 占 폚 (2 parts by mass as spherical cross-linked polystyrene), and the vent holes were maintained at a reduced pressure of 1 kPa or less to remove water. Polyester pellets having an intrinsic viscosity of 0.61 containing 2 parts by mass of spherical crosslinked polystyrene particles having an average diameter of 0.3 m 3.

Subsequently, to the extruder A heated to 270 DEG C, 6 parts by mass of the PET / PEI blend chip produced by the pelletizing operation, 74 parts by mass of the homopolyester pellet 1, 20 parts by mass of the polyester pellets 2 Were fed after drying under reduced pressure at 160 캜 for 3 hours.

The above-mentioned spherical silica particles are obtained by adding an aqueous sodium silicate solution and water to prepare an aqueous sodium silicate solution, adding an aqueous sulfuric acid solution under refluxing, and then refluxing and aging the obtained silica sol, which is then concentrated using an ultrafiltration membrane, Glycol was added and solvent substitution was carried out at 100 占 폚 in a rotary evaporator to obtain silica sol.

The above spherical crosslinked polystyrene particles were prepared by synthesizing seed particles by soap-free emulsion polymerization, swelling them with a swelling aid, and polymerizing them by absorbing the polymerizable monomers. As a method for absorbing the polymerizable monomer, a method of collectively adding the water-soluble dispersion obtained by synthesizing the seed particles is adopted.

On the other hand, the extruder B was also heated to 270 DEG C, and 6 parts by mass of the PET / PEI blend chip produced by the pelletizing operation, 78 parts by mass of the homopolyester pellet 1, 20 parts by mass of the polyester pellets 3 And the mass part were dried after reduced-pressure drying at 160 DEG C for 3 hours.

In the extruders A and B, they are respectively filtered with a high-precision filter having a collecting efficiency of 95% or more of 5 μm or more and then joined and laminated in a rectangular two-layer confluence block. The polyester supplied from the extruder A described above is supplied from the extruder B And the thickness of the polyester was 6: 1. Thereafter, the film was cooled and solidified on a casting roll having a surface temperature of 25 DEG C by using an electrostatic casting method through a slit die maintained at 285 DEG C to obtain an unstretched film. This unstretched film was led to a simultaneous biaxial stretching tenter and stretched at the same time in the longitudinal direction and the width direction at a temperature of 95 占 폚, 3.50 times 占 3.65 times. The rate of temperature rise in this stretching step was 1 占 폚 / sec or less. Subsequently, the laminate was re-stretched at a temperature of 190 占 폚 at a stretch ratio of 1.20 times 1.35 times in both the longitudinal direction and the width direction without going through a cooling step. Thereafter, after heat treatment at a temperature of 215 캜 for 5.5 seconds, a relaxation treatment of 1.75% in the width direction was performed. Thereafter, the film was wound at a film conveying speed of 130 m / min to produce an intermediate product roll having a width of 5 m. From the middle product roll, the polyester film roll with a thickness of 5 占 퐉 was prepared for evaluation by slitting and winding up in the width of the evaluation roll described in Table 1. [ When evaluating the properties of the evaluation rolls (polyester film rolls of the present embodiment) produced, evaluation rolls having widths as shown in Table 1 were taken from intermediate rolls of 5 m in width so as to include their ends, and sample films were cut out and collected The characteristic values were measured and evaluated, and the obtained results are shown in Table 1.

Example 2, Comparative Example 1:

Except that the film forming conditions such as the stretching condition, the cooling condition, the heat treatment temperature, and the like were changed as described in Table 1. The properties of the obtained film are shown in Table 1.

Examples 3 to 4, Comparative Example 2:

99 parts by mass of the homopolyester pellets 1 described above and 20 parts by mass of the polyester pellets 2 described above were supplied to the extruder A after being dried under reduced pressure at 160 DEG C for 3 hours, Thus, the biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions such as the stretching condition, the cooling condition and the heat treatment temperature were changed. The properties of the obtained film are shown in Table 1.

Evaluation as a film for retardation plate in Examples and Comparative Examples:

One polarizing plate having a size matching the light emitting surface of a flat illuminator (HF-SL-100WLCG; manufactured by Dentsu Sangyo Co., Ltd.) was placed and laminated films of Examples and Comparative Examples of the same size to be observed, And a state in which linearly polarized light passed through the target film was made. In this state, another polarizing plate of the same size is additionally placed, and only the polarizing plate placed on the target film is rotated by 0 to 360 ° to observe the film. During the rotation, Respectively.

It was confirmed that the films of Examples 1 to 4 exhibited less unevenness and change in color tone at each position and could be suitably used as an optical phase difference film. On the other hand, the films of Comparative Examples 1 and 2 were found to be inappropriate for use as an optical phase-difference film, because the positions were uneven and the change in color tone was large.

&Lt; Industrial applicability >

The polyester film roll for an optical phase difference plate according to the present invention can be widely used as a material constituting a member for liquid crystal display and the like.

Claims (4)

An in-plane retardation value of 50 to 200 nm, and an in-plane retardation value (in-plane retardation value) in the film width direction is within a range of 6 DEG or less, a width is 1,200 mm or more and 2,000 mm or less, Wherein the retardation film has a retardation of 20 nm or less and a thickness of 2 to 10 mu m. An in-plane retardation value of 50 to 200 nm, and an in-plane retardation value of retardation (in the in-plane retardation value) with respect to the film width direction is within a range of 10 DEG or less, a width of 2,000 mm or more, Wherein the film has a variation of 20 nm or less and a thickness of 2 탆 or more and 10 탆 or less. The polyester film roll for an optical phase difference plate according to claim 1 or 2, wherein the local phase difference unevenness is less than 10 nm for the entire width of the film roll and the range of 1,200 mm or more in the longitudinal direction. The method for producing a polyester film roll for an optical phase difference plate according to any one of claims 1 to 3, wherein the film conveying speed in the step of winding the film roll is less than 50 m / min and less than 200 m / min.