JPWO2013027414A1 - Manufacturing method of long stretched film and manufacturing method of circularly polarizing plate - Google Patents

Abstract

One aspect of the present invention is a long film original fabric supplying step for supplying a long film original fabric made of a thermoplastic resin, oblique stretching in which the long film original fabric is obliquely stretched in a predetermined direction with respect to the width direction. And a step of winding the long stretched film after the oblique stretching step, and in the long film original fabric supplying step, the long film is taken from a direction different from the winding direction of the long stretched film. The raw film is supplied, and in the oblique stretching step, the long film original fabric is stretched in a predetermined oblique direction with respect to the winding direction, and in the long film original fabric supplying step, the oblique stretching step occurs. It is the manufacturing method of the elongate stretched film which supplies the elongate film original fabric which has a bowing of a reverse direction with respect to the bowing to do.

Description

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

  A stretched film formed by stretching a resin is used as an optical film that performs various optical functions in various image display (display) devices by utilizing its optical anisotropy. It is known that such a stretched film is used as an optical compensation film for optical compensation such as coloring prevention and viewing angle expansion in a liquid crystal display device, for example. Further, it is known that the stretched film is used as a retardation film that also serves as a polarizing plate protective film by being bonded to a polarizer.

  On the other hand, in recent years, a self-luminous display device such as an organic electroluminescence (organic EL) display device has attracted attention as a new display device. The self-luminous display device has a room for suppressing power consumption with respect to the liquid crystal display device in which the backlight is always turned on. Furthermore, a self-luminous display device such as an organic EL display device in which light sources corresponding to the respective colors are lit does not need to be provided with a color filter that can cause a reduction in contrast. For this reason, a self-luminous display device such as an organic EL display device can have higher contrast than a liquid crystal display device. However, the organic EL display device also has a factor that reduces the contrast of an image. Specifically, the organic EL display device is provided with a reflector such as an aluminum plate on the back side of the image display unit (display) of the organic EL display device in order to increase the light extraction efficiency. For this reason, there is a problem in that the external light incident on the display is reflected by the reflector to reduce the contrast of the image. For this reason, it is known to use a circularly polarizing plate in which the stretched film and a polarizer are bonded on the surface side of the display in order to improve contrast of light and darkness by preventing reflection of external light.

  Said circularly-polarizing plate is manufactured by bonding the stretched film in such an arrangement that the in-plane slow axis of the stretched film is inclined at a desired angle with respect to the transmission axis of the polarizer.

  Such a circularly polarizing plate is generally manufactured by a batch method in which the stretched film is bonded to a polarizer one by one. Specifically, first, a general polarizer (polarizing film) is obtained by stretching at high magnification in the transport direction, and its transmission axis coincides with the transport direction. Further, the conventional retardation film is a stretched film produced by longitudinal stretching or lateral stretching, and in principle, the in-plane slow axis is 0 ° or 90 ° with respect to the longitudinal direction of the film. Therefore, as described above, in order to incline the transmission axis of the polarizer and the slow axis of the stretched film at a desired angle, at least one of the long polarizing film and the long stretched film is used. Need to be cut at a specific angle. And it had to carry out by the batch type which bonds the cut-out film one sheet at a time to the other film, and the fall of the yield of the product by adhesion of the deterioration of productivity or chips etc. was mentioned as a problem.

  On the other hand, there are various methods for producing a long stretched film that is stretched obliquely at a desired angle and whose slow axis is freely controllable in a direction that is neither 0 ° nor 90 ° with respect to the longitudinal direction of the film. It has been proposed (for example, see Patent Documents 1 to 3). In these methods, the resin film is unwound from a direction different from the film winding direction after stretching, and the both ends of the resin film are gripped and transported by a pair of gripping tools while changing the transport direction. The resin film is stretched obliquely by making the moving distance between the gripping part and the other gripping part different. By doing so, the elongate stretched film which has a slow axis in the desired angle of more than 0 degree and less than 90 degrees with respect to the longitudinal direction is manufactured. By using a stretched film whose slow axis is inclined with respect to the long direction, a long polarizing film and a stretched film are bonded together by roll-to-roll instead of the conventional batch-type bonding. Thus, it becomes possible to manufacture a circularly polarizing plate. As a result, productivity can be dramatically improved and yield can be greatly improved.

  However, when the stretched film obtained by such a method is used as an optical film for a circularly polarizing plate used in a display device having a very high contrast, such as an organic EL display device, depending on the manufactured display device. A phenomenon was observed in which the color due to external light reflection was slightly different. Specifically, it is manufactured using a display device having a circularly polarizing plate manufactured using a region near the center of the stretched film in the width direction and a region near the end of the stretched film in the width direction. It was observed that the display device provided with a circularly polarizing plate had a slightly different color due to external light reflection. Such a problem causes a color mismatch at the center and the end of the screen in a large display device. Further, when used in a small display device, the color characteristics of each product do not match. For this reason, improvement is necessary.

  As a result of examining the causes of these problems, it has been found that the cause is a phenomenon called a bowing phenomenon that occurs in the film during the above-described oblique stretching.

  In the oblique stretching as described above, the mechanical shrinkage force relating to the film in the portion where the film is stretched in the oblique direction with respect to the feeding direction is schematically shown in FIG. As shown in FIG. 1, the film 2 conveyed from the feeding direction (conveying direction) of the film is stretched obliquely by the obliquely extending portion 1, thereby causing a mechanical contraction force 3.

  At this time, the shrinkage speed of the resin film cannot catch up with the mechanical shrinkage in the feeding direction of the film, and the resin film relaxes in the feeding direction (conveying direction). For this reason, the film has a convex bowing phenomenon on the feeding side (upstream in the conveying direction), that is, a slow axis in the film surface is curved, and the slow axis direction is wide and uneven. It was. That is, a phenomenon has occurred in which the direction of the slow axis (orientation angle) differs between the vicinity of the center and the end of the stretched film.

  Patent Documents 1 to 3 below disclose improvements in the uniformity of the film thickness in the width direction and the uniformity of the retardation value in the width direction. However, in the inventions described in Patent Documents 1 to 3 below, the bowing phenomenon has not been recognized, and it cannot be said that the uniformity of the slow axis (orientation angle) in the width direction is sufficient.

  On the other hand, with respect to the suppression of the bowing phenomenon in the stretched film, it has been devised to suppress the occurrence of bowing by controlling the temperature during film preheating and stretching in a uniaxial stretching machine in the width direction (for example, Patent Documents). 4).

  As in the invention described in Patent Document 4 below, suppressing the occurrence of bowing by controlling the temperature during film preheating and stretching is an effective technique when uniaxially stretching in the horizontal or vertical direction. . However, in the above-described stretching in the oblique direction as in the invention described in Patent Document 4 described above, it is caused by contraction in the mechanical feeding direction, and the bowing phenomenon is generated only by controlling the temperature of the film. It was not possible to suppress it sufficiently.

  As a result, when a circularly polarizing plate was produced using the obtained stretched film, the unevenness of the color of the display device could not be sufficiently suppressed, and an improvement was necessary.

JP 2008-80674 A JP 2009-78474 A JP 2010-173261 A JP 2005-254812 A

  In view of the circumstances described above, the object of the present invention is to suppress the occurrence of the bowing phenomenon when the film is stretched in an oblique direction, and a method for producing a long stretched film in which the direction of the slow axis is uniform in the width direction, And the manufacturing method of the circularly-polarizing plate using the elongate stretched film is provided.

  The above object of the present invention is achieved by the following configurations.

  One aspect of the present invention is a long film original fabric supplying step for supplying a long film original fabric made of a thermoplastic resin, a direction in which the long film original fabric is greater than 0 ° and less than 90 ° with respect to the width direction. The method for producing a long stretched film comprising a step of obliquely stretching the film and a step of winding the long stretched film after the oblique stretch step, wherein the oblique stretch is performed in the long film original fabric supplying step. The long film original fabric is supplied from a direction different from the conveying direction of the long stretched film after the process, and in the oblique stretching step, the both ends of the supplied long film original fabric are conveyed while being gripped by a gripping tool. Then, by changing the conveying direction while maintaining the gripping state, the moving distance between one gripping part and the other gripping part is made different, whereby the long film original fabric is larger than 0 ° with respect to the winding direction by 90 °. Diagonal less than ° In the long film original fabric supplying step, a long film original having a bowing in the opposite direction is supplied to the bowing generated in the oblique stretching step. It is a manufacturing method of a stretched film.

  Another aspect of the present invention is a method for producing a circularly polarizing plate, characterized in that a long stretched film obtained by the method for producing a long stretched film is bonded to a long polarizing film.

  Objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

FIG. 1 is a schematic diagram expressing the shrinkage force applied in the film transport direction during oblique stretching. FIG. 2 is a schematic view of an obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention. FIG. 3 is a schematic view showing an example of the manufacturing method according to the embodiment of the present invention (an example in which the film is drawn from a long film original roll and then obliquely stretched). FIG. 4 is a schematic diagram showing an example of a manufacturing method according to an embodiment of the present invention (an example of continuous oblique stretching without winding a long film original fabric). FIG. 5 is a cross-sectional view showing an example of an organic EL display device using a long stretched film obtained by the manufacturing method according to the embodiment of the present invention. FIG. 6 is a schematic diagram of the obliquely stretched tenter used in the examples. FIG. 7 is a schematic view showing a specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant. FIG. 8 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant. FIG. 9 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant. FIG. 10 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant. FIG. 11 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant. FIG. 12 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to these.

  As a result of studies conducted by the present inventors to achieve the above object, in a method for producing a long stretched film with a slow axis inclined using a diagonal stretching process, the long film original fabric is generated in a diagonal stretching step. The present inventors have found that the above-mentioned object can be achieved by giving a bowing in the opposite direction to a bowing to be performed. And further examination was advanced and it came to complete this invention based on these knowledge.

  That is, in an embodiment according to the present invention, a long film original fabric supplying step of supplying a long film original fabric made of a thermoplastic resin, the long film original fabric is greater than 0 ° and 90 ° larger than the width direction. An oblique stretching step that obliquely stretches in a direction less than the length, and a method for producing a long stretched film that includes a step of winding the long stretched film after the oblique stretching step, wherein in the long film original fabric supply step, The long film original fabric is supplied from a direction different from the conveying direction of the long stretched film immediately after the oblique stretching step. In the oblique stretching step, both ends of the supplied long film original fabric are gripped by a gripping tool. The length of the original film is changed from 0 ° with respect to the winding direction by changing the conveyance direction while keeping the holding state and changing the moving distance between one holding part and the other holding part. Large 90 ° It is a step of stretching in a fully diagonal direction, and in the long film original fabric supplying step, a long film original having a bowing in the opposite direction is supplied to the bowing generated in the oblique stretching step. It is a manufacturing method of the elongate stretched film characterized by these.

  In addition, the direction of the bowing in the above represents the direction in the longitudinal direction. That is, in the present embodiment, when the bowing generated in the oblique stretching process has a convex arcuate shape with respect to the upstream side in the transport direction (the supply side of the long film original fabric), the long film original The long film original fabric supplied in the anti-supplying process represents that it has a convex arch shape on the downstream side in the conveying direction (winding side of the long stretched film).

  According to such a structure, generation | occurrence | production of the bowing at the time of performing diagonal stretch can be suppressed effectively, and the manufacturing method of the elongate stretched film excellent in the breadth uniformity of the slow axis inclination angle can be provided. . Moreover, if the elongate stretched film obtained by such a manufacturing method is used, a circularly-polarizing plate can be obtained by bonding together a elongate polarizing film with a roll-to-roll. For this reason, productivity and yield can be significantly improved, and the display device using the obtained circularly polarizing plate exhibits excellent color uniformity.

  Hereinafter, the present invention will be specifically described with reference to the drawings as appropriate.

<Method for producing long stretched film>
The method for producing a long stretched film according to this embodiment is a method for producing a long stretched film that provides an in-plane slow axis at an arbitrary angle with respect to the extending direction of the film by obliquely stretching the long film original. It is a manufacturing method.

  Here, the long length means that the length of the film is at least about 5 times the width of the film, and is preferably 10 times or more. That is, the long film refers to a film having a length of at least about 5 times the width of the film. The long film is specifically wound in a roll shape and has a length that can be stored or transported as a film roll. In the manufacturing method of a long film, a film can be manufactured to desired arbitrary length by manufacturing a film continuously.

  Moreover, the manufacturing method of a elongate stretched film pays off a long film original fabric from a film roll, after winding a long film original fabric into a winding core once after forming into a wound body (film roll). Alternatively, it may be supplied to the oblique stretching step. Moreover, you may supply a long film original fabric from a film forming process to the diagonal stretch process continuously, without winding up the long film original fabric after film forming. It is preferable to perform the film forming step and the oblique stretching step continuously because the film thickness after the stretching and the result of the optical value are fed back to change the film forming conditions to obtain a desired long stretched film. .

  Specifically, the following methods are mentioned as a manufacturing method of a elongate stretched film.

  First, a long film original fabric is supplied by rolling out a film material made of a thermosetting resin and then winding it once to form a roll-shaped long film original fabric, and then feeding it out again. The film material is preferably manufactured under conditions that generate bowing in the same direction with respect to the bowing generated in the oblique stretching step before the roll-shaped long film original.

  By doing so, when producing the roll-shaped long film original fabric, the generated bowing is fed out in the direction opposite to the winding direction when the roll-shaped long film original fabric is fed out. In the long film original fabric supplying process, a long film having a bowing having a bowing in the opposite direction to the bowing generated in the oblique stretching process can be continuously supplied. That is, it is possible to more easily produce a long stretched film that effectively suppresses the occurrence of bowing during oblique stretching and is excellent in width uniformity of the slow axis tilt angle.

  Moreover, the following methods are mentioned as another method.

  It is preferable that the long film is supplied to the oblique stretching step without being wound up after undergoing a step of generating a bowing in the opposite direction to the bowing generated in the oblique stretching step.

  By doing so, in a long film original fabric supply process, the long film which has a bowing which has a bowing of a reverse direction with respect to the bowing which generate | occur | produces in a diagonal stretch process can be supplied continuously. That is, it is possible to more easily produce a long stretched film that effectively suppresses the occurrence of bowing during oblique stretching and is excellent in width uniformity of the slow axis tilt angle.

  In addition, the process of generating the reverse direction bowing will be described later.

  In the manufacturing method of the elongate stretched film which concerns on this embodiment, the elongate stretched film which has a slow axis in the angle of more than 0 degree and less than 90 degrees with respect to the width direction of a film is manufactured. Here, the angle with respect to the width direction of the film is an angle in the film plane. Since the slow axis is usually expressed in the stretching direction or a direction perpendicular to the stretching direction, in the production method according to the present embodiment, the slow axis is at an angle of more than 0 ° and less than 90 ° with respect to the extending direction (longitudinal direction) of the film. A stretched film having such a slow axis can be produced by stretching.

  The angle formed by the extension direction (longitudinal direction) of the long stretched film and the slow axis, that is, the orientation angle can be arbitrarily set to a desired angle within a range of more than 0 ° and less than 90 °. The angle is preferably 10 ° to 80 °, more preferably 40 ° to 50 °, and a specific example may be 45 °.

<Manufacturing method of long film original fabric>
The long film original fabric used for preparing the long stretched film can be obtained by a known method, for example, a solution cast molding method, an extrusion molding method, an inflation molding method, or the like. Among these, the solution cast molding method is preferable because it is excellent in the flatness and transparency of the film. Further, the extrusion molding method is preferable because it becomes easy to reduce the retardation Rt in the thickness direction after oblique stretching, the amount of residual volatile components is small, and the dimensional stability of the film is excellent. This long film 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 co-casting molding method, a film lamination method, or a coating method. Of these, the coextrusion molding method and the co-casting molding method are preferable.

  In the present embodiment, the thickness unevenness σm in the flow direction of the long film source supplied for stretching maintains the film take-up tension at the entrance of the oblique stretching tenter, which will be described later, and has optical characteristics such as orientation angle and retardation. From the viewpoint of stabilization, it is preferably less than 0.30 μm, preferably less than 0.25 μm, more preferably less than 0.20 μm. If the thickness unevenness σm in the flow direction of the long film is too large, variations in optical properties such as retardation and orientation angle of the long stretched film tend to be remarkably deteriorated.

  In order to make the thickness unevenness σm in the flow direction of the long film original in the above range, in the case of the extrusion molding method, it is achieved by a method of keeping the molten thermoplastic resin in a stable state when closely contacting the cooling drum. Is possible. For example, this can be achieved by the method described in Japanese Patent Application Laid-Open No. 2004-233604. Specifically, 1) A method in which a sheet-like thermoplastic resin extruded from a die is brought into close contact with a cooling drum under a pressure of 50 kPa or less when a long film original fabric is produced by a melt extrusion method; 2 ) When manufacturing a long film original fabric by the melt extrusion method, cover from the die opening to the cooling drum to which it first adheres with a surrounding member, and the distance from the enclosure member to the die opening or the cooling drum to which it first adheres 3) Method of producing a long film original by melt extrusion method, and heating the temperature of the atmosphere within 10 mm from the sheet-like thermoplastic resin extruded from the die opening to a specific temperature. 4) A method in which a sheet-like thermoplastic resin extruded from a die so as to satisfy the relationship is brought into close contact with a cooling drum under a pressure of 50 kPa or less; 5) by a melt extrusion method A method of blowing a wind having a speed difference of 0.2 m / s or less with respect to the cooling speed of the cooling drum that is first brought into contact with the sheet-like thermoplastic resin extruded from the die opening when producing the original film. ;

  Moreover, the film which has the thickness gradient of the width direction may be supplied as a long film original fabric. The thickness gradient of the long film so that the film thickness at the position where stretching has been completed is the most uniform can be determined empirically by stretching films with various thickness gradients experimentally. be able to. The gradient of the thickness of the long film original fabric can be adjusted so that, for example, the thickness of the end portion on the thick side is about 0.5 to 3% thicker than the end portion on the thin side.

  Although the width | variety of a elongate film original fabric is not specifically limited, 500-4000 mm, Preferably it can be 1000-2000 mm. Moreover, the total film thickness of a long film original fabric is although it does not specifically limit, It is preferable to exist in the range of 20-400 micrometers, Preferably it is 20-200 micrometers.

  A preferable elastic modulus at a stretching temperature at the time of oblique stretching of the long film original fabric is 0.01 MPa or more and 5000 MPa or less, more preferably 0.1 MPa or more and 500 MPa or less, expressed as Young's modulus. If the elastic modulus is too low, the shrinkage rate during and after stretching tends to be low, and wrinkles tend not to disappear. On the other hand, if the elastic modulus is too high, the tension applied at the time of stretching increases, and it is necessary to increase the strength of the portion that holds both side edges of the film, which tends to increase the load on the subsequent tenter.

  In oblique stretching, as shown in FIG. 1, a mechanical contraction force 3 acts on the film feeding direction. On the other hand, since the contraction speed of the film cannot keep up and relaxation occurs in the center in the width direction of the film, a convex bowing occurs on the upstream side in the transport direction.

  In order to eliminate the convex bowing formed on the upstream side in the transport direction, it is necessary to use a long film original having a convex bow formed on the downstream side in the transport direction.

  In addition, for example, as in the invention described in Patent Document 4, it is possible to suppress the occurrence of bowing by controlling the temperature during film preheating and stretching, and the temperature during film stretching and the temperature immediately after stretching. This is an effective technique when uniaxially stretching in the longitudinal direction. However, as to the stretching in the oblique direction, as described above, since the force for contracting in the film feeding direction is large, the film temperature control alone is not sufficient to suppress the occurrence of bowing.

  In this embodiment, the long film original fabric is manufactured so as to have a convex bowing 13-1 on the downstream side in the transport direction in advance as shown in FIG. Is desirable.

  The step of generating the reverse direction bowing is not particularly limited as long as the reverse direction of the bowing generated in the oblique stretching step can be generated. Specifically, for example, a method of giving a convex bowing to the downstream side of the transport direction in the long film original fabric, which will be described later, is mentioned.

  As a method of giving a convex bowing to the downstream side of the transport direction in the long film original fabric, the temperature of the long film original fabric in the transverse stretching tenter or the longitudinal stretching tenter is controlled at the time of film stretching and immediately after stretching. Examples of the method include lateral stretching or longitudinal stretching. Specifically, if stretching is performed at a relatively high temperature, convex bowing is likely to occur on the upstream side in the transport direction, and therefore it is possible to adjust the degree of bowing by adjusting the temperature conditions. Moreover, it is also possible to generate a convex bowing upstream in the conveying direction by providing a reheating region after the stretching step and heating the tenter while conveying it. In this way, a film having a convex bowing on the upstream side in the conveying direction is wound up once, and then fed out again and used as a long film original, so that the long film original having a convex bowing on the downstream side in the conveying direction is used. It is possible to supply the opposite to the oblique stretching process. In addition, in the method of longitudinal stretching using the speed difference of multiple nip rolls provided in the transport direction, splitting the nip rolls in the width direction and creating nip rolls with different rotation speeds in the width direction generates arbitrary bowing. Is possible.

  In addition, it is possible to generate arbitrary bowing by providing an area for conveying the tenter in a direction perpendicular to the ground while heating the film. For example, when tenter transport is performed under high temperature conditions with the downstream side in the transport direction facing downward, convex bowing tends to occur on the downstream side in the transport direction, and conversely, the downstream side in the transport direction faces upward. Thus, when the tenter is transported under a high temperature condition, convex bowing is likely to occur on the upstream side in the transport direction.

  In addition, the definition and analysis direction of the amount of bowing generated by oblique stretching in the present invention will be described in detail with reference to FIG.

  However, the method for measuring the bowing amount in the present invention is not particularly limited, and it is also possible to calculate the bowing amount by measuring the direction of the slow axis in at least a plurality of locations in the width direction of the film. Further, the amount of bowing can be simply calculated by marking at a plurality of positions in the width direction on the film surface before oblique stretching and detecting the position after oblique stretching.

  Note that the bowing amount of the long film is + (plus) for the convex bowing on the downstream side in the transport direction (winding side of the long stretched film), and-(minus) for the convex bowing on the upstream side in the transport direction. And

  Moreover, the bowing amount in a long film original fabric can be measured by the same method. In addition, the bowing amount in the long film original fabric is defined as how much the resin in the central portion of the film has shifted with respect to the straight line connecting the end portions at the same position in the transport direction. In this case, as described above, the case where the resin at the center of the film is shifted to the downstream side in the transport direction is represented as + (plus), and the case where the resin is shifted to the upstream side in the transport direction is represented as-(minus).

  After forming a long film original fabric, if it is continuously supplied to the oblique stretching process without winding up the film original fabric after film formation, after forming the long film original fabric, it is downstream in the transport direction. In order to impart convex bowing to the side, transverse stretching or longitudinal stretching may be performed by the above-described method, and then continuously supplied to the oblique stretching step.

  In addition, when a long film original fabric is formed and then wound on a core once to form a wound body and then supplied to the oblique stretching step, the long film original fabric is formed into a film, and then stretched horizontally or longitudinally. When a convex bowing is applied to the upstream side in the conveying direction by stretching and then wound around the core to form a wound body, when supplying from the wound body to the oblique stretching tenter, on the downstream side in the conveying direction The film can be unwound to have a convex bowing.

  In the present embodiment, it is also possible to use a long film original that does not have bowing in advance when supplied to the obliquely stretched tenter.

  When using the film material that does not have the bowing in advance, as shown in FIG. 2, a convex bowing 13-2 may be provided on the downstream side in the transport direction in any region before oblique stretching. is necessary.

  As a specific method for providing convex bowing on the downstream side in the transport direction, for example, the zone before the oblique stretching zone is divided by the following combination, and the upstream zone and the downstream side of the transverse stretching zone By providing a temperature difference in these zones and making the temperature of the downstream zone lower than the temperature of the upstream zone, convex bowing can be imparted to the downstream side in the transport direction.

  More specifically, for example, when the zone configuration as shown in (1) below is adopted, the temperature of the oblique stretching zone on the downstream side with respect to the transverse stretching zone A is set lower than the temperature of the preheating zone. You only have to set it.

  In addition, a plurality of transverse stretching zones may be provided in front of the oblique stretching zone. In that case, the temperature relationship between the upstream and downstream zones of any of the transverse stretching zones may satisfy the above-described relationship. For example, when the zone configuration is as shown in (2) below, the temperature of the transverse stretching zone B on the downstream side of the transverse stretching zone A is set to be lower than the temperature of the preheating zone on the upstream side. Alternatively, the temperature of the oblique stretching zone on the downstream side of the transverse stretching zone B may be set to be lower than the temperature of the transverse stretching zone A, or both are satisfied. Also good. What is necessary is just to set suitably according to the magnitude | size of the concave bowing generate | occur | produced at the time of diagonal extending | stretching.

However, when a plurality of transverse stretching zones are provided, the above relationship is reversed, i.e., including a relationship in which the temperature of the upstream zone of the transverse stretching zone is lower than that of the downstream zone. In order to cancel the bowing, when a plurality of transverse stretching zones are provided, the downstream temperature is low on the upstream side and the downstream side of all transverse stretching zones, or the upstream and downstream temperatures are low. Preferably they are equal. Other configurations such as (3) to (6) are conceivable as the zone configuration before the oblique stretching zone, but the size of the bowing can be adjusted by appropriately adjusting the temperature relationship in the same manner as described above. Can be adjusted. Needless to say, the zone configuration is not limited to the following configuration.
(1) Preheating zone / transverse stretching zone A / oblique stretching zone (2) Preheating zone / transverse stretching zone A / transverse stretching zone B / oblique stretching zone (3) Preheating zone / transverse stretching zone A / holding zone / oblique stretching zone (4) Preheating zone / transverse stretching zone A / transverse stretching zone B / transverse stretching zone C / oblique stretching zone (5) Preheating zone / transverse stretching zone A / holding zone / transverse stretching zone B / oblique stretching zone (6) Preheating Zone / lateral stretching zone A / lateral stretching zone B / holding zone / oblique stretching zone

  In the above steps, the transverse stretching ratios in the transverse stretching zone A, transverse stretching zone B, and transverse stretching zone C may be the same or different.

<Stretching with an oblique stretching tenter>
An obliquely stretched tenter is used in order to impart an oblique orientation to an elongated long film original fabric subjected to stretching in the production method according to the present embodiment. The obliquely stretched tenter used in this embodiment can freely set the orientation angle of the film by changing the rail pattern in various ways, and the film orientation axis can be set to the left and right with high precision across the film width direction. A film stretching apparatus that can be oriented and can control the film thickness and retardation with high accuracy is preferable.

  FIG. 2 is a schematic diagram of a tenter that can be stretched obliquely and used in the method for producing a long stretched film according to an embodiment of the present invention. However, this is an example, and the present invention is not limited to this.

  The long film original fabric 4 whose direction is controlled by the guide roll 12-1 on the tenter entrance side is first gripped at the positions of the outer film holding start point 8-1 and the inner film holding start point 8-2 ( (Also referred to as a clip gripping portion). Then, the supported long film original 4 is conveyed and stretched in the oblique direction indicated by the locus 7-1 of the outer film holding means and the locus 7-2 of the inner film holding means by the oblique stretching tenter 6. The gripping is released by the outer film holding end point 9-1 and the inner film holding end point 9-2, and the conveyance is controlled by the guide roll 12-2 on the tenter outlet side, whereby the obliquely stretched film 5 is formed. In the drawing, the original film is stretched obliquely at an angle (orientation angle θ) in the film stretching direction 14 with respect to the film feeding direction 15-2.

  The manufacturing method of the elongate stretched film which concerns on embodiment of this invention is performed using the tenter which can be extended diagonally. This tenter is an apparatus that widens a long film original fabric in an oblique direction with respect to its traveling direction (moving direction of the middle point in the film width direction) in an environment heated by an oven. The tenter includes an oven, a pair of rails on the left and right on which a gripping tool for transporting the film travels, and a number of gripping tools that travel on the rails. Both ends of the film fed out from the film roll and sequentially supplied to the entrance portion of the tenter are gripped by a gripping tool, the film is guided into the oven, and the film is released from the gripping tool at the exit portion of the tenter. The film released from the gripping tool is wound around the core. Each of the pair of rails has an endless continuous track, and the gripping tool which has released the grip of the film at the exit portion of the tenter travels outside and is sequentially returned to the entrance portion.

  The rail shape of the tenter is asymmetrical on the left and right depending on the orientation angle θ, the draw ratio, etc. given to the long stretched film to be manufactured, and can be finely adjusted manually or automatically. Yes. In the present embodiment, a long thermoplastic resin film is stretched so that the orientation angle θ can be set to an arbitrary angle within the range of 10 ° to 80 °, preferably in the winding direction after stretching. It has become. In the embodiment of the present invention, the tenter gripping tool travels at a constant speed with a constant distance from the front and rear gripping tools.

  Although the traveling speed of a holding | gripping tool can be selected suitably, it is 1-100 m / min normally. The difference in travel speed between the pair of left and right grippers is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because wrinkles and shifts at the exit of the stretching process tend to occur when there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process. That is, it is preferable that the left and right gripping tools have substantially the same speed. In general tenter devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

  In the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention, it is preferable that the positions of the rail portions and the rail connecting portions can be set freely. Therefore, the oblique stretch tenter can be set to a draw ratio according to an arbitrary entrance width and exit width (the circled portion in FIG. 2 below is an example of a connecting portion).

  In the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention, a large bending rate is often required for the rail that regulates the locus of the gripping tool. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a curve at the bent portion.

  Further, in the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention, undesired deformation (for bending) occurs in the rail of the bent portion due to the stretching stress applied when the gripping tool that holds the film passes through the bent portion. In order to prevent occurrence of unrelated deformation, it is desirable to have a mechanism for keeping the curved shape at the bent portion constant.

  In the following description, some specific examples of the mechanism for maintaining the curved shape in the bent portion will be described. However, the present invention is not limited to this, and a mechanism having the same function may be provided.

  The curve shape is not particularly limited, and may be left-right symmetric or left-right asymmetric when viewed from the center of the curve shape, and may be an arc shape or an elliptical shape. These curved shapes can be arbitrarily selected depending on the production conditions of the long film.

  FIG. 7 is a schematic view showing a specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31, which is a mechanism for holding the curved shape constant, includes a bent portion rail 32, a rail width extending lead 33, a rail base connecting portion 34, a bent portion rail base 35, a bent portion holding member 36, an arm frame 37, a bent portion. A part holding arm 38 and a bent part holding arm fulcrum 39 are provided.

  The bent portion rail 32 is disposed on the bent portion rail base 35. The bent portion rail base 35 can be opened and closed at an arbitrary angle with the rail base connecting portion 34 as a rotation center, and can be slid along the rail width extending lead 33.

  In addition, the bent portion rail base 35 holds the curved shape of the bent portion by a bent portion holding arm 38 supported by the arm frame 37. The bent portion holding arm 38 can be opened and closed at an arbitrary angle with the bent portion holding arm fulcrum 39 as a rotation center, and can be slid along the arm frame 37. The bent portion holding arm 38 can slide on the bisector of the intersection angle between the rail 41 before bending and the rail 42 after bending. The rail 41 before bending and the rail 42 after bending are placed on the rail base 43 before bending and the rail base 44 after bending.

  The bent portion holding member 36 located at the center of the bent portion rail 32 is always supported by the bent portion holding arm 38 that can slide on the bisector of the intersection angle between the rail 41 before bending and the rail 42 after bending. Is retained. Thereby, the shape of the bent portion rail 32 can be maintained in an arbitrary curved shape.

  In addition, the arm frame 37 and the rail width extending lead 33 are not fixed, and the arm frame 37 can rotate independently of the rail width extending lead 33, so that the bent frame rail 32 has a curved shape. The distortion of the bent part rail 32 can be eliminated.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed.

  FIG. 8 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31 includes a bent portion rail 32, a rail width extending lead 33, a rail base connecting portion 34, a bent portion rail base 35, and a bent portion holding member 36.

  The bent portion rail 32 is disposed on the bent portion rail base 35. The bent portion rail base 35 can be opened and closed at an arbitrary angle with the rail base connecting portion 34 as a rotation center, and can be slid along the rail width extending lead 33.

  Further, after adjusting the shape of the bent portion rail 32 to be an arbitrary curved shape, that is, an optimum shape for the required stretching conditions, the shape of the bent portion rail 32 is fixed using the bent portion holding member 36. can do. In addition, in FIG. 8, although the figure fixed to one place in the extending direction of the bending part rail 32 was illustrated, you may fix in several places in the extending direction of the bending part rail 32. FIG.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed. Moreover, since the shape of the bending part rail 32 is fixed using the bending part holding member 36, after adjusting the shape of the bending part rail 32 so that it may become arbitrary curved shapes, the bending part rail 32 is made into various curve shapes. Can be.

  FIG. 9 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31 includes a bent portion rail 32, a rail width extending lead 33, a rail base connecting portion 34, a bent portion rail base 35, and a bent portion slide holding member 45.

  The bent portion rail 32 is disposed on the bent portion rail base 35. The bent portion rail base 35 can be opened and closed at an arbitrary angle with the rail base connecting portion 34 as a rotation center, and can be slid along the rail width extending lead 33.

  Further, the bent portion slide holding member 45 can fix the bent portion rail 32 so as to be movable in the extending direction, that is, slidable. By doing so, the shape of the bent rail 32 can be adjusted to an arbitrary curved shape, that is, an optimal shape for the required stretching conditions. Further, since the bent portion slide holding member 45 does not completely fix the position of the bent portion rail 32 but holds the bent portion rail 32 so as to be slidable, the bent portion rail 32 has a curved shape depending on the curved shape of the bent portion rail 32. Distortion can be eliminated.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed.

  FIG. 10 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31 includes a bent portion rail 32, a rail width extending lead 33, a rail base connecting portion 34, a bent portion rail base 35, an arm frame 37, a bent portion holding arm 38, a bent portion holding arm fulcrum 39, a bent portion. Part slide holding member 45 is provided.

  The bent portion rail 32 is disposed on the bent portion rail base 35. The bent portion rail base 35 can be opened and closed at an arbitrary angle with the rail base connecting portion 34 as a rotation center, and can be slid along the rail width extending lead 33.

  Further, the bent portion slide holding member 45 can fix the bent portion rail 32 so as to be movable in the extending direction, that is, slidable. By doing so, the shape of the bent rail 32 can be adjusted to an arbitrary curved shape, that is, an optimal shape for the required stretching conditions. Further, since the bent portion slide holding member 45 does not completely fix the position of the bent portion rail 32 but holds the bent portion rail 32 so as to be slidable, the bent portion rail 32 has a curved shape depending on the curved shape of the bent portion rail 32. Distortion can be eliminated.

  In addition, the bent portion rail base 35 holds the curved shape of the bent portion by a bent portion holding arm 38 supported by the arm frame 37. The bent portion holding arm 38 can be opened and closed at an arbitrary angle with the bent portion holding arm fulcrum 39 as a rotation center, and can be slid along the arm frame 37. The bent portion holding arm 38 is not limited to the bisector of the intersection angle between the pre-bending rail 41 and the post-bending rail 42 because the bent portion slide holding member 45 holds the bent portion rail 32 in a slidable manner. Can move relatively freely.

  In addition, the arm frame 37 and the rail width extending lead 33 are not fixed, and the arm frame 37 can rotate independently of the rail width extending lead 33, so that the bent frame rail 32 has a curved shape. The distortion of the bent part rail 32 can be eliminated.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed. In addition, this mechanism is particularly preferable because the distortion of the bent portion rail 32 according to the curved shape of the bent portion rail 32 can be further eliminated by the holding by the bent portion slide holding member 45 and the rotation of the arm frame 37. .

  FIG. 11 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31 includes a bent portion rail 32, a rail width extending lead 33, a rail base connecting portion 34, a bent portion rail base 35, a bent portion holding member 36, an arm frame 37, a bent portion holding arm 38, a bent portion. A holding arm fulcrum 39 and an arm frame lead 46 are provided.

  The bent portion rail 32 is disposed on the bent portion rail base 35. The bent portion rail base 35 can be opened and closed at an arbitrary angle with the rail base connecting portion 34 as a rotation center, and can be slid along the rail width extending lead 33.

  Further, the bent portion rail base 35 is held by the bent portion holding member 36 located at the tip of the bent portion holding arm 38 supported by the arm frame 37 and the curved shape of the bent portion is held. The bent portion holding arm 38 can be opened and closed at an arbitrary angle with the bent portion holding arm fulcrum 39 as a rotation center, and can be slid along the arm frame 37. The arm frame 37 can slide along the arm frame lead 46. Further, the bent portion holding arm 38 can move in a direction perpendicular to or substantially perpendicular to the moving direction of the rail width extending lead 33 and the arm frame lead 46. The bent portion rail 32 can change the shape of the bent portion rail 32 into a desired curved shape depending on the opening / closing state of the bent portion holding arm 38, the position of the bent portion holding arm fulcrum 39, the position of the arm frame 37, and the like. .

  Further, the arm frame 37 and the rail width extending lead 33 are not fixed, the arm frame 37 can rotate independently of the rail width extending lead 33, and the arm frame 37 and the rail base connecting portion 34. Can be moved separately, so that the distortion of the bent portion rail 32 can be eliminated according to the curved shape of the bent portion rail 32.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed.

  FIG. 12 is a schematic view showing another specific example of a mechanism that keeps the curved shape of the bent portion of the obliquely stretched tenter used in the manufacturing method according to the embodiment of the present invention constant.

  The holding mechanism 31 here includes a bent portion rail 32, a rail width extending lead 33, a bent portion holding member 36, and a bent holding member slide plate 47.

  The bent portion rail 32 is disposed on the bent holding member slide plate 47. The bending holding member slide plate 47 connects the rail base 43 before bending and the rail base 44 after bending to both ends thereof. The crossing angle between the rail base 43 before bending and the rail base 44 after bending can be changed. The rail 41 before bending and the rail 42 after bending are placed on the rail base 43 before bending and the rail base 44 after bending. The bent portion holding member 36 is movably held on the bent holding member slide plate 47.

  The bent portion rail 32 changes the shape of the bent portion rail 32 by moving the bent portion holding member 36 on the bent holding member slide plate 47 or changing the crossing angle between the rail base 43 before bending and the rail base 44 after bending. , Can be transformed into a desired curved shape.

  By this mechanism, even when a strong stretching stress is applied to the bent portion rail 32, the curved shape can be kept constant without the bent portion rail 32 being deformed.

  The traveling direction 15-1 at the tenter entrance of the long film original is different from the traveling direction 15-2 at the tenter exit side of the stretched film, whereby a stretched film having a relatively large orientation angle θ. It is possible to obtain a wide and uniform optical characteristic. The feeding angle θi is an angle formed by the traveling direction 15-1 at the tenter entrance and the traveling direction 15-2 on the tenter exit side of the stretched film. In the present embodiment, as described above, in order to produce a film having an orientation angle θ of preferably 10 ° to 80 °, the feeding angle θi is 10 ° <θi <60 °, preferably 15 ° <θi <50. Set in °. By setting the feeding angle θi in the above range, the variation in the optical characteristics in the width direction of the obtained film becomes good (smaller).

  At the tenter entrance (position a), both ends (both sides) are sequentially held by the left and right gripping tools at the tenter entrance (position a), and run as the gripping tool travels. At the tenter entrance (position a), the left and right gripping tools facing the direction substantially perpendicular to the film traveling direction (15-1) run on the left-right asymmetric rail, preheating zone, and lateral stretching. It passes through an oven having a zone, an oblique stretching zone, a holding zone, and a cooling zone. Here, “substantially perpendicular” indicates that the angle formed by the straight line connecting the gripping tools facing each other and the film feeding direction (film traveling direction) 15-1 is within 90 ± 1 °.

  The preheating zone refers to a section in which the vehicle travels while maintaining a constant interval between the gripping tools gripping both ends at the oven entrance.

  The transverse stretching zone refers to a section where the interval between the gripping tools gripping both ends starts to reach a predetermined interval. At this time, the opening angle of the rail on which the gripping tools at both ends run may be opened at the same angle for both rails, or may be opened at different angles.

  The diagonally extending zone means that the gripping tool that grips both ends starts running on a bending rail while keeping the gripping tool spacing constant or spreads, and then both gripping tools start running on a straight rail again. Refers to the interval.

  The holding zone refers to a section in which the gripping tools at both ends travel while being parallel to each other in a period in which the interval between the gripping tools after the transverse stretching zone or the oblique stretching zone becomes constant again.

  The cooling zone refers to a section where the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg ° C. of the thermoplastic resin constituting the film in the section after the holding zone.

  At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the gap between the opposing grippers in advance may be used.

  The temperature of each zone is set to Tg to Tg + 30 ° C., the temperature of the stretching zone is set to Tg to Tg + 30 ° C., and the temperature of the cooling zone is set to Tg−30 to Tg ° C. with respect to the glass transition temperature Tg of the thermoplastic resin. It is preferable to do.

  In order to control the thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretching zone. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used. The length of the preheating zone, the stretching zone and the cooling zone can be appropriately selected. The length of the preheating zone is usually 100 to 150% and the length of the fixed zone is usually 50 to 100% with respect to the length of the stretching zone. .

  Moreover, in this embodiment, you may implement reducing convex bowing itself in the conveyance direction upstream generate | occur | produced in the case of the diagonal stretch mentioned above.

  Specifically, the convex bowing itself is formed on the upstream side in the conveying direction by assigning a temperature division so that the temperature of the preheating zone is higher than the temperature of the oblique stretching zone or the transverse stretching zone before the oblique stretching zone. Can be reduced.

  The difference between the temperature of the preheating zone and the temperature of the oblique stretching zone or the temperature of the transverse stretching zone before the oblique stretching zone is preferably 1 to 30 ° C, and more preferably 1 to 10 ° C.

  Further, it is also effective as a means for reducing the bowing to some extent to perform lateral stretching after oblique stretching in the oblique stretching zone.

  Furthermore, in order to solve the occurrence of wrinkles and shifts in the long stretched film, the film is supported while being stretched, stretched in a state where the volatile content is 5% by volume or more, and then volatilized while shrinking. It is also preferable to reduce the fraction. To maintain the support of the film means to grip both side edges without impairing the film property of the film. As for the volatile content, the state of 5% by volume or more may always be maintained in the stretching operation process, and the state of the volatile content is maintained at 5% by volume or more only in a part of the stretching operation process. May be. In the latter case, it is preferable that the entrance position is a starting point, and that the section of 50% or more of the entire stretching section and the volatile content rate are 12% by volume or more. In any case, it is preferable to have a volatile content of 12% by volume or more before stretching. Here, the volatile fraction (unit: volume%) represents the volume of the volatile component contained per unit volume of the film, and is a value obtained by dividing the volatile component volume by the film volume.

  The draw ratio R (W / W0) in the drawing step is preferably 1.3 to 3.0, more preferably 1.5 to 2.5. If the draw ratio is in this range, thickness unevenness in the width direction is reduced, which is preferable. In the stretching zone of the oblique stretching tenter, if the stretching temperature is differentiated in the width direction, the thickness unevenness in the width direction can be further improved. W0 represents the width of the film before stretching, and W represents the width of the film after stretching.

  The guide roll closest to the entrance of the tenter is a follower roll that guides the travel of the film, and is rotatably supported by bearings (not shown). As the material of the roll, a known material can be used, but it is preferable to reduce the weight by applying a ceramic coat to prevent the film from being scratched or applying a chrome plating to a light metal such as aluminum. is there. This roll is provided in order to stabilize the track when the film travels.

  Moreover, it is preferable that one of the rolls on the upstream side of the roll is nipped by pressing the rubber roll. This is because such a nip roll can suppress fluctuations in the drawing tension in the film flow direction.

  A pair of bearing portions at both ends (left and right) of the guide roll closest to the entrance of the tenter are provided with a first tension detecting device and a second film tension detecting device for detecting the tension generated in the film in the roll. It has been. For example, a load cell can be used as the film tension detection device. As the load cell, a known tensile or compression type can be used. A load cell is a device that detects a load acting on an applied point by converting it into an electrical signal using a strain gauge attached to the strain generating body.

  The load cell is installed on the left and right bearings of the guide roll closest to the entrance of the diagonally stretched tenter, so that the force that the running film exerts on the roll, that is, the tension in the film traveling direction that is generated near both side edges of the film Are detected independently on the left and right. In addition, a strain gauge may be directly attached to a support that constitutes the bearing portion of the roll, and a load, that is, a film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension is measured in advance and is known.

  The film tension detection device as described above is provided so that the tension in the vicinity of both side edges of the film in the guide roll closest to the entrance of the oblique stretching tenter is detected because the position and direction of the film is the same as that of the film stretching device. If there is a deviation with respect to the position and direction of the entrance, depending on the amount of deviation, there will be a difference in the tension in the vicinity of both side edges of the film in the guide roll closest to the entrance of the obliquely stretched tenter. This is because the degree of deviation is determined by detecting this tension difference. If the position and direction of the film are appropriate in relation to the position and direction of the inlet portion of the film stretching apparatus, the load acting on the roll will be roughly equal on the left and right, and if the positions are misaligned, the left and right films There is a difference in tension.

  Therefore, if the film position and angle are adjusted appropriately so that the difference in film tension between the left and right sides of the guide roll closest to the entrance of the oblique stretching tenter is equal, gripping by the gripping tool at the entrance of the film stretching apparatus is stable. In addition, the occurrence of obstacles such as detachment of the gripping tool can be reduced. Furthermore, the physical properties in the width direction of the film after oblique stretching by the film stretching apparatus can be stabilized.

  In order to cope with fine adjustment of the orientation angle and product variations, it is necessary to adjust the angle formed by the film traveling direction at the entrance of the oblique stretching tenter and the film traveling direction at the exit of the oblique stretching tenter. In that case, it is preferable from a viewpoint of productivity or a yield to perform film forming and diagonal stretch continuously. When the film forming process, the oblique stretching process, and the winding process are successively performed, it is preferable that the film traveling direction in the film forming process and the winding process coincide with each other in that the width of the process can be reduced. For such a process, in order to change the film transport direction to guide the formed film to the oblique stretching tenter inlet and / or to return the film exiting the oblique stretching tenter outlet to the winding device direction. A method for changing the film transport direction is required. As a device for changing the film transport direction, a known method such as an air flow roll can be used. It is preferable that the apparatus (winder apparatus, accumulator apparatus, drive apparatus, etc.) after the obliquely extending tenter exit is slidable in the lateral direction.

  About the example of the manufacturing method which concerns on the said various this embodiment, it showed as a schematic diagram as (d) and (e) in FIG. 3, (a)-(c), and FIG. FIG. 3 shows a pattern in which a long film original fabric once wound up in a roll shape is drawn out and obliquely stretched. FIG. 4 shows a pattern in which an oblique stretching process is continuously performed without winding a long film original.

  In the drawing, a film feeding device 16, a transport direction changing device 17, a winding device 18, and a film forming device 19 are shown. In each figure, symbols indicating the same thing may be omitted.

  The film feeding device 16 is slidable and pivotable so that the film can be fed at a predetermined angle with respect to the obliquely stretched tenter entrance, or the film feeding device 16 is slidable, and the transport direction changing device It is preferable that the film can be sent out to the entrance of the obliquely stretched tenter by 17. By configuring the film feeding device 16 and the transport direction changing device 17 in such a configuration, the width of the entire manufacturing apparatus can be further reduced, and the film feeding position and angle can be finely controlled. This makes it possible to obtain a long stretched film with small variations in film thickness and optical value. In addition, by making the film feeding device 16 and the transport direction changing device 17 movable, it is possible to effectively prevent the left and right clips from being caught in the film.

  By forming the winding device 18 so that the film can be pulled at a predetermined angle with respect to the outlet of the obliquely stretched tenter, it is possible to finely control the film take-up position and angle, and there are variations in film thickness and optical value. A small elongated stretched film can be obtained. Therefore, the generation of wrinkles in the film can be effectively prevented, and the winding property of the film is improved, so that the film can be wound up in a long length. In the present embodiment, the take-up tension T (N / m) of the stretched film is preferably adjusted between 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. .

  When the take-up tension is 100 N / m or less, sagging and wrinkles of the film are likely to occur, and the retardation and the profile in the width direction of the orientation axis are also deteriorated. On the other hand, when the take-up tension is 300 N / m or more, the variation in the orientation angle in the width direction is deteriorated, and the width yield (taking efficiency in the width direction) is deteriorated.

  In the present embodiment, it is preferable to control the fluctuation of the take-up tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the fluctuation of the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction becomes large. As a method for controlling the fluctuation of the take-up tension T within the above range, general PID control is performed so that the load applied to the first roll at the tenter outlet, that is, the film tension is measured and the value is kept constant. A method of controlling the rotation speed of the take-up roll by a method is mentioned. Examples of the method for measuring the load include a method in which a load cell is attached to a bearing portion of a roll and a load applied to the roll, that is, a film tension is measured. As the load cell, a known tensile type or compression type can be used.

  The stretched film is released from the tenter outlet after being gripped by the gripping tool, trimmed at both ends (both sides) of the film, and then wound around a winding core (winding roll) in order to be a long stretched film The wound body can be made.

  Moreover, you may trim the both ends of the film currently hold | gripped with the holding tool of a tenter before winding up to a winding roll as needed. Further, before winding, for the purpose of preventing blocking between the films, the masking film may be overlapped and wound up at the same time, or at least one of the long stretched films, preferably while winding tape or the like on both ends. You may take it. The masking film is not particularly limited as long as it can protect the film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

  In the long stretched film obtained by the production method according to the embodiment of the present invention, the orientation angle θ is inclined in the range of, for example, 10 ° to 80 ° with respect to the winding direction, and the width is at least 1300 mm. It is preferable that the variation in the in-plane retardation Ro in the width direction is 4 nm or less and the variation in the orientation angle θ is 1.0 ° or less.

  The variation of the in-plane retardation Ro of the long stretched film obtained by the production method according to the embodiment of the present invention is 4 nm or less, preferably 3 nm or less, at least 1300 mm in the width direction. By setting the variation of the in-plane retardation Ro within the above range, the display quality can be improved when used as a retardation film for a liquid crystal display device.

  The variation of the orientation angle θ of the long stretched film obtained by the production method according to the embodiment of the present invention is 1.0 ° or less, preferably 0.80 ° or less, at least 1300 mm in the width direction. . A long stretched film with a variation in the orientation angle θ exceeding 1.0 ° is bonded to a polarizer to obtain a circularly polarizing plate, and when this is installed in a liquid crystal display device, light leakage may occur and the contrast may be lowered. .

  The optimum value of the in-plane retardation Ro of the long stretched film obtained by the manufacturing method according to the embodiment of the present invention is selected depending on the design of the display device used. Note that Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the direction perpendicular to the slow axis by the average thickness d of the film (Ro = (nx −ny) × d).

  In addition, the long stretched film obtained by the production method according to the embodiment of the present invention preferably has a bowing amount of −1.0% to 1.0% after oblique stretching. That is, the smaller the amount of bowing of the obtained long stretched film, the better. By doing so, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

  The average thickness of the long stretched film obtained by the production method according to the embodiment of the present invention is preferably 20 to 80 μm, more preferably 30 to 60 μm, and particularly preferably 30 to 40 μm from the viewpoint of mechanical strength and the like. is there.

  Moreover, since the thickness unevenness in the width direction affects the availability of winding, it is preferably 3 μm or less, and more preferably 2 μm or less.

<Film raw material>
As a raw material for the film, a thermoplastic resin is mainly used. Here, the “thermoplastic resin” refers to a resin that becomes soft when heated to the glass transition temperature or melting point and can be molded into a desired shape.

  Polycarbonate, polyester, polyethersulfone, polyarylate, polyimide, polyolefin or the like as a general resin for optical films can be used. Also, cellulose terephthalate such as polyethylene terephthalate, polyimide, polymethyl methacrylate, polysulfone, polyethylene, polyvinyl chloride, alicyclic olefin polymer, acrylic polymer, cellulose diacetate, cellulose triacetate, cellulose acetate propionate, etc. may be used. Good. In particular, cellulose esters such as cellulose diacetate, cellulose triacetate, and cellulose acetate propionate, acrylic polymers having a lactone ring structure, and the like are more preferable. These raw materials may be used alone or in combination with different thermoplastic resins. When mixed and used, a mixture of cellulose ester and acrylic polymer is more preferable. The transparent resin contains colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, antioxidants, lubricants, solvents, etc. It may be what was done.

  The film may be a single layer film or a multilayer film.

  As the film, a long original film is mainly used, but it may be a film that has already been subjected to any one of longitudinal stretching, lateral stretching, and oblique stretching alone or a plurality of times.

<Cellulose ester>
Although the elongate stretched film obtained by the manufacturing method which concerns on embodiment of this invention can be produced using various resin base materials, it is preferable that it is the aspect containing a cellulose ester. Therefore, hereinafter, a long stretched film obtained by the production method according to the embodiment of the present invention or a film before stretching (long film original fabric) used in the present embodiment may be referred to as a cellulose ester film.

  The cellulose ester that can be used in the present embodiment is selected from cellulose (di, tri) acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. It is preferable that there is at least one.

  Among these, particularly preferable cellulose esters include cellulose triacetate, cellulose diacetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

As a substitution degree of the mixed fatty acid ester, when having an acyl group having 2 to 4 carbon atoms as a substituent, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, A cellulose ester that simultaneously satisfies the following formulas (I) and (II) is preferred.
Formula (I) 2.0 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5

  Furthermore, the cellulose ester used in the present embodiment is preferably one having a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, More preferably, it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The cellulose ester raw material cellulose used in this embodiment may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

  In this embodiment, 1 g of cellulose ester is added to 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and the pH when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr is 6 It is preferable that the electric conductivity is 1 to 100 μS / cm.

  In addition, as long as the effect of this invention is not impaired, thermoplastic resins other than the said cellulose acetate can also be used together for the elongate stretched film obtained by the manufacturing method which concerns on embodiment of this invention.

  General thermoplastic resins include polyethylene (PE), high density polyethylene, medium density polyethylene, low density polyethylene, polypropylene (PP), polyvinyl chloride (PVC), polyvinylidene chloride, polystyrene (PS). Polyvinyl acetate (PVAc), Teflon (registered trademark) (polytetrafluoroethylene, PTFE), ABS resin (acrylonitrile butadiene styrene resin), AS resin, acrylic resin (PMMA), and the like can be used.

  When strength and resistance to breakage are particularly required, polyamide (PA), nylon, polyacetal (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE, modified PPE, PPO), polybutylene terephthalate (PBT) ), Polyethylene terephthalate (PET), glass fiber reinforced polyethylene terephthalate (GF-PET), cyclic polyolefin (COP), and the like.

  Furthermore, when high heat distortion temperature and long-term use characteristics are required, polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone, polyethersulfone, amorphous polyarylate, liquid crystal polymer, polyether Ether ketone, thermoplastic polyimide (PI), polyamideimide (PAI), or the like can be used.

  In addition, it is possible to perform the kind of resin and the combination of molecular weight according to the use of this invention.

  In addition, cellulose ester is synthesized industrially using sulfuric acid as a catalyst, but this sulfuric acid is not completely removed, and the residual sulfuric acid causes various decomposition reactions during melt film formation, resulting in cellulose ester obtained. In order to affect the quality of the film, the residual sulfuric acid content in the cellulose ester used in the present embodiment is preferably in the range of 0.1 to 40 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 40 ppm, the deposit on the die lip during heat melting increases, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable. A smaller amount is preferable, but if it is less than 0.1, it is not preferable because the load of the cellulose ester washing process becomes too large, and it is not preferable because it may easily break. This is not well understood, although an increase in the number of washings may affect the resin. Furthermore, the range of 0.1-30 ppm is preferable. The residual sulfuric acid content can be similarly measured by ASTM-D817-96.

  Further, the total residual acid amount including other (such as acetic acid) residual acids is preferably 1000 ppm or less, more preferably 500 ppm or less, and even more preferably 100 ppm or less.

  For washing cellulose ester, in addition to water, a poor solvent such as methanol or ethanol, or, as a result, a mixed solvent of a poor solvent and a good solvent can be used as long as it is a poor solvent. Organic impurities can be removed.

  In order to improve the heat resistance, mechanical properties, optical properties, etc. of cellulose ester, it can be dissolved in a good solvent of cellulose ester and then reprecipitated in a poor solvent to remove low molecular weight components and other impurities of cellulose ester. it can. Furthermore, another polymer or a low molecular weight compound may be added after the cellulose ester reprecipitation treatment.

  Moreover, it is preferable that the cellulose ester used by this embodiment is a thing with few bright spot foreign materials when it is set as the film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is placed between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed. At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used. The cause of bright spot foreign matter is considered to be one of the causes of unacetylated or low acetylated cellulose contained in the cellulose ester. Use a cellulose ester with little bright spot foreign matter and filter the melted cellulose ester or cellulose ester solution. In at least one of the later stage of synthesis of cellulose ester and the process of obtaining a precipitate, the bright spot foreign matter can be removed once again in the solution state via the filtration step. Since the molten resin has a high viscosity, the latter method is more efficient.

  The long stretched film obtained by the production method according to the embodiment of the present invention may be obtained by appropriately mixing polymer components other than the cellulose ester described later. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more. .

<Additives>
Additives added to the dope include plasticizers, ultraviolet absorbers, retardation adjusters, antioxidants, deterioration inhibitors, peeling aids, surfactants, dyes, fine particles, and the like. In the present embodiment, additives other than the fine particles may be added during the preparation of the cellulose ester solution, or may be added during the preparation of the fine particle dispersion. It is preferable to add a plasticizer, an antioxidant, an ultraviolet absorber, or the like that imparts heat and moisture resistance to the polarizing plate used in the liquid crystal image display device.

  It is preferable that these compounds are contained so that it may become 1-30 mass% with respect to a cellulose ester, Preferably it is 1-20 mass%. In order to suppress bleeding out during stretching and drying, a compound having a vapor pressure at 200 ° C. of 1400 Pa or less is preferable.

  These compounds may be added together with the cellulose ester or the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

(Retardation adjuster)
As a compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in EP 911,656A2 can be used.

  Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

<Polymer or oligomer>
The cellulose ester film in this embodiment has a cellulose ester and a substituent selected from a carboxyl group, a hydroxyl group, an amino group, an amide group, and a sulfonic acid group, and has a weight average molecular weight in the range of 500 to 200,000. It is preferable to contain the polymer or oligomer of the vinyl compound which is. The mass ratio of the content of the cellulose ester and the polymer or oligomer is preferably in the range of 95: 5 to 50:50.

(Matting agent)
In the present embodiment, fine particles can be contained in the stretched film as a matting agent, whereby when the stretched film is a long film, it can be easily conveyed and wound.

  The particle size of the matting agent is preferably primary particles or secondary particles of 10 nm to 0.1 μm. A substantially spherical matting agent having a primary particle acicular ratio of 1.1 or less is preferably used.

  As the fine particles, those containing silicon are preferable, and silicon dioxide is particularly preferable. As fine particles of silicon dioxide preferable for this embodiment, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.) manufactured by Nippon Aerosil Co., Ltd. And commercially available products such as Aerosil 200V, R972, R972V, R974, R202, and R812 can be preferably used. Examples of polymer fine particles include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. Examples include Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.). Can do.

  The fine particles of silicon dioxide preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / L or more. The average diameter of primary particles is more preferably 5 to 16 nm, further preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / L or more, and more preferably 100 to 200 g / L or more. Higher apparent specific gravity makes it possible to produce a high-concentration fine particle dispersion, which is preferable because no haze or aggregates are generated.

The amount of the matting agent added in this embodiment is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and further preferably 0.08 to 0.16 g per 1 m ^{2 of the} long stretched film.

(Other additives)
In addition, heat stabilizers such as inorganic fine particles such as kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina, and alkaline earth metal salts such as calcium and magnesium may be added. Further, a surfactant, a peeling accelerator, an antistatic agent, a flame retardant, a lubricant, an oil agent and the like may be added.

<Manufacture of cellulose ester film>
The cellulose ester film in the present embodiment may be produced by either a solution casting method or a melt casting method. Hereinafter, the solution casting method will be described.

  In the present embodiment, the cellulose ester film is produced by dissolving a cellulose ester and additives such as the plasticizer in a solvent to prepare a dope, and casting the dope on a belt-shaped or drum-shaped metal support. , A process of drying the cast dope as a web, a process of peeling from the metal support, a process of stretching, a process of further drying, a process of further heat treating the obtained film if necessary, and a process of winding after cooling Is called. The cellulose ester film in the present embodiment preferably contains 60 to 95% by mass of cellulose ester in the solid content.

  The process for preparing the dope will be described. The concentration of the cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy deteriorates. The concentration for achieving both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

  Organic solvents that dissolve cellulose esters and are useful for forming cellulose ester solutions or dopes include chlorinated organic solvents and non-chlorinated organic solvents. Methylene chloride (methylene chloride) can be mentioned as a chlorinated organic solvent, and it is suitable for dissolving cellulose esters, particularly cellulose triacetate. Due to recent environmental problems, the use of non-chlorine organic solvents has been studied. Examples of the non-chlorine organic solvent include methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1, Examples include 1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, and the like. When these organic solvents are used for cellulose triacetate, a dissolution method at room temperature can be used, but an insoluble material can be obtained by using a dissolution method such as a high-temperature dissolution method, a cooling dissolution method, or a high-pressure dissolution method. Can be reduced, which is preferable. Methylene chloride can be used for cellulose esters other than cellulose triacetate, but methyl acetate, ethyl acetate, and acetone are preferably used. Particularly preferred is methyl acetate. In the present embodiment, an organic solvent having good solubility in the cellulose ester is referred to as a good solvent, and has a main effect on dissolution, and an organic solvent used in a large amount among them is a main (organic) solvent or a main solvent. It is called (organic) solvent.

  The dope used in the present embodiment preferably contains 1 to 40% by mass of an alcohol having 1 to 4 carbon atoms in addition to the organic solvent. These are gelling solvents that make dope film (web) gel when the dope is cast on a metal support and the solvent starts to evaporate and the ratio of alcohol increases, making the web strong and easy to peel off from the metal support. When these ratios are small, there is also a role of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, and has good drying properties. These organic solvents are called poor solvents because they are not soluble in cellulose esters alone.

  It is preferable that the concentration of the cellulose ester in the dope is adjusted to 15 to 30% by mass and the dope viscosity is adjusted to a range of 100 to 500 Pa · s in order to obtain good film surface quality.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  A higher heating temperature with the addition of a solvent is preferable from the viewpoint of the solubility of the cellulose ester. However, if the heating temperature is too high, the required pressure increases and productivity decreases. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. The filter medium preferably has a smaller absolute filtration accuracy in order to remove insoluble matters and the like. However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

A bright spot foreign material is when two polarizing plates are placed in a crossed Nicol state, a cellulose ester film is placed between them, light is applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, Most preferably, it is 0-10 pieces / cm < ² >. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and even more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting process is preferably a mirror finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is set to −50 ° C. to a temperature at which the solvent boils and does not foam. Higher temperatures are preferred because the web can be dried faster. However, if it is too high, the web may foam or the flatness may deteriorate. A preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  In order for the cellulose ester film to exhibit good planarity, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%. The temperature at the peeling position on the metal support is preferably −50 to 40 ° C., more preferably 10 to 40 ° C., and most preferably 15 to 30 ° C.

In the present embodiment, the residual solvent amount is defined by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Moreover, in the drying process of the cellulose ester film, the web is peeled from the metal support, further dried, and dried until the residual solvent amount is 0.5% by mass or less.

  In the film drying step, generally, a roll drying method (a method in which a plurality of rolls arranged at the top and bottom are alternately passed through and dried) or a tenter method is used to transport the web, and if necessary, a method of drying while stretching.

  When peeling from the metal support, the web is stretched in the longitudinal direction due to the peeling tension and the subsequent conveying tension. Therefore, in this embodiment, when peeling the web from the casting support, the peeling and conveying tension is lowered as much as possible. It is preferable to carry out in the state. Specifically, for example, it is effective to set it to 50 to 170 N / m or less. At that time, it is preferable to apply a cold air of 20 ° C. or less to fix the web rapidly.

Next, the dried film is stretched in a direction (Transverse Direction: TD direction) orthogonal to the transport direction using a transverse stretching tenter. Specifically, both ends in a direction perpendicular to the film transport direction are gripped with a clip or the like, and the distance between the opposing clips is increased to extend in the TD direction. In that case, it is preferable to extend | stretch so that the extending | stretching rate calculated | required by a following formula may be 1-30%.
Stretch rate (%) = {(length in the width direction after stretching−length in the width direction before stretching) / length in the width direction before stretching} × 100

  When stretching the film, the film is heated. The film may be heated by, for example, blowing a heating air onto the film, or may be heated by a heating device such as an infrared heater.

  As the transverse stretching tenter, an oven having a preheating zone, a transverse stretching zone, a holding zone, and a cooling zone is used.

  The preheating zone refers to a section in which the vehicle travels while maintaining a constant interval between the gripping tools gripping both ends at the oven entrance.

  The transverse stretching zone refers to a section where the interval between the gripping tools gripping both ends starts to reach a predetermined interval. At this time, the opening angle of the rail on which the gripping tools at both ends run may be opened at the same angle for both rails, or may be opened at different angles.

  The holding zone refers to a section in which the gripping tools at both ends travel while being parallel to each other in a period in which the interval between the gripping tools after the transverse stretching zone or the oblique stretching zone becomes constant again.

  The cooling zone refers to a section where the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg ° C. of the thermoplastic resin constituting the film in the section after the holding zone. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern that narrows the gap between the opposing grippers in advance may be used.

  The temperature of each zone is set to Tg to Tg + 30 ° C., the temperature of the stretching zone is set to Tg to Tg + 30 ° C., and the temperature of the cooling zone is set to Tg−30 to Tg ° C. with respect to the glass transition temperature Tg of the thermoplastic resin. It is preferable to do.

  Next, using the prepared film as a long film original, the film is stretched at a desired angle by the oblique stretching tenter according to the above-described embodiment to obtain a long stretched film.

<Circularly polarizing plate>
The long stretched film obtained by the production method according to the embodiment of the present invention is preferably a λ / 4 plate having the following characteristics.

(Λ / 4 plate)
The λ / 4 plate refers to a plate having a function of converting linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). The λ / 4 plate is designed such that the in-plane retardation value Ro is about 1/4 with respect to a predetermined wavelength of light (usually in the visible light region). The retardation value Ro (550) measured at a wavelength of 550 nm is preferably in the range of 100 to 160 nm, more preferably 120 to 150 nm.

  Further, the λ / 4 plate is preferably a retardation plate having a retardation of approximately ¼ of the wavelength in the visible light wavelength range in order to obtain almost perfect circularly polarized light in the visible light wavelength range. .

The term “retardation of approximately ¼ in the wavelength range of visible light” means a retardation value represented by the following formula (i) measured at a wavelength of 450 nm, with a larger retardation at a wavelength of 400 to 700 nm. It is preferable that Ro (590) which is a retardation value measured at a certain Ro (450) and a wavelength of 590 nm satisfies 1 <Ro (590) / Ro (450) ≦ 1.6. Furthermore, in order to function effectively as a λ / 4 plate, Ro (450) is in the range of 100 to 125 nm, the retardation value Ro (550) measured at a wavelength of 550 nm is in the range of 125 to 142 nm, It is more preferable that Ro (590) is a retardation film in the range of 130 to 152 nm.
Formula (i): Ro = (nx−ny) × d
Formula (ii): Rt = {(nx + ny) / 2−nz} × d
In the formula, nx and ny are refractive indexes nx (also referred to as the maximum in-plane refractive index and refractive index in the slow axis direction) at 23 ° C./55% RH, 450 nm, 550 nm, and 590 nm, ny. (Refractive index in the direction perpendicular to the slow axis in the film plane) and nz (refractive index in the film thickness direction of the film), and d is the thickness (nm) of the film.

  Ro and Rt can be measured using an automatic birefringence meter. Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), Ro is calculated by birefringence measurement at each wavelength in an environment of 23 ° C. and 55% RH.

  A circularly polarizing plate is obtained by laminating so that the angle between the slow axis of the λ / 4 plate and the transmission axis of a polarizer (long polarizing film) described later is substantially 45 °. “Substantially 45 °” means 40 to 50 °. The angle between the slow axis in the plane of the λ / 4 plate and the transmission axis of the polarizer is preferably 41 to 49 °, more preferably 42 to 48 °, and 43 to 47 °. Is more preferable, and it is most preferable that it is 44-46 degrees.

  That is, the long stretched film according to this embodiment has an in-plane retardation Ro (550) represented by the above formula (i) of 100 to 160 nm, and has a slow axis with respect to the width direction of the long stretched film. The orientation angle θ, which is an angle, is preferably 40 to 50 °.

  By doing so, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

  The circularly polarizing plate (also referred to as a polarizing plate) according to the present embodiment uses a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer, and is manufactured by the manufacturing method according to the embodiment of the present invention. It can be manufactured by laminating with the constitution of λ / 4 plate / polarizer / optical film which is the obtained long stretched film. When using the circularly-polarizing plate (long polarizing plate) which concerns on this embodiment for the liquid crystal display device which is a stereoscopic video display device, the said (lambda) / 4 board is bonded by the visual recognition side.

  The optical film is preferably a polymer film, preferably manufactured easily, optically uniform, and optically transparent. Any of these may be used, for example, cellulose ester film, polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) film, polyethylene terephthalate, polyethylene naphthalate. Polyester film such as polyethylene film, polypropylene film, cellophane, cellulose diacetate film, cellulose acetate butyrate film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, norbornene resin Film, polymethylpentene film, polyetherketone film, Polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, a cycloolefin polymer film, a polyvinyl acetal resin film, there may be mentioned polymethyl methacrylate film, or an acrylic film or the like, but are not limited to.

  In the case of a cellulose ester film, the cellulose acetate, plasticizer, UV absorber, antioxidant, retardation adjuster, matting agent, deterioration inhibitor, peeling aid, surfactant, etc. used in the stretched film described above are used. It can be preferably used.

  The retardation values Ro and Rt defined by the above formula are 20 to 150 nm and 70 to 400 nm, respectively, for the optical film bonded to the surface opposite to the surface on which the λ / 4 plate is bonded to the polarizer. Or an optical film of 0 nm ≦ Ro ≦ 2 nm and −15 nm ≦ Rt ≦ 15 nm.

  As the optical film, for example, a method of supporting a discotic liquid crystalline compound, which is a compound having negative uniaxiality, on a support (see, for example, JP-A-7-325221), positive optical anisotropy. A method in which a nematic polymer liquid crystalline compound having a hybrid orientation in which the pretilt angle of liquid crystal molecules changes in the depth direction is supported on a support (see, for example, JP-A-10-186356), positive By forming a nematic liquid crystal compound having optical anisotropy of 2 layers on a support and setting the orientation direction of each layer to approximately 90 °, pseudo-uniaxially similar optical characteristics are imparted. Instead of a conventional TAC film or an optical film having an optically anisotropic layer provided on a support by a method (for example, see JP-A-8-15681). An optical film having the function of a retardation film by developing a retardation of the rosin derivative film by saponification and laminating a PVA polarizer (see, for example, JP-A-2003-270442), Examples include, but are not limited to, optical compensation films obtained by adding a retardation adjusting agent to a cellulose ester film to obtain a retardation film (see, for example, JP-A Nos. 2000-275434 and 2003-344655). Is not to be done.

  For example, as a commercially available cellulose ester film, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC16UR, KC4UE, KC4UE, KC4FR, KC4FR-1 And the like) are also preferably used.

  The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

  Although the manufacturing method of a polarizing plate is not specifically limited, For example, the method of bonding the said elongate stretched film with a elongate polarizing film is mentioned. A more specific manufacturing method will be described later.

  By doing so, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

  The polarizing plate can be produced by a general method. The long stretched film obtained by the production method according to the embodiment of the present invention, which has been subjected to alkali saponification treatment, has a fully saponified type on at least one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution. It is preferable to bond using an aqueous polyvinyl alcohol solution. It is preferable to paste the optical film on the other surface.

  The polarizing plate can be constituted by further bonding a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

<Liquid crystal display device>
A liquid crystal display device can be produced by using a polarizing plate obtained by using the long stretched film according to the present embodiment as a liquid crystal display device bonded to the surface on the viewing side of the liquid crystal cell. The circularly polarizing plate according to the present embodiment is a reflective, transmissive, transflective LCD, super twisted nematic (STN) mode, twisted nematic (TN) mode, in-plane switching (IPS) mode, or vertical alignment (VA) mode. The liquid crystal display device can be used in a liquid crystal display device of an optically aligned birefringence (OCB) mode and a hybrid alignment (HAN) mode.

  In addition, the λ / 4 plate using the long stretched film according to the present embodiment can be used in various modes in a stereoscopic image display device. For example, a stereoscopic image display device including a liquid crystal display device and liquid crystal shutter glasses, wherein the liquid crystal shutter glasses are (1) a λ / 4 plate, a liquid crystal cell, and a polarizer are provided in this order, or ( 2) The liquid crystal shutter glasses in which the λ / 4 plate, the polarizer, the liquid crystal cell, and the polarizer are provided in this order can be used in a stereoscopic image display device according to an aspect.

  In any case, the front polarizing plate of the liquid crystal display device has a configuration in which a λ / 4 plate, a polarizer, an optical film cell, and a polarizer are provided in this order.

  In the present embodiment, the above-described aspect and configuration can reduce crosstalk or luminance reduction and color change when tilting the head when viewing a stereoscopic (3D) image, and maintain excellent visibility in the usage environment. Therefore, it is possible to provide a stereoscopic image display device having higher durability against the use environment.

<Embodiment with EL element>
In addition, the λ / 4 plate using the long stretched film according to the embodiment of the present invention is particularly preferably used as a circularly polarizing plate used for antireflection of a self-luminous display device such as an organic EL display device. . The long stretched film according to the embodiment of the present invention is excellent in uniformity in the direction of the slow axis (orientation angle) in the width direction. Therefore, when used in an organic EL display device, the color is particularly uniform. A display device with excellent performance can be obtained.

  FIG. 5 is a schematic view of a preferred embodiment when the λ / 4 plate (circularly polarizing element) according to this embodiment is used for an EL element.

  Here, the absorption linear polarizing plate 1 is obtained by sandwiching both surfaces of an absorption linear polarizer 501 between polarizing plate protective films. On the other hand, the long stretched film 502 according to the embodiment of the present invention is used as a quarter wavelength plate, the transmission axis of the absorption linear polarizer 501 and the slow phase of the long stretched film 502 according to the embodiment of the present invention. The circularly polarizing element 503 is formed by bonding so that the axes have a relationship of about 45 ° (or 135 °). Here, although the polarizing plate protective film is bonded to both surfaces of the absorption linear polarizer 501, a form in which the long stretched film 502 according to the embodiment of the present invention is also used as the protective film on the light source side is preferable.

  As shown in FIG. 5, the EL element 10 according to this embodiment includes a circularly polarizing element 503 having an absorption linearly polarizing plate 1 and a long stretched film 502 according to an embodiment of the present invention as a quarter-wave plate. It has.

  Here, the transmission axis of the absorption linear polarizing plate 1 and the slow axis of the long stretched film 502 according to the embodiment of the present invention are arranged to intersect at 45 ° (or 135 °), The linearly polarized light transmitted through the absorption type linearly polarizing plate 1 is converted into circularly polarized light by the long stretched film 502 according to the embodiment of the present invention.

  The EL element 10 includes a transparent substrate 504 disposed opposite to the circularly polarizing element 503, an anode 505 formed on the transparent substrate 504, a cathode 506 disposed opposite to the anode 505, an anode 505 and a cathode 506. A light emitting layer 507 disposed therebetween.

  In the EL element 10 having such a configuration, electrons are injected from the cathode 506 and holes are injected from the anode 505, and both are recombined in the light emitting layer 507, so that visible light corresponding to the light emission characteristics of the light emitting layer 507 can be obtained. Luminescence occurs. The light generated in the light emitting layer 7 is directly or after being reflected by the cathode 506, and then extracted to the outside through the anode 505, the transparent substrate 504, and the circularly polarizing element 503.

  On the other hand, half of the external light I1 (external light incident from a direction perpendicular to the surface of the absorption linear polarizing plate 1) incident from the outside of the EL element 10 due to room lighting or the like is absorbed by the absorption linear polarizing plate 1, The other half is transmitted as linearly polarized light and is incident on the long stretched film 502 according to the embodiment which is a quarter wave plate.

  The light incident on the stretched film 502 is disposed so that the transmission axis of the absorption linear polarizing plate 1 and the slow axis of the long stretched film 502 intersect at 45 ° (or 135 °). Is converted into circularly polarized light R2 by passing through the long stretched film 502.

  When the circularly polarized light R2 emitted from the long stretched film 502 is specularly reflected by the cathode 506, the phase is inverted by 180 degrees and reflected as circularly polarized light R1 in the reverse direction.

  The reflected light R1 is converted into linearly polarized light parallel to the absorption axis (axis perpendicular to the optical axis) of the absorption linear polarizing plate 1 by being incident on the elongated stretched film 502. Therefore, the absorption linear polarizing plate 1 is completely absorbed and is not emitted to the outside.

  On the other hand, when the external light I2 incident from an oblique direction passes through the long stretched film 502, the optical path length becomes long, so that it deviates from circularly polarized light and becomes elliptically polarized light. Light (light indicated by a dotted line in FIG. 5) may leak to the outside and be visually recognized by an observer.

  On the other hand, when Rt of the long stretched film is set to -20 to 20 nm, light leakage of incident light from an oblique direction can be reduced, and the color change can be further reduced.

  The circularly polarizing element according to this embodiment can be used not only for the bottom emission method but also for the top emission method.

  As described above, the present specification discloses various modes of technology, of which the main technologies are summarized below.

  One aspect of the present invention is a long film original fabric supplying step for supplying a long film original fabric made of a thermoplastic resin, a direction in which the long film original fabric is greater than 0 ° and less than 90 ° relative to the width direction The method for producing a long stretched film comprising a step of obliquely stretching the film and a step of winding the long stretched film after the oblique stretch step, wherein the oblique stretch is performed in the long film original fabric supplying step. The long film original fabric is supplied from a direction different from the conveying direction of the long stretched film immediately after the process, and in the oblique stretching step, the both ends of the supplied long film original fabric are conveyed while being gripped by a gripping tool. Then, by changing the conveying direction while maintaining the gripping state, the moving distance between one gripping part and the other gripping part is made different, whereby the long film original fabric is larger than 0 ° with respect to the winding direction by 90 °. Less than ° In the long film original fabric supply step, the long film original fabric having a bowing in the opposite direction is supplied to the bowing generated in the oblique stretching step. It is a manufacturing method of a stretched film.

  In addition, the direction of the bowing in the above represents the direction in the longitudinal direction. That is, in the present embodiment, when the bowing generated in the oblique stretching process has a convex arcuate shape with respect to the upstream side in the transport direction (the supply side of the long film original fabric), the long film original The long film original fabric supplied in the anti-supplying process represents that it has a convex arch shape on the downstream side in the conveying direction (winding side of the long stretched film).

  According to such a structure, generation | occurrence | production of the bowing at the time of performing diagonal stretch can be suppressed effectively, and the manufacturing method of the elongate stretched film excellent in the breadth uniformity of the slow axis inclination angle can be provided. . Moreover, if the elongate stretched film obtained by such a manufacturing method is used, a circularly-polarizing plate can be obtained by bonding together a elongate polarizing film with a roll-to-roll. For this reason, productivity and yield can be significantly improved, and the display device using the obtained circularly polarizing plate exhibits excellent color uniformity.

  Moreover, in the method for producing a long stretched film, the long film original fabric is once wound up after the film material made of the thermoplastic resin is formed into a roll-shaped long film original fabric, The film material is supplied to the oblique stretching process by feeding out again, and the film material is in the same direction with respect to the bowing generated in the oblique stretching process before being made into the roll-shaped long film original fabric. It is preferable to be manufactured under conditions that generate bowing.

  According to such a configuration, when producing a roll-shaped long film original fabric, the generated bowing is fed in a direction opposite to the winding direction when the roll-shaped long film original fabric is fed out. Therefore, in a long film original fabric supply process, the long film which has a bowing which has a bowing of a reverse direction with respect to the bowing which generate | occur | produces in a diagonal stretch process can be supplied continuously. That is, it is possible to more easily produce a long stretched film that effectively suppresses the occurrence of bowing during oblique stretching and is excellent in width uniformity of the slow axis tilt angle.

  Further, in the method for producing a long stretched film, the long film original fabric is subjected to a step of generating a bowing in a reverse direction with respect to the bowing generated in the oblique stretching step, and then the oblique film is not wound up thereafter. It is preferable to be supplied to the stretching step.

  According to such a configuration, in the long film original fabric supply process, it is possible to continuously supply the long film having the bowing having the bowing in the opposite direction to the bowing generated in the oblique stretching process. it can. That is, it is possible to more easily produce a long stretched film that effectively suppresses the occurrence of bowing during oblique stretching and is excellent in width uniformity of the slow axis tilt angle.

  Moreover, in the manufacturing method of a elongate stretched film, it is preferable that the said elongate stretched film has the bowing amount after diagonal stretch of -1.0% or more + 1.0% or less.

  According to such a structure, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

Moreover, in the manufacturing method of a long stretched film, the in-plane retardation Ro (550) represented by the following formula of the said long stretched film is 100-160 nm, and the slow axis with respect to the width direction of a long stretched film It is preferable that the orientation angle θ which is an angle of 40 to 50 °.
Ro = (nx−ny) × d
Nx represents a refractive index with respect to light having a wavelength of 550 nm in the slow axis direction in the plane of the long stretched film, and ny represents a wavelength of 550 nm in a direction perpendicular to nx in the plane of the long stretched film. Represents the refractive index with respect to light, and d represents the thickness (nm) of the long stretched film.

  According to such a structure, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

  Another aspect of the present invention is a method for producing a circularly polarizing plate, wherein a long stretched film obtained by the method for producing a long stretched film is bonded to a long polarizing film.

  According to such a structure, the circularly-polarizing plate which can fully suppress the nonuniformity of the color of a display apparatus can be manufactured.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Preparation of dope solution>
(Preparation of polyester A)
In a nitrogen atmosphere, 4.85 g of dimethyl terephthalate, 4.4 g of 1,2-propylene glycol, 6.8 g of p-toluic acid, and 10 mg of tetraisopropyl titanate were mixed and stirred at 140 ° C. for 2 hours. Stirring was carried out at ° C for 16 hours. Next, the temperature was lowered to 170 ° C., and unreacted 1,2-propylene glycol was distilled off under reduced pressure to obtain polyester A.

<Fine particle dispersion 1>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.)
11 parts by mass Ethanol 89 parts by mass The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion 1

A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester, sugar ester compound, polyester A, TINUVIN 928, and fine particle additive solution 1 were charged into a pressure dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and this was dissolved in Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.
<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose ester (cellulose acetate propionate: acetyl group substitution degree 1.5, propionyl group 0.9, total substitution degree 2.4) 100 parts by mass Sugar ester compound (1-22) 7.0 parts by mass Polyester A 2.5 parts by mass TINUVIN 928 (manufactured by BASF Japan Ltd.) 1.5 parts by mass Fine particle additive liquid 1 1 part by mass The above was put into a sealed container and dissolved while stirring to prepare a dope solution. .

<Example 1>
(Creation of long film stock 1)
Using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 2000 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 110 N / m.

  The peeled cellulose ester film was stretched 1.1 times in the width direction by a transverse stretching tenter. The temperature conditions of the transverse stretching tenter oven at that time were adjusted to 160 ° C for the preheating zone, 165 ° C for the stretching zone, 172 ° C for the holding zone, and 110 ° C for the cooling zone.

  Next, the tenter clip marks on both ends of the film are trimmed, the drying temperature is 130 ° C., the transport tension is 100 N / m, and the film is dried while being transported in the drying zone using a number of rolls. After finishing, it was wound up as a wound body in the winding step.

  As described above, a roll-shaped long film original fabric 1 having a dry film thickness of 80 μm was obtained.

  In order to measure the bowing amount of the long film original after the transverse stretching, a jig for drawing in the width direction was provided for the film immediately before entering the transverse stretching tenter.

  Specifically, a tengu thread or kite thread with black ink on the top of the film is handed over in a direction perpendicular to the film transport direction, and the tengu thread or kite thread is played at an arbitrary position. A jig with a mechanism capable of drawing a straight line across the width direction of the film was provided.

  The definition and analysis method of the bowing amount in the present invention will be described with reference to FIG.

  Using the jig, a straight line L601 is drawn on the film surface before entering the tenter. Under the condition that bowing occurs, the shape of the straight line L601 changes from a straight line state to a curved line C corresponding to the bowing state after passing through the tenter.

このとき湾曲線Ｃが搬送方向下流側に向かって凸状に湾曲している状態を、搬送方向に対して凸型のボウイングと表現し、ボウイング量を＋として定義した。At this time, the length of a straight line (broken line) L603 connecting both ends of the curved line C is a (equal to the width in the width direction) [mm], and parallel to the conveyance direction from the midpoint M604 of the straight line L603 to the curved line C602. The bowing amount B when the length of the straight line L605 drawn on the surface is b [mm] was defined by the following formula (1).

At this time, the state where the curved line C is curved in a convex shape toward the downstream side in the transport direction is expressed as convex bowing in the transport direction, and the bowing amount is defined as +.

  On the contrary, the state where the curved line C is curved in a convex shape toward the side opposite to the transport direction, that is, the upstream side, is expressed as concave bowing with respect to the transport direction, and the bowing amount is defined as-.

  The curved line drawn on the long film original fabric 1 has a concave bowing in the tenter transport direction, and the bowing amount at that time was -8%.

(Creation of long stretched film 1)
Next, an oblique stretching process in which the long film original fabric 1 is unwound from the film unwinding process and obliquely stretched using an oblique stretching tenter as shown in FIG. 2 will be described.

  At this time, it was set as the form which unwinds from the tail in the film winding body wound up by the previous process.

  That is, the concave bowing with respect to the transport direction in the previous process, which is given in the previous process, is transported as a convex bowing downstream in the obliquely stretched tenter transport direction.

  The roll-shaped long film original 1 was set in the slidable feeding device of the apparatus of FIG. 2 and supplied to an obliquely stretched tenter in which a rail pattern was set so that the angle θi = 47 °. The oblique stretching tenter has a preheating zone, a lateral stretching zone, an oblique stretching zone, a holding zone, and a cooling zone. At that time, the distance between the main axis of the guide roll closest to the inlet portion of the obliquely stretched tenter and the gripping tool (clip gripping portion) of the obliquely stretched tenter was 80 cm. The clip had a length of 2 inches in the conveying direction, and the guide roll had a diameter of 10 cm. In the oblique stretching tenter, the temperature of the preheating zone was 180 ° C., the temperature of the transverse stretching zone was 177 ° C., the temperature of the oblique stretching zone was 177 ° C., the temperature of the holding zone was 177 ° C., and the temperature of the cooling zone was 110 ° C. . Further, the drawing tension at the tenter outlet was 200 N / m, the transverse stretching ratio was stretched to 1.3 times in the transverse stretching zone, and the oblique stretching ratio was stretched to 1.5 times in the oblique stretching zone. . At this time, the orientation angle θ was stretched in an oblique direction so as to be 45 °. The stretched film was controlled so that the fluctuation in the take-up tension was less than 3% by performing feedback control in which the change in the tension measured with the first roll on the outlet side of the obliquely stretched tenter was reflected in the take-up motor rotation speed. Then, both ends of the film were trimmed, the conveyance direction was changed with a conveyance direction changing device composed of an airflow roll, and the film was wound up with a slidable winding device to obtain a roll-like long stretched film 1 having a width of 2000 mm.

  The stretch ratio in the oblique stretch tenter described here is a value defined by the ratio of the ratio W / Wo when the distance Wo between both ends of the clip gripped at the tenter inlet becomes the distance W at the tenter outlet. It becomes.

  The film moving speed during heating and stretching was 5 m / min.

  Moreover, it extended | stretched using the heating apparatus for temperature control over the width direction of a film. The heating device controlled the temperature so that the thickness of the film in the film width direction after stretching was approximately the same as the thickness direction film thickness distribution before stretching.

  The curved line drawn on the long stretched film 1 has a convex bowing on the upstream side in the transport direction, and the bowing amount at that time was −0.2%.

  The total film thickness of the long stretched film 1 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

<Example 2>
(Creation of long film stock 2)
A long film original fabric 2 was prepared in the same manner as the long film original fabric 1 except that the holding zone was adjusted to 158 ° C. among the temperature conditions of the transversely stretched tenter oven.

  The curved line drawn on the long film original fabric 2 has a convex bowing on the downstream side in the tenter conveying direction, and the bowing amount at that time was + 8%.

  At this time, the film thickness of the long original film 2 was 80 μm.

(Creation of long stretched film 2)
In the same manner as the method for producing the long stretched film 1, except that the created long film original fabric 2 was directly and continuously introduced into the obliquely stretched tenter without being wound in the previous step. A stretched film 2 was obtained.

  The curved line drawn on the long stretched film 2 has a concave bowing in the tenter transport direction, and the bowing amount at that time was -0.2%.

  The film thickness of the long stretched film 2 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

<Comparative Example 1>
(Creation of long film web 3)
A long film original fabric 3 was prepared in the same manner as the long film original fabric 1 except that the holding zone was adjusted to 164 ° C. among the temperature conditions of the transversely stretched tenter oven.

  At this time, the 3 bowing amount of the long film original fabric 3 was 0%.

(Creation of long stretched film 3)
A long stretched film 3 was obtained in the same manner as the method for producing the long stretched film 1 except that the produced long film original fabric 3 was used as an obliquely stretched tenter raw fabric.

  At that time, the film thickness of the long original film 3 was 80 μm.

  At this time, the curved line drawn on the elongate stretched film 3 had a concave bowing with respect to the tenter conveyance direction, and the bowing amount at that time was -7.5%.

  The film thickness of the long stretched film 3 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

<Comparative example 2>
(Creation of long film stock 4)
The long film original fabric 4 was prepared in the same manner as the production of the long film original fabric 3.

  At this time, the bowing amount of the long film original fabric 4 was 0%.

(Creation of long stretched film 4)
The long film raw fabric 4 prepared above was not wound up in the previous step, but was directly and continuously introduced into the obliquely stretched tenter. A stretched film 4 was obtained.

  At that time, the film thickness of the long original film 4 was 80 μm.

  At this time, the curved line drawn on the long stretched film 4 had a convex bowing on the upstream side in the transport direction, and the bowing amount at that time was −7.5%.

  The film thickness of the long stretched film 4 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

  Next, in the following examples, the rail pattern of the diagonally stretched tenter is changed to a preheating zone, a first laterally stretched zone, a first holding zone, a second laterally stretched zone, an obliquely stretched zone, a second laterally stretched zone, Modification was made to have a second holding zone, a third transverse stretching zone and a cooling zone.

<Example 3>
(Creation of long film web 5)
In the same manner as the production method of the long film original fabric 1, a long film original fabric 5 was prepared. The curved line drawn on the long film original fabric 5 has a concave bowing with respect to the tenter transport direction, and the bowing amount at that time was -8%.

(Creation of long stretched film 5)
As the temperature conditions of the oblique stretching tenter oven, the preheating zone is 180 ° C., the first transverse stretching zone is 177 ° C., the first holding zone is 173 ° C., the second transverse stretching zone is 177 ° C., and the oblique stretching zone temperature is 177 The second holding zone was 177 ° C., the third transverse stretching zone was 173 ° C., and the cooling zone was 110 ° C. Further, the drawing tension at the tenter outlet is 200 N / m, the film is stretched so that the transverse stretching ratio in the transverse stretching zone 1 is 1.2 times, and is further stretched so that the stretching ratio in the transverse stretching zone 2 is 1.1 times. The film was stretched so that the oblique stretching ratio in the oblique stretching zone was 1.5 times, and further stretched so that the stretching ratio in the lateral stretching 3 zone was 1.02 times. Others were obtained in the same manner as the method for producing the long stretched film 1, and a long stretched film 5 was obtained.

  The film thickness of the long original film 5 at that time was 80 μm.

  The curved line drawn on the long stretched film 5 has a convex bowing in the tenter transport direction, and the bowing amount at that time was + 0.2%.

  The film thickness of the long stretched film 5 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

<Example 4>
(Creation of long film web 6)
Except for changing the rail pattern and temperature condition of the obliquely stretched tenter in the same manner as in Example 3, a long film original fabric 6 was prepared in the same manner as the method for producing the long film original fabric 1. The curved line drawn on the long film original fabric 6 has a convex bowing on the upstream side in the tenter transport direction, and the bowing amount at that time was -8%.

  The film thickness of the long film original fabric 6 at that time was 80 μm.

(Creation of long stretched film 6)
The long film original fabric 6 was not wound in the previous step, but was directly and continuously introduced into the obliquely stretched tenter. A stretched film 6 was obtained.

  The curved line drawn on the long stretched film 6 has a convex bowing with respect to the tenter transport direction, and the bowing amount at that time was + 0.2%.

  The film thickness of the long stretched film 6 at that time was 60 μm.

  Other optical characteristics are shown in Table 1.

<Evaluation conditions>
The orientation angle θ, the in-plane direction retardation Ro, and the thickness direction retardation Rt of the created long stretched films 1 to 6 were measured using a phase difference measuring device (manufactured by Oji Scientific Co., Ltd., KOBRA-WXK).

  As an evaluation method, measurement was performed at an interval of 50 mm of the film in the film width direction, and an average of all data was taken. Further, the maximum value-minimum value of all measured values was evaluated as variations.

In addition, film thickness direction retardation Rt was computed using the following formula.
Formula (i): Ro = (nx−ny) × d
Formula (ii): Rt = {(nx + ny) / 2−nz} × d
In the formula, nx and ny are the refractive index nx at 23 ° C./55% RH and 590 nm (the maximum refractive index in the plane of the film, also referred to as the refractive index in the slow axis direction), ny (slow in the plane of the film). The refractive index in the direction perpendicular to the phase axis) and nz (the refractive index in the film thickness direction), and d is the thickness (nm) of the film.

<Production of circularly polarizing plates 1 to 6>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

  This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer (long polarizing film).

  Next, according to the following steps 1 to 5, a polarizer, the long stretched films 1 to 6, and KC4UY (TAC film having a film thickness of 40 μm) which is a commercially available polarizing plate protective film on the back side are rolled so as to match the longitudinal direction. -The circularly-polarizing plates 1-6 were produced by bonding with a toe roll. Here, the long stretched films 1 to 6 are used as the function of the polarizing plate protective film on one side of the polarizer.

  Step 1: Dipped in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain long stretched films 1 to 6 saponified on the side to be bonded to the polarizer.

  Step 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off, and this was placed on the long stretched films 1 to 6 processed in Step 1.

Step 4: Step 3 long was laminated with a stretched film 1-6 between the polarizer and the pressure polarizing plate protective film 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Process 5: The sample which bonded the polarizer produced in the process 4, the elongate stretched films 1-6, and the polarizing plate protective film in the dryer of 80 degreeC was dried for 2 minutes, and each elongate stretched film 1 The circularly-polarizing plates 1-6 corresponding to 6 were produced.

<Production of organic EL display device>
An organic EL display panel for performing viewing angle measurement was produced as follows, and the characteristics as an organic EL display device were evaluated.

<Evaluation>
About the produced circularly-polarizing plates 1-6, the 50-mm location was cut out as a 15-mm square sample piece from the width center part and the edge part. Subsequently, the surface film attached to the mobile phone GALAXY S (manufactured by Samsung Electronics Co., Ltd.) on which the organic EL panel was mounted was peeled off, and the sample pieces at the center and end portions of the cut circular polarizing plates 1 to 6 were attached.

<Measurement of external light reflectance>
About the place which stuck the sample piece of the center part and edge part of this organic EL display device, the external light reflectance in the wavelength of 480 nm was measured using the spectrocolorimeter (CM-2500d), respectively, and the center part and edge The ratio of the external light reflectance was calculated at the location corresponding to the part.

<Evaluation scale for color change>
Furthermore, the difference of the color of the location which affixed the sample piece of the center part and edge part of said organic EL display apparatus was visually evaluated on the following reference | standard.
◎: There is no difference in the color tone of each part of the pasted sample piece. ○: A slight difference is seen in the color of each part of the pasted sample piece, but there is no problem. △: The pasted sample piece. Level that can be used although there is a difference in color for each part of ×: Level that can not be used as a product because the color difference is large for each part of the pasted sample piece

  The above evaluation results are shown in Table 2.

  From the above table, the long stretched film obtained by the production method according to the present invention has a very uniform light distribution angle in the width direction, and the circularly polarizing plate and the organic EL display device using the same have a width of It can be seen that an excellent display device having uniform external light reflection characteristics in the hand and suppressed color change can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the production | generation method of the elongate stretched film which suppressed generation | occurrence | production of the bowing at the time of performing diagonal stretch effectively, and was excellent in the width uniformity of the slow axis inclination angle is provided. Moreover, if the elongate stretched film obtained by such a manufacturing method is used, a circularly-polarizing plate can be obtained by bonding together a elongate polarizing film with a roll-to-roll. For this reason, productivity and yield can be significantly improved, and the display device using the obtained circularly polarizing plate exhibits excellent color uniformity.

Claims (6)

A long film original fabric supplying step for supplying a long film original fabric made of a thermoplastic resin, and an oblique stretching step for obliquely stretching the long film original fabric in a direction greater than 0 ° and less than 90 ° with respect to the width direction. And a method for producing a long stretched film having a step of winding the long stretched film after the oblique stretching step,
In the long film original fabric supply step, the long film original fabric is supplied from a direction different from the winding direction of the long stretched film after the oblique stretching step,
In the oblique stretching process, the both ends of the supplied long film original are transported while being gripped by a gripping tool, and the gripping state is maintained and the transport direction is changed to move one gripping part and the other gripping part. By varying the distance, the long film original fabric is stretched in an oblique direction greater than 0 ° and less than 90 ° with respect to the winding direction,
In the long film original fabric supply step, a long film original fabric having a bowing in the opposite direction to the bowing generated in the oblique stretching step is supplied. . The long film original fabric is a film material made of the thermoplastic resin, and is wound up once, and after being made into a roll-shaped long film original fabric, it is supplied by feeding again,
The film material is manufactured under the condition of generating bowing in the same direction with respect to the bowing generated in the oblique stretching step before the roll-shaped long film original is formed. The manufacturing method of the elongate stretched film of Claim 1.   The long film original fabric is supplied to the oblique stretching step without being wound up after passing through a step of generating a bowing in the reverse direction with respect to the bowing generated in the oblique stretching step. The manufacturing method of the elongate stretched film of Claim 1.   The long stretched film according to any one of claims 1 to 3, wherein a bowing amount after oblique stretching is -1.0% or more and + 1.0% or less. Production method. In-plane retardation Ro (550) represented by the following formula of the long stretched film is 100 to 160 nm,
The long stretched film according to any one of claims 1 to 4, wherein an orientation angle θ, which is an angle of a slow axis with respect to the width direction of the long stretched film, is 40 to 50 °. Production method.
Ro = (nx−ny) × d
Nx represents a refractive index with respect to light having a wavelength of 550 nm in the slow axis direction in the plane of the long stretched film, and ny represents a wavelength of 550 nm in a direction perpendicular to nx in the plane of the long stretched film. Represents the refractive index with respect to light, and d represents the thickness (nm) of the long stretched film.   The manufacturing method of the circularly-polarizing plate characterized by sticking the elongate stretched film obtained by the manufacturing method of any one of Claims 1-5 with a elongate polarizing film.

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