WO2014073021A1

WO2014073021A1 - Method for producing longitudinally-stretching film

Info

Publication number: WO2014073021A1
Application number: PCT/JP2012/007117
Authority: WO
Inventors: 晋平畠山
Original assignee: コニカミノルタ株式会社
Priority date: 2012-11-06
Filing date: 2012-11-06
Publication date: 2014-05-15
Also published as: JP5339017B1; KR20150060815A; JPWO2014073021A1; KR101747566B1

Abstract

One aspect of the present invention is a method for producing a longitudinally-stretching film equipped at least with a constant-speed-conveying step for gripping both ends of a thermoplastic longitudinal film using a plurality of gripping tools and conveying the gripping tools gripping both ends at a constant speed, a diagonal-stretching step for angling the optical axis of the longitudinal film by accelerating first gripping tools gripping one end faster than second gripping tools gripping the other end and advancing the first gripping tools farther than the second gripping tools, and an after-conveying step for conveying in a state of gripping both ends of the longitudinal film with the plurality of gripping tools, after completing the diagonal-stretching step, the method for producing a longitudinally-stretching film being characterized in that a relaxing treatment is performed for relaxing the bowing produced in the diagonal-stretching step on the late-side of the longitudinal film being gripped by the second gripping tools.

Description

Manufacturing method of long stretched film

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

A stretched film obtained by stretching a resin film is used as an optical film that performs various optical functions in various display devices by utilizing its optical anisotropy. For example, in an image display device such as a liquid crystal display device, it is known to use a stretched film as an optical compensation film for optical compensation such as coloring prevention and viewing angle expansion. Moreover, it is known that the circularly-polarizing plate which used the stretched film as a retardation film which served as the polarizing plate protective film will be obtained by bonding a stretched film and a polarizer (polarizing film).

Depending on the applied image display device, such a circularly polarizing plate is attached in such an arrangement that the optical axis such as the in-plane slow axis of the stretched film is inclined at a desired angle with respect to the absorption axis of the polarizer. You may need to match.

However, since the polarizer is generally obtained by stretching at a high magnification in the longitudinal direction, the absorption axis formed by the stretching often coincides with the longitudinal direction. On the other hand, since a conventional retardation film is produced by longitudinal stretching or longitudinal stretching, an optical axis (orientation axis) such as an in-plane slow axis is in principle the longitudinal direction (conveying direction) of the film. In contrast, it becomes 0 ° or 90 °. Therefore, as described above, in order to incline the absorption axis of the polarizer and the in-plane slow axis of the stretched film so that the relationship between them is a desired angle, a long polarizer and a retardation film ( At least one of the stretched film) is cut out at a specific angle, and the film pieces must be bonded together one by one. For this reason, an unnecessary part arises in the film, there is a problem in that the use efficiency is lowered and the production cost is increased. In addition, since at least one of the long polarizer and the retardation film (stretched film) is pasted as a film piece, the problem is that the axes are shifted from a desired angle during the pasting, resulting in shaft unevenness. May occur.

In order to solve such a problem, the resin film is stretched in an oblique direction at a desired angle using an oblique stretching apparatus, and an optical axis such as a slow axis is 0 ° with respect to the width direction (width direction) of the film. However, various methods for producing a stretched film that can be freely controlled in directions other than 90 ° have been proposed.

As such a manufacturing method, first, a method of obliquely stretching by inclining a direction in which a long film is drawn out and a direction in which a long stretched film obtained by stretching the long film is wound, that is, a bending-type oblique Examples include a method using a stretching apparatus. Specifically, there is a method in which a travel support tool such as a rail on which the left and right gripping tools travel is bent to provide a difference in the movement trajectory length of the left and right gripping tools, and the resin film is stretched obliquely.

However, in such a bending-type oblique stretching apparatus, although a suitable long stretched film may be obtained, the traveling support tool such as a rail on which the gripping tool travels is bent and the direction in which the long film is fed out, Since the direction in which the long stretched film obtained by stretching the long film is tilted, the long stretched film manufacturing apparatus spreads in the width direction of the long film, and the entire apparatus becomes large. There was a trend. For example, the method described in Patent Document 1 can be mentioned.

Therefore, as an oblique stretching method capable of saving space, a straight traveling oblique stretching apparatus that does not bend the stretching direction for oblique stretching is used, and the direction in which the long film is fed and the length of the long film stretched. The method which does not need to incline with the direction which winds a stretched film is mentioned. Specifically, the both ends of the resin film are gripped by a plurality of grippers, and while the resin film is conveyed, the traveling speed of the gripper gripping one end and the gripper gripping the other end is adjusted. There is a simultaneous biaxial oblique stretching method in which a difference is provided and the resin film is obliquely stretched. For example, the method described in Patent Document 2 can be mentioned.

The simultaneous biaxial oblique stretching method refers to a method of stretching obliquely by using a stretching apparatus that can widen or shrink a film in the transport direction and in a direction orthogonal to the transport direction.

In Patent Document 2, both right and left side edges of a sheet or film to be stretched are each gripped by a variable-pitch left and right clip whose longitudinal clip pitch changes with traveling movement. The clip position in the vertical direction of the tool is given a difference with respect to the moving direction of the sheet and film between the left clip and the right clip, and the vertical direction of the clip as the clip moves Describes a method of obliquely stretching a sheet or film that is obliquely stretched by increasing the clip pitch. Further, it is disclosed that according to such a method, oblique stretching can be performed without giving a difference in the movement trajectory length of the left and right clips.

However, according to the study of the present inventor, a straight-ahead oblique stretching device as described in Patent Document 2 is used for an organic electroluminescence (organic EL) display device having high contrast performance required from a liquid crystal display device. When using a long stretched film manufactured in this manner, color unevenness may occur.

International Publication No. 2007/111313 JP 2008-23775 A

The present invention is a circularly polarizing plate that can sufficiently suppress variation in the orientation angle of the optical axis even when oblique stretching is performed using a simultaneous biaxial stretching apparatus capable of saving space, and is provided in an image display device It aims at providing the manufacturing method of the elongate stretched film which can fully suppress generation | occurrence | production of the color nonuniformity in the case of using for.

One aspect of the present invention is to hold both ends of a thermoplastic long film with a plurality of gripping tools and transport the gripping tool gripping both ends at a constant speed, and grip one end. The first gripping tool is accelerated more than the second gripping tool gripping the other end, and the optical axis of the long film is tilted by causing the first gripping tool to precede the second gripping tool. And holding the both ends of the long film after the oblique stretching step while being held by the plurality of gripping tools, and gripping the long film by the second gripping tool. It is the manufacturing method of the elongate stretched film characterized by performing the relaxation process which relieve | moderates the bowing which generate | occur | produces by the said diagonal stretch process on the delay side currently performed.

The object, 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 conceptual diagram showing the state of a long film when obliquely stretched using a simultaneous biaxial stretching apparatus. FIG. 2 is a conceptual diagram for explaining an example of the manufacturing method according to the present embodiment. FIG. 3 is a conceptual diagram for explaining another example of the manufacturing method according to the present embodiment. FIG. 4 is a conceptual diagram for explaining another example of the manufacturing method according to the present embodiment. FIG. 5 is a schematic view showing an oblique stretching apparatus used in the manufacturing method according to the present embodiment. FIG. 6 is a schematic diagram illustrating an example of a layer structure of an image display unit of an organic electroluminescence display device to which a long stretched film obtained by the manufacturing method according to the present embodiment can be applied.

According to the study of the present inventor, the cause of color unevenness that occurs when a long stretched film obtained by using the simultaneous biaxial oblique stretching method such as the method described in Patent Document 2 is analyzed. As a result, the occurrence of uneven color was confirmed on the delay side of the obtained long stretched film. Furthermore, as a result of detailed examination, it was confirmed that bowing of the optical axis of the long film occurred on the delay side of the long film. The bow of the optical axis was a convex bow on the upstream side in the conveyance direction of the long film. This is because the first gripping tool that grips the leading end of the long film precedes the second gripping tool that grips the end of the delay side. The force for inclining the axis is considered to be stronger than the force for inclining the optical axis on the delay side of the long film. The optical axis cannot be tilted sufficiently on the delay side of a long film with weak force to tilt the optical axis, and a convex bowing occurs on the delay side of the long film on the upstream side in the transport direction of the long film. I think that.

In addition, the leading side of the long film refers to a region from the center in the width direction of the long film to the end portion that is gripped by the first gripping tool that precedes the second gripping tool. Moreover, the delay side of a long film refers to the area | region from the center of the width direction of a long film to the edge currently hold | gripped with the 2nd holding tool delayed from a 1st holding tool.

In addition, the bowing is a phenomenon in which an optical axis such as a slow axis in the film plane is deformed in a bow shape in the longitudinal direction of the long film with respect to a desired optical axis.

Based on these findings, the present inventor has arrived at the present invention as follows.

In the method for producing a long stretched film according to an embodiment of the present invention, after gripping both ends of a thermoplastic long film with a plurality of gripping tools and transporting the gripping tools gripping the both ends at a constant speed, The first gripping tool gripping one end is accelerated more than the second gripping tool gripping the other end so that the first gripping tool precedes the second gripping tool. It is a method including at least an oblique stretching step of tilting the optical axis of the film. In addition, the process of conveying the gripping tool before the oblique stretching process at a constant speed corresponds to the constant speed conveying process. Moreover, the manufacturing method of the elongate stretched film which concerns on embodiment of this invention is after carrying out conveying the both ends of the said elongate film after the said diagonal stretch process, hold | grip with the said several holding tool after the diagonal stretch process. A transport process is provided. As the oblique stretching step, for example, while gripping and transporting both ends of a thermoplastic long film with a plurality of grippers, one end is gripped while stretching in the width direction of the long film. The process etc. which incline the optical axis of the said elongate film by making the 1st holding tool precede the 2nd holding tool which hold | gripped the other edge part, etc. are mentioned. And the manufacturing method of the elongate stretched film which concerns on this embodiment relieve | moderates the bowing generate | occur | produced by the said diagonal stretch process at the delay side currently hold | gripped with the said 2nd holding tool of the said elongate film in the said diagonal stretch process. This is a method of performing relaxation treatment.

According to such a manufacturing method, it is possible to suppress the deviation of the optical axis that occurs on the delay side of the long film due to this bowing by performing a treatment that reduces the bowing that occurs on the delay side of the long film. . Therefore, even when oblique stretching is performed using a simultaneous biaxial stretching apparatus capable of saving space, variation in the orientation angle of the optical axis can be sufficiently suppressed, and the circular polarizing plate provided in the image display device can be used. In this case, it is possible to produce a long stretched film that can sufficiently suppress the occurrence of uneven color.

In addition, the relaxation treatment for relaxing the bowing that occurs on the delay side (the delay side of the long film) where the second gripping tool of the long film is gripped is the bowing that occurs on the delay side of the long film, Since it is a convex bowing on the upstream side in the conveyance direction of the long film, a process of offsetting the bowing by giving a convex bowing on the downstream side in the conveyance direction of the long film, on the delay side of the long film, This is a process for reducing the convex bowing on the upstream side in the conveyance direction of the long film.

In addition, the long length here means that the length with respect to the width is 5 times or more, and preferably 10 times or more. That is, the long film refers to a film having a length of 5 times or more with respect to 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.

<Method for producing long stretched film>
Hereinafter, the manufacturing method of a elongate stretched film is demonstrated.

The method for producing a long stretched film of the present embodiment includes a simultaneous biaxial oblique stretching step, whereby a slow axis (orientation) is formed at an angle of more than 0 ° and less than 90 ° with respect to the width direction of the long film. A long stretched film having an axis) can be produced.

In the present embodiment, the simultaneous biaxial oblique stretching step includes a constant-velocity transporting step of gripping both ends of the long film with a plurality of gripping tools and transporting the gripping tools gripping the both ends at a constant speed, one end. The first gripping tool that grips the second film is accelerated more quickly than the second gripping tool that grips the other end, and the first gripping tool precedes the second gripping tool, thereby setting the optical axis of the long film. An oblique stretching step including a step of inclining, and a post-conveying step of conveying both ends of the long film after the oblique stretching step while being held by the plurality of gripping tools. The “simultaneous biaxial oblique stretching process” in the present embodiment means a process from gripping a long film with a gripping tool to releasing the long film from the gripping tool.

First, the simultaneous biaxial oblique stretching process in the method for producing a long stretched film will be described.

In the simultaneous biaxial oblique stretching step, the long film is stretched in an oblique direction with respect to the width direction from the time when it is released by the gripping tool to the width direction of the long film. Thus, a slow axis (orientation axis) is provided at a desired angle greater than 0 ° and less than 90 °. In the method for producing a long stretched film, a long stretched film having a desired length can be produced by continuously supplying the long film to the simultaneous biaxial stretching step. In addition, the manufacturing method of a elongate stretched film is such that after the elongate film is formed, it is wound around a core once to form a wound body (also referred to as an original fabric) and then supplied to the simultaneous biaxial oblique stretching step. Or you may supply to a simultaneous biaxial diagonal stretch process continuously from a film forming process, without winding up the elongate film after film forming. Continuously performing the film forming step and the simultaneous biaxial oblique stretching step can feed back the film thickness and optical value results after stretching, change the film forming conditions, and obtain a desired long stretched film. It is preferable because it is possible.

In this embodiment, the angle with respect to the width direction of the long film is an angle in the film plane. The slow axis is expressed only in the stretching direction or the direction perpendicular to the stretching direction when the stretching is performed only in the longitudinal stretching or the lateral stretching and the oblique stretching is not performed. On the other hand, in the manufacturing method of the present embodiment, by performing stretching at an angle of more than 0 ° and less than 90 ° with respect to the stretching direction of the long film, a long axis having a slow axis in such an oblique direction. A stretched film can be produced.

In addition, in the simultaneous biaxial oblique stretching process, the occurrence of bowing on the delay side of the long stretched film is considered to be due to the following factors. Specifically, as shown in FIG. 1, it is considered that bowing occurs. In addition, FIG. 1 is the schematic which shows the state of a elongate film at the time of carrying out diagonal stretch using a simultaneous biaxial stretching apparatus.

As shown in FIG. 1, oblique stretching of a long film using a simultaneous biaxial oblique stretching apparatus is performed while holding both ends of the long film 11 with a plurality of

gripping tools

12 and 13 and transporting them. The film is stretched in the width direction of the long film by gradually increasing the distance between the first gripping tool 12 that grips the end and the second gripping tool 13 that grips the other end. That is, it stretches transversely. During the lateral stretching, the first gripping tool 12 is preceded by the second gripping tool 13 by gradually increasing the distance between the adjacent first gripping tools 12. As a result, the slow axis (optical axis) 14 of the long film 11 is inclined. In the present embodiment, when simply referred to as “oblique stretching process”, the distance between the first gripping tools 12 is gradually increased so that the first gripping tool 12 precedes the second gripping tool 13, thereby causing a slow axis. It shall refer to the process of inclining. After the oblique stretching step, the distance between the adjacent second gripping tools 13 may be increased so that the distance between the adjacent first gripping tools 12 and the distance between the second gripping tools 13 are equal. Such a step of gradually increasing the distance between the second gripping tools 13 is included in the “post-transfer step”.

Since the first gripping tool 12 that grips the leading end of the long film 11 precedes the second gripping tool 13, the leading side of the long film 11 is longer than the delay side of the long film 11. A large force is applied in the conveying direction of the scale film 11. Thereby, the optical axis 14 on the leading side of the long film can be sufficiently inclined. On the other hand, since the force applied to the delay side of the long film 11 is relatively weak, the optical axis 14 on the delay side of the long film cannot be sufficiently inclined. As a result, bowing occurs on the optical axis 14 on the delay side of the long film, and it is displaced from the desired optical axis 15. When the distance between the adjacent second gripping tools 13 is increased, the distance between the adjacent first gripping tools 12 is gradually increased and then gradually increased.

Even when the stretching in the width direction is not performed, bowing occurs on the optical axis 14 on the delay side of the long film, and the desired optical axis 15 is deviated.

On the other hand, in the case of simultaneous biaxial vertical / horizontal stretching, there is no great difference in the force applied in the transport direction in the width direction of the long film, so the above bowing occurs and the desired There is almost no deviation from the optical axis 15.

From the above, the above axial misalignment does not necessarily occur when using the simultaneous biaxial stretching apparatus, but is a problem that occurs when oblique stretching is performed using the simultaneous biaxial stretching apparatus. As a result of the study by the present inventors, it has been newly found.

And the manufacturing method of the elongate stretched film which concerns on this embodiment performs the relaxation process which relieve | moderates the bowing which generate | occur | produces on the delay side of a elongate film by the diagonal stretch process which precedes a 1st holding tool as mentioned above. Thus, the above problem is solved. That is, even when oblique stretching is performed using a simultaneous biaxial stretching apparatus capable of saving space, variation in the orientation angle of the optical axis can be sufficiently suppressed, and the circular polarizing plate provided in the image display apparatus can be used. In this case, it is possible to produce a long stretched film that can sufficiently suppress the occurrence of uneven color.

In addition, the oblique stretching process in the present embodiment may be a process in which the first gripping tool precedes the second gripping tool to incline the optical axis of the long film. After the oblique stretching step, as described above, the post-conveying step includes a step of conveying while holding both ends of the long film with the plurality of gripping tools. After the distance between the first gripping tools is widened before the second gripping tool, the distance between the adjacent second gripping tools is widened so that the traveling speeds of the first gripping tool and the second gripping tool are the same. It is preferable to have such a process. By doing so, the first gripping tool is preceded to incline the optical axis of the long film, and then the traveling speed of the second gripping tool is increased to increase the travel speed of the second gripping tool. The traveling speeds of the first gripping tool and the second gripping tool can be made the same. Thereby, the optical axis of the long film can be inclined, and furthermore, since the speed when the holding tool is opened is constant, the occurrence of wrinkles or the like in the long stretched film can be suppressed.

Further, the relaxation treatment is not particularly limited as long as it can relax the bowing that occurs on the delay side of the long film. As described above, the bowing generated here is a convex bowing on the upstream side in the conveyance direction of the long film. Therefore, as the relaxation process, specifically, the process of offsetting the convex bowing on the upstream side in the transport direction by providing the convex bow on the downstream side in the transport direction of the long film on the delay side of the long film And a process for reducing the convex bowing on the upstream side in the transport direction. For example, a process as described later can be given.

First, as an example of the relaxation treatment, as shown in FIG. 2, on the delay side of the long film 11, the temperature downstream from the oblique stretching step in the conveying direction of the long film 11 (downstream temperature) is long. The process which makes it lower than the temperature (upstream temperature) of the upstream in the said diagonal stretch process in the conveyance direction of the scale film 11 or the said diagonal stretch process is mentioned. That is, the temperature on the delay side of the long film 11 after the first gripping tool 12 is advanced (the temperature after the preceding) of the long film 11 before or before the first gripping tool 12 is advanced. A process of lowering the temperature on the delay side (preceding temperature) can be mentioned. That is, the process which makes upstream temperature (preceding temperature) higher than downstream temperature (preceding temperature) is mentioned. By doing so, on the delay side of the long film 11, the upstream side in the transport direction of the long film 11 is softened from the downstream side. Thereby, even if the tension in the transport direction (transport tension) applied to the long film 11 is uniform in the width direction, the delay side of the long film 11 is softened. Even if the force applied to the delay side of the long film 11 is relatively weak due to the stretching in the oblique direction, the optical axis on the delay side of the long film 11 is used as the long film. Can be shifted downstream in the transport direction. That is, a convex bow on the downstream side in the transport direction can be generated on the delay side of the long film 11 by the transport tension, and a convex bow on the upstream side in the transport direction generated on the delay side of the long film can be relaxed. The optical axis 16 of the long film 11 can be brought close to the desired optical axis 15. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. . FIG. 2 is a conceptual diagram for explaining an example of the manufacturing method according to the present embodiment. FIG. 2 is a drawing that focuses on the bowing, and omits modifications such as so-called neck-in.

Further, the processing for lowering the downstream temperature from the upstream temperature as described above is not particularly limited as long as the downstream temperature can be made lower than the upstream temperature. Specifically, there is a method of increasing the amount of hot air applied to the long film or increasing the temperature of the hot air when the first gripping tool is advanced or before it is advanced. Moreover, the method of reducing the quantity of the hot air applied to a elongate film after making a 1st holding | gripping tool precede, or reducing the temperature of a hot air is mentioned.

In the treatment for lowering the downstream temperature from the upstream temperature, the downstream temperature may be lower than the upstream temperature, but the temperature difference is preferably 1 to 35 ° C. The temperature is more preferably 30 ° C, and further preferably 5 to 20 ° C. That is, the downstream temperature is preferably 2 to 30 ° C. lower than the upstream temperature. Further, the upstream temperature is preferably 2 to 30 ° C. higher than the downstream temperature. With such a temperature difference, the bowing can be reduced without excessively softening or solidifying the long film more than necessary. Accordingly, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device.

Further, the downstream temperature preferably has the above relationship with the upstream temperature, but the downstream temperature and the upstream temperature are more preferably the following temperatures. The upstream temperature is preferably Tg to Tg + 30 ° C., and more preferably Tg to Tg + 25 ° C. The downstream temperature is preferably Tg-30 to Tg + 28 ° C, more preferably Tg-20 to Tg + 20 ° C.

Next, as another example of the relaxation treatment, as shown in FIG. 3, after the long film 11 is obliquely stretched, that is, after the first gripping tool 12 is preceded, the delay side of the long film 11 is processed. The process of extending in the width direction of the long film 11 in a state where the temperature (delay side temperature) is higher than the temperature on the preceding side (preceding side temperature) on which the first gripping tool 12 of the long film is gripped. It is done. By doing so, since the delay side of the long film 11 is softer than the preceding side, the delay side is more easily deformed than the preceding side. In this state, the second gripping tool 13 is moved in a direction away from the first gripping tool 12, that is, stretched in the width direction, thereby suppressing the deformation on the leading side of the long film 11 and delaying. Only the side can be deformed. By doing so, bowing generated on the delay side of the long film can be relaxed, and the optical axis 16 of the long film 11 can be brought close to the desired optical axis 15. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. . FIG. 3 is a conceptual diagram for explaining an example of the manufacturing method according to the present embodiment. FIG. 3 is a drawing that focuses on the bowing, and omits modifications such as so-called neck-in.

In addition, as described above, the process of transverse stretching in a state where the delay side temperature is higher than the preceding side temperature can make the delay side temperature higher than the preceding side temperature, and in that state, the transverse stretching is performed. If it is possible, there is no particular limitation. Specifically, a method of increasing the amount of hot air applied to the delay side of the long film or increasing the temperature of the hot air can be mentioned. Moreover, the method of reducing the quantity of the hot air which hits the front side of a long film, or lowering | hanging the temperature of a hot air is mentioned. And the process of carrying out the transverse stretch in the state which made the delay side temperature higher than the preceding side temperature can apply normal transverse stretch.

Further, the process of transverse stretching in a state where the delay side temperature is higher than the preceding side temperature may be a process that satisfies this condition, but first, the temperature difference is preferably 1 to 50 ° C., The temperature is more preferably 2 to 40 ° C, and further preferably 5 to 30 ° C. The delay side temperature is preferably 2 to 40 ° C. higher than the preceding side temperature. With such a temperature difference, it is possible to carry out lateral stretching for relaxing the bowing without excessively softening or solidifying the long film excessively.

Further, the draw ratio (stretch ratio in the transverse stretching process) at this time is preferably 1.01 to 1.5 times, more preferably 1.05 to 1.3 times, More preferably, it is ˜1.25 times. With such a stretching ratio, an extremely thin region is formed in the long stretched film, or the occurrence of defects such as wrinkles is suppressed, and the optical axis of the long film is set to an optical axis having a desired orientation angle. be able to. From these, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. it can.

Also, the relationship between the leading side temperature and the delay side temperature preferably satisfies the above relationship, but the leading side temperature and the delay side temperature are more preferably the following temperatures. The leading side temperature is preferably Tg to Tg + 30 ° C., and more preferably Tg to Tg + 25 ° C. The delay side temperature is preferably Tg + 1 to Tg + 80 ° C., and more preferably Tg + 2 to Tg + 65 ° C.

Next, as another example of the relaxation processing, as shown in FIG. 4, the transport tension on the delay side of the long film 11 (delay side transport tension) is set to the transport tension on the front side of the long film 11 (previous side). For example, a process of making the tension higher than (conveying tension). By doing so, the optical axis on the delay side of the long film 11 can be shifted to the downstream side in the transport direction of the long film. That is, bowing that occurs on the delay side of the long film can be relaxed, and the optical axis 16 of the long film 11 can be brought close to the desired optical axis 15. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. . FIG. 4 is a conceptual diagram for explaining an example of the manufacturing method according to the present embodiment. FIG. 4 is a drawing that focuses on the bowing, and omits modifications such as so-called neck-in.

Further, the processing for making the delay side transport tension higher than the preceding side transport tension as described above is not particularly limited as long as the delay side transport tension can be made higher than the preceding side transport tension. Specifically, as a transport roller for transporting a long film after oblique stretching, a method using a roller as described below, in which the material constituting the surface is composed of two or more materials different in the width direction of the long film Etc. Examples of the roller used in such a method include a roller in which a portion that contacts the delay side of the long film is made of a material that has a stronger conveying force for the long film than a portion that contacts the leading side of the long film. . More specifically, a roller or the like in which a portion in contact with the delay side of the long film and a portion in contact with the leading side of the long film are made of a material having a high friction coefficient can be used. Other methods include providing a tension application step in the step after stretching the long stretched film, and providing a plurality of nip rolls or the like installed in the width direction in the tension application step. By the said structure, the tension | tensile_strength difference given can be given so that the tension | tensile_strength provided by taking up of a elongate stretched film may differ in each roll part. For example, if it is considered that it is composed of two roll parts, (1) the rotational speed of each roll is made different, (2) the positional relationship between the two rolls is changed relatively (for example, relative to roll A) By moving the roll B to the upstream side or the downstream side, the tension applied to the long stretched film can be made different between the two roll portions.

In addition, in the processing for making the delay side conveyance tension higher than the preceding side conveyance tension, it is only necessary that the delay side conveyance tension can be made higher than the preceding side conveyance tension, but the difference in the conveyance tension is 5 to 200 N / m. It is preferably 10 to 150 N / m. Further, it is preferable that the delay-side transport tension is 5 to 200 N / m higher than the preceding-side transport tension. With such a difference in transport tension, the optical axis of the long film can be changed to an optical axis having a desired orientation angle while suppressing occurrence of defects such as wrinkles in the long stretched film. Accordingly, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device.

(Oblique stretching device)
In order to impart an oblique orientation to the long film to be stretched in the present embodiment, a straight type oblique stretching apparatus is used. That is, the manufacturing method according to the present embodiment is performed using an oblique stretching apparatus capable of performing a simultaneous biaxial stretching oblique stretching method as described later. The oblique stretching apparatus used in the present embodiment includes gripping tool travel support tools on which a plurality of gripping tools that grip both ends of the long film travel on both ends of the traveling long film. This oblique stretching apparatus grips both ends of a long film sequentially supplied to the inlet of the apparatus with a gripping tool, guides the long film into a heating zone, and at an arbitrary temperature at which the long film can be stretched. Biaxial stretching can be carried out simultaneously in the vertical and horizontal directions by bringing the gripping tool gripping one end of the long film ahead of the gripping tool gripping the other end of the long film while heating. The oblique stretching apparatus includes a heating device that heats the long film, a pair of gripping tool travel support tools on the left and right that the gripping tool for transporting the long film travels, and the gripping tool travel support tool. And a number of gripping tools that travel.

Here, the simultaneous biaxially extending oblique stretching method here refers to holding both ends in the width direction of the supplied long film with each gripping tool and transporting the long film while moving each gripping tool. A method of stretching a long film in an oblique direction with respect to the width direction by making the moving speed of one gripping tool different from the moving speed of the other gripping tool while keeping the conveying direction of the long film constant Say. The specific method of simultaneous biaxial stretching and the mechanism of the oblique stretching apparatus will be described later.

The gripping tool travel support tool has an endless continuous track, and the gripping tool that has released the grip of the long stretched film at the exit of the stretching device is sequentially returned to the grip start point by the gripping tool travel support tool. It is configured.

The gripping tool travel support tool is, for example, a form in which an endless guide rail includes a gripping tool. That is, the gripping tool travels along the path of the gripping tool travel support tool itself.

Also, the route pattern may be a rail pattern when the gripping tool travel support tool is a guide rail.

Further, the number of gripping tools provided in each gripping tool travel support tool is not particularly limited, but it is preferable that the same number of gripping tools on the left and right.

In this embodiment, the traveling speed of the gripping tool, that is, the transport speed of the long film can be selected as appropriate, and is preferably 1 to 150 m / min. With such a speed, local stress applied to the end of the film can be suppressed, wrinkles and shifts that can occur at the end of the film are suppressed, and as a non-defective product out of the total width of the film obtained after completion of stretching. The effective width obtained tends to be wide.

Further, when the conveying speed of the long film is set to a relatively high speed of 7 to 150 m / min, and further 20 to 150 m / min, the production efficiency of the long stretched film is increased. However, if the transport speed of the long film is such a high speed, the difference in force applied between the leading side and the delay side tends to increase, and the optical axis tends to be misaligned. If it is the manufacturing method which concerns on, the axial shift of an optical axis can fully be suppressed. Accordingly, it is possible to efficiently produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. . Accordingly, the conveying speed of the long film can be appropriately selected, but is preferably 7 to 150 m / min, more preferably 20 to 150 m / min.

In the present embodiment, as will be described later, the gripping tool that travels on one gripping tool travel support tool precedes the gripping tool that travels on the other gripping tool travel support tool only in some sections. Travel speed is accelerated. Except for this accelerated section, at least the difference in travel speed between the gripper pair holding the long film is usually 1% or less, preferably 0.5% or less, more preferably 0.1% of the travel speed. And can be adjusted at substantially constant speed. This is because if there is a difference in running speed between the left and right sides of the long stretched film at the exit of the stretching process, wrinkles and shifts at the exit of the stretching process are likely to occur. For this reason, it is preferable that the speeds of the left and right gripping tools constituting the gripping tool pair are substantially constant.

The length (full length) of the gripping tool travel support tool is not particularly limited, and may be the same or different.

Examples of the oblique stretching apparatus include a linear motor system, a pantograph system, and a motor chain drive system. For example, in the case of the pantograph system, an endless link device composed of a plurality of equal-length link devices formed in a fold shape is provided, and the endless link device is driven by an inlet-side sprocket so that it is arranged in the traveling direction. The guide rail is guided, and the distance between the gripping tools is gradually increased to travel. Further, the gripping tool is configured to be driven by the outlet side sprocket and return to the inlet side sprocket.

The gripper travels on an endless gripper travel support tool. The gripper grips and stretches the long film supplied at the grip start point, and then releases the long stretched film at the grip release point. The separation distance between the gripping tool pair at the gripping start point corresponds to the width of the supplied long film.

In this embodiment, when the oblique stretching apparatus for producing a long film is divided from the viewpoint of temperature, the long film sequentially passes through a heating zone having a preheating zone, a stretching zone, and a heat fixing zone of the oblique stretching apparatus; Become.

The preheating zone is a zone that includes a part of the constant-velocity conveyance process in the simultaneous biaxial oblique stretching process, and in the heating zone inlet section, the section in which the distance between the gripping tools gripping both ends is kept constant. Point. In the latter half of the constant speed conveyance process, a process of stretching in the width direction may be included before the oblique stretching process, but such a process is included in a stretching zone described later.

The stretching zone is a zone for performing an oblique stretching step in the simultaneous biaxial oblique stretching step, and refers to a section until the gap between the gripping tools gripping both ends of the long film starts and reaches a predetermined interval. In the present embodiment, the process includes a step of stretching in the oblique direction in the stretching zone, but is not limited to stretching in the oblique direction. You may extend | stretch in the width direction. After the longitudinal stretching, the stretching may be performed obliquely, or after the oblique stretching, the longitudinal stretching may be further performed. That is, in the stretching zone, longitudinal stretching, stretching in the width direction, and stretching in the oblique direction may be appropriately combined. Therefore, the oblique stretching zone includes a part of the constant speed conveyance process, the oblique stretching process, and a part of the post-conveying process in the simultaneous biaxial oblique stretching process.

The heat setting zone refers to the section in which the gripping tools at both ends run parallel to each other during the period when the spacing between the gripping tools after the stretching zone becomes constant again. Therefore, the heat setting zone includes a part of the post-conveying step in the simultaneous biaxial oblique stretching step. You may pass through the area (cooling zone) by which the temperature in a zone is set to below the glass transition temperature Tg degreeC of the thermoplastic resin which comprises a elongate film, after passing through a heat setting zone. At this time, in consideration of the shrinkage of the long stretched film due to cooling, a rail pattern that narrows the gap between the opposing grippers in advance may be used.

In this embodiment, for the purpose of adjusting the mechanical properties and optical properties of the long film, transverse stretching and longitudinal stretching may be performed as necessary in the steps before and after introducing the long film into the oblique stretching apparatus.

The temperature in each zone is Tg to Tg + 30 ° C. in the preheating zone, Tg to Tg + 30 ° C. in the stretching zone, and Tg−Tg + 30 ° C. in the cooling zone, with respect to the glass transition temperature Tg of the thermoplastic resin constituting the long film. It is preferably set to 30 to Tg + 30 ° C.

Note that a temperature difference in the width direction may be applied in the stretching zone in order to control thickness unevenness in the width direction. 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 30 to 100% and the length of the fixed zone is usually 30 to 100% with respect to the length of the stretching zone. . Further, a cooling zone may be provided after the heat setting zone.

The stretching ratio in this stretching zone is preferably in the following range. The stretching ratio is the ratio of the length after stretching to the length before stretching.

First, the draw ratio in the machine direction (conveyance direction) is preferably 1.05 to 3 times, more preferably 1.1 to 2 times, and preferably 1.15 to 1.5 times. Further preferred. Thus, when the stretching ratio in the machine direction is stretched to a relatively high ratio, the orientation angle of the optical axis can be set in a wide range, and the film thickness can be set relatively freely. However, when the stretching ratio in the longitudinal direction is relatively high as described above, the optical axis tends to be misaligned normally. However, the manufacturing method according to the present embodiment has sufficient misalignment of the optical axis. Can be suppressed. Therefore, it is possible to reduce the variation in the orientation angle of the optical axis, and to produce a long stretched film with various orientation angles and film thicknesses that can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. Can be manufactured.

The stretching ratio in the transverse direction (width direction) is preferably 1.3 to 3 times, more preferably 1.5 to 2.8 times. 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.

Next, a specific mechanism for obliquely stretching a long film will be described in detail. FIG. 5 is a schematic diagram showing an oblique stretching apparatus T used in the manufacturing method according to the present embodiment. However, this is an example, and the present embodiment is not limited to this.

As shown in FIG. 5, the long film F is an entrance of the oblique stretching apparatus T (a gripping start point at which the gripper grips the long film F, and a straight line connecting the gripping start points is denoted by a reference symbol A. 2), both ends thereof are gripped by the left and right gripping tools (a pair of gripping tools), and are transported as the gripping tool travels.

The gripping tool pair is an entrance of the oblique stretching device T, and the left and right gripping tools C1 (first gripping tool) and gripping tool C2 (second gripping) that are opposed in a direction substantially perpendicular to the transport direction of the long film. Ingredients). The left and right gripping tool C1 and gripping tool C2 travel along the gripping tool travel support tool R1 and gripping tool travel support tool R2 formed substantially in contrast, respectively, and the position at the end of stretching (the gripping tool releases gripping). The long stretched film gripped by the grip release point and indicated by the reference sign B) is released.

Specifically, in the oblique stretching apparatus T of the present embodiment, the gripping tool C1 and the gripping tool C2 each grip both ends of the long film F at the grip start point A, and start conveying the long film F. . When the gripping tool C1 travels to the position indicated by the reference symbol P1, the gripping tool C1 is accelerated to precede the gripping tool C2. A mechanism for accelerating the gripping tool C1 will be described later. The acceleration of the gripper C1 is continued up to the position indicated by the reference symbol P2. While the gripping tool C1 is accelerating, the traveling speed of the gripping tool C2 is maintained. Therefore, the gripping tool C1 travels on the gripping tool travel support tool R1 prior to the gripping tool C2, and moves to the downstream side in the transport direction of the long film F. Reference sign P3 indicates the position of the gripping tool C2 when the gripping tool C1 reaches P2.

The gripping tool C1 that has reached P2 travels to the grip release point B while maintaining the speed. On the other hand, the gripping tool C2 that has reached P3 is accelerated in the same manner as the gripping tool C1. A mechanism for accelerating the gripping tool C2 will be described later. The acceleration of the gripping tool C2 is continued until P4. As a result, the speed of the gripping tool C2 reaching P4 is the same as the speed of the preceding gripping tool C1. The gripping tool C2 that has reached P4 travels to the grip release point B while maintaining the speed.

As shown in FIG. 5, from P1 to P4, the distance between the gripping tool travel support tool R1 and the gripping tool travel support tool R2 is increased. Therefore, when the gripping tool C1 and the gripping tool C2 that grip the long film F travel from P1 to P4, the long film F is stretched in the lateral direction (TD direction, width direction). Further, as described above, the gripping tool C1 is accelerated at P1 and precedes the gripping tool C2. The distance that the gripping tool C1 travels after acceleration (P1 to gripping release point B) is longer than the distance that the gripping tool C2 travels after acceleration (P3 to gripping release point B). Therefore, the gripping tool C1 reaches the grip release point B ahead of the gripping tool C2. Therefore, the long film F is stretched in the longitudinal direction (MD direction, longitudinal direction). As a result, the long film F is biaxially stretched simultaneously in the vertical and horizontal directions, and orientation is imparted in an oblique direction.

In the present embodiment, the gripping tool C1 and the gripping tool C2 move at a constant speed from the gripping start point A to P1, and only the gripping tool C1 is accelerated at P1. The configuration is not limited to this. That is, the position where acceleration is started and the acceleration can be appropriately set so that a desired orientation angle can be obtained. For example, the gripping tool C1 may start to be accelerated at the gripping start point A, or the gripping tool C1 may be accelerated at a constant acceleration from the gripping start point A to the gripping release point B.

In the present embodiment, the case where the gripping tool C2 is accelerated so as to become the same speed as the gripping tool C1 from P3 to P4 is illustrated, but the traveling speed of the gripping tool C2 may not be adjusted in this way. That is, in order to give the long film F an oblique orientation, the gripping tool C1 may reach the grip release point B in advance. Therefore, it is not necessary to accelerate the gripping tool C2, and even when accelerating, it is not necessary to accelerate until the gripping tool C1 is at the same speed. In addition, by adjusting the gripping tool C1 and the gripping tool C2 to travel at a constant speed at the grip release point B, the stress applied to the long stretched film at the time of grip release (contraction force toward the center of the width) is canceled out. For this reason, axial displacement is unlikely to occur in the obtained long stretched film.

The method of accelerating the gripping tool C1 and the gripping tool C2 is not particularly limited, and is a method that can change the pitch of the continuous gripping tool C1 or the gripping tool C2 (the distance between the gripping tools in the transport direction of the long film F). I just need it. For example, as a method of changing the pitch, for example, a method using a pantograph mechanism or a linear guide mechanism can be employed.

(Processes other than simultaneous biaxial oblique stretching process)
Next, other steps that can be adopted by the present embodiment will be described. In addition, this embodiment should just have the above-mentioned simultaneous biaxial diagonal extending process, and it does not specifically limit about other processes. For this reason, the other steps described below are examples, and the design can be changed as appropriate. Examples of the other processes include a film forming process for forming a long film, a winding process for winding the long stretched film after the simultaneous biaxial oblique stretching process, and the like.

(Film forming process)
The film forming step is a step of forming a thermoplastic long film.

The long film formed in this embodiment is not particularly limited as long as it is thermoplastic. Specifically, the long film includes a thermoplastic resin and includes a long film that is thermoplastic. The long film may be a film made of a thermoplastic resin.

For example, when using a stretched long stretched film for optical applications, a film made of a resin having a property transparent to a desired wavelength is preferable. Such resins include polycarbonate resins, polyether sulfone resins, polyethylene terephthalate resins, polyimide resins, polymethyl methacrylate resins, polysulfone resins, polyarylate resins, polyethylene resins, polyvinyl chloride resins. Examples thereof include resins, olefin polymer resins having an alicyclic structure, and cellulose ester resins. Among these, polycarbonate resins, olefin polymer resins having an alicyclic structure, and cellulose ester resins are preferable from the viewpoint of transparency and mechanical strength, and polycarbonate resins are more preferable. That is, it is preferable to use a polycarbonate film as the long film. By doing so, it is possible not only to suppress variation in the orientation angle of the optical axis, but also to produce a long stretched film excellent in transparency and mechanical strength.

<Polycarbonate resin>
Various polycarbonate resins can be used without particular limitation, and aromatic polycarbonate resins are preferable from the viewpoint of chemical properties and physical properties, and polycarbonates having a fluorene skeleton and bisphenol A polycarbonate resins are particularly preferable. Among these, those using a bisphenol A derivative in which a benzene ring, a cyclohexane ring, an aliphatic hydrocarbon group and the like are introduced into bisphenol A are more preferable. Furthermore, a polycarbonate resin having a structure in which the anisotropy in the unit molecule is reduced, obtained by using a derivative in which the functional group is introduced asymmetrically with respect to the central carbon of bisphenol A, is particularly preferable. As such a polycarbonate resin, for example, two methyl groups in the center carbon of bisphenol A are replaced by benzene rings, and one hydrogen of each benzene ring of bisphenol A is centered by a methyl group or a phenyl group. A polycarbonate resin obtained by using an asymmetrically substituted carbon is particularly preferable. Specifically, 4,4′-dihydroxydiphenylalkane or a halogen-substituted product thereof can be obtained by a phosgene method or a transesterification method. For example, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenyl Examples include ethane and 4,4'-dihydroxydiphenylbutane. In addition to these, specific examples of polycarbonate resins include, for example, JP-A-2006-215465, JP-A-2006-91836, JP-A-2005-121813, JP-A-2003-167121. And polycarbonate resins described in JP-A No. 2009-126128, JP-A 2012-67300, and International Publication No. 2000/026705.

The polycarbonate resin may be used by mixing with a transparent resin such as polystyrene resin, methyl methacrylate resin, and cellulose acetate resin. Moreover, you may laminate | stack the resin layer containing a polycarbonate-type resin on the at least one surface of the resin film formed using the cellulose acetate type resin.

The polycarbonate resin preferably has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate (measured under conditions of 23 ° C. water and 24 hours) of 0.3% or less. Yes. Moreover, Tg is 120 degreeC or more, and a water absorption rate is 0.2% or less more preferable.

The polycarbonate-based resin film that can be used in the present embodiment can be formed by a known method, and among them, the solution casting method and the melt casting method are preferable.

<Alicyclic olefin polymer resin>
Examples of the alicyclic olefin polymer-based resin include cyclic olefin random multi-component copolymers described in JP-A No. 05-310845, hydrogenated polymers described in JP-A No. 05-97978, and JP-A No. 11 The thermoplastic dicyclopentadiene ring-opening polymer and hydrogenated product thereof described in JP-A-124429 can be employed.

The olefin polymer resin having an alicyclic structure will be described more specifically. The alicyclic olefin polymer resin is a polymer having an alicyclic structure such as a saturated alicyclic hydrocarbon (cycloalkane) structure or an unsaturated alicyclic hydrocarbon (cycloalkene) structure. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but when it is usually in the range of 4 to 30, preferably 5 to 20, more preferably 5 to 15, the mechanical strength, The properties of heat resistance and formability of the long film are highly balanced and suitable.

The proportion of the repeating unit containing the alicyclic structure in the alicyclic olefin polymer may be appropriately selected, but is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight. That's it. When the ratio of the repeating unit having an alicyclic structure in the alicyclic polyolefin resin is within this range, the transparency and heat resistance of an optical material such as a retardation film obtained from the long stretched film of the present embodiment are improved. Therefore, it is preferable.

Examples of the olefin polymer resin having an alicyclic structure include norbornene resins, monocyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins, and hydrides thereof. Among these, norbornene-based resins can be suitably used because of their good transparency and moldability.

Examples of the norbornene-based resin include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and another monomer, a hydride thereof, and a norbornene structure. And an addition copolymer of a monomer having a norbornene structure and an addition copolymer of another monomer or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability and lightness. Can be used.

As a method for forming a long film using the above preferred norbornene-based resin, a solution casting method or a melt extrusion method is preferred. Examples of the melt extrusion method include an inflation method using a die, but a method using a T die is preferable in terms of excellent productivity and thickness accuracy.

The extrusion molding method using a T-die is a method for maintaining retardation and orientation by a method of keeping a molten thermoplastic resin in a stable state when closely contacting a cooling drum as described in JP-A-2004-233604. A long film with small variations in optical properties such as corners can be manufactured.

Specifically, 1) When producing a long film by the melt extrusion method, 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; 2) melting When producing a long film by extrusion, the enclosure member covers from the die opening to the first cooling drum that is in close contact, and the distance from the enclosure member to the die opening or the first contact cooling drum is 100 mm or less. Method: 3) Method of heating the temperature of the atmosphere within 10 mm to a specific temperature from the sheet-like thermoplastic resin extruded from the die opening when producing a long film by the melt extrusion method; A sheet-like thermoplastic resin extruded from a die so as to satisfy the above condition is taken into close contact with a cooling drum under a pressure of 50 kPa or less; A method in which a wind having a speed difference of 0.2 m / s or less from the cooling speed of the cooling drum that is first brought into close contact with the sheet-like thermoplastic resin extruded from the die opening is produced. It is done.

This long film 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.

<Cellulose ester resin>
Preferred examples of the cellulose ester-based resin include those characterized by containing cellulose acylate satisfying the following formulas (1) and (2) and containing a compound represented by the following general formula (A). It is done.

Formula (1) 2.0 <= Z1 <3.0
Formula (2) 0.5 <= X
(In Formula (1) and Formula (2), Z1 represents the total acyl substitution degree of cellulose acylate, and X represents the sum of the propionyl substitution degree and butyryl substitution degree of cellulose acylate.)

(Compound of general formula (A))
Hereinafter, the general formula (A) will be described in detail.

In the general formula (A), L ₁ and L ₂ each independently represent a single bond or a divalent linking group.

Examples of L ₁ and L ₂ include the following structures. (The following R represents a hydrogen atom or a substituent.)

L ₁ and L ₂ are preferably —O—, —COO—, and —OCO—. R ₁ , R ₂ and R ₃ each independently represent a substituent.

R ₁ and R ₂ are preferably a substituted or unsubstituted phenyl group or a substituted or unsubstituted cyclohexyl group. More preferred are a phenyl group having a substituent and a cyclohexyl group having a substituent, and further preferred are a phenyl group having a substituent at the 4-position and a cyclohexyl group having a substituent at the 4-position.

R ₃ is preferably a hydrogen atom, halogen atom, alkyl group, alkenyl group, aryl group, heterocyclic group, hydroxyl group, carboxyl group, alkoxy group, aryloxy group, acyloxy group, cyano group, amino group, More preferably, they are a hydrogen atom, a halogen atom, an alkyl group, a cyano group, and an alkoxy group.

Wa and Wb represent a hydrogen atom or a substituent, but (I) Wa and Wb may be bonded to each other to form a ring, and (II) at least one of Wa and Wb may have a ring structure Or (III) at least one of Wa and Wb may be an alkenyl group or an alkynyl group.

The above substituents may be further substituted with the above groups.

(1) When Wa and Wb are bonded to each other to form a ring, the following structures may be mentioned.

When Wa and Wb are bonded to each other to form a ring, it is preferably a nitrogen-containing 5-membered ring or a sulfur-containing 5-membered ring, particularly preferably represented by the following general formula (1) or general formula (2). It is a compound.

In the general formula (1), A ₁ and A ₂ each independently represent —O—, —S—, —NRx— (Rx represents a hydrogen atom or a substituent) or CO—. The example of the substituent represented by Rx is synonymous with the specific example of the substituent represented by said Wa and Wb. Rx is preferably a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

In the general formula (1), X represents a nonmetallic atom belonging to Groups 14-16.

X is preferably = O, = S, = NRc, = C (Rd) Re. Here, Rc, Rd, and Re represent substituents, and examples thereof are synonymous with specific examples of the substituents represented by Wa and Wb.

_{_{_{_{L 1, L 2, R 1}}}} , R _{2, R} 3, n is _{_{_{_{L 1, L 2, R 1}}}} , same meanings as R _{2, R} 3, n in the general formula (A).

In the general formula (2), Q ₁ is —O—, —S—, —NRy— (Ry represents a hydrogen atom or a substituent), —CRaRb— (Ra and Rb represent a hydrogen atom or a substituent) or Represents —CO—. Here, Ry, Ra, and Rb represent substituents, and examples thereof are synonymous with the specific examples of the substituents represented by Wa and Wb.

Y represents a substituent.

Examples of the substituent represented by Y are the same as the specific examples of the substituent represented by Wa and Wb.

Y is preferably an aryl group, a heterocyclic group, an alkenyl group, or an alkynyl group.

Examples of the aryl group represented by Y include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a biphenyl group. A phenyl group and a naphthyl group are preferable, and a phenyl group is more preferable.

(2) In the general formula (A), a specific example when at least one of Wa and Wb has a ring structure is preferably the following general formula (3).

In the general formula (3), Q ₃ represents ═N— or ═CRz— (Rz represents a hydrogen atom or a substituent), and Q ₄ represents a nonmetallic atom belonging to Groups 14-16. Z represents a nonmetallic atom group that forms a ring with Q ₃ and Q ₄ .

The ring formed from Q ₃ , Q ₄ and Z may be further condensed with another ring.

The ring formed from Q ₃ , Q ₄ and Z is preferably a nitrogen-containing 5-membered ring or 6-membered ring condensed with a benzene ring.

(3) When at least one of Wa and Wb is an alkenyl group or an alkynyl group, a vinyl group having a substituent and an ethynyl group are preferable.

Among the compounds represented by the above general formula (1), general formula (2), and general formula (3), the compound represented by general formula (3) is particularly preferable.

The compound represented by the general formula (3) is superior in heat resistance and light resistance to the compound represented by the general formula (1), and is an organic solvent compared to the compound represented by the general formula (2). The solubility with respect to and the compatibility with a polymer are favorable.

The compound represented by the general formula (A) can be contained by appropriately adjusting the amount for imparting desired wavelength dispersibility and anti-bleeding property. The content is preferably 1 to 15% by mass, and particularly preferably 2 to 10% by mass. If it is in this range, sufficient wavelength dispersibility and bleeding prevention property can be imparted to the cellulose derivative.

In addition, the compound represented by general formula (A), general formula (1), general formula (2), and general formula (3) can be performed with reference to a known method. For example, the method described in Journal of Chemical Crystallography (1997); 27 (9); 512-526, JP 2010-31223 A, and JP 2008-107767 A is specifically exemplified. Etc.

<Cellulose acylate>
The cellulose acylate film that can be used in the present embodiment contains cellulose acylate as a main component.

The cellulose acylate film that can be used in the present embodiment preferably contains cellulose acylate in the range of 60 to 100% by mass with respect to the total mass of the film. In addition, the total acyl group substitution degree of cellulose acylate is 2 or more and less than 3, and more preferably 2.2 to 2.7.

Examples of the cellulose acylate include esters of cellulose and aliphatic carboxylic acids and / or aromatic carboxylic acids having about 2 to 22 carbon atoms, particularly esters of cellulose and lower fatty acids having 6 or less carbon atoms. Preferably there is.

The acyl group bonded to the hydroxyl group of cellulose may be linear or branched, and may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms described above is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The degree of propionyl substitution and the degree of butyryl substitution are preferred. Is a sum of 0.5 or more. The cellulose acylate preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

Specifically, cellulose acylate includes propionate group, butyrate group or phthalyl group in addition to acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate or cellulose acetate phthalate. Bound cellulose mixed fatty acid esters can be used. The butyryl group forming butyrate may be linear or branched.

In the present embodiment, cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate is particularly preferably used as the cellulose acylate.

In addition, the cellulose acylate according to the present embodiment preferably satisfies the following formula (i) and formula (ii) at the same time.

Formula (i) 2 ≦ X + Y <3
Formula (ii) 0 ≦ X <3
In the formula, Y represents the degree of substitution of the acetyl group, and X represents the degree of substitution of the propionyl group or butyryl group.

Also, in order to obtain optical properties that meet the purpose, resins having different degrees of substitution may be mixed and used. In this case, the mixing ratio is preferably 1:99 to 99: 1 (mass ratio).

Among the above, cellulose acetate propionate is particularly preferably used as the cellulose acylate. In cellulose acetate propionate, 0 ≦ Y ≦ 2.5 and 0.5 ≦ X ≦ 3 (where 2 ≦ X + Y <3) are preferable, and 0.5 ≦ Y ≦ 2 It is more preferable that 1 ≦ X ≦ 2 (where 2 ≦ X + Y <3). The substitution degree of the acyl group can be measured according to ASTM-D817-96.

There are no particular limitations on cellulose as a raw material for cellulose acylate, but examples include cotton linter, wood pulp, and kenaf. Moreover, the cellulose acylate obtained from them can be mixed and used at an arbitrary ratio.

Cellulose acylate can be produced by a known method. Specific examples of the synthesis method include the method described in JP-A No. 10-45804.

<Additives>
The long stretched film obtained according to the present embodiment 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 long stretched film is 80% or more, more preferably 90% or more, and further preferably 92% or more. preferable.

Additives that can be added include plasticizers, UV absorbers, retardation modifiers, antioxidants, deterioration inhibitors, peeling aids, surfactants, dyes, and fine particles. 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 a polarizing plate used in an image display device such as an organic EL display.

These compounds are preferably contained in an amount of 1 to 30% by mass, preferably 1 to 20% by mass, based on the cellulose ester. 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 and the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

<Retardation adjuster>
Examples of the compound to be added for adjusting the retardation include a retardation adjusting agent composed of an aromatic compound having two or more aromatic rings. Specific examples of the compounds include those described in the specification of European Patent 911,656A2. 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 the present embodiment has a cellulose ester and a substituent selected from a carboxyl group, a hydroxyl group, an amino group, an amide group, and a sulfo group, and has a weight average molecular weight in the range of 500 to 200,000. It is preferable to contain a polymer or oligomer of a certain vinyl compound. 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 long stretched film as a matting agent, whereby when the stretched film is long, conveyance and winding can be facilitated.

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 silicon dioxide particles preferably have a primary average particle diameter 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} 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.

(Long film production method)
The long film used in the manufacturing method according to the present embodiment can be formed by a known method, and examples thereof include a solution casting method and a melt casting method. Good.

Hereinafter, the solution casting method and the melt casting method will be described.

<Solution casting method>
In the solution casting method, a dope is prepared by dissolving a resin and an additive in an organic solvent, the dope is cast on a belt-shaped or drum-shaped metal support, and the cast dope is dried as a web. It is carried out by a step, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

The solution casting method is preferably used because it is excellent in suppressing coloration of the film, suppressing foreign matter defects, suppressing optical defects such as die lines, and having excellent flatness and transparency of the film.

The concentration of the resin in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of the resin is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass. The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

The surface temperature of the metal support in the casting process is set to −50 ° C. to a temperature at which the solvent boils and does not foam. Higher temperatures are preferable because the web can be dried faster, but if the temperature is too high, the web may foam or 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, but there are a method of blowing warm air or cold air, and a method of bringing hot water into contact 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 is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there.

Particularly, it is preferable to efficiently dry 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 long film (resin film) to exhibit good flatness, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60%. ˜130 mass%, particularly preferably 20˜30 mass% or 70˜120 mass%.

The amount of residual solvent 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 production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

Further, in the resin film drying step, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. The content is preferably 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

The organic solvent useful for forming the dope when the long film (resin film) according to this embodiment is produced by the solution casting method is not limited as long as it dissolves the resin and other additives simultaneously. Can be used.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, 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, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy, and when the proportion of alcohol is small, the role of promoting the dissolution of the resin in a non-chlorine organic solvent system also is there.

In the case of a cellulose ester-based resin film, particularly, a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, an acrylic resin, a cellulose ester resin, and acrylic particles. Is preferably a dope composition in which at least 15 to 45% by mass is dissolved.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

<Melt casting method>
The melt film forming method is a preferable film forming method from the viewpoints that it is 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. The melt film forming method refers to heating and melting a composition containing an additive such as a resin and a plasticizer to a temperature showing fluidity, and then casting the fluid melt containing the resin. Methods formed by melt casting can be classified into melt extrusion molding methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like. Among these, the melt extrusion method is preferable, in which a film having excellent mechanical strength and surface accuracy can be obtained.

It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded and pelletized in advance.

Pelletization may be performed by a known method. For example, dried resin, plasticizer, and other additives are fed to an extruder using a feeder and kneaded using a single-screw or twin-screw extruder, and then formed into a strand from a die. It can be done by extrusion, water cooling or air cooling and cutting.

Additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders.

A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

The extruder is preferably processed at as low a temperature as possible so that it can be pelletized so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

Using a single-screw or twin-screw type extruder, the melting temperature at the time of extrusion is about 200 to 300 ° C, filtered through a leaf disk type filter, etc. to remove foreign matter, and then formed into a film from the T die. The film is nipped by a cooling roll and an elastic touch roll, and solidified on the cooling roll.

When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

The extrusion flow rate is preferably carried out stably by introducing a gear pump. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. The stainless steel fiber sintered filter is a united stainless steel fiber body that is intricately intertwined and compressed, and the contact points are sintered and integrated. The density of the fiber is changed depending on the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

The film temperature on the touch roll side when the film is nipped by the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. A well-known roll can be used for the roll which has the elastic body surface used for such a purpose.

The elastic touch roll is also called a pinching rotator. As the elastic touch roll, a commercially available one can be used.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

The long film formed by the above method 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.

[Winding process]
The step of winding the long stretched film after the oblique stretching (winding step) is a step of winding the long stretched film after the oblique stretching step. Below, the film winding apparatus used for a winding process is demonstrated.

The winding device is provided at the outlet of the oblique stretching device. The winding device is not particularly limited as long as the long stretched film stretched by the oblique stretching apparatus can be wound. In this embodiment, the take-up tension T (N / m) of the long stretched film after stretching is adjusted between 100 N / m <T <300 N / m, preferably 150 N / m <T <250 N / m. It is preferable. When the take-up tension is 100 N / m or less, sagging and wrinkles of the long stretched film tend to occur, and the retardation and the profile in the width direction of the orientation axis may deteriorate. On the contrary, when the take-up tension is 300 N / m or more, the variation in the orientation angle in the width direction tends to be deteriorated, so that the width yield (taken efficiency in the width direction) may be 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 variation of the take-up tension T is ± 5% or more, there is a tendency that variations in the optical characteristics in the width direction and the flow direction become large. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll at the outlet of the oblique stretching apparatus, that is, the tension of the long stretched film is measured, and the value is made constant. A method of controlling the rotation speed of the take-up roll by a general PID control 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 tension of a long stretched film is measured. As the load cell, a known tensile type or compression type can be used.

The long film after the oblique stretching is released from the oblique stretching device outlet after being held by the gripper, and is wound up around the winding core (winding roll) to form a wound body of the long stretched film. Can do.

Further, if necessary, both ends of the film held by the holding tool of the oblique stretching apparatus may be cut before winding on the winding roll. The cutting may be performed at a time or may be performed in a plurality of times. Moreover, after winding up a long stretched film once, if necessary, a long stretched film is drawn out again, both ends of a long stretched film are cut | disconnected (trimmed), and it winds up again and winds up a long stretched film. It may be a round body. 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.

Also, a film thickness meter or an optical value measuring device capable of online measurement may be arranged in the middle of the arrangement of the transport roll.

In addition, before or after the arrangement of the conveyance rolls, or between a plurality of conveyance rolls, a neutralization device for neutralizing the long stretched film may be provided, or may be installed before the winding device. A well-known thing can be used for the said static elimination apparatus without a restriction | limiting.

[Manufacturing equipment]
The manufacturing apparatus of the elongate stretched film which concerns on other embodiment of this invention will not be specifically limited if it is a manufacturing apparatus which can implement | achieve the manufacturing method which concerns on this embodiment as mentioned above. Specifically, for example, a manufacturing apparatus provided with the oblique stretching apparatus can be used.

Using such a manufacturing apparatus, a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. Can be manufactured. That is, a film in which the variation in the orientation angle in the width direction of the obtained long stretched film is sufficiently suppressed can be obtained.

In addition, when this long stretched film is used in a circularly polarizing plate provided in an image display device having a very high contrast such as an organic electroluminescence display device, an image forming apparatus in which the occurrence of color unevenness is sufficiently suppressed can be obtained. .

[Long stretched film]
The manufacturing method according to the present embodiment uses a long film, for example, a long film formed by the above method.

Hereinafter, the long film used in the manufacturing method according to the present embodiment will be described.

The film thickness of the long film before oblique stretching is preferably 20 to 400 μm, more preferably 30 to 200 μm.

In this embodiment, the thickness unevenness σm in the flow direction of the long film supplied to the oblique stretching apparatus keeps the film take-up tension constant at the entrance of the oblique stretching apparatus described later, and stabilizes the optical characteristics such as the orientation angle and retardation. From the viewpoint of achieving the above, it is preferably less than 0.30 μm, more preferably less than 0.25 μm, and still more preferably less than 0.20 μm. If the thickness unevenness σm in the flow direction of the long film before oblique stretching is too large, variations in optical properties such as retardation and orientation angle of the long stretched film tend to be remarkably deteriorated. Here, σm is a value represented by an average value of the standard deviation σ in the flow direction at each width position.

Further, a film having a thickness gradient in the width direction may be supplied as the long film before oblique stretching. The gradient of the thickness of the long film before the oblique stretching is to stretch a film with various thickness gradients experimentally changed so that the film thickness at the position where stretching in the subsequent process is completed can be made the most uniform. This can be determined empirically. The gradient of the thickness of the long film before oblique stretching can be adjusted, for example, so that the end on the thick side is about 0.5 to 3% thicker than the end on the thin side. it can.

Further, the width of the long film before oblique stretching, that is, the length in the width direction of the long film subjected to the oblique stretching step is not particularly limited, but is preferably 200 to 3000 mm, more preferably 900 to 2700 mm. Is preferred. When such a wide long film is supplied to the oblique stretching step, the width of the obtained long stretched film is increased, and the utilization efficiency of the obtained long stretched film is increased. However, when such a long film having a wide width is supplied to the oblique stretching process, the area on the delay side of the long film is widened, bowing occurs on the delay side, and the optical axis tends to be misaligned. However, the manufacturing method according to the present embodiment can sufficiently suppress the axial deviation of the optical axis. Therefore, variation in the orientation angle of the optical axis can be further suppressed, generation of color unevenness when used in a circularly polarizing plate provided in an image display device can be further suppressed, and a wide elongated stretched film can be produced. Can do.

The width of the long film after oblique stretching is not particularly limited, but is preferably 500 to 4000 mm, more preferably 1000 to 3000 mm.

The preferable elastic modulus at the stretching temperature at the time of oblique stretching of the long film is represented by Young's modulus, and is preferably 0.01 Mpa or more and 5000 Mpa or less, more preferably 0.1 Mpa or more and 500 Mpa or less. 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.

As the long film before oblique stretching, a non-oriented film may be used, or a film having an orientation in advance may be supplied. Further, if necessary, the width distribution of the orientation of the long film before oblique stretching may be bowed, so-called bowing. In short, the orientation state of the long film before oblique stretching can be adjusted so that the orientation of the film at the position where stretching in the subsequent step is completed can be made desirable.

Further, the long stretched film obtained in the present embodiment only needs to be tilted in the range of the orientation angle larger than 0 ° and smaller than 90 °. That is, the optical axis may be greater than 0 ° and less than 90 ° with respect to the width direction of the long film. The orientation angle is preferably 30 ° or more and less than 90 °, and more preferably 40 ° or more and 60 ° or less. With such an orientation angle, oblique stretching is preferably performed, but the optical axis is likely to be displaced due to bowing that occurs on the delay side of the long film. However, the manufacturing method according to the present embodiment can sufficiently suppress the misalignment of the optical axis even with such an orientation angle. Therefore, manufacturing a long stretched film with various orientation angles that can further suppress variation in the orientation angle of the optical axis and can further suppress occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. Can do.

Further, the variation of the orientation angle θ of the long stretched film obtained in the present embodiment (difference between the maximum value and the minimum value of the orientation angle) is preferably less than 0.6 °, and preferably less than 0.4 °. More preferred. A long stretched film with a variation in orientation angle θ of less than 0.6 ° is bonded to a polarizer to obtain a circularly polarizing plate, and when this is installed in an image display device such as an organic electroluminescence display device, the display quality is improved. It becomes possible to make the uniformity good.

The in-plane retardation value Re (550) measured at a wavelength of 550 nm of the long stretched film is preferably in the range of 120 nm to 160 nm, and more preferably in the range of 130 nm to 150 nm. Further, the variation of the in-plane retardation value Re of the long stretched film is preferably 3 nm or less, and more preferably 1 nm or less. By setting the variation of the in-plane retardation value Re within the above range, the uniformity of display quality can be improved when used as a film for an organic electroluminescence display device.

Note that the in-plane retardation value Re of the long stretched film is selected as the optimum value depending on the design of the display device used. The Re 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 in the plane (Re = (nx −ny) × d).

The average thickness of the long stretched film is preferably 10 to 200 μm, more preferably 10 to 60 μm, and further preferably 15 to 35 μm from the viewpoint of mechanical strength.

Further, the thickness unevenness in the width direction of the long stretched film affects whether or not it can be wound, and is preferably 3 μm or less, and more preferably 2 μm or less.

[Circularly polarizing plate]
The circularly polarizing plate when the long stretched film according to this embodiment is used will be described.

In the circularly polarizing plate, for example, a polarizing plate protective film, a polarizer, a λ / 4 retardation film, and an adhesive layer are laminated in this order, and the slow axis of the λ / 4 retardation film and the polarizer are laminated. A laminate formed so that the angle formed with the absorption axis is 45 °. That is, the circularly polarizing plate is formed by laminating a long polarizing plate protective film, a long polarizer, and a long λ / 4 retardation film (long stretched film obtained in this embodiment) in this order. It is preferable to be formed.

The circularly polarizing plate may be manufactured by using a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer, and laminating with a configuration of a λ / 4 retardation film and a polarizer. it can.

The film thickness of the circularly polarizing plate is preferably 5 to 40 μm, more preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

The circularly polarizing plate can be produced by a general method. The λ / 4 retardation film subjected to the alkali saponification treatment is preferably bonded to one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

The circularly polarizing plate can be configured by further bonding a release film on the opposite surface of the polarizing plate protective film of the polarizing plate. The protective film and the release film are used for the purpose of protecting the polarizing plate at the time of shipment of the polarizing plate, product inspection, and the like.

[Display device]
By incorporating a circularly polarizing plate produced using the long stretched film according to the present embodiment into a display device, various display devices with excellent visibility can be produced. The display device is preferably an organic electroluminescence display device (organic EL display device).

FIG. 6 is a schematic diagram illustrating an example of a layer structure of an image display unit of an organic electroluminescence display device to which a long stretched film obtained by the manufacturing method according to the present embodiment can be applied. The configuration example of the organic EL display device shown in FIG. 6 is an example, and the present invention is not limited to this.

As shown in FIG. 6, the layer structure of the image display unit of the organic electroluminescence display device includes a substrate 201, a metal electrode 202, a light emitting layer 203, a transparent electrode (ITO, etc.) 204, a sealing layer 205, an adhesive layer 206, Examples include a layer in which a λ / 4 retardation film 207, a polarizer 208, a protective film 209, and the like are sequentially laminated. Specifically, an adhesive layer 206 is formed on an organic electroluminescent element having a metal electrode 202, a light emitting layer 203, a transparent electrode (ITO, etc.) 204, and a sealing layer 205 in this order on a substrate 201 made of glass, polyimide, or the like. Accordingly, a circularly polarizing plate in which a polarizer 208 is sandwiched between a λ / 4 retardation film 207 and a protective film 209 is provided to constitute an organic electroluminescence image display device. The protective film 209 is preferably laminated with a cured layer. The cured layer not only prevents scratches on the surface of the organic electroluminescence image display device but also has an effect of preventing warpage due to the circularly polarizing plate. Further, an antireflection layer may be provided on the cured layer. The thickness of the organic electroluminescence element itself is about 1 μm.

Generally, in an organic electroluminescence image display device, a metal electrode, a light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form a light emitting element (organic electroluminescence element). Here, the light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or Structures with various combinations, such as a laminate of such a light-emitting layer and an electron injection layer composed of a perylene derivative, and / or a laminate of these hole injection layer, light-emitting layer, and electron injection layer, are known. ing.

In an organic electroluminescence image display device, holes and electrons are injected into the light emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by the recombination of these holes and electrons is reduced by the fluorescent material. It emits light on the principle that it is excited and emits light when the excited fluorescent material returns to the ground state. The mechanism of recombination on the way is the same as that of a general diode, and as can be expected from this, the current and the light emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

In an organic electroluminescence image display device, in order to extract light emitted from the light emitting layer, at least one of the electrodes must be transparent, and usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. Used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

In the organic electroluminescence image display device having such a configuration, the light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the light emitting layer transmits light almost completely like the transparent electrode. As a result, the light that is incident from the surface of the transparent substrate when not emitting light, passes through the transparent electrode and the light emitting layer, and is reflected by the metal electrode again exits to the surface side of the transparent substrate. The display surface of the electroluminescence image display device looks like a mirror surface.

The circularly polarizing plate for an organic electroluminescence display device using the long stretched film according to this embodiment is suitable for a display device for organic electroluminescence in which such external light reflection is particularly problematic.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

According to such a configuration, it is possible to suppress the deviation of the optical axis that occurs on the delay side of the long film due to the bowing by performing the process of relaxing the bowing that occurs on the delay side of the long film. Therefore, even when oblique stretching is performed using a simultaneous biaxial stretching apparatus capable of saving space, variation in the orientation angle of the optical axis can be sufficiently suppressed, and the circular polarizing plate provided in the image display device can be used. In this case, it is possible to produce a long stretched film that can sufficiently suppress the occurrence of uneven color.

Moreover, in the manufacturing method of the said elongate stretched film, the said relaxation process is the delay side of the said elongate film, The temperature downstream from the said diagonal stretch process in the conveyance direction of the said elongate film, It is preferable that the treatment is performed at a temperature lower than the temperature on the upstream side of the oblique stretching step or the oblique stretching step in the transport direction.

According to such a configuration, on the delay side of the long film, the upstream side in the conveyance direction of the long film is softened from the downstream side. As a result, the upstream side in the transport direction of the long film is easier to deform than the downstream side, and the optical axis on the delay side of the long film can be changed even if the force applied to the delay side of the long film is relatively weak. The film can be moved downstream in the conveyance direction of the long film by the conveyance tension. That is, bowing that occurs on the delay side of the long film can be relaxed, and the optical axis of the long film can be brought close to the desired optical axis. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. .

In the method for producing the long stretched film, it is preferable that the temperature on the upstream side in the transport direction of the long film is 2 to 30 ° C. higher than the temperature on the downstream side in the transport direction of the long film.

According to such a configuration, the bowing can be relaxed without excessively softening or solidifying the long film more than necessary. Accordingly, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device.

Moreover, in the manufacturing method of the said elongate stretched film, the said relaxation process WHEREIN: The said 1st holding tool of the said elongate film is hold | gripped before the said back conveyance process, the temperature of the delay side of the said elongate film is hold | gripped It is preferable that it is the process extended | stretched in the width direction of the said elongate film in the state made higher than the temperature of the side.

According to such a configuration, the delay side of the long film is softened more than the preceding side, so that the delay side is more easily deformed than the preceding side. In this state, by stretching in the width direction, it is possible to deform only the delay side while suppressing deformation of the leading side of the long film. By doing so, bowing generated on the delay side of the long film can be relaxed, and the optical axis of the long film can be brought close to the desired optical axis. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. .

In the method for producing the long stretched film, the temperature on the delay side of the long film is 2 to 40 ° C. higher than the temperature on the leading side of the long film, and the stretch ratio in the relaxation treatment is 1. It is preferably from 05 to 1.3 times.

According to such a configuration, if the temperature difference is as described above, lateral stretching for relaxing the bowing is performed without excessively softening or solidifying the long film more than necessary. be able to. And if the draw ratio of the transverse stretch at that time is the above magnification, the optical axis of the long film while suppressing the occurrence of defects such as an extremely thin region in the long stretched film or wrinkles Can be the optical axis of the desired orientation angle. From these, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. it can.

In the method for producing a long stretched film, it is preferable that the relaxation treatment is a treatment in which the transport tension on the delay side of the long film is higher than the transport tension on the leading side of the long film.

According to such a configuration, the optical axis on the delay side of the long film can be shifted to the downstream side in the conveyance direction of the long film. That is, bowing that occurs on the delay side of the long film can be relaxed, and the optical axis of the long film can be brought close to the desired optical axis. Therefore, it is possible to easily produce a long stretched film that can sufficiently suppress variation in the orientation angle of the optical axis and can sufficiently suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. .

In the method for producing the long stretched film, it is preferable that the transport tension on the delay side of the long film is 5 to 200 N / m higher than the transport tension on the leading side of the long film.

According to such a configuration, it is possible to set the optical axis of the long film to an optical axis having a desired orientation angle while suppressing the occurrence of defects such as wrinkles in the long stretched film. Accordingly, it is possible to easily produce a long stretched film that can further suppress variation in the orientation angle of the optical axis and can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device.

Moreover, in the manufacturing method of the said elongate stretched film, the said back conveyance process expands the distance between the said adjacent 2nd holding tools, and the traveling speed of the said 1st holding tool and the said 2nd holding tool is made the same. It is preferable to have such a process.

According to such a configuration, by causing the first gripping tool to precede, the optical axis of the long film is tilted, and then, after increasing the traveling speed of the second gripping tool, after the oblique stretching step, The traveling speeds of the first gripping tool and the second gripping tool are the same. Thereby, the optical axis of the long film can be inclined, and furthermore, since the speed when the holding tool is opened is constant, the occurrence of wrinkles or the like in the long stretched film can be suppressed.

In the above manufacturing method, the photoelastic coefficient of the long film made of the thermoplastic resin is 1.0 × 10 ⁻¹¹ (Pa ⁻¹ ) or more and 1.0 × 10 ⁻¹⁰ (Pa ⁻¹ ) or less. preferable.

Conventionally, when a long film having a relatively large range of photoelastic modulus as described above is obliquely stretched using an oblique stretching device of a linear speed difference method, expression of the optical axis is particularly caused by bowing that occurs on the delay side. There was a tendency to cause unevenness in sex. However, according to the manufacturing method according to the present embodiment, the photoelastic modulus of the long film is 1.0 × 10 ⁻¹¹ (Pa ⁻¹ ) or more and 1.0 × 10 ⁻ Even in the case of ¹⁰ (Pa ⁻¹ ) or less, the effect of suppressing the shift of the optical axis is particularly remarkable.

In the method for producing the long stretched film, the long film is preferably a polycarbonate film.

According to such a configuration, it is possible to produce a long stretched film that not only suppresses variations in the orientation angle of the optical axis but also has excellent transparency and mechanical strength.

In the method for producing a long stretched film, the optical axis is preferably 30 ° or more and less than 90 ° with respect to the width direction of the long film.

According to such a configuration, it is possible to further suppress the variation in the orientation angle of the optical axis, and to reduce the occurrence of color unevenness when used for the circularly polarizing plate provided in the image display device. It can be manufactured with an orientation angle.

Further, in the method for producing the long stretched film, the transport speed of the long film is preferably 7 to 150 m / min.

According to such a configuration, it is possible to efficiently suppress a variation in the orientation angle of the optical axis, and to efficiently produce a long stretched film that can further suppress the occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device. Can be manufactured.

In the method for producing a long stretched film, it is preferable that the length of the long film subjected to the oblique stretching step in the width direction is 900 to 2700 mm.

According to such a configuration, variation in the orientation angle of the optical axis can be further suppressed, occurrence of color unevenness when used in a circularly polarizing plate provided in an image display device can be further suppressed, and a wider elongated stretch A film can be produced.

Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

[Manufacture of long film]
First, the manufacturing method of the long film used by a present Example is demonstrated. In this example, a polycarbonate film, a cellulose ester film, and a cycloolefin polymer film were used as the long film.

(Manufacture of polycarbonate film)
First, 152400 parts by mass of ion-exchanged water and 84320 parts by mass of a 25% by mass aqueous sodium hydroxide solution were placed in a thermometer, a stirrer, and a reactor equipped with a reflux condenser. Thereafter, 34,848 parts by mass of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (biscresol fluorene) having a purity of 99.8% by mass and 2,2-bis (4-hydroxy) were added to the container. 9008 parts by mass of phenyl) propane (bisphenol A) and 88 parts by mass of hydrosulfite were added and dissolved in the liquid in the container. Thereafter, 178400 parts by mass of methylene chloride was further added to the vessel, and 18248 parts by mass of phosgene was blown in at 60 ° C. for 15 minutes with stirring. After the phosgene blowing is completed, a solution obtained by dissolving 177.8 parts by mass of p-tert-butylphenol in 2640 parts by mass of methylene chloride and 10560 parts by mass of a 25% by mass aqueous sodium hydroxide solution are added to the vessel and emulsified. It was. Thereafter, 32 parts by mass of triethylamine was added to the vessel and stirred at 28 to 33 ° C. for 1 hour. By doing so, the contents in the container reacted. After completion of the reaction, the product is diluted with methylene chloride, washed with water, acidified with hydrochloric acid and washed with water. When the conductivity of the aqueous phase is almost the same as that of ion-exchanged water, the methylene chloride phase is concentrated and dehydrated. A solution having a polycarbonate concentration of 20% was obtained. The polycarbonate (copolymer A) obtained by removing the solvent from this solution had a molar ratio of biscresol fluorene to bisphenol A of 70:30 (polymer yield 97%). Further, this polymer had an intrinsic viscosity of 0.674 and a Tg of 226 ° C.

25 parts by mass of the polycarbonate was dissolved with stirring at 25 ° C. with respect to 75 parts by mass of a mixed solvent of methylene chloride and ethanol containing 4 parts by mass of ethanol to obtain a transparent and viscous dope.

The dope was poured on a stainless steel belt having a dew point controlled to 12 ° C. or less by blowing dry air and peeled off. The residual solvent concentration at that time was 35% by mass. Thereafter, when the residual solvent concentration was 2% by mass, the width was kept and dried. Then, it was dried until the residual solvent concentration became 1% by mass or less. By doing so, the polycarbonate film (long film A) was obtained. The film thickness was 90 μm. The width was 800 mm. The photoelastic coefficient was 3.5 × 10 ⁻¹¹ Pa ⁻¹ .

Also, a film having a film thickness of 50 μm was produced by the same method as described above.

(Manufacture of cellulose ester film)
Next, the manufacturing method of a cellulose-ester film is demonstrated.

<< Synthesis of sugar ester compounds >>
First, a method for synthesizing a sugar ester compound, which is one of raw materials for a cellulose ester film, will be described. A sugar ester compound was synthesized by the following steps.

More specifically, it was synthesized as follows.

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while agitating (bubbling) nitrogen gas through a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of Kolben was decompressed to 4 × 10 ² Pa or less, and excess pyridine was distilled off at 60 ° C. Thereafter, the inside of Kolben was depressurized to 1.3 × 10 Pa or less, and the temperature was raised to 120 ° C. to distill off most of benzoic anhydride and the produced benzoic acid.

Finally, 100 g of water was added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer was collected, and toluene was distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). As a result, a mixture of compounds A-1, A-2, A-3, A-4 and A-5 was obtained. The above formula is a chemical formula showing a method for synthesizing the sugar ester compound used in the examples.

When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 1.3% by mass, A-2 was 13.4% by mass, A-3 was 13.1% by mass, A- 4 was 31.7% by mass, and A-5 was 40.5% by mass. The average degree of substitution was 5.5.

The measurement conditions for the HPLC-MASS are as follows.

1) LC section Equipment: Column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50) manufactured by JASCO Corporation
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min Mobile phase: THF (1% by mass acetic acid): H ₂ O (50:50 (mass ratio))
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by ThermoQuest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

<< Synthesis of ester compounds >>
Next, a method for synthesizing an ester compound, which is one of raw materials for a cellulose ester film, will be described.

251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with thermometer, stirrer, and slow cooling tube The flask was charged and gradually heated with stirring until it reached 230 ° C. in a nitrogen stream. A dehydration condensation reaction was carried out for 15 hours, and after the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. By doing so, an ester compound was obtained.

The ester compound had an ester of benzoic acid at the end of the polyester chain formed by condensation of 1,2-propylene glycol, phthalic anhydride and adipic acid. The ester compound 1 had an acid value of 0.10 and a number average molecular weight of 450.

<< Preparation of fine particle additive liquid >>
Next, a method for preparing a fine particle additive solution, which is one of the raw materials for the cellulose ester film, will be described.

11 parts by mass of fine particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) and 89 parts by mass of ethanol were mixed with stirring by a dissolver for 50 minutes, and then dispersed with Manton Gorin. By doing so, a fine particle dispersion was obtained.

Subsequently, 5 parts by mass of the fine particle dispersion was slowly added while sufficiently stirring the dissolution tank containing 99 parts by mass of methylene chloride. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. By doing so, the fine particle addition liquid was obtained.

<Preparation of dope solution>
Next, the preparation method of the dope liquid used when manufacturing a cellulose-ester film is demonstrated.

First, methylene chloride, ethanol, cellulose acetate propionate, compound (B) shown in the following formula, sugar ester compound, ester compound, and fine particle additive solution described above are charged into a pressure dissolution tank so as to have the composition described below. did. And the inside of this pressure dissolution tank was heated, and it stirred until the component which can melt | dissolve was melt | dissolved completely. This was designated as Azumi Filter Paper No. Filtered using 244. By doing so, a dope solution was obtained.

Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.39, propionyl group substitution degree 0.50, total substitution degree 1.89) 100 parts by mass Compound (B) 5.0 parts by mass Sugar ester compound 5.0 parts by mass Ester compound 2.5 parts by mass Particulate additive solution 1 part by mass

(Film formation)
Next, a method for forming a film using the obtained main dope solution will be described.

Using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support. On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and the film was peeled off from the stainless steel belt support. Then, it was dried while being conveyed by many rolls. By doing so, the cellulose-ester film (long film B) of width 800mm and thickness 90micrometer was obtained. The photoelastic coefficient was 2.0 × 10 ⁻¹² Pa ⁻¹ .

(Manufacture of cycloolefin polymer film)
In a nitrogen atmosphere, 500 parts by mass of dehydrated cyclohexane, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether, and 0.30 parts by mass of triisobutylaluminum were mixed in a reactor at room temperature, and then mixed at 45 ° C. 20 parts by mass of tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1,4,4a, 140 parts by mass of 9a-tetrahydrofluorene (hereinafter abbreviated as MTF) and 40 parts by mass of 8-methyl-tetracyclo [4.4.0.12, 5.17,10] -dodec-3-ene (hereinafter abbreviated as MTD) A norbornene-based monomer mixture composed of parts and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to deactivate the polymerization catalyst and stop the polymerization reaction.

Next, 270 parts by mass of cyclohexane is added to 100 parts by mass of the resulting reaction solution containing the ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Catalysts & Chemicals) is added as a hydrogenation catalyst. In addition, the pressure was increased to 5 MPa with hydrogen and the mixture was heated to 200 ° C. with stirring and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MTF / MTD ring-opening polymer hydrogenated polymer.

After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (manufactured by Ciba Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the resulting solutions, respectively. And dissolved (both 0.1 parts by mass per 100 parts by mass of the polymer). Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in a strand form from an extruder in a molten state. After cooling, it was pelletized and collected. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

The obtained pellets of the ring-opened polymer hydrogenated product were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture. Next, the pellets were melted by using a short-shaft extruder having a coat hanger type T die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip member quality is tungsten carbide, peel strength 44N from molten resin). Extrusion molding produced a cycloolefin polymer film having a thickness of 80 μm. Extrusion molding provides an alicyclic olefin polymer film (long film C) having a width of 1000 mm and a thickness of 90 μm under molding conditions of a molten resin temperature of 240 ° C. and a T-die temperature of 240 ° C. in a clean room of class 10,000 or less. It was. The photoelastic coefficient was 5.0 × 10 ⁻¹² Pa ⁻¹ .

The method for measuring the photoelastic coefficient of the long films A to C was carried out by the following procedure.

The obtained long films A to C were cut into a sample size of 30 mm × 50 mm, and the film thickness was measured using a cell gap inspection device (RETS-1200, measurement diameter: diameter 5 mm, light source: 589 nm) manufactured by Otsuka Electronics Co., Ltd. A sample with a d (nm) was sandwiched between supports and a stress σ (Pa) of 9.81 × 10 ⁶ was applied in the longitudinal direction. The phase difference R1 (nm) under this stress was measured. The photoelastic coefficient Cσ (Pa ⁻¹ ) was obtained by substituting the phase difference before applying stress as R0 (nm) into the following equation.
Cσ (Pa ⁻¹ ) = (R1−R0) / (σ × d)

The obtained polycarbonate film (long film A: film thickness 90 μm) was obliquely stretched under the conditions of the production method according to this embodiment. By doing so, the elongate stretched film which concerns on Example 1 was obtained. And the obtained elongate stretched film was wound up and made into roll shape.

Specifically, the film was obliquely stretched under the following conditions.

First, the long film was obliquely stretched using the oblique stretching apparatus T shown in FIG. The conveyance speed of the long film was 5 m / min. By accelerating the gripping tool C1 (first gripping tool) from P1 to P2, the gripping tool C1 precedes the gripping tool C2 (second gripping tool). Further, the gripping tool C2 was accelerated from P3 to P4, and the gripping tool C1 and the gripping tool C2 were set to release the long stretched film at a constant speed. Then, it wound up in roll shape with the take-up tension | tensile_strength 200 (N / m) with the winding device provided in the exit.

Using the oblique stretching apparatus T, the long film A was obliquely stretched in an oblique direction by adjusting the acceleration of the gripping tool C1 and the gripping tool C2 so that the orientation angle θ of the long stretched film was 45 °. . At this time, the stretching ratio in the longitudinal direction (conveying direction) was 1.2 times, and the stretching ratio in the transverse direction (width direction) was 1.5 times. And in the extending | stretching zone, the process (temperature difference provision process) which makes upstream temperature (preceding temperature) higher than downstream temperature (preceding temperature) was performed. More specifically, the heating conditions in the stretching zone, such as the temperature and the amount of hot air blown in the stretching zone, were adjusted so that the preceding temperature was 32 ° C. higher than the preceding and following temperature.

And the width | variety of the obtained elongate stretched film was 1200 mm, and thickness was 45 micrometers.

Each condition at the time of manufacturing is shown in Table 1 below.

[Example 2]
In the stretching zone, Example 1 except that the heating conditions in the stretching zone such as the temperature and the amount of hot air blown in the stretching zone were adjusted so that the upstream temperature was 15 ° C. higher than the downstream temperature. It is the same.

[Example 3]
Instead of the above temperature difference applying process, after the first gripping tool is advanced, the process is performed except that the lateral side stretching (delay side widening process) is performed in a state where the delay side temperature is higher than the preceding side temperature. Similar to Example 1. At that time, the heating conditions in the stretching zone such as the temperature and the amount of hot air blown in the stretching zone were adjusted so that the delay side temperature was 41 ° C. higher than the preceding side temperature. Moreover, the draw ratio of the transverse drawing at this time was 1.04.

[Example 4]
During the delay-side widening process, the heating conditions in the stretching zone, such as the temperature and air volume of the hot air blown in the stretching zone, are adjusted so that the delay-side temperature is 24 ° C. higher than the preceding temperature. The draw ratio was the same as in Example 3 except that the draw ratio was 1.1 times.

[Example 5]
It is the same as that of Example 1 except having performed the process (tensile difference provision process) which makes delay side conveyance tension | tensile_strength higher than preceding side conveyance tension instead of the said temperature difference provision process. At that time, the delay-side conveyance tension was set to be 10 N / m higher than the preceding-side conveyance tension. Specifically, in the post-stretching step, the tension was adjusted in the width direction of the long stretched film using a tension applying portion. That is, the roll part was constituted by two roll parts arranged in the rotation axis direction. In addition, each roll part was comprised with the nip roll which clamps a stretched film. And the difference of the width direction of the tension | tensile_strength which a tension | tensile_strength provision part provides to a stretched film was 4 N / m as mentioned above.

[Example 6]
This is the same as Example 5 except that the conveyance conditions for the long film are adjusted so that the delay-side conveyance tension is 40 N / m higher than the preceding-side conveyance tension.

[Example 7]
The same as Example 1 except that a polycarbonate film having a width of 1600 mm is used as the long film to be subjected to the oblique stretching apparatus. In addition, the manufacturing method of a polycarbonate film is the same as that of Example 2 except having adjusted so that a width | variety may become 1600 mm.

[Example 8]
The same as Example 2 except that the conveying speed of the long film was set to 15 m / min.

[Example 9]
Using the oblique stretching apparatus T, the long film A was obliquely stretched in an oblique direction by adjusting the acceleration of the gripping tool C1 and the gripping tool C2 so that the orientation angle θ of the long stretched film was 50 °. Except for this, the second embodiment is the same as the second embodiment.

[Example 10]
The conveyance speed of the long film was set to 15 m / min, and the same as Example 2 except that the long film B (cellulose ester film) was used as the long film.

[Example 11]
The conveyance speed of the long film was set to 15 m / min, and the same as Example 2 except that the long film C (cycloolefin polymer film) was used as the long film.

[Example 12]
Using a long film A having a thickness (film thickness) of 50 μm before stretching, in the stretching zone, the temperature and amount of hot air blown in the stretching zone so that the upstream temperature is 5 ° C. higher than the downstream temperature. This is the same as Example 2 except that the heating conditions in the stretching zone were adjusted.

[Comparative Example 1]
The same as Example 1 except that the temperature difference application process is not performed.

[Comparative Example 2]
Example 7 is the same as Example 7 except that the temperature difference application process is not performed.

[Comparative Example 3]
Example 8 is the same as Example 8 except that the temperature difference application process is not performed.

[Comparative Example 4]
Example 9 is the same as Example 9 except that the temperature difference application process is not performed.

[Evaluation]
The long stretched films according to the above Examples and Comparative Examples were evaluated according to the following evaluation criteria.

(Evaluation of uneven orientation)
Twenty samples were cut out from the long stretched films according to the above Examples and Comparative Examples at equal intervals in the width direction. The (orientation axis) slow axis angle (orientation angle) θ of the sample was measured using an automatic birefringence measuring apparatus (KOBRA-21ADH manufactured by Oji Scientific Instruments). The above measurement (measurement over a plurality of places in the width direction) was performed three times in the transport direction (travel direction). A difference between the maximum value and the minimum value was calculated from the obtained orientation angle value, and the difference was evaluated as a variation in the orientation angle according to the following criteria. That is, the greater the variation in the orientation angle, the greater the orientation unevenness, and the smaller the orientation angle variation, the smaller the orientation unevenness.

A: Variation in orientation angle is less than 0.4 ° B: Variation in orientation angle is not less than 0.4 ° and less than 0.6 ° C: Variation in orientation angle is not less than 0.6 ° and 1. It is less than 0 ° D: The variation in orientation angle is 1.0 ° or more and less than 1.5 ° E: The variation in orientation angle is 1.5 ° or more.

(Evaluation of uneven color)
First, the organic EL display apparatus demonstrated above was created using the elongate stretched film which concerns on each Example and a comparative example. Black was displayed on the entire surface of the image display portion of the obtained organic EL display device. The display state was visually observed to evaluate uneven color. That is, color unevenness on the entire display surface when black was displayed was visually evaluated according to the following criteria.

A: Color difference (uneven color) cannot be confirmed for each location on the entire display surface. B: A slight difference in color (uneven color) can be confirmed at the edge of the screen on the entire display surface. Difference in taste is a level at which there is no particular problem. C: Level where color difference (unevenness in color) can be confirmed at the edge of the screen on the entire display surface, and the resulting organic EL display device cannot be used as a product. D: There is a large difference in color (uneven color) at each location of the pasted sample piece, and the resulting organic EL display device cannot be used as a product.

The above evaluation results are shown in Table 1 together with the conditions during the production of the long stretched film.

As can be seen from Table 1, when the temperature difference application process, the delay side widening process and the tension difference application process were performed (Examples 1 to 12), the case where such a process was not performed (Comparative Examples 1 to 4). Compared to this, a long stretched film with small alignment unevenness can be obtained. Further, it was found that the elongated stretched films according to Examples 1 to 12 can be obtained with less uneven color than Comparative Examples 1 to 4 when applied to an organic EL display device.

Further, from Examples 10 and 11, etc., it is possible to suppress the occurrence of uneven alignment and uneven color even when the long film is a polycarbonate film, a cellulose ester film, or a cycloolefin polymer film. I understood. From this, it was found that, regardless of the material of the long film, when the manufacturing method according to the present embodiment is applied, a long stretched film in which the uneven orientation is sufficiently suppressed can be obtained.

According to the present invention, even when oblique stretching is performed using a simultaneous biaxial stretching apparatus capable of saving space, variation in the orientation angle of the optical axis can be sufficiently suppressed, and the circle provided in the image display apparatus A method for producing a long stretched film that can sufficiently suppress the occurrence of color unevenness when used in a polarizing plate is provided.

Claims

A constant-velocity transporting step of gripping both ends of the thermoplastic long film with a plurality of grippers and transporting the grippers gripping the both ends at a constant speed, the first gripper gripping one end of the other An oblique stretching step in which the optical axis of the long film is tilted by accelerating the second gripping tool gripping the end of the first film and causing the first gripping tool to precede the second gripping tool; And at least a post-conveying step of conveying the both ends of the long film after the stretching step while being held by the plurality of gripping tools,
A method for producing a long stretched film, comprising: subjecting the delay side of the long film held by the second gripping tool to a relaxation treatment for relaxing the bowing generated by the oblique stretching step.
The relaxation treatment is performed on the delay side of the long film, at a temperature downstream of the oblique stretching step in the transport direction of the long film, during the oblique stretching step in the transport direction of the long film or in the oblique stretching. The manufacturing method of the elongate stretched film of Claim 1 which is the process made lower than the temperature of an upstream from a process.
The temperature in the oblique stretching step in the transport direction of the long film or upstream of the oblique stretching step is 2 to 30 ° C higher than the temperature downstream of the oblique stretching step in the transport direction of the long film. 2. A method for producing a long stretched film according to 2.
In the post-conveying step, the relaxation treatment is performed such that the temperature on the delay side of the long film is higher than the temperature on the preceding side where the first gripping tool of the long film is gripped. The method for producing a long stretched film according to claim 1, which is a treatment of stretching in the width direction of the film.
5. The delay side temperature of the long film is 2 to 40 ° C. higher than the temperature of the leading side of the long film, and the draw ratio in the relaxation treatment is 1.05 to 1.3 times. The manufacturing method of the elongate stretched film of description.
2. The method for producing a long stretched film according to claim 1, wherein the relaxation treatment is a treatment in which the transport tension on the delay side of the long film is made higher than the transport tension on the leading side of the long film.
The method for producing a long stretched film according to claim 6, wherein the transport tension on the delay side of the long film is higher by 5 to 200 N / m than the transport tension on the leading side of the long film.
8. The post-conveying step includes a step of widening a distance between the adjacent second gripping tools so that traveling speeds of the first gripping tool and the second gripping tool are the same. The manufacturing method of the elongate stretched film of any one.
The long film according to any one of claims 1 to 8, wherein the photoelastic coefficient of the long film is 1.0 x 10 -11 Pa -1 or more and 1.0 x 10 -10 Pa -1 or less. A method for producing a stretched film.
The method for producing a long stretched film according to any one of claims 1 to 9, wherein the long film is a polycarbonate film.
The method for producing a long stretched film according to any one of claims 1 to 10, wherein the optical axis is 30 ° or more and less than 90 ° with respect to the width direction of the long film.
The method for producing a long stretched film according to any one of claims 1 to 11, wherein a transport speed of the long film is 7 to 150 m / min.
The method for producing a long stretched film according to any one of claims 1 to 12, wherein a length in a width direction of the long film subjected to the oblique stretching step is 900 to 2700 mm.