WO2012029599A1

WO2012029599A1 - Resin film manufacturing method, resin film manufacturing device, resin film, polarizing plate, and liquid crystal display device

Info

Publication number: WO2012029599A1
Application number: PCT/JP2011/069022
Authority: WO
Inventors: 田中　博文
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-09-01
Filing date: 2011-08-24
Publication date: 2012-03-08

Abstract

In order to provide a resin film manufacturing method that is capable of producing resin films that have a sufficiently uniform optical value, even if the resin film is stretched in the width direction, and that minimize the generation of foreign matter, a resin film manufacturing method involving smooth holding members is used, wherein: both edges of an elongated resin film are held by a plurality of holding members in the width direction of the resin film, and said holding members move in the longitudinal direction of the resin film, and also move in a direction in which, among the holding members, the distance between a plurality of first holding parts that holds one edge of the resin film of the resin film, and a plurality of second holding parts that holds the other edge of the resin film gradually widens in the width direction of the resin film; and when the plurality of holding members used on such occasion holds the resin film, the total value of the maximum height (Ry), at normal temperature, of a first contact surface that comes into contact with one surface of the resin film, and of a second contact surface that comes into contact with the other surface of the film is 1 μm to 24 μm.

Description

Resin film manufacturing method, resin film manufacturing apparatus, resin film, polarizing plate, and liquid crystal display device

The present invention relates to a resin film manufacturing method, a resin film manufacturing apparatus, a resin film obtained by the manufacturing method, a polarizing plate using the resin film as a transparent protective film, and a liquid crystal display device including the polarizing plate. .

Resin films are used in various fields, such as liquid crystal display devices, in view of their chemical characteristics, mechanical characteristics, electrical characteristics, and the like. Specifically, a transparent protective film for protecting various resin films, for example, polarizing elements of polarizing plates, is disposed in the image display area of the liquid crystal display device. As such a resin film, for example, a resin film excellent in transparency such as a cellulose ester film is widely used.

Further, an image forming apparatus, particularly a liquid crystal display device used as a television receiver is required to have a large screen. Therefore, as a resin film applied to the image forming apparatus, it is required to manufacture a wide film having a wide width. As a method for producing such a wide film, for example, a method of stretching the film can be considered.

As a method for obtaining such a wide film by stretching such a film, for example, the width direction of the long film, that is, both side ends in the short side direction are gripped with a plurality of pairs of gripping tools. For example, a method of moving the gripping tool in a direction that gradually increases the distance between the gripping tools that form the above. Specific examples include those described in Patent Document 1 and Patent Document 2.

In Patent Document 1, in a tenter, both ends of the film are held by a plurality of clips on a tenter rail while being heated by a plurality of hot air blowing nozzles provided on the upper and lower surfaces of the film so as to face each other. In the method for producing a thermoplastic resin film stretched in the width direction while transporting the film, the tenter rail width at the stretching start point is wider than the tenter rail width at the tenter inlet from the tenter inlet to the stretching start point. The manufacturing method of the thermoplastic resin film which provided the preheating process preheated while conveying the film in is described.

Patent Document 2 discloses a method for stretching a polymer film in which a polymer film is stretched at a predetermined magnification in the width direction by gripping both side edges of the polymer film with an openable / closable gripper that moves in the running direction of the polymer film. Then, after gripping the polymer film with the gripping tool, the gripping width of the polymer film is gradually increased and stretched below a predetermined magnification, and the gripping tool is urged in the closing direction by the contraction force of the stretched polymer film to grip the polymer film. A method of stretching a polymer film is described, which includes a gripping stabilization step for stabilization, and a main stretching step that is provided after the gripping stabilization step and gradually increases the gripping width of the polymer film and stretches the polymer film to a predetermined magnification.

JP 2009-178992 A JP 2009-234075 A

According to Patent Document 1, it is disclosed that a method for producing a thermoplastic resin film having uniform retardation in the in-plane direction and retardation in the thickness direction can be provided.

Further, according to Patent Document 2, it is disclosed that the occurrence of twisting in the side where the polymer film side edge, which may occur due to poor gripping, is depressed toward the center side can be suppressed.

However, the resin films obtained by these methods are not sufficiently high in uniformity of optical values such as retardation and orientation in the width direction, and the generation of foreign matters due to poor gripping cannot be suppressed.

The present invention has been made in view of such circumstances, and even when the resin film is stretched in the width direction, it is possible to produce a resin film in which optical values are sufficiently uniform and generation of foreign matter is suppressed. It aims at providing the manufacturing method of a resin film. In addition, a resin film manufacturing apparatus that realizes a resin film manufacturing method, a resin film obtained by the resin film manufacturing method, a polarizing plate using the resin film as a transparent protective film, and a liquid crystal display device including the polarizing plate The purpose is to provide.

The present inventor has inferred that when the resin film is stretched in the width direction, the optical value in the width direction becomes non-uniform as follows.

First, the present inventor, as described above, is a method in which both ends in the width direction of the resin film are stretched by a plurality of pairs of gripping members, and deformed in the vicinity of the region gripped by the resin film gripping members during stretching. Found that there is a tendency to occur. When such deformation occurs, optical values such as retardation and orientation in the width direction of the obtained resin film become uneven, particularly at the end of the resin film held by the holding member, and the optical characteristics are I thought it would be inferior. As a result, the optical value was considered to be non-uniform. In addition, in the methods described in Patent Document 1 and Patent Document 2, the reason why the uniformity of the optical value could not be sufficiently increased is the reason for the vicinity of the region gripped by the resin film gripping member during stretching. It was considered that the occurrence of deformation could not be sufficiently suppressed. In the methods described in Patent Document 1 and Patent Document 2, it has not been studied to reduce the stress load applied to the resin film by the gripping member.

The present inventor has paid attention to the reduction of the stress load applied to the resin film by the gripping part, and as a result of various studies, has found that the above object is achieved by the present invention described below.

The method for producing a resin film according to the present invention includes the gripping member moving in the longitudinal direction of the resin film while gripping both side ends of the long resin film in the width direction with a plurality of gripping members. The distance between the 1st holding part which has a plurality of holding members which hold one end part of a resin film among the 2nd holding part which has a plurality of holding members which hold the other end part of a resin film Is provided with a stretching process that gradually moves in the width direction of the resin film, and a plurality of gripping members used in the stretching process are in contact with one surface of the resin film when gripping the resin film. It includes a smooth gripping member in which the total value of the maximum height Ry of the surface at normal temperature and the maximum height Ry of the second contact surface in contact with the other surface of the resin film at normal temperature is 1 μm to 25 μm. Features Is.

In the present invention, the gripping member refers to a member that grips the resin film with a first contact surface that contacts one surface of the resin film and a second contact surface that contacts the other surface of the resin film. The smooth gripping member refers to a gripping member having a total value of the maximum height Ry of the first contact surface and the second contact surface at the normal temperature of 1 μm to 25 μm among the gripping members.

According to such a configuration, even if the resin film is stretched in the width direction, a resin film having a sufficiently uniform optical value can be produced. This is considered to be due to the following. First, when a smooth gripping member is used, it is considered that the stress load applied to the film by the gripping member can be reduced. In this way, if the stress load applied to the film can be reduced, deformation that may occur near the region gripped by the resin film gripping member during stretching can be suppressed, and optical value non-uniformity due to stretching. It is considered that the occurrence of cracks can be sufficiently suppressed and cracking due to deformation can be suppressed. Therefore, it is considered that even if the resin film is stretched in the width direction, a resin film having no uniform foreign matter due to cracking and having a sufficiently uniform optical value can be produced.

Further, when the resin film is produced as described above, the resin film obtained by stretching can be smoothly conveyed. This is considered to be because the deformation that can occur in the vicinity of the region gripped by the resin film gripper during stretching can be suppressed.

In the method for producing a resin film of the present invention, the number of smooth gripping members constituting the first gripping part is 98% or more with respect to the number of all gripping members constituting the first gripping part. In addition, the number of smooth gripping members constituting the second gripping portion is preferably 98% or more with respect to the number of all gripping members constituting the second gripping portion.

According to such a configuration, even when a gripping member other than the smooth gripping member is included as the gripping member, a resin film having a sufficiently uniform optical value can be manufactured. Originally, it is preferable to use only a smooth gripping member as a gripping member, but the number of smooth gripping members constituting the first gripping part and the second gripping part is the number of all gripping members. On the other hand, as long as 98% or more is satisfied, a resin film having a sufficiently uniform optical value can be manufactured even if gripping members other than the smooth gripping member are included. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Furthermore, if a gripping member different from the smooth gripping member is included as the gripping portion, the transportability of the resin film tends to decrease, but the smooth gripping member constituting the first gripping portion and the second gripping portion The resin film manufacturing method having excellent transportability of the resin film even if a gripping member other than the smooth gripping member is included, as long as the total number of the gripping members satisfies 98% or more with respect to the total number of the gripping members Can provide.

In the method for producing a resin film of the present invention, the number of gripping members other than the smooth gripping member, wherein the gripping member adjacent to the smooth gripping member is a gripping member other than the smooth gripping member is the smooth gripping member. It is preferable that it is 5% or less with respect to the total number of other gripping members.

According to such a configuration, even when a gripping member other than the smooth gripping member is included as the gripping member, a resin film having a sufficiently uniform optical value can be manufactured. Originally, it is preferable to use only a smooth gripping member as the gripping member, but it is preferable that the number of gripping members other than the smooth gripping member is the total number of gripping members other than the smooth gripping member. If it satisfies 5% or less, a resin film having a sufficiently uniform optical value can be produced even if gripping members other than the smooth gripping member are included. This is considered to be because even if gripping members other than the smooth gripping member are included, they are less affected if they are dispersed. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Furthermore, if a gripping member different from the smooth gripping member is included as the gripping member, the transportability of the resin film tends to decrease, but the number of gripping members other than the smooth gripping member is smooth gripping. As long as 5% or less is satisfied with respect to the total number of gripping members other than the member, even if gripping members other than the smooth gripping member are included, a resin film manufacturing method excellent in resin film transportability is provided. Can be provided. This is considered to be because even if gripping members other than the smooth gripping member are included, they are less affected if they are dispersed.

In the method for producing a resin film of the present invention, the number of smooth gripping members disposed between gripping members other than the smooth gripping member is preferably 5% or more with respect to the total number of smooth gripping members. .

According to such a configuration, even when a gripping member other than the smooth gripping member is included as the gripping member, a resin film having a sufficiently uniform optical value can be manufactured. Originally, it is preferable to stretch using only a smooth gripping member as the gripping member, but the number of smooth gripping members arranged between gripping members other than the smooth gripping member is the total number of smooth gripping members. On the other hand, if 5% or more is satisfied, a resin film having a sufficiently uniform optical value can be produced even if a gripping member other than the smooth gripping member is included. This means that even if a gripping member other than the smooth gripping member is included, the effect of increasing the uniformity of the optical value by the smooth gripping part can be sufficiently exerted by the smooth gripping member being continued to some extent. It is thought that. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Furthermore, if different gripping portions are included as described above, the film transportability tends to decrease, but the number of smooth gripping members arranged between gripping members other than the smooth gripping members However, if it satisfies 5% or more with respect to the total number of smooth gripping members, even if gripping members other than the smooth gripping members are included, a method for producing a resin film excellent in film transportability is provided. it can.

Moreover, in the manufacturing method of the resin film of this invention, the 1st holding | grip part has the part which goes around in the direction parallel to the surface direction of a resin film, and moves along one edge part of a resin film. A plurality of second endless rotating parts that are held by the part at equal intervals and have a portion that the second gripping part circulates in a direction parallel to the surface direction of the resin film and moves along one end of the resin film It is preferable that a plurality are held at regular intervals.

According to such a configuration, even if the resin film is stretched in the width direction, it is possible to easily realize a resin film manufacturing method that can manufacture a resin film having a sufficiently uniform optical value.

In the method for producing a resin film of the present invention, it is preferable to use a wet resin film containing a solvent as the resin film to be stretched in the stretching step.

Another method for producing a resin film of the present invention is to cast a resin solution containing a transparent resin (hereinafter also referred to as a dope) from a casting die onto a support that runs as a dope film. (Hereinafter also referred to as a web) a casting step, a peeling step in which the casting film is used as a resin film, and a peeling step from the support, and a plurality of grips on both sides in the width direction of the peeled resin film before stretching. While gripping with the member, the gripping member moves in the longitudinal direction of the resin film, and has a first gripping portion having a plurality of gripping members for gripping one end of the resin film before stretching among the gripping members; A stretching step of moving the distance between the second gripping portion having a plurality of gripping members gripping the other end of the resin film before stretching in a direction of gradually widening in the width direction of the resin film; Used in When the number of gripping members grips the resin film before stretching, the maximum height Ry of the first contact surface that comes into contact with one surface of the resin film before stretching at room temperature and the other of the resin films before stretching A smooth gripping member having a total value of the maximum height Ry of the second contact surface in contact with the surface at the normal temperature is 1 μm to 25 μm is included.

According to such a configuration, even when the resin film is stretched in the width direction, a resin film having a sufficiently uniform optical value can be continuously produced.

In addition, the resin film manufacturing apparatus of the present invention includes a first gripping part that grips one end in the width direction of the long resin film, and a second gripping part that grips the other end of the resin film. Each of the first gripping portion and the second gripping portion has a plurality of gripping members and moves in the longitudinal direction of the resin film, and the distance between the first gripping portion and the second gripping portion is The first height of contact Ry of the first contact surface that contacts one surface of the resin film when gripping the resin film is gradually increased in the width direction of the resin film, and the other height of the resin film A smooth gripping member having a total value of the maximum height Ry of the second contact surface in contact with the surface at the normal temperature is 1 μm to 25 μm is included.

According to such a configuration, even if the resin film is stretched in the width direction, a resin film having a sufficiently uniform optical value can be produced.

The resin film of the present invention is obtained by the method for producing a resin film of the present invention.

According to such a configuration, a wide resin film having a sufficiently uniform optical value can be obtained. For this reason, it can be suitably used as an optical film of a liquid crystal display device that is required to have a uniform optical value. Furthermore, it can be suitably used as an optical film for a liquid crystal display device having a large screen.

Moreover, the polarizing plate of this invention is equipped with a polarizing element and the transparent protective film arrange | positioned on the surface of a polarizing element, and a transparent protective film is the resin film manufactured with the manufacturing method of the resin film of this invention. It is characterized by this.

According to such a configuration, since the resin film having a uniform optical value is applied as the transparent protective film of the polarizing element, for example, when applied to a liquid crystal display device, a liquid crystal display device excellent in contrast and the like is obtained. A polarizing plate that can be realized is obtained. That is, a polarizing plate that can realize high image quality of the liquid crystal display device is obtained. Furthermore, when a wide resin film is used as the transparent protective film of the polarizing plate, it can be applied to a liquid crystal display device having a large screen.

The liquid crystal display device of the present invention includes a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the two polarizing plates uses the resin film of the present invention. Thus, the polarizing plate is manufactured.

According to such a configuration, since the polarizing plate provided with the resin film having a uniform optical value is used, a high-quality liquid crystal display device excellent in contrast and the like can be obtained. Further, when a polarizing plate provided with a wide resin film is used, a large screen of the liquid crystal display device can be realized.

According to the present invention, it is possible to provide a method for producing a resin film that can produce a resin film having a sufficiently uniform optical value even if the resin film is stretched in the width direction. In addition, a resin film manufacturing apparatus that realizes a resin film manufacturing method, a resin film obtained by a resin film manufacturing method, a polarizing plate using the resin film as a transparent protective film, and a liquid crystal display device including the polarizing plate Provided.

It is the schematic which shows an example of the fundamental structure of the manufacturing apparatus of a resin film. It is the schematic which shows the structure of the extending | stretching apparatus with which the manufacturing apparatus of the resin film shown in FIG. FIG. 3 is a schematic cross-sectional view of a gripping member along a cutting plane line AA ′ in the stretching apparatus shown in FIG. 2.

Hereinafter, although the manufacturing method of the resin film of this invention is demonstrated, this invention is not limited to these.

The method for producing a resin film of the present invention is such that the gripping member moves in the longitudinal direction of the resin film before stretching while gripping both side ends in the width direction of the long resin film with a plurality of gripping members, Among the gripping members, a first gripping portion having a plurality of gripping members that grip one end portion of the resin film before stretching, and a plurality of gripping members that grip the other end portion of the resin film before stretching. A stretching step of gradually moving the distance between the two gripping portions in the width direction of the resin film before stretching, and a plurality of gripping members used in the stretching step grip the resin film before stretching. The maximum height Ry (normally Ry1 for convenience) of the first contact surface in contact with one surface of the resin film before stretching and the second contact surface in contact with the other surface of the resin film before stretching Maximum height at room temperature Total (Ry1 + Ry2) value of Ry (for convenience and Ry2) is intended to include smooth gripping member is 25μm from 1 [mu] m.

According to such a production method, a resin film having a sufficiently uniform optical value can be produced even if the resin film is stretched in the width direction. This is considered to be due to the following.

First, it is considered that when a smooth gripping member is used, the stress load applied to the resin film by the gripping member can be reduced. Thus, if the stress load applied to the resin film can be reduced, deformation that may occur in the vicinity of the region gripped by the resin film gripping member at the time of stretching can be suppressed, and non-uniform optical values due to stretching. It is considered that the generation of sex can be sufficiently suppressed. Therefore, it is considered that even if the resin film is stretched in the width direction, a resin film having a sufficiently uniform optical value can be produced.

Further, when a resin film is produced by the method for producing a resin film of the present invention, the resin film obtained by stretching can be smoothly conveyed. This is considered to be because the deformation that can occur in the vicinity of the region gripped by the film gripping member during stretching can be suppressed.

The method for producing an optical film of the present invention is not particularly limited as long as it includes a stretching process. Specifically, for example, a method of producing a resin film by peeling a resin film formed on a support from the support and then subjecting the peeled resin film to a stretching process, can be mentioned. Specifically, for example, a casting process in which a casting solution is formed by casting a resin solution containing a transparent resin from a casting die on a traveling support, and the casting film is used as a resin film. The manufacturing method by what is called a solution casting film forming method provided with the peeling process which peels from, and the extending process which extends | stretches with respect to the peeled resin film etc. are mentioned.

Another method is a melt casting film forming method in which a molten resin is cast on a support to form a film.

Such a manufacturing method by the solution casting film forming method is performed by, for example, a resin film manufacturing apparatus as shown in FIG. In addition, as a manufacturing apparatus of a resin film, if it has the extending | stretching process, it will not specifically limit to what is shown in FIG. 1, The thing of another structure may be sufficient. The resin film herein refers to a film after the cast film made of dope cast on the support is dried on the support and can be peeled off from the support.

FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a resin film manufacturing apparatus. The resin film manufacturing apparatus 11 includes an endless belt support 12, a casting die 13, a peeling roller 14, a stretching device 21, a drying device 15, a winding device 16, and the like. The casting die 13 casts a dope in which a transparent resin is dissolved as a dope film 19 on the surface of the endless belt support 12 to form a casting film. The endless belt support 12 is supported to be drivable by a pair of driving rollers and driven rollers, and the dope film 19 discharged from the casting die 13 is cast on the endless belt support 12 to form a casting film. Then, it is dried while being conveyed so that it can be peeled off from the endless belt support 12. Then, the peeling roller 14 peels the cast film from the endless belt support 12. The stretching device 21 stretches the resin film 17 before stretching under the conditions described later. The drying device 15 dries the stretched film 18 while being transported by a transport roller. And the winding apparatus 16 winds up the stretched and dried film 18, and makes it a film roll.

As shown in FIG. 1, the casting die 13 is supplied with a dope from a dope supply pipe connected to the upper end portion of the casting die 13. Then, the supplied dope is discharged as a dope film 19 from the casting die 13 and cast onto the endless belt support 12, and a casting film is formed on the endless belt support 12.

As shown in FIG. 1, the endless belt support 12 is a metal endless belt having a mirror surface and traveling infinitely. As the endless belt, for example, an endless belt made of stainless steel or the like is preferably used from the viewpoint of the peelability of the resin film. From the viewpoint of effectively utilizing the width of the endless belt support 12, the width of the cast film discharged from the casting die 13 as the dope film 19 and cast on the endless belt support 12 is the endless belt support. The width of 12 is preferably 80% to 99%. Further, instead of the endless belt support, a rotating metal drum (endless drum support) having a mirror surface may be used.

The endless belt support 12 dries the solvent in the casting film while conveying the casting film formed on the surface thereof. Drying is performed by, for example, heating the endless belt support 12 or blowing heated air onto the casting membrane. At this time, although the temperature of the cast film varies depending on the dope solution, the range of −5 ° C. to 70 ° C. is preferable and 0 ° C. to 60 ° C. in consideration of the transport speed and productivity accompanying the evaporation time of the solvent. A range of ° C is more preferred. The higher the temperature of the cast film, the higher the drying speed of the solvent, which is preferable. However, when the temperature is too high, foaming and flatness tend to deteriorate.

When the endless belt support 12 is heated, for example, a method of heating the casting film on the endless belt support 12 with an infrared heater, a method of heating the back surface of the endless belt support 12 with an infrared heater, an endless belt support 12 There is a method of heating by heating air on the back surface, and it can be appropriately selected if necessary.

Further, when the heated air is blown, the wind pressure of the heated air is preferably 50 Pa to 5000 Pa in consideration of the uniformity of solvent evaporation and the like. The temperature of the heating air may be dried at a constant temperature, or may be supplied in several steps in the running direction of the endless belt support 12.

The time from casting the dope film 19 on the endless belt support 12 to forming the cast film and then peeling the cast film from the endless belt support 12 is the thickness of the optical film to be produced. Although it varies depending on the solvent, it is preferably in the range of 0.5 to 5 minutes in consideration of the peelability from the endless belt support 12.

The transport speed of the cast film by the endless belt support 12 is preferably about 50 m / min to 200 m / min, for example. Further, the ratio (draft ratio) of the casting film conveying speed to the traveling speed of the endless belt support 12 is preferably about 0.8 to 1.2. When the draft ratio is within this range, the cast film can be stably formed. For example, if the draft ratio is too large, there is a tendency to cause a phenomenon called neck-in in which the cast film is reduced in the width direction, and if so, a wide resin film cannot be formed.

The peeling roller 14 is in contact with the surface of the endless belt support 12 on which the dope film 19 is cast, and the dried cast film is peeled by applying pressure to the endless belt support 12 side. In the present invention, the peeled cast film is referred to as a resin film before stretching. When the cast film is peeled from the endless belt support 12, the cast film is stretched in the transport direction (Machine Direction: MD direction) of the resin film before stretching by the peeling tension and the subsequent transport tension. For this reason, it is preferable that the peeling tension and the conveying tension when peeling the cast film from the endless belt support 12 are 50 N / m to 400 N / m.

Further, the residual solvent ratio of the cast film when the cast film is peeled from the endless belt support 12 is the peelability from the endless belt support 12, the residual solvent ratio at the time of peel, the transportability after peeling, Considering the physical properties of the resin film obtained after drying, it is preferably 30% by mass to 200% by mass. The residual solvent ratio of the cast film is defined by the following formula (I).

Residual solvent ratio (mass%) = {(M1-M2) / M2} × 100 (I)
Here, M1 represents the mass of the cast film at an arbitrary point in time, and M2 represents the mass after drying the cast film measured for M1 at 115 ° C. for 1 hour.

The stretching device 21 has a configuration that will be described later, and stretches the resin film 17 before stretching in a direction (Transverse Direction: TD direction, width direction) orthogonal to the transport direction of the resin film 17 before stretching. Specifically, as shown in FIG. 2, both end portions in the direction perpendicular to the transport direction of the resin film 17 before stretching are gripped by the gripping

members

24 and 25, and the distance between the opposing gripping

members

24 and 25 is set. By enlarging, it extends in the TD direction.

The drying device 15 includes a plurality of transport rollers, and dries the resin film while transporting the resin film between the rollers. In that case, you may dry using heating air, infrared rays, etc. independently, and you may dry using heating air and infrared rays together. It is preferable to use heated air from the viewpoint of simplicity. The drying temperature varies depending on the residual solvent ratio of the resin film. However, the drying temperature is appropriately selected depending on the residual solvent ratio in the range of 30 ° C. to 180 ° C. in consideration of drying time, shrinkage unevenness, stability of expansion and contraction, etc. You can decide. Moreover, it may be dried at a constant temperature, or may be divided into two to four stages of temperature and divided into several stages of temperature. Further, the resin film can be stretched in the MD direction while being transported in the drying device 15.

The winding device 16 winds the resin film stretched by the stretching device 21 and dried by the drying device 15 to a required length to be wound around the winding core. In addition, it is preferable that the temperature at the time of winding is cooled to room temperature in order to prevent abrasion, loosening, and the like due to shrinkage after winding. The winder to be used can be used without any particular limitation, and may be a commonly used one, such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

FIG. 2 is a schematic diagram showing the configuration of the stretching apparatus 21 provided in the resin film manufacturing apparatus shown in FIG. In addition, this figure has shown the case where a clip as shown in FIG. 3 is used as a holding member.

The stretching device 21 includes a first grip 21 a having a first rail 22 having a plurality of grip members 24, a second grip 21 b having a second rail 23 having a plurality of grip members 25, and a grip member 24. A first endless rotating part 21c having a pair of

sprockets

26, 28 that hold an endless chain (not shown) in which is disposed, and a pair of sprockets 27 that hold an endless chain (not shown) in which a gripping member 24 is placed, 2nd endless rotation part 21d which has 29. FIG. 2 is a schematic view, and the number of

grip members

24 and 25 is generally larger than that shown in FIG.

The first rail 22 extends along one end of the resin film 17 before stretching, and determines the traveling direction of the gripping member 24 as will be described later. Moreover, the 2nd rail 23 is extended along the other edge part of the resin film 17 before extending | stretching, and determines the running direction of the holding member 25 so that it may mention later.

The

grip members

24 and 25 each grip the end portion in the width direction of the resin film 17 before stretching. In addition, the

grip members

24 and 25 are arranged at predetermined intervals on an endless chain (not shown). An endless chain (not shown) on which the grip member 24 is arranged is stretched between a pair of

sprockets

26 and 28. Further, an endless chain (not shown) on which the gripping member 25 is arranged is stretched around a pair of

sprockets

27 and 29. The

sprockets

28 and 29 are rotationally driven by a driving source such as a stepping motor, and give a driving force for endlessly rotating each endless chain (not shown). The

sprockets

26 and 27 are rotatably provided, and are driven to rotate along with endless rotation of an endless chain (not shown) by the

sprockets

28 and 29. Endless rotation of each endless chain (not shown) is guided by the first rail 22 and the second rail 23. Thus, the endless chain in which the gripping member 24 and the gripping member 25 are arranged rotates endlessly while being guided by the first rail 22 and the second rail 23, so that the gripping

members

24 and 25 are each stretched. While gripping the end portion in the width direction of the previous resin film 17, the first rail 22 and the second rail 23 are sequentially run in the transport direction of the resin film 17 before stretching.

The traveling direction of the gripping

members

24 and 25 is determined as follows.

First, the holding

members

24 and 25 move only along the longitudinal direction of the resin film 17 before stretching while holding both ends in the width direction of the resin film 17 before stretching. That is, it moves so that the distance between the gripping member 24 and the gripping member 25 is hardly changed.

Thereafter, each gripping

member

24, 25 moves along the longitudinal direction of the resin film 17 before stretching, and gradually moves between the gripping member 24 and the gripping member 25 in the width direction of the resin film 17 before stretching. Move in the direction of spreading. By doing so, the resin film 17 before stretching is stretched in the width direction. At that time, the angle θ formed by the longitudinal direction of the film 17 before stretching and the gripping member 24 or gripping member 25 during stretching is preferably 1 ° to 50 °. If the angle θ is too small, the stretch ratio becomes low, and there is a tendency that the widening of the resin film cannot be sufficiently achieved. In addition, if the angle θ is too large, there is a tendency for deformation to occur around the portion gripped by the gripping

members

24 and 25, and in some cases, the resin film 17 before stretching may be torn.

Finally, the gripping

members

24 and 25 move so that the distance between them hardly changes. That is, it moves so as to maintain the interval widened by stretching. By doing so, the shrinkage | contraction of the width direction of the film 17 after opening each holding

member

24 and 25 is suppressed.

Further, when the resin film 17 before stretching is stretched, the resin film 17 before stretching is usually heated. Although heating of this resin film 17 before extending | stretching is not specifically limited, For example, you may carry out by spraying a heating air on the resin film 17 before extending | stretching, and you may heat with heating apparatuses, such as infrared rays. Moreover, although the temperature of the resin film 17 before extending | stretching at the time of extending | stretching changes with composition etc. of a resin film, it is preferable that it is 100 to 150 degreeC, for example.

In addition, as described above, the gripping member 24 constituting the first gripping portion and the gripping member 25 constituting the second gripping portion are the resin before stretching when gripping the resin film 17 before stretching. The maximum height Ry1 at normal temperature of the first contact surface in contact with one surface of the film 17 and the maximum height Ry2 at normal temperature of the second contact surface in contact with the other surface of the resin film 17 before stretching. A smooth gripping member having a total (Ry1 + Ry2) value of 1 μm to 25 μm is included. That is, the

grip members

24 and 25 may be made of a smooth grip member, or may be made of a grip member other than the smooth grip member and the smooth grip member.

As long as the gripping

members

24 and 25 include a smooth gripping member, the structure thereof is not particularly limited. Specifically, for example, a structure as shown in FIG. 3 is a schematic cross-sectional view of the gripping member along the cutting plane line AA ′ in the stretching apparatus 21 shown in FIG.

As shown in FIG. 3, the grip member 24 includes a movable part 31 and a pedestal 32. The movable part 31 is pivotally supported by the pedestal 32 so as to be rotatable. The holding member 24 holds the resin film 17 before stretching by rotating the movable part 31 and sandwiching the resin film 17 before stretching in the pedestal 32 by the movable part 31.

The 1st contact surface 33 which contacts the resin film 17 before extending | stretching of the movable part 31 is a surface which has an unevenness | corrugation. Further, the second contact surface 34 of the pedestal 32 that contacts the unstretched resin film 17 is also a surface having irregularities, like the first contact surface 33.

When the gripping member 24 is a smooth gripping member, the maximum height Ry1 indicating the surface roughness at normal temperature of the first contact surface 33 of the movable portion 31 that contacts the resin film 17 before stretching, and the pedestal 32, The total value (Ry1 + Ry2) of the maximum height Ry2 indicating the surface roughness at normal temperature of the second contact surface 34 in contact with the resin film 17 before stretching is 1 μm to 25 μm. If the total value is too small, the contact pressure applied to the resin film 17 before stretching when the film 17 is gripped by the movable part 31 and the pedestal 32 increases, and the stress applied to the resin film 17 before stretching by the gripping member 24. Tend to increase the load. Moreover, when the film 17 is heated, the heat | fever may cause the malfunction that the resin film 17 before extending | stretching sticks to the movable part 31 or the base 32. When the total (Ry1 + Ry2) value is too large, the resin film 17 before stretching is sandwiched between specific portions of the movable portion 31 and the pedestal 32, so that the resin film 17 before stretching is applied to the resin film 17 before stretching by the gripping member 24. There is a tendency for stress loading to increase.

Here, the normal temperature is a temperature in a standard state in accordance with JIS Z 8703, and specifically, 20 ° C. ± 15 ° C.

Further, the maximum height Ry is a value measured by a method according to JIS B 0601: 1994. Specifically, for example, measurement can be performed using Mitutoyo SURFTEST SV-3100 manufactured by Mitutoyo Corporation.

Further, the structure of the smooth gripping member can be gripped between a surface that contacts one surface of the resin film and a surface that contacts the other surface, and the maximum height Ry1 and the first height on the first contact surface 33 There is no particular limitation as long as the total (Ry1 + Ry2) value of the maximum height Ry2 on the two contact surfaces 34 is 1 μm to 25 μm. The structure of the gripping member is preferably the same as that of the smooth gripping member.

Specifically, for example, a plating process or a polishing process is performed so that the total value (Ry1 + Ry2) of the maximum height Ry1 on the first contact surface 33 and the maximum height Ry2 on the second contact surface 34 is 1 μm to 25 μm. What you gave.

Moreover, as the resin film 17 before stretching that is stretched in the stretching process, it is preferable to use a wet resin film containing a solvent. Moreover, it is more preferable that the residual solvent ratio of the resin film 17 before being stretched in the stretching step is 1% by mass to 0% by mass. By doing so, even if the resin film 17 before stretching is stretched in the width direction, it is possible to easily realize a method for producing a resin film that can produce a resin film having a sufficiently uniform optical value.

Further, as described above, the

grip members

24 and 25 may include grip members other than the smooth grip member as long as the

grip members

24 and 25 include the smooth grip member. In that case, it is preferable to satisfy the following.

Further, the number of the smooth gripping members among the plurality of gripping members 24 constituting the first gripping portion is 98% or more with respect to the total number of the gripping members 24, and the second gripping portion is configured. The number of smooth gripping members in the plurality of gripping members 25 is preferably 98% or more with respect to the total number of gripping members 25. The ratio of the number of smooth gripping members to the total number of gripping members is called the smooth gripping member rate.

By doing so, a resin film having a sufficiently uniform optical value can be manufactured even if a gripping member other than the smooth gripping member is included as the gripping member. Originally, it is preferable to use only a smooth gripping member as the gripping member, but if the above range is satisfied, the optical value is sufficient even if gripping members other than the smooth gripping member are included. A uniform resin film can be produced. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Further, if the gripping member includes a gripping member different from the smooth gripping member as described above, the transportability of the resin film tends to decrease, but the plurality of gripping members constituting the first gripping portion The number of smooth gripping members in 24 is 98% or more with respect to the total number of gripping members 24, and the number of smooth gripping members in the plurality of gripping members 25 constituting the second gripping portion is gripped. As long as 98% or more is satisfied with respect to the total number of members 25, even if a gripping member other than the smooth gripping member is included, a method for producing a resin film excellent in resin film transportability can be provided.

In addition, the number of gripping members other than the smooth gripping member is a gripping member other than the smooth gripping member, and the gripping member adjacent to the gripping member is a gripping member other than the smooth gripping member. It is preferable that it is 5% or less. The ratio of the number of gripping members whose gripping members adjacent to the gripping member are gripping members other than the smooth gripping member to the total number of gripping members other than the smooth gripping member is called the adjacent number ratio of gripping members other than the smooth gripping member. .

By doing so, a resin film having a sufficiently uniform optical value can be manufactured even if a gripping member other than the smooth gripping member is included as the gripping member. Originally, it is preferable to use only a smooth gripping member as a gripping member, but it is a gripping member other than the smooth gripping member, and the gripping member adjacent to the gripping member is a gripping member other than the smooth gripping member. If the number of gripping members satisfies 5% or less with respect to the total number of gripping members other than the smooth gripping member, the optical value is sufficiently high even if gripping members other than the smooth gripping member are included. A uniform resin film can be produced. This is considered to be because even if gripping members other than the smooth gripping member are included, they are less affected if they are dispersed. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Furthermore, if the gripping member includes a gripping member different from the smooth gripping member as described above, the transportability of the resin film tends to decrease, but the gripping member is a gripping member other than the smooth gripping member. If the number of grip members whose grip members adjacent to the grip member are grip members other than the smooth grip member satisfies 5% or less with respect to the total number of grip members other than the smooth grip member, grips other than the smooth grip member Even if a member is included, a method for producing a resin film excellent in resin film transportability can be provided. This is considered to be because even if gripping members other than the smooth gripping member are included, they are less affected if they are dispersed.

Further, the number of smooth gripping members disposed between gripping members other than the smooth gripping members is preferably 5% or more with respect to the total number of smooth gripping members. The ratio of the number of smooth gripping members arranged between gripping members other than the smooth gripping members to the total number of smooth gripping members is called the adjacent number ratio of the smooth gripping members.

According to such a configuration, even when a gripping member other than the smooth gripping member is included as the gripping member, a resin film having a sufficiently uniform optical value can be manufactured. Originally, it is preferable to stretch using only a smooth gripping member as the gripping member, but the number of smooth gripping members arranged between gripping members other than the smooth gripping member is the total number of smooth gripping members. On the other hand, if 5% or more is satisfied, a resin film having a sufficiently uniform optical value can be produced even if a gripping member other than the smooth gripping member is included. This means that even if a gripping member other than the smooth gripping member is included, the smooth gripping member can sufficiently exhibit the effect of increasing the uniformity of the optical value by the smooth gripping member by being continued to some extent. It is thought that. Moreover, since it can extend | stretch uniformly, generation | occurrence | production of a foreign material can be suppressed in the obtained resin film.

Furthermore, if the gripping member includes a gripping member different from the smooth gripping member as described above, the transportability of the resin film tends to decrease, but the gripping member is disposed between gripping members other than the smooth gripping member. If the number of smooth gripping members satisfies 5% or more with respect to the total number of smooth gripping members, even if a gripping member other than the smooth gripping member is included, a resin excellent in resin film transportability A method for producing a film can be provided.

By using the manufacturing apparatus shown in FIG. 1 as described above and the stretching process shown in FIG. 2 using the gripping member shown in FIG. 3, a resin film having a uniform optical value can be obtained even if stretched in the width direction. it can. That is, a wide resin film having a sufficiently uniform optical value can be obtained. Examples of the optical value include in-plane direction retardation Ro and slow axis angle θ. Therefore, by using the manufacturing apparatus shown in FIG. 1 and the stretching process shown in FIG. 2 using the gripping member shown in FIG. 3, the optical values such as the in-plane direction retardation Ro and the slow axis angle θ are brought to the position of the resin film. Regardless, a uniform resin film can be obtained. For this reason, the obtained resin film can be suitably used as an optical film of a liquid crystal display device that is required to have a uniform optical value. Furthermore, it can be suitably used as an optical film for a liquid crystal display device having a large screen.

Moreover, it is preferable that the difference between the maximum value and the minimum value of the in-plane direction retardation Ro of the resin film obtained here is 1 nm or less. The difference between the maximum value and the minimum value of the slow axis angle θ is preferably 0.2 ° or less. The in-plane retardation Ro and the slow axis angle θ can be measured by the methods described in the examples described later.

Further, the stretching ratio in the TD direction of the resin film here is preferably about 1% to 50%. In general, the optical value of the resin film tends to be non-uniform when such a high stretch is used, but the optical value is non-uniform when the film is stretched under a condition where the stretch ratio in the TD direction is 1% to 50%. Can be suppressed. Accordingly, a wide resin film having a uniform optical value can be obtained. Moreover, when the width | variety of a resin film is wide, it is preferable also from the point of use to a large sized liquid crystal display device, the use efficiency of the film at the time of polarizing plate processing, and production efficiency. The stretching ratio is defined by the following formula (1).

Stretch rate (%) = {(L ₂ −L ₁ ) / L ₁ } × 100 (1)
Here, L ₁ indicates the length before stretching between the end portions at a predetermined position of the film, and L ₂ indicates the length after stretching between the end portions at the predetermined position of the film. In addition, the width | variety of a film is the value which measured the width | variety with the C-type JIS1 grade steel scale.

The width of the resin film is preferably 1000 mm to 3000 mm. When trying to produce such a wide resin film, the optical value of the resin film generally tends to be non-uniform. However, when the film is stretched under a stretching ratio in the TD direction of 1% to 50%, It can suppress that a value becomes non-uniform | heterogenous. Accordingly, a wide resin film having a uniform optical value can be obtained. Moreover, when the width | variety of a resin film is wide, it is preferable also from the point of use to a large sized liquid crystal display device, the use efficiency of the film at the time of polarizing plate processing, and production efficiency. The film thickness of the resin film is preferably 10 μm to 90 μm from the viewpoint of thinning the liquid crystal display device and stabilizing the production of the film. Here, the film thickness means an average film thickness, and the film thickness is measured from 20 to 200 in the width direction of the resin film with a contact-type film thickness meter manufactured by Mitutoyo Corporation, and the average of the measured values. Values are shown as film thickness.

1 to 3 describe a method for producing a resin film by stretching a resin film obtained by the solution casting film forming method. The resin film to be stretched is produced by a solution casting film forming method. It is not limited to the made resin film, For example, the resin film obtained by the melt casting film forming method may be sufficient, and the resin film obtained by the other method may be sufficient. According to the manufacturing method by the solution casting film forming method, the uniformity of the film thickness of the resin film before stretching is high, so that the decrease in the uniformity of the optical value due to the non-uniform film thickness is suppressed after stretching in the width direction. Thus, it is possible to obtain a resin film in which the occurrence of optical value defects is further suppressed. And the resin film with a uniform optical value can be manufactured continuously. From these points, it is preferable.

Hereinafter, the composition of the dope used in the present invention will be described.

The dope used in the present invention is obtained by dissolving a transparent resin in a solvent.

The transparent resin is not particularly limited as long as it is a resin having transparency when formed into a film by a solution casting film forming method, etc., but is easy to manufacture by a solution casting film forming method, It is preferable that the adhesiveness with other functional layers, such as a hard-coat layer, is excellent, and that it is optically isotropic. Here, the transparency means that the visible light transmittance is 60% or more, preferably 80% or more, and more preferably 90% or more.

Specific examples of the transparent resin include cellulose ester resins such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin; polyethylene terephthalate resin, polyethylene naphthalate resin, and the like. Acrylic resins such as polymethyl methacrylate resin; Polysulfone (including polyethersulfone) resin, polyethylene resin, polypropylene resin, cellophane, polyvinylidene chloride resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, syndiotactic Vinyl resins such as tick polystyrene resins, cycloolefin resins and polymethylpentene resins; polycarbonate resins; polyarylate resins; It can be mentioned fluorine-based resin or the like; Li ether ketone resins; polyether ketone imide resin; polyamide resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. Furthermore, cellulose ester resins are preferred, and among cellulose ester resins, cellulose acetate resins, cellulose propionate resins, cellulose butyrate resins, cellulose acetate butyrate resins, cellulose acetate propionate resins, and cellulose triacetate resins are preferred, Cellulose triacetate resin is particularly preferred. In addition, as the transparent resin, the above exemplified transparent resins may be used alone, or two or more kinds may be used in combination.

Next, the cellulose ester resin will be described.

The number average molecular weight of the cellulose ester-based resin is preferably from 30,000 to 200,000 because the mechanical strength when molded into a resin film is strong and the dope viscosity is appropriate in the solution casting film forming method. The weight average molecular weight (Mw) / number average molecular weight (Mn) is preferably in the range of 1 to 5, more preferably in the range of 1.4 to 3.0.

Further, the average molecular weight and molecular weight distribution of a resin such as a cellulose ester resin can be measured using gel permeation chromatography or high performance liquid chromatography. Therefore, the number average molecular weight (Mn) and the mass average molecular weight (Mw) can be calculated using these, and the ratio can be calculated.

The cellulose ester resin preferably has an acyl group having 2 to 4 carbon atoms as a substituent. As the substitution degree, for example, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, the total value of X and Y is 2.2 or more and 2.95 or less, X is preferably more than 0 and 2.95 or less.

Further, the portion not substituted with an acyl group usually exists as a hydroxyl group. These cellulose ester resins can be synthesized by a known method. The method for measuring the substitution degree of the acyl group can be measured in accordance with the provisions of ASTM-D817-96.

The cellulose that is a raw material of the cellulose ester resin is not particularly limited, and examples thereof include cotton linters, wood pulp (derived from coniferous trees and hardwoods), kenaf and the like. The cellulose ester resins obtained from them can be mixed and used at an arbitrary ratio, but it is preferable to use 50% by mass or more of cotton linter. When the acylating agent is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), these cellulose ester resins use an organic acid such as acetic acid or an organic solvent such as methylene chloride, It can be obtained by reacting with a cellulose raw material using such a protic catalyst.

Further, the dope may contain a compound having negative orientation birefringence described later.

The compound having negative orientation birefringence means a material exhibiting negative birefringence in the stretching direction of the film in the resin film. As the resin film, for example, in the case of a film composed of a cellulose ester resin, specifically, for example, an acrylic resin, a polyester resin, a compound having a furanose structure or a pyranose structure, a sulfone compound, and the like can be mentioned. Of these, acrylic resins are preferably used.

Whether or not the film has negative orientation birefringence can be determined by measuring the birefringence of the film in a system not added with the compound with a birefringence meter and comparing the difference.

The acrylic resin is preferably an acrylic resin having a negative orientation birefringence in the stretching direction and having a mass average molecular weight Mw of 500 or more and 30000 or less and having an aromatic ring in the side chain. And an acrylic resin having a cyclohexyl group in the side chain is more preferable.

The acrylic resin polymerization method includes, for example, a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a polymerization method. A method using a chain transfer agent such as a mercapto compound or carbon tetrachloride in addition to the initiator, a method using a polymerization terminator such as benzoquinone or dinitrobenzene in addition to the polymerization initiator, JP-A-2000-128911 or A method of bulk polymerization using a compound having one thiol group and a secondary hydroxyl group as described in JP-A-2000-344823, or a polymerization catalyst in which the compound and an organometallic compound are used in combination. Can be mentioned. In particular, the method described in JP-A No. 2000-128911 or JP-A No. 2000-344823 is preferably used.

Further, the acrylic resin preferably has a hydroxyl value measured according to JIS K 0070 (1992) of 30 mgKOH / g to 150 mgKOH / g.

As the solvent for the dope, a solvent containing a good solvent for the transparent resin can be used, and a poor solvent may be contained as long as the transparent resin does not precipitate. Examples of the good solvent for the cellulose ester resin include organic halogen compounds such as methylene chloride. In addition, examples of the poor solvent for the cellulose ester resin include alcohols having 1 to 8 carbon atoms such as methanol.

The dope used in the present invention may contain other components (additives) other than the transparent resin and the solvent as long as the effects of the present invention are not impaired. Examples of additives include fine particles, plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, conductive substances, flame retardants, lubricants, and matting agents.

The fine particles are appropriately selected according to the purpose of use, but are preferably fine particles that can scatter visible light when contained in a transparent resin. The fine particles may be inorganic fine particles such as silicon oxide, or organic fine particles such as acrylic resin.

Also, a cellulose ester resin solution can be obtained by mixing the above-mentioned compositions. The obtained cellulose ester resin solution is preferably filtered using a suitable filter medium such as filter paper.

The plasticizer can be used without any particular limitation. For example, a phosphate ester plasticizer, a phthalate ester plasticizer, a trimellitic ester plasticizer, a pyromellitic acid plasticizer, a glycolate plasticizer, a quencher Examples include acid ester plasticizers and polyester plasticizers. When the plasticizer is contained, the content is preferably 1% by mass to 40% by mass with respect to the cellulose ester resin in consideration of dimensional stability and processability, and 3% by mass to 20%. More preferably, the content is 4% by mass to 15% by mass. If the content of the plasticizer is too small, a smooth cut surface cannot be obtained when slitting or punching, and there is a tendency for generation of chips. That is, the effect of including a plasticizer cannot be sufficiently exhibited.

The antioxidant can be used without any particular limitation, and for example, a hindered phenol compound is preferably used. Moreover, when antioxidant is contained, the content of the antioxidant is preferably 1 ppm to 1.0%, more preferably 10 ppm to 1000 ppm in terms of mass ratio with respect to the cellulose ester resin.

The resin film produced by the method for producing a resin film of the present invention can be used for a polarizing plate or a liquid crystal display member because of its high dimensional stability. In this case, the polarizing plate or the liquid crystal is deteriorated. For prevention, an ultraviolet absorber is preferably used.

As the ultraviolet absorber, those which are excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and have little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specifically, the transmittance at 380 nm is preferably less than 10%, more preferably less than 5%. Specific examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds (benzotriazole ultraviolet absorbers), salicylic acid ester compounds, benzophenone compounds (benzophenone ultraviolet absorbers), and cyanoacrylates. Examples thereof include compounds, nickel complex salts, and triazine compounds. In these, a benzotriazole type ultraviolet absorber and a benzophenone type ultraviolet absorber are preferable. The content of the ultraviolet absorber is preferably from 0.1% by mass to 2.5% by mass, considering the effect as an ultraviolet absorber, transparency, etc., and from 0.8% by mass to 2.0% by mass. It is more preferable that

Examples of the heat stabilizer include kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, inorganic fine particles such as alumina, and alkaline earth metal salts such as calcium and magnesium.

The conductive material is not particularly limited, and examples thereof include ionic conductive materials such as anionic polymer compounds, conductive fine particles such as metal oxide fine particles, and antistatic agents. By containing a conductive substance, a resin film having a preferable impedance can be obtained. Here, the ion conductive substance is a substance that shows electric conductivity and contains ions that are carriers for carrying electricity.

Next, as an example of a method for preparing a dope, a case where a cellulose ester resin is used as a transparent resin will be described.

The method for dissolving the cellulose ester resin when preparing the dope is not particularly limited, and a general method can be used. By combining heating and pressurization, it is possible to heat above the boiling point of the solvent at normal pressure, and it is possible to dissolve the cellulose ester resin in the solvent above the boiling point at normal pressure. It is preferable from the viewpoint of preventing the occurrence of. In addition, a method in which a cellulose ester resin is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

The pressurization may be performed by a method in which an inert gas such as nitrogen gas is injected, or a method in which the solvent is heated in a sealed container and the vapor pressure of the solvent is increased by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

A higher solvent temperature (heating temperature) for dissolving the cellulose ester resin is preferable from the viewpoint of the solubility of the cellulose ester. However, when the heating temperature is increased, the pressure in the container is increased by pressurization. It must be done and productivity deteriorates. Therefore, the heating temperature is preferably 45 ° C to 120 ° C. Further, the pressure is adjusted to such a pressure that the solvent does not boil at the set temperature. Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester resin can be dissolved in a solvent such as methyl acetate.

Next, the obtained cellulose ester resin solution is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like. However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, and a filter medium of 0.001 mm to 0.008 mm is more preferable.

There is no restriction | limiting in particular in the material of a filter medium, A normal filter medium can be used. For example, a plastic filter material such as polypropylene or Teflon (registered trademark) or a metal filter material such as stainless steel is preferable because fibers do not fall off. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester resin solution by filtration. The bright spot foreign matter is opposite when two polarizing plates are placed in a crossed Nicols state, a resin film is placed between them, light is applied from one polarizing plate, and observation is performed from the other polarizing plate. It is a point (foreign matter) where light from the side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

The filtration is not particularly limited and can be carried out by a usual method, but the method of filtration while heating at a temperature not lower than the boiling point of the solvent at normal pressure and at which the solvent does not boil under pressure may be performed before and after the filtration. The increase in the difference in filtration pressure (referred to as differential pressure) is small and preferable. The temperature is preferably 45 ° C to 120 ° C. The filtration pressure is preferably smaller, for example, 1.6 MPa or less.

When each additive is contained in the dope, for example, the agent may be dissolved in an organic solvent such as alcohol, methylene chloride, dioxolane, etc. and then added to the dope, or may be added directly into the dope composition. In addition, for inorganic powders that do not dissolve in organic solvents, the additive and cellulose ester resin are added to the dope using a dissolver or sand mill with the additive dispersed in the cellulose ester resin. It is preferable.

Fine particles are dispersed in the obtained cellulose ester resin solution. The method for dispersing is not particularly limited, and can be performed, for example, as follows. For example, first, a dispersion solvent and fine particles are stirred and mixed, and then dispersed using a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the cellulose ester resin solution and stirred.

Examples of the dispersion solvent include lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Moreover, although it does not specifically limit to lower alcohol, It is preferable to use the thing similar to the solvent used when preparing the solution of a cellulose-ester-type resin.

Dispersers can be used without any particular limitation, and general dispersers can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. Medialess dispersers are preferred from the viewpoint of lower haze (higher translucency). Examples of the media disperser include a ball mill, a sand mill, and a dyno mill. Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type, and a high pressure type dispersing device is preferable. A high-pressure dispersion device is a device that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube. Examples of the high-pressure dispersing device include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, a nanomizer manufactured by Nanomizer, and the like, and other examples include a Manton Gorin type high-pressure dispersing device. Examples of the Menton Gorin type high-pressure dispersing device include a homogenizer manufactured by Izumi Food Machinery, UHN-01 manufactured by Sanwa Machinery Co., Ltd., and the like.

The resin film produced by the method for producing a resin film of the present invention is a resin film having a sufficiently low retardation and a wide width. For this reason, it can apply to image display apparatuses, such as a liquid crystal display device, as a phase difference film for which retardation is required low enough, especially a phase contrast film for IPS.

(Polarizer)
The polarizing plate of this invention is equipped with a polarizing element and the transparent protective film arrange | positioned on the surface of a polarizing element, and a transparent protective film is a resin film manufactured with the manufacturing method of the resin film of this invention. The polarizing element is an optical element that emits incident light by converting it into polarized light.

As a polarizing plate, for example, a resin film or a resin film is prepared by using a completely saponified polyvinyl alcohol aqueous solution on at least one surface of a polarizing element produced by immersing and stretching a polyvinyl alcohol film in an iodine solution. What laminated | stacked the laminated | multilayer film which laminated | stacked this is preferable. Further, a resin film may be laminated on the other surface of the polarizing element, or a transparent protective film for another polarizing plate may be laminated. As the transparent protective film for this polarizing plate, for example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA (above, manufactured by Konica Minolta Opto Co., Ltd.) Etc. are preferably used. Or you may use resin films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

As described above, the polarizing plate uses a resin film as a protective film laminated on at least one surface side of the polarizing element. At that time, when the resin film works as a retardation film, it is preferable that the slow axis of the resin film is arranged so as to be substantially parallel or orthogonal to the absorption axis of the polarizing element.

Further, specific examples of the polarizing element include, for example, a polyvinyl alcohol polarizing film. Polyvinyl alcohol polarizing films include those obtained by dyeing iodine on polyvinyl alcohol films and those obtained by dyeing dichroic dyes. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used.

The polarizing element is obtained as follows, for example. First, a film is formed using a polyvinyl alcohol aqueous solution. The obtained polyvinyl alcohol film is uniaxially stretched and then dyed or dyed and then uniaxially stretched. And preferably, a durability treatment is performed with a boron compound.

The film thickness of the polarizing element is preferably 5 μm to 40 μm, more preferably 5 μm to 30 μm, and even more preferably 5 μm to 20 μm.

When laminating a cellulose ester resin film on the surface of the polarizing element, it is preferable to bond the cellulose ester resin film with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like. Moreover, in the case of resin films other than a cellulose ester-type resin film, it is preferable to carry out the adhesive process to a polarizing plate through a suitable adhesion layer.

The polarizing plate as described above can be applied to a liquid crystal display device having a large screen by using a wide resin film according to the method for producing a resin film of the present invention as a transparent protective film.

(Liquid crystal display device)
The liquid crystal display device of the present invention includes a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the two polarizing plates is a polarizing plate. Note that the liquid crystal cell is a cell in which a liquid crystal substance is filled between a pair of electrodes, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. Such a liquid crystal display device can have a large screen by using a wide resin film according to the method for producing a resin film of the present invention as a transparent protective film for a polarizing plate.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

A resin film was produced by the following method.

(Preparation of dope)
First, in a dissolution tank containing 400 parts by mass of methylene chloride and 45 parts by mass of ethanol, cellulose triacetate propione (acyl group substitution degree: 2.5 (acetylation degree: 61.0%), mass average molecular weight as a transparent resin) Mw: 300,000, number average molecular weight Mn: 100000) 100 parts by mass were added, and 5.5 parts by mass of triphenyl phosphate and 5.5 parts by mass of ethylphthalyl ethyl glycolate were further added. And after raising the liquid temperature to 80 ° C., the mixture was stirred for 3 hours. By doing so, a cellulose triacetate resin solution was obtained. Then, stirring was complete | finished and it was left until liquid temperature became 43 degreeC. Then, the obtained resin solution was filtered using a filter paper having a filtration accuracy of 0.005 mm. Air bubbles in the resin solution were degassed by allowing the resin solution after filtration to stand overnight. Using the resin solution thus obtained as a dope, a resin film (cellulose triacetate propione film) was produced as follows.

(Manufacture of cellulose triacetate film)
First, the temperature of the obtained dope was adjusted to 35 ° C., and the temperature of the endless belt support was adjusted to 25 ° C. Then, using the resin film manufacturing apparatus as shown in FIG. 1, the prepared dope is cast as a dope film from a casting die to an endless belt support, and a web is formed on the endless belt support and dried. , Transported. And the resin film before extending | stretching is peeled from an endless belt support body, the both ends of the resin film before extending | stretching are hold | gripped with the holding member of the conditions shown in Table 1 using the extending | stretching apparatus. However, it was stretched in the MD direction at a stretch rate of 5%. In that case, the conveyance speed of the resin film film before extending | stretching was 50 m / min. By doing so, each cellulose triacetate propione film according to Examples 1 to 8 and Comparative Examples 1 to 8 was produced.

As the conditions of the gripping member, first, among the plurality of gripping members, the maximum height Ry1 at the normal temperature of the first contact surface of the surface that contacts the resin film before stretching, and the maximum at the normal temperature of the second contact surface 34 The height Ry2 and the total value (Ry1 + Ry2) are mentioned. Ry is a value measured by a method based on JIS B 0601: 1994, using Mitutoyo SURFTEST SV-3100 manufactured by Mitutoyo Corporation.

In addition, this smooth holding member is a holding member, and its Ry is about 40 μm. In addition to Ry1 + Ry2, conditions for the smooth gripping member include the following. The ratio of the number of smooth gripping members to the total number of gripping members (smooth gripping member ratio) can be mentioned. Next, the ratio of the number of gripping members other than the smooth gripping members, wherein the gripping members other than the smooth gripping members are gripping members other than the smooth gripping members, to the total number of gripping members other than the smooth gripping members. (Adjacent number ratio of gripping members other than the smooth gripping member). Finally, the ratio of the number of smooth gripping members arranged between gripping members other than the smooth gripping members to the total number of smooth gripping members (adjacent number ratio of smooth gripping members) can be mentioned.

Table 1 shows the gripping member conditions.

The resin films (resin films according to Examples 1 to 8 and Comparative Examples 1 to 8) obtained as described above were evaluated by the following methods.

(Optical value)
The in-plane direction retardation Ro and the slow axis angle θ of 10 samples used in the evaluation of the transparency were measured using an automatic birefringence measuring apparatus (KOBRA-21ADH manufactured by Oji Scientific Instruments).

Specifically, first, using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the retardation of each sample was measured at a wavelength of 590 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH. The angle θ of the axis, the refractive index Nx in the slow axis direction, and the refractive index Ny in the fast axis direction were measured. Next, the film thickness d of the resin film was measured using a contact-type film thickness meter manufactured by Mitutoyo Corporation.

The in-plane direction retardation Ro of each sample was calculated from the obtained measured values using the following formula (2).

Ro = (Nx−Ny) × d (2)
In the formula, Nx represents the refractive index in the slow axis direction of the resin film, Ny represents the refractive index in the fast axis direction, and d represents the film thickness (nm) of the film.

First, if the difference between the maximum value Romax and the minimum value Romin in the in-plane direction retardation Ro of each obtained sample is 1 or less, it is evaluated as “◯”, and if it exceeds 1 and is 2 or less, It evaluated as "(triangle | delta)", if it exceeded 2 and 4 or less, it evaluated as "x", and if it exceeded 4, it evaluated as "xx".

Next, if the difference between the maximum value θmax and the minimum value θmin among the slow axis angles θ of the obtained samples is 0.2 or less, it is evaluated as “◯” and exceeds 0.2. When it was 0.3 or less, it was evaluated as “Δ”, when it exceeded 0.3 and was 0.4 or less, it was evaluated as “x”, and when it exceeded 0.4, it was evaluated as “xx”.

(Transportability)
The end of the resin film immediately after being stretched by the stretching apparatus was photographed with a camera. In that case, the movement distance of the edge part of the resin film in the width direction of the resin film was measured, and the movement distance per hour was defined as the meandering width. When the meandering width is 1 mm or less, it is evaluated as “◎”, when it exceeds 1 mm and 2 mm or less, it is evaluated as “◯”, and when it exceeds 2 mm and 3 mm or less, it is evaluated as “Δ”. If it exceeded 3 mm and 4 mm or less, it evaluated as "*", and if it exceeded 4 mm, it evaluated as "xx". In addition, this meandering width | variety becomes evaluation of a conveyance property, and it turns out that a conveyance property is excellent, so that a meandering width | variety is small.

(Number of foreign objects)
The obtained resin film is placed between two polarizing plates in an orthogonal (crossed Nicols) state, light is applied from one polarizing plate side, and the other polarizing plate side is used with a transmission microscope. And observed at a magnification of 50 times. At that time, the number of foreign matters having a size of 50 μm or more recognized in the polarization crossed Nicol state in an area of 25 cm ² was counted, and the value converted into the number per 1 cm ² was defined as the number of foreign matters.

If the number of foreign matters is 0.15 or less, it is evaluated as “◎”, and if it exceeds 0.15 and is 0.2 or less, it is evaluated as “◯”, and 0.2 If it exceeds 0.25, it is evaluated as “Δ”. If it exceeds 0.25 and is 0.35 or less, it is evaluated as “X”. If it exceeds 0.35, “XX” is evaluated. ".

Here, the foreign matter is a foreign matter recognized in the polarization crossed Nicol state, and in the polarized crossed Nicol state, only the location of the foreign matter is observed in the dark field, so that the number can be easily measured. it can.

The results are shown in Table 2.

As can be seen from Table 1 and Table 2, when Ry1 + Ry2 is stretched using a smooth gripping member having 1 to 25 μm (Examples 1 to 8), compared to other cases (Comparative Examples 1 to 8), A resin film having a uniform optical value can be obtained.

DESCRIPTION OF SYMBOLS 11 Resin film manufacturing apparatus 12 Endless belt support 13 Casting die 14 Peeling roller 15 Drying device 16 Winding device 17 Film 19 Resin solution (dope)
21 Stretching device 22 First rail 23

Second rail

24, 25

Holding member

26, 27, 28, 29 Sprocket 31 Movable part 32 Base 33 First contact surface 34 Second contact surface

Claims

The gripping member moves in the longitudinal direction of the resin film while gripping both end portions in the width direction of the long resin film with a plurality of gripping members, and one of the resin films of the gripping members The distance between the first gripping part having a plurality of gripping members for gripping the end of the resin film and the second gripping part having the plurality of gripping members for gripping the other end of the resin film, With a stretching process that moves in the direction of widening in the width direction,
When the plurality of gripping members used in the stretching step grip the resin film, the maximum height Ry of the first contact surface that comes into contact with one surface of the resin film at room temperature and the other of the resin film A method for producing a resin film, comprising: a smooth gripping member having a total value of a maximum height Ry at normal temperature of a second contact surface in contact with the surface of 1 μm to 25 μm.
The number of the smooth gripping members in the first gripping part is 98% or more with respect to the total number of gripping members in the first gripping part,
The method for producing a resin film according to claim 1, wherein the number of the smooth gripping members in the second gripping portion is 98% or more with respect to the total number of gripping members in the second gripping portion.
The number of gripping members other than the smooth gripping member, wherein the gripping member adjacent to the gripping member is a gripping member other than the smooth gripping member, is the total number of gripping members other than the smooth gripping member. The method for producing a resin film according to claim 1 or 2, wherein the content is 5% or less.
The number of the smooth gripping members disposed between gripping portions other than the smooth gripping member is 5% or more with respect to the total number of the smooth gripping members. Manufacturing method of resin film.
A plurality of the first gripping portions are held at equal intervals by a first endless rotating portion having a portion that circulates in a direction parallel to the surface direction of the resin film and moves along one end portion of the resin film. And
A plurality of the second gripping parts are held at equal intervals in a second endless rotating part having a portion that circulates in a direction parallel to the surface direction of the resin film and moves along one end of the resin film. The manufacturing method of the resin film of any one of Claim 1 to 4.
The method for producing a resin film according to any one of claims 1 to 5, wherein a wet resin film containing a solvent is used as the resin film stretched in the stretching step.
A casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film;
A peeling step of peeling the cast film from the support as a resin film;
While gripping the both side ends of the peeled resin film in the width direction with a plurality of gripping portions, the gripping portion moves in the longitudinal direction of the resin film, and one of the resin films in the gripping portion A stretching step of moving the distance between the first gripping portion gripping the end portion and the second gripping portion gripping the other end portion of the resin film in a direction of gradually widening the width direction of the resin film; Prepared,
The maximum height Ry of the first contact surface that comes into contact with one surface of the resin film when the plurality of grip portions used in the stretching step grip the resin film, and the other of the resin film A method for producing a resin film, comprising: a smooth gripping part having a total value of a maximum height Ry of the second contact surface in contact with the surface at room temperature of 1 μm to 25 μm.
A first gripping part for gripping one end in the width direction of the long resin film;
A second gripping part for gripping the other end of the resin film,
There are a plurality of the first grip portion and the second grip portion, respectively.
While moving in the longitudinal direction of the resin film, the distance between the first gripping portion and the second gripping portion is moved in a direction that gradually widens in the width direction of the resin film,
When gripping the resin film, the maximum height Ry of the first contact surface in contact with one surface of the resin film at room temperature and the second contact surface in contact with the other surface of the resin film at room temperature. A resin film manufacturing apparatus including a smooth gripping portion having a total value with a maximum height Ry of 1 μm to 25 μm.
A resin film obtained by the method for producing a resin film according to any one of claims 1 to 7.
A polarizing plate comprising: a polarizing element; and a transparent protective film disposed on a surface of the polarizing element, wherein the transparent protective film is the resin film according to claim 9.
A liquid crystal cell and two polarizing plates disposed so as to sandwich the liquid crystal cell, wherein at least one of the two polarizing plates is the polarizing plate according to claim 10. Liquid crystal display device.