JP2011016246A - Method for producing stretched film, retardation film, polarizing plate and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for acquiring a wide retardation film having such optical properties that the visibility of a liquid crystal display device or the like can be improved, at a low cost.SOLUTION: A method for producing a stretched film comprises the steps of: conveying a long film stretched to the vertical/uniaxial direction to the stretched direction; holding both ends of the film on a conveyance unit, in a state where a partial region or the whole region of the film is loosened beforehand in the stretched direction by using rugged shape-arranged members; and heating the film while the film is conveyed in the stretched direction by the conveyance unit while holding both ends of the film, to thermally shrink the film in the stretched direction. The retardation film comprises the stretched film produced by this producing method. A polarizing plate utilizing the retardation film and an image display apparatus including the retardation film are also provided.

Description

  The present invention relates to a method for producing a stretched film, a retardation film, a polarizing plate, and an image display device, and more specifically, a method for producing a stretched film suitably used as a retardation film, and the method. The present invention relates to a retardation film, a polarizing plate using the retardation film, and an image display device provided with the retardation film.

  Liquid crystal display devices represented by monitors (displays) for personal computers and television receivers are widely used as various display means. Then, in order to improve the decrease in visibility due to contrast viewing angle, especially when viewed from an oblique direction, the improvement in liquid crystal cells such as IPS mode and VA mode has been proposed (Patent Document 1, Patent Document 2).

  Generally, polarizers are arranged on both sides of these liquid crystal cells, and it is known that display visibility is greatly improved by providing a retardation film between the liquid crystal cell and the polarizer. . In particular, a retardation film having an NZ value of 0.1 or more and 0.9 or less (0.1 ≦ NZ ≦ 0.9), which is an index of optical properties of the retardation film, has an orientation angle and a polarizer. It has been confirmed that the visibility of the display is remarkably improved when it is used by being laminated so that the absorption axis thereof is orthogonal (Patent Document 3). Here, the NZ value is defined as follows.

NZ = (nx-nz) / (nx-ny)
[Nx represents the refractive index in the slow axis direction of the retardation film,
Here, the slow axis direction refers to the direction in which the refractive index in the retardation film surface is maximized,
ny represents the refractive index in the fast axis direction of the retardation film,
nz represents the refractive index in the thickness direction of the retardation film. ]

  Moreover, the method of manufacturing the retardation film used as the range of 0.1 <= NZ <= 0.9 by using a heat-shrinkable film is proposed (patent document 4).

JP 2001-31948 A JP-A-11-305217 JP 2008-247933 A JP 2006-72309 A

With the increase in the screen size of liquid crystal display devices, the required quality of retardation films used for improving the visibility of liquid crystal display devices is rapidly increasing. In particular, the orientation angle accuracy and phase difference variation are required to be good over a large area of the film.
In addition, in order for liquid crystal display devices to become widespread in the world, innovative cost reduction of materials used in liquid crystal display devices, that is, innovations in structure, materials, manufacturing methods, supply, etc., and productivity through standardization Need to be improved.

As described above, when a retardation film having a NZ value in the range of 0.1 ≦ NZ ≦ 0.9 is used, display visibility is improved. As a method of producing a retardation film having such optical characteristics, a method of producing a film by stretching in the longitudinal direction after bonding a heat-shrinkable film to one or both sides of a polymer film with an adhesive or the like (patent) Document 4) is disclosed. However, since this method gives heat shrinkage due to the heat-shrinkable film bonded while longitudinally stretching the polymer film, the stretched retardation film has a very narrow width. In addition, a secondary member such as a heat-shrinkable film or a pressure-sensitive adhesive is required, and a process of bonding is also required, so that it is difficult to reduce manufacturing costs. Furthermore, when a polymer film and a heat-shrinkable film are bonded together, not only a small amount of fine foreign matter is mixed in, but also reducing the product yield is one factor that hinders the reduction in manufacturing cost.
As described above, a technique for obtaining a wide retardation film in a range of 0.1 ≦ NZ ≦ 0.9 that improves the visibility of a liquid crystal display device at low cost is desired.

  As a result of intensive studies in view of the above problems, the present inventors have found that the above object can be achieved by a method for producing a stretched film, a retardation film, and an image display device described below, and have completed the present invention. . That is, the present invention is as follows.

1. A long film stretched in the longitudinal uniaxial direction is transported in the stretching direction, and both ends of the film are partially slackened in the stretching direction in advance by a member provided with an uneven shape. A method for producing a stretched film, wherein the film is heated and contracted in the stretching direction by heating the film while being transported in the stretching direction while holding both ends of the film by the transport device.

2. It is characterized by holding the both ends of the film in the conveying device by holding the end of the film with a holding member provided with a holding member piece that is uneven in a state where a partial region or the entire region of the film is slackened in the stretching direction. 2. The method for producing a stretched film as described in 1 above.

3. 3. The film according to 1 or 2 above, wherein both ends of the film are held in a conveying device after slackening a partial region or the entire region of the film by alternately pressing one surface and the other surface of the film. A method for producing a stretched film.

4). When shrinking the film in the stretching direction, the film is held without changing the distance between both ends of the film, or the both ends are widened in the transverse direction with respect to the conveying direction. The manufacturing method of the stretched film as described in any one of.

5. A retardation film comprising a stretched film produced by the method according to any one of 1 to 4 above.

6). Following formula (1):
0.1 ≦ NZ ≦ 0.9 (1)
[NZ = (nx−nz) / (nx−ny),
nx represents the refractive index in the slow axis direction of the retardation film,
Here, the slow axis direction refers to the direction in which the refractive index in the retardation film surface is maximized,
ny represents the refractive index in the fast axis direction of the retardation film,
nz represents the refractive index in the thickness direction of the retardation film. ]
6. The retardation film as described in 5 above, which has optical characteristics satisfying the above.

7). The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (2):
20 nm ≦ Re ≦ 70 nm (2)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film as described in 6 above, wherein

8). The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (3):
100 nm ≦ Re ≦ 350 nm (3)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film as described in 6 above, wherein

9. The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (4):
400 nm ≦ Re ≦ 700 nm (4)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film as described in 6 above, wherein

10. 10. The retardation film as described in any one of 5 to 9 above, wherein the orientation angle in the film plane is within ± 1.0 °.

11. A polarizing plate in which a polarizer is laminated directly or via a polarizer protective film on at least one surface of the retardation film according to any one of 5 to 10 above.

12 An image display device comprising the retardation film according to any one of 5 to 10 above.

  In the present invention, a stretched film having excellent optical properties can be easily produced. In particular, according to the present invention, a stretched film having optical characteristics satisfying 0.1 ≦ NZ ≦ 0.9 can be easily produced, which contributes to the cost reduction of a liquid crystal display device with good visibility.

(A) is a side view of a clip in the first embodiment (broken lines are wavy gripping members), and (b) is an explanatory view showing the relationship between the clip and the film. (A) is a side view of a clip in the second embodiment (broken lines are wavy gripping members), and (b) is an explanatory view showing the relationship between the clip and the film. It is a schematic plan view which shows an example of the film extending machine which can be used for the manufacturing method of the stretched film of this invention, and shows the form in the case of extending | stretching a film to a horizontal direction. It is a front view of a clip and a wavelike holding member. FIG. 4 is a side view of the feeder chain and the wavy gripping member of FIG. 3. FIG. 4 is a partially enlarged side view of the feeder chain and the wavy gripping member of FIG. 3. It is a perspective view of the film extending machine of FIG. It is a cross-sectional perspective view of the film stretching machine in the state holding the film. It is a perspective view of the clip in a first embodiment. (A) is a front view of the clip immediately before holding the film in the first embodiment, and (b) is a side view of the clip immediately before holding the film in the first embodiment. (A) is a front view of the clip in the state which hold | maintained the film in 1st embodiment, (b) is a side view of the clip in the state which hold | maintained the film in 1st embodiment. It is a perspective view of a wavy holding member. It is explanatory drawing which shows the relationship between the position of the film in 1st embodiment, and the attitude | position of a clip and a wavy holding member. It is a perspective view of the clip in 2nd embodiment. (A) is a front view of the clip immediately before holding the film in 2nd embodiment, (b) is a side view of the clip just before holding the film in 2nd embodiment. (A) is a front view of the clip in the state which hold | maintained the film in 2nd embodiment, (b) is a side view of the clip in the state which hold | maintained the film in 2nd embodiment. It is explanatory drawing which shows the relationship between the position of the film in 2nd embodiment, and the attitude | position of a clip and a wave-shaped holding member. It is sectional drawing which shows the behavior of the film at the time of hold | maintaining a film with the clip in 1st embodiment. It is sectional drawing which shows the behavior of the film at the time of hold | maintaining a film with the clip in 2nd embodiment. It is a front view which shows the modification of the member provided with the uneven | corrugated shape. It is a perspective view which shows the other modification of the member provided with the uneven | corrugated shape. It is a side view which shows the modification of a feeder chain and a wave-shaped holding member. It is a conceptual diagram which shows the modification of the method to wave a film. It is a conceptual diagram which shows the other modification of the method of making a film wave. It is a conceptual diagram which shows the further another modification of the method of making a film wave. It is a schematic plan view of the film extending machine of embodiment shown in FIG. 3, and shows the form in the case of not extending | stretching a film to a horizontal direction.

  In the present invention, a film previously stretched in one direction (for example, a longitudinal uniaxial direction) is transported in the stretching direction, and a partial region or the entire region thereof is slackened in the transport direction, and heated to stretch the film. It is based on the ability to manufacture a film oriented in the thickness direction by heat shrinkage.

  In the method for producing a stretched film of the present invention, a long film stretched in a longitudinal uniaxial direction is transported in the stretch direction, and the stretch direction is preliminarily formed by a member provided with a concavo-convex shape in a partial region or the entire region of the film. The film is heated and contracted in the stretching direction by heating the film while being transported in the stretching direction while holding both ends of the film by the transporting device while holding the both ends of the film in a state of being slackened. Features.

That is, in the present invention, a long film stretched in the longitudinal uniaxial direction is used. Here, generally, a film stretched in one direction has a property of returning to a shape before stretching by applying heat.
And in this invention, the elongate film extended | stretched to the vertical uniaxial direction is conveyed in the extending | stretching direction (longitudinal direction, a longitudinal direction), and the said film | membrane is a part of the whole area | region or the whole area previously by the member provided with uneven | corrugated shape Both ends of the film are held in the transport device in a state of being slackened in the stretching direction. Then, the film is heated and contracted in the stretching direction by heating the film while being transported in the stretching direction while holding both ends of the film by the transport device.
Here, in this invention, since both ends of a film are hold | maintained to a conveyance apparatus in the state which slackened the film, there is a shrinkage margin by heat shrink and it is hard to produce the stress which prevents shrinkage.
Further, since both ends of the film are held, the film does not shrink in the lateral direction (perpendicular to the transport direction).
Therefore, the film stretched in the longitudinal uniaxial direction is deformed only in the shrinking direction, and in this process, the resin is oriented in the thickness direction.

  In a preferred embodiment, the film ends are held by a holding member having an uneven holding member piece in a state in which a partial region or the entire region of the film is slackened in the stretching direction, and both ends of the film are held by the transport device. To do.

  In a preferred embodiment, both ends of the film are held in the transport device after the partial area or the entire area of the film is loosened by alternately pressing one side and the other side of the film.

  When the film is contracted in the stretching direction, the film may be held without changing the distance between both ends of the film, or both ends may be widened in the transverse direction with respect to the transport direction.

  In an embodiment to be described later, in order to hold the film in a corrugated (loosened) state, at least one of the upper and lower holding members of the flapper-type clip has a corrugated shape. At this time, as a general rule, the film is waved by sandwiching the film with corrugated clips. Here, the meaning of “shaping” does not mean that the film is plastically deformed, but means that the film is not flat but waved.

Further, the following embodiment provides means for producing a stretched film having an orientation component in the thickness direction by smoothly and surely sandwiching and transporting the film with the corrugated holding member. is there.
That is, when the holding member of the flapper clip is made into a waveform, the upper teeth (protrusions) and lower teeth (protrusions) of the holding member that are in contact with the flat film when the film is gripped by the flapper are upstream in the process. It is necessary to pull in the film from the side. At this time, since a large frictional force acts between the upper teeth and lower teeth of the holding member and the film, if the flapper is not rotated with a considerably large force, the film can be gripped in a corrugated shape by the clip. There is a problem that it cannot be done.

  Generally, the flapper swings like a pendulum and moves close to and away from the film placement surface, and the swinging direction is perpendicular to the film transport direction. Therefore, the flapper is initially outside the side of the film, swings in a circular arc locus, and moves toward the center of the film. Finally, the tip of the flapper comes into contact with the film. After that, the flapper continues to swing while drawing an arc trajectory, so the flapper swings toward the center of the film even after coming into contact with the film, and not only presses the surface of the film but also applies force to the inside. End up.

  Thus, the flapper presses the film while moving in the width direction of the film. Therefore, when the flapper is remodeled into a corrugated shape, the frictional force with the film increases. For this reason, the flapper modified to corrugation generates considerable frictional force with the film, so the edge of the film moves in the center direction along with the lateral movement of the flapper, causing wrinkles on the film, Could be damaged.

  Therefore, in order not to generate a frictional force between the film and the clip, the film is not overdrawn from the upstream side by the occlusal force of the clip, but the film is overfeeded so as to wave in accordance with the gripping shape of the clip. do it.

Therefore, in the following embodiment, a film overfeed device capable of overfeeding while forming a film into a waveform is used, and the film is gripped into a waveform without difficulty.
The meaning of “shaping” is as described above, and does not mean that the film is plastically deformed, but means that the film is not flat but waved.
When using a film overfeed device that can overfeed while shaping the film into a corrugated shape, it is recommended that at least one of the upper and lower holding members hold the film with a corrugated clip and stretch the film. However, it is also possible to stretch the film while holding the film with other known clips.

In the present invention, the state of “loosening” refers to a state in which the actual length of the film existing at a specific interval in the conveying state is longer than the specific interval described above. It can be said that the film is excessively supplied.
When the shape in the “loosening” state is appearance, for example, a wavy state can be considered. The “wavy state” may be a state in which the shape and period of the peaks and valleys are irregular, but for the purpose of uniform quality, it is desirable that the shape and period of the peaks and valleys be regular. .
As a recommended form of "sagging" state, in addition to the state where peaks and valleys like sine curves exist regularly, only the state where valleys exist and valleys like pulsation only The state which exists is mentioned. Further, it may be in the form of fine vibration.
In the present invention, the film is slackened so as to be in a state of being shaped into a corrugated shape and thermally contracted in the vertical direction, but the method of slackening the film (shaped into a corrugated shape) is arbitrary. As one measure, the film can be formed into a corrugated shape by the holding member piece itself. That is, a pair of holding member pieces each having a concavo-convex shape are used, and the film is loosened by being sandwiched between the holding member pieces.
In one embodiment, both holding member pieces each have a convex portion and a concave portion. The uneven shape is not particularly limited, and a shape having a round peak shape or a valley bottom shape or a flat shape may be considered. Specific examples of the concavo-convex shape include those in which peaks and valleys appear alternately, such as a sine curve, but also include those in which only ridges or valleys exist and appear to be external concavo-convex shapes. Needle-like shapes are also included in the irregular shape.
The most recommended uneven shape is a corrugated shape having peaks and valleys like a sine curve.
As described above, it is recommended to use a pair of holding member pieces that are both concavo-convex and sandwich the film between the holding member pieces so that the film is waved, but the present invention is limited to this configuration. It is not something. That is, it is possible to shape the film into a corrugated shape by using a holding member piece having only one of the concave and convex shapes and pressing the film with the holding member piece. In this aspect, one holding member piece has a convex part and a concave part.
Furthermore, it is also possible to shape the film into a corrugated shape using one holding member piece having only a convex portion or one holding member piece having only a concave portion.
Furthermore, a device for shaping the film into a corrugated shape may be prepared separately, and the film may be shaped into a corrugated shape using this device.

  With such a configuration, it is possible to prevent lateral shrinkage while the film is loosened (preferably in a waveform shape), and heat shrink only in the longitudinal direction.

  As another aspect of the present invention, at least one surface of the film is transported while sandwiching both ends of the film with the holding member and before sandwiching both ends of the film with the holding member, or when sandwiching both ends of the film with the holding member. A method may be considered in which a partial region or the entire region of the film is slackened by pressing at a distance in the transport direction, and the film is thermally shrunk in a relaxed state.

Here, “pressing at least one surface of the film with an interval in the transport direction” means pressing a part of the film and then pressing a position away from the film in the transport direction. For example, it is possible to “press at least one surface of the film at an interval in the transport direction” by sandwiching the film between members provided with uneven shapes such as corrugations.
That is, since the convex portion is formed with a certain interval in the member provided with the uneven shape, when the film is sandwiched between the members provided with the uneven shape, both surfaces of the film are spaced in the transport direction. Open and pressed.
Moreover, you may press a film with the member which has only convex shape.
Further, a typical external shape in the “sag” state is a waved state as described above.

  Examples of the member provided with the uneven shape include a wave-like gripping member provided with supercharging protrusions that protrude alternately toward the film. The wavy gripping member is preferably a member that forms a gap larger than the thickness of the film at the time of occlusion.

  According to this method, an excessive pressure is not applied to the central portion of the film to cause scratches, or wrinkles are not formed on the film due to excessive supply.

  As still another aspect of the present invention, a step of loosening both ends of the film by a member provided with a concavo-convex shape, a holding step of holding both ends of the loose film in a transport device, and transporting the film by the transport device And a step of heat shrinking.

  With such a configuration, it is possible to hold the continuously supplied film in advance (preferably after forming it into a waveform) and then hold it on the conveying device while maintaining the loose state (preferably the waveform). It becomes possible to heat-shrink the film shaped into a waveform in the longitudinal direction.

  The step of loosening (preferably the step of undulating, the same applies hereinafter) may be a step of gradually pressing the member provided with the uneven shape against the film.

  Here, “gradually” refers to a situation in which a certain amount of time is required from the start to the completion of the operation, and refers to a situation in which the member provided with the concavo-convex shape is operated at an operation speed at which the state of movement can be visually confirmed. It is desirable that one second or more be required between the start and completion of the loosening process (rippling process).

  Another preferred embodiment relates to the method for producing a stretched film, wherein the loosening step is a step of gradually sandwiching the film between the members provided with the uneven shape.

  According to the two aspects described above, the continuously supplied film can be more smoothly shaped into a waveform.

  You may change the wave shape of the film shape | molded in the process to loosen by changing the distance of the members provided with the uneven | corrugated shape.

  According to this aspect, it is possible to freely adjust the slack state of the film, for example, the shape of the waveform, and it is possible to freely control the effect of suppressing the stretching of the film in the transport direction.

  For example, the step of holding the both ends of the film shaped into a waveform in the conveying device may be a step of sandwiching by a holding member having a member that approaches and separates.

  A typical example of the “holding member having a member that approaches and separates” is a clip. According to this aspect, for example, it is possible to hold the film in a waveform while maintaining the shape of the film shaped into a waveform.

  The holding member has a pair of holding member pieces, and sandwiches the end portions of the film between the holding member pieces, and a configuration in which both of the pair of holding member pieces have an uneven shape is recommended.

  According to this aspect, for example, it becomes possible to hold the film waveform shaped into a waveform on the conveying device while reliably maintaining the waveform.

  In another preferred aspect of the present invention, the holding member has a pair of holding member pieces, and the end portions of the film are sandwiched between the holding member pieces, and one of the pair of holding member pieces has an uneven shape. Yes, and the other relates to a method for producing the stretched film having a planar shape.

  According to this aspect, for example, it is possible to reliably fix the film to the transport device regardless of the size of the waveform of the film previously shaped into the waveform or the period of the wave.

In addition, it is recommended that the step of loosening (waving step) is performed using a film overfeed device.
The recommended film overfeed device here is
In a film overfeed device that constitutes a film stretching machine in combination with a film stretching unit,
The film stretching unit has a configuration for holding a side end of a film in a transported state, and the film overfeed device is arranged at an upstream side of the film stretching unit or at a position equivalent to the film stretching unit,
It has a corrugated gripping member with a front gripping piece and a back gripping piece, each of the front gripping piece and the back gripping piece has a supercharging projection, and the supercharging projection of the front gripping piece and the supercharging projection of the back gripping piece In a state where the front side gripping piece and the back side gripping piece are close to each other in the conveying direction, the supercharging protrusions are engaged with each other,
The front-side grip piece and the back-side grip piece are disposed opposite to the front and back sides of the film, and the wavy gripping member sandwiches the film between the front-side grip piece and the back-side grip piece while moving in the film transport direction, and relaxes the film. This is a film overfeed device.

Here, the biting posture refers to a state in which the concave and convex shapes face each other and the other convex portion enters into one concave portion in addition to a state of fitting like a gear.
The film overfeed device employed in the present invention can temporarily wave a film sent in a plane and supply the film to the film stretching section in this waved state.
That is, the film overfeed device of this embodiment is disposed upstream of the film stretching section or at a position equivalent to the film stretching section, and before the film stretching section holds the film, or the film stretching section is Functions simultaneously with holding the film.
Hereinafter, in order to simplify the description, it will be described that the film overfeed device functions before the film stretching unit holds the film.
The film overfeed device of the present embodiment has a wave-like gripping member having a front-side gripping piece and a back-side gripping piece, and sandwiches the film before the film stretching unit holds the film.
In the film overfeed device of this embodiment, there are supercharging protrusions on both the front side gripping piece and the backside gripping piece, and the supercharging protrusion on the front side gripping piece and the supercharging protrusion on the backside gripping piece are staggered in the film transport direction. In a state where the front side grip piece and the back side grip piece are close to each other, the supercharging protrusions are engaged with each other.
Therefore, when the film is sandwiched between wavy gripping members having a front side gripping piece and a back side gripping piece, the film undulates.
Therefore, according to the film overfeed device of this embodiment, the film can be waved in advance and supplied to the film stretching section.

  The film overfeed device according to another aspect is disposed to face both the front and back sides of the film, and includes a waved gripping member that sandwiches the film while moving in the film transport direction. Supercharging protrusions arranged in the transport direction and projecting alternately toward the film so as to extend in the width direction of the film are provided.

  According to this configuration, the supercharging protrusion pulls the film from the upstream side and loosens it by sandwiching the film with the wavy gripping member. As a result, the film can be supplied in a shape that is held by the film stretching machine, so that the film stretching machine can easily grip the film in a wave shape.

  A plurality of the wavy gripping members may be held at equal intervals by an annular endless member that circulates in a plane orthogonal to the film conveyance surface.

  By doing so, the plurality of wavy gripping members can be regularly rotated so as to sandwich the film from the front and back at regular intervals.

  Further, in the film overfeed device of the present embodiment, the wave-shaped gripping member may be released after gradually sandwiching the film, gripping and transporting the sandwiched film for a certain period of time.

  According to this configuration, the wavy gripping member slowly sandwiches the film, so that the film can be pulled in from the upstream side without difficulty. In addition, both sides of the film can be easily gripped by the film stretching machine while gripping the film.

  Further, in the film overfeed device of the present embodiment, the wavy gripping member may form a gap larger than the thickness of the film at the time of occlusion.

  According to this configuration, an excessive pressure is not applied to the central portion of the film to cause scratches, or wrinkles are not formed on the film due to excessive supply.

  The film stretching machine has a plurality of clips that respectively circulate on both sides of the film at a speed equal to that of the wavy gripping member of the film overfeed device, and grip the side edges of the film. A tooth portion for engaging the corrugated waveform corresponding to the supercharging protrusion of the corrugated gripping member to grip the film is provided, and the side edge of the film is gripped when sandwiched between the corrugated gripping members.

  According to this configuration, since the film waved by the wavy gripping member is gripped by the clip having the corrugated shape, the clip can grip the film without difficulty, and the film cannot be wrinkled or scratched.

  In another aspect of the present invention, a long film, which has been previously stretched in the longitudinal direction, is transported in the longitudinal direction, while a partial region or the entire region of the film is previously slackened in the longitudinal direction. The film is thermally shrunk only in the longitudinal direction (longitudinal direction, transport direction).

  Moreover, the partial area | region or the whole region of a film can be slackened to a longitudinal direction previously by pressing at least one surface of the said film at intervals in a conveyance direction.

  It is recommended that a partial region or the entire region of the film is loosened in the longitudinal direction in advance by alternately pressing one surface and the other surface of the film.

  Moreover, it is also possible to press the film by sandwiching the film between the members provided with the concavo-convex shape, and partially relax the partial region or the entire region of the film in the longitudinal direction in advance.

  It is recommended that a partial region or the entire region of the film is previously loosened in the longitudinal direction by pressing the central portion in the width direction of the film.

  In other words, the film may be loosened by sandwiching both ends in the width direction of the film with an instrument, but loosening the film uniformly by sandwiching the part other than the end (center part) with the instrument will loosen the whole evenly. Cheap.

  Further, a long film is transported by a transporting means, and the film is in a state where a part of the film or a whole region is waved with the film being given a degree of freedom in the transporting direction with respect to the transporting means. It is recommended to relax.

  In this embodiment, since the film has a degree of freedom in the transport direction with respect to the transport means, it is easy to pull in the film on the upstream side or the downstream side in the transport direction when the film is sandwiched by an instrument. For example, it is desirable to use this embodiment together when a holding member that sandwiches both ends of the film is provided with a concavo-convex shape and the film is loosened by sandwiching both ends of the film with the holding member.

  In addition, it is recommended to hold both ends of the film in a state where a partial region or the entire region of the film is previously slackened in the longitudinal direction, and heat shrink in the longitudinal direction with respect to the transport direction while transporting in the longitudinal direction.

  Next, the manufacturing method of the stretched film of this invention and the example of the apparatus for manufacturing are explained in full detail below, referring drawings. However, the present invention is not limited to these.

  In the present invention, the film F stretched in the vertical uniaxial direction in advance is held by the holding members 2 and 55 having a specific shape, and heated, so that the film F is shaped into a waveform and vertically The film F can be shrunk in the transport direction while being oriented in the thickness direction by thermal shrinkage, and the film F oriented in the thickness direction can be produced. This is the basic idea.

  Furthermore, another essential point of the present invention is to supply the film F stretched in advance in the longitudinal uniaxial direction in order to realize the heat shrinking operation continuously and smoothly, continuously along the transport direction of the film F. The process of shaping into a waveform, the process of gripping both ends of the film F shaped into a waveform with a conveying device, and the process of heat shrinking by heating while conveying the film F stretched in the longitudinal uniaxial direction are carried out continuously. There is to do.

  In the present invention, as a preferable mode of the holding member 2 for holding the film F in a wave shape and holding the film F in the transverse direction with respect to the conveyance direction, and further heat-shrinking the film F without difficulty, A clip with an uneven shape that engages the upper and lower teeth. If the clip having such a structure is used, the film F can be shaped into a corrugated shape, and the film F can be thermally contracted in the transport direction. The period and size of the shape of the unevenness that bites the film F is arbitrarily selected according to the physical properties of the film F and the stretching ratio.

An example (first embodiment) of the clip-type holding member 2 is shown in FIG. The surface of the holding member 2 sandwiching the film F is composed of an upper tooth portion (holding member piece) 12 and a lower tooth portion (holding member piece) 11 that are corrugated with each other. Since the film F gripped by such a clip forms a wave shape, the object of the present invention can be achieved.
As another preferred embodiment of the holding member for allowing thermal contraction in the transport direction in a state where the film F is shaped into a corrugated shape, as shown in FIG. A clip having a structure in which one of 57 has an uneven shape and the other has a planar shape (second embodiment). A clip having such a structure is preferable because the film F can be shaped and stretched into a waveform having an arbitrary height or period. Furthermore, when using an apparatus that continuously shapes the film F into a waveform, such as the above-described film overfeed apparatus, the film F can be used even if the waveform period and height of the shaped film F are not constant. It is possible to securely insert the end portion, which is the most preferable embodiment.

  The upper surface of the surface of the holding member 55 sandwiching the film F is an upper tooth portion (holding member piece) 56 having a corrugated uneven shape. On the other hand, the lower surface is a flat surface 57. When such a clip is used to grip a film F shaped in a waveform with a film overfeed device described later, the film F can be thermally contracted in the vertical direction while maintaining a shrinkage margin.

  Next, the outline | summary is demonstrated about the film extending machine 1 which can be used for the manufacturing method of the stretched film of this invention.

3 and 26 show a film stretching machine 1 according to one embodiment of the present invention. The film stretching machine 1 includes a tenter chain 3 in which clips 2 that hold both side ends of the film F are provided at equal intervals, and a heating furnace 4 that heats the film F held by the tenter chain 3 with hot air, The film F is stretched in the width direction by widening the interval between the tenter chains 3 that hold the film F. Note that the interval between the tenter chains 3 can be changed by an adjusting device (not shown), and as shown in FIG. 26, the interval between the tenter chains 3 can be always constant. As shown in FIG. 26, if the distance between the tenter chains 3 is always constant, the film F is not stretched in the width direction, and only contracts in the width direction.
The film stretching machine 1 has two pairs of feeder chains (endless members) that circulate in a plane perpendicular to the conveyance surface (horizontal plane) of the film F on the front and back sides of the film F and parallel to the conveyance direction of the film F, respectively. 5 and a film overfeed device 7 that is held in the feeder chain 5 at equal intervals with the clip 2 and includes wavy gripping members 6a and 6b that sandwich the film F from the front and back.

The structure of the apparatus for continuously shaping the film F used in the present invention into a waveform along the conveying direction is not particularly limited as long as the apparatus can continuously shape the film F into a waveform. For example, the film overfeed device 7 as shown in FIGS. 3 and 26 is preferable because it does not give excessive friction and tension to the film F, and can smoothly shape the waveform.
The figure which looked at the film overfeed apparatus 7 from the side in FIG. 5 is shown. In this film overfeed device 7, wave-shaped gripping members (front-side gripping pieces and back-side gripping pieces) 6a, 6b that are arranged to face both front and back surfaces of the film F and sandwich the film F while moving in the transport direction of the film F The corrugated gripping member 6 includes supercharging protrusions 15 that are arranged in the transport direction of the film F and protrude from each other.

  The wavy gripping members (front side gripping pieces and back side gripping pieces) 6a and 6b of the film overfeed device 7 are fixed to the frames of the upper and lower feeder chains 5 at equal intervals. As shown in FIGS. 5 and 6, the wavy gripping members (front gripping pieces and back gripping pieces) 6 a and 6 b have the waveform of the lower tooth portion 11 and the upper tooth portion 12 of the clip 2 in the transport direction of the film F. Supercharging protrusions 15 that protrude toward the film F so as to extend in the width direction (perpendicular to the conveying direction) of the film F are formed alternately at the same pitch as the period. The wavy gripping members (front side gripping pieces and back side gripping pieces) 6a and 6b are engaged with each other when the upper and lower feeder chains 5 are brought close to each other by the feeder guides 16 and 17.

However, the corrugated gripping members (front gripping pieces and back gripping pieces) 6a and 6b do not come into contact with each other even when reapproaching so as to receive the supercharging protrusions 15, and are sufficiently larger than the thickness of the film F. Engage so as to leave a gap. Thereby, excessive compressive stress is applied to the central portion of the film F so as not to be damaged.
In addition, the supercharging protrusion 15 slacks the whole area | region of a film in a longitudinal direction previously by pressing the surface of the film F at intervals in a conveyance direction.
Further, in the film overfeed device 7 used in the present invention, the wavy gripping members (front side gripping pieces and back side gripping pieces) 6a and 6b are annular endless members that circulate in a plane orthogonal to the transport surface of the film F. A plurality of them may be held at regular intervals.
The height, width, shape, period, and the speed at which the upper and lower supercharging protrusions 15 approach each other, such as the length required to shrink the film F, the film It is possible to select freely from the minimum bend radius or the like to avoid F breakage.

In the film stretching machine 1 having the above configuration, before the clip 2 grips the film F, first, the wavy gripping members 6a and 6b of the film overfeed device 7 gradually sandwich the film F from the upper and lower surfaces. That is, the supercharging protrusion 15 gradually presses the surface of the film F.
The clip 2 is configured to grip both side ends of the film F with the holding member 2 while the film overfeed device 7 approaches the wave-shaped gripping members 6 a and 6 b to sandwich the film F.

  The position at which the film F is sandwiched from above and below by the wavy gripping member 6 is arbitrary, but it is necessary to sandwich the film F inside the end portion of the film F. That is, it is necessary to hold the end portion of the corrugated film F on the transport device while maintaining the corrugated film F. As a specific position for sandwiching the film F, if it is too close to both ends of the film F, it will interfere with the holding member (clip) 2 and the like. It is more preferable that the inner side is sandwiched by 10 mm or more from both ends from the viewpoint of securely fixing. On the other hand, if the position where the film F is sandwiched from above and below is too far from both ends of the film, the waveform of the portion sandwiched between the holding members (clips) 2 will weaken and the film F will be wasted, so within 20 mm from both ends It is preferable that it is a position.

As a device for stretching the film F in the lateral direction while conveying the film F (or preventing the shrinkage in the lateral direction), a conventional stretching device can be used without any particular limitation. Generally, two sets of chains are passed through a tenter furnace (heating furnace 4), a device for fixing both ends of the film F is attached to the chain, and the distance between the two sets of chains increases as the chain moves. And is also suitable for the present invention. As described above, the apparatus employed in the present embodiment can maintain a parallel state with a constant distance between the two sets of chains (FIG. 26).
Conditions such as the temperature of the tenter furnace, the stretching ratio of the film F, and the stretching step are arbitrary, and an optimum value can be selected according to the physical properties of the film F.
As described above, the film F is previously stretched in the longitudinal uniaxial direction. As is well known, a film stretched in the longitudinal direction contracts in the longitudinal direction (stretching direction) when heated.

Next, a specific structure of the film stretching machine 1 for carrying out the present invention will be described.
As shown in FIGS. 3 and 7, the film stretching machine 1 includes a film stretching unit 20, a heating furnace 4, and a film overfeed device 7.
The film stretching section 20 includes two systems of tenter chains 3a and 3b, and clips 2 that hold both ends of the film F (previously stretched in the longitudinal uniaxial direction) on the tenter chains 3a and 3b are equally spaced. Is provided.
The tenter chains 3a and 3b are suspended from the drive side sprockets 21a and 21b and the driven side sprockets 22a and 22b.
The four sprockets 21a, 21b, 22a, 22b that suspend the tenter chains 3a, 3b are all arranged in the same plane as shown in FIGS. 3 and 7, the four sprockets 21a, 21b, 22a, and 22b that suspend the tenter chains 3a and 3b all have a rotation axis in the direction perpendicular to the paper surface, and the four sprockets 21a , 21b, 22a, 22b are all arranged on a plane parallel to the paper surface.

  As shown in FIGS. 3 and 7, the two tenter chains 3 a and 3 b are arranged so that one running surface faces each other. The opposing running surfaces of the two systems of tenta chains 3 a and 3 b function as the extending action portion 27.

The opposite running surfaces (extension acting portions 27) of the two systems of tenta chains 3a and 3b are constituted by an introduction-side straight portion 23, an inclined portion 24, and a terminal-side straight portion 25.
The running surfaces of the tenter chains 3a and 3b (the extending action portion 27) are such that the introduction-side straight portion 23 and the distal-side straight portion 25 are opposed to the introduction-side straight portion 23 and the distal-side straight portion 25 of the opposing tenta chains 3a and 3b. Parallel. Further, a tapered portion is formed by the inclined portion 24 of the opposing tenta chains 3a and 3b. As described above, the apparatus employed in the present embodiment can maintain a parallel state in which the distance between the two sets of tenter chains 3a and 3b is always constant (FIG. 26).

Clips (holding members) 2 are provided at equal intervals on the tenter chains 3a and 3b, and both ends of the film F are gripped by the clips 2.
The shape of the clip 2 will be described later.

The heating furnace 4 heats the film F held by the tenter chains 3a and 3b with hot air.
In this embodiment, since the film F previously stretched in the longitudinal uniaxial direction is heated in the heating furnace 4, the film F contracts in the longitudinal direction (stretching direction).

Next, the film overfeed device 7 will be described.
The film overfeed device 7 includes two pairs (four systems) of feeder chains 5a, 5b, 5c, and 5d.
As shown in FIG. 7, the feeder chains 5a, 5b, 5c, and 5d are a pair of feeder chains 5a and 5b, and the feeder chains 5c and 5d form another pair.
The four sprockets 30, 31, 32, 33 for suspending the pair of feeder chains 5a, 5b are all arranged in the same plane as shown in FIGS. However, the plane formed by the four sprockets 30, 31, 32, 33 is a plane orthogonal to the plane formed by the four sprockets 21a, 21b, 22a, 22b that suspend the tenter chains 3a, 3b. is there.

  Of the four sprockets 30, 31, 32, 33, the sprockets 30, 32 are drive side sprockets, and the sprockets 31, 33 are driven side sprockets.

The other pair of feeder chains 5c and 5d is arranged in parallel with the aforementioned feeder chains 5a and 5b.
Further, the sprockets 30, 31, 32, 33 included in one pair and the sprockets 30 ', 31', 32 ', 33' included in the other pair have shafts 36, 37, 38 that have the same corresponding sprockets. , 39. Accordingly, the sprockets 30, 31, 32, 33 rotate synchronously, and the feeder chains 5c, 5d also run synchronously.

Among the two pairs (four systems) of feeder chains 5a, 5b, 5c, 5d, a plurality of front side gripping pieces 6a are attached to the upper feeder chains 5a, 5c with reference to FIG. On the other hand, a plurality of back side gripping pieces 6b are attached at equal intervals to the lower feeder chains 5b and 5d with reference to FIG.
A front gripping piece 6a attached to the upper feeder chains 5a and 5c and a back gripping piece 6b attached to the lower feeder chains 5b and 5d constitute a pair of wavy gripping members 6. The shapes of the front gripping piece 6a and the back gripping piece 6b will be described later.

The two pairs (four systems) of feeder chains 5a, 5b, 5c, and 5d described above are all in a region that is substantially surrounded by the tenter chains 3a and 3b of the film extending portion 20.
However, the length of the feeder chains 5 a, 5 b, 5 c, 5 d of the film overfeed device 7 (sprocket axis distance) is shorter than the tenter chains 3 a, b of the film extending portion 20.
Therefore, the starting ends of the feeder chains 5a, 5b, 5c, 5d of the film overfeed device 7 are slightly upstream from the starting ends of the tenter chains 3a, 3b of the film stretching section 20, and the feeder chains 5a, 5b, The end portions 5c and 5d are located at the end portion of the introduction-side straight portion 23.

  The feeder chains 5a, 5b, 5c and 5d of the film overfeed device 7 and the tenter chains 3a and 3b run synchronously.

  The heating furnace 4 is provided at the position of the inclined portion 24 of the tenter chains 3 a and 3 b in the film stretching portion 20.

  Next, the clip (holding member) 2 attached to the tenter chains 3a and 3b will be described.

The clip 2 is attached to the tenter chain 3 via the base 8 as shown in FIGS. That is, the base 8 is fixed to the pin of the tenter chain 3 by known means, and the clip 2 is placed on the base 8.
As shown in FIGS. 4, 9, 10, and 11, the clip 2 has a substantially U-shaped frame 9 opened to the film F side, and a flapper 10 is attached to the frame 9.
That is, the frame 9 has a U shape having an upper side 40, a vertical side 41, and a lower side 42. The upper surface (inner surface) of the lower side 42 of the frame 9 functions as the film mounting surface 45, and has a waveform (lower tooth portion 11) in this embodiment. That is, the film mounting surface 45 as a holding member piece is corrugated and has both a convex portion and a concave portion. In addition, it can be said that the film mounting surface 45 has convex portions provided at a constant interval.

Further, the flapper 10 has a flange portion 46 and a pressing portion 47, and an intermediate portion of the flange portion 46 is fixed to the upper side 40 of the frame 9, and the flapper 10 swings like a pendulum. The swinging direction of the flapper 10 is the width direction of the film F. That is, the pressing portion 47 of the flapper 10 moves along an arc locus. Therefore, as shown in FIG. 10, when the flange portion 46 is in an oblique posture, the pressing portion 47 is separated from the film placement surface 45. On the other hand, when the collar portion 46 is in the hanging posture, the lower surface of the pressing portion 47 approaches the film placement surface 45 and presses the film placement surface 45.
Here, in the flapper 10 of this embodiment, the lower surface of the pressing portion 47 has a waveform (upper tooth portion 12). That is, the pressing portion 47 as the holding member piece is also corrugated and has both a convex portion and a concave portion. It can also be said that the pressing portion 47 is also provided with convex portions with a certain interval.
When the flange 46 is in the hanging position, the corrugated shape of the lower surface of the pressing portion 47 (upper tooth portion 12) matches the corrugated shape of the film placement surface 45 (lower tooth portion 11).

As described above, in the flapper 10, since the intermediate portion of the flange portion 46 is fixed to the upper side of the frame 9, the upper end of the flange portion 46 protrudes above the upper side 40 of the frame 9.
Therefore, the flapper 10 can be swung by pressing the upper end of the flange portion 46 in the lateral direction, and the pressing portion 47 of the flapper 10 can be moved close to and away from the film mounting surface 45 as described above.
In this embodiment, a long clip guide 14 is provided in the vicinity of the tenter chains 3a and 3b, and the upper end of the collar portion is brought into contact with the clip guide 14. The positional relationship between the clip guide 14 and the frame 9 is designed to change from place to place, and the flap guide 10 is swung by pressing the upper end of the flange 46 with the clip guide 14.

  FIG. 4 shows details of the clip 2 holding the film F and the wavy gripping member 6. The clip 2 is fixed to a base 8 attached to the frame of the tenter chain 3 at equal intervals, and is pivotally pivotable to the top end of the upper side of the frame 9 and a frame 9 having a substantially U-shape opened to the film F side. And a supported flapper 10. The flapper 10 is provided with an upper tooth portion 12 that engages with a lower tooth portion 11 provided at the lower end of the lower side of the frame 9 at the front end. Further, the flapper 10 swings while an arm portion 13 extending above the frame is guided by a clip guide 14. The clip 2 grips or releases the side edge of the film F with the lower tooth portion 11 and the upper tooth portion 12 by the swing of the flapper 10.

  As shown in FIG. 9, the lower teeth portion 11 and the upper teeth portion 12 of the clip 2 are engaged with a waveform that periodically rises and falls at a predetermined pitch in the film F conveyance direction.

Next, the front side gripping piece 6a and the back side gripping piece 6b attached to the feeder chains 5a, 5b, 5c, and 5d will be described.
As described above, the four feeder chains 5a, 5b, 5c, and 5d are arranged in two pairs, and the pair of feeder chains (5a, 5b) and (5c, 5d) are arranged one above the other. ing. FIG. 5 shows a pair of feeder chains 5a and 5b. FIG. 6 is an enlarged view of a part of FIG. 5 and shows a wave-like gripping member 6 constituted by a front-side gripping piece 6a and a back-side gripping piece 6b.
In the present embodiment, as shown in FIG. 5, the opposite running surfaces of the feeder chains 5 a and 5 b (or 5 c and 5 d) function as the feed operation unit 50.
In the present embodiment, the feeder guide 16 is provided in the travel path on the feed operation unit 50 side, which is an area surrounded by the feeder chain 5a located on the upper side. The feeder guide 16 has a length over substantially the entire traveling path on the feed operation unit 50 side. And the feeder guide 16 becomes a shape which protrudes the intermediate part of a driving | running | working path outside (it is a lower side on the basis of a figure). More specifically, the feeder guide 16 has a gently inclined guide surface, and the vicinity of the end of the travel path projects outward.

  Similarly, a feeder guide 17 is provided for the feeder chain 5b located in the lower part. The feeder guide 17 has a guide surface that is gently inclined, and the vicinity of the end of the traveling path projects outward.

In this embodiment, the front gripping piece 6a is attached to the upper feeder chain 5a, and the back gripping piece 6b is attached to the lower feeder chain 5b.
The front gripping piece 6a provided in the feeder chain 5a has three supercharging projections 15 formed on the lower surface as shown in FIG.
The supercharging protrusion 15 protrudes toward the film F side, has a rib shape, and has a length at the peak. That is, one supercharging protrusion 15 extends over the entire width of the front side gripping piece 6a. The direction of the peak of the supercharging protrusion 15 is along the width direction of the film F.
A portion where the supercharging protrusion 15 does not exist, that is, a valley portion of the supercharging protrusion 15 is flat. The width W of the supercharging protrusion 15 is smaller than the interval w between the supercharging protrusions 15.
It can be said that the front-side gripping piece 6a is provided with the supercharging protrusions 15 with a certain interval. In the present embodiment, the interval between the supercharging protrusions 15 is constant as a recommended configuration, but the interval between the supercharging protrusions 15 may be irregular. The same applies to the back side gripping piece 6b described later.
Note that the lower surface of the front-side gripping piece 6a may be a corrugated surface like a sine curve.
In the present embodiment, a plurality of front side gripping pieces 6a are provided at equal intervals in the upper feeder chain 5a. From this point as well, it can be said that the supercharging protrusions 15 are provided at regular intervals.
The distance between the front gripping pieces 6a is equal to the distance between the clips 2 described above.

A supercharging protrusion 15 is also provided on the back side gripping piece 6b provided in the lower feeder chain 5b.
It can be said that the supercharging protrusion 15 is also provided with a fixed interval also about the back side holding piece 6b.
The shape and interval of the supercharging protrusion 15 provided on the lower back side gripping piece 6b are the same as those of the front side gripping piece 6a described above. However, the front side gripping piece 6a described above has three supercharging protrusions 15, whereas the lower backside gripping piece 6b has four supercharging protrusions 15.
In the present embodiment, a plurality of back side gripping pieces 6b are provided at equal intervals on the lower feeder chain 5b.
From this point as well, it can be said that the supercharging protrusions 15 are provided at regular intervals.
The interval between the back-side gripping pieces 6b is equal to that of the front-side gripping piece 6a.

The feeder chain 5a located on the upper side and the feeder chain 5b located on the lower side run synchronously, and on the running surface (feed action part) 50 where both face each other, the shafts of the front side gripping piece 6a and the back side gripping piece 6b The hearts always match.
However, as described above, feeder guides 16 and 17 are provided in the feeder chains 5a and 5b, respectively, and the running trajectories of the feeder chains 5a and 5b swell outward in the center. The relative distance from the gripping piece 6b varies depending on the travel position of the feeder chains 5a and 5b.
That is, since the feeder guides 16 and 17 both project the end portions of the feed action portions 50 of the feeder chains 5a and 5b to the outside, the front side gripping pieces 6a and the back side are provided at the end portions of the feed action portions 50 of the feeder chains 5a and 5b. When the gripping piece 6b moves, the distance between the two becomes closest (FIG. 13C row).
On the other hand, at the starting end portion of the feed operating unit 50, the front side gripping piece 6a and the back side gripping piece 6b are open as shown in the A row of FIG. 8 and the A row of FIG.

  Therefore, when the feeder chains 5a and 5b travel and the front side gripping piece 6a and the back side gripping piece 6b circulate and reach the feed operation part 50 (opposing travel surface) side, the front side gripping piece 6a and the back side gripping piece 6b face each other. Thus, thereafter, the front side gripping piece 6a and the back side gripping piece 6b travel through the feed operating portion 50 in the facing posture.

At the starting end of the feed operation unit 50, a gap between the front side gripping piece 6a and the back side gripping piece 6b is greatly opened as shown in the row A of FIG.
Specifically, the peak of the front side gripping piece 6a and the peak of the back side gripping piece 6b are separated from each other in the vertical direction as shown in row A of FIG. As the feed action unit 50 travels, the distance between the two becomes narrower as shown in row B of FIG. 13, and the peaks of the front gripping piece 6a and the peaks of the back gripping piece 6b bite.

Then, as the feed action unit 50 travels, the distance between the two becomes closer, and the front gripping piece 6a and the back gripping piece 6b press the surface of the film F. Here, the front gripping piece 6a and the back gripping piece 6b have supercharging projections 15 at alternate positions. For example, the front end of the supercharging projection 15 on the front gripping piece 6a side faces the surface of the film F downward in the drawing. The reaction force at the time of pressing is held by the supercharging protrusion 15 of the back side gripping piece 6b at the opposite position.
Therefore, the film F is shaped into a corrugated shape only at the portion sandwiched between the wave-like gripping members 6 without moving up and down as a whole.
As described above, it can be said that both the front-side gripping piece 6a and the back-side gripping piece 6b are provided with the supercharging projections 15 at a certain interval, so that the front and back surfaces of the film F are spaced in the transport direction. As a result, only the portion sandwiched between the wave-like gripping members 6 is loosened and shaped into a waveform.

  Further, since the front side gripping piece 6a and the back side gripping piece 6b gradually approach each other as the feeder chains 5a and 5b travel, the film F is gradually sandwiched between the front side gripping piece 6a and the back side gripping piece 6b. .

When the front side gripping piece 6a and the back side gripping piece 6b reach the vicinity of the terminal portion of the feed operation unit 50, the front side gripping piece 6a and the back side gripping piece 6b are closest to each other.
When the front-side gripping piece 6a and the back-side gripping piece 6b reach the vicinity of the terminal end of the feed operating portion 50, the front-side gripping piece 6a and the back-side gripping piece 6b are engaged with each other as shown in the C and C rows of FIG. Although it becomes an attitude | position, the front side holding piece 6a and the back side holding piece 6b do not contact.
More specifically, even if the front side gripping piece 6a and the back side gripping piece 6b are closest, the peak of the front side gripping piece 6a does not contact the valley of the back side gripping piece 6b, and the valley of the front side gripping piece 6a is The back side gripping piece 6b does not come into contact with the mountain.

  Further, since the width W of the supercharging protrusion 15 is smaller than the interval w between the supercharging protrusions 15, the supercharging protrusion 15 of the front side gripping piece 6 a and the supercharging protrusion 15 of the back side gripping piece 6 b are nested, Will not touch.

  The tenter chain 3 and the feeder chain 5 circulate at the same peripheral speed. As shown in FIGS. 3 and 8, the clip 2 and the wave-like gripping members 6a and 6b both grip the film F. At the same time, they are arranged at equal intervals so as to be in the same position in the transport direction of the film F. Further, the same number of supercharging protrusions 15 of the wavy gripping members 6a and 6b are provided corresponding to the vertices of the corrugations of the lower tooth portion 11 and the upper tooth portion 12 of the clip 2, respectively.

  Next, the operation of the film stretching machine 1 will be described.

First, the film F previously stretched in the longitudinal uniaxial direction is sandwiched between the wavy gripping members 6a and 6b of the film overfeed device 7, and the supercharging protrusions 15 are alternately pressed from above and below. A waveform having the protrusion 15 as the apex is formed (see column B in FIGS. 8 and 13). That is, it relaxes. At this time, since the film F needs to have an extra length as long as it undulates, the film overfeed device 7 has a speed (for example, 1.2 times faster) than the conveying speed (for example, 15 m / sec) of the feeder chain 5. 18m / sec), the film F is drawn from the upstream side.
The transport speed of the film overfeed device 7 is preferably faster than the transport speed of the feeder chain 5 as described above, and the appropriate speed range is 1.05 times or more and 1.50 times or less of the transport speed of the feeder chain 5. It is.

  When the film overfeed device 7 pulls in the film F from the upstream side, the film F scrapes the supercharging protrusion 15, so the supercharging protrusion 15 is formed of a material that reduces the friction with the film F. It is desirable. Further, the supercharging protrusion 15 may be a roller that can rotate independently.

  In addition, it is ideal that the length of the film F sandwiched between the wave-like gripping members 6a and 6b completely matches the length of the occlusal shape of the lower tooth portion 11 and the upper tooth portion 12 of the clip 2. If the film F is supplied in excess of the grip shape of the clip 2, the clip 2 may form pleats on the film F. In this embodiment, the length of the film F sandwiched between the wavy gripping members 6a and 6b is adjusted to be slightly shorter than the length of the gripping shape of the clip 2, and the clip (holding member) 2 is When the film F is gripped, the film F is further drawn from the upstream side. However, since the length that the clip 2 draws the film F is very small, an excessive force is not applied to the clip guide 14 or the film F is not damaged.

  When the clip 2 reaches a position where the both ends of the film F are completely held, the wave-shaped gripping members 6a and 6b are separated from each other as shown in the row D of FIG. 13 and the wave-shaped gripping members 6a and 6b open the film F.

Even after the wave-like holding members 6a and 6b of the film overfeed device 7 release the film F, the film stretching machine 1 holds the film F with the clip (holding member) 2 and holds and conveys it. That is, the film stretching machine 1 starts stretching in the transverse direction with a partial region of the film F being slackened in the longitudinal direction in advance.
The film F is heated in the heating furnace 4. Here, since the film F is previously stretched in the longitudinal uniaxial direction, the film F is contracted in the longitudinal direction (prestretched direction) by being heated in the heating furnace 4. At this time, the film is oriented in the thickness direction.
Here, as shown in FIG. 26, when the interval between the tenter chains 3 is constant, the shrinkage of the film F in the width direction is prevented. That is, in this embodiment, since both ends of the film F are held by the clip (holding member) 2, the film F is prevented from contracting in the lateral direction. Moreover, when the structure which expands the space | interval of the tenter chain 3 like FIG. 3 is employ | adopted, not only the shrinkage | contraction to the horizontal direction of the film F will be prevented, but conversely, the film F will be extended | stretched slightly (widened) in the width direction. .

  In the film stretching machine 1, each clip (holding member) 2 undulates and holds the film F. Therefore, when the film F is thermally contracted in the heating furnace 4, the effective portion at the center of the film F is longitudinally ( It can be shrunk freely in the conveying direction). Thereby, the orientation axis (direction of molecular chain) of the film F can be aligned in the thickness direction. It should be noted that the vicinity of both side ends of the film F gripped by the clip 2 is cut out in a subsequent process.

The film overfeed device 7 shown in FIG. 3 and subsequent figures has a clip 2 that holds the end of the film F, and the clip 2 has a corrugated surface on both the pressing portion 47 side and the film placement surface 45. ing. That is, in FIGS. 9, 10, 11, and 13 in the previous embodiment, the clip (holding member) 2 in which both the pressing portion 47 side and the film mounting surface 45 are corrugated is illustrated.
However, the clip 2 is not limited to the one in which the pressing portion 47 side and the film mounting surface 45 are corrugated. As shown in FIG. 2, only one of them is a corrugated shape, a tooth profile, etc. May be flat.

14, 15, 16, and 17 show the outer shape and operation when only the pressing portion 47 side is corrugated and the other (film mounting surface 53) adopts a flat plate-like clip 55. . 14 is a perspective view of the clip corresponding to FIG. 9, FIG. 15 is a side view and a plan view of the clip corresponding to FIG. 10, and FIG. 16 is a side view and a plane of the clip corresponding to FIG. FIG. 17 is an explanatory diagram corresponding to FIG. 13.
The clip 55 includes both a convex portion and a concave portion only on one holding member piece. It can be said that the clip 55 is formed by providing convex portions on one holding member piece with a certain interval.

  However, in FIG. 13 of the previous embodiment, the clip 2 is illustrated so as to close slowly in synchronization with the operation of the wavy gripping members 6a and 6b. However, in the embodiment shown in FIG. The clip 2 is in a fully open state until it is bitten, and after the wave-like gripping member 6 is completely bitten, it is closed by a momentary movement and is shown as holding the film F.

  Since the other structure regarding the clip 55 is the same as the clip 2 mentioned above, the same number is attached | subjected to the same member and the overlapping description is abbreviate | omitted.

The clip 2 having a waveform on both sides as shown in FIGS. 1, 9, 10, 11, and 13 and only one side as shown in FIGS. When compared with a certain clip 55, there are the following advantages and disadvantages.
That is, when both are corrugated like the former, since the film F is stretched while being held in a wide area, the tensile force applied to the film F becomes more uniform.
On the other hand, when both are corrugated like the former, there exists a possibility that a wrinkle may generate | occur | produce in the film F, when the waveform of the film F collapses before holding the film F with the clip 2. FIG.
That is, in the previous embodiment, before the film F is held by the clip 2, the film F is shaped into a waveform by the film overfeed device 7. It is ideal that the shaped waveform completely coincides with the clip 2, but depending on the thickness and material of the film F, both shapes may slightly differ. For example, in rare cases, as shown in FIG. 18 (a), a part of the wave shape of the film F may collapse, and in such a state, when the film F is sandwiched between the clips 2 each having a waveform, As shown in FIG. 18B, a part of the wave is doubled and the film F is wrinkled.

  On the other hand, in the clip 2 in which only one side is corrugated as shown in FIGS. 2, 14, 15, 16, and 17, there is a gap 52 between the pressing portion 47 and the film mounting surface 46 as shown in FIG. Even if a part of the wave shape collapses, the part escapes into the gap 52, and a situation where the film F is doubled is avoided.

  In the embodiment described above, the wave-like gripping member 6 composed of the front-side gripping piece 6a and the back-side gripping piece 6b is used as an apparatus for loosening and corrugating the film F stretched in the longitudinal uniaxial direction in advance, By sandwiching the film F, the film F was shaped like a wave.

  However, the present invention is not limited to this configuration. For example, a rack-like member and a gear-like member are provided using a member provided with an uneven shape having a structure similar to the rack 58 and the gear 59 as shown in FIG. You may employ | adopt the structure which pinches | interposes the film F in between.

Moreover, you may employ | adopt the structure which pinches | interposes the film F between the two gear-like members (member provided with the uneven | corrugated shape) 60 like FIG.
20 and 21, both surfaces of the film F are pressed at intervals in the transport direction, and a partial region or the entire region of the film F is slackened in the longitudinal direction.

  In the above-described embodiment, the film overfeed device 7 has the wave-like gripping members (front-side gripping pieces and back-side gripping pieces) 6a and 6b, and the film F is sandwiched between the wave-like gripping members 6a and 6b. As shown in FIG. 22, a block 61 having only one protrusion is provided, and the film F may press both surfaces with this block 61. Also in the aspect of FIG. 22, both surfaces of the film F are pressed with a gap in the transport direction, and a partial region or the entire region of the film F is slackened in the longitudinal direction.

Further, the surface of the film F may be pressed by the cylinder 62 regardless of the chain. FIG. 23 shows a configuration in which the surface of the film F is pressed by the cylinder 62.
In the configuration shown in FIG. 23, a dancer roll 63 is arranged on the film F conveyance path, and the film F below the cylinder 62 has a degree of freedom in the conveyance direction with respect to the conveyance means (not shown). That is, the film F is given a certain tension by a roll (dancer roll 63) provided so as to be movable up and down (FIG. 23A). However, since the dancer roll 63 has a degree of freedom in the up-and-down direction, when an external force is applied to the film F and pulled in the traveling direction, the dancer roll 63 rises as shown in FIG. .
In this embodiment, as shown in FIG. 23B, when the surface of the film F is pressed by the cylinder 62, the dancer roll 63 rises and the film F is fed out, and the film F is loosened. The cylinder 62 moves up and down at regular time intervals, and the film F is pressed on the surface side with an interval in the transport direction, and a partial region or the entire region of the film F is slackened in the longitudinal direction (FIG. 23C).

Moreover, you may make it wavy by pinching | interposing the film F with the clip (holding member) 2 irrespective of the film overfeed apparatus 7. FIG.
In the case where the film F is waved by sandwiching the film F with the clip (holding member) 2, a dancer roll 63 is arranged on the film F conveyance path as shown in FIG. 24 to give the film F a degree of freedom in the conveyance direction. It is desirable.

  As yet another measure for making the film F wave (sag), a method of supplying the film F excessively can be considered. For example, as shown in FIG. 25, a plurality of feeding devices 75 are arranged, and the film F is fed in the direction of the arrow by the feeding device 75. And the feed speed of each roll is slowed down to the downstream. As a result, the film F gradually undulates as shown in FIG.

Next, a long film (stretched in the longitudinal uniaxial direction in advance) used in the method for producing a stretched film of the present invention will be sequentially described.
As the raw material resin for the long film used in the present invention, an appropriate one is appropriately selected according to the purpose. Specific examples include polycarbonate resins, norbornene resins, polyolefin resins, cellulose resins, urethane resins, styrene resins, polyvinyl chloride resins, acrylonitrile / styrene resins, polymethyl methacrylate, polyvinyl acetate, Polyvinylidene chloride resin, acrylonitrile / butadiene / styrene resin, polyamide resin, polyacetal resin, modified polyphenylene ether resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene sulfide resin, polysulfone resin, polyether Sulfone resin, polyether ether ketone resin, polyarylate resin, liquid crystalline resin, polyamideimide resin, polyimide resin, polytetrafluoroethylene resin, etc. And the like. In particular, polycarbonate resins, norbornene resins, polyolefin resins, cellulose resins, urethane resins, styrene resins, polyimide resins, and polyamide resins are preferable because they have good optical properties and strength when formed into a film. .

  Said raw material resin is used individually or in combination of 2 or more types. Moreover, said raw material resin can also be used after performing arbitrary appropriate polymer modification | denaturation. Examples of the polymer modification include modifications such as copolymerization, crosslinking, molecular terminals, and stereoregularity.

  The film employed in the present invention can be molded and obtained by various methods. For example, it is obtained by a casting method in which a resin is dissolved in an organic solvent and cast on a support, and the solvent is dried by heating to form a film, or a melt extrusion method in which the resin is melted and extruded from a T-die to form a film. be able to. Further, it is possible to adopt a laminated film in which a thin film layer is further formed on one side or both sides of a molded polymer film by a gravure coater or the like.

  The film may contain other components such as a plasticizer, a stabilizer, a residual solvent, an antistatic agent, and an ultraviolet absorber as necessary, as long as the object of the present invention is not impaired. Further, a leveling agent can be added to reduce the surface roughness. Those having good compatibility with the resin are preferable.

  The range of the thickness of the film can be selected according to the designed retardation value, stretchability, expression of retardation, etc., but those having a thickness of 10 to 500 μm are preferably used. More preferably, it is 10-200 micrometers. If it is said range, sufficient self-supporting property of a film will be obtained and a wide range retardation value can be obtained.

  The light transmittance of the film is preferably 85% or more, more preferably 90% or more at a wavelength of 590 nm in order to reduce the influence on the luminance and contrast of the liquid crystal display device. Moreover, about the haze of the said film, 2% or less is preferable, More preferably, it is 1% or less. It is preferable that the obtained retardation film has the same light transmittance and haze. The light transmittance and haze are measured using an integrating sphere haze meter according to JIS K 7105.

  The glass transition temperature (Tg) of the film is not particularly limited, but is preferably 110 to 200 ° C. That is, if Tg is 110 ° C. or higher, a highly durable film can be easily obtained, and if it is 200 ° C. or lower, the in-plane and thickness direction retardation values can be easily controlled by stretching. More preferably, it is 120-195 degreeC. Especially preferably, it is 130-195 degreeC. Tg is a value determined by a DSC method according to JIS K7121.

  Next, the retardation film of the present invention will be described. The retardation film of this invention consists of a stretched film manufactured by the manufacturing method of the stretched film of this invention.

  NZ in the retardation film of the present invention is preferably 0.1 ≦ NZ ≦ 0.9. More preferably, 0.2 ≦ NZ ≦ 0.8. More preferably, 0.3 ≦ NZ ≦ 0.7. Particularly preferably, 0.4 ≦ NZ ≦ 0.6. Most preferably, 0.45 ≦ NZ ≦ 0.55. The value of NZ needs to be designed in a timely manner according to the driving method of the liquid crystal display device and the compensation method of optical characteristics, but by setting it to 0.5, the visibility of the liquid crystal display can be greatly improved. The definition of NZ is as shown in the above formula (1).

  Although there is no restriction | limiting in particular about the phase difference (Re) of the phase difference film of this invention, It is the range of 0 nm <= Re <= 2000nm (nm is nanometer) as a phase difference in the film surface with respect to the light of wavelength 590nm. preferable. Re is more preferably 0 nm ≦ Re ≦ 70 nm, 100 nm ≦ Re ≦ 350 nm, or 400 nm ≦ Re ≦ 700 nm. More preferably, 20 nm ≦ Re ≦ 70 nm, 120 nm ≦ Re ≦ 200 nm, 240 nm ≦ Re ≦ 300 nm, or 500 nm ≦ Re ≦ 700 nm. Particularly preferably, 40 nm ≦ Re ≦ 60 nm, 130 nm ≦ Re ≦ 150 nm, 180 nm ≦ Re ≦ 200 nm, 260 nm ≦ Re ≦ 280 nm, or 550 nm ≦ Re ≦ 700 nm. The value of Re needs to be designed in a timely manner according to the driving method of the liquid crystal display device and the compensation method of optical characteristics, but by setting the value within the above range, the visibility of the liquid crystal display device can be further improved. The definition of Re is as shown in the above formulas (2), (3), and (4).

The angle of orientation angle of the retardation film of the present invention is preferably within ± 1.0 ° within the range of the orientation angle variation measured at intervals of 5 cm in the film width direction. More preferably, it is within ± 0.7 °. More preferably, it is within ± 0.5 °. Particularly preferably, it is within ± 0.3 °. If the orientation angle varies greatly, the degree of polarization decreases when it is laminated on a polarizer or polarizing plate. Therefore, the smaller the orientation angle variation, the better.
The range of the thickness of the retardation film of the present invention can be selected according to the designed retardation value, stretchability, expression of retardation, etc., but is preferably 5 to 450 μm. More preferably, it is 5-200 micrometers. More preferably, it is 5-100 micrometers. If it is said range, sufficient self-supporting property of a film will be obtained and a wide range retardation value can be obtained.
The width of the retardation film of the present invention is preferably 1000 mm or more from the viewpoint of increasing the screen size of the liquid crystal display device and taking the retardation film size according to each screen size. More preferably, the width is 1200 mm or more. More preferably, it is 1300 mm or more. Particularly preferably, the width is 1400 mm or more.

  Next, the polarizing plate of the present invention will be described. The polarizing plate of the present invention is obtained by laminating a polarizer directly or via a polarizer protective film on at least one surface of the retardation film of the present invention.

  The laminated polarizer is not particularly limited, and various types can be used. For example, a polyvinyl alcohol (PVA) film is dyed with iodine or dichroic dye having dichroism, and is stretched and oriented, and then a crosslinked and dried polarizer and a transparent protective film are bonded together. The absorption type polarizing plate to be used can be preferably used. The polarizer is preferably excellent in light transmittance and degree of polarization. The light transmittance is preferably 30% to 50%, more preferably 41% to 50%, and most preferably 43% to 50%. The degree of polarization is preferably 97% or more, more preferably 98% or more, and most preferably 99% or more. When the light transmittance is less than 41% or the polarization degree is less than 97%, the luminance and contrast of the liquid crystal display device are low, and the display quality is deteriorated. The thickness of the polarizer is preferably 1 to 50 μm, more preferably 1 to 40 μm, and most preferably 8 to 30 μm.

  The polarizer is provided with a transparent protective film on one side or both sides. In the present invention, the adhesive treatment between the polarizer and the transparent protective film is not particularly limited. For example, an adhesive made of a vinyl alcohol polymer, boric acid, borax, glutaraldehyde, melamine, or oxalic acid. It can be carried out via an adhesive comprising at least a water-soluble cross-linking agent of a vinyl alcohol polymer. In particular, it is preferable to use a polyvinyl alcohol-based adhesive because it has the best adhesion to the polyvinyl alcohol-based film. Such an adhesive layer can be formed as a coating / drying layer of an aqueous solution, but other additives and a catalyst such as an acid can be blended as necessary when preparing the aqueous solution.

  Examples of the material for forming the transparent protective film include, from the viewpoint of transparency, thermal stability and strength, for example, cellulose resins such as diacetyl cellulose and triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, poly Acrylic resins such as methyl methacrylate, polystyrene, acrylonitrile / styrene copolymer, styrene resin, acrylonitrile / styrene resin, acrylonitrile / butadiene / styrene resin, acrylonitrile / ethylene / styrene resin, styrene / maleimide copolymer, styrene / maleic anhydride Examples thereof include styrene resins such as acid copolymers, polycarbonate resins, and the like. In addition, cycloolefin resin, norbornene resin, polyolefin resin such as polyethylene, polypropylene, ethylene / propylene copolymer, vinyl chloride resin, amide resin such as nylon and aromatic polyamide, aromatic polyimide, polyimide amide, etc. Imide resins, sulfone resins, polyether sulfone resins, polyether ether ketone resins, polyphenylene sulfide resins, vinyl alcohol resins, vinylidene chloride resins, vinyl butyral resins, arylate resins, polyoxymethylene resins Examples of the resin that forms the transparent protective film include a polymer film made of a resin, an epoxy-based resin, or a blend of the resins. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, or silicone. In particular, cellulose resins, norbornene resins, and cycloolefin resins are preferable from the viewpoints of transparency and thermal stability.

  Next, the image display apparatus of the present invention will be described. The image display device of the present invention includes the retardation film of the present invention.

Although there is no restriction | limiting in particular in the kind of image display apparatus of this invention, As an example, a liquid crystal display, an organic electroluminescent display (organic EL), a plasma display, a projector, a projection television etc. are mentioned.
In particular, the display performance of a liquid crystal display varies depending on the angle at which an image is viewed. The retardation film of the present invention is particularly preferably used because it has a function of compensating for the change in display performance caused by the viewing angle. The type of the liquid crystal display is not particularly limited, and any of a transmissive type, a reflective type, and a reflective / transmissive type can be used. Examples of the liquid crystal cell used in the liquid crystal display include twisted nematic (TN) mode, super twisted nematic (STN) mode, vertical alignment (VA) mode, in-plane switching (IPS) mode, horizontal alignment (ECB) mode, Examples include various liquid crystal cells such as fringe field switching (FSS) mode, bend nematic (OCB) mode, hybrid alignment (HAN) mode, ferroelectric liquid crystal (SSFLC) mode, and antiferroelectric liquid crystal (AFLC) mode. . Among these, the retardation film of the present invention is particularly preferably used in combination with a liquid crystal cell of TN mode, VA mode, IPS mode, OCB mode, FSS mode, and OCB mode. Most preferably, the retardation film of the present invention is used in combination with an IPS mode or VA mode liquid crystal cell.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  The measuring methods for various physical properties and optical properties are as follows.

(1) Phase difference (Re), NZ measurement, orientation angle Using an automatic birefringence meter KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd., the width direction was measured at a measurement wavelength of 590 nm at intervals of 5 cm. Moreover, the inclination angle at the time of NZ measurement was measured at 45 degrees. Re and NZ were average values, and the orientation angle was in the range of variation.

(2) Thickness The thickness was measured using Mitutoyo Corp. thickness gauge Digimatic Indicator ID-C112.

[Example 1]
Using the clip shown in FIG. 2, the stretching device shown in FIG. 3, and the film overfeed device shown in FIGS. 4 to 5, a long polycarbonate film stretched uniaxially (manufactured by Kaneka Corporation, Elmec R) -Both ends of the film were held in a state where the film (570 nm) was loosened by 18% in the conveying direction, and the process was allowed to pass without stretching at 150 ° C. The properties of the obtained retardation film were as shown in Table 1. The “magnification” in Table 1 indicates the transverse stretching ratio relative to the original fabric width. For example, when the original fabric width is 1000 mm and the magnification is 5%, the width after stretching is 1050 mm. “Loose amount” in Table 1 indicates the amount of slack in the film transport direction. For example, when the length in the transport direction is 1000 mm and the amount of slack is 10%, the film is slacked by 100 mm.

[Example 2]
Using the clip shown in FIG. 2, the stretching device shown in FIG. 3, and the film overfeed device shown in FIGS. 4 to 5, a long polycarbonate film stretched uniaxially (manufactured by Kaneka Corporation, Elmec R) -Both ends of the film were held with the film 570 nm) loosened 18% in the transport direction, and stretched 5% in the transverse direction to the transport direction at 150 ° C. The properties of the obtained retardation film were as shown in Table 1.

Example 3
As a polycarbonate film, Kaneka Co., Ltd. product, Elmec R-film 900nm was used, the process was allowed to pass similarly to Example 1 except having made the extending | stretching temperature 155 degreeC and the film loosening amount 30%. The properties of the obtained retardation film were as shown in Table 1.

Example 4
As a polycarbonate film, an Elmec R-film 900 nm manufactured by Kaneka Corporation was used, and the film was stretched in the transverse direction in the same manner as in Example 2 except that the stretching temperature was 155 ° C., the film slack amount was 30%, and the stretching ratio was 8%. went. The properties of the obtained retardation film were as shown in Table 1.

1 Film stretcher (conveyor)
2 Clip (holding member)
6 Wavy gripping member 6a Front side gripping piece 6b Back side gripping piece 11 Lower teeth (holding member piece, wavy gripping member)
12 Upper teeth (holding piece)
55 Holding member 56 Upper tooth part (holding member piece)
57 Plane (holding piece)
F film

Claims (12)

  A long film stretched in the longitudinal uniaxial direction is transported in the stretching direction, and both ends of the film are partially slackened in the stretching direction in advance by a member provided with an uneven shape. A method for producing a stretched film, wherein the film is heated and contracted in the stretching direction by heating the film while being transported in the stretching direction while holding both ends of the film by the transport device.   It is characterized by holding the both ends of the film in the conveying device by holding the end of the film with a holding member provided with a holding member piece that is uneven in a state where a partial region or the entire region of the film is slackened in the stretching direction. The manufacturing method of the stretched film of Claim 1 to do.   3. The both ends of the film are held in the conveying device after the partial area or the entire area of the film is loosened by alternately pressing one surface and the other surface of the film. A method for producing a stretched film.   When shrinking the film in the stretching direction, the film is held without changing the distance between both ends of the film, or both ends are widened in the transverse direction with respect to the transport direction. A method for producing a stretched film according to claim 1.   A retardation film comprising a stretched film produced by the method according to claim 1. Following formula (1):
0.1 ≦ NZ ≦ 0.9 (1)
[NZ = (nx−nz) / (nx−ny),
nx represents the refractive index in the slow axis direction of the retardation film,
Here, the slow axis direction refers to the direction in which the refractive index in the retardation film surface is maximized,
ny represents the refractive index in the fast axis direction of the retardation film,
nz represents the refractive index in the thickness direction of the retardation film. ]
The retardation film according to claim 5, having optical characteristics satisfying The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (2):
20 nm ≦ Re ≦ 70 nm (2)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film according to claim 6, wherein: The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (3):
100 nm ≦ Re ≦ 350 nm (3)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film according to claim 6, wherein: The retardation (Re) in the film plane with respect to light having a wavelength of 590 nm is expressed by the following formula (4):
400 nm ≦ Re ≦ 700 nm (4)
[Re = (nx−ny) × d,
d (nm) indicates the thickness of the film,
nx and ny have the same meaning as in the formula (1). ]
The retardation film according to claim 6, wherein:   The retardation film according to claim 5, wherein an orientation angle in the film plane is within ± 1.0 °.   The polarizing plate by which a polarizer is laminated | stacked on the at least single side | surface of the retardation film in any one of Claims 5-10 directly or through a polarizer protective film.   An image display device comprising the retardation film according to claim 5.

Images