JP2016126292A - Manufacturing method of retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing a retardation film having a slow axis in an oblique direction, at high manufacturing efficiency.SOLUTION: A manufacturing method of a retardation film includes: a step of obliquely drawing a long-sized film; and a step of joining a terminal end part of the long-sized film having previously undergone the oblique drawing step and a starting end part of a new long-sized film to be joined to the long-sized film, with a pressure-sensitive adhesive tape. A crosswise direction of the long-sized film is at an angle from -10° to 10° with respect to a junction line of the terminal end part of the long-sized film and the starting end part of the other long-sized film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a retardation film.

  In an image display device such as a liquid crystal display device (LCD) or an organic electroluminescence display device (OLED), a circularly polarizing plate is used for the purpose of improving display characteristics and preventing reflection. In a circularly polarizing plate, typically, a polarizer and a retardation film (typically λ / 4 plate) form an angle of 45 ° between an absorption axis of the polarizer and a slow axis of the retardation film. Thus, they are laminated. Conventionally, a retardation film is typically produced by uniaxially or biaxially stretching in the machine direction and / or the transverse direction, so that the slow axis is often the transverse direction of the original film. Appears in the direction (width direction) or longitudinal direction (long direction). As a result, in order to produce a circularly polarizing plate, it was necessary to cut the retardation film so as to form an angle of 45 ° with respect to the horizontal direction or the vertical direction and to bond them one by one.

  In order to solve such a problem, a technique has been proposed in which the slow axis of the retardation film is expressed in the oblique direction by stretching in the oblique direction. However, stretching in the oblique direction has a problem that it is difficult to switch the raw roll, and as a result, it is difficult to continuously produce a retardation film having a slow axis in the oblique direction.

Japanese Patent No. 4845619

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a method capable of producing a retardation film having a slow axis in an oblique direction with high production efficiency. is there.

The method for producing a retardation film of the present invention includes a step of obliquely stretching a long film, a terminal portion of the long film previously subjected to the oblique stretching step, and a new length for joining the long film. Joining the starting end of the scale film with an adhesive tape. The angle formed by the joining line between the end portion of the long film previously subjected to the oblique stretching step and the starting end portion of a new long film to be joined to the long film and the width direction of the long film Is −10 ° to 10 °.
In one embodiment, the pressure-sensitive adhesive tape includes a base material and a pressure-sensitive adhesive layer, and an absolute value of a difference in elastic modulus between the base material and the long film when heated to 135 ° C. is 500 N / mm ^2. It is as follows.
In one embodiment, the width of the adhesive tape is 60 mm or more.
In one embodiment, the elongate film includes at least one resin selected from the group consisting of a polycarbonate resin, a cycloolefin resin, a polyester resin, and a polyester carbonate resin.
In one embodiment, the long film and the base material of the adhesive tape contain the same resin.
In one embodiment, the oblique stretching is performed using a tenter stretching machine.
In one embodiment, the oblique stretching is performed by stretching in the direction of 45 ° ± 10 ° or 135 ° ± 10 ° with respect to the width direction of the long film.

  In the method for producing a retardation film of the present invention, two long films are formed so that the angle formed by the width direction of the long film and the bonding line is −10 ° to 10 ° in the bonding process of the long film. Place and stick the adhesive tape. By using a long film bonded at such an angle, a retardation film having a slow axis in an oblique direction can be obtained with high production efficiency without problems such as separation of the bonded long film. it can. Moreover, in the obtained retardation film, the malfunction that retardation characteristics differ for every joined elongate film can also be prevented. Therefore, a retardation film having a uniform retardation characteristic can be continuously produced.

It is a schematic plan view explaining the process of the manufacturing method of this invention. It is a schematic plan view explaining the process of the manufacturing method of this invention. It is a schematic sectional drawing of the junction part of the joined elongate film in the case of joining by butt | matching. It is a schematic sectional drawing of the joined part of the joined elongate film in the case of superposing and joining a part. It is a schematic plan view explaining the whole structure of an example of the extending | stretching apparatus which can be used for the manufacturing method of this invention. FIG. 5 is a schematic plan view of a main part for explaining a link mechanism that changes the clip pitch in the stretching apparatus of FIG. 4, and shows a state in which the clip pitch is minimum. It is a principal part schematic plan view for demonstrating the link mechanism which changes a clip pitch in the extending | stretching apparatus of FIG. 4, and shows a state with the largest clip pitch. It is a schematic diagram explaining an example of the diagonal stretch in the manufacturing method by one embodiment of this invention. It is a graph which shows the relationship between each zone of the extending | stretching apparatus in the case of the diagonal extending | stretching shown in FIG. 7, and a clip pitch. It is a graph which shows the relationship between each zone of the extending | stretching apparatus in the case of diagonal extending | stretching of another embodiment, and a clip pitch.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

  The method for producing a retardation film of the present invention includes a step of obliquely stretching a long film, and a terminal portion of a long film (hereinafter also referred to as a preceding long film) previously subjected to the oblique stretching step. And a step of joining the starting end portion of a new long film (hereinafter also referred to as other long film) to be bonded to the long film with an adhesive tape. In the step of bonding the long film, the angle formed by the width direction of the long film and the bonding line is −10 ° to 10 °. By joining the long films at such an angle using an adhesive tape, and subjecting the joined long films to oblique stretching, there is no problem such as separation of the joined long films, and the oblique direction. In addition, a retardation film having a slow axis can be obtained with high production efficiency. The angle formed by the width direction of the long film and the joining line is preferably −5 ° to 5 °, more preferably −2 ° to 2 °. In this specification, a joining line means the straight line which the termination | terminus part of a preceding elongate film and the starting end part of another elongate film make.

  The manufacturing method of the retardation film of this invention includes the process of joining a elongate film as above-mentioned. By including the step of joining the long film, it is possible to continuously produce a retardation film having a slow axis in an oblique direction while joining two or more long films. Manufacturing efficiency can be further improved. 1 and 2 are schematic plan views for explaining the production process of the production method of the present invention. In the production method of the present invention, by joining two or more long films, these are continuously conveyed and subjected to an oblique stretching step. More specifically, before the preceding long film 11 is all subjected to the oblique stretching step, the terminal portion of the preceding long film 11 and the starting end portion of the other long film 12 are arbitrarily selected. Bonding is performed using a suitable adhesive tape 20. The long line is formed so that the joining line (not shown) between the long films 11 and 12 forms an angle of −10 ° to 10 ° with the width direction of the long films 11 and 12 (W in FIG. 1). Films 11 and 12 are placed and joined with an adhesive tape (FIG. 1). Typically, the pressure-sensitive adhesive tape is selected to include a joining line within its width.

  The joined long film 100 is subjected to an oblique stretching process, and the adhesive tape 20 can follow the movement of the elongated films 11 and 12 to be stretched. By the adhesive tape 20 following the movement accompanying the stretching of the long films 11 and 12, separation of the joined long films 11 and 12 can be prevented. Therefore, the retardation film can be continuously produced while joining two or more long films, and the production efficiency can be further improved. In one embodiment, after being subjected to the stretching process, the pressure-sensitive adhesive tape 20 can be substantially parallel to the stretching direction (the double-headed arrow in FIG. 2). Depending on the stretching conditions and the like, in the long film after oblique stretching, the joining line and the stretching direction may not be substantially parallel. For example, there may occur a case where a gap is generated in the joining portion of the long film and the joining line set in the joining process is damaged (that is, not a straight line). Even in this case, it is sufficient that the adhesive tape is substantially parallel to the stretching direction. In this specification, the joining line (or adhesive tape) and the stretching direction being substantially parallel means that the angle between the desired stretching angle in oblique stretching and the joining line (or adhesive tape) is ± 10 °. Say.

<1. Process for joining long films>
The joining of the end portion of the preceding long film and the start portion of the other long film is performed using any appropriate adhesive tape. The adhesive tape used for joining includes a base material and an adhesive layer. Affixing the adhesive tape may be performed by hand or using any appropriate apparatus.

  Adhesive tape is arranged so that the end portion of the preceding long film and the start end portion of the other long film are aligned so that the end portions in the width direction of the two long films coincide with each other. Secure with. Typically, the adhesive tape is affixed so that a joining line is included in the width. The adhesive tape may be affixed only on one side of the joining portion, or may be affixed on both sides.

  The joining portion of the long film may be joined by abutting both end portions (so-called butt splice) or may be joined by overlapping a part thereof. When a part of the long film is overlapped and joined, either the preceding long film or the other long film may be on the upper side. When a part of the long film is overlapped and joined, the length of the overlapped part in the transport direction is, for example, 20 mm or less, preferably 10 mm or less, more preferably 5 mm or less, particularly Preferably it is 0 mm (that is, butt). If the length of the overlapped portion is in such a range, it is possible to prevent the thickness of the bonded portion from becoming excessively thick in the obtained retardation film.

  3A and 3B are schematic cross-sectional views of the joined portion of the joined long film 100 used in the present invention. FIG. 3A is a schematic cross-sectional view of a joining portion when joining both ends of a long film by butt joining. When joining by butt | matching, typically, it arrange | positions so that the width direction edge part of the elongate films 11 and 12 may correspond, both ends are butt | matched, and at least one surface is fixed with the adhesive tape 20. FIG. The adhesive tape 20 is attached so that the adhesive layer 21 and the long films 11 and 12 are in contact with each other. FIG. 3B is a schematic cross-sectional view of a joining portion in the case where the preceding long film 11 and another long film 12 are joined with a part thereof being overlapped. In the example of illustration, the elongate film 11 which precedes from the upper side, and the other elongate film 12 are piled up in order, and are fixed with the adhesive tape 20 from the other elongate film 12 side. When the long films 11 and 12 are partially overlapped and joined, a step may be formed between these films. The pressure-sensitive adhesive layer 21 of the pressure-sensitive adhesive tape 20 can follow this step and fix the long films 11 and 12. In these illustrated examples, the adhesive tape is affixed only to one side, but the adhesive tape may be affixed to the surface opposite to the illustrated example or may be affixed to both sides.

  When the preceding long film 11 and another long film 12 are partially overlapped and joined, the joining line can be a straight line having a certain width. Even in such a case, the angle formed by the joining line and the width direction W of the long films 11 and 12 may be -10 ° to 10 °. As described above, typically, an adhesive tape that includes a joining line within its width is selected. Even in such a case, by using an adhesive tape in which the joining line is included in the width, even when the joined long film is subjected to an oblique stretching process, the joined long film is separated. Etc. can be prevented.

<1-1. Long film>
As the long film, any appropriate resin film can be used according to desired characteristics. Specific examples of the resin contained in this resin film include polycarbonate resin, polyvinyl acetal resin, cycloolefin resin, acrylic resin, cellulose ester resin, cellulose resin, polyester resin, polyester carbonate resin, olefin resin. And polyurethane resins. Polycarbonate resins, polyvinyl acetal resins, cellulose ester resins, polyester resins, and polyester carbonate resins are preferable. This is because with these resins, a retardation film showing the wavelength dependence of reverse dispersion can be obtained. These resins may be used alone or in combination according to desired properties.

  Any appropriate polycarbonate resin is used as the polycarbonate resin. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. Specific examples of the dihydroxy compound include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxy-3- Ethylphenyl) fluorene, 9,9-bis (4-hydroxy-3-n-propylphenyl) fluorene, 9,9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9,9-bis (4-hydroxy) -3-n-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9, 9-bis (4-hydroxy-3-cyclohexylphenyl) fluorene, 9,9-bis (4-hydroxy-3-phenyl) Enyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis ( 4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4- (2-hydroxy Ethoxy) -3-tert-butylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3 -Phenylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3,5-dimethylphenyl) fluorene 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9,9-bis (4- (3-hydroxy-2,2-dimethylpropoxy) phenyl ) Fluorene and the like. The polycarbonate resin contains structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and bisphenols in addition to the structural units derived from the dihydroxy compound. You may go out.

  Details of the polycarbonate resin as described above are described in, for example, Japanese Patent Application Laid-Open No. 2012-67300, Japanese Patent No. 3325560, and WO 2014/061677. The description of the patent document is incorporated herein by reference.

  The glass transition temperature of the polycarbonate resin is preferably 110 ° C. or higher and 250 ° C. or lower, more preferably 120 ° C. or higher and 230 ° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, and there is a possibility of causing a dimensional change after film formation. If the glass transition temperature is excessively high, the molding stability at the time of film molding may deteriorate, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

  Any appropriate polyvinyl acetal resin can be used as the polyvinyl acetal resin. Typically, the polyvinyl acetal resin can be obtained by a condensation reaction of at least two types of aldehyde compounds and / or ketone compounds and a polyvinyl alcohol resin. Specific examples and detailed production methods of the polyvinyl acetal resin are described, for example, in JP-A-2007-161994. The description is incorporated herein by reference.

<1-2. Adhesive tape>
The pressure-sensitive adhesive tape 20 used for joining the preceding long film 11 and the other long film 12 includes a base material 22 and a pressure-sensitive adhesive layer 21. The thickness of the adhesive tape 20 can be set to any appropriate value. The thickness of the adhesive tape is, for example, 100 μm to 200 μm.

  The width of the adhesive tape can typically be designed to include a joining line within the width. By using an adhesive tape whose joining line is included in the width, it is possible to prevent problems such as separation of the joined long film even when the joined long film is subjected to an oblique stretching process. . The width | variety of an adhesive tape is 60 mm or more, for example, Preferably it is 75 mm or more, More preferably, it is 100 mm or more. There is no restriction | limiting in particular in the upper limit of the width | variety of an adhesive tape, For example, it is 300 mm.

The adhesive tape preferably has an absolute value of the difference between the elastic modulus of the substrate and the elastic modulus of the long film when heated to 135 ° C., preferably 500 N / mm ² or less, more preferably 200 N / mm ² or less. It is. If the absolute value of the difference in elastic modulus when heated to 135 ° C between the substrate and the long film is within the above range, the adhesive tape is good for the movement accompanying the stretching of the long film in the oblique stretching process Can follow. Therefore, it is possible to prevent an excessive load from being applied to the joining portion and to prevent the joined long film from being separated in the oblique stretching step. In addition, the elasticity modulus when heating the base material of a long film and an adhesive tape to 135 degreeC is a value measured after heating for 135 minutes with a 135 degreeC thermostat, and then according to JISK7127.

  As for the adhesive layer of an adhesive tape, it is preferable that the adhesive force with respect to a glass plate is 5 N / 25mm or more. If the adhesive strength of the pressure-sensitive adhesive layer is within the above range, it is possible to satisfactorily maintain the state in which the preceding long film and the other long film are joined. The adhesive force with respect to a glass plate means the adhesive force (90 degree peel adhesive force) (N / 25mm) measured according to JISZ0237.

<1-2-1. Base material>
Any appropriate base material is used as the base material 22 of the adhesive tape 20. The thickness of the substrate is, for example, 75 μm to 180 μm, preferably 100 μm to 150 μm. When the thickness of the base material is less than 75 μm, the adhesive tape is broken because the strength of the adhesive tape is low, and the bonded long film may be separated in the oblique stretching step. Moreover, when the thickness of a base material exceeds 180 micrometers, the thickness of a junction part will become thick too much and may have a bad influence on a diagonal stretch process.

  Arbitrary appropriate resin can be used for resin which comprises a base material. The resin constituting the substrate is preferably the same as the resin contained in the long film. When the base material of the adhesive tape and the long film contain the same resin, the long film and the adhesive tape can exhibit the same behavior in the oblique stretching step. Therefore, it can prevent that the adhesive tape follows favorably by the movement of a long film in a diagonal stretch process, and the joined long film separates. Specifically, the resins exemplified in the above item 1-1 can be mentioned.

<1-2-2. Adhesive layer>
The pressure-sensitive adhesive layer 21 of the pressure-sensitive adhesive tape 20 is formed using any appropriate pressure-sensitive adhesive composition. The thickness of the pressure-sensitive adhesive layer is, for example, 10 μm to 30 μm, preferably 10 μm to 25 μm. If the thickness of the pressure-sensitive adhesive layer is within the above range, it is possible to satisfactorily maintain the state in which the long film 11 and the other long film 12 that precede each other at the bonding portion are bonded. Further, even when the preceding long film 11 and the other long film 12 are partially overlapped and joined, the pressure-sensitive adhesive layer can satisfactorily follow the steps between these films.

  Arbitrary appropriate adhesives are used as an adhesive composition contained in an adhesive layer. Examples include acrylic adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, and emulsion (solvent-free) adhesives.

<2. Diagonal stretching process>
The joined long film 100 is subjected to an oblique stretching step in order to obtain a desired retardation film. Any appropriate method can be used as the method of oblique stretching. The oblique stretching step is preferably performed using a tenter stretching machine.

  The stretching angle in the oblique stretching step is preferably 45 ° ± 10 ° or 135 ° ± 10 ° with respect to the width direction of the long film. By obliquely stretching at such a stretching angle, a retardation film suitable for a circularly polarizing plate can be obtained.

  In one embodiment, the manufacturing method of the present invention grips the left and right ends of the film to be stretched by variable pitch type left and right clips whose longitudinal clip pitches change before the oblique stretching step, respectively. And a step of preheating the film (hereinafter referred to as a preheating step). In this embodiment, the oblique stretching step is performed by independently changing the clip pitches of the left and right clips. In this embodiment, after the oblique stretching step, an arbitrary step (hereinafter referred to as a heat treatment step) for heat-treating the film and a clip for gripping the film are released in a state where the clip pitch of the left and right clips is constant. The method further includes a step (hereinafter, release step). Hereinafter, this embodiment will be specifically described.

<2-1. Gripping process>
First, with reference to FIGS. 4-6, the extending | stretching apparatus which can be used for the manufacturing method of this embodiment is demonstrated. FIG. 4 is a schematic plan view illustrating the overall configuration of an example of a stretching apparatus that can be used in the manufacturing method of the present invention. 5 and 6 are each a schematic plan view of a main part for explaining a link mechanism for changing the clip pitch in the stretching apparatus of FIG. 4, FIG. 5 shows a state in which the clip pitch is minimum, and FIG. Indicates the maximum clip pitch. The stretching device 400 has an endless loop 40L and an endless loop 40R having a large number of clips 50 for gripping the film on both the left and right sides in a plan view. In this specification, the left endless loop as viewed from the film entrance side is referred to as the left endless loop 40L, and the right endless loop is referred to as the right endless loop 40R. The clips 50 of the left and right endless loops 40L and 40R are guided by the reference rail 70 and move in a loop. The left endless loop 40R moves in a counterclockwise direction, and the right endless loop 40R moves in a clockwise direction. In the stretching apparatus, a gripping zone A, a preheating zone B, an oblique stretching zone C, a heat treatment zone D, and a release zone E are provided in this order from the inlet side to the outlet side of the sheet. Each of these zones means a zone where a film to be stretched is substantially gripped, preheated, obliquely stretched, heat treated and released, and does not mean a mechanically and structurally independent section. . It should also be noted that the length ratio of each zone is different from the actual length ratio.

  In the gripping zone A and the preheating zone B, the left and right endless loops 40R and 40L are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the oblique stretching zone C, the distance between the left and right endless loops 40R and 40L gradually increases as it goes from the preheating zone B side to the heat treatment zone D until it corresponds to the width after stretching of the film. In the heat treatment zone D, the left and right endless loops 40R, 40L are configured to be substantially parallel to each other at a separation distance corresponding to the width of the film after stretching.

  The clip 50L of the left endless loop 40L (left clip) and the clip 50 (right clip) 50R of the right endless loop 40R can each independently move around. For example, the driving sprockets 41 and 42 of the left endless loop 40L are rotationally driven counterclockwise by the electric motors 43 and 44, and the driving sprockets 41 and 42 of the right endless loop 40R are rotated by the electric motors 43 and 44. It is driven to rotate around. As a result, traveling force is applied to the clip carrying member 60 of the drive roller (not shown) engaged with the drive sprockets 41 and 42. As a result, the left endless loop 40L cyclically moves in the counterclockwise direction, and the right endless loop 40R cyclically moves in the clockwise direction. By driving the left electric motor and the right electric motor independently of each other, the left endless loop 40L and the right endless loop 40R can be independently cyclically moved.

  Furthermore, the clip 50L of the left endless loop 40L (left clip) and the clip 50R of the right endless loop 40R (right clip) are each of a variable pitch type. That is, the left and right clips 50 and 50 can independently change the clip pitch (distance between clips) in the vertical direction (MD) with movement. The variable pitch type can be realized by any appropriate configuration. Hereinafter, a link mechanism (pantograph mechanism) will be described as an example.

  As shown in FIGS. 5 and 6, an elongated rectangular clip carrying member 60 is provided in the lateral direction in plan view for carrying the clips 50 individually. Although not shown, the clip carrying member 60 is formed into a strong frame structure with a closed cross section by an upper beam, a lower beam, a front wall (wall on the clip side), and a rear wall (wall on the side opposite to the clip). The clip holding member 60 is provided to roll on the traveling road surfaces 81 and 82 by the traveling wheels 68 at both ends thereof. 5 and 6, the traveling wheels on the front wall side (the traveling wheels that roll on the traveling road surface 81) are not shown. The traveling road surfaces 81 and 82 are parallel to the reference rail 70 over the entire area. A long hole 61 is formed along the longitudinal direction of the clip carrying member on the rear side (on the opposite side of the clip) of the upper and lower beams of the clip carrying member 60, and the slider 62 can slide in the longitudinal direction of the long hole 61. Is engaged. In the vicinity of the clip 50 side end portion of the clip carrying member 60, a single first shaft member 63 is provided vertically through the upper beam and the lower beam. On the other hand, a single second shaft member 64 is vertically provided through the slider 62 of the clip carrying member 60. One end of a main link member 65 is pivotally connected to the first shaft member 63 of each clip carrying member 60. The main link member 65 is pivotally connected to the second shaft member 64 of the adjacent clip carrier member 60 at the other end. In addition to the main link member 65, one end of the sub link member 66 is pivotally connected to the first shaft member 63 of each clip holding member 60. The other end of the sub link member 66 is pivotally connected to the intermediate portion of the main link member 65 by a pivot 67. As the slider 62 moves to the rear side of the clip carrying member 60 (opposite the clip side) by the link mechanism using the main link member 65 and the sub link member 66, the clip carrying members 60 are connected to each other as shown in FIG. As the slider 62 moves to the front side (clip side) of the clip carrying member 60, as shown in FIG. 6, the clip pitch increases. . Positioning of the slider 62 is performed by the pitch setting rail 90. As shown in FIGS. 5 and 6, the larger the clip pitch, the smaller the separation distance between the reference rail 70 and the pitch setting rail 90. Since the link mechanism is well known in the art, a more detailed description is omitted.

  By performing oblique stretching of the film using the stretching apparatus as described above, a retardation film having a slow axis in an oblique direction (for example, a direction of 45 ° with respect to the longitudinal direction) can be produced. First, in the gripping zone A (the entrance of the film take-in of the stretching device 400), the left and right endless loops 40R and 40L are gripped at the same clip pitch on both sides of the film to be stretched by the clips 50 of the left and right ends. The film is fed to the preheating zone B by the movement of the endless loops 40R and 40L (substantially, the movement of the clip holding members 60 guided by the reference rail 70).

<2-2. Preheating process>
In the preheating zone (preheating step) B, the left and right endless loops 40R and 40L are basically parallel to each other at a distance corresponding to the initial width of the film to be stretched as described above. The film is heated without performing transverse stretching or longitudinal stretching. However, the distance between the left and right clips (distance in the width direction) may be slightly increased in order to avoid problems such as film deflection due to preheating and contact with the nozzles in the oven.

  In the preheating step, the film is heated to a temperature T1 (° C.). It is preferable that temperature T1 is more than the glass transition temperature (Tg) of a film, More preferably, it is Tg + 2 degreeC or more, More preferably, it is Tg + 5 degreeC or more. On the other hand, the heating temperature T1 is preferably Tg + 40 ° C. or lower, more preferably Tg + 30 ° C. or lower. Although it changes with films to be used, temperature T1 is 70 to 190 degreeC, for example, Preferably it is 80 to 180 degreeC.

  The temperature raising time to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent material of the film and the manufacturing conditions (for example, the film conveyance speed). These temperature raising time and holding time can be controlled by adjusting the moving speed of the clip 50, the length of the preheating zone, the temperature of the preheating zone, and the like.

C. Stretching Step In the stretching zone (stretching step) C, the film is stretched obliquely by changing the clip pitch of the left and right clips 50 independently. The film may be stretched obliquely by increasing or decreasing the clip pitch of the other clip while maintaining the clip pitch of one of the left and right clips. The oblique stretching can be performed while increasing the distance between the left and right clips (distance in the width direction), for example, as in the illustrated example. This will be specifically described below. In the following description, for convenience, the stretching zone C is described as being divided into an inlet-side stretching zone (first oblique stretching zone) C1 and an outlet-side stretching zone (second oblique stretching zone) C2. The lengths of the first oblique stretching zone C1 and the second oblique stretching zone C2 and the ratio of the lengths to each other can be appropriately set according to the purpose.

In one embodiment, the oblique stretching is performed such that a position where the clip pitch of one of the left and right clips starts to increase and a position where the clip pitch of the other clip starts increasing are different positions in the vertical direction. In the state, the clip pitch of each clip is expanded to a predetermined pitch. This embodiment will be specifically described with reference to FIGS. First, in the preheating zone B, the right and left clip pitch are both set to P _1. P ₁ is the clip pitch at the time of gripping the film. Next, as soon as the film enters the first oblique stretching zone C1, the increase of the clip pitch of one (right side in the illustrated example) clip is started. In the first oblique stretching zone C1, increases the clip pitch of the right clip to the P _2. On the other hand, the clip pitch of the left clip is maintained at P1 in the _first oblique stretching zone C1. Therefore, the end portion of the first oblique stretching zone C1 in (beginning of the second oblique stretching zone C2), left clip moves the clip pitch P _1, right clip is a moving clip pitch P ₂ ing. Next, as soon as the film enters the second oblique stretching zone C2, the clip pitch of the left clip starts to increase. In the second oblique stretching zone C2, it increases the clip pitch of the left clip to the P _2. On the other hand, the clip pitch of the right clip is maintained at P2 in the _second oblique stretching zone C2. Therefore, the end portion of the second oblique stretching zone C2 in (end of extension zone C), the left clip and right clips together, there is a moving clip pitch P _2. In the illustrated example, for the sake of simplicity, the position where the clip pitch of the right clip begins to increase is the start of the first oblique stretching zone C1, and the position where the clip pitch of the left clip begins to increase is the second oblique stretching zone. Although it is a start part of C2, the position can be set at any appropriate position in the stretching zone. For example, the position at which the clip pitch of the left clip begins to increase may be the middle portion of the first oblique stretching zone C1, or may be the middle portion of the second oblique stretching zone C2, and the clip pitch of the right clip begins to increase. The position may be an intermediate portion of the first oblique stretching zone C1. The clip pitch ratio can generally correspond to the clip moving speed ratio. Therefore, the ratio of the clip pitch of the left and right clips can generally correspond to the ratio of the stretching ratio in the MD direction between the right side edge and the left side edge of the film.

  As described above, the clip pitch can be adjusted by positioning the slider by adjusting the distance between the pitch setting rail of the stretching device and the reference rail.

In the present embodiment, the ratio P ₂ / P ₁ (hereinafter also referred to as clip pitch change rate) between the clip pitch P ₁ and the clip pitch P ₂ is preferably 1.2 to 1.9, and more. Preferably it is 1.4-1.7. If the clip pitch change rate is in such a range, there is an advantage that the film can be prevented from being broken and the film is less likely to be wrinkled.

In another embodiment, the diagonal stretching (i) increases the clip pitch of one of the left and right clips and decreases the clip pitch of the other clip, and (ii) reduces the clip Increasing the clip pitch to the same pitch as the enlarged clip pitch, and setting the clip pitch of each clip to a predetermined pitch. This embodiment will be specifically described with reference to FIG. First, in the preheating zone B, the right and left clip pitch are both set to P _1. P ₁ is the clip pitch at the time of gripping the film. Next, as soon as the film enters the first oblique stretching zone C1, the clip pitch of one (right side in the illustrated example) starts to increase, and the clip pitch of the other (left side in the illustrated example) Start decreasing. In the first oblique stretching zone C1, it increases the clip pitch of the right clip to the P _2, to reduce the clip pitch of the left clip to the P _3. Therefore, the end portion of the first oblique stretching zone C1 in (beginning of the second oblique stretching zone C2), left clip moves the clip pitch P _3, right clip is a moving clip pitch P ₂ ing. Next, as soon as the film enters the second oblique stretching zone C2, the clip pitch of the left clip starts to increase. In the second oblique stretching zone C2, it increases the clip pitch of the left clip to the P _2. On the other hand, the clip pitch of the right clip is maintained at P2 in the _second oblique stretching zone C2. Therefore, the end portion of the second oblique stretching zone C2 in (end of extension zone C), the left clip and right clips together, there is a moving clip pitch P _2. In the illustrated example, for the sake of simplicity, the decrease start position of the clip pitch of the left clip and the increase start position of the clip pitch of the right clip are both set as the start portion of the first oblique extension zone C1, but these positions are shown in the above figure. Similar to the embodiment of FIGS. 7 and 8, it can be set at any suitable position in the stretching zone.

  In FIG. 9, both the position where the clip pitch of the right clip starts to increase and the position where the clip pitch of the left clip begins to decrease are both the start points of the first diagonally extending zone C1, but unlike the illustrated example, the clip of the right clip The clip pitch of the left clip may begin to decrease after the pitch begins to increase, and the clip pitch of the right clip may begin to increase after the clip pitch of the left clip begins to decrease (both not shown). In one embodiment, the clip pitch of the clip on the other side (eg, the left side) begins to decrease after the clip pitch of the clip on one side (eg, the right side) begins to increase. According to such an embodiment, when the oblique stretching is performed while increasing the distance between the left and right clips (distance in the width direction) as in the illustrated example, the film is already in the width direction to a certain extent (preferably Since it is stretched (approximately 1.2 to 2.0 times), wrinkles are unlikely to occur even if the clip pitch on the other side is greatly reduced.

  Similarly, in FIG. 9, the increase in the clip pitch of the right clip and the decrease in the clip pitch of the left clip continue until the end point of the first oblique stretching zone C1 (the start point of the second oblique stretching zone C2). Unlike the above, either the increase or decrease of the clip pitch may end before the end point of the first oblique stretching zone C1, and the clip pitch may be maintained as it is until the end point of the first oblique stretching zone C1.

In this embodiment, the clip pitch change rate _(P 2 / _{P 1)} is preferably 1.1 to 1.9, more preferably from 1.15 to 1.7, more preferably 1.2 ~ 1.6. When P ₂ / P ₁ is in such a range, there is an advantage that the film can be prevented from being broken. Furthermore, the clip pitch change rate (P ₃ / P ₁ ) is preferably 0.5 to 0.9, and more preferably 0.6 to 0.8. If P ₃ / P ₁ is in such a range, there is an advantage that wrinkles are unlikely to enter the film.

  In the oblique stretching in the production method of the present invention, the product of the clip pitch change rate of one clip and the clip pitch change rate of the other clip at the end of the first oblique stretching (stretching in the first oblique stretching zone C1). However, it is preferably 1.0 to 1.7. When the product of the change rates is within such a range, a retardation film having excellent axial accuracy, small retardation unevenness, and small dimensional change can be obtained.

  The oblique stretching can typically be performed at a temperature T2. The temperature T2 is preferably Tg-20 ° C to Tg + 30 ° C, more preferably Tg-10 ° C to Tg + 20 ° C, and particularly preferably about Tg with respect to the glass transition temperature (Tg) of the resin film. Although it changes with resin films to be used, the temperature T2 is, for example, 70 ° C to 180 ° C, and preferably 80 ° C to 170 ° C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ± 2 ° C. or more, more preferably ± 5 ° C. or more. In one embodiment, T1> T2, and thus the film heated to temperature T1 in the preheating step can be cooled to temperature T2.

The oblique stretching described above may include stretching in the lateral direction, and may not include stretching in the lateral direction. In other words, the width of the film after oblique stretching may be larger than the initial width of the film, or may be substantially the same as the initial width. Needless to say, the illustrated example shows an embodiment including transverse stretching. When the oblique stretching includes lateral stretching as in the illustrated example, the transverse stretching ratio (ratio W ₂ / W ₁ between the initial width W ₁ of the film and the width W ₂ of the film after oblique stretching) is preferably 1 It is 0.0-4.0, More preferably, it is 1.3-3.0. If the draw ratio is too small, tin-like wrinkles may occur in the resulting retardation film. When the draw ratio is too large, the biaxiality of the obtained retardation film becomes high, and the viewing angle characteristics may be deteriorated when applied to a circularly polarizing plate or the like.

D. Heat Treatment Step In the heat treatment zone (heat treatment step) D, the film is heat treated with the clip pitch of the left and right clips 50 being constant. That is, in a state where the clip pitches of the left and right clips 50 were both P _2, is heated while conveying the film. The heat treatment step can be performed as necessary.

  The heat treatment can typically be performed at a temperature T3. The temperature T3 varies depending on the stretched film, and may be T2 ≧ T3 or T2 <T3. In general, when the film is an amorphous material, T2 ≧ T3, and when the film is a crystalline material, the crystallization treatment may be performed by setting T2 <T3. In the case of T2 ≧ T3, the difference (T2−T3) between the temperatures T2 and T3 is preferably 0 ° C. to 50 ° C. The heat treatment time is typically 10 seconds to 10 minutes. The heat treatment time can be controlled by adjusting the length of the heat treatment zone and / or the film transport speed.

E. Release process Finally, the clip holding the film is released to obtain a retardation film. In addition, the width W ₃ of the film after oblique stretching corresponds to the width of the obtained retardation film (FIG. 7). When the oblique stretching does not include transverse stretching, the width of the obtained retardation film is substantially equal to the initial width of the film.

<III. Application of retardation film>
The retardation film obtained by the production method of the present invention can be suitably used for a circularly polarizing plate. The circularly polarizing plate including the retardation film obtained by the production method of the present invention is suitably used for image display devices such as a liquid crystal display device (LCD) and an organic electroluminescence display device (OLED).

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measurement and evaluation method in an Example are as follows.

(1) Adhesive strength of adhesive tape The adhesive strength (90 ° peel adhesive strength) of the adhesive tape obtained in Production Examples 2 to 5 to the glass plate was measured according to JIS Z0237 (N / 25 mm).
(2) Elastic modulus when heated to 135 ° C. The elastic modulus of the film used as the base material of the adhesive tape in Production Examples 2 to 5 was measured. Specifically, the film as a substrate was placed in a thermostat at 135 ° C. for 5 minutes. Thereafter, the elastic modulus of the sample was measured according to JISK 7127.
(3) Separation of the joined part after oblique stretching When the joined elongated film obtained in Examples 1 to 5 and Comparative Examples 1 to 2 is obliquely stretched, the elongated film is separated at the joined part. The presence or absence of was confirmed visually. In the case where the joined state is maintained, it is indicated as “◯”, and when the long film is separated into two pieces, it is indicated as “x”.
(4) Thickness It measured using the micro gauge type thickness meter (made by Mitutoyo Corporation).

[Production Example 1] Production of polycarbonate resin film 1 Polymerization was carried out using a batch polymerization apparatus composed of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100 ° C. 9,9- [4- (2-Hydroxyethoxy) phenyl] fluorene (BHEPF), isosorbide (ISB), DEG (diethylene glycol), diphenyl carbonate (DPC), and magnesium acetate tetrahydrate in a molar ratio of BHEPF / ISB / DEG / DPC / magnesium acetate = 0.348 / 0.490 / 0.162 / 1.005 / 1.00 × 10 ⁻⁵ was charged. After sufficiently replacing the inside of the reactor with nitrogen (oxygen concentration 0.0005 to 0.001 vol%), heating was performed with a heating medium, and stirring was started when the internal temperature reached 100 ° C. After 40 minutes from the start of temperature increase, the internal temperature was reached to 220 ° C., and control was performed so as to maintain this temperature. The phenol vapor produced as a by-product with the polymerization reaction was led to a reflux condenser at 100 ° C., and a monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the phenol vapor not condensed was led to a condenser at 45 ° C. and recovered.

  Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Subsequently, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was obtained. When a predetermined power is reached, nitrogen is introduced into the reactor, the pressure is restored, the reaction solution is withdrawn in the form of a strand, pelletized with a rotary cutter, and BHEPF / ISB / DEG = 34.8 / 49.0 / A polycarbonate resin A having a copolymer composition of 16.2 [mol%] was obtained. This polycarbonate resin had a reduced viscosity of 0.430 dL / g and a glass transition temperature of 128 ° C.

  The obtained polycarbonate resin was vacuum-dried at 80 ° C. for 5 hours, and then a single-screw extruder (manufactured by Isuzu Chemical Industries, screw diameter 25 mm, cylinder set temperature: 220 ° C.), T die (width 275 mm, set temperature: 220) ° C.), a chill roll (set temperature: 120 to 130 ° C.), and a film-forming apparatus equipped with a winder, to produce a polycarbonate resin film 1 having a thickness of 195 μm.

[Production Example 2] Production of pressure-sensitive adhesive tape 1 A polycarbonate resin film 2 was produced in the same manner as in Production Example 1 except that the thickness of the resulting resin film was 130 µm. An acrylic pressure-sensitive adhesive was applied to the polycarbonate-based resin film obtained in Production Example 2 so that the thickness after drying was 23 μm to obtain a pressure-sensitive adhesive tape. The adhesive force of the obtained adhesive tape to the glass plate was 12 N / 25 mm.

[Production Example 3] Production of pressure-sensitive adhesive tape 2 A polycarbonate resin film 3 was produced in the same manner as in Production Example 1 except that the thickness of the resulting resin film was 100 µm. An adhesive tape was obtained in the same manner as in Production Example 2, except that the polycarbonate resin film obtained in Production Example 3 was used instead of the polycarbonate resin film obtained in Production Example 2. The adhesive force of the obtained adhesive tape to the glass plate was 12 N / 25 mm.

[Production Example 4] Production of pressure-sensitive adhesive tape 3 A pressure-sensitive adhesive tape was obtained in the same manner as in Production Example 2 except that an acrylic pressure-sensitive adhesive was applied so that the thickness after drying was 12 m. The adhesive force of the obtained adhesive tape to the glass plate was 8 N / 25 mm.

[Production Example 5] Production of pressure-sensitive adhesive tape 4 In the same manner as in Production Example 2 except that a cycloolefin-based resin film (“Zeonor ZF-14 film” manufactured by Nippon Zeon Co., Ltd., thickness 100 μm) was used instead of the polycarbonate-based resin film. Thus, an adhesive tape was obtained. The adhesive force of the obtained adhesive tape to the glass plate was 12 N / 25 mm.

<Example 1>
The polycarbonate resin film obtained in Production Example 1 was cut into a width of 765 mm and a length of 500 m to obtain a long film. Two obtained long films were butted at the ends. At this time, the angle formed by the joining line and the width direction of the long film was 0 °. Next, the pressure-sensitive adhesive tape 1 was cut to a width of 100 mm, the pressure-sensitive adhesive tape was affixed to both sides of the portion where the end portions were butted together, the butted portions were fixed, and the long film was joined. The joined long film was stretched obliquely at a stretching angle of 45 ° using a tenter stretching machine to obtain a retardation film. Further, the long film bonded in the same manner was stretched obliquely at a stretching angle of 135 ° to obtain a retardation film. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability in the obtained retardation film were evaluated. The results are shown in Table 1.

<Example 2>
A retardation film was obtained in the same manner as in Example 1 except that the adhesive tape 1 was cut to a width of 200 mm and a long film was joined. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability in the obtained retardation film were evaluated. The results are shown in Table 1.

<Example 3>
A retardation film was obtained in the same manner as in Example 1 except that the adhesive tape 2 was used instead of the adhesive tape 1. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability of the obtained retardation film were evaluated. The results are shown in Table 1.

<Example 4>
A retardation film was obtained in the same manner as in Example 1 except that the adhesive tape 3 was used in place of the adhesive tape 1. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability of the obtained retardation film were evaluated. The results are shown in Table 1.

<Example 5>
A cycloolefin-based resin film (“Zeonor ZF-14 film” manufactured by Nippon Zeon Co., Ltd., thickness: 100 μm) was cut into a width of 800 mm and a length of 300 m to obtain a long film. A retardation film was obtained in the same manner as in Example 1 except that this long film was used and that the adhesive tape 4 was used instead of the adhesive tape 1. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability in the obtained retardation film were evaluated. The results are shown in Table 1.

(Comparative Example 1)
A retardation film was obtained in the same manner as in Example 1 except that the joining portion of the long film was not fixed with an adhesive tape. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability in the obtained retardation film were evaluated. The results are shown in Table 1.

(Comparative Example 2)
A retardation film was obtained in the same manner as in Example 1 except that the two long films were cut so that the angle formed by the joining line and the width direction of the long film was 135 ° and joined. About each retardation film, the presence or absence of isolation | separation of a junction part and the retardation stability in the obtained retardation film were evaluated. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, in Examples 1 to 5 where the angle formed between the bonding line and the width direction of the long film is −10 ° to 10 °, bonding is performed even when the film is obliquely stretched. The separation of the part did not occur and the film could be stretched well. When separation of the long film occurs at the joining portion, a film loss of several tens of meters may occur in order to stably obtain a retardation film having a desired retardation from a new long film. Since separation of the joining portion does not occur, the retardation film obtained in Examples 1 to 5 does not cause such film loss, and the desired retardation can be obtained even when the long film is switched. A retardation film having the same can be obtained stably.

  In Comparative Example 1 in which the joint portion was not fixed with the adhesive tape, the long film was separated and could not be obliquely stretched. Further, in Comparative Example 2 in which the angle formed by the joining line and the width direction of the long film was 135 °, the oblique stretching at a stretching angle of 45 ° could be satisfactorily performed. On the other hand, when the film was obliquely stretched at a stretching angle of 135 °, which is the same as the angle formed by the joining line and the width direction of the long film, the long film was separated and could not be obliquely stretched. .

  The retardation film obtained by the production method of the present invention is suitably used for a circularly polarizing plate, and as a result, is suitably used for an image display device such as a liquid crystal display device (LCD) or an organic electroluminescence display device (OLED). .

11 Long film that has been previously subjected to the oblique stretching process (leading long film)
12 New long film (other long films) to be joined to the long film previously subjected to the oblique stretching process
20 Adhesive Tape 21 Adhesive Layer 22 Base Material 100 Bonded Long Film 40L Endless Loop 40R Endless Loop 50 Clip 60 Clip Holding Member 70 Reference Rail 90 Pitch Setting Rail 400 Stretching Device

Claims (7)

With the adhesive tape, the step of obliquely stretching the long film, the end of the long film previously subjected to the oblique stretching step, and the start of the new long film joined to the long film A method for producing a retardation film comprising a step of bonding,
The joining line between the end portion of the long film previously subjected to the oblique stretching step and the starting end portion of a new long film to be joined to the long film and the width direction of the long film The manufacturing method of retardation film whose angle is -10 degrees-10 degrees. The said adhesive tape contains a base material and an adhesive layer, The absolute value of the difference of an elastic modulus when heated at 135 degreeC with this base material and the said elongate film is 500 N / mm < ² > or less, A method for producing the retardation film according to 1.   The manufacturing method of the retardation film of Claim 1 or 2 whose width | variety of the said adhesive tape is 60 mm or more.   The said elongate film contains at least 1 sort (s) of resin selected from the group which consists of a polycarbonate resin, a cycloolefin type resin, a polyester-type resin, and a polyester carbonate-type resin in any one of Claim 1 to 3 A method for producing a retardation film.   The manufacturing method of the phase difference film in any one of Claim 1 to 4 with which the said elongate film and the base material of the said adhesive tape contain the same resin.   The method for producing a retardation film according to claim 1, wherein the oblique stretching is performed using a tenter stretching machine.   The retardation film according to claim 1, wherein the oblique stretching is performed by stretching in a direction of 45 ° ± 10 ° or 135 ° ± 10 ° with respect to a width direction of the long film. Production method.