WO2018142991A1 - Method for producing obliquely stretched film, method for producing polarizing plate, and method for producing liquid crystal display device - Google Patents

Abstract

Provided is a method for producing an obliquely stretched film, in which there is minimal rupturing in the joining portion of thermoplastic resin films in an oblique stretching step, and obliquely stretched films can be continuously produced. A method for producing an obliquely stretched film comprising a joining step in which a thermoplastic resin film conveyed first and a thermoplastic resin film conveyed subsequently are joined with a joining portion interposed therebetween, a preheating step in which the thermoplastic resin films joined with the joining portion interposed therebetween are preheated while being continuously conveyed, and an oblique stretching step in which the preheated thermoplastic resin films are obliquely stretched while being continuously conveying, wherein the thermoplastic resin film conveyed first and the thermoplastic resin film conveyed subsequently are identical thermoplastic resin films, and formulae (1) and (2) below hold, where T (°C) is the preheating temperature of the joining portion in the preheating step, t (seconds) is the preheating time of the joining portion in the preheating step, and Tg (°C) is the glass transition temperature of the thermoplastic resin in the thermoplastic resin film. Tg < T ≤ Tg + 60 (1) 2≤ t (2)

Description

Manufacturing method of obliquely stretched film, manufacturing method of polarizing plate, and manufacturing method of liquid crystal display device

The present invention relates to a method for producing an obliquely stretched film, a method for producing a polarizing plate, and a method for producing a liquid crystal display device.

In the liquid crystal display device, an optical member such as a retardation film is used to improve performance. For example, when the retardation film is used for antireflection of a mobile device, an organic EL television or the like, or for optical compensation of a liquid crystal display device, its slow axis is neither parallel nor perpendicular to the transmission axis of the polarizer. It is required to be at an angle. On the other hand, the transmission axis of the polarizer is usually parallel to the long side direction or the short side direction of the rectangular display surface of the apparatus. Therefore, there is a demand for a rectangular retardation film having a slow axis in an oblique direction with respect to its side.

Conventionally, a retardation film has been produced by longitudinally stretching or transversely stretching a long film before stretching. Here, the longitudinal stretching represents stretching in the longitudinal direction of the long film, and the lateral stretching represents stretching in the width direction of the long film. In order to obtain a rectangular retardation film having a slow axis in an oblique direction from a longitudinally stretched or laterally stretched long film, the film is cut out so that the sides are directed in an oblique direction from the width direction of the long film. Is required. However, if the film is cut so that the sides are oriented diagonally from the width direction of the long film, the amount of film to be discarded becomes large, and it becomes difficult to manufacture roll-to-roll. Lower. Therefore, in order to improve production efficiency, it has been proposed to obliquely stretch a long film before stretching (see, for example, Patent Document 1).

In order to efficiently produce an obliquely stretched film, it is preferable to continuously obliquely stretch the continuously conveyed thermoplastic resin film. Here, in order to continuously convey the film, for example, joining the leading edge of the subsequent film fed from the second film roll to the trailing edge of the preceding film fed from the first film roll. (For example, refer to Patent Document 2).

International Publication No. 2015/064645 International Publication No. 2012/053218

However, in order to continuously convey the film, even if the leading edge of the subsequent film fed from the second film roll is joined to the trailing edge of the preceding film fed from the first film roll, the film is obliquely stretched. In doing so, the joint portion breaks, and as a result, the obliquely stretched film may not be continuously manufactured.

Then, this invention suppresses that the junction part of a thermoplastic resin film fractures | ruptures in a diagonal stretch process, The manufacturing method of the diagonal stretch film which can manufacture a diagonal stretch film continuously, Manufacturing method of polarizing plate which manufactures polarizing plate provided with obliquely stretched film manufactured by manufacturing method, and manufacturing method of liquid crystal display device which manufactures liquid crystal display device provided with polarizing plate manufactured by the manufacturing method of this polarizing plate The purpose is to provide.

This invention aims to solve the above-mentioned problem advantageously, and the manufacturing method of the diagonally stretched film of the present invention is followed by the thermoplastic resin film that is transported in advance and is transported downstream. A joining step for joining a thermoplastic resin film via a joining portion, a preheating step for preheating while continuously conveying the thermoplastic resin film joined via the joining portion, and the preheated thermoplastic resin film An obliquely stretching step of obliquely stretching while continuously transporting the film, and a method for producing an obliquely stretched film, wherein the thermoplastic resin film transported in advance and the thermoplastic resin transported downstream The film is the same thermoplastic resin film, the preheating temperature of the joint in the preheating step is T (° C.), and the preheating time of the joint in the preheating step is t (seconds). And, when the glass transition temperature of the thermoplastic resin in the thermoplastic resin film was Tg (° C.), the following equation (1) and satisfying the (2), characterized in that.
Tg <T ≦ Tg + 60 (1)
2 ≦ t (2)
As described above, when the thermoplastic resin film transported in advance and the thermoplastic resin film transported downstream are the same thermoplastic resin film, the above formulas (1) and (2) If it satisfies, it can suppress that the junction part of a thermoplastic resin film fractures | ruptures in a diagonal stretch process, and can manufacture a diagonal stretch film continuously.
In addition, the preheating temperature T (° C.) of the joint portion was measured by measuring the temperature of a space having a distance of 100 mm in the film normal direction from the joint portion of the thermoplastic resin film using a thermocouple in the preheating step. Adopted as the preheating temperature T (° C.) of the joint in the preheating process.
Further, the glass transition temperature Tg of the thermoplastic resin was measured by the measuring method described in JIS K7121.
Furthermore, in the present invention, the “same thermoplastic resin film” includes, in addition to the case where the thermoplastic resin films are completely the same in a strict sense, within the range in which the effects of the present invention can be obtained. This includes cases where the composition and thickness are inevitably different due to errors and the like.

Further, in the method for producing an obliquely stretched film of the present invention, it is preferable to join the thermoplastic resin film transported in advance and the thermoplastic resin film transported in the subsequent manner by thermal fusion. In particular, when the thermoplastic resin film transported in advance and the thermoplastic resin film transported downstream are joined by thermal fusion, the above formulas (1) and (2) are satisfied. This is because the effect of suppressing breakage is excellent.

Moreover, the manufacturing method of the diagonally stretched film of this invention WHEREIN: The thermoplastic resin film conveyed ahead and the thermoplastic resin film conveyed downstream are that average thickness is 50 micrometers or more and 300 micrometers or less. preferable. The thermoplastic resin film that is transported in advance and the thermoplastic resin film that is transported in a subsequent manner have an average thickness of 50 μm or more and 300 μm or less, so that the joining portion of the thermoplastic resin film can be formed in the oblique stretching step. It can suppress more reliably that it fractures.
In addition, the average thickness of the thermoplastic resin film transported in advance and the thermoplastic resin film transported downstream is determined by snap gauges at a plurality of points at intervals of 5 cm in the width direction of the thermoplastic resin film. It calculates | requires by calculating by the average value of those measured values.

In the method for producing an obliquely stretched film of the present invention, it is preferable that the glass transition temperature Tg of the thermoplastic resin in the thermoplastic resin film is 100 ° C. or higher and 180 ° C. or lower. By setting the glass transition temperature of the thermoplastic resin to be equal to or higher than the lower limit of the above range, the durability of the film in a high temperature environment can be enhanced. Moreover, the extending | stretching process can be easily performed by making the glass transition temperature of the said thermoplastic resin below into the upper limit of the said range.

Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the polarizing plate of this invention is the diagonally stretched film manufactured with the manufacturing method of the diagonally stretched film mentioned above, and polarized light. A polarizing plate is produced by laminating a child. Thus, if the manufacturing method of the diagonally stretched film mentioned above is used, a diagonally stretched film can be manufactured continuously and efficiently, and a polarizing plate can be manufactured efficiently by extension.

Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the liquid crystal display device of this invention is a liquid crystal display provided with the polarizing plate manufactured with the manufacturing method of the polarizing plate mentioned above. A device is manufactured. Thus, if the manufacturing method of the polarizing plate mentioned above is used, a polarizing plate can be manufactured efficiently and by extension, a liquid crystal display device can be manufactured efficiently.

According to the present invention, it is possible to continuously produce obliquely stretched films while suppressing breakage of the joint portion of the thermoplastic resin film in the obliquely stretching step.

It is a figure which shows typically the structural example of the heat sealer apparatus which can be used in order to implement the manufacturing method of the diagonally stretched film which concerns on this invention. It is a figure which shows typically the structural example of the diagonal stretch machine used in order to implement the manufacturing method of the diagonal stretch film which concerns on this invention.

Embodiments of the present invention are described in detail below.
Here, the manufacturing method of the diagonally stretched film of this invention can be used when manufacturing a diagonally stretched film. Moreover, the manufacturing method of the polarizing plate of this invention can be used when manufacturing a polarizing plate provided with the diagonally stretched film manufactured by the manufacturing method of the diagonally stretched film of this invention. Furthermore, the manufacturing method of the liquid crystal display device of this invention can be used when manufacturing a liquid crystal display device provided with the polarizing plate manufactured by the manufacturing method of the polarizing plate of this invention.

(Manufacturing method of obliquely stretched film)
The method for producing an obliquely stretched film of the present invention is a method for producing an obliquely stretched film. And the manufacturing method of the diagonally stretched film of this invention is a process (joining process) which joins the thermoplastic resin film conveyed ahead and the thermoplastic resin film conveyed behind, via a junction part. ), A step of preheating (preheating step) under predetermined conditions while continuously conveying the thermoplastic resin film bonded through the bonding portion, and obliquely stretching while continuously conveying the preheated thermoplastic resin film A process (oblique stretching process), and optionally further includes other processes.

And in the manufacturing method of the diagonally stretched film of this invention, the thermoplastic resin film conveyed ahead and the thermoplastic resin film conveyed downstream are joined via a junction part, The said junction part When the thermoplastic resin film joined through the film is preheated under predetermined conditions while being continuously conveyed, and obliquely stretched while continuously conveying the preheated thermoplastic resin film, the thermoplastic resin is It is possible to continuously manufacture obliquely stretched films while suppressing breakage of the joint portion of the film.

<Joint process>
In the joining step of the manufacturing method of the obliquely stretched film of the present invention, by joining the thermoplastic resin film transported in advance and the thermoplastic resin film transported in the subsequent way through the joint portion, Enables continuous production of obliquely stretched films.
In addition, the thermoplastic resin film conveyed ahead and the thermoplastic resin film conveyed downstream are the same thermoplastic resin film.
The bonding method is not particularly limited, and is heat fusion (sometimes referred to as “thermal welding”), tape bonding, ultrasonic fusion (sometimes referred to as “ultrasonic welding”), laser fusion (“laser”). Sometimes referred to as “welding”). Among these, thermal bonding and tape bonding are preferred, and thermal fusion is more preferable in that the effect of suppressing breakage of the bonded portion of the thermoplastic resin film when the bonded portion is preheated under predetermined conditions is particularly excellent. preferable.

[Thermoplastic resin film]
Although there is no restriction | limiting in particular as average thickness of the said thermoplastic resin film, 50 micrometers or more are preferable, 100 micrometers or more are more preferable, 300 micrometers or less are preferable, and 200 micrometers or less are more preferable. When the average thickness of the thermoplastic resin film is within the above range, the joint portion of the thermoplastic resin film can be more reliably suppressed from breaking in the oblique stretching step.

-Thermoplastic resin-
Specific examples of the thermoplastic resin include, for example, alicyclic structure-containing polymer resins such as norbornene resins; polyolefin resins such as polyethylene resins and polypropylene resins; cellulose resins such as diacetyl cellulose resins and triacetyl cellulose resins; Polyimide resin, polyamideimide resin, polyamide resin, polyetherimide resin, polyetheretherketone resin, polyetherketone resin, polyketone sulfide resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, polyphenylene oxide resin, polyethylene terephthalate resin, Polybutylene terephthalate resin, polyethylene naphthalate resin, polyacetal resin, polycarbonate resin, polyarylate resin, (meth) acrylic resin Other resins such as polyvinyl alcohol resin, polypropylene resin, cellulose resin, epoxy resin, phenol resin; (meth) acrylic acid ester-vinyl aromatic compound copolymer resin, isobutene / N-methylmaleimide copolymer resin, Copolymer resins such as styrene / acrylonitrile copolymer resins; and the like. One of these may be used alone, or two or more of these may be combined in any ratio. Among these, alicyclic structure-containing polymer resins such as norbornene resins are preferable.
The details of the alicyclic structure and the norbornene-based resin are as described in Patent Document 1.

The weight average molecular weight (Mw) of the thermoplastic resin is not particularly limited, but is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100,000 or less, more preferably 80,000 or less, and 50,000 or less. Is particularly preferred. When the weight average molecular weight (Mw) of the thermoplastic resin is within the above range, the mechanical strength and molding processability of the obliquely stretched film can be highly balanced. Here, the weight average molecular weight (Mw) of the thermoplastic resin is a weight average molecular weight in terms of polyisoprene measured by gel permeation chromatography using cyclohexane as a solvent. However, in the gel permeation chromatography, toluene may be used as a solvent when the sample does not dissolve in cyclohexane. When toluene is used as the solvent, the weight average molecular weight in terms of polystyrene is used.

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the thermoplastic resin is not particularly limited, but is preferably 1.2 or more, more preferably 1.5 or more, and more preferably 1.8 or more. Particularly preferred is 3.5 or less, more preferred is 3.0 or less, and particularly preferred is 2.7 or less. By setting the molecular weight distribution of the thermoplastic resin to be equal to or higher than the lower limit, the productivity of the thermoplastic resin can be increased and the manufacturing cost can be suppressed. In addition, by making the molecular weight distribution of the thermoplastic resin not more than the above upper limit value, the amount of low molecular components becomes small, so that relaxation during high temperature exposure can be suppressed and the stability of the obliquely stretched film can be improved. .

The glass transition temperature Tg of the thermoplastic resin is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, preferably 180 ° C. or lower, more preferably 170 ° C. or lower. By setting the glass transition temperature of the thermoplastic resin to be equal to or higher than the lower limit of the above range, the durability of the film in a high temperature environment can be enhanced. Moreover, the extending | stretching process can be easily performed by making the glass transition temperature of the said thermoplastic resin below into the upper limit of the said range.

(Heat fusion)
In the heat fusion, bonding is usually performed using a heat sealer device. The heat sealer is heated (heated) with a heater so as to sandwich a thermoplastic resin film, and is fused (welded). The heater is heated to a predetermined temperature that dissolves the thermoplastic resin film but does not decompose it. When the heater is in contact with the thermoplastic resin film for a predetermined period of time, a part of the thermoplastic resin film is melted and bonded, and the preceding thermoplastic resin film and the subsequent thermoplastic resin film are joined. Can do.
More specifically, for example, as shown in FIG. 1, the preceding thermoplastic resin film A and the following thermoplastic resin film B are heat-sealed using a heat sealer device 10.

As shown in FIG. 1, in order to supply a continuous film 3 to an oblique stretching machine 60 (tenter stretching machine) described later in FIG. The leading end portion of the succeeding film B fed out is overlapped and joined by heat fusion (heat welding) using the heat sealer device 10. The heat sealer device 10 includes an upper welding head 21 and a lower welding head 22 that are provided so as to sandwich the conveyance path of the film 3 vertically. The upper welding head 21 has a heater 23 exposed from the lower surface, and the lower welding head 22 has a heater 24 exposed from the upper surface. The welding heads 21 and 22 are moved between a heating position where the heaters 23 and 24 are brought into contact with the film 3 and a retreat position where the heaters 23 and 24 are separated from the film 3 by a shift mechanism (not shown). The heaters 23 and 24 are temperature controlled by temperature controllers 25 and 26.

The procedure for bonding the film using the heat sealer 10 will be described. The leading edge of the trailing film B is superimposed on the trailing edge of the preceding film A. The upper welding head 21 and the lower welding head 22 are moved to the heating position. The temperature of each heater 23 and 24 is set to a predetermined temperature that dissolves the film 3 but does not decompose it. The heaters 23 and 24 are brought into contact with a region where the films A and B are overlapped. A part of the film is melted and bonded by heating with the heaters 23 and 24 for a predetermined time. The heaters 23 and 24 are heated for a predetermined time and then stopped, and the joint portion 28 is naturally cooled in a compressed state. Next, the upper welding head 21 and the lower welding head 22 are moved to the retracted position.

Next, using the roller 10a and the roller 10b, the thermoplastic resin films A and B joined by thermal fusion are conveyed to the oblique stretching machine 60.

Finally, only the thermoplastic resin film B is conveyed to the oblique stretching machine 60 using the roller 10a and the roller 10b.

Thereafter, when the thermoplastic resin film B disappears, the thermoplastic resin film A is joined to the thermoplastic resin film B by heat fusion in the same operation as described above, and the joined thermoplastic films A, B is conveyed to the oblique stretching machine 60, and finally, only the thermoplastic resin film A is conveyed to the oblique stretching machine 60. Moreover, when the thermoplastic resin film A runs out, the operation shown above is performed. By repeating these operations, the thermoplastic resin film can be continuously supplied to the oblique stretching machine 60.

[Tape bonding]
In the tape joining, for example, a double-sided tape in which an adhesive layer is provided on both surfaces of a substrate exhibiting substantially the same stretching behavior as a thermoplastic resin film (raw film) in a temperature range of a stretching temperature at which an oblique stretching process is performed. Use to join.
Specifically, instead of performing heat fusion using the heat sealer device 10, after attaching a double-sided tape or the like to one of the thermoplastic resin films A and B, the other is bonded by bonding the other. They can be joined in the same manner as described above.

[Ultrasonic fusion]
The ultrasonic fusion is a method in which electric energy is converted into mechanical vibration energy, and at the same time, strong frictional heat is generated on the joining surface of the thermoplastic resin film to melt and bond the thermoplastic resin. is there. In the ultrasonic fusion, for example, a thermoplastic resin film can be mechanically vibrated at an amplitude of 0.05 mm and 20,000 to 28,000 times per second to generate heat and be instantly fused (welded).
Specifically, instead of performing heat fusion using the heat sealer device 10, ultrasonic welding is performed using an ultrasonic bonding device (for example, see FIG. 7 of JP 2009-90650 A). Except for joining, joining can be performed in the same manner as described above.

[Laser welding]
In the laser fusion, for example, a fusion laser beam is irradiated along the joining line from the normal direction of the thermoplastic resin film. The fusion laser beam melts and joins the preceding thermoplastic resin film and the subsequent thermoplastic resin film. At this time, the laser fusion apparatus that performs laser fusion irradiates the fusion laser beam with the joining surface of the preceding thermoplastic resin film (the joining surface of the subsequent thermoplastic resin film) as the focal position. When the fusion laser beam is irradiated, heat is generated and melted at the joining surface of the preceding thermoplastic resin film, and the heat is transferred to the joining surface of the succeeding thermoplastic resin film and melted. As a result, the preceding thermoplastic resin film and the subsequent thermoplastic resin film are fused (welded) at the joint.
Specifically, instead of performing heat fusion using the heat sealer device 10, bonding can be performed in the same manner as described above except that laser fusion is performed using a laser fusion device or the like.

<Preheating process>
In the preheating step of the manufacturing method of the obliquely stretched film of the present invention, the joined portion is preheated under the conditions satisfying the following formulas (1) and (2) while continuously transporting the thermoplastic resin film joined through the joined portion. Thereby, it can suppress that the junction part of a thermoplastic resin film fractures | ruptures in the diagonal stretch process mentioned later. In the preheating step, if at least the joint is preheated under the following conditions, parts other than the joint (parts consisting only of the thermoplastic resin film A and parts consisting only of the thermoplastic resin film B) are subject to conditions other than the following. You may preheat. However, from the viewpoint of ease of manufacture of the obliquely stretched film, it is preferable to preheat the joint and the portion other than the joint under the same conditions.
Tg <T ≦ Tg + 60 (1)
2 ≦ t (2)
Here, T in Formula (1) represents the preheating temperature (° C.) of the joint in the preheating step, and Tg in Formula (1) represents the glass transition temperature (° C.) of the thermoplastic resin in the thermoplastic resin film. T in equation (2) represents the preheating time (seconds) of the joint in the preheating step.

The preheating temperature T (° C.) of the joint in the preheating step is not particularly limited as long as it is more than Tg (° C.) and Tg + 60 (° C.), preferably Tg + 10 (° C.) or more, more preferably Tg + 20 (° C.) or more. Tg + 30 (° C.) or higher is particularly preferable, Tg + 50 (° C.) or lower is preferable, and Tg + 40 (° C.) or lower is more preferable.
When the preheating temperature T (° C.) of the joint in the preheating step is higher than Tg (° C.), the joint of the thermoplastic resin film can be prevented from breaking in the oblique stretching step, and Tg + 60 (° C.). When it is below, it is possible to prevent the thermoplastic resin film from becoming too soft and hindering the conveyance of the thermoplastic resin film.

The preheating time t (second) of the joint in the preheating step is not particularly limited as long as it is 2 seconds or more, preferably 5 seconds or more, more preferably 7 seconds or more, and preferably 20 seconds or less. By setting the preheating time t (seconds) of the joint in the preheating step to 2 seconds or more, the joint of the thermoplastic resin film can be prevented from breaking in the oblique stretching step, and in the preheating step. By setting the preheating time t (second) of the bonded portion to 20 seconds or less, it is possible to prevent the productivity of the obliquely stretched film from being lowered.

When the thickness of the thermoplastic resin film is as thick as 100 μm or more, the preheating temperature T (° C.) of the joint in the preheating step is preferably Tg + 10 (° C.) or more, more preferably Tg + 20 (° C.) or more, and Tg + 60 (° C.) or less. Is preferable, Tg + 50 (° C.) or less is more preferable, and Tg + 40 (° C.) or less is particularly preferable. Further, the preheating time t (second) of the joint in the preheating step is preferably 5 (seconds) or more, more preferably 7 (seconds) or more, and preferably 15 (seconds) or less.
On the other hand, when the thickness of the thermoplastic resin film is as thin as less than 100 μm, the preheating temperature T (° C.) of the joint in the preheating step is preferably more than Tg (° C.), more preferably Tg + 10 (° C.) or more, and Tg + 50 (° C. In addition, the preheating time t (second) of the joint in the preheating step is preferably 2 (seconds) or more, preferably 12 (seconds) or less, and more preferably 7 (seconds) or less.

<An oblique stretching process>
In the oblique stretching step of the method for producing an obliquely stretched film of the present invention, an obliquely stretched film can be produced by obliquely stretching the preheated thermoplastic resin film while continuously conveying the thermoplastic resin film.

The stretching temperature T ′ (° C.) of the joint in the oblique stretching step is not particularly limited, but is preferably Tg + 3 (° C.) or higher, more preferably Tg + 8 (° C.) or higher, further preferably Tg + 10 (° C.) or higher, and Tg + 30. (° C.) or less is preferable, and Tg + 25 (° C.) or less is more preferable.
When the stretching temperature T ′ (° C.) is within the above range, the molecules contained in the thermoplastic resin film can be stably oriented by oblique stretching, and a desired retardation can be obtained. The stretching temperature T ′ (° C.) may be the same as or different from the preheating temperature T (° C.).

When the thickness of the thermoplastic resin film is as thick as 100 μm or more, the stretching temperature T ′ (° C.) of the joint in the oblique stretching step is preferably Tg + 10 (° C.) or more, more preferably Tg + 15 (° C.) or more, and Tg + 40 (° C. ) Or less is preferable, Tg + 30 (° C.) or less is more preferable, and Tg + 25 (° C.) or less is particularly preferable.
On the other hand, when the thickness of the thermoplastic resin film is as thin as less than 100 μm, the stretching temperature T ′ (° C.) of the joint in the oblique stretching process is preferably more than Tg (° C.), more preferably Tg + 10 (° C.) or more, and Tg + 30. (° C.) or less is preferable, and Tg + 20 (° C.) or less is more preferable.

The stretching ratio in the oblique stretching step is not particularly limited, but is preferably 1.1 times or more, more preferably 1.2 times or more, particularly preferably 1.3 times or more, and preferably 3.0 times or less. .5 times or less is more preferable, and 2.0 times or less is particularly preferable. By setting the draw ratio to 1.1 times or more, the size and direction of molecular orientation in the obliquely stretched film can be controlled more accurately, and the draw ratio is made 3.0 times or less. Thus, it is possible to stably obtain a long film having a slow axis in an oblique direction by suppressing breakage of the obliquely stretched film.

The obliquely stretched film has a slow axis in a predetermined range on average in the width direction. Specifically, for example, it has a slow axis in an angle range of 5 ° to 85 ° on average with respect to the width direction. Here, the obliquely stretched film has a slow axis in a predetermined range on average with respect to the width direction, which means that the oblique direction of the obliquely stretched film is in the width direction and the slow phase at a plurality of points in the width direction of the obliquely stretched film. This means that when the angles formed with the axes are measured, the average value of the angles measured at those points falls within the predetermined range. Hereinafter, the angle formed by the width direction of the obliquely stretched film and the slow axis may be appropriately referred to as “orientation angle”. Furthermore, the average value of the orientation angle θ is sometimes referred to as “average orientation angle” as appropriate. The average orientation angle θ of the obliquely stretched film is not particularly limited, but is usually 5 ° to 85 °, preferably 40 ° or more, and preferably 50 ° or less. Since the slow axis is expressed by stretching the thermoplastic resin film in an oblique direction, the specific value of the average orientation angle θ can be adjusted by the stretching conditions in the manufacturing method described above. .
The average orientation angle θ is an average of the orientation angle values measured at each point by measuring the orientation angle using a phase difference meter at a plurality of points at intervals of 5 cm in the width direction of the obliquely stretched film. It can be obtained by calculating the value.

Further, the variation in the orientation angle formed by the width direction of the obliquely stretched film and the slow axis is not particularly limited, but is preferably 1.0 ° or less in the longitudinal direction of the obliquely stretched film, It is more preferably at most 0 °, particularly preferably at most 0.3 °, and ideally 0 °. Here, the variation in the orientation angle represents the difference between the maximum value and the minimum value of the orientation angle of the obliquely stretched film. By reducing the variation in the orientation angle as described above, the contrast of the liquid crystal display device can be improved when the film cut out from the obliquely stretched film is used as an optical compensation film of the liquid crystal display device. .

By appropriately setting the average thickness of the obliquely stretched film, the mechanical strength of the obliquely stretched film can be increased.
Here, the average thickness of the obliquely stretched film can be obtained by measuring the thickness at a plurality of points at intervals of 5 cm in the width direction of the film and calculating the average value of the measured values.

The width of the obliquely stretched film is not particularly limited, but is preferably 1000 mm or more, more preferably 1330 mm or more, preferably 1800 mm or less, and more preferably 1600 mm or less. By setting the width of the obliquely stretched film within the above range, the obliquely stretched film can be applied to a large display device (such as an organic EL display device).

The average in-plane retardation Re of the obliquely stretched film is not particularly limited, but is preferably 80 nm or more, more preferably 120 nm or more, particularly preferably 140 nm or more, preferably 300 nm or less, more preferably 200 nm or less, and 150 nm or less. Is particularly preferred. By setting the average in-plane retardation Re within the above range, a film cut out from the obliquely stretched film can be suitably used as an optical compensation film of a display device. However, depending on the configuration of the display device to be applied, the average in-plane retardation Re of the obliquely stretched film can be arbitrarily set to an appropriate value.
The average in-plane retardation Re is measured at in-plane retardation using a phase difference meter at a plurality of points at intervals of 5 cm in the width direction of the obliquely stretched film. It can be obtained by calculating an average value of retardation values.

The variation in in-plane retardation of the obliquely stretched film is not particularly limited, but is preferably 10 nm or less, more preferably 5 nm or less, particularly preferably 2 nm or less, and ideally 0 nm. Here, the dispersion of the in-plane retardation means a difference between the maximum value and the minimum value of the in-plane retardation at an arbitrary point of the obliquely stretched film. By reducing variations in in-plane retardation of the obliquely stretched film, when a film cut out from the obliquely stretched film is applied to a display device, the image quality of the display device can be improved.

The preheating process and the oblique stretching process described above are performed using, for example, an oblique stretching machine described below.
FIG. 2 is a diagram schematically showing a configuration example of an oblique stretching machine used for carrying out the method for producing an obliquely stretched film according to the present invention.
As shown in FIG. 2, the oblique stretching machine 60 is a so-called tenter stretching machine, and includes two gripping devices 101L and 101R that grip the end portions of the thermoplastic resin film F1 joined by the heat sealer device 10, respectively. A pair of gripping means 110 and a temperature control chamber 70 for adjusting the temperature of the thermoplastic resin film F1 gripped by the pair of gripping means 110.

The temperature control chamber 70 is a region that keeps the thermoplastic resin film F1 gripped by the gripping means 110 at an appropriate temperature for oblique stretching. This region includes, for example, a preheating zone X, an oblique stretching zone Y, and a heat fixing zone. The temperature of each zone can be adjusted independently. When the preheating temperature T (° C.) and the stretching temperature T ′ (° C.) are the same, the preheating zone X and the oblique stretching zone Y do not have to be separated.
In the preheating zone X, a preheating process is performed, and in the oblique stretching zone Y, an oblique stretching process is performed.

Each gripping device 101L, 101R includes clips 110L, 110R as a plurality of grips for gripping the end portion of the thermoplastic resin film F1, and endless chains 120L, 120R in which the clips 110L, 110R are installed at predetermined intervals (partly (Not shown), a pair of sprockets 12L, 13L, 12R, and 13R over which endless chains 120L and 120R are spanned, a drive mechanism (not shown) that rotates the sprockets 12L and 12R, and a sprocket 12L that is rotated by the drive mechanism. , 12R is provided with a rail (not shown) that guides the direction of the clips 110L and 110R that move with rotation. In the present embodiment, the rotation speed of the sprocket 12L and the rotation speed of the sprocket 12R are adjusted to be the same. For this reason, the moving speeds of the clips 110L and 110R are the same. The gripping device 101L and the gripping device 101R have substantially the same constituent elements, but differ in the arrangement direction and length of the rail.

In the rail, the direction in which the thermoplastic resin film F1 is supplied and the direction in which the obliquely stretched film F2 after oblique stretching is wound are different, that is, the rails proceed in the directions of arrows D1, D2, and D3. Specifically, as shown in FIG. 2, when the film is observed from upstream to downstream in the flow direction of the film, the film is arranged so that the traveling direction of the film bends to the left in the middle. . Further, the rail on the gripping device 101L side and the rail on the gripping device 101R side are arranged in parallel at a constant interval on the inlet side (first parallel portion: preheating zone X) to which the film is supplied. In the bent portion (diagonal stretching zone Y), the interval is gradually widened, and on the exit side (second parallel portion) of the film, it is parallel with a larger interval than the interval of the first parallel portion. Is arranged. In this embodiment, the film is arranged so that the traveling direction of the film bends to the left, but may be arranged to bend to the right.

Since the rail is arranged as described above, the rail length on the gripping device 101R side that is the outside of the bent portion is longer than the rail length on the gripping device 101L side that is on the inside of the bent portion. For this reason, in the first parallel portion (preheating zone X), the pair of clips that simultaneously grips both ends in the width direction of the thermoplastic resin film F1 have a rail length when passing through the bent portion (obliquely extending zone Y). Since the relative position shifts accordingly, the clip on the gripping device 101L side moves ahead of the clip on the gripping device 101R side in the second parallel portion. For this reason, after the pair of clips pass through the bent portion of the rail, the thermoplastic resin film F1 is obliquely stretched in an oblique direction that is neither the width direction nor the longitudinal direction, and the molecular orientation direction becomes the oblique direction. The obliquely stretched film F2 can be manufactured.

When the thermoplastic resin film F1 is supplied to such an oblique stretching machine 60, the thermoplastic resin film F1 is continuously supplied from the upstream (upper left in FIG. 2) to the oblique stretching machine 60 along the direction of the arrow D1. The The supplied thermoplastic resin film F1 is gripped by a pair of clips 110L and 110R at both ends in the width direction before entering the temperature control chamber 70. Next, the thermoplastic resin film F1 gripped by the clips 110L and 110R enters the temperature control chamber 70, and in the temperature control chamber 70, by the circular movement along the rail on each side of each clip 110L and 110R, Stretched in the direction. The obliquely stretched film F2 stretched in the oblique direction is released from the temperature control chamber 70 and then released from being gripped by the clips 110L and 110R, and is carried out in the direction of the arrow D3.

More specifically, both end portions in the width direction of the thermoplastic resin film F1 are simultaneously grasped at the time of the dotted line CS1, and are carried into the temperature control chamber 70 to start the preheating process. Subsequently, the oblique stretching process is started from the position where the rail interval starts to widen, and when the position reaches, for example, the dotted line CS2, the film is stretched in the direction of the dotted line CS2. Then, the oblique stretching process is terminated at a position where the rail spacing becomes the same again. Therefore, the conveyance time from the position where the temperature is adjusted into the temperature control chamber 70 to the position where the rail interval begins to increase becomes the preheating time t. When the clips 110L and 110R further move and reach the position indicated by the dotted line CS3, the stretch ratio is further increased, and an obliquely stretched film F2 having optical anisotropy in which molecules are oriented in the direction of the dotted line CS3 is obtained.

(Production method of polarizing plate)
The manufacturing method of the polarizing plate of this invention is a method of manufacturing a polarizing plate by laminating | stacking the diagonally stretched film manufactured by the manufacturing method of the diagonally stretched film mentioned above, and a polarizer.

<Polarizing plate>
The polarizing plate includes an obliquely stretched film manufactured by the above-described method for manufacturing an obliquely stretched film and a polarizer, and may further include an arbitrary member as necessary.

The polarizing plate can be manufactured by laminating a long polarizer and a long obliquely stretched film by roll-to-roll with the longitudinal direction thereof being parallel. In bonding, an adhesive may be used as necessary. By producing using a long film, it is possible to efficiently produce a long polarizing plate.

[Polarizer]
Examples of the polarizer include, for example, a film of a suitable vinyl alcohol polymer such as polyvinyl alcohol and partially formalized polyvinyl alcohol, a dyeing process using an dichroic substance such as iodine and a dichroic dye, a stretching process, and a crosslinking process. And the like, which have been subjected to appropriate processing in an appropriate order and manner. Such a polarizer is capable of transmitting linearly polarized light when natural light is incident thereon, and in particular, a polarizer excellent in light transmittance and degree of polarization is preferable. The thickness of the polarizer is generally 5 μm or more and 80 μm or less, but is not limited thereto.

The obliquely stretched film may be provided on both sides of the polarizer or on one side. Conventionally, a protective film has been provided on the surface of the polarizer. However, by combining the obliquely stretched film with the polarizer, the obliquely stretched film can serve as the protective film for the polarizer. Therefore, the polarizing plate provided with the obliquely stretched film and the polarizer in combination can omit the conventionally used protective film and can contribute to thinning.

[Arbitrary members]
As said arbitrary member, the protective film for protecting a polarizer is mentioned, for example. Any transparent film can be used as the protective film. Among these, a resin film excellent in transparency, mechanical strength, thermal stability, moisture shielding properties and the like is preferable.

(Manufacturing method of liquid crystal display device)
The manufacturing method of the liquid crystal display device of this invention is a method of manufacturing a liquid crystal display device using the polarizing plate mentioned above.

<Liquid crystal display device>
The liquid crystal display device can be manufactured, for example, by using what is cut out to a predetermined size from the polarizing plate.
Examples of the liquid crystal display device include those having liquid crystal cells of various driving methods. Liquid crystal cell driving methods include, for example, in-plane switching (IPS) mode, vertical alignment (VA) mode, multi-domain vertical alignment (MVA) mode, continuous spin wheel alignment (CPA) mode, and hybrid alignment nematic (HAN) Mode, twisted nematic (TN) mode, super twisted nematic (STN) mode, optical compensated bend (OCB) mode, and the like.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples. The present invention can be implemented with any modifications without departing from the scope of the claims of the present invention and its equivalent scope.
The operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified. In the following examples and comparative examples, “%” and “parts” representing amounts are based on mass unless otherwise specified.

〔Evaluation methods〕
-Measurement method of average thickness (μm) of thermoplastic resin film-
Using a snap gauge (“ID-C112BS” manufactured by Mitutoyo Corporation), the thickness was measured at a plurality of points at intervals of 5 cm in the width direction of the thermoplastic resin film. By calculating the average value of these measured values, the average thickness of the thermoplastic resin film was determined. In addition, the thermoplastic resin film conveyed ahead is made into sheet A, and the thermoplastic resin film conveyed behind is made into sheet B.

-Calculation method for preheating time t (seconds) of thermoplastic resin film-
The preheating time t (second) of the thermoplastic resin film was calculated from the conveyance speed of the thermoplastic resin film and the conveyance distance of the thermoplastic resin film in the preheating zone X.

-Measuring method of preheating temperature T (° C) of thermoplastic resin film-
The temperature of the thermoplastic resin film in the preheating zone X conveyed to the oblique stretching machine (tenter stretching machine) 60 of FIG. 2 was measured as follows.
The temperature of the space with a distance of 100 mm in the film normal direction from the joint of the thermoplastic resin film in the preheating zone X is measured using a thermocouple, and this is adopted as the preheating temperature T (° C.) of the thermoplastic resin film. did.

-Measurement Method of Stretching Temperature T '(° C) of Thermoplastic Resin Film-
The temperature of the thermoplastic resin film in the oblique stretching zone Y conveyed to the oblique stretching machine 60 in FIG. 2 was measured as follows.
The temperature of the space at a distance of 100 mm in the film normal direction from the joint of the thermoplastic resin film in the oblique stretching zone Y was measured using a thermocouple, and this was measured as the stretching temperature T ′ (° C.) of the thermoplastic resin film. Adopted as.

-Evaluation of fracture-
The fracture was evaluated according to the following evaluation criteria.
○: No fracture caused by the joint occurs at all.
(Triangle | delta): The time which can be continuously drive | operated without the fracture | rupture resulting from a junction part generating is 24 hours or more.
X: The time which can be continuously operated without the occurrence of breakage due to the joint is less than 24 hours.

-Measurement method of average in-plane retardation Re (nm) of obliquely stretched film-
In-plane retardation at a plurality of points at intervals of 5 cm in the width direction of the obliquely stretched film was measured using a phase difference meter (“Muula Matrix Polarimeter (Axo Scan)” manufactured by Opt Science). The average value of the in-plane retardation at each point was calculated, and this was determined as the average in-plane retardation Re of the obliquely stretched film. At this time, the measurement wavelength was 590 nm.

-Measuring method of average orientation angle θ (°) of obliquely stretched film-
Using a phase difference meter ("Muula Matrix Polarimeter (Axo Scan)" manufactured by Opt Science), the slow axis at each point is measured at a plurality of locations in the width direction of the obliquely stretched film. Calculated the orientation angle formed with the width direction of the obliquely stretched film. The average value of the orientation angles at each point was calculated and obtained as the average orientation angle θ of the obliquely stretched film. At this time, the measurement wavelength was 590 nm.

Example 1
A norbornene resin pellet (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg 126 ° C.) is molded with a T-die type film extruder to produce a long norbornene resin film having a width of 1200 mm and a thickness of 120 μm. Rolled up into a roll. In this way, two norbornene resin films wound up in a roll shape are prepared, and using a heat sealer, the norbornene resin film (sheet A) transported in advance and the norbornene resin transported downstream. The film (sheet B) was bonded by heat fusion.

Next, as shown in FIG. 2, an oblique stretching machine 60 having the configuration described in the above-described embodiment is prepared, and a norbornene resin film bonded to the oblique stretching machine 60 by the thermal fusion is used as a thermoplastic resin. The film F1 was supplied from the heat sealer device 10. In the oblique stretching machine 60, the thermoplastic resin film F1 was preheated or obliquely stretched under the conditions shown in the column of Example 1 in Table 1 below to produce an obliquely stretched film F2.
The obliquely stretched film F2 thus obtained was evaluated for breakage, average in-plane retardation Re, and average orientation angle θ by the methods described above. The obtained evaluation results are shown in Table 1.

(Example 2)
In Example 1, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 1 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Example 2 in Table 1 below. Except having been preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 1, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Example 3)
In Example 1, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 1 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Example 3 in Table 1 below. Except having been preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 1, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

Example 4
In Example 1, instead of producing a long norbornene resin film having a thickness of 120 μm, a long norbornene resin film having a thickness of 70 μm was produced. In Example 1, Example 1 in Table 1 below was used. Instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column, Example 1 except that the thermoplastic resin film F1 was preheated or obliquely stretched under the conditions shown in the column of Example 4 in Table 1 below. In the same manner as described above, an obliquely stretched film F2 was produced, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Example 5)
In Example 4, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 4 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Example 5 in Table 1 below. Except having been preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 4, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Example 6)
In Example 1, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 1 of Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Example 6 of Table 1 below. The slanted stretched film F2 was produced in the same manner as in Example 1 except that the slanted stretched film F2 was produced by preheating or obliquely stretching the film, and the obtained slanted stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Example 7)
In Example 6, instead of thermally bonding the norbornene resin film transported in advance and the norbornene resin film transported in the following, the norbornene resin film transported in advance, The obliquely stretched film F2 was produced in the same manner as in Example 6 except that the norbornene resin film conveyed in line was tape-joined, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Example 8)
In Example 2, the norbornene resin pellet (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg 126 ° C.) was changed to another norbornene resin pellet (“ZEONOR manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg 163 ° C.)”. Except having done, it carried out similarly to Example 2, manufactured the diagonally stretched film F2, and evaluated about the obtained diagonally stretched film F2. The obtained evaluation results are shown in Table 1.

(Comparative Example 1)
In Example 1, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 1 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Comparative Example 1 in Table 1 below. Except having been preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 1, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Comparative Example 2)
In Example 1, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 1 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Comparative Example 2 in Table 1 below. Except having been preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 1, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Comparative Example 3)
In Example 4, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 4 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Comparative Example 3 in Table 1 below. Except that was preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 4, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Comparative Example 4)
In Example 7, instead of preheating or obliquely stretching the thermoplastic resin film F1 under the conditions shown in the column of Example 7 in Table 1 below, the thermoplastic resin film F1 under the conditions shown in the column of Comparative Example 4 in Table 1 below. Except that was preheated or obliquely stretched, the obliquely stretched film F2 was produced in the same manner as in Example 7, and the obtained obliquely stretched film F2 was evaluated. The obtained evaluation results are shown in Table 1.

(Comparative Example 5)
In Comparative Example 2, the norbornene resin pellet (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg 126 ° C.) was changed to another norbornene resin pellet (“ZEONOR manufactured by Nippon Zeon Co., Ltd., glass transition temperature Tg 163 ° C.)”. Except having done, it carried out similarly to the comparative example 2, and manufactured the diagonally stretched film F2, and evaluated about the obtained diagonally stretched film F2. The obtained evaluation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 8 in which the preheating time t is 2 seconds or more and the preheating temperature T is more than the glass transition temperature Tg of the norbornene resin Tg + 60 ° C. or less, the thermoplasticity in the oblique stretching step It was possible to continuously manufacture obliquely stretched films while suppressing breakage of the joint portion of the resin film.
In addition, in Example 6 in which the joining means is heat fusion, rather than Example 7 in which the joining means is a tape, the joint portion of the thermoplastic resin film is further prevented from breaking in the oblique stretching step. The obliquely stretched film could be continuously produced more reliably.
On the other hand, in Comparative Examples 1 and 4 in which the preheating time t in the preheating process was as short as 1.7 seconds, it was not possible to suppress the breakage of the joint portion of the thermoplastic resin film in the oblique stretching process.
Moreover, in Comparative Examples 2, 3, and 5 in which the preheating temperature T is the glass transition temperature Tg of the norbornene resin, it was not possible to suppress the breakage of the joint portion of the thermoplastic resin film in the oblique stretching process.

According to the present invention, it is possible to continuously manufacture obliquely stretched films while suppressing breakage of the joint portion of the thermoplastic resin film in the obliquely stretching step.

3 Film 10 Heat Sealer 10a Roller 10b Roller 12L Sprocket 12R Sprocket 13L Sprocket 13R Sprocket 21 Upper Welding Head 22 Lower Welding Head 23 Heater 24 Heater 25 Temperature Controller 26 Temperature Controller 28 Joining Section 60 Angle Stretching Machine L 70 Temperature Control Room 70 Gripping device 101R Gripping device 110 Gripping means 110L Clip 110R Clip 120L Endless chain 120R Endless chain A Thermoplastic resin film (preceding sheet)
B Thermoplastic resin film (following sheet)
CS1 dotted line CS2 dotted line CS3 dotted line D1 arrow D2 arrow D3 arrow F1 thermoplastic resin film F2 obliquely stretched film X preheating zone Y obliquely stretched zone

Claims (6)

1. A joining step of joining the thermoplastic resin film transported in advance and the thermoplastic resin film transported in a subsequent manner via a joint portion;
   A preheating step of preheating while continuously transporting the thermoplastic resin film bonded through the bonding portion;
   An oblique stretching step in which the preheated thermoplastic resin film is obliquely stretched while continuously conveyed, and a method for producing an obliquely stretched film,
   The thermoplastic film transported in advance and the thermoplastic resin film transported in succession are the same thermoplastic resin film,
   The preheating temperature of the joint in the preheating step is T (° C.), the preheating time of the joint in the preheating step is t (seconds), and the glass transition temperature of the thermoplastic resin in the thermoplastic resin film is Tg ( C)), a method for producing an obliquely stretched film that satisfies the following formulas (1) and (2).
   Tg <T ≦ Tg + 60 (1)
   2 ≦ t (2)
2. The manufacturing method of the diagonally stretched film of Claim 1 which joins the thermoplastic resin film conveyed ahead and the thermoplastic resin film conveyed downstream and carried out by heat sealing | fusion.
3. The manufacturing method of the diagonally stretched film of Claim 1 or 2 whose average thickness is 50 micrometers or more and 300 micrometers or less of the thermoplastic resin film conveyed preceding and the thermoplastic resin film conveyed downstream. .
4. The method for producing an obliquely stretched film according to any one of claims 1 to 3, wherein a glass transition temperature Tg of the thermoplastic resin in the thermoplastic resin film is 100 ° C or higher and 180 ° C or lower.
5. A method for producing a polarizing plate, wherein a polarizing plate is produced by laminating an obliquely stretched film produced by the method for producing an obliquely stretched film according to any one of claims 1 to 4 and a polarizer.
6. A method for producing a liquid crystal display device, comprising producing a liquid crystal display device comprising the polarizing plate produced by the method for producing a polarizing plate according to claim 5.

Images