WO2019188857A1

WO2019188857A1 - Method for producing long stretched film and long polarizing film

Info

Publication number: WO2019188857A1
Application number: PCT/JP2019/012274
Authority: WO
Inventors: 次郎石原
Original assignee: 日本ゼオン株式会社
Priority date: 2018-03-27
Filing date: 2019-03-22
Publication date: 2019-10-03
Also published as: CN111712371A; JP7124864B2; TW201941912A; KR20200133332A; TWI783132B; JPWO2019188857A1; CN111712371B

Abstract

This method for producing a long stretched film includes, in the stated order, a first step for stretching a long unstretched film in a direction at an angle of 15-50° with respect to the width direction to obtain a long first stretched film, and a second step for stretching the long first stretched film in the width direction to obtain a long second stretched film. The long second stretched film has a slow axis that forms an angle of 10-30° with respect to the width direction.

Description

Manufacturing method of long stretched film and long polarizing film

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

In the liquid crystal display device, an optical member such as a retardation film is used to improve performance. When the retardation film is used for antireflection of, for example, mobile devices and organic EL televisions, and for optical compensation of liquid crystal display devices, the slow axis thereof is neither parallel nor perpendicular to the transmission axis of the polarizer. It is required to be at an angle (oblique direction).

If the slow retardation film is in an oblique direction, the long retardation film is formed by laminating a long polarizer whose transmission axis is perpendicular or parallel to the flow direction by a roll-to-roll method. A polarizing film can be manufactured. Therefore, a method for producing a long retardation film having a slow axis in an oblique direction has been proposed by a method including a step of stretching a long unstretched film in an oblique direction (Patent Documents 1 to 3). .

JP 2012-101466 A International Publication No. 2015/072518 (corresponding publication: US Patent Application Publication No. 2016/318233) Japanese Patent No. 5257505

If the stretch ratio of the pre-stretched film is increased in order to sufficiently develop the retardation in the stretched film, the binding force in the thickness direction of the resulting stretched film may be decreased. As a result, when the stretched film was bonded to an element such as a polarizer and a peeling force was applied thereto, the stretched film sometimes peeled from the element.
Therefore, a method for producing a long stretched film excellent in peel strength while sufficiently expressing the phase difference; including a long stretched film excellent in peel strength while sufficiently expressing the phase difference, There is a demand for a method for producing a long polarizing film.

As a result of intensive studies to solve the above problems, the inventors of the present invention have excellent peel strength while a phase difference is sufficiently expressed by a production method in which a pre-stretch film is stretched stepwise in a predetermined direction. It discovered that a elongate stretched film was obtained and completed this invention. That is, the present invention provides the following.

[1] A method for producing a long stretched film,
A first step of obtaining a long first stretched film by stretching the long pre-stretched film in a direction of 15 ° or more and 50 ° or less with respect to the width direction;
A second step of stretching the long first stretched film in the width direction to obtain a long second stretched film in this order,
The long second stretched film has a slow axis that forms an angle of 10 ° to 30 ° with respect to the width direction.
A method for producing a long stretched film.
[2] The average NZ coefficient of the long second stretched film is 1.2 or more and 1.5 or less,
When the draw ratio in the first step is A1, and the draw ratio in the second step is A2, A1 is 1.2 times or more and 1.6 times or less, and (A1 × A2) is larger than 1.2 times. The manufacturing method of the elongate stretched film as described in [1] which is 2.0 times or less.
[3] The method for producing a long stretched film according to [1] or [2], wherein an average in-plane retardation Re2 of the long second stretched film is 200 nm or more and 300 nm or less.
[4] The method for producing a long stretched film according to any one of [1] to [3], wherein the stretched film contains a polymer containing an alicyclic structure.
[5] A method for producing a long polarizing film,
Including a third step of laminating a long polarizer on a long stretched film obtained by the method for producing a long stretched film according to any one of [1] to [4].
A method for producing a long polarizing film.

According to the present invention, a method for producing a long stretched film excellent in peel strength while sufficiently expressing the phase difference; a long stretch excellent in peel strength while sufficiently expressing the phase difference And a method for producing a long polarizing film comprising the film.

FIG. 1 is a plan view schematically showing a tenter device for carrying out a manufacturing method according to an embodiment of the present invention. FIG. 2 is a plan view schematically showing a transverse stretching apparatus for carrying out the manufacturing method according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, a “long” film refers to a film having a length of at least 5 times the width, preferably 10 times or more, specifically, A film having such a length that it is wound up in a roll and stored or transported. The upper limit of the ratio of the length to the width is not particularly limited, but may be, for example, 100,000 times or less.

In the following description, the in-plane retardation Re of the film is a value represented by (nx−ny) × d unless otherwise specified. The thickness direction retardation Rth of the film is a value represented by {(nx + ny) / 2−nz} × d unless otherwise specified. Further, the NZ coefficient is a value represented by (nx−nz) / (nx−ny) unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the film and perpendicular to the nx direction. nz represents the refractive index in the thickness direction of the film. d represents the thickness of the film. The measurement wavelength is 590 nm unless otherwise specified.

The NZ coefficient can be determined from the in-plane retardation Re and the thickness direction retardation Rth of the film according to the following formula.
NZ coefficient = (Rth / Re) +0.5

In the following description, the directions of the elements “parallel”, “vertical”, and “orthogonal” include errors within a range that does not impair the effects of the present invention, for example, ± 5 °, unless otherwise specified. You may go out.

In the following description, the longitudinal direction of the long film is usually parallel to the film flow direction in the production line. The oblique direction is an in-plane direction of the film, and is neither a width direction nor a longitudinal direction.

[1. Manufacturing method of long stretched film]
The manufacturing method of the elongate stretched film which concerns on one Embodiment of this invention stretches | stretches the elongate film before extending | stretching in the direction of 15 degrees or more and 50 degrees or less with respect to the width direction, and is 1st elongate drawing A first step of obtaining a film and a second step of stretching the long first stretched film in the width direction to obtain a long second stretched film are included in this order.

(Film before stretching)
Usually, a resin film is used as the film before stretching. As a material for the resin film, a thermoplastic resin is usually used.

Examples of thermoplastic resins include: polyolefin resins such as polyethylene resins and polypropylene resins; polymer resins having an alicyclic structure such as norbornene resins; cellulose resins such as triacetyl cellulose resins; polyimide resins, polyamideimide resins, Polyamide resin, polyetherimide resin, polyether ether ketone resin, polyether ketone resin, polyketone sulfide resin, polyether sulfone resin, polysulfone resin, polyphenylene sulfide resin, polyphenylene oxide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate Phthalate resin, polyacetal resin, polycarbonate resin, polyarylate resin, (meth) acrylic resin, polyvinyl alcohol resin, (meth) Acrylic acid ester - vinyl aromatic compound copolymer resins, isobutene / N- methylmaleimide copolymer resins, styrene / acrylonitrile copolymer resins.
The thermoplastic resin can usually contain a polymer and further optional components. A polymer may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As the resin forming the film before stretching, a resin containing a polymer containing an alicyclic structure is preferable. Hereinafter, a polymer containing an alicyclic structure may be referred to as an “alicyclic structure-containing polymer” as appropriate.

The alicyclic structure-containing polymer is a polymer containing an alicyclic structure in a repeating unit. Examples of the alicyclic structure-containing polymer include a polymer that can be obtained by a polymerization reaction using a cyclic olefin as a monomer; and a hydride thereof. Moreover, as said alicyclic structure containing polymer, both the polymer which contains alicyclic structure in a principal chain, and the polymer which contains alicyclic structure in a side chain can be used. Especially, it is preferable that an alicyclic structure containing polymer contains an alicyclic structure in a principal chain. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and a cycloalkane structure is preferable from the viewpoint of thermal stability.

The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, more preferably 6 or more, preferably 30 or less, more preferably 20 or less, Particularly preferred is 15 or less. When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability are highly balanced.

The ratio of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is preferably 30% by weight or more, more preferably 50% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight. It is above and may be 100 weight% or less. Heat resistance can be improved by increasing the ratio of the repeating unit having an alicyclic structure as described above.
In the alicyclic structure-containing polymer, the remainder other than the repeating unit having an alicyclic structure is not particularly limited and can be appropriately selected according to the purpose of use.

Examples of the alicyclic structure-containing polymer include (1) a norbornene polymer, (2) a monocyclic olefin polymer, (3) a cyclic conjugated diene polymer, and (4) a vinyl alicyclic hydrocarbon polymer. And hydrides thereof. Among these, a norbornene-based polymer and a hydride thereof are more preferable from the viewpoints of transparency and moldability.

Examples of the norbornene-based polymer include a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer of a norbornene-based monomer and another monomer capable of ring-opening copolymerization, and a hydride thereof; Examples thereof include addition polymers and addition copolymers with other monomers copolymerizable with norbornene monomers. Among these, a ring-opening polymer hydride of a norbornene monomer is particularly preferable from the viewpoint of transparency.
The above alicyclic structure-containing polymer is selected from, for example, polymers disclosed in JP-A No. 2002-321302.

Since various products are commercially available as the resin containing the alicyclic structure-containing polymer, those having desired characteristics can be appropriately selected and used. Examples of such commercially available products include “ZEONOR” (manufactured by ZEON Corporation), “ARTON” (manufactured by JSR Corporation), “Apel” (manufactured by Mitsui Chemicals), “TOPAS” (polyplastics company) Product group).

A stretched film containing an alicyclic structure-containing polymer can be obtained by forming the pre-stretched film with a resin containing an alicyclic structure-containing polymer.

The glass transition temperature Tg of the resin forming the film before stretching is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, preferably 190 ° C. or lower, more preferably 180 ° C. or lower, particularly Preferably it is 170 degrees C or less. By setting the glass transition temperature to be equal to or higher than the lower limit of the above range, it is possible to enhance the durability of the stretched film in a high temperature environment. In addition, the stretching process can be easily performed by setting the upper limit value or less.

The thickness of the pre-stretched film can be determined according to the stretching ratio, the desired stretched film thickness, and the like, preferably 20 μm or more, more preferably 30 μm or more, preferably 120 μm or less, more preferably 100 μm or less. .

In this embodiment, an unstretched film that has not been stretched is used as the pre-stretch film. However, a stretched film may be used as the pre-stretch film.

The unstretched film can be obtained by a method such as a cast molding method, an extrusion molding method, or an inflation molding method. Of these, the extrusion molding method is preferable because it has a small amount of residual volatile components and is excellent in dimensional stability.

(First step)
In the method for producing a long stretched film of the present embodiment, the long stretched film is stretched in the direction of 15 ° or more and 50 ° or less with respect to the width direction to obtain a long first stretched film. One step is performed.

In the first step, stretching is usually performed using a tenter apparatus while continuously transporting the unstretched film in the longitudinal direction.

The tenter device includes, for example, a pair of guide rails and a plurality of grippers that run along the pair of guide rails, and the pair of guide rails is a film before stretching that is conveyed by the plurality of grippers. It is possible to use an apparatus that is formed so as to bend the traveling direction and that is provided with an extension zone in which the distance between the pair of guide rails becomes wider toward the downstream.

FIG. 1 is a plan view schematically showing a tenter device 100 for carrying out a manufacturing method according to an embodiment of the present invention.
As shown in FIG. 1, the tenter device 100 stretches the unstretched film 20 fed from the feed roll 10 in a direction of 15 ° or more and 50 ° or less with respect to the width direction in a heating environment by an oven (not shown). It is a device.

The tenter device 100 includes a plurality of

grippers

110R and 110L and a pair of

guide rails

120R and 120L. The

grippers

110R and 110L are provided so as to grip the

end portions

21 and 22 in the width direction of the unstretched film 20, respectively. In addition, the

guide rails

120R and 120L are provided on both sides of the film transport path to guide the

grippers

110R and 110L.

The

grippers

110R and 110L are provided so as to be able to travel along the

guide rails

120R and 120L. In addition, the

grippers

110R and 110L are provided so as to be able to travel at a constant speed with a certain distance from the front and

rear grippers

110R and 110L, respectively. Further, the

grippers

110R and 110L respectively grip the

end portions

21 and 22 in the width direction of the unstretched film 20 sequentially supplied to the tenter device 100 at the inlet portion 130 of the tenter device 100, and the outlet portion of the tenter device 100. 140 has a configuration that can be opened.

The guide rails 120R and 120L have an asymmetric shape according to conditions such as a stretching direction and a stretching ratio of the first stretched film 30 to be manufactured. The tenter device 100 according to the present embodiment is provided with an extension zone 150 in which the distance between the

guide rails

120R and 120L increases toward the downstream. In the extension zone 150, the shape of the

guide rails

120R and 120L is set so that the moving distance of one gripper 110R is longer than the moving distance of the other gripper 110L. Therefore, the shape of the

guide rails

120R and 120L in the tenter device 100 is such that the

grippers

110R and 110L guided by the

guide rails

120R and 120L bend the traveling direction of the pre-stretch film 20 in the left direction. The shape is set so that the film 20 can be conveyed. Here, in the present embodiment, the traveling direction of the long film refers to the moving direction of the middle point in the width direction of the film unless otherwise specified. Further, in the present embodiment, “right” and “left” indicate directions when a horizontally transported film is observed from upstream to downstream in the transport direction unless otherwise specified.

Further, the

guide rails

120R and 120L have endless continuous tracks so that the

grippers

110R and 110L can go around a predetermined track. For this reason, the tenter device 100 has a configuration in which the

grippers

110R and 110L, which have opened the unstretched film 20 at the outlet 140 of the tenter device 100, can be sequentially returned to the inlet 130.

Stretching of the pre-stretching film 20 using the tenter device 100 is performed as follows.
The unstretched film 20 is unwound from the feed roll 10 and the unstretched film 20 is continuously supplied to the tenter apparatus 100.
The tenter device 100 sequentially grips both

end portions

21 and 22 of the unstretched film 20 with

grippers

110R and 110L at the entrance 130 thereof. The unstretched film 20 gripped at both ends 21 and 22 is transported as the

grippers

110R and 110L travel. As described above, in the present embodiment, the shapes of the

guide rails

120R and 120L are set so that the traveling direction of the unstretched film 20 is bent leftward. Therefore, the distance of the track on which one gripper 110R travels while gripping the unstretched film 20 is longer than the distance of the track on which the other gripper 110L travels while gripping the unstretched film 20. Accordingly, the pair of

grippers

110R and 110L that are opposed to the direction perpendicular to the traveling direction of the unstretched film 20 at the inlet portion 130 of the tenter device 100 are the left grippers at the outlet portion 140 of the tenter device 100. Since 110L precedes the right gripper 110R, the pre-stretching film 20 is stretched in an oblique direction, and the long first stretched film 30 is obtained. The obtained first stretched film 30 is released from the grippers 110 R and 110 L at the outlet 140 of the tenter device 100, wound up, and collected as a roll 40.

The extending direction in the first step is 15 ° or more and 50 ° or less with respect to the width direction.
The stretching direction in the first step is preferably 20 ° or more, more preferably 25 ° or more, preferably 48 ° or less, more preferably 45 ° or less with respect to the width direction. By making the extending | stretching direction in a 1st process into the said range, the stretched film which has a slow axis in a diagonal direction with respect to the width direction can be obtained.

The draw ratio A1 in the first step is preferably 1.2 times or more, more preferably 1.25 times or more, still more preferably 1.3 times or more, preferably 1.6 times or less, more preferably 1. 5 times or less, more preferably 1.4 times or less. The in-plane retardation of the stretched film can be increased by setting the stretch ratio A1 in the first step to be equal to or greater than the lower limit of the above range. Moreover, the peeling strength of a stretched film can be enlarged by setting it as an upper limit or less.

The stretching direction and stretching ratio in the first step can be adjusted by the stretching conditions in the first step described above. For example, the stretching direction of the first stretched film 30 can be adjusted by adjusting the feeding angle φ formed by the feeding direction D20 of the pre-stretching film 20 from the feeding roll 10 and the winding direction D30 of the first stretched film 30. . Here, the feeding direction D 20 of the pre-stretching film 20 indicates the traveling direction of the pre-stretching film 20 that is fed from the feeding roll 10. The winding direction D30 of the first stretched film 30 indicates the traveling direction of the first stretched film 30 that is wound as the roll 40.
Moreover, the draw ratio of the 1st stretched film 30 in a 1st process can be adjusted by adjusting the width | variety of the guide rail 120R and the guide rail 120L.

The stretching temperature T1 in the first step is preferably (Tg) ° C. or higher, more preferably (Tg + 2) ° C. or higher, particularly preferably (Tg + 5) ° C. or higher, preferably (Tg + 40) ° C. or lower, more preferably (Tg + 35). ) ° C. or lower, particularly preferably (Tg + 30) ° C. or lower. Here, Tg refers to the glass transition temperature of the resin that forms the pre-stretched film. In the present embodiment, the stretching temperature T1 in the first step refers to the temperature in the stretching zone 150 of the tenter apparatus 100. By setting the stretching temperature T1 in the first step within the above range, the molecules contained in the pre-stretching film 20 can be reliably oriented, so that the first stretched film 30 having desired optical characteristics can be easily obtained. Can do.

The average in-plane retardation Re1 of the first stretched film 30 is preferably 180 nm or more, more preferably 200 nm or more, preferably 260 nm or less, more preferably 240 nm or less. By setting the average in-plane retardation Re1 of the first stretched film 30 within the above range, a second stretched film having a desired average in-plane retardation Re2 can be easily obtained.
The average in-plane retardation of the film can be obtained by measuring the in-plane retardation at a plurality of points at intervals of 50 mm arranged in the width direction of the film and calculating the average value of the in-plane retardation at these points. .

The direction of the slow axis of the first stretched film 30 is preferably set according to the direction of the slow axis of the second stretched film. Usually, the angle (orientation angle) formed by the slow axis of the second stretched film obtained in the second step with respect to the width direction is larger than the angle formed by the slow axis of the first stretched film with respect to the width direction. Becomes smaller. Therefore, it is preferable that the angle formed by the slow axis of the first stretched film 30 with respect to the width direction is larger than the angle formed by the slow axis of the second stretched film with respect to the width direction. For example, the first stretched film 30 has an average of preferably 20 ° or more, more preferably 25 ° or more, and preferably 60 ° or less, more preferably 55 ° or less with respect to the width direction. Has a phase axis. Thereby, the 2nd stretched film whose orientation angle is 10 degrees or more and 30 degrees or less can be obtained easily. The direction of the slow axis of the first stretched film 30 can be adjusted by adjusting the stretch direction of the first step.

The average orientation angle of the film can be obtained by measuring the orientation angle at a plurality of points at intervals of 50 mm arranged in the width direction of the film and calculating the average value of the orientation angles at these points.

(Second step)
In the manufacturing method of the elongate stretched film of this embodiment, the 2nd process of extending a 1st stretched film to the width direction and obtaining a elongate 2nd stretched film is performed after the said 1st process.
Here, “stretching in the width direction” means stretching so that an angle formed by the width direction and the stretching direction is within a range of 0 ° ± 5 °.
Stretching in the width direction in the second step is usually performed using a lateral stretching apparatus while continuously transporting the first stretched film in the longitudinal direction.

FIG. 2 is a plan view schematically showing a transverse stretching apparatus for carrying out the manufacturing method according to one embodiment of the present invention.
As shown in FIG. 2, the transverse stretching device 400 is a device that stretches the first stretched film 30 fed from the roll 40 in the width direction perpendicular to the flow direction in a heating environment by an oven (not shown).

The lateral stretching device 400 includes a plurality of

grippers

410R and 410L and a pair of

guide rails

420R and 420L. The

grippers

410R and 410L are provided so as to grip the

end portions

31 and 32 in the width direction of the first stretched film 30, respectively. In addition, the

guide rails

420R and 420L are provided on both sides of the film transport path to guide the

grippers

410R and 410L.

The

grippers

410R and 410L are provided so as to be able to travel along the

guide rails

420R and 420L. In addition, the

grippers

410R and 410L are provided so as to be able to travel at a constant speed with a predetermined distance from the front and

rear grippers

410R and 410L, respectively. Further, the

grippers

410R and 410L respectively grip the widthwise ends 31 and 32 of the first stretched film 30 sequentially supplied to the transverse stretching device 400 at the inlet portion 430 of the transverse stretching device 400, and the transverse stretching device. It has a configuration that can be opened at 400 outlet portions 440.

The guide rails 420R and 420L are provided with an extension zone 450 in which the distance between the guide rail 420R and the guide rail 420L increases toward the downstream. The shapes of the guide rail 420R and the guide rail 420L in the stretching zone 450 are symmetric with respect to the line LN40 passing through the midpoint in the width direction of the first stretched film 30 to be conveyed, and the guide rail 420R in the stretching zone 450 is. The distance between the guide rail 420L and the guide rail 420L can be adjusted according to the draw ratio in the second step.

The guide rails 420R and 420L have endless continuous tracks so that the

grippers

410R and 410L can go around a predetermined track. For this reason, the transverse stretching apparatus 400 has a configuration in which the

grippers

410R and 410L having the first stretched film 30 opened at the outlet 440 of the transverse stretching apparatus 400 can be sequentially returned to the inlet 430.

The first stretched film 30 is stretched using the transverse stretching apparatus 400 as follows.
The first stretched film 30 is fed from the roll 40, and the first stretched film 30 is continuously supplied to the transverse stretching apparatus 400.
The transverse stretching apparatus 400 sequentially grips the widthwise ends 31 and 32 of the first stretched film 30 at its inlet 430 by

grippers

410R and 410L. The first stretched film 30 gripped by the

end portions

31 and 32 is conveyed as the

grippers

410R and 410L travel.

As described above, the

guide rails

420R and 420L on which the

grippers

410R and 410L travel are symmetrical with respect to the line LN40 passing through the midpoint in the width direction of the first stretched film 30 to be conveyed in the stretching zone 450, Since it is arranged so that the interval becomes larger toward the downstream, the first stretched film 30 gripped by the

grippers

410R and 410L is stretched in the width direction of the first stretched film 30 in the stretching zone 450, and is elongated. The second stretched film 50 is obtained. The obtained second stretched film 50 is released from the grippers 410 R and 410 L at the outlet 440 of the transverse stretching device 400, wound up, and collected as a roll 60.

The draw ratio A2 in the second step is preferably set so that the product (A1 × A2) with the draw ratio A1 in the first step becomes a predetermined value.
(A1 × A2) is preferably larger than 1.2 times, more preferably 1.25 times or more, preferably 2.0 times or less, more preferably 1.85 times or less, and further preferably 1.65. Is less than double.
By setting (A1 × A2) within the range of the lower limit, sufficient in-plane retardation can be expressed in the second stretched film 50. Moreover, the peeling strength of a stretched film can be enlarged by setting it as the said upper limit or less.

The stretching temperature T2 in the second step may be the same as the stretching temperature T1 in the first step. Specifically, it is preferably (Tg) ° C. or more, more preferably (Tg + 2) ° C. or more, particularly preferably (Tg + 5) ° C. or more, preferably (Tg + 40) ° C. or less, more preferably (Tg + 35) ° C. or less. Particularly preferably, it is (Tg + 30) ° C. or lower. Here, Tg refers to the glass transition temperature of the resin that forms the pre-stretched film. In the present embodiment, the stretching temperature T2 in the second step refers to the temperature in the stretching zone 450 of the transverse stretching apparatus 400.

The stretching temperature T2 may be a temperature different from the stretching temperature T1. When the stretching temperature T2 is different from the stretching temperature T1, it is preferable that the stretching temperature T2 is lower than the stretching temperature T1. The stretching temperature T2 is preferably (T1-15) ° C. or higher, more preferably (T1-10) ° C. or higher, preferably (T1-2) ° C. or lower, more preferably (T1-5) ° C. or lower. .

The second stretched film 50 has an average in-plane retardation Re2 of preferably 200 nm or more, more preferably 210 nm or more, still more preferably 220 nm or more, preferably 300 nm or less, more preferably 290 nm or less, and even more preferably 280 nm or less. It is.
The average in-plane retardation Re2 of the second stretched film 50 can be adjusted by adjusting the product (A1 × A2) of the stretch ratio A1 in the first step and the stretch ratio A2 in the second step. For example, the average in-plane retardation Re2 can be increased by increasing (A1 × A2).

Since the second stretched film 50 is stretched in the oblique direction in the first step, it has a slow axis in the oblique direction. Specifically, the second stretched film 50 has a slow axis that forms an angle of 10 ° to 30 ° with respect to the width direction.

The second stretched film 50 has an average NZ coefficient of preferably 1.2 or more, more preferably 1.21 or more, still more preferably 1.22 or more, preferably 1.5 or less, more preferably 1.48. Hereinafter, it is more preferably 1.46 or less.
The average NZ coefficient can be adjusted by adjusting the draw ratio A1 in the first step and the draw ratio A2 in the second step. For example, the average NZ coefficient can be reduced by increasing the draw ratio A2.

The average NZ coefficient of the film can be obtained by measuring the NZ coefficient at a plurality of points at intervals of 50 mm arranged in the width direction of the film and calculating the average value of the NZ coefficients at these points.

In a method for producing a stretched film including stretching in an oblique direction, a desired retardation may be difficult to obtain. In this case, when the stretching ratio is increased in order to obtain a desired retardation, the stretched film tends to cause cohesive failure, and the peel strength between the stretched film and another film may be insufficient. On the other hand, as in this embodiment, by stretching the pre-stretched film in two steps in a predetermined direction by the first step and the second step, a long stretch having a large average in-plane retardation and a high peel strength is achieved. A film can be obtained. The reason why a stretched film having a large average in-plane retardation and a high peel strength can be obtained by the production method of the present embodiment is that the degree of orientation in the plane of the polymer contained in the film is the production method of the present embodiment. It is considered that the bonding force of the polymer in the thickness direction is balanced, but the present invention is not limited thereto.

(Modification)
The present invention is not limited to the above embodiment, and may be further modified.
For example, the manufacturing method described above may further include an optional step in addition to the first step and the second step. Examples of such steps include a step of providing a protective layer on the surface of the stretched film and a step of subjecting the stretched film to surface treatment such as corona treatment.

For example, a film obtained by stretching an unstretched film in an arbitrary direction may be used as the pre-stretch film. As described above, as a method of stretching the pre-stretched film before being subjected to the first step, for example, a roll-type, float-type longitudinal stretch method, a lateral stretch method using a tenter device, or the like can be used.

Moreover, in embodiment mentioned above, although the 1st stretched film 30 was wound up and made into the roll 40, the 1st stretched film 30 was drawn | fed out from the roll 40, and it supplied to the 2nd process, The 1st stretch obtained at the 1st process The film 30 may be supplied to the second step without being wound up.

[2. Manufacturing method of polarizing film]
A long polarizing film can be manufactured using the long stretched film obtained by the manufacturing method of the present invention.
The manufacturing method of the polarizing film which concerns on one Embodiment of this invention is the 3rd process of laminating | stacking a elongate polarizer on the elongate stretched film obtained by the manufacturing method of the elongate stretched film which concerns on the said one Embodiment. including.

For the method for producing a long stretched film according to an embodiment of the present invention, the above item [1. This is the same as the method described in [Method for producing long stretched film].

According to the method for producing a long polarizing film of this embodiment, since the peel strength of the stretched film included in the polarizing film is high, a polarizing film having excellent mechanical strength can be obtained.

(Polarizer)
As a polarizer used in the present embodiment, a film of an appropriate vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol, a dyeing process using an dichroic substance such as iodine and a dichroic dye, and a stretching process. And those subjected to appropriate treatment such as crosslinking treatment 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. Arbitrary members (for example, protective films) may be laminated on the polarizer.

(Third step)
In the third step, a step of laminating a long polarizer on a long stretched film is performed.
Lamination can be performed, for example, by laminating a long polarizer and a long stretched film in a roll-to-roll manner with their longitudinal directions parallel. In bonding, an adhesive may be used as necessary. Thus, a long polarizing film can be efficiently manufactured by manufacturing using a long film.

Further, in the third step, a film in which an arbitrary member such as a protective film is laminated on a long polarizer may be laminated on the long stretched film.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications within the scope of the claims of the present invention and the equivalents thereof.

The following operations were performed in a normal temperature and atmospheric pressure atmosphere unless otherwise specified.

[Evaluation methods]
(Average in-plane retardation Re of film)
With respect to the film to be evaluated, in-plane retardation was measured at a plurality of points at intervals of 50 mm aligned in the width direction of the film using a phase difference measuring device (product name “Axoscan” manufactured by Axometric) at a wavelength of 590 nm. The average value of in-plane retardation at these points was calculated, and this average value was defined as the average in-plane retardation Re of the film.

(Average NZ coefficient of film)
With respect to the film to be evaluated, the NZ coefficient was measured at a plurality of points at intervals of 50 mm aligned in the width direction of the film using a phase difference measuring device (product name “Axoscan” manufactured by Axometric) at a wavelength of 590 nm. The average value of the NZ coefficients at these points was calculated, and this average value was used as the average NZ coefficient of the film.

The NZ coefficient is a value obtained by measuring the in-plane retardation Re and the thickness direction retardation Rth according to the following formula.
NZ coefficient = (Rth / Re) +0.5

(Average orientation angle of film)
Using a phase difference measuring device (product name “Axoscan” manufactured by Axometric), the orientation angle between the slow axis and the film width direction was measured at a plurality of points at intervals of 50 mm aligned in the film width direction. The average value of the orientation angles at these points was calculated, and this average value was taken as the average orientation angle of the film.

(Peel strength of film)
An unstretched film (glass transition temperature 160 ° C., thickness 100 μm, manufactured by Nippon Zeon Co., Ltd.) made of a resin containing a polymer (cycloolefin polymer) containing an alicyclic structure was prepared. One side of the stretched film to be evaluated and the unstretched film was subjected to corona treatment. An adhesive was attached to the corona-treated surface of the stretched film and the corona-treated surface of the unstretched film, and the surfaces to which the adhesive was adhered were bonded together. At this time, a UV adhesive was used as the adhesive. This obtained the sample film provided with a stretched film and an unstretched film.
Thereafter, the sample film was cut into a width of 15 mm, and the stretched film side was bonded to the surface of the slide glass with an adhesive. At this time, a double-sided adhesive tape (manufactured by Nitto Denko Corporation, product number “CS9621”) was used as the adhesive.
A 90-degree peel test was performed by sandwiching the unstretched film at the tip of a force gauge and pulling in the normal direction of the surface of the slide glass. At this time, since the force measured when the unstretched film peels is the force required to peel the stretched film and the unstretched film, the magnitude of this force is the peel strength of the stretched film to be evaluated. It was.

[Example 1]
(Manufacture of long unstretched film)
Pellet of resin A (norbornene polymer resin having a glass transition temperature of 126 ° C., manufactured by Nippon Zeon Co., Ltd.) containing a polymer containing a cycloaliphatic structure (cycloolefin polymer hydride) is dried at 100 ° C. for 5 hours. did. The pellets were supplied to an extruder, melted in the extruder, and extruded from a T die onto a casting drum through a polymer pipe and a polymer filter. The extruded resin was cooled and cured on a casting drum, and a long unstretched film 20 having a thickness of 70 μm was obtained. This unstretched film was wound up to obtain a feeding roll 10.

(First step)
As shown in FIG. 1, a long unstretched film 20 is fed from a feeding roll 10 and supplied to a tenter apparatus 100 having the structure described in the above-described embodiment, and stretched in an oblique direction under the conditions shown in Table 1. The 1st stretched film 30 was obtained. The obtained first stretched film 30 was wound up and collected as a roll 40. At this time, the feeding angle φ formed by the feeding direction D20 of the pre-stretching film 20 from the feeding roll 10 and the winding direction D30 of the first stretched film 30 was set to 45 °. Using a portion of the obtained first stretched film 30, the average in-plane retardation Re1 and the average orientation angle θ1 were measured.

(Second step)
The first stretched film obtained in the first step was supplied to a transverse stretching apparatus under the conditions shown in Table 1 and uniaxially stretched to obtain a stretched film as a second stretched film. Using this stretched film, the average in-plane retardation Re2, the average orientation angle θ2, the average NZ coefficient, and the peel strength were evaluated.

[Examples 2 to 4]
In the same manner as in Example 1 except that the stretching direction in the first step and the stretching ratio and stretching temperature in the second step were changed as shown in Table 1, production of the long first stretched film and stretched film and Evaluation was performed. The results are shown in Table 1.

[Example 5]
Instead of resin A pellets, resin B (norbornene polymer resin having a glass transition temperature of 135 ° C., manufactured by Nippon Zeon Co., Ltd.) containing a polymer (cycloolefin polymer hydride) containing an alicyclic structure is used. A long roll was produced in the same manner as in Example 1 except that the roll of the pre-stretching film was produced using pellets, and the stretching temperature in the first step and the stretching temperature in the second step were changed as shown in Table 1. The first stretched film and stretched film were prepared and evaluated. The results are shown in Table 1.

[Comparative Examples 1 and 2]
Production and evaluation of a long stretched film in the same manner as in Example 1 except that the stretching direction, stretching ratio, and stretching temperature in the first step were changed as shown in Table 2 and the second step was not performed. Was done. The results are shown in Table 2. Table 2 shows the value of A1 as the value of A1 × A2. Peel strength shows the value measured about the elongate stretched film (1st stretched film) obtained at the 1st process.

[Comparative Examples 3 and 4]
In the same manner as in Example 1 except that the stretching direction and stretching ratio in the first step and the stretching ratio in the second step were changed as shown in Table 2, production of a long first stretched film and stretched film and Evaluation was performed. The results are shown in Table 2.

[Description of table]
In the following Tables 1 and 2, the stretching angle and the average orientation angles θ1 and θ2 indicate values with respect to the width direction of the film.

From the above results, it can be seen that the stretched films (second stretched films) obtained in Examples 1 to 5 exhibit sufficient in-plane retardation and have high peel strength.
On the other hand, the stretched films (first stretched films) obtained in Comparative Examples 1 and 2 in which the second step was not performed were inferior in in-plane retardation or peel strength and excellent in in-plane retardation. It can be seen that the peel strength cannot be compatible.
Further, the stretched film obtained by Comparative Examples 3 to 4 (second stretched film) in which the stretching angle in the first step is larger than 50 ° with respect to the width direction is also inferior in in-plane retardation or peel strength, It can be seen that sufficient in-plane retardation and excellent peel strength cannot be achieved at the same time.

DESCRIPTION OF SYMBOLS 10 Feeding roll 20 Films before extending | stretching 21 and 22 End part of width direction of film before extending | stretching 30 1st extending | stretching

film

31 and 32 End part of width direction of 1st extending | stretching film 40 Roll 50 2nd extending | stretching film 60 Roll 100 Tenter apparatus 110R And

110L Gripper

120R and 120L Guide rail 130 Tenter device inlet portion 140 Tenter device outlet portion 150 Tenter device stretching zone 400

Lateral stretching device

410R and

410L Gripper

420R and 420L Guide rail 430 Lateral stretching device inlet portion 440 Lateral Outlet part of stretching apparatus 450 Stretching zone of transverse stretching apparatus

Claims

A method for producing a long stretched film,
A first step of obtaining a long first stretched film by stretching the long pre-stretched film in a direction of 15 ° or more and 50 ° or less with respect to the width direction;
A second step of stretching the long first stretched film in the width direction to obtain a long second stretched film in this order,
The long second stretched film has a slow axis that forms an angle of 10 ° to 30 ° with respect to the width direction.
A method for producing a long stretched film.
The average NZ coefficient of the long second stretched film is 1.2 or more and 1.5 or less,
When the draw ratio in the first step is A1, and the draw ratio in the second step is A2, A1 is 1.2 times or more and 1.6 times or less, and (A1 × A2) is larger than 1.2 times. The manufacturing method of the elongate stretched film of Claim 1 which is 2.0 times or less.
The method for producing a long stretched film according to claim 1 or 2, wherein an average in-plane retardation Re2 of the long second stretched film is 200 nm or more and 300 nm or less.
The method for producing a long stretched film according to any one of claims 1 to 3, wherein the stretched film contains a polymer containing an alicyclic structure.
A method for producing a long polarizing film,
Including a third step of laminating a long polarizer on a long stretched film obtained by the method for producing a long stretched film according to any one of claims 1 to 4.
A method for producing a long polarizing film.