CN115847790B

CN115847790B - Method for producing stretched film and method for producing optical laminate

Info

Publication number: CN115847790B
Application number: CN202211158891.4A
Authority: CN
Inventors: 中原步梦; 北岸一志; 清水享
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-09-24
Filing date: 2022-09-22
Publication date: 2023-11-14
Anticipated expiration: 2042-09-22
Also published as: KR102531079B1; JP2023047022A; JP7076036B1; KR20230043753A; CN115847790A

Abstract

A stretched film is produced with high production efficiency while suppressing breakage during stretching. The method for producing a stretched film according to an embodiment of the present invention comprises: holding the end of the elongated stretched film in the width direction by a clamp; stretching the stretching target film in an oblique direction by moving the jig; and releasing the film to be stretched from the jig, wherein an attached film is disposed at an end portion in the width direction of the film to be stretched at the time of the holding, the film to be stretched and the attached film are held by the jig, and the attached film is disposed by attaching an adhesive tape to the film to be stretched.

Description

Method for producing stretched film and method for producing optical laminate

Technical Field

The present invention relates to a method for producing a stretched film and a method for producing an optical laminate.

Background

In image display devices such as liquid crystal display devices (LCDs) and organic electroluminescence display devices (OLEDs), polarizing plates with retardation layers are typically used for the purpose of improving display characteristics, antireflection, and the like. The polarizing plate with a retardation layer (for example, a circular polarizing plate) may be configured by stacking a polarizer and a retardation film (for example, a λ/4 plate) such that the absorption axis of the polarizer forms a predetermined angle (for example, 45 °) with the slow axis of the retardation film. Conventionally, a retardation film is typically produced by uniaxial stretching or biaxial stretching in the machine direction and/or the transverse direction, and therefore the slow axis thereof often exhibits in the transverse direction (width direction) or the longitudinal direction (longitudinal direction) of a film raw material. As a result, in order to produce a polarizing plate with a retardation layer, the retardation film may be cut at a predetermined angle with respect to the transverse direction or the longitudinal direction, and 1 sheet may be bonded to 1 sheet.

In order to solve such productivity problems, a technique has been proposed in which a slow axis of a retardation film is expressed in an oblique direction by stretching in the oblique direction with respect to a longitudinal direction (for example, patent document 1). However, stretching in the oblique direction tends to break the film to be stretched easily during stretching.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 4845619

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and has a main object to manufacture a stretched film with high manufacturing efficiency while suppressing breakage at the time of stretching.

Means for solving the problems

The method for producing a stretched film according to an embodiment of the present invention comprises: holding the end of the elongated stretched film in the width direction by a clamp; stretching the stretching target film in an oblique direction by moving the jig; and releasing the film to be stretched from the jig, wherein an attached film is disposed at an end portion in the width direction of the film to be stretched at the time of the holding, the film to be stretched and the attached film are held by the jig, and the attached film is disposed by attaching an adhesive tape to the film to be stretched.

In 1 embodiment, the difference (Tg 1-Tg 2) between the glass transition temperature Tg1 of the film to be stretched and the glass transition temperature Tg2 of the film to be attached exceeds 0 ℃ and is 25 ℃ or less.

In 1 embodiment, the difference (E1-E2) between the elastic modulus E1 of the film to be stretched and the elastic modulus E2 of the film to be attached is 100MPa to 800MPa.

In 1 embodiment, the adhesive tape has an adhesion force to the film to be stretched of 0.1N/15mm or more.

In 1 embodiment, the width of the additional film is 20mm to 100mm.

In one embodiment, the additional film includes at least one of a polyethylene naphthalate resin and a cycloolefin resin.

In one embodiment, the film to be stretched includes at least one resin selected from the group consisting of a polycarbonate-based resin, a cycloolefin-based resin, a polyester-based resin, and a polyester carbonate-based resin.

According to another aspect of the present invention, a method of manufacturing an optical laminate is provided. The method for manufacturing the optical laminate comprises the following steps: obtaining an elongated stretched film by the above-mentioned production method; and continuously laminating the elongated stretched film and the elongated optical film while conveying them so that the elongated directions of the films coincide with each other.

In 1 embodiment, the optical film is a polarizer.

Effects of the invention

According to the embodiment of the present invention, a stretched film can be produced with high production efficiency while suppressing breakage at the time of stretching.

Drawings

Fig. 1 is a schematic plan view showing the overall configuration of an example of a stretching apparatus used for producing a stretched film according to embodiment 1 of the present invention.

Fig. 2 is a cross-sectional view schematically showing an example of a gripping state of the film end portion.

Fig. 3 is a diagram illustrating an example of a bonding method of the adhesive tape.

Fig. 4 is a cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to 1 embodiment of the present invention.

Description of symbols

1. Stretching target film

2. Adhesive tape

2a attached film

2b adhesive layer

51. Stretch film (phase difference film)

61. Adhesive layer

71. Polarizing plate

72. Polarizer

73. Protective layer

80. Polarizing plate with phase difference layer

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. In addition, although the width, thickness, shape, and the like of each portion are schematically shown in the drawings in order to make the description clearer, the explanation of the present invention is not limited to the examples.

(definition of terms and symbols)

The definitions of terms and symbols in the present specification are as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., a slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis (i.e., a fast axis direction), and "nz" is a refractive index in a thickness direction.

(2) In-plane phase difference (Re)

"Re (λ)" is the in-plane retardation measured by light having a wavelength of λnm at 23 ℃. For example, "Re (550)" is the in-plane retardation measured at 23℃by light having a wavelength of 550 nm. When the thickness of the layer (film) is set to d (nm), re (λ) passes through the formula: re (λ) = (nx-ny) ×d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured by light having a wavelength of λnm at 23 ℃. For example, "Rth (550)" is a phase difference in the thickness direction measured at 23℃by light having a wavelength of 550 nm. When the thickness of the layer (film) is set to d (nm), rth (λ) is represented by the formula: rth (λ) = (nx-nz) ×d.

(4) Nz coefficient

The Nz coefficient is obtained by nz=rth/Re.

(5) Angle of

In the present specification, when referring to an angle, the angle includes both clockwise and counterclockwise with respect to a reference direction. Thus, for example, "45" means ± 45 °.

A. Method for producing stretched film

The method for producing a stretched film according to embodiment 1 of the present invention comprises: holding the end of the elongated stretched film in the width direction by a clamp; stretching the stretching target film in an oblique direction by moving the jig in a traveling manner; and releasing the stretching target film from the jig.

Fig. 1 is a schematic plan view showing the overall configuration of an example of a stretching apparatus used for producing a stretched film according to embodiment 1 of the present invention. The stretching apparatus 100 has an endless ring 10L and an endless ring 10R including a plurality of jigs 20 for holding a film, symmetrically on both left and right sides in a plan view. The left endless ring as viewed from the inlet side of the film to be stretched is referred to as a left endless ring 10L, and the right endless ring is referred to as a right endless ring 10R. The jigs 20 of the left and right endless loops 10L, 10R are guided by the reference rails 30, respectively, and move in a loop-like cycle. The gripper 20 of the endless loop 10L on the left side is cyclically moved in the counterclockwise direction, and the gripper 20 of the endless loop 10R on the right side is cyclically moved in the clockwise direction. In the stretching apparatus 100, a holding section a, a preheating section B, a stretching section C, and a discharging section D are provided in this order from the inlet side toward the outlet side of the sheet. These respective regions are regions where the film to be stretched is substantially gripped, preheated, stretched (inclined stretched), and released, and are not mechanically and structurally independent regions. Further, it is noted that the ratio of the lengths of the respective regions in the stretching apparatus of fig. 1 is different from the ratio of the actual lengths.

Although not shown, a region for performing any appropriate treatment may be provided between the stretching region C and the releasing region D as needed. Examples of such a treatment include a longitudinal shrinkage treatment and a transverse shrinkage treatment. Although not shown, the stretching apparatus 100 is typically provided with a heating apparatus (for example, various ovens of a hot air type, a near infrared type, a far infrared type, or the like) for setting each region from the preheating region B to the discharge region D as a heating environment. In the embodiment 1, preheating, stretching and releasing are performed in an oven set to a predetermined temperature.

In the holding zone a and the preheating zone B, the left and right endless loops 10L, 10R are configured so that the separation distances corresponding to the initial width of the film to be stretched become substantially parallel to each other. In the stretching region C, the following constitution is set: the distance separating the left and right endless loops 10L, 10R gradually increases from the side of the preheating zone B toward the releasing zone D until it corresponds to the stretched width of the film. In the release zone D, the left and right endless loops 10L, 10R are formed so that the separation distances corresponding to the stretched width of the film become substantially parallel to each other. However, the configuration of the left and right endless loops 10L, 10R is not limited to the example of the drawing. For example, the left and right endless loops 10L, 10R may be configured such that the separation distances from the grip region a to the release region D, which correspond to the initial width of the film to be stretched, become substantially parallel to each other.

The left clamp (left clamp) 20 of the endless loop 10L and the right clamp (right clamp) 20 of the endless loop 10R are independently circulated. For example, the driving sprockets 11 and 12 of the left endless loop 10L are driven to rotate in the counterclockwise direction by the electric motors 13 and 14, and the driving sprockets 11 and 12 of the right endless loop 10R are driven to rotate in the clockwise direction by the electric motors 13 and 14. As a result, a running force is applied to a jig supporting member (not shown) of a driving roller (not shown) engaged with the driving sprockets 11 and 12. Thus, the left endless ring 10L is circularly moved in the counterclockwise direction, and the right endless ring 10R is circularly moved in the clockwise direction. By driving the left electric motor and the right electric motor independently, the left endless ring 10L and the right endless ring 10R can be circulated independently.

For example, the left clamp (left clamp) 20 of the endless loop 10L and the right clamp (right clamp) 20 of the endless loop 10R may be set to be variable pitch, respectively. That is, the left and right jigs 20, 20 can be moved independently to change the longitudinal jig pitch. The configuration of the variable pitch type can be realized by a drive system such as a zoom system, a linear motor system, a motor and chain system. For example, patent document 1, japanese patent application laid-open No. 2008-44339, and the like describe a simultaneous biaxial stretching apparatus of a tenter type using a link mechanism of a zoom type.

In the holding area a (the entrance of the stretching apparatus 100 where the film is taken in), both side edges of the film to be stretched are held at a constant clip pitch equal to each other or at different clip pitches from each other by the clips 20 of the left and right endless rings 10L, 10R. The film is fed to the preheating zone B by the movement of the jigs 20 of the left and right endless rings 10L, 10R (substantially the movement of each jig carrying member guided by the reference rail).

In the preheating zone B, the left and right endless loops 10L, 10R are configured so that the separation distances corresponding to the initial width of the film to be stretched become substantially parallel to each other as described above. Therefore, the film is heated without being substantially stretched in the transverse direction or in the longitudinal direction, but the distance between the left and right clamps (the distance in the width direction) may be increased in order to avoid, for example, the problem of deflection of the film due to preheating.

In the preheating, the film is heated to a temperature T1. The temperature T1 is preferably not less than the glass transition temperature (Tg) of the film, more preferably not less than tg+2℃, still more preferably not less than tg+5℃. On the other hand, the heating temperature T1 is preferably tg+40 ℃ or lower, more preferably tg+30 ℃ or lower. The temperature T1 is, for example, 70℃to 190℃and preferably 80℃to 180 ℃.

The temperature rise time to the temperature T1 and the holding time of the temperature T1 can be appropriately set according to, for example, the constituent materials of the film and the manufacturing conditions (the film conveyance speed and the like). The temperature rise time and the holding time can be controlled by adjusting the moving speed of the jig 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

In the stretching region C, the film is obliquely stretched by moving the left and right clamps 20 while changing the vertical clamp pitch of at least one side thereof. More specifically, the film is obliquely stretched by increasing or decreasing the clip pitch of the left and right clips at different positions, changing (increasing and/or decreasing) the clip pitch of the left and right clips at different changing speeds, and the like.

Oblique stretching may also include transverse stretching. In this case, for example, as shown in fig. 1, the oblique stretching may be performed while expanding the distance between the left and right jigs (the distance in the width direction). Alternatively, unlike the configuration shown in fig. 1, this may be performed while maintaining the distance between the left and right jigs.

In the case where oblique stretching includes transverse stretching, the stretching ratio in the Transverse Direction (TD) (width W of the film after oblique stretching _final Relative to the initial width W of the film _initial Ratio (W) _final /W _initial ) Preferably 1.05 to 6.00, more preferably 1.10 to 5.00.

In the 1-embodiment, the oblique stretching may be performed by increasing or decreasing the clip pitch of each clip to a predetermined pitch in a state where the clip pitch of one clip of the left and right clips starts to increase or decrease and the clip pitch of the other clip starts to increase or decrease are set to different positions in the longitudinal direction. For the oblique stretching in this embodiment, for example, refer to the descriptions of japanese patent No. 4845619 and japanese patent application laid-open No. 2014-238524.

In another embodiment, the oblique stretching may be performed by increasing or decreasing the clip pitch of one clip to a predetermined pitch and then returning to the original clip pitch in a state where the clip pitch of the other clip is fixed. For the oblique stretching in this embodiment, for example, refer to the descriptions of Japanese patent application laid-open No. 2013-54338 and Japanese patent application laid-open No. 2014-194482.

In still another embodiment, the oblique stretching may be performed by (i) increasing the clip pitch of one clip and decreasing the clip pitch of the other clip of the left and right clips, and (ii) changing the clip pitches of the respective clips so that the decreased clip pitch and the increased clip pitch become a predetermined equal pitch. For the oblique stretching in this embodiment, for example, refer to the description of japanese patent application laid-open No. 2014-194484. The oblique stretching of this embodiment may comprise: the film is obliquely stretched by increasing the pitch of one clamp and decreasing the pitch of the other clamp while expanding the distance between the left and right clamps (1 st oblique stretching step), and the film is obliquely stretched by maintaining or decreasing the pitch of the one clamp and increasing the pitch of the other clamp so that the pitch of the left and right clamps becomes equal while expanding the distance between the left and right clamps (2 nd oblique stretching step).

In the above-described oblique stretching step 1, one side edge portion of the film is stretched in the longitudinal direction and the other side edge portion is contracted in the longitudinal direction, and the oblique stretching is performed, whereby the film can exhibit a slow axis with high uniaxiality and in-plane orientation in a desired direction (for example, a direction of 45 ° with respect to the longitudinal direction). In the 2 nd oblique stretching step, the difference between the left and right clamp pitches is reduced, and the oblique stretching is performed, whereby the excessive stress can be relaxed and the stretching can be performed sufficiently in the oblique direction. Further, since the film can be released from the grippers in a state where the moving speeds of the left and right grippers become equal, unevenness in the conveying speed and the like of the film is less likely to occur at the time of releasing the left and right grippers, and the subsequent winding of the film can be suitably performed.

The stretching temperature T2 may be (Tg-20) to (Tg+30) DEG C, or (Tg-10) to (Tg+20) DEG C, preferably at least Tg, more preferably (Tg+1) to (Tg+10) DEG C, and still more preferably (Tg+1) to (Tg+5) DEG C, with respect to the glass transition temperature (Tg) of the film to be stretched. The stretching temperature is, for example, 70℃to 180℃and preferably 80℃to 170 ℃.

The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably + -2 ℃ or higher, more preferably + -5 ℃ or higher. In 1 embodiment, T1> T2, therefore, the film heated to temperature T1 in the preheating zone can be cooled to temperature T2.

At any position of the release zone D, the film is released from the clamp. In the release zone D, generally, neither transverse stretching nor longitudinal stretching is performed, and the film is heat-treated to fix (heat-fix) the stretched state and/or cooled to Tg or less as needed, and then released from the jig. In the case of thermosetting, the stress may be relaxed by reducing the pitch of the clamps in the longitudinal direction.

The temperature T3 at which the heat treatment can be performed in the release zone D may be different depending on the film to be stretched, and may be T2 or more than T3, or may be T2< T3. In general, when the film is an amorphous material, T2. Gtoreq.T3, and when the film is a crystalline material, T2< T3 is set, for example, a crystallization treatment is performed. In the case where T2. Gtoreq.T3, the difference between the temperatures T2 and T3 (T2-T3) is preferably 0℃to 50 ℃. The time of the heat treatment is typically 10 seconds to 10 minutes.

[ stretched film ]

As the resin constituting the film to be stretched (film to be stretched), any suitable resin may be used as long as the desired optical characteristics are satisfied. Examples of the resin constituting the film to be stretched include polycarbonate-based resins, polyvinyl acetal-based resins, cycloolefin-based resins, acrylic resins, cellulose ester-based resins, cellulose-based resins, polyester carbonate-based resins, olefin-based resins, and polyurethane-based resins. Preferred are polycarbonate resins, cycloolefin resins, polyester resins and polyester carbonate resins. This is because, if these resins are used, a retardation film exhibiting a wavelength dependence of so-called reverse dispersion can be obtained. These resins may be used alone or in combination of 2 or more.

As the polycarbonate resin, any suitable polycarbonate resin may be used. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. As a specific example of the dihydroxy compound, examples thereof include 9, 9-bis (4-hydroxyphenyl) fluorene, 9-bis (4-hydroxy-3-methylphenyl) fluorene, 9-bis (4-hydroxy-3-ethylphenyl) fluorene, 9-bis (4-hydroxy-3-n-propylphenyl) fluorene 9, 9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9-bis (4-hydroxy-3-n-butylphenyl) fluorene, 9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9-bis (4-hydroxy-3-tert-butylphenyl) fluorene 9, 9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9-bis (4-hydroxy-3-n-butylphenyl) fluorene 9, 9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9, 9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3, 5-dimethylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9-bis (4- (3-hydroxy-2, 2-dimethylpropoxy) phenyl) fluorene, and the like. The polycarbonate resin may contain, in addition to the structural units derived from the above-mentioned dihydroxy compounds, structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidide, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), bisphenols and the like.

Details of the polycarbonate resin described above are described in, for example, japanese patent application laid-open No. 2012-67300 and japanese patent No. 3325560. The disclosure of this patent document is incorporated by reference into the present specification.

The glass transition temperature of the polycarbonate resin is preferably 110 to 250 ℃, more preferably 120 to 230 ℃. If the glass transition temperature is too low, the heat resistance tends to be poor, and there is a possibility that dimensional change may occur after film formation. If the glass transition temperature is too high, the film may have poor molding stability during film molding, and the transparency of the film may be impaired. The glass transition temperature was determined in accordance with JIS K7121 (1987).

Any suitable polyvinyl acetal resin can be used as the polyvinyl acetal resin. Typically, the polyvinyl acetal resin is obtained by subjecting at least 2 aldehyde compounds and/or ketone compounds to condensation reaction with the polyvinyl alcohol resin. Specific examples of the polyvinyl acetal resin and a detailed production method thereof are described in, for example, JP-A2007-161994. This description is incorporated by reference into this specification.

The thickness of the stretched film can be appropriately set according to, for example, the thickness of the obtained stretched film, the in-plane retardation, and the like. The thickness of the film to be stretched is, for example, 40 μm to 150 μm.

Attached film

Fig. 2 is a cross-sectional view schematically showing an example of a gripping state of the film end portion. The stretching target film 1 is stretched in a state where the attached film 2a is disposed at the end in the width direction thereof. Specifically, at the time of the above-described gripping, the attached film 2a is disposed at the end portion in the width direction of the film to be stretched 1, and the film to be stretched 1 and the attached film 2a are gripped by the upper and lower clamp members 20a, 20b of the clamp 20.

The attached film 2a is disposed on the film 1 to be stretched by attaching the adhesive tape 2 to the film 1 to be stretched. Specifically, the adhesive tape 2 includes an attachment film 2a and an adhesive layer 2b, and the attachment film 2a is laminated on the stretch film 1 via the adhesive layer 2 b. By using the adhesive tape 2, continuous production is enabled. For example, as shown in fig. 3, by attaching the adhesive tape 2 to the first film material 1 to be stretched and then continuously attaching the adhesive tape 2 to the second film material (not shown), different film materials to be stretched can be continuously supplied to stretching, which can contribute to improvement of the production efficiency.

The adhesion of the adhesive tape 2 to the film to be stretched 1 is preferably 0.1N/15mm or more, more preferably 0.15N/15mm or more. With such adhesion, the adhesive tape 2 does not peel from the film 1 to be stretched during stretching, and is excellent in handling property. The portion (widthwise end portion) to which the adhesive tape 2 is attached may be cut (slit) and removed after stretching.

The adhesive layer 2b of the adhesive tape 2 is formed of any suitable adhesive that can satisfy the above-described adhesive force. The thickness of the adhesive layer 2b is, for example, 15 μm to 30 μm.

As shown in fig. 2, the end surfaces of the film 1 to be stretched and the attached film 2a (the adhesive tape 2) do not need to be identical, as long as the clamp 20 can hold the overlapping portion of the film 1 to be stretched and the attached film 2 a. The width of the attached film 2a (adhesive tape 2) is, for example, 20mm to 100mm. In the drawing, the attached film 2a is disposed above the film 1 to be stretched, but may be disposed below. Further, the heat generating elements may be disposed on the upper side and the lower side. In this case, different attachment films may be disposed on the upper side and the lower side, respectively, or one end of one attachment film may be disposed on the upper side and the other end may be disposed on the lower side.

As described above, in the stretching region C, the film is obliquely stretched by moving the left and right jigs 20 while changing the longitudinal jig pitch of at least one side thereof. In such a mode, since a large stress is applied to the widthwise end portion of the film to be stretched, breakage tends to occur during stretching or tailing tends to occur at the widthwise end portion of the obtained stretched film, but such occurrence of defects can be suppressed by arranging the additional film for stretching. In the example shown in fig. 3, the adhesive tape 2 is attached to both ends of the film 1 to be stretched in the width direction, but the adhesive tape may be attached at least to one side where the clip pitch in the longitudinal direction is changed.

The glass transition temperature Tg2 of the attached film 2a is preferably lower than the glass transition temperature Tg1 of the film to be stretched 1. The difference (Tg 1 to Tg 2) between the glass transition temperature Tg1 of the film 1 to be stretched and the glass transition temperature Tg2 of the film 2a to be attached is preferably more than 0 ℃ and 25 ℃ or less, more preferably 5 to 20 ℃. By using such an attached film, it is possible to effectively suppress the occurrence of the breakage and tailing and to perform stretching satisfactorily.

The elastic modulus E2 of the additional film 2a is preferably smaller than the elastic modulus E1 of the film to be stretched 1. The elastic modulus E1 of the film to be stretched is, for example, 1500MPa to 3500MPa. The difference (E1-E2) between the elastic modulus E1 of the film 1 to be stretched and the elastic modulus E2 of the additional film 2a is preferably 100MPa to 800MPa, more preferably 200MPa to 500MPa. By using such an attached film, it is possible to effectively suppress the occurrence of the breakage and tailing and to perform stretching satisfactorily.

The thickness of the additional film 2a is, for example, 50 μm to 200 μm. Examples of the resin constituting the additional film 2a include polyethylene naphthalate resin and cycloolefin resin.

B. Optical laminate

The stretched film obtained in the above embodiment is typically used as an optical laminate by being laminated on an optical film. For example, the stretched film may be laminated on a polarizing plate to function as a retardation layer (retardation film).

Fig. 4 is a cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer as an example of a method of using a stretched film according to 1 embodiment of the present invention. The polarizing plate 80 with a retardation layer includes a polarizing plate 71 and a stretched film (retardation film) 51 bonded to one side of the polarizing plate 71 via an adhesive layer 61. The polarizer 71 has a polarizer 72 and a protective layer 73 disposed on one side of the polarizer 72, and the retardation film 51 is bonded to the polarizer 72 via the adhesive layer 61. Although not shown, a second protective layer may be disposed on the other side of the polarizer 72 (between the polarizer 72 and the retardation film 51).

The polarizing plate 80 with a retardation layer can be obtained by laminating the polarizing plate 71 and the retardation film 51 via an adhesive or an adhesive, for example. In 1 embodiment, the long polarizing plate 71 and the long retardation film 51 are continuously laminated while being conveyed so that the longitudinal directions of the films coincide with each other. Specifically, the layers are stacked by reel-to-reel. The term "long" refers to an elongated shape having a length sufficiently long with respect to the width, and for example, refers to an elongated shape having a length of 10 times or more, preferably 20 times or more, with respect to the width.

B-1 retardation film

The retardation film may have an in-plane retardation. The in-plane retardation Re (550) of the retardation film is, for example, 100nm to 310nm. In 1 embodiment, the retardation film can function as a λ/4 plate. Specifically, the in-plane retardation Re (550) of the retardation film is preferably 100nm to 190nm, more preferably 110nm to 180nm, still more preferably 130nm to 160nm, particularly preferably 135nm to 155nm. In another embodiment, the retardation film may function as a λ/2 plate. Specifically, the in-plane retardation Re (550) of the retardation film is preferably 230nm to 310nm, more preferably 250nm to 290nm.

The retardation film typically has refractive index characteristics of nx > ny.gtoreq.nz. Where "ny=nz" includes not only the case where ny is exactly equal to nz but also the case where ny is substantially equal. Therefore, ny < nz may be the case. The Nz coefficient of the retardation film is preferably 0.9 to 3.0, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. According to such Nz coefficient, for example, when a phase difference film (polarizing plate with a phase difference layer) is used for an image display device, an excellent reflection hue can be achieved.

The retardation film may exhibit an inverse dispersion wavelength characteristic in which the phase difference value becomes larger according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the phase difference value becomes smaller according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the phase difference value does not substantially change according to the wavelength of the measurement light. In 1 embodiment, the phase difference film exhibits an inverse dispersion wavelength characteristic. In this case, re (450)/Re (550) of the retardation film is preferably 0.8 or more and less than 1, more preferably 0.8 to 0.95. According to such wavelength characteristics, for example, when a phase difference film (polarizing plate with a phase difference layer) is used for an image display device, excellent reflection preventing characteristics can be achieved.

The thickness of the retardation film can be appropriately set according to the purpose. The thickness of the retardation film is preferably 15 μm to 60 μm, more preferably 25 μm to 45 μm.

The retardation film is constituted by a stretched film obtained by continuously stretching a long stretched film in a direction (oblique direction) of an angle θ with respect to the long direction as described above. In this case, the retardation film has a slow axis (orientation angle of angle θ) in the oblique direction (direction of angle θ) with respect to the longitudinal direction. The oblique direction is preferably a direction of 30 ° to 60 °, more preferably 40 ° to 50 °, still more preferably 42 ° to 48 °, particularly preferably about 45 °, with respect to the longitudinal direction of the retardation film. Since the polarizer generally has an absorption axis in the longitudinal direction, a polarizing plate with a retardation layer can be manufactured from a long retardation film by roll-to-roll, and the manufacturing process can be simplified.

B-2 polarizer

The polarizer is typically an absorption polarizer. The angle between the slow axis of the retardation film and the absorption axis of the polarizer can be appropriately set according to the application and purpose. In the embodiment 1, the angle between the slow axis of the retardation film and the absorption axis of the polarizer is preferably 30 ° to 60 °, more preferably 40 ° to 50 °, further preferably 42 ° to 48 °, and particularly preferably about 45 °.

The polarizer preferably exhibits absorption dichroism at any one of wavelengths 380nm to 780 nm. The polarizer has a single transmittance of, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

The polarizer is typically a resin film containing a dichroic substance (e.g., iodine). Examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene-vinyl acetate copolymer partially saponified films.

The polarizer has a thickness of, for example, 1 μm to 80 μm. In 1 embodiment, the thickness of the polarizer is preferably 1 μm to 25. Mu.m, more preferably 3 μm to 10. Mu.m, particularly preferably 3 μm to 8. Mu.m.

The polarizer may be fabricated by any suitable method. Specifically, the polarizer may be made of a single-layer resin film, or may be made of a laminate of two or more layers.

A typical method of producing a polarizer from a single-layer resin film includes dyeing and stretching the resin film with a dichroic substance such as iodine or a dichroic dye. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film is used. The method may further comprise insolubilization treatment, swelling treatment, crosslinking treatment, and the like. Such a manufacturing method is well known and commonly used in the art, and thus a detailed description thereof will be omitted.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, and a polarizer obtained by coating a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate. Details of such a method for producing a polarizer are described in, for example, japanese patent application laid-open No. 2012-73580 and japanese patent No. 6470455. The entire disclosures of these publications are incorporated by reference into this specification.

B-3 protective layer

The protective layer may be formed from any suitable film that may be used as the protective layer for the polarizer. Specific examples of the material that is the main component of the film include cellulose resins such as triacetyl cellulose (TAC), transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, cycloolefin resins, polyolefin resins, (meth) acrylic resins, and acetate resins.

The polarizing plate with a retardation layer is typically disposed on the visible side of the image display device. Therefore, the protective layer may be subjected to surface treatments such as Hard Coat (HC) treatment, antireflection treatment, anti-blocking treatment, and antiglare treatment, as necessary.

The thickness of the protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and still more preferably 10 μm to 30 μm. In the case of performing the surface treatment, the thickness of the protective layer includes the thickness of the surface treatment layer.

The second protective layer is preferably optically isotropic in embodiment 1. In the present specification, "optically isotropic" means that the in-plane retardation Re (550) is 0nm to 10nm, and the retardation Rth (550) in the thickness direction is-10 nm to +10nm.

B-4 adhesive layer

Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. In 1 embodiment, an adhesive layer is used as the adhesive layer. The adhesive layer is typically composed of an active energy ray-curable adhesive. Any suitable adhesive may be used as long as it is curable by irradiation with active energy rays. Examples of the active energy ray-curable adhesive include ultraviolet ray-curable adhesives and electron ray-curable adhesives. Specific examples of the curing type of the active energy ray-curable adhesive include radical curing type, cation curing type, anion curing type, and combinations thereof (for example, a mixture of radical curing type and cation curing type). Examples of the active energy ray-curable adhesive include adhesives containing a compound having a radical polymerizable group such as a (meth) acrylate group or a (meth) acrylamide group (e.g., a monomer and/or an oligomer) as a curing component. Specific examples of the active energy ray-curable adhesive and the curing method thereof are described in, for example, japanese patent application laid-open No. 2012-144690. The disclosure of this publication is incorporated by reference into the present specification.

The thickness of the cured active energy ray-curable adhesive (the thickness of the adhesive layer) is, for example, 0.2 μm to 3.0 μm, preferably 0.4 μm to 2.0 μm, and more preferably 0.6 μm to 1.5 μm.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measurement method and evaluation method of each characteristic are as follows.

(1) Thickness of (L)

The measurement was performed using a dial gauge (product name "DG-205type pds-2" manufactured by PEACOCK Co.).

(2) Phase difference value

The in-plane retardation Re was measured using Axoscan manufactured by Axometrics, inc. (550).

(3) Orientation angle (representing direction of slow axis)

The center of the film to be measured was cut into a square shape having a width of 50mm and a length of 50mm so that one side thereof was parallel to the width direction of the film, to obtain a test piece. The test piece was measured using Axoscan manufactured by Axometrics, inc., and the orientation angle θ was measured at a wavelength of 550 nm.

(4) Glass transition temperature (Tg)

The measurement was performed in accordance with JIS K7121.

(5) Modulus of elasticity

According to ISO527-3:2012, measurement is performed.

(6) Adhesion force

The measurement was performed by a 180 ° peel adhesion test method.

Example 1

(production of polyester carbonate resin film)

The polymerization was carried out using a batch polymerization apparatus comprising two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100 ℃. Adding bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl]29.60 parts by mass (0.046 mol) of methane, 29.21 parts by mass (0.200 mol) of ISB, 42.28 parts by mass (0.139 mol) of SPG, 63.77 parts by mass (0.298 mol) of DPC and 1.19X10 of calcium acetate monohydrate as a catalyst ^-2 Parts by mass (6.78X10) ^-5 mol). After the reduced pressure nitrogen substitution was performed in the reactor, the reactor was warmed with a heat medium, and stirring was started at the time when the internal temperature reached 100 ℃. After 40 minutes from the start of the temperature increase, the internal temperature was controlled to 220℃and the pressure was reduced so as to maintain the temperature, and after 220℃the pressure was set to 13.3kPa for 90 minutes. The phenol vapor produced as a by-product of the polymerization reaction was introduced into a reflux condenser at 100 ℃, a certain amount of monomer components contained in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was introduced into a condenser at 45 ℃ and recovered. After nitrogen was introduced into the 1 st reactor and the pressure was temporarily returned to the atmospheric pressure, the oligomerization reaction liquid in the 1 st reactor was transferred to the 2 nd reactor. Then, the temperature rise and pressure reduction in the 2 nd reactor were started, and the internal temperature was set at 240℃and the pressure was set at 0.2kPa for 50 minutes. Thereafter, polymerization was performed until a predetermined stirring power was reached. At the time of reaching the predetermined power, nitrogen was introduced into the reactor to restore the air pressure, and the produced polyester carbonate was extruded into water to cut the strands to obtain pellets. The Tg of the resulting polyester carbonate resin was 140 ℃.

The obtained polyester-carbonate resin was vacuum-dried at 80℃for 5 hours, and then a film-forming apparatus comprising a single screw extruder (manufactured by Toshiba machine Co., ltd., cylinder set temperature: 250 ℃), a T die (width: 250mm, set temperature: 250 ℃), a chilled roll (set temperature: 120 to 130 ℃) and a winding machine was used to prepare a polyester-carbonate resin film having a thickness of 135 μm and an elastic modulus of 2400 MPa.

(bonding of adhesive tape)

As shown in fig. 3, the adhesive tapes were bonded to both ends in the width direction by using rolls R1 and R2, respectively, while the obtained polyester-carbonate resin film was roll-fed in the longitudinal direction (the direction of the arrow). Here, the width of the polyester carbonate resin film was 250mm, and the width of the adhesive tape was 20mm. The adhesive tape contained a substrate (thickness: 100 μm, tg:130 ℃ C., elastic modulus: 2200 MPa) composed of polyethylene naphthalate (PEN) resin, and the adhesion to the polyester-carbonate resin film was 0.15N/15mm.

(oblique stretching)

The polyester-carbonate resin film having the adhesive tapes bonded to both ends in the width direction was subjected to oblique stretching using a stretching apparatus as shown in fig. 1, that is, a stretching apparatus provided with an oven capable of controlling the preheating zone, the oblique stretching zone, and the release zone to predetermined temperatures independently, to obtain a retardation film.

Specifically, in the holding section, both ends in the width direction of the film to which the adhesive tape is attached were held by left and right jigs, and preheated to 145 ℃ in the preheating section. In the preheating zone, the clamp pitch (P ₁ ) 125mm.

Then, at the same time as the film enters the oblique stretching region, the increase of the clamp pitch of the right clamp and the decrease of the clamp pitch of the left clamp are started, and the clamp pitch of the right clamp is increased to P ₂ And the clamp spacing of the left clamp is reduced to P ₃ . At this time, the jig pitch change rate (P ₂ /P ₁ ) 1.42, the clip pitch change rate (P ₃ /P ₁ ) The transverse stretching ratio was 0.78 and 1.45 times the original width of the film. Then, the clamp pitch of the right clamp is maintained at P ₂ In the state of (2), starting to increase the clamp pitch of the left clamp from P ₃ Increase to P ₂ . Rate of change of clip pitch of left clip therebetween (P ₂ /P ₃ ) The transverse stretching ratio was 1.82 and 1.9 times the original width of the film. The stretching region was set to tg+3.2 ℃ (143.2 ℃).

Next, in the release zone, the film was thermally fixed by holding at 125 ℃ for 60 seconds. After cooling the heat-fixed film to 100 ℃, the left and right clamps were released and sent out from the outlet of the stretching device.

In this manner, a stretched (retardation) film (thickness: 53 μm, re (550): 140nm, angle formed by the slow axis direction and the long axis direction: 45 °) was obtained.

Example 2

A stretched film was obtained in the same manner as in example 1, except that the adhesive of the adhesive tape was changed.

Example 3

A stretched film was obtained in the same manner as in example 1, except that the base material of the adhesive tape was changed to a base material (thickness: 100 μm, tg:120 ℃ C. And elastic modulus: 2200 MPa) composed of cycloolefin resin (COP).

Example 4

A stretched film was obtained in the same manner as in example 1 except that the base material of the adhesive tape was changed to a base material composed of a polyethylene resin (PE) (thickness: 100 μm, tg: -125 ℃ C., elastic modulus: 1100 MPa).

Example 5

A stretched film was obtained in the same manner as in example 1 except that the base material of the adhesive tape was changed to a base material composed of a polypropylene resin (PP) (thickness: 100 μm, tg:0 ℃ C., elastic modulus: 1500 MPa).

For each example, the following evaluation was performed. The evaluation results are summarized in table 1.

< evaluation >

1. Fracture during stretching

It was confirmed whether or not a break occurred in the film to be stretched during stretching.

2. Appearance and handleability

The appearance and handling properties of the obtained stretched film were evaluated by visual observation based on the following criteria.

Good: wrinkles and looseness were not observed in the stretched film (stretched film) during roll transport

Poor: wrinkles and/or looseness were observed in the stretched film (stretched film) during roll transport

TABLE 1

In examples 4 and 5, breakage of the film to be stretched was not generated during stretching, but the tailing was confirmed at the widthwise end.

Industrial applicability

The stretched film according to the embodiment of the present invention is suitably used for an optical member, for example, and such an optical member is suitably used for an image display device.

Claims

1. A method of making a stretched film comprising:

holding the end of the elongated stretched film in the width direction by a clamp;

stretching the stretching target film in an oblique direction by moving the jig in a traveling manner; and

releasing the stretched object film from the jig,

wherein an additional film is disposed at the end in the width direction of the film to be stretched during the holding, the film to be stretched and the additional film are held by the jig,

the attached film is disposed by attaching an adhesive tape to the film to be stretched,

the difference (Tg 1-Tg 2) between the glass transition temperature Tg1 of the film to be stretched and the glass transition temperature Tg2 of the film to be attached exceeds 0 ℃ and is 25 ℃ or lower.

2. The method according to claim 1, wherein the difference (E1-E2) between the elastic modulus E1 of the film to be stretched and the elastic modulus E2 of the additional film is 100MPa to 800MPa.

3. The production method according to claim 1 or 2, wherein an adhesion force of the adhesive tape to the film to be stretched is 0.1N/15mm or more.

4. The production method according to claim 1 or 2, wherein the width of the additional film is 20mm to 100mm.

5. The production method according to claim 1 or 2, wherein the additional film comprises at least one of a polyethylene naphthalate resin or a cycloolefin resin.

6. The production method according to claim 1 or 2, wherein the film to be stretched comprises at least one resin selected from the group consisting of a polycarbonate-based resin, a cycloolefin-based resin, a polyester-based resin and a polyester carbonate-based resin.

7. A method of manufacturing an optical laminate, comprising:

an elongated stretched film obtained by the production method according to any one of claims 1 to 6; and

the elongated stretched film and the elongated optical film are continuously laminated while being aligned in the longitudinal direction of each other while being conveyed.

8. The method of manufacturing of claim 7, wherein the optical film is a polarizer.