JP2023047022A - Method for producing stretched film and method for producing optical laminate - Google Patents

Abstract

To produce a stretched film with high production efficiency while suppressing breakage during stretching.SOLUTION: There is provided a method for producing a stretched film which comprises: gripping a widthwise edge of a long film to be stretched by a clip; stretching the film to be stretched in an oblique direction by running and moving the clip; and releasing the film to be stretched from the clip, wherein an attached film is disposed at the widthwise edge of the film to be stretched at the time of the gripping, the film to be stretched and the attached film are gripped by the clip and the attached film is disposed by laminating an adhesive tape on the film to be stretched.SELECTED DRAWING: Figure 2

Description

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

In an image display device such as a liquid crystal display device (LCD) and an organic electroluminescence display device (OLED), a polarizing plate with a retardation layer is typically used for the purpose of improving display characteristics, preventing reflection, and the like. A polarizing plate with a retardation layer (e.g., circular polarizing plate) is a polarizer and a retardation film (e.g., λ / 4 plate), and the absorption axis of the polarizer and the slow axis of the retardation film are at a predetermined angle. (eg, 45°). Conventionally, a retardation film is typically produced by uniaxial stretching or biaxial stretching in the machine direction and / or the transverse direction, so the slow axis is often the transverse direction of the original film. It is expressed in the direction (width direction) or the longitudinal direction (longitudinal direction). As a result, in order to produce a polarizing plate with a retardation layer, there is a case where the retardation film is cut so as to form a predetermined angle with respect to the horizontal direction or the vertical direction, and then laminated one by one.

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

Japanese Patent No. 4845619

The present invention has been made in view of the above, and its main object is to produce a stretched film with high production efficiency while suppressing breakage during stretching.

In the method for producing a stretched film according to an embodiment of the present invention, the end of a long film to be stretched is gripped by a clip in the width direction, and the clip is run to stretch the film to be stretched in an oblique direction. and releasing the film to be stretched from the clip, wherein an attachment film is arranged at an end portion in the width direction of the film to be stretched during the gripping, and the film to be stretched and the attachment film is gripped by the clip, and the attached film is arranged by bonding an adhesive tape to the film to be stretched.
In one embodiment, the difference (Tg1−Tg2) between the glass transition temperature Tg1 of the film to be stretched and the glass transition temperature Tg2 of the attached film is more than 0° C. and 25° C. or less.
In one embodiment, the difference (E1-E2) between the elastic modulus E1 of the film to be stretched and the elastic modulus E2 of the attached film is 100 MPa or more and 800 MPa or less.
In one embodiment, the adhesive strength of the pressure-sensitive adhesive tape to the film to be stretched is 0.1 N/15 mm or more.
In one embodiment, the width of the attachment film is 20 mm or more and 100 mm or less.
In one embodiment, the attached film contains at least one of polyethylene naphthalate-based resin and cycloolefin-based resin.
In one embodiment, the film to be stretched contains at least one resin selected from the group consisting of polycarbonate resins, cycloolefin resins, polyester resins, and polyester carbonate resins.
According to another aspect of the invention, a method for manufacturing an optical laminate is provided. This method for producing an optical laminate includes obtaining a long stretched film by the above-mentioned production method, and conveying the long stretched film and the long optical film in the longitudinal direction of each other. sequentially laminating in alignment.
In one embodiment, the optical film is a polarizer.

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

BRIEF DESCRIPTION OF THE DRAWINGS It is a top view which shows the outline of the whole structure of an example of the stretching apparatus used for manufacture of the stretched film by one Embodiment of this invention. FIG. 4 is a cross-sectional view schematically showing an example of a gripping state of film edges. It is a figure explaining an example of the bonding method of an adhesive tape. 1 is a cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer according to one embodiment of the present invention; FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In addition, in order to make the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part compared to the embodiment, but this is only an example and limits the interpretation of the present invention. not something to do.

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the in-plane direction orthogonal to the slow axis (i.e., fast axis direction) and "nz" is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re(λ)” is an in-plane retardation measured at 23° C. with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Thickness direction retardation (Rth)
“Rth(λ)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of λ nm. For example, “Rth(550)” is the retardation in the thickness direction measured at 23° C. with light having a wavelength of 550 nm. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is obtained by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Stretched Film Production Method A stretched film production method according to one embodiment of the present invention comprises gripping a widthwise end of a long stretched film with a clip and moving the clip to move the stretched film. and releasing the film to be stretched from the clip.

FIG. 1 is a plan view schematically showing the overall configuration of an example of a stretching apparatus used for producing a stretched film according to one embodiment of the present invention. The stretching apparatus 100 has endless loops 10L and 10R having a large number of clips 20 for gripping the film symmetrically on both left and right sides in a plan view. The endless loop on the left side as viewed from the inlet side of the film to be stretched is called the left endless loop 10L, and the endless loop on the right side is called the right endless loop 10R. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 30 and circulate in a loop shape. The clip 20 of the left endless loop 10L circulates counterclockwise, and the clip 20 of the right endless loop 10R circulates clockwise. In the stretching apparatus 100, a gripping zone A, a preheating zone B, a stretching zone C and a releasing zone D are provided in order from the sheet entrance side to the sheet exit side. These respective zones mean zones in which the film to be stretched is substantially gripped, preheated, stretched (obliquely stretched) and released, and do not mean mechanically and structurally independent compartments. Also note that the length ratios of the respective zones in the drawing apparatus of FIG. 1 differ from the actual length ratios.

Although not shown, a zone for any suitable treatment may be provided between the drawing zone C and the release zone D as required. Examples of such processing include vertical contraction processing and horizontal contraction processing. In addition, although not shown, the stretching apparatus 100 typically includes a heating apparatus (for example, hot air type, near infrared type, far infrared Various types of ovens such as ovens) are provided. In one embodiment, preheating, stretching and releasing are each performed in an oven set at a predetermined temperature.

In the gripping zone A and the preheating zone B, the left and right endless loops 10L, 10R are arranged substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched. In the stretching zone C, the separation distance between the left and right endless loops 10L and 10R gradually increases from the preheating zone B toward the releasing zone D until it corresponds to the width of the film after stretching. In the release zone D, the left and right endless loops 10L, 10R are configured to be substantially parallel to each other with a separation distance corresponding to the width of the film after stretching. However, the configuration of the left and right endless loops 10L and 10R is not limited to the illustrated example. For example, the left and right endless loops 10L, 10R may be arranged substantially parallel to each other from the grip zone A to the release zone D with a separation corresponding to the initial width of the film to be stretched.

The clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R can independently cyclically move. For example, the driving sprockets 11 and 12 of the left endless loop 10L are rotated counterclockwise by the electric motors 13 and 14, and the driving sprockets 11 and 12 of the right endless loop 10R are rotated clockwise by the electric motors 13 and 14. It is rotationally driven in the direction of rotation. As a result, a running force is applied to the clip carrying members (not shown) of the drive rollers (not shown) that are engaged with these drive sprockets 11 and 12 . As a result, the left endless loop 10L circulates counterclockwise, and the right endless loop 10R circulates clockwise. By independently driving the left electric motor and the right electric motor, the left endless loop 10L and the right endless loop 10R can be cyclically moved independently.

For example, the clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R are each of a variable pitch type. That is, the left and right clips 20, 20 can independently change their clip pitches in the vertical direction as they move. A variable pitch configuration can be realized by adopting a drive system such as a pantograph system, a linear motor system, a motor chain system, or the like. For example, Patent Document 1, Japanese Patent Application Laid-Open No. 2008-44339, etc., describe in detail a tenter-type simultaneous biaxial stretching apparatus using a pantograph-type link mechanism.

In the gripping zone A (entrance of the film take-in of the stretching device 100), the clip 20 of the left and right endless loops 10L and 10R allows the both side edges of the film to be stretched to be at a constant clip pitch or at different clip pitches. is grasped by The film is sent to the preheating zone B by movement of the clips 20 of the left and right endless loops 10L, 10R (substantially movement of each clip carrying member guided by a reference rail).

In the preheating zone B, the left and right endless loops 10L and 10R are arranged substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched, as described above. Therefore, the film is heated without being substantially stretched laterally or longitudinally. You can spread it.

In preheating, the film is heated to temperature T1. The temperature T1 is preferably the glass transition temperature (Tg) of the film or higher, more preferably Tg+2° C. or higher, and even more preferably Tg+5° C. or higher. On the other hand, the heating temperature T1 is preferably Tg+40° C. or lower, more preferably Tg+30° C. or lower. The temperature T1 is, for example, 70°C to 190°C, preferably 80°C to 180°C.

The heating time up to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to, for example, the constituent materials of the film and manufacturing conditions (transportation speed of the film, etc.). The heating time and holding time can be controlled by adjusting the moving speed of the clip 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

In the stretching zone C, the left and right clips 20 are run while changing the clip pitch in at least one of the vertical directions to diagonally stretch the film. More specifically, by increasing or decreasing the clip pitches of the left and right clips at different positions, changing (increasing and/or decreasing) the clip pitches of the left and right clips at different change speeds, etc. The film is diagonally stretched.

Diagonal stretching may include lateral stretching. In this case, the diagonal stretching can be performed while enlarging the distance between the left and right clips (distance in the width direction), for example, as shown in FIG. Alternatively, unlike the configuration shown in FIG. 1, it can be performed while maintaining the distance between the left and right clips.

When the diagonal stretching includes lateral stretching, the stretching ratio in the transverse direction (TD) (the ratio of the width W _final of the film after diagonal stretching to the initial width W _initial of the film (W _final /W _initial ) is preferably 1.05. ~6.00, more preferably 1.10 to 5.00.

In one embodiment, the diagonal stretching is such that the position where the clip pitch of one of the left and right clips starts to increase or decrease and the position where the clip pitch of the other clip starts to increase or decrease are different in the vertical direction. This can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch while in position. For the oblique stretching of the embodiment, for example, reference can be made to the descriptions of Japanese Patent No. 4845619, Japanese Patent Application Laid-Open No. 2014-238524, and the like.

In another embodiment, the diagonal stretching is performed by increasing or decreasing the clip pitch of one of the left and right clips while fixing the clip pitch of the other clip to a predetermined pitch, followed by can be done by returning to For the diagonal stretching of the embodiment, for example, reference can be made to the descriptions of JP-A-2013-54338, JP-A-2014-194482, and the like.

In yet another embodiment, the diagonal stretching includes (i) increasing the clip pitch of one of the left and right clips while decreasing the clip pitch of the other clip, and (ii) the decreasing By changing the clip pitch of each clip so that the increased clip pitch and the increased clip pitch have a predetermined equal pitch. For the oblique stretching of the embodiment, for example, the description of JP-A-2014-194484 can be referred to. In the diagonal stretching of the embodiment, the film is diagonally stretched by increasing the clip pitch of one clip and decreasing the clip pitch of the other clip while increasing the distance between the left and right clips (first 1 oblique stretching step), and while increasing the distance between the left and right clips, maintaining or reducing the clip pitch of the one clip so that the clip pitches of the left and right clips are equal, and the other It may include diagonally stretching the film by increasing the clip pitch of the clips (second diagonal stretching step).

In the first oblique stretching step, one side edge of the film is stretched in the longitudinal direction while the other side edge is shrunk in the longitudinal direction while performing oblique stretching to obtain a desired direction ( For example, the slow axis can be expressed with high uniaxiality and in-plane orientation in the direction at 45° to the longitudinal direction. Further, in the second diagonal stretching step, the diagonal stretching is performed while reducing the difference between the left and right clip pitches, thereby allowing sufficient stretching in the diagonal direction while relieving excess stress. Furthermore, since the film can be released from the clip while the left and right clips are moving at the same speed, it is difficult for the film transport speed to vary when the left and right clips are released, and the film can be wound afterward. can be done in

The stretching temperature T2 may be (Tg−20)° C. to (Tg+30)° C., or (Tg−10)° C. to (Tg+20)° C. relative to the glass transition temperature (Tg) of the film to be stretched. preferably Tg or higher, more preferably (Tg+1)°C to (Tg+10)°C, still more preferably (Tg+1)°C to (Tg+5)°C. The stretching temperature is, for example, 70°C to 180°C, preferably 80°C to 170°C.

The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ±2° C. or more, more preferably ±5° C. or more. In one embodiment, T1>T2, so the film heated to temperature T1 in the preheat zone can be cooled to temperature T2.

At any position in release zone D, the film is released from the clip. In the release zone D, neither lateral stretching nor longitudinal stretching is usually performed, and if necessary, the film is heat-treated to fix the stretched state (heat setting) and / or cooled to Tg or less, and then the film from the clip. When heat-fixing, the clip pitch in the vertical direction may be decreased to relieve the stress.

The temperature T3 of the heat treatment that may be performed in the release zone D varies depending on the film to be stretched, and may be T2≧T3 or T2<T3. Generally, T2≧T3 if the film is an amorphous material, and T2<T3 if the film is a crystalline material, for example by crystallization. If T2≧T3, the difference between temperatures T2 and T3 (T2-T3) is preferably between 0.degree. C. and 50.degree. The heat treatment time is typically 10 seconds to 10 minutes.

[Film to be stretched]
As the resin constituting the film to be stretched (film to be stretched), any appropriate resin can be used as long as the desired optical properties can be satisfied. Examples of resins constituting the film to be stretched include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, and olefin resins. resins, polyurethane-based resins, and the like. Polycarbonate-based resins, cycloolefin-based resins, polyester-based resins, and polyester carbonate-based resins are preferred. This is because, with these resins, it is possible to obtain a retardation film exhibiting so-called inverse wavelength dependence of dispersion. These resins may be used alone or in combination of two or more.

Any appropriate polycarbonate-based resin is used as the polycarbonate-based resin. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferred. Specific examples of dihydroxy compounds include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3- ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy -3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9, 9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis( 4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2 -hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3 ,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2 , 2-dimethylpropoxy)phenyl)fluorene and the like. In addition to the structural units derived from the dihydroxy compound, the polycarbonate resin includes isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol. (CHDM), tricyclodecanedimethanol (TCDDM), and structural units derived from dihydroxy compounds such as bisphenols.

Details of the above polycarbonate resins are described, for example, in JP-A-2012-67300 and JP-A-3325560. The description of the patent document is incorporated herein by reference.

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

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

The thickness of the film to be stretched can be appropriately set according to, for example, the thickness of the stretched film to be obtained, 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 edge. The film to be stretched 1 is stretched with the attached film 2a arranged at its widthwise end. Specifically, when the gripping is performed, the attachment film 2a is arranged at the width direction end of the stretch target film 1, and the stretch target film 1 and the attachment film 2a are held by the upper and lower clip members 20a and 20b of the clip 20. Grasped.

The attached film 2 a is arranged on the stretched film 1 by bonding the adhesive tape 2 to the stretched film 1 . Specifically, the adhesive tape 2 has an attached film 2a and an adhesive layer 2b, and the attached film 2a is laminated on the stretched film 1 via the adhesive layer 2b. Continuous production can be made possible by using the adhesive tape 2 . For example, as shown in FIG. 3, after bonding an adhesive tape 2 to a first raw film to be stretched 1, the adhesive tape 2 is continuously applied to a second raw film to be stretched (not shown). By laminating together, different original film sheets to be stretched can be continuously stretched, which can contribute to improvement of production efficiency.

The adhesive strength of the adhesive tape 2 to the film 1 to be stretched is preferably 0.1 N/15 mm or more, more preferably 0.15 N/15 mm or more. Such adhesive strength prevents the adhesive tape 2 from being peeled off from the film 1 to be stretched during stretching, resulting in excellent handleability. In addition, the part (width direction edge part) which bonded the adhesive tape 2 together may be cut|disconnected (slit) and may be removed after extending|stretching.

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

As shown in FIG. 2, the end faces of the stretch target film 1 and the attached film 2a (adhesive tape 2) do not need to match, and the clip 20 can grip the overlapped portion of the stretch target film 1 and the attached film 2a. good. The width of the attachment film 2a (adhesive tape 2) is, for example, 20 mm or more and 100 mm or less. Further, in the drawing, the attached film 2a is arranged above the film 1 to be stretched, but it may be arranged below. Moreover, you may arrange|position above and below. In this case, different attachment films may be arranged on the upper side and the lower side respectively, or one end of one attachment film may be arranged on the upper side and the other end may be arranged on the lower side.

As described above, in the stretching zone C, the left and right clips 20 are moved while changing the clip pitch in at least one of the vertical directions to diagonally stretch the film. In such a form, since a large stress is applied to the width direction end portions of the film to be stretched, there is a tendency for breakage to occur during stretching, or for the width direction end portions of the resulting stretched film to be turned up. By arranging and stretching the film, the occurrence of such problems can be suppressed. In the example shown in FIG. 3, the adhesive tapes 2 are attached to both ends of the film 1 to be stretched in the width direction.

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

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

The thickness of the attached film 2a is, for example, 50 μm to 200 μm. Examples of the resin forming the attachment film 2a include polyethylene naphthalate-based resins and cycloolefin-based resins.

B. Optical Laminate The stretched film obtained by the above embodiment is typically used as an optical laminate by being laminated on an optical film. For example, a stretched film can function as a retardation layer (retardation film) by being laminated on a polarizing plate.

FIG. 4 is a cross-sectional view showing a schematic configuration of a polarizing plate with a retardation layer as an example of how to use the stretched film in one embodiment of the present invention. The retardation layer-attached polarizing plate 80 has a polarizing plate 71 and a stretched film (retardation film) 51 attached to one side of the polarizing plate 71 via an adhesive layer 61 . The polarizing plate 71 has a polarizer 72 and a protective layer 73 arranged on one side of the polarizer 72 , and the retardation film 51 is attached to the polarizer 72 via an adhesive layer 61 . Although not shown, a second protective layer may be arranged on the other side of the polarizer 72 (between the polarizer 72 and the retardation film 51).

The retardation layer-attached polarizing plate 80 can be obtained, for example, by laminating the polarizing plate 71 and the retardation film 51 via an adhesive or pressure-sensitive adhesive. In one embodiment, the elongated polarizing plate 71 and the elongated retardation film 51 are continuously laminated while being transported while aligning their longitudinal directions. Specifically, lamination is performed by roll-to-roll. The term "long shape" refers to an elongated shape whose length is sufficiently longer than its width, for example, an elongated shape whose length is 10 times or more, preferably 20 times or more, its width.

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

A retardation film typically has a refractive index characteristic of nx>ny≧nz. Here, "ny=nz" includes not only the case where ny and nz are completely equal but also the case where ny and nz are substantially equal. Therefore, it is possible that ny<nz. 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, particularly preferably 0 .9 to 1.3. According to such an Nz coefficient, for example, when a retardation film (retardation layer-attached polarizing plate) is used in an image display device, an excellent reflection hue can be achieved.

The retardation film may exhibit a reverse wavelength dispersion characteristic in which the retardation value increases according to the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may well exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes even with the wavelength of the measurement light. In one embodiment, the retardation film exhibits reverse wavelength dispersion characteristics. 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 or more and 0.95 or less. According to such wavelength characteristics, for example, when the retardation film (polarizing plate with retardation layer) is used in an image display device, excellent antireflection characteristics can be achieved.

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

As described above, the retardation film is composed of a stretched film obtained by continuously stretching a long film to be stretched in a direction (oblique direction) at an angle θ with respect to the longitudinal direction. In this case, the retardation film has a slow axis (orientation angle of angle θ) in a direction oblique to the longitudinal direction (direction of angle θ). The oblique direction is preferably 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. be. Since a polarizer usually has an absorption axis in the longitudinal direction, a long retardation film makes it possible to produce a polarizing plate with a retardation layer by roll-to-roll, which simplifies the manufacturing process. be able to.

B-2. Polarizer The polarizer is typically an absorptive 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 one embodiment, 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°, more preferably 42° to 48°, particularly preferably about 45°.

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

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

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

A polarizer can be made by any suitable method. Specifically, the polarizer may be produced from a single-layer resin film, or may be produced using a laminate of two or more layers.

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

Specific examples of the polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and the resin A polarizer obtained by using a laminate with a PVA-based resin layer formed by coating on a substrate can be mentioned. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. These publications are incorporated herein by reference in their entirety.

B-3. Protective Layer The protective layer can be formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based resins. , polystyrene-based, polynorbornene-based cycloolefin-based, polyolefin-based, (meth)acrylic-based, and acetate-based transparent resins.

The retardation layer-attached polarizing plate is typically arranged on the viewing side of the image display device. Therefore, the protective layer may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, anti-glare treatment, etc., if necessary.

The thickness of the protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, still more preferably 10 μm to 30 μm. In addition, when the said surface treatment is performed, the thickness of a protective layer is thickness including the thickness of a surface treatment layer.

The second protective layer is preferably optically isotropic in one embodiment. As used herein, “optically isotropic” means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is −10 nm to +10 nm. say.

B-4. Adhesive layer Specific examples of the adhesive layer include an adhesive layer and a pressure-sensitive adhesive layer. In one embodiment, an adhesive layer is employed as the adhesive layer. The adhesive layer is typically composed of an active energy ray-curable adhesive. Any appropriate adhesive can be used as the active energy ray-curable adhesive as long as it is an adhesive that can be cured by irradiation with an active energy ray. Examples of active energy ray-curable adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Specific examples of curing types of active energy ray-curable adhesives include radical curing, cationic curing, anionic curing, and combinations thereof (for example, hybrids of radical curing and cationic curing). Active energy ray-curable adhesives include, for example, adhesives containing compounds (eg, monomers and/or oligomers) having radically polymerizable groups such as (meth)acrylate groups and (meth)acrylamide groups as curing components. mentioned. Specific examples of the active energy ray-curable adhesive and its curing method are described, for example, in JP-A-2012-144690. The description of the publication is incorporated herein by reference.

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

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The measurement method and evaluation method for each characteristic are as follows.
(1) Thickness Measured using a dial gauge (manufactured by PEACOCK, product name “DG-205 type pds-2”).
(2) Retardation value In-plane retardation Re (550) was measured using Axoscan manufactured by Axometrics.
(3) Orientation angle (development direction of slow axis)
A square having a width of 50 mm and a length of 50 mm was cut out from the central portion of the film to be measured so that one side was parallel to the width direction of the film to obtain a test piece. This test piece was measured using Axoscan manufactured by Axometrics to measure the orientation angle θ at a wavelength of 550 nm.
(4) Glass transition temperature (Tg)
Measured according to JIS K 7121.
(5) Elastic modulus Measured according to ISO527-3:2012.
(6) Adhesive strength Measured by the 180° peel adhesive strength test method.

[Example 1]
(Preparation of polyester carbonate resin film)
Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled at 100°C. Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 parts by mass (0. 139 mol), 63.77 parts by mass (0.298 mol) of DPC, and 1.19×10 ⁻² parts by mass (6.78×10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst were charged. After the interior of the reactor was replaced with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. After 40 minutes from the start of heating, the internal temperature was allowed to reach 220°C, and the pressure was reduced at the same time as controlling to maintain this temperature. Phenol vapor produced as a by-product of the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. After nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was brought to 240° C. and the pressure to 0.2 kPa in 50 minutes. After that, polymerization was allowed to proceed until a predetermined stirring power was obtained. When a predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, the polyester carbonate produced was extruded into water, and strands were cut to obtain pellets. The Tg of the obtained polyester carbonate resin was 140°C.

After vacuum drying the obtained polyester carbonate resin at 80 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machine Co., cylinder set temperature: 250 ° C.), T die (width: 250 mm, set temperature: 250 ° C.), A polyester carbonate resin film having a thickness of 135 μm and an elastic modulus of 2400 MPa was produced using a film forming apparatus equipped with a chill roll (set temperature: 120 to 130° C.) and a winder.

(Lamination of adhesive tape)
As shown in FIG. 3, the obtained polyester carbonate resin film was conveyed by rolls in the longitudinal direction (direction of the arrow), and adhesive tapes were attached to both ends in the width direction using rolls R1 and R2. . Here, the width of the polyester carbonate resin film was 250 mm, and the width of the adhesive tape was 20 mm. In addition, the adhesive tape contains a base material (thickness: 100 μm, Tg: 130° C., elastic modulus: 2200 MPa) composed of polyethylene naphthalate (PEN) resin, and has an adhesive strength of 0.15 N/15 mm to a polyester carbonate resin film. Met.

(Diagonal stretching)
A polyester carbonate resin film having adhesive tapes attached to both ends in the width direction is stretched by a stretching apparatus as shown in FIG. A retardation film was obtained by oblique stretching using a stretching device equipped with a possible oven.
Specifically, in the gripping zone, both ends in the width direction of the film to which the adhesive tape was attached were gripped with left and right clips, and preheated to 145° C. in the preheating zone. In the preheat zone, the clip pitch (P ₁ ) of the left and right clips was 125 mm.
Then, as soon as the film enters the diagonal stretching zone, it starts increasing the clip pitch of the right clip and decreasing the clip pitch of the left clip, increasing the clip pitch of the right clip to _P2 and decreasing the clip pitch of the left clip. reduced to _P3 . At this time, the clip pitch change rate (P ₂ /P ₁ ) of the right clip is 1.42, the clip pitch change rate (P ₃ /P ₁ ) of the left clip is 0.78, and the original width of the film is The transverse draw ratio for the film was 1.45 times. Then, while maintaining the clip pitch of the right clip at _P2 , the clip pitch of the left clip started to increase from _P3 to _P2 . The clip pitch change ratio (P ₂ /P ₃ ) of the left clip during this period was 1.82, and the lateral draw ratio with respect to the original width of the film was 1.9 times. The stretching zone was set at Tg+3.2°C (143.2°C).
Heat setting was then performed by holding the film at 125° C. for 60 seconds in the release zone. After the heat-set film was cooled to 100° C., the left and right clips were released, and the film was sent out from the outlet of the stretching device.

In this way, a stretched (retardation) film (thickness: 53 μm, Re(550): 140 nm, angle between slow axis direction and longitudinal 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 prepared 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 cycloolefin resin (COP) (thickness: 100 μm, Tg: 120 ° C., elastic modulus: 2200 MPa). got

[Example 4]
A stretched film was prepared 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 polyethylene resin (PE) (thickness: 100 μm, Tg: −125° C., elastic modulus: 1100 MPa). Obtained.

[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 polypropylene resin (PP) (thickness: 100 μm, Tg: 0° C., elastic modulus: 1500 MPa). rice field.

Each example was evaluated as follows. The evaluation results are summarized in Table 1.
<Evaluation>
1. Breakage during stretching It was confirmed whether or not the film to be stretched would break during stretching.
2. Appearance and Handleability The appearance and handleability of the obtained stretched film were visually evaluated based on the following criteria.
Good: No wrinkles and slack are observed in the stretched film (film to be stretched) during roll transportation Bad: Wrinkles and/or slack are confirmed in the stretched film (film to be stretched) during roll transportation

In Examples 4 and 5, the films to be stretched did not break during stretching, but curling was observed at the edges in the width direction.

The stretched film according to the embodiment of the present invention is suitable for optical members, for example, and such optical members are suitable for image display devices.

REFERENCE SIGNS LIST 1 Film to be stretched 2 Adhesive tape 2a Attached film 2b Adhesive layer 51 Stretched film (retardation film)
61 adhesive layer 71 polarizing plate 72 polarizer 73 protective layer 80 polarizing plate with retardation layer

Claims (9)

gripping the ends in the width direction of the elongated film to be stretched with a clip;
Stretching the film to be stretched in an oblique direction by moving the clip, and
releasing the stretched film from the clip;
At the time of gripping, an attachment film is arranged at the width direction end of the target film to be stretched, and the target film to be stretched and the attachment film are gripped by the clip,
Arranging the attached film by attaching an adhesive tape to the film to be stretched;
A method for producing a stretched film. The production method according to claim 1, wherein the difference (Tg1-Tg2) between the glass transition temperature Tg1 of the film to be stretched and the glass transition temperature Tg2 of the attached film is more than 0°C and 25°C or less. 3. The production 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 attached film is 100 MPa or more and 800 MPa or less. The manufacturing method according to any one of claims 1 to 3, wherein the adhesive strength of the adhesive tape to the film to be stretched is 0.1 N/15 mm or more. 5. The manufacturing method according to any one of claims 1 to 4, wherein the width of said attached film is 20 mm or more and 100 mm or less. The manufacturing method according to any one of claims 1 to 5, wherein the attachment film contains at least one of polyethylene naphthalate resin and cycloolefin resin. The film to be stretched contains at least one resin selected from the group consisting of polycarbonate resins, cycloolefin resins, polyester resins, and polyester carbonate resins, according to any one of claims 1 to 6. Production method. Obtaining a long stretched film by the production method according to any one of claims 1 to 7, and
Continuously laminating the elongated stretched film and the elongated optical film while aligning their longitudinal directions with each other while conveying the elongated stretched film and the elongated optical film;
A method of manufacturing an optical laminate, comprising: The manufacturing method according to claim 9, wherein the optical film is a polarizer.

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