KR102531541B1 - Method for producing stretched film and method for producing optical laminate - Google Patents

Abstract

This invention manufactures a stretched film by suppressing the fracture|rupture at the time of extending|stretching.
A method for producing a stretched film according to an embodiment of the present invention includes holding an end of a long film to be stretched with a clip in the width direction, stretching the film to be stretched in an oblique direction by running the clip, and , Comprising releasing the film to be stretched from the clip, wherein during the gripping, a laying film is disposed at an end portion of the target film in the width direction of the film to be stretched, the film to be stretched and the laying film are fused together, and the target film to be stretched is fused. An area where the film and the laying film overlap is held by the clip, and the laying film is a turn-up part obtained by turning up an end of the film to be stretched inward.

Description

Stretched film manufacturing method and optical laminate manufacturing method {METHOD FOR PRODUCING STRETCHED FILM AND METHOD FOR PRODUCING OPTICAL LAMINATE}

This invention relates to the manufacturing method of a stretched film, and the manufacturing method of an optical laminated body.

BACKGROUND ART In image display devices such as liquid crystal displays (LCDs) and organic electroluminescent displays (OLEDs), polarizing plates with retardation layers are typically used for the purpose of improving display characteristics or preventing reflection. In a polarizing plate with a retardation layer (e.g. circular polarizing plate), the polarizer and the retardation film (e.g. λ/4 plate) have an absorption axis of the polarizer and a slow axis of the retardation film at a predetermined angle (e.g. 45°). ) It can be configured by being laminated to achieve. Conventionally, since retardation films are typically produced by uniaxial stretching or biaxial stretching in the machine direction and/or transverse direction, the slow axis thereof is, in most cases, the transverse direction (width direction) or longitudinal direction of the original film. It is expressed in the direction (length direction). As a result, in order to produce a polarizing plate with a retardation layer, the retardation film may be cut so as to form a predetermined angle with respect to the transverse direction or the longitudinal direction, and bonded one by one.

In order to solve such a problem of productivity, a technique of developing the slow axis of the retardation film in an oblique direction by stretching in an oblique direction with respect to the direction of a long picture has been proposed (for example, Patent Document 1). However, stretching in an oblique direction tends to cause the film to be stretched to break easily during stretching. Such a tendency is so remarkable that the film used as an extending|stretching object is thin.

Japanese Patent Publication No. 4845619

The present invention was made in view of the above, and its main purpose is to manufacture a stretched film while suppressing breakage during stretching.

A method for producing a stretched film according to an embodiment of the present invention includes holding an end of a long film to be stretched with a clip in the width direction, stretching the film to be stretched in an oblique direction by running the clip, and , Comprising releasing the film to be stretched from the clip, wherein during the gripping, a laying film is disposed at an end portion of the target film in the width direction of the film to be stretched, the film to be stretched and the laying film are fused together, and the target film to be stretched is fused. An area where the film and the laying film overlap is gripped by the clip, and the laying film is a turn-up part obtained by turning an end of the film to be stretched inward.

In one embodiment, the fusion is performed by ultrasonic waves.

In one embodiment, the thickness of the film to be stretched is 70 μm or less.

In one embodiment, the turn-up is performed once.

In one embodiment, the thickness of the region where the film to be stretched and the laying film overlap is 40 μm or more.

In one embodiment, the width of the turn-up portion is 25 mm or more.

According to another aspect of the present invention, a method for manufacturing an optical laminate is provided. The manufacturing method of this optical layered body includes: obtaining a long stretched film by the above manufacturing method, and continuously laminating the long picture-shaped stretched film and the long picture-shaped optical film while aligning the directions of each other while conveying them. include

In one embodiment, the optical film is a polarizer.

According to an embodiment of the present invention, a stretched film can be manufactured while suppressing breakage during stretching.

1 is a plan view schematically illustrating the overall configuration of an example of a stretching apparatus used for production of a stretched film according to one embodiment of the present invention.
Fig. 2 is a cross-sectional view schematically showing an example of a holding state of a film end portion.
Fig. 3 is a cross-sectional view showing the schematic configuration of a polarizing plate with a retardation layer in one embodiment of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described referring drawings, this invention is not limited to these embodiment. In addition, in order to make explanation more clear, although there are cases where the width, thickness, shape, etc. of each part are schematically shown compared to the embodiment, they are examples only and do not limit the interpretation of the present invention.

(Definition of Terms and Symbols)

Definitions of terms and symbols in this specification 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 maximized (ie, the slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the fast axis direction), , 'nz' is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

'Re(λ)' is an in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, 'Re(550)' is an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is set to d(nm).

(3) Phase difference in thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, 'Rth(550)' is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d (nm).

(4) Nz factor

The Nz coefficient can be obtained by Nz=Rth/Re.

(5) Angle

When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Thus, for example, '45°' means ±45°.

A. Manufacturing method of stretched film

A method for producing a stretched film according to one embodiment of the present invention includes holding an end of a long film to be stretched with a clip in the width direction, stretching the film to be stretched in an oblique direction by moving the clip, and , and releasing the film to be stretched from the clip.

1 is a plan view schematically illustrating the overall configuration of an example of a stretching apparatus used for production of a stretched film according to one embodiment of the present invention. The stretching device 100 has, in a planar view, an endless loop 10L and an endless loop 10R having a large number of clips 20 for gripping the film on both left and right sides symmetrically. In addition, when viewed from the entrance side of the film to be stretched, the left endless loop is called the left endless loop 10L, and the right endless loop is called the right endless loop 10R. The clips 20 of the left and right endless loops 10L and 10R are each guided by the standard rail 30 and move circularly in a loop shape. The clip 20 of the endless loop 10L on the left side rotates counterclockwise, and the clip 20 of the endless loop 10R on the right side circularly moves clockwise. In the stretching device 100, a holding zone A, a preheating zone B, a stretching zone C, and a release zone D are provided in this order from the inlet side to the outlet side of the sheet. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, stretched (obliquely stretched), and released, and does not mean a mechanically or structurally independent section. It should be noted that the length ratio of each zone in the stretching device of FIG. 1 is different from the actual length ratio.

Although not shown, a zone may be provided between the stretching zone C and the releasing zone D to perform any appropriate treatment as needed. Examples of such processing include longitudinal shrinkage and transverse shrinkage. Although not shown, the stretching device 100 typically includes a heating device (for example, hot air type, near infrared type, far red type) for setting each zone from the preheating zone B to the release zone D to a heating environment. Various ovens such as eating out) are provided. In one embodiment, preheating, stretching, and release are each 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 and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the stretching zone C, the distance between the left and right endless loops 10L and 10R gradually expands from the preheating zone B side toward the release zone D until the distance between the left and right endless loops 10L and 10R corresponds to the width of the film after stretching. is composed of In the release zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at 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 and 10R may be configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched from the holding zone A to the release zone D.

The clip (left clip) 20 of the endless loop 10L on the left side and the clip (clip on the right side) 20 of the endless loop 10R on the right side can each independently tour. For example, the driving sprockets 11 and 12 of the endless loop 10L on the left are rotationally driven in a counterclockwise direction by the electric motors 13 and 14, and the driving sprockets 11 and 12 of the endless loop 10R on the right 12) is rotationally driven clockwise by the electric motors 13 and 14. As a result, a driving force is applied to a clip holding member (not shown) of a driving roller (not shown) engaged with these driving sprockets 11 and 12. Accordingly, the endless loop 10L on the left side rotates in a counterclockwise direction, and the endless loop 10R on the right side rotates in a clockwise direction. By independently driving the electric motor on the left and the electric motor on the right, respectively, the left endless loop 10L and the right endless loop 10R can each independently make a circular movement.

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 variable pitch type. That is, the left and right clips 20 and 20 can each independently change the clip pitch in the vertical direction according to the movement. The configuration of the variable pitch type can be realized by employing a driving method such as a pantograph method, a linear motor method, or a motor/chain method. For example, Patent Document 1 and Japanese Unexamined Patent Publication No. 2008-44339 describe in detail a tenter type simultaneous biaxial stretching device using a pantograph type link mechanism.

In the gripping zone A (entrance of film introduction of the stretching device 100), by the clips 20 of the left and right endless loops 10L and 10R, both edges of the film to be stretched have the same constant clip pitch. , or gripped with mutually different clip pitches. By the movement of the clip 20 of the left and right endless loops 10L and 10R (actually, the movement of each clip holding member guided by the standard rail), the film is sent to the preheating zone B.

In the preheating zone B, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched as described above. Accordingly, neither transverse nor longitudinal stretching is substantially carried out and the film is heated, but the distance between the left and right clips (distance in the width direction) may be increased to avoid, for example, problems caused by warping of the film due to preheating.

In preheating, the film is heated to temperature T1. The temperature (T1) is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably equal to or higher than Tg+2°C, still more preferably equal to or higher than Tg+5°C. 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 to reach the temperature T1 and the holding time of the temperature T1 can be appropriately set depending on, for example, the constituent materials of the film and the manufacturing conditions (such as the conveying speed of the film). 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 clips 20 on either side are run and moved while changing the clip pitch in at least one longitudinal direction thereof, and the film is stretched obliquely. More specifically, by increasing or reducing the clip pitches of the left and right clips at different positions, by changing (increasing and/or reducing) the clip pitches of the left and right clips at different changing speeds, respectively, is obliquely stretched.

Oblique stretching may also include lateral stretching. In this case, oblique stretching may be performed while increasing the distance between the left and right clips (distance in the width direction), as shown in FIG. 1 , for example. Alternatively, unlike the configuration shown in Fig. 1, it may be performed while maintaining the distance between the left and right clips.

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

In one embodiment, in the oblique stretching, 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 positions in the longitudinal direction. In this state, it can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch. Regarding the oblique stretching of the embodiment, descriptions such as Japanese Patent Publication No. 4845619 and Japanese Unexamined Patent Publication No. 2014-238524 can be referred to, for example.

In another embodiment, oblique stretching may be performed by increasing or decreasing the clip pitch of one of the left and right clips to a predetermined pitch while fixing the clip pitch of the other clip, and then returning it to the original clip pitch. there is. Regarding the oblique stretching of the embodiment, descriptions such as Unexamined-Japanese-Patent No. 2013-54338 and Unexamined-Japanese-Patent No. 2014-194482 can be referred to, for example.

In another embodiment, the oblique stretching comprises: (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 corresponding reduced clip pitch and corresponding increase. This can be done by changing the clip pitch of each clip so that the selected clip pitch becomes the same predetermined pitch. Regarding the oblique stretching of the embodiment, descriptions such as Unexamined-Japanese-Patent No. 2014-194484 can be referred, for example. In the oblique stretching of the embodiment, the film is obliquely stretched by increasing the distance between the left and right clips, increasing the clip pitch of one clip, and decreasing the clip pitch of the other clip (first oblique stretching step). , and, while increasing the distance between the left and right clips, maintaining or reducing the clip pitch of one clip so that the clip pitch of the left and right clips is the same, and also increasing the clip pitch of the other clip, so that the clip pitch of the left and right clips is the same, It may include obliquely stretching (second oblique stretching process).

In the first oblique stretching step, oblique stretching is performed while extending one side edge of the film in the direction of a long picture and contracting the other side edge in the direction of a long picture, in a desired direction (for example, in a direction of 45° with respect to the direction of a long picture). A slow axis can be developed with high uniaxiality and in-plane orientation. Further, in the second oblique stretching step, oblique stretching can be performed while reducing the difference between left and right clip pitches, so that the film can be sufficiently stretched in an oblique direction while relieving excess stress. In addition, since the film can be released from the clip in a state where the moving speed of the left and right clips is the same, there is little variation in film conveyance speed or the like when the left and right clips are released, and the subsequent film winding is performed appropriately. can lose

The stretching temperature (T2) may be (Tg-20)°C to (Tg+30)°C, or (Tg-10)°C to (Tg+20) relative to the glass transition temperature (Tg) of the film to be stretched. It may be °C, 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, and thus a film heated to temperature T1 in the preheat zone may be cooled to temperature T2.

At any position in the release zone D, the film is released from the clip. In the release zone D, neither transverse stretching nor longitudinal stretching is normally performed, and the film is heat-treated to fix the stretched state (heat-set) as necessary, and/or cooled to Tg or less, and then the film from the clip. Further, when heat fixing, the clip pitch in the longitudinal direction may be reduced, thereby relieving stress.

The temperature T3 of the heat treatment that may be performed in the release zone D is different depending on the film to be stretched, and may be T2≥T3 or T2<T3. In general, when the film is an amorphous material, T2 ≥ T3, and when the film is a crystalline material, T2 < T3, for example, crystallization treatment is performed. When T2≥T3, the difference between the temperatures T2 and T3 (T2-T3) is preferably 0°C to 50°C. The heat treatment time is typically 10 seconds to 10 minutes.

[Target film for stretching]

As the resin constituting the film to be stretched (film to be stretched), any suitable resin can be used as long as it can satisfy desired optical properties. 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-based resins, polyester carbonate-based resins, Olefin type resin, polyurethane type resin, etc. are mentioned. Preferably, they are polycarbonate-type resin, cycloolefin-type resin, polyester-type resin, and polyester carbonate-type resin. This is because, with these resins, a retardation film exhibiting the so-called wavelength dependence of reverse dispersion can be obtained. These resins may be used alone or in combination of two or more.

As the polycarbonate-based resin, any suitable polycarbonate-based resin is used. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferred. As a specific example of a dihydroxy compound, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxyl) Roxy-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-dimethyl Phenyl) 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. Polycarbonate-based resins, in addition to the structural units derived from the dihydroxy compounds, are isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), Structural units derived from dihydroxy compounds such as polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecane dimethanol (TCDDM), and bisphenols may be included.

Details of the above polycarbonate-based resins are described in, for example, Japanese Unexamined Patent Publication No. 2012-67300 and Japanese Patent No. 3325560. Description of the said patent document is used as a reference in this specification.

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 deteriorate, and there is a possibility of causing dimensional change after forming the film. If the glass transition temperature is excessively high, the molding stability during film molding may deteriorate, and the transparency of the film may also be impaired. In addition, the glass transition temperature can be obtained according to JIS K 7121 (1987).

Any appropriate polyvinyl acetal-based resin can be used as the polyvinyl acetal-based resin. Typically, polyvinyl acetal-based resin can be obtained by subjecting at least two types of aldehyde compounds and/or ketone compounds to a condensation reaction of polyvinyl alcohol-based resin. The specific example and detailed manufacturing method of polyvinyl acetal-type resin are described, for example in Unexamined-Japanese-Patent No. 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 resulting stretched film, the in-plane retardation, and the like. The thickness of the film to be stretched is preferably 70 μm or less, and more preferably 20 μm to 65 μm.

[Laying film]

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

The laying film 2 is a turn-up portion obtained by turning up an end portion of the film 1 to be stretched inward. Specifically, the film to be stretched 1 is bent at the bent portion 1a at the end portion in the width direction, and turned up 180° inward to form the laid film 2 (turnup portion 2). In the example of illustration, although the turn-up part 2 is arrange|positioned on the upper side of the film 1 to be stretched, you may arrange|position it on the lower side. The width of the turn-up portion 2 is not particularly limited as long as the clip 20 can hold the folding area, but is preferably 25 mm or more.

The turn-up of the film to be stretched at the end portion in the width direction is performed, for example, while conveying the film to be stretched in its elongated direction before the holding. During the turn-up, the turn-up may be performed using a guide having a plate shape, a U-shape in cross section, or a V-shape in cross section.

In the folding region, a junction 3 between the turn-up portion 2 and the film 1 to be stretched is formed, and the folding region becomes a thicker portion thicker than the film 1 to be stretched. The bonding portion 3 may be formed in the entire folding region or may be partially formed. Preferably, it is partially formed. In the illustrated example, the bonding portion 3 is formed in a line shape along the direction of a long picture at the inner end of the folding region.

The bonding portion 3 may be formed using an ultrasonic welding method, a laser welding method, a thermal welding method, or the like. Specifically, the bonding portion 3 is a fused portion of the melted portion of the turn-up portion 2 and the melted portion of the film 1 to be stretched. By forming the fusion part, the thickness of the junction part 3 can be further increased. According to such an aspect, breakage at the time of extending|stretching can be suppressed more reliably.

The thickness of the folding region is preferably 40 μm or more, more preferably 60 μm or more and 140 μm or less.

In the example shown in FIG. 2, although the edge part of the film 1 to be stretched is folded twice, you may fold it three or more times. In the case of folding in three or more folds, at least a junction between the film to be stretched and the turn-up portion adjacent thereto may be formed, but a junction may be formed at a turn-up portion other than that. From the viewpoint of efficiency or accuracy, as shown in the figure, double folding (turn-up once) is preferable.

As described above, in the stretching zone C, the clips 20 on either side are run while changing the clip pitch in at least one of the longitudinal directions, and the film is stretched obliquely. In such a form, large stress is applied to the end of the film to be stretched in the width direction, so breakage tends to occur during stretching. The turn-up of the edge part in the width direction of the film to be stretched and the formation of the joining portion may be performed at least on the side where the clip pitch in the longitudinal direction is changed, but may be performed on both sides. In addition, you may remove the turn-up part of the edge part in the width direction by cutting (slitting) after extending|stretching.

B. Optical stack

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

Fig. 3 is a cross-sectional view showing the schematic configuration of a polarizing plate with a retardation layer as an example of a method of using a stretched film in one embodiment of the present invention. The polarizing plate 80 with a retardation layer has a polarizing plate 71 and a stretched film (retardation film) 51 bonded to one side of the polarizing plate 71 with an adhesive layer 61 interposed therebetween. The polarizing plate 71 has a polarizer 72 and a protective layer 73 disposed on one side of the polarizer 72, and a retardation film 51 is bonded to the polarizer 72 via an 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 the retardation layer can be obtained by, for example, laminating the polarizing plate 71 and the retardation film 51 via an adhesive or a pressure-sensitive adhesive. In one embodiment, the elongated polarizing plate 71 and the elongated retardation film 51 are continuously laminated while aligning the directions of each other while conveying the elongated polarizing plate 71 . Specifically, it is laminated by roll-to-roll. In addition, "elongate shape" refers to an elongate shape in which the length is sufficiently long relative to the width, for example, an elongate shape in which the length is 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, 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, and particularly preferably is 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.

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 they are substantially equal. Therefore, there may be cases where 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, and particularly preferably 0.9 to 1.3. According to such an Nz coefficient, when a retardation film (polarizing plate with a retardation layer) is used for an image display device, excellent reflection color can be achieved, for example.

The retardation film may exhibit reverse dispersion wavelength characteristics in which the retardation value increases with the wavelength of the measurement light, or may exhibit positive wavelength dispersion characteristics in which the retardation value decreases with the wavelength of the measurement light. A flat wavelength dispersion characteristic that hardly changes even with the wavelength may be exhibited. In one embodiment, the retardation film exhibits reverse dispersion wavelength 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, excellent antireflection properties can be achieved, for example, when a retardation film (polarizing plate with a retardation layer) is used in an image display device.

The thickness of the retardation film may be appropriately set depending on the use and purpose. The thickness of the retardation film is preferably 10 μm to 60 μm, more preferably 20 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) of an angle θ with respect to the direction of a long picture. In this case, the retardation film has a slow axis (orientation angle of angle θ) in an oblique direction (direction of angle θ) with respect to the direction of a long picture. The inclination direction is preferably 30° to 60°, more preferably 40° to 50°, still more preferably 42° to 48°, and particularly preferably about 45° with respect to the elongated direction of the retardation film. am. Usually, since a polarizer has an absorption axis in the direction of a long picture, according to the retardation film of the shape of a long picture, it becomes possible to produce a polarizing plate with a retardation layer by roll-to-roll, and a manufacturing process can be simplified.

B-2. polarizer

The polarizer is typically an absorption type polarizer. The angle formed by the slow axis of the retardation film and the absorption axis of the polarizer may be appropriately set depending on the use and purpose. In one embodiment, the angle formed by the slow axis of the retardation film and the absorption axis of the polarizer is preferably 30° to 60°, more preferably 40° to 50°, still 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%, 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, still more preferably 99.9% or more.

A polarizer is typically a resin film containing a dichroic substance (eg, iodine). Examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene/vinyl acetate copolymer-based 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, and particularly preferably 3 μm to 8 μm.

A polarizer can be produced by arbitrary suitable methods. 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 performing a dyeing process by a dichroic substance such as iodine or a dichroic dye and an stretching process on a resin film. As the resin film, a hydrophilic polymer film such as a polyvinyl alcohol (PVA)-based film, a partially formalized PVA-based film, or an ethylene/vinyl acetate copolymer-based partially saponified film is used, for example. The method may further include insolubilization treatment, swelling treatment, crosslinking treatment, and the like. Since such a manufacturing method is well known and commonly used in the art, a detailed description thereof will be omitted.

As a specific example of a polarizer obtained using a laminate, 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 a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a layered product of and is mentioned. The details of the manufacturing method of such a polarizer are described, for example in Unexamined-Japanese-Patent No. 2012-73580 and Japanese Patent No. 6470455. As for these publications, the entire description is incorporated herein by reference.

B-3. protective layer

The protective layer may be formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material serving as 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, Transparent resins, such as cycloolefin types, such as a polysulfone type, polystyrene type, and polynorbornene type, a polyolefin type, (meth)acryl type, and an acetate type, are mentioned.

The said polarizing plate with a retardation layer is typically arrange|positioned on the viewing side of an image display apparatus. Therefore, the protective layer may be subjected to surface treatment such as hard coat (HC) treatment, antireflection treatment, anti-sticking treatment, and antiglare treatment as needed.

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 a thickness including the thickness of a surface treatment layer.

In one embodiment, the second protective layer is preferably optically isotropic. In this specification, '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.

B-4. adhesive layer

As a specific example of an adhesive layer, an adhesive bond layer and an adhesive layer are mentioned. 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. As the active energy ray-curable adhesive, any appropriate adhesive can be used 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 the curing type of the active energy ray curing type adhesive include a radical curing type, a cation curing type, an anion curing type, and a combination thereof (for example, a hybrid of a radical curing type and a cation curing type). Examples of the active energy ray curable adhesive include adhesives containing a compound (eg, monomer and/or oligomer) having a radically polymerizable group such as a (meth)acrylate group or a (meth)acrylamide group as a curing component. Specific examples of an active energy ray curable adhesive and a method for curing the same are described in, for example, Japanese Unexamined Patent Publication No. 2012-144690. The description of the said publication is incorporated as a reference in this specification.

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

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. In addition, the measuring method and evaluation method of each characteristic are as follows.

(1) Thickness

It was measured using a dial gauge (manufactured by PEACOCK, product name 'DG-205 type pds-2').

(2) Phase difference value

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

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

The central part of the film to be measured was cut into a square shape having a width of 50 mm and a length of 50 mm with one side parallel to the width direction of the film to obtain a test piece. This test piece was measured using Axoscan manufactured by Axometrics, and the orientation angle (θ) at a wavelength of 550 nm was measured.

(4) Glass transition temperature (Tg)

It was measured according to JIS K 7121.

[Example 1]

(Production of polyester carbonate resin film)

Polymerization was performed using a batch polymerization apparatus composed of two vertical reactors equipped with stirring blades and a reflux condenser 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), DPC 63.77 parts by mass part (0.298 mol) and 1.19 × 10 ^-2 parts by mass (6.78 × 10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After replacing the inside of the reactor with reduced pressure nitrogen, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100°C. The internal temperature reached 220°C 40 minutes after the start of the temperature rise, and while controlling to maintain this temperature, the pressure reduction was started, and after reaching 220°C, it was set to 13.3 kPa in 90 minutes. Phenol vapor produced as a by-product of the polymerization reaction was directed 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 directed to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor to once restore the pressure to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature increase and pressure reduction in the 2nd reactor were started, and it set the internal temperature to 240 degreeC and the pressure to 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined agitation power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, and the produced polyester carbonate was extruded into water to cut the strands to obtain pellets. Tg of the obtained polyester carbonate resin was 140 degreeC.

After vacuum drying the obtained polyester carbonate resin at 80 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250 ° C.), T die (width 250 mm, set temperature: 250 ° C.), chilled roll ( A polyester carbonate resin film having a thickness of 30 μm was produced using a film forming apparatus equipped with a set temperature: 120 to 130° C.) and a winder.

(formation of turn-up part)

While roll-conveying the obtained polyester carbonate resin film in its elongated direction, both ends in the width direction were turned up once using a guide to a width of 25 mm, respectively, to form a turn-up part.

(formation of joints)

In the folding region of both ends of the polyester carbonate resin film in the width direction, a joint (fused portion) was formed by ultrasonic waves. Specifically, fusion was performed by applying vibration of 20 kHz.

(oblique stretching)

A stretching device as shown in FIG. 1 for a polyester carbonate resin film having a turn-up portion and a joint portion formed thereon, the stretching device having an oven capable of independently controlling each of a preheating zone, an oblique stretching zone, and a release zone to a predetermined temperature. It obliquely stretched using, and obtained the retardation film.

Specifically, in the holding zone, the folding regions at both ends in the width direction of the film were held with clips on the left and right, and preheated at 145°C in the preheating zone. In the preheating zone, the clip pitch (P ₁ ) of the left and right clips was 125 mm.

Next, as soon as the film enters the oblique stretching zone, the increase in the clip pitch of the right clip and the decrease of the clip pitch of the left clip are started, and the clip pitch of the right clip is increased to P ₂ while the clip pitch of the left clip is started. was reduced to P ₃ . At this time, the clip pitch change rate (P ₂ /P ₁ ) of the right clip was 1.42, the clip pitch change rate (P ₃ /P ₁ ) of the left clip was 0.78, and the transverse stretch ratio to the original width of the film was 1.45 times. Then set the clip pitch of the right clip to P ₂ While holding, start increasing the clip pitch of the left clip, from P ₃ to P ₂ Increased. The rate of change of the clip pitch of the left clip between them (P ₂ /P ₃ ) was 1.82, and the transverse stretch ratio to the original width of the film was 1.9 times. Moreover, the drawing zone was set to Tg+3.2 degreeC (143.2 degreeC).

Then, in the release zone, heat setting was performed by holding the film at 125°C for 60 seconds. After the heat-set film was cooled to 100°C, the left and right clips were released and sent out from the exit of the stretching device.

In this way, a stretched (retardation) film (thickness: 12 μm, Re (550): 140 nm, angle formed by the slow axis direction and the elongated direction: 45°) was obtained.

[Example 2]

A stretched film (thickness: 16 μm) was obtained in the same manner as in Example 1 except that the thickness of the original fabric (polyester carbonate resin film before stretching) was changed to 40 μm.

[Example 3]

A stretched film (thickness: 26 μm) was obtained in the same manner as in Example 1 except that the thickness of the original fabric (polyester carbonate resin film before stretching) was changed to 65 μm.

[Comparative Example 1]

A stretched film was obtained in the same manner as in Example 1 except for not forming a junction.

[Comparative Example 2]

A stretched film was obtained in the same manner as in Example 1 except that the turn-up portion and the bonding portion were not formed.

About Examples and Comparative Examples, the following evaluation was performed. The evaluation results are summarized in Table 1.

<evaluation>

1. Fracture during stretching

It was confirmed whether breakage occurred in the film to be stretched during stretching.

2. Appearance and Handling

About the obtained stretched film, the appearance and handleability were visually evaluated based on the following criteria.

Good: Wrinkles and warping are not observed on the stretched film (stretching target film) during roll conveyance.

Defect: Wrinkles and/or warping are observed on the stretched film (stretching target film) during roll conveyance

[Table 1]

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

1: film to be stretched
2: laying film (turn-up part)
3: junction (fusion zone)
51: stretched film (phase difference film)
61: adhesive layer
71: polarizer
72: polarizer
73: protective layer
80: polarizing plate with retardation layer

Claims (8)

holding the end of the elongated film to be stretched in the width direction with a clip;
Stretching the film to be stretched in an oblique direction by driving the clip, and
and releasing the film to be stretched from the clip,
During the gripping, a laying film is disposed at an end of the film to be stretched in the width direction, the film to be stretched and the laid film are fused, and a region where the film to be stretched and the film overlap is gripped by the clip. and
The laying film is a turn-up portion obtained by turning up an end of the film to be stretched inward,
The junction between the film to be stretched and the laid film by the fusion bonding is formed in a line shape along the long direction of the film to be stretched,
A method for producing a stretched film. According to claim 1,
A manufacturing method in which the fusion is performed by ultrasonic waves. According to claim 1 or 2,
The manufacturing method in which the thickness of the film to be stretched before the stretching is 70 μm or less. According to claim 1 or 2,
The manufacturing method which performs the said turn-up once. According to claim 1 or 2,
The manufacturing method, wherein the thickness of the region where the film to be stretched and the laying film overlap is 40 μm or more. According to claim 1 or 2,
The width of the turn-up portion is 25 mm or more, manufacturing method. Obtaining a long stretched film by the manufacturing method according to claim 1 or 2, and
Continuously stacking the elongated stretched film and the elongated optical film while aligning the directions of each other while conveying the elongated optical film;
Including, the manufacturing method of the optical laminate. According to claim 7,
The optical film is a polarizer, the manufacturing method.

Images