JP6965757B2 - Method for manufacturing stretched film - Google Patents

Description

The present invention relates to a method for producing a stretched film in which an optical film is stretched to produce a stretched film.

Generally, image display devices such as televisions, notebook computers, and smartphones are equipped with polarizing plates. The polarizing plate is attached to a component of an image display device depending on the application. For example, in a liquid crystal display device which is a kind of image display device, polarizing plates are attached to the front surface side and the back surface side of the liquid crystal cell.

The above-mentioned polarizing plate includes a polarizing element and an optical film that protects the polarizing element. Usually, a polarizing plate is produced by adhering an optical film on one side or both sides of a polarizing element using an adhesive.

When mounting the polarizing plate on the liquid crystal display device, depending on the situation such as poor bonding or defects of the polarizing plate, it may be necessary to remove the polarizing plate from the liquid crystal cell and reattach it, so-called rework. In order to enable rework, it is essential to ensure the adhesiveness between the polarizing element constituting the polarizing plate and the optical film when the polarizing plate is peeled from the liquid crystal cell (peeling occurs between the two). Because it cannot be used as a polarizing plate). As a method for improving the adhesiveness between the polarizer and the optical film, an easy-adhesion treatment in which a corona treatment, a plasma treatment, an excimer light irradiation treatment, or the like is performed on the surface of the optical film has been conventionally known.

On the other hand, in the production of an optical film, in order to obtain an optical film having a desired form, it has been conventionally practiced to adjust the width and thickness of the optical film by stretching. Since the stretched optical film (hereinafter, also referred to as “stretched film”) is fragile, even if the adhesiveness at the interface between the stretched film and the polarizer can be ensured by the above-mentioned easy-adhesion treatment, the polarized light is polarized. When the plate is peeled from the liquid crystal cell, the stretched film itself is destroyed by applying stress in the thickness direction, so-called cohesive destruction (internal destruction, material destruction) often occurs. Since the cohesive failure of the stretched film occurs at an arbitrary position in the thickness direction of the stretched film, the easy-adhesion treatment performed on the surface of the stretched film is not an effective means for the above-mentioned cohesive breakage.

Here, an example of a method for suppressing cohesive failure is disclosed in Patent Document 1. In Patent Document 1, the stretched optical film is irradiated with an electron beam or a γ-ray. It is considered that the formation of crosslinks in the thickness direction in the stretched film by irradiation with an electron beam or the like is one of the reasons why the effect of suppressing cohesive fracture can be obtained.

JP-A-2017-134305 (see claim 1, paragraphs [0009], [0108], etc.)

By the way, in recent years, with the demand for larger (larger screen) or thinner liquid crystal display devices, there is an increasing demand for wider or thinner optical films (stretched films) used for polarizing plates. In order to produce an optical film that meets such demands, it is necessary to stretch the optical film at a higher magnification than before.

However, when the optical film is stretched at a high magnification, the degree of orientation of the polymer molecules (matrix molecules) of the optical film in the in-plane direction becomes high, which makes it easy for the entanglement between the matrix molecules in the thickness direction of the film to be dissociated. , Aggregation failure is likely to occur. In the method of Patent Document 1 described above, since the optical film in a state where the entanglement between the matrix molecules in the thickness direction is dissociated by stretching in the in-plane direction is irradiated with an electron beam or the like, a crosslink is formed in the thickness direction to be described above. The effect of suppressing the coagulation failure is insufficient, and it is considered that further improvement is necessary.

The present invention has been made to solve the above problems, and an object of the present invention is to ensure good adhesion to a polarizer and to prevent cohesive fracture during rework even when stretched at a high magnification. An object of the present invention is to provide a method for producing a stretched film that can be suppressed.

The above object of the present invention is achieved by the following manufacturing method.

1. 1. A method for producing a stretched film, which comprises at least one stretching step for stretching the optical film.
A shrinking step of shrinking the optical film in-plane and
The optical film is further provided with an irradiation step of irradiating the optical film with an electron beam or a γ-ray.
A method for producing a stretched film, which comprises performing the shrinkage step and the irradiation step before the final stretching step of at least one of the stretching steps.

2. The method for producing a stretched film according to 1, wherein the shrinking step and the irradiation step are performed in this order before the final stretching step.

3. 3. The method for producing a stretched film according to 1 or 2 above, wherein the optical film contains a cycloolefin resin.

According to the above-mentioned production method, the shrinkage step can promote the entanglement between the matrix molecules in the film thickness direction. In addition, the irradiation step can enhance the cross-linking between matrix molecules in the film thickness direction. Since the final stretching step is performed after these two steps, even if the optical film is stretched in the in-plane direction at a high magnification, the dissociation of the entanglement between the matrix molecules in the film thickness direction can be suppressed. As a result, even when a polarizing plate is formed using an optical film (stretched film) stretched at a high magnification and the polarizing plate is reworked (even when the polarizing plate is peeled off from the liquid crystal cell), the stretched film is coagulated and broken. Can be suppressed. Further, in the stretched film, the entanglement between the matrix molecules is promoted and the cross-linking is enhanced, so that when the stretched film and the polarizer are adhered with an adhesive to prepare a polarizing plate, the entangled portion between the molecules is formed. The adhesive easily penetrates into the inside of the stretched film. As a result, the peel strength of the stretched film with respect to the polarizer can be improved, and good adhesion to the polarizer can be ensured.

It is a flowchart which shows the flow of the process by the manufacturing method of the stretch film which concerns on embodiment of this invention. It is explanatory drawing which shows typically the schematic structure of the apparatus which manufactures an optical film by a solution casting film forming method. It is a flowchart which shows the flow of the manufacturing process of the said optical film. It is a top view which shows typically the schematic structure of the oblique stretching apparatus. It is a top view which shows typically an example of the rail pattern of the stretch part of the said diagonal stretching apparatus. It is sectional drawing which shows the schematic structure of the liquid crystal display device to which the said stretch film is applied.

An embodiment of the present invention will be described below with reference to the drawings. In this specification, when the numerical range is expressed as A to B, the numerical range includes the values of the lower limit A and the upper limit B. Further, in the present specification, the "stretched film" refers to a film after stretching the "optical film". The present invention is not limited to the following contents.

[Manufacturing method of stretched film]
FIG. 1 is a flowchart showing a processing flow according to the method for producing a stretched film of the present embodiment. The method for producing a stretched film of the present embodiment includes a shrinkage step (S1), an irradiation step (S2), and at least one stretching step (S3).

The shrinkage step is a step of shrinking the optical film in-plane. In this shrinkage step, for example, in the film formation of an optical film by the solution casting film forming method described later, the casting film (web, optical film) after peeling from the support is stretched in the MD direction (Machine Direction). It is done by. In this case, the optical film shrinks in the TD direction (Traverse Direction) orthogonal to the MD direction in the film plane.

The irradiation step is an irradiation step of irradiating an optical film with an electron beam or a γ-ray. The electron beam irradiation can be performed using, for example, an electron beam irradiation device or the like. The irradiation amount of the electron beam can be appropriately adjusted so as to obtain a desired peeling intensity. Specifically, the absorbed dose is preferably 500 kGy or more, more preferably 6000 kGy or more, preferably 1500 kGy or less, and more preferably 1200 kGy or less. The acceleration voltage when irradiating the electron beam is preferably 150 kV or more, preferably 250 kV or less. Irradiation of γ-rays can be performed using, for example, a γ-ray irradiation device. The irradiation dose of γ-rays can be the same as that of electron beams as the absorbed dose.

The atmosphere when the irradiation step is performed is not particularly limited, and may be an air atmosphere or an inert gas atmosphere. As the inert gas, a gas such as nitrogen, argon or helium can be used. In particular, it is preferable to create an atmosphere in which the oxygen concentration is less than 300 ppm because the inhibition of cross-linking by oxygen can be suppressed. The temperature at which the irradiation step is performed is not particularly limited, and can be, for example, a normal temperature of 10 ° C. or higher and 30 ° C. or lower. The conditions for irradiating the electron beam or the like may be the same as the conditions disclosed in Patent Document 1 described above, except for the timing of the irradiation of the electron beam or the like (before or after the stretching step). It is possible, and in particular, it is preferable to use the conditions of Example 1 of Patent Document 1.

The stretching step may be a step of stretching the optical film only in the MD direction in the film surface, a step of stretching only in the TD direction, or an oblique step with respect to both the MD direction and the TD direction. It may be a step of stretching in the direction. Such stretching can be performed using a stretching machine (including a diagonal stretching device). Further, the stretching step may be performed before winding the formed optical film, or is performed on the optical film that is once wound to form a film roll and then unwound from the film roll. You may.

In the production of the optical film, the stretching step is performed at least once in this embodiment. However, the above-mentioned shrinking step of S1 and the irradiation step of S2 are performed before the final stretching step of at least one of the above. Therefore, for example, when the stretching step is once, the shrinking step, the irradiation step, and the stretching step may be performed in this order, or the irradiation step, the shrinking step, and the stretching step may be performed in this order. When the stretching step is performed twice, the shrinking step, the stretching step (first stretching step), the irradiation step, and the stretching step (second stretching step) may be performed in this order. The stretching step (for example, the first stretching step) may also serve as a shrinking step.

According to the method for producing a stretched film of the present embodiment, the shrinkage step promotes entanglement between polymer molecules (matrix molecules) in the film thickness direction. In addition, the irradiation step enhances the cross-linking between the matrix molecules in the thickness direction of the optical film. Therefore, even if the optical film is stretched at a high magnification in the final stretching step after that, the dissociation of the entanglement between the matrix molecules can be effectively suppressed. As a result, even when a polarizing plate is formed using an optical film (stretched film) stretched at a high magnification, the polarizing plate is attached to a liquid crystal cell, and then the polarizing plate is peeled off and reattached, the rework is performed. It is possible to suppress the cohesive failure of the stretched film at the time.

Moreover, since the entanglement between the matrix molecules is promoted in the stretched film and the cross-linking is enhanced, the adhesive is entangled between the matrix molecules even when the stretched film is adhered to the stretched film via an adhesive at the time of producing the polarizing plate. It becomes easy to penetrate into the film through the portion (crosslinked portion). As a result, the stretched film can be firmly fixed to the polarizer via an adhesive, and the peel strength of the stretched film with respect to the polarizer can be improved. That is, good adhesion between the stretched film and the polarizer can be ensured.

Further, by performing the shrinkage step and the irradiation step in this order before the final stretching step, the entanglement between the matrix molecules promoted by the shrinkage step can be further strengthened by the irradiation step, and the cross-linking can be performed. Can be surely increased. As a result, the dissociation of the entanglement between the matrix molecules due to the subsequent high-magnification stretching can be reliably suppressed, and the cohesive failure of the stretched film stretched at the high-magnification can be reliably suppressed. Further, since the adhesive is more easily penetrated into the stretched film at the time of adhering to the polarizing element, good adhesiveness between the stretched film and the polarizer can be surely ensured.

The shrinkage step may be performed after the irradiation step, that is, after irradiating the optical film with an electron beam or the like. However, it was found that when a polarizing plate is formed using the stretched film produced in this manner, the adhesiveness at the interface between the polarizer and the stretched film tends to be slightly deteriorated. It is presumed that this is because when the matrix molecules are shrunk in a state of being entangled with each other by irradiating them with an electron beam or the like, the density of the molecules increases excessively and the adhesive becomes difficult to penetrate into the film. Therefore, from the viewpoint of avoiding the deterioration of the adhesiveness of the polarizing plate, the shrinkage step is preferably performed before the irradiation step.

Further, as the resin constituting the above optical film, a cycloolefin-based resin (COP), a cellulose ester-based resin, a polycarbonate-based resin, or the like can be used. However, it is desirable to use COP because it is easy to control the stretchability and crystallinity, and it is easy for the adhesive to penetrate and it is possible to secure better adhesiveness with the polarizer. That is, it is desirable that the optical film is composed of COP.

Here, in the shrinkage step, if the shrinkage rate of the optical film is too small, the effect of promoting entanglement between matrix molecules is insufficient, and if it is too large, there is a concern that the production efficiency of the optical film (stretched film) is lowered. Will be done. Therefore, the shrinkage rate of the optical film in the shrinkage step is preferably 5% to 50%, more preferably 10% to 30%.

Further, in order to secure a high phase difference, secure a wide width, and promote the penetration of the adhesive when adhering to the polarizer, it is preferable to stretch the optical film at a high magnification in the stretching step. However, if the draw ratio is too high, the stretch stress causes craze in the film or dissociates the entanglement between the matrix molecules that maintain the film strength, weakening the film. Therefore, the stretching ratio in the stretching step is preferably 1.1 times to 5 times, more preferably 1.3 times to 3 times. Further, although the stretching direction is not limited, it is preferable to include stretching in the width direction at least from the viewpoint of obtaining a wide stretched film.

When the stretching is performed a plurality of times, it is preferable that the stretching at the highest magnification, which has the highest risk of dissociation of the matrix molecules, is performed in the final stretching. That is, among the plurality of stretchings, the stretching at the highest magnification is preferably performed after obtaining the shrinkage step and the irradiation step (for example, shrinkage (low magnification stretching), irradiation, high magnification stretching, etc.). In this case, the entanglement of the matrix molecules can be strengthened by the contraction step and the irradiation step until the stretching at the maximum magnification. It can be suppressed.

[Physical characteristics of stretched film]
The in-plane retardation Ro of the stretched film obtained by the production method of the present embodiment is preferably 10 nm to 300 nm, more preferably 30 nm to 180 nm. The retardation Rt in the thickness direction of the stretched film is preferably 10 nm to 300 nm, more preferably 50 nm to 200 nm. Further, the film thickness of the stretched film is preferably 10 μm to 70 μm, more preferably 30 to 50 μm.

[Manufacturing method of optical film]
Next, a method for producing an optical film that is the basis of the stretched film described above will be described. The method for producing the optical film is not particularly limited, and for example, the optical film can be produced by using the solution casting film forming method or the melt casting film forming method shown below.

(Solution casting film forming method)
FIG. 2 schematically shows a schematic configuration of an apparatus for producing an optical film by a solution casting film forming method. Further, FIG. 3 is a flowchart showing the flow of the manufacturing process of the optical film. The method for producing an optical film by the solution casting film forming method includes a stirring preparation step (S11), a casting step (S12), a peeling step (S13), a shrinkage step (S14), a first drying step (S15), and an irradiation step. (S16), a stretching step (S17), a second drying step (S18), a cutting step (S19), an embossing step (S20), and a winding step (S21) are included. The manufacturing method does not have to include both the first drying step (S15) and the second drying step (S18), and may include at least one of the steps.

The shrinkage step (S1) and the irradiation step (S2) shown in FIG. 1 correspond to, for example, the shrinkage step (S14) and the irradiation step (S16) of FIG. Further, the stretching step (S3) shown in FIG. 1 corresponds to, for example, the stretching step (S17) of FIG. In the winding step of S21, a wound body (film roll) of the stretched film is obtained. The optical film was re-wound from the wound body of the optical film formed by a normal method (for example, without a shrinking step and an irradiation step), and the unwound optical film was subjected to the shrinking step (S1) of FIG. All of the irradiation step (S2) and the stretching step (S3) may be performed.

<Stirring preparation process>
In the stirring preparation step of S11, at least the resin and the solvent are stirred in the stirring tank 1a of the stirring device 1 to prepare a dope to be cast on the support 3 (endless belt). As the resin, a cycloolefin resin (COP), a cellulose ester resin, a polycarbonate resin, or the like can be assumed. As the solvent, a mixed solvent of a good solvent and a poor solvent is used.

<Hypersalivation process>
In the casting step of S12, the dope prepared in the stirring preparation step is sent to the casting die 2 by a conduit through a pressurized metering gear pump or the like, and is transferred indefinitely to a support made of a rotary drive stainless steel endless belt. Dope is spread from the casting die 2 to the casting position on 3. Then, the cast dope is dried on the support 3 to form a cast film 5 (web). The inclination of the casting die 2, that is, the ejection direction of the dope from the casting die 2 to the support 3, is 0 ° to 90 ° at an angle with respect to the normal of the surface of the support 3 (the surface on which the dope is cast). It may be appropriately set so as to be within the range of.

The support 3 is composed of, for example, a stainless steel belt, and is held by a pair of rolls 3a and 3b and a plurality of rolls (not shown) located between them. One or both of the rolls 3a and 3b is provided with a driving device (not shown) for applying tension to the support 3, whereby the support 3 is used in a tensioned state. The support 3 may be a drum.

In the casting step, the casting film 5 formed by the dope spread on the support 3 is heated on the support 3, and the casting film 5 can be peeled from the support 3 by the peeling roll 4. Evaporate the solvent until. To evaporate the solvent, there are a method of blowing wind from the web side, a method of transferring heat from the back surface of the support 3 with a liquid, a method of transferring heat from the front and back surfaces by radiant heat, etc., and they are used individually or in combination as appropriate. Just do it.

<Peeling process>
In the casting step of S12, the casting film 5 is dried and solidified or cooled and solidified until the film strength becomes peelable on the support 3, and then in the peeling step of S13, the casting film 5 is self-supporting. It is peeled off by the peeling roll 4 while holding the above.

The amount of residual solvent on the casting film 5 on the support 3 at the time of peeling is preferably in the range of 50 to 120% by mass depending on the strength of the drying conditions, the length of the support 3, and the like. When peeling at a time when the amount of residual solvent is larger, if the casting film 5 is too soft, the flatness at the time of peeling is impaired, and wrinkles and vertical streaks are likely to occur due to the peeling tension. The amount of residual solvent is determined. The amount of residual solvent is defined by the following formula.

Residual solvent amount (mass%) = (mass before heat treatment of web-mass after heat treatment of web) /
(Mass after heat treatment of web) x 100
Here, the heat treatment for measuring the amount of residual solvent means that the heat treatment is performed at 115 ° C. for 1 hour.

<Shrinking process>
In the shrinking step of S14, the casting film 5 (optical film F) is shrunk in the width direction. As a method of contracting the flow film 5, for example, (1) the flow film 5 is treated at a high temperature without holding the width to increase the density of the flow film 5, and (2) with respect to the flow film 5. By applying tension in the transport direction (MD direction), the flow film 5 is contracted in the width direction (TD direction), (3) the amount of residual solvent in the flow film 5 is sharply reduced, and the like. be.

<First drying process>
In the first drying step of S15, the casting film 5 (optical film F) peeled off from the support 3 is dried by the drying device 6. In the drying device 6, the casting film 5 is conveyed by a plurality of conveying rolls arranged in a staggered pattern when viewed from the side surface, and the casting film 5 is dried between them. The drying method in the drying device 6 is not particularly limited, and generally, the casting film 5 is dried using hot air, infrared rays, a heating roll, microwaves, or the like. From the viewpoint of simplicity, a method of drying the cast film 5 with hot air is preferable. The first drying step may be performed as needed.

<Irradiation process>
In the irradiation step of S16, the irradiation device 7 irradiates the optical film F with electron beams or γ-rays. This irradiation step enhances the cross-linking between the matrix molecules in the thickness direction of the optical film F. The irradiation device 7 may be provided at any position on the upstream side of the tenter 8 in the transport direction, and may be provided between the peeling roll 4 and the drying device 6, for example.

<Stretching process>
In the stretching step of S17, the optical film F irradiated with the electron beam or γ-ray in S16 is stretched by the tenter 8. The stretching direction at this time is one of the MD direction, the TD direction, and both of these directions. In the stretching step, a tenter method in which both side edges of the optical film F are fixed with clips or the like and stretched is preferable in order to improve the flatness and dimensional stability of the film. In the tenter 8, drying may be performed in addition to stretching.

<Second drying process>
In the second drying step of S18, the optical film F stretched by the tenter 8 is dried by the drying device 9. In the drying device 9, the optical film F is conveyed by a plurality of conveying rolls arranged in a staggered pattern when viewed from the side surface, and the optical film F is dried between them. The drying method in the drying device 9 is not particularly limited, and generally, the optical film F is dried using hot air, infrared rays, a heating roll, microwaves, or the like. From the viewpoint of simplicity, a method of drying the optical film F with hot air is preferable. The optical film F is dried by the drying device 9 and then conveyed toward the winding device 12.

<Cutting process, embossing process>
In the cutting step of S19, the cutting portion 10 made of a slitter cuts both ends of the formed optical film F in the width direction. In the optical film F, the portion remaining after cutting both ends constitutes a product portion to be a film product. On the other hand, the portion cut from the optical film F is recovered by a shooter and reused as a part of the raw material for film formation.

After the cutting step of S19, in the embossing step of S20, the embossing section 11 performs embossing (nerling) on both ends of the optical film F in the width direction. The embossing process is performed by pressing a heated embossing roller against both ends of the optical film F. Fine irregularities are formed on the surface of the embossing roller, and by pressing the embossing roller against both ends of the optical film F, the irregularities are formed on both ends. By such embossing, winding misalignment and blocking (sticking between films) in the next winding process can be suppressed as much as possible.

<Winding process>
Finally, in the winding step of S21, the optical film F having been embossed is wound by the winding device 12 to obtain a film roll. That is, in the winding step, a film roll is manufactured by winding the optical film F around the winding core while conveying it. As the winding method of the optical film F, a commonly used winder may be used, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, and a program tension control method with a constant internal stress. You can use them properly.

(Melting flow film forming method)
In the melt casting film forming method, a resin composition containing an additive such as a resin and a plasticizer is heated and melted to a temperature showing fluidity, and then the fluidized melt is cast to produce an optical film. It is a method of filming. A stretched film is obtained by performing the shrinkage step (S1), the irradiation step (S2), and the stretching step (S3) shown in FIG. 1 on the optical film formed by the melt casting film forming method. Can be done.

The method formed by melt casting can be classified into a melt extrusion (molding) method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method and the like. Among these, a melt extrusion method that can obtain a film having excellent mechanical strength and surface accuracy is preferable. Further, it is usually preferable that the plurality of raw materials used in the melt extrusion method are kneaded in advance and pelletized.

Pelletization may be carried out by a known method. For example, dry resin, plasticizer, and other additives are supplied to the extruder with a feeder, kneaded using a single-screw or twin-screw extruder, extruded from a die into strands, water-cooled or air-cooled, and cut. Can be pelletized with.

The additive may be mixed with the resin before being supplied to the extruder, or the additive and the resin may be supplied to the extruder by separate feeders. Further, since a small amount of additives such as particles and antioxidants are mixed uniformly, it is preferable to mix them with the resin in advance.

It is preferable that the extruder can be pelletized and processed at a low temperature as much as possible so as to suppress the shearing force and prevent the resin from deteriorating (reducing molecular weight, coloring, gel formation, etc.). For example, in the case of a twin-screw extruder, it is preferable to use a deep groove type screw to rotate in the same direction. The meshing type is preferable because of the uniformity of kneading.

Film formation is performed using the pellets obtained as described above. Of course, it is also possible to supply the raw material powder as it is to the extruder by a feeder without pelletizing it and to form a film as it is.

The pellets are extruded using a single-screw or two-screw type extruder to a melting temperature of about 200 to 300 ° C., and filtered with a leaf disc type filter to remove foreign matter, and then the film is removed from the T-die. The film is cast in a shape, the film is nipped with a cooling roll and an elastic touch roll, and the film is solidified on the cooling roll.

When the pellets are introduced from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or an atmosphere of an inert gas.

It is preferable that the extrusion flow rate is stable by introducing a gear pump or the like. Further, as the filter used for removing foreign substances, a stainless fiber sintered filter is preferably used. The stainless fiber sintered filter is made by creating a complicated entangled state of stainless steel fibers, compressing them, and sintering the contact points to integrate them. The density is changed according to the thickness and compression amount of the fibers to improve the filtration accuracy. Can be adjusted.

Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. It is preferable to use a mixing device such as a static mixer for uniform addition.

The film temperature on the touch roll side when niping the film with the cooling roll and the elastic touch roll is preferably Tg (glass transition temperature) or more and Tg + 110 ° C. or less of the film. A known roll can be used as the roll having an elastic surface used for such a purpose.

The elastic touch roll is also called a pinching rotating body. As the elastic touch roll, a commercially available one can also be used.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent the film from being deformed.

[Details of polymer resin]
The polymer resin (matrix resin) contained in the optical film or stretched film of the present embodiment is not particularly limited, but when the stretched film is used for optical applications, it has a property of being transparent to a desired wavelength. It is preferable to use a resin. Examples of such resins include cycloolefin-based resins, cellulose ester-based resins, polycarbonate-based resins, polyether sulfone-based resins, polyethylene terephthalate-based resins, polyimide-based resins, polymethylmethacrylate-based resins, polysulfone-based resins, and polyarylate-based resins. Examples thereof include resins, polyethylene-based resins, and polyvinyl chloride-based resins.

Among these, it is preferable to use a cycloolefin resin, a cellulose ester resin, or a polycarbonate resin from the viewpoint of transparency and mechanical strength. Hereinafter, the details of the cycloolefin-based resin, the cellulose ester-based resin, and the polycarbonate-based resin preferably used in the present embodiment will be described.

<Cycloolefin resin>
Examples of the cycloolefin-based resin include (co) polymers having the following structures.

式中、Ｒ^１〜Ｒ^４は、それぞれ独立に、水素原子、炭化水素基、ハロゲン原子、ヒドロキシ基、エステル基、アルコキシ基、シアノ基、アミド基、イミド基、シリル基、または極性基（すなわち、ハロゲン原子、ヒドロキシ基、エステル基、アルコキシ基、シアノ基、アミド基、イミド基、またはシリル基）で置換された炭化水素基である。ただし、Ｒ^１〜Ｒ^４は、２つ以上が互いに結合して、不飽和結合、単環又は多環を形成していてもよく、この単環または多環は、二重結合を有していても、芳香環を形成してもよい。Ｒ^１とＲ^２とで、またはＲ^３とＲ^４とで、アルキリデン基を形成していてもよい。ｐ、ｍは０以上の整数である。

In the formula, R ^{1 to} R ⁴ independently represent a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxy group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, a silyl group, or a polar group (that is, a polar group). , Halogen atom, hydroxy group, ester group, alkoxy group, cyano group, amide group, imide group, or silyl group). However, in R ^{1 to} R ⁴ , two or more of them may be bonded to each other to form an unsaturated bond, a monocyclic ring or a polycyclic ring, and the monocyclic or polycyclic ring has a double bond. Alternatively, an aromatic ring may be formed. R ¹ and R ² or R ³ and R ⁴ may form an alkylidene group. p and m are integers of 0 or more.

In the above general formula, R ¹ and R ³ are hydrogen atoms or hydrocarbon groups having 1 to 10 carbon atoms, more preferably 1 to 4, particularly preferably 1 to ^2, and R ^{2 and R 4} are hydrogen atoms. Alternatively, it is a monovalent organic group, ^{and at least one of R 2} and R ⁴ represents a polar group having a polarity other than a hydrogen atom and a hydrocarbon group, m is an integer of 0 to 3, and p is 0 to 3. It is an integer of m + p = 0 to 4, more preferably 0 to 2, and particularly preferably m = 1 and p = 0. The specific monomer having m = 1 and p = 0 is preferable because the obtained cycloolefin resin has a high glass transition temperature and excellent mechanical strength.

Examples of the polar group of the specific monomer include a carboxy group, a hydroxy group, an alkoxycarbonyl group, an allyloxycarbonyl group, an amino group, an amide group, a cyano group and the like, and these polar groups are linking groups such as a methylene group. It may be connected via. Further, a hydrocarbon group to which a polar divalent organic group such as a carbonyl group, an ether group, a silyl ether group, a thioether group and an imino group is bonded as a linking group is also mentioned as a polar group. Among these, a carboxy group, a hydroxy group, an alkoxycarbonyl group or an aryloxycarbonyl group is preferable, and an alkoxycarbonyl group or an aryloxycarbonyl group is particularly preferable.

Further, as for the monomer in which at least one of ^{R 2} and R ⁴ _{is a polar group represented by the formula − (CH 2} ) _n COOR, the obtained cycloolefin resin has a high glass transition temperature, low hygroscopicity, and various types. It is preferable in that it has excellent adhesion to the material. In the above formula for the specific polar group, R is a hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 4, particularly preferably 1 to 2, an alkyl group.

Specific examples of the copolymerizable monomer include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene, and norbornene.

The number of carbon atoms of the cycloolefin is preferably 4 to 20, and more preferably 5 to 12.

In the present embodiment, the cycloolefin-based resin can be composed of one type alone or in combination of two or more types.

The cycloolefin-based resin of the present embodiment has an intrinsic viscosity [η] inh of 0.2 to 5 dL / g, more preferably 0.3 to 3 dL / g, and particularly preferably 0.4 to 1.5 dL / g. The polystyrene-equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) is 8,000 to 100,000, more preferably 1,000 to 80,000, particularly preferably 12,000 to 50,000, and the weight average molecular weight (Mw) is 20,000. It is preferably in the range of ~ 300,000, more preferably 30,000 to 250,000, and particularly preferably 40,000 to 200,000.

When the intrinsic viscosity [η] inh, the number average molecular weight and the weight average molecular weight are in the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties of the cycloolefin resin and the molding processability as a cycloolefin film are obtained. And become good.

The glass transition temperature (Tg) of the cycloolefin resin of the present embodiment is usually 110 ° C. or higher, preferably 110 to 350 ° C., more preferably 120 to 250 ° C., and particularly preferably 120 to 220 ° C. If the Tg is less than 110 ° C., it is not preferable because it is deformed by use under high temperature conditions or by secondary processing such as coating and printing. On the other hand, if Tg exceeds 350 ° C., the molding process becomes difficult, and the possibility that the resin is deteriorated by the heat during the molding process increases.

The polarizing plate protective film has a resin layer containing a cycloolefin resin as a main component. The main component means that 50% by mass or more of the resin layer is a cycloolefin-based resin, and preferably 70 to 90% by mass or more.

The cycloolefin-based resin is a specific hydrocarbon-based resin described in, for example, JP-A-9-221577 and JP-A-10-287732, or a known hydrocarbon-based resin, as long as the effects of the present embodiment are not impaired. A thermoplastic resin, a thermoplastic elastomer, a rubber polymer, organic fine particles, inorganic fine particles, etc. may be blended, and a specific wavelength dispersant, a sugar ester compound (also simply referred to as a sugar ester), an antioxidant, a peeling accelerator, etc. may be blended. , Rubber particles, plasticizers, and other additives may be included. The details of the additive will be described later.

As the cycloolefin-based resin described above, a commercially available product can be preferably used. Examples of commercially available products include those sold by JSR Corporation under the trade names of ARTON G, ARTON F, ARTON R, and ARTON RX, and ZEONOR from Nippon Zeon Corporation. ) ZF14, ZF16, ZEONEX 250 or ZEONEX 280, which are commercially available under the trade name, can be used.

<Cellulose ester resin>
Preferred cellulose ester-based resins include cellulose acylates satisfying the following formulas (1) and (2).
Equation (1) 2.0 ≤ Z1 <3.0
Equation (2) 0 ≤ X <3.0
(In formulas (1) and (2), Z1 represents the total acyl group substitution of cellulose acylate, and X represents the sum of the propionyl group substitution and butyryl group substitution of cellulose acylate.)

Examples of cellulose as a raw material for the cellulose ester include, but are not limited to, cotton linter, wood pulp, and kenaf. In addition, the cellulose esters obtained from them can be mixed and used in arbitrary proportions.

The cellulose acylate is preferably a cellulose acylate having a total acyl group substitution degree in the range of 2.2 to 2.8 from the viewpoint of improving water resistance, and also has flowability and stretching during film formation. From the viewpoint of improving the properties and further improving the uniformity of the film thickness, the total acyl group substitution degree of the cellulose acylate is preferably 2.1 to 2.5.

The degree of substitution of acetyl groups and the degree of substitution of other acyl groups are specified in ASTM-D817-96, which is one of the standards established and issued by ASTM (American Society for Testing and Materials). It can be measured according to the above.

The cellulose acylate must be at least one selected from cellulose acetate (cellulose diacetate, cellulose triacetate), cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate. Of these, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate are more preferable.

The weight average molecular weight (Mw) of the cellulose acylate is preferably 75,000 or more, more preferably in the range of 75,000 to 300,000, further preferably in the range of 100,000 to 240000, and 160000 to 240000. Especially preferable. When the weight average molecular weight (Mw) of the cellulose acylate resin is 75,000 or more, the effect of improving the self-deposition property and adhesion of the cellulose acylate layer itself is exhibited, which is preferable. In the present embodiment, two or more kinds of cellulose acylate resins can be mixed and used.

The average molecular weight (Mn, Mw) of cellulose acylate can be measured by gel permeation chromatography under the following measurement conditions.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Three made by Showa Denko KK were connected and used)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) A calibration curve with 13 samples in the range of Mw = 500 to 2800000 was used. The 13 samples are preferably used at approximately equal intervals.

<Polycarbonate resin>
As the polycarbonate-based resin, various ones can be used without particular limitation, and an aromatic polycarbonate resin is preferable from the viewpoint of chemical properties and physical properties, and a bisphenol A-based polycarbonate resin is particularly preferable. Among them, those using a bisphenol A derivative in which a benzene ring, a cyclohexane ring, an aliphatic hydrocarbon group and the like are introduced into bisphenol A are more preferable. Further, a polycarbonate resin having a structure in which the anisotropy in the unit molecule is reduced, which is obtained by using a derivative in which the functional group is asymmetrically introduced with respect to the central carbon of bisphenol A, is particularly preferable. Examples of such a polycarbonate-based resin include those in which the two methyl groups of the central carbon of bisphenol A are replaced with benzene rings, and the hydrogen of one benzene ring of bisphenol A is replaced by a methyl group or a phenyl group. A polycarbonate resin obtained by substituting asymmetrically with respect to the central carbon is particularly preferable.

Specifically, it is obtained from 4,4'-dihydroxydiphenylalkane or a halogen-substituted product thereof by a phosgene method or a transesterification method, for example, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl. Examples thereof include ethane, 4,4'-dihydroxydiphenylbutane and the like. In addition, for example, Japanese Patent Application Laid-Open No. 2006-215465, Japanese Patent Application Laid-Open No. 2006-91836, Japanese Patent Application Laid-Open No. 2005-121813, Japanese Patent Application Laid-Open No. 2003-167121, Japanese Patent Application Laid-Open No. 2009-126128, Japanese Patent Application Laid-Open No. Examples thereof include polycarbonate-based resins described in Japanese Patent Application Laid-Open No. 2012-31369, Japanese Patent Application Laid-Open No. 2012-67300, International Publication No. 00/26705, and the like.

The polycarbonate-based resin may be mixed with a transparent resin such as a polystyrene-based resin, a methyl methacrylate-based resin, and a cellulose acetate-based resin. Further, a resin layer containing a polycarbonate resin may be laminated on at least one surface of a resin film formed by using a cellulose acetate resin.

The polycarbonate resin preferably has a glass transition point (Tg) of 110 ° C. or higher and a water absorption rate of 0.3% or less (measured in water at 23 ° C. for 24 hours). Further, it is more preferable that the Tg is 120 ° C. or higher and the water absorption rate is 0.2% or lower.

〔Additive〕
The optical film or stretched film of the present embodiment may appropriately contain additives depending on the intended use. As the additive, for example, a benzotriazole-based ultraviolet absorber, a triazine-based ultraviolet absorber, a polyester-based additive, fine particles, and the like are particularly preferably used.

The preferable range of the amount added to the cycloolefin resin differs depending on the additive. In the case of a benzotriazole-based or triazine-based ultraviolet absorber, the amount added thereof is preferably in the range of 0.5 to 5% by mass, more preferably in the range of 1 to 4% by mass. In the case of a polyester-based additive having a structure represented by the following general formula (1), the addition amount thereof is preferably in the range of 1 to 10% by mass, more preferably in the range of 3 to 8% by mass. Is.

(Benzotriazole-based UV absorber and triazine-based UV absorber)
The benzotriazole-based ultraviolet absorber is not particularly limited, and is, for example, 2- (2'-hydroxy-5-methylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-t-. Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2,2'-methylenebis [6- (2H-benzotriazole-2-yl)- 4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; LA31 of ADEKA Co., Ltd. as an example of a commercially available product), 2- (2H-benzotriazole-2-yl) -4,6 -Bis (1-methyl-1-phenylethyl) phenol (molecular weight 447.6; examples of commercially available products include tinuvin 234 and 928 of BASF Japan Ltd.).

The triazine-based ultraviolet absorber is not particularly limited, and is, for example, 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6-. (2-Hydroxy-4-ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-Hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4- Diphenyl-6- (2-hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5- Triazine, 2,4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl)- 1,3,5-Triazine, [2- (4,6-diphenyl-1,3,5-triazine-2-yl) -5- (hexyl) oxyphenol] (Tinubin 1577FF, trade name, manufactured by BASF Japan, Inc.) ), [2- [4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine-2-yl] -5- (octyloxy) phenol] (CYASORB UV-1164, trade name, (Made by Cytec Industries) and the like.

(Polyester additive)
In the polyester-based additive, after the dehydration condensation reaction of the diol and the dicarboxylic acid, the hydroxy group (derived from the diol) at the molecular end of the obtained reaction product is changed to the carboxy group of the hydroxy group-containing monocarboxylic acid having a ring structure. It is a compound obtained by undergoing a dehydration condensation reaction with.

The polyester-based additive is a compound having a structure represented by the following general formula (1).
General formula (1): B- (GA _{) n-GB}
In the formula, B is a group derived from a hydroxy group-containing monocarboxylic acid having a ring structure. The ring structure refers to a structure having an aliphatic hydrocarbon ring, an aliphatic hetero ring, an aromatic hydrocarbon ring or an aromatic hetero ring, and preferably a structure having an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring. .. The hydroxy group-containing monocarboxylic acid having a ring structure can be an alicyclic monocarboxylic acid having 5 to 20 carbon atoms, an aromatic monocarboxylic acid having 7 to 20 carbon atoms, or a mixture thereof.

The alicyclic monocarboxylic acid having 5 to 20 carbon atoms can be preferably an alicyclic monocarboxylic acid having 6 to 15 carbon atoms. Examples of alicyclic monocarboxylic acids include 4-hydroxycyclohexyl acetic acid, 3-hydroxycyclohexyl acetic acid, 2-hydroxycyclohexyl acetic acid, 4-hydroxycyclohexylpropionic acid, 4-hydroxycyclohexylbutyric acid, 4-hydroxycyclohexylglycolic acid, 4 -Hydroxy-o-methylcyclohexylacetic acid, 4-hydroxy-m-methylcyclohexylacetic acid, 4-hydroxy-p-methylcyclohexylacetic acid, 5-hydroxy-m-methylcyclohexylacetic acid, 6-hydroxy-o-methylcyclohexylacetic acid, 2 , 4-Dihydroxycyclohexylacetic acid, 2,5-dihydroxycyclohexylacetic acid, 2- (hydroxymethyl) cyclohexylacetic acid, 3- (hydroxymethyl)cyclohexylacetic acid, 4- (hydroxymethyl)cyclohexylacetic acid, 2- (1-hydroxy-1) -Methylethyl) cyclohexyl acetic acid, 3- (1-hydroxy-1-methylethyl) cyclohexyl acetic acid, 4- (1-hydroxy-1-methylethyl) cyclohexyl acetic acid and the like are included.

The aromatic monocarboxylic acid having 5 to 20 carbon atoms can be preferably an aromatic monocarboxylic acid having 6 to 15 carbon atoms. Examples of aromatic monocarboxylic acids include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-o-toluic acid, 3-hydroxy-p-toluic acid, 5-hydroxy-. m-toluic acid, 6-hydroxy-o-toluic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2- (hydroxymethyl) benzoic acid, 3- (hydroxymethyl) benzoic acid, 4- (Hydroxymethyl) benzoic acid, 2- (1-hydroxy-1-methylethyl) benzoic acid, 3- (1-hydroxy-1-methylethyl) benzoic acid, 4- (1-hydroxy-1-methylethyl) benzoic acid Contains acids and the like.

Among these, a hydroxy group-containing monocarboxylic acid containing an aromatic ring (aromatic monocarboxylic acid containing a hydroxy group) is provided with sufficient hydrophobicity to the polarizing plate protective film and is easy to suppress deterioration of the polarizer due to moisture. ) Is preferable.

In the formula, G is a group consisting of an alkylene diol having 2 to 12 carbon atoms, a cycloalkylene diol having 6 to 12 carbon atoms, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms. It is a group derived from at least one selected from the above.

Examples of alkylene diols having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, and 1,2-propane. Diol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl -1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptan), 3-methyl-1,5- Pentandiol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9- Nonanediol, 1,10-decanediol, 1,12-octadecanediol and the like are included.

Examples of cycloalkylene diols having 6 to 12 carbon atoms include hydrogenated bisphenol A (2,2-bis (4-hydroxycyclohexyl) propane) and hydrogenated bisphenol B (2,2-bis (4-hydroxycyclohexyl)). Butane etc. are included.

Examples of oxyalkylene diols having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like.

Examples of arylene diols having 6 to 12 carbon atoms include bisphenol A, bisphenol B and the like.

The diol is used as one or a mixture of two or more. Of these, alkylene glycols having 2 to 12 carbon atoms are preferable because they have excellent compatibility with cycloolefin resins.

In the formula, A is selected from at least one selected from the group consisting of an alkylene dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkylene dicarboxylic acid having 6 to 12 carbon atoms, and an allylene dicarboxylic acid having 8 to 16 carbon atoms. It is the group to be induced.

Examples of alkylenedicarboxylic acids having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecandicarboxylic acid and the like.

Examples of cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, Includes 1,4-decahydronaphthalenedicarboxylic acid and the like.

Examples of allylenedicarboxylic acids having 8 to 16 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid and the like.

The dicarboxylic acid is used as one or a mixture of two or more. The dicarboxylic acid is preferably a mixture of an alkylenedicarboxylic acid and an allylene carboxylic acid. The content ratio of the alkylenedicarboxylic acid to the allylenedicarboxylic acid is preferably alkylenedicarboxylic acid: allylenedicarboxylic acid = 40: 60 to 99: 1, and more preferably 50:50 to 90:10.

In the formula, n is an integer greater than or equal to 0.

The number average molecular weight of the polyester-based additive is preferably 300 to 30,000, more preferably 300 or more and less than 700, and further preferably 300 to 600. When the number average molecular weight is above a certain level, bleed-out is likely to be suppressed. When the number average molecular weight is not more than a certain level, for example, the compatibility with the cycloolefin resin is not easily impaired and the haze increase is easily suppressed.

The number average molecular weight of the polyester-based additive can be measured by gel permeation chromatography. Specifically, using a gel permeation chromatography (GPC) measuring device (“HLC-8330” manufactured by Tosoh Corporation), the number average molecular weight (Mn) of the ester compound in terms of standard polystyrene can be determined under the following measurement conditions. Can be measured.

"Measurement condition"
Columns: "TSK gel SuperHZM-M" x 2 and "TSK gel SuperHZ-2000" x 2 Guard columns: "TSK SuperH-H"
Developing solvent: tetrahydrofuran Flow velocity: 0.35 mL / min The number average molecular weight of the polyester-based additive can be adjusted by the reaction time of condensation or polycondensation.

The acid value of the polyester-based additive is preferably 0.5 mgKOH / g or less, more preferably 0.3 mgKOH / g or less. The hydroxyl value of the polyester-based additive is preferably 25 mgKOH / g or less, more preferably 15 mgKOH / g or less.

The synthesis of the polyester-based additive is carried out by an esterification reaction of a dicarboxylic acid, a diol, and a monocarboxylic acid for terminal encapsulation or a thermal melt condensation method by an ester exchange reaction, or a dicarboxylic acid and a monocarboxylic acid for end encapsulation. It can be carried out by any method of interfacial condensation method of acid chloride and diol. The charging ratio of diol to dicarboxylic acid is adjusted so that the molecular end is diol.

(Fine particles)
The optical film or stretched film of the present embodiment may further contain fine particles (matting agent) in order to impart slipperiness or the like to the surface. The fine particles may be composed of an inorganic compound or a resin.

Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Can be mentioned.

Examples of resins include silicone resins, fluororesins and acrylic resins, styrene resins and acrylic / styrene polymer resins. Of these, silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (all manufactured by Toshiba Silicone Co., Ltd.). Examples are those commercially available under the product name.

Among these, fine particles of silicon dioxide are preferable because they can reduce the turbidity of the film. Examples of fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, and TT600 (all manufactured by Nippon Aerosil Co., Ltd.). Aerosil 200V and Aerosil R972V are preferable because they have a large effect of lowering the friction coefficient while keeping the haze of the film low.

The average particle size of the primary particles of the fine particles is preferably 5 to 400 nm, more preferably 10 to 300 nm. The fine particles may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and particles having an average particle size of 100 to 400 nm may be contained as primary particles without agglomeration. ..

(Sugar ester)
The optical film or stretched film of the present embodiment preferably contains a sugar ester as an organic ester. Since the sugar ester functions as a water-resistant plasticizer, it is effective in suppressing fluctuations in the retardation Rth due to water content in optical films and the like.

The sugar ester is a compound containing at least one of a furanose ring and a pyranose ring, and may be a monosaccharide or a polysaccharide in which 2 to 12 sugar structures are linked. The sugar ester is preferably a compound in which at least one of the OH groups of the sugar structure is esterified. The average transesterification degree in the sugar ester is preferably in the range of 4.0 to 8.0, and more preferably in the range of 5.0 to 7.5.

The sugar ester is not particularly limited, and examples thereof include sugar esters represented by the following general formula (A).

General formula (A)
(HO) _m- G- (OC (= O) -R ² ) _n
In the above general formula (A), G represents a residue of a monosaccharide or a disaccharide, R ² represents an aliphatic group or an aromatic group, and m represents a residue of a monosaccharide or a disaccharide directly attached. It is the total number of hydroxy groups that are present, where n is the total number ^{of-(OC (= O) -R 2) groups that are directly attached to the residue of the monosaccharide or disaccharide.} 3 ≦ m + n ≦ 8 and n ≠ 0.

The sugar ester having a structure represented by the general formula (A) ^{is a single type in which the number of hydroxy groups (m) and the number of-(OC (= O) -R 2} ) groups (n) are fixed. It is difficult to isolate as a compound, and it is known that several kinds of components having different m and n in the formula are mixed to form a compound. Therefore, the performance as a mixture in which the number of hydroxy groups (m) and the number of − (OC (= O) -R ² ) groups (n) are changed is important, and in the case of the optical film of the present embodiment. , Sugar esters having an average ester substitution degree in the range of 5.0 to 7.5 are preferable.

In the above general formula (A), G represents a residue of a monosaccharide or a disaccharide. Specific examples of monosaccharides include allose, altrose, glucose, mannose, growth, idose, galactose, tarose, ribose, arabinose, xylose, lyxose and the like.

Specific examples of the compound having a monosaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the compounds are not limited to these exemplified compounds.

Specific examples of the disaccharide residue include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, isotrehalose and the like.

Specific examples of the compound having a disaccharide residue of the sugar ester represented by the general formula (A) are shown below, but the compounds are not limited to these exemplified compounds.

In the general formula (A), R ² represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each have an independent substituent.

Further, in the general formula (A), m is the total number of hydroxy groups directly bonded to the residue of the monosaccharide or disaccharide, and n is the total number of hydroxy groups directly bonded to the residue of the monosaccharide or disaccharide. It is the total number of-(OC (= O) -R ^{2) groups.} Then, it is necessary that 3 ≦ m + n ≦ 8, and 4 ≦ m + n ≦ 8 is preferable. Also, n ≠ 0. When n is 2 or more, the-(OC (= O) -R ² ) groups may be the same or different from each other.

Aliphatic group in the definition of R ² may be a straight chain, be branched, may be cyclic, preferably one having 1 to 25 carbon atoms, more preferably having 1 to 20, 2 ~ 15 are particularly preferable. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n-. Examples thereof include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

Further, the ^{aromatic group in the definition of R 2} may be an aromatic hydrocarbon group, an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include rings of benzene, naphthalene, anthracene, biphenyl, terphenyl and the like. As the aromatic hydrocarbon group, a benzene ring, a naphthalene ring, and a biphenyl ring are particularly preferable. As the aromatic heterocyclic group, a ring containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom is preferable. Specific examples of the heterocycle include, for example, furan, pyrrol, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazole, indol, indazole, purine, thiazoline, thiadiazol, oxazoline, oxazole, oxazole, quinoline, Examples thereof include rings of isoquinoline, phthalazine, naphthylidine, quinoxalin, quinazoline, cinnoline, pteridine, aclysine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, tetrazyneden and the like. As the aromatic heterocyclic group, a pyridine ring, a triazine ring and a quinoline ring are particularly preferable.

The sugar ester may contain two or more different substituents in one molecule, and contains an aromatic substituent and an aliphatic substituent in one molecule, and two or more different aromatic substituents. Can be contained in one molecule, and two or more different aliphatic substituents can be contained in one molecule.

It is also preferable to mix and contain two or more types of sugar esters. It is also preferable to simultaneously contain a sugar ester containing an aromatic substituent and a sugar ester containing an aliphatic substituent.

Hereinafter, preferred examples of the sugar ester represented by the general formula (A) are shown below, but the compounds are not limited to these exemplified compounds.

The amount of the sugar ester added is preferably in the range of 0.1 to 20% by mass, preferably in the range of 1 to 15% by mass, based on the resin (for example, cellulose acylate) constituting the optical film. More preferred.

As the sugar ester, those having a hue of 10 to 300 are preferable, and those having a hue of 10 to 40 are preferable.

(Ritaration enhancer)
The optical film or stretched film of the present embodiment preferably contains a retardation enhancer. The retardation enhancer refers to a compound having a function of increasing the retardation (particularly the retardation Rth in the thickness direction) of the film at the measurement wavelength of 590 nm as compared with the one to which the retardation enhancer is not added.

As the retardation increasing agent, a nitrogen-containing heterocyclic compound can be used. It is desirable that the nitrogen-containing heterocyclic compound has a pyrazole ring, a triazole ring, and an imidazole ring from the viewpoint of surely obtaining the effect of suppressing an increase in retardation due to water content of the film. The following is an example of a nitrogen-containing heterocyclic compound as a retardation enhancer, but the present invention is not limited thereto.

[Diagonal stretching device]
Next, an oblique stretching device, which is an example of the stretching device used in the stretching step (S3) shown in FIG. 1, will be described.

FIG. 4 is a plan view schematically showing a schematic configuration of the oblique stretching device 21. The oblique stretching device 21 includes, in order from the upstream side in the film transport direction, the film feeding section 22, the transport direction changing section 23, the guide roll 24, the stretching section 25, the guide roll 26, the transport direction changing section 27, and the like. It includes a film winding unit 28. The details of the stretched portion 25 will be described later.

The film feeding portion 22 feeds out an optical film to be obliquely stretched and supplies it to the stretched portion 25. The film feeding portion 22 may be configured separately from the apparatus shown in FIG. 2, or may be integrally configured. In the former case, a winder of an optical film (corresponding to the optical film F of FIG. 2) obtained by winding with the winding device 12 of FIG. 2 is loaded into the film feeding portion 22, and the optical film is released from the film feeding portion 22. It is paid out. On the other hand, in the latter case, the film feeding portion 22 is fed to the stretched portion 25 without winding the film after forming the optical film.

The transport direction changing section 23 changes the transport direction of the optical film fed from the film feeding section 22 toward the inlet of the stretching section 25 as the oblique stretching tenter. Such a transport direction changing unit 23 includes, for example, a turn bar that changes the transport direction by folding back while transporting the film, and a rotary table that rotates the turn bar in a plane parallel to the film.

By changing the transport direction of the optical film in the transport direction changing unit 23 as described above, the width of the entire oblique stretching device 21 can be narrowed, and the film feeding position and angle can be finely controlled. This makes it possible to obtain a stretched film having a small variation in film thickness and optical value. Further, if the film feeding portion 22 and the transport direction changing portion 23 are movable (sliding and swivelable), the films of the left and right clips (grasping tools) that sandwich both ends of the optical film in the width direction in the stretched portion 25. It is possible to effectively prevent poor biting into the film.

The film feeding portion 22 may be slidable and swivelable so that the optical film can be fed at a predetermined angle with respect to the inlet of the stretched portion 25. In this case, the configuration may be such that the installation of the transport direction changing unit 23 is omitted.

At least one guide roll 24 is provided on the upstream side of the stretched portion 25 in order to stabilize the trajectory of the optical film during traveling. The guide roll 24 may be composed of a pair of upper and lower rolls sandwiching the film, or may be composed of a plurality of roll pairs. The guide roll 24 closest to the inlet of the stretched portion 25 is a driven roll that guides the running of the film, and is rotatably supported by a bearing portion (not shown). As the material of the guide roll 24, a known material can be used. In order to prevent the film from being scratched, it is preferable to reduce the weight of the guide roll 24 by applying a ceramic coat to the surface of the guide roll 24 or chrome plating a light metal such as aluminum.

Further, it is preferable that one of the rolls on the upstream side of the guide roll 24 closest to the inlet of the stretched portion 25 is niped by pressure-welding the rubber roll. By using such a nip roll, it is possible to suppress fluctuations in the feeding tension in the film flow direction.

A pair of bearing portions at both ends (left and right) of the guide roll 24 closest to the inlet of the stretched portion 25 have a first tension detecting device as a film tension detecting device for detecting the tension generated in the film in the roll. A second tension detection device is provided for each. As the film tension detection device, for example, a load cell can be used. As the load cell, a known tension or compression type load cell can be used. A load cell is a device that converts a load acting on a force point into an electric signal by a strain gauge attached to a strain generating body and detects it.

The load cell is installed in the left and right bearing portions of the guide roll 24 closest to the inlet of the stretched portion 25, so that the force exerted on the roll by the running film, that is, in the film traveling direction generated near both side edges of the film. The tension is detected independently on the left and right. A strain gauge may be directly attached to the support constituting the bearing portion of the roll, and the load, that is, the film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension shall be measured and known in advance.

If the position and transport direction of the film supplied from the film feeding portion 22 or the transport direction changing portion 23 to the stretched portion 25 deviate from the position toward the inlet of the stretched portion 25 and the transport direction, depending on the amount of this deviation. There will be a difference in tension near both edges of the film on the guide roll 24 closest to the inlet of the stretched portion 25. Therefore, the degree of the deviation can be determined by providing the film tension detecting device as described above and detecting the tension difference described above. That is, if the transport position and transport direction of the film are appropriate (if the position and direction are toward the inlet of the stretched portion 25), the load acting on the guide roll 24 is roughly equal at both ends in the axial direction. If it is not appropriate, there will be a difference in film tension between the left and right.

Therefore, for example, the position and the transport direction (angle of the stretched portion 25 with respect to the inlet) of the film are set by the above-mentioned transport direction changing portion 23 so that the difference in film tension between the left and right of the guide roll 24 closest to the inlet of the stretched portion 25 becomes equal. If properly adjusted, the gripping tool at the inlet of the stretched portion 25 can stably grip the film, and the occurrence of obstacles such as the gripping tool coming off can be reduced. Further, it is possible to stabilize the physical characteristics of the film in the width direction after the film is diagonally stretched by the stretched portion 25.

At least one guide roll 26 is provided on the downstream side of the stretched portion 25 in order to stabilize the trajectory of the film diagonally stretched by the stretched portion 25 (also referred to as a diagonally stretched film) during traveling.

The transport direction changing section 27 changes the transport direction of the obliquely stretched film transported from the stretched section 25 toward the film winding section 28. The transport direction changing portion 27 can be configured by, for example, a folding mechanism that folds the diagonally stretched film at least once along a direction parallel to or perpendicular to the stretching direction in the plane of the diagonally stretched film.

Here, in order to fine-tune the orientation angle (direction of the in-plane slow-phase axis of the film) and to cope with product variations, the film advancing direction at the inlet of the stretched portion 25 and the film advancing direction at the outlet of the stretched portion 25. It is necessary to adjust the angle of the film.

In addition, continuous film formation and diagonal stretching are preferable in terms of productivity and yield. When the film-forming step, the diagonal stretching step, and the winding step are continuously performed, the traveling direction of the film is changed by the transport direction changing section 23 and / or the transport direction changing section 27, and the film is formed in the film-forming step and the winding step. That is, as shown in FIG. 4, the traveling direction of the film unwound from the film feeding unit 22 (feeding direction) and the traveling direction of the film immediately before being wound by the film winding unit 28 (the traveling direction of the film). By matching the winding direction), the width of the entire device with respect to the film traveling direction can be reduced.

Although it is not always necessary to match the traveling directions of the film between the film forming process and the winding process, the transport direction changing unit 23 and the transport direction changing unit 23 and the film winding unit 28 are arranged so that the film feeding portion 22 and the film winding portion 28 do not interfere with each other. / Or it is preferable to change the traveling direction of the film by the transport direction changing unit 27.

The transport direction changing unit 23.7 as described above can be realized by a known method such as using an air flow roll.

The film winding unit 28 winds the obliquely stretched film transported from the stretching unit 25 via the transport direction changing unit 27, and is composed of, for example, a winder device, an accumulator device, a drive device, and the like. The film winding portion 28 preferably has a structure that can slide in the lateral direction in order to adjust the winding position of the obliquely stretched film.

The film take-up portion 28 can finely control the take-up position and angle of the film so that the film can be taken up at a predetermined angle with respect to the outlet of the stretched portion 25. This makes it possible to obtain a diagonally stretched film having a small variation in film thickness and optical value. In addition, it is possible to effectively prevent the occurrence of wrinkles in the film and improve the windability of the film, so that the film can be wound in a long length. In the present embodiment, the take-back tension T (N / m) of the stretched film is preferably adjusted between 100 N / m <T <700 N / m, preferably 150 N / m <T <250 N / m.

When the take-up tension is 100 N / m or less, the film is liable to sag or wrinkle, and the retardation and the profile of the orientation angle in the film width direction are also deteriorated. On the contrary, when the take-up tension is 700 N / m or more, the variation of the orientation angle in the film width direction is deteriorated, and the width yield (take-up efficiency in the width direction) may be deteriorated.

Further, in the present embodiment, it is preferable to control the fluctuation of the take-back tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the fluctuation of the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction (conveyance direction) becomes large. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll (guide roll 26) on the outlet side of the stretched portion 25, that is, the tension of the film is measured, and the value becomes constant. As described above, a method of controlling the rotation speed of the take-up roll (the take-up roll of the film take-up unit 28) by a general PID control method can be mentioned. Examples of the method for measuring the load include a method in which a load cell is attached to the bearing portion of the guide roll 26 and the load applied to the guide roll 26, that is, the tension of the film is measured. As the load cell, a known tension type or compression type can be used.

The stretched film is released from the gripping tool of the stretched portion 25, discharged from the outlet of the stretched portion 25, and both ends (both sides) of the film gripped by the gripping tool are trimmed, and then the winding core is sequentially wound. It is wound on a (winding roll) to form a wound body of a long diagonally stretched film. The above trimming may be performed as needed.

Further, before winding the long diagonally stretched film, the masking film may be laminated on the long diagonally stretched film and wound at the same time for the purpose of preventing blocking between the films, or they may be wound by winding. A tape or the like may be attached to at least one (preferably both) ends of the elongated diagonally stretched film and wound up. The masking film is not particularly limited as long as it can protect a long diagonally stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

(Details of stretched part)
Next, the details of the stretched portion 25 described above will be described. FIG. 5 is a plan view schematically showing an example of the rail pattern of the stretched portion 25. However, this is an example, and the configuration of the stretched portion 25 is not limited to this.

The stretched film in the present embodiment is produced by using a tenter (diagonal stretching machine) capable of diagonally stretching as the stretching portion 25. This tenter is a device that heats a long optical film to an arbitrary temperature at which it can be stretched and stretches it diagonally. This tenter includes a heating zone Z, a pair of rails Ri / Ro on the left and right, and a large number of gripping tools Ci / Co (in FIG. 5, one set of gripping tools) that travel along the rails Ri / Ro to convey the film. Only shown) and. The details of the heating zone Z will be described later. Each of the rails Ri and Ro is configured by connecting a plurality of rail portions with connecting portions (white circles in FIG. 5 are examples of connecting portions). The gripping tools Ci and Co are composed of clips that grip both ends of the film in the width direction.

In FIG. 5, the feeding direction D1 of the optical film is different from the winding direction D2 of the stretched film (long diagonally stretched film), and a feeding angle θi is formed with the winding direction D2. There is. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

As described above, since the feeding direction D1 and the winding direction D2 are different, the rail pattern of the tenter has an asymmetrical shape on the left and right, and the film transport path is bent in the middle. Then, the rail pattern can be manually or automatically adjusted according to the orientation angle θ given to the stretched film to be manufactured, the stretch ratio, and the like. In the diagonal stretching machine used in the manufacturing method of the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions constituting the rails Ri and Ro can be freely set and the rail pattern can be arbitrarily changed.

In the present embodiment, the plurality of gripping tools Ci / Co of the tenter are designed to travel at a constant speed while maintaining a constant interval with the front and rear gripping tools Ci / Co. The traveling speed of the gripping tool Ci / Co can be appropriately selected, but is usually 1 to 150 m / min. In this embodiment, it is preferably 20 to 100 m / min in consideration of film productivity. The difference in running speed between the pair of left and right grippers Ci and Co is usually 1% or less, preferably 0.5% or less, and more preferably 0.1% or less of the running speed. This is because if there is a difference in traveling speed between the left and right sides of the film at the outlet of the stretching process, wrinkles and deviations occur at the exit of the stretching process, so that the speed difference between the left and right grippers Ci and Co is substantially the same. Is required. In a general tenter device, there is speed unevenness that occurs on the order of seconds or less depending on the tooth cycle of the sprocket that drives the chain, the frequency of the drive motor, etc., and often causes unevenness of several percent. It does not correspond to the speed difference described in the embodiment.

In the oblique stretching machine used in the manufacturing method of the present embodiment, a rail that regulates the trajectory of the gripper is often required to have a large refractive index, especially in a place where the film is conveyed at an angle. For the purpose of avoiding interference between grippers due to sudden bending or local stress concentration, it is desirable that the locus of the gripping tool draws a curve at the bent portion.

In this way, the diagonally stretched tenter used to impart diagonal orientation to the optical film can freely set the orientation angle of the film by changing the rail pattern in various ways, and further, the orientation axis of the film ( It is preferable that the tenter is capable of aligning the slow axis) evenly on the left and right sides in the film width direction with high accuracy, and can control the film thickness and retardation with high accuracy.

Next, the stretching operation in the stretching portion 25 will be described. Both ends of the optical film are gripped by the left and right gripping tools Ci / Co, and the optical film is conveyed in the heating zone Z as the gripping tools Ci / Co travel. The left and right gripping tools Ci and Co face each other in a direction substantially perpendicular to the film traveling direction (feeding direction D1) at the inlet portion (position A in the figure) of the stretched portion 25, and are asymmetrical rails. The film runs on Ri and Ro, respectively, and the film gripped at the outlet portion (position B in the figure) at the end of stretching is released. The film released from the gripping tool Ci · Co is wound around the winding core by the film winding unit 28 described above. The pair of rails Ri and Ro each have an endless continuous track, and the gripping tool Ci and Co that have released the film grip at the outlet of the tenter travel on the outer rail and are sequentially returned to the inlet. It is designed to be used.

At this time, since the rails Ri and Ro are asymmetrical, in the example of FIG. 5, the left and right gripping tools Ci and Co, which were opposed to each other at the position A in the figure, move on the rails Ri and Ro as they travel on the rails. The gripping tool Ci running on the Ri side (in-course side) has a positional relationship that precedes the gripping tool Co running on the rail Ro side (out-course side).

That is, of the gripping tools Ci and Co that were opposed to the film feeding direction D1 at the position A in the drawing, one gripping tool Ci precedes the position B at the end of stretching the film. When it reaches, the straight line connecting the gripping tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the film winding direction D2. With the above actions, the long film is stretched diagonally at an angle of θL with respect to the width direction. Here, substantially vertical means that it is in the range of 90 ± 1 °.

Next, the details of the heating zone Z described above will be described. The heating zone Z of the stretched portion 25 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretched portion 25, the film gripped by the gripping tool Ci · Co passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order.

The preheating zone Z1 refers to a section at the entrance of the heating zone Z where the gripping tools Ci and Co that grip both ends of the film travel while maintaining a constant distance (in the film width direction) on the left and right sides.

The stretching zone Z2 refers to a section in which the above-mentioned diagonal stretching step is performed. At this time, if necessary, the film may be stretched in the vertical direction or the horizontal direction before and after the diagonal stretching.

The heat fixing zone Z3 is a section in which a heat fixing step of fixing the optical axis (slow phase axis) of the film is performed after the diagonal stretching step is completed.

After passing through the heat-fixing zone Z3, the stretched film passes through a section (cooling zone) in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the film. You may. At this time, in consideration of the shrinkage of the film due to cooling, the rail pattern may be formed so as to narrow the distance between the gripping tools Ci and Co that face each other in advance.

The temperature of the preheating zone Z1 should be set to Tg to Tg + 30 ° C., the temperature of the stretching zone Z2 should be set to Tg to Tg + 30 ° C., and the temperature of the heat fixing zone Z3 should be set to Tg-30 to Tg ° C. with respect to the glass transition temperature Tg of the thermoplastic resin. Is preferable.

In addition, in order to control the thickness unevenness of the film in the width direction, a temperature difference may be provided in the width direction in the stretch zone Z2. In order to make a temperature difference in the width direction in the stretching zone, there are known methods such as adjusting the opening degree of the nozzle that sends warm air into the constant temperature room so as to make a difference in the width direction, and arranging heaters in the width direction to control heating. Method can be used. The lengths of the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 can be appropriately selected, and the length of the preheating zone Z1 is usually 100 to 150% with respect to the length of the stretching zone Z2, and the length of the heat fixing zone Z3. Is usually 50-100%.

Further, assuming that the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the stretching ratio R (W / Wo) in the stretching step is preferably 1.3 to 3. It is 0, more preferably 1.5 to 2.8. When the draw ratio is in this range, the thickness unevenness in the width direction of the film is reduced, which is preferable. In the stretching zone Z2 of the diagonally stretched tenter, if the stretching temperature is different in the width direction, the thickness unevenness in the width direction can be further improved. The stretch ratio R is equal to the magnification (W2 / W1) when the distance W1 between both ends of the clip gripped at the tenter inlet portion becomes the distance W2 at the tenter outlet portion.

[Liquid crystal display]
The stretched film of the present embodiment can be applied to, for example, a polarizing plate of a liquid crystal display device. Hereinafter, the configuration of the liquid crystal display device including the polarizing plate will be described.

FIG. 6 is a cross-sectional view showing a schematic configuration of the liquid crystal display device 31 according to the present embodiment. The liquid crystal display device 31 includes a liquid crystal display panel 32 and a backlight 33. The backlight 33 is a light source for illuminating the liquid crystal display panel 32.

The liquid crystal display panel 32 is configured by arranging the polarizing plate 35 on the visual side of the liquid crystal cell 34 and arranging the polarizing plate 36 on the backlight 33 side. The liquid crystal cell 34 is formed by sandwiching a liquid crystal layer between a pair of transparent substrates (not shown). The liquid crystal cell 34 has a so-called color filter-on-array (COA) structure in which a color filter is arranged on a transparent substrate on the backlight 33 side with respect to the liquid crystal layer, that is, a substrate on the TFT (Thin Film Transistor) forming side. However, the liquid crystal cell may be a liquid crystal cell in which the color filter is arranged on the transparent substrate on the visual side with respect to the liquid crystal layer. The liquid crystal cell 34 is driven by, for example, a VA (Vertical Alignment) method, but may be driven by another method such as an IPS (In-Plane-Switching) method or a TN (Twisted Nematic) method.

The polarizing plate 35 includes a polarizing element 41 and optical films 42 and 43. The polarizer 41 transmits a predetermined linearly polarized light. The optical film 42 is a protective film arranged on the visual side of the polarizer 41. The optical film 43 is a protective film and retardation film arranged on the backlight 33 side (liquid crystal cell 34 side) of the polarizer 41. The optical films 42 and 43 are respectively adhered to the polarizer 41 via an ultraviolet curable adhesive or water glue.

Such a polarizing plate 35 is attached to the visible side of the liquid crystal cell 34 via an adhesive layer 37. That is, the polarizing plate 35 is attached to the liquid crystal cell 34 so that the polarizing plate 35 is located on the visual side with respect to the liquid crystal cell 34 and the optical film 43 is on the liquid crystal cell 34 side with respect to the polarizer 41.

The polarizing plate 36 includes a polarizing element 44 and optical films 45 and 46. The polarizer 44 transmits a predetermined linearly polarized light. The optical film 45 is a protective film arranged on the visual side of the polarizer 44, and can also function as a retardation film. The optical film 46 is a protective film arranged on the backlight 33 side of the polarizer 44. The optical films 45 and 46 are respectively adhered to the polarizer 44 via an ultraviolet curable adhesive or water glue.

Such a polarizing plate 36 is attached to the backlight 33 side of the liquid crystal cell 34 via an adhesive layer 38. The optical film 45 on the visual side may be omitted, and the polarizing element 44 may be brought into direct contact with the adhesive layer 38. The polarizer 41 and the polarizer 44 are arranged so as to be in a cross Nicol state.

The stretched film of the present embodiment (for example, a diagonally stretched film) is applied to the optical film 43 of the polarizing plate 35 or the optical film 45 of the polarizing plate 36 in, for example, the VA type liquid crystal display device 31.

〔Example〕
Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

<Preparation of stretched film F-1>
A stretched film F-1 was produced in the same manner as in Example 1 of Patent Document 1. More specifically, it is as follows.

(Production of hydrogenated product of ring-opening polymer of dicyclopentadiene)
The metal pressure-resistant reactor was sufficiently dried and then replaced with nitrogen. In this metal pressure resistant reactor, 154.5 parts of cyclohexane, 42.8 parts of a 70% cyclohexane solution of dicyclopentadiene (endo content 99% or more) (30 parts as the amount of dicyclopentadiene), and 1- 1.9 parts of hexene was added and heated to 53 ° C.

To a solution prepared by dissolving 0.014 parts of a tetrachlorotungene phenylimide (tetrahydrofuran) complex in 0.70 parts of toluene, 0.061 parts of a diethylaluminum ethoxide / n-hexane solution having a concentration of 19% was added, and the mixture was stirred for 10 minutes. To prepare a catalytic solution. This catalyst solution was added to a pressure resistant reactor to initiate a ring-opening polymerization reaction. Then, the reaction was carried out for 4 hours while maintaining 53 ° C. to obtain a solution of a ring-opening polymer of dicyclopentadiene. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the obtained ring-opening polymer of dicyclopentadiene are 8750 and 28100, respectively, and the molecular weight distribution (Mw / Mn) obtained from these is 3. It was 21.

To 200 parts of the obtained solution of the ring-opening polymer of dicyclopentadiene, 0.037 parts of 1,2-ethanediol was added as a terminator, heated to 60 ° C., and stirred for 1 hour to stop the polymerization reaction. I let you. A part of a hydrotalcite-like compound (“Kyoward (registered trademark) 2000” manufactured by Kyowa Chemical Industry Co., Ltd.) was added thereto, and the mixture was heated to 60 ° C. and stirred for 1 hour. After that, 0.4 part of a filtration aid ("Radiolite (registered trademark) # 1500" manufactured by Showa Kagaku Kogyo Co., Ltd.) was added, and a PP pleated cartridge filter ("TCP-HX" manufactured by ADVANTEC Toyo Co., Ltd.) was used as an adsorbent. The solution was filtered off.

To 200 parts of the filtered dicyclopentadiene ring-opening polymer solution (30 parts of polymer amount), 100 parts of cyclohexane was added, 0.0043 parts of chlorohydride carbonyltris (triphenylphosphine) ruthenium was added, and hydrogen was added. The hydrogenation reaction was carried out at a pressure of 6 MPa and 180 ° C. for 4 hours. As a result, a reaction solution containing a hydrogenated compound of a ring-opening polymer of dicyclopentadiene was obtained. In this reaction solution, hydrogenated substances were precipitated to form a slurry solution.

The hydrogenated product and the solution contained in the reaction solution are separated using a centrifuge and dried under reduced pressure at 60 ° C. for 24 hours to produce a hydrogenated product of a crystallized dicyclopentadiene ring-opening polymer. 28.5 copies were obtained. The hydrogenation rate of this hydrogenated product was 99% or more, the glass transition temperature (Tg) was 95 ° C., and the melting point (Tm) was 262 ° C.

(Preparation of resin)
100 parts of the hydrogenated compound of the dicyclopentadiene ring-opening polymer obtained above is added with an antioxidant (tetrakis [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate). ] Methane; 1.1 parts of "Irganox (registered trademark) 1010" manufactured by BASF Japan Ltd.) was mixed to obtain a resin as a material for a film.

(Manufacturing of stretched film)
The resin obtained above was put into a twin-screw extruder equipped with four die holes having an inner diameter of 3 mm. Then, the resin was formed into a strand-shaped molded product by hot melt extrusion molding by a twin-screw extruder. This molded product was shredded with a strand cutter to obtain resin pellets. The operating conditions of the twin-screw extruder are shown below.
-Barrel set temperature: 270 ° C to 280 ° C
・ Die set temperature: 250 ℃
・ Screw rotation speed: 145 rpm
・ Feeder rotation speed: 50 rpm

Subsequently, the obtained pellets were supplied to a heat melt extrusion film forming machine equipped with a T-die. By extruding the resin from the T-die and winding it on a roll at a speed of 1 m / min, a long raw film (thickness 50 μm) made of the above resin was produced. The operating conditions of the film forming machine are shown below.
-Barrel temperature setting: 280 ° C to 290 ° C
-Die temperature: 270 ° C
・ Screw rotation speed: 30 rpm

After that, the raw film was cut into a size of 100 mm × 100 mm, and the four side ends of the film were gripped with clips using a small biaxial stretching machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the stretching temperature was 110 ° C. Fixed-end uniaxial stretching was continuously carried out at a stretching ratio of 2 times to obtain a stretched film. The crystallinity of the polymer in the stretched film at this time was 4%.

(Electron beam irradiation)
Finally, using an electron beam irradiation device (manufactured by iElectron Beam), the absorbed dose of the stretched film obtained above is adjusted to 1200 kGy under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV. The electron beam was irradiated. As a result, a stretched film F-1 was obtained.

<Preparation of stretched film F-2>
In the production of the stretched film F-1, after cutting the raw film into a size of 100 mm × 100 mm, the ends of the two sides in the raw film transport direction are gripped by the clips of a small biaxial stretching machine, and the stretching temperature is 110. Free-end uniaxial stretching was performed at ° C. and a stretching ratio of 1.1 times, and the film was shrunk by 5% in the width direction.

Then, the shrunk film was irradiated with an electron beam under the same conditions as when the stretched film F-1 was produced. Then, the ends of the four sides of the film were clipped to a small biaxial stretching machine again, and the raw film was doubled in the width direction and uniaxially stretched at a fixed end at a stretching temperature of 110 ° C. As a result, a stretched film F-2 was obtained.

<Preparation of stretched film F-3>
(Preparation of fine particle additive liquid)
Fine particles (Aerosil R812: manufactured by Nippon Aerosil Co., Ltd., primary average particle size: 7 nm, apparent specific gravity 50 g / L)
4 parts by mass Dichloromethane 48 parts by mass Ethanol 48 parts by mass or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with menton golin. Further, the particles were dispersed by an attritor so that the particle size of the secondary particles became a predetermined size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(Preparation of dope)
A dope having the following composition was prepared. First, dichloromethane and ethanol were added to the pressurized dissolution tank. A cycloolefin resin (ARTON G7810, manufactured by JSR Corporation) was put into a pressurized dissolution tank containing a mixed solution of dichloromethane and ethanol with stirring. Further, 15 minutes after the start of solvent addition, the fine particle-added solution prepared above was added, and the mixture was heated to 80 ° C. and completely dissolved while stirring. At this time, the temperature was raised from room temperature to 5 ° C./min, dissolved in 30 minutes, and then lowered to 3 ° C./min. The obtained solution was used as Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. Filtration was performed using 244 to prepare a dope.
<< Composition of dope >>
Cycloolefin resin (ARTON G7810, manufactured by JSR Corporation) 100 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Fine particle addition liquid 1 part by mass

Then, using an endless belt casting device, the dope was uniformly cast on the stainless steel belt at a temperature of 31 ° C. and a width of 1800 mm. The temperature of the stainless steel belt was controlled to 28 ° C. Then, the solvent was evaporated on the stainless steel belt until the amount of the residual solvent in the cast film reached 30% by mass, and the cast film was peeled off from the stainless steel belt.

The peeled cast film is dried while being conveyed by a large number of rollers in a drying zone to obtain an optical film having a residual solvent amount of less than 0.1% by mass, and then the width is increased by a tenter under the condition of 170 ° C. It was stretched 1.5 times in the hand direction.

Subsequently, the end portion sandwiched between the tenter clips is slit with a laser cutter, and then, using an electron beam irradiation device, the absorbed dose to the optical film under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV. An electron beam was irradiated to obtain 1200 kGy and the film was wound to obtain a stretched film F-3 having a thickness of 40 μm and a width of 2000 mm.

<Preparation of stretched film F-4>
A stretched film F-4 having a thickness of 40 μm and a width of 2000 mm was produced in the same manner as in the production of the stretched film F-3, except that the following two steps were changed.
(1) When the casting film (optical film) was peeled off from the stainless steel belt, the optical film was shrunk by 15% in the width direction by stretching 1.2 times in the transport direction.
(2) After the drying was completed, electron beam irradiation was performed before stretching in the width direction.

<Preparation of stretched film F-5>
The stretched film F-5 having a thickness of 40 μm and a width of 2500 mm was similarly stretched in the width direction in the same manner as in the production of the stretched film F-4, except that the stretching in the width direction was performed under the condition of 180 ° C. at a stretching ratio of 3.0 times. Was produced.

<Preparation of stretched film F-6>
The stretched film F-6 having a thickness of 40 μm and a width of 2000 mm was obtained in the same manner as in the production of the stretched film F-4, except that the electron beam irradiation was performed immediately before the casting film (optical film) was peeled off from the stainless belt. Was produced.

<Preparation of stretched film F-7>
When the casting film (optical film) is peeled off from the stainless steel belt, the process is the same as that for producing the stretched film F-4 until it is stretched 1.2 times in the transport direction and contracted by 15% in the width direction. Was done. After that, a stretched film F-7 having a thickness of 40 μm and a width of 2000 mm was produced as follows.

After shrinking the optical film in the width direction, an electron beam irradiation device is used under the condition of 145 ° C., and the absorbed dose is applied to the optical film under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV. After irradiating an electron beam so as to reach 1200 kGy, it was stretched 1.5 times in the width direction. The amount of residual solvent at the start of stretching was 5% by mass.

Next, the optical film was dried while being conveyed by a large number of rollers in the drying zone, and then the end portion sandwiched between the tenter clips was slit by a laser cutter and wound up.

<Preparation of stretched film F-8>
The thickness and width were 40 μm in the same manner as in the production of the stretched film F-7, except that the residual solvent amount at the start of stretching was set to 15% by mass by performing electron beam irradiation and width stretching under the condition of 95 ° C. A 2000 mm stretched film F-8 was produced.

<Preparation of stretched film F-9>
A stretched film F-9 having a thickness of 40 μm and a width of 2000 mm was produced in the same manner as in the production of the stretched film F-7, except that the composition of the dope was changed as follows.
<< Composition of dope >>
Cellulose acylate (acetyl group substitution degree 1.5, propionyl group substitution degree 0.9)
100 parts by mass Dichloromethane 340 parts by mass Ethanol 60 parts by mass Sugar ester 10 parts by mass Retention increasing agent 2 parts by mass Fine particle addition liquid 1 part by mass

As the sugar ester, BzSc (benzyl saccharose: a mixture of compounds a1 to a4 having a sugar residue of B-2 (see Chemical formulas 3 and 4), average ester substitution degree = 5.5) was used. Further, as the retardation increasing agent, the nitrogen-containing heterocyclic compound (pyrazole-based compound) shown in Chemical formula 7 was used.

<Preparation of stretched film F-10>
First, the dope was prepared in the same manner as in the preparation of the stretched film F-3, except that the composition of the dope was changed as follows.
(Main dope)
Cycloolefin resin (ARTON G7810, manufactured by JSR Corporation) 100 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Tinubin 928 (manufactured by BASF Japan Ltd.) 3 parts by mass Fine particle addition liquid 1 part by mass

Then, using an endless belt casting device, the dope was uniformly cast on the stainless steel belt at a temperature of 31 ° C. and a width of 1800 mm. At this time, the temperature of the stainless steel belt was controlled to 28 ° C.

Subsequently, the solvent was evaporated on the stainless steel belt until the amount of residual solvent in the cast film reached 30% by mass, and the cast film (optical film) was peeled off from the stainless steel belt. Then, the peeled optical film is dried while being conveyed by a large number of rollers in the drying zone to reduce the residual solvent amount to less than 0.1% by mass, and then the end portion sandwiched between the tenter clips of the optical film is laser-machined. Slit with a cutter. Then, using an electron beam irradiator, the optical film is irradiated with an electron beam so that the absorbed dose is 1200 kGy under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV, and then the optical film is wound up. A raw film having a thickness of 36 μm and a width of 1500 mm was produced.

Next, the raw film produced above was diagonally stretched using the diagonal stretching device 21 shown in FIG. 4 and the like. That is, the raw film is set in the film feeding section 2 of the diagonal stretching device 21, the raw film is fed from the film feeding section 2 and supplied to the stretching section 25 for diagonal stretching, and the stretched film F-10 is performed. (Long diagonal stretched film) was obtained. At this time, the stretched portion 25 was diagonally stretched so that the orientation angle φ (angle formed by the slow axis and the width direction) of the film was approximately 45 °. Further, in the stretch zone Z2 of the stretched portion 25, the raw film was first stretched 1.5 times in the width direction and then shrunk by 20% at the time of bending. Then, the transport speed of the film was set to 15 m / min, and both ends in the width direction were cut with a film cutting device (not shown) to obtain a stretched film F-10 having a thickness of 30 μm and a width of 1300 mm.

<Preparation of stretched film F-11>
(Manufacturing of polycarbonate resin)
3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane (hereinafter abbreviated as SPG) 76.6 parts, 9,9- Bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter abbreviated as BCF) 51.4 parts, 1,6-hexanediol (hereinafter abbreviated as HD) 1.4 parts, diphenyl carbonate 87.8 parts, and as a catalyst 1.6 × 10 ^-4 parts of sodium hydrogen carbonate was heated to 180 ° C. in a nitrogen atmosphere to melt it. Then, the degree of decompression was adjusted to 13.4 kPa over 30 minutes. Then, the temperature was raised to 260 ° C. at a rate of 60 ° C./hr, held at that temperature for 10 minutes, and then the degree of decompression was reduced to 133 Pa over 1 hour. The reaction was carried out under stirring for a total of 5 hours. After completion of the reaction, 1.5 times the molar amount of the tetrabutylphosphonium salt of dodecylbenzenesulfonate was added to deactivate the catalyst, and then nitrogen pressurization was performed from the bottom of the reaction vessel. Pellets were obtained by discharging and cutting with a pelletizer while cooling in a water tank.

(Preparation of raw film)
Next, the obtained pellets (polycarbonate resin) were supplied to an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter, and extruded into a film from a T die onto a casting drum. The extruded resin was cooled by a casting drum and wound up to prepare a raw film having a thickness of 90 μm and a width of 1500 mm.

(Preparation of stretched film)
The raw film produced above was diagonally stretched using the diagonal stretching device 21 shown in FIG. 4 and the like. At this time, in the stretched zone Z2, the thickness was 50 μm in the same manner as in the production of the stretched film F-10, except that the raw film was stretched 2.5 times in the width direction and then shrunk by 25% at the time of bending. A long stretched film (diagonal stretched film) F-11 having a width of 1300 mm was produced.

<Preparation of stretched film F-12>
<< Preparation of fine particle dispersion >>
Fine Particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with manton gorin to prepare a fine particle dispersion.

≪Preparation of fine particle additive liquid≫
Based on the following composition, the fine particle dispersion was slowly added to the dissolution tank containing methylene chloride while sufficiently stirring. Further, the particles were dispersed by an attritor so that the particle size of the secondary particles became a predetermined size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.
Methylene chloride 99 parts by mass Fine particle dispersion 15 parts by mass

≪Preparation of dope≫
A dope having the following composition was prepared. First, methylene chloride and ethanol were added to the pressurized dissolution tank. Then, the cellulose acetate was put into the pressure dissolution tank containing the solvent with stirring. This is heated and completely melted while stirring, and this is Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. Filtration was performed using 244 to prepare the main doping solution. Then, the main doping solution and each material were put into a closed container so as to have the following ratio, and dissolved with stirring to prepare a doping. As the sugar ester compound and the ester compound, compounds synthesized by the following synthesis examples were used.

(Composition of dope)
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.50, propionyl group substitution degree 0.90, total substitution degree 2.40) 100 parts by mass sugar ester compound 5.0 parts by mass ester Compound (polyester additive) 5.0 parts by mass Ultraviolet absorber (Chinubin 928 (manufactured by BASF Japan Co., Ltd.)) 1.5 parts by mass Fine particle additive solution 1 part by mass

<< Synthesis of sugar ester compounds >>
A sugar ester compound was synthesized by the following steps.

34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, and pyridine in a four-headed corben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas introduction tube. 379.7 g (4.8 mol) of each was charged, the temperature was raised while bubbling nitrogen gas from the nitrogen gas introduction tube under stirring, and the esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of Kolben ^{was depressurized to 4 × 10 2} Pa or less, excess pyridine was distilled off at 60 ° C., and then the inside of Kolben was depressurized to 1.3 × 10 Pa or less, the temperature was raised to 120 ° C., and benzoic anhydride was used. The acid, most of the benzoic acid produced, was distilled off. Then, 1 L of toluene and 300 g of a 0.5 mass% sodium carbonate aqueous solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate the toluene layer. Finally, 100 g of water was added to the separated toluene layer, washed with water at room temperature for 30 minutes, then the toluene layer was separated, and toluene was distilled off at 60 ° C. ^{under reduced pressure (4 × 10 2 Pa or less).} Mixtures of compounds A-1, A-2, A-3, A-4 and A-5 were obtained.

When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 1.3% by mass, A-2 was 13.4% by mass, A-3 was 13.1% by mass, and A-4 was 31. It was 0.7% by mass and A-5 was 40.5% by mass. The average degree of substitution was 5.5.

<Measurement conditions for HPLC-MS>
1) LC unit Equipment: JASCO Corporation column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Co., Ltd.)
Column temperature: 40 ° C
Flow velocity: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Equipment: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

<< Synthesis of ester compounds >>
The ester compound was synthesized by the following steps.

251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, and a 2 L four-neck equipped with a thermometer, a stirrer, and a slow-speed cooling tube. The temperature was gradually increased while stirring until the temperature reached 230 ° C. in a nitrogen stream. A dehydration condensation reaction was carried out for 15 hours, and after completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain an ester compound. The ester compound has an ester of benzoic acid at the end of a polyester chain formed by condensing 1,2-propylene glycol, phthalic anhydride and adipic acid. The acid value of the ester compound was 0.10, and the number average molecular weight was 450.

≪Manufacturing of raw film≫
The dope was uniformly spread on the stainless steel belt at a temperature of 35 ° C. and a width of 1800 mm using a belt spreading device. The solvent was evaporated on the stainless steel belt until the residual solvent amount became 100% by mass, and the casting film (optical film) was peeled off from the stainless steel belt. The peeled optical film was conveyed while being dried at 50 ° C., both ends were slit, and then stretched at a magnification of 20% under a temperature condition of 160 ° C. in the width direction with a tenter. The amount of residual solvent at the start of stretching was 15% by mass.

Then, the optical film was dried while being conveyed in a drying device at 120 ° C. with a large number of rolls, the amount of residual solvent was less than 0.1% by mass, and the end portion sandwiched between the tenter clips was slit with a laser cutter. .. Then, using an electron beam irradiator, the optical film was irradiated with an electron beam so that the absorbed dose was 1200 kGy under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV. Then, the optical film was wound up to obtain a raw film having a thickness of 36 μm and a width of 1500 mm.

≪Preparation of stretched film≫
The produced raw film was stretched in the same manner as in the production of the stretched film F-10 to prepare a long stretched film (diagonal stretched film) F-12 having a thickness of 30 μm and a width of 1300 mm.

<Preparation of stretched film F-13>
Pellets of a thermoplastic resin containing a norbornene polymer, which is a kind of alicyclic structure-containing polymer (“ZEONOR 1420” manufactured by Zeon Corporation, glass transition point 137 ° C.), were dried at 100 ° C. for 5 hours. Then, the pellets were supplied to an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter, and extruded into a film from a T-die onto a casting drum. The extruded resin was cooled by a casting drum, thereby obtaining a long unstretched film having a thickness of 55 μm and a width of 1500 mm. The unstretched film thus obtained was stretched (longitudinal stretching) in the longitudinal direction at a stretching temperature of 145 ° C. and a stretching ratio of 1.5 times to obtain a long longitudinally stretched film having a thickness of 45 μm and a width of 1000 mm. It should be noted that the above-mentioned longitudinal stretching has confirmed a contraction of 19% in the width direction.

Then, using an electron beam irradiator, the vertically stretched film is irradiated with an electron beam so that the absorbed dose is 1200 kGy under the conditions of an electron beam irradiation atmosphere oxygen concentration of 300 ppm or less and an acceleration voltage of 150 kV, and then the stretched film F. Diagonal stretching was performed in the same manner as in the production of -10. The stretching conditions at this time are a stretching ratio of 2.0 times (corresponding to W / Wo in FIG. 5) and a stretching temperature of 142 ° C. As a result, a long stretched film (diagonal stretched film) F-13 having a thickness of 22 μm and a width of 1330 mm was produced.

<Manufacturing of polarizing plate>
Using one of the bonding methods shown below (UV bonding or water-based bonding), the stretched film prepared above is attached to one surface side of the polarizing element, and a protective film (Konica Minolta) is attached to the other surface side of the polarizing element. Tack KC6UA, thickness 58 μm, manufactured by Konica Minolta Co., Ltd. was bonded to prepare polarizing plates P-1 to P-13. At this time, the stretched film and the polarizer were bonded so that the angle formed by the slow axis of the stretched film and the absorption axis of the polarizer was 90 °.

(1. UV adhesion)
<< Preparation of adhesive >>
After mixing each of the following components, defoaming was performed to prepare an ultraviolet curable adhesive. The triarylsulfonium hexafluorophosphate was used as a 50% by mass propylene carbonate solution, and in the following configuration, the triarylsulfonium hexafluorophosphate was indicated as the solid content.
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Co., Ltd.) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass

《Adhesion method》
The surface of the stretched film was subjected to a corona discharge treatment. The conditions for the corona discharge treatment were a corona output strength of 2.0 kW and a line speed of 18 m / min. Next, the ultraviolet curable adhesive prepared above was applied to the corona discharge-treated surface of the stretched film with a bar coater so that the film thickness after curing was about 3 μm to form an ultraviolet curable adhesive layer. Then, the above-prepared polarizer was attached to the obtained ultraviolet curable adhesive layer.

Further, the protective film (KC6UA) was also subjected to the same treatment as the above-mentioned stretched film to form an ultraviolet curable adhesive layer. Then, a polarizing element having a stretched film bonded to one side is bonded to the UV-curable adhesive layer of this protective film, and a laminate (stretched film / UV-curable adhesive layer / polarizer / UV-curable adhesive) is bonded. The layer structure of the agent layer / protective film) was obtained.

From both sides of this laminate, using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), ultraviolet rays were irradiated so that the ^{integrated light amount was 750 mJ / cm 2.} The ultraviolet curable adhesive layer of No. 1 was cured to prepare a polarizing plate.

(2. Adhesion of water system (water glue))
By going through the following steps in order, a stretched film, a polarizer, and a protective film (Konica Minolta Tack KC6UA, thickness 58 μm, manufactured by Konica Minolta Co., Ltd.) were laminated to prepare a polarizing plate.

Step 1: The stretched film and the protective film (KC6UA) are immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried, and placed on the side to be bonded to the polarizer of each film. It was saponified.

Step 2: The polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

Step 3: The excess adhesive adhering to the polarizer in step 2 was lightly wiped off, and the stretched film treated in step 1 was placed on one surface of the stretched film and the protective film was placed on the other surface.

Step 4: The stretched film, the polarizer, and the protective film laminated in Step 3 were bonded together at a pressure of 20 to 30 N / cm ² and a transport speed of about 2 m / min.

Step 5: The laminate bonded in Step 4 was dried for 2 minutes in a dryer at 80 ° C. to prepare a polarizing plate.

<Evaluation>
(Aggregate fracture)
The polarizing plate prepared above was left at 23 ° C. in an environment with a relative humidity of 55% for 24 hours. Then, the adhesive surface between the polarizer and the stretched film was peeled off by hand, and the presence or absence and degree of cohesive fracture in the stretched film were visually observed and evaluated according to the following criteria. If it is ○ or higher, it is judged that there is no problem in practical use.
"Evaluation criteria"
⊚: Does not come off.
◯: After peeling off the stretched film, even if the surface on the polarizer side was checked with a microscope, no fragments of the stretched film were confirmed.
X: After peeling off the stretched film, the surface on the polarizer side was confirmed with a microscope, and fragments of the stretched film were confirmed.

(Adhesiveness)
The (interface) adhesiveness between the polarizer of the polarizing plate produced above and the stretched film was evaluated by measuring the peel strength. That is, the polarizing plate produced above was left to stand for 24 hours in an environment of 23 ° C. and a relative humidity of 55%, and then cut into a size of 25 mm parallel to the stretching direction and 15 mm in the orthogonal direction thereof. Then, a notch was made between the stretched film and the polarizer with a cutter knife, and the polarizing plate was attached to the glass plate. Then, the stretched film and the polarizer were peeled off at a peeling speed of 300 mm / min in the 90-degree direction (direction perpendicular to the film surface) with Tencilon, and the peeling strength was measured. It can be said that the larger the peel strength, the better the adhesiveness between the polarizer and the stretched film, and if it is ◯ or higher, it is good, and Δ is judged to be a level that does not cause any practical problem. It should be noted that the above-mentioned adhesiveness is improved when the cohesive failure is improved and when the cohesive failure is the same, but when the permeability of the adhesive (glue) is changed due to the difference in the resin or the drawing conditions. There is. Here, the adhesiveness was evaluated including both of them.
"Evaluation criteria"
⊚: The peel strength is 4.0 N or more.
◯: The peel strength is 3.0 N or more and less than 4.0 N.
Δ: The peel strength is 2.0 N or more and less than 3.0 N.
X: The peel strength is less than 2.0 N.

The results of the evaluation of the polarizing plates P-1 to P-13 are shown in Table 1. In the table, COP indicates a cycloolefin resin, CE indicates a cellulose ester resin (cellulose acylate resin), and PC indicates a polycarbonate resin. The methods for producing the stretched films F-9, F-11, and F-12 are merely reference examples of the present invention and do not belong to the scope of the present invention.

Both the polarizing plates P-1 and P-3 have poor cohesive failure and adhesiveness. In the production of the stretched film F-1 (F-3) used for the polarizing plate P-1 (P-3), the film is formed in a state where the entanglement between the matrix molecules in the thickness direction is dissociated by stretching in the in-plane direction. Since the electron beam is irradiated, it is considered that the effect of the electron beam irradiation (the effect of enhancing the cross-linking between matrix molecules) is difficult to obtain, and as a result, cohesive destruction is likely to occur.

On the other hand, the polarizing plates P-2 and P-4-1 to P-13 have good cohesive failure and adhesiveness. In the production of stretched film F-2 and the like used for the polarizing plate P-2 and the like, the film is shrunk before stretching to promote entanglement between matrix molecules in the thickness direction and irradiate the film with an electron beam. By doing so, the cross-linking between the matrix molecules is enhanced, so that the dissociation of the entanglement between the matrix molecules due to the subsequent stretching can be effectively suppressed, and as a result, the cohesive failure of the stretched film is suppressed. Be done. Further, since the adhesive permeates the inside of the film through the crosslinked portion between the matrix molecules, it is considered that the adhesiveness of the stretched film to the polarizer is also good.

Further, from the results of the polarizing plates P-4-1 and P-6, it is more likely that the shrinkage step and the irradiation step are performed in this order before stretching than the case where the irradiation step and the shrinkage step are performed in this order. The effect of suppressing and improving the adhesiveness is high. It is considered that this is because the entanglement between the matrix molecules promoted by the shrinkage step can be strengthened by the irradiation step, and the cross-linking can be surely enhanced.

Further, from the results of the polarizing plates P-10 to P-12, the adhesiveness is better when COP is used as the resin used for the stretched film (optical film) than when PC and CE are used. It is considered that COP has high permeability of a solvent generally used for UV adhesive, and as a result, the permeability of the adhesive is also high, and the adhesiveness at the interface is better than that of PC and CE.

The stretched film F-8 of the polarizing plate P-8 has a lower evaluation of cohesive failure than the stretched film F-7 of the polarizing plate P-7. When the stretched film F-8 is produced, the amount of residual solvent at the start of wide stretching is larger than that when the stretched film F-7 is produced, so that creas (cracks) are likely to occur on the surface, which makes the film fragile. It is thought that coagulation failure is likely to occur. However, shrinkage before stretching and electron beam irradiation enhance cross-linking between matrix molecules in the film, which improves the permeability of the adhesive, thus reducing agglomeration failure due to crazes to some extent, resulting in practical use. There is no problem. Regarding the adhesiveness, the same evaluation as that of the stretched film F-7 has been obtained due to the improvement of the permeability of the adhesive.

In the above examples, an example of irradiating the optical film with an electron beam in the irradiation step at the time of producing the stretched film has been described, but even when γ-rays are irradiated instead of the electron beams, the electron beams are irradiated. It was confirmed that the same result as the case was obtained.

The stretched film of the present invention can be used, for example, as a polarizing plate of a liquid crystal display device.

F optical film

Claims (2)

A method for producing a stretched film, which comprises at least one stretching step for stretching the optical film.
A shrinking step of shrinking the optical film in-plane and
The optical film is further provided with an irradiation step of irradiating the optical film with an electron beam or a γ-ray.
The shrinking step and the irradiation step are performed before the final stretching step of at least one of the above steps.
A method for producing a stretched film, wherein the optical film contains a cycloolefin resin. The method for producing a stretched film according to claim 1, wherein the shrinkage step and the irradiation step are performed in this order before the final stretching step.

Images